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

Comparing libev/ev.pod (file contents):
Revision 1.88 by ayin, Tue Dec 18 13:06:18 2007 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 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;
…		…
53	The newest version of this document is also available as a html-formatted	53	The newest version of this document is also available as a html-formatted
54	web page you might find easier to navigate when reading it for the first	54	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
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 like	340	but it scales phenomenally better. While poll and select usually scale
319	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	341	like O(total_fds) where n is the total number of fds (or the highest fd),
320	either O(1) or O(active_fds).	342	epoll scales either O(1) or O(active_fds). The epoll design has a number
		343	of shortcomings, such as silently dropping events in some hard-to-detect
		344	cases and rewiring a syscall per fd change, no fork support and bad
		345	support for dup.
321		346
322	While stopping and starting an I/O watcher in the same iteration will	347	While stopping, setting and starting an I/O watcher in the same iteration
323	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
324	(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
325	best to avoid that. Also, dup()ed file descriptors might not work very	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
326	well if you register events for both fds.	351	very well if you register events for both fds.
327		352
328	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
329	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
330	(or space) is available.	355	(or space) is available.
331		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
332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
333		365
334	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
335	was broken on all BSDs except NetBSD (usually it doesn't work with	367	was broken on all BSDs except NetBSD (usually it doesn't work reliably
336	anything but sockets and pipes, except on Darwin, where of course its	368	with anything but sockets and pipes, except on Darwin, where of course
337	completely useless). For this reason its not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
338	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
339	C<EVBACKEND_KQUEUE>).	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		372	system like NetBSD.
		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.
340		377
341	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
342	kernel is more efficient (which says nothing about its actual speed, of	379	kernel is more efficient (which says nothing about its actual speed, of
343	course). While starting and stopping an I/O watcher does not cause an	380	course). While stopping, setting and starting an I/O watcher does never
344	extra syscall as with epoll, it still adds up to four event changes per	381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
345	incident, so its best to avoid that.	382	two event changes per incident, support for C<fork ()> is very bad and it
		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.
346		393
347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
348		395
349	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.
350		400
351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
352		402
353	This uses the Solaris 10 port mechanism. As with everything on Solaris,	403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
354	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)).
355		405
356	Please note that solaris ports can result in a lot of spurious	406	Please note that solaris event ports can deliver a lot of spurious
357	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
358	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
		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.
359		418
360	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
361		420
362	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
363	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
364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
365		424
		425	It is definitely not recommended to use this flag.
		426
366	=back	427	=back
367		428
368	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
369	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
370	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
371	order of their flag values :)
372		432
373	The most typical usage is like this:	433	The most typical usage is like this:
374		434
375	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
423	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
424	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
425		485
426	=item ev_default_fork ()	486	=item ev_default_fork ()
427		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
428	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
429	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
430	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
431	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.
432		494
433	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
434	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
435	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
436		498
437	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
438	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
439	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
440		502
441	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
442		504
443	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
444	without calling this function, so if you force one of those backends you
445	do not need to care.
446
447	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
448		506
449	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
450	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
451	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
452		514
453	=item unsigned int ev_loop_count (loop)	515	=item unsigned int ev_loop_count (loop)
454		516
455	Returns the count of loop iterations for the loop, which is identical to	517	Returns the count of loop iterations for the loop, which is identical to
456	the number of times libev did poll for new events. It starts at C<0> and	518	the number of times libev did poll for new events. It starts at C<0> and
…		…
469		531
470	Returns the current "event loop time", which is the time the event loop	532	Returns the current "event loop time", which is the time the event loop
471	received events and started processing them. This timestamp does not	533	received events and started processing them. This timestamp does not
472	change as long as callbacks are being processed, and this is also the base	534	change as long as callbacks are being processed, and this is also the base
473	time used for relative timers. You can treat it as the timestamp of the	535	time used for relative timers. You can treat it as the timestamp of the
474	event occuring (or more correctly, libev finding out about it).	536	event occurring (or more correctly, libev finding out about it).
475		537
476	=item ev_loop (loop, int flags)	538	=item ev_loop (loop, int flags)
477		539
478	Finally, this is it, the event handler. This function usually is called	540	Finally, this is it, the event handler. This function usually is called
479	after you initialised all your watchers and you want to start handling	541	after you initialised all your watchers and you want to start handling
…		…
501	usually a better approach for this kind of thing.	563	usually a better approach for this kind of thing.
502		564
503	Here are the gory details of what C<ev_loop> does:	565	Here are the gory details of what C<ev_loop> does:
504		566
505	- Before the first iteration, call any pending watchers.	567	- Before the first iteration, call any pending watchers.
506	* If there are no active watchers (reference count is zero), return.	568	* If EVFLAG_FORKCHECK was used, check for a fork.
507	- Queue all prepare watchers and then call all outstanding watchers.	569	- If a fork was detected, queue and call all fork watchers.
		570	- Queue and call all prepare watchers.
508	- If we have been forked, recreate the kernel state.	571	- If we have been forked, recreate the kernel state.
509	- Update the kernel state with all outstanding changes.	572	- Update the kernel state with all outstanding changes.
510	- Update the "event loop time".	573	- Update the "event loop time".
511	- Calculate for how long to block.	574	- Calculate for how long to sleep or block, if at all
		575	(active idle watchers, EVLOOP_NONBLOCK or not having
		576	any active watchers at all will result in not sleeping).
		577	- Sleep if the I/O and timer collect interval say so.
512	- Block the process, waiting for any events.	578	- Block the process, waiting for any events.
513	- Queue all outstanding I/O (fd) events.	579	- Queue all outstanding I/O (fd) events.
514	- Update the "event loop time" and do time jump handling.	580	- Update the "event loop time" and do time jump handling.
515	- Queue all outstanding timers.	581	- Queue all outstanding timers.
516	- Queue all outstanding periodics.	582	- Queue all outstanding periodics.
517	- If no events are pending now, queue all idle watchers.	583	- If no events are pending now, queue all idle watchers.
518	- Queue all check watchers.	584	- Queue all check watchers.
519	- Call all queued watchers in reverse order (i.e. check watchers first).	585	- Call all queued watchers in reverse order (i.e. check watchers first).
520	Signals and child watchers are implemented as I/O watchers, and will	586	Signals and child watchers are implemented as I/O watchers, and will
521	be handled here by queueing them when their watcher gets executed.	587	be handled here by queueing them when their watcher gets executed.
522	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
523	were used, return, otherwise continue with step *.	589	were used, or there are no active watchers, return, otherwise
		590	continue with step *.
524		591
525	Example: Queue some jobs and then loop until no events are outsanding	592	Example: Queue some jobs and then loop until no events are outstanding
526	anymore.	593	anymore.
527		594
528	... queue jobs here, make sure they register event watchers as long	595	... queue jobs here, make sure they register event watchers as long
529	... as they still have work to do (even an idle watcher will do..)	596	... as they still have work to do (even an idle watcher will do..)
530	ev_loop (my_loop, 0);	597	ev_loop (my_loop, 0);
…		…
534		601
535	Can be used to make a call to C<ev_loop> return early (but only after it	602	Can be used to make a call to C<ev_loop> return early (but only after it
536	has processed all outstanding events). The C<how> argument must be either	603	has processed all outstanding events). The C<how> argument must be either
537	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
538	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		606
		607	This "unloop state" will be cleared when entering C<ev_loop> again.
539		608
540	=item ev_ref (loop)	609	=item ev_ref (loop)
541		610
542	=item ev_unref (loop)	611	=item ev_unref (loop)
543		612
…		…
548	returning, ev_unref() after starting, and ev_ref() before stopping it. For	617	returning, ev_unref() after starting, and ev_ref() before stopping it. For
549	example, libev itself uses this for its internal signal pipe: It is not	618	example, libev itself uses this for its internal signal pipe: It is not
550	visible to the libev user and should not keep C<ev_loop> from exiting if	619	visible to the libev user and should not keep C<ev_loop> from exiting if
551	no event watchers registered by it are active. It is also an excellent	620	no event watchers registered by it are active. It is also an excellent
552	way to do this for generic recurring timers or from within third-party	621	way to do this for generic recurring timers or from within third-party
553	libraries. Just remember to I<unref after start> and I<ref before stop>.	622	libraries. Just remember to I<unref after start> and I<ref before stop>
		623	(but only if the watcher wasn't active before, or was active before,
		624	respectively).
554		625
555	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
556	running when nothing else is active.	627	running when nothing else is active.
557		628
558	struct ev_signal exitsig;	629	struct ev_signal exitsig;
…		…
562		633
563	Example: For some weird reason, unregister the above signal handler again.	634	Example: For some weird reason, unregister the above signal handler again.
564		635
565	ev_ref (loop);	636	ev_ref (loop);
566	ev_signal_stop (loop, &exitsig);	637	ev_signal_stop (loop, &exitsig);
		638
		639	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		640
		641	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		642
		643	These advanced functions influence the time that libev will spend waiting
		644	for events. Both are by default C<0>, meaning that libev will try to
		645	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		646
		647	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		648	allows libev to delay invocation of I/O and timer/periodic callbacks to
		649	increase efficiency of loop iterations.
		650
		651	The background is that sometimes your program runs just fast enough to
		652	handle one (or very few) event(s) per loop iteration. While this makes
		653	the program responsive, it also wastes a lot of CPU time to poll for new
		654	events, especially with backends like C<select ()> which have a high
		655	overhead for the actual polling but can deliver many events at once.
		656
		657	By setting a higher I<io collect interval> you allow libev to spend more
		658	time collecting I/O events, so you can handle more events per iteration,
		659	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		660	C<ev_timer>) will be not affected. Setting this to a non-null value will
		661	introduce an additional C<ev_sleep ()> call into most loop iterations.
		662
		663	Likewise, by setting a higher I<timeout collect interval> you allow libev
		664	to spend more time collecting timeouts, at the expense of increased
		665	latency (the watcher callback will be called later). C<ev_io> watchers
		666	will not be affected. Setting this to a non-null value will not introduce
		667	any overhead in libev.
		668
		669	Many (busy) programs can usually benefit by setting the io collect
		670	interval to a value near C<0.1> or so, which is often enough for
		671	interactive servers (of course not for games), likewise for timeouts. It
		672	usually doesn't make much sense to set it to a lower value than C<0.01>,
		673	as this approsaches the timing granularity of most systems.
567		674
568	=back	675	=back
569		676
570		677
571	=head1 ANATOMY OF A WATCHER	678	=head1 ANATOMY OF A WATCHER
…		…
670		777
671	=item C<EV_FORK>	778	=item C<EV_FORK>
672		779
673	The event loop has been resumed in the child process after fork (see	780	The event loop has been resumed in the child process after fork (see
674	C<ev_fork>).	781	C<ev_fork>).
		782
		783	=item C<EV_ASYNC>
		784
		785	The given async watcher has been asynchronously notified (see C<ev_async>).
675		786
676	=item C<EV_ERROR>	787	=item C<EV_ERROR>
677		788
678	An unspecified error has occured, the watcher has been stopped. This might	789	An unspecified error has occured, the watcher has been stopped. This might
679	happen because the watcher could not be properly started because libev	790	happen because the watcher could not be properly started because libev
…		…
897	In general you can register as many read and/or write event watchers per	1008	In general you can register as many read and/or write event watchers per
898	fd as you want (as long as you don't confuse yourself). Setting all file	1009	fd as you want (as long as you don't confuse yourself). Setting all file
899	descriptors to non-blocking mode is also usually a good idea (but not	1010	descriptors to non-blocking mode is also usually a good idea (but not
900	required if you know what you are doing).	1011	required if you know what you are doing).
901		1012
902	You have to be careful with dup'ed file descriptors, though. Some backends
903	(the linux epoll backend is a notable example) cannot handle dup'ed file
904	descriptors correctly if you register interest in two or more fds pointing
905	to the same underlying file/socket/etc. description (that is, they share
906	the same underlying "file open").
907
908	If you must do this, then force the use of a known-to-be-good backend	1013	If you must do this, then force the use of a known-to-be-good backend
909	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1014	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
910	C<EVBACKEND_POLL>).	1015	C<EVBACKEND_POLL>).
911		1016
912	Another thing you have to watch out for is that it is quite easy to	1017	Another thing you have to watch out for is that it is quite easy to
…		…
924	such as poll (fortunately in our Xlib example, Xlib already does this on	1029	such as poll (fortunately in our Xlib example, Xlib already does this on
925	its own, so its quite safe to use).	1030	its own, so its quite safe to use).
926		1031
927	=head3 The special problem of disappearing file descriptors	1032	=head3 The special problem of disappearing file descriptors
928		1033
929	Some backends (e.g kqueue, epoll) need to be told about closing a file	1034	Some backends (e.g. kqueue, epoll) need to be told about closing a file
930	descriptor (either by calling C<close> explicitly or by any other means,	1035	descriptor (either by calling C<close> explicitly or by any other means,
931	such as C<dup>). The reason is that you register interest in some file	1036	such as C<dup>). The reason is that you register interest in some file
932	descriptor, but when it goes away, the operating system will silently drop	1037	descriptor, but when it goes away, the operating system will silently drop
933	this interest. If another file descriptor with the same number then is	1038	this interest. If another file descriptor with the same number then is
934	registered with libev, there is no efficient way to see that this is, in	1039	registered with libev, there is no efficient way to see that this is, in
…		…
943		1048
944	This is how one would do it normally anyway, the important point is that	1049	This is how one would do it normally anyway, the important point is that
945	the libev application should not optimise around libev but should leave	1050	the libev application should not optimise around libev but should leave
946	optimisations to libev.	1051	optimisations to libev.
947		1052
		1053	=head3 The special problem of dup'ed file descriptors
		1054
		1055	Some backends (e.g. epoll), cannot register events for file descriptors,
		1056	but only events for the underlying file descriptions. That means when you
		1057	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1058	events for them, only one file descriptor might actually receive events.
		1059
		1060	There is no workaround possible except not registering events
		1061	for potentially C<dup ()>'ed file descriptors, or to resort to
		1062	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1063
		1064	=head3 The special problem of fork
		1065
		1066	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1067	useless behaviour. Libev fully supports fork, but needs to be told about
		1068	it in the child.
		1069
		1070	To support fork in your programs, you either have to call
		1071	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1072	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1073	C<EVBACKEND_POLL>.
		1074
948		1075
949	=head3 Watcher-Specific Functions	1076	=head3 Watcher-Specific Functions
950		1077
951	=over 4	1078	=over 4
952		1079
…		…
965	=item int events [read-only]	1092	=item int events [read-only]
966		1093
967	The events being watched.	1094	The events being watched.
968		1095
969	=back	1096	=back
		1097
		1098	=head3 Examples
970		1099
971	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
972	readable, but only once. Since it is likely line-buffered, you could	1101	readable, but only once. Since it is likely line-buffered, you could
973	attempt to read a whole line in the callback.	1102	attempt to read a whole line in the callback.
974		1103
…		…
1027	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
1028	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
1029	the timer (because it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
1030	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
1031		1160
1032	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
1033		1162
1034	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
1035	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
1036		1165
1037	If the timer is pending, its pending status is cleared.	1166	If the timer is pending, its pending status is cleared.
…		…
1072	or C<ev_timer_again> is called and determines the next timeout (if any),	1201	or C<ev_timer_again> is called and determines the next timeout (if any),
1073	which is also when any modifications are taken into account.	1202	which is also when any modifications are taken into account.
1074		1203
1075	=back	1204	=back
1076		1205
		1206	=head3 Examples
		1207
1077	Example: Create a timer that fires after 60 seconds.	1208	Example: Create a timer that fires after 60 seconds.
1078		1209
1079	static void	1210	static void
1080	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1211	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1081	{	1212	{
…		…
1144	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
1145	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1146	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
1147	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
1148		1279
1149	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1150		1281
1151	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
1152	C<at + N * interval> time (for some integer N, which can also be negative)	1283	C<at + N * interval> time (for some integer N, which can also be negative)
1153	and then repeat, regardless of any time jumps.	1284	and then repeat, regardless of any time jumps.
1154		1285
…		…
1237		1368
1238	When active, contains the absolute time that the watcher is supposed to	1369	When active, contains the absolute time that the watcher is supposed to
1239	trigger next.	1370	trigger next.
1240		1371
1241	=back	1372	=back
		1373
		1374	=head3 Examples
1242		1375
1243	Example: Call a callback every hour, or, more precisely, whenever the	1376	Example: Call a callback every hour, or, more precisely, whenever the
1244	system clock is divisible by 3600. The callback invocation times have	1377	system clock is divisible by 3600. The callback invocation times have
1245	potentially a lot of jittering, but good long-term stability.	1378	potentially a lot of jittering, but good long-term stability.
1246		1379
…		…
1303		1436
1304	The signal the watcher watches out for.	1437	The signal the watcher watches out for.
1305		1438
1306	=back	1439	=back
1307		1440
		1441	=head3 Examples
		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
1308		1455
1309	=head2 C<ev_child> - watch out for process status changes	1456	=head2 C<ev_child> - watch out for process status changes
1310		1457
1311	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
1312	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
1313		1485
1314	=head3 Watcher-Specific Functions and Data Members	1486	=head3 Watcher-Specific Functions and Data Members
1315		1487
1316	=over 4	1488	=over 4
1317		1489
1318	=item ev_child_init (ev_child *, callback, int pid)	1490	=item ev_child_init (ev_child *, callback, int pid, int trace)
1319		1491
1320	=item ev_child_set (ev_child *, int pid)	1492	=item ev_child_set (ev_child *, int pid, int trace)
1321		1493
1322	Configures the watcher to wait for status changes of process C<pid> (or	1494	Configures the watcher to wait for status changes of process C<pid> (or
1323	I<any> process if C<pid> is specified as C<0>). The callback can look	1495	I<any> process if C<pid> is specified as C<0>). The callback can look
1324	at the C<rstatus> member of the C<ev_child> watcher structure to see	1496	at the C<rstatus> member of the C<ev_child> watcher structure to see
1325	the status word (use the macros from C<sys/wait.h> and see your systems	1497	the status word (use the macros from C<sys/wait.h> and see your systems
1326	C<waitpid> documentation). The C<rpid> member contains the pid of the	1498	C<waitpid> documentation). The C<rpid> member contains the pid of the
1327	process causing the status change.	1499	process causing the status change. C<trace> must be either C<0> (only
		1500	activate the watcher when the process terminates) or C<1> (additionally
		1501	activate the watcher when the process is stopped or continued).
1328		1502
1329	=item int pid [read-only]	1503	=item int pid [read-only]
1330		1504
1331	The process id this watcher watches out for, or C<0>, meaning any process id.	1505	The process id this watcher watches out for, or C<0>, meaning any process id.
1332		1506
…		…
1339	The process exit/trace status caused by C<rpid> (see your systems	1513	The process exit/trace status caused by C<rpid> (see your systems
1340	C<waitpid> and C<sys/wait.h> documentation for details).	1514	C<waitpid> and C<sys/wait.h> documentation for details).
1341		1515
1342	=back	1516	=back
1343		1517
1344	Example: Try to exit cleanly on SIGINT and SIGTERM.	1518	=head3 Examples
		1519
		1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
1345		1524
1346	static void	1525	static void
1347	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1526	child_cb (EV_P_ struct ev_child *w, int revents)
1348	{	1527	{
1349	ev_unloop (loop, EVUNLOOP_ALL);	1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1350	}	1530	}
1351		1531
1352	struct ev_signal signal_watcher;	1532	pid_t pid = fork ();
1353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1533
1354	ev_signal_start (loop, &sigint_cb);	1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
1355		1546
1356		1547
1357	=head2 C<ev_stat> - did the file attributes just change?	1548	=head2 C<ev_stat> - did the file attributes just change?
1358		1549
1359	This watches a filesystem path for attribute changes. That is, it calls	1550	This watches a filesystem path for attribute changes. That is, it calls
…		…
1388	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1579	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1389	to fall back to regular polling again even with inotify, but changes are	1580	to fall back to regular polling again even with inotify, but changes are
1390	usually detected immediately, and if the file exists there will be no	1581	usually detected immediately, and if the file exists there will be no
1391	polling.	1582	polling.
1392		1583
		1584	=head3 Inotify
		1585
		1586	When C<inotify (7)> support has been compiled into libev (generally only
		1587	available on Linux) and present at runtime, it will be used to speed up
		1588	change detection where possible. The inotify descriptor will be created lazily
		1589	when the first C<ev_stat> watcher is being started.
		1590
		1591	Inotify presense does not change the semantics of C<ev_stat> watchers
		1592	except that changes might be detected earlier, and in some cases, to avoid
		1593	making regular C<stat> calls. Even in the presense of inotify support
		1594	there are many cases where libev has to resort to regular C<stat> polling.
		1595
		1596	(There is no support for kqueue, as apparently it cannot be used to
		1597	implement this functionality, due to the requirement of having a file
		1598	descriptor open on the object at all times).
		1599
		1600	=head3 The special problem of stat time resolution
		1601
		1602	The C<stat ()> syscall only supports full-second resolution portably, and
		1603	even on systems where the resolution is higher, many filesystems still
		1604	only support whole seconds.
		1605
		1606	That means that, if the time is the only thing that changes, you might
		1607	miss updates: on the first update, C<ev_stat> detects a change and calls
		1608	your callback, which does something. When there is another update within
		1609	the same second, C<ev_stat> will be unable to detect it.
		1610
		1611	The solution to this is to delay acting on a change for a second (or till
		1612	the next second boundary), using a roughly one-second delay C<ev_timer>
		1613	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1614	is added to work around small timing inconsistencies of some operating
		1615	systems.
		1616
1393	=head3 Watcher-Specific Functions and Data Members	1617	=head3 Watcher-Specific Functions and Data Members
1394		1618
1395	=over 4	1619	=over 4
1396		1620
1397	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1621	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1406		1630
1407	The callback will be receive C<EV_STAT> when a change was detected,	1631	The callback will be receive C<EV_STAT> when a change was detected,
1408	relative to the attributes at the time the watcher was started (or the	1632	relative to the attributes at the time the watcher was started (or the
1409	last change was detected).	1633	last change was detected).
1410		1634
1411	=item ev_stat_stat (ev_stat *)	1635	=item ev_stat_stat (loop, ev_stat *)
1412		1636
1413	Updates the stat buffer immediately with new values. If you change the	1637	Updates the stat buffer immediately with new values. If you change the
1414	watched path in your callback, you could call this fucntion to avoid	1638	watched path in your callback, you could call this fucntion to avoid
1415	detecting this change (while introducing a race condition). Can also be	1639	detecting this change (while introducing a race condition). Can also be
1416	useful simply to find out the new values.	1640	useful simply to find out the new values.
…		…
1434	=item const char *path [read-only]	1658	=item const char *path [read-only]
1435		1659
1436	The filesystem path that is being watched.	1660	The filesystem path that is being watched.
1437		1661
1438	=back	1662	=back
		1663
		1664	=head3 Examples
1439		1665
1440	Example: Watch C</etc/passwd> for attribute changes.	1666	Example: Watch C</etc/passwd> for attribute changes.
1441		1667
1442	static void	1668	static void
1443	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1669	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1456	}	1682	}
1457		1683
1458	...	1684	...
1459	ev_stat passwd;	1685	ev_stat passwd;
1460		1686
1461	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1687	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1462	ev_stat_start (loop, &passwd);	1688	ev_stat_start (loop, &passwd);
		1689
		1690	Example: Like above, but additionally use a one-second delay so we do not
		1691	miss updates (however, frequent updates will delay processing, too, so
		1692	one might do the work both on C<ev_stat> callback invocation I<and> on
		1693	C<ev_timer> callback invocation).
		1694
		1695	static ev_stat passwd;
		1696	static ev_timer timer;
		1697
		1698	static void
		1699	timer_cb (EV_P_ ev_timer *w, int revents)
		1700	{
		1701	ev_timer_stop (EV_A_ w);
		1702
		1703	/* now it's one second after the most recent passwd change */
		1704	}
		1705
		1706	static void
		1707	stat_cb (EV_P_ ev_stat *w, int revents)
		1708	{
		1709	/* reset the one-second timer */
		1710	ev_timer_again (EV_A_ &timer);
		1711	}
		1712
		1713	...
		1714	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1715	ev_stat_start (loop, &passwd);
		1716	ev_timer_init (&timer, timer_cb, 0., 1.01);
1463		1717
1464		1718
1465	=head2 C<ev_idle> - when you've got nothing better to do...	1719	=head2 C<ev_idle> - when you've got nothing better to do...
1466		1720
1467	Idle watchers trigger events when no other events of the same or higher	1721	Idle watchers trigger events when no other events of the same or higher
…		…
1493	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1747	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1494	believe me.	1748	believe me.
1495		1749
1496	=back	1750	=back
1497		1751
		1752	=head3 Examples
		1753
1498	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1499	callback, free it. Also, use no error checking, as usual.	1755	callback, free it. Also, use no error checking, as usual.
1500		1756
1501	static void	1757	static void
1502	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1758	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1503	{	1759	{
1504	free (w);	1760	free (w);
1505	// now do something you wanted to do when the program has	1761	// now do something you wanted to do when the program has
1506	// no longer asnything immediate to do.	1762	// no longer anything immediate to do.
1507	}	1763	}
1508		1764
1509	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1510	ev_idle_init (idle_watcher, idle_cb);	1766	ev_idle_init (idle_watcher, idle_cb);
1511	ev_idle_start (loop, idle_cb);	1767	ev_idle_start (loop, idle_cb);
…		…
1553		1809
1554	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1810	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1555	priority, to ensure that they are being run before any other watchers	1811	priority, to ensure that they are being run before any other watchers
1556	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1812	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1557	too) should not activate ("feed") events into libev. While libev fully	1813	too) should not activate ("feed") events into libev. While libev fully
1558	supports this, they will be called before other C<ev_check> watchers did	1814	supports this, they will be called before other C<ev_check> watchers
1559	their job. As C<ev_check> watchers are often used to embed other event	1815	did their job. As C<ev_check> watchers are often used to embed other
1560	loops those other event loops might be in an unusable state until their	1816	(non-libev) event loops those other event loops might be in an unusable
1561	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1817	state until their C<ev_check> watcher ran (always remind yourself to
1562	others).	1818	coexist peacefully with others).
1563		1819
1564	=head3 Watcher-Specific Functions and Data Members	1820	=head3 Watcher-Specific Functions and Data Members
1565		1821
1566	=over 4	1822	=over 4
1567		1823
…		…
1572	Initialises and configures the prepare or check watcher - they have no	1828	Initialises and configures the prepare or check watcher - they have no
1573	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1574	macros, but using them is utterly, utterly and completely pointless.	1830	macros, but using them is utterly, utterly and completely pointless.
1575		1831
1576	=back	1832	=back
		1833
		1834	=head3 Examples
1577		1835
1578	There are a number of principal ways to embed other event loops or modules	1836	There are a number of principal ways to embed other event loops or modules
1579	into libev. Here are some ideas on how to include libadns into libev	1837	into libev. Here are some ideas on how to include libadns into libev
1580	(there is a Perl module named C<EV::ADNS> that does this, which you could	1838	(there is a Perl module named C<EV::ADNS> that does this, which you could
1581	use for an actually working example. Another Perl module named C<EV::Glib>	1839	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1750	portable one.	2008	portable one.
1751		2009
1752	So when you want to use this feature you will always have to be prepared	2010	So when you want to use this feature you will always have to be prepared
1753	that you cannot get an embeddable loop. The recommended way to get around	2011	that you cannot get an embeddable loop. The recommended way to get around
1754	this is to have a separate variables for your embeddable loop, try to	2012	this is to have a separate variables for your embeddable loop, try to
1755	create it, and if that fails, use the normal loop for everything:	2013	create it, and if that fails, use the normal loop for everything.
		2014
		2015	=head3 Watcher-Specific Functions and Data Members
		2016
		2017	=over 4
		2018
		2019	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		2020
		2021	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		2022
		2023	Configures the watcher to embed the given loop, which must be
		2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2025	invoked automatically, otherwise it is the responsibility of the callback
		2026	to invoke it (it will continue to be called until the sweep has been done,
		2027	if you do not want thta, you need to temporarily stop the embed watcher).
		2028
		2029	=item ev_embed_sweep (loop, ev_embed *)
		2030
		2031	Make a single, non-blocking sweep over the embedded loop. This works
		2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2033	apropriate way for embedded loops.
		2034
		2035	=item struct ev_loop *other [read-only]
		2036
		2037	The embedded event loop.
		2038
		2039	=back
		2040
		2041	=head3 Examples
		2042
		2043	Example: Try to get an embeddable event loop and embed it into the default
		2044	event loop. If that is not possible, use the default loop. The default
		2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2047	used).
1756		2048
1757	struct ev_loop *loop_hi = ev_default_init (0);	2049	struct ev_loop *loop_hi = ev_default_init (0);
1758	struct ev_loop *loop_lo = 0;	2050	struct ev_loop *loop_lo = 0;
1759	struct ev_embed embed;	2051	struct ev_embed embed;
1760		2052
…		…
1771	ev_embed_start (loop_hi, &embed);	2063	ev_embed_start (loop_hi, &embed);
1772	}	2064	}
1773	else	2065	else
1774	loop_lo = loop_hi;	2066	loop_lo = loop_hi;
1775		2067
1776	=head3 Watcher-Specific Functions and Data Members	2068	Example: Check if kqueue is available but not recommended and create
		2069	a kqueue backend for use with sockets (which usually work with any
		2070	kqueue implementation). Store the kqueue/socket-only event loop in
		2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1777		2072
1778	=over 4	2073	struct ev_loop *loop = ev_default_init (0);
		2074	struct ev_loop *loop_socket = 0;
		2075	struct ev_embed embed;
		2076
		2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2079	{
		2080	ev_embed_init (&embed, 0, loop_socket);
		2081	ev_embed_start (loop, &embed);
		2082	}
1779		2083
1780	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2084	if (!loop_socket)
		2085	loop_socket = loop;
1781		2086
1782	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	2087	// now use loop_socket for all sockets, and loop for everything else
1783
1784	Configures the watcher to embed the given loop, which must be
1785	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1786	invoked automatically, otherwise it is the responsibility of the callback
1787	to invoke it (it will continue to be called until the sweep has been done,
1788	if you do not want thta, you need to temporarily stop the embed watcher).
1789
1790	=item ev_embed_sweep (loop, ev_embed *)
1791
1792	Make a single, non-blocking sweep over the embedded loop. This works
1793	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1794	apropriate way for embedded loops.
1795
1796	=item struct ev_loop *loop [read-only]
1797
1798	The embedded event loop.
1799
1800	=back
1801		2088
1802		2089
1803	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1804		2091
1805	Fork watchers are called when a C<fork ()> was detected (usually because	2092	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1821	believe me.	2108	believe me.
1822		2109
1823	=back	2110	=back
1824		2111
1825		2112
		2113	=head2 C<ev_async> - how to wake up another event loop
		2114
		2115	In general, you cannot use an C<ev_loop> from multiple threads or other
		2116	asynchronous sources such as signal handlers (as opposed to multiple event
		2117	loops - those are of course safe to use in different threads).
		2118
		2119	Sometimes, however, you need to wake up another event loop you do not
		2120	control, for example because it belongs to another thread. This is what
		2121	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2122	can signal it by calling C<ev_async_send>, which is thread- and signal
		2123	safe.
		2124
		2125	This functionality is very similar to C<ev_signal> watchers, as signals,
		2126	too, are asynchronous in nature, and signals, too, will be compressed
		2127	(i.e. the number of callback invocations may be less than the number of
		2128	C<ev_async_sent> calls).
		2129
		2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2131	just the default loop.
		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
		2221	=over 4
		2222
		2223	=item ev_async_init (ev_async *, callback)
		2224
		2225	Initialises and configures the async watcher - it has no parameters of any
		2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2227	believe me.
		2228
		2229	=item ev_async_send (loop, ev_async *)
		2230
		2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2233	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2235	section below on what exactly this means).
		2236
		2237	This call incurs the overhead of a syscall only once per loop iteration,
		2238	so while the overhead might be noticable, it doesn't apply to repeated
		2239	calls to C<ev_async_send>.
		2240
		2241	=back
		2242
		2243
1826	=head1 OTHER FUNCTIONS	2244	=head1 OTHER FUNCTIONS
1827		2245
1828	There are some other functions of possible interest. Described. Here. Now.	2246	There are some other functions of possible interest. Described. Here. Now.
1829		2247
1830	=over 4	2248	=over 4
…		…
2057	Example: Define a class with an IO and idle watcher, start one of them in	2475	Example: Define a class with an IO and idle watcher, start one of them in
2058	the constructor.	2476	the constructor.
2059		2477
2060	class myclass	2478	class myclass
2061	{	2479	{
2062	ev_io io; void io_cb (ev::io &w, int revents);	2480	ev::io io; void io_cb (ev::io &w, int revents);
2063	ev_idle idle void idle_cb (ev::idle &w, int revents);	2481	ev:idle idle void idle_cb (ev::idle &w, int revents);
2064		2482
2065	myclass ();	2483	myclass (int fd)
2066	}
2067
2068	myclass::myclass (int fd)
2069	{	2484	{
2070	io .set <myclass, &myclass::io_cb > (this);	2485	io .set <myclass, &myclass::io_cb > (this);
2071	idle.set <myclass, &myclass::idle_cb> (this);	2486	idle.set <myclass, &myclass::idle_cb> (this);
2072		2487
2073	io.start (fd, ev::READ);	2488	io.start (fd, ev::READ);
		2489	}
2074	}	2490	};
2075		2491
2076		2492
2077	=head1 MACRO MAGIC	2493	=head1 MACRO MAGIC
2078		2494
2079	Libev can be compiled with a variety of options, the most fundamantal	2495	Libev can be compiled with a variety of options, the most fundamantal
…		…
2140	Libev can (and often is) directly embedded into host	2556	Libev can (and often is) directly embedded into host
2141	applications. Examples of applications that embed it include the Deliantra	2557	applications. Examples of applications that embed it include the Deliantra
2142	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2558	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2143	and rxvt-unicode.	2559	and rxvt-unicode.
2144		2560
2145	The goal is to enable you to just copy the neecssary files into your	2561	The goal is to enable you to just copy the necessary files into your
2146	source directory without having to change even a single line in them, so	2562	source directory without having to change even a single line in them, so
2147	you can easily upgrade by simply copying (or having a checked-out copy of	2563	you can easily upgrade by simply copying (or having a checked-out copy of
2148	libev somewhere in your source tree).	2564	libev somewhere in your source tree).
2149		2565
2150	=head2 FILESETS	2566	=head2 FILESETS
…		…
2240		2656
2241	If defined to be C<1>, libev will try to detect the availability of the	2657	If defined to be C<1>, libev will try to detect the availability of the
2242	monotonic clock option at both compiletime and runtime. Otherwise no use	2658	monotonic clock option at both compiletime and runtime. Otherwise no use
2243	of the monotonic clock option will be attempted. If you enable this, you	2659	of the monotonic clock option will be attempted. If you enable this, you
2244	usually have to link against librt or something similar. Enabling it when	2660	usually have to link against librt or something similar. Enabling it when
2245	the functionality isn't available is safe, though, althoguh you have	2661	the functionality isn't available is safe, though, although you have
2246	to make sure you link against any libraries where the C<clock_gettime>	2662	to make sure you link against any libraries where the C<clock_gettime>
2247	function is hiding in (often F<-lrt>).	2663	function is hiding in (often F<-lrt>).
2248		2664
2249	=item EV_USE_REALTIME	2665	=item EV_USE_REALTIME
2250		2666
2251	If defined to be C<1>, libev will try to detect the availability of the	2667	If defined to be C<1>, libev will try to detect the availability of the
2252	realtime clock option at compiletime (and assume its availability at	2668	realtime clock option at compiletime (and assume its availability at
2253	runtime if successful). Otherwise no use of the realtime clock option will	2669	runtime if successful). Otherwise no use of the realtime clock option will
2254	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2670	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2255	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2671	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2256	in the description of C<EV_USE_MONOTONIC>, though.	2672	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2673
		2674	=item EV_USE_NANOSLEEP
		2675
		2676	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2677	and will use it for delays. Otherwise it will use C<select ()>.
2257		2678
2258	=item EV_USE_SELECT	2679	=item EV_USE_SELECT
2259		2680
2260	If undefined or defined to be C<1>, libev will compile in support for the	2681	If undefined or defined to be C<1>, libev will compile in support for the
2261	C<select>(2) backend. No attempt at autodetection will be done: if no	2682	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2279	wants osf handles on win32 (this is the case when the select to	2700	wants osf handles on win32 (this is the case when the select to
2280	be used is the winsock select). This means that it will call	2701	be used is the winsock select). This means that it will call
2281	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2282	it is assumed that all these functions actually work on fds, even	2703	it is assumed that all these functions actually work on fds, even
2283	on win32. Should not be defined on non-win32 platforms.	2704	on win32. Should not be defined on non-win32 platforms.
		2705
		2706	=item EV_FD_TO_WIN32_HANDLE
		2707
		2708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2709	file descriptors to socket handles. When not defining this symbol (the
		2710	default), then libev will call C<_get_osfhandle>, which is usually
		2711	correct. In some cases, programs use their own file descriptor management,
		2712	in which case they can provide this function to map fds to socket handles.
2284		2713
2285	=item EV_USE_POLL	2714	=item EV_USE_POLL
2286		2715
2287	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2716	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2288	backend. Otherwise it will be enabled on non-win32 platforms. It	2717	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2322		2751
2323	If defined to be C<1>, libev will compile in support for the Linux inotify	2752	If defined to be C<1>, libev will compile in support for the Linux inotify
2324	interface to speed up C<ev_stat> watchers. Its actual availability will	2753	interface to speed up C<ev_stat> watchers. Its actual availability will
2325	be detected at runtime.	2754	be detected at runtime.
2326		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
2327	=item EV_H	2767	=item EV_H
2328		2768
2329	The name of the F<ev.h> header file used to include it. The default if	2769	The name of the F<ev.h> header file used to include it. The default if
2330	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2331	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2771	used to virtually rename the F<ev.h> header file in case of conflicts.
2332		2772
2333	=item EV_CONFIG_H	2773	=item EV_CONFIG_H
2334		2774
2335	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2775	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2336	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2776	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2337	C<EV_H>, above.	2777	C<EV_H>, above.
2338		2778
2339	=item EV_EVENT_H	2779	=item EV_EVENT_H
2340		2780
2341	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2781	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2342	of how the F<event.h> header can be found.	2782	of how the F<event.h> header can be found, the default is C<"event.h">.
2343		2783
2344	=item EV_PROTOTYPES	2784	=item EV_PROTOTYPES
2345		2785
2346	If defined to be C<0>, then F<ev.h> will not define any function	2786	If defined to be C<0>, then F<ev.h> will not define any function
2347	prototypes, but still define all the structs and other symbols. This is	2787	prototypes, but still define all the structs and other symbols. This is
…		…
2398	=item EV_FORK_ENABLE	2838	=item EV_FORK_ENABLE
2399		2839
2400	If undefined or defined to be C<1>, then fork watchers are supported. If	2840	If undefined or defined to be C<1>, then fork watchers are supported. If
2401	defined to be C<0>, then they are not.	2841	defined to be C<0>, then they are not.
2402		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
		2846	defined to be C<0>, then they are not.
		2847
2403	=item EV_MINIMAL	2848	=item EV_MINIMAL
2404		2849
2405	If you need to shave off some kilobytes of code at the expense of some	2850	If you need to shave off some kilobytes of code at the expense of some
2406	speed, define this symbol to C<1>. Currently only used for gcc to override	2851	speed, define this symbol to C<1>. Currently only used for gcc to override
2407	some inlining decisions, saves roughly 30% codesize of amd64.	2852	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2413	than enough. If you need to manage thousands of children you might want to	2858	than enough. If you need to manage thousands of children you might want to
2414	increase this value (I<must> be a power of two).	2859	increase this value (I<must> be a power of two).
2415		2860
2416	=item EV_INOTIFY_HASHSIZE	2861	=item EV_INOTIFY_HASHSIZE
2417		2862
2418	C<ev_staz> watchers use a small hash table to distribute workload by	2863	C<ev_stat> watchers use a small hash table to distribute workload by
2419	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2864	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2420	usually more than enough. If you need to manage thousands of C<ev_stat>	2865	usually more than enough. If you need to manage thousands of C<ev_stat>
2421	watchers you might want to increase this value (I<must> be a power of	2866	watchers you might want to increase this value (I<must> be a power of
2422	two).	2867	two).
2423		2868
…		…
2440		2885
2441	=item ev_set_cb (ev, cb)	2886	=item ev_set_cb (ev, cb)
2442		2887
2443	Can be used to change the callback member declaration in each watcher,	2888	Can be used to change the callback member declaration in each watcher,
2444	and the way callbacks are invoked and set. Must expand to a struct member	2889	and the way callbacks are invoked and set. Must expand to a struct member
2445	definition and a statement, respectively. See the F<ev.v> header file for	2890	definition and a statement, respectively. See the F<ev.h> header file for
2446	their default definitions. One possible use for overriding these is to	2891	their default definitions. One possible use for overriding these is to
2447	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2892	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2448	method calls instead of plain function calls in C++.	2893	method calls instead of plain function calls in C++.
		2894
		2895	=head2 EXPORTED API SYMBOLS
		2896
		2897	If you need to re-export the API (e.g. via a dll) and you need a list of
		2898	exported symbols, you can use the provided F<Symbol.*> files which list
		2899	all public symbols, one per line:
		2900
		2901	Symbols.ev for libev proper
		2902	Symbols.event for the libevent emulation
		2903
		2904	This can also be used to rename all public symbols to avoid clashes with
		2905	multiple versions of libev linked together (which is obviously bad in
		2906	itself, but sometimes it is inconvinient to avoid this).
		2907
		2908	A sed command like this will create wrapper C<#define>'s that you need to
		2909	include before including F<ev.h>:
		2910
		2911	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2912
		2913	This would create a file F<wrap.h> which essentially looks like this:
		2914
		2915	#define ev_backend myprefix_ev_backend
		2916	#define ev_check_start myprefix_ev_check_start
		2917	#define ev_check_stop myprefix_ev_check_stop
		2918	...
2449		2919
2450	=head2 EXAMPLES	2920	=head2 EXAMPLES
2451		2921
2452	For a real-world example of a program the includes libev	2922	For a real-world example of a program the includes libev
2453	verbatim, you can have a look at the EV perl module	2923	verbatim, you can have a look at the EV perl module
…		…
2494		2964
2495	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2965	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2496		2966
2497	This means that, when you have a watcher that triggers in one hour and	2967	This means that, when you have a watcher that triggers in one hour and
2498	there are 100 watchers that would trigger before that then inserting will	2968	there are 100 watchers that would trigger before that then inserting will
2499	have to skip those 100 watchers.	2969	have to skip roughly seven (C<ld 100>) of these watchers.
2500		2970
2501	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2502		2972
2503	That means that for changing a timer costs less than removing/adding them	2973	That means that changing a timer costs less than removing/adding them
2504	as only the relative motion in the event queue has to be paid for.	2974	as only the relative motion in the event queue has to be paid for.
2505		2975
2506	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2507		2977
2508	These just add the watcher into an array or at the head of a list.	2978	These just add the watcher into an array or at the head of a list.
		2979
2509	=item Stopping check/prepare/idle watchers: O(1)	2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2510		2981
2511	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2512		2983
2513	These watchers are stored in lists then need to be walked to find the	2984	These watchers are stored in lists then need to be walked to find the
2514	correct watcher to remove. The lists are usually short (you don't usually	2985	correct watcher to remove. The lists are usually short (you don't usually
2515	have many watchers waiting for the same fd or signal).	2986	have many watchers waiting for the same fd or signal).
2516		2987
2517	=item Finding the next timer per loop iteration: O(1)	2988	=item Finding the next timer in each loop iteration: O(1)
		2989
		2990	By virtue of using a binary heap, the next timer is always found at the
		2991	beginning of the storage array.
2518		2992
2519	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2993	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2520		2994
2521	A change means an I/O watcher gets started or stopped, which requires	2995	A change means an I/O watcher gets started or stopped, which requires
2522	libev to recalculate its status (and possibly tell the kernel).	2996	libev to recalculate its status (and possibly tell the kernel, depending
		2997	on backend and wether C<ev_io_set> was used).
2523		2998
2524	=item Activating one watcher: O(1)	2999	=item Activating one watcher (putting it into the pending state): O(1)
2525		3000
2526	=item Priority handling: O(number_of_priorities)	3001	=item Priority handling: O(number_of_priorities)
2527		3002
2528	Priorities are implemented by allocating some space for each	3003	Priorities are implemented by allocating some space for each
2529	priority. When doing priority-based operations, libev usually has to	3004	priority. When doing priority-based operations, libev usually has to
2530	linearly search all the priorities.	3005	linearly search all the priorities, but starting/stopping and activating
		3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
2531		3017
2532	=back	3018	=back
2533		3019
2534		3020
		3021	=head1 Win32 platform limitations and workarounds
		3022
		3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3024	requires, and its I/O model is fundamentally incompatible with the POSIX
		3025	model. Libev still offers limited functionality on this platform in
		3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3027	descriptors. This only applies when using Win32 natively, not when using
		3028	e.g. cygwin.
		3029
		3030	There is no supported compilation method available on windows except
		3031	embedding it into other applications.
		3032
		3033	Due to the many, low, and arbitrary limits on the win32 platform and the
		3034	abysmal performance of winsockets, using a large number of sockets is not
		3035	recommended (and not reasonable). If your program needs to use more than
		3036	a hundred or so sockets, then likely it needs to use a totally different
		3037	implementation for windows, as libev offers the POSIX model, which cannot
		3038	be implemented efficiently on windows (microsoft monopoly games).
		3039
		3040	=over 4
		3041
		3042	=item The winsocket select function
		3043
		3044	The winsocket C<select> function doesn't follow POSIX in that it requires
		3045	socket I<handles> and not socket I<file descriptors>. This makes select
		3046	very inefficient, and also requires a mapping from file descriptors
		3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3049	symbols for more info.
		3050
		3051	The configuration for a "naked" win32 using the microsoft runtime
		3052	libraries and raw winsocket select is:
		3053
		3054	#define EV_USE_SELECT 1
		3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3056
		3057	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3058	complexity in the O(n²) range when using win32.
		3059
		3060	=item Limited number of file descriptors
		3061
		3062	Windows has numerous arbitrary (and low) limits on things. Early versions
		3063	of winsocket's select only supported waiting for a max. of C<64> handles
		3064	(probably owning to the fact that all windows kernels can only wait for
		3065	C<64> things at the same time internally; microsoft recommends spawning a
		3066	chain of threads and wait for 63 handles and the previous thread in each).
		3067
		3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3069	to some high number (e.g. C<2048>) before compiling the winsocket select
		3070	call (which might be in libev or elsewhere, for example, perl does its own
		3071	select emulation on windows).
		3072
		3073	Another limit is the number of file descriptors in the microsoft runtime
		3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3075	or something like this inside microsoft). You can increase this by calling
		3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3077	arbitrary limit), but is broken in many versions of the microsoft runtime
		3078	libraries.
		3079
		3080	This might get you to about C<512> or C<2048> sockets (depending on
		3081	windows version and/or the phase of the moon). To get more, you need to
		3082	wrap all I/O functions and provide your own fd management, but the cost of
		3083	calling select (O(n²)) will likely make this unworkable.
		3084
		3085	=back
		3086
		3087
2535	=head1 AUTHOR	3088	=head1 AUTHOR
2536		3089
2537	Marc Lehmann <libev@schmorp.de>.	3090	Marc Lehmann <libev@schmorp.de>.
2538		3091

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Comparing libev/ev.pod (file contents): Revision 1.88 by ayin, Tue Dec 18 13:06:18 2007 UTC vs. Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.88 by ayin, Tue Dec 18 13:06:18 2007 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC