[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 1.121 by root, Mon Jan 28 12:13:54 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
…		…
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		261
256	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
257	function.	263	function.
258		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
259	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
261		274
262	The following flags are supported:	275	The following flags are supported:
263		276
…		…
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		314
302	This is your standard select(2) backend. Not I<completely> standard, as	315	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,	316	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	317	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	318	using this backend. It doesn't scale too well (O(highest_fd)), but its
306	the fastest backend for a low number of fds.	319	usually the fastest backend for a low number of (low-numbered :) fds.
		320
		321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
307		327
308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309		329
310	And this is your standard poll(2) backend. It's more complicated than	330	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	331	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	332	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).	333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
314		336
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		338
317	For few fds, this backend is a bit little slower than poll and select,	339	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	340	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),	341	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	342	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	343	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	344	cases and rewiring a syscall per fd change, no fork support and bad
323	support for dup:	345	support for dup.
324		346
325	While stopping, setting and starting an I/O watcher in the same iteration	347	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	348	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	349	(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	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
330		352
331	Please note that epoll sometimes generates spurious notifications, so you	353	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	354	need to use non-blocking I/O or other means to avoid blocking when no data
333	(or space) is available.	355	(or space) is available.
334		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		365
337	Kqueue deserves special mention, as at the time of this writing, it	366	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	367	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	368	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"	369	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	370	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)	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	372	system like NetBSD.
345		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
		377
346	It scales in the same way as the epoll backend, but the interface to the	378	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,	379	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	380	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	381	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	382	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
352		393
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		395
355	This is not implemented yet (and might never be).	396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
356		400
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		402
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	403	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)).	404	it's really slow, but it still scales very well (O(active_fds)).
361		405
362	Please note that solaris event ports can deliver a lot of spurious	406	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	407	notifications, so you need to use non-blocking I/O or other means to avoid
364	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
365		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
		418
366	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
367		420
368	Try all backends (even potentially broken ones that wouldn't be tried	421	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	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		424
		425	It is definitely not recommended to use this flag.
		426
372	=back	427	=back
373		428
374	If one or more of these are ored into the flags value, then only these	429	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	430	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	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		432
379	The most typical usage is like this:	433	The most typical usage is like this:
380		434
381	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
429	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
430	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
431		485
432	=item ev_default_fork ()	486	=item ev_default_fork ()
433		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
435	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
436	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
437	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
438		494
439	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
440	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
441	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
442		498
443	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
444	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
445	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
446		502
447	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
448
449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
450	without calling this function, so if you force one of those backends you
451	do not need to care.
452		504
453	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
454		506
455	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
456	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
…		…
507	usually a better approach for this kind of thing.	559	usually a better approach for this kind of thing.
508		560
509	Here are the gory details of what C<ev_loop> does:	561	Here are the gory details of what C<ev_loop> does:
510		562
511	- Before the first iteration, call any pending watchers.	563	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	564	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	565	- If a fork was detected, queue and call all fork watchers.
		566	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	567	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	568	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	569	- Update the "event loop time".
517	- Calculate for how long to block.	570	- Calculate for how long to sleep or block, if at all
		571	(active idle watchers, EVLOOP_NONBLOCK or not having
		572	any active watchers at all will result in not sleeping).
		573	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	574	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	575	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	576	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	577	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	578	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	579	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	580	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	581	- 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	582	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	583	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	585	were used, or there are no active watchers, return, otherwise
		586	continue with step *.
530		587
531	Example: Queue some jobs and then loop until no events are outsanding	588	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	589	anymore.
533		590
534	... queue jobs here, make sure they register event watchers as long	591	... 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..)	592	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	593	ev_loop (my_loop, 0);
…		…
540		597
541	Can be used to make a call to C<ev_loop> return early (but only after it	598	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	599	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	600	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.	601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		602
		603	This "unloop state" will be cleared when entering C<ev_loop> again.
545		604
546	=item ev_ref (loop)	605	=item ev_ref (loop)
547		606
548	=item ev_unref (loop)	607	=item ev_unref (loop)
549		608
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	613	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	614	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	615	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	616	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	617	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>.	618	libraries. Just remember to I<unref after start> and I<ref before stop>
		619	(but only if the watcher wasn't active before, or was active before,
		620	respectively).
560		621
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	623	running when nothing else is active.
563		624
564	struct ev_signal exitsig;	625	struct ev_signal exitsig;
…		…
568		629
569	Example: For some weird reason, unregister the above signal handler again.	630	Example: For some weird reason, unregister the above signal handler again.
570		631
571	ev_ref (loop);	632	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	633	ev_signal_stop (loop, &exitsig);
		634
		635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		636
		637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		638
		639	These advanced functions influence the time that libev will spend waiting
		640	for events. Both are by default C<0>, meaning that libev will try to
		641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		642
		643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		644	allows libev to delay invocation of I/O and timer/periodic callbacks to
		645	increase efficiency of loop iterations.
		646
		647	The background is that sometimes your program runs just fast enough to
		648	handle one (or very few) event(s) per loop iteration. While this makes
		649	the program responsive, it also wastes a lot of CPU time to poll for new
		650	events, especially with backends like C<select ()> which have a high
		651	overhead for the actual polling but can deliver many events at once.
		652
		653	By setting a higher I<io collect interval> you allow libev to spend more
		654	time collecting I/O events, so you can handle more events per iteration,
		655	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		656	C<ev_timer>) will be not affected. Setting this to a non-null value will
		657	introduce an additional C<ev_sleep ()> call into most loop iterations.
		658
		659	Likewise, by setting a higher I<timeout collect interval> you allow libev
		660	to spend more time collecting timeouts, at the expense of increased
		661	latency (the watcher callback will be called later). C<ev_io> watchers
		662	will not be affected. Setting this to a non-null value will not introduce
		663	any overhead in libev.
		664
		665	Many (busy) programs can usually benefit by setting the io collect
		666	interval to a value near C<0.1> or so, which is often enough for
		667	interactive servers (of course not for games), likewise for timeouts. It
		668	usually doesn't make much sense to set it to a lower value than C<0.01>,
		669	as this approsaches the timing granularity of most systems.
573		670
574	=back	671	=back
575		672
576		673
577	=head1 ANATOMY OF A WATCHER	674	=head1 ANATOMY OF A WATCHER
…		…
903	In general you can register as many read and/or write event watchers per	1000	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	1001	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	1002	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1003	required if you know what you are doing).
907		1004
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	1005	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	1006	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1007	C<EVBACKEND_POLL>).
917		1008
918	Another thing you have to watch out for is that it is quite easy to	1009	Another thing you have to watch out for is that it is quite easy to
…		…
952	optimisations to libev.	1043	optimisations to libev.
953		1044
954	=head3 The special problem of dup'ed file descriptors	1045	=head3 The special problem of dup'ed file descriptors
955		1046
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1047	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1048	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	1049	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1050	events for them, only one file descriptor might actually receive events.
960		1051
961	There is no workaorund possible except not registering events	1052	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1053	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1054	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1055
965	=head3 The special problem of fork	1056	=head3 The special problem of fork
966		1057
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1058	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
993	=item int events [read-only]	1084	=item int events [read-only]
994		1085
995	The events being watched.	1086	The events being watched.
996		1087
997	=back	1088	=back
		1089
		1090	=head3 Examples
998		1091
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1092	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	1093	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1094	attempt to read a whole line in the callback.
1002		1095
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1193	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.	1194	which is also when any modifications are taken into account.
1102		1195
1103	=back	1196	=back
1104		1197
		1198	=head3 Examples
		1199
1105	Example: Create a timer that fires after 60 seconds.	1200	Example: Create a timer that fires after 60 seconds.
1106		1201
1107	static void	1202	static void
1108	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1203	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1109	{	1204	{
…		…
1266	When active, contains the absolute time that the watcher is supposed to	1361	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1362	trigger next.
1268		1363
1269	=back	1364	=back
1270		1365
		1366	=head3 Examples
		1367
1271	Example: Call a callback every hour, or, more precisely, whenever the	1368	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1369	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1370	potentially a lot of jittering, but good long-term stability.
1274		1371
1275	static void	1372	static void
…		…
1341		1438
1342	=head3 Watcher-Specific Functions and Data Members	1439	=head3 Watcher-Specific Functions and Data Members
1343		1440
1344	=over 4	1441	=over 4
1345		1442
1346	=item ev_child_init (ev_child *, callback, int pid)	1443	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1444
1348	=item ev_child_set (ev_child *, int pid)	1445	=item ev_child_set (ev_child *, int pid, int trace)
1349		1446
1350	Configures the watcher to wait for status changes of process C<pid> (or	1447	Configures the watcher to wait for status changes of process C<pid> (or
1351	I<any> process if C<pid> is specified as C<0>). The callback can look	1448	I<any> process if C<pid> is specified as C<0>). The callback can look
1352	at the C<rstatus> member of the C<ev_child> watcher structure to see	1449	at the C<rstatus> member of the C<ev_child> watcher structure to see
1353	the status word (use the macros from C<sys/wait.h> and see your systems	1450	the status word (use the macros from C<sys/wait.h> and see your systems
1354	C<waitpid> documentation). The C<rpid> member contains the pid of the	1451	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1452	process causing the status change. C<trace> must be either C<0> (only
		1453	activate the watcher when the process terminates) or C<1> (additionally
		1454	activate the watcher when the process is stopped or continued).
1356		1455
1357	=item int pid [read-only]	1456	=item int pid [read-only]
1358		1457
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1458	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1459
…		…
1366		1465
1367	The process exit/trace status caused by C<rpid> (see your systems	1466	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1467	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1468
1370	=back	1469	=back
		1470
		1471	=head3 Examples
1371		1472
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1473	Example: Try to exit cleanly on SIGINT and SIGTERM.
1373		1474
1374	static void	1475	static void
1375	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1476	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	1517	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	1518	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	1519	usually detected immediately, and if the file exists there will be no
1419	polling.	1520	polling.
1420		1521
		1522	=head3 Inotify
		1523
		1524	When C<inotify (7)> support has been compiled into libev (generally only
		1525	available on Linux) and present at runtime, it will be used to speed up
		1526	change detection where possible. The inotify descriptor will be created lazily
		1527	when the first C<ev_stat> watcher is being started.
		1528
		1529	Inotify presense does not change the semantics of C<ev_stat> watchers
		1530	except that changes might be detected earlier, and in some cases, to avoid
		1531	making regular C<stat> calls. Even in the presense of inotify support
		1532	there are many cases where libev has to resort to regular C<stat> polling.
		1533
		1534	(There is no support for kqueue, as apparently it cannot be used to
		1535	implement this functionality, due to the requirement of having a file
		1536	descriptor open on the object at all times).
		1537
		1538	=head3 The special problem of stat time resolution
		1539
		1540	The C<stat ()> syscall only supports full-second resolution portably, and
		1541	even on systems where the resolution is higher, many filesystems still
		1542	only support whole seconds.
		1543
		1544	That means that, if the time is the only thing that changes, you might
		1545	miss updates: on the first update, C<ev_stat> detects a change and calls
		1546	your callback, which does something. When there is another update within
		1547	the same second, C<ev_stat> will be unable to detect it.
		1548
		1549	The solution to this is to delay acting on a change for a second (or till
		1550	the next second boundary), using a roughly one-second delay C<ev_timer>
		1551	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1552	is added to work around small timing inconsistencies of some operating
		1553	systems.
		1554
1421	=head3 Watcher-Specific Functions and Data Members	1555	=head3 Watcher-Specific Functions and Data Members
1422		1556
1423	=over 4	1557	=over 4
1424		1558
1425	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1559	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1462	=item const char *path [read-only]	1596	=item const char *path [read-only]
1463		1597
1464	The filesystem path that is being watched.	1598	The filesystem path that is being watched.
1465		1599
1466	=back	1600	=back
		1601
		1602	=head3 Examples
1467		1603
1468	Example: Watch C</etc/passwd> for attribute changes.	1604	Example: Watch C</etc/passwd> for attribute changes.
1469		1605
1470	static void	1606	static void
1471	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1607	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1484	}	1620	}
1485		1621
1486	...	1622	...
1487	ev_stat passwd;	1623	ev_stat passwd;
1488		1624
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1626	ev_stat_start (loop, &passwd);
		1627
		1628	Example: Like above, but additionally use a one-second delay so we do not
		1629	miss updates (however, frequent updates will delay processing, too, so
		1630	one might do the work both on C<ev_stat> callback invocation I<and> on
		1631	C<ev_timer> callback invocation).
		1632
		1633	static ev_stat passwd;
		1634	static ev_timer timer;
		1635
		1636	static void
		1637	timer_cb (EV_P_ ev_timer *w, int revents)
		1638	{
		1639	ev_timer_stop (EV_A_ w);
		1640
		1641	/* now it's one second after the most recent passwd change */
		1642	}
		1643
		1644	static void
		1645	stat_cb (EV_P_ ev_stat *w, int revents)
		1646	{
		1647	/* reset the one-second timer */
		1648	ev_timer_again (EV_A_ &timer);
		1649	}
		1650
		1651	...
		1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1653	ev_stat_start (loop, &passwd);
		1654	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1655
1492		1656
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1657	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1658
1495	Idle watchers trigger events when no other events of the same or higher	1659	Idle watchers trigger events when no other events of the same or higher
…		…
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1685	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1686	believe me.
1523		1687
1524	=back	1688	=back
1525		1689
		1690	=head3 Examples
		1691
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1692	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1693	callback, free it. Also, use no error checking, as usual.
1528		1694
1529	static void	1695	static void
1530	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1696	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1531	{	1697	{
1532	free (w);	1698	free (w);
1533	// now do something you wanted to do when the program has	1699	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1700	// no longer anything immediate to do.
1535	}	1701	}
1536		1702
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1703	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1704	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1705	ev_idle_start (loop, idle_cb);
…		…
1581		1747
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1748	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	1749	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,	1750	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	1751	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	1752	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	1753	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	1754	(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	1755	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1756	coexist peacefully with others).
1591		1757
1592	=head3 Watcher-Specific Functions and Data Members	1758	=head3 Watcher-Specific Functions and Data Members
1593		1759
1594	=over 4	1760	=over 4
1595		1761
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1766	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>	1767	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.	1768	macros, but using them is utterly, utterly and completely pointless.
1603		1769
1604	=back	1770	=back
		1771
		1772	=head3 Examples
1605		1773
1606	There are a number of principal ways to embed other event loops or modules	1774	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	1775	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	1776	(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>	1777	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	1902	=head2 C<ev_embed> - when one backend isn't enough...
1735		1903
1736	This is a rather advanced watcher type that lets you embed one event loop	1904	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	1905	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	1906	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	1907	fashion and must not be used).
1740		1908
1741	There are primarily two reasons you would want that: work around bugs and	1909	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	1910	prioritise I/O.
1743		1911
1744	As an example for a bug workaround, the kqueue backend might only support	1912	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	1946	portable one.
1779		1947
1780	So when you want to use this feature you will always have to be prepared	1948	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	1949	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	1950	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:	1951	create it, and if that fails, use the normal loop for everything.
		1952
		1953	=head3 Watcher-Specific Functions and Data Members
		1954
		1955	=over 4
		1956
		1957	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1958
		1959	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1960
		1961	Configures the watcher to embed the given loop, which must be
		1962	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1963	invoked automatically, otherwise it is the responsibility of the callback
		1964	to invoke it (it will continue to be called until the sweep has been done,
		1965	if you do not want thta, you need to temporarily stop the embed watcher).
		1966
		1967	=item ev_embed_sweep (loop, ev_embed *)
		1968
		1969	Make a single, non-blocking sweep over the embedded loop. This works
		1970	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1971	apropriate way for embedded loops.
		1972
		1973	=item struct ev_loop *other [read-only]
		1974
		1975	The embedded event loop.
		1976
		1977	=back
		1978
		1979	=head3 Examples
		1980
		1981	Example: Try to get an embeddable event loop and embed it into the default
		1982	event loop. If that is not possible, use the default loop. The default
		1983	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1984	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1985	used).
1784		1986
1785	struct ev_loop *loop_hi = ev_default_init (0);	1987	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	1988	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	1989	struct ev_embed embed;
1788		1990
…		…
1799	ev_embed_start (loop_hi, &embed);	2001	ev_embed_start (loop_hi, &embed);
1800	}	2002	}
1801	else	2003	else
1802	loop_lo = loop_hi;	2004	loop_lo = loop_hi;
1803		2005
1804	=head2 Portability notes	2006	Example: Check if kqueue is available but not recommended and create
		2007	a kqueue backend for use with sockets (which usually work with any
		2008	kqueue implementation). Store the kqueue/socket-only event loop in
		2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2010
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2011	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2012	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2013	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2014
1810	will always eport the epoll fd as ready, even when no events are pending.	2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2017	{
		2018	ev_embed_init (&embed, 0, loop_socket);
		2019	ev_embed_start (loop, &embed);
		2020	}
1811		2021
1812	While libev allows embedding these backends (they are contained in	2022	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2023	loop_socket = loop;
1814	work.
1815		2024
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2025	// 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		2026
1846		2027
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2028	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2029
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2030	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2101	Example: Define a class with an IO and idle watcher, start one of them in	2282	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2283	the constructor.
2103		2284
2104	class myclass	2285	class myclass
2105	{	2286	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2287	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2288	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2289
2109	myclass ();	2290	myclass (int fd)
2110	}
2111
2112	myclass::myclass (int fd)
2113	{	2291	{
2114	io .set <myclass, &myclass::io_cb > (this);	2292	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2293	idle.set <myclass, &myclass::idle_cb> (this);
2116		2294
2117	io.start (fd, ev::READ);	2295	io.start (fd, ev::READ);
		2296	}
2118	}	2297	};
2119		2298
2120		2299
2121	=head1 MACRO MAGIC	2300	=head1 MACRO MAGIC
2122		2301
2123	Libev can be compiled with a variety of options, the most fundamantal	2302	Libev can be compiled with a variety of options, the most fundamantal
…		…
2297	runtime if successful). Otherwise no use of the realtime clock option will	2476	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2477	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2478	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2479	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2480
		2481	=item EV_USE_NANOSLEEP
		2482
		2483	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2484	and will use it for delays. Otherwise it will use C<select ()>.
		2485
2302	=item EV_USE_SELECT	2486	=item EV_USE_SELECT
2303		2487
2304	If undefined or defined to be C<1>, libev will compile in support for the	2488	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	2489	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	2490	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	2507	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	2508	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,	2509	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	2510	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2511	on win32. Should not be defined on non-win32 platforms.
		2512
		2513	=item EV_FD_TO_WIN32_HANDLE
		2514
		2515	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2516	file descriptors to socket handles. When not defining this symbol (the
		2517	default), then libev will call C<_get_osfhandle>, which is usually
		2518	correct. In some cases, programs use their own file descriptor management,
		2519	in which case they can provide this function to map fds to socket handles.
2328		2520
2329	=item EV_USE_POLL	2521	=item EV_USE_POLL
2330		2522
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2523	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	2524	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2369	be detected at runtime.	2561	be detected at runtime.
2370		2562
2371	=item EV_H	2563	=item EV_H
2372		2564
2373	The name of the F<ev.h> header file used to include it. The default if	2565	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	2566	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2567	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2568
2377	=item EV_CONFIG_H	2569	=item EV_CONFIG_H
2378		2570
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2571	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	2572	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2573	C<EV_H>, above.
2382		2574
2383	=item EV_EVENT_H	2575	=item EV_EVENT_H
2384		2576
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2577	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.	2578	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2579
2388	=item EV_PROTOTYPES	2580	=item EV_PROTOTYPES
2389		2581
2390	If defined to be C<0>, then F<ev.h> will not define any function	2582	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	2583	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	2649	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).	2650	increase this value (I<must> be a power of two).
2459		2651
2460	=item EV_INOTIFY_HASHSIZE	2652	=item EV_INOTIFY_HASHSIZE
2461		2653
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2654	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>),	2655	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>	2656	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	2657	watchers you might want to increase this value (I<must> be a power of
2466	two).	2658	two).
2467		2659
…		…
2563		2755
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2756	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		2757
2566	This means that, when you have a watcher that triggers in one hour and	2758	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	2759	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	2760	have to skip roughly seven (C<ld 100>) of these watchers.
2569		2761
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2762	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		2763
2572	That means that for changing a timer costs less than removing/adding them	2764	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.	2765	as only the relative motion in the event queue has to be paid for.
2574		2766
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2767	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2576		2768
2577	These just add the watcher into an array or at the head of a list.	2769	These just add the watcher into an array or at the head of a list.
		2770
2578	=item Stopping check/prepare/idle watchers: O(1)	2771	=item Stopping check/prepare/idle watchers: O(1)
2579		2772
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2773	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		2774
2582	These watchers are stored in lists then need to be walked to find the	2775	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	2776	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	2777	have many watchers waiting for the same fd or signal).
2585		2778
2586	=item Finding the next timer per loop iteration: O(1)	2779	=item Finding the next timer in each loop iteration: O(1)
		2780
		2781	By virtue of using a binary heap, the next timer is always found at the
		2782	beginning of the storage array.
2587		2783
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2784	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		2785
2590	A change means an I/O watcher gets started or stopped, which requires	2786	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	2787	libev to recalculate its status (and possibly tell the kernel, depending
		2788	on backend and wether C<ev_io_set> was used).
2592		2789
2593	=item Activating one watcher: O(1)	2790	=item Activating one watcher (putting it into the pending state): O(1)
2594		2791
2595	=item Priority handling: O(number_of_priorities)	2792	=item Priority handling: O(number_of_priorities)
2596		2793
2597	Priorities are implemented by allocating some space for each	2794	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	2795	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	2796	linearly search all the priorities, but starting/stopping and activating
		2797	watchers becomes O(1) w.r.t. prioritiy handling.
2600		2798
2601	=back	2799	=back
2602		2800
2603		2801
		2802	=head1 Win32 platform limitations and workarounds
		2803
		2804	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2805	requires, and its I/O model is fundamentally incompatible with the POSIX
		2806	model. Libev still offers limited functionality on this platform in
		2807	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2808	descriptors. This only applies when using Win32 natively, not when using
		2809	e.g. cygwin.
		2810
		2811	There is no supported compilation method available on windows except
		2812	embedding it into other applications.
		2813
		2814	Due to the many, low, and arbitrary limits on the win32 platform and the
		2815	abysmal performance of winsockets, using a large number of sockets is not
		2816	recommended (and not reasonable). If your program needs to use more than
		2817	a hundred or so sockets, then likely it needs to use a totally different
		2818	implementation for windows, as libev offers the POSIX model, which cannot
		2819	be implemented efficiently on windows (microsoft monopoly games).
		2820
		2821	=over 4
		2822
		2823	=item The winsocket select function
		2824
		2825	The winsocket C<select> function doesn't follow POSIX in that it requires
		2826	socket I<handles> and not socket I<file descriptors>. This makes select
		2827	very inefficient, and also requires a mapping from file descriptors
		2828	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2829	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2830	symbols for more info.
		2831
		2832	The configuration for a "naked" win32 using the microsoft runtime
		2833	libraries and raw winsocket select is:
		2834
		2835	#define EV_USE_SELECT 1
		2836	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2837
		2838	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2839	complexity in the O(n²) range when using win32.
		2840
		2841	=item Limited number of file descriptors
		2842
		2843	Windows has numerous arbitrary (and low) limits on things. Early versions
		2844	of winsocket's select only supported waiting for a max. of C<64> handles
		2845	(probably owning to the fact that all windows kernels can only wait for
		2846	C<64> things at the same time internally; microsoft recommends spawning a
		2847	chain of threads and wait for 63 handles and the previous thread in each).
		2848
		2849	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2850	to some high number (e.g. C<2048>) before compiling the winsocket select
		2851	call (which might be in libev or elsewhere, for example, perl does its own
		2852	select emulation on windows).
		2853
		2854	Another limit is the number of file descriptors in the microsoft runtime
		2855	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2856	or something like this inside microsoft). You can increase this by calling
		2857	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2858	arbitrary limit), but is broken in many versions of the microsoft runtime
		2859	libraries.
		2860
		2861	This might get you to about C<512> or C<2048> sockets (depending on
		2862	windows version and/or the phase of the moon). To get more, you need to
		2863	wrap all I/O functions and provide your own fd management, but the cost of
		2864	calling select (O(n²)) will likely make this unworkable.
		2865
		2866	=back
		2867
		2868
2604	=head1 AUTHOR	2869	=head1 AUTHOR
2605		2870
2606	Marc Lehmann <libev@schmorp.de>.	2871	Marc Lehmann <libev@schmorp.de>.
2607		2872

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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 1.121 by root, Mon Jan 28 12:13:54 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 1.121 by root, Mon Jan 28 12:13:54 2008 UTC