[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 1.60 by root, Wed Nov 28 18:29:30 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	54	file descriptor being readable or a timeout occuring), and it will manage
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME REPRESENTATION	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	97	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	98	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	99	it, you should treat it as such.
52		100
53
54	=head1 GLOBAL FUNCTIONS	101	=head1 GLOBAL FUNCTIONS
55		102
56	These functions can be called anytime, even before initialising the	103	These functions can be called anytime, even before initialising the
57	library in any way.	104	library in any way.
58		105
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	127	not a problem.
81		128
82	Example: make sure we haven't accidentally been linked against the wrong	129	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	130	version.
84		131
85	assert (("libev version mismatch",	132	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	133	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	134	&& ev_version_minor () >= EV_VERSION_MINOR));
88		135
…		…
118		165
119	See the description of C<ev_embed> watchers for more info.	166	See the description of C<ev_embed> watchers for more info.
120		167
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	168	=item ev_set_allocator (void (cb)(void *ptr, long size))
122		169
123	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	171	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	172	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	173	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	174	potentially destructive action. The default is your system realloc
		175	function.
128		176
129	You could override this function in high-availability programs to, say,	177	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	178	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	179	or even to sleep a while and retry until some memory is available.
132		180
133	Example: replace the libev allocator with one that waits a bit and then	181	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	182	retries).
135		183
136	static void *	184	static void *
137	persistent_realloc (void *ptr, long size)	185	persistent_realloc (void *ptr, size_t size)
138	{	186	{
139	for (;;)	187	for (;;)
140	{	188	{
141	void *newptr = realloc (ptr, size);	189	void *newptr = realloc (ptr, size);
142		190
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	206	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	207	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	208	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	209	(such as abort).
162		210
163	Example: do the same thing as libev does internally:	211	Example: This is basically the same thing that libev does internally, too.
164		212
165	static void	213	static void
166	fatal_error (const char *msg)	214	fatal_error (const char *msg)
167	{	215	{
168	perror (msg);	216	perror (msg);
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	362	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	363	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	364	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).	365	undefined behaviour (or a failed assertion if assertions are enabled).
318		366
319	Example: try to create a event loop that uses epoll and nothing else.	367	Example: Try to create a event loop that uses epoll and nothing else.
320		368
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	369	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	370	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	371	fatal ("no epoll found here, maybe it hides under your chair");
324		372
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	471	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	472	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	473	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	474	were used, return, otherwise continue with step *.
427		475
428	Example: queue some jobs and then loop until no events are outsanding	476	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	477	anymore.
430		478
431	... queue jobs here, make sure they register event watchers as long	479	... 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..)	480	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	481	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	501	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	502	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	503	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>.	504	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		505
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	506	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	507	running when nothing else is active.
460		508
461	struct dv_signal exitsig;	509	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	510	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	511	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	512	evf_unref (loop);
465		513
466	Example: for some weird reason, unregister the above signal handler again.	514	Example: For some weird reason, unregister the above signal handler again.
467		515
468	ev_ref (myloop);	516	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	517	ev_signal_stop (loop, &exitsig);
470		518
471	=back	519	=back
		520
472		521
473	=head1 ANATOMY OF A WATCHER	522	=head1 ANATOMY OF A WATCHER
474		523
475	A watcher is a structure that you create and register to record your	524	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	525	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.	592	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		593
545	=item C<EV_CHILD>	594	=item C<EV_CHILD>
546		595
547	The pid specified in the C<ev_child> watcher has received a status change.	596	The pid specified in the C<ev_child> watcher has received a status change.
		597
		598	=item C<EV_STAT>
		599
		600	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		601
549	=item C<EV_IDLE>	602	=item C<EV_IDLE>
550		603
551	The C<ev_idle> watcher has determined that you have nothing better to do.	604	The C<ev_idle> watcher has determined that you have nothing better to do.
552		605
…		…
560	received events. Callbacks of both watcher types can start and stop as	613	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	614	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	615	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	616	C<ev_loop> from blocking).
564		617
		618	=item C<EV_EMBED>
		619
		620	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		621
		622	=item C<EV_FORK>
		623
		624	The event loop has been resumed in the child process after fork (see
		625	C<ev_fork>).
		626
565	=item C<EV_ERROR>	627	=item C<EV_ERROR>
566		628
567	An unspecified error has occured, the watcher has been stopped. This might	629	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	630	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	631	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	638	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	639	programs, though, so beware.
578		640
579	=back	641	=back
580		642
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	643	=head2 GENERIC WATCHER FUNCTIONS
582		644
583	In the following description, C<TYPE> stands for the watcher type,	645	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.	646	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		647
586	=over 4	648	=over 4
…		…
595	which rolls both calls into one.	657	which rolls both calls into one.
596		658
597	You can reinitialise a watcher at any time as long as it has been stopped	659	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.	660	(or never started) and there are no pending events outstanding.
599		661
600	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	662	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
601	int revents)>.	663	int revents)>.
602		664
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	665	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		666
605	This macro initialises the type-specific parts of a watcher. You need to	667	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	705	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	706	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	707	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).	708	libev (e.g. you cnanot C<free ()> it).
647		709
648	=item callback = ev_cb (ev_TYPE *watcher)	710	=item callback ev_cb (ev_TYPE *watcher)
649		711
650	Returns the callback currently set on the watcher.	712	Returns the callback currently set on the watcher.
651		713
652	=item ev_cb_set (ev_TYPE *watcher, callback)	714	=item ev_cb_set (ev_TYPE *watcher, callback)
653		715
…		…
681	{	743	{
682	struct my_io w = (struct my_io )w_;	744	struct my_io w = (struct my_io )w_;
683	...	745	...
684	}	746	}
685		747
686	More interesting and less C-conformant ways of catsing your callback type	748	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	749	instead have been omitted.
		750
		751	Another common scenario is having some data structure with multiple
		752	watchers:
		753
		754	struct my_biggy
		755	{
		756	int some_data;
		757	ev_timer t1;
		758	ev_timer t2;
		759	}
		760
		761	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		762	you need to use C<offsetof>:
		763
		764	#include <stddef.h>
		765
		766	static void
		767	t1_cb (EV_P_ struct ev_timer *w, int revents)
		768	{
		769	struct my_biggy big = (struct my_biggy *
		770	(((char *)w) - offsetof (struct my_biggy, t1));
		771	}
		772
		773	static void
		774	t2_cb (EV_P_ struct ev_timer *w, int revents)
		775	{
		776	struct my_biggy big = (struct my_biggy *
		777	(((char *)w) - offsetof (struct my_biggy, t2));
		778	}
688		779
689		780
690	=head1 WATCHER TYPES	781	=head1 WATCHER TYPES
691		782
692	This section describes each watcher in detail, but will not repeat	783	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	784	information given in the last section. Any initialisation/set macros,
		785	functions and members specific to the watcher type are explained.
694		786
		787	Members are additionally marked with either I<[read-only]>, meaning that,
		788	while the watcher is active, you can look at the member and expect some
		789	sensible content, but you must not modify it (you can modify it while the
		790	watcher is stopped to your hearts content), or I<[read-write]>, which
		791	means you can expect it to have some sensible content while the watcher
		792	is active, but you can also modify it. Modifying it may not do something
		793	sensible or take immediate effect (or do anything at all), but libev will
		794	not crash or malfunction in any way.
695		795
		796
696	=head2 C<ev_io> - is this file descriptor readable or writable	797	=head2 C<ev_io> - is this file descriptor readable or writable?
697		798
698	I/O watchers check whether a file descriptor is readable or writable	799	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	800	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	801	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	802	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	803	receiving events as long as the condition persists. Remember you can stop
		804	the watcher if you don't want to act on the event and neither want to
		805	receive future events.
703		806
704	In general you can register as many read and/or write event watchers per	807	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	808	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	809	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	810	required if you know what you are doing).
708		811
709	You have to be careful with dup'ed file descriptors, though. Some backends	812	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	813	(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	814	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	815	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	816	the same underlying "file open").
714		817
715	If you must do this, then force the use of a known-to-be-good backend	818	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	819	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	820	C<EVBACKEND_POLL>).
718		821
		822	Another thing you have to watch out for is that it is quite easy to
		823	receive "spurious" readyness notifications, that is your callback might
		824	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		825	because there is no data. Not only are some backends known to create a
		826	lot of those (for example solaris ports), it is very easy to get into
		827	this situation even with a relatively standard program structure. Thus
		828	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		829	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		830
		831	If you cannot run the fd in non-blocking mode (for example you should not
		832	play around with an Xlib connection), then you have to seperately re-test
		833	wether a file descriptor is really ready with a known-to-be good interface
		834	such as poll (fortunately in our Xlib example, Xlib already does this on
		835	its own, so its quite safe to use).
		836
719	=over 4	837	=over 4
720		838
721	=item ev_io_init (ev_io *, callback, int fd, int events)	839	=item ev_io_init (ev_io *, callback, int fd, int events)
722		840
723	=item ev_io_set (ev_io *, int fd, int events)	841	=item ev_io_set (ev_io *, int fd, int events)
724		842
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	843	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 \|	844	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	845	C<EV_READ \| EV_WRITE> to receive the given events.
728		846
729	Please note that most of the more scalable backend mechanisms (for example	847	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	848
731	for file descriptors, so you practically need to use non-blocking I/O (and	849	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	850
733	interface before doing I/O (XLib can do this), or force the use of either	851	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	852
735	problem. Also note that it is quite easy to have your callback invoked	853	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		854
740	=back	855	=back
741		856
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	857	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	858	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	859	attempt to read a whole line in the callback.
745		860
746	static void	861	static void
747	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	862	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
748	{	863	{
749	ev_io_stop (loop, w);	864	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	871	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	872	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	873	ev_loop (loop, 0);
759		874
760		875
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	876	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		877
763	Timer watchers are simple relative timers that generate an event after a	878	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	879	given time, and optionally repeating in regular intervals after that.
765		880
766	The timers are based on real time, that is, if you register an event that	881	The timers are based on real time, that is, if you register an event that
…		…
807		922
808	If the timer is repeating, either start it if necessary (with the repeat	923	If the timer is repeating, either start it if necessary (with the repeat
809	value), or reset the running timer to the repeat value.	924	value), or reset the running timer to the repeat value.
810		925
811	This sounds a bit complicated, but here is a useful and typical	926	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	927	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	928	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	929	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	930	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	931	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	932	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.	933	socket, you can stop the timer, and again will automatically restart it if
		934	need be.
		935
		936	You can also ignore the C<after> value and C<ev_timer_start> altogether
		937	and only ever use the C<repeat> value:
		938
		939	ev_timer_init (timer, callback, 0., 5.);
		940	ev_timer_again (loop, timer);
		941	...
		942	timer->again = 17.;
		943	ev_timer_again (loop, timer);
		944	...
		945	timer->again = 10.;
		946	ev_timer_again (loop, timer);
		947
		948	This is more efficient then stopping/starting the timer eahc time you want
		949	to modify its timeout value.
		950
		951	=item ev_tstamp repeat [read-write]
		952
		953	The current C<repeat> value. Will be used each time the watcher times out
		954	or C<ev_timer_again> is called and determines the next timeout (if any),
		955	which is also when any modifications are taken into account.
819		956
820	=back	957	=back
821		958
822	Example: create a timer that fires after 60 seconds.	959	Example: Create a timer that fires after 60 seconds.
823		960
824	static void	961	static void
825	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	962	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
826	{	963	{
827	.. one minute over, w is actually stopped right here	964	.. one minute over, w is actually stopped right here
…		…
829		966
830	struct ev_timer mytimer;	967	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	968	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	969	ev_timer_start (loop, &mytimer);
833		970
834	Example: create a timeout timer that times out after 10 seconds of	971	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	972	inactivity.
836		973
837	static void	974	static void
838	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	975	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
839	{	976	{
…		…
848	// and in some piece of code that gets executed on any "activity":	985	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	986	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	987	ev_timer_again (&mytimer);
851		988
852		989
853	=head2 C<ev_periodic> - to cron or not to cron	990	=head2 C<ev_periodic> - to cron or not to cron?
854		991
855	Periodic watchers are also timers of a kind, but they are very versatile	992	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	993	(and unfortunately a bit complex).
857		994
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	995	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	1087	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1088	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	1089	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1090	program when the crontabs have changed).
954		1091
		1092	=item ev_tstamp interval [read-write]
		1093
		1094	The current interval value. Can be modified any time, but changes only
		1095	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1096	called.
		1097
		1098	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1099
		1100	The current reschedule callback, or C<0>, if this functionality is
		1101	switched off. Can be changed any time, but changes only take effect when
		1102	the periodic timer fires or C<ev_periodic_again> is being called.
		1103
955	=back	1104	=back
956		1105
957	Example: call a callback every hour, or, more precisely, whenever the	1106	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1107	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1108	potentially a lot of jittering, but good long-term stability.
960		1109
961	static void	1110	static void
962	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1111	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
966		1115
967	struct ev_periodic hourly_tick;	1116	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1117	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1118	ev_periodic_start (loop, &hourly_tick);
970		1119
971	Example: the same as above, but use a reschedule callback to do it:	1120	Example: The same as above, but use a reschedule callback to do it:
972		1121
973	#include <math.h>	1122	#include <math.h>
974		1123
975	static ev_tstamp	1124	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1125	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1127	return fmod (now, 3600.) + 3600.;
979	}	1128	}
980		1129
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1130	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1131
983	Example: call a callback every hour, starting now:	1132	Example: Call a callback every hour, starting now:
984		1133
985	struct ev_periodic hourly_tick;	1134	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1135	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1136	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1137	ev_periodic_start (loop, &hourly_tick);
989		1138
990		1139
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1140	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1141
993	Signal watchers will trigger an event when the process receives a specific	1142	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	1143	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	1144	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1145	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1158	=item ev_signal_set (ev_signal *, int signum)
1010		1159
1011	Configures the watcher to trigger on the given signal number (usually one	1160	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1161	of the C<SIGxxx> constants).
1013		1162
		1163	=item int signum [read-only]
		1164
		1165	The signal the watcher watches out for.
		1166
1014	=back	1167	=back
1015		1168
1016		1169
1017	=head2 C<ev_child> - wait for pid status changes	1170	=head2 C<ev_child> - watch out for process status changes
1018		1171
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1172	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).	1173	some child status changes (most typically when a child of yours dies).
1021		1174
1022	=over 4	1175	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1183	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	1184	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	1185	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1186	process causing the status change.
1034		1187
		1188	=item int pid [read-only]
		1189
		1190	The process id this watcher watches out for, or C<0>, meaning any process id.
		1191
		1192	=item int rpid [read-write]
		1193
		1194	The process id that detected a status change.
		1195
		1196	=item int rstatus [read-write]
		1197
		1198	The process exit/trace status caused by C<rpid> (see your systems
		1199	C<waitpid> and C<sys/wait.h> documentation for details).
		1200
1035	=back	1201	=back
1036		1202
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1203	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1204
1039	static void	1205	static void
1040	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1206	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1041	{	1207	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1208	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1211	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1212	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1213	ev_signal_start (loop, &sigint_cb);
1048		1214
1049		1215
		1216	=head2 C<ev_stat> - did the file attributes just change?
		1217
		1218	This watches a filesystem path for attribute changes. That is, it calls
		1219	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1220	compared to the last time, invoking the callback if it did.
		1221
		1222	The path does not need to exist: changing from "path exists" to "path does
		1223	not exist" is a status change like any other. The condition "path does
		1224	not exist" is signified by the C<st_nlink> field being zero (which is
		1225	otherwise always forced to be at least one) and all the other fields of
		1226	the stat buffer having unspecified contents.
		1227
		1228	The path I<should> be absolute and I<must not> end in a slash. If it is
		1229	relative and your working directory changes, the behaviour is undefined.
		1230
		1231	Since there is no standard to do this, the portable implementation simply
		1232	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1233	can specify a recommended polling interval for this case. If you specify
		1234	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1235	unspecified default> value will be used (which you can expect to be around
		1236	five seconds, although this might change dynamically). Libev will also
		1237	impose a minimum interval which is currently around C<0.1>, but thats
		1238	usually overkill.
		1239
		1240	This watcher type is not meant for massive numbers of stat watchers,
		1241	as even with OS-supported change notifications, this can be
		1242	resource-intensive.
		1243
		1244	At the time of this writing, only the Linux inotify interface is
		1245	implemented (implementing kqueue support is left as an exercise for the
		1246	reader). Inotify will be used to give hints only and should not change the
		1247	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1248	to fall back to regular polling again even with inotify, but changes are
		1249	usually detected immediately, and if the file exists there will be no
		1250	polling.
		1251
		1252	=over 4
		1253
		1254	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1255
		1256	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1257
		1258	Configures the watcher to wait for status changes of the given
		1259	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1260	be detected and should normally be specified as C<0> to let libev choose
		1261	a suitable value. The memory pointed to by C<path> must point to the same
		1262	path for as long as the watcher is active.
		1263
		1264	The callback will be receive C<EV_STAT> when a change was detected,
		1265	relative to the attributes at the time the watcher was started (or the
		1266	last change was detected).
		1267
		1268	=item ev_stat_stat (ev_stat *)
		1269
		1270	Updates the stat buffer immediately with new values. If you change the
		1271	watched path in your callback, you could call this fucntion to avoid
		1272	detecting this change (while introducing a race condition). Can also be
		1273	useful simply to find out the new values.
		1274
		1275	=item ev_statdata attr [read-only]
		1276
		1277	The most-recently detected attributes of the file. Although the type is of
		1278	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1279	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1280	was some error while C<stat>ing the file.
		1281
		1282	=item ev_statdata prev [read-only]
		1283
		1284	The previous attributes of the file. The callback gets invoked whenever
		1285	C<prev> != C<attr>.
		1286
		1287	=item ev_tstamp interval [read-only]
		1288
		1289	The specified interval.
		1290
		1291	=item const char *path [read-only]
		1292
		1293	The filesystem path that is being watched.
		1294
		1295	=back
		1296
		1297	Example: Watch C</etc/passwd> for attribute changes.
		1298
		1299	static void
		1300	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1301	{
		1302	/* /etc/passwd changed in some way */
		1303	if (w->attr.st_nlink)
		1304	{
		1305	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1306	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1307	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1308	}
		1309	else
		1310	/* you shalt not abuse printf for puts */
		1311	puts ("wow, /etc/passwd is not there, expect problems. "
		1312	"if this is windows, they already arrived\n");
		1313	}
		1314
		1315	...
		1316	ev_stat passwd;
		1317
		1318	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1319	ev_stat_start (loop, &passwd);
		1320
		1321
1050	=head2 C<ev_idle> - when you've got nothing better to do	1322	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1323
1052	Idle watchers trigger events when there are no other events are pending	1324	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	1325	(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,	1326	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	1327	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,	1345	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1346	believe me.
1075		1347
1076	=back	1348	=back
1077		1349
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1350	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1351	callback, free it. Also, use no error checking, as usual.
1080		1352
1081	static void	1353	static void
1082	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1354	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1083	{	1355	{
1084	free (w);	1356	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1361	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1362	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1363	ev_idle_start (loop, idle_cb);
1092		1364
1093		1365
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1366	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1367
1096	Prepare and check watchers are usually (but not always) used in tandem:	1368	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1369	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1370	afterwards.
1099		1371
		1372	You I<must not> call C<ev_loop> or similar functions that enter
		1373	the current event loop from either C<ev_prepare> or C<ev_check>
		1374	watchers. Other loops than the current one are fine, however. The
		1375	rationale behind this is that you do not need to check for recursion in
		1376	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1377	C<ev_check> so if you have one watcher of each kind they will always be
		1378	called in pairs bracketing the blocking call.
		1379
1100	Their main purpose is to integrate other event mechanisms into libev and	1380	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	1381	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	1382	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1383	coroutine library and lots more. They are also occasionally useful if
		1384	you cache some data and want to flush it before blocking (for example,
		1385	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1386	watcher).
1104		1387
1105	This is done by examining in each prepare call which file descriptors need	1388	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	1389	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	1390	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	1391	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>	1413	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.	1414	macros, but using them is utterly, utterly and completely pointless.
1132		1415
1133	=back	1416	=back
1134		1417
1135	Example: TODO.	1418	Example: To include a library such as adns, you would add IO watchers
		1419	and a timeout watcher in a prepare handler, as required by libadns, and
		1420	in a check watcher, destroy them and call into libadns. What follows is
		1421	pseudo-code only of course:
1136		1422
		1423	static ev_io iow [nfd];
		1424	static ev_timer tw;
1137		1425
		1426	static void
		1427	io_cb (ev_loop loop, ev_io w, int revents)
		1428	{
		1429	// set the relevant poll flags
		1430	// could also call adns_processreadable etc. here
		1431	struct pollfd fd = (struct pollfd )w->data;
		1432	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1433	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1434	}
		1435
		1436	// create io watchers for each fd and a timer before blocking
		1437	static void
		1438	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1439	{
		1440	int timeout = 3600000;truct pollfd fds [nfd];
		1441	// actual code will need to loop here and realloc etc.
		1442	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1443
		1444	/* the callback is illegal, but won't be called as we stop during check */
		1445	ev_timer_init (&tw, 0, timeout * 1e-3);
		1446	ev_timer_start (loop, &tw);
		1447
		1448	// create on ev_io per pollfd
		1449	for (int i = 0; i < nfd; ++i)
		1450	{
		1451	ev_io_init (iow + i, io_cb, fds [i].fd,
		1452	((fds [i].events & POLLIN ? EV_READ : 0)
		1453	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1454
		1455	fds [i].revents = 0;
		1456	iow [i].data = fds + i;
		1457	ev_io_start (loop, iow + i);
		1458	}
		1459	}
		1460
		1461	// stop all watchers after blocking
		1462	static void
		1463	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1464	{
		1465	ev_timer_stop (loop, &tw);
		1466
		1467	for (int i = 0; i < nfd; ++i)
		1468	ev_io_stop (loop, iow + i);
		1469
		1470	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1471	}
		1472
		1473
1138	=head2 C<ev_embed> - when one backend isn't enough	1474	=head2 C<ev_embed> - when one backend isn't enough...
1139		1475
1140	This is a rather advanced watcher type that lets you embed one event loop	1476	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	1477	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	1478	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1479	fashion and must not be used).
…		…
1221		1557
1222	Make a single, non-blocking sweep over the embedded loop. This works	1558	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	1559	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1560	apropriate way for embedded loops.
1225		1561
		1562	=item struct ev_loop *loop [read-only]
		1563
		1564	The embedded event loop.
		1565
		1566	=back
		1567
		1568
		1569	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1570
		1571	Fork watchers are called when a C<fork ()> was detected (usually because
		1572	whoever is a good citizen cared to tell libev about it by calling
		1573	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1574	event loop blocks next and before C<ev_check> watchers are being called,
		1575	and only in the child after the fork. If whoever good citizen calling
		1576	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1577	handlers will be invoked, too, of course.
		1578
		1579	=over 4
		1580
		1581	=item ev_fork_init (ev_signal *, callback)
		1582
		1583	Initialises and configures the fork watcher - it has no parameters of any
		1584	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1585	believe me.
		1586
1226	=back	1587	=back
1227		1588
1228		1589
1229	=head1 OTHER FUNCTIONS	1590	=head1 OTHER FUNCTIONS
1230		1591
…		…
1392		1753
1393	=item w->sweep () C<ev::embed> only	1754	=item w->sweep () C<ev::embed> only
1394		1755
1395	Invokes C<ev_embed_sweep>.	1756	Invokes C<ev_embed_sweep>.
1396		1757
		1758	=item w->update () C<ev::stat> only
		1759
		1760	Invokes C<ev_stat_stat>.
		1761
1397	=back	1762	=back
1398		1763
1399	=back	1764	=back
1400		1765
1401	Example: Define a class with an IO and idle watcher, start one of them in	1766	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1414	idle (this, &myclass::idle_cb)	1779	idle (this, &myclass::idle_cb)
1415	{	1780	{
1416	io.start (fd, ev::READ);	1781	io.start (fd, ev::READ);
1417	}	1782	}
1418		1783
		1784
		1785	=head1 MACRO MAGIC
		1786
		1787	Libev can be compiled with a variety of options, the most fundemantal is
		1788	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1789	callbacks have an initial C<struct ev_loop *> argument.
		1790
		1791	To make it easier to write programs that cope with either variant, the
		1792	following macros are defined:
		1793
		1794	=over 4
		1795
		1796	=item C<EV_A>, C<EV_A_>
		1797
		1798	This provides the loop I<argument> for functions, if one is required ("ev
		1799	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1800	C<EV_A_> is used when other arguments are following. Example:
		1801
		1802	ev_unref (EV_A);
		1803	ev_timer_add (EV_A_ watcher);
		1804	ev_loop (EV_A_ 0);
		1805
		1806	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1807	which is often provided by the following macro.
		1808
		1809	=item C<EV_P>, C<EV_P_>
		1810
		1811	This provides the loop I<parameter> for functions, if one is required ("ev
		1812	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1813	C<EV_P_> is used when other parameters are following. Example:
		1814
		1815	// this is how ev_unref is being declared
		1816	static void ev_unref (EV_P);
		1817
		1818	// this is how you can declare your typical callback
		1819	static void cb (EV_P_ ev_timer *w, int revents)
		1820
		1821	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1822	suitable for use with C<EV_A>.
		1823
		1824	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1825
		1826	Similar to the other two macros, this gives you the value of the default
		1827	loop, if multiple loops are supported ("ev loop default").
		1828
		1829	=back
		1830
		1831	Example: Declare and initialise a check watcher, working regardless of
		1832	wether multiple loops are supported or not.
		1833
		1834	static void
		1835	check_cb (EV_P_ ev_timer *w, int revents)
		1836	{
		1837	ev_check_stop (EV_A_ w);
		1838	}
		1839
		1840	ev_check check;
		1841	ev_check_init (&check, check_cb);
		1842	ev_check_start (EV_DEFAULT_ &check);
		1843	ev_loop (EV_DEFAULT_ 0);
		1844
		1845
		1846	=head1 EMBEDDING
		1847
		1848	Libev can (and often is) directly embedded into host
		1849	applications. Examples of applications that embed it include the Deliantra
		1850	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1851	and rxvt-unicode.
		1852
		1853	The goal is to enable you to just copy the neecssary files into your
		1854	source directory without having to change even a single line in them, so
		1855	you can easily upgrade by simply copying (or having a checked-out copy of
		1856	libev somewhere in your source tree).
		1857
		1858	=head2 FILESETS
		1859
		1860	Depending on what features you need you need to include one or more sets of files
		1861	in your app.
		1862
		1863	=head3 CORE EVENT LOOP
		1864
		1865	To include only the libev core (all the C<ev_*> functions), with manual
		1866	configuration (no autoconf):
		1867
		1868	#define EV_STANDALONE 1
		1869	#include "ev.c"
		1870
		1871	This will automatically include F<ev.h>, too, and should be done in a
		1872	single C source file only to provide the function implementations. To use
		1873	it, do the same for F<ev.h> in all files wishing to use this API (best
		1874	done by writing a wrapper around F<ev.h> that you can include instead and
		1875	where you can put other configuration options):
		1876
		1877	#define EV_STANDALONE 1
		1878	#include "ev.h"
		1879
		1880	Both header files and implementation files can be compiled with a C++
		1881	compiler (at least, thats a stated goal, and breakage will be treated
		1882	as a bug).
		1883
		1884	You need the following files in your source tree, or in a directory
		1885	in your include path (e.g. in libev/ when using -Ilibev):
		1886
		1887	ev.h
		1888	ev.c
		1889	ev_vars.h
		1890	ev_wrap.h
		1891
		1892	ev_win32.c required on win32 platforms only
		1893
		1894	ev_select.c only when select backend is enabled (which is by default)
		1895	ev_poll.c only when poll backend is enabled (disabled by default)
		1896	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1897	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1898	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1899
		1900	F<ev.c> includes the backend files directly when enabled, so you only need
		1901	to compile this single file.
		1902
		1903	=head3 LIBEVENT COMPATIBILITY API
		1904
		1905	To include the libevent compatibility API, also include:
		1906
		1907	#include "event.c"
		1908
		1909	in the file including F<ev.c>, and:
		1910
		1911	#include "event.h"
		1912
		1913	in the files that want to use the libevent API. This also includes F<ev.h>.
		1914
		1915	You need the following additional files for this:
		1916
		1917	event.h
		1918	event.c
		1919
		1920	=head3 AUTOCONF SUPPORT
		1921
		1922	Instead of using C<EV_STANDALONE=1> and providing your config in
		1923	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1924	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1925	include F<config.h> and configure itself accordingly.
		1926
		1927	For this of course you need the m4 file:
		1928
		1929	libev.m4
		1930
		1931	=head2 PREPROCESSOR SYMBOLS/MACROS
		1932
		1933	Libev can be configured via a variety of preprocessor symbols you have to define
		1934	before including any of its files. The default is not to build for multiplicity
		1935	and only include the select backend.
		1936
		1937	=over 4
		1938
		1939	=item EV_STANDALONE
		1940
		1941	Must always be C<1> if you do not use autoconf configuration, which
		1942	keeps libev from including F<config.h>, and it also defines dummy
		1943	implementations for some libevent functions (such as logging, which is not
		1944	supported). It will also not define any of the structs usually found in
		1945	F<event.h> that are not directly supported by the libev core alone.
		1946
		1947	=item EV_USE_MONOTONIC
		1948
		1949	If defined to be C<1>, libev will try to detect the availability of the
		1950	monotonic clock option at both compiletime and runtime. Otherwise no use
		1951	of the monotonic clock option will be attempted. If you enable this, you
		1952	usually have to link against librt or something similar. Enabling it when
		1953	the functionality isn't available is safe, though, althoguh you have
		1954	to make sure you link against any libraries where the C<clock_gettime>
		1955	function is hiding in (often F<-lrt>).
		1956
		1957	=item EV_USE_REALTIME
		1958
		1959	If defined to be C<1>, libev will try to detect the availability of the
		1960	realtime clock option at compiletime (and assume its availability at
		1961	runtime if successful). Otherwise no use of the realtime clock option will
		1962	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1963	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1964	in the description of C<EV_USE_MONOTONIC>, though.
		1965
		1966	=item EV_USE_SELECT
		1967
		1968	If undefined or defined to be C<1>, libev will compile in support for the
		1969	C<select>(2) backend. No attempt at autodetection will be done: if no
		1970	other method takes over, select will be it. Otherwise the select backend
		1971	will not be compiled in.
		1972
		1973	=item EV_SELECT_USE_FD_SET
		1974
		1975	If defined to C<1>, then the select backend will use the system C<fd_set>
		1976	structure. This is useful if libev doesn't compile due to a missing
		1977	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1978	exotic systems. This usually limits the range of file descriptors to some
		1979	low limit such as 1024 or might have other limitations (winsocket only
		1980	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1981	influence the size of the C<fd_set> used.
		1982
		1983	=item EV_SELECT_IS_WINSOCKET
		1984
		1985	When defined to C<1>, the select backend will assume that
		1986	select/socket/connect etc. don't understand file descriptors but
		1987	wants osf handles on win32 (this is the case when the select to
		1988	be used is the winsock select). This means that it will call
		1989	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1990	it is assumed that all these functions actually work on fds, even
		1991	on win32. Should not be defined on non-win32 platforms.
		1992
		1993	=item EV_USE_POLL
		1994
		1995	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1996	backend. Otherwise it will be enabled on non-win32 platforms. It
		1997	takes precedence over select.
		1998
		1999	=item EV_USE_EPOLL
		2000
		2001	If defined to be C<1>, libev will compile in support for the Linux
		2002	C<epoll>(7) backend. Its availability will be detected at runtime,
		2003	otherwise another method will be used as fallback. This is the
		2004	preferred backend for GNU/Linux systems.
		2005
		2006	=item EV_USE_KQUEUE
		2007
		2008	If defined to be C<1>, libev will compile in support for the BSD style
		2009	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2010	otherwise another method will be used as fallback. This is the preferred
		2011	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2012	supports some types of fds correctly (the only platform we found that
		2013	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2014	not be used unless explicitly requested. The best way to use it is to find
		2015	out whether kqueue supports your type of fd properly and use an embedded
		2016	kqueue loop.
		2017
		2018	=item EV_USE_PORT
		2019
		2020	If defined to be C<1>, libev will compile in support for the Solaris
		2021	10 port style backend. Its availability will be detected at runtime,
		2022	otherwise another method will be used as fallback. This is the preferred
		2023	backend for Solaris 10 systems.
		2024
		2025	=item EV_USE_DEVPOLL
		2026
		2027	reserved for future expansion, works like the USE symbols above.
		2028
		2029	=item EV_USE_INOTIFY
		2030
		2031	If defined to be C<1>, libev will compile in support for the Linux inotify
		2032	interface to speed up C<ev_stat> watchers. Its actual availability will
		2033	be detected at runtime.
		2034
		2035	=item EV_H
		2036
		2037	The name of the F<ev.h> header file used to include it. The default if
		2038	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2039	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2040
		2041	=item EV_CONFIG_H
		2042
		2043	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2044	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2045	C<EV_H>, above.
		2046
		2047	=item EV_EVENT_H
		2048
		2049	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2050	of how the F<event.h> header can be found.
		2051
		2052	=item EV_PROTOTYPES
		2053
		2054	If defined to be C<0>, then F<ev.h> will not define any function
		2055	prototypes, but still define all the structs and other symbols. This is
		2056	occasionally useful if you want to provide your own wrapper functions
		2057	around libev functions.
		2058
		2059	=item EV_MULTIPLICITY
		2060
		2061	If undefined or defined to C<1>, then all event-loop-specific functions
		2062	will have the C<struct ev_loop *> as first argument, and you can create
		2063	additional independent event loops. Otherwise there will be no support
		2064	for multiple event loops and there is no first event loop pointer
		2065	argument. Instead, all functions act on the single default loop.
		2066
		2067	=item EV_PERIODIC_ENABLE
		2068
		2069	If undefined or defined to be C<1>, then periodic timers are supported. If
		2070	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2071	code.
		2072
		2073	=item EV_EMBED_ENABLE
		2074
		2075	If undefined or defined to be C<1>, then embed watchers are supported. If
		2076	defined to be C<0>, then they are not.
		2077
		2078	=item EV_STAT_ENABLE
		2079
		2080	If undefined or defined to be C<1>, then stat watchers are supported. If
		2081	defined to be C<0>, then they are not.
		2082
		2083	=item EV_FORK_ENABLE
		2084
		2085	If undefined or defined to be C<1>, then fork watchers are supported. If
		2086	defined to be C<0>, then they are not.
		2087
		2088	=item EV_MINIMAL
		2089
		2090	If you need to shave off some kilobytes of code at the expense of some
		2091	speed, define this symbol to C<1>. Currently only used for gcc to override
		2092	some inlining decisions, saves roughly 30% codesize of amd64.
		2093
		2094	=item EV_PID_HASHSIZE
		2095
		2096	C<ev_child> watchers use a small hash table to distribute workload by
		2097	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2098	than enough. If you need to manage thousands of children you might want to
		2099	increase this value (I<must> be a power of two).
		2100
		2101	=item EV_INOTIFY_HASHSIZE
		2102
		2103	C<ev_staz> watchers use a small hash table to distribute workload by
		2104	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2105	usually more than enough. If you need to manage thousands of C<ev_stat>
		2106	watchers you might want to increase this value (I<must> be a power of
		2107	two).
		2108
		2109	=item EV_COMMON
		2110
		2111	By default, all watchers have a C<void *data> member. By redefining
		2112	this macro to a something else you can include more and other types of
		2113	members. You have to define it each time you include one of the files,
		2114	though, and it must be identical each time.
		2115
		2116	For example, the perl EV module uses something like this:
		2117
		2118	#define EV_COMMON \
		2119	SV self; / contains this struct */ \
		2120	SV cb_sv, fh /* note no trailing ";" */
		2121
		2122	=item EV_CB_DECLARE (type)
		2123
		2124	=item EV_CB_INVOKE (watcher, revents)
		2125
		2126	=item ev_set_cb (ev, cb)
		2127
		2128	Can be used to change the callback member declaration in each watcher,
		2129	and the way callbacks are invoked and set. Must expand to a struct member
		2130	definition and a statement, respectively. See the F<ev.v> header file for
		2131	their default definitions. One possible use for overriding these is to
		2132	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2133	method calls instead of plain function calls in C++.
		2134
		2135	=head2 EXAMPLES
		2136
		2137	For a real-world example of a program the includes libev
		2138	verbatim, you can have a look at the EV perl module
		2139	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2140	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2141	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2142	will be compiled. It is pretty complex because it provides its own header
		2143	file.
		2144
		2145	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2146	that everybody includes and which overrides some autoconf choices:
		2147
		2148	#define EV_USE_POLL 0
		2149	#define EV_MULTIPLICITY 0
		2150	#define EV_PERIODICS 0
		2151	#define EV_CONFIG_H <config.h>
		2152
		2153	#include "ev++.h"
		2154
		2155	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2156
		2157	#include "ev_cpp.h"
		2158	#include "ev.c"
		2159
		2160
		2161	=head1 COMPLEXITIES
		2162
		2163	In this section the complexities of (many of) the algorithms used inside
		2164	libev will be explained. For complexity discussions about backends see the
		2165	documentation for C<ev_default_init>.
		2166
		2167	=over 4
		2168
		2169	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2170
		2171	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2172
		2173	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2174
		2175	=item Stopping check/prepare/idle watchers: O(1)
		2176
		2177	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2178
		2179	=item Finding the next timer per loop iteration: O(1)
		2180
		2181	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2182
		2183	=item Activating one watcher: O(1)
		2184
		2185	=back
		2186
		2187
1419	=head1 AUTHOR	2188	=head1 AUTHOR
1420		2189
1421	Marc Lehmann <libev@schmorp.de>.	2190	Marc Lehmann <libev@schmorp.de>.
1422		2191

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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 1.60 by root, Wed Nov 28 18:29:30 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.60 by root, Wed Nov 28 18:29:30 2007 UTC