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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as such.
52		104
53
54	=head1 GLOBAL FUNCTIONS	105	=head1 GLOBAL FUNCTIONS
55		106
56	These functions can be called anytime, even before initialising the	107	These functions can be called anytime, even before initialising the
57	library in any way.	108	library in any way.
58		109
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	131	not a problem.
81		132
82	Example: make sure we haven't accidentally been linked against the wrong	133	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	134	version.
84		135
85	assert (("libev version mismatch",	136	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	137	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	138	&& ev_version_minor () >= EV_VERSION_MINOR));
88		139
…		…
118		169
119	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
120		171
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		173
123	Sets the allocation function to use (the prototype is similar to the	174	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	175	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	176	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	177	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
128		180
129	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
132		184
133	Example: replace the libev allocator with one that waits a bit and then	185	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	186	retries).
135		187
136	static void *	188	static void *
137	persistent_realloc (void *ptr, long size)	189	persistent_realloc (void *ptr, size_t size)
138	{	190	{
139	for (;;)	191	for (;;)
140	{	192	{
141	void *newptr = realloc (ptr, size);	193	void *newptr = realloc (ptr, size);
142		194
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	210	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	211	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	212	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	213	(such as abort).
162		214
163	Example: do the same thing as libev does internally:	215	Example: This is basically the same thing that libev does internally, too.
164		216
165	static void	217	static void
166	fatal_error (const char *msg)	218	fatal_error (const char *msg)
167	{	219	{
168	perror (msg);	220	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
221	around bugs.	273	around bugs.
222		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		296
225	This is your standard select(2) backend. Not I<completely> standard, as	297	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	298	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	299	but if that fails, expect a fairly low limit on the number of fds when
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	387	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	388	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	389	undefined behaviour (or a failed assertion if assertions are enabled).
318		390
319	Example: try to create a event loop that uses epoll and nothing else.	391	Example: Try to create a event loop that uses epoll and nothing else.
320		392
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	394	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	395	fatal ("no epoll found here, maybe it hides under your chair");
324		396
325	=item ev_default_destroy ()	397	=item ev_default_destroy ()
326		398
327	Destroys the default loop again (frees all memory and kernel state	399	Destroys the default loop again (frees all memory and kernel state
328	etc.). This stops all registered event watchers (by not touching them in	400	etc.). None of the active event watchers will be stopped in the normal
329	any way whatsoever, although you cannot rely on this :).	401	sense, so e.g. C<ev_is_active> might still return true. It is your
		402	responsibility to either stop all watchers cleanly yoursef I<before>
		403	calling this function, or cope with the fact afterwards (which is usually
		404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		405	for example).
330		406
331	=item ev_loop_destroy (loop)	407	=item ev_loop_destroy (loop)
332		408
333	Like C<ev_default_destroy>, but destroys an event loop created by an	409	Like C<ev_default_destroy>, but destroys an event loop created by an
334	earlier call to C<ev_loop_new>.	410	earlier call to C<ev_loop_new>.
…		…
357	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
358		434
359	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
360	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
361	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
362		448
363	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
364		450
365	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
366	use.	452	use.
…		…
419	Signals and child watchers are implemented as I/O watchers, and will	505	Signals and child watchers are implemented as I/O watchers, and will
420	be handled here by queueing them when their watcher gets executed.	506	be handled here by queueing them when their watcher gets executed.
421	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
422	were used, return, otherwise continue with step *.	508	were used, return, otherwise continue with step *.
423		509
424	Example: queue some jobs and then loop until no events are outsanding	510	Example: Queue some jobs and then loop until no events are outsanding
425	anymore.	511	anymore.
426		512
427	... queue jobs here, make sure they register event watchers as long	513	... queue jobs here, make sure they register event watchers as long
428	... as they still have work to do (even an idle watcher will do..)	514	... as they still have work to do (even an idle watcher will do..)
429	ev_loop (my_loop, 0);	515	ev_loop (my_loop, 0);
…		…
449	visible to the libev user and should not keep C<ev_loop> from exiting if	535	visible to the libev user and should not keep C<ev_loop> from exiting if
450	no event watchers registered by it are active. It is also an excellent	536	no event watchers registered by it are active. It is also an excellent
451	way to do this for generic recurring timers or from within third-party	537	way to do this for generic recurring timers or from within third-party
452	libraries. Just remember to I<unref after start> and I<ref before stop>.	538	libraries. Just remember to I<unref after start> and I<ref before stop>.
453		539
454	Example: create a signal watcher, but keep it from keeping C<ev_loop>	540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
455	running when nothing else is active.	541	running when nothing else is active.
456		542
457	struct dv_signal exitsig;	543	struct ev_signal exitsig;
458	ev_signal_init (&exitsig, sig_cb, SIGINT);	544	ev_signal_init (&exitsig, sig_cb, SIGINT);
459	ev_signal_start (myloop, &exitsig);	545	ev_signal_start (loop, &exitsig);
460	evf_unref (myloop);	546	evf_unref (loop);
461		547
462	Example: for some weird reason, unregister the above signal handler again.	548	Example: For some weird reason, unregister the above signal handler again.
463		549
464	ev_ref (myloop);	550	ev_ref (loop);
465	ev_signal_stop (myloop, &exitsig);	551	ev_signal_stop (loop, &exitsig);
466		552
467	=back	553	=back
		554
468		555
469	=head1 ANATOMY OF A WATCHER	556	=head1 ANATOMY OF A WATCHER
470		557
471	A watcher is a structure that you create and register to record your	558	A watcher is a structure that you create and register to record your
472	interest in some event. For instance, if you want to wait for STDIN to	559	interest in some event. For instance, if you want to wait for STDIN to
…		…
505	*) >>), and you can stop watching for events at any time by calling the	592	*) >>), and you can stop watching for events at any time by calling the
506	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	593	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
507		594
508	As long as your watcher is active (has been started but not stopped) you	595	As long as your watcher is active (has been started but not stopped) you
509	must not touch the values stored in it. Most specifically you must never	596	must not touch the values stored in it. Most specifically you must never
510	reinitialise it or call its set macro.	597	reinitialise it or call its C<set> macro.
511
512	You can check whether an event is active by calling the C<ev_is_active
513	(watcher *)> macro. To see whether an event is outstanding (but the
514	callback for it has not been called yet) you can use the C<ev_is_pending
515	(watcher *)> macro.
516		598
517	Each and every callback receives the event loop pointer as first, the	599	Each and every callback receives the event loop pointer as first, the
518	registered watcher structure as second, and a bitset of received events as	600	registered watcher structure as second, and a bitset of received events as
519	third argument.	601	third argument.
520		602
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	626	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		627
546	=item C<EV_CHILD>	628	=item C<EV_CHILD>
547		629
548	The pid specified in the C<ev_child> watcher has received a status change.	630	The pid specified in the C<ev_child> watcher has received a status change.
		631
		632	=item C<EV_STAT>
		633
		634	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		635
550	=item C<EV_IDLE>	636	=item C<EV_IDLE>
551		637
552	The C<ev_idle> watcher has determined that you have nothing better to do.	638	The C<ev_idle> watcher has determined that you have nothing better to do.
553		639
…		…
561	received events. Callbacks of both watcher types can start and stop as	647	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	648	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	649	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	650	C<ev_loop> from blocking).
565		651
		652	=item C<EV_EMBED>
		653
		654	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		655
		656	=item C<EV_FORK>
		657
		658	The event loop has been resumed in the child process after fork (see
		659	C<ev_fork>).
		660
566	=item C<EV_ERROR>	661	=item C<EV_ERROR>
567		662
568	An unspecified error has occured, the watcher has been stopped. This might	663	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	664	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	665	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	your callbacks is well-written it can just attempt the operation and cope	671	your callbacks is well-written it can just attempt the operation and cope
577	with the error from read() or write(). This will not work in multithreaded	672	with the error from read() or write(). This will not work in multithreaded
578	programs, though, so beware.	673	programs, though, so beware.
579		674
580	=back	675	=back
		676
		677	=head2 GENERIC WATCHER FUNCTIONS
		678
		679	In the following description, C<TYPE> stands for the watcher type,
		680	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		681
		682	=over 4
		683
		684	=item C<ev_init> (ev_TYPE *watcher, callback)
		685
		686	This macro initialises the generic portion of a watcher. The contents
		687	of the watcher object can be arbitrary (so C<malloc> will do). Only
		688	the generic parts of the watcher are initialised, you I<need> to call
		689	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		690	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		691	which rolls both calls into one.
		692
		693	You can reinitialise a watcher at any time as long as it has been stopped
		694	(or never started) and there are no pending events outstanding.
		695
		696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		697	int revents)>.
		698
		699	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		700
		701	This macro initialises the type-specific parts of a watcher. You need to
		702	call C<ev_init> at least once before you call this macro, but you can
		703	call C<ev_TYPE_set> any number of times. You must not, however, call this
		704	macro on a watcher that is active (it can be pending, however, which is a
		705	difference to the C<ev_init> macro).
		706
		707	Although some watcher types do not have type-specific arguments
		708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		709
		710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		711
		712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		713	calls into a single call. This is the most convinient method to initialise
		714	a watcher. The same limitations apply, of course.
		715
		716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		717
		718	Starts (activates) the given watcher. Only active watchers will receive
		719	events. If the watcher is already active nothing will happen.
		720
		721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		722
		723	Stops the given watcher again (if active) and clears the pending
		724	status. It is possible that stopped watchers are pending (for example,
		725	non-repeating timers are being stopped when they become pending), but
		726	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		727	you want to free or reuse the memory used by the watcher it is therefore a
		728	good idea to always call its C<ev_TYPE_stop> function.
		729
		730	=item bool ev_is_active (ev_TYPE *watcher)
		731
		732	Returns a true value iff the watcher is active (i.e. it has been started
		733	and not yet been stopped). As long as a watcher is active you must not modify
		734	it.
		735
		736	=item bool ev_is_pending (ev_TYPE *watcher)
		737
		738	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		739	events but its callback has not yet been invoked). As long as a watcher
		740	is pending (but not active) you must not call an init function on it (but
		741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		742	libev (e.g. you cnanot C<free ()> it).
		743
		744	=item callback ev_cb (ev_TYPE *watcher)
		745
		746	Returns the callback currently set on the watcher.
		747
		748	=item ev_cb_set (ev_TYPE *watcher, callback)
		749
		750	Change the callback. You can change the callback at virtually any time
		751	(modulo threads).
		752
		753	=item ev_set_priority (ev_TYPE *watcher, priority)
		754
		755	=item int ev_priority (ev_TYPE *watcher)
		756
		757	Set and query the priority of the watcher. The priority is a small
		758	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		759	(default: C<-2>). Pending watchers with higher priority will be invoked
		760	before watchers with lower priority, but priority will not keep watchers
		761	from being executed (except for C<ev_idle> watchers).
		762
		763	This means that priorities are I<only> used for ordering callback
		764	invocation after new events have been received. This is useful, for
		765	example, to reduce latency after idling, or more often, to bind two
		766	watchers on the same event and make sure one is called first.
		767
		768	If you need to suppress invocation when higher priority events are pending
		769	you need to look at C<ev_idle> watchers, which provide this functionality.
		770
		771	The default priority used by watchers when no priority has been set is
		772	always C<0>, which is supposed to not be too high and not be too low :).
		773
		774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		775	fine, as long as you do not mind that the priority value you query might
		776	or might not have been adjusted to be within valid range.
		777
		778	=back
		779
581		780
582	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
583		782
584	Each watcher has, by default, a member C<void *data> that you can change	783	Each watcher has, by default, a member C<void *data> that you can change
585	and read at any time, libev will completely ignore it. This can be used	784	and read at any time, libev will completely ignore it. This can be used
…		…
603	{	802	{
604	struct my_io *w = (struct my_io *)w_;	803	struct my_io *w = (struct my_io *)w_;
605	...	804	...
606	}	805	}
607		806
608	More interesting and less C-conformant ways of catsing your callback type	807	More interesting and less C-conformant ways of casting your callback type
609	have been omitted....	808	instead have been omitted.
		809
		810	Another common scenario is having some data structure with multiple
		811	watchers:
		812
		813	struct my_biggy
		814	{
		815	int some_data;
		816	ev_timer t1;
		817	ev_timer t2;
		818	}
		819
		820	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		821	you need to use C<offsetof>:
		822
		823	#include <stddef.h>
		824
		825	static void
		826	t1_cb (EV_P_ struct ev_timer *w, int revents)
		827	{
		828	struct my_biggy big = (struct my_biggy *
		829	(((char *)w) - offsetof (struct my_biggy, t1));
		830	}
		831
		832	static void
		833	t2_cb (EV_P_ struct ev_timer *w, int revents)
		834	{
		835	struct my_biggy big = (struct my_biggy *
		836	(((char *)w) - offsetof (struct my_biggy, t2));
		837	}
610		838
611		839
612	=head1 WATCHER TYPES	840	=head1 WATCHER TYPES
613		841
614	This section describes each watcher in detail, but will not repeat	842	This section describes each watcher in detail, but will not repeat
615	information given in the last section.	843	information given in the last section. Any initialisation/set macros,
		844	functions and members specific to the watcher type are explained.
616		845
		846	Members are additionally marked with either I<[read-only]>, meaning that,
		847	while the watcher is active, you can look at the member and expect some
		848	sensible content, but you must not modify it (you can modify it while the
		849	watcher is stopped to your hearts content), or I<[read-write]>, which
		850	means you can expect it to have some sensible content while the watcher
		851	is active, but you can also modify it. Modifying it may not do something
		852	sensible or take immediate effect (or do anything at all), but libev will
		853	not crash or malfunction in any way.
617		854
		855
618	=head2 C<ev_io> - is this file descriptor readable or writable	856	=head2 C<ev_io> - is this file descriptor readable or writable?
619		857
620	I/O watchers check whether a file descriptor is readable or writable	858	I/O watchers check whether a file descriptor is readable or writable
621	in each iteration of the event loop (This behaviour is called	859	in each iteration of the event loop, or, more precisely, when reading
622	level-triggering because you keep receiving events as long as the	860	would not block the process and writing would at least be able to write
623	condition persists. Remember you can stop the watcher if you don't want to	861	some data. This behaviour is called level-triggering because you keep
624	act on the event and neither want to receive future events).	862	receiving events as long as the condition persists. Remember you can stop
		863	the watcher if you don't want to act on the event and neither want to
		864	receive future events.
625		865
626	In general you can register as many read and/or write event watchers per	866	In general you can register as many read and/or write event watchers per
627	fd as you want (as long as you don't confuse yourself). Setting all file	867	fd as you want (as long as you don't confuse yourself). Setting all file
628	descriptors to non-blocking mode is also usually a good idea (but not	868	descriptors to non-blocking mode is also usually a good idea (but not
629	required if you know what you are doing).	869	required if you know what you are doing).
630		870
631	You have to be careful with dup'ed file descriptors, though. Some backends	871	You have to be careful with dup'ed file descriptors, though. Some backends
632	(the linux epoll backend is a notable example) cannot handle dup'ed file	872	(the linux epoll backend is a notable example) cannot handle dup'ed file
633	descriptors correctly if you register interest in two or more fds pointing	873	descriptors correctly if you register interest in two or more fds pointing
634	to the same underlying file/socket etc. description (that is, they share	874	to the same underlying file/socket/etc. description (that is, they share
635	the same underlying "file open").	875	the same underlying "file open").
636		876
637	If you must do this, then force the use of a known-to-be-good backend	877	If you must do this, then force the use of a known-to-be-good backend
638	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
639	C<EVBACKEND_POLL>).	879	C<EVBACKEND_POLL>).
640		880
		881	Another thing you have to watch out for is that it is quite easy to
		882	receive "spurious" readyness notifications, that is your callback might
		883	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		884	because there is no data. Not only are some backends known to create a
		885	lot of those (for example solaris ports), it is very easy to get into
		886	this situation even with a relatively standard program structure. Thus
		887	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		888	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		889
		890	If you cannot run the fd in non-blocking mode (for example you should not
		891	play around with an Xlib connection), then you have to seperately re-test
		892	whether a file descriptor is really ready with a known-to-be good interface
		893	such as poll (fortunately in our Xlib example, Xlib already does this on
		894	its own, so its quite safe to use).
		895
641	=over 4	896	=over 4
642		897
643	=item ev_io_init (ev_io *, callback, int fd, int events)	898	=item ev_io_init (ev_io *, callback, int fd, int events)
644		899
645	=item ev_io_set (ev_io *, int fd, int events)	900	=item ev_io_set (ev_io *, int fd, int events)
646		901
647	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	902	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
648	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	903	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
649	EV_WRITE> to receive the given events.	904	C<EV_READ | EV_WRITE> to receive the given events.
650		905
651	Please note that most of the more scalable backend mechanisms (for example	906	=item int fd [read-only]
652	epoll and solaris ports) can result in spurious readyness notifications	907
653	for file descriptors, so you practically need to use non-blocking I/O (and	908	The file descriptor being watched.
654	treat callback invocation as hint only), or retest separately with a safe	909
655	interface before doing I/O (XLib can do this), or force the use of either	910	=item int events [read-only]
656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	911
657	problem. Also note that it is quite easy to have your callback invoked	912	The events being watched.
658	when the readyness condition is no longer valid even when employing
659	typical ways of handling events, so its a good idea to use non-blocking
660	I/O unconditionally.
661		913
662	=back	914	=back
663		915
664	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
665	readable, but only once. Since it is likely line-buffered, you could	917	readable, but only once. Since it is likely line-buffered, you could
666	attempt to read a whole line in the callback:	918	attempt to read a whole line in the callback.
667		919
668	static void	920	static void
669	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	921	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
670	{	922	{
671	ev_io_stop (loop, w);	923	ev_io_stop (loop, w);
…		…
678	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	930	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
679	ev_io_start (loop, &stdin_readable);	931	ev_io_start (loop, &stdin_readable);
680	ev_loop (loop, 0);	932	ev_loop (loop, 0);
681		933
682		934
683	=head2 C<ev_timer> - relative and optionally recurring timeouts	935	=head2 C<ev_timer> - relative and optionally repeating timeouts
684		936
685	Timer watchers are simple relative timers that generate an event after a	937	Timer watchers are simple relative timers that generate an event after a
686	given time, and optionally repeating in regular intervals after that.	938	given time, and optionally repeating in regular intervals after that.
687		939
688	The timers are based on real time, that is, if you register an event that	940	The timers are based on real time, that is, if you register an event that
…		…
723	=item ev_timer_again (loop)	975	=item ev_timer_again (loop)
724		976
725	This will act as if the timer timed out and restart it again if it is	977	This will act as if the timer timed out and restart it again if it is
726	repeating. The exact semantics are:	978	repeating. The exact semantics are:
727		979
		980	If the timer is pending, its pending status is cleared.
		981
728	If the timer is started but nonrepeating, stop it.	982	If the timer is started but nonrepeating, stop it (as if it timed out).
729		983
730	If the timer is repeating, either start it if necessary (with the repeat	984	If the timer is repeating, either start it if necessary (with the
731	value), or reset the running timer to the repeat value.	985	C<repeat> value), or reset the running timer to the C<repeat> value.
732		986
733	This sounds a bit complicated, but here is a useful and typical	987	This sounds a bit complicated, but here is a useful and typical
734	example: Imagine you have a tcp connection and you want a so-called idle	988	example: Imagine you have a tcp connection and you want a so-called idle
735	timeout, that is, you want to be called when there have been, say, 60	989	timeout, that is, you want to be called when there have been, say, 60
736	seconds of inactivity on the socket. The easiest way to do this is to	990	seconds of inactivity on the socket. The easiest way to do this is to
737	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	991	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
738	time you successfully read or write some data. If you go into an idle	992	C<ev_timer_again> each time you successfully read or write some data. If
739	state where you do not expect data to travel on the socket, you can stop	993	you go into an idle state where you do not expect data to travel on the
740	the timer, and again will automatically restart it if need be.	994	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		995	automatically restart it if need be.
		996
		997	That means you can ignore the C<after> value and C<ev_timer_start>
		998	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		999
		1000	ev_timer_init (timer, callback, 0., 5.);
		1001	ev_timer_again (loop, timer);
		1002	...
		1003	timer->again = 17.;
		1004	ev_timer_again (loop, timer);
		1005	...
		1006	timer->again = 10.;
		1007	ev_timer_again (loop, timer);
		1008
		1009	This is more slightly efficient then stopping/starting the timer each time
		1010	you want to modify its timeout value.
		1011
		1012	=item ev_tstamp repeat [read-write]
		1013
		1014	The current C<repeat> value. Will be used each time the watcher times out
		1015	or C<ev_timer_again> is called and determines the next timeout (if any),
		1016	which is also when any modifications are taken into account.
741		1017
742	=back	1018	=back
743		1019
744	Example: create a timer that fires after 60 seconds.	1020	Example: Create a timer that fires after 60 seconds.
745		1021
746	static void	1022	static void
747	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
748	{	1024	{
749	.. one minute over, w is actually stopped right here	1025	.. one minute over, w is actually stopped right here
…		…
751		1027
752	struct ev_timer mytimer;	1028	struct ev_timer mytimer;
753	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
754	ev_timer_start (loop, &mytimer);	1030	ev_timer_start (loop, &mytimer);
755		1031
756	Example: create a timeout timer that times out after 10 seconds of	1032	Example: Create a timeout timer that times out after 10 seconds of
757	inactivity.	1033	inactivity.
758		1034
759	static void	1035	static void
760	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1036	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
761	{	1037	{
…		…
770	// and in some piece of code that gets executed on any "activity":	1046	// and in some piece of code that gets executed on any "activity":
771	// reset the timeout to start ticking again at 10 seconds	1047	// reset the timeout to start ticking again at 10 seconds
772	ev_timer_again (&mytimer);	1048	ev_timer_again (&mytimer);
773		1049
774		1050
775	=head2 C<ev_periodic> - to cron or not to cron	1051	=head2 C<ev_periodic> - to cron or not to cron?
776		1052
777	Periodic watchers are also timers of a kind, but they are very versatile	1053	Periodic watchers are also timers of a kind, but they are very versatile
778	(and unfortunately a bit complex).	1054	(and unfortunately a bit complex).
779		1055
780	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1056	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
781	but on wallclock time (absolute time). You can tell a periodic watcher	1057	but on wallclock time (absolute time). You can tell a periodic watcher
782	to trigger "at" some specific point in time. For example, if you tell a	1058	to trigger "at" some specific point in time. For example, if you tell a
783	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
784	+ 10.>) and then reset your system clock to the last year, then it will	1060	+ 10.>) and then reset your system clock to the last year, then it will
785	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
786	roughly 10 seconds later and of course not if you reset your system time	1062	roughly 10 seconds later and of course not if you reset your system time
787	again).	1063	again).
788		1064
…		…
872	Simply stops and restarts the periodic watcher again. This is only useful	1148	Simply stops and restarts the periodic watcher again. This is only useful
873	when you changed some parameters or the reschedule callback would return	1149	when you changed some parameters or the reschedule callback would return
874	a different time than the last time it was called (e.g. in a crond like	1150	a different time than the last time it was called (e.g. in a crond like
875	program when the crontabs have changed).	1151	program when the crontabs have changed).
876		1152
		1153	=item ev_tstamp interval [read-write]
		1154
		1155	The current interval value. Can be modified any time, but changes only
		1156	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1157	called.
		1158
		1159	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1160
		1161	The current reschedule callback, or C<0>, if this functionality is
		1162	switched off. Can be changed any time, but changes only take effect when
		1163	the periodic timer fires or C<ev_periodic_again> is being called.
		1164
877	=back	1165	=back
878		1166
879	Example: call a callback every hour, or, more precisely, whenever the	1167	Example: Call a callback every hour, or, more precisely, whenever the
880	system clock is divisible by 3600. The callback invocation times have	1168	system clock is divisible by 3600. The callback invocation times have
881	potentially a lot of jittering, but good long-term stability.	1169	potentially a lot of jittering, but good long-term stability.
882		1170
883	static void	1171	static void
884	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1172	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
888		1176
889	struct ev_periodic hourly_tick;	1177	struct ev_periodic hourly_tick;
890	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
891	ev_periodic_start (loop, &hourly_tick);	1179	ev_periodic_start (loop, &hourly_tick);
892		1180
893	Example: the same as above, but use a reschedule callback to do it:	1181	Example: The same as above, but use a reschedule callback to do it:
894		1182
895	#include <math.h>	1183	#include <math.h>
896		1184
897	static ev_tstamp	1185	static ev_tstamp
898	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
900	return fmod (now, 3600.) + 3600.;	1188	return fmod (now, 3600.) + 3600.;
901	}	1189	}
902		1190
903	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1191	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
904		1192
905	Example: call a callback every hour, starting now:	1193	Example: Call a callback every hour, starting now:
906		1194
907	struct ev_periodic hourly_tick;	1195	struct ev_periodic hourly_tick;
908	ev_periodic_init (&hourly_tick, clock_cb,	1196	ev_periodic_init (&hourly_tick, clock_cb,
909	fmod (ev_now (loop), 3600.), 3600., 0);	1197	fmod (ev_now (loop), 3600.), 3600., 0);
910	ev_periodic_start (loop, &hourly_tick);	1198	ev_periodic_start (loop, &hourly_tick);
911		1199
912		1200
913	=head2 C<ev_signal> - signal me when a signal gets signalled	1201	=head2 C<ev_signal> - signal me when a signal gets signalled!
914		1202
915	Signal watchers will trigger an event when the process receives a specific	1203	Signal watchers will trigger an event when the process receives a specific
916	signal one or more times. Even though signals are very asynchronous, libev	1204	signal one or more times. Even though signals are very asynchronous, libev
917	will try it's best to deliver signals synchronously, i.e. as part of the	1205	will try it's best to deliver signals synchronously, i.e. as part of the
918	normal event processing, like any other event.	1206	normal event processing, like any other event.
…		…
931	=item ev_signal_set (ev_signal *, int signum)	1219	=item ev_signal_set (ev_signal *, int signum)
932		1220
933	Configures the watcher to trigger on the given signal number (usually one	1221	Configures the watcher to trigger on the given signal number (usually one
934	of the C<SIGxxx> constants).	1222	of the C<SIGxxx> constants).
935		1223
		1224	=item int signum [read-only]
		1225
		1226	The signal the watcher watches out for.
		1227
936	=back	1228	=back
937		1229
938		1230
939	=head2 C<ev_child> - wait for pid status changes	1231	=head2 C<ev_child> - watch out for process status changes
940		1232
941	Child watchers trigger when your process receives a SIGCHLD in response to	1233	Child watchers trigger when your process receives a SIGCHLD in response to
942	some child status changes (most typically when a child of yours dies).	1234	some child status changes (most typically when a child of yours dies).
943		1235
944	=over 4	1236	=over 4
…		…
952	at the C<rstatus> member of the C<ev_child> watcher structure to see	1244	at the C<rstatus> member of the C<ev_child> watcher structure to see
953	the status word (use the macros from C<sys/wait.h> and see your systems	1245	the status word (use the macros from C<sys/wait.h> and see your systems
954	C<waitpid> documentation). The C<rpid> member contains the pid of the	1246	C<waitpid> documentation). The C<rpid> member contains the pid of the
955	process causing the status change.	1247	process causing the status change.
956		1248
		1249	=item int pid [read-only]
		1250
		1251	The process id this watcher watches out for, or C<0>, meaning any process id.
		1252
		1253	=item int rpid [read-write]
		1254
		1255	The process id that detected a status change.
		1256
		1257	=item int rstatus [read-write]
		1258
		1259	The process exit/trace status caused by C<rpid> (see your systems
		1260	C<waitpid> and C<sys/wait.h> documentation for details).
		1261
957	=back	1262	=back
958		1263
959	Example: try to exit cleanly on SIGINT and SIGTERM.	1264	Example: Try to exit cleanly on SIGINT and SIGTERM.
960		1265
961	static void	1266	static void
962	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
963	{	1268	{
964	ev_unloop (loop, EVUNLOOP_ALL);	1269	ev_unloop (loop, EVUNLOOP_ALL);
…		…
967	struct ev_signal signal_watcher;	1272	struct ev_signal signal_watcher;
968	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
969	ev_signal_start (loop, &sigint_cb);	1274	ev_signal_start (loop, &sigint_cb);
970		1275
971		1276
		1277	=head2 C<ev_stat> - did the file attributes just change?
		1278
		1279	This watches a filesystem path for attribute changes. That is, it calls
		1280	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1281	compared to the last time, invoking the callback if it did.
		1282
		1283	The path does not need to exist: changing from "path exists" to "path does
		1284	not exist" is a status change like any other. The condition "path does
		1285	not exist" is signified by the C<st_nlink> field being zero (which is
		1286	otherwise always forced to be at least one) and all the other fields of
		1287	the stat buffer having unspecified contents.
		1288
		1289	The path I<should> be absolute and I<must not> end in a slash. If it is
		1290	relative and your working directory changes, the behaviour is undefined.
		1291
		1292	Since there is no standard to do this, the portable implementation simply
		1293	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1294	can specify a recommended polling interval for this case. If you specify
		1295	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1296	unspecified default> value will be used (which you can expect to be around
		1297	five seconds, although this might change dynamically). Libev will also
		1298	impose a minimum interval which is currently around C<0.1>, but thats
		1299	usually overkill.
		1300
		1301	This watcher type is not meant for massive numbers of stat watchers,
		1302	as even with OS-supported change notifications, this can be
		1303	resource-intensive.
		1304
		1305	At the time of this writing, only the Linux inotify interface is
		1306	implemented (implementing kqueue support is left as an exercise for the
		1307	reader). Inotify will be used to give hints only and should not change the
		1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1309	to fall back to regular polling again even with inotify, but changes are
		1310	usually detected immediately, and if the file exists there will be no
		1311	polling.
		1312
		1313	=over 4
		1314
		1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1316
		1317	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1318
		1319	Configures the watcher to wait for status changes of the given
		1320	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1321	be detected and should normally be specified as C<0> to let libev choose
		1322	a suitable value. The memory pointed to by C<path> must point to the same
		1323	path for as long as the watcher is active.
		1324
		1325	The callback will be receive C<EV_STAT> when a change was detected,
		1326	relative to the attributes at the time the watcher was started (or the
		1327	last change was detected).
		1328
		1329	=item ev_stat_stat (ev_stat *)
		1330
		1331	Updates the stat buffer immediately with new values. If you change the
		1332	watched path in your callback, you could call this fucntion to avoid
		1333	detecting this change (while introducing a race condition). Can also be
		1334	useful simply to find out the new values.
		1335
		1336	=item ev_statdata attr [read-only]
		1337
		1338	The most-recently detected attributes of the file. Although the type is of
		1339	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1340	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1341	was some error while C<stat>ing the file.
		1342
		1343	=item ev_statdata prev [read-only]
		1344
		1345	The previous attributes of the file. The callback gets invoked whenever
		1346	C<prev> != C<attr>.
		1347
		1348	=item ev_tstamp interval [read-only]
		1349
		1350	The specified interval.
		1351
		1352	=item const char *path [read-only]
		1353
		1354	The filesystem path that is being watched.
		1355
		1356	=back
		1357
		1358	Example: Watch C</etc/passwd> for attribute changes.
		1359
		1360	static void
		1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1362	{
		1363	/* /etc/passwd changed in some way */
		1364	if (w->attr.st_nlink)
		1365	{
		1366	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1367	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1368	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1369	}
		1370	else
		1371	/* you shalt not abuse printf for puts */
		1372	puts ("wow, /etc/passwd is not there, expect problems. "
		1373	"if this is windows, they already arrived\n");
		1374	}
		1375
		1376	...
		1377	ev_stat passwd;
		1378
		1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1380	ev_stat_start (loop, &passwd);
		1381
		1382
972	=head2 C<ev_idle> - when you've got nothing better to do	1383	=head2 C<ev_idle> - when you've got nothing better to do...
973		1384
974	Idle watchers trigger events when there are no other events are pending	1385	Idle watchers trigger events when no other events of the same or higher
975	(prepare, check and other idle watchers do not count). That is, as long	1386	priority are pending (prepare, check and other idle watchers do not
976	as your process is busy handling sockets or timeouts (or even signals,	1387	count).
977	imagine) it will not be triggered. But when your process is idle all idle	1388
978	watchers are being called again and again, once per event loop iteration -	1389	That is, as long as your process is busy handling sockets or timeouts
		1390	(or even signals, imagine) of the same or higher priority it will not be
		1391	triggered. But when your process is idle (or only lower-priority watchers
		1392	are pending), the idle watchers are being called once per event loop
979	until stopped, that is, or your process receives more events and becomes	1393	iteration - until stopped, that is, or your process receives more events
980	busy.	1394	and becomes busy again with higher priority stuff.
981		1395
982	The most noteworthy effect is that as long as any idle watchers are	1396	The most noteworthy effect is that as long as any idle watchers are
983	active, the process will not block when waiting for new events.	1397	active, the process will not block when waiting for new events.
984		1398
985	Apart from keeping your process non-blocking (which is a useful	1399	Apart from keeping your process non-blocking (which is a useful
…		…
995	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
996	believe me.	1410	believe me.
997		1411
998	=back	1412	=back
999		1413
1000	Example: dynamically allocate an C<ev_idle>, start it, and in the	1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1001	callback, free it. Alos, use no error checking, as usual.	1415	callback, free it. Also, use no error checking, as usual.
1002		1416
1003	static void	1417	static void
1004	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1418	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1005	{	1419	{
1006	free (w);	1420	free (w);
…		…
1011	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1012	ev_idle_init (idle_watcher, idle_cb);	1426	ev_idle_init (idle_watcher, idle_cb);
1013	ev_idle_start (loop, idle_cb);	1427	ev_idle_start (loop, idle_cb);
1014		1428
1015		1429
1016	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1430	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1017		1431
1018	Prepare and check watchers are usually (but not always) used in tandem:	1432	Prepare and check watchers are usually (but not always) used in tandem:
1019	prepare watchers get invoked before the process blocks and check watchers	1433	prepare watchers get invoked before the process blocks and check watchers
1020	afterwards.	1434	afterwards.
1021		1435
		1436	You I<must not> call C<ev_loop> or similar functions that enter
		1437	the current event loop from either C<ev_prepare> or C<ev_check>
		1438	watchers. Other loops than the current one are fine, however. The
		1439	rationale behind this is that you do not need to check for recursion in
		1440	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1441	C<ev_check> so if you have one watcher of each kind they will always be
		1442	called in pairs bracketing the blocking call.
		1443
1022	Their main purpose is to integrate other event mechanisms into libev and	1444	Their main purpose is to integrate other event mechanisms into libev and
1023	their use is somewhat advanced. This could be used, for example, to track	1445	their use is somewhat advanced. This could be used, for example, to track
1024	variable changes, implement your own watchers, integrate net-snmp or a	1446	variable changes, implement your own watchers, integrate net-snmp or a
1025	coroutine library and lots more.	1447	coroutine library and lots more. They are also occasionally useful if
		1448	you cache some data and want to flush it before blocking (for example,
		1449	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1450	watcher).
1026		1451
1027	This is done by examining in each prepare call which file descriptors need	1452	This is done by examining in each prepare call which file descriptors need
1028	to be watched by the other library, registering C<ev_io> watchers for	1453	to be watched by the other library, registering C<ev_io> watchers for
1029	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1454	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1030	provide just this functionality). Then, in the check watcher you check for	1455	provide just this functionality). Then, in the check watcher you check for
…		…
1052	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1053	macros, but using them is utterly, utterly and completely pointless.	1478	macros, but using them is utterly, utterly and completely pointless.
1054		1479
1055	=back	1480	=back
1056		1481
1057	Example: *TODO*.	1482	Example: To include a library such as adns, you would add IO watchers
		1483	and a timeout watcher in a prepare handler, as required by libadns, and
		1484	in a check watcher, destroy them and call into libadns. What follows is
		1485	pseudo-code only of course:
1058		1486
		1487	static ev_io iow [nfd];
		1488	static ev_timer tw;
1059		1489
		1490	static void
		1491	io_cb (ev_loop *loop, ev_io *w, int revents)
		1492	{
		1493	// set the relevant poll flags
		1494	// could also call adns_processreadable etc. here
		1495	struct pollfd *fd = (struct pollfd *)w->data;
		1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1498	}
		1499
		1500	// create io watchers for each fd and a timer before blocking
		1501	static void
		1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1503	{
		1504	int timeout = 3600000;
		1505	struct pollfd fds [nfd];
		1506	// actual code will need to loop here and realloc etc.
		1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1508
		1509	/* the callback is illegal, but won't be called as we stop during check */
		1510	ev_timer_init (&tw, 0, timeout * 1e-3);
		1511	ev_timer_start (loop, &tw);
		1512
		1513	// create on ev_io per pollfd
		1514	for (int i = 0; i < nfd; ++i)
		1515	{
		1516	ev_io_init (iow + i, io_cb, fds [i].fd,
		1517	((fds [i].events & POLLIN ? EV_READ : 0)
		1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1519
		1520	fds [i].revents = 0;
		1521	iow [i].data = fds + i;
		1522	ev_io_start (loop, iow + i);
		1523	}
		1524	}
		1525
		1526	// stop all watchers after blocking
		1527	static void
		1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1529	{
		1530	ev_timer_stop (loop, &tw);
		1531
		1532	for (int i = 0; i < nfd; ++i)
		1533	ev_io_stop (loop, iow + i);
		1534
		1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1536	}
		1537
		1538
1060	=head2 C<ev_embed> - when one backend isn't enough	1539	=head2 C<ev_embed> - when one backend isn't enough...
1061		1540
1062	This is a rather advanced watcher type that lets you embed one event loop	1541	This is a rather advanced watcher type that lets you embed one event loop
1063	into another.	1542	into another (currently only C<ev_io> events are supported in the embedded
		1543	loop, other types of watchers might be handled in a delayed or incorrect
		1544	fashion and must not be used).
1064		1545
1065	There are primarily two reasons you would want that: work around bugs and	1546	There are primarily two reasons you would want that: work around bugs and
1066	prioritise I/O.	1547	prioritise I/O.
1067		1548
1068	As an example for a bug workaround, the kqueue backend might only support	1549	As an example for a bug workaround, the kqueue backend might only support
…		…
1076	As for prioritising I/O: rarely you have the case where some fds have	1557	As for prioritising I/O: rarely you have the case where some fds have
1077	to be watched and handled very quickly (with low latency), and even	1558	to be watched and handled very quickly (with low latency), and even
1078	priorities and idle watchers might have too much overhead. In this case	1559	priorities and idle watchers might have too much overhead. In this case
1079	you would put all the high priority stuff in one loop and all the rest in	1560	you would put all the high priority stuff in one loop and all the rest in
1080	a second one, and embed the second one in the first.	1561	a second one, and embed the second one in the first.
		1562
		1563	As long as the watcher is active, the callback will be invoked every time
		1564	there might be events pending in the embedded loop. The callback must then
		1565	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1566	their callbacks (you could also start an idle watcher to give the embedded
		1567	loop strictly lower priority for example). You can also set the callback
		1568	to C<0>, in which case the embed watcher will automatically execute the
		1569	embedded loop sweep.
1081		1570
1082	As long as the watcher is started it will automatically handle events. The	1571	As long as the watcher is started it will automatically handle events. The
1083	callback will be invoked whenever some events have been handled. You can	1572	callback will be invoked whenever some events have been handled. You can
1084	set the callback to C<0> to avoid having to specify one if you are not	1573	set the callback to C<0> to avoid having to specify one if you are not
1085	interested in that.	1574	interested in that.
…		…
1117	else	1606	else
1118	loop_lo = loop_hi;	1607	loop_lo = loop_hi;
1119		1608
1120	=over 4	1609	=over 4
1121		1610
1122	=item ev_embed_init (ev_embed *, callback, struct ev_loop *loop)	1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1123		1612
1124	=item ev_embed_set (ev_embed *, callback, struct ev_loop *loop)	1613	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1125		1614
1126	Configures the watcher to embed the given loop, which must be embeddable.	1615	Configures the watcher to embed the given loop, which must be
		1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1617	invoked automatically, otherwise it is the responsibility of the callback
		1618	to invoke it (it will continue to be called until the sweep has been done,
		1619	if you do not want thta, you need to temporarily stop the embed watcher).
		1620
		1621	=item ev_embed_sweep (loop, ev_embed *)
		1622
		1623	Make a single, non-blocking sweep over the embedded loop. This works
		1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1625	apropriate way for embedded loops.
		1626
		1627	=item struct ev_loop *loop [read-only]
		1628
		1629	The embedded event loop.
		1630
		1631	=back
		1632
		1633
		1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1635
		1636	Fork watchers are called when a C<fork ()> was detected (usually because
		1637	whoever is a good citizen cared to tell libev about it by calling
		1638	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1639	event loop blocks next and before C<ev_check> watchers are being called,
		1640	and only in the child after the fork. If whoever good citizen calling
		1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1642	handlers will be invoked, too, of course.
		1643
		1644	=over 4
		1645
		1646	=item ev_fork_init (ev_signal *, callback)
		1647
		1648	Initialises and configures the fork watcher - it has no parameters of any
		1649	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1650	believe me.
1127		1651
1128	=back	1652	=back
1129		1653
1130		1654
1131	=head1 OTHER FUNCTIONS	1655	=head1 OTHER FUNCTIONS
…		…
1164	/* stdin might have data for us, joy! */;	1688	/* stdin might have data for us, joy! */;
1165	}	1689	}
1166		1690
1167	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1691	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1168		1692
1169	=item ev_feed_event (loop, watcher, int events)	1693	=item ev_feed_event (ev_loop *, watcher *, int revents)
1170		1694
1171	Feeds the given event set into the event loop, as if the specified event	1695	Feeds the given event set into the event loop, as if the specified event
1172	had happened for the specified watcher (which must be a pointer to an	1696	had happened for the specified watcher (which must be a pointer to an
1173	initialised but not necessarily started event watcher).	1697	initialised but not necessarily started event watcher).
1174		1698
1175	=item ev_feed_fd_event (loop, int fd, int revents)	1699	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
1176		1700
1177	Feed an event on the given fd, as if a file descriptor backend detected	1701	Feed an event on the given fd, as if a file descriptor backend detected
1178	the given events it.	1702	the given events it.
1179		1703
1180	=item ev_feed_signal_event (loop, int signum)	1704	=item ev_feed_signal_event (ev_loop *loop, int signum)
1181		1705
1182	Feed an event as if the given signal occured (loop must be the default loop!).	1706	Feed an event as if the given signal occured (C<loop> must be the default
		1707	loop!).
1183		1708
1184	=back	1709	=back
1185		1710
1186		1711
1187	=head1 LIBEVENT EMULATION	1712	=head1 LIBEVENT EMULATION
…		…
1211		1736
1212	=back	1737	=back
1213		1738
1214	=head1 C++ SUPPORT	1739	=head1 C++ SUPPORT
1215		1740
1216	TBD.	1741	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1742	you to use some convinience methods to start/stop watchers and also change
		1743	the callback model to a model using method callbacks on objects.
		1744
		1745	To use it,
		1746
		1747	#include <ev++.h>
		1748
		1749	This automatically includes F<ev.h> and puts all of its definitions (many
		1750	of them macros) into the global namespace. All C++ specific things are
		1751	put into the C<ev> namespace. It should support all the same embedding
		1752	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1753
		1754	Care has been taken to keep the overhead low. The only data member the C++
		1755	classes add (compared to plain C-style watchers) is the event loop pointer
		1756	that the watcher is associated with (or no additional members at all if
		1757	you disable C<EV_MULTIPLICITY> when embedding libev).
		1758
		1759	Currently, functions, and static and non-static member functions can be
		1760	used as callbacks. Other types should be easy to add as long as they only
		1761	need one additional pointer for context. If you need support for other
		1762	types of functors please contact the author (preferably after implementing
		1763	it).
		1764
		1765	Here is a list of things available in the C<ev> namespace:
		1766
		1767	=over 4
		1768
		1769	=item C<ev::READ>, C<ev::WRITE> etc.
		1770
		1771	These are just enum values with the same values as the C<EV_READ> etc.
		1772	macros from F<ev.h>.
		1773
		1774	=item C<ev::tstamp>, C<ev::now>
		1775
		1776	Aliases to the same types/functions as with the C<ev_> prefix.
		1777
		1778	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1779
		1780	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1781	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1782	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1783	defines by many implementations.
		1784
		1785	All of those classes have these methods:
		1786
		1787	=over 4
		1788
		1789	=item ev::TYPE::TYPE ()
		1790
		1791	=item ev::TYPE::TYPE (struct ev_loop *)
		1792
		1793	=item ev::TYPE::~TYPE
		1794
		1795	The constructor (optionally) takes an event loop to associate the watcher
		1796	with. If it is omitted, it will use C<EV_DEFAULT>.
		1797
		1798	The constructor calls C<ev_init> for you, which means you have to call the
		1799	C<set> method before starting it.
		1800
		1801	It will not set a callback, however: You have to call the templated C<set>
		1802	method to set a callback before you can start the watcher.
		1803
		1804	(The reason why you have to use a method is a limitation in C++ which does
		1805	not allow explicit template arguments for constructors).
		1806
		1807	The destructor automatically stops the watcher if it is active.
		1808
		1809	=item w->set<class, &class::method> (object *)
		1810
		1811	This method sets the callback method to call. The method has to have a
		1812	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1813	first argument and the C<revents> as second. The object must be given as
		1814	parameter and is stored in the C<data> member of the watcher.
		1815
		1816	This method synthesizes efficient thunking code to call your method from
		1817	the C callback that libev requires. If your compiler can inline your
		1818	callback (i.e. it is visible to it at the place of the C<set> call and
		1819	your compiler is good :), then the method will be fully inlined into the
		1820	thunking function, making it as fast as a direct C callback.
		1821
		1822	Example: simple class declaration and watcher initialisation
		1823
		1824	struct myclass
		1825	{
		1826	void io_cb (ev::io &w, int revents) { }
		1827	}
		1828
		1829	myclass obj;
		1830	ev::io iow;
		1831	iow.set <myclass, &myclass::io_cb> (&obj);
		1832
		1833	=item w->set (void (*function)(watcher &w, int), void *data = 0)
		1834
		1835	Also sets a callback, but uses a static method or plain function as
		1836	callback. The optional C<data> argument will be stored in the watcher's
		1837	C<data> member and is free for you to use.
		1838
		1839	See the method-C<set> above for more details.
		1840
		1841	=item w->set (struct ev_loop *)
		1842
		1843	Associates a different C<struct ev_loop> with this watcher. You can only
		1844	do this when the watcher is inactive (and not pending either).
		1845
		1846	=item w->set ([args])
		1847
		1848	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1849	called at least once. Unlike the C counterpart, an active watcher gets
		1850	automatically stopped and restarted when reconfiguring it with this
		1851	method.
		1852
		1853	=item w->start ()
		1854
		1855	Starts the watcher. Note that there is no C<loop> argument, as the
		1856	constructor already stores the event loop.
		1857
		1858	=item w->stop ()
		1859
		1860	Stops the watcher if it is active. Again, no C<loop> argument.
		1861
		1862	=item w->again () C<ev::timer>, C<ev::periodic> only
		1863
		1864	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1865	C<ev_TYPE_again> function.
		1866
		1867	=item w->sweep () C<ev::embed> only
		1868
		1869	Invokes C<ev_embed_sweep>.
		1870
		1871	=item w->update () C<ev::stat> only
		1872
		1873	Invokes C<ev_stat_stat>.
		1874
		1875	=back
		1876
		1877	=back
		1878
		1879	Example: Define a class with an IO and idle watcher, start one of them in
		1880	the constructor.
		1881
		1882	class myclass
		1883	{
		1884	ev_io io; void io_cb (ev::io &w, int revents);
		1885	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1886
		1887	myclass ();
		1888	}
		1889
		1890	myclass::myclass (int fd)
		1891	{
		1892	io .set <myclass, &myclass::io_cb > (this);
		1893	idle.set <myclass, &myclass::idle_cb> (this);
		1894
		1895	io.start (fd, ev::READ);
		1896	}
		1897
		1898
		1899	=head1 MACRO MAGIC
		1900
		1901	Libev can be compiled with a variety of options, the most fundemantal is
		1902	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		1903	callbacks have an initial C<struct ev_loop *> argument.
		1904
		1905	To make it easier to write programs that cope with either variant, the
		1906	following macros are defined:
		1907
		1908	=over 4
		1909
		1910	=item C<EV_A>, C<EV_A_>
		1911
		1912	This provides the loop I<argument> for functions, if one is required ("ev
		1913	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1914	C<EV_A_> is used when other arguments are following. Example:
		1915
		1916	ev_unref (EV_A);
		1917	ev_timer_add (EV_A_ watcher);
		1918	ev_loop (EV_A_ 0);
		1919
		1920	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1921	which is often provided by the following macro.
		1922
		1923	=item C<EV_P>, C<EV_P_>
		1924
		1925	This provides the loop I<parameter> for functions, if one is required ("ev
		1926	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1927	C<EV_P_> is used when other parameters are following. Example:
		1928
		1929	// this is how ev_unref is being declared
		1930	static void ev_unref (EV_P);
		1931
		1932	// this is how you can declare your typical callback
		1933	static void cb (EV_P_ ev_timer *w, int revents)
		1934
		1935	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1936	suitable for use with C<EV_A>.
		1937
		1938	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1939
		1940	Similar to the other two macros, this gives you the value of the default
		1941	loop, if multiple loops are supported ("ev loop default").
		1942
		1943	=back
		1944
		1945	Example: Declare and initialise a check watcher, utilising the above
		1946	macros so it will work regardless of whether multiple loops are supported
		1947	or not.
		1948
		1949	static void
		1950	check_cb (EV_P_ ev_timer *w, int revents)
		1951	{
		1952	ev_check_stop (EV_A_ w);
		1953	}
		1954
		1955	ev_check check;
		1956	ev_check_init (&check, check_cb);
		1957	ev_check_start (EV_DEFAULT_ &check);
		1958	ev_loop (EV_DEFAULT_ 0);
		1959
		1960	=head1 EMBEDDING
		1961
		1962	Libev can (and often is) directly embedded into host
		1963	applications. Examples of applications that embed it include the Deliantra
		1964	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1965	and rxvt-unicode.
		1966
		1967	The goal is to enable you to just copy the neecssary files into your
		1968	source directory without having to change even a single line in them, so
		1969	you can easily upgrade by simply copying (or having a checked-out copy of
		1970	libev somewhere in your source tree).
		1971
		1972	=head2 FILESETS
		1973
		1974	Depending on what features you need you need to include one or more sets of files
		1975	in your app.
		1976
		1977	=head3 CORE EVENT LOOP
		1978
		1979	To include only the libev core (all the C<ev_*> functions), with manual
		1980	configuration (no autoconf):
		1981
		1982	#define EV_STANDALONE 1
		1983	#include "ev.c"
		1984
		1985	This will automatically include F<ev.h>, too, and should be done in a
		1986	single C source file only to provide the function implementations. To use
		1987	it, do the same for F<ev.h> in all files wishing to use this API (best
		1988	done by writing a wrapper around F<ev.h> that you can include instead and
		1989	where you can put other configuration options):
		1990
		1991	#define EV_STANDALONE 1
		1992	#include "ev.h"
		1993
		1994	Both header files and implementation files can be compiled with a C++
		1995	compiler (at least, thats a stated goal, and breakage will be treated
		1996	as a bug).
		1997
		1998	You need the following files in your source tree, or in a directory
		1999	in your include path (e.g. in libev/ when using -Ilibev):
		2000
		2001	ev.h
		2002	ev.c
		2003	ev_vars.h
		2004	ev_wrap.h
		2005
		2006	ev_win32.c required on win32 platforms only
		2007
		2008	ev_select.c only when select backend is enabled (which is enabled by default)
		2009	ev_poll.c only when poll backend is enabled (disabled by default)
		2010	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2011	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2012	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2013
		2014	F<ev.c> includes the backend files directly when enabled, so you only need
		2015	to compile this single file.
		2016
		2017	=head3 LIBEVENT COMPATIBILITY API
		2018
		2019	To include the libevent compatibility API, also include:
		2020
		2021	#include "event.c"
		2022
		2023	in the file including F<ev.c>, and:
		2024
		2025	#include "event.h"
		2026
		2027	in the files that want to use the libevent API. This also includes F<ev.h>.
		2028
		2029	You need the following additional files for this:
		2030
		2031	event.h
		2032	event.c
		2033
		2034	=head3 AUTOCONF SUPPORT
		2035
		2036	Instead of using C<EV_STANDALONE=1> and providing your config in
		2037	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2038	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2039	include F<config.h> and configure itself accordingly.
		2040
		2041	For this of course you need the m4 file:
		2042
		2043	libev.m4
		2044
		2045	=head2 PREPROCESSOR SYMBOLS/MACROS
		2046
		2047	Libev can be configured via a variety of preprocessor symbols you have to define
		2048	before including any of its files. The default is not to build for multiplicity
		2049	and only include the select backend.
		2050
		2051	=over 4
		2052
		2053	=item EV_STANDALONE
		2054
		2055	Must always be C<1> if you do not use autoconf configuration, which
		2056	keeps libev from including F<config.h>, and it also defines dummy
		2057	implementations for some libevent functions (such as logging, which is not
		2058	supported). It will also not define any of the structs usually found in
		2059	F<event.h> that are not directly supported by the libev core alone.
		2060
		2061	=item EV_USE_MONOTONIC
		2062
		2063	If defined to be C<1>, libev will try to detect the availability of the
		2064	monotonic clock option at both compiletime and runtime. Otherwise no use
		2065	of the monotonic clock option will be attempted. If you enable this, you
		2066	usually have to link against librt or something similar. Enabling it when
		2067	the functionality isn't available is safe, though, althoguh you have
		2068	to make sure you link against any libraries where the C<clock_gettime>
		2069	function is hiding in (often F<-lrt>).
		2070
		2071	=item EV_USE_REALTIME
		2072
		2073	If defined to be C<1>, libev will try to detect the availability of the
		2074	realtime clock option at compiletime (and assume its availability at
		2075	runtime if successful). Otherwise no use of the realtime clock option will
		2076	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2077	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2078	in the description of C<EV_USE_MONOTONIC>, though.
		2079
		2080	=item EV_USE_SELECT
		2081
		2082	If undefined or defined to be C<1>, libev will compile in support for the
		2083	C<select>(2) backend. No attempt at autodetection will be done: if no
		2084	other method takes over, select will be it. Otherwise the select backend
		2085	will not be compiled in.
		2086
		2087	=item EV_SELECT_USE_FD_SET
		2088
		2089	If defined to C<1>, then the select backend will use the system C<fd_set>
		2090	structure. This is useful if libev doesn't compile due to a missing
		2091	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2092	exotic systems. This usually limits the range of file descriptors to some
		2093	low limit such as 1024 or might have other limitations (winsocket only
		2094	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2095	influence the size of the C<fd_set> used.
		2096
		2097	=item EV_SELECT_IS_WINSOCKET
		2098
		2099	When defined to C<1>, the select backend will assume that
		2100	select/socket/connect etc. don't understand file descriptors but
		2101	wants osf handles on win32 (this is the case when the select to
		2102	be used is the winsock select). This means that it will call
		2103	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2104	it is assumed that all these functions actually work on fds, even
		2105	on win32. Should not be defined on non-win32 platforms.
		2106
		2107	=item EV_USE_POLL
		2108
		2109	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2110	backend. Otherwise it will be enabled on non-win32 platforms. It
		2111	takes precedence over select.
		2112
		2113	=item EV_USE_EPOLL
		2114
		2115	If defined to be C<1>, libev will compile in support for the Linux
		2116	C<epoll>(7) backend. Its availability will be detected at runtime,
		2117	otherwise another method will be used as fallback. This is the
		2118	preferred backend for GNU/Linux systems.
		2119
		2120	=item EV_USE_KQUEUE
		2121
		2122	If defined to be C<1>, libev will compile in support for the BSD style
		2123	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2124	otherwise another method will be used as fallback. This is the preferred
		2125	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2126	supports some types of fds correctly (the only platform we found that
		2127	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2128	not be used unless explicitly requested. The best way to use it is to find
		2129	out whether kqueue supports your type of fd properly and use an embedded
		2130	kqueue loop.
		2131
		2132	=item EV_USE_PORT
		2133
		2134	If defined to be C<1>, libev will compile in support for the Solaris
		2135	10 port style backend. Its availability will be detected at runtime,
		2136	otherwise another method will be used as fallback. This is the preferred
		2137	backend for Solaris 10 systems.
		2138
		2139	=item EV_USE_DEVPOLL
		2140
		2141	reserved for future expansion, works like the USE symbols above.
		2142
		2143	=item EV_USE_INOTIFY
		2144
		2145	If defined to be C<1>, libev will compile in support for the Linux inotify
		2146	interface to speed up C<ev_stat> watchers. Its actual availability will
		2147	be detected at runtime.
		2148
		2149	=item EV_H
		2150
		2151	The name of the F<ev.h> header file used to include it. The default if
		2152	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2153	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2154
		2155	=item EV_CONFIG_H
		2156
		2157	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2158	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2159	C<EV_H>, above.
		2160
		2161	=item EV_EVENT_H
		2162
		2163	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2164	of how the F<event.h> header can be found.
		2165
		2166	=item EV_PROTOTYPES
		2167
		2168	If defined to be C<0>, then F<ev.h> will not define any function
		2169	prototypes, but still define all the structs and other symbols. This is
		2170	occasionally useful if you want to provide your own wrapper functions
		2171	around libev functions.
		2172
		2173	=item EV_MULTIPLICITY
		2174
		2175	If undefined or defined to C<1>, then all event-loop-specific functions
		2176	will have the C<struct ev_loop *> as first argument, and you can create
		2177	additional independent event loops. Otherwise there will be no support
		2178	for multiple event loops and there is no first event loop pointer
		2179	argument. Instead, all functions act on the single default loop.
		2180
		2181	=item EV_MINPRI
		2182
		2183	=item EV_MAXPRI
		2184
		2185	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2186	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2187	provide for more priorities by overriding those symbols (usually defined
		2188	to be C<-2> and C<2>, respectively).
		2189
		2190	When doing priority-based operations, libev usually has to linearly search
		2191	all the priorities, so having many of them (hundreds) uses a lot of space
		2192	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2193	fine.
		2194
		2195	If your embedding app does not need any priorities, defining these both to
		2196	C<0> will save some memory and cpu.
		2197
		2198	=item EV_PERIODIC_ENABLE
		2199
		2200	If undefined or defined to be C<1>, then periodic timers are supported. If
		2201	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2202	code.
		2203
		2204	=item EV_IDLE_ENABLE
		2205
		2206	If undefined or defined to be C<1>, then idle watchers are supported. If
		2207	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2208	code.
		2209
		2210	=item EV_EMBED_ENABLE
		2211
		2212	If undefined or defined to be C<1>, then embed watchers are supported. If
		2213	defined to be C<0>, then they are not.
		2214
		2215	=item EV_STAT_ENABLE
		2216
		2217	If undefined or defined to be C<1>, then stat watchers are supported. If
		2218	defined to be C<0>, then they are not.
		2219
		2220	=item EV_FORK_ENABLE
		2221
		2222	If undefined or defined to be C<1>, then fork watchers are supported. If
		2223	defined to be C<0>, then they are not.
		2224
		2225	=item EV_MINIMAL
		2226
		2227	If you need to shave off some kilobytes of code at the expense of some
		2228	speed, define this symbol to C<1>. Currently only used for gcc to override
		2229	some inlining decisions, saves roughly 30% codesize of amd64.
		2230
		2231	=item EV_PID_HASHSIZE
		2232
		2233	C<ev_child> watchers use a small hash table to distribute workload by
		2234	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2235	than enough. If you need to manage thousands of children you might want to
		2236	increase this value (I<must> be a power of two).
		2237
		2238	=item EV_INOTIFY_HASHSIZE
		2239
		2240	C<ev_staz> watchers use a small hash table to distribute workload by
		2241	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2242	usually more than enough. If you need to manage thousands of C<ev_stat>
		2243	watchers you might want to increase this value (I<must> be a power of
		2244	two).
		2245
		2246	=item EV_COMMON
		2247
		2248	By default, all watchers have a C<void *data> member. By redefining
		2249	this macro to a something else you can include more and other types of
		2250	members. You have to define it each time you include one of the files,
		2251	though, and it must be identical each time.
		2252
		2253	For example, the perl EV module uses something like this:
		2254
		2255	#define EV_COMMON \
		2256	SV *self; /* contains this struct */ \
		2257	SV *cb_sv, *fh /* note no trailing ";" */
		2258
		2259	=item EV_CB_DECLARE (type)
		2260
		2261	=item EV_CB_INVOKE (watcher, revents)
		2262
		2263	=item ev_set_cb (ev, cb)
		2264
		2265	Can be used to change the callback member declaration in each watcher,
		2266	and the way callbacks are invoked and set. Must expand to a struct member
		2267	definition and a statement, respectively. See the F<ev.v> header file for
		2268	their default definitions. One possible use for overriding these is to
		2269	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2270	method calls instead of plain function calls in C++.
		2271
		2272	=head2 EXAMPLES
		2273
		2274	For a real-world example of a program the includes libev
		2275	verbatim, you can have a look at the EV perl module
		2276	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2277	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2278	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2279	will be compiled. It is pretty complex because it provides its own header
		2280	file.
		2281
		2282	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2283	that everybody includes and which overrides some configure choices:
		2284
		2285	#define EV_MINIMAL 1
		2286	#define EV_USE_POLL 0
		2287	#define EV_MULTIPLICITY 0
		2288	#define EV_PERIODIC_ENABLE 0
		2289	#define EV_STAT_ENABLE 0
		2290	#define EV_FORK_ENABLE 0
		2291	#define EV_CONFIG_H <config.h>
		2292	#define EV_MINPRI 0
		2293	#define EV_MAXPRI 0
		2294
		2295	#include "ev++.h"
		2296
		2297	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2298
		2299	#include "ev_cpp.h"
		2300	#include "ev.c"
		2301
		2302
		2303	=head1 COMPLEXITIES
		2304
		2305	In this section the complexities of (many of) the algorithms used inside
		2306	libev will be explained. For complexity discussions about backends see the
		2307	documentation for C<ev_default_init>.
		2308
		2309	All of the following are about amortised time: If an array needs to be
		2310	extended, libev needs to realloc and move the whole array, but this
		2311	happens asymptotically never with higher number of elements, so O(1) might
		2312	mean it might do a lengthy realloc operation in rare cases, but on average
		2313	it is much faster and asymptotically approaches constant time.
		2314
		2315	=over 4
		2316
		2317	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2318
		2319	This means that, when you have a watcher that triggers in one hour and
		2320	there are 100 watchers that would trigger before that then inserting will
		2321	have to skip those 100 watchers.
		2322
		2323	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2324
		2325	That means that for changing a timer costs less than removing/adding them
		2326	as only the relative motion in the event queue has to be paid for.
		2327
		2328	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2329
		2330	These just add the watcher into an array or at the head of a list.
		2331	=item Stopping check/prepare/idle watchers: O(1)
		2332
		2333	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2334
		2335	These watchers are stored in lists then need to be walked to find the
		2336	correct watcher to remove. The lists are usually short (you don't usually
		2337	have many watchers waiting for the same fd or signal).
		2338
		2339	=item Finding the next timer per loop iteration: O(1)
		2340
		2341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2342
		2343	A change means an I/O watcher gets started or stopped, which requires
		2344	libev to recalculate its status (and possibly tell the kernel).
		2345
		2346	=item Activating one watcher: O(1)
		2347
		2348	=item Priority handling: O(number_of_priorities)
		2349
		2350	Priorities are implemented by allocating some space for each
		2351	priority. When doing priority-based operations, libev usually has to
		2352	linearly search all the priorities.
		2353
		2354	=back
		2355
1217		2356
1218	=head1 AUTHOR	2357	=head1 AUTHOR
1219		2358
1220	Marc Lehmann <libev@schmorp.de>.	2359	Marc Lehmann <libev@schmorp.de>.
1221		2360

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