[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 1.55 by root, Tue Nov 27 20:38:07 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)> regulalry 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, no specific OS backends are implemented, but
		1240	if demand increases, at least a kqueue and inotify backend will be added.
		1241
		1242	=over 4
		1243
		1244	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1245
		1246	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1247
		1248	Configures the watcher to wait for status changes of the given
		1249	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1250	be detected and should normally be specified as C<0> to let libev choose
		1251	a suitable value. The memory pointed to by C<path> must point to the same
		1252	path for as long as the watcher is active.
		1253
		1254	The callback will be receive C<EV_STAT> when a change was detected,
		1255	relative to the attributes at the time the watcher was started (or the
		1256	last change was detected).
		1257
		1258	=item ev_stat_stat (ev_stat *)
		1259
		1260	Updates the stat buffer immediately with new values. If you change the
		1261	watched path in your callback, you could call this fucntion to avoid
		1262	detecting this change (while introducing a race condition). Can also be
		1263	useful simply to find out the new values.
		1264
		1265	=item ev_statdata attr [read-only]
		1266
		1267	The most-recently detected attributes of the file. Although the type is of
		1268	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1269	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1270	was some error while C<stat>ing the file.
		1271
		1272	=item ev_statdata prev [read-only]
		1273
		1274	The previous attributes of the file. The callback gets invoked whenever
		1275	C<prev> != C<attr>.
		1276
		1277	=item ev_tstamp interval [read-only]
		1278
		1279	The specified interval.
		1280
		1281	=item const char *path [read-only]
		1282
		1283	The filesystem path that is being watched.
		1284
		1285	=back
		1286
		1287	Example: Watch C</etc/passwd> for attribute changes.
		1288
		1289	static void
		1290	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1291	{
		1292	/* /etc/passwd changed in some way */
		1293	if (w->attr.st_nlink)
		1294	{
		1295	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1296	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1297	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1298	}
		1299	else
		1300	/* you shalt not abuse printf for puts */
		1301	puts ("wow, /etc/passwd is not there, expect problems. "
		1302	"if this is windows, they already arrived\n");
		1303	}
		1304
		1305	...
		1306	ev_stat passwd;
		1307
		1308	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1309	ev_stat_start (loop, &passwd);
		1310
		1311
1050	=head2 C<ev_idle> - when you've got nothing better to do	1312	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1313
1052	Idle watchers trigger events when there are no other events are pending	1314	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	1315	(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,	1316	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	1317	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,	1335	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1336	believe me.
1075		1337
1076	=back	1338	=back
1077		1339
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1340	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1341	callback, free it. Also, use no error checking, as usual.
1080		1342
1081	static void	1343	static void
1082	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1344	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1083	{	1345	{
1084	free (w);	1346	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1351	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1352	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1353	ev_idle_start (loop, idle_cb);
1092		1354
1093		1355
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1356	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1357
1096	Prepare and check watchers are usually (but not always) used in tandem:	1358	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1359	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1360	afterwards.
1099		1361
		1362	You I<must not> call C<ev_loop> or similar functions that enter
		1363	the current event loop from either C<ev_prepare> or C<ev_check>
		1364	watchers. Other loops than the current one are fine, however. The
		1365	rationale behind this is that you do not need to check for recursion in
		1366	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1367	C<ev_check> so if you have one watcher of each kind they will always be
		1368	called in pairs bracketing the blocking call.
		1369
1100	Their main purpose is to integrate other event mechanisms into libev and	1370	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	1371	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	1372	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1373	coroutine library and lots more. They are also occasionally useful if
		1374	you cache some data and want to flush it before blocking (for example,
		1375	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1376	watcher).
1104		1377
1105	This is done by examining in each prepare call which file descriptors need	1378	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	1379	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	1380	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	1381	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>	1403	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.	1404	macros, but using them is utterly, utterly and completely pointless.
1132		1405
1133	=back	1406	=back
1134		1407
1135	Example: TODO.	1408	Example: To include a library such as adns, you would add IO watchers
		1409	and a timeout watcher in a prepare handler, as required by libadns, and
		1410	in a check watcher, destroy them and call into libadns. What follows is
		1411	pseudo-code only of course:
1136		1412
		1413	static ev_io iow [nfd];
		1414	static ev_timer tw;
1137		1415
		1416	static void
		1417	io_cb (ev_loop loop, ev_io w, int revents)
		1418	{
		1419	// set the relevant poll flags
		1420	// could also call adns_processreadable etc. here
		1421	struct pollfd fd = (struct pollfd )w->data;
		1422	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1423	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1424	}
		1425
		1426	// create io watchers for each fd and a timer before blocking
		1427	static void
		1428	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1429	{
		1430	int timeout = 3600000;truct pollfd fds [nfd];
		1431	// actual code will need to loop here and realloc etc.
