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…		…
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 occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	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	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
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
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floatingpoint value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
104		121
105	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
106		123
107	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
108	library in any way.	125	library in any way.
…		…
113		130
114	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
115	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
116	you actually want to know.	133	you actually want to know.
117		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
118	=item int ev_version_major ()	141	=item int ev_version_major ()
119		142
120	=item int ev_version_minor ()	143	=item int ev_version_minor ()
121		144
122	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	149	version of the library your program was compiled against.
127		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
128	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	157	not a problem.
132		158
133	Example: Make sure we haven't accidentally been linked against the wrong	159	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	160	version.
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		276
251	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
252	function.	278	function.
253		279
		280	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
254	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		293
257	The following flags are supported:	294	The following flags are supported:
258		295
…		…
279	enabling this flag.	316	enabling this flag.
280		317
281	This works by calling C<getpid ()> on every iteration of the loop,	318	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	319	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	320	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
287		324
288	The big advantage of this flag is that you can forget about fork (and	325	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	326	forget about forgetting to tell libev about forking) when you use this
290	flag.	327	flag.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		333
297	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
302		346
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		348
305	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
309		355
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		357
312	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	359	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	360	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
		362	of shortcomings, such as silently dropping events in some hard-to-detect
		363	cases and requiring a syscall per fd change, no fork support and bad
		364	support for dup.
316		365
317	While stopping and starting an I/O watcher in the same iteration will	366	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
319	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	370	very well if you register events for both fds.
322		371
323	Please note that epoll sometimes generates spurious notifications, so you	372	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	373	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	374	(or space) is available.
326		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		384
329	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	387	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	388	it's completely useless). For this reason it's not being "autodetected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	389	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		391	system like NetBSD.
		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
335		396
336	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	398	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	399	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	401	two event changes per incident, support for C<fork ()> is very bad and it
		402	drops fds silently in similarly hard-to-detect cases.
		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
341		412
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		414
344	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
345		419
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		421
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	423	it's really slow, but it still scales very well (O(active_fds)).
350		424
351	Please note that solaris ports can result in a lot of spurious	425	Please note that solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	426	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
354		437
355	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
356		439
357	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		443
		444	It is definitely not recommended to use this flag.
		445
361	=back	446	=back
362		447
363	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		451
368	The most typical usage is like this:	452	The most typical usage is like this:
369		453
370	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
385		469
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
387	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
388	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
389	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
390		478
391	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
392		480
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	482	if (!epoller)
…		…
399	Destroys the default loop again (frees all memory and kernel state	487	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	488	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	489	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	490	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	491	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	492	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	493	for example).
		494
		495	Note that certain global state, such as signal state, will not be freed by
		496	this function, and related watchers (such as signal and child watchers)
		497	would need to be stopped manually.
		498
		499	In general it is not advisable to call this function except in the
		500	rare occasion where you really need to free e.g. the signal handling
		501	pipe fds. If you need dynamically allocated loops it is better to use
		502	C<ev_loop_new> and C<ev_loop_destroy>).
406		503
407	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
408		505
409	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
411		508
412	=item ev_default_fork ()	509	=item ev_default_fork ()
413		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
417	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
418		517
419	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
422		521
423	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
426		525
427	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
428		527
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
434		529
435	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
438		537
439	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
440		539
441	Returns the count of loop iterations for the loop, which is identical to	540	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	541	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		554
456	Returns the current "event loop time", which is the time the event loop	555	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	556	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	557	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	558	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	559	event occurring (or more correctly, libev finding out about it).
461		560
462	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
463		562
464	Finally, this is it, the event handler. This function usually is called	563	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	564	after you initialised all your watchers and you want to start handling
…		…
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
488		587
489	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
490		589
491	* If there are no active watchers (reference count is zero), return.	590	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
		592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	596	- Update the "event loop time".
496	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	604	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	607	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	609	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
509		614
510	Example: Queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	616	anymore.
512		617
513	... queue jobs here, make sure they register event watchers as long	618	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	619	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
519		624
520	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
524		631
525	=item ev_ref (loop)	632	=item ev_ref (loop)
526		633
527	=item ev_unref (loop)	634	=item ev_unref (loop)
528		635
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
539		648
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	650	running when nothing else is active.
542		651
543	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
547		656
548	Example: For some weird reason, unregister the above signal handler again.	657	Example: For some weird reason, unregister the above signal handler again.
549		658
550	ev_ref (loop);	659	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	660	ev_signal_stop (loop, &exitsig);
		661
		662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		663
		664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		665
		666	These advanced functions influence the time that libev will spend waiting
		667	for events. Both are by default C<0>, meaning that libev will try to
		668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		669
		670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		671	allows libev to delay invocation of I/O and timer/periodic callbacks to
		672	increase efficiency of loop iterations.
		673
		674	The background is that sometimes your program runs just fast enough to
		675	handle one (or very few) event(s) per loop iteration. While this makes
		676	the program responsive, it also wastes a lot of CPU time to poll for new
		677	events, especially with backends like C<select ()> which have a high
		678	overhead for the actual polling but can deliver many events at once.
		679
		680	By setting a higher I<io collect interval> you allow libev to spend more
		681	time collecting I/O events, so you can handle more events per iteration,
		682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
		685
		686	Likewise, by setting a higher I<timeout collect interval> you allow libev
		687	to spend more time collecting timeouts, at the expense of increased
		688	latency (the watcher callback will be called later). C<ev_io> watchers
		689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
		691
		692	Many (busy) programs can usually benefit by setting the io collect
		693	interval to a value near C<0.1> or so, which is often enough for
		694	interactive servers (of course not for games), likewise for timeouts. It
		695	usually doesn't make much sense to set it to a lower value than C<0.01>,
		696	as this approsaches the timing granularity of most systems.
552		697
553	=back	698	=back
554		699
555		700
556	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
…		…
655		800
656	=item C<EV_FORK>	801	=item C<EV_FORK>
657		802
658	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
660		809
661	=item C<EV_ERROR>	810	=item C<EV_ERROR>
662		811
663	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
…		…
882	In general you can register as many read and/or write event watchers per	1031	In general you can register as many read and/or write event watchers per
883	fd as you want (as long as you don't confuse yourself). Setting all file	1032	fd as you want (as long as you don't confuse yourself). Setting all file
884	descriptors to non-blocking mode is also usually a good idea (but not	1033	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	1034	required if you know what you are doing).
886		1035
887	You have to be careful with dup'ed file descriptors, though. Some backends
888	(the linux epoll backend is a notable example) cannot handle dup'ed file
889	descriptors correctly if you register interest in two or more fds pointing
890	to the same underlying file/socket/etc. description (that is, they share
891	the same underlying "file open").
892
893	If you must do this, then force the use of a known-to-be-good backend	1036	If you must do this, then force the use of a known-to-be-good backend
894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
896		1039
897	Another thing you have to watch out for is that it is quite easy to	1040	Another thing you have to watch out for is that it is quite easy to
…		…
907	play around with an Xlib connection), then you have to seperately re-test	1050	play around with an Xlib connection), then you have to seperately re-test
908	whether a file descriptor is really ready with a known-to-be good interface	1051	whether a file descriptor is really ready with a known-to-be good interface
909	such as poll (fortunately in our Xlib example, Xlib already does this on	1052	such as poll (fortunately in our Xlib example, Xlib already does this on
910	its own, so its quite safe to use).	1053	its own, so its quite safe to use).
911		1054
		1055	=head3 The special problem of disappearing file descriptors
		1056
		1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1058	descriptor (either by calling C<close> explicitly or by any other means,
		1059	such as C<dup>). The reason is that you register interest in some file
		1060	descriptor, but when it goes away, the operating system will silently drop
		1061	this interest. If another file descriptor with the same number then is
		1062	registered with libev, there is no efficient way to see that this is, in
		1063	fact, a different file descriptor.
		1064
		1065	To avoid having to explicitly tell libev about such cases, libev follows
		1066	the following policy: Each time C<ev_io_set> is being called, libev
		1067	will assume that this is potentially a new file descriptor, otherwise
		1068	it is assumed that the file descriptor stays the same. That means that
		1069	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1070	descriptor even if the file descriptor number itself did not change.
		1071
		1072	This is how one would do it normally anyway, the important point is that
		1073	the libev application should not optimise around libev but should leave
		1074	optimisations to libev.
		1075
		1076	=head3 The special problem of dup'ed file descriptors
		1077
		1078	Some backends (e.g. epoll), cannot register events for file descriptors,
		1079	but only events for the underlying file descriptions. That means when you
		1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1081	events for them, only one file descriptor might actually receive events.
		1082
		1083	There is no workaround possible except not registering events
		1084	for potentially C<dup ()>'ed file descriptors, or to resort to
		1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1086
		1087	=head3 The special problem of fork
		1088
		1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1090	useless behaviour. Libev fully supports fork, but needs to be told about
		1091	it in the child.
		1092
		1093	To support fork in your programs, you either have to call
		1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1096	C<EVBACKEND_POLL>.
		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
		1110
		1111	=head3 Watcher-Specific Functions
		1112
912	=over 4	1113	=over 4
913		1114
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1115	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1116
916	=item ev_io_set (ev_io *, int fd, int events)	1117	=item ev_io_set (ev_io *, int fd, int events)
…		…
926	=item int events [read-only]	1127	=item int events [read-only]
927		1128
928	The events being watched.	1129	The events being watched.
929		1130
930	=back	1131	=back
		1132
		1133	=head3 Examples
931		1134
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
933	readable, but only once. Since it is likely line-buffered, you could	1136	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
935		1138
…		…
969		1172
970	The callback is guarenteed to be invoked only when its timeout has passed,	1173	The callback is guarenteed to be invoked only when its timeout has passed,
971	but if multiple timers become ready during the same loop iteration then	1174	but if multiple timers become ready during the same loop iteration then
972	order of execution is undefined.	1175	order of execution is undefined.
973		1176
		1177	=head3 Watcher-Specific Functions and Data Members
		1178
974	=over 4	1179	=over 4
975		1180
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1182
978	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
986	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
987	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
988	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
989	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
990		1195
991	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
992		1197
993	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
994	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
995		1200
996	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1031	or C<ev_timer_again> is called and determines the next timeout (if any),	1236	or C<ev_timer_again> is called and determines the next timeout (if any),
1032	which is also when any modifications are taken into account.	1237	which is also when any modifications are taken into account.
1033		1238
1034	=back	1239	=back
1035		1240
		1241	=head3 Examples
		1242
1036	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
1037		1244
1038	static void	1245	static void
1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1040	{	1247	{
…		…
1073	but on wallclock time (absolute time). You can tell a periodic watcher	1280	but on wallclock time (absolute time). You can tell a periodic watcher
1074	to trigger "at" some specific point in time. For example, if you tell a	1281	to trigger "at" some specific point in time. For example, if you tell a
1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1076	+ 10.>) and then reset your system clock to the last year, then it will	1283	+ 10.>) and then reset your system clock to the last year, then it will
1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1078	roughly 10 seconds later and of course not if you reset your system time	1285	roughly 10 seconds later).
1079	again).
1080		1286
1081	They can also be used to implement vastly more complex timers, such as	1287	They can also be used to implement vastly more complex timers, such as
1082	triggering an event on eahc midnight, local time.	1288	triggering an event on each midnight, local time or other, complicated,
		1289	rules.
1083		1290
1084	As with timers, the callback is guarenteed to be invoked only when the	1291	As with timers, the callback is guarenteed to be invoked only when the
1085	time (C<at>) has been passed, but if multiple periodic timers become ready	1292	time (C<at>) has been passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1293	during the same loop iteration then order of execution is undefined.
1087		1294
		1295	=head3 Watcher-Specific Functions and Data Members
		1296
1088	=over 4	1297	=over 4
1089		1298
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1300
1092	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1094	Lots of arguments, lets sort it out... There are basically three modes of	1303	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1304	operation, and we will explain them from simplest to complex:
1096		1305
1097	=over 4	1306	=over 4
1098		1307
1099	=item * absolute timer (interval = reschedule_cb = 0)	1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1309
1101	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1102	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1103	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1104	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1105		1314
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1316
1108	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1109	C<at + N * interval> time (for some integer N) and then repeat, regardless	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1319	and then repeat, regardless of any time jumps.
1111		1320
1112	This can be used to create timers that do not drift with respect to system	1321	This can be used to create timers that do not drift with respect to system
1113	time:	1322	time:
1114		1323
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1324	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1121		1330
1122	Another way to think about it (for the mathematically inclined) is that	1331	Another way to think about it (for the mathematically inclined) is that
1123	C<ev_periodic> will try to run the callback in this mode at the next possible	1332	C<ev_periodic> will try to run the callback in this mode at the next possible
1124	time where C<time = at (mod interval)>, regardless of any time jumps.	1333	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1334
		1335	For numerical stability it is preferable that the C<at> value is near
		1336	C<ev_now ()> (the current time), but there is no range requirement for
		1337	this value.
		1338
1126	=item * manual reschedule mode (reschedule_cb = callback)	1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1340
1128	In this mode the values for C<interval> and C<at> are both being	1341	In this mode the values for C<interval> and C<at> are both being
1129	ignored. Instead, each time the periodic watcher gets scheduled, the	1342	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1343	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1344	current time as second argument.
1132		1345
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1134	ever, or make any event loop modifications>. If you need to stop it,	1347	ever, or make any event loop modifications>. If you need to stop it,
1135	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1136	starting a prepare watcher).	1349	starting an C<ev_prepare> watcher, which is legal).
1137		1350
1138	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1139	ev_tstamp now)>, e.g.:	1352	ev_tstamp now)>, e.g.:
1140		1353
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1377	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1378	when you changed some parameters or the reschedule callback would return
1166	a different time than the last time it was called (e.g. in a crond like	1379	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1380	program when the crontabs have changed).
1168		1381
		1382	=item ev_tstamp offset [read-write]
		1383
		1384	When repeating, this contains the offset value, otherwise this is the
		1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1386
		1387	Can be modified any time, but changes only take effect when the periodic
		1388	timer fires or C<ev_periodic_again> is being called.
		1389
1169	=item ev_tstamp interval [read-write]	1390	=item ev_tstamp interval [read-write]
1170		1391
1171	The current interval value. Can be modified any time, but changes only	1392	The current interval value. Can be modified any time, but changes only
1172	take effect when the periodic timer fires or C<ev_periodic_again> is being	1393	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1394	called.
…		…
1176		1397
1177	The current reschedule callback, or C<0>, if this functionality is	1398	The current reschedule callback, or C<0>, if this functionality is
1178	switched off. Can be changed any time, but changes only take effect when	1399	switched off. Can be changed any time, but changes only take effect when
1179	the periodic timer fires or C<ev_periodic_again> is being called.	1400	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1401
		1402	=item ev_tstamp at [read-only]
		1403
		1404	When active, contains the absolute time that the watcher is supposed to
		1405	trigger next.
		1406
1181	=back	1407	=back
		1408
		1409	=head3 Examples
1182		1410
1183	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1186		1414
…		…
1226	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1227	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1228	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1229	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1230		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
		1465	=head3 Watcher-Specific Functions and Data Members
		1466
1231	=over 4	1467	=over 4
1232		1468
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1470
1235	=item ev_signal_set (ev_signal *, int signum)	1471	=item ev_signal_set (ev_signal *, int signum)
…		…
1241		1477
1242	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1243		1479
1244	=back	1480	=back
1245		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1246		1496
1247	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1248		1498
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1250	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
		1526
		1527	=head3 Watcher-Specific Functions and Data Members
1251		1528
1252	=over 4	1529	=over 4
1253		1530
1254	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1255		1532
1256	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1257		1534
1258	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1259	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1260	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1261	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1262	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1263	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1264		1543
1265	=item int pid [read-only]	1544	=item int pid [read-only]
1266		1545
1267	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1268		1547
…		…
1275	The process exit/trace status caused by C<rpid> (see your systems	1554	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1556
1278	=back	1557	=back
1279		1558
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1281		1565
1282	static void	1566	static void
1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1284	{	1568	{
1285	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1286	}	1571	}
1287		1572
1288	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1290	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1291		1587
1292		1588
1293	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1294		1590
1295	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1325	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1326	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1327	polling.	1623	polling.
1328		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
		1669	=head3 Watcher-Specific Functions and Data Members
		1670
1329	=over 4	1671	=over 4
1330		1672
1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1332		1674
1333	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1675	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1340		1682
1341	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1342	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1343	last change was detected).	1685	last change was detected).
1344		1686
1345	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1346		1688
1347	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1348	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1349	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1350	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1368	=item const char *path [read-only]	1710	=item const char *path [read-only]
1369		1711
1370	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1371		1713
1372	=back	1714	=back
		1715
		1716	=head3 Examples
1373		1717
1374	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1375		1719
1376	static void	1720	static void
1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1390	}	1734	}
1391		1735
1392	...	1736	...
1393	ev_stat passwd;	1737	ev_stat passwd;
1394		1738
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	1740	ev_stat_start (loop, &passwd);
		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
1397		1769
1398		1770
1399	=head2 C<ev_idle> - when you've got nothing better to do...	1771	=head2 C<ev_idle> - when you've got nothing better to do...
1400		1772
1401	Idle watchers trigger events when no other events of the same or higher	1773	Idle watchers trigger events when no other events of the same or higher
…		…
1415	Apart from keeping your process non-blocking (which is a useful	1787	Apart from keeping your process non-blocking (which is a useful
1416	effect on its own sometimes), idle watchers are a good place to do	1788	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	1789	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	1790	event loop has handled all outstanding events.
1419		1791
		1792	=head3 Watcher-Specific Functions and Data Members
		1793
1420	=over 4	1794	=over 4
1421		1795
1422	=item ev_idle_init (ev_signal *, callback)	1796	=item ev_idle_init (ev_signal *, callback)
1423		1797
1424	Initialises and configures the idle watcher - it has no parameters of any	1798	Initialises and configures the idle watcher - it has no parameters of any
1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	1800	believe me.
1427		1801
1428	=back	1802	=back
		1803
		1804	=head3 Examples
1429		1805
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1432		1808
1433	static void	1809	static void
1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1435	{	1811	{
1436	free (w);	1812	free (w);
1437	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1438	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1439	}	1815	}
1440		1816
1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1442	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1443	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1481	with priority higher than or equal to the event loop and one coroutine	1857	with priority higher than or equal to the event loop and one coroutine
1482	of lower priority, but only once, using idle watchers to keep the event	1858	of lower priority, but only once, using idle watchers to keep the event
1483	loop from blocking if lower-priority coroutines are active, thus mapping	1859	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	1860	low-priority coroutines to idle/background tasks).
1485		1861
		1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1863	priority, to ensure that they are being run before any other watchers
		1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1865	too) should not activate ("feed") events into libev. While libev fully
		1866	supports this, they will be called before other C<ev_check> watchers
		1867	did their job. As C<ev_check> watchers are often used to embed other
		1868	(non-libev) event loops those other event loops might be in an unusable
		1869	state until their C<ev_check> watcher ran (always remind yourself to
		1870	coexist peacefully with others).
		1871
		1872	=head3 Watcher-Specific Functions and Data Members
		1873
1486	=over 4	1874	=over 4
1487		1875
1488	=item ev_prepare_init (ev_prepare *, callback)	1876	=item ev_prepare_init (ev_prepare *, callback)
1489		1877
1490	=item ev_check_init (ev_check *, callback)	1878	=item ev_check_init (ev_check *, callback)
…		…
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1494	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1495		1883
1496	=back	1884	=back
1497		1885
1498	Example: To include a library such as adns, you would add IO watchers	1886	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	1887
		1888	There are a number of principal ways to embed other event loops or modules
		1889	into libev. Here are some ideas on how to include libadns into libev
		1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1891	use for an actually working example. Another Perl module named C<EV::Glib>
		1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1893	into the Glib event loop).
		1894
		1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1500	in a check watcher, destroy them and call into libadns. What follows is	1896	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	1897	is pseudo-code only of course. This requires you to either use a low
		1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1899	the callbacks for the IO/timeout watchers might not have been called yet.
1502		1900
1503	static ev_io iow [nfd];	1901	static ev_io iow [nfd];
1504	static ev_timer tw;	1902	static ev_timer tw;
1505		1903
1506	static void	1904	static void
1507	io_cb (ev_loop *loop, ev_io *w, int revents)	1905	io_cb (ev_loop *loop, ev_io *w, int revents)
1508	{	1906	{
1509	// set the relevant poll flags
1510	// could also call adns_processreadable etc. here
1511	struct pollfd *fd = (struct pollfd *)w->data;
1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1514	}	1907	}
1515		1908
1516	// create io watchers for each fd and a timer before blocking	1909	// create io watchers for each fd and a timer before blocking
1517	static void	1910	static void
1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1524		1917
1525	/* the callback is illegal, but won't be called as we stop during check */	1918	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	1919	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	1920	ev_timer_start (loop, &tw);
1528		1921
1529	// create on ev_io per pollfd	1922	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	1923	for (int i = 0; i < nfd; ++i)
1531	{	1924	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	1925	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	1926	((fds [i].events & POLLIN ? EV_READ : 0)
1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		1928
1536	fds [i].revents = 0;	1929	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	1930	ev_io_start (loop, iow + i);
1539	}	1931	}
1540	}	1932	}
1541		1933
1542	// stop all watchers after blocking	1934	// stop all watchers after blocking
…		…
1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1545	{	1937	{
1546	ev_timer_stop (loop, &tw);	1938	ev_timer_stop (loop, &tw);
1547		1939
1548	for (int i = 0; i < nfd; ++i)	1940	for (int i = 0; i < nfd; ++i)
		1941	{
		1942	// set the relevant poll flags
		1943	// could also call adns_processreadable etc. here
		1944	struct pollfd *fd = fds + i;
		1945	int revents = ev_clear_pending (iow + i);
		1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1948
		1949	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	1950	ev_io_stop (loop, iow + i);
		1951	}
1550		1952
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1954	}
		1955
		1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1957	in the prepare watcher and would dispose of the check watcher.
		1958
		1959	Method 3: If the module to be embedded supports explicit event
		1960	notification (adns does), you can also make use of the actual watcher
		1961	callbacks, and only destroy/create the watchers in the prepare watcher.
		1962
		1963	static void
		1964	timer_cb (EV_P_ ev_timer *w, int revents)
		1965	{
		1966	adns_state ads = (adns_state)w->data;
		1967	update_now (EV_A);
		1968
		1969	adns_processtimeouts (ads, &tv_now);
		1970	}
		1971
		1972	static void
		1973	io_cb (EV_P_ ev_io *w, int revents)
		1974	{
		1975	adns_state ads = (adns_state)w->data;
		1976	update_now (EV_A);
		1977
		1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1980	}
		1981
		1982	// do not ever call adns_afterpoll
		1983
		1984	Method 4: Do not use a prepare or check watcher because the module you
		1985	want to embed is too inflexible to support it. Instead, youc na override
		1986	their poll function. The drawback with this solution is that the main
		1987	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1988	this.
		1989
		1990	static gint
		1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1992	{
		1993	int got_events = 0;
		1994
		1995	for (n = 0; n < nfds; ++n)
		1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1997
		1998	if (timeout >= 0)
		1999	// create/start timer
		2000
		2001	// poll
		2002	ev_loop (EV_A_ 0);
		2003
		2004	// stop timer again
		2005	if (timeout >= 0)
		2006	ev_timer_stop (EV_A_ &to);
		2007
		2008	// stop io watchers again - their callbacks should have set
		2009	for (n = 0; n < nfds; ++n)
		2010	ev_io_stop (EV_A_ iow [n]);
		2011
		2012	return got_events;
1552	}	2013	}
1553		2014
1554		2015
1555	=head2 C<ev_embed> - when one backend isn't enough...	2016	=head2 C<ev_embed> - when one backend isn't enough...
1556		2017
…		…
1599	portable one.	2060	portable one.
1600		2061
1601	So when you want to use this feature you will always have to be prepared	2062	So when you want to use this feature you will always have to be prepared
1602	that you cannot get an embeddable loop. The recommended way to get around	2063	that you cannot get an embeddable loop. The recommended way to get around
1603	this is to have a separate variables for your embeddable loop, try to	2064	this is to have a separate variables for your embeddable loop, try to
1604	create it, and if that fails, use the normal loop for everything:	2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
1605		2100
1606	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1607	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1608	struct ev_embed embed;	2103	struct ev_embed embed;
1609		2104
…		…
1620	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1621	}	2116	}
1622	else	2117	else
1623	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1624		2119
1625	=over 4	2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1626		2124
1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
1628		2135
1629	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2136	if (!loop_socket)
		2137	loop_socket = loop;
1630		2138
1631	Configures the watcher to embed the given loop, which must be	2139	// now use loop_socket for all sockets, and loop for everything else
1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1633	invoked automatically, otherwise it is the responsibility of the callback
1634	to invoke it (it will continue to be called until the sweep has been done,
1635	if you do not want thta, you need to temporarily stop the embed watcher).
1636
1637	=item ev_embed_sweep (loop, ev_embed *)
1638
1639	Make a single, non-blocking sweep over the embedded loop. This works
1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.
1642
1643	=item struct ev_loop *loop [read-only]
1644
1645	The embedded event loop.
1646
1647	=back
1648		2140
1649		2141
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2143
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2144	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1655	event loop blocks next and before C<ev_check> watchers are being called,	2147	event loop blocks next and before C<ev_check> watchers are being called,
1656	and only in the child after the fork. If whoever good citizen calling	2148	and only in the child after the fork. If whoever good citizen calling
1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2150	handlers will be invoked, too, of course.
1659		2151
		2152	=head3 Watcher-Specific Functions and Data Members
		2153
1660	=over 4	2154	=over 4
1661		2155
1662	=item ev_fork_init (ev_signal *, callback)	2156	=item ev_fork_init (ev_signal *, callback)
1663		2157
1664	Initialises and configures the fork watcher - it has no parameters of any	2158	Initialises and configures the fork watcher - it has no parameters of any
1665	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1666	believe me.	2160	believe me.
		2161
		2162	=back
		2163
		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
1667		2306
1668	=back	2307	=back
1669		2308
1670		2309
1671	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
…		…
1844		2483
1845	myclass obj;	2484	myclass obj;
1846	ev::io iow;	2485	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2486	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2487
1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2488	=item w->set<function> (void *data = 0)
1850		2489
1851	Also sets a callback, but uses a static method or plain function as	2490	Also sets a callback, but uses a static method or plain function as
1852	callback. The optional C<data> argument will be stored in the watcher's	2491	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2492	C<data> member and is free for you to use.
1854		2493
		2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2495
1855	See the method-C<set> above for more details.	2496	See the method-C<set> above for more details.
		2497
		2498	Example:
		2499
		2500	static void io_cb (ev::io &w, int revents) { }
		2501	iow.set <io_cb> ();
1856		2502
1857	=item w->set (struct ev_loop *)	2503	=item w->set (struct ev_loop *)
1858		2504
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2505	Associates a different C<struct ev_loop> with this watcher. You can only
1860	do this when the watcher is inactive (and not pending either).	2506	do this when the watcher is inactive (and not pending either).
…		…
1873		2519
1874	=item w->stop ()	2520	=item w->stop ()
1875		2521
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2522	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2523
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2524	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2525
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2526	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2527	C<ev_TYPE_again> function.
1882		2528
1883	=item w->sweep () C<ev::embed> only	2529	=item w->sweep () (C<ev::embed> only)
1884		2530
1885	Invokes C<ev_embed_sweep>.	2531	Invokes C<ev_embed_sweep>.
1886		2532
1887	=item w->update () C<ev::stat> only	2533	=item w->update () (C<ev::stat> only)
1888		2534
1889	Invokes C<ev_stat_stat>.	2535	Invokes C<ev_stat_stat>.
1890		2536
1891	=back	2537	=back
1892		2538
…		…
1895	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
1896	the constructor.	2542	the constructor.
1897		2543
1898	class myclass	2544	class myclass
1899	{	2545	{
1900	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
1901	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
1902		2548
1903	myclass ();	2549	myclass (int fd)
1904	}
1905
1906	myclass::myclass (int fd)
1907	{	2550	{
1908	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
1909	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
1910		2553
1911	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
1912	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
1913		2592
1914		2593
1915	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
1916		2595
1917	Libev can be compiled with a variety of options, the most fundemantal is	2596	Libev can be compiled with a variety of options, the most fundamantal
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2598	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2599
1921	To make it easier to write programs that cope with either variant, the	2600	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2601	following macros are defined:
1923		2602
1924	=over 4	2603	=over 4
…		…
1953		2632
1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1955		2634
1956	Similar to the other two macros, this gives you the value of the default	2635	Similar to the other two macros, this gives you the value of the default
1957	loop, if multiple loops are supported ("ev loop default").	2636	loop, if multiple loops are supported ("ev loop default").
		2637
		2638	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2639
		2640	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2641	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2642	is undefined when the default loop has not been initialised by a previous
		2643	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2644
		2645	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2646	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1958		2647
1959	=back	2648	=back
1960		2649
1961	Example: Declare and initialise a check watcher, utilising the above	2650	Example: Declare and initialise a check watcher, utilising the above
1962	macros so it will work regardless of whether multiple loops are supported	2651	macros so it will work regardless of whether multiple loops are supported
…		…
1978	Libev can (and often is) directly embedded into host	2667	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	2668	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2669	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	2670	and rxvt-unicode.
1982		2671
1983	The goal is to enable you to just copy the neecssary files into your	2672	The goal is to enable you to just copy the necessary files into your
1984	source directory without having to change even a single line in them, so	2673	source directory without having to change even a single line in them, so
1985	you can easily upgrade by simply copying (or having a checked-out copy of	2674	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	2675	libev somewhere in your source tree).
1987		2676
1988	=head2 FILESETS	2677	=head2 FILESETS
…		…
2058		2747
2059	libev.m4	2748	libev.m4
2060		2749
2061	=head2 PREPROCESSOR SYMBOLS/MACROS	2750	=head2 PREPROCESSOR SYMBOLS/MACROS
2062		2751
2063	Libev can be configured via a variety of preprocessor symbols you have to define	2752	Libev can be configured via a variety of preprocessor symbols you have to
2064	before including any of its files. The default is not to build for multiplicity	2753	define before including any of its files. The default in the absense of
2065	and only include the select backend.	2754	autoconf is noted for every option.
2066		2755
2067	=over 4	2756	=over 4
2068		2757
2069	=item EV_STANDALONE	2758	=item EV_STANDALONE
2070		2759
…		…
2078		2767
2079	If defined to be C<1>, libev will try to detect the availability of the	2768	If defined to be C<1>, libev will try to detect the availability of the
2080	monotonic clock option at both compiletime and runtime. Otherwise no use	2769	monotonic clock option at both compiletime and runtime. Otherwise no use
2081	of the monotonic clock option will be attempted. If you enable this, you	2770	of the monotonic clock option will be attempted. If you enable this, you
2082	usually have to link against librt or something similar. Enabling it when	2771	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	2772	the functionality isn't available is safe, though, although you have
2084	to make sure you link against any libraries where the C<clock_gettime>	2773	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	2774	function is hiding in (often F<-lrt>).
2086		2775
2087	=item EV_USE_REALTIME	2776	=item EV_USE_REALTIME
2088		2777
2089	If defined to be C<1>, libev will try to detect the availability of the	2778	If defined to be C<1>, libev will try to detect the availability of the
2090	realtime clock option at compiletime (and assume its availability at	2779	realtime clock option at compiletime (and assume its availability at
2091	runtime if successful). Otherwise no use of the realtime clock option will	2780	runtime if successful). Otherwise no use of the realtime clock option will
2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2781	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2782	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	2783	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2784
		2785	=item EV_USE_NANOSLEEP
		2786
		2787	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2788	and will use it for delays. Otherwise it will use C<select ()>.
		2789
		2790	=item EV_USE_EVENTFD
		2791
		2792	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2793	available and will probe for kernel support at runtime. This will improve
		2794	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2795	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2796	2.7 or newer, otherwise disabled.
2095		2797
2096	=item EV_USE_SELECT	2798	=item EV_USE_SELECT
2097		2799
2098	If undefined or defined to be C<1>, libev will compile in support for the	2800	If undefined or defined to be C<1>, libev will compile in support for the
2099	C<select>(2) backend. No attempt at autodetection will be done: if no	2801	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2118	be used is the winsock select). This means that it will call	2820	be used is the winsock select). This means that it will call
2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2821	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2120	it is assumed that all these functions actually work on fds, even	2822	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	2823	on win32. Should not be defined on non-win32 platforms.
2122		2824
		2825	=item EV_FD_TO_WIN32_HANDLE
		2826
		2827	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2828	file descriptors to socket handles. When not defining this symbol (the
		2829	default), then libev will call C<_get_osfhandle>, which is usually
		2830	correct. In some cases, programs use their own file descriptor management,
		2831	in which case they can provide this function to map fds to socket handles.
		2832
2123	=item EV_USE_POLL	2833	=item EV_USE_POLL
2124		2834
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2835	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2126	backend. Otherwise it will be enabled on non-win32 platforms. It	2836	backend. Otherwise it will be enabled on non-win32 platforms. It
2127	takes precedence over select.	2837	takes precedence over select.
2128		2838
2129	=item EV_USE_EPOLL	2839	=item EV_USE_EPOLL
2130		2840
2131	If defined to be C<1>, libev will compile in support for the Linux	2841	If defined to be C<1>, libev will compile in support for the Linux
2132	C<epoll>(7) backend. Its availability will be detected at runtime,	2842	C<epoll>(7) backend. Its availability will be detected at runtime,
2133	otherwise another method will be used as fallback. This is the	2843	otherwise another method will be used as fallback. This is the preferred
2134	preferred backend for GNU/Linux systems.	2844	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2845	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2135		2846
2136	=item EV_USE_KQUEUE	2847	=item EV_USE_KQUEUE
2137		2848
2138	If defined to be C<1>, libev will compile in support for the BSD style	2849	If defined to be C<1>, libev will compile in support for the BSD style
2139	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2850	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2158		2869
2159	=item EV_USE_INOTIFY	2870	=item EV_USE_INOTIFY
2160		2871
2161	If defined to be C<1>, libev will compile in support for the Linux inotify	2872	If defined to be C<1>, libev will compile in support for the Linux inotify
2162	interface to speed up C<ev_stat> watchers. Its actual availability will	2873	interface to speed up C<ev_stat> watchers. Its actual availability will
2163	be detected at runtime.	2874	be detected at runtime. If undefined, it will be enabled if the headers
		2875	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2876
		2877	=item EV_ATOMIC_T
		2878
		2879	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2880	access is atomic with respect to other threads or signal contexts. No such
		2881	type is easily found in the C language, so you can provide your own type
		2882	that you know is safe for your purposes. It is used both for signal handler "locking"
		2883	as well as for signal and thread safety in C<ev_async> watchers.
		2884
		2885	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2886	(from F<signal.h>), which is usually good enough on most platforms.
2164		2887
2165	=item EV_H	2888	=item EV_H
2166		2889
2167	The name of the F<ev.h> header file used to include it. The default if	2890	The name of the F<ev.h> header file used to include it. The default if
2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2891	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2892	used to virtually rename the F<ev.h> header file in case of conflicts.
2170		2893
2171	=item EV_CONFIG_H	2894	=item EV_CONFIG_H
2172		2895
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2896	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2897	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	2898	C<EV_H>, above.
2176		2899
2177	=item EV_EVENT_H	2900	=item EV_EVENT_H
2178		2901
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2902	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2180	of how the F<event.h> header can be found.	2903	of how the F<event.h> header can be found, the default is C<"event.h">.
2181		2904
2182	=item EV_PROTOTYPES	2905	=item EV_PROTOTYPES
2183		2906
2184	If defined to be C<0>, then F<ev.h> will not define any function	2907	If defined to be C<0>, then F<ev.h> will not define any function
2185	prototypes, but still define all the structs and other symbols. This is	2908	prototypes, but still define all the structs and other symbols. This is
…		…
2236	=item EV_FORK_ENABLE	2959	=item EV_FORK_ENABLE
2237		2960
2238	If undefined or defined to be C<1>, then fork watchers are supported. If	2961	If undefined or defined to be C<1>, then fork watchers are supported. If
2239	defined to be C<0>, then they are not.	2962	defined to be C<0>, then they are not.
2240		2963
		2964	=item EV_ASYNC_ENABLE
		2965
		2966	If undefined or defined to be C<1>, then async watchers are supported. If
		2967	defined to be C<0>, then they are not.
		2968
2241	=item EV_MINIMAL	2969	=item EV_MINIMAL
2242		2970
2243	If you need to shave off some kilobytes of code at the expense of some	2971	If you need to shave off some kilobytes of code at the expense of some
2244	speed, define this symbol to C<1>. Currently only used for gcc to override	2972	speed, define this symbol to C<1>. Currently only used for gcc to override
2245	some inlining decisions, saves roughly 30% codesize of amd64.	2973	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2251	than enough. If you need to manage thousands of children you might want to	2979	than enough. If you need to manage thousands of children you might want to
2252	increase this value (I<must> be a power of two).	2980	increase this value (I<must> be a power of two).
2253		2981
2254	=item EV_INOTIFY_HASHSIZE	2982	=item EV_INOTIFY_HASHSIZE
2255		2983
2256	C<ev_staz> watchers use a small hash table to distribute workload by	2984	C<ev_stat> watchers use a small hash table to distribute workload by
2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2985	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2258	usually more than enough. If you need to manage thousands of C<ev_stat>	2986	usually more than enough. If you need to manage thousands of C<ev_stat>
2259	watchers you might want to increase this value (I<must> be a power of	2987	watchers you might want to increase this value (I<must> be a power of
2260	two).	2988	two).
2261		2989
…		…
2278		3006
2279	=item ev_set_cb (ev, cb)	3007	=item ev_set_cb (ev, cb)
2280		3008
2281	Can be used to change the callback member declaration in each watcher,	3009	Can be used to change the callback member declaration in each watcher,
2282	and the way callbacks are invoked and set. Must expand to a struct member	3010	and the way callbacks are invoked and set. Must expand to a struct member
2283	definition and a statement, respectively. See the F<ev.v> header file for	3011	definition and a statement, respectively. See the F<ev.h> header file for
2284	their default definitions. One possible use for overriding these is to	3012	their default definitions. One possible use for overriding these is to
2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3013	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2286	method calls instead of plain function calls in C++.	3014	method calls instead of plain function calls in C++.
		3015
		3016	=head2 EXPORTED API SYMBOLS
		3017
		3018	If you need to re-export the API (e.g. via a dll) and you need a list of
		3019	exported symbols, you can use the provided F<Symbol.*> files which list
		3020	all public symbols, one per line:
		3021
		3022	Symbols.ev for libev proper
		3023	Symbols.event for the libevent emulation
		3024
		3025	This can also be used to rename all public symbols to avoid clashes with
		3026	multiple versions of libev linked together (which is obviously bad in
		3027	itself, but sometimes it is inconvinient to avoid this).
		3028
		3029	A sed command like this will create wrapper C<#define>'s that you need to
		3030	include before including F<ev.h>:
		3031
		3032	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3033
		3034	This would create a file F<wrap.h> which essentially looks like this:
		3035
		3036	#define ev_backend myprefix_ev_backend
		3037	#define ev_check_start myprefix_ev_check_start
		3038	#define ev_check_stop myprefix_ev_check_stop
		3039	...
2287		3040
2288	=head2 EXAMPLES	3041	=head2 EXAMPLES
2289		3042
2290	For a real-world example of a program the includes libev	3043	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	3044	verbatim, you can have a look at the EV perl module
…		…
2332		3085
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3086	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		3087
2335	This means that, when you have a watcher that triggers in one hour and	3088	This means that, when you have a watcher that triggers in one hour and
2336	there are 100 watchers that would trigger before that then inserting will	3089	there are 100 watchers that would trigger before that then inserting will
2337	have to skip those 100 watchers.	3090	have to skip roughly seven (C<ld 100>) of these watchers.
2338		3091
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3092	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		3093
2341	That means that for changing a timer costs less than removing/adding them	3094	That means that changing a timer costs less than removing/adding them
2342	as only the relative motion in the event queue has to be paid for.	3095	as only the relative motion in the event queue has to be paid for.
2343		3096
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3097	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2345		3098
2346	These just add the watcher into an array or at the head of a list.	3099	These just add the watcher into an array or at the head of a list.
		3100
2347	=item Stopping check/prepare/idle watchers: O(1)	3101	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2348		3102
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3103	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		3104
2351	These watchers are stored in lists then need to be walked to find the	3105	These watchers are stored in lists then need to be walked to find the
2352	correct watcher to remove. The lists are usually short (you don't usually	3106	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	3107	have many watchers waiting for the same fd or signal).
2354		3108
2355	=item Finding the next timer per loop iteration: O(1)	3109	=item Finding the next timer in each loop iteration: O(1)
		3110
		3111	By virtue of using a binary heap, the next timer is always found at the
		3112	beginning of the storage array.
2356		3113
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3114	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		3115
2359	A change means an I/O watcher gets started or stopped, which requires	3116	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	3117	libev to recalculate its status (and possibly tell the kernel, depending
		3118	on backend and wether C<ev_io_set> was used).
2361		3119
2362	=item Activating one watcher: O(1)	3120	=item Activating one watcher (putting it into the pending state): O(1)
2363		3121
2364	=item Priority handling: O(number_of_priorities)	3122	=item Priority handling: O(number_of_priorities)
2365		3123
2366	Priorities are implemented by allocating some space for each	3124	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	3125	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	3126	linearly search all the priorities, but starting/stopping and activating
		3127	watchers becomes O(1) w.r.t. priority handling.
		3128
		3129	=item Sending an ev_async: O(1)
		3130
		3131	=item Processing ev_async_send: O(number_of_async_watchers)
		3132
		3133	=item Processing signals: O(max_signal_number)
		3134
		3135	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3136	calls in the current loop iteration. Checking for async and signal events
		3137	involves iterating over all running async watchers or all signal numbers.
2369		3138
2370	=back	3139	=back
2371		3140
2372		3141
		3142	=head1 Win32 platform limitations and workarounds
		3143
		3144	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3145	requires, and its I/O model is fundamentally incompatible with the POSIX
		3146	model. Libev still offers limited functionality on this platform in
		3147	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3148	descriptors. This only applies when using Win32 natively, not when using
		3149	e.g. cygwin.
		3150
		3151	There is no supported compilation method available on windows except
		3152	embedding it into other applications.
		3153
		3154	Due to the many, low, and arbitrary limits on the win32 platform and the
		3155	abysmal performance of winsockets, using a large number of sockets is not
		3156	recommended (and not reasonable). If your program needs to use more than
		3157	a hundred or so sockets, then likely it needs to use a totally different
		3158	implementation for windows, as libev offers the POSIX model, which cannot
		3159	be implemented efficiently on windows (microsoft monopoly games).
		3160
		3161	=over 4
		3162
		3163	=item The winsocket select function
		3164
		3165	The winsocket C<select> function doesn't follow POSIX in that it requires
		3166	socket I<handles> and not socket I<file descriptors>. This makes select
		3167	very inefficient, and also requires a mapping from file descriptors
		3168	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3169	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3170	symbols for more info.
		3171
		3172	The configuration for a "naked" win32 using the microsoft runtime
		3173	libraries and raw winsocket select is:
		3174
		3175	#define EV_USE_SELECT 1
		3176	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3177
		3178	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3179	complexity in the O(n²) range when using win32.
		3180
		3181	=item Limited number of file descriptors
		3182
		3183	Windows has numerous arbitrary (and low) limits on things. Early versions
		3184	of winsocket's select only supported waiting for a max. of C<64> handles
		3185	(probably owning to the fact that all windows kernels can only wait for
		3186	C<64> things at the same time internally; microsoft recommends spawning a
		3187	chain of threads and wait for 63 handles and the previous thread in each).
		3188
		3189	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3190	to some high number (e.g. C<2048>) before compiling the winsocket select
		3191	call (which might be in libev or elsewhere, for example, perl does its own
		3192	select emulation on windows).
		3193
		3194	Another limit is the number of file descriptors in the microsoft runtime
		3195	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3196	or something like this inside microsoft). You can increase this by calling
		3197	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3198	arbitrary limit), but is broken in many versions of the microsoft runtime
		3199	libraries.
		3200
		3201	This might get you to about C<512> or C<2048> sockets (depending on
		3202	windows version and/or the phase of the moon). To get more, you need to
		3203	wrap all I/O functions and provide your own fd management, but the cost of
		3204	calling select (O(n²)) will likely make this unworkable.
		3205
		3206	=back
		3207
		3208
2373	=head1 AUTHOR	3209	=head1 AUTHOR
2374		3210
2375	Marc Lehmann <libev@schmorp.de>.	3211	Marc Lehmann <libev@schmorp.de>.
2376		3212

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