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

Comparing libev/ev.pod (file contents):
Revision 1.149 by root, Fri May 2 08:36:20 2008 UTC vs.
Revision 1.160 by root, Thu May 22 03:06:58 2008 UTC

…		…
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floatingpoint value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
121		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a syscall indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
126		147
…		…
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelity (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
342		363
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		365
345	And this is your standard poll(2) backend. It's more complicated	366	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
425	While this backend scales well, it requires one system call per active	446	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	447	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	449	might perform better.
429		450
430	On the positive side, ignoring the spurious readyness notifications, this	451	On the positive side, ignoring the spurious readiness notifications, this
431	backend actually performed to specification in all tests and is fully	452	backend actually performed to specification in all tests and is fully
432	embeddable, which is a rare feat among the OS-specific backends.	453	embeddable, which is a rare feat among the OS-specific backends.
433		454
434	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
435		456
…		…
689	interval to a value near C<0.1> or so, which is often enough for	710	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	711	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	712	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	713	as this approsaches the timing granularity of most systems.
693		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
		725
694	=back	726	=back
695		727
696		728
697	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
698		730
…		…
1032	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1034	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
1035		1067
1036	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
…		…
1151		1183
1152	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1154		1186
1155	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to january last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1160		1192
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1165	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1166		1198
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1200
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guarenteed to be invoked only after its timeout has passed,
1170	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1171	order of execution is undefined.	1203	order of execution is undefined.
1172		1204
1173	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1174		1206
…		…
1176		1208
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1210
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1212
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1185		1218
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1191		1224
1192	=item ev_timer_again (loop, ev_timer *)	1225	=item ev_timer_again (loop, ev_timer *)
1193		1226
1194	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
…		…
1272	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1274		1307
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wallclock time (absolute time). You can tell a periodic watcher
1277	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1279	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to january of the previous year, then it will take more than year
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1282		1316
1283	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1284	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1285	rules.	1319	complicated, rules.
1286		1320
1287	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guarenteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1290		1324
1291	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1292		1326
1293	=over 4	1327	=over 4
…		…
1301		1335
1302	=over 4	1336	=over 4
1303		1337
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1339
1306	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wallclock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1310		1344
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1346
1313	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1316		1350
1317	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1318	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1319		1354
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1356
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1358	but only that the the callback will be called when the system time shows a
…		…
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1365
1331	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (cpu
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course detoriate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1334		1374
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1376
1337	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1380	current time as second argument.
1341		1381
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1347	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1348	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1349		1391
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1351	{	1393	{
1352	return now + 60.;	1394	return now + 60.;
1353	}	1395	}
…		…
1355	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1400	might be called at other times, too.
1359		1401
1360	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1362		1404
1363	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1409	reason I omitted it as an example).
1368		1410
1369	=back	1411	=back
…		…
1610	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1653	resource-intensive.
1612		1654
1613	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1614	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1615	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1617	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1618	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1619	polling.	1662	will be no polling.
1620		1663
1621	=head3 ABI Issues (Largefile Support)	1664	=head3 ABI Issues (Largefile Support)
1622		1665
1623	Libev by default (unless the user overrides this) uses the default	1666	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	1667	compilation environment, which means that on systems with optionally
…		…
1649		1692
1650	The C<stat ()> syscall only supports full-second resolution portably, and	1693	The C<stat ()> syscall only supports full-second resolution portably, and
1651	even on systems where the resolution is higher, many filesystems still	1694	even on systems where the resolution is higher, many filesystems still
1652	only support whole seconds.	1695	only support whole seconds.
1653		1696
1654	That means that, if the time is the only thing that changes, you might	1697	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	1698	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	1699	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
1658		1702
1659	The solution to this is to delay acting on a change for a second (or till	1703	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	1704	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	1706	ev_timer_again (loop, w)>).
