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

Comparing libev/ev.pod (file contents):
Revision 1.95 by root, Fri Dec 21 05:10:01 2007 UTC vs.
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
115		115
116	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
117	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	118	you actually want to know.
119		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
120	=item int ev_version_major ()	126	=item int ev_version_major ()
121		127
122	=item int ev_version_minor ()	128	=item int ev_version_minor ()
123		129
124	You can find out the major and minor ABI version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
…		…
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		307
302	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
303	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
304	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
306	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
307		320
308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309		322
310	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
311	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
312	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
314		329
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		331
317	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
318	but it scales phenomenally better. While poll and select usually scale	333	but it scales phenomenally better. While poll and select usually scale
319	like O(total_fds) where n is the total number of fds (or the highest fd),	334	like O(total_fds) where n is the total number of fds (or the highest fd),
320	epoll scales either O(1) or O(active_fds). The epoll design has a number	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
321	of shortcomings, such as silently dropping events in some hard-to-detect	336	of shortcomings, such as silently dropping events in some hard-to-detect
322	cases and rewuiring a syscall per fd change, no fork support and bad	337	cases and rewiring a syscall per fd change, no fork support and bad
323	support for dup:	338	support for dup.
324		339
325	While stopping, setting and starting an I/O watcher in the same iteration	340	While stopping, setting and starting an I/O watcher in the same iteration
326	will result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
327	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
330		345
331	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
332	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
333	(or space) is available.	348	(or space) is available.
334		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		358
337	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
338	was broken on I<all> BSDs (usually it doesn't work with anything but	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
339	sockets and pipes, except on Darwin, where of course it's completely	361	with anything but sockets and pipes, except on Darwin, where of course
340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
341	is used by default there). For this reason it's not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
342	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	365	system like NetBSD.
345		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
		370
346	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
347	kernel is more efficient (which says nothing about its actual speed,	372	kernel is more efficient (which says nothing about its actual speed, of
348	of course). While stopping, setting and starting an I/O watcher does	373	course). While stopping, setting and starting an I/O watcher does never
349	never cause an extra syscall as with epoll, it still adds up to two event	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
350	changes per incident, support for C<fork ()> is very bad and it drops fds	375	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
352		386
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		388
355	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
356		393
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		395
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
360	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
361		398
362	Please note that solaris event ports can deliver a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
363	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
364	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
365		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
		407
		408	On the positive side, ignoring the spurious readyness notifications, this
		409	backend actually performed to specification in all tests and is fully
		410	embeddable, which is a rare feat among the OS-specific backends.
		411
366	=item C<EVBACKEND_ALL>	412	=item C<EVBACKEND_ALL>
367		413
368	Try all backends (even potentially broken ones that wouldn't be tried	414	Try all backends (even potentially broken ones that wouldn't be tried
369	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	415	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	416	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		417
		418	It is definitely not recommended to use this flag.
		419
372	=back	420	=back
373		421
374	If one or more of these are ored into the flags value, then only these	422	If one or more of these are ored into the flags value, then only these
375	backends will be tried (in the reverse order as given here). If none are	423	backends will be tried (in the reverse order as listed here). If none are
376	specified, most compiled-in backend will be tried, usually in reverse	424	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		425
379	The most typical usage is like this:	426	The most typical usage is like this:
380		427
381	if (!ev_default_loop (0))	428	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	429	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
507	usually a better approach for this kind of thing.	554	usually a better approach for this kind of thing.
508		555
509	Here are the gory details of what C<ev_loop> does:	556	Here are the gory details of what C<ev_loop> does:
510		557
511	- Before the first iteration, call any pending watchers.	558	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	559	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	560	- If a fork was detected, queue and call all fork watchers.
		561	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	562	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	563	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	564	- Update the "event loop time".
517	- Calculate for how long to block.	565	- Calculate for how long to sleep or block, if at all
		566	(active idle watchers, EVLOOP_NONBLOCK or not having
		567	any active watchers at all will result in not sleeping).
		568	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	569	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	570	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	571	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	572	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	573	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	574	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	575	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	576	- Call all queued watchers in reverse order (i.e. check watchers first).
526	Signals and child watchers are implemented as I/O watchers, and will	577	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	578	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	579	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	580	were used, or there are no active watchers, return, otherwise
		581	continue with step *.
530		582
531	Example: Queue some jobs and then loop until no events are outsanding	583	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	584	anymore.
533		585
534	... queue jobs here, make sure they register event watchers as long	586	... queue jobs here, make sure they register event watchers as long
535	... as they still have work to do (even an idle watcher will do..)	587	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	588	ev_loop (my_loop, 0);
…		…
540		592
541	Can be used to make a call to C<ev_loop> return early (but only after it	593	Can be used to make a call to C<ev_loop> return early (but only after it
542	has processed all outstanding events). The C<how> argument must be either	594	has processed all outstanding events). The C<how> argument must be either
543	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	595	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
544	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	596	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		597
		598	This "unloop state" will be cleared when entering C<ev_loop> again.
545		599
546	=item ev_ref (loop)	600	=item ev_ref (loop)
547		601
548	=item ev_unref (loop)	602	=item ev_unref (loop)
549		603
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	608	returning, ev_unref() after starting, and ev_ref() before stopping it. For
555	example, libev itself uses this for its internal signal pipe: It is not	609	example, libev itself uses this for its internal signal pipe: It is not
556	visible to the libev user and should not keep C<ev_loop> from exiting if	610	visible to the libev user and should not keep C<ev_loop> from exiting if
557	no event watchers registered by it are active. It is also an excellent	611	no event watchers registered by it are active. It is also an excellent
558	way to do this for generic recurring timers or from within third-party	612	way to do this for generic recurring timers or from within third-party
559	libraries. Just remember to I<unref after start> and I<ref before stop>.	613	libraries. Just remember to I<unref after start> and I<ref before stop>
		614	(but only if the watcher wasn't active before, or was active before,
		615	respectively).
560		616
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	617	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	618	running when nothing else is active.
563		619
564	struct ev_signal exitsig;	620	struct ev_signal exitsig;
…		…
568		624
569	Example: For some weird reason, unregister the above signal handler again.	625	Example: For some weird reason, unregister the above signal handler again.
570		626
571	ev_ref (loop);	627	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	628	ev_signal_stop (loop, &exitsig);
		629
		630	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		631
		632	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		633
		634	These advanced functions influence the time that libev will spend waiting
		635	for events. Both are by default C<0>, meaning that libev will try to
		636	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		637
		638	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		639	allows libev to delay invocation of I/O and timer/periodic callbacks to
		640	increase efficiency of loop iterations.
		641
		642	The background is that sometimes your program runs just fast enough to
		643	handle one (or very few) event(s) per loop iteration. While this makes
		644	the program responsive, it also wastes a lot of CPU time to poll for new
		645	events, especially with backends like C<select ()> which have a high
		646	overhead for the actual polling but can deliver many events at once.
		647
		648	By setting a higher I<io collect interval> you allow libev to spend more
		649	time collecting I/O events, so you can handle more events per iteration,
		650	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		651	C<ev_timer>) will be not affected. Setting this to a non-null value will
		652	introduce an additional C<ev_sleep ()> call into most loop iterations.
		653
		654	Likewise, by setting a higher I<timeout collect interval> you allow libev
		655	to spend more time collecting timeouts, at the expense of increased
		656	latency (the watcher callback will be called later). C<ev_io> watchers
		657	will not be affected. Setting this to a non-null value will not introduce
		658	any overhead in libev.
		659
		660	Many (busy) programs can usually benefit by setting the io collect
		661	interval to a value near C<0.1> or so, which is often enough for
		662	interactive servers (of course not for games), likewise for timeouts. It
		663	usually doesn't make much sense to set it to a lower value than C<0.01>,
		664	as this approsaches the timing granularity of most systems.
573		665
574	=back	666	=back
575		667
576		668
577	=head1 ANATOMY OF A WATCHER	669	=head1 ANATOMY OF A WATCHER
…		…
903	In general you can register as many read and/or write event watchers per	995	In general you can register as many read and/or write event watchers per
904	fd as you want (as long as you don't confuse yourself). Setting all file	996	fd as you want (as long as you don't confuse yourself). Setting all file
905	descriptors to non-blocking mode is also usually a good idea (but not	997	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	998	required if you know what you are doing).
907		999
908	You have to be careful with dup'ed file descriptors, though. Some backends
909	(the linux epoll backend is a notable example) cannot handle dup'ed file
910	descriptors correctly if you register interest in two or more fds pointing
911	to the same underlying file/socket/etc. description (that is, they share
912	the same underlying "file open").
913
914	If you must do this, then force the use of a known-to-be-good backend	1000	If you must do this, then force the use of a known-to-be-good backend
915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1001	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1002	C<EVBACKEND_POLL>).
917		1003
918	Another thing you have to watch out for is that it is quite easy to	1004	Another thing you have to watch out for is that it is quite easy to
…		…
952	optimisations to libev.	1038	optimisations to libev.
953		1039
954	=head3 The special problem of dup'ed file descriptors	1040	=head3 The special problem of dup'ed file descriptors
955		1041
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1042	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1043	but only events for the underlying file descriptions. That means when you
958	have C<dup ()>'ed file descriptors and register events for them, only one	1044	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1045	events for them, only one file descriptor might actually receive events.
960		1046
961	There is no workaorund possible except not registering events	1047	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1048	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1049	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1050
965	=head3 The special problem of fork	1051	=head3 The special problem of fork
966		1052
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1053	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
993	=item int events [read-only]	1079	=item int events [read-only]
994		1080
995	The events being watched.	1081	The events being watched.
996		1082
997	=back	1083	=back
		1084
		1085	=head3 Examples
998		1086
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1087	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1000	readable, but only once. Since it is likely line-buffered, you could	1088	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1089	attempt to read a whole line in the callback.
1002		1090
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1188	or C<ev_timer_again> is called and determines the next timeout (if any),
1101	which is also when any modifications are taken into account.	1189	which is also when any modifications are taken into account.
1102		1190
1103	=back	1191	=back
1104		1192
		1193	=head3 Examples
		1194
1105	Example: Create a timer that fires after 60 seconds.	1195	Example: Create a timer that fires after 60 seconds.
1106		1196
1107	static void	1197	static void
1108	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1198	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1109	{	1199	{
…		…
1266	When active, contains the absolute time that the watcher is supposed to	1356	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1357	trigger next.
1268		1358
1269	=back	1359	=back
1270		1360
		1361	=head3 Examples
		1362
1271	Example: Call a callback every hour, or, more precisely, whenever the	1363	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1364	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1365	potentially a lot of jittering, but good long-term stability.
1274		1366
1275	static void	1367	static void
…		…
1366		1458
1367	The process exit/trace status caused by C<rpid> (see your systems	1459	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1460	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1461
1370	=back	1462	=back
		1463
		1464	=head3 Examples
1371		1465
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1466	Example: Try to exit cleanly on SIGINT and SIGTERM.
1373		1467
1374	static void	1468	static void
1375	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1469	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
…		…
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1510	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1417	to fall back to regular polling again even with inotify, but changes are	1511	to fall back to regular polling again even with inotify, but changes are
1418	usually detected immediately, and if the file exists there will be no	1512	usually detected immediately, and if the file exists there will be no
1419	polling.	1513	polling.
1420		1514
		1515	=head3 Inotify
		1516
		1517	When C<inotify (7)> support has been compiled into libev (generally only
		1518	available on Linux) and present at runtime, it will be used to speed up
		1519	change detection where possible. The inotify descriptor will be created lazily
		1520	when the first C<ev_stat> watcher is being started.
		1521
		1522	Inotify presense does not change the semantics of C<ev_stat> watchers
		1523	except that changes might be detected earlier, and in some cases, to avoid
		1524	making regular C<stat> calls. Even in the presense of inotify support
		1525	there are many cases where libev has to resort to regular C<stat> polling.
		1526
		1527	(There is no support for kqueue, as apparently it cannot be used to
		1528	implement this functionality, due to the requirement of having a file
		1529	descriptor open on the object at all times).
		1530
		1531	=head3 The special problem of stat time resolution
		1532
		1533	The C<stat ()> syscall only supports full-second resolution portably, and
		1534	even on systems where the resolution is higher, many filesystems still
		1535	only support whole seconds.
		1536
		1537	That means that, if the time is the only thing that changes, you might
		1538	miss updates: on the first update, C<ev_stat> detects a change and calls
		1539	your callback, which does something. When there is another update within
		1540	the same second, C<ev_stat> will be unable to detect it.
		1541
		1542	The solution to this is to delay acting on a change for a second (or till
		1543	the next second boundary), using a roughly one-second delay C<ev_timer>
		1544	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1545	is added to work around small timing inconsistencies of some operating
		1546	systems.
		1547
1421	=head3 Watcher-Specific Functions and Data Members	1548	=head3 Watcher-Specific Functions and Data Members
1422		1549
1423	=over 4	1550	=over 4
1424		1551
1425	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1552	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1462	=item const char *path [read-only]	1589	=item const char *path [read-only]
1463		1590
1464	The filesystem path that is being watched.	1591	The filesystem path that is being watched.
1465		1592
1466	=back	1593	=back
		1594
		1595	=head3 Examples
1467		1596
1468	Example: Watch C</etc/passwd> for attribute changes.	1597	Example: Watch C</etc/passwd> for attribute changes.
1469		1598
1470	static void	1599	static void
1471	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1600	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1484	}	1613	}
1485		1614
1486	...	1615	...
1487	ev_stat passwd;	1616	ev_stat passwd;
1488		1617
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1618	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1619	ev_stat_start (loop, &passwd);
		1620
		1621	Example: Like above, but additionally use a one-second delay so we do not
		1622	miss updates (however, frequent updates will delay processing, too, so
		1623	one might do the work both on C<ev_stat> callback invocation I<and> on
		1624	C<ev_timer> callback invocation).
		1625
		1626	static ev_stat passwd;
		1627	static ev_timer timer;
		1628
		1629	static void
		1630	timer_cb (EV_P_ ev_timer *w, int revents)
		1631	{
		1632	ev_timer_stop (EV_A_ w);
		1633
		1634	/* now it's one second after the most recent passwd change */
		1635	}
		1636
		1637	static void
		1638	stat_cb (EV_P_ ev_stat *w, int revents)
		1639	{
		1640	/* reset the one-second timer */
		1641	ev_timer_again (EV_A_ &timer);
		1642	}
		1643
		1644	...
		1645	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1646	ev_stat_start (loop, &passwd);
		1647	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1648
1492		1649
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1650	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1651
1495	Idle watchers trigger events when no other events of the same or higher	1652	Idle watchers trigger events when no other events of the same or higher
…		…
1520	Initialises and configures the idle watcher - it has no parameters of any	1677	Initialises and configures the idle watcher - it has no parameters of any
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1678	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1679	believe me.
1523		1680
1524	=back	1681	=back
		1682
		1683	=head3 Examples
1525		1684
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1685	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1686	callback, free it. Also, use no error checking, as usual.
1528		1687
1529	static void	1688	static void
…		…
1581		1740
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1741	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1583	priority, to ensure that they are being run before any other watchers	1742	priority, to ensure that they are being run before any other watchers
1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1743	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1585	too) should not activate ("feed") events into libev. While libev fully	1744	too) should not activate ("feed") events into libev. While libev fully
1586	supports this, they will be called before other C<ev_check> watchers did	1745	supports this, they will be called before other C<ev_check> watchers
1587	their job. As C<ev_check> watchers are often used to embed other event	1746	did their job. As C<ev_check> watchers are often used to embed other
1588	loops those other event loops might be in an unusable state until their	1747	(non-libev) event loops those other event loops might be in an unusable
1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1748	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1749	coexist peacefully with others).
1591		1750
1592	=head3 Watcher-Specific Functions and Data Members	1751	=head3 Watcher-Specific Functions and Data Members
1593		1752
1594	=over 4	1753	=over 4
1595		1754
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1759	Initialises and configures the prepare or check watcher - they have no
1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1760	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1602	macros, but using them is utterly, utterly and completely pointless.	1761	macros, but using them is utterly, utterly and completely pointless.
1603		1762
1604	=back	1763	=back
		1764
		1765	=head3 Examples
1605		1766
1606	There are a number of principal ways to embed other event loops or modules	1767	There are a number of principal ways to embed other event loops or modules
1607	into libev. Here are some ideas on how to include libadns into libev	1768	into libev. Here are some ideas on how to include libadns into libev
1608	(there is a Perl module named C<EV::ADNS> that does this, which you could	1769	(there is a Perl module named C<EV::ADNS> that does this, which you could
1609	use for an actually working example. Another Perl module named C<EV::Glib>	1770	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	1895	=head2 C<ev_embed> - when one backend isn't enough...
1735		1896
1736	This is a rather advanced watcher type that lets you embed one event loop	1897	This is a rather advanced watcher type that lets you embed one event loop
1737	into another (currently only C<ev_io> events are supported in the embedded	1898	into another (currently only C<ev_io> events are supported in the embedded
1738	loop, other types of watchers might be handled in a delayed or incorrect	1899	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	1900	fashion and must not be used).
1740		1901
1741	There are primarily two reasons you would want that: work around bugs and	1902	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	1903	prioritise I/O.
1743		1904
1744	As an example for a bug workaround, the kqueue backend might only support	1905	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	1939	portable one.
1779		1940
1780	So when you want to use this feature you will always have to be prepared	1941	So when you want to use this feature you will always have to be prepared
1781	that you cannot get an embeddable loop. The recommended way to get around	1942	that you cannot get an embeddable loop. The recommended way to get around
1782	this is to have a separate variables for your embeddable loop, try to	1943	this is to have a separate variables for your embeddable loop, try to
1783	create it, and if that fails, use the normal loop for everything:	1944	create it, and if that fails, use the normal loop for everything.
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
		1947
		1948	=over 4
		1949
		1950	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1951
		1952	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1953
		1954	Configures the watcher to embed the given loop, which must be
		1955	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1956	invoked automatically, otherwise it is the responsibility of the callback
		1957	to invoke it (it will continue to be called until the sweep has been done,
		1958	if you do not want thta, you need to temporarily stop the embed watcher).
		1959
		1960	=item ev_embed_sweep (loop, ev_embed *)
		1961
		1962	Make a single, non-blocking sweep over the embedded loop. This works
		1963	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1964	apropriate way for embedded loops.
		1965
		1966	=item struct ev_loop *other [read-only]
		1967
		1968	The embedded event loop.
		1969
		1970	=back
		1971
		1972	=head3 Examples
		1973
		1974	Example: Try to get an embeddable event loop and embed it into the default
		1975	event loop. If that is not possible, use the default loop. The default
		1976	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1977	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1978	used).
1784		1979
1785	struct ev_loop *loop_hi = ev_default_init (0);	1980	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	1981	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	1982	struct ev_embed embed;
1788		1983
…		…
1799	ev_embed_start (loop_hi, &embed);	1994	ev_embed_start (loop_hi, &embed);
1800	}	1995	}
1801	else	1996	else
1802	loop_lo = loop_hi;	1997	loop_lo = loop_hi;
1803		1998
1804	=head2 Portability notes	1999	Example: Check if kqueue is available but not recommended and create
		2000	a kqueue backend for use with sockets (which usually work with any
		2001	kqueue implementation). Store the kqueue/socket-only event loop in
		2002	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2003
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2004	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2005	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2006	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2007
1810	will always eport the epoll fd as ready, even when no events are pending.	2008	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2009	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2010	{
		2011	ev_embed_init (&embed, 0, loop_socket);
		2012	ev_embed_start (loop, &embed);
		2013	}
1811		2014
1812	While libev allows embedding these backends (they are contained in	2015	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2016	loop_socket = loop;
1814	work.
1815		2017
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2018	// now use loop_socket for all sockets, and loop for everything else
1817	usually works) and possibly another thread and a pipe or so to report to
1818	your main event loop.
1819
1820	=head3 Watcher-Specific Functions and Data Members
1821
1822	=over 4
1823
1824	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1825
1826	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
1827
1828	Configures the watcher to embed the given loop, which must be
1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1830	invoked automatically, otherwise it is the responsibility of the callback
1831	to invoke it (it will continue to be called until the sweep has been done,
1832	if you do not want thta, you need to temporarily stop the embed watcher).
1833
1834	=item ev_embed_sweep (loop, ev_embed *)
1835
1836	Make a single, non-blocking sweep over the embedded loop. This works
1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1838	apropriate way for embedded loops.
1839
1840	=item struct ev_loop *other [read-only]
1841
1842	The embedded event loop.
1843
1844	=back
1845		2019
1846		2020
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2021	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2022
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2023	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2297	runtime if successful). Otherwise no use of the realtime clock option will	2471	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2472	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2473	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2474	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2475
		2476	=item EV_USE_NANOSLEEP
		2477
		2478	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2479	and will use it for delays. Otherwise it will use C<select ()>.
		2480
2302	=item EV_USE_SELECT	2481	=item EV_USE_SELECT
2303		2482
2304	If undefined or defined to be C<1>, libev will compile in support for the	2483	If undefined or defined to be C<1>, libev will compile in support for the
2305	C<select>(2) backend. No attempt at autodetection will be done: if no	2484	C<select>(2) backend. No attempt at autodetection will be done: if no
2306	other method takes over, select will be it. Otherwise the select backend	2485	other method takes over, select will be it. Otherwise the select backend
…		…
2323	wants osf handles on win32 (this is the case when the select to	2502	wants osf handles on win32 (this is the case when the select to
2324	be used is the winsock select). This means that it will call	2503	be used is the winsock select). This means that it will call
2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2504	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2326	it is assumed that all these functions actually work on fds, even	2505	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2506	on win32. Should not be defined on non-win32 platforms.
		2507
		2508	=item EV_FD_TO_WIN32_HANDLE
		2509
		2510	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2511	file descriptors to socket handles. When not defining this symbol (the
		2512	default), then libev will call C<_get_osfhandle>, which is usually
		2513	correct. In some cases, programs use their own file descriptor management,
		2514	in which case they can provide this function to map fds to socket handles.
2328		2515
2329	=item EV_USE_POLL	2516	=item EV_USE_POLL
2330		2517
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2518	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2332	backend. Otherwise it will be enabled on non-win32 platforms. It	2519	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2369	be detected at runtime.	2556	be detected at runtime.
2370		2557
2371	=item EV_H	2558	=item EV_H
2372		2559
2373	The name of the F<ev.h> header file used to include it. The default if	2560	The name of the F<ev.h> header file used to include it. The default if
2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2561	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2562	virtually rename the F<ev.h> header file in case of conflicts.
2376		2563
2377	=item EV_CONFIG_H	2564	=item EV_CONFIG_H
2378		2565
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2566	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2567	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2568	C<EV_H>, above.
2382		2569
2383	=item EV_EVENT_H	2570	=item EV_EVENT_H
2384		2571
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2572	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2386	of how the F<event.h> header can be found.	2573	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2387		2574
2388	=item EV_PROTOTYPES	2575	=item EV_PROTOTYPES
2389		2576
2390	If defined to be C<0>, then F<ev.h> will not define any function	2577	If defined to be C<0>, then F<ev.h> will not define any function
2391	prototypes, but still define all the structs and other symbols. This is	2578	prototypes, but still define all the structs and other symbols. This is
…		…
2457	than enough. If you need to manage thousands of children you might want to	2644	than enough. If you need to manage thousands of children you might want to
2458	increase this value (I<must> be a power of two).	2645	increase this value (I<must> be a power of two).
2459		2646
2460	=item EV_INOTIFY_HASHSIZE	2647	=item EV_INOTIFY_HASHSIZE
2461		2648
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2649	C<ev_stat> watchers use a small hash table to distribute workload by
2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2650	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2464	usually more than enough. If you need to manage thousands of C<ev_stat>	2651	usually more than enough. If you need to manage thousands of C<ev_stat>
2465	watchers you might want to increase this value (I<must> be a power of	2652	watchers you might want to increase this value (I<must> be a power of
2466	two).	2653	two).
2467		2654
…		…
2563		2750
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2751	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		2752
2566	This means that, when you have a watcher that triggers in one hour and	2753	This means that, when you have a watcher that triggers in one hour and
2567	there are 100 watchers that would trigger before that then inserting will	2754	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	2755	have to skip roughly seven (C<ld 100>) of these watchers.
2569		2756
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2757	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		2758
2572	That means that for changing a timer costs less than removing/adding them	2759	That means that changing a timer costs less than removing/adding them
2573	as only the relative motion in the event queue has to be paid for.	2760	as only the relative motion in the event queue has to be paid for.
2574		2761
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2762	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2576		2763
2577	These just add the watcher into an array or at the head of a list.	2764	These just add the watcher into an array or at the head of a list.
		2765
2578	=item Stopping check/prepare/idle watchers: O(1)	2766	=item Stopping check/prepare/idle watchers: O(1)
2579		2767
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2768	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		2769
2582	These watchers are stored in lists then need to be walked to find the	2770	These watchers are stored in lists then need to be walked to find the
2583	correct watcher to remove. The lists are usually short (you don't usually	2771	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	2772	have many watchers waiting for the same fd or signal).
2585		2773
2586	=item Finding the next timer per loop iteration: O(1)	2774	=item Finding the next timer in each loop iteration: O(1)
		2775
		2776	By virtue of using a binary heap, the next timer is always found at the
		2777	beginning of the storage array.
2587		2778
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2779	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		2780
2590	A change means an I/O watcher gets started or stopped, which requires	2781	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	2782	libev to recalculate its status (and possibly tell the kernel, depending
		2783	on backend and wether C<ev_io_set> was used).
2592		2784
2593	=item Activating one watcher: O(1)	2785	=item Activating one watcher (putting it into the pending state): O(1)
2594		2786
2595	=item Priority handling: O(number_of_priorities)	2787	=item Priority handling: O(number_of_priorities)
2596		2788
2597	Priorities are implemented by allocating some space for each	2789	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	2790	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	2791	linearly search all the priorities, but starting/stopping and activating
		2792	watchers becomes O(1) w.r.t. prioritiy handling.
2600		2793
2601	=back	2794	=back
2602		2795
2603		2796
		2797	=head1 Win32 platform limitations and workarounds
		2798
		2799	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2800	requires, and its I/O model is fundamentally incompatible with the POSIX
		2801	model. Libev still offers limited functionality on this platform in
		2802	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2803	descriptors. This only applies when using Win32 natively, not when using
		2804	e.g. cygwin.
		2805
		2806	There is no supported compilation method available on windows except
		2807	embedding it into other applications.
		2808
		2809	Due to the many, low, and arbitrary limits on the win32 platform and the
		2810	abysmal performance of winsockets, using a large number of sockets is not
		2811	recommended (and not reasonable). If your program needs to use more than
		2812	a hundred or so sockets, then likely it needs to use a totally different
		2813	implementation for windows, as libev offers the POSIX model, which cannot
		2814	be implemented efficiently on windows (microsoft monopoly games).
		2815
		2816	=over 4
		2817
		2818	=item The winsocket select function
		2819
		2820	The winsocket C<select> function doesn't follow POSIX in that it requires
		2821	socket I<handles> and not socket I<file descriptors>. This makes select
		2822	very inefficient, and also requires a mapping from file descriptors
		2823	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2824	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2825	symbols for more info.
		2826
		2827	The configuration for a "naked" win32 using the microsoft runtime
		2828	libraries and raw winsocket select is:
		2829
		2830	#define EV_USE_SELECT 1
		2831	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2832
		2833	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2834	complexity in the O(n²) range when using win32.
		2835
		2836	=item Limited number of file descriptors
		2837
		2838	Windows has numerous arbitrary (and low) limits on things. Early versions
		2839	of winsocket's select only supported waiting for a max. of C<64> handles
		2840	(probably owning to the fact that all windows kernels can only wait for
		2841	C<64> things at the same time internally; microsoft recommends spawning a
		2842	chain of threads and wait for 63 handles and the previous thread in each).
		2843
		2844	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2845	to some high number (e.g. C<2048>) before compiling the winsocket select
		2846	call (which might be in libev or elsewhere, for example, perl does its own
		2847	select emulation on windows).
		2848
		2849	Another limit is the number of file descriptors in the microsoft runtime
		2850	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2851	or something like this inside microsoft). You can increase this by calling
		2852	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2853	arbitrary limit), but is broken in many versions of the microsoft runtime
		2854	libraries.
		2855
		2856	This might get you to about C<512> or C<2048> sockets (depending on
		2857	windows version and/or the phase of the moon). To get more, you need to
		2858	wrap all I/O functions and provide your own fd management, but the cost of
		2859	calling select (O(n²)) will likely make this unworkable.
		2860
		2861	=back
		2862
		2863
2604	=head1 AUTHOR	2864	=head1 AUTHOR
2605		2865
2606	Marc Lehmann <libev@schmorp.de>.	2866	Marc Lehmann <libev@schmorp.de>.
2607		2867

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Comparing libev/ev.pod (file contents): Revision 1.95 by root, Fri Dec 21 05:10:01 2007 UTC vs. Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.95 by root, Fri Dec 21 05:10:01 2007 UTC vs.
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC