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

Comparing libev/ev.pod (file contents):
Revision 1.146 by root, Fri Apr 11 00:31:19 2008 UTC vs.
Revision 1.156 by root, Tue May 20 20:00:34 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
…		…
336	To get good performance out of this backend you need a high amount of	336	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	337	parallelity (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	338	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	339	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	341	readiness notifications you get per iteration.
342		342
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		344
345	And this is your standard poll(2) backend. It's more complicated	345	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	346	than select, but handles sparse fds better and has no artificial
…		…
425	While this backend scales well, it requires one system call per active	425	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	426	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	428	might perform better.
429		429
430	On the positive side, ignoring the spurious readyness notifications, this	430	On the positive side, ignoring the spurious readiness notifications, this
431	backend actually performed to specification in all tests and is fully	431	backend actually performed to specification in all tests and is fully
432	embeddable, which is a rare feat among the OS-specific backends.	432	embeddable, which is a rare feat among the OS-specific backends.
433		433
434	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
435		435
…		…
1032	If you must do this, then force the use of a known-to-be-good backend	1032	If you must do this, then force the use of a known-to-be-good backend
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1034	C<EVBACKEND_POLL>).	1034	C<EVBACKEND_POLL>).
1035		1035
1036	Another thing you have to watch out for is that it is quite easy to	1036	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1037	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1039	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1040	lot of those (for example solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1041	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning
…		…
1373	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
1374	when you changed some parameters or the reschedule callback would return	1374	when you changed some parameters or the reschedule callback would return
1375	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
1376	program when the crontabs have changed).	1376	program when the crontabs have changed).
1377		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
1378	=item ev_tstamp offset [read-write]	1383	=item ev_tstamp offset [read-write]
1379		1384
1380	When repeating, this contains the offset value, otherwise this is the	1385	When repeating, this contains the offset value, otherwise this is the
1381	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>).
1382		1387
…		…
1392	=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]
1393		1398
1394	The current reschedule callback, or C<0>, if this functionality is	1399	The current reschedule callback, or C<0>, if this functionality is
1395	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
1396	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.
1397
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402		1402
1403	=back	1403	=back
1404		1404
1405	=head3 Examples	1405	=head3 Examples
1406		1406
…		…
1610	as even with OS-supported change notifications, this can be	1610	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1611	resource-intensive.
1612		1612
1613	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
1614	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
1615	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
1616	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
1617	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,
1618	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
1619	polling.	1620	will be no polling.
1620		1621
1621	=head3 ABI Issues (Largefile Support)	1622	=head3 ABI Issues (Largefile Support)
1622		1623
1623	Libev by default (unless the user overrides this) uses the default	1624	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	1625	compilation environment, which means that on systems with optionally
…		…
1634	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
1635	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
1636	change detection where possible. The inotify descriptor will be created lazily	1637	change detection where possible. The inotify descriptor will be created lazily
1637	when the first C<ev_stat> watcher is being started.	1638	when the first C<ev_stat> watcher is being started.
1638		1639
1639	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
1640	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
1641	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
1642	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.
1643		1644
1644	(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
1645	implement this functionality, due to the requirement of having a file	1646	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	1647	descriptor open on the object at all times).
…		…
1649		1650
1650	The C<stat ()> syscall only supports full-second resolution portably, and	1651	The C<stat ()> syscall only supports full-second resolution portably, and
1651	even on systems where the resolution is higher, many filesystems still	1652	even on systems where the resolution is higher, many filesystems still
1652	only support whole seconds.	1653	only support whole seconds.
1653		1654
1654	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
1655	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
1656	your callback, which does something. When there is another update within	1657	calls your callback, which does something. When there is another update
1657	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.
1658		1660
1659	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
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	1662	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	1664	ev_timer_again (loop, w)>).
1663	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).
1664		1674
1665	=head3 Watcher-Specific Functions and Data Members	1675	=head3 Watcher-Specific Functions and Data Members
1666		1676
1667	=over 4	1677	=over 4
1668		1678
…		…
1674	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
1675	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
1676	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
1677	path for as long as the watcher is active.	1687	path for as long as the watcher is active.
1678		1688
1679	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
1680	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
1681	last change was detected).	1691	was detected).
1682		1692
1683	=item ev_stat_stat (loop, ev_stat *)	1693	=item ev_stat_stat (loop, ev_stat *)
1684		1694
1685	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
1686	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
1687	detecting this change (while introducing a race condition). Can also be	1697	detecting this change (while introducing a race condition if you are not
1688	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.
1689		1700
1690	=item ev_statdata attr [read-only]	1701	=item ev_statdata attr [read-only]
1691		1702
1692	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
1693	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
1694	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
1695	was some error while C<stat>ing the file.	1707	some error while C<stat>ing the file.
1696		1708
1697	=item ev_statdata prev [read-only]	1709	=item ev_statdata prev [read-only]
1698		1710
1699	The previous attributes of the file. The callback gets invoked whenever	1711	The previous attributes of the file. The callback gets invoked whenever
1700	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>.
1701		1715
1702	=item ev_tstamp interval [read-only]	1716	=item ev_tstamp interval [read-only]
1703		1717
1704	The specified interval.	1718	The specified interval.
1705		1719
…		…
1759	}	1773	}
1760		1774
1761	...	1775	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	1777	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	1778	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		1779
1766		1780
1767	=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...
1768		1782
1769	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
…		…
1857		1871
1858	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>)
1859	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
1860	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,
1861	too) should not activate ("feed") events into libev. While libev fully	1875	too) should not activate ("feed") events into libev. While libev fully
1862	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
1863	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
1864	(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
1865	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
1866	coexist peacefully with others).	1880	coexist peacefully with others).
1867		1881
…		…
1882	=head3 Examples	1896	=head3 Examples
1883		1897
1884	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
1885	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
1886	(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
1887	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
1888	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
1889	into the Glib event loop).	1903	Glib event loop).
1890		1904
1891	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,
1892	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
1893	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
1894	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
…		…
2966	defined to be C<0>, then they are not.	2980	defined to be C<0>, then they are not.
2967		2981
2968	=item EV_MINIMAL	2982	=item EV_MINIMAL
2969		2983
2970	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
2971	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
2972	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.
2973		2988
2974	=item EV_PID_HASHSIZE	2989	=item EV_PID_HASHSIZE
2975		2990
2976	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
2977	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
…		…
2983	C<ev_stat> watchers use a small hash table to distribute workload by	2998	C<ev_stat> watchers use a small hash table to distribute workload by
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2999	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3000	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3001	watchers you might want to increase this value (I<must> be a power of
2987	two).	3002	two).
		3003
		3004	=item EV_USE_4HEAP
		3005
		3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3008	to C<1>. The 4-heap uses more complicated (longer) code but has
		3009	noticably faster performance with many (thousands) of watchers.
		3010
		3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3012	(disabled).
		3013
		3014	=item EV_HEAP_CACHE_AT
		3015
		3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3017	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3020	but avoids random read accesses on heap changes. This improves performance
		3021	noticably with with many (hundreds) of watchers.
		3022
		3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3024	(disabled).
2988		3025
2989	=item EV_COMMON	3026	=item EV_COMMON
2990		3027
2991	By default, all watchers have a C<void *data> member. By redefining	3028	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3029	this macro to a something else you can include more and other types of
…		…
3162	correct watcher to remove. The lists are usually short (you don't usually	3199	correct watcher to remove. The lists are usually short (you don't usually
3163	have many watchers waiting for the same fd or signal).	3200	have many watchers waiting for the same fd or signal).
3164		3201
3165	=item Finding the next timer in each loop iteration: O(1)	3202	=item Finding the next timer in each loop iteration: O(1)
3166		3203
3167	By virtue of using a binary heap, the next timer is always found at the	3204	By virtue of using a binary or 4-heap, the next timer is always found at a
3168	beginning of the storage array.	3205	fixed position in the storage array.
3169		3206
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3208
3172	A change means an I/O watcher gets started or stopped, which requires	3209	A change means an I/O watcher gets started or stopped, which requires
3173	libev to recalculate its status (and possibly tell the kernel, depending	3210	libev to recalculate its status (and possibly tell the kernel, depending
…		…
3202	model. Libev still offers limited functionality on this platform in	3239	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3241	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3242	e.g. cygwin.
3206		3243
		3244	Lifting these limitations would basically require the full
		3245	re-implementation of the I/O system. If you are into these kinds of
		3246	things, then note that glib does exactly that for you in a very portable
		3247	way (note also that glib is the slowest event library known to man).
		3248
3207	There is no supported compilation method available on windows except	3249	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3250	embedding it into other applications.
3209		3251
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3252	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	3253	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3254	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	3255	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	3256	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3257	notification model, which cannot be implemented efficiently on windows
		3258	(microsoft monopoly games).
3216		3259
3217	=over 4	3260	=over 4
3218		3261
3219	=item The winsocket select function	3262	=item The winsocket select function
3220		3263
…		…
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3277	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	3278	complexity in the O(n²) range when using win32.
3236		3279
3237	=item Limited number of file descriptors	3280	=item Limited number of file descriptors
3238		3281
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3282	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3283
		3284	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	3285	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	3286	can only wait for C<64> things at the same time internally; microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	3287	recommends spawning a chain of threads and wait for 63 handles and the
		3288	previous thread in each. Great).
3244		3289
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	3291	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	3292	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3293	select emulation on windows).
…		…
3260	calling select (O(n²)) will likely make this unworkable.	3305	calling select (O(n²)) will likely make this unworkable.
3261		3306
3262	=back	3307	=back
3263		3308
3264		3309
		3310	=head1 PORTABILITY REQUIREMENTS
		3311
		3312	In addition to a working ISO-C implementation, libev relies on a few
		3313	additional extensions:
		3314
		3315	=over 4
		3316
		3317	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3318
		3319	The type C<sig_atomic_t volatile> (or whatever is defined as
		3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3321	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3322	believed to be sufficiently portable.
		3323
		3324	=item C<sigprocmask> must work in a threaded environment
		3325
		3326	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3327	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3328	pthread implementations will either allow C<sigprocmask> in the "main
		3329	thread" or will block signals process-wide, both behaviours would
		3330	be compatible with libev. Interaction between C<sigprocmask> and
		3331	C<pthread_sigmask> could complicate things, however.
		3332
		3333	The most portable way to handle signals is to block signals in all threads
		3334	except the initial one, and run the default loop in the initial thread as
		3335	well.
		3336
		3337	=item C<long> must be large enough for common memory allocation sizes
		3338
		3339	To improve portability and simplify using libev, libev uses C<long>
		3340	internally instead of C<size_t> when allocating its data structures. On
		3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3342	is still at least 31 bits everywhere, which is enough for hundreds of
		3343	millions of watchers.
		3344
		3345	=item C<double> must hold a time value in seconds with enough accuracy
		3346
		3347	The type C<double> is used to represent timestamps. It is required to
		3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3349	enough for at least into the year 4000. This requirement is fulfilled by
		3350	implementations implementing IEEE 754 (basically all existing ones).
		3351
		3352	=back
		3353
		3354	If you know of other additional requirements drop me a note.
		3355
		3356
		3357	=head1 VALGRIND
		3358
		3359	Valgrind has a special section here because it is a popular tool that is
		3360	highly useful, but valgrind reports are very hard to interpret.
		3361
		3362	If you think you found a bug (memory leak, uninitialised data access etc.)
		3363	in libev, then check twice: If valgrind reports something like:
		3364
		3365	==2274== definitely lost: 0 bytes in 0 blocks.
		3366	==2274== possibly lost: 0 bytes in 0 blocks.
		3367	==2274== still reachable: 256 bytes in 1 blocks.
		3368
		3369	then there is no memory leak. Similarly, under some circumstances,
		3370	valgrind might report kernel bugs as if it were a bug in libev, or it
		3371	might be confused (it is a very good tool, but only a tool).
		3372
		3373	If you are unsure about something, feel free to contact the mailing list
		3374	with the full valgrind report and an explanation on why you think this is
		3375	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3376	no bug" answer and take the chance of learning how to interpret valgrind
		3377	properly.
		3378
		3379	If you need, for some reason, empty reports from valgrind for your project
		3380	I suggest using suppression lists.
		3381
		3382
3265	=head1 AUTHOR	3383	=head1 AUTHOR
3266		3384
3267	Marc Lehmann <libev@schmorp.de>.	3385	Marc Lehmann <libev@schmorp.de>.
3268		3386

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Comparing libev/ev.pod (file contents): Revision 1.146 by root, Fri Apr 11 00:31:19 2008 UTC vs. Revision 1.156 by root, Tue May 20 20:00:34 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.146 by root, Fri Apr 11 00:31:19 2008 UTC vs.
Revision 1.156 by root, Tue May 20 20:00:34 2008 UTC