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

Comparing libev/ev.pod (file contents):
Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC vs.
Revision 1.228 by root, Sat Mar 28 08:22:30 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
389		409
390	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	418	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	419	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	420	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
405		428
406	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	430	all kernel versions tested so far.
408		431
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	433	C<EVBACKEND_POLL>.
411		434
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		436
414	Kqueue deserves special mention, as at the time of this writing, it was	437	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	440	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	441	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	442	without API changes to existing programs. For this reason it's not being
		443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
420		446
421	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
424		450
425	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
431		458
432	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
433		460
434	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
440		467
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	470	C<NOTE_EOF>.
444		471
…		…
464	might perform better.	491	might perform better.
465		492
466	On the positive side, with the exception of the spurious readiness	493	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	494	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	495	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	496	OS-specific backends (I vastly prefer correctness over speed hacks).
470		497
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
473		500
474	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	557	for example).
531		558
532	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
535		562
536	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	658	the loop.
632		659
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	661	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	662	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	663	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	664	user-registered callback will be called), and will return after one
638	iteration of the loop.	665	iteration of the loop.
639		666
640	This is useful if you are waiting for some external event in conjunction	667	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	668	with something not expressible using other libev watchers (i.e. "roll your
…		…
710	respectively).	737	respectively).
711		738
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	740	running when nothing else is active.
714		741
715	struct ev_signal exitsig;	742	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	745	evf_unref (loop);
719		746
720	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
…		…
768	they fire on, say, one-second boundaries only.	795	they fire on, say, one-second boundaries only.
769		796
770	=item ev_loop_verify (loop)	797	=item ev_loop_verify (loop)
771		798
772	This function only does something when C<EV_VERIFY> support has been	799	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	800	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	801	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	802	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	803	error and call C<abort ()>.
777		804
778	This can be used to catch bugs inside libev itself: under normal	805	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	809	=back
783		810
784		811
785	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
786		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
		817
787	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
790		821
791	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	822	static void my_cb (struct ev_loop loop, ev_io w, int revents)
792	{	823	{
793	ev_io_stop (w);	824	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
795	}	826	}
796		827
797	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
798	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
799	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
802	ev_loop (loop, 0);	836	ev_loop (loop, 0);
803		837
804	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		844
808	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	847	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	849	is readable and/or writable).
813		850
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
818		855
819	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		860
824	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
827		864
828	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
830	third argument.	867	third argument.
831		868
…		…
894	=item C<EV_ERROR>	931	=item C<EV_ERROR>
895		932
896	An unspecified error has occurred, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
899	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
901		942
902	Libev will usually signal a few "dummy" events together with an error, for	943	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	944	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	945	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	946	the error from read() or write(). This will not work in multi-threaded
…		…
908		949
909	=back	950	=back
910		951
911	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
912		953
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	954	=over 4
917		955
918	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
919		957
920	This macro initialises the generic portion of a watcher. The contents	958	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	963	which rolls both calls into one.
926		964
927	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
929		967
930	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	968	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
931	int revents)>.	969	int revents)>.
932		970
933	Example: Initialise an C<ev_io> watcher in two steps.	971	Example: Initialise an C<ev_io> watcher in two steps.
934		972
935	ev_io w;	973	ev_io w;
…		…
969		1007
970	ev_io_start (EV_DEFAULT_UC, &w);	1008	ev_io_start (EV_DEFAULT_UC, &w);
971		1009
972	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1010	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
973		1011
974	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
975	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1020
981	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
982		1022
983	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1026	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
1028		1068
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1030	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
1031	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
1032		1072
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1074
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1058	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
1059	data:	1099	data:
1060		1100
1061	struct my_io	1101	struct my_io
1062	{	1102	{
1063	struct ev_io io;	1103	ev_io io;
1064	int otherfd;	1104	int otherfd;
1065	void *somedata;	1105	void *somedata;
1066	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
1067	};	1107	};
1068		1108
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1112
1073	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1114	can cast it back to your own type:
1075		1115
1076	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1116	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1077	{	1117	{
1078	struct my_io w = (struct my_io )w_;	1118	struct my_io w = (struct my_io )w_;
1079	...	1119	...