1663	systems.	1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
1664		1716
1665	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1666		1718
1667	=over 4	1719	=over 4
1668		1720
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1678		1730
1679	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1680	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1681	last change was detected).	1733	was detected).
1682		1734
1683	=item ev_stat_stat (loop, ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1684		1736
1685	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1689		1742
1690	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1691		1744
1692	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1696		1750
1697	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1698		1752
1699	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		1757
1702	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1703		1759
1704	The specified interval.	1760	The specified interval.
1705		1761
…		…
1759	}	1815	}
1760		1816
1761	...	1817	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	1819	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		1821
1766		1822
1767	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1768		1824
1769	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1857		1913
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	1915	priority, to ensure that they are being run before any other watchers
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1861	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1862	supports this, they will be called before other C<ev_check> watchers	1918	supports this, they might get executed before other C<ev_check> watchers
1863	did their job. As C<ev_check> watchers are often used to embed other	1919	did their job. As C<ev_check> watchers are often used to embed other
1864	(non-libev) event loops those other event loops might be in an unusable	1920	(non-libev) event loops those other event loops might be in an unusable
1865	state until their C<ev_check> watcher ran (always remind yourself to	1921	state until their C<ev_check> watcher ran (always remind yourself to
1866	coexist peacefully with others).	1922	coexist peacefully with others).
1867		1923
…		…
1882	=head3 Examples	1938	=head3 Examples
1883		1939
1884	There are a number of principal ways to embed other event loops or modules	1940	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	1941	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	1945	Glib event loop).
1890		1946
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	1948	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	1949	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
2966	defined to be C<0>, then they are not.	3022	defined to be C<0>, then they are not.
2967		3023
2968	=item EV_MINIMAL	3024	=item EV_MINIMAL
2969		3025
2970	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2973		3030
2974	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2975		3032
2976	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2983	C<ev_stat> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2987	two).	3044	two).
		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
2988		3080
2989	=item EV_COMMON	3081	=item EV_COMMON
2990		3082
2991	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
…		…
3162	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
3163	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
3164		3256
3165	=item Finding the next timer in each loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
3166		3258
3167	By virtue of using a binary heap, the next timer is always found at the	3259	By virtue of using a binary or 4-heap, the next timer is always found at a
3168	beginning of the storage array.	3260	fixed position in the storage array.
3169		3261
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3263
3172	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
3173	libev to recalculate its status (and possibly tell the kernel, depending	3265	libev to recalculate its status (and possibly tell the kernel, depending
…		…
3202	model. Libev still offers limited functionality on this platform in	3294	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3296	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3297	e.g. cygwin.
3206		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
3207	There is no supported compilation method available on windows except	3304	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3305	embedding it into other applications.
3209		3306
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3307	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	3308	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3309	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	3310	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	3311	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3312	notification model, which cannot be implemented efficiently on windows
		3313	(microsoft monopoly games).
3216		3314
3217	=over 4	3315	=over 4
3218		3316
3219	=item The winsocket select function	3317	=item The winsocket select function
3220		3318
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3319	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	3320	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3321	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3322	requires a mapping from file descriptors to socket handles. See the
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3226	symbols for more info.	3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3325
3228	The configuration for a "naked" win32 using the microsoft runtime	3326	The configuration for a "naked" win32 using the microsoft runtime
3229	libraries and raw winsocket select is:	3327	libraries and raw winsocket select is:
3230		3328
3231	#define EV_USE_SELECT 1	3329	#define EV_USE_SELECT 1
…		…
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3332	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	3333	complexity in the O(n²) range when using win32.
3236		3334
3237	=item Limited number of file descriptors	3335	=item Limited number of file descriptors
3238		3336
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3337	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3338
		3339	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	3340	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	3341	can only wait for C<64> things at the same time internally; microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	3342	recommends spawning a chain of threads and wait for 63 handles and the
		3343	previous thread in each. Great).
3244		3344
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	3346	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	3347	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3348	select emulation on windows).
…		…
3287		3387
3288	The most portable way to handle signals is to block signals in all threads	3388	The most portable way to handle signals is to block signals in all threads
3289	except the initial one, and run the default loop in the initial thread as	3389	except the initial one, and run the default loop in the initial thread as
3290	well.	3390	well.
3291		3391
		3392	=item C<long> must be large enough for common memory allocation sizes
		3393
		3394	To improve portability and simplify using libev, libev uses C<long>
		3395	internally instead of C<size_t> when allocating its data structures. On
		3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3397	is still at least 31 bits everywhere, which is enough for hundreds of
		3398	millions of watchers.
		3399
		3400	=item C<double> must hold a time value in seconds with enough accuracy
		3401
		3402	The type C<double> is used to represent timestamps. It is required to
		3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3404	enough for at least into the year 4000. This requirement is fulfilled by
		3405	implementations implementing IEEE 754 (basically all existing ones).
		3406
3292	=back	3407	=back
3293		3408
3294	If you know of other additional requirements drop me a note.	3409	If you know of other additional requirements drop me a note.
3295		3410
3296		3411
		3412	=head1 COMPILER WARNINGS
		3413
		3414	Depending on your compiler and compiler settings, you might get no or a
		3415	lot of warnings when compiling libev code. Some people are apparently
		3416	scared by this.
		3417
		3418	However, these are unavoidable for many reasons. For one, each compiler
		3419	has different warnings, and each user has different tastes regarding
		3420	warning options. "Warn-free" code therefore cannot be a goal except when
		3421	targetting a specific compiler and compiler-version.
		3422
		3423	Another reason is that some compiler warnings require elaborate
		3424	workarounds, or other changes to the code that make it less clear and less
		3425	maintainable.
		3426
		3427	And of course, some compiler warnings are just plain stupid, or simply
		3428	wrong (because they don't actually warn about the cindition their message
		3429	seems to warn about).
		3430
		3431	While libev is written to generate as few warnings as possible,
		3432	"warn-free" code is not a goal, and it is recommended not to build libev
		3433	with any compiler warnings enabled unless you are prepared to cope with
		3434	them (e.g. by ignoring them). Remember that warnings are just that:
		3435	warnings, not errors, or proof of bugs.
		3436
		3437
		3438	=head1 VALGRIND
		3439
		3440	Valgrind has a special section here because it is a popular tool that is
		3441	highly useful, but valgrind reports are very hard to interpret.
		3442
		3443	If you think you found a bug (memory leak, uninitialised data access etc.)
		3444	in libev, then check twice: If valgrind reports something like:
		3445
		3446	==2274== definitely lost: 0 bytes in 0 blocks.
		3447	==2274== possibly lost: 0 bytes in 0 blocks.
		3448	==2274== still reachable: 256 bytes in 1 blocks.
		3449
		3450	then there is no memory leak. Similarly, under some circumstances,
		3451	valgrind might report kernel bugs as if it were a bug in libev, or it
		3452	might be confused (it is a very good tool, but only a tool).
		3453
		3454	If you are unsure about something, feel free to contact the mailing list
		3455	with the full valgrind report and an explanation on why you think this is
		3456	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3457	no bug" answer and take the chance of learning how to interpret valgrind
		3458	properly.
		3459
		3460	If you need, for some reason, empty reports from valgrind for your project
		3461	I suggest using suppression lists.
		3462
		3463
3297	=head1 AUTHOR	3464	=head1 AUTHOR
3298		3465
3299	Marc Lehmann <libev@schmorp.de>.	3466	Marc Lehmann <libev@schmorp.de>.
3300		3467

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Comparing libev/ev.pod (file contents): Revision 1.149 by root, Fri May 2 08:36:20 2008 UTC vs. Revision 1.160 by root, Thu May 22 03:06:58 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.149 by root, Fri May 2 08:36:20 2008 UTC vs.
Revision 1.160 by root, Thu May 22 03:06:58 2008 UTC