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

Comparing libev/ev.pod (file contents):
Revision 1.142 by root, Sun Apr 6 09:53:18 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
…		…
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size))
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260		284
261	If you use threads, a common model is to run the default event loop
262	in your main thread (or in a separate thread) and for each thread you
263	create, you also create another event loop. Libev itself does no locking
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267
268	=over 4	285	=over 4
269		286
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		288
272	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
340	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
341	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
342	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
343	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
344	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
345	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
346		363
347	=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)
348		365
349	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
350	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
429	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
430	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
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	449	might perform better.
433		450
434	On the positive side, ignoring the spurious readyness notifications, this	451	On the positive side, ignoring the spurious readiness notifications, this
435	backend actually performed to specification in all tests and is fully	452	backend actually performed to specification in all tests and is fully
436	embeddable, which is a rare feat among the OS-specific backends.	453	embeddable, which is a rare feat among the OS-specific backends.
437		454
438	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
439		456
…		…
693	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
694	interactive servers (of course not for games), likewise for timeouts. It	711	interactive servers (of course not for games), likewise for timeouts. It
695	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>,
696	as this approsaches the timing granularity of most systems.	713	as this approsaches the timing granularity of most systems.
697		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
698	=back	726	=back
699		727
700		728
701	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
702		730
…		…
1036	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
1037	(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
1038	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
1039		1067
1040	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
1041	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
1042	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
1043	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
1044	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
1045	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
1046	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
…		…
1155		1183
1156	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
1157	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1158		1186
1159	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
1160	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
1161	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
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1164		1192
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1166	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
…		…
1168	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
1169	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:
1170		1198
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1200
1173	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,
1174	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
1175	order of execution is undefined.	1203	order of execution is undefined.
1176		1204
1177	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1178		1206
…		…
1180		1208
1181	=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)
1182		1210
1183	=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)
1184		1212
1185	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>
1186	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
1187	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1189		1218
1190	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
1191	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
1192	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1193	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
1194	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.
1195		1224
1196	=item ev_timer_again (loop, ev_timer *)	1225	=item ev_timer_again (loop, ev_timer *)
1197		1226
1198	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
1199	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
…		…
1276	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
1277	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1278		1307
1279	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)
1280	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
1281	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
1282	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 ()
1283	+ 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
1284	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
1285	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1286		1316
1287	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,
1288	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1289	rules.	1319	complicated, rules.
1290		1320
1291	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
1292	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
1293	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1294		1324
1295	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1296		1326
1297	=over 4	1327	=over 4
…		…
1305		1335
1306	=over 4	1336	=over 4
1307		1337
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1309		1339
1310	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wallclock
1311	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
1312	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
1313	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1314		1344
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1316		1346
1317	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
1318	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)
1319	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1320		1350
1321	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
1322	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1323		1354
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1356
1326	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,
1327	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
…		…
1332	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
1333	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.
1334		1365
1335	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
1336	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
1337	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).
1338		1374
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1340		1376
1341	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
1342	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	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
1344	current time as second argument.	1380	current time as second argument.
1345		1381
1346	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,
1347	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1349	starting an C<ev_prepare> watcher, which is legal).
1350		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
1351	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
1352	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1353		1391
1354	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)
1355	{	1393	{
1356	return now + 60.;	1394	return now + 60.;
1357	}	1395	}
…		…
1359	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
1360	(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
1361	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
1362	might be called at other times, too.	1400	might be called at other times, too.
1363		1401
1364	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
1365	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1366		1404
1367	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
1368	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
1369	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
1370	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
1371	reason I omitted it as an example).	1409	reason I omitted it as an example).
1372		1410
1373	=back	1411	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1379	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1418	program when the crontabs have changed).
1381		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1382	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1383		1426
1384	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1386		1429
…		…
1396	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1439	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1397		1440
1398	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1399	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1400	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1401
1402	=item ev_tstamp at [read-only]
1403
1404	When active, contains the absolute time that the watcher is supposed to
1405	trigger next.
1406		1444
1407	=back	1445	=back
1408		1446
1409	=head3 Examples	1447	=head3 Examples
1410		1448
…		…
1614	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1615	resource-intensive.	1653	resource-intensive.
1616		1654
1617	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
1618	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
1619	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
1620	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
1621	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,
1622	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
1623	polling.	1662	will be no polling.
1624		1663
1625	=head3 ABI Issues (Largefile Support)	1664	=head3 ABI Issues (Largefile Support)
1626		1665
1627	Libev by default (unless the user overrides this) uses the default	1666	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	1667	compilation environment, which means that on systems with optionally
…		…
1638	When C<inotify (7)> support has been compiled into libev (generally only	1677	When C<inotify (7)> support has been compiled into libev (generally only
1639	available on Linux) and present at runtime, it will be used to speed up	1678	available on Linux) and present at runtime, it will be used to speed up
1640	change detection where possible. The inotify descriptor will be created lazily	1679	change detection where possible. The inotify descriptor will be created lazily
1641	when the first C<ev_stat> watcher is being started.	1680	when the first C<ev_stat> watcher is being started.
1642		1681
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	1682	Inotify presence does not change the semantics of C<ev_stat> watchers
1644	except that changes might be detected earlier, and in some cases, to avoid	1683	except that changes might be detected earlier, and in some cases, to avoid
1645	making regular C<stat> calls. Even in the presense of inotify support	1684	making regular C<stat> calls. Even in the presence of inotify support
1646	there are many cases where libev has to resort to regular C<stat> polling.	1685	there are many cases where libev has to resort to regular C<stat> polling.
1647		1686
1648	(There is no support for kqueue, as apparently it cannot be used to	1687	(There is no support for kqueue, as apparently it cannot be used to
1649	implement this functionality, due to the requirement of having a file	1688	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	1689	descriptor open on the object at all times).
…		…
1653		1692
1654	The C<stat ()> syscall only supports full-second resolution portably, and	1693	The C<stat ()> syscall only supports full-second resolution portably, and
1655	even on systems where the resolution is higher, many filesystems still	1694	even on systems where the resolution is higher, many filesystems still
1656	only support whole seconds.	1695	only support whole seconds.
1657		1696
1658	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
1659	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
1660	your callback, which does something. When there is another update within	1699	calls your callback, which does something. When there is another update
1661	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.
1662		1702
1663	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
1664	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
1665	(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);
1666	is added to work around small timing inconsistencies of some operating	1706	ev_timer_again (loop, w)>).
1667	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).
1668		1716
1669	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1670		1718
1671	=over 4	1719	=over 4
1672		1720
…		…
1678	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
1679	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
1680	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
1681	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1682		1730
1683	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
1684	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
1685	last change was detected).	1733	was detected).
1686		1734
1687	=item ev_stat_stat (loop, ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1688		1736
1689	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
1690	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
1691	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1692	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.
1693		1742
1694	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1695		1744
1696	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
1697	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
1698	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
1699	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1700		1750
1701	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1702		1752
1703	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1704	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>.
1705		1757
1706	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1707		1759
1708	The specified interval.	1760	The specified interval.
1709		1761
…		…
1763	}	1815	}
1764		1816
1765	...	1817	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	1819	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		1821
1770		1822
1771	=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...
1772		1824
1773	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
…		…
1861		1913
1862	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>)
1863	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
1864	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,
1865	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1866	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
1867	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
1868	(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
1869	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
1870	coexist peacefully with others).	1922	coexist peacefully with others).
1871		1923
…		…
1886	=head3 Examples	1938	=head3 Examples
1887		1939
1888	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
1889	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
1890	(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
1891	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
1892	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
1893	into the Glib event loop).	1945	Glib event loop).
1894		1946
1895	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,
1896	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
1897	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
1898	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
…		…
2382		2434
2383	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
2384	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
2385	is an ev_pri field.	2437	is an ev_pri field.
2386		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
2387	=item * Other members are not supported.	2442	=item * Other members are not supported.
2388		2443
2389	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2390	to use the libev header file and library.	2445	to use the libev header file and library.
2391		2446
…		…
2632		2687
2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2634		2689
2635	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
2636	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2637		2702
2638	=back	2703	=back
2639		2704
2640	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
2641	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
…		…
2957	defined to be C<0>, then they are not.	3022	defined to be C<0>, then they are not.
2958		3023
2959	=item EV_MINIMAL	3024	=item EV_MINIMAL
2960		3025
2961	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
2962	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
2963	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.
2964		3030
2965	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2966		3032
2967	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
2968	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
…		…
2974	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
2975	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>),
2976	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>
2977	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
2978	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.>
2979		3080
2980	=item EV_COMMON	3081	=item EV_COMMON
2981		3082
2982	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
2983	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
…		…
3057		3158
3058	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
3059	#include "ev.c"	3160	#include "ev.c"
3060		3161
3061		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely threadsafe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a seperate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robbin fashion.
		3196
		3197	Chosing a model is hard - look around, learn, know that usually you cna do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accomodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
		3218
		3219
3062	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
3063		3221
3064	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
3065	libev will be explained. For complexity discussions about backends see the	3223	libev will be explained. For complexity discussions about backends see the
3066	documentation for C<ev_default_init>.	3224	documentation for C<ev_default_init>.
…		…
3096	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
3097	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
3098		3256
3099	=item Finding the next timer in each loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
3100		3258
3101	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
3102	beginning of the storage array.	3260	fixed position in the storage array.
3103		3261
3104	=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)
3105		3263
3106	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
3107	libev to recalculate its status (and possibly tell the kernel, depending	3265	libev to recalculate its status (and possibly tell the kernel, depending
…		…
3136	model. Libev still offers limited functionality on this platform in	3294	model. Libev still offers limited functionality on this platform in
3137	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
3138	descriptors. This only applies when using Win32 natively, not when using	3296	descriptors. This only applies when using Win32 natively, not when using
3139	e.g. cygwin.	3297	e.g. cygwin.
3140		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
3141	There is no supported compilation method available on windows except	3304	There is no supported compilation method available on windows except
3142	embedding it into other applications.	3305	embedding it into other applications.
3143		3306
3144	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
3145	abysmal performance of winsockets, using a large number of sockets is not	3308	the abysmal performance of winsockets, using a large number of sockets
3146	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
3147	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
3148	implementation for windows, as libev offers the POSIX model, which cannot	3311	different implementation for windows, as libev offers the POSIX readiness
3149	be implemented efficiently on windows (microsoft monopoly games).	3312	notification model, which cannot be implemented efficiently on windows
		3313	(microsoft monopoly games).
3150		3314
3151	=over 4	3315	=over 4
3152		3316
3153	=item The winsocket select function	3317	=item The winsocket select function
3154		3318
3155	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
3156	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
3157	very inefficient, and also requires a mapping from file descriptors	3321	also extremely buggy). This makes select very inefficient, and also
3158	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
3159	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
3160	symbols for more info.	3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3161		3325
3162	The configuration for a "naked" win32 using the microsoft runtime	3326	The configuration for a "naked" win32 using the microsoft runtime
3163	libraries and raw winsocket select is:	3327	libraries and raw winsocket select is:
3164		3328
3165	#define EV_USE_SELECT 1	3329	#define EV_USE_SELECT 1
…		…
3168	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
3169	complexity in the O(n²) range when using win32.	3333	complexity in the O(n²) range when using win32.
3170		3334
3171	=item Limited number of file descriptors	3335	=item Limited number of file descriptors
3172		3336
3173	Windows has numerous arbitrary (and low) limits on things. Early versions	3337	Windows has numerous arbitrary (and low) limits on things.
3174	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
3175	(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
3176	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
3177	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).
3178		3344
3179	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>
3180	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
3181	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
3182	select emulation on windows).	3348	select emulation on windows).
…		…
3194	calling select (O(n²)) will likely make this unworkable.	3360	calling select (O(n²)) will likely make this unworkable.
3195		3361
3196	=back	3362	=back
3197		3363
3198		3364
		3365	=head1 PORTABILITY REQUIREMENTS
		3366
		3367	In addition to a working ISO-C implementation, libev relies on a few
		3368	additional extensions:
		3369
		3370	=over 4
		3371
		3372	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3373
		3374	The type C<sig_atomic_t volatile> (or whatever is defined as
		3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3376	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3377	believed to be sufficiently portable.
		3378
		3379	=item C<sigprocmask> must work in a threaded environment
		3380
		3381	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3382	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3383	pthread implementations will either allow C<sigprocmask> in the "main
		3384	thread" or will block signals process-wide, both behaviours would
		3385	be compatible with libev. Interaction between C<sigprocmask> and
		3386	C<pthread_sigmask> could complicate things, however.
		3387
		3388	The most portable way to handle signals is to block signals in all threads
		3389	except the initial one, and run the default loop in the initial thread as
		3390	well.
		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
		3407	=back
		3408
		3409	If you know of other additional requirements drop me a note.
		3410
		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
3199	=head1 AUTHOR	3464	=head1 AUTHOR
3200		3465
3201	Marc Lehmann <libev@schmorp.de>.	3466	Marc Lehmann <libev@schmorp.de>.
3202		3467

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Comparing libev/ev.pod (file contents):
Revision 1.142 by root, Sun Apr 6 09:53:18 2008 UTC vs.
Revision 1.160 by root, Thu May 22 03:06:58 2008 UTC