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

Comparing libev/ev.pod (file contents):
Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs.
Revision 1.284 by root, Sun Mar 14 21:05:52 2010 UTC

…		…
98	=head2 FEATURES	98	=head2 FEATURES
99		99
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
110		111
111	It also is quite fast (see this	112	It also is quite fast (see this
112	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	114	for example).
114		115
…		…
117	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	124	this argument.
124		125
125	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
126		127
127	Libev represents time as a single floating point number, representing	128	Libev represents time as a single floating point number, representing
…		…
362	flag.	363	flag.
363		364
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	366	environment variable.
366		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		389
369	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
371	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
…		…
394		415
395	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	416	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
397		418
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
399		423
400	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
401	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
402	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
403	epoll scales either O(1) or O(active_fds).	427	epoll scales either O(1) or O(active_fds).
…		…
518		542
519	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
520		544
521	=back	545	=back
522		546
523	If one or more of these are or'ed into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
526		551
527	Example: This is the most typical usage.	552	Example: This is the most typical usage.
528		553
529	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
574		599
575	In general it is not advisable to call this function except in the	600	In general it is not advisable to call this function except in the
576	rare occasion where you really need to free e.g. the signal handling	601	rare occasion where you really need to free e.g. the signal handling
577	pipe fds. If you need dynamically allocated loops it is better to use	602	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
579		604
580	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
581		606
582	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
621		646
622	This value can sometimes be useful as a generation counter of sorts (it	647	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	648	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	649	C<ev_prepare> and C<ev_check> calls.
625		650
		651	=item unsigned int ev_loop_depth (loop)
		652
		653	Returns the number of times C<ev_loop> was entered minus the number of
		654	times C<ev_loop> was exited, in other words, the recursion depth.
		655
		656	Outside C<ev_loop>, this number is zero. In a callback, this number is
		657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		658	in which case it is higher.
		659
		660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		661	etc.), doesn't count as exit.
		662
626	=item unsigned int ev_backend (loop)	663	=item unsigned int ev_backend (loop)
627		664
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	666	use.
630		667
…		…
675	event loop time (see C<ev_now_update>).	712	event loop time (see C<ev_now_update>).
676		713
677	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
678		715
679	Finally, this is it, the event handler. This function usually is called	716	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	717	after you have initialised all your watchers and you want to start
681	events.	718	handling events.
682		719
683	If the flags argument is specified as C<0>, it will not return until	720	If the flags argument is specified as C<0>, it will not return until
684	either no event watchers are active anymore or C<ev_unloop> was called.	721	either no event watchers are active anymore or C<ev_unloop> was called.
685		722
686	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
…		…
760		797
761	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
762	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
763	count is nonzero, C<ev_loop> will not return on its own.	800	count is nonzero, C<ev_loop> will not return on its own.
764		801
765	If you have a watcher you never unregister that should not keep C<ev_loop>	802	This is useful when you have a watcher that you never intend to
766	from returning, call ev_unref() after starting, and ev_ref() before	803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
767	stopping it.	805	before stopping it.
768		806
769	As an example, libev itself uses this for its internal signal pipe: It	807	As an example, libev itself uses this for its internal signal pipe: It
770	is not visible to the libev user and should not keep C<ev_loop> from	808	is not visible to the libev user and should not keep C<ev_loop> from
771	exiting if no event watchers registered by it are active. It is also an	809	exiting if no event watchers registered by it are active. It is also an
772	excellent way to do this for generic recurring timers or from within	810	excellent way to do this for generic recurring timers or from within
…		…
844	more often than 100 times per second:	882	more often than 100 times per second:
845		883
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
		951
849	=item ev_loop_verify (loop)	952	=item ev_loop_verify (loop)
850		953
851	This function only does something when C<EV_VERIFY> support has been	954	This function only does something when C<EV_VERIFY> support has been
852	compiled in, which is the default for non-minimal builds. It tries to go	955	compiled in, which is the default for non-minimal builds. It tries to go
853	through all internal structures and checks them for validity. If anything	956	through all internal structures and checks them for validity. If anything
…		…
1029		1132
1030	ev_io w;	1133	ev_io w;
1031	ev_init (&w, my_cb);	1134	ev_init (&w, my_cb);
1032	ev_io_set (&w, STDIN_FILENO, EV_READ);	1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
1033		1136
1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1035		1138
1036	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
1037	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
1038	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
1039	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
…		…
1052		1155
1053	Example: Initialise and set an C<ev_io> watcher in one step.	1156	Example: Initialise and set an C<ev_io> watcher in one step.
1054		1157
1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1056		1159
1057	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1058		1161
1059	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
1060	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
1061		1164
1062	Example: Start the C<ev_io> watcher that is being abused as example in this	1165	Example: Start the C<ev_io> watcher that is being abused as example in this
1063	whole section.	1166	whole section.
1064		1167
1065	ev_io_start (EV_DEFAULT_UC, &w);	1168	ev_io_start (EV_DEFAULT_UC, &w);
1066		1169
1067	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1068		1171
1069	Stops the given watcher if active, and clears the pending status (whether	1172	Stops the given watcher if active, and clears the pending status (whether
1070	the watcher was active or not).	1173	the watcher was active or not).
1071		1174
1072	It is possible that stopped watchers are pending - for example,	1175	It is possible that stopped watchers are pending - for example,
…		…
1097	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
1098		1201
1099	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
1100	(modulo threads).	1203	(modulo threads).
1101		1204
1102	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
1103		1206
1104	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
1105		1208
1106	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
1107	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1138	returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
1139	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
1140		1243
1141	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1142	callback to be invoked, which can be accomplished with this function.	1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
1143		1260
1144	=back	1261	=back
1145		1262
1146		1263
1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1421		1538
1422	So when you encounter spurious, unexplained daemon exits, make sure you	1539	So when you encounter spurious, unexplained daemon exits, make sure you
1423	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1424	somewhere, as that would have given you a big clue).	1541	somewhere, as that would have given you a big clue).
1425		1542
		1543	=head3 The special problem of accept()ing when you can't
		1544
		1545	Many implementations of the POSIX C<accept> function (for example,
		1546	found in port-2004 Linux) have the peculiar behaviour of not removing a
		1547	connection from the pending queue in all error cases.
		1548
		1549	For example, larger servers often run out of file descriptors (because
		1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1551	rejecting the connection, leading to libev signalling readiness on
		1552	the next iteration again (the connection still exists after all), and
		1553	typically causing the program to loop at 100% CPU usage.
		1554
		1555	Unfortunately, the set of errors that cause this issue differs between
		1556	operating systems, there is usually little the app can do to remedy the
		1557	situation, and no known thread-safe method of removing the connection to
		1558	cope with overload is known (to me).
		1559
		1560	One of the easiest ways to handle this situation is to just ignore it
		1561	- when the program encounters an overload, it will just loop until the
		1562	situation is over. While this is a form of busy waiting, no OS offers an
		1563	event-based way to handle this situation, so it's the best one can do.
		1564
		1565	A better way to handle the situation is to log any errors other than
		1566	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1567	messages, and continue as usual, which at least gives the user an idea of
		1568	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1569	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1570	usage.
		1571
		1572	If your program is single-threaded, then you could also keep a dummy file
		1573	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1574	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1575	close that fd, and create a new dummy fd. This will gracefully refuse
		1576	clients under typical overload conditions.
		1577
		1578	The last way to handle it is to simply log the error and C<exit>, as
		1579	is often done with C<malloc> failures, but this results in an easy
		1580	opportunity for a DoS attack.
1426		1581
1427	=head3 Watcher-Specific Functions	1582	=head3 Watcher-Specific Functions
1428		1583
1429	=over 4	1584	=over 4
1430		1585
…		…
1480		1635
1481	The callback is guaranteed to be invoked only I<after> its timeout has	1636	The callback is guaranteed to be invoked only I<after> its timeout has
1482	passed (not I<at>, so on systems with very low-resolution clocks this	1637	passed (not I<at>, so on systems with very low-resolution clocks this
1483	might introduce a small delay). If multiple timers become ready during the	1638	might introduce a small delay). If multiple timers become ready during the
1484	same loop iteration then the ones with earlier time-out values are invoked	1639	same loop iteration then the ones with earlier time-out values are invoked
1485	before ones with later time-out values (but this is no longer true when a	1640	before ones of the same priority with later time-out values (but this is
1486	callback calls C<ev_loop> recursively).	1641	no longer true when a callback calls C<ev_loop> recursively).
1487		1642
1488	=head3 Be smart about timeouts	1643	=head3 Be smart about timeouts
1489		1644
1490	Many real-world problems involve some kind of timeout, usually for error	1645	Many real-world problems involve some kind of timeout, usually for error
1491	recovery. A typical example is an HTTP request - if the other side hangs,	1646	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1678		1833
1679	If the event loop is suspended for a long time, you can also force an	1834	If the event loop is suspended for a long time, you can also force an
1680	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1835	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1681	()>.	1836	()>.
1682		1837
		1838	=head3 The special problems of suspended animation
		1839
		1840	When you leave the server world it is quite customary to hit machines that
		1841	can suspend/hibernate - what happens to the clocks during such a suspend?
		1842
		1843	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1844	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1845	to run until the system is suspended, but they will not advance while the
		1846	system is suspended. That means, on resume, it will be as if the program
		1847	was frozen for a few seconds, but the suspend time will not be counted
		1848	towards C<ev_timer> when a monotonic clock source is used. The real time
		1849	clock advanced as expected, but if it is used as sole clocksource, then a
		1850	long suspend would be detected as a time jump by libev, and timers would
		1851	be adjusted accordingly.
		1852
		1853	I would not be surprised to see different behaviour in different between
		1854	operating systems, OS versions or even different hardware.
		1855
		1856	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1857	time jump in the monotonic clocks and the realtime clock. If the program
		1858	is suspended for a very long time, and monotonic clock sources are in use,
		1859	then you can expect C<ev_timer>s to expire as the full suspension time
		1860	will be counted towards the timers. When no monotonic clock source is in
		1861	use, then libev will again assume a timejump and adjust accordingly.
		1862
		1863	It might be beneficial for this latter case to call C<ev_suspend>
		1864	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1865	deterministic behaviour in this case (you can do nothing against
		1866	C<SIGSTOP>).
		1867
1683	=head3 Watcher-Specific Functions and Data Members	1868	=head3 Watcher-Specific Functions and Data Members
1684		1869
1685	=over 4	1870	=over 4
1686		1871
1687	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1872	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1712	If the timer is repeating, either start it if necessary (with the	1897	If the timer is repeating, either start it if necessary (with the
1713	C<repeat> value), or reset the running timer to the C<repeat> value.	1898	C<repeat> value), or reset the running timer to the C<repeat> value.
1714		1899
1715	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1900	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1716	usage example.	1901	usage example.
		1902
		1903	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1904
		1905	Returns the remaining time until a timer fires. If the timer is active,
		1906	then this time is relative to the current event loop time, otherwise it's
		1907	the timeout value currently configured.
		1908
		1909	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1910	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1911	will return C<4>. When the timer expires and is restarted, it will return
		1912	roughly C<7> (likely slightly less as callback invocation takes some time,
		1913	too), and so on.
1717		1914
1718	=item ev_tstamp repeat [read-write]	1915	=item ev_tstamp repeat [read-write]
1719		1916
1720	The current C<repeat> value. Will be used each time the watcher times out	1917	The current C<repeat> value. Will be used each time the watcher times out
1721	or C<ev_timer_again> is called, and determines the next timeout (if any),	1918	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1957	Signal watchers will trigger an event when the process receives a specific	2154	Signal watchers will trigger an event when the process receives a specific
1958	signal one or more times. Even though signals are very asynchronous, libev	2155	signal one or more times. Even though signals are very asynchronous, libev
1959	will try it's best to deliver signals synchronously, i.e. as part of the	2156	will try it's best to deliver signals synchronously, i.e. as part of the
1960	normal event processing, like any other event.	2157	normal event processing, like any other event.
1961		2158
1962	If you want signals asynchronously, just use C<sigaction> as you would	2159	If you want signals to be delivered truly asynchronously, just use
1963	do without libev and forget about sharing the signal. You can even use	2160	C<sigaction> as you would do without libev and forget about sharing
1964	C<ev_async> from a signal handler to synchronously wake up an event loop.	2161	the signal. You can even use C<ev_async> from a signal handler to
		2162	synchronously wake up an event loop.
1965		2163
1966	You can configure as many watchers as you like per signal. Only when the	2164	You can configure as many watchers as you like for the same signal, but
		2165	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2166	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2167	C<SIGINT> in both the default loop and another loop at the same time. At
		2168	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2169
1967	first watcher gets started will libev actually register a signal handler	2170	When the first watcher gets started will libev actually register something
1968	with the kernel (thus it coexists with your own signal handlers as long as	2171	with the kernel (thus it coexists with your own signal handlers as long as
1969	you don't register any with libev for the same signal). Similarly, when	2172	you don't register any with libev for the same signal).
1970	the last signal watcher for a signal is stopped, libev will reset the
1971	signal handler to SIG_DFL (regardless of what it was set to before).
1972		2173
1973	If possible and supported, libev will install its handlers with	2174	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2175	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2176	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2177	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2178	and unblock them in an C<ev_prepare> watcher.
		2179
		2180	=head3 The special problem of inheritance over fork/execve/pthread_create
		2181
		2182	Both the signal mask (C<sigprocmask>) and the signal disposition
		2183	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2184	stopping it again), that is, libev might or might not block the signal,
		2185	and might or might not set or restore the installed signal handler.
		2186
		2187	While this does not matter for the signal disposition (libev never
		2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2189	C<execve>), this matters for the signal mask: many programs do not expect
		2190	certain signals to be blocked.
		2191
		2192	This means that before calling C<exec> (from the child) you should reset
		2193	the signal mask to whatever "default" you expect (all clear is a good
		2194	choice usually).
		2195
		2196	The simplest way to ensure that the signal mask is reset in the child is
		2197	to install a fork handler with C<pthread_atfork> that resets it. That will
		2198	catch fork calls done by libraries (such as the libc) as well.
		2199
		2200	In current versions of libev, the signal will not be blocked indefinitely
		2201	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2202	the window of opportunity for problems, it will not go away, as libev
		2203	I<has> to modify the signal mask, at least temporarily.
		2204
		2205	So I can't stress this enough: I<If you do not reset your signal mask when
		2206	you expect it to be empty, you have a race condition in your code>. This
		2207	is not a libev-specific thing, this is true for most event libraries.
1978		2208
1979	=head3 Watcher-Specific Functions and Data Members	2209	=head3 Watcher-Specific Functions and Data Members
1980		2210
1981	=over 4	2211	=over 4
1982		2212
…		…
2020	in the next callback invocation is not.	2250	in the next callback invocation is not.
2021		2251
2022	Only the default event loop is capable of handling signals, and therefore	2252	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2253	you can only register child watchers in the default event loop.
2024		2254
		2255	Due to some design glitches inside libev, child watchers will always be
		2256	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2257	libev)
		2258
2025	=head3 Process Interaction	2259	=head3 Process Interaction
2026		2260
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2261	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2262	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2263	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2264	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2265	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2266	children, even ones not watched.
2033		2267
2034	=head3 Overriding the Built-In Processing	2268	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2278	=head3 Stopping the Child Watcher
2045		2279
2046	Currently, the child watcher never gets stopped, even when the	2280	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2281	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2282	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2283	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2284	problem).
2050		2285
2051	=head3 Watcher-Specific Functions and Data Members	2286	=head3 Watcher-Specific Functions and Data Members
2052		2287
2053	=over 4	2288	=over 4
2054		2289
…		…
2794	=head3 Queueing	3029	=head3 Queueing
2795		3030
2796	C<ev_async> does not support queueing of data in any way. The reason	3031	C<ev_async> does not support queueing of data in any way. The reason
2797	is that the author does not know of a simple (or any) algorithm for a	3032	is that the author does not know of a simple (or any) algorithm for a
2798	multiple-writer-single-reader queue that works in all cases and doesn't	3033	multiple-writer-single-reader queue that works in all cases and doesn't
2799	need elaborate support such as pthreads.	3034	need elaborate support such as pthreads or unportable memory access
		3035	semantics.
2800		3036
2801	That means that if you want to queue data, you have to provide your own	3037	That means that if you want to queue data, you have to provide your own
2802	queue. But at least I can tell you how to implement locking around your	3038	queue. But at least I can tell you how to implement locking around your
2803	queue:	3039	queue:
2804		3040
…		…
2962	/* doh, nothing entered */;	3198	/* doh, nothing entered */;
2963	}	3199	}
2964		3200
2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2966		3202
2967	=item ev_feed_event (struct ev_loop , watcher , int revents)
2968
2969	Feeds the given event set into the event loop, as if the specified event
2970	had happened for the specified watcher (which must be a pointer to an
2971	initialised but not necessarily started event watcher).
2972
2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3203	=item ev_feed_fd_event (loop, int fd, int revents)
2974		3204
2975	Feed an event on the given fd, as if a file descriptor backend detected	3205	Feed an event on the given fd, as if a file descriptor backend detected
2976	the given events it.	3206	the given events it.
2977		3207
2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3208	=item ev_feed_signal_event (loop, int signum)
2979		3209
2980	Feed an event as if the given signal occurred (C<loop> must be the default	3210	Feed an event as if the given signal occurred (C<loop> must be the default
2981	loop!).	3211	loop!).
2982		3212
2983	=back	3213	=back
…		…
3063		3293
3064	=over 4	3294	=over 4
3065		3295
3066	=item ev::TYPE::TYPE ()	3296	=item ev::TYPE::TYPE ()
3067		3297
3068	=item ev::TYPE::TYPE (struct ev_loop *)	3298	=item ev::TYPE::TYPE (loop)
3069		3299
3070	=item ev::TYPE::~TYPE	3300	=item ev::TYPE::~TYPE
3071		3301
3072	The constructor (optionally) takes an event loop to associate the watcher	3302	The constructor (optionally) takes an event loop to associate the watcher
3073	with. If it is omitted, it will use C<EV_DEFAULT>.	3303	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3150	Example: Use a plain function as callback.	3380	Example: Use a plain function as callback.
3151		3381
3152	static void io_cb (ev::io &w, int revents) { }	3382	static void io_cb (ev::io &w, int revents) { }
3153	iow.set <io_cb> ();	3383	iow.set <io_cb> ();
3154		3384
3155	=item w->set (struct ev_loop *)	3385	=item w->set (loop)
3156		3386
3157	Associates a different C<struct ev_loop> with this watcher. You can only	3387	Associates a different C<struct ev_loop> with this watcher. You can only
3158	do this when the watcher is inactive (and not pending either).	3388	do this when the watcher is inactive (and not pending either).
3159		3389
3160	=item w->set ([arguments])	3390	=item w->set ([arguments])
…		…
3257	=item Ocaml	3487	=item Ocaml
3258		3488
3259	Erkki Seppala has written Ocaml bindings for libev, to be found at	3489	Erkki Seppala has written Ocaml bindings for libev, to be found at
3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3490	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3261		3491
		3492	=item Lua
		3493
		3494	Brian Maher has written a partial interface to libev for lua (at the
		3495	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3496	L<http://github.com/brimworks/lua-ev>.
		3497
3262	=back	3498	=back
3263		3499
3264		3500
3265	=head1 MACRO MAGIC	3501	=head1 MACRO MAGIC
3266		3502
…		…
3419	libev.m4	3655	libev.m4
3420		3656
3421	=head2 PREPROCESSOR SYMBOLS/MACROS	3657	=head2 PREPROCESSOR SYMBOLS/MACROS
3422		3658
3423	Libev can be configured via a variety of preprocessor symbols you have to	3659	Libev can be configured via a variety of preprocessor symbols you have to
3424	define before including any of its files. The default in the absence of	3660	define before including (or compiling) any of its files. The default in
3425	autoconf is documented for every option.	3661	the absence of autoconf is documented for every option.
		3662
		3663	Symbols marked with "(h)" do not change the ABI, and can have different
		3664	values when compiling libev vs. including F<ev.h>, so it is permissible
		3665	to redefine them before including F<ev.h> without breakign compatibility
		3666	to a compiled library. All other symbols change the ABI, which means all
		3667	users of libev and the libev code itself must be compiled with compatible
		3668	settings.
3426		3669
3427	=over 4	3670	=over 4
3428		3671
3429	=item EV_STANDALONE	3672	=item EV_STANDALONE (h)
3430		3673
3431	Must always be C<1> if you do not use autoconf configuration, which	3674	Must always be C<1> if you do not use autoconf configuration, which
3432	keeps libev from including F<config.h>, and it also defines dummy	3675	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	3676	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	3677	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	3678	F<event.h> that are not directly supported by the libev core alone.
3436		3679
3437	In stanbdalone mode, libev will still try to automatically deduce the	3680	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	3681	configuration, but has to be more conservative.
3439		3682
3440	=item EV_USE_MONOTONIC	3683	=item EV_USE_MONOTONIC
3441		3684
3442	If defined to be C<1>, libev will try to detect the availability of the	3685	If defined to be C<1>, libev will try to detect the availability of the
…		…
3507	be used is the winsock select). This means that it will call	3750	be used is the winsock select). This means that it will call
3508	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3751	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3509	it is assumed that all these functions actually work on fds, even	3752	it is assumed that all these functions actually work on fds, even
3510	on win32. Should not be defined on non-win32 platforms.	3753	on win32. Should not be defined on non-win32 platforms.
3511		3754
3512	=item EV_FD_TO_WIN32_HANDLE	3755	=item EV_FD_TO_WIN32_HANDLE(fd)
3513		3756
3514	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3757	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3515	file descriptors to socket handles. When not defining this symbol (the	3758	file descriptors to socket handles. When not defining this symbol (the
3516	default), then libev will call C<_get_osfhandle>, which is usually	3759	default), then libev will call C<_get_osfhandle>, which is usually
3517	correct. In some cases, programs use their own file descriptor management,	3760	correct. In some cases, programs use their own file descriptor management,
3518	in which case they can provide this function to map fds to socket handles.	3761	in which case they can provide this function to map fds to socket handles.
		3762
		3763	=item EV_WIN32_HANDLE_TO_FD(handle)
		3764
		3765	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3766	using the standard C<_open_osfhandle> function. For programs implementing
		3767	their own fd to handle mapping, overwriting this function makes it easier
		3768	to do so. This can be done by defining this macro to an appropriate value.
		3769
		3770	=item EV_WIN32_CLOSE_FD(fd)
		3771
		3772	If programs implement their own fd to handle mapping on win32, then this
		3773	macro can be used to override the C<close> function, useful to unregister
		3774	file descriptors again. Note that the replacement function has to close
		3775	the underlying OS handle.
3519		3776
3520	=item EV_USE_POLL	3777	=item EV_USE_POLL
3521		3778
3522	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3779	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3523	backend. Otherwise it will be enabled on non-win32 platforms. It	3780	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3570	as well as for signal and thread safety in C<ev_async> watchers.	3827	as well as for signal and thread safety in C<ev_async> watchers.
3571		3828
3572	In the absence of this define, libev will use C<sig_atomic_t volatile>	3829	In the absence of this define, libev will use C<sig_atomic_t volatile>
3573	(from F<signal.h>), which is usually good enough on most platforms.	3830	(from F<signal.h>), which is usually good enough on most platforms.
3574		3831
3575	=item EV_H	3832	=item EV_H (h)
3576		3833
3577	The name of the F<ev.h> header file used to include it. The default if	3834	The name of the F<ev.h> header file used to include it. The default if
3578	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3835	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3579	used to virtually rename the F<ev.h> header file in case of conflicts.	3836	used to virtually rename the F<ev.h> header file in case of conflicts.
3580		3837
3581	=item EV_CONFIG_H	3838	=item EV_CONFIG_H (h)
3582		3839
3583	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3840	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3584	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3841	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3585	C<EV_H>, above.	3842	C<EV_H>, above.
3586		3843
3587	=item EV_EVENT_H	3844	=item EV_EVENT_H (h)
3588		3845
3589	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3846	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3590	of how the F<event.h> header can be found, the default is C<"event.h">.	3847	of how the F<event.h> header can be found, the default is C<"event.h">.
3591		3848
3592	=item EV_PROTOTYPES	3849	=item EV_PROTOTYPES (h)
3593		3850
3594	If defined to be C<0>, then F<ev.h> will not define any function	3851	If defined to be C<0>, then F<ev.h> will not define any function
3595	prototypes, but still define all the structs and other symbols. This is	3852	prototypes, but still define all the structs and other symbols. This is
3596	occasionally useful if you want to provide your own wrapper functions	3853	occasionally useful if you want to provide your own wrapper functions
3597	around libev functions.	3854	around libev functions.
…		…
3619	fine.	3876	fine.
3620		3877
3621	If your embedding application does not need any priorities, defining these	3878	If your embedding application does not need any priorities, defining these
3622	both to C<0> will save some memory and CPU.	3879	both to C<0> will save some memory and CPU.
3623		3880
3624	=item EV_PERIODIC_ENABLE	3881	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3625		3884
3626	If undefined or defined to be C<1>, then periodic timers are supported. If	3885	If undefined or defined to be C<1> (and the platform supports it), then
3627	defined to be C<0>, then they are not. Disabling them saves a few kB of	3886	the respective watcher type is supported. If defined to be C<0>, then it
3628	code.	3887	is not. Disabling watcher types mainly saves codesize.
3629
3630	=item EV_IDLE_ENABLE
3631
3632	If undefined or defined to be C<1>, then idle watchers are supported. If
3633	defined to be C<0>, then they are not. Disabling them saves a few kB of
3634	code.
3635
3636	=item EV_EMBED_ENABLE
3637
3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3639	defined to be C<0>, then they are not. Embed watchers rely on most other
3640	watcher types, which therefore must not be disabled.
3641
3642	=item EV_STAT_ENABLE
3643
3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3645	defined to be C<0>, then they are not.
3646
3647	=item EV_FORK_ENABLE
3648
3649	If undefined or defined to be C<1>, then fork watchers are supported. If
3650	defined to be C<0>, then they are not.
3651
3652	=item EV_ASYNC_ENABLE
3653
3654	If undefined or defined to be C<1>, then async watchers are supported. If
3655	defined to be C<0>, then they are not.
3656		3888
3657	=item EV_MINIMAL	3889	=item EV_MINIMAL
3658		3890
3659	If you need to shave off some kilobytes of code at the expense of some	3891	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	3892	speed (but with the full API), define this symbol to C<1>. Currently this
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3893	is used to override some inlining decisions, saves roughly 30% code size
3662	much smaller 2-heap for timer management over the default 4-heap.	3894	on amd64. It also selects a much smaller 2-heap for timer management over
		3895	the default 4-heap.
		3896
		3897	You can save even more by disabling watcher types you do not need
		3898	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3899	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,
		3900	eventfd and signalfd will further help, and disabling backends one doesn't
		3901	need (e.g. poll, epoll, kqueue, ports) will help further.
		3902
		3903	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3904	provide a bare-bones event library. See C<ev.h> for details on what parts
		3905	of the API are still available, and do not complain if this subset changes
		3906	over time.
		3907
		3908	This example set of settings reduces the compiled size of libev from
		3909	23.9Kb to 7.7Kb on my GNU/Linux amd64 system (and leaves little
		3910	in - there is also an effect on the amount of memory used). With
		3911	an intelligent-enough linker (gcc+binutils do this when you use
		3912	C<-Wl,--gc-sections -ffunction-sections>) further unused functions might
		3913	be left out as well automatically - a binary starting a timer and an I/O
		3914	watcher then might come out at only 5Kb.
		3915
		3916	// tuning and API changes
		3917	#define EV_MINIMAL 2
		3918	#define EV_MULTIPLICITY 0
		3919	#define EV_MINPRI 0
		3920	#define EV_MAXPRI 0
		3921
		3922	// OS-specific backends
		3923	#define EV_USE_INOTIFY 0
		3924	#define EV_USE_EVENTFD 0
		3925	#define EV_USE_SIGNALFD 0
		3926	#define EV_USE_REALTIME 0
		3927	#define EV_USE_MONOTONIC 0
		3928	#define EV_USE_CLOCK_SYSCALL 0
		3929
		3930	// disable all backends except select
		3931	#define EV_USE_POLL 0
		3932	#define EV_USE_PORT 0
		3933	#define EV_USE_KQUEUE 0
		3934	#define EV_USE_EPOLL 0
		3935
		3936	// disable all watcher types that cna be disabled
		3937	#define EV_STAT_ENABLE 0
		3938	#define EV_PERIODIC_ENABLE 0
		3939	#define EV_IDLE_ENABLE 0
		3940	#define EV_CHECK_ENABLE 0
		3941	#define EV_PREPARE_ENABLE 0
		3942	#define EV_FORK_ENABLE 0
		3943	#define EV_SIGNAL_ENABLE 0
		3944	#define EV_CHILD_ENABLE 0
		3945	#define EV_ASYNC_ENABLE 0
		3946	#define EV_EMBED_ENABLE 0
		3947
		3948	=item EV_AVOID_STDIO
		3949
		3950	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3951	functions (printf, scanf, perror etc.). This will increase the codesize
		3952	somewhat, but if your program doesn't otherwise depend on stdio and your
		3953	libc allows it, this avoids linking in the stdio library which is quite
		3954	big.
		3955
		3956	Note that error messages might become less precise when this option is
		3957	enabled.
		3958
		3959	=item EV_NSIG
		3960
		3961	The highest supported signal number, +1 (or, the number of
		3962	signals): Normally, libev tries to deduce the maximum number of signals
		3963	automatically, but sometimes this fails, in which case it can be
		3964	specified. Also, using a lower number than detected (C<32> should be
		3965	good for about any system in existance) can save some memory, as libev
		3966	statically allocates some 12-24 bytes per signal number.
3663		3967
3664	=item EV_PID_HASHSIZE	3968	=item EV_PID_HASHSIZE
3665		3969
3666	C<ev_child> watchers use a small hash table to distribute workload by	3970	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4157	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4158	watcher callback into the event loop interested in the signal.
3855		4159
3856	=back	4160	=back
3857		4161
		4162	=head4 THREAD LOCKING EXAMPLE
		4163
		4164	Here is a fictitious example of how to run an event loop in a different
		4165	thread than where callbacks are being invoked and watchers are
		4166	created/added/removed.
		4167
		4168	For a real-world example, see the C<EV::Loop::Async> perl module,
		4169	which uses exactly this technique (which is suited for many high-level
		4170	languages).
		4171
		4172	The example uses a pthread mutex to protect the loop data, a condition
		4173	variable to wait for callback invocations, an async watcher to notify the
		4174	event loop thread and an unspecified mechanism to wake up the main thread.
		4175
		4176	First, you need to associate some data with the event loop:
		4177
		4178	typedef struct {
		4179	mutex_t lock; /* global loop lock */
		4180	ev_async async_w;
		4181	thread_t tid;
		4182	cond_t invoke_cv;
		4183	} userdata;
		4184
		4185	void prepare_loop (EV_P)
		4186	{
		4187	// for simplicity, we use a static userdata struct.
		4188	static userdata u;
		4189
		4190	ev_async_init (&u->async_w, async_cb);
		4191	ev_async_start (EV_A_ &u->async_w);
		4192
		4193	pthread_mutex_init (&u->lock, 0);
		4194	pthread_cond_init (&u->invoke_cv, 0);
		4195
		4196	// now associate this with the loop
		4197	ev_set_userdata (EV_A_ u);
		4198	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4199	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4200
		4201	// then create the thread running ev_loop
		4202	pthread_create (&u->tid, 0, l_run, EV_A);
		4203	}
		4204
		4205	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4206	solely to wake up the event loop so it takes notice of any new watchers
		4207	that might have been added:
		4208
		4209	static void
		4210	async_cb (EV_P_ ev_async *w, int revents)
		4211	{
		4212	// just used for the side effects
		4213	}
		4214
		4215	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4216	protecting the loop data, respectively.
		4217
		4218	static void
		4219	l_release (EV_P)
		4220	{
		4221	userdata *u = ev_userdata (EV_A);
		4222	pthread_mutex_unlock (&u->lock);
		4223	}
		4224
		4225	static void
		4226	l_acquire (EV_P)
		4227	{
		4228	userdata *u = ev_userdata (EV_A);
		4229	pthread_mutex_lock (&u->lock);
		4230	}
		4231
		4232	The event loop thread first acquires the mutex, and then jumps straight
		4233	into C<ev_loop>:
		4234
		4235	void *
		4236	l_run (void *thr_arg)
		4237	{
		4238	struct ev_loop loop = (struct ev_loop )thr_arg;
		4239
		4240	l_acquire (EV_A);
		4241	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4242	ev_loop (EV_A_ 0);
		4243	l_release (EV_A);
		4244
		4245	return 0;
		4246	}
		4247
		4248	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4249	signal the main thread via some unspecified mechanism (signals? pipe
		4250	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4251	have been called (in a while loop because a) spurious wakeups are possible
		4252	and b) skipping inter-thread-communication when there are no pending
		4253	watchers is very beneficial):
		4254
		4255	static void
		4256	l_invoke (EV_P)
		4257	{
		4258	userdata *u = ev_userdata (EV_A);
		4259
		4260	while (ev_pending_count (EV_A))
		4261	{
		4262	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4263	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4264	}
		4265	}
		4266
		4267	Now, whenever the main thread gets told to invoke pending watchers, it
		4268	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4269	thread to continue:
		4270
		4271	static void
		4272	real_invoke_pending (EV_P)
		4273	{
		4274	userdata *u = ev_userdata (EV_A);
		4275
		4276	pthread_mutex_lock (&u->lock);
		4277	ev_invoke_pending (EV_A);
		4278	pthread_cond_signal (&u->invoke_cv);
		4279	pthread_mutex_unlock (&u->lock);
		4280	}
		4281
		4282	Whenever you want to start/stop a watcher or do other modifications to an
		4283	event loop, you will now have to lock:
		4284
		4285	ev_timer timeout_watcher;
		4286	userdata *u = ev_userdata (EV_A);
		4287
		4288	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4289
		4290	pthread_mutex_lock (&u->lock);
		4291	ev_timer_start (EV_A_ &timeout_watcher);
		4292	ev_async_send (EV_A_ &u->async_w);
		4293	pthread_mutex_unlock (&u->lock);
		4294
		4295	Note that sending the C<ev_async> watcher is required because otherwise
		4296	an event loop currently blocking in the kernel will have no knowledge
		4297	about the newly added timer. By waking up the loop it will pick up any new
		4298	watchers in the next event loop iteration.
		4299
3858	=head3 COROUTINES	4300	=head3 COROUTINES
3859		4301
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4302	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4303	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4304	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4305	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4306	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4307	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4308
3867	Care has been taken to ensure that libev does not keep local state inside	4309	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4310	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4311	they do not call any callbacks.
3870		4312

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Comparing libev/ev.pod (file contents): Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs. Revision 1.284 by root, Sun Mar 14 21:05:52 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs.
Revision 1.284 by root, Sun Mar 14 21:05:52 2010 UTC