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

Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.200 by root, Thu Oct 23 07:33:45 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
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	689	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.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		691
688	This "unloop state" will be cleared when entering C<ev_loop> again.	692	This "unloop state" will be cleared when entering C<ev_loop> again.
689		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
690	=item ev_ref (loop)	696	=item ev_ref (loop)
691		697
692	=item ev_unref (loop)	698	=item ev_unref (loop)
693		699
694	Ref/unref can be used to add or remove a reference count on the event	700	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	714	respectively).
709		715
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	717	running when nothing else is active.
712		718
713	struct ev_signal exitsig;	719	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	722	evf_unref (loop);
717		723
718	Example: For some weird reason, unregister the above signal handler again.	724	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	772	they fire on, say, one-second boundaries only.
767		773
768	=item ev_loop_verify (loop)	774	=item ev_loop_verify (loop)
769		775
770	This function only does something when C<EV_VERIFY> support has been	776	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	777	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	778	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	779	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	780	error and call C<abort ()>.
775		781
776	This can be used to catch bugs inside libev itself: under normal	782	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	786	=back
781		787
782		788
783	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
784		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
		794
785	A watcher is a structure that you create and register to record your	795	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	796	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:	797	become readable, you would create an C<ev_io> watcher for that:
788		798
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	799	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	800	{
791	ev_io_stop (w);	801	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
793	}	803	}
794		804
795	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
796	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
797	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
800	ev_loop (loop, 0);	813	ev_loop (loop, 0);
801		814
802	As you can see, you are responsible for allocating the memory for your	815	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,	816	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		821
806	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	823	(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	824	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	825	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	826	is readable and/or writable).
811		827
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	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	829	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	830	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
816		832
817	To make the watcher actually watch out for events, you have to start it	833	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	834	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	835	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		837
822	As long as your watcher is active (has been started but not stopped) you	838	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	839	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
825		841
826	Each and every callback receives the event loop pointer as first, the	842	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	843	registered watcher structure as second, and a bitset of received events as
828	third argument.	844	third argument.
829		845
…		…
892	=item C<EV_ERROR>	908	=item C<EV_ERROR>
893		909
894	An unspecified error has occurred, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	911	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	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
897	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
899		919
900	Libev will usually signal a few "dummy" events together with an error, for	920	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	921	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	922	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	923	the error from read() or write(). This will not work in multi-threaded
…		…
906		926
907	=back	927	=back
908		928
909	=head2 GENERIC WATCHER FUNCTIONS	929	=head2 GENERIC WATCHER FUNCTIONS
910		930
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	931	=over 4
915		932
916	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
917		934
918	This macro initialises the generic portion of a watcher. The contents	935	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	940	which rolls both calls into one.
924		941
925	You can reinitialise a watcher at any time as long as it has been stopped	942	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.	943	(or never started) and there are no pending events outstanding.
927		944
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	945	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	946	int revents)>.
930		947
931	Example: Initialise an C<ev_io> watcher in two steps.	948	Example: Initialise an C<ev_io> watcher in two steps.
932		949
933	ev_io w;	950	ev_io w;
…		…
967		984
968	ev_io_start (EV_DEFAULT_UC, &w);	985	ev_io_start (EV_DEFAULT_UC, &w);
969		986
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	987	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		988
972	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
973	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	993	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	994	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	995	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.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		997
979	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
980		999
981	Returns a true value iff the watcher is active (i.e. it has been started	1000	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	1001	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1075	member, you can also "subclass" the watcher type and provide your own
1057	data:	1076	data:
1058		1077
1059	struct my_io	1078	struct my_io
1060	{	1079	{
1061	struct ev_io io;	1080	ev_io io;
1062	int otherfd;	1081	int otherfd;
1063	void *somedata;	1082	void *somedata;
1064	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
1065	};	1084	};
1066		1085
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1089
1071	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1091	can cast it back to your own type:
1073		1092
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1093	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1094	{
1076	struct my_io w = (struct my_io )w_;	1095	struct my_io w = (struct my_io )w_;
1077	...	1096	...
1078	}	1097	}
1079		1098
…		…
1097	programmers):	1116	programmers):
1098		1117
1099	#include <stddef.h>	1118	#include <stddef.h>
1100		1119
1101	static void	1120	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1122	{
1104	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1125	}
1107		1126
1108	static void	1127	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1129	{
1111	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1132	}
1114		1133
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	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	1269	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
1252		1271
1253	static void	1272	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1273	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1274	{
1256	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1277	}
1259		1278
1260	...	1279	...
1261	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
1266		1285
1267		1286
…		…
1278		1297
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1298	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	1299	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1300	then order of execution is undefined.
1282		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
		1476
1283	=head3 The special problem of time updates	1477	=head3 The special problem of time updates
1284		1478
1285	Establishing the current time is a costly operation (it usually takes at	1479	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	1480	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	1481	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).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1525
1332	If the timer is repeating, either start it if necessary (with the	1526	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.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1528
1335	This sounds a bit complicated, but here is a useful and typical	1529	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	1530	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		1531
1366	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1367		1533
1368	The current C<repeat> value. Will be used each time the watcher times out	1534	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),	1535	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1540	=head3 Examples
1375		1541
1376	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1377		1543
1378	static void	1544	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1545	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1546	{
1381	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1382	}	1548	}
1383		1549
1384	struct ev_timer mytimer;	1550	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1387		1553
1388	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1555	inactivity.
1390		1556
1391	static void	1557	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1558	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1559	{
1394	.. ten seconds without any activity	1560	.. ten seconds without any activity
1395	}	1561	}
1396		1562
1397	struct ev_timer mytimer;	1563	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1401		1567
1402	// and in some piece of code that gets executed on any "activity":	1568	// and in some piece of code that gets executed on any "activity":
…		…
1488		1654
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1655	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	1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1657	only event loop modification you are allowed to do).
1492		1658
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1495		1661
		1662	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1664	{
1498	return now + 60.;	1665	return now + 60.;
1499	}	1666	}
1500		1667
1501	It must return the next time to trigger, based on the passed time value	1668	It must return the next time to trigger, based on the passed time value
…		…
1538		1705
1539	The current interval value. Can be modified any time, but changes only	1706	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	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1708	called.
1542		1709
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1711
1545	The current reschedule callback, or C<0>, if this functionality is	1712	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	1713	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.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1715
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1556		1723
1557	static void	1724	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1725	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1726	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1728	}
1562		1729
1563	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1566		1733
1567	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1568		1735
1569	#include <math.h>	1736	#include <math.h>
1570		1737
1571	static ev_tstamp	1738	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1740	{
1574	return now + (3600. - fmod (now, 3600.));	1741	return now + (3600. - fmod (now, 3600.));
1575	}	1742	}
1576		1743
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1745
1579	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1580		1747
1581	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1585		1752
1586		1753
…		…
1625		1792
1626	=back	1793	=back
1627		1794
1628	=head3 Examples	1795	=head3 Examples
1629		1796
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1797	Example: Try to exit cleanly on SIGINT.
1631		1798
1632	static void	1799	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1800	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1801	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1802	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1803	}
1637		1804
1638	struct ev_signal signal_watcher;	1805	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1807	ev_signal_start (loop, &signal_watcher);
1641		1808
1642		1809
1643	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1644		1811
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1812	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1885	its completion.
1719		1886
1720	ev_child cw;	1887	ev_child cw;
1721		1888
1722	static void	1889	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1891	{
1725	ev_child_stop (EV_A_ w);	1892	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1894	}
1728		1895
…		…
1792	to exchange stat structures with application programs compiled using the	1959	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1960	default compilation environment.
1794		1961
1795	=head3 Inotify and Kqueue	1962	=head3 Inotify and Kqueue
1796		1963
1797	When C<inotify (7)> support has been compiled into libev (generally only	1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	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	1966	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1967	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1968	lazily when the first C<ev_stat> watcher is being started.
1801		1969
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1970	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	1971	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	1972	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,	1973	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1979		2147
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1982		2150
1983	static void	2151	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2152	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2153	{
1986	free (w);	2154	free (w);
1987	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2156	// no longer anything immediate to do.
1989	}	2157	}
1990		2158
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1994		2162
1995		2163
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2245
2078	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
2079	static ev_timer tw;	2247	static ev_timer tw;
2080		2248
2081	static void	2249	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2250	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2251	{
2084	}	2252	}
2085		2253
2086	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
2087	static void	2255	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2256	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2257	{
2090	int timeout = 3600000;	2258	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2276	}
2109	}	2277	}
2110		2278
2111	// stop all watchers after blocking	2279	// stop all watchers after blocking
2112	static void	2280	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2281	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2282	{
2115	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
2116		2284
2117	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
2118	{	2286	{
…		…
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2234	but you will also have to stop and restart any C<ev_embed> watchers	2402	but you will also have to stop and restart any C<ev_embed> watchers
2235	yourself - but you can use a fork watcher to handle this automatically,	2403	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2404	and future versions of libev might do just that.
2237		2405
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2408	portable one.
2241		2409
2242	So when you want to use this feature you will always have to be prepared	2410	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	2411	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	2412	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.	2413	create it, and if that fails, use the normal loop for everything.
		2414
		2415	=head3 C<ev_embed> and fork
		2416
		2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2418	automatically be applied to the embedded loop as well, so no special
		2419	fork handling is required in that case. When the watcher is not running,
		2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2421	as applicable.
2246		2422
2247	=head3 Watcher-Specific Functions and Data Members	2423	=head3 Watcher-Specific Functions and Data Members
2248		2424
2249	=over 4	2425	=over 4
2250		2426
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2455	used).
2280		2456
2281	struct ev_loop *loop_hi = ev_default_init (0);	2457	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2458	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2459	ev_embed embed;
2284		2460
2285	// see if there is a chance of getting one that works	2461	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2462	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2478	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2480
2305	struct ev_loop *loop = ev_default_init (0);	2481	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2482	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2483	ev_embed embed;
2308		2484
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2487	{
2312	ev_embed_init (&embed, 0, loop_socket);	2488	ev_embed_init (&embed, 0, loop_socket);
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2544	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2545	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2546	need elaborate support such as pthreads.
2371		2547
2372	That means that if you want to queue data, you have to provide your own	2548	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2549	queue. But at least I can tell you how to implement locking around your
2374	queue:	2550	queue:
2375		2551
2376	=over 4	2552	=over 4
2377		2553
2378	=item queueing from a signal handler context	2554	=item queueing from a signal handler context
2379		2555
2380	To implement race-free queueing, you simply add to the queue in the signal	2556	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	2557	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2558	an example that does that for some fictitious SIGUSR1 handler:
2383		2559
2384	static ev_async mysig;	2560	static ev_async mysig;
2385		2561
2386	static void	2562	static void
2387	sigusr1_handler (void)	2563	sigusr1_handler (void)
…		…
2454		2630
2455	=item ev_async_init (ev_async *, callback)	2631	=item ev_async_init (ev_async *, callback)
2456		2632
2457	Initialises and configures the async watcher - it has no parameters of any	2633	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2635	trust me.
2460		2636
2461	=item ev_async_send (loop, ev_async *)	2637	=item ev_async_send (loop, ev_async *)
2462		2638
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2641	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2643	section below on what exactly this means).
2468		2644
2469	This call incurs the overhead of a system call only once per loop iteration,	2645	This call incurs the overhead of a system call only once per loop iteration,
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2646	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2670	=over 4
2495		2671
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2673
2498	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2675	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	2676	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	2677	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2678	more watchers yourself.
2503		2679
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	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	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2682	the given C<fd> and C<events> set will be created and started.
2507		2683
2508	If C<timeout> is less than 0, then no timeout watcher will be	2684	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	2685	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	2686	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2687
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2688	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	2689	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>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2696
2518	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
2519	{	2698	{
		2699	if (revents & EV_READ)
		2700	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2701	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2702	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2703	}
2525		2704
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2706
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2707	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2708
2530	Feeds the given event set into the event loop, as if the specified event	2709	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	2710	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
2533		2712
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2714
2536	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2716	the given events it.
2538		2717
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2719
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2721	loop!).
2543		2722
2544	=back	2723	=back
…		…
2676		2855
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2857
2679	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
2680		2859
2681	Example:	2860	Example: Use a plain function as callback.
2682		2861
2683	static void io_cb (ev::io &w, int revents) { }	2862	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2863	iow.set <io_cb> ();
2685		2864
2686	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2904	the constructor.
2726		2905
2727	class myclass	2906	class myclass
2728	{	2907	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2910
2732	myclass (int fd)	2911	myclass (int fd)
2733	{	2912	{
2734	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2930	=item Perl
2752		2931
2753	The EV module implements the full libev API and is actually used to test	2932	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	2933	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2934	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2935	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
2758		2938
2759	It can be found and installed via CPAN, its homepage is at	2939	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2940	L<http://software.schmorp.de/pkg/EV>.
2761		2941
2762	=item Python	2942	=item Python
…		…
2941		3121
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3122	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3123
2944	Libev can be configured via a variety of preprocessor symbols you have to	3124	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3125	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3126	autoconf is documented for every option.
2947		3127
2948	=over 4	3128	=over 4
2949		3129
2950	=item EV_STANDALONE	3130	=item EV_STANDALONE
2951		3131
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3301	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3302	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3303	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3304	fine.
3125		3305
3126	If your embedding application does not need any priorities, defining these both to	3306	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3307	both to C<0> will save some memory and CPU.
3128		3308
3129	=item EV_PERIODIC_ENABLE	3309	=item EV_PERIODIC_ENABLE
3130		3310
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3311	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3312	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3319	code.
3140		3320
3141	=item EV_EMBED_ENABLE	3321	=item EV_EMBED_ENABLE
3142		3322
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3323	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3324	defined to be C<0>, then they are not. Embed watchers rely on most other
		3325	watcher types, which therefore must not be disabled.
3145		3326
3146	=item EV_STAT_ENABLE	3327	=item EV_STAT_ENABLE
3147		3328
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3329	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3330	defined to be C<0>, then they are not.
…		…
3181	two).	3362	two).
3182		3363
3183	=item EV_USE_4HEAP	3364	=item EV_USE_4HEAP
3184		3365
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3366	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3367	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3368	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3369	faster performance with many (thousands) of watchers.
3189		3370
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3372	(disabled).
3192		3373
3193	=item EV_HEAP_CACHE_AT	3374	=item EV_HEAP_CACHE_AT
3194		3375
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3376	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3377	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3378	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3379	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3380	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3381	noticeably with many (hundreds) of watchers.
3201		3382
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3383	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3384	(disabled).
3204		3385
3205	=item EV_VERIFY	3386	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3392	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3393	verification code will be called very frequently, which will slow down
3213	libev considerably.	3394	libev considerably.
3214		3395
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3396	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3397	C<0>.
3217		3398
3218	=item EV_COMMON	3399	=item EV_COMMON
3219		3400
3220	By default, all watchers have a C<void *data> member. By redefining	3401	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3402	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3419	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3420	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3421	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3422	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3423	method calls instead of plain function calls in C++.
		3424
		3425	=back
3243		3426
3244	=head2 EXPORTED API SYMBOLS	3427	=head2 EXPORTED API SYMBOLS
3245		3428
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3429	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3430	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3477	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3478
3296	#include "ev_cpp.h"	3479	#include "ev_cpp.h"
3297	#include "ev.c"	3480	#include "ev.c"
3298		3481
		3482	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3483
3300	=head1 THREADS AND COROUTINES	3484	=head2 THREADS AND COROUTINES
3301		3485
3302	=head2 THREADS	3486	=head3 THREADS
3303		3487
3304	Libev itself is thread-safe (unless the opposite is specifically	3488	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3489	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3490	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3491	are no concurrent calls into any libev function with the same loop
		3492	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3493	of course): libev guarantees that different event loops share no data
3309	need locking.	3494	structures that need any locking.
3310		3495
3311	Or to put it differently: calls with different loop parameters can be done	3496	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3497	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3498	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3499	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3500	a mutex per loop).
3316		3501
3317	Specifically to support threads (and signal handlers), libev implements	3502	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3503	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3504	concurrency on the same event loop, namely waking it up "from the
		3505	outside".
3320		3506
3321	If you want to know which design (one loop, locking, or multiple loops	3507	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3508	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3509	help you, but here is some generic advice:
3324		3510
3325	=over 4	3511	=over 4
3326		3512
3327	=item * most applications have a main thread: use the default libev loop	3513	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3514	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3538	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3539	watcher callback into the event loop interested in the signal.
3354		3540
3355	=back	3541	=back
3356		3542
3357	=head2 COROUTINES	3543	=head3 COROUTINES
3358		3544
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3545	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3546	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3547	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3548	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3549	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3550	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3551
3366	Care has been taken to ensure that libev does not keep local state inside	3552	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	3553	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3554	they do not clal any callbacks.
3368		3555
		3556	=head2 COMPILER WARNINGS
3369		3557
3370	=head1 COMPLEXITIES	3558	Depending on your compiler and compiler settings, you might get no or a
		3559	lot of warnings when compiling libev code. Some people are apparently
		3560	scared by this.
3371		3561
3372	In this section the complexities of (many of) the algorithms used inside	3562	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3563	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3564	warning options. "Warn-free" code therefore cannot be a goal except when
		3565	targeting a specific compiler and compiler-version.
3375		3566
3376	All of the following are about amortised time: If an array needs to be	3567	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3568	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	3569	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3570
3382	=over 4	3571	And of course, some compiler warnings are just plain stupid, or simply
		3572	wrong (because they don't actually warn about the condition their message
		3573	seems to warn about). For example, certain older gcc versions had some
		3574	warnings that resulted an extreme number of false positives. These have
		3575	been fixed, but some people still insist on making code warn-free with
		3576	such buggy versions.
3383		3577
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3578	While libev is written to generate as few warnings as possible,
		3579	"warn-free" code is not a goal, and it is recommended not to build libev
		3580	with any compiler warnings enabled unless you are prepared to cope with
		3581	them (e.g. by ignoring them). Remember that warnings are just that:
		3582	warnings, not errors, or proof of bugs.
3385		3583
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3584
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3585	=head2 VALGRIND
3391		3586
3392	That means that changing a timer costs less than removing/adding them	3587	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	3588	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3589
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3590	If you think you found a bug (memory leak, uninitialised data access etc.)
		3591	in libev, then check twice: If valgrind reports something like:
3396		3592
3397	These just add the watcher into an array or at the head of a list.	3593	==2274== definitely lost: 0 bytes in 0 blocks.
		3594	==2274== possibly lost: 0 bytes in 0 blocks.
		3595	==2274== still reachable: 256 bytes in 1 blocks.
3398		3596
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3597	Then there is no memory leak, just as memory accounted to global variables
		3598	is not a memleak - the memory is still being refernced, and didn't leak.
3400		3599
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3600	Similarly, under some circumstances, valgrind might report kernel bugs
		3601	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3602	although an acceptable workaround has been found here), or it might be
		3603	confused.
3402		3604
3403	These watchers are stored in lists then need to be walked to find the	3605	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	3606	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3607
3407	=item Finding the next timer in each loop iteration: O(1)	3608	If you are unsure about something, feel free to contact the mailing list
		3609	with the full valgrind report and an explanation on why you think this
		3610	is a bug in libev (best check the archives, too :). However, don't be
		3611	annoyed when you get a brisk "this is no bug" answer and take the chance
		3612	of learning how to interpret valgrind properly.
3408		3613
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3614	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3615	I suggest using suppression lists.
3411		3616
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3617
3414	A change means an I/O watcher gets started or stopped, which requires	3618	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3619
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3620	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3621
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3622	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	3623	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3624	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3625	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3636
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3637	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3638	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3639	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3640	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3641	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3642	available).
3463		3643
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3644	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3645	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3646	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3657	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3658
3479	#include "ev.h"	3659	#include "ev.h"
3480		3660
3481	And compile the following F<evwrap.c> file into your project (make sure	3661	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3662	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3663
3484	#include "evwrap.h"	3664	#include "evwrap.h"
3485	#include "ev.c"	3665	#include "ev.c"
3486		3666
3487	=over 4	3667	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3712	wrap all I/O functions and provide your own fd management, but the cost of
3533	calling select (O(n²)) will likely make this unworkable.	3713	calling select (O(n²)) will likely make this unworkable.
3534		3714
3535	=back	3715	=back
3536		3716
3537
3538	=head1 PORTABILITY REQUIREMENTS	3717	=head2 PORTABILITY REQUIREMENTS
3539		3718
3540	In addition to a working ISO-C implementation, libev relies on a few	3719	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3720	backend-specific APIs, libev relies on a few additional extensions:
3542		3721
3543	=over 4	3722	=over 4
3544		3723
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3724	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3725	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3731	calls them using an C<ev_watcher *> internally.
3553		3732
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3733	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3734
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3735	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3736	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3737	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3738	believed to be sufficiently portable.
3560		3739
3561	=item C<sigprocmask> must work in a threaded environment	3740	=item C<sigprocmask> must work in a threaded environment
3562		3741
…		…
3571	except the initial one, and run the default loop in the initial thread as	3750	except the initial one, and run the default loop in the initial thread as
3572	well.	3751	well.
3573		3752
3574	=item C<long> must be large enough for common memory allocation sizes	3753	=item C<long> must be large enough for common memory allocation sizes
3575		3754
3576	To improve portability and simplify using libev, libev uses C<long>	3755	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3756	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3757	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3758	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3759	watchers.
3581		3760
3582	=item C<double> must hold a time value in seconds with enough accuracy	3761	=item C<double> must hold a time value in seconds with enough accuracy
3583		3762
3584	The type C<double> is used to represent timestamps. It is required to	3763	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3764	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3768	=back
3590		3769
3591	If you know of other additional requirements drop me a note.	3770	If you know of other additional requirements drop me a note.
3592		3771
3593		3772
3594	=head1 COMPILER WARNINGS	3773	=head1 ALGORITHMIC COMPLEXITIES
3595		3774
3596	Depending on your compiler and compiler settings, you might get no or a	3775	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3776	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3777	the documentation for C<ev_default_init>.
3599		3778
3600	However, these are unavoidable for many reasons. For one, each compiler	3779	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	3780	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3781	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3782	mean that libev does a lengthy realloc operation in rare cases, but on
		3783	average it is much faster and asymptotically approaches constant time.
3604		3784
3605	Another reason is that some compiler warnings require elaborate	3785	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3786
3609	And of course, some compiler warnings are just plain stupid, or simply	3787	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3788
3613	While libev is written to generate as few warnings as possible,	3789	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	3790	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	3791	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3792
		3793	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3794
3620	=head1 VALGRIND	3795	That means that changing a timer costs less than removing/adding them,
		3796	as only the relative motion in the event queue has to be paid for.
3621		3797
3622	Valgrind has a special section here because it is a popular tool that is	3798	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3799
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3800	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		3801
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3802	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3803
3632	Then there is no memory leak. Similarly, under some circumstances,	3804	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3805
3636	If you are unsure about something, feel free to contact the mailing list	3806	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	3807	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	3808	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	3809	is rare).
3640	properly.
3641		3810
3642	If you need, for some reason, empty reports from valgrind for your project	3811	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3812
		3813	By virtue of using a binary or 4-heap, the next timer is always found at a
		3814	fixed position in the storage array.
		3815
		3816	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3817
		3818	A change means an I/O watcher gets started or stopped, which requires
		3819	libev to recalculate its status (and possibly tell the kernel, depending
		3820	on backend and whether C<ev_io_set> was used).
		3821
		3822	=item Activating one watcher (putting it into the pending state): O(1)
		3823
		3824	=item Priority handling: O(number_of_priorities)
		3825
		3826	Priorities are implemented by allocating some space for each
		3827	priority. When doing priority-based operations, libev usually has to
		3828	linearly search all the priorities, but starting/stopping and activating
		3829	watchers becomes O(1) with respect to priority handling.
		3830
		3831	=item Sending an ev_async: O(1)
		3832
		3833	=item Processing ev_async_send: O(number_of_async_watchers)
		3834
		3835	=item Processing signals: O(max_signal_number)
		3836
		3837	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3838	calls in the current loop iteration. Checking for async and signal events
		3839	involves iterating over all running async watchers or all signal numbers.
		3840
		3841	=back
3644		3842
3645		3843
3646	=head1 AUTHOR	3844	=head1 AUTHOR
3647		3845
3648	Marc Lehmann <libev@schmorp.de>.	3846	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs. Revision 1.200 by root, Thu Oct 23 07:33:45 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.200 by root, Thu Oct 23 07:33:45 2008 UTC