		1432	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1433
		1434	/* the callback is illegal, but won't be called as we stop during check */
		1435	ev_timer_init (&tw, 0, timeout * 1e-3);
		1436	ev_timer_start (loop, &tw);
		1437
		1438	// create on ev_io per pollfd
		1439	for (int i = 0; i < nfd; ++i)
		1440	{
		1441	ev_io_init (iow + i, io_cb, fds [i].fd,
		1442	((fds [i].events & POLLIN ? EV_READ : 0)
		1443	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1444
		1445	fds [i].revents = 0;
		1446	iow [i].data = fds + i;
		1447	ev_io_start (loop, iow + i);
		1448	}
		1449	}
		1450
		1451	// stop all watchers after blocking
		1452	static void
		1453	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1454	{
		1455	ev_timer_stop (loop, &tw);
		1456
		1457	for (int i = 0; i < nfd; ++i)
		1458	ev_io_stop (loop, iow + i);
		1459
		1460	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1461	}
		1462
		1463
1138	=head2 C<ev_embed> - when one backend isn't enough	1464	=head2 C<ev_embed> - when one backend isn't enough...
1139		1465
1140	This is a rather advanced watcher type that lets you embed one event loop	1466	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	1467	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	1468	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1469	fashion and must not be used).
…		…
1221		1547
1222	Make a single, non-blocking sweep over the embedded loop. This works	1548	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	1549	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1550	apropriate way for embedded loops.
1225		1551
		1552	=item struct ev_loop *loop [read-only]
		1553
		1554	The embedded event loop.
		1555
		1556	=back
		1557
		1558
		1559	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1560
		1561	Fork watchers are called when a C<fork ()> was detected (usually because
		1562	whoever is a good citizen cared to tell libev about it by calling
		1563	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1564	event loop blocks next and before C<ev_check> watchers are being called,
		1565	and only in the child after the fork. If whoever good citizen calling
		1566	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1567	handlers will be invoked, too, of course.
		1568
		1569	=over 4
		1570
		1571	=item ev_fork_init (ev_signal *, callback)
		1572
		1573	Initialises and configures the fork watcher - it has no parameters of any
		1574	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1575	believe me.
		1576
1226	=back	1577	=back
1227		1578
1228		1579
1229	=head1 OTHER FUNCTIONS	1580	=head1 OTHER FUNCTIONS
1230		1581
…		…
1392		1743
1393	=item w->sweep () C<ev::embed> only	1744	=item w->sweep () C<ev::embed> only
1394		1745
1395	Invokes C<ev_embed_sweep>.	1746	Invokes C<ev_embed_sweep>.
1396		1747
		1748	=item w->update () C<ev::stat> only
		1749
		1750	Invokes C<ev_stat_stat>.
		1751
1397	=back	1752	=back
1398		1753
1399	=back	1754	=back
1400		1755
1401	Example: Define a class with an IO and idle watcher, start one of them in	1756	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1414	idle (this, &myclass::idle_cb)	1769	idle (this, &myclass::idle_cb)
1415	{	1770	{
1416	io.start (fd, ev::READ);	1771	io.start (fd, ev::READ);
1417	}	1772	}
1418		1773
		1774
		1775	=head1 MACRO MAGIC
		1776
		1777	Libev can be compiled with a variety of options, the most fundemantal is
		1778	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1779	callbacks have an initial C<struct ev_loop *> argument.
		1780
		1781	To make it easier to write programs that cope with either variant, the
		1782	following macros are defined:
		1783
		1784	=over 4
		1785
		1786	=item C<EV_A>, C<EV_A_>
		1787
		1788	This provides the loop I<argument> for functions, if one is required ("ev
		1789	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1790	C<EV_A_> is used when other arguments are following. Example:
		1791
		1792	ev_unref (EV_A);
		1793	ev_timer_add (EV_A_ watcher);
		1794	ev_loop (EV_A_ 0);
		1795
		1796	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1797	which is often provided by the following macro.
		1798
		1799	=item C<EV_P>, C<EV_P_>
		1800
		1801	This provides the loop I<parameter> for functions, if one is required ("ev
		1802	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1803	C<EV_P_> is used when other parameters are following. Example:
		1804
		1805	// this is how ev_unref is being declared
		1806	static void ev_unref (EV_P);
		1807
		1808	// this is how you can declare your typical callback
		1809	static void cb (EV_P_ ev_timer *w, int revents)
		1810
		1811	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1812	suitable for use with C<EV_A>.
		1813
		1814	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1815
		1816	Similar to the other two macros, this gives you the value of the default
		1817	loop, if multiple loops are supported ("ev loop default").
		1818
		1819	=back
		1820
		1821	Example: Declare and initialise a check watcher, working regardless of
		1822	wether multiple loops are supported or not.
		1823
		1824	static void
		1825	check_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_check_stop (EV_A_ w);
		1828	}
		1829
		1830	ev_check check;
		1831	ev_check_init (&check, check_cb);
		1832	ev_check_start (EV_DEFAULT_ &check);
		1833	ev_loop (EV_DEFAULT_ 0);
		1834
		1835
		1836	=head1 EMBEDDING
		1837
		1838	Libev can (and often is) directly embedded into host
		1839	applications. Examples of applications that embed it include the Deliantra
		1840	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1841	and rxvt-unicode.
		1842
		1843	The goal is to enable you to just copy the neecssary files into your
		1844	source directory without having to change even a single line in them, so
		1845	you can easily upgrade by simply copying (or having a checked-out copy of
		1846	libev somewhere in your source tree).
		1847
		1848	=head2 FILESETS
		1849
		1850	Depending on what features you need you need to include one or more sets of files
		1851	in your app.
		1852
		1853	=head3 CORE EVENT LOOP
		1854
		1855	To include only the libev core (all the C<ev_*> functions), with manual
		1856	configuration (no autoconf):
		1857
		1858	#define EV_STANDALONE 1
		1859	#include "ev.c"
		1860
		1861	This will automatically include F<ev.h>, too, and should be done in a
		1862	single C source file only to provide the function implementations. To use
		1863	it, do the same for F<ev.h> in all files wishing to use this API (best
		1864	done by writing a wrapper around F<ev.h> that you can include instead and
		1865	where you can put other configuration options):
		1866
		1867	#define EV_STANDALONE 1
		1868	#include "ev.h"
		1869
		1870	Both header files and implementation files can be compiled with a C++
		1871	compiler (at least, thats a stated goal, and breakage will be treated
		1872	as a bug).
		1873
		1874	You need the following files in your source tree, or in a directory
		1875	in your include path (e.g. in libev/ when using -Ilibev):
		1876
		1877	ev.h
		1878	ev.c
		1879	ev_vars.h
		1880	ev_wrap.h
		1881
		1882	ev_win32.c required on win32 platforms only
		1883
		1884	ev_select.c only when select backend is enabled (which is by default)
		1885	ev_poll.c only when poll backend is enabled (disabled by default)
		1886	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1887	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1888	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1889
		1890	F<ev.c> includes the backend files directly when enabled, so you only need
		1891	to compile this single file.
		1892
		1893	=head3 LIBEVENT COMPATIBILITY API
		1894
		1895	To include the libevent compatibility API, also include:
		1896
		1897	#include "event.c"
		1898
		1899	in the file including F<ev.c>, and:
		1900
		1901	#include "event.h"
		1902
		1903	in the files that want to use the libevent API. This also includes F<ev.h>.
		1904
		1905	You need the following additional files for this:
		1906
		1907	event.h
		1908	event.c
		1909
		1910	=head3 AUTOCONF SUPPORT
		1911
		1912	Instead of using C<EV_STANDALONE=1> and providing your config in
		1913	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1914	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1915	include F<config.h> and configure itself accordingly.
		1916
		1917	For this of course you need the m4 file:
		1918
		1919	libev.m4
		1920
		1921	=head2 PREPROCESSOR SYMBOLS/MACROS
		1922
		1923	Libev can be configured via a variety of preprocessor symbols you have to define
		1924	before including any of its files. The default is not to build for multiplicity
		1925	and only include the select backend.
		1926
		1927	=over 4
		1928
		1929	=item EV_STANDALONE
		1930
		1931	Must always be C<1> if you do not use autoconf configuration, which
		1932	keeps libev from including F<config.h>, and it also defines dummy
		1933	implementations for some libevent functions (such as logging, which is not
		1934	supported). It will also not define any of the structs usually found in
		1935	F<event.h> that are not directly supported by the libev core alone.
		1936
		1937	=item EV_USE_MONOTONIC
		1938
		1939	If defined to be C<1>, libev will try to detect the availability of the
		1940	monotonic clock option at both compiletime and runtime. Otherwise no use
		1941	of the monotonic clock option will be attempted. If you enable this, you
		1942	usually have to link against librt or something similar. Enabling it when
		1943	the functionality isn't available is safe, though, althoguh you have
		1944	to make sure you link against any libraries where the C<clock_gettime>
		1945	function is hiding in (often F<-lrt>).
		1946
		1947	=item EV_USE_REALTIME
		1948
		1949	If defined to be C<1>, libev will try to detect the availability of the
		1950	realtime clock option at compiletime (and assume its availability at
		1951	runtime if successful). Otherwise no use of the realtime clock option will
		1952	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1953	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1954	in the description of C<EV_USE_MONOTONIC>, though.
		1955
		1956	=item EV_USE_SELECT
		1957
		1958	If undefined or defined to be C<1>, libev will compile in support for the
		1959	C<select>(2) backend. No attempt at autodetection will be done: if no
		1960	other method takes over, select will be it. Otherwise the select backend
		1961	will not be compiled in.
		1962
		1963	=item EV_SELECT_USE_FD_SET
		1964
		1965	If defined to C<1>, then the select backend will use the system C<fd_set>
		1966	structure. This is useful if libev doesn't compile due to a missing
		1967	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1968	exotic systems. This usually limits the range of file descriptors to some
		1969	low limit such as 1024 or might have other limitations (winsocket only
		1970	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1971	influence the size of the C<fd_set> used.
		1972
		1973	=item EV_SELECT_IS_WINSOCKET
		1974
		1975	When defined to C<1>, the select backend will assume that
		1976	select/socket/connect etc. don't understand file descriptors but
		1977	wants osf handles on win32 (this is the case when the select to
		1978	be used is the winsock select). This means that it will call
		1979	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1980	it is assumed that all these functions actually work on fds, even
		1981	on win32. Should not be defined on non-win32 platforms.
		1982
		1983	=item EV_USE_POLL
		1984
		1985	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1986	backend. Otherwise it will be enabled on non-win32 platforms. It
		1987	takes precedence over select.
		1988
		1989	=item EV_USE_EPOLL
		1990
		1991	If defined to be C<1>, libev will compile in support for the Linux
		1992	C<epoll>(7) backend. Its availability will be detected at runtime,
		1993	otherwise another method will be used as fallback. This is the
		1994	preferred backend for GNU/Linux systems.
		1995
		1996	=item EV_USE_KQUEUE
		1997
		1998	If defined to be C<1>, libev will compile in support for the BSD style
		1999	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2000	otherwise another method will be used as fallback. This is the preferred
		2001	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2002	supports some types of fds correctly (the only platform we found that
		2003	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2004	not be used unless explicitly requested. The best way to use it is to find
		2005	out whether kqueue supports your type of fd properly and use an embedded
		2006	kqueue loop.
		2007
		2008	=item EV_USE_PORT
		2009
		2010	If defined to be C<1>, libev will compile in support for the Solaris
		2011	10 port style backend. Its availability will be detected at runtime,
		2012	otherwise another method will be used as fallback. This is the preferred
		2013	backend for Solaris 10 systems.
		2014
		2015	=item EV_USE_DEVPOLL
		2016
		2017	reserved for future expansion, works like the USE symbols above.
		2018
		2019	=item EV_H
		2020
		2021	The name of the F<ev.h> header file used to include it. The default if
		2022	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2023	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2024
		2025	=item EV_CONFIG_H
		2026
		2027	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2028	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2029	C<EV_H>, above.
		2030
		2031	=item EV_EVENT_H
		2032
		2033	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2034	of how the F<event.h> header can be found.
		2035
		2036	=item EV_PROTOTYPES
		2037
		2038	If defined to be C<0>, then F<ev.h> will not define any function
		2039	prototypes, but still define all the structs and other symbols. This is
		2040	occasionally useful if you want to provide your own wrapper functions
		2041	around libev functions.
		2042
		2043	=item EV_MULTIPLICITY
		2044
		2045	If undefined or defined to C<1>, then all event-loop-specific functions
		2046	will have the C<struct ev_loop *> as first argument, and you can create
		2047	additional independent event loops. Otherwise there will be no support
		2048	for multiple event loops and there is no first event loop pointer
		2049	argument. Instead, all functions act on the single default loop.
		2050
		2051	=item EV_PERIODIC_ENABLE
		2052
		2053	If undefined or defined to be C<1>, then periodic timers are supported. If
		2054	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2055	code.
		2056
		2057	=item EV_EMBED_ENABLE
		2058
		2059	If undefined or defined to be C<1>, then embed watchers are supported. If
		2060	defined to be C<0>, then they are not.
		2061
		2062	=item EV_STAT_ENABLE
		2063
		2064	If undefined or defined to be C<1>, then stat watchers are supported. If
		2065	defined to be C<0>, then they are not.
		2066
		2067	=item EV_FORK_ENABLE
		2068
		2069	If undefined or defined to be C<1>, then fork watchers are supported. If
		2070	defined to be C<0>, then they are not.
		2071
		2072	=item EV_MINIMAL
		2073
		2074	If you need to shave off some kilobytes of code at the expense of some
		2075	speed, define this symbol to C<1>. Currently only used for gcc to override
		2076	some inlining decisions, saves roughly 30% codesize of amd64.
		2077
		2078	=item EV_PID_HASHSIZE
		2079
		2080	C<ev_child> watchers use a small hash table to distribute workload by
		2081	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2082	than enough. If you need to manage thousands of children you might want to
		2083	increase this value.
		2084
		2085	=item EV_COMMON
		2086
		2087	By default, all watchers have a C<void *data> member. By redefining
		2088	this macro to a something else you can include more and other types of
		2089	members. You have to define it each time you include one of the files,
		2090	though, and it must be identical each time.
		2091
		2092	For example, the perl EV module uses something like this:
		2093
		2094	#define EV_COMMON \
		2095	SV self; / contains this struct */ \
		2096	SV cb_sv, fh /* note no trailing ";" */
		2097
		2098	=item EV_CB_DECLARE (type)
		2099
		2100	=item EV_CB_INVOKE (watcher, revents)
		2101
		2102	=item ev_set_cb (ev, cb)
		2103
		2104	Can be used to change the callback member declaration in each watcher,
		2105	and the way callbacks are invoked and set. Must expand to a struct member
		2106	definition and a statement, respectively. See the F<ev.v> header file for
		2107	their default definitions. One possible use for overriding these is to
		2108	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2109	method calls instead of plain function calls in C++.
		2110
		2111	=head2 EXAMPLES
		2112
		2113	For a real-world example of a program the includes libev
		2114	verbatim, you can have a look at the EV perl module
		2115	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2116	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2117	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2118	will be compiled. It is pretty complex because it provides its own header
		2119	file.
		2120
		2121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2122	that everybody includes and which overrides some autoconf choices:
		2123
		2124	#define EV_USE_POLL 0
		2125	#define EV_MULTIPLICITY 0
		2126	#define EV_PERIODICS 0
		2127	#define EV_CONFIG_H <config.h>
		2128
		2129	#include "ev++.h"
		2130
		2131	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2132
		2133	#include "ev_cpp.h"
		2134	#include "ev.c"
		2135
		2136
		2137	=head1 COMPLEXITIES
		2138
		2139	In this section the complexities of (many of) the algorithms used inside
		2140	libev will be explained. For complexity discussions about backends see the
		2141	documentation for C<ev_default_init>.
		2142
		2143	=over 4
		2144
		2145	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2146
		2147	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2148
		2149	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2150
		2151	=item Stopping check/prepare/idle watchers: O(1)
		2152
		2153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		2154
		2155	=item Finding the next timer per loop iteration: O(1)
		2156
		2157	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2158
		2159	=item Activating one watcher: O(1)
		2160
		2161	=back
		2162
		2163
1419	=head1 AUTHOR	2164	=head1 AUTHOR
1420		2165
1421	Marc Lehmann <libev@schmorp.de>.	2166	Marc Lehmann <libev@schmorp.de>.
1422		2167

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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 1.55 by root, Tue Nov 27 20:38:07 2007 UTC

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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 1.55 by root, Tue Nov 27 20:38:07 2007 UTC