[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 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	There are a number of principal ways to embed other event loops or modules
		1499	into libev. Here are some ideas on how to include libadns into libev
		1500	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1501	use for an actually working example. Another Perl module named C<EV::Glib>
		1502	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1503	into the Glib event loop).
1136		1504
		1505	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1506	and in a check watcher, destroy them and call into libadns. What follows
		1507	is pseudo-code only of course. This requires you to either use a low
		1508	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1509	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1510
		1511	static ev_io iow [nfd];
		1512	static ev_timer tw;
		1513
		1514	static void
		1515	io_cb (ev_loop loop, ev_io w, int revents)
		1516	{
		1517	}
		1518
		1519	// create io watchers for each fd and a timer before blocking
		1520	static void
		1521	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1522	{
		1523	int timeout = 3600000;
		1524	struct pollfd fds [nfd];
		1525	// actual code will need to loop here and realloc etc.
		1526	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1527
		1528	/* the callback is illegal, but won't be called as we stop during check */
		1529	ev_timer_init (&tw, 0, timeout * 1e-3);
		1530	ev_timer_start (loop, &tw);
		1531
		1532	// create one ev_io per pollfd
		1533	for (int i = 0; i < nfd; ++i)
		1534	{
		1535	ev_io_init (iow + i, io_cb, fds [i].fd,
		1536	((fds [i].events & POLLIN ? EV_READ : 0)
		1537	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1538
		1539	fds [i].revents = 0;
		1540	ev_io_start (loop, iow + i);
		1541	}
		1542	}
		1543
		1544	// stop all watchers after blocking
		1545	static void
		1546	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1547	{
		1548	ev_timer_stop (loop, &tw);
		1549
		1550	for (int i = 0; i < nfd; ++i)
		1551	{
		1552	// set the relevant poll flags
		1553	// could also call adns_processreadable etc. here
		1554	struct pollfd *fd = fds + i;
		1555	int revents = ev_clear_pending (iow + i);
		1556	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1557	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1558
		1559	// now stop the watcher
		1560	ev_io_stop (loop, iow + i);
		1561	}
		1562
		1563	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1564	}
		1565
		1566	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1567	in the prepare watcher and would dispose of the check watcher.
		1568
		1569	Method 3: If the module to be embedded supports explicit event
		1570	notification (adns does), you can also make use of the actual watcher
		1571	callbacks, and only destroy/create the watchers in the prepare watcher.
		1572
		1573	static void
		1574	timer_cb (EV_P_ ev_timer *w, int revents)
		1575	{
		1576	adns_state ads = (adns_state)w->data;
		1577	update_now (EV_A);
		1578
		1579	adns_processtimeouts (ads, &tv_now);
		1580	}
		1581
		1582	static void
		1583	io_cb (EV_P_ ev_io *w, int revents)
		1584	{
		1585	adns_state ads = (adns_state)w->data;
		1586	update_now (EV_A);
		1587
		1588	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1589	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1590	}
		1591
		1592	// do not ever call adns_afterpoll
		1593
		1594	Method 4: Do not use a prepare or check watcher because the module you
		1595	want to embed is too inflexible to support it. Instead, youc na override
		1596	their poll function. The drawback with this solution is that the main
		1597	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1598	this.
		1599
		1600	static gint
		1601	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1602	{
		1603	int got_events = 0;
		1604
		1605	for (n = 0; n < nfds; ++n)
		1606	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1607
		1608	if (timeout >= 0)
		1609	// create/start timer
		1610
		1611	// poll
		1612	ev_loop (EV_A_ 0);
		1613
		1614	// stop timer again
		1615	if (timeout >= 0)
		1616	ev_timer_stop (EV_A_ &to);
		1617
		1618	// stop io watchers again - their callbacks should have set
		1619	for (n = 0; n < nfds; ++n)
		1620	ev_io_stop (EV_A_ iow [n]);
		1621
		1622	return got_events;
		1623	}
		1624
		1625
1138	=head2 C<ev_embed> - when one backend isn't enough	1626	=head2 C<ev_embed> - when one backend isn't enough...
1139		1627
1140	This is a rather advanced watcher type that lets you embed one event loop	1628	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	1629	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	1630	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1631	fashion and must not be used).
…		…
1221		1709
1222	Make a single, non-blocking sweep over the embedded loop. This works	1710	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	1711	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1712	apropriate way for embedded loops.
1225		1713
		1714	=item struct ev_loop *loop [read-only]
		1715
		1716	The embedded event loop.
		1717
		1718	=back
		1719
		1720
		1721	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1722
		1723	Fork watchers are called when a C<fork ()> was detected (usually because
		1724	whoever is a good citizen cared to tell libev about it by calling
		1725	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1726	event loop blocks next and before C<ev_check> watchers are being called,
		1727	and only in the child after the fork. If whoever good citizen calling
		1728	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1729	handlers will be invoked, too, of course.
		1730
		1731	=over 4
		1732
		1733	=item ev_fork_init (ev_signal *, callback)
		1734
		1735	Initialises and configures the fork watcher - it has no parameters of any
		1736	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1737	believe me.
		1738
1226	=back	1739	=back
1227		1740
1228		1741
1229	=head1 OTHER FUNCTIONS	1742	=head1 OTHER FUNCTIONS
1230		1743
…		…
1318		1831
1319	To use it,	1832	To use it,
1320		1833
1321	#include <ev++.h>	1834	#include <ev++.h>
1322		1835
1323	(it is not installed by default). This automatically includes F<ev.h>	1836	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	1837	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.	1838	put into the C<ev> namespace. It should support all the same embedding
		1839	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		1840
1327	It should support all the same embedding options as F<ev.h>, most notably	1841	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	1842	classes add (compared to plain C-style watchers) is the event loop pointer
		1843	that the watcher is associated with (or no additional members at all if
		1844	you disable C<EV_MULTIPLICITY> when embedding libev).
		1845
		1846	Currently, functions, and static and non-static member functions can be
		1847	used as callbacks. Other types should be easy to add as long as they only
		1848	need one additional pointer for context. If you need support for other
		1849	types of functors please contact the author (preferably after implementing
		1850	it).
1329		1851
1330	Here is a list of things available in the C<ev> namespace:	1852	Here is a list of things available in the C<ev> namespace:
1331		1853
1332	=over 4	1854	=over 4
1333		1855
…		…
1349		1871
1350	All of those classes have these methods:	1872	All of those classes have these methods:
1351		1873
1352	=over 4	1874	=over 4
1353		1875
1354	=item ev::TYPE::TYPE (object , object::method )	1876	=item ev::TYPE::TYPE ()
1355		1877
1356	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1878	=item ev::TYPE::TYPE (struct ev_loop *)
1357		1879
1358	=item ev::TYPE::~TYPE	1880	=item ev::TYPE::~TYPE
1359		1881
1360	The constructor takes a pointer to an object and a method pointer to	1882	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	1883	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	1884
1363	before starting it. If you do not specify a loop then the constructor	1885	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	1886	C<set> method before starting it.
		1887
		1888	It will not set a callback, however: You have to call the templated C<set>
		1889	method to set a callback before you can start the watcher.
		1890
		1891	(The reason why you have to use a method is a limitation in C++ which does
		1892	not allow explicit template arguments for constructors).
1365		1893
1366	The destructor automatically stops the watcher if it is active.	1894	The destructor automatically stops the watcher if it is active.
		1895
		1896	=item w->set<class, &class::method> (object *)
		1897
		1898	This method sets the callback method to call. The method has to have a
		1899	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1900	first argument and the C<revents> as second. The object must be given as
		1901	parameter and is stored in the C<data> member of the watcher.
		1902
		1903	This method synthesizes efficient thunking code to call your method from
		1904	the C callback that libev requires. If your compiler can inline your
		1905	callback (i.e. it is visible to it at the place of the C<set> call and
		1906	your compiler is good :), then the method will be fully inlined into the
		1907	thunking function, making it as fast as a direct C callback.
