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

Comparing libev/ev.pod (file contents):
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.57 by root, Wed Nov 28 11:27:29 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>), relative timers (C<ev_timer>),
29	events (related to SIGCHLD), and event watchers dealing with the event	71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	signals (C<ev_signal>), process status change events (C<ev_child>), and
		73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,
		74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		75	file watchers (C<ev_stat>) and even limited support for fork events
		76	(C<ev_fork>).
		77
		78	It also is quite fast (see this
31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	79	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	80	for example).
33		81
34	=head1 CONVENTIONS	82	=head1 CONVENTIONS
35		83
36	Libev is very configurable. In this manual the default configuration	84	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	85	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	86	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	87	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	88	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 *>)	89	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		90
44	=head1 TIME REPRESENTATION	91	=head1 TIME REPRESENTATION
45		92
46	Libev represents time as a single floating point number, representing the	93	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	94	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	95	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	96	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	97	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	98	it, you should treat it as such.
52		99
53
54	=head1 GLOBAL FUNCTIONS	100	=head1 GLOBAL FUNCTIONS
55		101
56	These functions can be called anytime, even before initialising the	102	These functions can be called anytime, even before initialising the
57	library in any way.	103	library in any way.
58		104
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	123	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	124	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	125	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	126	not a problem.
81		127
82	Example: make sure we haven't accidentally been linked against the wrong	128	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	129	version.
84		130
85	assert (("libev version mismatch",	131	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	132	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	133	&& ev_version_minor () >= EV_VERSION_MINOR));
88		134
…		…
116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
117	recommended ones.	163	recommended ones.
118		164
119	See the description of C<ev_embed> watchers for more info.	165	See the description of C<ev_embed> watchers for more info.
120		166
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	167	=item ev_set_allocator (void (cb)(void *ptr, size_t size))
122		168
123	Sets the allocation function to use (the prototype is similar to the	169	Sets the allocation function to use (the prototype and semantics are
124	realloc C function, the semantics are identical). It is used to allocate	170	identical to the realloc C function). It is used to allocate and free
125	and free memory (no surprises here). If it returns zero when memory	171	memory (no surprises here). If it returns zero when memory needs to be
126	needs to be allocated, the library might abort or take some potentially	172	allocated, the library might abort or take some potentially destructive
127	destructive action. The default is your system realloc function.	173	action. The default is your system realloc function.
128		174
129	You could override this function in high-availability programs to, say,	175	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,	176	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.	177	or even to sleep a while and retry until some memory is available.
132		178
133	Example: replace the libev allocator with one that waits a bit and then	179	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	180	retries).
135		181
136	static void *	182	static void *
137	persistent_realloc (void *ptr, long size)	183	persistent_realloc (void *ptr, size_t size)
138	{	184	{
139	for (;;)	185	for (;;)
140	{	186	{
141	void *newptr = realloc (ptr, size);	187	void *newptr = realloc (ptr, size);
142		188
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	204	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	205	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	206	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	207	(such as abort).
162		208
163	Example: do the same thing as libev does internally:	209	Example: This is basically the same thing that libev does internally, too.
164		210
165	static void	211	static void
166	fatal_error (const char *msg)	212	fatal_error (const char *msg)
167	{	213	{
168	perror (msg);	214	perror (msg);
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	360	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	361	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	362	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).	363	undefined behaviour (or a failed assertion if assertions are enabled).
318		364
319	Example: try to create a event loop that uses epoll and nothing else.	365	Example: Try to create a event loop that uses epoll and nothing else.
320		366
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	367	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	368	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	369	fatal ("no epoll found here, maybe it hides under your chair");
324		370
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	469	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	470	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	471	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	472	were used, return, otherwise continue with step *.
427		473
428	Example: queue some jobs and then loop until no events are outsanding	474	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	475	anymore.
430		476
431	... queue jobs here, make sure they register event watchers as long	477	... 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..)	478	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	479	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	499	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	500	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	501	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>.	502	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		503
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	504	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	505	running when nothing else is active.
460		506
461	struct dv_signal exitsig;	507	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	508	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	509	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	510	evf_unref (loop);
465		511
466	Example: for some weird reason, unregister the above signal handler again.	512	Example: For some weird reason, unregister the above signal handler again.
467		513
468	ev_ref (myloop);	514	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	515	ev_signal_stop (loop, &exitsig);
470		516
471	=back	517	=back
		518
472		519
473	=head1 ANATOMY OF A WATCHER	520	=head1 ANATOMY OF A WATCHER
474		521
475	A watcher is a structure that you create and register to record your	522	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	523	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.	590	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		591
545	=item C<EV_CHILD>	592	=item C<EV_CHILD>
546		593
547	The pid specified in the C<ev_child> watcher has received a status change.	594	The pid specified in the C<ev_child> watcher has received a status change.
		595
		596	=item C<EV_STAT>
		597
		598	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		599
549	=item C<EV_IDLE>	600	=item C<EV_IDLE>
550		601
551	The C<ev_idle> watcher has determined that you have nothing better to do.	602	The C<ev_idle> watcher has determined that you have nothing better to do.
552		603
…		…
560	received events. Callbacks of both watcher types can start and stop as	611	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	612	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	613	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	614	C<ev_loop> from blocking).
564		615
		616	=item C<EV_EMBED>
		617
		618	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		619
		620	=item C<EV_FORK>
		621
		622	The event loop has been resumed in the child process after fork (see
		623	C<ev_fork>).
		624
565	=item C<EV_ERROR>	625	=item C<EV_ERROR>
566		626
567	An unspecified error has occured, the watcher has been stopped. This might	627	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	628	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	629	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	636	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	637	programs, though, so beware.
578		638
579	=back	639	=back
580		640
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	641	=head2 GENERIC WATCHER FUNCTIONS
582		642
583	In the following description, C<TYPE> stands for the watcher type,	643	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.	644	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		645
586	=over 4	646	=over 4
…		…
595	which rolls both calls into one.	655	which rolls both calls into one.
596		656
597	You can reinitialise a watcher at any time as long as it has been stopped	657	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.	658	(or never started) and there are no pending events outstanding.
599		659
600	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	660	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
601	int revents)>.	661	int revents)>.
602		662
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	663	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		664
605	This macro initialises the type-specific parts of a watcher. You need to	665	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	703	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	704	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	705	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).	706	libev (e.g. you cnanot C<free ()> it).
647		707
648	=item callback = ev_cb (ev_TYPE *watcher)	708	=item callback ev_cb (ev_TYPE *watcher)
649		709
650	Returns the callback currently set on the watcher.	710	Returns the callback currently set on the watcher.
651		711
652	=item ev_cb_set (ev_TYPE *watcher, callback)	712	=item ev_cb_set (ev_TYPE *watcher, callback)
653		713
…		…
681	{	741	{
682	struct my_io w = (struct my_io )w_;	742	struct my_io w = (struct my_io )w_;
683	...	743	...
684	}	744	}
685		745
686	More interesting and less C-conformant ways of catsing your callback type	746	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	747	instead have been omitted.
		748
		749	Another common scenario is having some data structure with multiple
		750	watchers:
		751
		752	struct my_biggy
		753	{
		754	int some_data;
		755	ev_timer t1;
		756	ev_timer t2;
		757	}
		758
		759	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		760	you need to use C<offsetof>:
		761
		762	#include <stddef.h>
		763
		764	static void
		765	t1_cb (EV_P_ struct ev_timer *w, int revents)
		766	{
		767	struct my_biggy big = (struct my_biggy *
		768	(((char *)w) - offsetof (struct my_biggy, t1));
		769	}
		770
		771	static void
		772	t2_cb (EV_P_ struct ev_timer *w, int revents)
		773	{
		774	struct my_biggy big = (struct my_biggy *
		775	(((char *)w) - offsetof (struct my_biggy, t2));
		776	}
688		777
689		778
690	=head1 WATCHER TYPES	779	=head1 WATCHER TYPES
691		780
692	This section describes each watcher in detail, but will not repeat	781	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	782	information given in the last section. Any initialisation/set macros,
		783	functions and members specific to the watcher type are explained.
694		784
		785	Members are additionally marked with either I<[read-only]>, meaning that,
		786	while the watcher is active, you can look at the member and expect some
		787	sensible content, but you must not modify it (you can modify it while the
		788	watcher is stopped to your hearts content), or I<[read-write]>, which
		789	means you can expect it to have some sensible content while the watcher
		790	is active, but you can also modify it. Modifying it may not do something
		791	sensible or take immediate effect (or do anything at all), but libev will
		792	not crash or malfunction in any way.
695		793
		794
696	=head2 C<ev_io> - is this file descriptor readable or writable	795	=head2 C<ev_io> - is this file descriptor readable or writable?
697		796
698	I/O watchers check whether a file descriptor is readable or writable	797	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	798	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	799	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	800	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	801	receiving events as long as the condition persists. Remember you can stop
		802	the watcher if you don't want to act on the event and neither want to
		803	receive future events.
703		804
704	In general you can register as many read and/or write event watchers per	805	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	806	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	807	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	808	required if you know what you are doing).
708		809
709	You have to be careful with dup'ed file descriptors, though. Some backends	810	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	811	(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	812	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	813	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	814	the same underlying "file open").
714		815
715	If you must do this, then force the use of a known-to-be-good backend	816	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	817	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	818	C<EVBACKEND_POLL>).
718		819
		820	Another thing you have to watch out for is that it is quite easy to
		821	receive "spurious" readyness notifications, that is your callback might
		822	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		823	because there is no data. Not only are some backends known to create a
		824	lot of those (for example solaris ports), it is very easy to get into
		825	this situation even with a relatively standard program structure. Thus
		826	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		827	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		828
		829	If you cannot run the fd in non-blocking mode (for example you should not
		830	play around with an Xlib connection), then you have to seperately re-test
		831	wether a file descriptor is really ready with a known-to-be good interface
		832	such as poll (fortunately in our Xlib example, Xlib already does this on
		833	its own, so its quite safe to use).
		834
719	=over 4	835	=over 4
720		836
721	=item ev_io_init (ev_io *, callback, int fd, int events)	837	=item ev_io_init (ev_io *, callback, int fd, int events)
722		838
723	=item ev_io_set (ev_io *, int fd, int events)	839	=item ev_io_set (ev_io *, int fd, int events)
724		840
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	841	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 \|	842	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	843	C<EV_READ \| EV_WRITE> to receive the given events.
728		844
729	Please note that most of the more scalable backend mechanisms (for example	845	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	846
731	for file descriptors, so you practically need to use non-blocking I/O (and	847	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	848
733	interface before doing I/O (XLib can do this), or force the use of either	849	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	850
735	problem. Also note that it is quite easy to have your callback invoked	851	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		852
740	=back	853	=back
741		854
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	855	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	856	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	857	attempt to read a whole line in the callback.
745		858
746	static void	859	static void
747	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	860	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
748	{	861	{
749	ev_io_stop (loop, w);	862	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	869	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	870	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	871	ev_loop (loop, 0);
759		872
760		873
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	874	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		875
763	Timer watchers are simple relative timers that generate an event after a	876	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	877	given time, and optionally repeating in regular intervals after that.
765		878
766	The timers are based on real time, that is, if you register an event that	879	The timers are based on real time, that is, if you register an event that
…		…
807		920
808	If the timer is repeating, either start it if necessary (with the repeat	921	If the timer is repeating, either start it if necessary (with the repeat
809	value), or reset the running timer to the repeat value.	922	value), or reset the running timer to the repeat value.
810		923
811	This sounds a bit complicated, but here is a useful and typical	924	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	925	example: Imagine you have a tcp connection and you want a so-called
813	timeout, that is, you want to be called when there have been, say, 60	926	idle timeout, that is, you want to be called when there have been,
814	seconds of inactivity on the socket. The easiest way to do this is to	927	say, 60 seconds of inactivity on the socket. The easiest way to do
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	928	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
816	time you successfully read or write some data. If you go into an idle	929	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	930	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.	931	socket, you can stop the timer, and again will automatically restart it if
		932	need be.
		933
		934	You can also ignore the C<after> value and C<ev_timer_start> altogether
		935	and only ever use the C<repeat> value:
		936
		937	ev_timer_init (timer, callback, 0., 5.);
		938	ev_timer_again (loop, timer);
		939	...
		940	timer->again = 17.;
		941	ev_timer_again (loop, timer);
		942	...
		943	timer->again = 10.;
		944	ev_timer_again (loop, timer);
		945
		946	This is more efficient then stopping/starting the timer eahc time you want
		947	to modify its timeout value.
		948
		949	=item ev_tstamp repeat [read-write]
		950
		951	The current C<repeat> value. Will be used each time the watcher times out
		952	or C<ev_timer_again> is called and determines the next timeout (if any),
		953	which is also when any modifications are taken into account.
819		954
820	=back	955	=back
821		956
822	Example: create a timer that fires after 60 seconds.	957	Example: Create a timer that fires after 60 seconds.
823		958
824	static void	959	static void
825	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	960	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
826	{	961	{
827	.. one minute over, w is actually stopped right here	962	.. one minute over, w is actually stopped right here
…		…
829		964
830	struct ev_timer mytimer;	965	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	966	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	967	ev_timer_start (loop, &mytimer);
833		968
834	Example: create a timeout timer that times out after 10 seconds of	969	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	970	inactivity.
836		971
837	static void	972	static void
838	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	973	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
839	{	974	{
…		…
848	// and in some piece of code that gets executed on any "activity":	983	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	984	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	985	ev_timer_again (&mytimer);
851		986
852		987
853	=head2 C<ev_periodic> - to cron or not to cron	988	=head2 C<ev_periodic> - to cron or not to cron?
854		989
855	Periodic watchers are also timers of a kind, but they are very versatile	990	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	991	(and unfortunately a bit complex).
857		992
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	993	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	1085	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1086	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	1087	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1088	program when the crontabs have changed).
954		1089
		1090	=item ev_tstamp interval [read-write]
		1091
		1092	The current interval value. Can be modified any time, but changes only
		1093	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1094	called.
		1095
		1096	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1097
		1098	The current reschedule callback, or C<0>, if this functionality is
		1099	switched off. Can be changed any time, but changes only take effect when
		1100	the periodic timer fires or C<ev_periodic_again> is being called.
		1101
955	=back	1102	=back
956		1103
957	Example: call a callback every hour, or, more precisely, whenever the	1104	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1105	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1106	potentially a lot of jittering, but good long-term stability.
960		1107
961	static void	1108	static void
962	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1109	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
966		1113
967	struct ev_periodic hourly_tick;	1114	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1115	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1116	ev_periodic_start (loop, &hourly_tick);
970		1117
971	Example: the same as above, but use a reschedule callback to do it:	1118	Example: The same as above, but use a reschedule callback to do it:
972		1119
973	#include <math.h>	1120	#include <math.h>
974		1121
975	static ev_tstamp	1122	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1123	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1125	return fmod (now, 3600.) + 3600.;
979	}	1126	}
980		1127
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1128	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1129
983	Example: call a callback every hour, starting now:	1130	Example: Call a callback every hour, starting now:
984		1131
985	struct ev_periodic hourly_tick;	1132	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1133	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1134	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1135	ev_periodic_start (loop, &hourly_tick);
989		1136
990		1137
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1138	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1139
993	Signal watchers will trigger an event when the process receives a specific	1140	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	1141	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	1142	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1143	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1156	=item ev_signal_set (ev_signal *, int signum)
1010		1157
1011	Configures the watcher to trigger on the given signal number (usually one	1158	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1159	of the C<SIGxxx> constants).
1013		1160
		1161	=item int signum [read-only]
		1162
		1163	The signal the watcher watches out for.
		1164
1014	=back	1165	=back
1015		1166
1016		1167
1017	=head2 C<ev_child> - wait for pid status changes	1168	=head2 C<ev_child> - watch out for process status changes
1018		1169
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1170	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).	1171	some child status changes (most typically when a child of yours dies).
1021		1172
1022	=over 4	1173	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1181	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	1182	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	1183	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1184	process causing the status change.
1034		1185
		1186	=item int pid [read-only]
		1187
		1188	The process id this watcher watches out for, or C<0>, meaning any process id.
		1189
		1190	=item int rpid [read-write]
		1191
		1192	The process id that detected a status change.
		1193
		1194	=item int rstatus [read-write]
		1195
		1196	The process exit/trace status caused by C<rpid> (see your systems
		1197	C<waitpid> and C<sys/wait.h> documentation for details).
		1198
1035	=back	1199	=back
1036		1200
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1201	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1202
1039	static void	1203	static void
1040	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1204	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1041	{	1205	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1206	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1209	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1210	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1211	ev_signal_start (loop, &sigint_cb);
1048		1212
1049		1213
		1214	=head2 C<ev_stat> - did the file attributes just change?
		1215
		1216	This watches a filesystem path for attribute changes. That is, it calls
		1217	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1218	compared to the last time, invoking the callback if it did.
		1219
		1220	The path does not need to exist: changing from "path exists" to "path does
		1221	not exist" is a status change like any other. The condition "path does
		1222	not exist" is signified by the C<st_nlink> field being zero (which is
		1223	otherwise always forced to be at least one) and all the other fields of
		1224	the stat buffer having unspecified contents.
		1225
		1226	Since there is no standard to do this, the portable implementation simply
		1227	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1228	can specify a recommended polling interval for this case. If you specify
		1229	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1230	unspecified default> value will be used (which you can expect to be around
		1231	five seconds, although this might change dynamically). Libev will also
		1232	impose a minimum interval which is currently around C<0.1>, but thats
		1233	usually overkill.
		1234
		1235	This watcher type is not meant for massive numbers of stat watchers,
		1236	as even with OS-supported change notifications, this can be
		1237	resource-intensive.
		1238
		1239	At the time of this writing, only the Linux inotify interface is
		1240	implemented (implementing kqueue support is left as an exercise for the
		1241	reader). Inotify will be used to give hints only and should not change the
		1242	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1243	to fall back to regular polling again even with inotify, but changes are
		1244	usually detected immediately, and if the file exists there will be no
		1245	polling.
		1246
		1247	=over 4
		1248
		1249	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1250
		1251	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1252
		1253	Configures the watcher to wait for status changes of the given
		1254	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1255	be detected and should normally be specified as C<0> to let libev choose
		1256	a suitable value. The memory pointed to by C<path> must point to the same
		1257	path for as long as the watcher is active.
		1258
		1259	The callback will be receive C<EV_STAT> when a change was detected,
		1260	relative to the attributes at the time the watcher was started (or the
		1261	last change was detected).
		1262
		1263	=item ev_stat_stat (ev_stat *)
		1264
		1265	Updates the stat buffer immediately with new values. If you change the
		1266	watched path in your callback, you could call this fucntion to avoid
		1267	detecting this change (while introducing a race condition). Can also be
		1268	useful simply to find out the new values.
		1269
		1270	=item ev_statdata attr [read-only]
		1271
		1272	The most-recently detected attributes of the file. Although the type is of
		1273	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1274	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1275	was some error while C<stat>ing the file.
		1276
		1277	=item ev_statdata prev [read-only]
		1278
		1279	The previous attributes of the file. The callback gets invoked whenever
		1280	C<prev> != C<attr>.
		1281
		1282	=item ev_tstamp interval [read-only]
		1283
		1284	The specified interval.
		1285
		1286	=item const char *path [read-only]
		1287
		1288	The filesystem path that is being watched.
		1289
		1290	=back
		1291
		1292	Example: Watch C</etc/passwd> for attribute changes.
		1293
		1294	static void
		1295	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1296	{
		1297	/* /etc/passwd changed in some way */
		1298	if (w->attr.st_nlink)
		1299	{
		1300	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1301	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1302	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1303	}
		1304	else
		1305	/* you shalt not abuse printf for puts */
		1306	puts ("wow, /etc/passwd is not there, expect problems. "
		1307	"if this is windows, they already arrived\n");
		1308	}
		1309
		1310	...
		1311	ev_stat passwd;
		1312
		1313	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1314	ev_stat_start (loop, &passwd);
		1315
		1316
1050	=head2 C<ev_idle> - when you've got nothing better to do	1317	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1318
1052	Idle watchers trigger events when there are no other events are pending	1319	Idle watchers trigger events when there are no other events are pending
1053	(prepare, check and other idle watchers do not count). That is, as long	1320	(prepare, check and other idle watchers do not count). That is, as long
1054	as your process is busy handling sockets or timeouts (or even signals,	1321	as your process is busy handling sockets or timeouts (or even signals,
1055	imagine) it will not be triggered. But when your process is idle all idle	1322	imagine) it will not be triggered. But when your process is idle all idle
…		…
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1340	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1341	believe me.
1075		1342
1076	=back	1343	=back
1077		1344
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1346	callback, free it. Also, use no error checking, as usual.
1080		1347
1081	static void	1348	static void
1082	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1349	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1083	{	1350	{
1084	free (w);	1351	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1356	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1357	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1358	ev_idle_start (loop, idle_cb);
1092		1359
1093		1360
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1362
1096	Prepare and check watchers are usually (but not always) used in tandem:	1363	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1364	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1365	afterwards.
1099		1366
		1367	You I<must not> call C<ev_loop> or similar functions that enter
		1368	the current event loop from either C<ev_prepare> or C<ev_check>
		1369	watchers. Other loops than the current one are fine, however. The
		1370	rationale behind this is that you do not need to check for recursion in
		1371	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1372	C<ev_check> so if you have one watcher of each kind they will always be
		1373	called in pairs bracketing the blocking call.
		1374
1100	Their main purpose is to integrate other event mechanisms into libev and	1375	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	1376	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	1377	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1378	coroutine library and lots more. They are also occasionally useful if
		1379	you cache some data and want to flush it before blocking (for example,
		1380	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1381	watcher).
1104		1382
1105	This is done by examining in each prepare call which file descriptors need	1383	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	1384	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	1385	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	1386	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>	1408	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.	1409	macros, but using them is utterly, utterly and completely pointless.
1132		1410
1133	=back	1411	=back
1134		1412
1135	Example: TODO.	1413	Example: To include a library such as adns, you would add IO watchers
		1414	and a timeout watcher in a prepare handler, as required by libadns, and
		1415	in a check watcher, destroy them and call into libadns. What follows is
		1416	pseudo-code only of course:
1136		1417
		1418	static ev_io iow [nfd];
		1419	static ev_timer tw;
1137		1420
		1421	static void
		1422	io_cb (ev_loop loop, ev_io w, int revents)
		1423	{
		1424	// set the relevant poll flags
		1425	// could also call adns_processreadable etc. here
		1426	struct pollfd fd = (struct pollfd )w->data;
		1427	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1428	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1429	}
		1430
		1431	// create io watchers for each fd and a timer before blocking
		1432	static void
		1433	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1434	{
		1435	int timeout = 3600000;truct pollfd fds [nfd];
		1436	// actual code will need to loop here and realloc etc.
		1437	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1438
		1439	/* the callback is illegal, but won't be called as we stop during check */
		1440	ev_timer_init (&tw, 0, timeout * 1e-3);
		1441	ev_timer_start (loop, &tw);
		1442
		1443	// create on ev_io per pollfd
		1444	for (int i = 0; i < nfd; ++i)
		1445	{
		1446	ev_io_init (iow + i, io_cb, fds [i].fd,
		1447	((fds [i].events & POLLIN ? EV_READ : 0)
		1448	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1449
		1450	fds [i].revents = 0;
		1451	iow [i].data = fds + i;
		1452	ev_io_start (loop, iow + i);
		1453	}
		1454	}
		1455
		1456	// stop all watchers after blocking
		1457	static void
		1458	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1459	{
		1460	ev_timer_stop (loop, &tw);
		1461
		1462	for (int i = 0; i < nfd; ++i)
		1463	ev_io_stop (loop, iow + i);
		1464
		1465	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1466	}
		1467
		1468
1138	=head2 C<ev_embed> - when one backend isn't enough	1469	=head2 C<ev_embed> - when one backend isn't enough...
1139		1470
1140	This is a rather advanced watcher type that lets you embed one event loop	1471	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	1472	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	1473	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1474	fashion and must not be used).
…		…
1221		1552
1222	Make a single, non-blocking sweep over the embedded loop. This works	1553	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	1554	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1555	apropriate way for embedded loops.
1225		1556
		1557	=item struct ev_loop *loop [read-only]
		1558
		1559	The embedded event loop.
		1560
		1561	=back
		1562
		1563
		1564	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1565
		1566	Fork watchers are called when a C<fork ()> was detected (usually because
		1567	whoever is a good citizen cared to tell libev about it by calling
		1568	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1569	event loop blocks next and before C<ev_check> watchers are being called,
		1570	and only in the child after the fork. If whoever good citizen calling
		1571	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1572	handlers will be invoked, too, of course.
		1573
		1574	=over 4
		1575
		1576	=item ev_fork_init (ev_signal *, callback)
		1577
		1578	Initialises and configures the fork watcher - it has no parameters of any
		1579	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1580	believe me.
		1581
1226	=back	1582	=back
1227		1583
1228		1584
1229	=head1 OTHER FUNCTIONS	1585	=head1 OTHER FUNCTIONS
1230		1586
…		…
1392		1748
1393	=item w->sweep () C<ev::embed> only	1749	=item w->sweep () C<ev::embed> only
1394		1750
1395	Invokes C<ev_embed_sweep>.	1751	Invokes C<ev_embed_sweep>.
1396		1752
		1753	=item w->update () C<ev::stat> only
		1754
		1755	Invokes C<ev_stat_stat>.
		1756
1397	=back	1757	=back
1398		1758
1399	=back	1759	=back
1400		1760
1401	Example: Define a class with an IO and idle watcher, start one of them in	1761	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1414	idle (this, &myclass::idle_cb)	1774	idle (this, &myclass::idle_cb)
1415	{	1775	{
1416	io.start (fd, ev::READ);	1776	io.start (fd, ev::READ);
1417	}	1777	}
1418		1778
		1779
		1780	=head1 MACRO MAGIC
		1781
		1782	Libev can be compiled with a variety of options, the most fundemantal is
		1783	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1784	callbacks have an initial C<struct ev_loop *> argument.
		1785
		1786	To make it easier to write programs that cope with either variant, the
		1787	following macros are defined:
		1788
		1789	=over 4
		1790
		1791	=item C<EV_A>, C<EV_A_>
		1792
		1793	This provides the loop I<argument> for functions, if one is required ("ev
		1794	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1795	C<EV_A_> is used when other arguments are following. Example:
		1796
		1797	ev_unref (EV_A);
		1798	ev_timer_add (EV_A_ watcher);
		1799	ev_loop (EV_A_ 0);
		1800
		1801	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1802	which is often provided by the following macro.
		1803
		1804	=item C<EV_P>, C<EV_P_>
		1805
		1806	This provides the loop I<parameter> for functions, if one is required ("ev
		1807	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1808	C<EV_P_> is used when other parameters are following. Example:
		1809
		1810	// this is how ev_unref is being declared
		1811	static void ev_unref (EV_P);
		1812
		1813	// this is how you can declare your typical callback
		1814	static void cb (EV_P_ ev_timer *w, int revents)
		1815
		1816	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1817	suitable for use with C<EV_A>.
		1818
		1819	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1820
		1821	Similar to the other two macros, this gives you the value of the default
		1822	loop, if multiple loops are supported ("ev loop default").
		1823
		1824	=back
		1825
		1826	Example: Declare and initialise a check watcher, working regardless of
		1827	wether multiple loops are supported or not.
		1828
		1829	static void
		1830	check_cb (EV_P_ ev_timer *w, int revents)
		1831	{
		1832	ev_check_stop (EV_A_ w);
		1833	}
		1834
		1835	ev_check check;
		1836	ev_check_init (&check, check_cb);
		1837	ev_check_start (EV_DEFAULT_ &check);
		1838	ev_loop (EV_DEFAULT_ 0);
		1839
		1840
		1841	=head1 EMBEDDING
		1842
		1843	Libev can (and often is) directly embedded into host
		1844	applications. Examples of applications that embed it include the Deliantra
		1845	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1846	and rxvt-unicode.
		1847
		1848	The goal is to enable you to just copy the neecssary files into your
		1849	source directory without having to change even a single line in them, so
		1850	you can easily upgrade by simply copying (or having a checked-out copy of
		1851	libev somewhere in your source tree).
		1852
		1853	=head2 FILESETS
		1854
		1855	Depending on what features you need you need to include one or more sets of files
		1856	in your app.
		1857
		1858	=head3 CORE EVENT LOOP
		1859
		1860	To include only the libev core (all the C<ev_*> functions), with manual
		1861	configuration (no autoconf):
		1862
		1863	#define EV_STANDALONE 1
		1864	#include "ev.c"
		1865
		1866	This will automatically include F<ev.h>, too, and should be done in a
		1867	single C source file only to provide the function implementations. To use
		1868	it, do the same for F<ev.h> in all files wishing to use this API (best
		1869	done by writing a wrapper around F<ev.h> that you can include instead and
		1870	where you can put other configuration options):
		1871
		1872	#define EV_STANDALONE 1
		1873	#include "ev.h"
		1874
		1875	Both header files and implementation files can be compiled with a C++
		1876	compiler (at least, thats a stated goal, and breakage will be treated
		1877	as a bug).
		1878
		1879	You need the following files in your source tree, or in a directory
		1880	in your include path (e.g. in libev/ when using -Ilibev):
		1881
		1882	ev.h
		1883	ev.c
		1884	ev_vars.h
		1885	ev_wrap.h
		1886
		1887	ev_win32.c required on win32 platforms only
		1888
		1889	ev_select.c only when select backend is enabled (which is by default)
		1890	ev_poll.c only when poll backend is enabled (disabled by default)
		1891	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1892	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1893	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1894
		1895	F<ev.c> includes the backend files directly when enabled, so you only need
		1896	to compile this single file.
		1897
		1898	=head3 LIBEVENT COMPATIBILITY API
		1899
		1900	To include the libevent compatibility API, also include:
		1901
		1902	#include "event.c"
		1903
		1904	in the file including F<ev.c>, and:
		1905
		1906	#include "event.h"
		1907
		1908	in the files that want to use the libevent API. This also includes F<ev.h>.
		1909
		1910	You need the following additional files for this:
		1911
		1912	event.h
		1913	event.c
		1914
		1915	=head3 AUTOCONF SUPPORT
		1916
		1917	Instead of using C<EV_STANDALONE=1> and providing your config in
		1918	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1919	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1920	include F<config.h> and configure itself accordingly.
		1921
		1922	For this of course you need the m4 file:
		1923
		1924	libev.m4
		1925
		1926	=head2 PREPROCESSOR SYMBOLS/MACROS
		1927
		1928	Libev can be configured via a variety of preprocessor symbols you have to define
		1929	before including any of its files. The default is not to build for multiplicity
		1930	and only include the select backend.
		1931
		1932	=over 4
		1933
		1934	=item EV_STANDALONE
		1935
		1936	Must always be C<1> if you do not use autoconf configuration, which
		1937	keeps libev from including F<config.h>, and it also defines dummy
		1938	implementations for some libevent functions (such as logging, which is not
		1939	supported). It will also not define any of the structs usually found in
		1940	F<event.h> that are not directly supported by the libev core alone.
		1941
		1942	=item EV_USE_MONOTONIC
		1943
		1944	If defined to be C<1>, libev will try to detect the availability of the
		1945	monotonic clock option at both compiletime and runtime. Otherwise no use
		1946	of the monotonic clock option will be attempted. If you enable this, you
		1947	usually have to link against librt or something similar. Enabling it when
		1948	the functionality isn't available is safe, though, althoguh you have
		1949	to make sure you link against any libraries where the C<clock_gettime>
		1950	function is hiding in (often F<-lrt>).
		1951
		1952	=item EV_USE_REALTIME
		1953
		1954	If defined to be C<1>, libev will try to detect the availability of the
		1955	realtime clock option at compiletime (and assume its availability at
		1956	runtime if successful). Otherwise no use of the realtime clock option will
		1957	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1958	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1959	in the description of C<EV_USE_MONOTONIC>, though.
		1960
		1961	=item EV_USE_SELECT
		1962
		1963	If undefined or defined to be C<1>, libev will compile in support for the
		1964	C<select>(2) backend. No attempt at autodetection will be done: if no
		1965	other method takes over, select will be it. Otherwise the select backend
		1966	will not be compiled in.
		1967
		1968	=item EV_SELECT_USE_FD_SET
		1969
		1970	If defined to C<1>, then the select backend will use the system C<fd_set>
		1971	structure. This is useful if libev doesn't compile due to a missing
		1972	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1973	exotic systems. This usually limits the range of file descriptors to some
		1974	low limit such as 1024 or might have other limitations (winsocket only
		1975	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1976	influence the size of the C<fd_set> used.
		1977
		1978	=item EV_SELECT_IS_WINSOCKET
		1979
		1980	When defined to C<1>, the select backend will assume that
		1981	select/socket/connect etc. don't understand file descriptors but
		1982	wants osf handles on win32 (this is the case when the select to
		1983	be used is the winsock select). This means that it will call
		1984	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1985	it is assumed that all these functions actually work on fds, even
		1986	on win32. Should not be defined on non-win32 platforms.
		1987
		1988	=item EV_USE_POLL
		1989
		1990	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1991	backend. Otherwise it will be enabled on non-win32 platforms. It
		1992	takes precedence over select.
		1993
		1994	=item EV_USE_EPOLL
		1995
		1996	If defined to be C<1>, libev will compile in support for the Linux
		1997	C<epoll>(7) backend. Its availability will be detected at runtime,
		1998	otherwise another method will be used as fallback. This is the
		1999	preferred backend for GNU/Linux systems.
		2000
		2001	=item EV_USE_KQUEUE
		2002
		2003	If defined to be C<1>, libev will compile in support for the BSD style
		2004	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2005	otherwise another method will be used as fallback. This is the preferred
		2006	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2007	supports some types of fds correctly (the only platform we found that
		2008	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2009	not be used unless explicitly requested. The best way to use it is to find
		2010	out whether kqueue supports your type of fd properly and use an embedded
		2011	kqueue loop.
		2012
		2013	=item EV_USE_PORT
		2014
		2015	If defined to be C<1>, libev will compile in support for the Solaris
		2016	10 port style backend. Its availability will be detected at runtime,
		2017	otherwise another method will be used as fallback. This is the preferred
		2018	backend for Solaris 10 systems.
		2019
		2020	=item EV_USE_DEVPOLL
		2021
		2022	reserved for future expansion, works like the USE symbols above.
		2023
		2024	=item EV_USE_INOTIFY
		2025
		2026	If defined to be C<1>, libev will compile in support for the Linux inotify
		2027	interface to speed up C<ev_stat> watchers. Its actual availability will
		2028	be detected at runtime.
		2029
		2030	=item EV_H
		2031
		2032	The name of the F<ev.h> header file used to include it. The default if
		2033	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2034	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2035
		2036	=item EV_CONFIG_H
		2037
		2038	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2039	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2040	C<EV_H>, above.
		2041
		2042	=item EV_EVENT_H
		2043
		2044	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2045	of how the F<event.h> header can be found.
		2046
		2047	=item EV_PROTOTYPES
		2048
		2049	If defined to be C<0>, then F<ev.h> will not define any function
		2050	prototypes, but still define all the structs and other symbols. This is
		2051	occasionally useful if you want to provide your own wrapper functions
		2052	around libev functions.
		2053
		2054	=item EV_MULTIPLICITY
		2055
		2056	If undefined or defined to C<1>, then all event-loop-specific functions
		2057	will have the C<struct ev_loop *> as first argument, and you can create
		2058	additional independent event loops. Otherwise there will be no support
		2059	for multiple event loops and there is no first event loop pointer
		2060	argument. Instead, all functions act on the single default loop.
		2061
		2062	=item EV_PERIODIC_ENABLE
		2063
		2064	If undefined or defined to be C<1>, then periodic timers are supported. If
		2065	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2066	code.
		2067
		2068	=item EV_EMBED_ENABLE
		2069
		2070	If undefined or defined to be C<1>, then embed watchers are supported. If
		2071	defined to be C<0>, then they are not.
		2072
		2073	=item EV_STAT_ENABLE
		2074
		2075	If undefined or defined to be C<1>, then stat watchers are supported. If
		2076	defined to be C<0>, then they are not.
		2077
		2078	=item EV_FORK_ENABLE
		2079
		2080	If undefined or defined to be C<1>, then fork watchers are supported. If
		2081	defined to be C<0>, then they are not.
		2082
		2083	=item EV_MINIMAL
		2084
		2085	If you need to shave off some kilobytes of code at the expense of some
		2086	speed, define this symbol to C<1>. Currently only used for gcc to override
		2087	some inlining decisions, saves roughly 30% codesize of amd64.
		2088
		2089	=item EV_PID_HASHSIZE
		2090
		2091	C<ev_child> watchers use a small hash table to distribute workload by
		2092	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2093	than enough. If you need to manage thousands of children you might want to
		2094	increase this value (I<must> be a power of two).
		2095
		2096	=item EV_INOTIFY_HASHSIZE
		2097
		2098	C<ev_staz> watchers use a small hash table to distribute workload by
		2099	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2100	usually more than enough. If you need to manage thousands of C<ev_stat>
		2101	watchers you might want to increase this value (I<must> be a power of
		2102	two).
		2103
		2104	=item EV_COMMON
		2105
		2106	By default, all watchers have a C<void *data> member. By redefining
		2107	this macro to a something else you can include more and other types of
		2108	members. You have to define it each time you include one of the files,
		2109	though, and it must be identical each time.
		2110
		2111	For example, the perl EV module uses something like this:
		2112
		2113	#define EV_COMMON \
		2114	SV self; / contains this struct */ \
		2115	SV cb_sv, fh /* note no trailing ";" */
		2116
		2117	=item EV_CB_DECLARE (type)
		2118
		2119	=item EV_CB_INVOKE (watcher, revents)
		2120
		2121	=item ev_set_cb (ev, cb)
		2122
		2123	Can be used to change the callback member declaration in each watcher,
		2124	and the way callbacks are invoked and set. Must expand to a struct member
		2125	definition and a statement, respectively. See the F<ev.v> header file for
		2126	their default definitions. One possible use for overriding these is to
		2127	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2128	method calls instead of plain function calls in C++.
		2129
		2130	=head2 EXAMPLES
		2131
		2132	For a real-world example of a program the includes libev
		2133	verbatim, you can have a look at the EV perl module
		2134	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2135	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2136	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2137	will be compiled. It is pretty complex because it provides its own header
		2138	file.
		2139
		2140	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2141	that everybody includes and which overrides some autoconf choices:
		2142
		2143	#define EV_USE_POLL 0
		2144	#define EV_MULTIPLICITY 0
		2145	#define EV_PERIODICS 0
		2146	#define EV_CONFIG_H <config.h>
		2147
		2148	#include "ev++.h"
		2149
		2150	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2151
		2152	#include "ev_cpp.h"
		2153	#include "ev.c"
		2154
		2155
		2156	=head1 COMPLEXITIES
		2157
		2158	In this section the complexities of (many of) the algorithms used inside
		2159	libev will be explained. For complexity discussions about backends see the
		2160	documentation for C<ev_default_init>.
		2161
		2162	=over 4
		2163
		2164	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2165
		2166	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2167
		2168	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2169
		2170	=item Stopping check/prepare/idle watchers: O(1)
		2171
		2172	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2173
		2174	=item Finding the next timer per loop iteration: O(1)
		2175
		2176	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2177
		2178	=item Activating one watcher: O(1)
		2179
		2180	=back
		2181
		2182
1419	=head1 AUTHOR	2183	=head1 AUTHOR
1420		2184
1421	Marc Lehmann <libev@schmorp.de>.	2185	Marc Lehmann <libev@schmorp.de>.
1422		2186

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Comparing libev/ev.pod (file contents):
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC