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

Comparing libev/ev.pod (file contents):
Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs.
Revision 1.206 by root, Tue Oct 28 12:31:38 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
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
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
…		…
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 syscalls are the most misdesigned of the more advanced event
388	support for dup.	392	mechanisms: problems include silently dropping fds, requiring a system
		393	call per change per fd (and unnecessary guessing of parameters), problems
		394	with dup and so on. The biggest issue is fork races, however - if a
		395	program forks then I<both> parent and child process have to recreate the
		396	epoll set, which can take considerable time (one syscall per fd) and is of
		397	course hard to detect.
		398
		399	Epoll is also notoriously buggy - embedding epoll fds should work, but
		400	of course doesn't, and epoll just loves to report events for totally
		401	I<different> file descriptors (even already closed ones, so one cannot
		402	even remove them from the set) than registered in the set (especially
		403	on SMP systems). Libev tries to counter these spurious notifications by
		404	employing an additional generation counter and comparing that against the
		405	events to filter out spurious ones.
389		406
390	While stopping, setting and starting an I/O watcher in the same iteration	407	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	408	will result in some caching, there is still a system call per such incident
392	(because the fd could point to a different file description now), so its	409	(because the fd could point to a different file description now), so its
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
394	very well if you register events for both fds.	411	very well if you register events for both fds.
395		412
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
400	Best performance from this backend is achieved by not unregistering all	413	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	414	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	415	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	416	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	417	extra overhead. A fork can both result in spurious notifications as well
		418	as in libev having to destroy and recreate the epoll object, which can
		419	take considerable time and thus should be avoided.
405		420
406	While nominally embeddable in other event loops, this feature is broken in	421	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	422	all kernel versions tested so far.
408		423
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
424		439
425	It scales in the same way as the epoll backend, but the interface to the	440	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	441	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	442	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	443	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	444	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		446	cases
431		447
432	This backend usually performs well under most conditions.	448	This backend usually performs well under most conditions.
433		449
434	While nominally embeddable in other event loops, this doesn't work	450	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	451	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	480	might perform better.
465		481
466	On the positive side, with the exception of the spurious readiness	482	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	483	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	484	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	485	OS-specific backends (I vastly prefer correctness over speed hacks).
470		486
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	488	C<EVBACKEND_POLL>.
473		489
474	=item C<EVBACKEND_ALL>	490	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	543	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	544	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	545	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	546	for example).
531		547
532	Note that certain global state, such as signal state, will not be freed by	548	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	549	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	550	as signal and child watchers) would need to be stopped manually.
535		551
536	In general it is not advisable to call this function except in the	552	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	553	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	554	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	555	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	701	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		703
688	This "unloop state" will be cleared when entering C<ev_loop> again.	704	This "unloop state" will be cleared when entering C<ev_loop> again.
689		705
		706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		707
690	=item ev_ref (loop)	708	=item ev_ref (loop)
691		709
692	=item ev_unref (loop)	710	=item ev_unref (loop)
693		711
694	Ref/unref can be used to add or remove a reference count on the event	712	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	726	respectively).
709		727
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	729	running when nothing else is active.
712		730
713	struct ev_signal exitsig;	731	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	732	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	733	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	734	evf_unref (loop);
717		735
718	Example: For some weird reason, unregister the above signal handler again.	736	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	784	they fire on, say, one-second boundaries only.
767		785
768	=item ev_loop_verify (loop)	786	=item ev_loop_verify (loop)
769		787
770	This function only does something when C<EV_VERIFY> support has been	788	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	789	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	790	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	791	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	792	error and call C<abort ()>.
775		793
776	This can be used to catch bugs inside libev itself: under normal	794	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	798	=back
781		799
782		800
783	=head1 ANATOMY OF A WATCHER	801	=head1 ANATOMY OF A WATCHER
784		802
		803	In the following description, uppercase C<TYPE> in names stands for the
		804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		805	watchers and C<ev_io_start> for I/O watchers.
		806
785	A watcher is a structure that you create and register to record your	807	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	808	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	809	become readable, you would create an C<ev_io> watcher for that:
788		810
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	811	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	812	{
791	ev_io_stop (w);	813	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	814	ev_unloop (loop, EVUNLOOP_ALL);
793	}	815	}
794		816
795	struct ev_loop *loop = ev_default_loop (0);	817	struct ev_loop *loop = ev_default_loop (0);
		818
796	struct ev_io stdin_watcher;	819	ev_io stdin_watcher;
		820
797	ev_init (&stdin_watcher, my_cb);	821	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	823	ev_io_start (loop, &stdin_watcher);
		824
800	ev_loop (loop, 0);	825	ev_loop (loop, 0);
801		826
802	As you can see, you are responsible for allocating the memory for your	827	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	828	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	829	stack).
		830
		831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		833
806	Each watcher structure must be initialised by a call to C<ev_init	834	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	835	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	836	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	837	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	838	is readable and/or writable).
811		839
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	841	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	842	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	843	ev_TYPE_init (watcher *, callback, ...) >>.
816		844
817	To make the watcher actually watch out for events, you have to start it	845	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	846	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	847	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		849
822	As long as your watcher is active (has been started but not stopped) you	850	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	851	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	852	reinitialise it or call its C<ev_TYPE_set> macro.
825		853
826	Each and every callback receives the event loop pointer as first, the	854	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	855	registered watcher structure as second, and a bitset of received events as
828	third argument.	856	third argument.
829		857
…		…
892	=item C<EV_ERROR>	920	=item C<EV_ERROR>
893		921
894	An unspecified error has occurred, the watcher has been stopped. This might	922	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	923	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	924	ran out of memory, a file descriptor was found to be closed or any other
		925	problem. Libev considers these application bugs.
		926
897	problem. You best act on it by reporting the problem and somehow coping	927	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	928	watcher being stopped. Note that well-written programs should not receive
		929	an error ever, so when your watcher receives it, this usually indicates a
		930	bug in your program.
899		931
900	Libev will usually signal a few "dummy" events together with an error, for	932	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	933	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	934	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	935	the error from read() or write(). This will not work in multi-threaded
…		…
906		938
907	=back	939	=back
908		940
909	=head2 GENERIC WATCHER FUNCTIONS	941	=head2 GENERIC WATCHER FUNCTIONS
910		942
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	943	=over 4
915		944
916	=item C<ev_init> (ev_TYPE *watcher, callback)	945	=item C<ev_init> (ev_TYPE *watcher, callback)
917		946
918	This macro initialises the generic portion of a watcher. The contents	947	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	952	which rolls both calls into one.
924		953
925	You can reinitialise a watcher at any time as long as it has been stopped	954	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	955	(or never started) and there are no pending events outstanding.
927		956
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	957	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	958	int revents)>.
930		959
931	Example: Initialise an C<ev_io> watcher in two steps.	960	Example: Initialise an C<ev_io> watcher in two steps.
932		961
933	ev_io w;	962	ev_io w;
…		…
967		996
968	ev_io_start (EV_DEFAULT_UC, &w);	997	ev_io_start (EV_DEFAULT_UC, &w);
969		998
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	999	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		1000
972	Stops the given watcher again (if active) and clears the pending	1001	Stops the given watcher if active, and clears the pending status (whether
		1002	the watcher was active or not).
		1003
973	status. It is possible that stopped watchers are pending (for example,	1004	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1005	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1006	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1007	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1008	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1009
979	=item bool ev_is_active (ev_TYPE *watcher)	1010	=item bool ev_is_active (ev_TYPE *watcher)
980		1011
981	Returns a true value iff the watcher is active (i.e. it has been started	1012	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1013	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1024	The default priority used by watchers when no priority has been set is	1055	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1056	always C<0>, which is supposed to not be too high and not be too low :).
1026		1057
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1028	fine, as long as you do not mind that the priority value you query might	1059	fine, as long as you do not mind that the priority value you query might
1029	or might not have been adjusted to be within valid range.	1060	or might not have been clamped to the valid range.
1030		1061
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1063
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1065	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1087	member, you can also "subclass" the watcher type and provide your own
1057	data:	1088	data:
1058		1089
1059	struct my_io	1090	struct my_io
1060	{	1091	{
1061	struct ev_io io;	1092	ev_io io;
1062	int otherfd;	1093	int otherfd;
1063	void *somedata;	1094	void *somedata;
1064	struct whatever *mostinteresting;	1095	struct whatever *mostinteresting;
1065	};	1096	};
1066		1097
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1101
1071	And since your callback will be called with a pointer to the watcher, you	1102	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1103	can cast it back to your own type:
1073		1104
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1105	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1106	{
1076	struct my_io w = (struct my_io )w_;	1107	struct my_io w = (struct my_io )w_;
1077	...	1108	...
1078	}	1109	}
1079		1110
…		…
1097	programmers):	1128	programmers):
1098		1129
1099	#include <stddef.h>	1130	#include <stddef.h>
1100		1131
1101	static void	1132	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1133	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1134	{
1104	struct my_biggy big = (struct my_biggy *	1135	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1136	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1137	}
1107		1138
1108	static void	1139	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1140	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1141	{
1111	struct my_biggy big = (struct my_biggy *	1142	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1143	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1144	}
1114		1145
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1280	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1281	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1282	attempt to read a whole line in the callback.
1252		1283
1253	static void	1284	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1285	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1286	{
1256	ev_io_stop (loop, w);	1287	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1288	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1289	}
1259		1290
1260	...	1291	...
1261	struct ev_loop *loop = ev_default_init (0);	1292	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1293	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1295	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1266		1297
1267		1298
…		…
1278		1309
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1310	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1311	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1312	then order of execution is undefined.
1282		1313
		1314	=head3 Be smart about timeouts
		1315
		1316	Many real-world problems involve some kind of timeout, usually for error
		1317	recovery. A typical example is an HTTP request - if the other side hangs,
		1318	you want to raise some error after a while.
		1319
		1320	What follows are some ways to handle this problem, from obvious and
		1321	inefficient to smart and efficient.
		1322
		1323	In the following, a 60 second activity timeout is assumed - a timeout that
		1324	gets reset to 60 seconds each time there is activity (e.g. each time some
		1325	data or other life sign was received).
		1326
		1327	=over 4
		1328
		1329	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1330
		1331	This is the most obvious, but not the most simple way: In the beginning,
		1332	start the watcher:
		1333
		1334	ev_timer_init (timer, callback, 60., 0.);
		1335	ev_timer_start (loop, timer);
		1336
		1337	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1338	and start it again:
		1339
		1340	ev_timer_stop (loop, timer);
		1341	ev_timer_set (timer, 60., 0.);
		1342	ev_timer_start (loop, timer);
		1343
		1344	This is relatively simple to implement, but means that each time there is
		1345	some activity, libev will first have to remove the timer from its internal
		1346	data structure and then add it again. Libev tries to be fast, but it's
		1347	still not a constant-time operation.
		1348
		1349	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1350
		1351	This is the easiest way, and involves using C<ev_timer_again> instead of
		1352	C<ev_timer_start>.
		1353
		1354	To implement this, configure an C<ev_timer> with a C<repeat> value
		1355	of C<60> and then call C<ev_timer_again> at start and each time you
		1356	successfully read or write some data. If you go into an idle state where
		1357	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1358	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1359
		1360	That means you can ignore both the C<ev_timer_start> function and the
		1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1362	member and C<ev_timer_again>.
		1363
		1364	At start:
		1365
		1366	ev_timer_init (timer, callback);
		1367	timer->repeat = 60.;
		1368	ev_timer_again (loop, timer);
		1369
		1370	Each time there is some activity:
		1371
		1372	ev_timer_again (loop, timer);
		1373
		1374	It is even possible to change the time-out on the fly, regardless of
		1375	whether the watcher is active or not:
		1376
		1377	timer->repeat = 30.;
		1378	ev_timer_again (loop, timer);
		1379
		1380	This is slightly more efficient then stopping/starting the timer each time
		1381	you want to modify its timeout value, as libev does not have to completely
		1382	remove and re-insert the timer from/into its internal data structure.
		1383
		1384	It is, however, even simpler than the "obvious" way to do it.
		1385
		1386	=item 3. Let the timer time out, but then re-arm it as required.
		1387
		1388	This method is more tricky, but usually most efficient: Most timeouts are
		1389	relatively long compared to the intervals between other activity - in
		1390	our example, within 60 seconds, there are usually many I/O events with
		1391	associated activity resets.
		1392
		1393	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1394	but remember the time of last activity, and check for a real timeout only
		1395	within the callback:
		1396
		1397	ev_tstamp last_activity; // time of last activity
		1398
		1399	static void
		1400	callback (EV_P_ ev_timer *w, int revents)
		1401	{
		1402	ev_tstamp now = ev_now (EV_A);
		1403	ev_tstamp timeout = last_activity + 60.;
		1404
		1405	// if last_activity + 60. is older than now, we did time out
		1406	if (timeout < now)
		1407	{
		1408	// timeout occured, take action
		1409	}
		1410	else
		1411	{
		1412	// callback was invoked, but there was some activity, re-arm
		1413	// the watcher to fire in last_activity + 60, which is
		1414	// guaranteed to be in the future, so "again" is positive:
		1415	w->again = timeout - now;
		1416	ev_timer_again (EV_A_ w);
		1417	}
		1418	}
		1419
		1420	To summarise the callback: first calculate the real timeout (defined
		1421	as "60 seconds after the last activity"), then check if that time has
		1422	been reached, which means something I<did>, in fact, time out. Otherwise
		1423	the callback was invoked too early (C<timeout> is in the future), so
		1424	re-schedule the timer to fire at that future time, to see if maybe we have
		1425	a timeout then.
		1426
		1427	Note how C<ev_timer_again> is used, taking advantage of the
		1428	C<ev_timer_again> optimisation when the timer is already running.
		1429
		1430	This scheme causes more callback invocations (about one every 60 seconds
		1431	minus half the average time between activity), but virtually no calls to
		1432	libev to change the timeout.
		1433
		1434	To start the timer, simply initialise the watcher and set C<last_activity>
		1435	to the current time (meaning we just have some activity :), then call the
		1436	callback, which will "do the right thing" and start the timer:
		1437
		1438	ev_timer_init (timer, callback);
		1439	last_activity = ev_now (loop);
		1440	callback (loop, timer, EV_TIMEOUT);
		1441
		1442	And when there is some activity, simply store the current time in
		1443	C<last_activity>, no libev calls at all:
		1444
		1445	last_actiivty = ev_now (loop);
		1446
		1447	This technique is slightly more complex, but in most cases where the
		1448	time-out is unlikely to be triggered, much more efficient.
		1449
		1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1451	callback :) - just change the timeout and invoke the callback, which will
		1452	fix things for you.
		1453
		1454	=item 4. Wee, just use a double-linked list for your timeouts.
		1455
		1456	If there is not one request, but many thousands (millions...), all
		1457	employing some kind of timeout with the same timeout value, then one can
		1458	do even better:
		1459
		1460	When starting the timeout, calculate the timeout value and put the timeout
		1461	at the I<end> of the list.
		1462
		1463	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1464	the list is expected to fire (for example, using the technique #3).
		1465
		1466	When there is some activity, remove the timer from the list, recalculate
		1467	the timeout, append it to the end of the list again, and make sure to
		1468	update the C<ev_timer> if it was taken from the beginning of the list.
		1469
		1470	This way, one can manage an unlimited number of timeouts in O(1) time for
		1471	starting, stopping and updating the timers, at the expense of a major
		1472	complication, and having to use a constant timeout. The constant timeout
		1473	ensures that the list stays sorted.
		1474
		1475	=back
		1476
		1477	So which method the best?
		1478
		1479	Method #2 is a simple no-brain-required solution that is adequate in most
		1480	situations. Method #3 requires a bit more thinking, but handles many cases
		1481	better, and isn't very complicated either. In most case, choosing either
		1482	one is fine, with #3 being better in typical situations.
		1483
		1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1485	rather complicated, but extremely efficient, something that really pays
		1486	off after the first million or so of active timers, i.e. it's usually
		1487	overkill :)
		1488
1283	=head3 The special problem of time updates	1489	=head3 The special problem of time updates
1284		1490
1285	Establishing the current time is a costly operation (it usually takes at	1491	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1492	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1493	time only before and after C<ev_loop> collects new events, which causes a
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1536	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1537
1332	If the timer is repeating, either start it if necessary (with the	1538	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1539	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1540
1335	This sounds a bit complicated, but here is a useful and typical	1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1542	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1543
1366	=item ev_tstamp repeat [read-write]	1544	=item ev_tstamp repeat [read-write]
1367		1545
1368	The current C<repeat> value. Will be used each time the watcher times out	1546	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1547	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1552	=head3 Examples
1375		1553
1376	Example: Create a timer that fires after 60 seconds.	1554	Example: Create a timer that fires after 60 seconds.
1377		1555
1378	static void	1556	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1557	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1558	{
1381	.. one minute over, w is actually stopped right here	1559	.. one minute over, w is actually stopped right here
1382	}	1560	}
1383		1561
1384	struct ev_timer mytimer;	1562	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1563	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1564	ev_timer_start (loop, &mytimer);
1387		1565
1388	Example: Create a timeout timer that times out after 10 seconds of	1566	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1567	inactivity.
1390		1568
1391	static void	1569	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1570	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1571	{
1394	.. ten seconds without any activity	1572	.. ten seconds without any activity
1395	}	1573	}
1396		1574
1397	struct ev_timer mytimer;	1575	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1577	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1401		1579
1402	// and in some piece of code that gets executed on any "activity":	1580	// and in some piece of code that gets executed on any "activity":
…		…
1488		1666
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1669	only event loop modification you are allowed to do).
1492		1670
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1671	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1672	*w, ev_tstamp now)>, e.g.:
1495		1673
		1674	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1675	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1676	{
1498	return now + 60.;	1677	return now + 60.;
1499	}	1678	}
1500		1679
1501	It must return the next time to trigger, based on the passed time value	1680	It must return the next time to trigger, based on the passed time value
…		…
1538		1717
1539	The current interval value. Can be modified any time, but changes only	1718	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1719	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1720	called.
1542		1721
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1722	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1723
1545	The current reschedule callback, or C<0>, if this functionality is	1724	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1725	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1726	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1727
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1732	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1733	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1734	potentially a lot of jitter, but good long-term stability.
1556		1735
1557	static void	1736	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1737	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1738	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1739	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1740	}
1562		1741
1563	struct ev_periodic hourly_tick;	1742	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1743	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1744	ev_periodic_start (loop, &hourly_tick);
1566		1745
1567	Example: The same as above, but use a reschedule callback to do it:	1746	Example: The same as above, but use a reschedule callback to do it:
1568		1747
1569	#include <math.h>	1748	#include <math.h>
1570		1749
1571	static ev_tstamp	1750	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1751	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1752	{
1574	return now + (3600. - fmod (now, 3600.));	1753	return now + (3600. - fmod (now, 3600.));
1575	}	1754	}
1576		1755
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1756	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1757
1579	Example: Call a callback every hour, starting now:	1758	Example: Call a callback every hour, starting now:
1580		1759
1581	struct ev_periodic hourly_tick;	1760	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1761	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1762	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1763	ev_periodic_start (loop, &hourly_tick);
1585		1764
1586		1765
…		…
1625		1804
1626	=back	1805	=back
1627		1806
1628	=head3 Examples	1807	=head3 Examples
1629		1808
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1809	Example: Try to exit cleanly on SIGINT.
1631		1810
1632	static void	1811	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1812	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1813	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1814	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1815	}
1637		1816
1638	struct ev_signal signal_watcher;	1817	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1819	ev_signal_start (loop, &signal_watcher);
1641		1820
1642		1821
1643	=head2 C<ev_child> - watch out for process status changes	1822	=head2 C<ev_child> - watch out for process status changes
1644		1823
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1824	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1897	its completion.
1719		1898
1720	ev_child cw;	1899	ev_child cw;
1721		1900
1722	static void	1901	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1902	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1903	{
1725	ev_child_stop (EV_A_ w);	1904	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1905	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1906	}
1728		1907
…		…
1792	to exchange stat structures with application programs compiled using the	1971	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1972	default compilation environment.
1794		1973
1795	=head3 Inotify and Kqueue	1974	=head3 Inotify and Kqueue
1796		1975
1797	When C<inotify (7)> support has been compiled into libev (generally only	1976	When C<inotify (7)> support has been compiled into libev (generally
		1977	only available with Linux 2.6.25 or above due to bugs in earlier
1798	available with Linux) and present at runtime, it will be used to speed up	1978	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1979	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1980	lazily when the first C<ev_stat> watcher is being started.
1801		1981
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1982	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	1983	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	1984	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	1985	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1979		2159
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2160	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2161	callback, free it. Also, use no error checking, as usual.
1982		2162
1983	static void	2163	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2164	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2165	{
1986	free (w);	2166	free (w);
1987	// now do something you wanted to do when the program has	2167	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2168	// no longer anything immediate to do.
1989	}	2169	}
1990		2170
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2171	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2172	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2173	ev_idle_start (loop, idle_cb);
1994		2174
1995		2175
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2176	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2257
2078	static ev_io iow [nfd];	2258	static ev_io iow [nfd];
2079	static ev_timer tw;	2259	static ev_timer tw;
2080		2260
2081	static void	2261	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2262	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2263	{
2084	}	2264	}
2085		2265
2086	// create io watchers for each fd and a timer before blocking	2266	// create io watchers for each fd and a timer before blocking
2087	static void	2267	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2268	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2269	{
2090	int timeout = 3600000;	2270	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2271	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2272	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2273	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2288	}
2109	}	2289	}
2110		2290
2111	// stop all watchers after blocking	2291	// stop all watchers after blocking
2112	static void	2292	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2293	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2294	{
2115	ev_timer_stop (loop, &tw);	2295	ev_timer_stop (loop, &tw);
2116		2296
2117	for (int i = 0; i < nfd; ++i)	2297	for (int i = 0; i < nfd; ++i)
2118	{	2298	{
…		…
2242	So when you want to use this feature you will always have to be prepared	2422	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2423	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2424	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2425	create it, and if that fails, use the normal loop for everything.
2246		2426
		2427	=head3 C<ev_embed> and fork
		2428
		2429	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2430	automatically be applied to the embedded loop as well, so no special
		2431	fork handling is required in that case. When the watcher is not running,
		2432	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2433	as applicable.
		2434
2247	=head3 Watcher-Specific Functions and Data Members	2435	=head3 Watcher-Specific Functions and Data Members
2248		2436
2249	=over 4	2437	=over 4
2250		2438
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2439	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2466	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2467	used).
2280		2468
2281	struct ev_loop *loop_hi = ev_default_init (0);	2469	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2470	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2471	ev_embed embed;
2284		2472
2285	// see if there is a chance of getting one that works	2473	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2474	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2475	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2476	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2490	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2491	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2492
2305	struct ev_loop *loop = ev_default_init (0);	2493	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2494	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2495	ev_embed embed;
2308		2496
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2497	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2498	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2499	{
2312	ev_embed_init (&embed, 0, loop_socket);	2500	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2564	=over 4
2377		2565
2378	=item queueing from a signal handler context	2566	=item queueing from a signal handler context
2379		2567
2380	To implement race-free queueing, you simply add to the queue in the signal	2568	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2569	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2570	an example that does that for some fictitious SIGUSR1 handler:
2383		2571
2384	static ev_async mysig;	2572	static ev_async mysig;
2385		2573
2386	static void	2574	static void
2387	sigusr1_handler (void)	2575	sigusr1_handler (void)
…		…
2494	=over 4	2682	=over 4
2495		2683
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2684	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2685
2498	This function combines a simple timer and an I/O watcher, calls your	2686	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2687	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2688	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2689	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2690	more watchers yourself.
2503		2691
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2692	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2693	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2694	the given C<fd> and C<events> set will be created and started.
2507		2695
2508	If C<timeout> is less than 0, then no timeout watcher will be	2696	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2697	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2698	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2699
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2700	The callback has the type C<void (cb)(int revents, void arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	2701	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2702	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2703	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2704	a timeout and an io event at the same time - you probably should give io
		2705	events precedence.
		2706
		2707	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2708
2518	static void stdin_ready (int revents, void *arg)	2709	static void stdin_ready (int revents, void *arg)
2519	{	2710	{
		2711	if (revents & EV_READ)
		2712	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2713	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2714	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2715	}
2525		2716
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2717	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2718
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2719	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2720
2530	Feeds the given event set into the event loop, as if the specified event	2721	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an	2722	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2723	initialised but not necessarily started event watcher).
2533		2724
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2725	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2726
2536	Feed an event on the given fd, as if a file descriptor backend detected	2727	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2728	the given events it.
2538		2729
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2730	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2731
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2732	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2733	loop!).
2543		2734
2544	=back	2735	=back
…		…
2778		2969
2779	=item D	2970	=item D
2780		2971
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2972	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2973	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2974
		2975	=item Ocaml
		2976
		2977	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2978	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2783		2979
2784	=back	2980	=back
2785		2981
2786		2982
2787	=head1 MACRO MAGIC	2983	=head1 MACRO MAGIC
…		…
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3494	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		3495
3300	#include "ev_cpp.h"	3496	#include "ev_cpp.h"
3301	#include "ev.c"	3497	#include "ev.c"
3302		3498
		3499	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		3500
3304	=head1 THREADS AND COROUTINES	3501	=head2 THREADS AND COROUTINES
3305		3502
3306	=head2 THREADS	3503	=head3 THREADS
3307		3504
3308	Libev itself is thread-safe (unless the opposite is specifically	3505	All libev functions are reentrant and thread-safe unless explicitly
3309	documented for a function), but it uses no locking itself. This means that	3506	documented otherwise, but libev implements no locking itself. This means
3310	you can use as many loops as you want in parallel, as long as only one	3507	that you can use as many loops as you want in parallel, as long as there
3311	thread ever calls into one libev function with the same loop parameter:	3508	are no concurrent calls into any libev function with the same loop
		3509	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3312	libev guarantees that different event loops share no data structures that	3510	of course): libev guarantees that different event loops share no data
3313	need locking.	3511	structures that need any locking.
3314		3512
3315	Or to put it differently: calls with different loop parameters can be done	3513	Or to put it differently: calls with different loop parameters can be done
3316	concurrently from multiple threads, calls with the same loop parameter	3514	concurrently from multiple threads, calls with the same loop parameter
3317	must be done serially (but can be done from different threads, as long as	3515	must be done serially (but can be done from different threads, as long as
3318	only one thread ever is inside a call at any point in time, e.g. by using	3516	only one thread ever is inside a call at any point in time, e.g. by using
3319	a mutex per loop).	3517	a mutex per loop).
3320		3518
3321	Specifically to support threads (and signal handlers), libev implements	3519	Specifically to support threads (and signal handlers), libev implements
3322	so-called C<ev_async> watchers, which allow some limited form of	3520	so-called C<ev_async> watchers, which allow some limited form of
3323	concurrency on the same event loop.	3521	concurrency on the same event loop, namely waking it up "from the
		3522	outside".
3324		3523
3325	If you want to know which design (one loop, locking, or multiple loops	3524	If you want to know which design (one loop, locking, or multiple loops
3326	without or something else still) is best for your problem, then I cannot	3525	without or something else still) is best for your problem, then I cannot
3327	help you. I can give some generic advice however:	3526	help you, but here is some generic advice:
3328		3527
3329	=over 4	3528	=over 4
3330		3529
3331	=item * most applications have a main thread: use the default libev loop	3530	=item * most applications have a main thread: use the default libev loop
3332	in that thread, or create a separate thread running only the default loop.	3531	in that thread, or create a separate thread running only the default loop.
…		…
3356	default loop and triggering an C<ev_async> watcher from the default loop	3555	default loop and triggering an C<ev_async> watcher from the default loop
3357	watcher callback into the event loop interested in the signal.	3556	watcher callback into the event loop interested in the signal.
3358		3557
3359	=back	3558	=back
3360		3559
3361	=head2 COROUTINES	3560	=head3 COROUTINES
3362		3561
3363	Libev is much more accommodating to coroutines ("cooperative threads"):	3562	Libev is very accommodating to coroutines ("cooperative threads"):
3364	libev fully supports nesting calls to it's functions from different	3563	libev fully supports nesting calls to its functions from different
3365	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3564	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3366	different coroutines and switch freely between both coroutines running the	3565	different coroutines, and switch freely between both coroutines running the
3367	loop, as long as you don't confuse yourself). The only exception is that	3566	loop, as long as you don't confuse yourself). The only exception is that
3368	you must not do this from C<ev_periodic> reschedule callbacks.	3567	you must not do this from C<ev_periodic> reschedule callbacks.
3369		3568
3370	Care has been taken to ensure that libev does not keep local state inside	3569	Care has been taken to ensure that libev does not keep local state inside
3371	C<ev_loop>, and other calls do not usually allow coroutine switches.	3570	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3571	they do not clal any callbacks.
3372		3572
		3573	=head2 COMPILER WARNINGS
3373		3574
3374	=head1 COMPLEXITIES	3575	Depending on your compiler and compiler settings, you might get no or a
		3576	lot of warnings when compiling libev code. Some people are apparently
		3577	scared by this.
3375		3578
3376	In this section the complexities of (many of) the algorithms used inside	3579	However, these are unavoidable for many reasons. For one, each compiler
3377	libev will be explained. For complexity discussions about backends see the	3580	has different warnings, and each user has different tastes regarding
3378	documentation for C<ev_default_init>.	3581	warning options. "Warn-free" code therefore cannot be a goal except when
		3582	targeting a specific compiler and compiler-version.
3379		3583
3380	All of the following are about amortised time: If an array needs to be	3584	Another reason is that some compiler warnings require elaborate
3381	extended, libev needs to realloc and move the whole array, but this	3585	workarounds, or other changes to the code that make it less clear and less
3382	happens asymptotically never with higher number of elements, so O(1) might	3586	maintainable.
3383	mean it might do a lengthy realloc operation in rare cases, but on average
3384	it is much faster and asymptotically approaches constant time.
3385		3587
3386	=over 4	3588	And of course, some compiler warnings are just plain stupid, or simply
		3589	wrong (because they don't actually warn about the condition their message
		3590	seems to warn about). For example, certain older gcc versions had some
		3591	warnings that resulted an extreme number of false positives. These have
		3592	been fixed, but some people still insist on making code warn-free with
		3593	such buggy versions.
3387		3594
3388	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3595	While libev is written to generate as few warnings as possible,
		3596	"warn-free" code is not a goal, and it is recommended not to build libev
		3597	with any compiler warnings enabled unless you are prepared to cope with
		3598	them (e.g. by ignoring them). Remember that warnings are just that:
		3599	warnings, not errors, or proof of bugs.
3389		3600
3390	This means that, when you have a watcher that triggers in one hour and
3391	there are 100 watchers that would trigger before that then inserting will
3392	have to skip roughly seven (C<ld 100>) of these watchers.
3393		3601
3394	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3602	=head2 VALGRIND
3395		3603
3396	That means that changing a timer costs less than removing/adding them	3604	Valgrind has a special section here because it is a popular tool that is
3397	as only the relative motion in the event queue has to be paid for.	3605	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3398		3606
3399	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3607	If you think you found a bug (memory leak, uninitialised data access etc.)
		3608	in libev, then check twice: If valgrind reports something like:
3400		3609
3401	These just add the watcher into an array or at the head of a list.	3610	==2274== definitely lost: 0 bytes in 0 blocks.
		3611	==2274== possibly lost: 0 bytes in 0 blocks.
		3612	==2274== still reachable: 256 bytes in 1 blocks.
3402		3613
3403	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3614	Then there is no memory leak, just as memory accounted to global variables
		3615	is not a memleak - the memory is still being refernced, and didn't leak.
3404		3616
3405	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3617	Similarly, under some circumstances, valgrind might report kernel bugs
		3618	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3619	although an acceptable workaround has been found here), or it might be
		3620	confused.
3406		3621
3407	These watchers are stored in lists then need to be walked to find the	3622	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3408	correct watcher to remove. The lists are usually short (you don't usually	3623	make it into some kind of religion.
3409	have many watchers waiting for the same fd or signal).
3410		3624
3411	=item Finding the next timer in each loop iteration: O(1)	3625	If you are unsure about something, feel free to contact the mailing list
		3626	with the full valgrind report and an explanation on why you think this
		3627	is a bug in libev (best check the archives, too :). However, don't be
		3628	annoyed when you get a brisk "this is no bug" answer and take the chance
		3629	of learning how to interpret valgrind properly.
3412		3630
3413	By virtue of using a binary or 4-heap, the next timer is always found at a	3631	If you need, for some reason, empty reports from valgrind for your project
3414	fixed position in the storage array.	3632	I suggest using suppression lists.
3415		3633
3416	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3417		3634
3418	A change means an I/O watcher gets started or stopped, which requires	3635	=head1 PORTABILITY NOTES
3419	libev to recalculate its status (and possibly tell the kernel, depending
3420	on backend and whether C<ev_io_set> was used).
3421		3636
3422	=item Activating one watcher (putting it into the pending state): O(1)
3423
3424	=item Priority handling: O(number_of_priorities)
3425
3426	Priorities are implemented by allocating some space for each
3427	priority. When doing priority-based operations, libev usually has to
3428	linearly search all the priorities, but starting/stopping and activating
3429	watchers becomes O(1) with respect to priority handling.
3430
3431	=item Sending an ev_async: O(1)
3432
3433	=item Processing ev_async_send: O(number_of_async_watchers)
3434
3435	=item Processing signals: O(max_signal_number)
3436
3437	Sending involves a system call I<iff> there were no other C<ev_async_send>
3438	calls in the current loop iteration. Checking for async and signal events
3439	involves iterating over all running async watchers or all signal numbers.
3440
3441	=back
3442
3443
3444	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3637	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3445		3638
3446	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3639	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3447	requires, and its I/O model is fundamentally incompatible with the POSIX	3640	requires, and its I/O model is fundamentally incompatible with the POSIX
3448	model. Libev still offers limited functionality on this platform in	3641	model. Libev still offers limited functionality on this platform in
3449	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3642	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3536	wrap all I/O functions and provide your own fd management, but the cost of	3729	wrap all I/O functions and provide your own fd management, but the cost of
3537	calling select (O(n²)) will likely make this unworkable.	3730	calling select (O(n²)) will likely make this unworkable.
3538		3731
3539	=back	3732	=back
3540		3733
3541
3542	=head1 PORTABILITY REQUIREMENTS	3734	=head2 PORTABILITY REQUIREMENTS
3543		3735
3544	In addition to a working ISO-C implementation, libev relies on a few	3736	In addition to a working ISO-C implementation and of course the
3545	additional extensions:	3737	backend-specific APIs, libev relies on a few additional extensions:
3546		3738
3547	=over 4	3739	=over 4
3548		3740
3549	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3741	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3550	calling conventions regardless of C<ev_watcher_type *>.	3742	calling conventions regardless of C<ev_watcher_type *>.
…		…
3575	except the initial one, and run the default loop in the initial thread as	3767	except the initial one, and run the default loop in the initial thread as
3576	well.	3768	well.
3577		3769
3578	=item C<long> must be large enough for common memory allocation sizes	3770	=item C<long> must be large enough for common memory allocation sizes
3579		3771
3580	To improve portability and simplify using libev, libev uses C<long>	3772	To improve portability and simplify its API, libev uses C<long> internally
3581	internally instead of C<size_t> when allocating its data structures. On	3773	instead of C<size_t> when allocating its data structures. On non-POSIX
3582	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3774	systems (Microsoft...) this might be unexpectedly low, but is still at
3583	is still at least 31 bits everywhere, which is enough for hundreds of	3775	least 31 bits everywhere, which is enough for hundreds of millions of
3584	millions of watchers.	3776	watchers.
3585		3777
3586	=item C<double> must hold a time value in seconds with enough accuracy	3778	=item C<double> must hold a time value in seconds with enough accuracy
3587		3779
3588	The type C<double> is used to represent timestamps. It is required to	3780	The type C<double> is used to represent timestamps. It is required to
3589	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3781	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3593	=back	3785	=back
3594		3786
3595	If you know of other additional requirements drop me a note.	3787	If you know of other additional requirements drop me a note.
3596		3788
3597		3789
3598	=head1 COMPILER WARNINGS	3790	=head1 ALGORITHMIC COMPLEXITIES
3599		3791
3600	Depending on your compiler and compiler settings, you might get no or a	3792	In this section the complexities of (many of) the algorithms used inside
3601	lot of warnings when compiling libev code. Some people are apparently	3793	libev will be documented. For complexity discussions about backends see
3602	scared by this.	3794	the documentation for C<ev_default_init>.
3603		3795
3604	However, these are unavoidable for many reasons. For one, each compiler	3796	All of the following are about amortised time: If an array needs to be
3605	has different warnings, and each user has different tastes regarding	3797	extended, libev needs to realloc and move the whole array, but this
3606	warning options. "Warn-free" code therefore cannot be a goal except when	3798	happens asymptotically rarer with higher number of elements, so O(1) might
3607	targeting a specific compiler and compiler-version.	3799	mean that libev does a lengthy realloc operation in rare cases, but on
		3800	average it is much faster and asymptotically approaches constant time.
3608		3801
3609	Another reason is that some compiler warnings require elaborate	3802	=over 4
3610	workarounds, or other changes to the code that make it less clear and less
3611	maintainable.
3612		3803
3613	And of course, some compiler warnings are just plain stupid, or simply	3804	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3614	wrong (because they don't actually warn about the condition their message
3615	seems to warn about).
3616		3805
3617	While libev is written to generate as few warnings as possible,	3806	This means that, when you have a watcher that triggers in one hour and
3618	"warn-free" code is not a goal, and it is recommended not to build libev	3807	there are 100 watchers that would trigger before that, then inserting will
3619	with any compiler warnings enabled unless you are prepared to cope with	3808	have to skip roughly seven (C<ld 100>) of these watchers.
3620	them (e.g. by ignoring them). Remember that warnings are just that:
3621	warnings, not errors, or proof of bugs.
3622		3809
		3810	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3623		3811
3624	=head1 VALGRIND	3812	That means that changing a timer costs less than removing/adding them,
		3813	as only the relative motion in the event queue has to be paid for.
3625		3814
3626	Valgrind has a special section here because it is a popular tool that is	3815	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3627	highly useful, but valgrind reports are very hard to interpret.
3628		3816
3629	If you think you found a bug (memory leak, uninitialised data access etc.)	3817	These just add the watcher into an array or at the head of a list.
3630	in libev, then check twice: If valgrind reports something like:
3631		3818
3632	==2274== definitely lost: 0 bytes in 0 blocks.	3819	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3633	==2274== possibly lost: 0 bytes in 0 blocks.
3634	==2274== still reachable: 256 bytes in 1 blocks.
3635		3820
3636	Then there is no memory leak. Similarly, under some circumstances,	3821	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3637	valgrind might report kernel bugs as if it were a bug in libev, or it
3638	might be confused (it is a very good tool, but only a tool).
3639		3822
3640	If you are unsure about something, feel free to contact the mailing list	3823	These watchers are stored in lists, so they need to be walked to find the
3641	with the full valgrind report and an explanation on why you think this is	3824	correct watcher to remove. The lists are usually short (you don't usually
3642	a bug in libev. However, don't be annoyed when you get a brisk "this is	3825	have many watchers waiting for the same fd or signal: one is typical, two
3643	no bug" answer and take the chance of learning how to interpret valgrind	3826	is rare).
3644	properly.
3645		3827
3646	If you need, for some reason, empty reports from valgrind for your project	3828	=item Finding the next timer in each loop iteration: O(1)
3647	I suggest using suppression lists.	3829
		3830	By virtue of using a binary or 4-heap, the next timer is always found at a
		3831	fixed position in the storage array.
		3832
		3833	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3834
		3835	A change means an I/O watcher gets started or stopped, which requires
		3836	libev to recalculate its status (and possibly tell the kernel, depending
		3837	on backend and whether C<ev_io_set> was used).
		3838
		3839	=item Activating one watcher (putting it into the pending state): O(1)
		3840
		3841	=item Priority handling: O(number_of_priorities)
		3842
		3843	Priorities are implemented by allocating some space for each
		3844	priority. When doing priority-based operations, libev usually has to
		3845	linearly search all the priorities, but starting/stopping and activating
		3846	watchers becomes O(1) with respect to priority handling.
		3847
		3848	=item Sending an ev_async: O(1)
		3849
		3850	=item Processing ev_async_send: O(number_of_async_watchers)
		3851
		3852	=item Processing signals: O(max_signal_number)
		3853
		3854	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3855	calls in the current loop iteration. Checking for async and signal events
		3856	involves iterating over all running async watchers or all signal numbers.
		3857
		3858	=back
3648		3859
3649		3860
3650	=head1 AUTHOR	3861	=head1 AUTHOR
3651		3862
3652	Marc Lehmann <libev@schmorp.de>.	3863	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs. Revision 1.206 by root, Tue Oct 28 12:31:38 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs.
Revision 1.206 by root, Tue Oct 28 12:31:38 2008 UTC