		1908
		1909	Example: simple class declaration and watcher initialisation
		1910
		1911	struct myclass
		1912	{
		1913	void io_cb (ev::io &w, int revents) { }
		1914	}
		1915
		1916	myclass obj;
		1917	ev::io iow;
		1918	iow.set <myclass, &myclass::io_cb> (&obj);
		1919
		1920	=item w->set<function> (void *data = 0)
		1921
		1922	Also sets a callback, but uses a static method or plain function as
		1923	callback. The optional C<data> argument will be stored in the watcher's
		1924	C<data> member and is free for you to use.
		1925
		1926	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1927
		1928	See the method-C<set> above for more details.
		1929
		1930	Example:
		1931
		1932	static void io_cb (ev::io &w, int revents) { }
		1933	iow.set <io_cb> ();
1367		1934
1368	=item w->set (struct ev_loop *)	1935	=item w->set (struct ev_loop *)
1369		1936
1370	Associates a different C<struct ev_loop> with this watcher. You can only	1937	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).	1938	do this when the watcher is inactive (and not pending either).
1372		1939
1373	=item w->set ([args])	1940	=item w->set ([args])
1374		1941
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1942	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	1943	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	1944	automatically stopped and restarted when reconfiguring it with this
		1945	method.
1378		1946
1379	=item w->start ()	1947	=item w->start ()
1380		1948
1381	Starts the watcher. Note that there is no C<loop> argument as the	1949	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	1950	constructor already stores the event loop.
1383		1951
1384	=item w->stop ()	1952	=item w->stop ()
1385		1953
1386	Stops the watcher if it is active. Again, no C<loop> argument.	1954	Stops the watcher if it is active. Again, no C<loop> argument.
1387		1955
…		…
1392		1960
1393	=item w->sweep () C<ev::embed> only	1961	=item w->sweep () C<ev::embed> only
1394		1962
1395	Invokes C<ev_embed_sweep>.	1963	Invokes C<ev_embed_sweep>.
1396		1964
		1965	=item w->update () C<ev::stat> only
		1966
		1967	Invokes C<ev_stat_stat>.
		1968
1397	=back	1969	=back
1398		1970
1399	=back	1971	=back
1400		1972
1401	Example: Define a class with an IO and idle watcher, start one of them in	1973	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1408		1980
1409	myclass ();	1981	myclass ();
1410	}	1982	}
1411		1983
1412	myclass::myclass (int fd)	1984	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	1985	{
		1986	io .set <myclass, &myclass::io_cb > (this);
		1987	idle.set <myclass, &myclass::idle_cb> (this);
		1988
1416	io.start (fd, ev::READ);	1989	io.start (fd, ev::READ);
1417	}	1990	}
		1991
		1992
		1993	=head1 MACRO MAGIC
		1994
		1995	Libev can be compiled with a variety of options, the most fundemantal is
		1996	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		1997	callbacks have an initial C<struct ev_loop *> argument.
		1998
		1999	To make it easier to write programs that cope with either variant, the
		2000	following macros are defined:
		2001
		2002	=over 4
		2003
		2004	=item C<EV_A>, C<EV_A_>
		2005
		2006	This provides the loop I<argument> for functions, if one is required ("ev
		2007	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2008	C<EV_A_> is used when other arguments are following. Example:
		2009
		2010	ev_unref (EV_A);
		2011	ev_timer_add (EV_A_ watcher);
		2012	ev_loop (EV_A_ 0);
		2013
		2014	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2015	which is often provided by the following macro.
		2016
		2017	=item C<EV_P>, C<EV_P_>
		2018
		2019	This provides the loop I<parameter> for functions, if one is required ("ev
		2020	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2021	C<EV_P_> is used when other parameters are following. Example:
		2022
		2023	// this is how ev_unref is being declared
		2024	static void ev_unref (EV_P);
		2025
		2026	// this is how you can declare your typical callback
		2027	static void cb (EV_P_ ev_timer *w, int revents)
		2028
		2029	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2030	suitable for use with C<EV_A>.
		2031
		2032	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2033
		2034	Similar to the other two macros, this gives you the value of the default
		2035	loop, if multiple loops are supported ("ev loop default").
		2036
		2037	=back
		2038
		2039	Example: Declare and initialise a check watcher, utilising the above
		2040	macros so it will work regardless of whether multiple loops are supported
		2041	or not.
		2042
		2043	static void
		2044	check_cb (EV_P_ ev_timer *w, int revents)
		2045	{
		2046	ev_check_stop (EV_A_ w);
		2047	}
		2048
		2049	ev_check check;
		2050	ev_check_init (&check, check_cb);
		2051	ev_check_start (EV_DEFAULT_ &check);
		2052	ev_loop (EV_DEFAULT_ 0);
1418		2053
1419	=head1 EMBEDDING	2054	=head1 EMBEDDING
1420		2055
1421	Libev can (and often is) directly embedded into host	2056	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	2057	applications. Examples of applications that embed it include the Deliantra
…		…
1462	ev_vars.h	2097	ev_vars.h
1463	ev_wrap.h	2098	ev_wrap.h
1464		2099
1465	ev_win32.c required on win32 platforms only	2100	ev_win32.c required on win32 platforms only
1466		2101
1467	ev_select.c only when select backend is enabled (which is is by default)	2102	ev_select.c only when select backend is enabled (which is enabled by default)
1468	ev_poll.c only when poll backend is enabled (disabled by default)	2103	ev_poll.c only when poll backend is enabled (disabled by default)
1469	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2104	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1470	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2105	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1471	ev_port.c only when the solaris port backend is enabled (disabled by default)	2106	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		2107
1473	F<ev.c> includes the backend files directly when enabled, so you only need	2108	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	2109	to compile this single file.
1475		2110
1476	=head3 LIBEVENT COMPATIBILITY API	2111	=head3 LIBEVENT COMPATIBILITY API
1477		2112
1478	To include the libevent compatibility API, also include:	2113	To include the libevent compatibility API, also include:
1479		2114
…		…
1492		2127
1493	=head3 AUTOCONF SUPPORT	2128	=head3 AUTOCONF SUPPORT
1494		2129
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	2130	Instead of using C<EV_STANDALONE=1> and providing your config in
1496	whatever way you want, you can also C<m4_include([libev.m4])> in your	2131	whatever way you want, you can also C<m4_include([libev.m4])> in your
1497	F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include	2132	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	2133	include F<config.h> and configure itself accordingly.
1499		2134
1500	For this of course you need the m4 file:	2135	For this of course you need the m4 file:
1501		2136
1502	libev.m4	2137	libev.m4
1503		2138
…		…
1583	otherwise another method will be used as fallback. This is the preferred	2218	otherwise another method will be used as fallback. This is the preferred
1584	backend for BSD and BSD-like systems, although on most BSDs kqueue only	2219	backend for BSD and BSD-like systems, although on most BSDs kqueue only
1585	supports some types of fds correctly (the only platform we found that	2220	supports some types of fds correctly (the only platform we found that
1586	supports ptys for example was NetBSD), so kqueue might be compiled in, but	2221	supports ptys for example was NetBSD), so kqueue might be compiled in, but
1587	not be used unless explicitly requested. The best way to use it is to find	2222	not be used unless explicitly requested. The best way to use it is to find
1588	out wether kqueue supports your type of fd properly and use an embedded	2223	out whether kqueue supports your type of fd properly and use an embedded
1589	kqueue loop.	2224	kqueue loop.
1590		2225
1591	=item EV_USE_PORT	2226	=item EV_USE_PORT
1592		2227
1593	If defined to be C<1>, libev will compile in support for the Solaris	2228	If defined to be C<1>, libev will compile in support for the Solaris
…		…
1596	backend for Solaris 10 systems.	2231	backend for Solaris 10 systems.
1597		2232
1598	=item EV_USE_DEVPOLL	2233	=item EV_USE_DEVPOLL
1599		2234
1600	reserved for future expansion, works like the USE symbols above.	2235	reserved for future expansion, works like the USE symbols above.
		2236
		2237	=item EV_USE_INOTIFY
		2238
		2239	If defined to be C<1>, libev will compile in support for the Linux inotify
		2240	interface to speed up C<ev_stat> watchers. Its actual availability will
		2241	be detected at runtime.
1601		2242
1602	=item EV_H	2243	=item EV_H
1603		2244
1604	The name of the F<ev.h> header file used to include it. The default if	2245	The name of the F<ev.h> header file used to include it. The default if
1605	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2246	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2270	will have the C<struct ev_loop *> as first argument, and you can create
1630	additional independent event loops. Otherwise there will be no support	2271	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2272	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2273	argument. Instead, all functions act on the single default loop.
1633		2274
		2275	=item EV_MINPRI
		2276
		2277	=item EV_MAXPRI
		2278
		2279	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2280	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2281	provide for more priorities by overriding those symbols (usually defined
		2282	to be C<-2> and C<2>, respectively).
		2283
		2284	When doing priority-based operations, libev usually has to linearly search
		2285	all the priorities, so having many of them (hundreds) uses a lot of space
		2286	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2287	fine.
		2288
		2289	If your embedding app does not need any priorities, defining these both to
		2290	C<0> will save some memory and cpu.
		2291
1634	=item EV_PERIODICS	2292	=item EV_PERIODIC_ENABLE
1635		2293
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2294	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2295	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2296	code.
		2297
		2298	=item EV_IDLE_ENABLE
		2299
		2300	If undefined or defined to be C<1>, then idle watchers are supported. If
		2301	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2302	code.
		2303
		2304	=item EV_EMBED_ENABLE
		2305
		2306	If undefined or defined to be C<1>, then embed watchers are supported. If
		2307	defined to be C<0>, then they are not.
		2308
		2309	=item EV_STAT_ENABLE
		2310
		2311	If undefined or defined to be C<1>, then stat watchers are supported. If
		2312	defined to be C<0>, then they are not.
		2313
		2314	=item EV_FORK_ENABLE
		2315
		2316	If undefined or defined to be C<1>, then fork watchers are supported. If
		2317	defined to be C<0>, then they are not.
		2318
		2319	=item EV_MINIMAL
		2320
		2321	If you need to shave off some kilobytes of code at the expense of some
		2322	speed, define this symbol to C<1>. Currently only used for gcc to override
		2323	some inlining decisions, saves roughly 30% codesize of amd64.
		2324
		2325	=item EV_PID_HASHSIZE
		2326
		2327	C<ev_child> watchers use a small hash table to distribute workload by
		2328	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2329	than enough. If you need to manage thousands of children you might want to
		2330	increase this value (I<must> be a power of two).
		2331
		2332	=item EV_INOTIFY_HASHSIZE
		2333
		2334	C<ev_staz> watchers use a small hash table to distribute workload by
		2335	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2336	usually more than enough. If you need to manage thousands of C<ev_stat>
		2337	watchers you might want to increase this value (I<must> be a power of
		2338	two).
1638		2339
1639	=item EV_COMMON	2340	=item EV_COMMON
1640		2341
1641	By default, all watchers have a C<void *data> member. By redefining	2342	By default, all watchers have a C<void *data> member. By redefining
1642	this macro to a something else you can include more and other types of	2343	this macro to a something else you can include more and other types of
…		…
1647		2348
1648	#define EV_COMMON \	2349	#define EV_COMMON \
1649	SV self; / contains this struct */ \	2350	SV self; / contains this struct */ \
1650	SV cb_sv, fh /* note no trailing ";" */	2351	SV cb_sv, fh /* note no trailing ";" */
1651		2352
1652	=item EV_CB_DECLARE(type)	2353	=item EV_CB_DECLARE (type)
1653		2354
1654	=item EV_CB_INVOKE(watcher,revents)	2355	=item EV_CB_INVOKE (watcher, revents)
1655		2356
1656	=item ev_set_cb(ev,cb)	2357	=item ev_set_cb (ev, cb)
1657		2358
1658	Can be used to change the callback member declaration in each watcher,	2359	Can be used to change the callback member declaration in each watcher,
1659	and the way callbacks are invoked and set. Must expand to a struct member	2360	and the way callbacks are invoked and set. Must expand to a struct member
1660	definition and a statement, respectively. See the F<ev.v> header file for	2361	definition and a statement, respectively. See the F<ev.v> header file for
1661	their default definitions. One possible use for overriding these is to	2362	their default definitions. One possible use for overriding these is to
1662	avoid the ev_loop pointer as first argument in all cases, or to use method	2363	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2364	method calls instead of plain function calls in C++.
1664		2365
1665	=head2 EXAMPLES	2366	=head2 EXAMPLES
1666		2367
1667	For a real-world example of a program the includes libev	2368	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2369	verbatim, you can have a look at the EV perl module
…		…
1671	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2372	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1672	will be compiled. It is pretty complex because it provides its own header	2373	will be compiled. It is pretty complex because it provides its own header
1673	file.	2374	file.
1674		2375
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2376	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1676	that everybody includes and which overrides some autoconf choices:	2377	that everybody includes and which overrides some configure choices:
1677		2378
		2379	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	2380	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	2381	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	2382	#define EV_PERIODIC_ENABLE 0
		2383	#define EV_STAT_ENABLE 0
		2384	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	2385	#define EV_CONFIG_H <config.h>
		2386	#define EV_MINPRI 0
		2387	#define EV_MAXPRI 0
1682		2388
1683	#include "ev++.h"	2389	#include "ev++.h"
1684		2390
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2391	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2392
1687	#include "ev_cpp.h"	2393	#include "ev_cpp.h"
1688	#include "ev.c"	2394	#include "ev.c"
1689		2395
		2396
		2397	=head1 COMPLEXITIES
		2398
		2399	In this section the complexities of (many of) the algorithms used inside
		2400	libev will be explained. For complexity discussions about backends see the
		2401	documentation for C<ev_default_init>.
		2402
		2403	All of the following are about amortised time: If an array needs to be
		2404	extended, libev needs to realloc and move the whole array, but this
		2405	happens asymptotically never with higher number of elements, so O(1) might
		2406	mean it might do a lengthy realloc operation in rare cases, but on average
		2407	it is much faster and asymptotically approaches constant time.
		2408
		2409	=over 4
		2410
		2411	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2412
		2413	This means that, when you have a watcher that triggers in one hour and
		2414	there are 100 watchers that would trigger before that then inserting will
		2415	have to skip those 100 watchers.
		2416
		2417	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2418
		2419	That means that for changing a timer costs less than removing/adding them
		2420	as only the relative motion in the event queue has to be paid for.
		2421
		2422	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2423
		2424	These just add the watcher into an array or at the head of a list.
		2425	=item Stopping check/prepare/idle watchers: O(1)
		2426
		2427	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2428
		2429	These watchers are stored in lists then need to be walked to find the
		2430	correct watcher to remove. The lists are usually short (you don't usually
		2431	have many watchers waiting for the same fd or signal).
		2432
		2433	=item Finding the next timer per loop iteration: O(1)
		2434
		2435	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2436
		2437	A change means an I/O watcher gets started or stopped, which requires
		2438	libev to recalculate its status (and possibly tell the kernel).
		2439
		2440	=item Activating one watcher: O(1)
		2441
		2442	=item Priority handling: O(number_of_priorities)
		2443
		2444	Priorities are implemented by allocating some space for each
		2445	priority. When doing priority-based operations, libev usually has to
		2446	linearly search all the priorities.
		2447
		2448	=back
		2449
		2450
1690	=head1 AUTHOR	2451	=head1 AUTHOR
1691		2452
1692	Marc Lehmann <libev@schmorp.de>.	2453	Marc Lehmann <libev@schmorp.de>.
1693		2454

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Comparing libev/ev.pod (file contents): Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs. Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC