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

Comparing libev/ev.pod (file contents):
Revision 1.137 by root, Sun Mar 16 16:42:56 2008 UTC vs.
Revision 1.152 by root, Wed May 7 14:45:17 2008 UTC

…		…
196	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
197		197
198	=item ev_set_allocator (void (cb)(void *ptr, long size))	198	=item ev_set_allocator (void (cb)(void *ptr, long size))
199		199
200	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	201	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	202	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	203	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
205	function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
206		209
207	You could override this function in high-availability programs to, say,	210	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,	211	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.	212	or even to sleep a while and retry until some memory is available.
210		213
211	Example: Replace the libev allocator with one that waits a bit and then	214	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	215	retries (example requires a standards-compliant C<realloc>).
213		216
214	static void *	217	static void *
215	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
216	{	219	{
217	for (;;)	220	for (;;)
…		…
256		259
257	An event loop is described by a C<struct ev_loop *>. The library knows two	260	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	261	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
260		263
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	264	=over 4
269		265
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		267
272	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
…		…
274	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		272
277	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
278	function.	274	function.
		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
279		279
280	The default loop is the only loop that can handle C<ev_signal> and	280	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	281	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	282	for C<SIGCHLD>. If this is a problem for your app you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
354	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	355	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	356	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	358	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and rewiring a syscall per fd change, no fork support and bad	359	cases and requiring a syscall per fd change, no fork support and bad
360	support for dup.	360	support for dup.
361		361
362	While stopping, setting and starting an I/O watcher in the same iteration	362	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
364	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
…		…
465		465
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	467	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	468	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	469	undefined behaviour (or a failed assertion if assertions are enabled).
		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
470		474
471	Example: Try to create a event loop that uses epoll and nothing else.	475	Example: Try to create a event loop that uses epoll and nothing else.
472		476
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
474	if (!epoller)	478	if (!epoller)
…		…
1085	To support fork in your programs, you either have to call	1089	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1092	C<EVBACKEND_POLL>.
1089		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
1090		1106
1091	=head3 Watcher-Specific Functions	1107	=head3 Watcher-Specific Functions
1092		1108
1093	=over 4	1109	=over 4
1094		1110
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1373	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1374	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	1375	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1376	program when the crontabs have changed).
1361		1377
		1378	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1379
		1380	When active, returns the absolute time that the watcher is supposed to
		1381	trigger next.
		1382
1362	=item ev_tstamp offset [read-write]	1383	=item ev_tstamp offset [read-write]
1363		1384
1364	When repeating, this contains the offset value, otherwise this is the	1385	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1386	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1387
…		…
1376	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1397	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1377		1398
1378	The current reschedule callback, or C<0>, if this functionality is	1399	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	1400	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	1401	the periodic timer fires or C<ev_periodic_again> is being called.
1381
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386		1402
1387	=back	1403	=back
1388		1404
1389	=head3 Examples	1405	=head3 Examples
1390		1406
…		…
1594	as even with OS-supported change notifications, this can be	1610	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1611	resource-intensive.
1596		1612
1597	At the time of this writing, only the Linux inotify interface is	1613	At the time of this writing, only the Linux inotify interface is
1598	implemented (implementing kqueue support is left as an exercise for the	1614	implemented (implementing kqueue support is left as an exercise for the
		1615	reader, note, however, that the author sees no way of implementing ev_stat
1599	reader). Inotify will be used to give hints only and should not change the	1616	semantics with kqueue). Inotify will be used to give hints only and should
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1617	not change the semantics of C<ev_stat> watchers, which means that libev
1601	to fall back to regular polling again even with inotify, but changes are	1618	sometimes needs to fall back to regular polling again even with inotify,
1602	usually detected immediately, and if the file exists there will be no	1619	but changes are usually detected immediately, and if the file exists there
1603	polling.	1620	will be no polling.
1604		1621
1605	=head3 ABI Issues (Largefile Support)	1622	=head3 ABI Issues (Largefile Support)
1606		1623
1607	Libev by default (unless the user overrides this) uses the default	1624	Libev by default (unless the user overrides this) uses the default
1608	compilation environment, which means that on systems with optionally	1625	compilation environment, which means that on systems with optionally
…		…
1618	When C<inotify (7)> support has been compiled into libev (generally only	1635	When C<inotify (7)> support has been compiled into libev (generally only
1619	available on Linux) and present at runtime, it will be used to speed up	1636	available on Linux) and present at runtime, it will be used to speed up
1620	change detection where possible. The inotify descriptor will be created lazily	1637	change detection where possible. The inotify descriptor will be created lazily
1621	when the first C<ev_stat> watcher is being started.	1638	when the first C<ev_stat> watcher is being started.
1622		1639
1623	Inotify presense does not change the semantics of C<ev_stat> watchers	1640	Inotify presence does not change the semantics of C<ev_stat> watchers
1624	except that changes might be detected earlier, and in some cases, to avoid	1641	except that changes might be detected earlier, and in some cases, to avoid
1625	making regular C<stat> calls. Even in the presense of inotify support	1642	making regular C<stat> calls. Even in the presence of inotify support
1626	there are many cases where libev has to resort to regular C<stat> polling.	1643	there are many cases where libev has to resort to regular C<stat> polling.
1627		1644
1628	(There is no support for kqueue, as apparently it cannot be used to	1645	(There is no support for kqueue, as apparently it cannot be used to
1629	implement this functionality, due to the requirement of having a file	1646	implement this functionality, due to the requirement of having a file
1630	descriptor open on the object at all times).	1647	descriptor open on the object at all times).
…		…
1633		1650
1634	The C<stat ()> syscall only supports full-second resolution portably, and	1651	The C<stat ()> syscall only supports full-second resolution portably, and
1635	even on systems where the resolution is higher, many filesystems still	1652	even on systems where the resolution is higher, many filesystems still
1636	only support whole seconds.	1653	only support whole seconds.
1637		1654
1638	That means that, if the time is the only thing that changes, you might	1655	That means that, if the time is the only thing that changes, you can
1639	miss updates: on the first update, C<ev_stat> detects a change and calls	1656	easily miss updates: on the first update, C<ev_stat> detects a change and
1640	your callback, which does something. When there is another update within	1657	calls your callback, which does something. When there is another update
1641	the same second, C<ev_stat> will be unable to detect it.	1658	within the same second, C<ev_stat> will be unable to detect it as the stat
		1659	data does not change.
1642		1660
1643	The solution to this is to delay acting on a change for a second (or till	1661	The solution to this is to delay acting on a change for slightly more
1644	the next second boundary), using a roughly one-second delay C<ev_timer>	1662	than second (or till slightly after the next full second boundary), using
1645	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1646	is added to work around small timing inconsistencies of some operating	1664	ev_timer_again (loop, w)>).
1647	systems.	1665
		1666	The C<.02> offset is added to work around small timing inconsistencies
		1667	of some operating systems (where the second counter of the current time
		1668	might be be delayed. One such system is the Linux kernel, where a call to
		1669	C<gettimeofday> might return a timestamp with a full second later than
		1670	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1671	update file times then there will be a small window where the kernel uses
		1672	the previous second to update file times but libev might already execute
		1673	the timer callback).
1648		1674
1649	=head3 Watcher-Specific Functions and Data Members	1675	=head3 Watcher-Specific Functions and Data Members
1650		1676
1651	=over 4	1677	=over 4
1652		1678
…		…
1658	C<path>. The C<interval> is a hint on how quickly a change is expected to	1684	C<path>. The C<interval> is a hint on how quickly a change is expected to
1659	be detected and should normally be specified as C<0> to let libev choose	1685	be detected and should normally be specified as C<0> to let libev choose
1660	a suitable value. The memory pointed to by C<path> must point to the same	1686	a suitable value. The memory pointed to by C<path> must point to the same
1661	path for as long as the watcher is active.	1687	path for as long as the watcher is active.
1662		1688
1663	The callback will be receive C<EV_STAT> when a change was detected,	1689	The callback will receive C<EV_STAT> when a change was detected, relative
1664	relative to the attributes at the time the watcher was started (or the	1690	to the attributes at the time the watcher was started (or the last change
1665	last change was detected).	1691	was detected).
1666		1692
1667	=item ev_stat_stat (loop, ev_stat *)	1693	=item ev_stat_stat (loop, ev_stat *)
1668		1694
1669	Updates the stat buffer immediately with new values. If you change the	1695	Updates the stat buffer immediately with new values. If you change the
1670	watched path in your callback, you could call this fucntion to avoid	1696	watched path in your callback, you could call this function to avoid
1671	detecting this change (while introducing a race condition). Can also be	1697	detecting this change (while introducing a race condition if you are not
1672	useful simply to find out the new values.	1698	the only one changing the path). Can also be useful simply to find out the
		1699	new values.
1673		1700
1674	=item ev_statdata attr [read-only]	1701	=item ev_statdata attr [read-only]
1675		1702
1676	The most-recently detected attributes of the file. Although the type is of	1703	The most-recently detected attributes of the file. Although the type is
1677	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1704	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1678	suitable for your system. If the C<st_nlink> member is C<0>, then there	1705	suitable for your system, but you can only rely on the POSIX-standardised
		1706	members to be present. If the C<st_nlink> member is C<0>, then there was
1679	was some error while C<stat>ing the file.	1707	some error while C<stat>ing the file.
1680		1708
1681	=item ev_statdata prev [read-only]	1709	=item ev_statdata prev [read-only]
1682		1710
1683	The previous attributes of the file. The callback gets invoked whenever	1711	The previous attributes of the file. The callback gets invoked whenever
1684	C<prev> != C<attr>.	1712	C<prev> != C<attr>, or, more precisely, one or more of these members
		1713	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1714	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1685		1715
1686	=item ev_tstamp interval [read-only]	1716	=item ev_tstamp interval [read-only]
1687		1717
1688	The specified interval.	1718	The specified interval.
1689		1719
…		…
1743	}	1773	}
1744		1774
1745	...	1775	...
1746	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1747	ev_stat_start (loop, &passwd);	1777	ev_stat_start (loop, &passwd);
1748	ev_timer_init (&timer, timer_cb, 0., 1.01);	1778	ev_timer_init (&timer, timer_cb, 0., 1.02);
1749		1779
1750		1780
1751	=head2 C<ev_idle> - when you've got nothing better to do...	1781	=head2 C<ev_idle> - when you've got nothing better to do...
1752		1782
1753	Idle watchers trigger events when no other events of the same or higher	1783	Idle watchers trigger events when no other events of the same or higher
…		…
1841		1871
1842	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1843	priority, to ensure that they are being run before any other watchers	1873	priority, to ensure that they are being run before any other watchers
1844	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1845	too) should not activate ("feed") events into libev. While libev fully	1875	too) should not activate ("feed") events into libev. While libev fully
1846	supports this, they will be called before other C<ev_check> watchers	1876	supports this, they might get executed before other C<ev_check> watchers
1847	did their job. As C<ev_check> watchers are often used to embed other	1877	did their job. As C<ev_check> watchers are often used to embed other
1848	(non-libev) event loops those other event loops might be in an unusable	1878	(non-libev) event loops those other event loops might be in an unusable
1849	state until their C<ev_check> watcher ran (always remind yourself to	1879	state until their C<ev_check> watcher ran (always remind yourself to
1850	coexist peacefully with others).	1880	coexist peacefully with others).
1851		1881
…		…
1866	=head3 Examples	1896	=head3 Examples
1867		1897
1868	There are a number of principal ways to embed other event loops or modules	1898	There are a number of principal ways to embed other event loops or modules
1869	into libev. Here are some ideas on how to include libadns into libev	1899	into libev. Here are some ideas on how to include libadns into libev
1870	(there is a Perl module named C<EV::ADNS> that does this, which you could	1900	(there is a Perl module named C<EV::ADNS> that does this, which you could
1871	use for an actually working example. Another Perl module named C<EV::Glib>	1901	use as a working example. Another Perl module named C<EV::Glib> embeds a
1872	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1902	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1873	into the Glib event loop).	1903	Glib event loop).
1874		1904
1875	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1905	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1876	and in a check watcher, destroy them and call into libadns. What follows	1906	and in a check watcher, destroy them and call into libadns. What follows
1877	is pseudo-code only of course. This requires you to either use a low	1907	is pseudo-code only of course. This requires you to either use a low
1878	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
2268		2298
2269	This call incurs the overhead of a syscall only once per loop iteration,	2299	This call incurs the overhead of a syscall only once per loop iteration,
2270	so while the overhead might be noticable, it doesn't apply to repeated	2300	so while the overhead might be noticable, it doesn't apply to repeated
2271	calls to C<ev_async_send>.	2301	calls to C<ev_async_send>.
2272		2302
		2303	=item bool = ev_async_pending (ev_async *)
		2304
		2305	Returns a non-zero value when C<ev_async_send> has been called on the
		2306	watcher but the event has not yet been processed (or even noted) by the
		2307	event loop.
		2308
		2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2310	the loop iterates next and checks for the watcher to have become active,
		2311	it will reset the flag again. C<ev_async_pending> can be used to very
		2312	quickly check wether invoking the loop might be a good idea.
		2313
		2314	Not that this does I<not> check wether the watcher itself is pending, only
		2315	wether it has been requested to make this watcher pending.
		2316
2273	=back	2317	=back
2274		2318
2275		2319
2276	=head1 OTHER FUNCTIONS	2320	=head1 OTHER FUNCTIONS
2277		2321
…		…
2348		2392
2349	=item * Priorities are not currently supported. Initialising priorities	2393	=item * Priorities are not currently supported. Initialising priorities
2350	will fail and all watchers will have the same priority, even though there	2394	will fail and all watchers will have the same priority, even though there
2351	is an ev_pri field.	2395	is an ev_pri field.
2352		2396
		2397	=item * In libevent, the last base created gets the signals, in libev, the
		2398	first base created (== the default loop) gets the signals.
		2399
2353	=item * Other members are not supported.	2400	=item * Other members are not supported.
2354		2401
2355	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2402	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2356	to use the libev header file and library.	2403	to use the libev header file and library.
2357		2404
…		…
2599	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2600		2647
2601	Similar to the other two macros, this gives you the value of the default	2648	Similar to the other two macros, this gives you the value of the default
2602	loop, if multiple loops are supported ("ev loop default").	2649	loop, if multiple loops are supported ("ev loop default").
2603		2650
		2651	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2652
		2653	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2654	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2655	is undefined when the default loop has not been initialised by a previous
		2656	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2657
		2658	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2659	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2660
2604	=back	2661	=back
2605		2662
2606	Example: Declare and initialise a check watcher, utilising the above	2663	Example: Declare and initialise a check watcher, utilising the above
2607	macros so it will work regardless of whether multiple loops are supported	2664	macros so it will work regardless of whether multiple loops are supported
2608	or not.	2665	or not.
…		…
2703		2760
2704	libev.m4	2761	libev.m4
2705		2762
2706	=head2 PREPROCESSOR SYMBOLS/MACROS	2763	=head2 PREPROCESSOR SYMBOLS/MACROS
2707		2764
2708	Libev can be configured via a variety of preprocessor symbols you have to define	2765	Libev can be configured via a variety of preprocessor symbols you have to
2709	before including any of its files. The default is not to build for multiplicity	2766	define before including any of its files. The default in the absense of
2710	and only include the select backend.	2767	autoconf is noted for every option.
2711		2768
2712	=over 4	2769	=over 4
2713		2770
2714	=item EV_STANDALONE	2771	=item EV_STANDALONE
2715		2772
…		…
2741	=item EV_USE_NANOSLEEP	2798	=item EV_USE_NANOSLEEP
2742		2799
2743	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2800	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2744	and will use it for delays. Otherwise it will use C<select ()>.	2801	and will use it for delays. Otherwise it will use C<select ()>.
2745		2802
		2803	=item EV_USE_EVENTFD
		2804
		2805	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2806	available and will probe for kernel support at runtime. This will improve
		2807	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2808	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2809	2.7 or newer, otherwise disabled.
		2810
2746	=item EV_USE_SELECT	2811	=item EV_USE_SELECT
2747		2812
2748	If undefined or defined to be C<1>, libev will compile in support for the	2813	If undefined or defined to be C<1>, libev will compile in support for the
2749	C<select>(2) backend. No attempt at autodetection will be done: if no	2814	C<select>(2) backend. No attempt at autodetection will be done: if no
2750	other method takes over, select will be it. Otherwise the select backend	2815	other method takes over, select will be it. Otherwise the select backend
…		…
2786		2851
2787	=item EV_USE_EPOLL	2852	=item EV_USE_EPOLL
2788		2853
2789	If defined to be C<1>, libev will compile in support for the Linux	2854	If defined to be C<1>, libev will compile in support for the Linux
2790	C<epoll>(7) backend. Its availability will be detected at runtime,	2855	C<epoll>(7) backend. Its availability will be detected at runtime,
2791	otherwise another method will be used as fallback. This is the	2856	otherwise another method will be used as fallback. This is the preferred
2792	preferred backend for GNU/Linux systems.	2857	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2858	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2793		2859
2794	=item EV_USE_KQUEUE	2860	=item EV_USE_KQUEUE
2795		2861
2796	If defined to be C<1>, libev will compile in support for the BSD style	2862	If defined to be C<1>, libev will compile in support for the BSD style
2797	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2863	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2816		2882
2817	=item EV_USE_INOTIFY	2883	=item EV_USE_INOTIFY
2818		2884
2819	If defined to be C<1>, libev will compile in support for the Linux inotify	2885	If defined to be C<1>, libev will compile in support for the Linux inotify
2820	interface to speed up C<ev_stat> watchers. Its actual availability will	2886	interface to speed up C<ev_stat> watchers. Its actual availability will
2821	be detected at runtime.	2887	be detected at runtime. If undefined, it will be enabled if the headers
		2888	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2822		2889
2823	=item EV_ATOMIC_T	2890	=item EV_ATOMIC_T
2824		2891
2825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	2892	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2826	access is atomic with respect to other threads or signal contexts. No such	2893	access is atomic with respect to other threads or signal contexts. No such
…		…
2913	defined to be C<0>, then they are not.	2980	defined to be C<0>, then they are not.
2914		2981
2915	=item EV_MINIMAL	2982	=item EV_MINIMAL
2916		2983
2917	If you need to shave off some kilobytes of code at the expense of some	2984	If you need to shave off some kilobytes of code at the expense of some
2918	speed, define this symbol to C<1>. Currently only used for gcc to override	2985	speed, define this symbol to C<1>. Currently this is used to override some
2919	some inlining decisions, saves roughly 30% codesize of amd64.	2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		2987	much smaller 2-heap for timer management over the default 4-heap.
2920		2988
2921	=item EV_PID_HASHSIZE	2989	=item EV_PID_HASHSIZE
2922		2990
2923	C<ev_child> watchers use a small hash table to distribute workload by	2991	C<ev_child> watchers use a small hash table to distribute workload by
2924	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2992	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3013		3081
3014	#include "ev_cpp.h"	3082	#include "ev_cpp.h"
3015	#include "ev.c"	3083	#include "ev.c"
3016		3084
3017		3085
		3086	=head1 THREADS AND COROUTINES
		3087
		3088	=head2 THREADS
		3089
		3090	Libev itself is completely threadsafe, but it uses no locking. This
		3091	means that you can use as many loops as you want in parallel, as long as
		3092	only one thread ever calls into one libev function with the same loop
		3093	parameter.
		3094
		3095	Or put differently: calls with different loop parameters can be done in
		3096	parallel from multiple threads, calls with the same loop parameter must be
		3097	done serially (but can be done from different threads, as long as only one
		3098	thread ever is inside a call at any point in time, e.g. by using a mutex
		3099	per loop).
		3100
		3101	If you want to know which design is best for your problem, then I cannot
		3102	help you but by giving some generic advice:
		3103
		3104	=over 4
		3105
		3106	=item * most applications have a main thread: use the default libev loop
		3107	in that thread, or create a seperate thread running only the default loop.
		3108
		3109	This helps integrating other libraries or software modules that use libev
		3110	themselves and don't care/know about threading.
		3111
		3112	=item * one loop per thread is usually a good model.
		3113
		3114	Doing this is almost never wrong, sometimes a better-performance model
		3115	exists, but it is always a good start.
		3116
		3117	=item * other models exist, such as the leader/follower pattern, where one
		3118	loop is handed through multiple threads in a kind of round-robbin fashion.
		3119
		3120	Chosing a model is hard - look around, learn, know that usually you cna do
		3121	better than you currently do :-)
		3122
		3123	=item * often you need to talk to some other thread which blocks in the
		3124	event loop - C<ev_async> watchers can be used to wake them up from other
		3125	threads safely (or from signal contexts...).
		3126
		3127	=back
		3128
		3129	=head2 COROUTINES
		3130
		3131	Libev is much more accomodating to coroutines ("cooperative threads"):
		3132	libev fully supports nesting calls to it's functions from different
		3133	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3134	different coroutines and switch freely between both coroutines running the
		3135	loop, as long as you don't confuse yourself). The only exception is that
		3136	you must not do this from C<ev_periodic> reschedule callbacks.
		3137
		3138	Care has been invested into making sure that libev does not keep local
		3139	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3140	switches.
		3141
		3142
3018	=head1 COMPLEXITIES	3143	=head1 COMPLEXITIES
3019		3144
3020	In this section the complexities of (many of) the algorithms used inside	3145	In this section the complexities of (many of) the algorithms used inside
3021	libev will be explained. For complexity discussions about backends see the	3146	libev will be explained. For complexity discussions about backends see the
3022	documentation for C<ev_default_init>.	3147	documentation for C<ev_default_init>.
…		…
3052	correct watcher to remove. The lists are usually short (you don't usually	3177	correct watcher to remove. The lists are usually short (you don't usually
3053	have many watchers waiting for the same fd or signal).	3178	have many watchers waiting for the same fd or signal).
3054		3179
3055	=item Finding the next timer in each loop iteration: O(1)	3180	=item Finding the next timer in each loop iteration: O(1)
3056		3181
3057	By virtue of using a binary heap, the next timer is always found at the	3182	By virtue of using a binary or 4-heap, the next timer is always found at a
3058	beginning of the storage array.	3183	fixed position in the storage array.
3059		3184
3060	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3185	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3061		3186
3062	A change means an I/O watcher gets started or stopped, which requires	3187	A change means an I/O watcher gets started or stopped, which requires
3063	libev to recalculate its status (and possibly tell the kernel, depending	3188	libev to recalculate its status (and possibly tell the kernel, depending
…		…
3092	model. Libev still offers limited functionality on this platform in	3217	model. Libev still offers limited functionality on this platform in
3093	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3218	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3094	descriptors. This only applies when using Win32 natively, not when using	3219	descriptors. This only applies when using Win32 natively, not when using
3095	e.g. cygwin.	3220	e.g. cygwin.
3096		3221
		3222	Lifting these limitations would basically require the full
		3223	re-implementation of the I/O system. If you are into these kinds of
		3224	things, then note that glib does exactly that for you in a very portable
		3225	way (note also that glib is the slowest event library known to man).
		3226
3097	There is no supported compilation method available on windows except	3227	There is no supported compilation method available on windows except
3098	embedding it into other applications.	3228	embedding it into other applications.
3099		3229
3100	Due to the many, low, and arbitrary limits on the win32 platform and the	3230	Due to the many, low, and arbitrary limits on the win32 platform and
3101	abysmal performance of winsockets, using a large number of sockets is not	3231	the abysmal performance of winsockets, using a large number of sockets
3102	recommended (and not reasonable). If your program needs to use more than	3232	is not recommended (and not reasonable). If your program needs to use
3103	a hundred or so sockets, then likely it needs to use a totally different	3233	more than a hundred or so sockets, then likely it needs to use a totally
3104	implementation for windows, as libev offers the POSIX model, which cannot	3234	different implementation for windows, as libev offers the POSIX readyness
3105	be implemented efficiently on windows (microsoft monopoly games).	3235	notification model, which cannot be implemented efficiently on windows
		3236	(microsoft monopoly games).
3106		3237
3107	=over 4	3238	=over 4
3108		3239
3109	=item The winsocket select function	3240	=item The winsocket select function
3110		3241
…		…
3124	Note that winsockets handling of fd sets is O(n), so you can easily get a	3255	Note that winsockets handling of fd sets is O(n), so you can easily get a
3125	complexity in the O(n²) range when using win32.	3256	complexity in the O(n²) range when using win32.
3126		3257
3127	=item Limited number of file descriptors	3258	=item Limited number of file descriptors
3128		3259
3129	Windows has numerous arbitrary (and low) limits on things. Early versions	3260	Windows has numerous arbitrary (and low) limits on things.
3130	of winsocket's select only supported waiting for a max. of C<64> handles	3261
		3262	Early versions of winsocket's select only supported waiting for a maximum
3131	(probably owning to the fact that all windows kernels can only wait for	3263	of C<64> handles (probably owning to the fact that all windows kernels
3132	C<64> things at the same time internally; microsoft recommends spawning a	3264	can only wait for C<64> things at the same time internally; microsoft
3133	chain of threads and wait for 63 handles and the previous thread in each).	3265	recommends spawning a chain of threads and wait for 63 handles and the
		3266	previous thread in each. Great).
3134		3267
3135	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3268	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3136	to some high number (e.g. C<2048>) before compiling the winsocket select	3269	to some high number (e.g. C<2048>) before compiling the winsocket select
3137	call (which might be in libev or elsewhere, for example, perl does its own	3270	call (which might be in libev or elsewhere, for example, perl does its own
3138	select emulation on windows).	3271	select emulation on windows).
…		…
3150	calling select (O(n²)) will likely make this unworkable.	3283	calling select (O(n²)) will likely make this unworkable.
3151		3284
3152	=back	3285	=back
3153		3286
3154		3287
		3288	=head1 PORTABILITY REQUIREMENTS
		3289
		3290	In addition to a working ISO-C implementation, libev relies on a few
		3291	additional extensions:
		3292
		3293	=over 4
		3294
		3295	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3296
		3297	The type C<sig_atomic_t volatile> (or whatever is defined as
		3298	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3299	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3300	believed to be sufficiently portable.
		3301
		3302	=item C<sigprocmask> must work in a threaded environment
		3303
		3304	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3305	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3306	pthread implementations will either allow C<sigprocmask> in the "main
		3307	thread" or will block signals process-wide, both behaviours would
		3308	be compatible with libev. Interaction between C<sigprocmask> and
		3309	C<pthread_sigmask> could complicate things, however.
		3310
		3311	The most portable way to handle signals is to block signals in all threads
		3312	except the initial one, and run the default loop in the initial thread as
		3313	well.
		3314
		3315	=item C<long> must be large enough for common memory allocation sizes
		3316
		3317	To improve portability and simplify using libev, libev uses C<long>
		3318	internally instead of C<size_t> when allocating its data structures. On
		3319	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3320	is still at least 31 bits everywhere, which is enough for hundreds of
		3321	millions of watchers.
		3322
		3323	=item C<double> must hold a time value in seconds with enough accuracy
		3324
		3325	The type C<double> is used to represent timestamps. It is required to
		3326	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3327	enough for at least into the year 4000. This requirement is fulfilled by
		3328	implementations implementing IEEE 754 (basically all existing ones).
		3329
		3330	=back
		3331
		3332	If you know of other additional requirements drop me a note.
		3333
		3334
3155	=head1 AUTHOR	3335	=head1 AUTHOR
3156		3336
3157	Marc Lehmann <libev@schmorp.de>.	3337	Marc Lehmann <libev@schmorp.de>.
3158		3338

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Comparing libev/ev.pod (file contents):
Revision 1.137 by root, Sun Mar 16 16:42:56 2008 UTC vs.
Revision 1.152 by root, Wed May 7 14:45:17 2008 UTC