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

Comparing libev/ev.pod (file contents):
Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC vs.
Revision 1.233 by root, Thu Apr 16 07:32:51 2009 UTC

…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
298	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
299	function.	301	function.
300		302
301	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
303	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
304		306
305	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
306	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
307	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		387
386	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	392
391	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
392	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
393		409
394	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
395	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
396	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
398	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
399		415	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		416
404	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
405	watchers for a file descriptor until it has been closed, if possible,	418	watchers for a file descriptor until it has been closed, if possible,
406	i.e. keep at least one watcher active per fd at all times. Stopping and	419	i.e. keep at least one watcher active per fd at all times. Stopping and
407	starting a watcher (without re-setting it) also usually doesn't cause	420	starting a watcher (without re-setting it) also usually doesn't cause
408	extra overhead.	421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
409		428
410	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
411	all kernel versions tested so far.	430	all kernel versions tested so far.
412		431
413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
414	C<EVBACKEND_POLL>.	433	C<EVBACKEND_POLL>.
415		434
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		436
418	Kqueue deserves special mention, as at the time of this writing, it was	437	Kqueue deserves special mention, as at the time of this writing, it
419	broken on all BSDs except NetBSD (usually it doesn't work reliably with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
420	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
421	completely useless). For this reason it's not being "auto-detected" unless	440	it's completely useless). Unlike epoll, however, whose brokenness
422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	441	is by design, these kqueue bugs can (and eventually will) be fixed
423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	442	without API changes to existing programs. For this reason it's not being
		443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
424		446
425	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
426	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
427	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
428		450
429	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
430	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
431	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
433	two event changes per incident. Support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
434	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
435		458
436	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
437		460
438	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
439	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
440	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
441	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
444		467
445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
447	C<NOTE_EOF>.	470	C<NOTE_EOF>.
448		471
…		…
468	might perform better.	491	might perform better.
469		492
470	On the positive side, with the exception of the spurious readiness	493	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	494	notifications, this backend actually performed fully to specification
472	in all tests and is fully embeddable, which is a rare feat among the	495	in all tests and is fully embeddable, which is a rare feat among the
473	OS-specific backends.	496	OS-specific backends (I vastly prefer correctness over speed hacks).
474		497
475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
476	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
477		500
478	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
531	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
532	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
533	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
534	for example).	557	for example).
535		558
536	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
537	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
539		562
540	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
541	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
542	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
543	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
611	very long time without entering the event loop, updating libev's idea of	634	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	635	the current time is a good idea.
613		636
614	See also "The special problem of time updates" in the C<ev_timer> section.	637	See also "The special problem of time updates" in the C<ev_timer> section.
615		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
616	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
617		666
618	Finally, this is it, the event handler. This function usually is called	667	Finally, this is it, the event handler. This function usually is called
619	after you initialised all your watchers and you want to start handling	668	after you initialised all your watchers and you want to start handling
620	events.	669	events.
…		…
635	the loop.	684	the loop.
636		685
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	687	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	688	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	689	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	690	user-registered callback will be called), and will return after one
642	iteration of the loop.	691	iteration of the loop.
643		692
644	This is useful if you are waiting for some external event in conjunction	693	This is useful if you are waiting for some external event in conjunction
645	with something not expressible using other libev watchers (i.e. "roll your	694	with something not expressible using other libev watchers (i.e. "roll your
…		…
703		752
704	If you have a watcher you never unregister that should not keep C<ev_loop>	753	If you have a watcher you never unregister that should not keep C<ev_loop>
705	from returning, call ev_unref() after starting, and ev_ref() before	754	from returning, call ev_unref() after starting, and ev_ref() before
706	stopping it.	755	stopping it.
707		756
708	As an example, libev itself uses this for its internal signal pipe: It is	757	As an example, libev itself uses this for its internal signal pipe: It
709	not visible to the libev user and should not keep C<ev_loop> from exiting	758	is not visible to the libev user and should not keep C<ev_loop> from
710	if no event watchers registered by it are active. It is also an excellent	759	exiting if no event watchers registered by it are active. It is also an
711	way to do this for generic recurring timers or from within third-party	760	excellent way to do this for generic recurring timers or from within
712	libraries. Just remember to I<unref after start> and I<ref before stop>	761	third-party libraries. Just remember to I<unref after start> and I<ref
713	(but only if the watcher wasn't active before, or was active before,	762	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
715		766
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
717	running when nothing else is active.	768	running when nothing else is active.
718		769
719	ev_signal exitsig;	770	ev_signal exitsig;
…		…
903		954
904	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
905		956
906	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
907		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
908	=item C<EV_ERROR>	964	=item C<EV_ERROR>
909		965
910	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
912	ran out of memory, a file descriptor was found to be closed or any other	968	ran out of memory, a file descriptor was found to be closed or any other
…		…
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
1031		1087
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1088	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1090
1040	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1092	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1093
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1095	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1096	or might not have been clamped to the valid range.
		1097
		1098	The default priority used by watchers when no priority has been set is
		1099	always C<0>, which is supposed to not be too high and not be too low :).
		1100
		1101	See L<WATCHER PRIORITIES>, below, for a more thorough treatment of
		1102	priorities.
1049		1103
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1105
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1183	{
1130	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1133		1290
1134		1291
1135	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1136		1293
1137	This section describes each watcher in detail, but will not repeat	1294	This section describes each watcher in detail, but will not repeat
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
1297		1454
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1455	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1456	passed. If multiple timers become ready during the same loop iteration
1300	then order of execution is undefined.	1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
1301		1460
1302	=head3 Be smart about timeouts	1461	=head3 Be smart about timeouts
1303		1462
1304	Many real-world problems involve some kind of timeout, usually for error	1463	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1464	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1398	else	1557	else
1399	{	1558	{
1400	// callback was invoked, but there was some activity, re-arm	1559	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1560	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1561	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1562	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1563	ev_timer_again (EV_A_ w);
1405	}	1564	}
1406	}	1565	}
1407		1566
1408	To summarise the callback: first calculate the real timeout (defined	1567	To summarise the callback: first calculate the real timeout (defined
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1525		1684
1526	If the timer is repeating, either start it if necessary (with the	1685	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		1687
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1688	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1689	usage example.
1531		1690
1532	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1533		1692
1534	The current C<repeat> value. Will be used each time the watcher times out	1693	The current C<repeat> value. Will be used each time the watcher times out
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1574		1733
1575	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1577		1736
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	1738	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	1739	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1740	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	1741	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	1742	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		1743
		1744	You can tell a periodic watcher to trigger after some specific point
		1745	in time: for example, if you tell a periodic watcher to trigger "in 10
		1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
		1751
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	1752	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	1753	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
1590		1756
1591	As with timers, the callback is guaranteed to be invoked only when the	1757	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	1758	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1594		1762
1595	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1596		1764
1597	=over 4	1765	=over 4
1598		1766
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		1768
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		1770
1603	Lots of arguments, lets sort it out... There are basically three modes of	1771	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	1772	operation, and we will explain them from simplest to most complex:
1605		1773
1606	=over 4	1774	=over 4
1607		1775
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		1777
1610	In this configuration the watcher triggers an event after the wall clock	1778	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	1779	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1780	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1614		1783
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		1785
1617	In this mode the watcher will always be scheduled to time out at the next	1786	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	1787	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1620		1790
1621	This can be used to create timers that do not drift with respect to the	1791	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	1792	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	1793	hour, on the hour (with respect to UTC):
1624		1794
1625	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1626		1796
1627	This doesn't mean there will always be 3600 seconds in between triggers,	1797	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	1798	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	1800	by 3600.
1631		1801
1632	Another way to think about it (for the mathematically inclined) is that	1802	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	1803	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		1805
1636	For numerical stability it is preferable that the C<at> value is near	1806	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	1807	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	1808	this value, and in fact is often specified as zero.
1639		1809
1640	Note also that there is an upper limit to how often a timer can fire (CPU	1810	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	1811	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	1812	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	1813	millisecond (if the OS supports it and the machine is fast enough).
1644		1814
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		1816
1647	In this mode the values for C<interval> and C<at> are both being	1817	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	1820	current time as second argument.
1651		1821
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	1823	or make ANY other event loop modifications whatsoever, unless explicitly
		1824	allowed by documentation here>.
1654		1825
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1826	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	1828	only event loop modification you are allowed to do).
1658		1829
…		…
1688	a different time than the last time it was called (e.g. in a crond like	1859	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	1860	program when the crontabs have changed).
1690		1861
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		1863
1693	When active, returns the absolute time that the watcher is supposed to	1864	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
1695		1868
1696	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1697		1870
1698	When repeating, this contains the offset value, otherwise this is the	1871	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1700		1874
1701	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1703		1877
1704	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
…		…
1910		2084
1911		2085
1912	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1913		2087
1914	This watches a file system path for attribute changes. That is, it calls	2088	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2089	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1917		2092
1918	The path does not need to exist: changing from "path exists" to "path does	2093	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2094	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2095	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1923		2099
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2102	your working directory changes, then the behaviour is undefined.
1926		2103
1927	Since there is no standard kernel interface to do this, the portable	2104	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2105	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2106	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2107	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2108	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2109	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2110	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1935		2112
1936	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2115	resource-intensive.
1939		2116
1940	At the time of this writing, the only OS-specific interface implemented	2117	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2118	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2119	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2120	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2121
1945	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1946		2123
1947	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2125	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2126	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2127	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2128	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2129	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2130	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2131	most noticeably displayed with ev_stat and large file support.
1955		2132
1956	The solution for this is to lobby your distribution maker to make large	2133	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2134	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2135	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2136	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2137	default compilation environment.
1961		2138
1962	=head3 Inotify and Kqueue	2139	=head3 Inotify and Kqueue
1963		2140
1964	When C<inotify (7)> support has been compiled into libev (generally	2141	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2142	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2144	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2145
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2146	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2147	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2148	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2149	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1975		2154
1976	There is no support for kqueue, as apparently it cannot be used to	2155	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2156	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2157	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2158	etc. is difficult.
1980		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
		2177
1981	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1982		2179
1983	The C<stat ()> system call only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2181	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2182	still only support whole seconds.
1986		2183
1987	That means that, if the time is the only thing that changes, you can	2184	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2185	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2186	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2187	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2330
2134	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
2135		2332
2136	=over 4	2333	=over 4
2137		2334
2138	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
2139		2336
2140	Initialises and configures the idle watcher - it has no parameters of any	2337	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2339	believe me.
2143		2340
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2579	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2580	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2581	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	2582	the rest in a second one, and embed the second one in the first.
2386		2583
2387	As long as the watcher is active, the callback will be invoked every time	2584	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	2585	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2586	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	2587	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	2588	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	2589	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2590
2395	As long as the watcher is started it will automatically handle events. The	2591	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	2592	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2593
2400	Also, there have not currently been made special provisions for forking:	2594	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2595	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2596	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2597	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2598
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2601	portable one.
2409		2602
…		…
2629	=over 4	2822	=over 4
2630		2823
2631	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2632		2825
2633	Initialises and configures the async watcher - it has no parameters of any	2826	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	2828	trust me.
2636		2829
2637	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2638		2831
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2833	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	2834	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	2836	section below on what exactly this means).
2644		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2645	This call incurs the overhead of a system call only once per loop iteration,	2843	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2648		2846
2649	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2650		2848
2651	Returns a non-zero value when C<ev_async_send> has been called on the	2849	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	2850	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2853	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	2854	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	2855	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	2856	quickly check whether invoking the loop might be a good idea.
2659		2857
2660	Not that this does I<not> check whether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2662		2862
2663	=back	2863	=back
2664		2864
2665		2865
2666	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2845		3045
2846	myclass obj;	3046	myclass obj;
2847	ev::io iow;	3047	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
		3079
2850	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2851		3081
2852	Also sets a callback, but uses a static method or plain function as	3082	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3083	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3084	C<data> member and is free for you to use.
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2941		3171
2942	=item Python	3172	=item Python
2943		3173
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3174	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3175	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3176
2951	=item Ruby	3177	=item Ruby
2952		3178
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3179	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3180	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3181	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
2957		3191
2958	=item D	3192	=item D
2959		3193
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
…		…
3072		3306
3073	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
3074	#include "ev.h"	3308	#include "ev.h"
3075		3309
3076	Both header files and implementation files can be compiled with a C++	3310	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	3311	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3312	as a bug).
3079		3313
3080	You need the following files in your source tree, or in a directory	3314	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	3315	in your include path (e.g. in libev/ when using -Ilibev):
3082		3316
…		…
3138	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3373	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3374	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3375	F<event.h> that are not directly supported by the libev core alone.
3142		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
3143	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
3144		3381
3145	If defined to be C<1>, libev will try to detect the availability of the	3382	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3383	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3384	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3385	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3386	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3387	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3389
3153	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
3154		3391
3155	If defined to be C<1>, libev will try to detect the availability of the	3392	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	3393	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3394	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
3161		3411
3162	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
3163		3413
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		3431
3182	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
3183		3433
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	3435	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3436	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	3437	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	3438	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
3191		3441
3192	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
3193		3443
3194	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
3554	loop, as long as you don't confuse yourself). The only exception is that	3804	loop, as long as you don't confuse yourself). The only exception is that
3555	you must not do this from C<ev_periodic> reschedule callbacks.	3805	you must not do this from C<ev_periodic> reschedule callbacks.
3556		3806
3557	Care has been taken to ensure that libev does not keep local state inside	3807	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	3809	they do not call any callbacks.
3560		3810
3561	=head2 COMPILER WARNINGS	3811	=head2 COMPILER WARNINGS
3562		3812
3563	Depending on your compiler and compiler settings, you might get no or a	3813	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	3814	lot of warnings when compiling libev code. Some people are apparently
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	3848	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	3849	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	3850	==2274== still reachable: 256 bytes in 1 blocks.
3601		3851
3602	Then there is no memory leak, just as memory accounted to global variables	3852	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	3853	is not a memleak - the memory is still being referenced, and didn't leak.
3604		3854
3605	Similarly, under some circumstances, valgrind might report kernel bugs	3855	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	3857	although an acceptable workaround has been found here), or it might be
3608	confused.	3858	confused.
…		…
3846	=back	4096	=back
3847		4097
3848		4098
3849	=head1 AUTHOR	4099	=head1 AUTHOR
3850		4100
3851	Marc Lehmann <libev@schmorp.de>.	4101	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4102

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Comparing libev/ev.pod (file contents): Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC vs. Revision 1.233 by root, Thu Apr 16 07:32:51 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC vs.
Revision 1.233 by root, Thu Apr 16 07:32:51 2009 UTC