1080	}	1120	}
1081		1121
…		…
1099	programmers):	1139	programmers):
1100		1140
1101	#include <stddef.h>	1141	#include <stddef.h>
1102		1142
1103	static void	1143	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1145	{
1106	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1148	}
1109		1149
1110	static void	1150	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1152	{
1113	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1155	}
1116		1156
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1254		1294
1255	static void	1295	static void
1256	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1296	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1257	{	1297	{
1258	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1300	}
1261		1301
1262	...	1302	...
1263	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1268		1308
1269		1309
…		…
1280		1320
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1321	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1322	passed, but if multiple timers become ready during the same loop iteration
1283	then order of execution is undefined.	1323	then order of execution is undefined.
1284		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
1285	=head3 The special problem of time updates	1500	=head3 The special problem of time updates
1286		1501
1287	Establishing the current time is a costly operation (it usually takes at	1502	Establishing the current time is a costly operation (it usually takes at
1288	least two system calls): EV therefore updates its idea of the current	1503	least two system calls): EV therefore updates its idea of the current
1289	time only before and after C<ev_loop> collects new events, which causes a	1504	time only before and after C<ev_loop> collects new events, which causes a
…		…
1332	If the timer is started but non-repeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1548
1334	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1551
1337	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1338	example: Imagine you have a TCP connection and you want a so-called idle	1553	usage example.
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346
1347	That means you can ignore the C<after> value and C<ev_timer_start>
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1349
1350	ev_timer_init (timer, callback, 0., 5.);
1351	ev_timer_again (loop, timer);
1352	...
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358
1359	This is more slightly efficient then stopping/starting the timer each time
1360	you want to modify its timeout value.
1361
1362	Note, however, that it is often even more efficient to remember the
1363	time of the last activity and let the timer time-out naturally. In the
1364	callback, you then check whether the time-out is real, or, if there was
1365	some activity, you reschedule the watcher to time-out in "last_activity +
1366	timeout - ev_now ()" seconds.
1367		1554
1368	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1369		1556
1370	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1563	=head3 Examples
1377		1564
1378	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1379		1566
1380	static void	1567	static void
1381	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1568	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1382	{	1569	{
1383	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1384	}	1571	}
1385		1572
1386	struct ev_timer mytimer;	1573	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1389		1576
1390	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1578	inactivity.
1392		1579
1393	static void	1580	static void
1394	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1581	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1395	{	1582	{
1396	.. ten seconds without any activity	1583	.. ten seconds without any activity
1397	}	1584	}
1398		1585
1399	struct ev_timer mytimer;	1586	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1403		1590
1404	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1410		1597
1411	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1413		1600
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	1602	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	1603	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1604	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	1605	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	1606	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		1607
		1608	You can tell a periodic watcher to trigger after some specific point
		1609	in time: for example, if you tell a periodic watcher to trigger "in 10
		1610	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1611	not a delay) and then reset your system clock to January of the previous
		1612	year, then it will take a year or more to trigger the event (unlike an
		1613	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1614	it, as it uses a relative timeout).
		1615
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	1616	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	1617	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	1618	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1619	those cannot react to time jumps.
1426		1620
1427	As with timers, the callback is guaranteed to be invoked only when the	1621	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	1622	point in time where it is supposed to trigger has passed, but if multiple
1429	during the same loop iteration, then order of execution is undefined.	1623	periodic timers become ready during the same loop iteration, then order of
		1624	execution is undefined.
1430		1625
1431	=head3 Watcher-Specific Functions and Data Members	1626	=head3 Watcher-Specific Functions and Data Members
1432		1627
1433	=over 4	1628	=over 4
1434		1629
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1630	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1631
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1632	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1633
1439	Lots of arguments, lets sort it out... There are basically three modes of	1634	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	1635	operation, and we will explain them from simplest to most complex:
1441		1636
1442	=over 4	1637	=over 4
1443		1638
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1639	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		1640
1446	In this configuration the watcher triggers an event after the wall clock	1641	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	1642	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1643	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	1644	will be stopped and invoked when the system clock reaches or surpasses
		1645	this point in time.
1450		1646
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1647	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		1648
1453	In this mode the watcher will always be scheduled to time out at the next	1649	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	1650	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	1651	negative) and then repeat, regardless of any time jumps. The C<offset>
		1652	argument is merely an offset into the C<interval> periods.
1456		1653
1457	This can be used to create timers that do not drift with respect to the	1654	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	1655	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	1656	hour, on the hour (with respect to UTC):
1460		1657
1461	ev_periodic_set (&periodic, 0., 3600., 0);	1658	ev_periodic_set (&periodic, 0., 3600., 0);
1462		1659
1463	This doesn't mean there will always be 3600 seconds in between triggers,	1660	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	1661	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	1662	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	1663	by 3600.
1467		1664
1468	Another way to think about it (for the mathematically inclined) is that	1665	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	1666	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	1667	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		1668
1472	For numerical stability it is preferable that the C<at> value is near	1669	For numerical stability it is preferable that the C<offset> value is near
1473	C<ev_now ()> (the current time), but there is no range requirement for	1670	C<ev_now ()> (the current time), but there is no range requirement for
1474	this value, and in fact is often specified as zero.	1671	this value, and in fact is often specified as zero.
1475		1672
1476	Note also that there is an upper limit to how often a timer can fire (CPU	1673	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	1674	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	1675	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	1676	millisecond (if the OS supports it and the machine is fast enough).
1480		1677
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1678	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		1679
1483	In this mode the values for C<interval> and C<at> are both being	1680	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	1681	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	1682	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	1683	current time as second argument.
1487		1684
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1685	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	1686	or make ANY other event loop modifications whatsoever, unless explicitly
		1687	allowed by documentation here>.
1490		1688
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1689	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1690	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	1691	only event loop modification you are allowed to do).
1494		1692
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1693	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	1694	*w, ev_tstamp now)>, e.g.:
1497		1695
		1696	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1697	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	1698	{
1500	return now + 60.;	1699	return now + 60.;
1501	}	1700	}
1502		1701
1503	It must return the next time to trigger, based on the passed time value	1702	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	1722	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	1723	program when the crontabs have changed).
1525		1724
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	1725	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		1726
1528	When active, returns the absolute time that the watcher is supposed to	1727	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	1728	to trigger next. This is not the same as the C<offset> argument to
		1729	C<ev_periodic_set>, but indeed works even in interval and manual
		1730	rescheduling modes.
1530		1731
1531	=item ev_tstamp offset [read-write]	1732	=item ev_tstamp offset [read-write]
1532		1733
1533	When repeating, this contains the offset value, otherwise this is the	1734	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1735	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1736	although libev might modify this value for better numerical stability).
1535		1737
1536	Can be modified any time, but changes only take effect when the periodic	1738	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	1739	timer fires or C<ev_periodic_again> is being called.
1538		1740
1539	=item ev_tstamp interval [read-write]	1741	=item ev_tstamp interval [read-write]
1540		1742
1541	The current interval value. Can be modified any time, but changes only	1743	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	1744	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	1745	called.
1544		1746
1545	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1747	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1546		1748
1547	The current reschedule callback, or C<0>, if this functionality is	1749	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	1750	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	1751	the periodic timer fires or C<ev_periodic_again> is being called.
1550		1752
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	1757	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	1758	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	1759	potentially a lot of jitter, but good long-term stability.
1558		1760
1559	static void	1761	static void
1560	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1762	clock_cb (struct ev_loop loop, ev_io w, int revents)
1561	{	1763	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	1764	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	1765	}
1564		1766
1565	struct ev_periodic hourly_tick;	1767	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1768	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	1769	ev_periodic_start (loop, &hourly_tick);
1568		1770
1569	Example: The same as above, but use a reschedule callback to do it:	1771	Example: The same as above, but use a reschedule callback to do it:
1570		1772
1571	#include <math.h>	1773	#include <math.h>
1572		1774
1573	static ev_tstamp	1775	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1776	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	1777	{
1576	return now + (3600. - fmod (now, 3600.));	1778	return now + (3600. - fmod (now, 3600.));
1577	}	1779	}
1578		1780
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1781	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		1782
1581	Example: Call a callback every hour, starting now:	1783	Example: Call a callback every hour, starting now:
1582		1784
1583	struct ev_periodic hourly_tick;	1785	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	1786	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	1787	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	1788	ev_periodic_start (loop, &hourly_tick);
1587		1789
1588		1790
…		…
1630	=head3 Examples	1832	=head3 Examples
1631		1833
1632	Example: Try to exit cleanly on SIGINT.	1834	Example: Try to exit cleanly on SIGINT.
1633		1835
1634	static void	1836	static void
1635	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1837	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1636	{	1838	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	1839	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	1840	}
1639		1841
1640	struct ev_signal signal_watcher;	1842	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1843	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	1844	ev_signal_start (loop, &signal_watcher);
1643		1845
1644		1846
1645	=head2 C<ev_child> - watch out for process status changes	1847	=head2 C<ev_child> - watch out for process status changes
…		…
1720	its completion.	1922	its completion.
1721		1923
1722	ev_child cw;	1924	ev_child cw;
1723		1925
1724	static void	1926	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	1927	child_cb (EV_P_ ev_child *w, int revents)
1726	{	1928	{
1727	ev_child_stop (EV_A_ w);	1929	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1930	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	1931	}
1730		1932
…		…
1745		1947
1746		1948
1747	=head2 C<ev_stat> - did the file attributes just change?	1949	=head2 C<ev_stat> - did the file attributes just change?
1748		1950
1749	This watches a file system path for attribute changes. That is, it calls	1951	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	1952	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	1953	and sees if it changed compared to the last time, invoking the callback if
		1954	it did.
1752		1955
1753	The path does not need to exist: changing from "path exists" to "path does	1956	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	1957	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	1958	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	1959	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	1960	least one) and all the other fields of the stat buffer having unspecified
		1961	contents.
1758		1962
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	1963	The path I<must not> end in a slash or contain special components such as
		1964	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	1965	your working directory changes, then the behaviour is undefined.
1761		1966
1762	Since there is no standard kernel interface to do this, the portable	1967	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	1968	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	1969	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	1970	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	1971	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	1972	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	1973	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	1974	currently around C<0.1>, but that's usually overkill.
1770		1975
1771	This watcher type is not meant for massive numbers of stat watchers,	1976	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	1977	as even with OS-supported change notifications, this can be
1773	resource-intensive.	1978	resource-intensive.
1774		1979
1775	At the time of this writing, the only OS-specific interface implemented	1980	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	1981	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	1982	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	1983	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		1984
1780	=head3 ABI Issues (Largefile Support)	1985	=head3 ABI Issues (Largefile Support)
1781		1986
1782	Libev by default (unless the user overrides this) uses the default	1987	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	1988	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	1989	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	1990	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	1991	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	1992	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	1993	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	1994	most noticeably displayed with ev_stat and large file support.
1790		1995
1791	The solution for this is to lobby your distribution maker to make large	1996	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	1997	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	1998	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	1999	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2000	default compilation environment.
1796		2001
1797	=head3 Inotify and Kqueue	2002	=head3 Inotify and Kqueue
1798		2003
1799	When C<inotify (7)> support has been compiled into libev (generally only	2004	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2005	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2006	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2007	watcher is being started.
1803		2008
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2009	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2010	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2011	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2012	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2013	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2014	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2015	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2016	xfs are fully working) libev usually gets away without polling.
1809		2017
1810	There is no support for kqueue, as apparently it cannot be used to	2018	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2019	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2020	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2021	etc. is difficult.
1814		2022
		2023	=head3 C<stat ()> is a synchronous operation
		2024
		2025	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2026	the process. The exception are C<ev_stat> watchers - those call C<stat
		2027	()>, which is a synchronous operation.
		2028
		2029	For local paths, this usually doesn't matter: unless the system is very
		2030	busy or the intervals between stat's are large, a stat call will be fast,
		2031	as the path data is usually in memory already (except when starting the
		2032	watcher).
		2033
		2034	For networked file systems, calling C<stat ()> can block an indefinite
		2035	time due to network issues, and even under good conditions, a stat call
		2036	often takes multiple milliseconds.
		2037
		2038	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2039	paths, although this is fully supported by libev.
		2040
1815	=head3 The special problem of stat time resolution	2041	=head3 The special problem of stat time resolution
1816		2042
1817	The C<stat ()> system call only supports full-second resolution portably, and	2043	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2044	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2045	still only support whole seconds.
