[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 1.211 by root, Mon Nov 3 14:34:16 2008 UTC

…		…
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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	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,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		385
382	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	390
387	cases and requiring a system call per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
389		407
390	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	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	410	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	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
395		413	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		414
400	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	416	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	417	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	418	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
405		422
406	While nominally embeddable in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	424	all kernel versions tested so far.
408		425
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	427	C<EVBACKEND_POLL>.
411		428
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		430
414	Kqueue deserves special mention, as at the time of this writing, it was	431	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	432	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	433	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	434	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	435	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.	436	without API changes to existing programs. For this reason it's not being
		437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		439	system like NetBSD.
420		440
421	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	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.	443	the target platform). See C<ev_embed> watchers for more info.
424		444
425	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
431		452
432	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
433		454
434	While nominally embeddable in other event loops, this doesn't work	455	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	456	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	485	might perform better.
465		486
466	On the positive side, with the exception of the spurious readiness	487	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	488	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	489	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	490	OS-specific backends (I vastly prefer correctness over speed hacks).
470		491
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	493	C<EVBACKEND_POLL>.
473		494
474	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	551	for example).
531		552
532	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
535		556
536	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	652	the loop.
632		653
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	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	658	user-registered callback will be called), and will return after one
638	iteration of the loop.	659	iteration of the loop.
639		660
640	This is useful if you are waiting for some external event in conjunction	661	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	662	with something not expressible using other libev watchers (i.e. "roll your
…		…
710	respectively).	731	respectively).
711		732
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	734	running when nothing else is active.
714		735
715	struct ev_signal exitsig;	736	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	739	evf_unref (loop);
719		740
720	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
…		…
768	they fire on, say, one-second boundaries only.	789	they fire on, say, one-second boundaries only.
769		790
770	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
771		792
772	This function only does something when C<EV_VERIFY> support has been	793	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	794	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	795	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	796	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	797	error and call C<abort ()>.
777		798
778	This can be used to catch bugs inside libev itself: under normal	799	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	803	=back
783		804
784		805
785	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
786		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
787	A watcher is a structure that you create and register to record your	812	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	813	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:	814	become readable, you would create an C<ev_io> watcher for that:
790		815
791	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	816	static void my_cb (struct ev_loop loop, ev_io w, int revents)
792	{	817	{
793	ev_io_stop (w);	818	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
795	}	820	}
796		821
797	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
798	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
799	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
802	ev_loop (loop, 0);	830	ev_loop (loop, 0);
803		831
804	As you can see, you are responsible for allocating the memory for your	832	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,	833	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		838
808	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	840	(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	841	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	842	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	843	is readable and/or writable).
813		844
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	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	846	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	847	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
818		849
819	To make the watcher actually watch out for events, you have to start it	850	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	851	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	852	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		854
824	As long as your watcher is active (has been started but not stopped) you	855	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	856	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
827		858
828	Each and every callback receives the event loop pointer as first, the	859	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	860	registered watcher structure as second, and a bitset of received events as
830	third argument.	861	third argument.
831		862
…		…
894	=item C<EV_ERROR>	925	=item C<EV_ERROR>
895		926
896	An unspecified error has occurred, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	928	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	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
899	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
901		936
902	Libev will usually signal a few "dummy" events together with an error, for	937	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	938	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	939	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	940	the error from read() or write(). This will not work in multi-threaded
…		…
908		943
909	=back	944	=back
910		945
911	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
912		947
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	948	=over 4
917		949
918	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
919		951
920	This macro initialises the generic portion of a watcher. The contents	952	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	957	which rolls both calls into one.
926		958
927	You can reinitialise a watcher at any time as long as it has been stopped	959	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.	960	(or never started) and there are no pending events outstanding.
929		961
930	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	962	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
931	int revents)>.	963	int revents)>.
932		964
933	Example: Initialise an C<ev_io> watcher in two steps.	965	Example: Initialise an C<ev_io> watcher in two steps.
934		966
935	ev_io w;	967	ev_io w;
…		…
969		1001
970	ev_io_start (EV_DEFAULT_UC, &w);	1002	ev_io_start (EV_DEFAULT_UC, &w);
971		1003
972	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1004	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
973		1005
974	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
975	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1010	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	1011	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	1012	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.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1014
981	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
982		1016
983	Returns a true value iff the watcher is active (i.e. it has been started	1017	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	1018	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	1060	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 :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
1028		1062
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	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	1064	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.	1065	or might not have been clamped to the valid range.
1032		1066
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1068
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	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	1070	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	1092	member, you can also "subclass" the watcher type and provide your own
1059	data:	1093	data:
1060		1094
1061	struct my_io	1095	struct my_io
1062	{	1096	{
1063	struct ev_io io;	1097	ev_io io;
1064	int otherfd;	1098	int otherfd;
1065	void *somedata;	1099	void *somedata;
1066	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
1067	};	1101	};
1068		1102
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1106
1073	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1108	can cast it back to your own type:
1075		1109
1076	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1110	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1077	{	1111	{
1078	struct my_io w = (struct my_io )w_;	1112	struct my_io w = (struct my_io )w_;
1079	...	1113	...
1080	}	1114	}
1081		1115
…		…
1099	programmers):	1133	programmers):
1100		1134
1101	#include <stddef.h>	1135	#include <stddef.h>
1102		1136
1103	static void	1137	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1139	{
1106	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1142	}
1109		1143
1110	static void	1144	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1146	{
1113	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1149	}
1116		1150
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	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	1286	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1254		1288
1255	static void	1289	static void
1256	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1290	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1257	{	1291	{
1258	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1294	}
1261		1295
1262	...	1296	...
1263	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1268		1302
1269		1303
…		…
1280		1314
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1315	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	1316	passed, but if multiple timers become ready during the same loop iteration
1283	then order of execution is undefined.	1317	then order of execution is undefined.
1284		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
1285	=head3 The special problem of time updates	1494	=head3 The special problem of time updates
1286		1495
1287	Establishing the current time is a costly operation (it usually takes at	1496	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	1497	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	1498	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).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1542
1334	If the timer is repeating, either start it if necessary (with the	1543	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.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1545
1337	This sounds a bit complicated, but here is a useful and typical	1546	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	1547	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		1548
1368	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1369		1550
1370	The current C<repeat> value. Will be used each time the watcher times out	1551	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),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1557	=head3 Examples
1377		1558
1378	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1379		1560
1380	static void	1561	static void
1381	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1562	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1382	{	1563	{
1383	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1384	}	1565	}
1385		1566
1386	struct ev_timer mytimer;	1567	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1389		1570
1390	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1572	inactivity.
1392		1573
1393	static void	1574	static void
1394	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1575	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1395	{	1576	{
1396	.. ten seconds without any activity	1577	.. ten seconds without any activity
1397	}	1578	}
1398		1579
1399	struct ev_timer mytimer;	1580	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1403		1584
1404	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
…		…
1490		1671
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	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	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1494		1675
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1497		1678
		1679	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	1681	{
1500	return now + 60.;	1682	return now + 60.;
1501	}	1683	}
1502		1684
1503	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1540		1722
1541	The current interval value. Can be modified any time, but changes only	1723	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	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	1725	called.
1544		1726
1545	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1546		1728
1547	The current reschedule callback, or C<0>, if this functionality is	1729	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	1730	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.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1550		1732
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1558		1740
1559	static void	1741	static void
1560	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1742	clock_cb (struct ev_loop loop, ev_io w, int revents)
1561	{	1743	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	1745	}
1564		1746
1565	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1568		1750
1569	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1570		1752
1571	#include <math.h>	1753	#include <math.h>
1572		1754
1573	static ev_tstamp	1755	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	1757	{
1576	return now + (3600. - fmod (now, 3600.));	1758	return now + (3600. - fmod (now, 3600.));
1577	}	1759	}
1578		1760
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		1762
1581	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1582		1764
1583	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1587		1769
1588		1770
…		…
1630	=head3 Examples	1812	=head3 Examples
1631		1813
1632	Example: Try to exit cleanly on SIGINT.	1814	Example: Try to exit cleanly on SIGINT.
1633		1815
1634	static void	1816	static void
1635	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1817	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1636	{	1818	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	1820	}
1639		1821
1640	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	1824	ev_signal_start (loop, &signal_watcher);
1643		1825
1644		1826
1645	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
…		…
1720	its completion.	1902	its completion.
1721		1903
1722	ev_child cw;	1904	ev_child cw;
1723		1905
1724	static void	1906	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1726	{	1908	{
1727	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	1911	}
1730		1912
…		…
1745		1927
1746		1928
1747	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1748		1930
1749	This watches a file system path for attribute changes. That is, it calls	1931	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	1932	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.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1752		1935
1753	The path does not need to exist: changing from "path exists" to "path does	1936	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	1937	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	1938	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	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1758		1942
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	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.	1945	your working directory changes, then the behaviour is undefined.
1761		1946
1762	Since there is no standard kernel interface to do this, the portable	1947	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	1948	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	1949	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!)	1950	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	1951	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	1952	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	1953	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1770		1955
1771	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1773	resource-intensive.	1958	resource-intensive.
1774		1959
1775	At the time of this writing, the only OS-specific interface implemented	1960	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	1961	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	1962	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	1963	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		1964
1780	=head3 ABI Issues (Largefile Support)	1965	=head3 ABI Issues (Largefile Support)
1781		1966
1782	Libev by default (unless the user overrides this) uses the default	1967	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	1968	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	1969	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	1970	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	1971	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	1972	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	1973	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.	1974	most noticeably displayed with ev_stat and large file support.
1790		1975
1791	The solution for this is to lobby your distribution maker to make large	1976	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	1977	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	1978	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	1979	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	1980	default compilation environment.
1796		1981
1797	=head3 Inotify and Kqueue	1982	=head3 Inotify and Kqueue
1798		1983
1799	When C<inotify (7)> support has been compiled into libev (generally only	1984	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	1985	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	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1803		1988
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	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	1990	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	1991	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,	1992	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.	1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1809		1997
1810	There is no support for kqueue, as apparently it cannot be used to	1998	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	1999	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2000	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2001	etc. is difficult.
1814		2002
1815	=head3 The special problem of stat time resolution	2003	=head3 The special problem of stat time resolution
1816		2004
1817	The C<stat ()> system call only supports full-second resolution portably, and	2005	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2006	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2007	still only support whole seconds.
1820		2008
1821	That means that, if the time is the only thing that changes, you can	2009	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	2010	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	2011	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	2012	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1981		2169
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2170	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2171	callback, free it. Also, use no error checking, as usual.
1984		2172
1985	static void	2173	static void
1986	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2174	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1987	{	2175	{
1988	free (w);	2176	free (w);
1989	// now do something you wanted to do when the program has	2177	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2178	// no longer anything immediate to do.
1991	}	2179	}
1992		2180
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2182	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2183	ev_idle_start (loop, idle_cb);
1996		2184
1997		2185
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2079		2267
2080	static ev_io iow [nfd];	2268	static ev_io iow [nfd];
2081	static ev_timer tw;	2269	static ev_timer tw;
2082		2270
2083	static void	2271	static void
2084	io_cb (ev_loop loop, ev_io w, int revents)	2272	io_cb (struct ev_loop loop, ev_io w, int revents)
2085	{	2273	{
2086	}	2274	}
2087		2275
2088	// create io watchers for each fd and a timer before blocking	2276	// create io watchers for each fd and a timer before blocking
2089	static void	2277	static void
2090	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2278	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2091	{	2279	{
2092	int timeout = 3600000;	2280	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2281	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2282	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2110	}	2298	}
2111	}	2299	}
2112		2300
2113	// stop all watchers after blocking	2301	// stop all watchers after blocking
2114	static void	2302	static void
2115	adns_check_cb (ev_loop loop, ev_check w, int revents)	2303	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2116	{	2304	{
2117	ev_timer_stop (loop, &tw);	2305	ev_timer_stop (loop, &tw);
2118		2306
2119	for (int i = 0; i < nfd; ++i)	2307	for (int i = 0; i < nfd; ++i)
2120	{	2308	{
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2476	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2477	used).
2290		2478
2291	struct ev_loop *loop_hi = ev_default_init (0);	2479	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2480	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2481	ev_embed embed;
2294		2482
2295	// see if there is a chance of getting one that works	2483	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2484	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2500	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2502
2315	struct ev_loop *loop = ev_default_init (0);	2503	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2504	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2505	ev_embed embed;
2318		2506
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2509	{
2322	ev_embed_init (&embed, 0, loop_socket);	2510	ev_embed_init (&embed, 0, loop_socket);
…		…
2463	=over 4	2651	=over 4
2464		2652
2465	=item ev_async_init (ev_async *, callback)	2653	=item ev_async_init (ev_async *, callback)
2466		2654
2467	Initialises and configures the async watcher - it has no parameters of any	2655	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,	2656	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	2657	trust me.
2470		2658
2471	=item ev_async_send (loop, ev_async *)	2659	=item ev_async_send (loop, ev_async *)
2472		2660
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2661	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
…		…
2536	/* doh, nothing entered */;	2724	/* doh, nothing entered */;
2537	}	2725	}
2538		2726
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		2728
2541	=item ev_feed_event (ev_loop , watcher , int revents)	2729	=item ev_feed_event (struct ev_loop , watcher , int revents)
2542		2730
2543	Feeds the given event set into the event loop, as if the specified event	2731	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	2732	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).	2733	initialised but not necessarily started event watcher).
2546		2734
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2548		2736
2549	Feed an event on the given fd, as if a file descriptor backend detected	2737	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	2738	the given events it.
2551		2739
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2553		2741
2554	Feed an event as if the given signal occurred (C<loop> must be the default	2742	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	2743	loop!).
2556		2744
2557	=back	2745	=back
…		…
2792	=item D	2980	=item D
2793		2981
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2982	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>.	2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2796		2984
		2985	=item Ocaml
		2986
		2987	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2989
2797	=back	2990	=back
2798		2991
2799		2992
2800	=head1 MACRO MAGIC	2993	=head1 MACRO MAGIC
2801		2994
…		…
2901		3094
2902	#define EV_STANDALONE 1	3095	#define EV_STANDALONE 1
2903	#include "ev.h"	3096	#include "ev.h"
2904		3097
2905	Both header files and implementation files can be compiled with a C++	3098	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	3099	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3100	as a bug).
2908		3101
2909	You need the following files in your source tree, or in a directory	3102	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):	3103	in your include path (e.g. in libev/ when using -Ilibev):
2911		3104
…		…
3383	loop, as long as you don't confuse yourself). The only exception is that	3576	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.	3577	you must not do this from C<ev_periodic> reschedule callbacks.
3385		3578
3386	Care has been taken to ensure that libev does not keep local state inside	3579	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	3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	3581	they do not call any callbacks.
3389		3582
3390	=head2 COMPILER WARNINGS	3583	=head2 COMPILER WARNINGS
3391		3584
3392	Depending on your compiler and compiler settings, you might get no or a	3585	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	3586	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	3620	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	3621	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	3622	==2274== still reachable: 256 bytes in 1 blocks.
3430		3623
3431	Then there is no memory leak, just as memory accounted to global variables	3624	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.	3625	is not a memleak - the memory is still being referenced, and didn't leak.
3433		3626
3434	Similarly, under some circumstances, valgrind might report kernel bugs	3627	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,	3628	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	3629	although an acceptable workaround has been found here), or it might be
3437	confused.	3630	confused.
…		…
3675	=back	3868	=back
3676		3869
3677		3870
3678	=head1 AUTHOR	3871	=head1 AUTHOR
3679		3872
3680	Marc Lehmann <libev@schmorp.de>.	3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		3874

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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 1.211 by root, Mon Nov 3 14:34:16 2008 UTC

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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 1.211 by root, Mon Nov 3 14:34:16 2008 UTC