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

Comparing libev/ev.pod (file contents):
Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC vs.
Revision 1.136 by root, Thu Mar 13 13:06:16 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	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	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	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	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	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
115		130
116	Returns the current time as libev would use it. Please note that the	131	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	132	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	133	you actually want to know.
119		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
120	=item int ev_version_major ()	141	=item int ev_version_major ()
121		142
122	=item int ev_version_minor ()	143	=item int ev_version_minor ()
123		144
124	You can find out the major and minor ABI version numbers of the library	145	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).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		276
256	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
257	function.	278	function.
258		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
259	The flags argument can be used to specify special behaviour or specific	287	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>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
261		289
262	The following flags are supported:	290	The following flags are supported:
263		291
…		…
284	enabling this flag.	312	enabling this flag.
285		313
286	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
287	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
288	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
289	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
290	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
291	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
292		320
293	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
294	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
295	flag.	323	flag.
…		…
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		329
302	This is your standard select(2) backend. Not I<completely> standard, as	330	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,	331	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	332	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	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
306	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
307		342
308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309		344
310	And this is your standard poll(2) backend. It's more complicated than	345	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	346	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	347	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).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
314		351
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		353
317	For few fds, this backend is a bit little slower than poll and select,	354	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	355	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),	356	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	357	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	358	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	359	cases and rewiring a syscall per fd change, no fork support and bad
323	support for dup:	360	support for dup.
324		361
325	While stopping, setting and starting an I/O watcher in the same iteration	362	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	363	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	364	(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	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
330		367
331	Please note that epoll sometimes generates spurious notifications, so you	368	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	369	need to use non-blocking I/O or other means to avoid blocking when no data
333	(or space) is available.	370	(or space) is available.
334		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		380
337	Kqueue deserves special mention, as at the time of this writing, it	381	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	382	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	383	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"	384	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	385	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)	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	387	system like NetBSD.
345		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
		392
346	It scales in the same way as the epoll backend, but the interface to the	393	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,	394	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	395	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	396	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	397	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
352		408
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		410
355	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
356		415
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		417
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	418	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)).	419	it's really slow, but it still scales very well (O(active_fds)).
361		420
362	Please note that solaris event ports can deliver a lot of spurious	421	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	422	notifications, so you need to use non-blocking I/O or other means to avoid
364	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
365		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
		433
366	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
367		435
368	Try all backends (even potentially broken ones that wouldn't be tried	436	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	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		439
		440	It is definitely not recommended to use this flag.
		441
372	=back	442	=back
373		443
374	If one or more of these are ored into the flags value, then only these	444	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	445	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	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		447
379	The most typical usage is like this:	448	The most typical usage is like this:
380		449
381	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
429	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
430	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
431		500
432	=item ev_default_fork ()	501	=item ev_default_fork ()
433		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	504	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	505	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	506	the child process (or both child and parent, but that again makes little
437	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
438		509
439	You I<must> call this function in the child process after forking if and	510	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	511	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.	512	you just fork+exec, you don't have to call it at all.
442		513
443	The function itself is quite fast and it's usually not a problem to call	514	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	515	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>:	516	quite nicely into a call to C<pthread_atfork>:
446		517
447	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
448		519
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
453	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
454		521
455	Like C<ev_default_fork>, but acts on an event loop created by	522	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	523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
457	after fork, and how you do this is entirely your own problem.	524	after fork, and how you do this is entirely your own problem.
		525
		526	=item int ev_is_default_loop (loop)
		527
		528	Returns true when the given loop actually is the default loop, false otherwise.
458		529
459	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
460		531
461	Returns the count of loop iterations for the loop, which is identical to	532	Returns the count of loop iterations for the loop, which is identical to
462	the number of times libev did poll for new events. It starts at C<0> and	533	the number of times libev did poll for new events. It starts at C<0> and
…		…
507	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
508		579
509	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
510		581
511	- Before the first iteration, call any pending watchers.	582	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	583	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	584	- If a fork was detected, queue and call all fork watchers.
		585	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	588	- Update the "event loop time".
517	- Calculate for how long to block.	589	- Calculate for how long to sleep or block, if at all
		590	(active idle watchers, EVLOOP_NONBLOCK or not having
		591	any active watchers at all will result in not sleeping).
		592	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	596	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	599	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	600	- 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	601	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
530		606
531	Example: Queue some jobs and then loop until no events are outsanding	607	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	608	anymore.
533		609
534	... queue jobs here, make sure they register event watchers as long	610	... 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..)	611	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
540		616
541	Can be used to make a call to C<ev_loop> return early (but only after it	617	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	618	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	619	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.	620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		621
		622	This "unloop state" will be cleared when entering C<ev_loop> again.
545		623
546	=item ev_ref (loop)	624	=item ev_ref (loop)
547		625
548	=item ev_unref (loop)	626	=item ev_unref (loop)
549		627
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	632	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	633	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	634	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	635	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	636	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>.	637	libraries. Just remember to I<unref after start> and I<ref before stop>
		638	(but only if the watcher wasn't active before, or was active before,
		639	respectively).
560		640
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	642	running when nothing else is active.
563		643
564	struct ev_signal exitsig;	644	struct ev_signal exitsig;
…		…
568		648
569	Example: For some weird reason, unregister the above signal handler again.	649	Example: For some weird reason, unregister the above signal handler again.
570		650
571	ev_ref (loop);	651	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	652	ev_signal_stop (loop, &exitsig);
		653
		654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		655
		656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		657
		658	These advanced functions influence the time that libev will spend waiting
		659	for events. Both are by default C<0>, meaning that libev will try to
		660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		661
		662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		663	allows libev to delay invocation of I/O and timer/periodic callbacks to
		664	increase efficiency of loop iterations.
		665
		666	The background is that sometimes your program runs just fast enough to
		667	handle one (or very few) event(s) per loop iteration. While this makes
		668	the program responsive, it also wastes a lot of CPU time to poll for new
		669	events, especially with backends like C<select ()> which have a high
		670	overhead for the actual polling but can deliver many events at once.
		671
		672	By setting a higher I<io collect interval> you allow libev to spend more
		673	time collecting I/O events, so you can handle more events per iteration,
		674	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		675	C<ev_timer>) will be not affected. Setting this to a non-null value will
		676	introduce an additional C<ev_sleep ()> call into most loop iterations.
		677
		678	Likewise, by setting a higher I<timeout collect interval> you allow libev
		679	to spend more time collecting timeouts, at the expense of increased
		680	latency (the watcher callback will be called later). C<ev_io> watchers
		681	will not be affected. Setting this to a non-null value will not introduce
		682	any overhead in libev.
		683
		684	Many (busy) programs can usually benefit by setting the io collect
		685	interval to a value near C<0.1> or so, which is often enough for
		686	interactive servers (of course not for games), likewise for timeouts. It
		687	usually doesn't make much sense to set it to a lower value than C<0.01>,
		688	as this approsaches the timing granularity of most systems.
573		689
574	=back	690	=back
575		691
576		692
577	=head1 ANATOMY OF A WATCHER	693	=head1 ANATOMY OF A WATCHER
…		…
676		792
677	=item C<EV_FORK>	793	=item C<EV_FORK>
678		794
679	The event loop has been resumed in the child process after fork (see	795	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	796	C<ev_fork>).
		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
681		801
682	=item C<EV_ERROR>	802	=item C<EV_ERROR>
683		803
684	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	805	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	1023	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	1024	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	1025	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1026	required if you know what you are doing).
907		1027
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	1028	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	1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1030	C<EVBACKEND_POLL>).
917		1031
918	Another thing you have to watch out for is that it is quite easy to	1032	Another thing you have to watch out for is that it is quite easy to
…		…
949		1063
950	This is how one would do it normally anyway, the important point is that	1064	This is how one would do it normally anyway, the important point is that
951	the libev application should not optimise around libev but should leave	1065	the libev application should not optimise around libev but should leave
952	optimisations to libev.	1066	optimisations to libev.
953		1067
954	=head3 Ths special problem of dup'ed file descriptors	1068	=head3 The special problem of dup'ed file descriptors
955		1069
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1070	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1071	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	1072	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1073	events for them, only one file descriptor might actually receive events.
960		1074
961	There is no workaorund possible except not registering events	1075	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1076	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1077	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1078
965	=head3 The special problem of fork	1079	=head3 The special problem of fork
966		1080
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1081	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
993	=item int events [read-only]	1107	=item int events [read-only]
994		1108
995	The events being watched.	1109	The events being watched.
996		1110
997	=back	1111	=back
		1112
		1113	=head3 Examples
998		1114
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1115	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	1116	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1117	attempt to read a whole line in the callback.
1002		1118
…		…
1055	configure a timer to trigger every 10 seconds, then it will trigger at	1171	configure a timer to trigger every 10 seconds, then it will trigger at
1056	exactly 10 second intervals. If, however, your program cannot keep up with	1172	exactly 10 second intervals. If, however, your program cannot keep up with
1057	the timer (because it takes longer than those 10 seconds to do stuff) the	1173	the timer (because it takes longer than those 10 seconds to do stuff) the
1058	timer will not fire more than once per event loop iteration.	1174	timer will not fire more than once per event loop iteration.
1059		1175
1060	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
1061		1177
1062	This will act as if the timer timed out and restart it again if it is	1178	This will act as if the timer timed out and restart it again if it is
1063	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
1064		1180
1065	If the timer is pending, its pending status is cleared.	1181	If the timer is pending, its pending status is cleared.
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1216	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.	1217	which is also when any modifications are taken into account.
1102		1218
1103	=back	1219	=back
1104		1220
		1221	=head3 Examples
		1222
1105	Example: Create a timer that fires after 60 seconds.	1223	Example: Create a timer that fires after 60 seconds.
1106		1224
1107	static void	1225	static void
1108	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1226	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1109	{	1227	{
…		…
1172	In this configuration the watcher triggers an event at the wallclock time	1290	In this configuration the watcher triggers an event at the wallclock time
1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1174	that is, if it is to be run at January 1st 2011 then it will run when the	1292	that is, if it is to be run at January 1st 2011 then it will run when the
1175	system time reaches or surpasses this time.	1293	system time reaches or surpasses this time.
1176		1294
1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1178		1296
1179	In this mode the watcher will always be scheduled to time out at the next	1297	In this mode the watcher will always be scheduled to time out at the next
1180	C<at + N * interval> time (for some integer N, which can also be negative)	1298	C<at + N * interval> time (for some integer N, which can also be negative)
1181	and then repeat, regardless of any time jumps.	1299	and then repeat, regardless of any time jumps.
1182		1300
…		…
1265		1383
1266	When active, contains the absolute time that the watcher is supposed to	1384	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1385	trigger next.
1268		1386
1269	=back	1387	=back
		1388
		1389	=head3 Examples
1270		1390
1271	Example: Call a callback every hour, or, more precisely, whenever the	1391	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1392	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1393	potentially a lot of jittering, but good long-term stability.
1274		1394
…		…
1314	with the kernel (thus it coexists with your own signal handlers as long	1434	with the kernel (thus it coexists with your own signal handlers as long
1315	as you don't register any with libev). Similarly, when the last signal	1435	as you don't register any with libev). Similarly, when the last signal
1316	watcher for a signal is stopped libev will reset the signal handler to	1436	watcher for a signal is stopped libev will reset the signal handler to
1317	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1318		1438
		1439	If possible and supported, libev will install its handlers with
		1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1441	interrupted. If you have a problem with syscalls getting interrupted by
		1442	signals you can block all signals in an C<ev_check> watcher and unblock
		1443	them in an C<ev_prepare> watcher.
		1444
1319	=head3 Watcher-Specific Functions and Data Members	1445	=head3 Watcher-Specific Functions and Data Members
1320		1446
1321	=over 4	1447	=over 4
1322		1448
1323	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1331		1457
1332	The signal the watcher watches out for.	1458	The signal the watcher watches out for.
1333		1459
1334	=back	1460	=back
1335		1461
		1462	=head3 Examples
		1463
		1464	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1465
		1466	static void
		1467	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1468	{
		1469	ev_unloop (loop, EVUNLOOP_ALL);
		1470	}
		1471
		1472	struct ev_signal signal_watcher;
		1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1474	ev_signal_start (loop, &sigint_cb);
		1475
1336		1476
1337	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1338		1478
1339	Child watchers trigger when your process receives a SIGCHLD in response to	1479	Child watchers trigger when your process receives a SIGCHLD in response to
1340	some child status changes (most typically when a child of yours dies).	1480	some child status changes (most typically when a child of yours dies). It
		1481	is permissible to install a child watcher I<after> the child has been
		1482	forked (which implies it might have already exited), as long as the event
		1483	loop isn't entered (or is continued from a watcher).
		1484
		1485	Only the default event loop is capable of handling signals, and therefore
		1486	you can only rgeister child watchers in the default event loop.
		1487
		1488	=head3 Process Interaction
		1489
		1490	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1491	initialised. This is necessary to guarantee proper behaviour even if
		1492	the first child watcher is started after the child exits. The occurance
		1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1494	synchronously as part of the event loop processing. Libev always reaps all
		1495	children, even ones not watched.
		1496
		1497	=head3 Overriding the Built-In Processing
		1498
		1499	Libev offers no special support for overriding the built-in child
		1500	processing, but if your application collides with libev's default child
		1501	handler, you can override it easily by installing your own handler for
		1502	C<SIGCHLD> after initialising the default loop, and making sure the
		1503	default loop never gets destroyed. You are encouraged, however, to use an
		1504	event-based approach to child reaping and thus use libev's support for
		1505	that, so other libev users can use C<ev_child> watchers freely.
1341		1506
1342	=head3 Watcher-Specific Functions and Data Members	1507	=head3 Watcher-Specific Functions and Data Members
1343		1508
1344	=over 4	1509	=over 4
1345		1510
1346	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1512
1348	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1349		1514
1350	Configures the watcher to wait for status changes of process C<pid> (or	1515	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	1516	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	1517	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	1518	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	1519	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1520	process causing the status change. C<trace> must be either C<0> (only
		1521	activate the watcher when the process terminates) or C<1> (additionally
		1522	activate the watcher when the process is stopped or continued).
1356		1523
1357	=item int pid [read-only]	1524	=item int pid [read-only]
1358		1525
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1526	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1527
…		…
1367	The process exit/trace status caused by C<rpid> (see your systems	1534	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1535	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1536
1370	=back	1537	=back
1371		1538
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1539	=head3 Examples
		1540
		1541	Example: C<fork()> a new process and install a child handler to wait for
		1542	its completion.
		1543
		1544	ev_child cw;
1373		1545
1374	static void	1546	static void
1375	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1376	{	1548	{
1377	ev_unloop (loop, EVUNLOOP_ALL);	1549	ev_child_stop (EV_A_ w);
		1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1378	}	1551	}
1379		1552
1380	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1382	ev_signal_start (loop, &sigint_cb);	1555	if (pid < 0)
		1556	// error
		1557	else if (pid == 0)
		1558	{
		1559	// the forked child executes here
		1560	exit (1);
		1561	}
		1562	else
		1563	{
		1564	ev_child_init (&cw, child_cb, pid, 0);
		1565	ev_child_start (EV_DEFAULT_ &cw);
		1566	}
1383		1567
1384		1568
1385	=head2 C<ev_stat> - did the file attributes just change?	1569	=head2 C<ev_stat> - did the file attributes just change?
1386		1570
1387	This watches a filesystem path for attribute changes. That is, it calls	1571	This watches a filesystem path for attribute changes. That is, it calls
…		…
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1600	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	1601	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	1602	usually detected immediately, and if the file exists there will be no
1419	polling.	1603	polling.
1420		1604
		1605	=head3 Inotify
		1606
		1607	When C<inotify (7)> support has been compiled into libev (generally only
		1608	available on Linux) and present at runtime, it will be used to speed up
		1609	change detection where possible. The inotify descriptor will be created lazily
		1610	when the first C<ev_stat> watcher is being started.
		1611
		1612	Inotify presense does not change the semantics of C<ev_stat> watchers
		1613	except that changes might be detected earlier, and in some cases, to avoid
		1614	making regular C<stat> calls. Even in the presense of inotify support
		1615	there are many cases where libev has to resort to regular C<stat> polling.
		1616
		1617	(There is no support for kqueue, as apparently it cannot be used to
		1618	implement this functionality, due to the requirement of having a file
		1619	descriptor open on the object at all times).
		1620
		1621	=head3 The special problem of stat time resolution
		1622
		1623	The C<stat ()> syscall only supports full-second resolution portably, and
		1624	even on systems where the resolution is higher, many filesystems still
		1625	only support whole seconds.
		1626
		1627	That means that, if the time is the only thing that changes, you might
		1628	miss updates: on the first update, C<ev_stat> detects a change and calls
		1629	your callback, which does something. When there is another update within
		1630	the same second, C<ev_stat> will be unable to detect it.
		1631
		1632	The solution to this is to delay acting on a change for a second (or till
		1633	the next second boundary), using a roughly one-second delay C<ev_timer>
		1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1635	is added to work around small timing inconsistencies of some operating
		1636	systems.
		1637
1421	=head3 Watcher-Specific Functions and Data Members	1638	=head3 Watcher-Specific Functions and Data Members
1422		1639
1423	=over 4	1640	=over 4
1424		1641
1425	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1642	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
…		…
1434		1651
1435	The callback will be receive C<EV_STAT> when a change was detected,	1652	The callback will be receive C<EV_STAT> when a change was detected,
1436	relative to the attributes at the time the watcher was started (or the	1653	relative to the attributes at the time the watcher was started (or the
1437	last change was detected).	1654	last change was detected).
1438		1655
1439	=item ev_stat_stat (ev_stat *)	1656	=item ev_stat_stat (loop, ev_stat *)
1440		1657
1441	Updates the stat buffer immediately with new values. If you change the	1658	Updates the stat buffer immediately with new values. If you change the
1442	watched path in your callback, you could call this fucntion to avoid	1659	watched path in your callback, you could call this fucntion to avoid
1443	detecting this change (while introducing a race condition). Can also be	1660	detecting this change (while introducing a race condition). Can also be
1444	useful simply to find out the new values.	1661	useful simply to find out the new values.
…		…
1462	=item const char *path [read-only]	1679	=item const char *path [read-only]
1463		1680
1464	The filesystem path that is being watched.	1681	The filesystem path that is being watched.
1465		1682
1466	=back	1683	=back
		1684
		1685	=head3 Examples
1467		1686
1468	Example: Watch C</etc/passwd> for attribute changes.	1687	Example: Watch C</etc/passwd> for attribute changes.
1469		1688
1470	static void	1689	static void
1471	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1690	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1484	}	1703	}
1485		1704
1486	...	1705	...
1487	ev_stat passwd;	1706	ev_stat passwd;
1488		1707
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1709	ev_stat_start (loop, &passwd);
		1710
		1711	Example: Like above, but additionally use a one-second delay so we do not
		1712	miss updates (however, frequent updates will delay processing, too, so
		1713	one might do the work both on C<ev_stat> callback invocation I<and> on
		1714	C<ev_timer> callback invocation).
		1715
		1716	static ev_stat passwd;
		1717	static ev_timer timer;
		1718
		1719	static void
		1720	timer_cb (EV_P_ ev_timer *w, int revents)
		1721	{
		1722	ev_timer_stop (EV_A_ w);
		1723
		1724	/* now it's one second after the most recent passwd change */
		1725	}
		1726
		1727	static void
		1728	stat_cb (EV_P_ ev_stat *w, int revents)
		1729	{
		1730	/* reset the one-second timer */
		1731	ev_timer_again (EV_A_ &timer);
		1732	}
		1733
		1734	...
		1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1736	ev_stat_start (loop, &passwd);
		1737	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1738
1492		1739
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1740	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1741
1495	Idle watchers trigger events when no other events of the same or higher	1742	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,	1768	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1769	believe me.
1523		1770
1524	=back	1771	=back
1525		1772
		1773	=head3 Examples
		1774
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1776	callback, free it. Also, use no error checking, as usual.
1528		1777
1529	static void	1778	static void
1530	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1779	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1531	{	1780	{
1532	free (w);	1781	free (w);
1533	// now do something you wanted to do when the program has	1782	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1783	// no longer anything immediate to do.
1535	}	1784	}
1536		1785
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1787	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1788	ev_idle_start (loop, idle_cb);
…		…
1581		1830
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1831	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	1832	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,	1833	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	1834	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	1835	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	1836	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	1837	(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	1838	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1839	coexist peacefully with others).
1591		1840
1592	=head3 Watcher-Specific Functions and Data Members	1841	=head3 Watcher-Specific Functions and Data Members
1593		1842
1594	=over 4	1843	=over 4
1595		1844
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1849	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>	1850	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.	1851	macros, but using them is utterly, utterly and completely pointless.
1603		1852
1604	=back	1853	=back
		1854
		1855	=head3 Examples
1605		1856
1606	There are a number of principal ways to embed other event loops or modules	1857	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	1858	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	1859	(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>	1860	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	1985	=head2 C<ev_embed> - when one backend isn't enough...
1735		1986
1736	This is a rather advanced watcher type that lets you embed one event loop	1987	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	1988	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	1989	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	1990	fashion and must not be used).
1740		1991
1741	There are primarily two reasons you would want that: work around bugs and	1992	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	1993	prioritise I/O.
1743		1994
1744	As an example for a bug workaround, the kqueue backend might only support	1995	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	2029	portable one.
1779		2030
1780	So when you want to use this feature you will always have to be prepared	2031	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	2032	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	2033	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:	2034	create it, and if that fails, use the normal loop for everything.
		2035
		2036	=head3 Watcher-Specific Functions and Data Members
		2037
		2038	=over 4
		2039
		2040	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		2041
		2042	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		2043
		2044	Configures the watcher to embed the given loop, which must be
		2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2046	invoked automatically, otherwise it is the responsibility of the callback
		2047	to invoke it (it will continue to be called until the sweep has been done,
		2048	if you do not want thta, you need to temporarily stop the embed watcher).
		2049
		2050	=item ev_embed_sweep (loop, ev_embed *)
		2051
		2052	Make a single, non-blocking sweep over the embedded loop. This works
		2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2054	apropriate way for embedded loops.
		2055
		2056	=item struct ev_loop *other [read-only]
		2057
		2058	The embedded event loop.
		2059
		2060	=back
		2061
		2062	=head3 Examples
		2063
		2064	Example: Try to get an embeddable event loop and embed it into the default
		2065	event loop. If that is not possible, use the default loop. The default
		2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2068	used).
1784		2069
1785	struct ev_loop *loop_hi = ev_default_init (0);	2070	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	2071	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	2072	struct ev_embed embed;
1788		2073
…		…
1799	ev_embed_start (loop_hi, &embed);	2084	ev_embed_start (loop_hi, &embed);
1800	}	2085	}
1801	else	2086	else
1802	loop_lo = loop_hi;	2087	loop_lo = loop_hi;
1803		2088
1804	=head2 Portability notes	2089	Example: Check if kqueue is available but not recommended and create
		2090	a kqueue backend for use with sockets (which usually work with any
		2091	kqueue implementation). Store the kqueue/socket-only event loop in
		2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2093
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2094	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2095	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2096	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2097
1810	will always eport the epoll fd as ready, even when no events are pending.	2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2100	{
		2101	ev_embed_init (&embed, 0, loop_socket);
		2102	ev_embed_start (loop, &embed);
		2103	}
1811		2104
1812	While libev allows embedding these backends (they are contained in	2105	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2106	loop_socket = loop;
1814	work.
1815		2107
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2108	// 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		2109
1846		2110
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2112
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2113	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2129	believe me.
1866		2130
1867	=back	2131	=back
1868		2132
1869		2133
		2134	=head2 C<ev_async> - how to wake up another event loop
		2135
		2136	In general, you cannot use an C<ev_loop> from multiple threads or other
		2137	asynchronous sources such as signal handlers (as opposed to multiple event
		2138	loops - those are of course safe to use in different threads).
		2139
		2140	Sometimes, however, you need to wake up another event loop you do not
		2141	control, for example because it belongs to another thread. This is what
		2142	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2143	can signal it by calling C<ev_async_send>, which is thread- and signal
		2144	safe.
		2145
		2146	This functionality is very similar to C<ev_signal> watchers, as signals,
		2147	too, are asynchronous in nature, and signals, too, will be compressed
		2148	(i.e. the number of callback invocations may be less than the number of
		2149	C<ev_async_sent> calls).
		2150
		2151	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2152	just the default loop.
		2153
		2154	=head3 Queueing
		2155
		2156	C<ev_async> does not support queueing of data in any way. The reason
		2157	is that the author does not know of a simple (or any) algorithm for a
		2158	multiple-writer-single-reader queue that works in all cases and doesn't
		2159	need elaborate support such as pthreads.
		2160
		2161	That means that if you want to queue data, you have to provide your own
		2162	queue. But at least I can tell you would implement locking around your
		2163	queue:
		2164
		2165	=over 4
		2166
		2167	=item queueing from a signal handler context
		2168
		2169	To implement race-free queueing, you simply add to the queue in the signal
		2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2171	some fictitiuous SIGUSR1 handler:
		2172
		2173	static ev_async mysig;
		2174
		2175	static void
		2176	sigusr1_handler (void)
		2177	{
		2178	sometype data;
		2179
		2180	// no locking etc.
		2181	queue_put (data);
		2182	ev_async_send (EV_DEFAULT_ &mysig);
		2183	}
		2184
		2185	static void
		2186	mysig_cb (EV_P_ ev_async *w, int revents)
		2187	{
		2188	sometype data;
		2189	sigset_t block, prev;
		2190
		2191	sigemptyset (&block);
		2192	sigaddset (&block, SIGUSR1);
		2193	sigprocmask (SIG_BLOCK, &block, &prev);
		2194
		2195	while (queue_get (&data))
		2196	process (data);
		2197
		2198	if (sigismember (&prev, SIGUSR1)
		2199	sigprocmask (SIG_UNBLOCK, &block, 0);
		2200	}
		2201
		2202	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2203	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2204	either...).
		2205
		2206	=item queueing from a thread context
		2207
		2208	The strategy for threads is different, as you cannot (easily) block
		2209	threads but you can easily preempt them, so to queue safely you need to
		2210	employ a traditional mutex lock, such as in this pthread example:
		2211
		2212	static ev_async mysig;
		2213	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2214
		2215	static void
		2216	otherthread (void)
		2217	{
		2218	// only need to lock the actual queueing operation
		2219	pthread_mutex_lock (&mymutex);
		2220	queue_put (data);
		2221	pthread_mutex_unlock (&mymutex);
		2222
		2223	ev_async_send (EV_DEFAULT_ &mysig);
		2224	}
		2225
		2226	static void
		2227	mysig_cb (EV_P_ ev_async *w, int revents)
		2228	{
		2229	pthread_mutex_lock (&mymutex);
		2230
		2231	while (queue_get (&data))
		2232	process (data);
		2233
		2234	pthread_mutex_unlock (&mymutex);
		2235	}
		2236
		2237	=back
		2238
		2239
		2240	=head3 Watcher-Specific Functions and Data Members
		2241
		2242	=over 4
		2243
		2244	=item ev_async_init (ev_async *, callback)
		2245
		2246	Initialises and configures the async watcher - it has no parameters of any
		2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2248	believe me.
		2249
		2250	=item ev_async_send (loop, ev_async *)
		2251
		2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2254	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2256	section below on what exactly this means).
		2257
		2258	This call incurs the overhead of a syscall only once per loop iteration,
		2259	so while the overhead might be noticable, it doesn't apply to repeated
		2260	calls to C<ev_async_send>.
		2261
		2262	=back
		2263
		2264
1870	=head1 OTHER FUNCTIONS	2265	=head1 OTHER FUNCTIONS
1871		2266
1872	There are some other functions of possible interest. Described. Here. Now.	2267	There are some other functions of possible interest. Described. Here. Now.
1873		2268
1874	=over 4	2269	=over 4
…		…
2101	Example: Define a class with an IO and idle watcher, start one of them in	2496	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2497	the constructor.
2103		2498
2104	class myclass	2499	class myclass
2105	{	2500	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2501	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2502	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2503
2109	myclass ();	2504	myclass (int fd)
2110	}
2111
2112	myclass::myclass (int fd)
2113	{	2505	{
2114	io .set <myclass, &myclass::io_cb > (this);	2506	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2507	idle.set <myclass, &myclass::idle_cb> (this);
2116		2508
2117	io.start (fd, ev::READ);	2509	io.start (fd, ev::READ);
		2510	}
2118	}	2511	};
		2512
		2513
		2514	=head1 OTHER LANGUAGE BINDINGS
		2515
		2516	Libev does not offer other language bindings itself, but bindings for a
		2517	numbe rof languages exist in the form of third-party packages. If you know
		2518	any interesting language binding in addition to the ones listed here, drop
		2519	me a note.
		2520
		2521	=over 4
		2522
		2523	=item Perl
		2524
		2525	The EV module implements the full libev API and is actually used to test
		2526	libev. EV is developed together with libev. Apart from the EV core module,
		2527	there are additional modules that implement libev-compatible interfaces
		2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2530
		2531	It can be found and installed via CPAN, its homepage is found at
		2532	L<http://software.schmorp.de/pkg/EV>.
		2533
		2534	=item Ruby
		2535
		2536	Tony Arcieri has written a ruby extension that offers access to a subset
		2537	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2538	more on top of it. It can be found via gem servers. Its homepage is at
		2539	L<http://rev.rubyforge.org/>.
		2540
		2541	=item D
		2542
		2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2545
		2546	=back
2119		2547
2120		2548
2121	=head1 MACRO MAGIC	2549	=head1 MACRO MAGIC
2122		2550
2123	Libev can be compiled with a variety of options, the most fundamantal	2551	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	2725	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2729
		2730	=item EV_USE_NANOSLEEP
		2731
		2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2733	and will use it for delays. Otherwise it will use C<select ()>.
		2734
2302	=item EV_USE_SELECT	2735	=item EV_USE_SELECT
2303		2736
2304	If undefined or defined to be C<1>, libev will compile in support for the	2737	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	2738	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	2739	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	2756	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	2757	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,	2758	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	2759	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2760	on win32. Should not be defined on non-win32 platforms.
		2761
		2762	=item EV_FD_TO_WIN32_HANDLE
		2763
		2764	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2765	file descriptors to socket handles. When not defining this symbol (the
		2766	default), then libev will call C<_get_osfhandle>, which is usually
		2767	correct. In some cases, programs use their own file descriptor management,
		2768	in which case they can provide this function to map fds to socket handles.
2328		2769
2329	=item EV_USE_POLL	2770	=item EV_USE_POLL
2330		2771
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2772	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	2773	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2366		2807
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2808	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	2809	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2810	be detected at runtime.
2370		2811
		2812	=item EV_ATOMIC_T
		2813
		2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2815	access is atomic with respect to other threads or signal contexts. No such
		2816	type is easily found in the C language, so you can provide your own type
		2817	that you know is safe for your purposes. It is used both for signal handler "locking"
		2818	as well as for signal and thread safety in C<ev_async> watchers.
		2819
		2820	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2821	(from F<signal.h>), which is usually good enough on most platforms.
		2822
2371	=item EV_H	2823	=item EV_H
2372		2824
2373	The name of the F<ev.h> header file used to include it. The default if	2825	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	2826	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.	2827	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2828
2377	=item EV_CONFIG_H	2829	=item EV_CONFIG_H
2378		2830
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2831	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	2832	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2833	C<EV_H>, above.
2382		2834
2383	=item EV_EVENT_H	2835	=item EV_EVENT_H
2384		2836
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2837	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.	2838	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2839
2388	=item EV_PROTOTYPES	2840	=item EV_PROTOTYPES
2389		2841
2390	If defined to be C<0>, then F<ev.h> will not define any function	2842	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	2843	prototypes, but still define all the structs and other symbols. This is
…		…
2442	=item EV_FORK_ENABLE	2894	=item EV_FORK_ENABLE
2443		2895
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	2896	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	2897	defined to be C<0>, then they are not.
2446		2898
		2899	=item EV_ASYNC_ENABLE
		2900
		2901	If undefined or defined to be C<1>, then async watchers are supported. If
		2902	defined to be C<0>, then they are not.
		2903
2447	=item EV_MINIMAL	2904	=item EV_MINIMAL
2448		2905
2449	If you need to shave off some kilobytes of code at the expense of some	2906	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	2907	speed, define this symbol to C<1>. Currently only used for gcc to override
2451	some inlining decisions, saves roughly 30% codesize of amd64.	2908	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2457	than enough. If you need to manage thousands of children you might want to	2914	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).	2915	increase this value (I<must> be a power of two).
2459		2916
2460	=item EV_INOTIFY_HASHSIZE	2917	=item EV_INOTIFY_HASHSIZE
2461		2918
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2919	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>),	2920	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>	2921	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	2922	watchers you might want to increase this value (I<must> be a power of
2466	two).	2923	two).
2467		2924
…		…
2563		3020
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3021	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		3022
2566	This means that, when you have a watcher that triggers in one hour and	3023	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	3024	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	3025	have to skip roughly seven (C<ld 100>) of these watchers.
2569		3026
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		3028
2572	That means that for changing a timer costs less than removing/adding them	3029	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.	3030	as only the relative motion in the event queue has to be paid for.
2574		3031
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		3033
2577	These just add the watcher into an array or at the head of a list.	3034	These just add the watcher into an array or at the head of a list.
		3035
2578	=item Stopping check/prepare/idle watchers: O(1)	3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		3037
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		3039
2582	These watchers are stored in lists then need to be walked to find the	3040	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	3041	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	3042	have many watchers waiting for the same fd or signal).
2585		3043
2586	=item Finding the next timer per loop iteration: O(1)	3044	=item Finding the next timer in each loop iteration: O(1)
		3045
		3046	By virtue of using a binary heap, the next timer is always found at the
		3047	beginning of the storage array.
2587		3048
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		3050
2590	A change means an I/O watcher gets started or stopped, which requires	3051	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	3052	libev to recalculate its status (and possibly tell the kernel, depending
		3053	on backend and wether C<ev_io_set> was used).
2592		3054
2593	=item Activating one watcher: O(1)	3055	=item Activating one watcher (putting it into the pending state): O(1)
2594		3056
2595	=item Priority handling: O(number_of_priorities)	3057	=item Priority handling: O(number_of_priorities)
2596		3058
2597	Priorities are implemented by allocating some space for each	3059	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	3060	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	3061	linearly search all the priorities, but starting/stopping and activating
		3062	watchers becomes O(1) w.r.t. priority handling.
		3063
		3064	=item Sending an ev_async: O(1)
		3065
		3066	=item Processing ev_async_send: O(number_of_async_watchers)
		3067
		3068	=item Processing signals: O(max_signal_number)
		3069
		3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3071	calls in the current loop iteration. Checking for async and signal events
		3072	involves iterating over all running async watchers or all signal numbers.
2600		3073
2601	=back	3074	=back
2602		3075
2603		3076
		3077	=head1 Win32 platform limitations and workarounds
		3078
		3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3080	requires, and its I/O model is fundamentally incompatible with the POSIX
		3081	model. Libev still offers limited functionality on this platform in
		3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3083	descriptors. This only applies when using Win32 natively, not when using
		3084	e.g. cygwin.
		3085
		3086	There is no supported compilation method available on windows except
		3087	embedding it into other applications.
		3088
		3089	Due to the many, low, and arbitrary limits on the win32 platform and the
		3090	abysmal performance of winsockets, using a large number of sockets is not
		3091	recommended (and not reasonable). If your program needs to use more than
		3092	a hundred or so sockets, then likely it needs to use a totally different
		3093	implementation for windows, as libev offers the POSIX model, which cannot
		3094	be implemented efficiently on windows (microsoft monopoly games).
		3095
		3096	=over 4
		3097
		3098	=item The winsocket select function
		3099
		3100	The winsocket C<select> function doesn't follow POSIX in that it requires
		3101	socket I<handles> and not socket I<file descriptors>. This makes select
		3102	very inefficient, and also requires a mapping from file descriptors
		3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3105	symbols for more info.
		3106
		3107	The configuration for a "naked" win32 using the microsoft runtime
		3108	libraries and raw winsocket select is:
		3109
		3110	#define EV_USE_SELECT 1
		3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3112
		3113	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3114	complexity in the O(n²) range when using win32.
		3115
		3116	=item Limited number of file descriptors
		3117
		3118	Windows has numerous arbitrary (and low) limits on things. Early versions
		3119	of winsocket's select only supported waiting for a max. of C<64> handles
		3120	(probably owning to the fact that all windows kernels can only wait for
		3121	C<64> things at the same time internally; microsoft recommends spawning a
		3122	chain of threads and wait for 63 handles and the previous thread in each).
		3123
		3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3125	to some high number (e.g. C<2048>) before compiling the winsocket select
		3126	call (which might be in libev or elsewhere, for example, perl does its own
		3127	select emulation on windows).
		3128
		3129	Another limit is the number of file descriptors in the microsoft runtime
		3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3131	or something like this inside microsoft). You can increase this by calling
		3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3133	arbitrary limit), but is broken in many versions of the microsoft runtime
		3134	libraries.
		3135
		3136	This might get you to about C<512> or C<2048> sockets (depending on
		3137	windows version and/or the phase of the moon). To get more, you need to
		3138	wrap all I/O functions and provide your own fd management, but the cost of
		3139	calling select (O(n²)) will likely make this unworkable.
		3140
		3141	=back
		3142
		3143
2604	=head1 AUTHOR	3144	=head1 AUTHOR
2605		3145
2606	Marc Lehmann <libev@schmorp.de>.	3146	Marc Lehmann <libev@schmorp.de>.
2607		3147

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.pod (file contents): Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC vs. Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC vs.
Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC