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

Comparing libev/ev.pod (file contents):
Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC vs.
Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		307
308	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
309	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
313		320
314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315		322
316	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
320		329
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		331
323	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
324	but it scales phenomenally better. While poll and select usually scale	333	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	334	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
327	of shortcomings, such as silently dropping events in some hard-to-detect	336	of shortcomings, such as silently dropping events in some hard-to-detect
328	cases and rewiring a syscall per fd change, no fork support and bad	337	cases and rewiring a syscall per fd change, no fork support and bad
329	support for dup:	338	support for dup.
330		339
331	While stopping, setting and starting an I/O watcher in the same iteration	340	While stopping, setting and starting an I/O watcher in the same iteration
332	will result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
333	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
336		345
337	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
338	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
339	(or space) is available.	348	(or space) is available.
340		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		358
343	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
344	was broken on I<all> BSDs (usually it doesn't work with anything but	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
345	sockets and pipes, except on Darwin, where of course it's completely	361	with anything but sockets and pipes, except on Darwin, where of course
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
347	is used by default there). For this reason it's not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
348	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
350	system like NetBSD.	365	system like NetBSD.
351		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
		370
352	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
353	kernel is more efficient (which says nothing about its actual speed,	372	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	373	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	375	two event changes per incident, support for C<fork ()> is very bad and it
357	silently in similarly hard-to-detetc cases.	376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
358		386
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		388
361	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
362		393
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		395
365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
366	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
367		398
368	Please note that solaris event ports can deliver a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
369	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
370	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
371		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
		407
372	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
373		409
374	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
377		415
378	=back	416	=back
379		417
380	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
381	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
596	overhead for the actual polling but can deliver many events at once.	634	overhead for the actual polling but can deliver many events at once.
597		635
598	By setting a higher I<io collect interval> you allow libev to spend more	636	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	637	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will	639	C<ev_timer>) will be not affected. Setting this to a non-null value will
602	introduce an additional C<ev_sleep ()> call into most loop iterations.	640	introduce an additional C<ev_sleep ()> call into most loop iterations.
603		641
604	Likewise, by setting a higher I<timeout collect interval> you allow libev	642	Likewise, by setting a higher I<timeout collect interval> you allow libev
605	to spend more time collecting timeouts, at the expense of increased	643	to spend more time collecting timeouts, at the expense of increased
606	latency (the watcher callback will be called later). C<ev_io> watchers	644	latency (the watcher callback will be called later). C<ev_io> watchers
…		…
945	In general you can register as many read and/or write event watchers per	983	In general you can register as many read and/or write event watchers per
946	fd as you want (as long as you don't confuse yourself). Setting all file	984	fd as you want (as long as you don't confuse yourself). Setting all file
947	descriptors to non-blocking mode is also usually a good idea (but not	985	descriptors to non-blocking mode is also usually a good idea (but not
948	required if you know what you are doing).	986	required if you know what you are doing).
949		987
950	You have to be careful with dup'ed file descriptors, though. Some backends
951	(the linux epoll backend is a notable example) cannot handle dup'ed file
952	descriptors correctly if you register interest in two or more fds pointing
953	to the same underlying file/socket/etc. description (that is, they share
954	the same underlying "file open").
955
956	If you must do this, then force the use of a known-to-be-good backend	988	If you must do this, then force the use of a known-to-be-good backend
957	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	989	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
958	C<EVBACKEND_POLL>).	990	C<EVBACKEND_POLL>).
959		991
960	Another thing you have to watch out for is that it is quite easy to	992	Another thing you have to watch out for is that it is quite easy to
…		…
994	optimisations to libev.	1026	optimisations to libev.
995		1027
996	=head3 The special problem of dup'ed file descriptors	1028	=head3 The special problem of dup'ed file descriptors
997		1029
998	Some backends (e.g. epoll), cannot register events for file descriptors,	1030	Some backends (e.g. epoll), cannot register events for file descriptors,
999	but only events for the underlying file descriptions. That menas when you	1031	but only events for the underlying file descriptions. That means when you
1000	have C<dup ()>'ed file descriptors and register events for them, only one	1032	have C<dup ()>'ed file descriptors or weirder constellations, and register
1001	file descriptor might actually receive events.	1033	events for them, only one file descriptor might actually receive events.
1002		1034
1003	There is no workaorund possible except not registering events	1035	There is no workaround possible except not registering events
1004	for potentially C<dup ()>'ed file descriptors or to resort to	1036	for potentially C<dup ()>'ed file descriptors, or to resort to
1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1037	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1006		1038
1007	=head3 The special problem of fork	1039	=head3 The special problem of fork
1008		1040
1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1041	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1035	=item int events [read-only]	1067	=item int events [read-only]
1036		1068
1037	The events being watched.	1069	The events being watched.
1038		1070
1039	=back	1071	=back
		1072
		1073	=head3 Examples
1040		1074
1041	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1075	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1042	readable, but only once. Since it is likely line-buffered, you could	1076	readable, but only once. Since it is likely line-buffered, you could
1043	attempt to read a whole line in the callback.	1077	attempt to read a whole line in the callback.
1044		1078
…		…
1142	or C<ev_timer_again> is called and determines the next timeout (if any),	1176	or C<ev_timer_again> is called and determines the next timeout (if any),
1143	which is also when any modifications are taken into account.	1177	which is also when any modifications are taken into account.
1144		1178
1145	=back	1179	=back
1146		1180
		1181	=head3 Examples
		1182
1147	Example: Create a timer that fires after 60 seconds.	1183	Example: Create a timer that fires after 60 seconds.
1148		1184
1149	static void	1185	static void
1150	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1186	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1151	{	1187	{
…		…
1308	When active, contains the absolute time that the watcher is supposed to	1344	When active, contains the absolute time that the watcher is supposed to
1309	trigger next.	1345	trigger next.
1310		1346
1311	=back	1347	=back
1312		1348
		1349	=head3 Examples
		1350
1313	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1314	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
1315	potentially a lot of jittering, but good long-term stability.	1353	potentially a lot of jittering, but good long-term stability.
1316		1354
1317	static void	1355	static void
…		…
1408		1446
1409	The process exit/trace status caused by C<rpid> (see your systems	1447	The process exit/trace status caused by C<rpid> (see your systems
1410	C<waitpid> and C<sys/wait.h> documentation for details).	1448	C<waitpid> and C<sys/wait.h> documentation for details).
1411		1449
1412	=back	1450	=back
		1451
		1452	=head3 Examples
1413		1453
1414	Example: Try to exit cleanly on SIGINT and SIGTERM.	1454	Example: Try to exit cleanly on SIGINT and SIGTERM.
1415		1455
1416	static void	1456	static void
1417	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1457	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
…		…
1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1498	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1459	to fall back to regular polling again even with inotify, but changes are	1499	to fall back to regular polling again even with inotify, but changes are
1460	usually detected immediately, and if the file exists there will be no	1500	usually detected immediately, and if the file exists there will be no
1461	polling.	1501	polling.
1462		1502
		1503	=head3 Inotify
		1504
		1505	When C<inotify (7)> support has been compiled into libev (generally only
		1506	available on Linux) and present at runtime, it will be used to speed up
		1507	change detection where possible. The inotify descriptor will be created lazily
		1508	when the first C<ev_stat> watcher is being started.
		1509
		1510	Inotify presense does not change the semantics of C<ev_stat> watchers
		1511	except that changes might be detected earlier, and in some cases, to avoid
		1512	making regular C<stat> calls. Even in the presense of inotify support
		1513	there are many cases where libev has to resort to regular C<stat> polling.
		1514
		1515	(There is no support for kqueue, as apparently it cannot be used to
		1516	implement this functionality, due to the requirement of having a file
		1517	descriptor open on the object at all times).
		1518
		1519	=head3 The special problem of stat time resolution
		1520
		1521	The C<stat ()> syscall only supports full-second resolution portably, and
		1522	even on systems where the resolution is higher, many filesystems still
		1523	only support whole seconds.
		1524
		1525	That means that, if the time is the only thing that changes, you might
		1526	miss updates: on the first update, C<ev_stat> detects a change and calls
		1527	your callback, which does something. When there is another update within
		1528	the same second, C<ev_stat> will be unable to detect it.
		1529
		1530	The solution to this is to delay acting on a change for a second (or till
		1531	the next second boundary), using a roughly one-second delay C<ev_timer>
		1532	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1533	is added to work around small timing inconsistencies of some operating
		1534	systems.
		1535
1463	=head3 Watcher-Specific Functions and Data Members	1536	=head3 Watcher-Specific Functions and Data Members
1464		1537
1465	=over 4	1538	=over 4
1466		1539
1467	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1540	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1504	=item const char *path [read-only]	1577	=item const char *path [read-only]
1505		1578
1506	The filesystem path that is being watched.	1579	The filesystem path that is being watched.
1507		1580
1508	=back	1581	=back
		1582
		1583	=head3 Examples
1509		1584
1510	Example: Watch C</etc/passwd> for attribute changes.	1585	Example: Watch C</etc/passwd> for attribute changes.
1511		1586
1512	static void	1587	static void
1513	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1588	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1526	}	1601	}
1527		1602
1528	...	1603	...
1529	ev_stat passwd;	1604	ev_stat passwd;
1530		1605
1531	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1606	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1532	ev_stat_start (loop, &passwd);	1607	ev_stat_start (loop, &passwd);
		1608
		1609	Example: Like above, but additionally use a one-second delay so we do not
		1610	miss updates (however, frequent updates will delay processing, too, so
		1611	one might do the work both on C<ev_stat> callback invocation I<and> on
		1612	C<ev_timer> callback invocation).
		1613
		1614	static ev_stat passwd;
		1615	static ev_timer timer;
		1616
		1617	static void
		1618	timer_cb (EV_P_ ev_timer *w, int revents)
		1619	{
		1620	ev_timer_stop (EV_A_ w);
		1621
		1622	/* now it's one second after the most recent passwd change */
		1623	}
		1624
		1625	static void
		1626	stat_cb (EV_P_ ev_stat *w, int revents)
		1627	{
		1628	/* reset the one-second timer */
		1629	ev_timer_again (EV_A_ &timer);
		1630	}
		1631
		1632	...
		1633	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1634	ev_stat_start (loop, &passwd);
		1635	ev_timer_init (&timer, timer_cb, 0., 1.01);
1533		1636
1534		1637
1535	=head2 C<ev_idle> - when you've got nothing better to do...	1638	=head2 C<ev_idle> - when you've got nothing better to do...
1536		1639
1537	Idle watchers trigger events when no other events of the same or higher	1640	Idle watchers trigger events when no other events of the same or higher
…		…
1562	Initialises and configures the idle watcher - it has no parameters of any	1665	Initialises and configures the idle watcher - it has no parameters of any
1563	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1666	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1564	believe me.	1667	believe me.
1565		1668
1566	=back	1669	=back
		1670
		1671	=head3 Examples
1567		1672
1568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1673	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1569	callback, free it. Also, use no error checking, as usual.	1674	callback, free it. Also, use no error checking, as usual.
1570		1675
1571	static void	1676	static void
…		…
1623		1728
1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1729	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1625	priority, to ensure that they are being run before any other watchers	1730	priority, to ensure that they are being run before any other watchers
1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1731	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1627	too) should not activate ("feed") events into libev. While libev fully	1732	too) should not activate ("feed") events into libev. While libev fully
1628	supports this, they will be called before other C<ev_check> watchers did	1733	supports this, they will be called before other C<ev_check> watchers
1629	their job. As C<ev_check> watchers are often used to embed other event	1734	did their job. As C<ev_check> watchers are often used to embed other
1630	loops those other event loops might be in an unusable state until their	1735	(non-libev) event loops those other event loops might be in an unusable
1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1736	state until their C<ev_check> watcher ran (always remind yourself to
1632	others).	1737	coexist peacefully with others).
1633		1738
1634	=head3 Watcher-Specific Functions and Data Members	1739	=head3 Watcher-Specific Functions and Data Members
1635		1740
1636	=over 4	1741	=over 4
1637		1742
…		…
1642	Initialises and configures the prepare or check watcher - they have no	1747	Initialises and configures the prepare or check watcher - they have no
1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1748	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1644	macros, but using them is utterly, utterly and completely pointless.	1749	macros, but using them is utterly, utterly and completely pointless.
1645		1750
1646	=back	1751	=back
		1752
		1753	=head3 Examples
1647		1754
1648	There are a number of principal ways to embed other event loops or modules	1755	There are a number of principal ways to embed other event loops or modules
1649	into libev. Here are some ideas on how to include libadns into libev	1756	into libev. Here are some ideas on how to include libadns into libev
1650	(there is a Perl module named C<EV::ADNS> that does this, which you could	1757	(there is a Perl module named C<EV::ADNS> that does this, which you could
1651	use for an actually working example. Another Perl module named C<EV::Glib>	1758	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1776	=head2 C<ev_embed> - when one backend isn't enough...	1883	=head2 C<ev_embed> - when one backend isn't enough...
1777		1884
1778	This is a rather advanced watcher type that lets you embed one event loop	1885	This is a rather advanced watcher type that lets you embed one event loop
1779	into another (currently only C<ev_io> events are supported in the embedded	1886	into another (currently only C<ev_io> events are supported in the embedded
1780	loop, other types of watchers might be handled in a delayed or incorrect	1887	loop, other types of watchers might be handled in a delayed or incorrect
1781	fashion and must not be used). (See portability notes, below).	1888	fashion and must not be used).
1782		1889
1783	There are primarily two reasons you would want that: work around bugs and	1890	There are primarily two reasons you would want that: work around bugs and
1784	prioritise I/O.	1891	prioritise I/O.
1785		1892
1786	As an example for a bug workaround, the kqueue backend might only support	1893	As an example for a bug workaround, the kqueue backend might only support
…		…
1820	portable one.	1927	portable one.
1821		1928
1822	So when you want to use this feature you will always have to be prepared	1929	So when you want to use this feature you will always have to be prepared
1823	that you cannot get an embeddable loop. The recommended way to get around	1930	that you cannot get an embeddable loop. The recommended way to get around
1824	this is to have a separate variables for your embeddable loop, try to	1931	this is to have a separate variables for your embeddable loop, try to
1825	create it, and if that fails, use the normal loop for everything:	1932	create it, and if that fails, use the normal loop for everything.
		1933
		1934	=head3 Watcher-Specific Functions and Data Members
		1935
		1936	=over 4
		1937
		1938	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1939
		1940	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1941
		1942	Configures the watcher to embed the given loop, which must be
		1943	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1944	invoked automatically, otherwise it is the responsibility of the callback
		1945	to invoke it (it will continue to be called until the sweep has been done,
		1946	if you do not want thta, you need to temporarily stop the embed watcher).
		1947
		1948	=item ev_embed_sweep (loop, ev_embed *)
		1949
		1950	Make a single, non-blocking sweep over the embedded loop. This works
		1951	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1952	apropriate way for embedded loops.
		1953
		1954	=item struct ev_loop *other [read-only]
		1955
		1956	The embedded event loop.
		1957
		1958	=back
		1959
		1960	=head3 Examples
		1961
		1962	Example: Try to get an embeddable event loop and embed it into the default
		1963	event loop. If that is not possible, use the default loop. The default
		1964	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1965	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1966	used).
1826		1967
1827	struct ev_loop *loop_hi = ev_default_init (0);	1968	struct ev_loop *loop_hi = ev_default_init (0);
1828	struct ev_loop *loop_lo = 0;	1969	struct ev_loop *loop_lo = 0;
1829	struct ev_embed embed;	1970	struct ev_embed embed;
1830		1971
…		…
1841	ev_embed_start (loop_hi, &embed);	1982	ev_embed_start (loop_hi, &embed);
1842	}	1983	}
1843	else	1984	else
1844	loop_lo = loop_hi;	1985	loop_lo = loop_hi;
1845		1986
1846	=head2 Portability notes	1987	Example: Check if kqueue is available but not recommended and create
		1988	a kqueue backend for use with sockets (which usually work with any
		1989	kqueue implementation). Store the kqueue/socket-only event loop in
		1990	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1847		1991
1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I	1992	struct ev_loop *loop = ev_default_init (0);
1849	tried, in various ways. Usually the embedded event loop will simply never	1993	struct ev_loop *loop_socket = 0;
1850	receive events, sometimes it will only trigger a few times, sometimes in a	1994	struct ev_embed embed;
1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions	1995
1852	will always eport the epoll fd as ready, even when no events are pending.	1996	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		1997	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		1998	{
		1999	ev_embed_init (&embed, 0, loop_socket);
		2000	ev_embed_start (loop, &embed);
		2001	}
1853		2002
1854	While libev allows embedding these backends (they are contained in	2003	if (!loop_socket)
1855	C<ev_embeddable_backends ()>), take extreme care that it will actually	2004	loop_socket = loop;
1856	work.
1857		2005
1858	When in doubt, create a dynamic event loop forced to use sockets (this	2006	// now use loop_socket for all sockets, and loop for everything else
1859	usually works) and possibly another thread and a pipe or so to report to
1860	your main event loop.
1861
1862	=head3 Watcher-Specific Functions and Data Members
1863
1864	=over 4
1865
1866	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1867
1868	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
1869
1870	Configures the watcher to embed the given loop, which must be
1871	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1872	invoked automatically, otherwise it is the responsibility of the callback
1873	to invoke it (it will continue to be called until the sweep has been done,
1874	if you do not want thta, you need to temporarily stop the embed watcher).
1875
1876	=item ev_embed_sweep (loop, ev_embed *)
1877
1878	Make a single, non-blocking sweep over the embedded loop. This works
1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1880	apropriate way for embedded loops.
1881
1882	=item struct ev_loop *other [read-only]
1883
1884	The embedded event loop.
1885
1886	=back
1887		2007
1888		2008
1889	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2009	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1890		2010
1891	Fork watchers are called when a C<fork ()> was detected (usually because	2011	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2416	be detected at runtime.	2536	be detected at runtime.
2417		2537
2418	=item EV_H	2538	=item EV_H
2419		2539
2420	The name of the F<ev.h> header file used to include it. The default if	2540	The name of the F<ev.h> header file used to include it. The default if
2421	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2541	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2422	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2542	virtually rename the F<ev.h> header file in case of conflicts.
2423		2543
2424	=item EV_CONFIG_H	2544	=item EV_CONFIG_H
2425		2545
2426	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2427	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2547	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2428	C<EV_H>, above.	2548	C<EV_H>, above.
2429		2549
2430	=item EV_EVENT_H	2550	=item EV_EVENT_H
2431		2551
2432	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2433	of how the F<event.h> header can be found.	2553	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2434		2554
2435	=item EV_PROTOTYPES	2555	=item EV_PROTOTYPES
2436		2556
2437	If defined to be C<0>, then F<ev.h> will not define any function	2557	If defined to be C<0>, then F<ev.h> will not define any function
2438	prototypes, but still define all the structs and other symbols. This is	2558	prototypes, but still define all the structs and other symbols. This is
…		…
2504	than enough. If you need to manage thousands of children you might want to	2624	than enough. If you need to manage thousands of children you might want to
2505	increase this value (I<must> be a power of two).	2625	increase this value (I<must> be a power of two).
2506		2626
2507	=item EV_INOTIFY_HASHSIZE	2627	=item EV_INOTIFY_HASHSIZE
2508		2628
2509	C<ev_staz> watchers use a small hash table to distribute workload by	2629	C<ev_stat> watchers use a small hash table to distribute workload by
2510	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2630	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2511	usually more than enough. If you need to manage thousands of C<ev_stat>	2631	usually more than enough. If you need to manage thousands of C<ev_stat>
2512	watchers you might want to increase this value (I<must> be a power of	2632	watchers you might want to increase this value (I<must> be a power of
2513	two).	2633	two).
2514		2634
…		…
2610		2730
2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2731	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2612		2732
2613	This means that, when you have a watcher that triggers in one hour and	2733	This means that, when you have a watcher that triggers in one hour and
2614	there are 100 watchers that would trigger before that then inserting will	2734	there are 100 watchers that would trigger before that then inserting will
2615	have to skip those 100 watchers.	2735	have to skip roughly seven (C<ld 100>) of these watchers.
2616		2736
2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2737	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2618		2738
2619	That means that for changing a timer costs less than removing/adding them	2739	That means that changing a timer costs less than removing/adding them
2620	as only the relative motion in the event queue has to be paid for.	2740	as only the relative motion in the event queue has to be paid for.
2621		2741
2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2623		2743
2624	These just add the watcher into an array or at the head of a list.	2744	These just add the watcher into an array or at the head of a list.
		2745
2625	=item Stopping check/prepare/idle watchers: O(1)	2746	=item Stopping check/prepare/idle watchers: O(1)
2626		2747
2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2628		2749
2629	These watchers are stored in lists then need to be walked to find the	2750	These watchers are stored in lists then need to be walked to find the
2630	correct watcher to remove. The lists are usually short (you don't usually	2751	correct watcher to remove. The lists are usually short (you don't usually
2631	have many watchers waiting for the same fd or signal).	2752	have many watchers waiting for the same fd or signal).
2632		2753
2633	=item Finding the next timer per loop iteration: O(1)	2754	=item Finding the next timer in each loop iteration: O(1)
		2755
		2756	By virtue of using a binary heap, the next timer is always found at the
		2757	beginning of the storage array.
2634		2758
2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2759	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2636		2760
2637	A change means an I/O watcher gets started or stopped, which requires	2761	A change means an I/O watcher gets started or stopped, which requires
2638	libev to recalculate its status (and possibly tell the kernel).	2762	libev to recalculate its status (and possibly tell the kernel, depending
		2763	on backend and wether C<ev_io_set> was used).
2639		2764
2640	=item Activating one watcher: O(1)	2765	=item Activating one watcher (putting it into the pending state): O(1)
2641		2766
2642	=item Priority handling: O(number_of_priorities)	2767	=item Priority handling: O(number_of_priorities)
2643		2768
2644	Priorities are implemented by allocating some space for each	2769	Priorities are implemented by allocating some space for each
2645	priority. When doing priority-based operations, libev usually has to	2770	priority. When doing priority-based operations, libev usually has to
2646	linearly search all the priorities.	2771	linearly search all the priorities, but starting/stopping and activating
		2772	watchers becomes O(1) w.r.t. prioritiy handling.
2647		2773
2648	=back	2774	=back
2649		2775
2650		2776
2651	=head1 AUTHOR	2777	=head1 AUTHOR

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Comparing libev/ev.pod (file contents): Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC vs. Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC vs.
Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC