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

Comparing libev/ev.pod (file contents):
Revision 1.41 by root, Sat Nov 24 10:19:14 2007 UTC vs.
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		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	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	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	54	file descriptor being readable or a timeout occuring), and it will manage
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	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	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	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 *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME REPRESENTATION	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	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	97	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	98	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	99	it, you should treat it as such.
52		100
53
54	=head1 GLOBAL FUNCTIONS	101	=head1 GLOBAL FUNCTIONS
55		102
56	These functions can be called anytime, even before initialising the	103	These functions can be called anytime, even before initialising the
57	library in any way.	104	library in any way.
58		105
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	127	not a problem.
81		128
82	Example: make sure we haven't accidentally been linked against the wrong	129	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	130	version.
84		131
85	assert (("libev version mismatch",	132	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	133	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	134	&& ev_version_minor () >= EV_VERSION_MINOR));
88		135
…		…
118		165
119	See the description of C<ev_embed> watchers for more info.	166	See the description of C<ev_embed> watchers for more info.
120		167
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	168	=item ev_set_allocator (void (cb)(void *ptr, long size))
122		169
123	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	171	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	172	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	173	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	174	potentially destructive action. The default is your system realloc
		175	function.
128		176
129	You could override this function in high-availability programs to, say,	177	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,	178	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.	179	or even to sleep a while and retry until some memory is available.
132		180
133	Example: replace the libev allocator with one that waits a bit and then	181	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	182	retries).
135		183
136	static void *	184	static void *
137	persistent_realloc (void *ptr, long size)	185	persistent_realloc (void *ptr, size_t size)
138	{	186	{
139	for (;;)	187	for (;;)
140	{	188	{
141	void *newptr = realloc (ptr, size);	189	void *newptr = realloc (ptr, size);
142		190
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	206	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	207	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	208	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	209	(such as abort).
162		210
163	Example: do the same thing as libev does internally:	211	Example: This is basically the same thing that libev does internally, too.
164		212
165	static void	213	static void
166	fatal_error (const char *msg)	214	fatal_error (const char *msg)
167	{	215	{
168	perror (msg);	216	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	267	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	268	useful to try out specific backends to test their performance, or to work
221	around bugs.	269	around bugs.
222		270
		271	=item C<EVFLAG_FORKCHECK>
		272
		273	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		274	a fork, you can also make libev check for a fork in each iteration by
		275	enabling this flag.
		276
		277	This works by calling C<getpid ()> on every iteration of the loop,
		278	and thus this might slow down your event loop if you do a lot of loop
		279	iterations and little real work, but is usually not noticeable (on my
		280	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		281	without a syscall and thus I<very> fast, but my Linux system also has
		282	C<pthread_atfork> which is even faster).
		283
		284	The big advantage of this flag is that you can forget about fork (and
		285	forget about forgetting to tell libev about forking) when you use this
		286	flag.
		287
		288	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		289	environment variable.
		290
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		292
225	This is your standard select(2) backend. Not I<completely> standard, as	293	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,	294	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	295	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	382	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	383	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	384	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).	385	undefined behaviour (or a failed assertion if assertions are enabled).
318		386
319	Example: try to create a event loop that uses epoll and nothing else.	387	Example: Try to create a event loop that uses epoll and nothing else.
320		388
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	390	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	391	fatal ("no epoll found here, maybe it hides under your chair");
324		392
…		…
361	=item ev_loop_fork (loop)	429	=item ev_loop_fork (loop)
362		430
363	Like C<ev_default_fork>, but acts on an event loop created by	431	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	432	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.	433	after fork, and how you do this is entirely your own problem.
		434
		435	=item unsigned int ev_loop_count (loop)
		436
		437	Returns the count of loop iterations for the loop, which is identical to
		438	the number of times libev did poll for new events. It starts at C<0> and
		439	happily wraps around with enough iterations.
		440
		441	This value can sometimes be useful as a generation counter of sorts (it
		442	"ticks" the number of loop iterations), as it roughly corresponds with
		443	C<ev_prepare> and C<ev_check> calls.
366		444
367	=item unsigned int ev_backend (loop)	445	=item unsigned int ev_backend (loop)
368		446
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	447	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	448	use.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	501	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	502	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	503	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	504	were used, return, otherwise continue with step *.
427		505
428	Example: queue some jobs and then loop until no events are outsanding	506	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	507	anymore.
430		508
431	... queue jobs here, make sure they register event watchers as long	509	... 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..)	510	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	511	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	531	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	532	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	533	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>.	534	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		535
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	536	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	537	running when nothing else is active.
460		538
461	struct dv_signal exitsig;	539	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	540	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	541	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	542	evf_unref (loop);
465		543
466	Example: for some weird reason, unregister the above signal handler again.	544	Example: For some weird reason, unregister the above signal handler again.
467		545
468	ev_ref (myloop);	546	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	547	ev_signal_stop (loop, &exitsig);
470		548
471	=back	549	=back
		550
472		551
473	=head1 ANATOMY OF A WATCHER	552	=head1 ANATOMY OF A WATCHER
474		553
475	A watcher is a structure that you create and register to record your	554	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	555	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.	622	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		623
545	=item C<EV_CHILD>	624	=item C<EV_CHILD>
546		625
547	The pid specified in the C<ev_child> watcher has received a status change.	626	The pid specified in the C<ev_child> watcher has received a status change.
		627
		628	=item C<EV_STAT>
		629
		630	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		631
549	=item C<EV_IDLE>	632	=item C<EV_IDLE>
550		633
551	The C<ev_idle> watcher has determined that you have nothing better to do.	634	The C<ev_idle> watcher has determined that you have nothing better to do.
552		635
…		…
560	received events. Callbacks of both watcher types can start and stop as	643	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	644	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	645	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	646	C<ev_loop> from blocking).
564		647
		648	=item C<EV_EMBED>
		649
		650	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		651
		652	=item C<EV_FORK>
		653
		654	The event loop has been resumed in the child process after fork (see
		655	C<ev_fork>).
		656
565	=item C<EV_ERROR>	657	=item C<EV_ERROR>
566		658
567	An unspecified error has occured, the watcher has been stopped. This might	659	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	660	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	661	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	668	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	669	programs, though, so beware.
578		670
579	=back	671	=back
580		672
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	673	=head2 GENERIC WATCHER FUNCTIONS
582		674
583	In the following description, C<TYPE> stands for the watcher type,	675	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.	676	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		677
586	=over 4	678	=over 4
…		…
595	which rolls both calls into one.	687	which rolls both calls into one.
596		688
597	You can reinitialise a watcher at any time as long as it has been stopped	689	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.	690	(or never started) and there are no pending events outstanding.
599		691
600	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	692	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
601	int revents)>.	693	int revents)>.
602		694
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	695	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		696
605	This macro initialises the type-specific parts of a watcher. You need to	697	This macro initialises the type-specific parts of a watcher. You need to
…		…
643	events but its callback has not yet been invoked). As long as a watcher	735	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	736	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	737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
646	libev (e.g. you cnanot C<free ()> it).	738	libev (e.g. you cnanot C<free ()> it).
647		739
648	=item callback = ev_cb (ev_TYPE *watcher)	740	=item callback ev_cb (ev_TYPE *watcher)
649		741
650	Returns the callback currently set on the watcher.	742	Returns the callback currently set on the watcher.
651		743
652	=item ev_cb_set (ev_TYPE *watcher, callback)	744	=item ev_cb_set (ev_TYPE *watcher, callback)
653		745
654	Change the callback. You can change the callback at virtually any time	746	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	747	(modulo threads).
		748
		749	=item ev_set_priority (ev_TYPE *watcher, priority)
		750
		751	=item int ev_priority (ev_TYPE *watcher)
		752
		753	Set and query the priority of the watcher. The priority is a small
		754	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		755	(default: C<-2>). Pending watchers with higher priority will be invoked
		756	before watchers with lower priority, but priority will not keep watchers
		757	from being executed (except for C<ev_idle> watchers).
		758
		759	This means that priorities are I<only> used for ordering callback
		760	invocation after new events have been received. This is useful, for
		761	example, to reduce latency after idling, or more often, to bind two
		762	watchers on the same event and make sure one is called first.
		763
		764	If you need to suppress invocation when higher priority events are pending
		765	you need to look at C<ev_idle> watchers, which provide this functionality.
		766
		767	The default priority used by watchers when no priority has been set is
		768	always C<0>, which is supposed to not be too high and not be too low :).
		769
		770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		771	fine, as long as you do not mind that the priority value you query might
		772	or might not have been adjusted to be within valid range.
656		773
657	=back	774	=back
658		775
659		776
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	798	{
682	struct my_io w = (struct my_io )w_;	799	struct my_io w = (struct my_io )w_;
683	...	800	...
684	}	801	}
685		802
686	More interesting and less C-conformant ways of catsing your callback type	803	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	804	instead have been omitted.
		805
		806	Another common scenario is having some data structure with multiple
		807	watchers:
		808
		809	struct my_biggy
		810	{
		811	int some_data;
		812	ev_timer t1;
		813	ev_timer t2;
		814	}
		815
		816	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		817	you need to use C<offsetof>:
		818
		819	#include <stddef.h>
		820
		821	static void
		822	t1_cb (EV_P_ struct ev_timer *w, int revents)
		823	{
		824	struct my_biggy big = (struct my_biggy *
		825	(((char *)w) - offsetof (struct my_biggy, t1));
		826	}
		827
		828	static void
		829	t2_cb (EV_P_ struct ev_timer *w, int revents)
		830	{
		831	struct my_biggy big = (struct my_biggy *
		832	(((char *)w) - offsetof (struct my_biggy, t2));
		833	}
688		834
689		835
690	=head1 WATCHER TYPES	836	=head1 WATCHER TYPES
691		837
692	This section describes each watcher in detail, but will not repeat	838	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	839	information given in the last section. Any initialisation/set macros,
		840	functions and members specific to the watcher type are explained.
694		841
		842	Members are additionally marked with either I<[read-only]>, meaning that,
		843	while the watcher is active, you can look at the member and expect some
		844	sensible content, but you must not modify it (you can modify it while the
		845	watcher is stopped to your hearts content), or I<[read-write]>, which
		846	means you can expect it to have some sensible content while the watcher
		847	is active, but you can also modify it. Modifying it may not do something
		848	sensible or take immediate effect (or do anything at all), but libev will
		849	not crash or malfunction in any way.
695		850
		851
696	=head2 C<ev_io> - is this file descriptor readable or writable	852	=head2 C<ev_io> - is this file descriptor readable or writable?
697		853
698	I/O watchers check whether a file descriptor is readable or writable	854	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	855	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	856	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	857	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	858	receiving events as long as the condition persists. Remember you can stop
		859	the watcher if you don't want to act on the event and neither want to
		860	receive future events.
703		861
704	In general you can register as many read and/or write event watchers per	862	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	863	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	864	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	865	required if you know what you are doing).
708		866
709	You have to be careful with dup'ed file descriptors, though. Some backends	867	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	868	(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	869	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	870	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	871	the same underlying "file open").
714		872
715	If you must do this, then force the use of a known-to-be-good backend	873	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	874	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	875	C<EVBACKEND_POLL>).
718		876
		877	Another thing you have to watch out for is that it is quite easy to
		878	receive "spurious" readyness notifications, that is your callback might
		879	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		880	because there is no data. Not only are some backends known to create a
		881	lot of those (for example solaris ports), it is very easy to get into
		882	this situation even with a relatively standard program structure. Thus
		883	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		884	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		885
		886	If you cannot run the fd in non-blocking mode (for example you should not
		887	play around with an Xlib connection), then you have to seperately re-test
		888	wether a file descriptor is really ready with a known-to-be good interface
		889	such as poll (fortunately in our Xlib example, Xlib already does this on
		890	its own, so its quite safe to use).
		891
719	=over 4	892	=over 4
720		893
721	=item ev_io_init (ev_io *, callback, int fd, int events)	894	=item ev_io_init (ev_io *, callback, int fd, int events)
722		895
723	=item ev_io_set (ev_io *, int fd, int events)	896	=item ev_io_set (ev_io *, int fd, int events)
724		897
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	898	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 \|	899	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	900	C<EV_READ \| EV_WRITE> to receive the given events.
728		901
729	Please note that most of the more scalable backend mechanisms (for example	902	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	903
731	for file descriptors, so you practically need to use non-blocking I/O (and	904	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	905
733	interface before doing I/O (XLib can do this), or force the use of either	906	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	907
735	problem. Also note that it is quite easy to have your callback invoked	908	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		909
740	=back	910	=back
741		911
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	912	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	913	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	914	attempt to read a whole line in the callback.
745		915
746	static void	916	static void
747	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	917	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
748	{	918	{
749	ev_io_stop (loop, w);	919	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	926	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	927	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	928	ev_loop (loop, 0);
759		929
760		930
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	931	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		932
763	Timer watchers are simple relative timers that generate an event after a	933	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	934	given time, and optionally repeating in regular intervals after that.
765		935
766	The timers are based on real time, that is, if you register an event that	936	The timers are based on real time, that is, if you register an event that
…		…
801	=item ev_timer_again (loop)	971	=item ev_timer_again (loop)
802		972
803	This will act as if the timer timed out and restart it again if it is	973	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	974	repeating. The exact semantics are:
805		975
		976	If the timer is pending, its pending status is cleared.
		977
806	If the timer is started but nonrepeating, stop it.	978	If the timer is started but nonrepeating, stop it (as if it timed out).
807		979
808	If the timer is repeating, either start it if necessary (with the repeat	980	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	981	C<repeat> value), or reset the running timer to the C<repeat> value.
810		982
811	This sounds a bit complicated, but here is a useful and typical	983	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	984	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	985	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	986	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	987	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	988	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	989	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.	990	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		991	automatically restart it if need be.
		992
		993	That means you can ignore the C<after> value and C<ev_timer_start>
		994	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		995
		996	ev_timer_init (timer, callback, 0., 5.);
		997	ev_timer_again (loop, timer);
		998	...
		999	timer->again = 17.;
		1000	ev_timer_again (loop, timer);
		1001	...
		1002	timer->again = 10.;
		1003	ev_timer_again (loop, timer);
		1004
		1005	This is more slightly efficient then stopping/starting the timer each time
		1006	you want to modify its timeout value.
		1007
		1008	=item ev_tstamp repeat [read-write]
		1009
		1010	The current C<repeat> value. Will be used each time the watcher times out
		1011	or C<ev_timer_again> is called and determines the next timeout (if any),
		1012	which is also when any modifications are taken into account.
819		1013
820	=back	1014	=back
821		1015
822	Example: create a timer that fires after 60 seconds.	1016	Example: Create a timer that fires after 60 seconds.
823		1017
824	static void	1018	static void
825	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1019	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
826	{	1020	{
827	.. one minute over, w is actually stopped right here	1021	.. one minute over, w is actually stopped right here
…		…
829		1023
830	struct ev_timer mytimer;	1024	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1025	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1026	ev_timer_start (loop, &mytimer);
833		1027
834	Example: create a timeout timer that times out after 10 seconds of	1028	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1029	inactivity.
836		1030
837	static void	1031	static void
838	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1032	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
839	{	1033	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1042	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1043	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1044	ev_timer_again (&mytimer);
851		1045
852		1046
853	=head2 C<ev_periodic> - to cron or not to cron	1047	=head2 C<ev_periodic> - to cron or not to cron?
854		1048
855	Periodic watchers are also timers of a kind, but they are very versatile	1049	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1050	(and unfortunately a bit complex).
857		1051
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1052	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	1144	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1145	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	1146	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1147	program when the crontabs have changed).
954		1148
		1149	=item ev_tstamp interval [read-write]
		1150
		1151	The current interval value. Can be modified any time, but changes only
		1152	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1153	called.
		1154
		1155	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1156
		1157	The current reschedule callback, or C<0>, if this functionality is
		1158	switched off. Can be changed any time, but changes only take effect when
		1159	the periodic timer fires or C<ev_periodic_again> is being called.
		1160
955	=back	1161	=back
956		1162
957	Example: call a callback every hour, or, more precisely, whenever the	1163	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1164	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1165	potentially a lot of jittering, but good long-term stability.
960		1166
961	static void	1167	static void
962	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1168	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
966		1172
967	struct ev_periodic hourly_tick;	1173	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1174	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1175	ev_periodic_start (loop, &hourly_tick);
970		1176
971	Example: the same as above, but use a reschedule callback to do it:	1177	Example: The same as above, but use a reschedule callback to do it:
972		1178
973	#include <math.h>	1179	#include <math.h>
974		1180
975	static ev_tstamp	1181	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1182	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1184	return fmod (now, 3600.) + 3600.;
979	}	1185	}
980		1186
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1187	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1188
983	Example: call a callback every hour, starting now:	1189	Example: Call a callback every hour, starting now:
984		1190
985	struct ev_periodic hourly_tick;	1191	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1192	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1193	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1194	ev_periodic_start (loop, &hourly_tick);
989		1195
990		1196
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1197	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1198
993	Signal watchers will trigger an event when the process receives a specific	1199	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	1200	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	1201	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1202	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1215	=item ev_signal_set (ev_signal *, int signum)
1010		1216
1011	Configures the watcher to trigger on the given signal number (usually one	1217	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1218	of the C<SIGxxx> constants).
1013		1219
		1220	=item int signum [read-only]
		1221
		1222	The signal the watcher watches out for.
		1223
1014	=back	1224	=back
1015		1225
1016		1226
1017	=head2 C<ev_child> - wait for pid status changes	1227	=head2 C<ev_child> - watch out for process status changes
1018		1228
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1229	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).	1230	some child status changes (most typically when a child of yours dies).
1021		1231
1022	=over 4	1232	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1240	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	1241	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	1242	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1243	process causing the status change.
1034		1244
		1245	=item int pid [read-only]
		1246
		1247	The process id this watcher watches out for, or C<0>, meaning any process id.
		1248
		1249	=item int rpid [read-write]
		1250
		1251	The process id that detected a status change.
		1252
		1253	=item int rstatus [read-write]
		1254
		1255	The process exit/trace status caused by C<rpid> (see your systems
		1256	C<waitpid> and C<sys/wait.h> documentation for details).
		1257
1035	=back	1258	=back
1036		1259
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1260	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1261
1039	static void	1262	static void
1040	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1263	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1041	{	1264	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1265	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1268	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1269	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1270	ev_signal_start (loop, &sigint_cb);
1048		1271
1049		1272
		1273	=head2 C<ev_stat> - did the file attributes just change?
		1274
		1275	This watches a filesystem path for attribute changes. That is, it calls
		1276	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1277	compared to the last time, invoking the callback if it did.
		1278
		1279	The path does not need to exist: changing from "path exists" to "path does
		1280	not exist" is a status change like any other. The condition "path does
		1281	not exist" is signified by the C<st_nlink> field being zero (which is
		1282	otherwise always forced to be at least one) and all the other fields of
		1283	the stat buffer having unspecified contents.
		1284
		1285	The path I<should> be absolute and I<must not> end in a slash. If it is
		1286	relative and your working directory changes, the behaviour is undefined.
		1287
		1288	Since there is no standard to do this, the portable implementation simply
		1289	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1290	can specify a recommended polling interval for this case. If you specify
		1291	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1292	unspecified default> value will be used (which you can expect to be around
		1293	five seconds, although this might change dynamically). Libev will also
		1294	impose a minimum interval which is currently around C<0.1>, but thats
		1295	usually overkill.
		1296
		1297	This watcher type is not meant for massive numbers of stat watchers,
		1298	as even with OS-supported change notifications, this can be
		1299	resource-intensive.
		1300
		1301	At the time of this writing, only the Linux inotify interface is
		1302	implemented (implementing kqueue support is left as an exercise for the
		1303	reader). Inotify will be used to give hints only and should not change the
		1304	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1305	to fall back to regular polling again even with inotify, but changes are
		1306	usually detected immediately, and if the file exists there will be no
		1307	polling.
		1308
		1309	=over 4
		1310
		1311	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1312
		1313	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1314
		1315	Configures the watcher to wait for status changes of the given
		1316	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1317	be detected and should normally be specified as C<0> to let libev choose
		1318	a suitable value. The memory pointed to by C<path> must point to the same
		1319	path for as long as the watcher is active.
		1320
		1321	The callback will be receive C<EV_STAT> when a change was detected,
		1322	relative to the attributes at the time the watcher was started (or the
		1323	last change was detected).
		1324
		1325	=item ev_stat_stat (ev_stat *)
		1326
		1327	Updates the stat buffer immediately with new values. If you change the
		1328	watched path in your callback, you could call this fucntion to avoid
		1329	detecting this change (while introducing a race condition). Can also be
		1330	useful simply to find out the new values.
		1331
		1332	=item ev_statdata attr [read-only]
		1333
		1334	The most-recently detected attributes of the file. Although the type is of
		1335	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1336	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1337	was some error while C<stat>ing the file.
		1338
		1339	=item ev_statdata prev [read-only]
		1340
		1341	The previous attributes of the file. The callback gets invoked whenever
		1342	C<prev> != C<attr>.
		1343
		1344	=item ev_tstamp interval [read-only]
		1345
		1346	The specified interval.
		1347
		1348	=item const char *path [read-only]
		1349
		1350	The filesystem path that is being watched.
		1351
		1352	=back
		1353
		1354	Example: Watch C</etc/passwd> for attribute changes.
		1355
		1356	static void
		1357	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1358	{
		1359	/* /etc/passwd changed in some way */
		1360	if (w->attr.st_nlink)
		1361	{
		1362	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1363	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1364	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1365	}
		1366	else
		1367	/* you shalt not abuse printf for puts */
		1368	puts ("wow, /etc/passwd is not there, expect problems. "
		1369	"if this is windows, they already arrived\n");
		1370	}
		1371
		1372	...
		1373	ev_stat passwd;
		1374
		1375	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1376	ev_stat_start (loop, &passwd);
		1377
		1378
1050	=head2 C<ev_idle> - when you've got nothing better to do	1379	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1380
1052	Idle watchers trigger events when there are no other events are pending	1381	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	1382	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1383	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1384
1056	watchers are being called again and again, once per event loop iteration -	1385	That is, as long as your process is busy handling sockets or timeouts
		1386	(or even signals, imagine) of the same or higher priority it will not be
		1387	triggered. But when your process is idle (or only lower-priority watchers
		1388	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	1389	iteration - until stopped, that is, or your process receives more events
1058	busy.	1390	and becomes busy again with higher priority stuff.
1059		1391
1060	The most noteworthy effect is that as long as any idle watchers are	1392	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.	1393	active, the process will not block when waiting for new events.
1062		1394
1063	Apart from keeping your process non-blocking (which is a useful	1395	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,	1405	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1406	believe me.
1075		1407
1076	=back	1408	=back
1077		1409
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1410	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1411	callback, free it. Also, use no error checking, as usual.
1080		1412
1081	static void	1413	static void
1082	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1414	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1083	{	1415	{
1084	free (w);	1416	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1421	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1422	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1423	ev_idle_start (loop, idle_cb);
1092		1424
1093		1425
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1426	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1427
1096	Prepare and check watchers are usually (but not always) used in tandem:	1428	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1429	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1430	afterwards.
1099		1431
		1432	You I<must not> call C<ev_loop> or similar functions that enter
		1433	the current event loop from either C<ev_prepare> or C<ev_check>
		1434	watchers. Other loops than the current one are fine, however. The
		1435	rationale behind this is that you do not need to check for recursion in
		1436	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1437	C<ev_check> so if you have one watcher of each kind they will always be
		1438	called in pairs bracketing the blocking call.
		1439
1100	Their main purpose is to integrate other event mechanisms into libev and	1440	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	1441	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	1442	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1443	coroutine library and lots more. They are also occasionally useful if
		1444	you cache some data and want to flush it before blocking (for example,
		1445	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1446	watcher).
1104		1447
1105	This is done by examining in each prepare call which file descriptors need	1448	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	1449	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	1450	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	1451	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>	1473	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.	1474	macros, but using them is utterly, utterly and completely pointless.
1132		1475
1133	=back	1476	=back
1134		1477
1135	Example: TODO.	1478	Example: To include a library such as adns, you would add IO watchers
		1479	and a timeout watcher in a prepare handler, as required by libadns, and
		1480	in a check watcher, destroy them and call into libadns. What follows is
		1481	pseudo-code only of course:
1136		1482
		1483	static ev_io iow [nfd];
		1484	static ev_timer tw;
1137		1485
		1486	static void
		1487	io_cb (ev_loop loop, ev_io w, int revents)
		1488	{
		1489	// set the relevant poll flags
		1490	// could also call adns_processreadable etc. here
		1491	struct pollfd fd = (struct pollfd )w->data;
		1492	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1493	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1494	}
		1495
		1496	// create io watchers for each fd and a timer before blocking
		1497	static void
		1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1499	{
		1500	int timeout = 3600000;
		1501	struct pollfd fds [nfd];
		1502	// actual code will need to loop here and realloc etc.
		1503	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1504
		1505	/* the callback is illegal, but won't be called as we stop during check */
		1506	ev_timer_init (&tw, 0, timeout * 1e-3);
		1507	ev_timer_start (loop, &tw);
		1508
		1509	// create on ev_io per pollfd
		1510	for (int i = 0; i < nfd; ++i)
		1511	{
		1512	ev_io_init (iow + i, io_cb, fds [i].fd,
		1513	((fds [i].events & POLLIN ? EV_READ : 0)
		1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1515
		1516	fds [i].revents = 0;
		1517	iow [i].data = fds + i;
		1518	ev_io_start (loop, iow + i);
		1519	}
		1520	}
		1521
		1522	// stop all watchers after blocking
		1523	static void
		1524	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1525	{
		1526	ev_timer_stop (loop, &tw);
		1527
		1528	for (int i = 0; i < nfd; ++i)
		1529	ev_io_stop (loop, iow + i);
		1530
		1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1532	}
		1533
		1534
1138	=head2 C<ev_embed> - when one backend isn't enough	1535	=head2 C<ev_embed> - when one backend isn't enough...
1139		1536
1140	This is a rather advanced watcher type that lets you embed one event loop	1537	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	1538	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	1539	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1540	fashion and must not be used).
…		…
1221		1618
1222	Make a single, non-blocking sweep over the embedded loop. This works	1619	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	1620	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1621	apropriate way for embedded loops.
1225		1622
		1623	=item struct ev_loop *loop [read-only]
		1624
		1625	The embedded event loop.
		1626
		1627	=back
		1628
		1629
		1630	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1631
		1632	Fork watchers are called when a C<fork ()> was detected (usually because
		1633	whoever is a good citizen cared to tell libev about it by calling
		1634	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1635	event loop blocks next and before C<ev_check> watchers are being called,
		1636	and only in the child after the fork. If whoever good citizen calling
		1637	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1638	handlers will be invoked, too, of course.
		1639
		1640	=over 4
		1641
		1642	=item ev_fork_init (ev_signal *, callback)
		1643
		1644	Initialises and configures the fork watcher - it has no parameters of any
		1645	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1646	believe me.
		1647
1226	=back	1648	=back
1227		1649
1228		1650
1229	=head1 OTHER FUNCTIONS	1651	=head1 OTHER FUNCTIONS
1230		1652
…		…
1392		1814
1393	=item w->sweep () C<ev::embed> only	1815	=item w->sweep () C<ev::embed> only
1394		1816
1395	Invokes C<ev_embed_sweep>.	1817	Invokes C<ev_embed_sweep>.
1396		1818
		1819	=item w->update () C<ev::stat> only
		1820
		1821	Invokes C<ev_stat_stat>.
		1822
1397	=back	1823	=back
1398		1824
1399	=back	1825	=back
1400		1826
1401	Example: Define a class with an IO and idle watcher, start one of them in	1827	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1413	: io (this, &myclass::io_cb),	1839	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)	1840	idle (this, &myclass::idle_cb)
1415	{	1841	{
1416	io.start (fd, ev::READ);	1842	io.start (fd, ev::READ);
1417	}	1843	}
		1844
		1845
		1846	=head1 MACRO MAGIC
		1847
		1848	Libev can be compiled with a variety of options, the most fundemantal is
		1849	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1850	callbacks have an initial C<struct ev_loop *> argument.
		1851
		1852	To make it easier to write programs that cope with either variant, the
		1853	following macros are defined:
		1854
		1855	=over 4
		1856
		1857	=item C<EV_A>, C<EV_A_>
		1858
		1859	This provides the loop I<argument> for functions, if one is required ("ev
		1860	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1861	C<EV_A_> is used when other arguments are following. Example:
		1862
		1863	ev_unref (EV_A);
		1864	ev_timer_add (EV_A_ watcher);
		1865	ev_loop (EV_A_ 0);
		1866
		1867	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1868	which is often provided by the following macro.
		1869
		1870	=item C<EV_P>, C<EV_P_>
		1871
		1872	This provides the loop I<parameter> for functions, if one is required ("ev
		1873	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1874	C<EV_P_> is used when other parameters are following. Example:
		1875
		1876	// this is how ev_unref is being declared
		1877	static void ev_unref (EV_P);
		1878
		1879	// this is how you can declare your typical callback
		1880	static void cb (EV_P_ ev_timer *w, int revents)
		1881
		1882	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1883	suitable for use with C<EV_A>.
		1884
		1885	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1886
		1887	Similar to the other two macros, this gives you the value of the default
		1888	loop, if multiple loops are supported ("ev loop default").
		1889
		1890	=back
		1891
		1892	Example: Declare and initialise a check watcher, utilising the above
		1893	macros so it will work regardless of wether multiple loops are supported
		1894	or not.
		1895
		1896	static void
		1897	check_cb (EV_P_ ev_timer *w, int revents)
		1898	{
		1899	ev_check_stop (EV_A_ w);
		1900	}
		1901
		1902	ev_check check;
		1903	ev_check_init (&check, check_cb);
		1904	ev_check_start (EV_DEFAULT_ &check);
		1905	ev_loop (EV_DEFAULT_ 0);
1418		1906
1419	=head1 EMBEDDING	1907	=head1 EMBEDDING
1420		1908
1421	Libev can (and often is) directly embedded into host	1909	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	1910	applications. Examples of applications that embed it include the Deliantra
…		…
1462	ev_vars.h	1950	ev_vars.h
1463	ev_wrap.h	1951	ev_wrap.h
1464		1952
1465	ev_win32.c required on win32 platforms only	1953	ev_win32.c required on win32 platforms only
1466		1954
1467	ev_select.c only when select backend is enabled (which is is by default)	1955	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)	1956	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)	1957	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)	1958	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)	1959	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		1960
1473	F<ev.c> includes the backend files directly when enabled, so you only need	1961	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	1962	to compile this single file.
1475		1963
1476	=head3 LIBEVENT COMPATIBILITY API	1964	=head3 LIBEVENT COMPATIBILITY API
1477		1965
1478	To include the libevent compatibility API, also include:	1966	To include the libevent compatibility API, also include:
1479		1967
…		…
1492		1980
1493	=head3 AUTOCONF SUPPORT	1981	=head3 AUTOCONF SUPPORT
1494		1982
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	1983	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	1984	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	1985	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	1986	include F<config.h> and configure itself accordingly.
1499		1987
1500	For this of course you need the m4 file:	1988	For this of course you need the m4 file:
1501		1989
1502	libev.m4	1990	libev.m4
1503		1991
…		…
1597		2085
1598	=item EV_USE_DEVPOLL	2086	=item EV_USE_DEVPOLL
1599		2087
1600	reserved for future expansion, works like the USE symbols above.	2088	reserved for future expansion, works like the USE symbols above.
1601		2089
		2090	=item EV_USE_INOTIFY
		2091
		2092	If defined to be C<1>, libev will compile in support for the Linux inotify
		2093	interface to speed up C<ev_stat> watchers. Its actual availability will
		2094	be detected at runtime.
		2095
1602	=item EV_H	2096	=item EV_H
1603		2097
1604	The name of the F<ev.h> header file used to include it. The default if	2098	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	2099	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1606	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2100	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2123	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	2124	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2125	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2126	argument. Instead, all functions act on the single default loop.
1633		2127
1634	=item EV_PERIODICS	2128	=item EV_PERIODIC_ENABLE
1635		2129
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2130	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2131	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2132	code.
		2133
		2134	=item EV_IDLE_ENABLE
		2135
		2136	If undefined or defined to be C<1>, then idle watchers are supported. If
		2137	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2138	code.
		2139
		2140	=item EV_EMBED_ENABLE
		2141
		2142	If undefined or defined to be C<1>, then embed watchers are supported. If
		2143	defined to be C<0>, then they are not.
		2144
		2145	=item EV_STAT_ENABLE
		2146
		2147	If undefined or defined to be C<1>, then stat watchers are supported. If
		2148	defined to be C<0>, then they are not.
		2149
		2150	=item EV_FORK_ENABLE
		2151
		2152	If undefined or defined to be C<1>, then fork watchers are supported. If
		2153	defined to be C<0>, then they are not.
		2154
		2155	=item EV_MINIMAL
		2156
		2157	If you need to shave off some kilobytes of code at the expense of some
		2158	speed, define this symbol to C<1>. Currently only used for gcc to override
		2159	some inlining decisions, saves roughly 30% codesize of amd64.
		2160
		2161	=item EV_PID_HASHSIZE
		2162
		2163	C<ev_child> watchers use a small hash table to distribute workload by
		2164	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2165	than enough. If you need to manage thousands of children you might want to
		2166	increase this value (I<must> be a power of two).
		2167
		2168	=item EV_INOTIFY_HASHSIZE
		2169
		2170	C<ev_staz> watchers use a small hash table to distribute workload by
		2171	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2172	usually more than enough. If you need to manage thousands of C<ev_stat>
		2173	watchers you might want to increase this value (I<must> be a power of
		2174	two).
1638		2175
1639	=item EV_COMMON	2176	=item EV_COMMON
1640		2177
1641	By default, all watchers have a C<void *data> member. By redefining	2178	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	2179	this macro to a something else you can include more and other types of
…		…
1647		2184
1648	#define EV_COMMON \	2185	#define EV_COMMON \
1649	SV self; / contains this struct */ \	2186	SV self; / contains this struct */ \
1650	SV cb_sv, fh /* note no trailing ";" */	2187	SV cb_sv, fh /* note no trailing ";" */
1651		2188
1652	=item EV_CB_DECLARE(type)	2189	=item EV_CB_DECLARE (type)
1653		2190
1654	=item EV_CB_INVOKE(watcher,revents)	2191	=item EV_CB_INVOKE (watcher, revents)
1655		2192
1656	=item ev_set_cb(ev,cb)	2193	=item ev_set_cb (ev, cb)
1657		2194
1658	Can be used to change the callback member declaration in each watcher,	2195	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	2196	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	2197	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	2198	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	2199	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2200	method calls instead of plain function calls in C++.
1664		2201
1665	=head2 EXAMPLES	2202	=head2 EXAMPLES
1666		2203
1667	For a real-world example of a program the includes libev	2204	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2205	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	2208	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	2209	will be compiled. It is pretty complex because it provides its own header
1673	file.	2210	file.
1674		2211
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2212	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:	2213	that everybody includes and which overrides some configure choices:
1677		2214
		2215	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	2216	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	2217	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	2218	#define EV_PERIODIC_ENABLE 0
		2219	#define EV_STAT_ENABLE 0
		2220	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	2221	#define EV_CONFIG_H <config.h>
		2222	#define EV_MINPRI 0
		2223	#define EV_MAXPRI 0
1682		2224
1683	#include "ev++.h"	2225	#include "ev++.h"
1684		2226
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2227	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2228
1687	#include "ev_cpp.h"	2229	#include "ev_cpp.h"
1688	#include "ev.c"	2230	#include "ev.c"
1689		2231
		2232
		2233	=head1 COMPLEXITIES
		2234
		2235	In this section the complexities of (many of) the algorithms used inside
		2236	libev will be explained. For complexity discussions about backends see the
		2237	documentation for C<ev_default_init>.
		2238
		2239	=over 4
		2240
		2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2242
		2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2244
		2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2246
		2247	=item Stopping check/prepare/idle watchers: O(1)
		2248
		2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2250
		2251	=item Finding the next timer per loop iteration: O(1)
		2252
		2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2254
		2255	=item Activating one watcher: O(1)
		2256
		2257	=back
		2258
		2259
1690	=head1 AUTHOR	2260	=head1 AUTHOR
1691		2261
1692	Marc Lehmann <libev@schmorp.de>.	2262	Marc Lehmann <libev@schmorp.de>.
1693		2263

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Comparing libev/ev.pod (file contents): Revision 1.41 by root, Sat Nov 24 10:19:14 2007 UTC vs. Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.41 by root, Sat Nov 24 10:19:14 2007 UTC vs.
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC