[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 1.130 by root, Wed Feb 6 18:34:24 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
…		…
676		773
677	=item C<EV_FORK>	774	=item C<EV_FORK>
678		775
679	The event loop has been resumed in the child process after fork (see	776	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	777	C<ev_fork>).
		778
		779	=item C<EV_ASYNC>
		780
		781	The given async watcher has been asynchronously notified (see C<ev_async>).
681		782
682	=item C<EV_ERROR>	783	=item C<EV_ERROR>
683		784
684	An unspecified error has occured, the watcher has been stopped. This might	785	An unspecified error has occured, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	786	happen because the watcher could not be properly started because libev
…		…
903	In general you can register as many read and/or write event watchers per	1004	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	1005	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	1006	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1007	required if you know what you are doing).
907		1008
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	1009	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	1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1011	C<EVBACKEND_POLL>).
917		1012
918	Another thing you have to watch out for is that it is quite easy to	1013	Another thing you have to watch out for is that it is quite easy to
…		…
952	optimisations to libev.	1047	optimisations to libev.
953		1048
954	=head3 The special problem of dup'ed file descriptors	1049	=head3 The special problem of dup'ed file descriptors
955		1050
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1051	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1052	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	1053	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1054	events for them, only one file descriptor might actually receive events.
960		1055
961	There is no workaorund possible except not registering events	1056	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1057	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1058	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1059
965	=head3 The special problem of fork	1060	=head3 The special problem of fork
966		1061
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1062	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
993	=item int events [read-only]	1088	=item int events [read-only]
994		1089
995	The events being watched.	1090	The events being watched.
996		1091
997	=back	1092	=back
		1093
		1094	=head3 Examples
998		1095
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1096	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	1097	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1098	attempt to read a whole line in the callback.
1002		1099
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1197	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.	1198	which is also when any modifications are taken into account.
1102		1199
1103	=back	1200	=back
1104		1201
		1202	=head3 Examples
		1203
1105	Example: Create a timer that fires after 60 seconds.	1204	Example: Create a timer that fires after 60 seconds.
1106		1205
1107	static void	1206	static void
1108	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1207	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1109	{	1208	{
…		…
1266	When active, contains the absolute time that the watcher is supposed to	1365	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1366	trigger next.
1268		1367
1269	=back	1368	=back
1270		1369
		1370	=head3 Examples
		1371
1271	Example: Call a callback every hour, or, more precisely, whenever the	1372	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1373	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1374	potentially a lot of jittering, but good long-term stability.
1274		1375
1275	static void	1376	static void
…		…
1341		1442
1342	=head3 Watcher-Specific Functions and Data Members	1443	=head3 Watcher-Specific Functions and Data Members
1343		1444
1344	=over 4	1445	=over 4
1345		1446
1346	=item ev_child_init (ev_child *, callback, int pid)	1447	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1448
1348	=item ev_child_set (ev_child *, int pid)	1449	=item ev_child_set (ev_child *, int pid, int trace)
1349		1450
1350	Configures the watcher to wait for status changes of process C<pid> (or	1451	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	1452	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	1453	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	1454	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	1455	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1456	process causing the status change. C<trace> must be either C<0> (only
		1457	activate the watcher when the process terminates) or C<1> (additionally
		1458	activate the watcher when the process is stopped or continued).
1356		1459
1357	=item int pid [read-only]	1460	=item int pid [read-only]
1358		1461
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1462	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1463
…		…
1366		1469
1367	The process exit/trace status caused by C<rpid> (see your systems	1470	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1471	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1472
1370	=back	1473	=back
		1474
		1475	=head3 Examples
1371		1476
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
1373		1478
1374	static void	1479	static void
1375	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1480	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	1521	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	1522	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	1523	usually detected immediately, and if the file exists there will be no
1419	polling.	1524	polling.
1420		1525
		1526	=head3 Inotify
		1527
		1528	When C<inotify (7)> support has been compiled into libev (generally only
		1529	available on Linux) and present at runtime, it will be used to speed up
		1530	change detection where possible. The inotify descriptor will be created lazily
		1531	when the first C<ev_stat> watcher is being started.
		1532
		1533	Inotify presense does not change the semantics of C<ev_stat> watchers
		1534	except that changes might be detected earlier, and in some cases, to avoid
		1535	making regular C<stat> calls. Even in the presense of inotify support
		1536	there are many cases where libev has to resort to regular C<stat> polling.
		1537
		1538	(There is no support for kqueue, as apparently it cannot be used to
		1539	implement this functionality, due to the requirement of having a file
		1540	descriptor open on the object at all times).
		1541
		1542	=head3 The special problem of stat time resolution
		1543
		1544	The C<stat ()> syscall only supports full-second resolution portably, and
		1545	even on systems where the resolution is higher, many filesystems still
		1546	only support whole seconds.
		1547
		1548	That means that, if the time is the only thing that changes, you might
		1549	miss updates: on the first update, C<ev_stat> detects a change and calls
		1550	your callback, which does something. When there is another update within
		1551	the same second, C<ev_stat> will be unable to detect it.
		1552
		1553	The solution to this is to delay acting on a change for a second (or till
		1554	the next second boundary), using a roughly one-second delay C<ev_timer>
		1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1556	is added to work around small timing inconsistencies of some operating
		1557	systems.
		1558
1421	=head3 Watcher-Specific Functions and Data Members	1559	=head3 Watcher-Specific Functions and Data Members
1422		1560
1423	=over 4	1561	=over 4
1424		1562
1425	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1563	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1462	=item const char *path [read-only]	1600	=item const char *path [read-only]
1463		1601
1464	The filesystem path that is being watched.	1602	The filesystem path that is being watched.
1465		1603
1466	=back	1604	=back
		1605
		1606	=head3 Examples
1467		1607
1468	Example: Watch C</etc/passwd> for attribute changes.	1608	Example: Watch C</etc/passwd> for attribute changes.
1469		1609
1470	static void	1610	static void
1471	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1611	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1484	}	1624	}
1485		1625
1486	...	1626	...
1487	ev_stat passwd;	1627	ev_stat passwd;
1488		1628
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1630	ev_stat_start (loop, &passwd);
		1631
		1632	Example: Like above, but additionally use a one-second delay so we do not
		1633	miss updates (however, frequent updates will delay processing, too, so
		1634	one might do the work both on C<ev_stat> callback invocation I<and> on
		1635	C<ev_timer> callback invocation).
		1636
		1637	static ev_stat passwd;
		1638	static ev_timer timer;
		1639
		1640	static void
		1641	timer_cb (EV_P_ ev_timer *w, int revents)
		1642	{
		1643	ev_timer_stop (EV_A_ w);
		1644
		1645	/* now it's one second after the most recent passwd change */
		1646	}
		1647
		1648	static void
		1649	stat_cb (EV_P_ ev_stat *w, int revents)
		1650	{
		1651	/* reset the one-second timer */
		1652	ev_timer_again (EV_A_ &timer);
		1653	}
		1654
		1655	...
		1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1657	ev_stat_start (loop, &passwd);
		1658	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1659
1492		1660
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1661	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1662
1495	Idle watchers trigger events when no other events of the same or higher	1663	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,	1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1690	believe me.
1523		1691
1524	=back	1692	=back
1525		1693
		1694	=head3 Examples
		1695
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1697	callback, free it. Also, use no error checking, as usual.
1528		1698
1529	static void	1699	static void
1530	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1700	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1531	{	1701	{
1532	free (w);	1702	free (w);
1533	// now do something you wanted to do when the program has	1703	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1704	// no longer anything immediate to do.
1535	}	1705	}
1536		1706
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1708	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1709	ev_idle_start (loop, idle_cb);
…		…
1581		1751
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1752	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	1753	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,	1754	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	1755	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	1756	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	1757	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	1758	(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	1759	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1760	coexist peacefully with others).
1591		1761
1592	=head3 Watcher-Specific Functions and Data Members	1762	=head3 Watcher-Specific Functions and Data Members
1593		1763
1594	=over 4	1764	=over 4
1595		1765
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1770	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>	1771	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.	1772	macros, but using them is utterly, utterly and completely pointless.
1603		1773
1604	=back	1774	=back
		1775
		1776	=head3 Examples
1605		1777
1606	There are a number of principal ways to embed other event loops or modules	1778	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	1779	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	1780	(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>	1781	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	1906	=head2 C<ev_embed> - when one backend isn't enough...
1735		1907
1736	This is a rather advanced watcher type that lets you embed one event loop	1908	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	1909	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	1910	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	1911	fashion and must not be used).
1740		1912
1741	There are primarily two reasons you would want that: work around bugs and	1913	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	1914	prioritise I/O.
1743		1915
1744	As an example for a bug workaround, the kqueue backend might only support	1916	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	1950	portable one.
1779		1951
1780	So when you want to use this feature you will always have to be prepared	1952	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	1953	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	1954	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:	1955	create it, and if that fails, use the normal loop for everything.
		1956
		1957	=head3 Watcher-Specific Functions and Data Members
		1958
		1959	=over 4
		1960
		1961	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1962
		1963	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1964
		1965	Configures the watcher to embed the given loop, which must be
		1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1967	invoked automatically, otherwise it is the responsibility of the callback
		1968	to invoke it (it will continue to be called until the sweep has been done,
		1969	if you do not want thta, you need to temporarily stop the embed watcher).
		1970
		1971	=item ev_embed_sweep (loop, ev_embed *)
		1972
		1973	Make a single, non-blocking sweep over the embedded loop. This works
		1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1975	apropriate way for embedded loops.
		1976
		1977	=item struct ev_loop *other [read-only]
		1978
		1979	The embedded event loop.
		1980
		1981	=back
		1982
		1983	=head3 Examples
		1984
		1985	Example: Try to get an embeddable event loop and embed it into the default
		1986	event loop. If that is not possible, use the default loop. The default
		1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1989	used).
1784		1990
1785	struct ev_loop *loop_hi = ev_default_init (0);	1991	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	1992	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	1993	struct ev_embed embed;
1788		1994
…		…
1799	ev_embed_start (loop_hi, &embed);	2005	ev_embed_start (loop_hi, &embed);
1800	}	2006	}
1801	else	2007	else
1802	loop_lo = loop_hi;	2008	loop_lo = loop_hi;
1803		2009
1804	=head2 Portability notes	2010	Example: Check if kqueue is available but not recommended and create
		2011	a kqueue backend for use with sockets (which usually work with any
		2012	kqueue implementation). Store the kqueue/socket-only event loop in
		2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2014
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2015	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2016	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2017	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2018
1810	will always eport the epoll fd as ready, even when no events are pending.	2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2021	{
		2022	ev_embed_init (&embed, 0, loop_socket);
		2023	ev_embed_start (loop, &embed);
		2024	}
1811		2025
1812	While libev allows embedding these backends (they are contained in	2026	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2027	loop_socket = loop;
1814	work.
1815		2028
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2029	// 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		2030
1846		2031
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2033
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2034	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2050	believe me.
1866		2051
1867	=back	2052	=back
1868		2053
1869		2054
		2055	=head2 C<ev_async> - how to wake up another event loop
		2056
		2057	In general, you cannot use an C<ev_loop> from multiple threads or other
		2058	asynchronous sources such as signal handlers (as opposed to multiple event
		2059	loops - those are of course safe to use in different threads).
		2060
		2061	Sometimes, however, you need to wake up another event loop you do not
		2062	control, for example because it belongs to another thread. This is what
		2063	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2064	can signal it by calling C<ev_async_send>, which is thread- and signal
		2065	safe.
		2066
		2067	This functionality is very similar to C<ev_signal> watchers, as signals,
		2068	too, are asynchronous in nature, and signals, too, will be compressed
		2069	(i.e. the number of callback invocations may be less than the number of
		2070	C<ev_async_sent> calls).
		2071
		2072	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2073	just the default loop.
		2074
		2075	=head3 Queueing
		2076
		2077	C<ev_async> does not support queueing of data in any way. The reason
		2078	is that the author does not know of a simple (or any) algorithm for a
		2079	multiple-writer-single-reader queue that works in all cases and doesn't
		2080	need elaborate support such as pthreads.
		2081
		2082	That means that if you want to queue data, you have to provide your own
		2083	queue. But at least I can tell you would implement locking around your
		2084	queue:
		2085
		2086	=over 4
		2087
		2088	=item queueing from a signal handler context
		2089
		2090	To implement race-free queueing, you simply add to the queue in the signal
		2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2092	some fictitiuous SIGUSR1 handler:
		2093
		2094	static ev_async mysig;
		2095
		2096	static void
		2097	sigusr1_handler (void)
		2098	{
		2099	sometype data;
		2100
		2101	// no locking etc.
		2102	queue_put (data);
		2103	ev_async_send (DEFAULT_ &mysig);
		2104	}
		2105
		2106	static void
		2107	mysig_cb (EV_P_ ev_async *w, int revents)
		2108	{
		2109	sometype data;
		2110	sigset_t block, prev;
		2111
		2112	sigemptyset (&block);
		2113	sigaddset (&block, SIGUSR1);
		2114	sigprocmask (SIG_BLOCK, &block, &prev);
		2115
		2116	while (queue_get (&data))
		2117	process (data);
		2118
		2119	if (sigismember (&prev, SIGUSR1)
		2120	sigprocmask (SIG_UNBLOCK, &block, 0);
		2121	}
		2122
		2123	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2124	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2125	either...).
		2126
		2127	=item queueing from a thread context
		2128
		2129	The strategy for threads is different, as you cannot (easily) block
		2130	threads but you can easily preempt them, so to queue safely you need to
		2131	employ a traditional mutex lock, such as in this pthread example:
		2132
		2133	static ev_async mysig;
		2134	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2135
		2136	static void
		2137	otherthread (void)
		2138	{
		2139	// only need to lock the actual queueing operation
		2140	pthread_mutex_lock (&mymutex);
		2141	queue_put (data);
		2142	pthread_mutex_unlock (&mymutex);
		2143
		2144	ev_async_send (DEFAULT_ &mysig);
		2145	}
		2146
		2147	static void
		2148	mysig_cb (EV_P_ ev_async *w, int revents)
		2149	{
		2150	pthread_mutex_lock (&mymutex);
		2151
		2152	while (queue_get (&data))
		2153	process (data);
		2154
		2155	pthread_mutex_unlock (&mymutex);
		2156	}
		2157
		2158	=back
		2159
		2160
		2161	=head3 Watcher-Specific Functions and Data Members
		2162
		2163	=over 4
		2164
		2165	=item ev_async_init (ev_async *, callback)
		2166
		2167	Initialises and configures the async watcher - it has no parameters of any
		2168	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2169	believe me.
		2170
		2171	=item ev_async_send (loop, ev_async *)
		2172
		2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2175	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2177	section below on what exactly this means).
		2178
		2179	This call incurs the overhead of a syscall only once per loop iteration,
		2180	so while the overhead might be noticable, it doesn't apply to repeated
		2181	calls to C<ev_async_send>.
		2182
		2183	=back
		2184
		2185
1870	=head1 OTHER FUNCTIONS	2186	=head1 OTHER FUNCTIONS
1871		2187
1872	There are some other functions of possible interest. Described. Here. Now.	2188	There are some other functions of possible interest. Described. Here. Now.
1873		2189
1874	=over 4	2190	=over 4
…		…
2101	Example: Define a class with an IO and idle watcher, start one of them in	2417	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2418	the constructor.
2103		2419
2104	class myclass	2420	class myclass
2105	{	2421	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2422	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2423	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2424
2109	myclass ();	2425	myclass (int fd)
2110	}
2111
2112	myclass::myclass (int fd)
2113	{	2426	{
2114	io .set <myclass, &myclass::io_cb > (this);	2427	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2428	idle.set <myclass, &myclass::idle_cb> (this);
2116		2429
2117	io.start (fd, ev::READ);	2430	io.start (fd, ev::READ);
		2431	}
2118	}	2432	};
2119		2433
2120		2434
2121	=head1 MACRO MAGIC	2435	=head1 MACRO MAGIC
2122		2436
2123	Libev can be compiled with a variety of options, the most fundamantal	2437	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	2611	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2612	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2613	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2614	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2615
		2616	=item EV_USE_NANOSLEEP
		2617
		2618	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2619	and will use it for delays. Otherwise it will use C<select ()>.
		2620
2302	=item EV_USE_SELECT	2621	=item EV_USE_SELECT
2303		2622
2304	If undefined or defined to be C<1>, libev will compile in support for the	2623	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	2624	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	2625	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	2642	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	2643	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,	2644	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	2645	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2646	on win32. Should not be defined on non-win32 platforms.
		2647
		2648	=item EV_FD_TO_WIN32_HANDLE
		2649
		2650	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2651	file descriptors to socket handles. When not defining this symbol (the
		2652	default), then libev will call C<_get_osfhandle>, which is usually
		2653	correct. In some cases, programs use their own file descriptor management,
		2654	in which case they can provide this function to map fds to socket handles.
2328		2655
2329	=item EV_USE_POLL	2656	=item EV_USE_POLL
2330		2657
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2658	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	2659	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2366		2693
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2694	If defined to be C<1>, libev will compile in support for the Linux inotify
2368	interface to speed up C<ev_stat> watchers. Its actual availability will	2695	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2696	be detected at runtime.
2370		2697
		2698	=item EV_ATOMIC_T
		2699
		2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2701	access is atomic with respect to other threads or signal contexts. No such
		2702	type is easily found in the C language, so you can provide your own type
		2703	that you know is safe for your purposes. It is used both for signal handler "locking"
		2704	as well as for signal and thread safety in C<ev_async> watchers.
		2705
		2706	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2707	(from F<signal.h>), which is usually good enough on most platforms.
		2708
2371	=item EV_H	2709	=item EV_H
2372		2710
2373	The name of the F<ev.h> header file used to include it. The default if	2711	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	2712	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.	2713	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2714
2377	=item EV_CONFIG_H	2715	=item EV_CONFIG_H
2378		2716
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2717	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	2718	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2719	C<EV_H>, above.
2382		2720
2383	=item EV_EVENT_H	2721	=item EV_EVENT_H
2384		2722
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2723	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.	2724	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2725
2388	=item EV_PROTOTYPES	2726	=item EV_PROTOTYPES
2389		2727
2390	If defined to be C<0>, then F<ev.h> will not define any function	2728	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	2729	prototypes, but still define all the structs and other symbols. This is
…		…
2442	=item EV_FORK_ENABLE	2780	=item EV_FORK_ENABLE
2443		2781
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	2782	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	2783	defined to be C<0>, then they are not.
2446		2784
		2785	=item EV_ASYNC_ENABLE
		2786
		2787	If undefined or defined to be C<1>, then async watchers are supported. If
		2788	defined to be C<0>, then they are not.
		2789
2447	=item EV_MINIMAL	2790	=item EV_MINIMAL
2448		2791
2449	If you need to shave off some kilobytes of code at the expense of some	2792	If you need to shave off some kilobytes of code at the expense of some
2450	speed, define this symbol to C<1>. Currently only used for gcc to override	2793	speed, define this symbol to C<1>. Currently only used for gcc to override
2451	some inlining decisions, saves roughly 30% codesize of amd64.	2794	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2457	than enough. If you need to manage thousands of children you might want to	2800	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).	2801	increase this value (I<must> be a power of two).
2459		2802
2460	=item EV_INOTIFY_HASHSIZE	2803	=item EV_INOTIFY_HASHSIZE
2461		2804
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2805	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>),	2806	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>	2807	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	2808	watchers you might want to increase this value (I<must> be a power of
2466	two).	2809	two).
2467		2810
…		…
2563		2906
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2907	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		2908
2566	This means that, when you have a watcher that triggers in one hour and	2909	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	2910	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	2911	have to skip roughly seven (C<ld 100>) of these watchers.
2569		2912
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2913	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		2914
2572	That means that for changing a timer costs less than removing/adding them	2915	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.	2916	as only the relative motion in the event queue has to be paid for.
2574		2917
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2918	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		2919
2577	These just add the watcher into an array or at the head of a list.	2920	These just add the watcher into an array or at the head of a list.
		2921
2578	=item Stopping check/prepare/idle watchers: O(1)	2922	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		2923
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2924	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		2925
2582	These watchers are stored in lists then need to be walked to find the	2926	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	2927	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	2928	have many watchers waiting for the same fd or signal).
2585		2929
2586	=item Finding the next timer per loop iteration: O(1)	2930	=item Finding the next timer in each loop iteration: O(1)
		2931
		2932	By virtue of using a binary heap, the next timer is always found at the
		2933	beginning of the storage array.
2587		2934
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		2936
2590	A change means an I/O watcher gets started or stopped, which requires	2937	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	2938	libev to recalculate its status (and possibly tell the kernel, depending
		2939	on backend and wether C<ev_io_set> was used).
2592		2940
2593	=item Activating one watcher: O(1)	2941	=item Activating one watcher (putting it into the pending state): O(1)
2594		2942
2595	=item Priority handling: O(number_of_priorities)	2943	=item Priority handling: O(number_of_priorities)
2596		2944
2597	Priorities are implemented by allocating some space for each	2945	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	2946	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	2947	linearly search all the priorities, but starting/stopping and activating
		2948	watchers becomes O(1) w.r.t. priority handling.
		2949
		2950	=item Sending an ev_async: O(1)
		2951
		2952	=item Processing ev_async_send: O(number_of_async_watchers)
		2953
		2954	=item Processing signals: O(max_signal_number)
		2955
		2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		2957	calls in the current loop iteration. Checking for async and signal events
		2958	involves iterating over all running async watchers or all signal numbers.
2600		2959
2601	=back	2960	=back
2602		2961
2603		2962
		2963	=head1 Win32 platform limitations and workarounds
		2964
		2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2966	requires, and its I/O model is fundamentally incompatible with the POSIX
		2967	model. Libev still offers limited functionality on this platform in
		2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2969	descriptors. This only applies when using Win32 natively, not when using
		2970	e.g. cygwin.
		2971
		2972	There is no supported compilation method available on windows except
		2973	embedding it into other applications.
		2974
		2975	Due to the many, low, and arbitrary limits on the win32 platform and the
		2976	abysmal performance of winsockets, using a large number of sockets is not
		2977	recommended (and not reasonable). If your program needs to use more than
		2978	a hundred or so sockets, then likely it needs to use a totally different
		2979	implementation for windows, as libev offers the POSIX model, which cannot
		2980	be implemented efficiently on windows (microsoft monopoly games).
		2981
		2982	=over 4
		2983
		2984	=item The winsocket select function
		2985
		2986	The winsocket C<select> function doesn't follow POSIX in that it requires
		2987	socket I<handles> and not socket I<file descriptors>. This makes select
		2988	very inefficient, and also requires a mapping from file descriptors
		2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2991	symbols for more info.
		2992
		2993	The configuration for a "naked" win32 using the microsoft runtime
		2994	libraries and raw winsocket select is:
		2995
		2996	#define EV_USE_SELECT 1
		2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2998
		2999	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3000	complexity in the O(n²) range when using win32.
		3001
		3002	=item Limited number of file descriptors
		3003
		3004	Windows has numerous arbitrary (and low) limits on things. Early versions
		3005	of winsocket's select only supported waiting for a max. of C<64> handles
		3006	(probably owning to the fact that all windows kernels can only wait for
		3007	C<64> things at the same time internally; microsoft recommends spawning a
		3008	chain of threads and wait for 63 handles and the previous thread in each).
		3009
		3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3011	to some high number (e.g. C<2048>) before compiling the winsocket select
		3012	call (which might be in libev or elsewhere, for example, perl does its own
		3013	select emulation on windows).
		3014
		3015	Another limit is the number of file descriptors in the microsoft runtime
		3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3017	or something like this inside microsoft). You can increase this by calling
		3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3019	arbitrary limit), but is broken in many versions of the microsoft runtime
		3020	libraries.
		3021
		3022	This might get you to about C<512> or C<2048> sockets (depending on
		3023	windows version and/or the phase of the moon). To get more, you need to
		3024	wrap all I/O functions and provide your own fd management, but the cost of
		3025	calling select (O(n²)) will likely make this unworkable.
		3026
		3027	=back
		3028
		3029
2604	=head1 AUTHOR	3030	=head1 AUTHOR
2605		3031
2606	Marc Lehmann <libev@schmorp.de>.	3032	Marc Lehmann <libev@schmorp.de>.
2607		3033

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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 1.130 by root, Wed Feb 6 18:34:24 2008 UTC

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Revision 1.95 by root, Fri Dec 21 05:10:01 2007 UTC vs.
Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC