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

Comparing libev/ev.pod (file contents):
Revision 1.355 by root, Tue Jan 11 01:41:56 2011 UTC vs.
Revision 1.410 by root, Fri May 4 20:46:17 2012 UTC

…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
174	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
175		175
176	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
177	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
178	you actually want to know. Also interesting is the combination of	178	you actually want to know. Also interesting is the combination of
179	C<ev_update_now> and C<ev_now>.	179	C<ev_now_update> and C<ev_now>.
180		180
181	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
182		182
183	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
184	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
185	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
186		192
187	=item int ev_version_major ()	193	=item int ev_version_major ()
188		194
189	=item int ev_version_minor ()	195	=item int ev_version_minor ()
190		196
…		…
241	the current system, you would need to look at C<ev_embeddable_backends ()	247	the current system, you would need to look at C<ev_embeddable_backends ()
242	& ev_supported_backends ()>, likewise for recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
243		249
244	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
245		251
246	=item ev_set_allocator (void (cb)(void *ptr, long size))	252	=item ev_set_allocator (void (cb)(void *ptr, long size) throw ())
247		253
248	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
250	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
251	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
277	}	283	}
278		284
279	...	285	...
280	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
281		287
282	=item ev_set_syserr_cb (void (cb)(const char msg))	288	=item ev_set_syserr_cb (void (cb)(const char msg) throw ())
283		289
284	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
285	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
287	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
435	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
436		442
437	=item C<EVFLAG_NOSIGMASK>	443	=item C<EVFLAG_NOSIGMASK>
438		444
439	When this flag is specified, then libev will avoid to modify the signal	445	When this flag is specified, then libev will avoid to modify the signal
440	mask. Specifically, this means you ahve to make sure signals are unblocked	446	mask. Specifically, this means you have to make sure signals are unblocked
441	when you want to receive them.	447	when you want to receive them.
442		448
443	This behaviour is useful when you want to do your own signal handling, or	449	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	450	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
446		455
447	This flag's behaviour will become the default in future versions of libev.	456	This flag's behaviour will become the default in future versions of libev.
448		457
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		459
…		…
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		490
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	492	kernels).
484		493
485	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
486	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
487	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
488	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
489		498
490	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	502	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
496	0.1ms) and so on. The biggest issue is fork races, however - if a program	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
497	forks then I<both> parent and child process have to recreate the epoll	506	forks then I<both> parent and child process have to recreate the epoll
498	set, which can take considerable time (one syscall per file descriptor)	507	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	508	and is of course hard to detect.
500		509
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
502	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
503	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
505	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
510		522
511	Epoll is truly the train wreck analog among event poll mechanisms,	523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
512	a frankenpoll, cobbled together in a hurry, no thought to design or	524	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	525	others. Oh, the pain, will it ever stop...
514		526
515	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
516	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
517	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
555		567
556	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
557	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
558	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
560	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
562	cases	574	drops fds silently in similarly hard-to-detect cases
563		575
564	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
565		577
566	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
567	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
596	among the OS-specific backends (I vastly prefer correctness over speed	608	among the OS-specific backends (I vastly prefer correctness over speed
597	hacks).	609	hacks).
598		610
599	On the negative side, the interface is I<bizarre> - so bizarre that	611	On the negative side, the interface is I<bizarre> - so bizarre that
600	even sun itself gets it wrong in their code examples: The event polling	612	even sun itself gets it wrong in their code examples: The event polling
601	function sometimes returning events to the caller even though an error	613	function sometimes returns events to the caller even though an error
602	occurred, but with no indication whether it has done so or not (yes, it's	614	occurred, but with no indication whether it has done so or not (yes, it's
603	even documented that way) - deadly for edge-triggered interfaces where	615	even documented that way) - deadly for edge-triggered interfaces where you
604	you absolutely have to know whether an event occurred or not because you	616	absolutely have to know whether an event occurred or not because you have
605	have to re-arm the watcher.	617	to re-arm the watcher.
606		618
607	Fortunately libev seems to be able to work around these idiocies.	619	Fortunately libev seems to be able to work around these idiocies.
608		620
609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
610	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
…		…
780	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
781		793
782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
783	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
784		796
785	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
786		798
787	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
788	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
789	handling events. It will ask the operating system for any new events, call	801	handling events. It will ask the operating system for any new events, call
790	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
791	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
792		804
793	If the flags argument is specified as C<0>, it will keep handling events	805	If the flags argument is specified as C<0>, it will keep handling events
794	until either no event watchers are active anymore or C<ev_break> was	806	until either no event watchers are active anymore or C<ev_break> was
795	called.	807	called.
		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
796		812
797	Please note that an explicit C<ev_break> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
798	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
799	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
800	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
801	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
802	beauty.	818	beauty.
803		819
804	This function is also I<mostly> exception-safe - you can break out of	820	This function is I<mostly> exception-safe - you can break out of a
805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
806	exception and so on. This does not decrement the C<ev_depth> value, nor	822	exception and so on. This does not decrement the C<ev_depth> value, nor
807	will it clear any outstanding C<EVBREAK_ONE> breaks.	823	will it clear any outstanding C<EVBREAK_ONE> breaks.
808		824
809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
810	those events and any already outstanding ones, but will not wait and	826	those events and any already outstanding ones, but will not wait and
…		…
822	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
823	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
825	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
826		842
827	Here are the gory details of what C<ev_run> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
828		846
829	- Increment loop depth.	847	- Increment loop depth.
830	- Reset the ev_break status.	848	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
832	LOOP:	850	LOOP:
…		…
865	anymore.	883	anymore.
866		884
867	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
871		889
872	=item ev_break (loop, how)	890	=item ev_break (loop, how)
873		891
874	Can be used to make a call to C<ev_run> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
…		…
938	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
939		957
940	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
941	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
943	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
944	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
945	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
946	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
947		966
948	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
949	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
950	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
951	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
997	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
998		1017
999	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
1000	callback.	1019	callback.
1001		1020
1002	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (release)(EV_P) throw (), void (acquire)(EV_P) throw ())
1003		1022
1004	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
1005	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
1006	each call to a libev function.	1025	each call to a libev function.
1007		1026
1008	However, C<ev_run> can run an indefinite time, so it is not feasible	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
1009	to wait for it to return. One way around this is to wake up the event	1028	to wait for it to return. One way around this is to wake up the event
1010	loop via C<ev_break> and C<av_async_send>, another way is to set these	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
1011	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
1012		1031
1013	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
1014	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
1015	afterwards.	1034	afterwards.
…		…
1155		1174
1156	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1157		1176
1158	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1159		1178
1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1161	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1162	C<ev_run> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1163	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1164	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1166	C<ev_run> from blocking).	1190	blocking).
1167		1191
1168	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1169		1193
1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1171		1195
…		…
1294		1318
1295	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1296		1320
1297	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1298		1322
1299	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1300		1324
1301	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1302	(modulo threads).	1326	(modulo threads).
1303		1327
1304	=item ev_set_priority (ev_TYPE *watcher, int priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1382	functions that do not need a watcher.
1359		1383
1360	=back	1384	=back
1361		1385
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1386	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
1363		1387	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1387	{
1388	struct my_io w = (struct my_io )w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1388
1427	=head2 WATCHER STATES	1389	=head2 WATCHER STATES
1428		1390
1429	There are various watcher states mentioned throughout this manual -	1391	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1392	active, pending and so on. In this section these states and the rules to
…		…
1433		1395
1434	=over 4	1396	=over 4
1435		1397
1436	=item initialiased	1398	=item initialiased
1437		1399
1438	Before a watcher can be registered with the event looop it has to be	1400	Before a watcher can be registered with the event loop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1403
1442	In this state it is simply some block of memory that is suitable for use	1404	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1405	use in an event loop. It can be moved around, freed, reused etc. at
		1406	will - as long as you either keep the memory contents intact, or call
		1407	C<ev_TYPE_init> again.
1444		1408
1445	=item started/running/active	1409	=item started/running/active
1446		1410
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1412	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1440	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1441	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1442	freeing it is often a good idea.
1479		1443
1480	While stopped (and not pending) the watcher is essentially in the	1444	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1445	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
1483		1448
1484	=back	1449	=back
1485		1450
1486	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1487		1452
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1645	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1646	write) will still block on the disk I/O.
1682		1647
1683	Another way to view it is that in the case of sockets, pipes, character	1648	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1649	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1650	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1651	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1652	wish to read - you would first have to request some data.
1688		1653
1689	Since files are typically not-so-well supported by advanced notification	1654	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1656	to files, even though you should not use it. The reason for this is
…		…
1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1816	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1817		1782
1818	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1819	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1820	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1821	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1822	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1823	no longer true when a callback calls C<ev_run> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1824		1790
1825	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1826		1792
1827	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1828	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1903		1869
1904	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1905	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1906	within the callback:	1872	within the callback:
1907		1873
		1874	ev_tstamp timeout = 60.;
1908	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1909		1877
1910	static void	1878	static void
1911	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1912	{	1880	{
1913	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1914	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1915		1883
1916	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1917	if (timeout < now)	1885	if (after < 0.)
1918	{	1886	{
1919	// timeout occurred, take action	1887	// timeout occurred, take action
1920	}	1888	}
1921	else	1889	else
1922	{	1890	{
1923	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1924	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1925	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1926	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1927	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1928	}	1897	}
1929	}	1898	}
1930		1899
1931	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1932	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1933	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1934	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1935	re-schedule the timer to fire at that future time, to see if maybe we have
1936	a timeout then.
1937		1904
1938	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1939	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1940		1914
1941	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1942	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1943	libev to change the timeout.	1917	libev to change the timeout.
1944		1918
1945	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1946	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1947	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1948		1923
		1924	last_activity = ev_now (EV_A);
1949	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1950	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1951	callback (loop, timer, EV_TIMER);
1952		1927
1953	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1954	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1955		1930
		1931	if (activity detected)
1956	last_activity = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1957		1941
1958	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1959	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1960
1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
1962	callback :) - just change the timeout and invoke the callback, which will
1963	fix things for you.
1964		1944
1965	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1966		1946
1967	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1968	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1996	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1997	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1998	overkill :)	1978	overkill :)
1999		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
2000	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
2001		2018
2002	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
2003	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
2004	time only before and after C<ev_run> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
2006	lots of events in one iteration.	2023	lots of events in one iteration.
2007		2024
2008	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
2015		2032
2016	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
2018	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
2019		2069
2020	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
2021		2071
2022	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
2023	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2067	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
2068	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
2069		2119
2070	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
2071		2121
2072	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
2073	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
2074		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
2075	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
2076		2132
2077	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
2078		2135
2079	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
2080	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
		2138
		2139	=back
2081		2140
2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
2083	usage example.	2142	usage example.
2084		2143
2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2207		2266
2208	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
2209	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
2210	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2270
2212	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
2213	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
2215		2277
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
2217	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
2218	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
2219	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2425
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2428	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2368		2431
2369	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2434	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2784	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2785	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2786	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2787	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2788		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L<< Abusing an C<ev_check> watcher for its side-effect >> for a longer
		2864	example.
		2865
2789	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2790		2867
2791	=over 4	2868	=over 4
2792		2869
2793	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2804	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2805		2882
2806	static void	2883	static void
2807	idle_cb (struct ev_loop loop, ev_idle w, int revents)	2884	idle_cb (struct ev_loop loop, ev_idle w, int revents)
2808	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2809	free (w);	2890	free (w);
		2891
2810	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2811	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2812	}	2894	}
2813		2895
2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2816	ev_idle_start (loop, idle_watcher);	2898	ev_idle_start (loop, idle_watcher);
2817		2899
2818		2900
2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2820		2902
2821	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2822	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2823	afterwards.	2905	afterwards.
2824		2906
2825	You I<must not> call C<ev_run> or similar functions that enter	2907	You I<must not> call C<ev_run> or similar functions that enter
2826	the current event loop from either C<ev_prepare> or C<ev_check>	2908	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2854	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2855	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2856	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2857	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2858		2940
2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2860	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2861	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2862		2945
2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2864	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2865	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2866	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2867	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2869	others).	2952	others).
		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2870		2973
2871	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2872		2975
2873	=over 4	2976	=over 4
2874		2977
…		…
3243	atexit (program_exits);	3346	atexit (program_exits);
3244		3347
3245		3348
3246	=head2 C<ev_async> - how to wake up an event loop	3349	=head2 C<ev_async> - how to wake up an event loop
3247		3350
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
3251		3354
3252	Sometimes, however, you need to wake up an event loop you do not control,	3355	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3356	for example because it belongs to another thread. This is what C<ev_async>
…		…
3255	it by calling C<ev_async_send>, which is thread- and signal safe.	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
3256		3359
3257	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
3258	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
3259	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3261	of "global async watchers" by using a watcher on an otherwise unused	3364	of "global async watchers" by using a watcher on an otherwise unused
3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3263	even without knowing which loop owns the signal.	3366	even without knowing which loop owns the signal.
3264
3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3266	just the default loop.
3267		3367
3268	=head3 Queueing	3368	=head3 Queueing
3269		3369
3270	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
3271	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
…		…
3363	trust me.	3463	trust me.
3364		3464
3365	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3366		3466
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3372		3474
3373	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3476	compressed into a single callback invocation (another way to look at
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3376	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3377		3479
3378	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3379	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3380	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3381		3486
3382	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3383		3488
3384	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3385	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3441		3546
3442	=item ev_feed_fd_event (loop, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3443		3548
3444	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3445	the given events it.	3550	the given events.
3446		3551
3447	=item ev_feed_signal_event (loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3448		3553
3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3450	which is async-safe.	3555	which is async-safe.
…		…
3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)	3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
3456		3561
3457	This section explains some common idioms that are not immediately	3562	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3563	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3591	{
		3592	struct my_io w = (struct my_io )w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
3460		3673
3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS	3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3462		3675
3463	Often (especially in GUI toolkits) there are places where you have	3676	Often (especially in GUI toolkits) there are places where you have
3464	I<modal> interaction, which is most easily implemented by recursively	3677	I<modal> interaction, which is most easily implemented by recursively
…		…
3478	int exit_main_loop = 0;	3691	int exit_main_loop = 0;
3479		3692
3480	while (!exit_main_loop)	3693	while (!exit_main_loop)
3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3482		3695
3483	// in a model watcher	3696	// in a modal watcher
3484	int exit_nested_loop = 0;	3697	int exit_nested_loop = 0;
3485		3698
3486	while (!exit_nested_loop)	3699	while (!exit_nested_loop)
3487	ev_run (EV_A_ EVRUN_ONCE);	3700	ev_run (EV_A_ EVRUN_ONCE);
3488		3701
…		…
3498	exit_main_loop = exit_nested_loop = 1;	3711	exit_main_loop = exit_nested_loop = 1;
3499		3712
3500	=head2 THREAD LOCKING EXAMPLE	3713	=head2 THREAD LOCKING EXAMPLE
3501		3714
3502	Here is a fictitious example of how to run an event loop in a different	3715	Here is a fictitious example of how to run an event loop in a different
3503	thread than where callbacks are being invoked and watchers are	3716	thread from where callbacks are being invoked and watchers are
3504	created/added/removed.	3717	created/added/removed.
3505		3718
3506	For a real-world example, see the C<EV::Loop::Async> perl module,	3719	For a real-world example, see the C<EV::Loop::Async> perl module,
3507	which uses exactly this technique (which is suited for many high-level	3720	which uses exactly this technique (which is suited for many high-level
3508	languages).	3721	languages).
…		…
3534	// now associate this with the loop	3747	// now associate this with the loop
3535	ev_set_userdata (EV_A_ u);	3748	ev_set_userdata (EV_A_ u);
3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3538		3751
3539	// then create the thread running ev_loop	3752	// then create the thread running ev_run
3540	pthread_create (&u->tid, 0, l_run, EV_A);	3753	pthread_create (&u->tid, 0, l_run, EV_A);
3541	}	3754	}
3542		3755
3543	The callback for the C<ev_async> watcher does nothing: the watcher is used	3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
3544	solely to wake up the event loop so it takes notice of any new watchers	3757	solely to wake up the event loop so it takes notice of any new watchers
…		…
3633	Note that sending the C<ev_async> watcher is required because otherwise	3846	Note that sending the C<ev_async> watcher is required because otherwise
3634	an event loop currently blocking in the kernel will have no knowledge	3847	an event loop currently blocking in the kernel will have no knowledge
3635	about the newly added timer. By waking up the loop it will pick up any new	3848	about the newly added timer. By waking up the loop it will pick up any new
3636	watchers in the next event loop iteration.	3849	watchers in the next event loop iteration.
3637		3850
3638	=back	3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3639		3908
3640		3909
3641	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3642		3911
3643	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3672	to use the libev header file and library.	3941	to use the libev header file and library.
3673		3942
3674	=back	3943	=back
3675		3944
3676	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3677		3979
3678	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3679	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3680	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3681		3983
…		…
3697	with C<operator ()> can be used as callbacks. Other types should be easy	3999	with C<operator ()> can be used as callbacks. Other types should be easy
3698	to add as long as they only need one additional pointer for context. If	4000	to add as long as they only need one additional pointer for context. If
3699	you need support for other types of functors please contact the author	4001	you need support for other types of functors please contact the author
3700	(preferably after implementing it).	4002	(preferably after implementing it).
3701		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
		4007
3702	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3703		4009
3704	=over 4	4010	=over 4
3705		4011
3706	=item C<ev::READ>, C<ev::WRITE> etc.	4012	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3715	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3716		4022
3717	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3718	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3719	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3720	defines by many implementations.	4026	defined by many implementations.
3721		4027
3722	All of those classes have these methods:	4028	All of those classes have these methods:
3723		4029
3724	=over 4	4030	=over 4
3725		4031
…		…
3858	watchers in the constructor.	4164	watchers in the constructor.
3859		4165
3860	class myclass	4166	class myclass
3861	{	4167	{
3862	ev::io io ; void io_cb (ev::io &w, int revents);	4168	ev::io io ; void io_cb (ev::io &w, int revents);
3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4169	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4170	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3865		4171
3866	myclass (int fd)	4172	myclass (int fd)
3867	{	4173	{
3868	io .set <myclass, &myclass::io_cb > (this);	4174	io .set <myclass, &myclass::io_cb > (this);
…		…
3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4225	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3920		4226
3921	=item D	4227	=item D
3922		4228
3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4229	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4230	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3925		4231
3926	=item Ocaml	4232	=item Ocaml
3927		4233
3928	Erkki Seppala has written Ocaml bindings for libev, to be found at	4234	Erkki Seppala has written Ocaml bindings for libev, to be found at
3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4235	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3977	suitable for use with C<EV_A>.	4283	suitable for use with C<EV_A>.
3978		4284
3979	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4285	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3980		4286
3981	Similar to the other two macros, this gives you the value of the default	4287	Similar to the other two macros, this gives you the value of the default
3982	loop, if multiple loops are supported ("ev loop default").	4288	loop, if multiple loops are supported ("ev loop default"). The default loop
		4289	will be initialised if it isn't already initialised.
		4290
		4291	For non-multiplicity builds, these macros do nothing, so you always have
		4292	to initialise the loop somewhere.
3983		4293
3984	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4294	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3985		4295
3986	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4296	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3987	default loop has been initialised (C<UC> == unchecked). Their behaviour	4297	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
4132	supported). It will also not define any of the structs usually found in	4442	supported). It will also not define any of the structs usually found in
4133	F<event.h> that are not directly supported by the libev core alone.	4443	F<event.h> that are not directly supported by the libev core alone.
4134		4444
4135	In standalone mode, libev will still try to automatically deduce the	4445	In standalone mode, libev will still try to automatically deduce the
4136	configuration, but has to be more conservative.	4446	configuration, but has to be more conservative.
		4447
		4448	=item EV_USE_FLOOR
		4449
		4450	If defined to be C<1>, libev will use the C<floor ()> function for its
		4451	periodic reschedule calculations, otherwise libev will fall back on a
		4452	portable (slower) implementation. If you enable this, you usually have to
		4453	link against libm or something equivalent. Enabling this when the C<floor>
		4454	function is not available will fail, so the safe default is to not enable
		4455	this.
4137		4456
4138	=item EV_USE_MONOTONIC	4457	=item EV_USE_MONOTONIC
4139		4458
4140	If defined to be C<1>, libev will try to detect the availability of the	4459	If defined to be C<1>, libev will try to detect the availability of the
4141	monotonic clock option at both compile time and runtime. Otherwise no	4460	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4271	If defined to be C<1>, libev will compile in support for the Linux inotify	4590	If defined to be C<1>, libev will compile in support for the Linux inotify
4272	interface to speed up C<ev_stat> watchers. Its actual availability will	4591	interface to speed up C<ev_stat> watchers. Its actual availability will
4273	be detected at runtime. If undefined, it will be enabled if the headers	4592	be detected at runtime. If undefined, it will be enabled if the headers
4274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4593	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4275		4594
		4595	=item EV_NO_SMP
		4596
		4597	If defined to be C<1>, libev will assume that memory is always coherent
		4598	between threads, that is, threads can be used, but threads never run on
		4599	different cpus (or different cpu cores). This reduces dependencies
		4600	and makes libev faster.
		4601
		4602	=item EV_NO_THREADS
		4603
		4604	If defined to be C<1>, libev will assume that it will never be called
		4605	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4606	above. This reduces dependencies and makes libev faster.
		4607
4276	=item EV_ATOMIC_T	4608	=item EV_ATOMIC_T
4277		4609
4278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4610	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4279	access is atomic with respect to other threads or signal contexts. No such	4611	access is atomic and serialised with respect to other threads or signal
4280	type is easily found in the C language, so you can provide your own type	4612	contexts. No such type is easily found in the C language, so you can
4281	that you know is safe for your purposes. It is used both for signal handler "locking"	4613	provide your own type that you know is safe for your purposes. It is used
4282	as well as for signal and thread safety in C<ev_async> watchers.	4614	both for signal handler "locking" as well as for signal and thread safety
		4615	in C<ev_async> watchers.
4283		4616
4284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4617	In the absence of this define, libev will use C<sig_atomic_t volatile>
4285	(from F<signal.h>), which is usually good enough on most platforms.	4618	(from F<signal.h>), which is usually good enough on most platforms,
		4619	although strictly speaking using a type that also implies a memory fence
		4620	is required.
4286		4621
4287	=item EV_H (h)	4622	=item EV_H (h)
4288		4623
4289	The name of the F<ev.h> header file used to include it. The default if	4624	The name of the F<ev.h> header file used to include it. The default if
4290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4625	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
4314	will have the C<struct ev_loop *> as first argument, and you can create	4649	will have the C<struct ev_loop *> as first argument, and you can create
4315	additional independent event loops. Otherwise there will be no support	4650	additional independent event loops. Otherwise there will be no support
4316	for multiple event loops and there is no first event loop pointer	4651	for multiple event loops and there is no first event loop pointer
4317	argument. Instead, all functions act on the single default loop.	4652	argument. Instead, all functions act on the single default loop.
4318		4653
		4654	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4655	default loop when multiplicity is switched off - you always have to
		4656	initialise the loop manually in this case.
		4657
4319	=item EV_MINPRI	4658	=item EV_MINPRI
4320		4659
4321	=item EV_MAXPRI	4660	=item EV_MAXPRI
4322		4661
4323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4662	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4359	#define EV_USE_POLL 1	4698	#define EV_USE_POLL 1
4360	#define EV_CHILD_ENABLE 1	4699	#define EV_CHILD_ENABLE 1
4361	#define EV_ASYNC_ENABLE 1	4700	#define EV_ASYNC_ENABLE 1
4362		4701
4363	The actual value is a bitset, it can be a combination of the following	4702	The actual value is a bitset, it can be a combination of the following
4364	values:	4703	values (by default, all of these are enabled):
4365		4704
4366	=over 4	4705	=over 4
4367		4706
4368	=item C<1> - faster/larger code	4707	=item C<1> - faster/larger code
4369		4708
…		…
4373	code size by roughly 30% on amd64).	4712	code size by roughly 30% on amd64).
4374		4713
4375	When optimising for size, use of compiler flags such as C<-Os> with	4714	When optimising for size, use of compiler flags such as C<-Os> with
4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4715	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4377	assertions.	4716	assertions.
		4717
		4718	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4719	(e.g. gcc with C<-Os>).
4378		4720
4379	=item C<2> - faster/larger data structures	4721	=item C<2> - faster/larger data structures
4380		4722
4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4723	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4382	hash table sizes and so on. This will usually further increase code size	4724	hash table sizes and so on. This will usually further increase code size
4383	and can additionally have an effect on the size of data structures at	4725	and can additionally have an effect on the size of data structures at
4384	runtime.	4726	runtime.
4385		4727
		4728	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4729	(e.g. gcc with C<-Os>).
		4730
4386	=item C<4> - full API configuration	4731	=item C<4> - full API configuration
4387		4732
4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4733	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4389	enables multiplicity (C<EV_MULTIPLICITY>=1).	4734	enables multiplicity (C<EV_MULTIPLICITY>=1).
4390		4735
…		…
4420		4765
4421	With an intelligent-enough linker (gcc+binutils are intelligent enough	4766	With an intelligent-enough linker (gcc+binutils are intelligent enough
4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4767	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4423	your program might be left out as well - a binary starting a timer and an	4768	your program might be left out as well - a binary starting a timer and an
4424	I/O watcher then might come out at only 5Kb.	4769	I/O watcher then might come out at only 5Kb.
		4770
		4771	=item EV_API_STATIC
		4772
		4773	If this symbol is defined (by default it is not), then all identifiers
		4774	will have static linkage. This means that libev will not export any
		4775	identifiers, and you cannot link against libev anymore. This can be useful
		4776	when you embed libev, only want to use libev functions in a single file,
		4777	and do not want its identifiers to be visible.
		4778
		4779	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4780	wants to use libev.
		4781
		4782	This option only works when libev is compiled with a C compiler, as C++
		4783	doesn't support the required declaration syntax.
4425		4784
4426	=item EV_AVOID_STDIO	4785	=item EV_AVOID_STDIO
4427		4786
4428	If this is set to C<1> at compiletime, then libev will avoid using stdio	4787	If this is set to C<1> at compiletime, then libev will avoid using stdio
4429	functions (printf, scanf, perror etc.). This will increase the code size	4788	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4932	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4574		4933
4575	#include "ev_cpp.h"	4934	#include "ev_cpp.h"
4576	#include "ev.c"	4935	#include "ev.c"
4577		4936
4578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4937	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4579		4938
4580	=head2 THREADS AND COROUTINES	4939	=head2 THREADS AND COROUTINES
4581		4940
4582	=head3 THREADS	4941	=head3 THREADS
4583		4942
…		…
4809	requires, and its I/O model is fundamentally incompatible with the POSIX	5168	requires, and its I/O model is fundamentally incompatible with the POSIX
4810	model. Libev still offers limited functionality on this platform in	5169	model. Libev still offers limited functionality on this platform in
4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5170	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4812	descriptors. This only applies when using Win32 natively, not when using	5171	descriptors. This only applies when using Win32 natively, not when using
4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5172	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4814	as every compielr comes with a slightly differently broken/incompatible	5173	as every compiler comes with a slightly differently broken/incompatible
4815	environment.	5174	environment.
4816		5175
4817	Lifting these limitations would basically require the full	5176	Lifting these limitations would basically require the full
4818	re-implementation of the I/O system. If you are into this kind of thing,	5177	re-implementation of the I/O system. If you are into this kind of thing,
4819	then note that glib does exactly that for you in a very portable way (note	5178	then note that glib does exactly that for you in a very portable way (note
…		…
4952		5311
4953	The type C<double> is used to represent timestamps. It is required to	5312	The type C<double> is used to represent timestamps. It is required to
4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5313	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4955	good enough for at least into the year 4000 with millisecond accuracy	5314	good enough for at least into the year 4000 with millisecond accuracy
4956	(the design goal for libev). This requirement is overfulfilled by	5315	(the design goal for libev). This requirement is overfulfilled by
4957	implementations using IEEE 754, which is basically all existing ones. With	5316	implementations using IEEE 754, which is basically all existing ones.
		5317
4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5318	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5319	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5320	is either obsolete or somebody patched it to use C<long double> or
		5321	something like that, just kidding).
4959		5322
4960	=back	5323	=back
4961		5324
4962	If you know of other additional requirements drop me a note.	5325	If you know of other additional requirements drop me a note.
4963		5326
…		…
5025	=item Processing ev_async_send: O(number_of_async_watchers)	5388	=item Processing ev_async_send: O(number_of_async_watchers)
5026		5389
5027	=item Processing signals: O(max_signal_number)	5390	=item Processing signals: O(max_signal_number)
5028		5391
5029	Sending involves a system call I<iff> there were no other C<ev_async_send>	5392	Sending involves a system call I<iff> there were no other C<ev_async_send>
5030	calls in the current loop iteration. Checking for async and signal events	5393	calls in the current loop iteration and the loop is currently
		5394	blocked. Checking for async and signal events involves iterating over all
5031	involves iterating over all running async watchers or all signal numbers.	5395	running async watchers or all signal numbers.
5032		5396
5033	=back	5397	=back
5034		5398
5035		5399
5036	=head1 PORTING FROM LIBEV 3.X TO 4.X	5400	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5153	The physical time that is observed. It is apparently strictly monotonic :)	5517	The physical time that is observed. It is apparently strictly monotonic :)
5154		5518
5155	=item wall-clock time	5519	=item wall-clock time
5156		5520
5157	The time and date as shown on clocks. Unlike real time, it can actually	5521	The time and date as shown on clocks. Unlike real time, it can actually
5158	be wrong and jump forwards and backwards, e.g. when the you adjust your	5522	be wrong and jump forwards and backwards, e.g. when you adjust your
5159	clock.	5523	clock.
5160		5524
5161	=item watcher	5525	=item watcher
5162		5526
5163	A data structure that describes interest in certain events. Watchers need	5527	A data structure that describes interest in certain events. Watchers need
…		…
5166	=back	5530	=back
5167		5531
5168	=head1 AUTHOR	5532	=head1 AUTHOR
5169		5533
5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5534	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5171	Magnusson and Emanuele Giaquinta.	5535	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5172		5536

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Comparing libev/ev.pod (file contents): Revision 1.355 by root, Tue Jan 11 01:41:56 2011 UTC vs. Revision 1.410 by root, Fri May 4 20:46:17 2012 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.355 by root, Tue Jan 11 01:41:56 2011 UTC vs.
Revision 1.410 by root, Fri May 4 20:46:17 2012 UTC