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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
…		…
66		117
67	=item int ev_version_major ()	118	=item int ev_version_major ()
68		119
69	=item int ev_version_minor ()	120	=item int ev_version_minor ()
70		121
71	You can find out the major and minor version numbers of the library	122	You can find out the major and minor API/ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	123	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	124	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	126	version of the library your program was compiled against.
76		127
		128	These version numbers refer to the API and ABI version of the library, not
		129	the release version.
		130
77	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	134	not a problem.
81		135
82	Example: make sure we haven't accidentally been linked against the wrong	136	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	137	version.
84		138
85	assert (("libev version mismatch",	139	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	140	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	141	&& ev_version_minor () >= EV_VERSION_MINOR));
88		142
…		…
118		172
119	See the description of C<ev_embed> watchers for more info.	173	See the description of C<ev_embed> watchers for more info.
120		174
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		176
123	Sets the allocation function to use (the prototype is similar to the	177	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	178	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	179	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	180	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	181	potentially destructive action. The default is your system realloc
		182	function.
128		183
129	You could override this function in high-availability programs to, say,	184	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,	185	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.	186	or even to sleep a while and retry until some memory is available.
132		187
133	Example: replace the libev allocator with one that waits a bit and then	188	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	189	retries).
135		190
136	static void *	191	static void *
137	persistent_realloc (void *ptr, long size)	192	persistent_realloc (void *ptr, size_t size)
138	{	193	{
139	for (;;)	194	for (;;)
140	{	195	{
141	void *newptr = realloc (ptr, size);	196	void *newptr = realloc (ptr, size);
142		197
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	213	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	214	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	215	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	216	(such as abort).
162		217
163	Example: do the same thing as libev does internally:	218	Example: This is basically the same thing that libev does internally, too.
164		219
165	static void	220	static void
166	fatal_error (const char *msg)	221	fatal_error (const char *msg)
167	{	222	{
168	perror (msg);	223	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	274	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	275	useful to try out specific backends to test their performance, or to work
221	around bugs.	276	around bugs.
222		277
		278	=item C<EVFLAG_FORKCHECK>
		279
		280	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		281	a fork, you can also make libev check for a fork in each iteration by
		282	enabling this flag.
		283
		284	This works by calling C<getpid ()> on every iteration of the loop,
		285	and thus this might slow down your event loop if you do a lot of loop
		286	iterations and little real work, but is usually not noticeable (on my
		287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		288	without a syscall and thus I<very> fast, but my Linux system also has
		289	C<pthread_atfork> which is even faster).
		290
		291	The big advantage of this flag is that you can forget about fork (and
		292	forget about forgetting to tell libev about forking) when you use this
		293	flag.
		294
		295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		296	environment variable.
		297
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		299
225	This is your standard select(2) backend. Not I<completely> standard, as	300	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,	301	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	302	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	389	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	390	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	391	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).	392	undefined behaviour (or a failed assertion if assertions are enabled).
318		393
319	Example: try to create a event loop that uses epoll and nothing else.	394	Example: Try to create a event loop that uses epoll and nothing else.
320		395
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	397	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	398	fatal ("no epoll found here, maybe it hides under your chair");
324		399
…		…
362		437
363	Like C<ev_default_fork>, but acts on an event loop created by	438	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	440	after fork, and how you do this is entirely your own problem.
366		441
		442	=item unsigned int ev_loop_count (loop)
		443
		444	Returns the count of loop iterations for the loop, which is identical to
		445	the number of times libev did poll for new events. It starts at C<0> and
		446	happily wraps around with enough iterations.
		447
		448	This value can sometimes be useful as a generation counter of sorts (it
		449	"ticks" the number of loop iterations), as it roughly corresponds with
		450	C<ev_prepare> and C<ev_check> calls.
		451
367	=item unsigned int ev_backend (loop)	452	=item unsigned int ev_backend (loop)
368		453
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	454	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	455	use.
371		456
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	490	usually a better approach for this kind of thing.
406		491
407	Here are the gory details of what C<ev_loop> does:	492	Here are the gory details of what C<ev_loop> does:
408		493
		494	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	499	- Update the "event loop time".
414	- Calculate for how long to block.	500	- Calculate for how long to block.
415	- Block the process, waiting for any events.	501	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	509	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	510	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	512	were used, return, otherwise continue with step *.
427		513
428	Example: queue some jobs and then loop until no events are outsanding	514	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	515	anymore.
430		516
431	... queue jobs here, make sure they register event watchers as long	517	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	518	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	519	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	539	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	540	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	541	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	542	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		543
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	545	running when nothing else is active.
460		546
461	struct dv_signal exitsig;	547	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	548	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	549	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	550	evf_unref (loop);
465		551
466	Example: for some weird reason, unregister the above signal handler again.	552	Example: For some weird reason, unregister the above signal handler again.
467		553
468	ev_ref (myloop);	554	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	555	ev_signal_stop (loop, &exitsig);
470		556
471	=back	557	=back
		558
472		559
473	=head1 ANATOMY OF A WATCHER	560	=head1 ANATOMY OF A WATCHER
474		561
475	A watcher is a structure that you create and register to record your	562	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	563	interest in some event. For instance, if you want to wait for STDIN to
…		…
543	The signal specified in the C<ev_signal> watcher has been received by a thread.	630	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		631
545	=item C<EV_CHILD>	632	=item C<EV_CHILD>
546		633
547	The pid specified in the C<ev_child> watcher has received a status change.	634	The pid specified in the C<ev_child> watcher has received a status change.
		635
		636	=item C<EV_STAT>
		637
		638	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		639
549	=item C<EV_IDLE>	640	=item C<EV_IDLE>
550		641
551	The C<ev_idle> watcher has determined that you have nothing better to do.	642	The C<ev_idle> watcher has determined that you have nothing better to do.
552		643
…		…
560	received events. Callbacks of both watcher types can start and stop as	651	received events. Callbacks of both watcher types can start and stop as
561	many watchers as they want, and all of them will be taken into account	652	many watchers as they want, and all of them will be taken into account
562	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	653	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	654	C<ev_loop> from blocking).
564		655
		656	=item C<EV_EMBED>
		657
		658	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		659
		660	=item C<EV_FORK>
		661
		662	The event loop has been resumed in the child process after fork (see
		663	C<ev_fork>).
		664
565	=item C<EV_ERROR>	665	=item C<EV_ERROR>
566		666
567	An unspecified error has occured, the watcher has been stopped. This might	667	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	668	happen because the watcher could not be properly started because libev
569	ran out of memory, a file descriptor was found to be closed or any other	669	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	with the error from read() or write(). This will not work in multithreaded	676	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	677	programs, though, so beware.
578		678
579	=back	679	=back
580		680
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	681	=head2 GENERIC WATCHER FUNCTIONS
582		682
583	In the following description, C<TYPE> stands for the watcher type,	683	In the following description, C<TYPE> stands for the watcher type,
584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.	684	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		685
586	=over 4	686	=over 4
…		…
595	which rolls both calls into one.	695	which rolls both calls into one.
596		696
597	You can reinitialise a watcher at any time as long as it has been stopped	697	You can reinitialise a watcher at any time as long as it has been stopped
598	(or never started) and there are no pending events outstanding.	698	(or never started) and there are no pending events outstanding.
599		699
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	701	int revents)>.
602		702
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	703	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		704
605	This macro initialises the type-specific parts of a watcher. You need to	705	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	740	=item bool ev_is_pending (ev_TYPE *watcher)
641		741
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
643	events but its callback has not yet been invoked). As long as a watcher	743	events but its callback has not yet been invoked). As long as a watcher
644	is pending (but not active) you must not call an init function on it (but	744	is pending (but not active) you must not call an init function on it (but
645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
647		748
648	=item callback = ev_cb (ev_TYPE *watcher)	749	=item callback ev_cb (ev_TYPE *watcher)
649		750
650	Returns the callback currently set on the watcher.	751	Returns the callback currently set on the watcher.
651		752
652	=item ev_cb_set (ev_TYPE *watcher, callback)	753	=item ev_cb_set (ev_TYPE *watcher, callback)
653		754
654	Change the callback. You can change the callback at virtually any time	755	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
656		797
657	=back	798	=back
658		799
659		800
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	822	{
682	struct my_io *w = (struct my_io *)w_;	823	struct my_io *w = (struct my_io *)w_;
683	...	824	...
684	}	825	}
685		826
686	More interesting and less C-conformant ways of catsing your callback type	827	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	828	instead have been omitted.
		829
		830	Another common scenario is having some data structure with multiple
		831	watchers:
		832
		833	struct my_biggy
		834	{
		835	int some_data;
		836	ev_timer t1;
		837	ev_timer t2;
		838	}
		839
		840	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		841	you need to use C<offsetof>:
		842
		843	#include <stddef.h>
		844
		845	static void
		846	t1_cb (EV_P_ struct ev_timer *w, int revents)
		847	{
		848	struct my_biggy big = (struct my_biggy *
		849	(((char *)w) - offsetof (struct my_biggy, t1));
		850	}
		851
		852	static void
		853	t2_cb (EV_P_ struct ev_timer *w, int revents)
		854	{
		855	struct my_biggy big = (struct my_biggy *
		856	(((char *)w) - offsetof (struct my_biggy, t2));
		857	}
688		858
689		859
690	=head1 WATCHER TYPES	860	=head1 WATCHER TYPES
691		861
692	This section describes each watcher in detail, but will not repeat	862	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	863	information given in the last section. Any initialisation/set macros,
		864	functions and members specific to the watcher type are explained.
694		865
		866	Members are additionally marked with either I<[read-only]>, meaning that,
		867	while the watcher is active, you can look at the member and expect some
		868	sensible content, but you must not modify it (you can modify it while the
		869	watcher is stopped to your hearts content), or I<[read-write]>, which
		870	means you can expect it to have some sensible content while the watcher
		871	is active, but you can also modify it. Modifying it may not do something
		872	sensible or take immediate effect (or do anything at all), but libev will
		873	not crash or malfunction in any way.
695		874
		875
696	=head2 C<ev_io> - is this file descriptor readable or writable	876	=head2 C<ev_io> - is this file descriptor readable or writable?
697		877
698	I/O watchers check whether a file descriptor is readable or writable	878	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	879	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	880	would not block the process and writing would at least be able to write
701	condition persists. Remember you can stop the watcher if you don't want to	881	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	882	receiving events as long as the condition persists. Remember you can stop
		883	the watcher if you don't want to act on the event and neither want to
		884	receive future events.
703		885
704	In general you can register as many read and/or write event watchers per	886	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	887	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	888	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	889	required if you know what you are doing).
708		890
709	You have to be careful with dup'ed file descriptors, though. Some backends	891	You have to be careful with dup'ed file descriptors, though. Some backends
710	(the linux epoll backend is a notable example) cannot handle dup'ed file	892	(the linux epoll backend is a notable example) cannot handle dup'ed file
711	descriptors correctly if you register interest in two or more fds pointing	893	descriptors correctly if you register interest in two or more fds pointing
712	to the same underlying file/socket etc. description (that is, they share	894	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	895	the same underlying "file open").
714		896
715	If you must do this, then force the use of a known-to-be-good backend	897	If you must do this, then force the use of a known-to-be-good backend
716	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	899	C<EVBACKEND_POLL>).
718		900
		901	Another thing you have to watch out for is that it is quite easy to
		902	receive "spurious" readyness notifications, that is your callback might
		903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		904	because there is no data. Not only are some backends known to create a
		905	lot of those (for example solaris ports), it is very easy to get into
		906	this situation even with a relatively standard program structure. Thus
		907	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		909
		910	If you cannot run the fd in non-blocking mode (for example you should not
		911	play around with an Xlib connection), then you have to seperately re-test
		912	whether a file descriptor is really ready with a known-to-be good interface
		913	such as poll (fortunately in our Xlib example, Xlib already does this on
		914	its own, so its quite safe to use).
		915
719	=over 4	916	=over 4
720		917
721	=item ev_io_init (ev_io *, callback, int fd, int events)	918	=item ev_io_init (ev_io *, callback, int fd, int events)
722		919
723	=item ev_io_set (ev_io *, int fd, int events)	920	=item ev_io_set (ev_io *, int fd, int events)
724		921
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	922	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
726	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	923	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	924	C<EV_READ | EV_WRITE> to receive the given events.
728		925
729	Please note that most of the more scalable backend mechanisms (for example	926	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	927
731	for file descriptors, so you practically need to use non-blocking I/O (and	928	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	929
733	interface before doing I/O (XLib can do this), or force the use of either	930	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	931
735	problem. Also note that it is quite easy to have your callback invoked	932	The events being watched.
736	when the readyness condition is no longer valid even when employing
737	typical ways of handling events, so its a good idea to use non-blocking
738	I/O unconditionally.
739		933
740	=back	934	=back
741		935
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	936	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	937	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	938	attempt to read a whole line in the callback.
745		939
746	static void	940	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	941	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	942	{
749	ev_io_stop (loop, w);	943	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	950	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	951	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	952	ev_loop (loop, 0);
759		953
760		954
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	955	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		956
763	Timer watchers are simple relative timers that generate an event after a	957	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	958	given time, and optionally repeating in regular intervals after that.
765		959
766	The timers are based on real time, that is, if you register an event that	960	The timers are based on real time, that is, if you register an event that
…		…
801	=item ev_timer_again (loop)	995	=item ev_timer_again (loop)
802		996
803	This will act as if the timer timed out and restart it again if it is	997	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	998	repeating. The exact semantics are:
805		999
		1000	If the timer is pending, its pending status is cleared.
		1001
806	If the timer is started but nonrepeating, stop it.	1002	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1003
808	If the timer is repeating, either start it if necessary (with the repeat	1004	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1005	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1006
811	This sounds a bit complicated, but here is a useful and typical	1007	This sounds a bit complicated, but here is a useful and typical
812	example: Imagine you have a tcp connection and you want a so-called idle	1008	example: Imagine you have a tcp connection and you want a so-called idle
813	timeout, that is, you want to be called when there have been, say, 60	1009	timeout, that is, you want to be called when there have been, say, 60
814	seconds of inactivity on the socket. The easiest way to do this is to	1010	seconds of inactivity on the socket. The easiest way to do this is to
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1011	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
816	time you successfully read or write some data. If you go into an idle	1012	C<ev_timer_again> each time you successfully read or write some data. If
817	state where you do not expect data to travel on the socket, you can stop	1013	you go into an idle state where you do not expect data to travel on the
818	the timer, and again will automatically restart it if need be.	1014	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1015	automatically restart it if need be.
		1016
		1017	That means you can ignore the C<after> value and C<ev_timer_start>
		1018	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1019
		1020	ev_timer_init (timer, callback, 0., 5.);
		1021	ev_timer_again (loop, timer);
		1022	...
		1023	timer->again = 17.;
		1024	ev_timer_again (loop, timer);
		1025	...
		1026	timer->again = 10.;
		1027	ev_timer_again (loop, timer);
		1028
		1029	This is more slightly efficient then stopping/starting the timer each time
		1030	you want to modify its timeout value.
		1031
		1032	=item ev_tstamp repeat [read-write]
		1033
		1034	The current C<repeat> value. Will be used each time the watcher times out
		1035	or C<ev_timer_again> is called and determines the next timeout (if any),
		1036	which is also when any modifications are taken into account.
819		1037
820	=back	1038	=back
821		1039
822	Example: create a timer that fires after 60 seconds.	1040	Example: Create a timer that fires after 60 seconds.
823		1041
824	static void	1042	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1043	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1044	{
827	.. one minute over, w is actually stopped right here	1045	.. one minute over, w is actually stopped right here
…		…
829		1047
830	struct ev_timer mytimer;	1048	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1049	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1050	ev_timer_start (loop, &mytimer);
833		1051
834	Example: create a timeout timer that times out after 10 seconds of	1052	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1053	inactivity.
836		1054
837	static void	1055	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1056	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1057	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1066	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1067	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1068	ev_timer_again (&mytimer);
851		1069
852		1070
853	=head2 C<ev_periodic> - to cron or not to cron	1071	=head2 C<ev_periodic> - to cron or not to cron?
854		1072
855	Periodic watchers are also timers of a kind, but they are very versatile	1073	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1074	(and unfortunately a bit complex).
857		1075
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1076	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
859	but on wallclock time (absolute time). You can tell a periodic watcher	1077	but on wallclock time (absolute time). You can tell a periodic watcher
860	to trigger "at" some specific point in time. For example, if you tell a	1078	to trigger "at" some specific point in time. For example, if you tell a
861	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1079	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
862	+ 10.>) and then reset your system clock to the last year, then it will	1080	+ 10.>) and then reset your system clock to the last year, then it will
863	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1081	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
864	roughly 10 seconds later and of course not if you reset your system time	1082	roughly 10 seconds later).
865	again).
866		1083
867	They can also be used to implement vastly more complex timers, such as	1084	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1085	triggering an event on each midnight, local time or other, complicated,
		1086	rules.
869		1087
870	As with timers, the callback is guarenteed to be invoked only when the	1088	As with timers, the callback is guarenteed to be invoked only when the
871	time (C<at>) has been passed, but if multiple periodic timers become ready	1089	time (C<at>) has been passed, but if multiple periodic timers become ready
872	during the same loop iteration then order of execution is undefined.	1090	during the same loop iteration then order of execution is undefined.
873		1091
…		…
880	Lots of arguments, lets sort it out... There are basically three modes of	1098	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1099	operation, and we will explain them from simplest to complex:
882		1100
883	=over 4	1101	=over 4
884		1102
885	=item * absolute timer (interval = reschedule_cb = 0)	1103	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1104
887	In this configuration the watcher triggers an event at the wallclock time	1105	In this configuration the watcher triggers an event at the wallclock time
888	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1106	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
889	that is, if it is to be run at January 1st 2011 then it will run when the	1107	that is, if it is to be run at January 1st 2011 then it will run when the
890	system time reaches or surpasses this time.	1108	system time reaches or surpasses this time.
891		1109
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1110	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1111
894	In this mode the watcher will always be scheduled to time out at the next	1112	In this mode the watcher will always be scheduled to time out at the next
895	C<at + N * interval> time (for some integer N) and then repeat, regardless	1113	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1114	and then repeat, regardless of any time jumps.
897		1115
898	This can be used to create timers that do not drift with respect to system	1116	This can be used to create timers that do not drift with respect to system
899	time:	1117	time:
900		1118
901	ev_periodic_set (&periodic, 0., 3600., 0);	1119	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1125
908	Another way to think about it (for the mathematically inclined) is that	1126	Another way to think about it (for the mathematically inclined) is that
909	C<ev_periodic> will try to run the callback in this mode at the next possible	1127	C<ev_periodic> will try to run the callback in this mode at the next possible
910	time where C<time = at (mod interval)>, regardless of any time jumps.	1128	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1129
		1130	For numerical stability it is preferable that the C<at> value is near
		1131	C<ev_now ()> (the current time), but there is no range requirement for
		1132	this value.
		1133
912	=item * manual reschedule mode (reschedule_cb = callback)	1134	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1135
914	In this mode the values for C<interval> and C<at> are both being	1136	In this mode the values for C<interval> and C<at> are both being
915	ignored. Instead, each time the periodic watcher gets scheduled, the	1137	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1138	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1139	current time as second argument.
918		1140
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1141	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
920	ever, or make any event loop modifications>. If you need to stop it,	1142	ever, or make any event loop modifications>. If you need to stop it,
921	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1143	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1144	starting an C<ev_prepare> watcher, which is legal).
923		1145
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1146	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1147	ev_tstamp now)>, e.g.:
926		1148
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1149	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1172	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1173	when you changed some parameters or the reschedule callback would return
952	a different time than the last time it was called (e.g. in a crond like	1174	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1175	program when the crontabs have changed).
954		1176
		1177	=item ev_tstamp offset [read-write]
		1178
		1179	When repeating, this contains the offset value, otherwise this is the
		1180	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1181
		1182	Can be modified any time, but changes only take effect when the periodic
		1183	timer fires or C<ev_periodic_again> is being called.
		1184
		1185	=item ev_tstamp interval [read-write]
		1186
		1187	The current interval value. Can be modified any time, but changes only
		1188	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1189	called.
		1190
		1191	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1192
		1193	The current reschedule callback, or C<0>, if this functionality is
		1194	switched off. Can be changed any time, but changes only take effect when
		1195	the periodic timer fires or C<ev_periodic_again> is being called.
		1196
955	=back	1197	=back
956		1198
957	Example: call a callback every hour, or, more precisely, whenever the	1199	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1200	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1201	potentially a lot of jittering, but good long-term stability.
960		1202
961	static void	1203	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1204	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1208
967	struct ev_periodic hourly_tick;	1209	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1210	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1211	ev_periodic_start (loop, &hourly_tick);
970		1212
971	Example: the same as above, but use a reschedule callback to do it:	1213	Example: The same as above, but use a reschedule callback to do it:
972		1214
973	#include <math.h>	1215	#include <math.h>
974		1216
975	static ev_tstamp	1217	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1218	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1220	return fmod (now, 3600.) + 3600.;
979	}	1221	}
980		1222
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1223	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1224
983	Example: call a callback every hour, starting now:	1225	Example: Call a callback every hour, starting now:
984		1226
985	struct ev_periodic hourly_tick;	1227	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1228	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1229	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1230	ev_periodic_start (loop, &hourly_tick);
989		1231
990		1232
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1233	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1234
993	Signal watchers will trigger an event when the process receives a specific	1235	Signal watchers will trigger an event when the process receives a specific
994	signal one or more times. Even though signals are very asynchronous, libev	1236	signal one or more times. Even though signals are very asynchronous, libev
995	will try it's best to deliver signals synchronously, i.e. as part of the	1237	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1238	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1251	=item ev_signal_set (ev_signal *, int signum)
1010		1252
1011	Configures the watcher to trigger on the given signal number (usually one	1253	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1254	of the C<SIGxxx> constants).
1013		1255
		1256	=item int signum [read-only]
		1257
		1258	The signal the watcher watches out for.
		1259
1014	=back	1260	=back
1015		1261
1016		1262
1017	=head2 C<ev_child> - wait for pid status changes	1263	=head2 C<ev_child> - watch out for process status changes
1018		1264
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1265	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1266	some child status changes (most typically when a child of yours dies).
1021		1267
1022	=over 4	1268	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1276	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1277	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1278	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1279	process causing the status change.
1034		1280
		1281	=item int pid [read-only]
		1282
		1283	The process id this watcher watches out for, or C<0>, meaning any process id.
		1284
		1285	=item int rpid [read-write]
		1286
		1287	The process id that detected a status change.
		1288
		1289	=item int rstatus [read-write]
		1290
		1291	The process exit/trace status caused by C<rpid> (see your systems
		1292	C<waitpid> and C<sys/wait.h> documentation for details).
		1293
1035	=back	1294	=back
1036		1295
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1296	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1297
1039	static void	1298	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1299	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1300	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1301	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1304	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1305	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1306	ev_signal_start (loop, &sigint_cb);
1048		1307
1049		1308
		1309	=head2 C<ev_stat> - did the file attributes just change?
		1310
		1311	This watches a filesystem path for attribute changes. That is, it calls
		1312	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1313	compared to the last time, invoking the callback if it did.
		1314
		1315	The path does not need to exist: changing from "path exists" to "path does
		1316	not exist" is a status change like any other. The condition "path does
		1317	not exist" is signified by the C<st_nlink> field being zero (which is
		1318	otherwise always forced to be at least one) and all the other fields of
		1319	the stat buffer having unspecified contents.
		1320
		1321	The path I<should> be absolute and I<must not> end in a slash. If it is
		1322	relative and your working directory changes, the behaviour is undefined.
		1323
		1324	Since there is no standard to do this, the portable implementation simply
		1325	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1326	can specify a recommended polling interval for this case. If you specify
		1327	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1328	unspecified default> value will be used (which you can expect to be around
		1329	five seconds, although this might change dynamically). Libev will also
		1330	impose a minimum interval which is currently around C<0.1>, but thats
		1331	usually overkill.
		1332
		1333	This watcher type is not meant for massive numbers of stat watchers,
		1334	as even with OS-supported change notifications, this can be
		1335	resource-intensive.
		1336
		1337	At the time of this writing, only the Linux inotify interface is
		1338	implemented (implementing kqueue support is left as an exercise for the
		1339	reader). Inotify will be used to give hints only and should not change the
		1340	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1341	to fall back to regular polling again even with inotify, but changes are
		1342	usually detected immediately, and if the file exists there will be no
		1343	polling.
		1344
		1345	=over 4
		1346
		1347	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1348
		1349	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1350
		1351	Configures the watcher to wait for status changes of the given
		1352	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1353	be detected and should normally be specified as C<0> to let libev choose
		1354	a suitable value. The memory pointed to by C<path> must point to the same
		1355	path for as long as the watcher is active.
		1356
		1357	The callback will be receive C<EV_STAT> when a change was detected,
		1358	relative to the attributes at the time the watcher was started (or the
		1359	last change was detected).
		1360
		1361	=item ev_stat_stat (ev_stat *)
		1362
		1363	Updates the stat buffer immediately with new values. If you change the
		1364	watched path in your callback, you could call this fucntion to avoid
		1365	detecting this change (while introducing a race condition). Can also be
		1366	useful simply to find out the new values.
		1367
		1368	=item ev_statdata attr [read-only]
		1369
		1370	The most-recently detected attributes of the file. Although the type is of
		1371	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1372	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1373	was some error while C<stat>ing the file.
		1374
		1375	=item ev_statdata prev [read-only]
		1376
		1377	The previous attributes of the file. The callback gets invoked whenever
		1378	C<prev> != C<attr>.
		1379
		1380	=item ev_tstamp interval [read-only]
		1381
		1382	The specified interval.
		1383
		1384	=item const char *path [read-only]
		1385
		1386	The filesystem path that is being watched.
		1387
		1388	=back
		1389
		1390	Example: Watch C</etc/passwd> for attribute changes.
		1391
		1392	static void
		1393	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1394	{
		1395	/* /etc/passwd changed in some way */
		1396	if (w->attr.st_nlink)
		1397	{
		1398	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1399	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1400	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1401	}
		1402	else
		1403	/* you shalt not abuse printf for puts */
		1404	puts ("wow, /etc/passwd is not there, expect problems. "
		1405	"if this is windows, they already arrived\n");
		1406	}
		1407
		1408	...
		1409	ev_stat passwd;
		1410
		1411	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1412	ev_stat_start (loop, &passwd);
		1413
		1414
1050	=head2 C<ev_idle> - when you've got nothing better to do	1415	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1416
1052	Idle watchers trigger events when there are no other events are pending	1417	Idle watchers trigger events when no other events of the same or higher
1053	(prepare, check and other idle watchers do not count). That is, as long	1418	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1419	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1420
1056	watchers are being called again and again, once per event loop iteration -	1421	That is, as long as your process is busy handling sockets or timeouts
		1422	(or even signals, imagine) of the same or higher priority it will not be
		1423	triggered. But when your process is idle (or only lower-priority watchers
		1424	are pending), the idle watchers are being called once per event loop
1057	until stopped, that is, or your process receives more events and becomes	1425	iteration - until stopped, that is, or your process receives more events
1058	busy.	1426	and becomes busy again with higher priority stuff.
1059		1427
1060	The most noteworthy effect is that as long as any idle watchers are	1428	The most noteworthy effect is that as long as any idle watchers are
1061	active, the process will not block when waiting for new events.	1429	active, the process will not block when waiting for new events.
1062		1430
1063	Apart from keeping your process non-blocking (which is a useful	1431	Apart from keeping your process non-blocking (which is a useful
…		…
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1441	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1442	believe me.
1075		1443
1076	=back	1444	=back
1077		1445
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1446	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1447	callback, free it. Also, use no error checking, as usual.
1080		1448
1081	static void	1449	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1450	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1451	{
1084	free (w);	1452	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1457	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1458	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1459	ev_idle_start (loop, idle_cb);
1092		1460
1093		1461
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1462	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1463
1096	Prepare and check watchers are usually (but not always) used in tandem:	1464	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1465	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1466	afterwards.
1099		1467
		1468	You I<must not> call C<ev_loop> or similar functions that enter
		1469	the current event loop from either C<ev_prepare> or C<ev_check>
		1470	watchers. Other loops than the current one are fine, however. The
		1471	rationale behind this is that you do not need to check for recursion in
		1472	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1473	C<ev_check> so if you have one watcher of each kind they will always be
		1474	called in pairs bracketing the blocking call.
		1475
1100	Their main purpose is to integrate other event mechanisms into libev and	1476	Their main purpose is to integrate other event mechanisms into libev and
1101	their use is somewhat advanced. This could be used, for example, to track	1477	their use is somewhat advanced. This could be used, for example, to track
1102	variable changes, implement your own watchers, integrate net-snmp or a	1478	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1479	coroutine library and lots more. They are also occasionally useful if
		1480	you cache some data and want to flush it before blocking (for example,
		1481	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1482	watcher).
1104		1483
1105	This is done by examining in each prepare call which file descriptors need	1484	This is done by examining in each prepare call which file descriptors need
1106	to be watched by the other library, registering C<ev_io> watchers for	1485	to be watched by the other library, registering C<ev_io> watchers for
1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1486	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1108	provide just this functionality). Then, in the check watcher you check for	1487	provide just this functionality). Then, in the check watcher you check for
…		…
1118	with priority higher than or equal to the event loop and one coroutine	1497	with priority higher than or equal to the event loop and one coroutine
1119	of lower priority, but only once, using idle watchers to keep the event	1498	of lower priority, but only once, using idle watchers to keep the event
1120	loop from blocking if lower-priority coroutines are active, thus mapping	1499	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1500	low-priority coroutines to idle/background tasks).
1122		1501
		1502	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1503	priority, to ensure that they are being run before any other watchers
		1504	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1505	too) should not activate ("feed") events into libev. While libev fully
		1506	supports this, they will be called before other C<ev_check> watchers did
		1507	their job. As C<ev_check> watchers are often used to embed other event
		1508	loops those other event loops might be in an unusable state until their
		1509	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1510	others).
		1511
1123	=over 4	1512	=over 4
1124		1513
1125	=item ev_prepare_init (ev_prepare *, callback)	1514	=item ev_prepare_init (ev_prepare *, callback)
1126		1515
1127	=item ev_check_init (ev_check *, callback)	1516	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1519	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1520	macros, but using them is utterly, utterly and completely pointless.
1132		1521
1133	=back	1522	=back
1134		1523
1135	Example: *TODO*.	1524	There are a number of principal ways to embed other event loops or modules
		1525	into libev. Here are some ideas on how to include libadns into libev
		1526	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1527	use for an actually working example. Another Perl module named C<EV::Glib>
		1528	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1529	into the Glib event loop).
1136		1530
		1531	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1532	and in a check watcher, destroy them and call into libadns. What follows
		1533	is pseudo-code only of course. This requires you to either use a low
		1534	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1535	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1536
		1537	static ev_io iow [nfd];
		1538	static ev_timer tw;
		1539
		1540	static void
		1541	io_cb (ev_loop *loop, ev_io *w, int revents)
		1542	{
		1543	}
		1544
		1545	// create io watchers for each fd and a timer before blocking
		1546	static void
		1547	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1548	{
		1549	int timeout = 3600000;
		1550	struct pollfd fds [nfd];
		1551	// actual code will need to loop here and realloc etc.
		1552	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1553
		1554	/* the callback is illegal, but won't be called as we stop during check */
		1555	ev_timer_init (&tw, 0, timeout * 1e-3);
		1556	ev_timer_start (loop, &tw);
		1557
		1558	// create one ev_io per pollfd
		1559	for (int i = 0; i < nfd; ++i)
		1560	{
		1561	ev_io_init (iow + i, io_cb, fds [i].fd,
		1562	((fds [i].events & POLLIN ? EV_READ : 0)
		1563	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1564
		1565	fds [i].revents = 0;
		1566	ev_io_start (loop, iow + i);
		1567	}
		1568	}
		1569
		1570	// stop all watchers after blocking
		1571	static void
		1572	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1573	{
		1574	ev_timer_stop (loop, &tw);
		1575
		1576	for (int i = 0; i < nfd; ++i)
		1577	{
		1578	// set the relevant poll flags
		1579	// could also call adns_processreadable etc. here
		1580	struct pollfd *fd = fds + i;
		1581	int revents = ev_clear_pending (iow + i);
		1582	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1583	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1584
		1585	// now stop the watcher
		1586	ev_io_stop (loop, iow + i);
		1587	}
		1588
		1589	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1590	}
		1591
		1592	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1593	in the prepare watcher and would dispose of the check watcher.
		1594
		1595	Method 3: If the module to be embedded supports explicit event
		1596	notification (adns does), you can also make use of the actual watcher
		1597	callbacks, and only destroy/create the watchers in the prepare watcher.
		1598
		1599	static void
		1600	timer_cb (EV_P_ ev_timer *w, int revents)
		1601	{
		1602	adns_state ads = (adns_state)w->data;
		1603	update_now (EV_A);
		1604
		1605	adns_processtimeouts (ads, &tv_now);
		1606	}
		1607
		1608	static void
		1609	io_cb (EV_P_ ev_io *w, int revents)
		1610	{
		1611	adns_state ads = (adns_state)w->data;
		1612	update_now (EV_A);
		1613
		1614	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1615	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1616	}
		1617
		1618	// do not ever call adns_afterpoll
		1619
		1620	Method 4: Do not use a prepare or check watcher because the module you
		1621	want to embed is too inflexible to support it. Instead, youc na override
		1622	their poll function. The drawback with this solution is that the main
		1623	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1624	this.
		1625
		1626	static gint
		1627	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1628	{
		1629	int got_events = 0;
		1630
		1631	for (n = 0; n < nfds; ++n)
		1632	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1633
		1634	if (timeout >= 0)
		1635	// create/start timer
		1636
		1637	// poll
		1638	ev_loop (EV_A_ 0);
		1639
		1640	// stop timer again
		1641	if (timeout >= 0)
		1642	ev_timer_stop (EV_A_ &to);
		1643
		1644	// stop io watchers again - their callbacks should have set
		1645	for (n = 0; n < nfds; ++n)
		1646	ev_io_stop (EV_A_ iow [n]);
		1647
		1648	return got_events;
		1649	}
		1650
		1651
1138	=head2 C<ev_embed> - when one backend isn't enough	1652	=head2 C<ev_embed> - when one backend isn't enough...
1139		1653
1140	This is a rather advanced watcher type that lets you embed one event loop	1654	This is a rather advanced watcher type that lets you embed one event loop
1141	into another (currently only C<ev_io> events are supported in the embedded	1655	into another (currently only C<ev_io> events are supported in the embedded
1142	loop, other types of watchers might be handled in a delayed or incorrect	1656	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1657	fashion and must not be used).
…		…
1221		1735
1222	Make a single, non-blocking sweep over the embedded loop. This works	1736	Make a single, non-blocking sweep over the embedded loop. This works
1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1737	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1738	apropriate way for embedded loops.
1225		1739
		1740	=item struct ev_loop *loop [read-only]
		1741
		1742	The embedded event loop.
		1743
		1744	=back
		1745
		1746
		1747	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1748
		1749	Fork watchers are called when a C<fork ()> was detected (usually because
		1750	whoever is a good citizen cared to tell libev about it by calling
		1751	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1752	event loop blocks next and before C<ev_check> watchers are being called,
		1753	and only in the child after the fork. If whoever good citizen calling
		1754	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1755	handlers will be invoked, too, of course.
		1756
		1757	=over 4
		1758
		1759	=item ev_fork_init (ev_signal *, callback)
		1760
		1761	Initialises and configures the fork watcher - it has no parameters of any
		1762	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1763	believe me.
		1764
1226	=back	1765	=back
1227		1766
1228		1767
1229	=head1 OTHER FUNCTIONS	1768	=head1 OTHER FUNCTIONS
1230		1769
…		…
1318		1857
1319	To use it,	1858	To use it,
1320		1859
1321	#include <ev++.h>	1860	#include <ev++.h>
1322		1861
1323	(it is not installed by default). This automatically includes F<ev.h>	1862	This automatically includes F<ev.h> and puts all of its definitions (many
1324	and puts all of its definitions (many of them macros) into the global	1863	of them macros) into the global namespace. All C++ specific things are
1325	namespace. All C++ specific things are put into the C<ev> namespace.	1864	put into the C<ev> namespace. It should support all the same embedding
		1865	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		1866
1327	It should support all the same embedding options as F<ev.h>, most notably	1867	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	1868	classes add (compared to plain C-style watchers) is the event loop pointer
		1869	that the watcher is associated with (or no additional members at all if
		1870	you disable C<EV_MULTIPLICITY> when embedding libev).
		1871
		1872	Currently, functions, and static and non-static member functions can be
		1873	used as callbacks. Other types should be easy to add as long as they only
		1874	need one additional pointer for context. If you need support for other
		1875	types of functors please contact the author (preferably after implementing
		1876	it).
1329		1877
1330	Here is a list of things available in the C<ev> namespace:	1878	Here is a list of things available in the C<ev> namespace:
1331		1879
1332	=over 4	1880	=over 4
1333		1881
…		…
1349		1897
1350	All of those classes have these methods:	1898	All of those classes have these methods:
1351		1899
1352	=over 4	1900	=over 4
1353		1901
1354	=item ev::TYPE::TYPE (object *, object::method *)	1902	=item ev::TYPE::TYPE ()
1355		1903
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	1904	=item ev::TYPE::TYPE (struct ev_loop *)
1357		1905
1358	=item ev::TYPE::~TYPE	1906	=item ev::TYPE::~TYPE
1359		1907
1360	The constructor takes a pointer to an object and a method pointer to	1908	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	1909	with. If it is omitted, it will use C<EV_DEFAULT>.
1362	C<ev_init> for you, which means you have to call the C<set> method	1910
1363	before starting it. If you do not specify a loop then the constructor	1911	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	1912	C<set> method before starting it.
		1913
		1914	It will not set a callback, however: You have to call the templated C<set>
		1915	method to set a callback before you can start the watcher.
		1916
		1917	(The reason why you have to use a method is a limitation in C++ which does
		1918	not allow explicit template arguments for constructors).
1365		1919
1366	The destructor automatically stops the watcher if it is active.	1920	The destructor automatically stops the watcher if it is active.
		1921
		1922	=item w->set<class, &class::method> (object *)
		1923
		1924	This method sets the callback method to call. The method has to have a
		1925	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1926	first argument and the C<revents> as second. The object must be given as
		1927	parameter and is stored in the C<data> member of the watcher.
		1928
		1929	This method synthesizes efficient thunking code to call your method from
		1930	the C callback that libev requires. If your compiler can inline your
		1931	callback (i.e. it is visible to it at the place of the C<set> call and
		1932	your compiler is good :), then the method will be fully inlined into the
		1933	thunking function, making it as fast as a direct C callback.
		1934
		1935	Example: simple class declaration and watcher initialisation
		1936
		1937	struct myclass
		1938	{
		1939	void io_cb (ev::io &w, int revents) { }
		1940	}
		1941
		1942	myclass obj;
		1943	ev::io iow;
		1944	iow.set <myclass, &myclass::io_cb> (&obj);
		1945
		1946	=item w->set<function> (void *data = 0)
		1947
		1948	Also sets a callback, but uses a static method or plain function as
		1949	callback. The optional C<data> argument will be stored in the watcher's
		1950	C<data> member and is free for you to use.
		1951
		1952	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1953
		1954	See the method-C<set> above for more details.
		1955
		1956	Example:
		1957
		1958	static void io_cb (ev::io &w, int revents) { }
		1959	iow.set <io_cb> ();
1367		1960
1368	=item w->set (struct ev_loop *)	1961	=item w->set (struct ev_loop *)
1369		1962
1370	Associates a different C<struct ev_loop> with this watcher. You can only	1963	Associates a different C<struct ev_loop> with this watcher. You can only
1371	do this when the watcher is inactive (and not pending either).	1964	do this when the watcher is inactive (and not pending either).
1372		1965
1373	=item w->set ([args])	1966	=item w->set ([args])
1374		1967
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1968	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1376	called at least once. Unlike the C counterpart, an active watcher gets	1969	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	1970	automatically stopped and restarted when reconfiguring it with this
		1971	method.
1378		1972
1379	=item w->start ()	1973	=item w->start ()
1380		1974
1381	Starts the watcher. Note that there is no C<loop> argument as the	1975	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	1976	constructor already stores the event loop.
1383		1977
1384	=item w->stop ()	1978	=item w->stop ()
1385		1979
1386	Stops the watcher if it is active. Again, no C<loop> argument.	1980	Stops the watcher if it is active. Again, no C<loop> argument.
1387		1981
…		…
1392		1986
1393	=item w->sweep () C<ev::embed> only	1987	=item w->sweep () C<ev::embed> only
1394		1988
1395	Invokes C<ev_embed_sweep>.	1989	Invokes C<ev_embed_sweep>.
1396		1990
		1991	=item w->update () C<ev::stat> only
		1992
		1993	Invokes C<ev_stat_stat>.
		1994
1397	=back	1995	=back
1398		1996
1399	=back	1997	=back
1400		1998
1401	Example: Define a class with an IO and idle watcher, start one of them in	1999	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1408		2006
1409	myclass ();	2007	myclass ();
1410	}	2008	}
1411		2009
1412	myclass::myclass (int fd)	2010	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	2011	{
		2012	io .set <myclass, &myclass::io_cb > (this);
		2013	idle.set <myclass, &myclass::idle_cb> (this);
		2014
1416	io.start (fd, ev::READ);	2015	io.start (fd, ev::READ);
1417	}	2016	}
1418		2017
		2018
		2019	=head1 MACRO MAGIC
		2020
		2021	Libev can be compiled with a variety of options, the most fundemantal is
		2022	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		2023	callbacks have an initial C<struct ev_loop *> argument.
		2024
		2025	To make it easier to write programs that cope with either variant, the
		2026	following macros are defined:
		2027
		2028	=over 4
		2029
		2030	=item C<EV_A>, C<EV_A_>
		2031
		2032	This provides the loop I<argument> for functions, if one is required ("ev
		2033	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2034	C<EV_A_> is used when other arguments are following. Example:
		2035
		2036	ev_unref (EV_A);
		2037	ev_timer_add (EV_A_ watcher);
		2038	ev_loop (EV_A_ 0);
		2039
		2040	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2041	which is often provided by the following macro.
		2042
		2043	=item C<EV_P>, C<EV_P_>
		2044
		2045	This provides the loop I<parameter> for functions, if one is required ("ev
		2046	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2047	C<EV_P_> is used when other parameters are following. Example:
		2048
		2049	// this is how ev_unref is being declared
		2050	static void ev_unref (EV_P);
		2051
		2052	// this is how you can declare your typical callback
		2053	static void cb (EV_P_ ev_timer *w, int revents)
		2054
		2055	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2056	suitable for use with C<EV_A>.
		2057
		2058	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2059
		2060	Similar to the other two macros, this gives you the value of the default
		2061	loop, if multiple loops are supported ("ev loop default").
		2062
		2063	=back
		2064
		2065	Example: Declare and initialise a check watcher, utilising the above
		2066	macros so it will work regardless of whether multiple loops are supported
		2067	or not.
		2068
		2069	static void
		2070	check_cb (EV_P_ ev_timer *w, int revents)
		2071	{
		2072	ev_check_stop (EV_A_ w);
		2073	}
		2074
		2075	ev_check check;
		2076	ev_check_init (&check, check_cb);
		2077	ev_check_start (EV_DEFAULT_ &check);
		2078	ev_loop (EV_DEFAULT_ 0);
		2079
		2080	=head1 EMBEDDING
		2081
		2082	Libev can (and often is) directly embedded into host
		2083	applications. Examples of applications that embed it include the Deliantra
		2084	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2085	and rxvt-unicode.
		2086
		2087	The goal is to enable you to just copy the neecssary files into your
		2088	source directory without having to change even a single line in them, so
		2089	you can easily upgrade by simply copying (or having a checked-out copy of
		2090	libev somewhere in your source tree).
		2091
		2092	=head2 FILESETS
		2093
		2094	Depending on what features you need you need to include one or more sets of files
		2095	in your app.
		2096
		2097	=head3 CORE EVENT LOOP
		2098
		2099	To include only the libev core (all the C<ev_*> functions), with manual
		2100	configuration (no autoconf):
		2101
		2102	#define EV_STANDALONE 1
		2103	#include "ev.c"
		2104
		2105	This will automatically include F<ev.h>, too, and should be done in a
		2106	single C source file only to provide the function implementations. To use
		2107	it, do the same for F<ev.h> in all files wishing to use this API (best
		2108	done by writing a wrapper around F<ev.h> that you can include instead and
		2109	where you can put other configuration options):
		2110
		2111	#define EV_STANDALONE 1
		2112	#include "ev.h"
		2113
		2114	Both header files and implementation files can be compiled with a C++
		2115	compiler (at least, thats a stated goal, and breakage will be treated
		2116	as a bug).
		2117
		2118	You need the following files in your source tree, or in a directory
		2119	in your include path (e.g. in libev/ when using -Ilibev):
		2120
		2121	ev.h
		2122	ev.c
		2123	ev_vars.h
		2124	ev_wrap.h
		2125
		2126	ev_win32.c required on win32 platforms only
		2127
		2128	ev_select.c only when select backend is enabled (which is enabled by default)
		2129	ev_poll.c only when poll backend is enabled (disabled by default)
		2130	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2131	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2132	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2133
		2134	F<ev.c> includes the backend files directly when enabled, so you only need
		2135	to compile this single file.
		2136
		2137	=head3 LIBEVENT COMPATIBILITY API
		2138
		2139	To include the libevent compatibility API, also include:
		2140
		2141	#include "event.c"
		2142
		2143	in the file including F<ev.c>, and:
		2144
		2145	#include "event.h"
		2146
		2147	in the files that want to use the libevent API. This also includes F<ev.h>.
		2148
		2149	You need the following additional files for this:
		2150
		2151	event.h
		2152	event.c
		2153
		2154	=head3 AUTOCONF SUPPORT
		2155
		2156	Instead of using C<EV_STANDALONE=1> and providing your config in
		2157	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2158	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2159	include F<config.h> and configure itself accordingly.
		2160
		2161	For this of course you need the m4 file:
		2162
		2163	libev.m4
		2164
		2165	=head2 PREPROCESSOR SYMBOLS/MACROS
		2166
		2167	Libev can be configured via a variety of preprocessor symbols you have to define
		2168	before including any of its files. The default is not to build for multiplicity
		2169	and only include the select backend.
		2170
		2171	=over 4
		2172
		2173	=item EV_STANDALONE
		2174
		2175	Must always be C<1> if you do not use autoconf configuration, which
		2176	keeps libev from including F<config.h>, and it also defines dummy
		2177	implementations for some libevent functions (such as logging, which is not
		2178	supported). It will also not define any of the structs usually found in
		2179	F<event.h> that are not directly supported by the libev core alone.
		2180
		2181	=item EV_USE_MONOTONIC
		2182
		2183	If defined to be C<1>, libev will try to detect the availability of the
		2184	monotonic clock option at both compiletime and runtime. Otherwise no use
		2185	of the monotonic clock option will be attempted. If you enable this, you
		2186	usually have to link against librt or something similar. Enabling it when
		2187	the functionality isn't available is safe, though, althoguh you have
		2188	to make sure you link against any libraries where the C<clock_gettime>
		2189	function is hiding in (often F<-lrt>).
		2190
		2191	=item EV_USE_REALTIME
		2192
		2193	If defined to be C<1>, libev will try to detect the availability of the
		2194	realtime clock option at compiletime (and assume its availability at
		2195	runtime if successful). Otherwise no use of the realtime clock option will
		2196	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2197	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2198	in the description of C<EV_USE_MONOTONIC>, though.
		2199
		2200	=item EV_USE_SELECT
		2201
		2202	If undefined or defined to be C<1>, libev will compile in support for the
		2203	C<select>(2) backend. No attempt at autodetection will be done: if no
		2204	other method takes over, select will be it. Otherwise the select backend
		2205	will not be compiled in.
		2206
		2207	=item EV_SELECT_USE_FD_SET
		2208
		2209	If defined to C<1>, then the select backend will use the system C<fd_set>
		2210	structure. This is useful if libev doesn't compile due to a missing
		2211	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2212	exotic systems. This usually limits the range of file descriptors to some
		2213	low limit such as 1024 or might have other limitations (winsocket only
		2214	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2215	influence the size of the C<fd_set> used.
		2216
		2217	=item EV_SELECT_IS_WINSOCKET
		2218
		2219	When defined to C<1>, the select backend will assume that
		2220	select/socket/connect etc. don't understand file descriptors but
		2221	wants osf handles on win32 (this is the case when the select to
		2222	be used is the winsock select). This means that it will call
		2223	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2224	it is assumed that all these functions actually work on fds, even
		2225	on win32. Should not be defined on non-win32 platforms.
		2226
		2227	=item EV_USE_POLL
		2228
		2229	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2230	backend. Otherwise it will be enabled on non-win32 platforms. It
		2231	takes precedence over select.
		2232
		2233	=item EV_USE_EPOLL
		2234
		2235	If defined to be C<1>, libev will compile in support for the Linux
		2236	C<epoll>(7) backend. Its availability will be detected at runtime,
		2237	otherwise another method will be used as fallback. This is the
		2238	preferred backend for GNU/Linux systems.
		2239
		2240	=item EV_USE_KQUEUE
		2241
		2242	If defined to be C<1>, libev will compile in support for the BSD style
		2243	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2244	otherwise another method will be used as fallback. This is the preferred
		2245	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2246	supports some types of fds correctly (the only platform we found that
		2247	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2248	not be used unless explicitly requested. The best way to use it is to find
		2249	out whether kqueue supports your type of fd properly and use an embedded
		2250	kqueue loop.
		2251
		2252	=item EV_USE_PORT
		2253
		2254	If defined to be C<1>, libev will compile in support for the Solaris
		2255	10 port style backend. Its availability will be detected at runtime,
		2256	otherwise another method will be used as fallback. This is the preferred
		2257	backend for Solaris 10 systems.
		2258
		2259	=item EV_USE_DEVPOLL
		2260
		2261	reserved for future expansion, works like the USE symbols above.
		2262
		2263	=item EV_USE_INOTIFY
		2264
		2265	If defined to be C<1>, libev will compile in support for the Linux inotify
		2266	interface to speed up C<ev_stat> watchers. Its actual availability will
		2267	be detected at runtime.
		2268
		2269	=item EV_H
		2270
		2271	The name of the F<ev.h> header file used to include it. The default if
		2272	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2273	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2274
		2275	=item EV_CONFIG_H
		2276
		2277	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2278	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2279	C<EV_H>, above.
		2280
		2281	=item EV_EVENT_H
		2282
		2283	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2284	of how the F<event.h> header can be found.
		2285
		2286	=item EV_PROTOTYPES
		2287
		2288	If defined to be C<0>, then F<ev.h> will not define any function
		2289	prototypes, but still define all the structs and other symbols. This is
		2290	occasionally useful if you want to provide your own wrapper functions
		2291	around libev functions.
		2292
		2293	=item EV_MULTIPLICITY
		2294
		2295	If undefined or defined to C<1>, then all event-loop-specific functions
		2296	will have the C<struct ev_loop *> as first argument, and you can create
		2297	additional independent event loops. Otherwise there will be no support
		2298	for multiple event loops and there is no first event loop pointer
		2299	argument. Instead, all functions act on the single default loop.
		2300
		2301	=item EV_MINPRI
		2302
		2303	=item EV_MAXPRI
		2304
		2305	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2306	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2307	provide for more priorities by overriding those symbols (usually defined
		2308	to be C<-2> and C<2>, respectively).
		2309
		2310	When doing priority-based operations, libev usually has to linearly search
		2311	all the priorities, so having many of them (hundreds) uses a lot of space
		2312	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2313	fine.
		2314
		2315	If your embedding app does not need any priorities, defining these both to
		2316	C<0> will save some memory and cpu.
		2317
		2318	=item EV_PERIODIC_ENABLE
		2319
		2320	If undefined or defined to be C<1>, then periodic timers are supported. If
		2321	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2322	code.
		2323
		2324	=item EV_IDLE_ENABLE
		2325
		2326	If undefined or defined to be C<1>, then idle watchers are supported. If
		2327	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2328	code.
		2329
		2330	=item EV_EMBED_ENABLE
		2331
		2332	If undefined or defined to be C<1>, then embed watchers are supported. If
		2333	defined to be C<0>, then they are not.
		2334
		2335	=item EV_STAT_ENABLE
		2336
		2337	If undefined or defined to be C<1>, then stat watchers are supported. If
		2338	defined to be C<0>, then they are not.
		2339
		2340	=item EV_FORK_ENABLE
		2341
		2342	If undefined or defined to be C<1>, then fork watchers are supported. If
		2343	defined to be C<0>, then they are not.
		2344
		2345	=item EV_MINIMAL
		2346
		2347	If you need to shave off some kilobytes of code at the expense of some
		2348	speed, define this symbol to C<1>. Currently only used for gcc to override
		2349	some inlining decisions, saves roughly 30% codesize of amd64.
		2350
		2351	=item EV_PID_HASHSIZE
		2352
		2353	C<ev_child> watchers use a small hash table to distribute workload by
		2354	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2355	than enough. If you need to manage thousands of children you might want to
		2356	increase this value (I<must> be a power of two).
		2357
		2358	=item EV_INOTIFY_HASHSIZE
		2359
		2360	C<ev_staz> watchers use a small hash table to distribute workload by
		2361	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2362	usually more than enough. If you need to manage thousands of C<ev_stat>
		2363	watchers you might want to increase this value (I<must> be a power of
		2364	two).
		2365
		2366	=item EV_COMMON
		2367
		2368	By default, all watchers have a C<void *data> member. By redefining
		2369	this macro to a something else you can include more and other types of
		2370	members. You have to define it each time you include one of the files,
		2371	though, and it must be identical each time.
		2372
		2373	For example, the perl EV module uses something like this:
		2374
		2375	#define EV_COMMON \
		2376	SV *self; /* contains this struct */ \
		2377	SV *cb_sv, *fh /* note no trailing ";" */
		2378
		2379	=item EV_CB_DECLARE (type)
		2380
		2381	=item EV_CB_INVOKE (watcher, revents)
		2382
		2383	=item ev_set_cb (ev, cb)
		2384
		2385	Can be used to change the callback member declaration in each watcher,
		2386	and the way callbacks are invoked and set. Must expand to a struct member
		2387	definition and a statement, respectively. See the F<ev.v> header file for
		2388	their default definitions. One possible use for overriding these is to
		2389	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2390	method calls instead of plain function calls in C++.
		2391
		2392	=head2 EXAMPLES
		2393
		2394	For a real-world example of a program the includes libev
		2395	verbatim, you can have a look at the EV perl module
		2396	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2397	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2398	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2399	will be compiled. It is pretty complex because it provides its own header
		2400	file.
		2401
		2402	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2403	that everybody includes and which overrides some configure choices:
		2404
		2405	#define EV_MINIMAL 1
		2406	#define EV_USE_POLL 0
		2407	#define EV_MULTIPLICITY 0
		2408	#define EV_PERIODIC_ENABLE 0
		2409	#define EV_STAT_ENABLE 0
		2410	#define EV_FORK_ENABLE 0
		2411	#define EV_CONFIG_H <config.h>
		2412	#define EV_MINPRI 0
		2413	#define EV_MAXPRI 0
		2414
		2415	#include "ev++.h"
		2416
		2417	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2418
		2419	#include "ev_cpp.h"
		2420	#include "ev.c"
		2421
		2422
		2423	=head1 COMPLEXITIES
		2424
		2425	In this section the complexities of (many of) the algorithms used inside
		2426	libev will be explained. For complexity discussions about backends see the
		2427	documentation for C<ev_default_init>.
		2428
		2429	All of the following are about amortised time: If an array needs to be
		2430	extended, libev needs to realloc and move the whole array, but this
		2431	happens asymptotically never with higher number of elements, so O(1) might
		2432	mean it might do a lengthy realloc operation in rare cases, but on average
		2433	it is much faster and asymptotically approaches constant time.
		2434
		2435	=over 4
		2436
		2437	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2438
		2439	This means that, when you have a watcher that triggers in one hour and
		2440	there are 100 watchers that would trigger before that then inserting will
		2441	have to skip those 100 watchers.
		2442
		2443	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2444
		2445	That means that for changing a timer costs less than removing/adding them
		2446	as only the relative motion in the event queue has to be paid for.
		2447
		2448	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2449
		2450	These just add the watcher into an array or at the head of a list.
		2451	=item Stopping check/prepare/idle watchers: O(1)
		2452
		2453	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2454
		2455	These watchers are stored in lists then need to be walked to find the
		2456	correct watcher to remove. The lists are usually short (you don't usually
		2457	have many watchers waiting for the same fd or signal).
		2458
		2459	=item Finding the next timer per loop iteration: O(1)
		2460
		2461	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2462
		2463	A change means an I/O watcher gets started or stopped, which requires
		2464	libev to recalculate its status (and possibly tell the kernel).
		2465
		2466	=item Activating one watcher: O(1)
		2467
		2468	=item Priority handling: O(number_of_priorities)
		2469
		2470	Priorities are implemented by allocating some space for each
		2471	priority. When doing priority-based operations, libev usually has to
		2472	linearly search all the priorities.
		2473
		2474	=back
		2475
		2476
1419	=head1 AUTHOR	2477	=head1 AUTHOR
1420		2478
1421	Marc Lehmann <libev@schmorp.de>.	2479	Marc Lehmann <libev@schmorp.de>.
1422		2480

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