1820		2046
1821	That means that, if the time is the only thing that changes, you can	2047	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2048	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2049	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2050	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1967		2193
1968	=head3 Watcher-Specific Functions and Data Members	2194	=head3 Watcher-Specific Functions and Data Members
1969		2195
1970	=over 4	2196	=over 4
1971		2197
1972	=item ev_idle_init (ev_signal *, callback)	2198	=item ev_idle_init (ev_idle *, callback)
1973		2199
1974	Initialises and configures the idle watcher - it has no parameters of any	2200	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2201	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2202	believe me.
1977		2203
…		…
1981		2207
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2208	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2209	callback, free it. Also, use no error checking, as usual.
1984		2210
1985	static void	2211	static void
1986	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2212	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1987	{	2213	{
1988	free (w);	2214	free (w);
1989	// now do something you wanted to do when the program has	2215	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2216	// no longer anything immediate to do.
1991	}	2217	}
1992		2218
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2219	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2220	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2221	ev_idle_start (loop, idle_cb);
1996		2222
1997		2223
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2224	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2079		2305
2080	static ev_io iow [nfd];	2306	static ev_io iow [nfd];
2081	static ev_timer tw;	2307	static ev_timer tw;
2082		2308
2083	static void	2309	static void
2084	io_cb (ev_loop loop, ev_io w, int revents)	2310	io_cb (struct ev_loop loop, ev_io w, int revents)
2085	{	2311	{
2086	}	2312	}
2087		2313
2088	// create io watchers for each fd and a timer before blocking	2314	// create io watchers for each fd and a timer before blocking
2089	static void	2315	static void
2090	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2316	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2091	{	2317	{
2092	int timeout = 3600000;	2318	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2319	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2320	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2321	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2110	}	2336	}
2111	}	2337	}
2112		2338
2113	// stop all watchers after blocking	2339	// stop all watchers after blocking
2114	static void	2340	static void
2115	adns_check_cb (ev_loop loop, ev_check w, int revents)	2341	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2116	{	2342	{
2117	ev_timer_stop (loop, &tw);	2343	ev_timer_stop (loop, &tw);
2118		2344
2119	for (int i = 0; i < nfd; ++i)	2345	for (int i = 0; i < nfd; ++i)
2120	{	2346	{
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	2442	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	2443	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	2444	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	2445	the rest in a second one, and embed the second one in the first.
2220		2446
2221	As long as the watcher is active, the callback will be invoked every time	2447	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	2448	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2449	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	2450	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	2451	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	2452	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		2453
2229	As long as the watcher is started it will automatically handle events. The	2454	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	2455	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		2456
2234	Also, there have not currently been made special provisions for forking:	2457	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2458	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	2459	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	2460	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		2461
2240	Unfortunately, not all backends are embeddable: only the ones returned by	2462	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2463	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	2464	portable one.
2243		2465
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2510	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2511	used).
2290		2512
2291	struct ev_loop *loop_hi = ev_default_init (0);	2513	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2514	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2515	ev_embed embed;
2294		2516
2295	// see if there is a chance of getting one that works	2517	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2518	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2519	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2520	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2534	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2535	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2536
2315	struct ev_loop *loop = ev_default_init (0);	2537	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2538	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2539	ev_embed embed;
2318		2540
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2541	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2542	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2543	{
2322	ev_embed_init (&embed, 0, loop_socket);	2544	ev_embed_init (&embed, 0, loop_socket);
…		…
2463	=over 4	2685	=over 4
2464		2686
2465	=item ev_async_init (ev_async *, callback)	2687	=item ev_async_init (ev_async *, callback)
2466		2688
2467	Initialises and configures the async watcher - it has no parameters of any	2689	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2690	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	2691	trust me.
2470		2692
2471	=item ev_async_send (loop, ev_async *)	2693	=item ev_async_send (loop, ev_async *)
2472		2694
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2695	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2696	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	2697	C<ev_feed_event>, this call is safe to do from other threads, signal or
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2698	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2477	section below on what exactly this means).	2699	section below on what exactly this means).
2478		2700
		2701	Note that, as with other watchers in libev, multiple events might get
		2702	compressed into a single callback invocation (another way to look at this
		2703	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2704	reset when the event loop detects that).
		2705
2479	This call incurs the overhead of a system call only once per loop iteration,	2706	This call incurs the overhead of a system call only once per event loop
2480	so while the overhead might be noticeable, it doesn't apply to repeated	2707	iteration, so while the overhead might be noticeable, it doesn't apply to
2481	calls to C<ev_async_send>.	2708	repeated calls to C<ev_async_send> for the same event loop.
2482		2709
2483	=item bool = ev_async_pending (ev_async *)	2710	=item bool = ev_async_pending (ev_async *)
2484		2711
2485	Returns a non-zero value when C<ev_async_send> has been called on the	2712	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	2713	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2716	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	2717	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	2718	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	2719	quickly check whether invoking the loop might be a good idea.
2493		2720
2494	Not that this does I<not> check whether the watcher itself is pending, only	2721	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	2722	only whether it has been requested to make this watcher pending: there
		2723	is a time window between the event loop checking and resetting the async
		2724	notification, and the callback being invoked.
2496		2725
2497	=back	2726	=back
2498		2727
2499		2728
2500	=head1 OTHER FUNCTIONS	2729	=head1 OTHER FUNCTIONS
…		…
2536	/* doh, nothing entered */;	2765	/* doh, nothing entered */;
2537	}	2766	}
2538		2767
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2768	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		2769
2541	=item ev_feed_event (ev_loop , watcher , int revents)	2770	=item ev_feed_event (struct ev_loop , watcher , int revents)
2542		2771
2543	Feeds the given event set into the event loop, as if the specified event	2772	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an	2773	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).	2774	initialised but not necessarily started event watcher).
2546		2775
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2776	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2548		2777
2549	Feed an event on the given fd, as if a file descriptor backend detected	2778	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	2779	the given events it.
2551		2780
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	2781	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2553		2782
2554	Feed an event as if the given signal occurred (C<loop> must be the default	2783	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	2784	loop!).
2556		2785
2557	=back	2786	=back
…		…
2678	}	2907	}
2679		2908
2680	myclass obj;	2909	myclass obj;
2681	ev::io iow;	2910	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	2911	iow.set <myclass, &myclass::io_cb> (&obj);
		2912
		2913	=item w->set (object *)
		2914
		2915	This is an B<experimental> feature that might go away in a future version.
		2916
		2917	This is a variation of a method callback - leaving out the method to call
		2918	will default the method to C<operator ()>, which makes it possible to use
		2919	functor objects without having to manually specify the C<operator ()> all
		2920	the time. Incidentally, you can then also leave out the template argument
		2921	list.
		2922
		2923	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2924	int revents)>.
		2925
		2926	See the method-C<set> above for more details.
		2927
		2928	Example: use a functor object as callback.
		2929
		2930	struct myfunctor
		2931	{
		2932	void operator() (ev::io &w, int revents)
		2933	{
		2934	...
		2935	}
		2936	}
		2937
		2938	myfunctor f;
		2939
		2940	ev::io w;
		2941	w.set (&f);
2683		2942
2684	=item w->set<function> (void *data = 0)	2943	=item w->set<function> (void *data = 0)
2685		2944
2686	Also sets a callback, but uses a static method or plain function as	2945	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	2946	callback. The optional C<data> argument will be stored in the watcher's
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	3033	L<http://software.schmorp.de/pkg/EV>.
2775		3034
2776	=item Python	3035	=item Python
2777		3036
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3037	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	3038	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		3039
2785	=item Ruby	3040	=item Ruby
2786		3041
2787	Tony Arcieri has written a ruby extension that offers access to a subset	3042	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	3043	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	3044	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	3045	L<http://rev.rubyforge.org/>.
2791		3046
		3047	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3048	makes rev work even on mingw.
		3049
		3050	=item Haskell
		3051
		3052	A haskell binding to libev is available at
		3053	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3054
2792	=item D	3055	=item D
2793		3056
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3057	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3058	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3059
		3060	=item Ocaml
		3061
		3062	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3063	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2796		3064
2797	=back	3065	=back
2798		3066
2799		3067
2800	=head1 MACRO MAGIC	3068	=head1 MACRO MAGIC
…		…
2901		3169
2902	#define EV_STANDALONE 1	3170	#define EV_STANDALONE 1
2903	#include "ev.h"	3171	#include "ev.h"
2904		3172
2905	Both header files and implementation files can be compiled with a C++	3173	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	3174	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3175	as a bug).
2908		3176
2909	You need the following files in your source tree, or in a directory	3177	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	3178	in your include path (e.g. in libev/ when using -Ilibev):
2911		3179
…		…
2967	keeps libev from including F<config.h>, and it also defines dummy	3235	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	3236	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	3237	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	3238	F<event.h> that are not directly supported by the libev core alone.
2971		3239
		3240	In stanbdalone mode, libev will still try to automatically deduce the
		3241	configuration, but has to be more conservative.
		3242
2972	=item EV_USE_MONOTONIC	3243	=item EV_USE_MONOTONIC
2973		3244
2974	If defined to be C<1>, libev will try to detect the availability of the	3245	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	3246	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	3247	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	3248	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	3249	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	3250	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	3251	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		3252
2982	=item EV_USE_REALTIME	3253	=item EV_USE_REALTIME
2983		3254
2984	If defined to be C<1>, libev will try to detect the availability of the	3255	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	3256	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	3257	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3258	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3259	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3260	correctness. See the note about libraries in the description of
		3261	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3262	C<EV_USE_CLOCK_SYSCALL>.
		3263
		3264	=item EV_USE_CLOCK_SYSCALL
		3265
		3266	If defined to be C<1>, libev will try to use a direct syscall instead
		3267	of calling the system-provided C<clock_gettime> function. This option
		3268	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3269	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3270	programs needlessly. Using a direct syscall is slightly slower (in
		3271	theory), because no optimised vdso implementation can be used, but avoids
		3272	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3273	higher, as it simplifies linking (no need for C<-lrt>).
2990		3274
2991	=item EV_USE_NANOSLEEP	3275	=item EV_USE_NANOSLEEP
2992		3276
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3277	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	3278	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		3294
3011	=item EV_SELECT_USE_FD_SET	3295	=item EV_SELECT_USE_FD_SET
3012		3296
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	3297	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	3298	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3299	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	3300	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	3301	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3302	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	3303	configures the maximum size of the C<fd_set>.
3020		3304
3021	=item EV_SELECT_IS_WINSOCKET	3305	=item EV_SELECT_IS_WINSOCKET
3022		3306
3023	When defined to C<1>, the select backend will assume that	3307	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	3308	select/socket/connect etc. don't understand file descriptors but
…		…
3383	loop, as long as you don't confuse yourself). The only exception is that	3667	loop, as long as you don't confuse yourself). The only exception is that
3384	you must not do this from C<ev_periodic> reschedule callbacks.	3668	you must not do this from C<ev_periodic> reschedule callbacks.
3385		3669
3386	Care has been taken to ensure that libev does not keep local state inside	3670	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3671	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	3672	they do not call any callbacks.
3389		3673
3390	=head2 COMPILER WARNINGS	3674	=head2 COMPILER WARNINGS
3391		3675
3392	Depending on your compiler and compiler settings, you might get no or a	3676	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	3677	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	3711	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	3712	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	3713	==2274== still reachable: 256 bytes in 1 blocks.
3430		3714
3431	Then there is no memory leak, just as memory accounted to global variables	3715	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	3716	is not a memleak - the memory is still being referenced, and didn't leak.
3433		3717
3434	Similarly, under some circumstances, valgrind might report kernel bugs	3718	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3719	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	3720	although an acceptable workaround has been found here), or it might be
3437	confused.	3721	confused.
…		…
3675	=back	3959	=back
3676		3960
3677		3961
3678	=head1 AUTHOR	3962	=head1 AUTHOR
3679		3963
3680	Marc Lehmann <libev@schmorp.de>.	3964	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		3965

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Comparing libev/ev.pod (file contents): Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC vs. Revision 1.228 by root, Sat Mar 28 08:22:30 2009 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC vs.
Revision 1.228 by root, Sat Mar 28 08:22:30 2009 UTC