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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://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
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.
…		…
170	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
171		197
172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
173		199
174	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
175	semantics is identical - to the realloc C function). It is used to	201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
176	allocate and free memory (no surprises here). If it returns zero when	202	used to allocate and free memory (no surprises here). If it returns zero
177	memory needs to be allocated, the library might abort or take some	203	when memory needs to be allocated (C<size != 0>), the library might abort
178	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
179	function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
180		209
181	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
182	free some memory if it cannot allocate memory, to use a special allocator,	211	free some memory if it cannot allocate memory, to use a special allocator,
183	or even to sleep a while and retry until some memory is available.	212	or even to sleep a while and retry until some memory is available.
184		213
185	Example: Replace the libev allocator with one that waits a bit and then	214	Example: Replace the libev allocator with one that waits a bit and then
186	retries).	215	retries (example requires a standards-compliant C<realloc>).
187		216
188	static void *	217	static void *
189	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
190	{	219	{
191	for (;;)	220	for (;;)
…		…
230		259
231	An event loop is described by a C<struct ev_loop *>. The library knows two	260	An event loop is described by a C<struct ev_loop *>. The library knows two
232	types of such loops, the I<default> loop, which supports signals and child	261	types of such loops, the I<default> loop, which supports signals and child
233	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
234		263
235	If you use threads, a common model is to run the default event loop
236	in your main thread (or in a separate thread) and for each thread you
237	create, you also create another event loop. Libev itself does no locking
238	whatsoever, so if you mix calls to the same event loop in different
239	threads, make sure you lock (this is usually a bad idea, though, even if
240	done correctly, because it's hideous and inefficient).
241
242	=over 4	264	=over 4
243		265
244	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
245		267
246	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
…		…
248	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		272
251	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
252	function.	274	function.
		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
253		286
254	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		289
257	The following flags are supported:	290	The following flags are supported:
…		…
279	enabling this flag.	312	enabling this flag.
280		313
281	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
287		320
288	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
290	flag.	323	flag.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		329
297	This is your standard select(2) backend. Not I<completely> standard, as	330	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	331	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	332	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readiness notifications you get per iteration.
302		342
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		344
305	And this is your standard poll(2) backend. It's more complicated than	345	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	346	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	347	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
309		351
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		353
312	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	355	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	356	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
		358	of shortcomings, such as silently dropping events in some hard-to-detect
		359	cases and requiring a syscall per fd change, no fork support and bad
		360	support for dup.
316		361
317	While stopping and starting an I/O watcher in the same iteration will	362	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	363	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	364	(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	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	366	very well if you register events for both fds.
322		367
323	Please note that epoll sometimes generates spurious notifications, so you	368	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	369	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	370	(or space) is available.
326		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		380
329	Kqueue deserves special mention, as at the time of this writing, it	381	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	382	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	383	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	384	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	385	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		387	system like NetBSD.
		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
335		392
336	It scales in the same way as the epoll backend, but the interface to the	393	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	394	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	395	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	396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	397	two event changes per incident, support for C<fork ()> is very bad and it
		398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
341		408
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		410
344	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
345		415
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		417
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	418	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)).	419	it's really slow, but it still scales very well (O(active_fds)).
350		420
351	Please note that solaris ports can result in a lot of spurious	421	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	422	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readiness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
354		433
355	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
356		435
357	Try all backends (even potentially broken ones that wouldn't be tried	436	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		439
		440	It is definitely not recommended to use this flag.
		441
361	=back	442	=back
362		443
363	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	445	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		447
368	The most typical usage is like this:	448	The most typical usage is like this:
369		449
370	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
385		465
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	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	467	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	468	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).	469	undefined behaviour (or a failed assertion if assertions are enabled).
		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
390		474
391	Example: Try to create a event loop that uses epoll and nothing else.	475	Example: Try to create a event loop that uses epoll and nothing else.
392		476
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	478	if (!epoller)
…		…
399	Destroys the default loop again (frees all memory and kernel state	483	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	484	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	485	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>	486	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	487	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	488	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	489	for example).
		490
		491	Note that certain global state, such as signal state, will not be freed by
		492	this function, and related watchers (such as signal and child watchers)
		493	would need to be stopped manually.
		494
		495	In general it is not advisable to call this function except in the
		496	rare occasion where you really need to free e.g. the signal handling
		497	pipe fds. If you need dynamically allocated loops it is better to use
		498	C<ev_loop_new> and C<ev_loop_destroy>).
406		499
407	=item ev_loop_destroy (loop)	500	=item ev_loop_destroy (loop)
408		501
409	Like C<ev_default_destroy>, but destroys an event loop created by an	502	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	503	earlier call to C<ev_loop_new>.
411		504
412	=item ev_default_fork ()	505	=item ev_default_fork ()
413		506
		507	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	508	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	509	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	510	the child process (or both child and parent, but that again makes little
417	again makes little sense).	511	sense). You I<must> call it in the child before using any of the libev
		512	functions, and it will only take effect at the next C<ev_loop> iteration.
418		513
419	You I<must> call this function in the child process after forking if and	514	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	515	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.	516	you just fork+exec, you don't have to call it at all.
422		517
423	The function itself is quite fast and it's usually not a problem to call	518	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	519	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>:	520	quite nicely into a call to C<pthread_atfork>:
426		521
427	pthread_atfork (0, 0, ev_default_fork);	522	pthread_atfork (0, 0, ev_default_fork);
428		523
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)	524	=item ev_loop_fork (loop)
434		525
435	Like C<ev_default_fork>, but acts on an event loop created by	526	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	527	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.	528	after fork, and how you do this is entirely your own problem.
		529
		530	=item int ev_is_default_loop (loop)
		531
		532	Returns true when the given loop actually is the default loop, false otherwise.
438		533
439	=item unsigned int ev_loop_count (loop)	534	=item unsigned int ev_loop_count (loop)
440		535
441	Returns the count of loop iterations for the loop, which is identical to	536	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	537	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		550
456	Returns the current "event loop time", which is the time the event loop	551	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	552	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	553	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	554	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).	555	event occurring (or more correctly, libev finding out about it).
461		556
462	=item ev_loop (loop, int flags)	557	=item ev_loop (loop, int flags)
463		558
464	Finally, this is it, the event handler. This function usually is called	559	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	560	after you initialised all your watchers and you want to start handling
…		…
487	usually a better approach for this kind of thing.	582	usually a better approach for this kind of thing.
488		583
489	Here are the gory details of what C<ev_loop> does:	584	Here are the gory details of what C<ev_loop> does:
490		585
491	- Before the first iteration, call any pending watchers.	586	- Before the first iteration, call any pending watchers.
492	* If there are no active watchers (reference count is zero), return.	587	* If EVFLAG_FORKCHECK was used, check for a fork.
493	- Queue all prepare watchers and then call all outstanding watchers.	588	- If a fork was detected, queue and call all fork watchers.
		589	- Queue and call all prepare watchers.
494	- If we have been forked, recreate the kernel state.	590	- If we have been forked, recreate the kernel state.
495	- Update the kernel state with all outstanding changes.	591	- Update the kernel state with all outstanding changes.
496	- Update the "event loop time".	592	- Update the "event loop time".
497	- Calculate for how long to block.	593	- Calculate for how long to sleep or block, if at all
		594	(active idle watchers, EVLOOP_NONBLOCK or not having
		595	any active watchers at all will result in not sleeping).
		596	- Sleep if the I/O and timer collect interval say so.
498	- Block the process, waiting for any events.	597	- Block the process, waiting for any events.
499	- Queue all outstanding I/O (fd) events.	598	- Queue all outstanding I/O (fd) events.
500	- Update the "event loop time" and do time jump handling.	599	- Update the "event loop time" and do time jump handling.
501	- Queue all outstanding timers.	600	- Queue all outstanding timers.
502	- Queue all outstanding periodics.	601	- Queue all outstanding periodics.
503	- If no events are pending now, queue all idle watchers.	602	- If no events are pending now, queue all idle watchers.
504	- Queue all check watchers.	603	- Queue all check watchers.
505	- Call all queued watchers in reverse order (i.e. check watchers first).	604	- Call all queued watchers in reverse order (i.e. check watchers first).
506	Signals and child watchers are implemented as I/O watchers, and will	605	Signals and child watchers are implemented as I/O watchers, and will
507	be handled here by queueing them when their watcher gets executed.	606	be handled here by queueing them when their watcher gets executed.
508	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
509	were used, return, otherwise continue with step *.	608	were used, or there are no active watchers, return, otherwise
		609	continue with step *.
510		610
511	Example: Queue some jobs and then loop until no events are outsanding	611	Example: Queue some jobs and then loop until no events are outstanding
512	anymore.	612	anymore.
513		613
514	... queue jobs here, make sure they register event watchers as long	614	... queue jobs here, make sure they register event watchers as long
515	... as they still have work to do (even an idle watcher will do..)	615	... as they still have work to do (even an idle watcher will do..)
516	ev_loop (my_loop, 0);	616	ev_loop (my_loop, 0);
…		…
520		620
521	Can be used to make a call to C<ev_loop> return early (but only after it	621	Can be used to make a call to C<ev_loop> return early (but only after it
522	has processed all outstanding events). The C<how> argument must be either	622	has processed all outstanding events). The C<how> argument must be either
523	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
524	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		625
		626	This "unloop state" will be cleared when entering C<ev_loop> again.
525		627
526	=item ev_ref (loop)	628	=item ev_ref (loop)
527		629
528	=item ev_unref (loop)	630	=item ev_unref (loop)
529		631
…		…
534	returning, ev_unref() after starting, and ev_ref() before stopping it. For	636	returning, ev_unref() after starting, and ev_ref() before stopping it. For
535	example, libev itself uses this for its internal signal pipe: It is not	637	example, libev itself uses this for its internal signal pipe: It is not
536	visible to the libev user and should not keep C<ev_loop> from exiting if	638	visible to the libev user and should not keep C<ev_loop> from exiting if
537	no event watchers registered by it are active. It is also an excellent	639	no event watchers registered by it are active. It is also an excellent
538	way to do this for generic recurring timers or from within third-party	640	way to do this for generic recurring timers or from within third-party
539	libraries. Just remember to I<unref after start> and I<ref before stop>.	641	libraries. Just remember to I<unref after start> and I<ref before stop>
		642	(but only if the watcher wasn't active before, or was active before,
		643	respectively).
540		644
541	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
542	running when nothing else is active.	646	running when nothing else is active.
543		647
544	struct ev_signal exitsig;	648	struct ev_signal exitsig;
…		…
548		652
549	Example: For some weird reason, unregister the above signal handler again.	653	Example: For some weird reason, unregister the above signal handler again.
550		654
551	ev_ref (loop);	655	ev_ref (loop);
552	ev_signal_stop (loop, &exitsig);	656	ev_signal_stop (loop, &exitsig);
		657
		658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		659
		660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		661
		662	These advanced functions influence the time that libev will spend waiting
		663	for events. Both are by default C<0>, meaning that libev will try to
		664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		665
		666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		667	allows libev to delay invocation of I/O and timer/periodic callbacks to
		668	increase efficiency of loop iterations.
		669
		670	The background is that sometimes your program runs just fast enough to
		671	handle one (or very few) event(s) per loop iteration. While this makes
		672	the program responsive, it also wastes a lot of CPU time to poll for new
		673	events, especially with backends like C<select ()> which have a high
		674	overhead for the actual polling but can deliver many events at once.
		675
		676	By setting a higher I<io collect interval> you allow libev to spend more
		677	time collecting I/O events, so you can handle more events per iteration,
		678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		679	C<ev_timer>) will be not affected. Setting this to a non-null value will
		680	introduce an additional C<ev_sleep ()> call into most loop iterations.
		681
		682	Likewise, by setting a higher I<timeout collect interval> you allow libev
		683	to spend more time collecting timeouts, at the expense of increased
		684	latency (the watcher callback will be called later). C<ev_io> watchers
		685	will not be affected. Setting this to a non-null value will not introduce
		686	any overhead in libev.
		687
		688	Many (busy) programs can usually benefit by setting the io collect
		689	interval to a value near C<0.1> or so, which is often enough for
		690	interactive servers (of course not for games), likewise for timeouts. It
		691	usually doesn't make much sense to set it to a lower value than C<0.01>,
		692	as this approsaches the timing granularity of most systems.
		693
		694	=item ev_loop_verify (loop)
		695
		696	This function only does something when C<EV_VERIFY> support has been
		697	compiled in. It tries to go through all internal structures and checks
		698	them for validity. If anything is found to be inconsistent, it will print
		699	an error message to standard error and call C<abort ()>.
		700
		701	This can be used to catch bugs inside libev itself: under normal
		702	circumstances, this function will never abort as of course libev keeps its
		703	data structures consistent.
553		704
554	=back	705	=back
555		706
556		707
557	=head1 ANATOMY OF A WATCHER	708	=head1 ANATOMY OF A WATCHER
…		…
656		807
657	=item C<EV_FORK>	808	=item C<EV_FORK>
658		809
659	The event loop has been resumed in the child process after fork (see	810	The event loop has been resumed in the child process after fork (see
660	C<ev_fork>).	811	C<ev_fork>).
		812
		813	=item C<EV_ASYNC>
		814
		815	The given async watcher has been asynchronously notified (see C<ev_async>).
661		816
662	=item C<EV_ERROR>	817	=item C<EV_ERROR>
663		818
664	An unspecified error has occured, the watcher has been stopped. This might	819	An unspecified error has occured, the watcher has been stopped. This might
665	happen because the watcher could not be properly started because libev	820	happen because the watcher could not be properly started because libev
…		…
883	In general you can register as many read and/or write event watchers per	1038	In general you can register as many read and/or write event watchers per
884	fd as you want (as long as you don't confuse yourself). Setting all file	1039	fd as you want (as long as you don't confuse yourself). Setting all file
885	descriptors to non-blocking mode is also usually a good idea (but not	1040	descriptors to non-blocking mode is also usually a good idea (but not
886	required if you know what you are doing).	1041	required if you know what you are doing).
887		1042
888	You have to be careful with dup'ed file descriptors, though. Some backends
889	(the linux epoll backend is a notable example) cannot handle dup'ed file
890	descriptors correctly if you register interest in two or more fds pointing
891	to the same underlying file/socket/etc. description (that is, they share
892	the same underlying "file open").
893
894	If you must do this, then force the use of a known-to-be-good backend	1043	If you must do this, then force the use of a known-to-be-good backend
895	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
896	C<EVBACKEND_POLL>).	1045	C<EVBACKEND_POLL>).
897		1046
898	Another thing you have to watch out for is that it is quite easy to	1047	Another thing you have to watch out for is that it is quite easy to
899	receive "spurious" readyness notifications, that is your callback might	1048	receive "spurious" readiness notifications, that is your callback might
900	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
901	because there is no data. Not only are some backends known to create a	1050	because there is no data. Not only are some backends known to create a
902	lot of those (for example solaris ports), it is very easy to get into	1051	lot of those (for example solaris ports), it is very easy to get into
903	this situation even with a relatively standard program structure. Thus	1052	this situation even with a relatively standard program structure. Thus
904	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning
…		…
908	play around with an Xlib connection), then you have to seperately re-test	1057	play around with an Xlib connection), then you have to seperately re-test
909	whether a file descriptor is really ready with a known-to-be good interface	1058	whether a file descriptor is really ready with a known-to-be good interface
910	such as poll (fortunately in our Xlib example, Xlib already does this on	1059	such as poll (fortunately in our Xlib example, Xlib already does this on
911	its own, so its quite safe to use).	1060	its own, so its quite safe to use).
912		1061
		1062	=head3 The special problem of disappearing file descriptors
		1063
		1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1065	descriptor (either by calling C<close> explicitly or by any other means,
		1066	such as C<dup>). The reason is that you register interest in some file
		1067	descriptor, but when it goes away, the operating system will silently drop
		1068	this interest. If another file descriptor with the same number then is
		1069	registered with libev, there is no efficient way to see that this is, in
		1070	fact, a different file descriptor.
		1071
		1072	To avoid having to explicitly tell libev about such cases, libev follows
		1073	the following policy: Each time C<ev_io_set> is being called, libev
		1074	will assume that this is potentially a new file descriptor, otherwise
		1075	it is assumed that the file descriptor stays the same. That means that
		1076	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1077	descriptor even if the file descriptor number itself did not change.
		1078
		1079	This is how one would do it normally anyway, the important point is that
		1080	the libev application should not optimise around libev but should leave
		1081	optimisations to libev.
		1082
		1083	=head3 The special problem of dup'ed file descriptors
		1084
		1085	Some backends (e.g. epoll), cannot register events for file descriptors,
		1086	but only events for the underlying file descriptions. That means when you
		1087	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1088	events for them, only one file descriptor might actually receive events.
		1089
		1090	There is no workaround possible except not registering events
		1091	for potentially C<dup ()>'ed file descriptors, or to resort to
		1092	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1093
		1094	=head3 The special problem of fork
		1095
		1096	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1097	useless behaviour. Libev fully supports fork, but needs to be told about
		1098	it in the child.
		1099
		1100	To support fork in your programs, you either have to call
		1101	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1103	C<EVBACKEND_POLL>.
		1104
		1105	=head3 The special problem of SIGPIPE
		1106
		1107	While not really specific to libev, it is easy to forget about SIGPIPE:
		1108	when reading from a pipe whose other end has been closed, your program
		1109	gets send a SIGPIPE, which, by default, aborts your program. For most
		1110	programs this is sensible behaviour, for daemons, this is usually
		1111	undesirable.
		1112
		1113	So when you encounter spurious, unexplained daemon exits, make sure you
		1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1115	somewhere, as that would have given you a big clue).
		1116
		1117
		1118	=head3 Watcher-Specific Functions
		1119
913	=over 4	1120	=over 4
914		1121
915	=item ev_io_init (ev_io *, callback, int fd, int events)	1122	=item ev_io_init (ev_io *, callback, int fd, int events)
916		1123
917	=item ev_io_set (ev_io *, int fd, int events)	1124	=item ev_io_set (ev_io *, int fd, int events)
…		…
927	=item int events [read-only]	1134	=item int events [read-only]
928		1135
929	The events being watched.	1136	The events being watched.
930		1137
931	=back	1138	=back
		1139
		1140	=head3 Examples
932		1141
933	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
934	readable, but only once. Since it is likely line-buffered, you could	1143	readable, but only once. Since it is likely line-buffered, you could
935	attempt to read a whole line in the callback.	1144	attempt to read a whole line in the callback.
936		1145
…		…
953		1162
954	Timer watchers are simple relative timers that generate an event after a	1163	Timer watchers are simple relative timers that generate an event after a
955	given time, and optionally repeating in regular intervals after that.	1164	given time, and optionally repeating in regular intervals after that.
956		1165
957	The timers are based on real time, that is, if you register an event that	1166	The timers are based on real time, that is, if you register an event that
958	times out after an hour and you reset your system clock to last years	1167	times out after an hour and you reset your system clock to january last
959	time, it will still time out after (roughly) and hour. "Roughly" because	1168	year, it will still time out after (roughly) and hour. "Roughly" because
960	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the
961	monotonic clock option helps a lot here).	1170	monotonic clock option helps a lot here).
962		1171
963	The relative timeouts are calculated relative to the C<ev_now ()>	1172	The relative timeouts are calculated relative to the C<ev_now ()>
964	time. This is usually the right thing as this timestamp refers to the time	1173	time. This is usually the right thing as this timestamp refers to the time
…		…
966	you suspect event processing to be delayed and you I<need> to base the timeout	1175	you suspect event processing to be delayed and you I<need> to base the timeout
967	on the current time, use something like this to adjust for this:	1176	on the current time, use something like this to adjust for this:
968		1177
969	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
970		1179
971	The callback is guarenteed to be invoked only when its timeout has passed,	1180	The callback is guarenteed to be invoked only after its timeout has passed,
972	but if multiple timers become ready during the same loop iteration then	1181	but if multiple timers become ready during the same loop iteration then
973	order of execution is undefined.	1182	order of execution is undefined.
974		1183
		1184	=head3 Watcher-Specific Functions and Data Members
		1185
975	=over 4	1186	=over 4
976		1187
977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1188	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978		1189
979	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1190	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
980		1191
981	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1192	Configure the timer to trigger after C<after> seconds. If C<repeat>
982	C<0.>, then it will automatically be stopped. If it is positive, then the	1193	is C<0.>, then it will automatically be stopped once the timeout is
983	timer will automatically be configured to trigger again C<repeat> seconds	1194	reached. If it is positive, then the timer will automatically be
984	later, again, and again, until stopped manually.	1195	configured to trigger again C<repeat> seconds later, again, and again,
		1196	until stopped manually.
985		1197
986	The timer itself will do a best-effort at avoiding drift, that is, if you	1198	The timer itself will do a best-effort at avoiding drift, that is, if
987	configure a timer to trigger every 10 seconds, then it will trigger at	1199	you configure a timer to trigger every 10 seconds, then it will normally
988	exactly 10 second intervals. If, however, your program cannot keep up with	1200	trigger at exactly 10 second intervals. If, however, your program cannot
989	the timer (because it takes longer than those 10 seconds to do stuff) the	1201	keep up with the timer (because it takes longer than those 10 seconds to
990	timer will not fire more than once per event loop iteration.	1202	do stuff) the timer will not fire more than once per event loop iteration.
991		1203
992	=item ev_timer_again (loop)	1204	=item ev_timer_again (loop, ev_timer *)
993		1205
994	This will act as if the timer timed out and restart it again if it is	1206	This will act as if the timer timed out and restart it again if it is
995	repeating. The exact semantics are:	1207	repeating. The exact semantics are:
996		1208
997	If the timer is pending, its pending status is cleared.	1209	If the timer is pending, its pending status is cleared.
…		…
1032	or C<ev_timer_again> is called and determines the next timeout (if any),	1244	or C<ev_timer_again> is called and determines the next timeout (if any),
1033	which is also when any modifications are taken into account.	1245	which is also when any modifications are taken into account.
1034		1246
1035	=back	1247	=back
1036		1248
		1249	=head3 Examples
		1250
1037	Example: Create a timer that fires after 60 seconds.	1251	Example: Create a timer that fires after 60 seconds.
1038		1252
1039	static void	1253	static void
1040	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1041	{	1255	{
…		…
1070	Periodic watchers are also timers of a kind, but they are very versatile	1284	Periodic watchers are also timers of a kind, but they are very versatile
1071	(and unfortunately a bit complex).	1285	(and unfortunately a bit complex).
1072		1286
1073	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1074	but on wallclock time (absolute time). You can tell a periodic watcher	1288	but on wallclock time (absolute time). You can tell a periodic watcher
1075	to trigger "at" some specific point in time. For example, if you tell a	1289	to trigger after some specific point in time. For example, if you tell a
1076	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1077	+ 10.>) and then reset your system clock to the last year, then it will	1291	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1292	clock to january of the previous year, then it will take more than year
1078	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1079	roughly 10 seconds later).	1294	roughly 10 seconds later as it uses a relative timeout).
1080		1295
1081	They can also be used to implement vastly more complex timers, such as	1296	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on each midnight, local time or other, complicated,	1297	such as triggering an event on each "midnight, local time", or other
1083	rules.	1298	complicated, rules.
1084		1299
1085	As with timers, the callback is guarenteed to be invoked only when the	1300	As with timers, the callback is guarenteed to be invoked only when the
1086	time (C<at>) has been passed, but if multiple periodic timers become ready	1301	time (C<at>) has passed, but if multiple periodic timers become ready
1087	during the same loop iteration then order of execution is undefined.	1302	during the same loop iteration then order of execution is undefined.
		1303
		1304	=head3 Watcher-Specific Functions and Data Members
1088		1305
1089	=over 4	1306	=over 4
1090		1307
1091	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092		1309
…		…
1097		1314
1098	=over 4	1315	=over 4
1099		1316
1100	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1101		1318
1102	In this configuration the watcher triggers an event at the wallclock time	1319	In this configuration the watcher triggers an event after the wallclock
1103	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1320	time C<at> has passed and doesn't repeat. It will not adjust when a time
1104	that is, if it is to be run at January 1st 2011 then it will run when the	1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1105	system time reaches or surpasses this time.	1322	run when the system time reaches or surpasses this time.
1106		1323
1107	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1108		1325
1109	In this mode the watcher will always be scheduled to time out at the next	1326	In this mode the watcher will always be scheduled to time out at the next
1110	C<at + N * interval> time (for some integer N, which can also be negative)	1327	C<at + N * interval> time (for some integer N, which can also be negative)
1111	and then repeat, regardless of any time jumps.	1328	and then repeat, regardless of any time jumps.
1112		1329
1113	This can be used to create timers that do not drift with respect to system	1330	This can be used to create timers that do not drift with respect to system
1114	time:	1331	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1332	the hour:
1115		1333
1116	ev_periodic_set (&periodic, 0., 3600., 0);	1334	ev_periodic_set (&periodic, 0., 3600., 0);
1117		1335
1118	This doesn't mean there will always be 3600 seconds in between triggers,	1336	This doesn't mean there will always be 3600 seconds in between triggers,
1119	but only that the the callback will be called when the system time shows a	1337	but only that the the callback will be called when the system time shows a
…		…
1124	C<ev_periodic> will try to run the callback in this mode at the next possible	1342	C<ev_periodic> will try to run the callback in this mode at the next possible
1125	time where C<time = at (mod interval)>, regardless of any time jumps.	1343	time where C<time = at (mod interval)>, regardless of any time jumps.
1126		1344
1127	For numerical stability it is preferable that the C<at> value is near	1345	For numerical stability it is preferable that the C<at> value is near
1128	C<ev_now ()> (the current time), but there is no range requirement for	1346	C<ev_now ()> (the current time), but there is no range requirement for
1129	this value.	1347	this value, and in fact is often specified as zero.
		1348
		1349	Note also that there is an upper limit to how often a timer can fire (cpu
		1350	speed for example), so if C<interval> is very small then timing stability
		1351	will of course detoriate. Libev itself tries to be exact to be about one
		1352	millisecond (if the OS supports it and the machine is fast enough).
1130		1353
1131	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1132		1355
1133	In this mode the values for C<interval> and C<at> are both being	1356	In this mode the values for C<interval> and C<at> are both being
1134	ignored. Instead, each time the periodic watcher gets scheduled, the	1357	ignored. Instead, each time the periodic watcher gets scheduled, the
1135	reschedule callback will be called with the watcher as first, and the	1358	reschedule callback will be called with the watcher as first, and the
1136	current time as second argument.	1359	current time as second argument.
1137		1360
1138	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1139	ever, or make any event loop modifications>. If you need to stop it,	1362	ever, or make ANY event loop modifications whatsoever>.
1140	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1141	starting an C<ev_prepare> watcher, which is legal).
1142		1363
		1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1366	only event loop modification you are allowed to do).
		1367
1143	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1144	ev_tstamp now)>, e.g.:	1369	*w, ev_tstamp now)>, e.g.:
1145		1370
1146	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1147	{	1372	{
1148	return now + 60.;	1373	return now + 60.;
1149	}	1374	}
…		…
1151	It must return the next time to trigger, based on the passed time value	1376	It must return the next time to trigger, based on the passed time value
1152	(that is, the lowest time value larger than to the second argument). It	1377	(that is, the lowest time value larger than to the second argument). It
1153	will usually be called just before the callback will be triggered, but	1378	will usually be called just before the callback will be triggered, but
1154	might be called at other times, too.	1379	might be called at other times, too.
1155		1380
1156	NOTE: I<< This callback must always return a time that is later than the	1381	NOTE: I<< This callback must always return a time that is higher than or
1157	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1382	equal to the passed C<now> value >>.
1158		1383
1159	This can be used to create very complex timers, such as a timer that	1384	This can be used to create very complex timers, such as a timer that
1160	triggers on each midnight, local time. To do this, you would calculate the	1385	triggers on "next midnight, local time". To do this, you would calculate the
1161	next midnight after C<now> and return the timestamp value for this. How	1386	next midnight after C<now> and return the timestamp value for this. How
1162	you do this is, again, up to you (but it is not trivial, which is the main	1387	you do this is, again, up to you (but it is not trivial, which is the main
1163	reason I omitted it as an example).	1388	reason I omitted it as an example).
1164		1389
1165	=back	1390	=back
…		…
1169	Simply stops and restarts the periodic watcher again. This is only useful	1394	Simply stops and restarts the periodic watcher again. This is only useful
1170	when you changed some parameters or the reschedule callback would return	1395	when you changed some parameters or the reschedule callback would return
1171	a different time than the last time it was called (e.g. in a crond like	1396	a different time than the last time it was called (e.g. in a crond like
1172	program when the crontabs have changed).	1397	program when the crontabs have changed).
1173		1398
		1399	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1400
		1401	When active, returns the absolute time that the watcher is supposed to
		1402	trigger next.
		1403
1174	=item ev_tstamp offset [read-write]	1404	=item ev_tstamp offset [read-write]
1175		1405
1176	When repeating, this contains the offset value, otherwise this is the	1406	When repeating, this contains the offset value, otherwise this is the
1177	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1178		1408
…		…
1190	The current reschedule callback, or C<0>, if this functionality is	1420	The current reschedule callback, or C<0>, if this functionality is
1191	switched off. Can be changed any time, but changes only take effect when	1421	switched off. Can be changed any time, but changes only take effect when
1192	the periodic timer fires or C<ev_periodic_again> is being called.	1422	the periodic timer fires or C<ev_periodic_again> is being called.
1193		1423
1194	=back	1424	=back
		1425
		1426	=head3 Examples
1195		1427
1196	Example: Call a callback every hour, or, more precisely, whenever the	1428	Example: Call a callback every hour, or, more precisely, whenever the
1197	system clock is divisible by 3600. The callback invocation times have	1429	system clock is divisible by 3600. The callback invocation times have
1198	potentially a lot of jittering, but good long-term stability.	1430	potentially a lot of jittering, but good long-term stability.
1199		1431
…		…
1239	with the kernel (thus it coexists with your own signal handlers as long	1471	with the kernel (thus it coexists with your own signal handlers as long
1240	as you don't register any with libev). Similarly, when the last signal	1472	as you don't register any with libev). Similarly, when the last signal
1241	watcher for a signal is stopped libev will reset the signal handler to	1473	watcher for a signal is stopped libev will reset the signal handler to
1242	SIG_DFL (regardless of what it was set to before).	1474	SIG_DFL (regardless of what it was set to before).
1243		1475
		1476	If possible and supported, libev will install its handlers with
		1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1478	interrupted. If you have a problem with syscalls getting interrupted by
		1479	signals you can block all signals in an C<ev_check> watcher and unblock
		1480	them in an C<ev_prepare> watcher.
		1481
		1482	=head3 Watcher-Specific Functions and Data Members
		1483
1244	=over 4	1484	=over 4
1245		1485
1246	=item ev_signal_init (ev_signal *, callback, int signum)	1486	=item ev_signal_init (ev_signal *, callback, int signum)
1247		1487
1248	=item ev_signal_set (ev_signal *, int signum)	1488	=item ev_signal_set (ev_signal *, int signum)
…		…
1254		1494
1255	The signal the watcher watches out for.	1495	The signal the watcher watches out for.
1256		1496
1257	=back	1497	=back
1258		1498
		1499	=head3 Examples
		1500
		1501	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1502
		1503	static void
		1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1505	{
		1506	ev_unloop (loop, EVUNLOOP_ALL);
		1507	}
		1508
		1509	struct ev_signal signal_watcher;
		1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1511	ev_signal_start (loop, &sigint_cb);
		1512
1259		1513
1260	=head2 C<ev_child> - watch out for process status changes	1514	=head2 C<ev_child> - watch out for process status changes
1261		1515
1262	Child watchers trigger when your process receives a SIGCHLD in response to	1516	Child watchers trigger when your process receives a SIGCHLD in response to
1263	some child status changes (most typically when a child of yours dies).	1517	some child status changes (most typically when a child of yours dies). It
		1518	is permissible to install a child watcher I<after> the child has been
		1519	forked (which implies it might have already exited), as long as the event
		1520	loop isn't entered (or is continued from a watcher).
		1521
		1522	Only the default event loop is capable of handling signals, and therefore
		1523	you can only rgeister child watchers in the default event loop.
		1524
		1525	=head3 Process Interaction
		1526
		1527	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1528	initialised. This is necessary to guarantee proper behaviour even if
		1529	the first child watcher is started after the child exits. The occurance
		1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1531	synchronously as part of the event loop processing. Libev always reaps all
		1532	children, even ones not watched.
		1533
		1534	=head3 Overriding the Built-In Processing
		1535
		1536	Libev offers no special support for overriding the built-in child
		1537	processing, but if your application collides with libev's default child
		1538	handler, you can override it easily by installing your own handler for
		1539	C<SIGCHLD> after initialising the default loop, and making sure the
		1540	default loop never gets destroyed. You are encouraged, however, to use an
		1541	event-based approach to child reaping and thus use libev's support for
		1542	that, so other libev users can use C<ev_child> watchers freely.
		1543
		1544	=head3 Watcher-Specific Functions and Data Members
1264		1545
1265	=over 4	1546	=over 4
1266		1547
1267	=item ev_child_init (ev_child *, callback, int pid)	1548	=item ev_child_init (ev_child *, callback, int pid, int trace)
1268		1549
1269	=item ev_child_set (ev_child *, int pid)	1550	=item ev_child_set (ev_child *, int pid, int trace)
1270		1551
1271	Configures the watcher to wait for status changes of process C<pid> (or	1552	Configures the watcher to wait for status changes of process C<pid> (or
1272	I<any> process if C<pid> is specified as C<0>). The callback can look	1553	I<any> process if C<pid> is specified as C<0>). The callback can look
1273	at the C<rstatus> member of the C<ev_child> watcher structure to see	1554	at the C<rstatus> member of the C<ev_child> watcher structure to see
1274	the status word (use the macros from C<sys/wait.h> and see your systems	1555	the status word (use the macros from C<sys/wait.h> and see your systems
1275	C<waitpid> documentation). The C<rpid> member contains the pid of the	1556	C<waitpid> documentation). The C<rpid> member contains the pid of the
1276	process causing the status change.	1557	process causing the status change. C<trace> must be either C<0> (only
		1558	activate the watcher when the process terminates) or C<1> (additionally
		1559	activate the watcher when the process is stopped or continued).
1277		1560
1278	=item int pid [read-only]	1561	=item int pid [read-only]
1279		1562
1280	The process id this watcher watches out for, or C<0>, meaning any process id.	1563	The process id this watcher watches out for, or C<0>, meaning any process id.
1281		1564
…		…
1288	The process exit/trace status caused by C<rpid> (see your systems	1571	The process exit/trace status caused by C<rpid> (see your systems
1289	C<waitpid> and C<sys/wait.h> documentation for details).	1572	C<waitpid> and C<sys/wait.h> documentation for details).
1290		1573
1291	=back	1574	=back
1292		1575
1293	Example: Try to exit cleanly on SIGINT and SIGTERM.	1576	=head3 Examples
		1577
		1578	Example: C<fork()> a new process and install a child handler to wait for
		1579	its completion.
		1580
		1581	ev_child cw;
1294		1582
1295	static void	1583	static void
1296	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1584	child_cb (EV_P_ struct ev_child *w, int revents)
1297	{	1585	{
1298	ev_unloop (loop, EVUNLOOP_ALL);	1586	ev_child_stop (EV_A_ w);
		1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1299	}	1588	}
1300		1589
1301	struct ev_signal signal_watcher;	1590	pid_t pid = fork ();
1302	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1591
1303	ev_signal_start (loop, &sigint_cb);	1592	if (pid < 0)
		1593	// error
		1594	else if (pid == 0)
		1595	{
		1596	// the forked child executes here
		1597	exit (1);
		1598	}
		1599	else
		1600	{
		1601	ev_child_init (&cw, child_cb, pid, 0);
		1602	ev_child_start (EV_DEFAULT_ &cw);
		1603	}
1304		1604
1305		1605
1306	=head2 C<ev_stat> - did the file attributes just change?	1606	=head2 C<ev_stat> - did the file attributes just change?
1307		1607
1308	This watches a filesystem path for attribute changes. That is, it calls	1608	This watches a filesystem path for attribute changes. That is, it calls
…		…
1331	as even with OS-supported change notifications, this can be	1631	as even with OS-supported change notifications, this can be
1332	resource-intensive.	1632	resource-intensive.
1333		1633
1334	At the time of this writing, only the Linux inotify interface is	1634	At the time of this writing, only the Linux inotify interface is
1335	implemented (implementing kqueue support is left as an exercise for the	1635	implemented (implementing kqueue support is left as an exercise for the
		1636	reader, note, however, that the author sees no way of implementing ev_stat
1336	reader). Inotify will be used to give hints only and should not change the	1637	semantics with kqueue). Inotify will be used to give hints only and should
1337	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1638	not change the semantics of C<ev_stat> watchers, which means that libev
1338	to fall back to regular polling again even with inotify, but changes are	1639	sometimes needs to fall back to regular polling again even with inotify,
1339	usually detected immediately, and if the file exists there will be no	1640	but changes are usually detected immediately, and if the file exists there
1340	polling.	1641	will be no polling.
		1642
		1643	=head3 ABI Issues (Largefile Support)
		1644
		1645	Libev by default (unless the user overrides this) uses the default
		1646	compilation environment, which means that on systems with optionally
		1647	disabled large file support, you get the 32 bit version of the stat
		1648	structure. When using the library from programs that change the ABI to
		1649	use 64 bit file offsets the programs will fail. In that case you have to
		1650	compile libev with the same flags to get binary compatibility. This is
		1651	obviously the case with any flags that change the ABI, but the problem is
		1652	most noticably with ev_stat and largefile support.
		1653
		1654	=head3 Inotify
		1655
		1656	When C<inotify (7)> support has been compiled into libev (generally only
		1657	available on Linux) and present at runtime, it will be used to speed up
		1658	change detection where possible. The inotify descriptor will be created lazily
		1659	when the first C<ev_stat> watcher is being started.
		1660
		1661	Inotify presence does not change the semantics of C<ev_stat> watchers
		1662	except that changes might be detected earlier, and in some cases, to avoid
		1663	making regular C<stat> calls. Even in the presence of inotify support
		1664	there are many cases where libev has to resort to regular C<stat> polling.
		1665
		1666	(There is no support for kqueue, as apparently it cannot be used to
		1667	implement this functionality, due to the requirement of having a file
		1668	descriptor open on the object at all times).
		1669
		1670	=head3 The special problem of stat time resolution
		1671
		1672	The C<stat ()> syscall only supports full-second resolution portably, and
		1673	even on systems where the resolution is higher, many filesystems still
		1674	only support whole seconds.
		1675
		1676	That means that, if the time is the only thing that changes, you can
		1677	easily miss updates: on the first update, C<ev_stat> detects a change and
		1678	calls your callback, which does something. When there is another update
		1679	within the same second, C<ev_stat> will be unable to detect it as the stat
		1680	data does not change.
		1681
		1682	The solution to this is to delay acting on a change for slightly more
		1683	than a second (or till slightly after the next full second boundary), using
		1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1685	ev_timer_again (loop, w)>).
		1686
		1687	The C<.02> offset is added to work around small timing inconsistencies
		1688	of some operating systems (where the second counter of the current time
		1689	might be be delayed. One such system is the Linux kernel, where a call to
		1690	C<gettimeofday> might return a timestamp with a full second later than
		1691	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1692	update file times then there will be a small window where the kernel uses
		1693	the previous second to update file times but libev might already execute
		1694	the timer callback).
		1695
		1696	=head3 Watcher-Specific Functions and Data Members
1341		1697
1342	=over 4	1698	=over 4
1343		1699
1344	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1700	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1345		1701
…		…
1349	C<path>. The C<interval> is a hint on how quickly a change is expected to	1705	C<path>. The C<interval> is a hint on how quickly a change is expected to
1350	be detected and should normally be specified as C<0> to let libev choose	1706	be detected and should normally be specified as C<0> to let libev choose
1351	a suitable value. The memory pointed to by C<path> must point to the same	1707	a suitable value. The memory pointed to by C<path> must point to the same
1352	path for as long as the watcher is active.	1708	path for as long as the watcher is active.
1353		1709
1354	The callback will be receive C<EV_STAT> when a change was detected,	1710	The callback will receive C<EV_STAT> when a change was detected, relative
1355	relative to the attributes at the time the watcher was started (or the	1711	to the attributes at the time the watcher was started (or the last change
1356	last change was detected).	1712	was detected).
1357		1713
1358	=item ev_stat_stat (ev_stat *)	1714	=item ev_stat_stat (loop, ev_stat *)
1359		1715
1360	Updates the stat buffer immediately with new values. If you change the	1716	Updates the stat buffer immediately with new values. If you change the
1361	watched path in your callback, you could call this fucntion to avoid	1717	watched path in your callback, you could call this function to avoid
1362	detecting this change (while introducing a race condition). Can also be	1718	detecting this change (while introducing a race condition if you are not
1363	useful simply to find out the new values.	1719	the only one changing the path). Can also be useful simply to find out the
		1720	new values.
1364		1721
1365	=item ev_statdata attr [read-only]	1722	=item ev_statdata attr [read-only]
1366		1723
1367	The most-recently detected attributes of the file. Although the type is of	1724	The most-recently detected attributes of the file. Although the type is
1368	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1725	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1369	suitable for your system. If the C<st_nlink> member is C<0>, then there	1726	suitable for your system, but you can only rely on the POSIX-standardised
		1727	members to be present. If the C<st_nlink> member is C<0>, then there was
1370	was some error while C<stat>ing the file.	1728	some error while C<stat>ing the file.
1371		1729
1372	=item ev_statdata prev [read-only]	1730	=item ev_statdata prev [read-only]
1373		1731
1374	The previous attributes of the file. The callback gets invoked whenever	1732	The previous attributes of the file. The callback gets invoked whenever
1375	C<prev> != C<attr>.	1733	C<prev> != C<attr>, or, more precisely, one or more of these members
		1734	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1735	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1376		1736
1377	=item ev_tstamp interval [read-only]	1737	=item ev_tstamp interval [read-only]
1378		1738
1379	The specified interval.	1739	The specified interval.
1380		1740
1381	=item const char *path [read-only]	1741	=item const char *path [read-only]
1382		1742
1383	The filesystem path that is being watched.	1743	The filesystem path that is being watched.
1384		1744
1385	=back	1745	=back
		1746
		1747	=head3 Examples
1386		1748
1387	Example: Watch C</etc/passwd> for attribute changes.	1749	Example: Watch C</etc/passwd> for attribute changes.
1388		1750
1389	static void	1751	static void
1390	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1403	}	1765	}
1404		1766
1405	...	1767	...
1406	ev_stat passwd;	1768	ev_stat passwd;
1407		1769
1408	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1409	ev_stat_start (loop, &passwd);	1771	ev_stat_start (loop, &passwd);
		1772
		1773	Example: Like above, but additionally use a one-second delay so we do not
		1774	miss updates (however, frequent updates will delay processing, too, so
		1775	one might do the work both on C<ev_stat> callback invocation I<and> on
		1776	C<ev_timer> callback invocation).
		1777
		1778	static ev_stat passwd;
		1779	static ev_timer timer;
		1780
		1781	static void
		1782	timer_cb (EV_P_ ev_timer *w, int revents)
		1783	{
		1784	ev_timer_stop (EV_A_ w);
		1785
		1786	/* now it's one second after the most recent passwd change */
		1787	}
		1788
		1789	static void
		1790	stat_cb (EV_P_ ev_stat *w, int revents)
		1791	{
		1792	/* reset the one-second timer */
		1793	ev_timer_again (EV_A_ &timer);
		1794	}
		1795
		1796	...
		1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1798	ev_stat_start (loop, &passwd);
		1799	ev_timer_init (&timer, timer_cb, 0., 1.02);
1410		1800
1411		1801
1412	=head2 C<ev_idle> - when you've got nothing better to do...	1802	=head2 C<ev_idle> - when you've got nothing better to do...
1413		1803
1414	Idle watchers trigger events when no other events of the same or higher	1804	Idle watchers trigger events when no other events of the same or higher
…		…
1428	Apart from keeping your process non-blocking (which is a useful	1818	Apart from keeping your process non-blocking (which is a useful
1429	effect on its own sometimes), idle watchers are a good place to do	1819	effect on its own sometimes), idle watchers are a good place to do
1430	"pseudo-background processing", or delay processing stuff to after the	1820	"pseudo-background processing", or delay processing stuff to after the
1431	event loop has handled all outstanding events.	1821	event loop has handled all outstanding events.
1432		1822
		1823	=head3 Watcher-Specific Functions and Data Members
		1824
1433	=over 4	1825	=over 4
1434		1826
1435	=item ev_idle_init (ev_signal *, callback)	1827	=item ev_idle_init (ev_signal *, callback)
1436		1828
1437	Initialises and configures the idle watcher - it has no parameters of any	1829	Initialises and configures the idle watcher - it has no parameters of any
1438	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1830	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1439	believe me.	1831	believe me.
1440		1832
1441	=back	1833	=back
		1834
		1835	=head3 Examples
1442		1836
1443	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1444	callback, free it. Also, use no error checking, as usual.	1838	callback, free it. Also, use no error checking, as usual.
1445		1839
1446	static void	1840	static void
1447	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1448	{	1842	{
1449	free (w);	1843	free (w);
1450	// now do something you wanted to do when the program has	1844	// now do something you wanted to do when the program has
1451	// no longer asnything immediate to do.	1845	// no longer anything immediate to do.
1452	}	1846	}
1453		1847
1454	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1455	ev_idle_init (idle_watcher, idle_cb);	1849	ev_idle_init (idle_watcher, idle_cb);
1456	ev_idle_start (loop, idle_cb);	1850	ev_idle_start (loop, idle_cb);
…		…
1498		1892
1499	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1500	priority, to ensure that they are being run before any other watchers	1894	priority, to ensure that they are being run before any other watchers
1501	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1502	too) should not activate ("feed") events into libev. While libev fully	1896	too) should not activate ("feed") events into libev. While libev fully
1503	supports this, they will be called before other C<ev_check> watchers did	1897	supports this, they might get executed before other C<ev_check> watchers
1504	their job. As C<ev_check> watchers are often used to embed other event	1898	did their job. As C<ev_check> watchers are often used to embed other
1505	loops those other event loops might be in an unusable state until their	1899	(non-libev) event loops those other event loops might be in an unusable
1506	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1900	state until their C<ev_check> watcher ran (always remind yourself to
1507	others).	1901	coexist peacefully with others).
		1902
		1903	=head3 Watcher-Specific Functions and Data Members
1508		1904
1509	=over 4	1905	=over 4
1510		1906
1511	=item ev_prepare_init (ev_prepare *, callback)	1907	=item ev_prepare_init (ev_prepare *, callback)
1512		1908
…		…
1516	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1517	macros, but using them is utterly, utterly and completely pointless.	1913	macros, but using them is utterly, utterly and completely pointless.
1518		1914
1519	=back	1915	=back
1520		1916
		1917	=head3 Examples
		1918
1521	There are a number of principal ways to embed other event loops or modules	1919	There are a number of principal ways to embed other event loops or modules
1522	into libev. Here are some ideas on how to include libadns into libev	1920	into libev. Here are some ideas on how to include libadns into libev
1523	(there is a Perl module named C<EV::ADNS> that does this, which you could	1921	(there is a Perl module named C<EV::ADNS> that does this, which you could
1524	use for an actually working example. Another Perl module named C<EV::Glib>	1922	use as a working example. Another Perl module named C<EV::Glib> embeds a
1525	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1923	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1526	into the Glib event loop).	1924	Glib event loop).
1527		1925
1528	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1926	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1529	and in a check watcher, destroy them and call into libadns. What follows	1927	and in a check watcher, destroy them and call into libadns. What follows
1530	is pseudo-code only of course. This requires you to either use a low	1928	is pseudo-code only of course. This requires you to either use a low
1531	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
1693	portable one.	2091	portable one.
1694		2092
1695	So when you want to use this feature you will always have to be prepared	2093	So when you want to use this feature you will always have to be prepared
1696	that you cannot get an embeddable loop. The recommended way to get around	2094	that you cannot get an embeddable loop. The recommended way to get around
1697	this is to have a separate variables for your embeddable loop, try to	2095	this is to have a separate variables for your embeddable loop, try to
1698	create it, and if that fails, use the normal loop for everything:	2096	create it, and if that fails, use the normal loop for everything.
		2097
		2098	=head3 Watcher-Specific Functions and Data Members
		2099
		2100	=over 4
		2101
		2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2103
		2104	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2105
		2106	Configures the watcher to embed the given loop, which must be
		2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2108	invoked automatically, otherwise it is the responsibility of the callback
		2109	to invoke it (it will continue to be called until the sweep has been done,
		2110	if you do not want thta, you need to temporarily stop the embed watcher).
		2111
		2112	=item ev_embed_sweep (loop, ev_embed *)
		2113
		2114	Make a single, non-blocking sweep over the embedded loop. This works
		2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2116	apropriate way for embedded loops.
		2117
		2118	=item struct ev_loop *other [read-only]
		2119
		2120	The embedded event loop.
		2121
		2122	=back
		2123
		2124	=head3 Examples
		2125
		2126	Example: Try to get an embeddable event loop and embed it into the default
		2127	event loop. If that is not possible, use the default loop. The default
		2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2130	used).
1699		2131
1700	struct ev_loop *loop_hi = ev_default_init (0);	2132	struct ev_loop *loop_hi = ev_default_init (0);
1701	struct ev_loop *loop_lo = 0;	2133	struct ev_loop *loop_lo = 0;
1702	struct ev_embed embed;	2134	struct ev_embed embed;
1703		2135
…		…
1714	ev_embed_start (loop_hi, &embed);	2146	ev_embed_start (loop_hi, &embed);
1715	}	2147	}
1716	else	2148	else
1717	loop_lo = loop_hi;	2149	loop_lo = loop_hi;
1718		2150
1719	=over 4	2151	Example: Check if kqueue is available but not recommended and create
		2152	a kqueue backend for use with sockets (which usually work with any
		2153	kqueue implementation). Store the kqueue/socket-only event loop in
		2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1720		2155
1721	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2156	struct ev_loop *loop = ev_default_init (0);
		2157	struct ev_loop *loop_socket = 0;
		2158	struct ev_embed embed;
		2159
		2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2162	{
		2163	ev_embed_init (&embed, 0, loop_socket);
		2164	ev_embed_start (loop, &embed);
		2165	}
1722		2166
1723	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2167	if (!loop_socket)
		2168	loop_socket = loop;
1724		2169
1725	Configures the watcher to embed the given loop, which must be	2170	// now use loop_socket for all sockets, and loop for everything else
1726	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1727	invoked automatically, otherwise it is the responsibility of the callback
1728	to invoke it (it will continue to be called until the sweep has been done,
1729	if you do not want thta, you need to temporarily stop the embed watcher).
1730
1731	=item ev_embed_sweep (loop, ev_embed *)
1732
1733	Make a single, non-blocking sweep over the embedded loop. This works
1734	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1735	apropriate way for embedded loops.
1736
1737	=item struct ev_loop *loop [read-only]
1738
1739	The embedded event loop.
1740
1741	=back
1742		2171
1743		2172
1744	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1745		2174
1746	Fork watchers are called when a C<fork ()> was detected (usually because	2175	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1749	event loop blocks next and before C<ev_check> watchers are being called,	2178	event loop blocks next and before C<ev_check> watchers are being called,
1750	and only in the child after the fork. If whoever good citizen calling	2179	and only in the child after the fork. If whoever good citizen calling
1751	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2180	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1752	handlers will be invoked, too, of course.	2181	handlers will be invoked, too, of course.
1753		2182
		2183	=head3 Watcher-Specific Functions and Data Members
		2184
1754	=over 4	2185	=over 4
1755		2186
1756	=item ev_fork_init (ev_signal *, callback)	2187	=item ev_fork_init (ev_signal *, callback)
1757		2188
1758	Initialises and configures the fork watcher - it has no parameters of any	2189	Initialises and configures the fork watcher - it has no parameters of any
1759	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2190	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1760	believe me.	2191	believe me.
		2192
		2193	=back
		2194
		2195
		2196	=head2 C<ev_async> - how to wake up another event loop
		2197
		2198	In general, you cannot use an C<ev_loop> from multiple threads or other
		2199	asynchronous sources such as signal handlers (as opposed to multiple event
		2200	loops - those are of course safe to use in different threads).
		2201
		2202	Sometimes, however, you need to wake up another event loop you do not
		2203	control, for example because it belongs to another thread. This is what
		2204	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2205	can signal it by calling C<ev_async_send>, which is thread- and signal
		2206	safe.
		2207
		2208	This functionality is very similar to C<ev_signal> watchers, as signals,
		2209	too, are asynchronous in nature, and signals, too, will be compressed
		2210	(i.e. the number of callback invocations may be less than the number of
		2211	C<ev_async_sent> calls).
		2212
		2213	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2214	just the default loop.
		2215
		2216	=head3 Queueing
		2217
		2218	C<ev_async> does not support queueing of data in any way. The reason
		2219	is that the author does not know of a simple (or any) algorithm for a
		2220	multiple-writer-single-reader queue that works in all cases and doesn't
		2221	need elaborate support such as pthreads.
		2222
		2223	That means that if you want to queue data, you have to provide your own
		2224	queue. But at least I can tell you would implement locking around your
		2225	queue:
		2226
		2227	=over 4
		2228
		2229	=item queueing from a signal handler context
		2230
		2231	To implement race-free queueing, you simply add to the queue in the signal
		2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2233	some fictitiuous SIGUSR1 handler:
		2234
		2235	static ev_async mysig;
		2236
		2237	static void
		2238	sigusr1_handler (void)
		2239	{
		2240	sometype data;
		2241
		2242	// no locking etc.
		2243	queue_put (data);
		2244	ev_async_send (EV_DEFAULT_ &mysig);
		2245	}
		2246
		2247	static void
		2248	mysig_cb (EV_P_ ev_async *w, int revents)
		2249	{
		2250	sometype data;
		2251	sigset_t block, prev;
		2252
		2253	sigemptyset (&block);
		2254	sigaddset (&block, SIGUSR1);
		2255	sigprocmask (SIG_BLOCK, &block, &prev);
		2256
		2257	while (queue_get (&data))
		2258	process (data);
		2259
		2260	if (sigismember (&prev, SIGUSR1)
		2261	sigprocmask (SIG_UNBLOCK, &block, 0);
		2262	}
		2263
		2264	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2265	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2266	either...).
		2267
		2268	=item queueing from a thread context
		2269
		2270	The strategy for threads is different, as you cannot (easily) block
		2271	threads but you can easily preempt them, so to queue safely you need to
		2272	employ a traditional mutex lock, such as in this pthread example:
		2273
		2274	static ev_async mysig;
		2275	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2276
		2277	static void
		2278	otherthread (void)
		2279	{
		2280	// only need to lock the actual queueing operation
		2281	pthread_mutex_lock (&mymutex);
		2282	queue_put (data);
		2283	pthread_mutex_unlock (&mymutex);
		2284
		2285	ev_async_send (EV_DEFAULT_ &mysig);
		2286	}
		2287
		2288	static void
		2289	mysig_cb (EV_P_ ev_async *w, int revents)
		2290	{
		2291	pthread_mutex_lock (&mymutex);
		2292
		2293	while (queue_get (&data))
		2294	process (data);
		2295
		2296	pthread_mutex_unlock (&mymutex);
		2297	}
		2298
		2299	=back
		2300
		2301
		2302	=head3 Watcher-Specific Functions and Data Members
		2303
		2304	=over 4
		2305
		2306	=item ev_async_init (ev_async *, callback)
		2307
		2308	Initialises and configures the async watcher - it has no parameters of any
		2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2310	believe me.
		2311
		2312	=item ev_async_send (loop, ev_async *)
		2313
		2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2316	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2318	section below on what exactly this means).
		2319
		2320	This call incurs the overhead of a syscall only once per loop iteration,
		2321	so while the overhead might be noticable, it doesn't apply to repeated
		2322	calls to C<ev_async_send>.
		2323
		2324	=item bool = ev_async_pending (ev_async *)
		2325
		2326	Returns a non-zero value when C<ev_async_send> has been called on the
		2327	watcher but the event has not yet been processed (or even noted) by the
		2328	event loop.
		2329
		2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2331	the loop iterates next and checks for the watcher to have become active,
		2332	it will reset the flag again. C<ev_async_pending> can be used to very
		2333	quickly check wether invoking the loop might be a good idea.
		2334
		2335	Not that this does I<not> check wether the watcher itself is pending, only
		2336	wether it has been requested to make this watcher pending.
1761		2337
1762	=back	2338	=back
1763		2339
1764		2340
1765	=head1 OTHER FUNCTIONS	2341	=head1 OTHER FUNCTIONS
…		…
1837		2413
1838	=item * Priorities are not currently supported. Initialising priorities	2414	=item * Priorities are not currently supported. Initialising priorities
1839	will fail and all watchers will have the same priority, even though there	2415	will fail and all watchers will have the same priority, even though there
1840	is an ev_pri field.	2416	is an ev_pri field.
1841		2417
		2418	=item * In libevent, the last base created gets the signals, in libev, the
		2419	first base created (== the default loop) gets the signals.
		2420
1842	=item * Other members are not supported.	2421	=item * Other members are not supported.
1843		2422
1844	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2423	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1845	to use the libev header file and library.	2424	to use the libev header file and library.
1846		2425
…		…
1974		2553
1975	=item w->stop ()	2554	=item w->stop ()
1976		2555
1977	Stops the watcher if it is active. Again, no C<loop> argument.	2556	Stops the watcher if it is active. Again, no C<loop> argument.
1978		2557
1979	=item w->again () C<ev::timer>, C<ev::periodic> only	2558	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1980		2559
1981	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2560	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1982	C<ev_TYPE_again> function.	2561	C<ev_TYPE_again> function.
1983		2562
1984	=item w->sweep () C<ev::embed> only	2563	=item w->sweep () (C<ev::embed> only)
1985		2564
1986	Invokes C<ev_embed_sweep>.	2565	Invokes C<ev_embed_sweep>.
1987		2566
1988	=item w->update () C<ev::stat> only	2567	=item w->update () (C<ev::stat> only)
1989		2568
1990	Invokes C<ev_stat_stat>.	2569	Invokes C<ev_stat_stat>.
1991		2570
1992	=back	2571	=back
1993		2572
…		…
1996	Example: Define a class with an IO and idle watcher, start one of them in	2575	Example: Define a class with an IO and idle watcher, start one of them in
1997	the constructor.	2576	the constructor.
1998		2577
1999	class myclass	2578	class myclass
2000	{	2579	{
2001	ev_io io; void io_cb (ev::io &w, int revents);	2580	ev::io io; void io_cb (ev::io &w, int revents);
2002	ev_idle idle void idle_cb (ev::idle &w, int revents);	2581	ev:idle idle void idle_cb (ev::idle &w, int revents);
2003		2582
2004	myclass ();	2583	myclass (int fd)
2005	}
2006
2007	myclass::myclass (int fd)
2008	{	2584	{
2009	io .set <myclass, &myclass::io_cb > (this);	2585	io .set <myclass, &myclass::io_cb > (this);
2010	idle.set <myclass, &myclass::idle_cb> (this);	2586	idle.set <myclass, &myclass::idle_cb> (this);
2011		2587
2012	io.start (fd, ev::READ);	2588	io.start (fd, ev::READ);
		2589	}
2013	}	2590	};
		2591
		2592
		2593	=head1 OTHER LANGUAGE BINDINGS
		2594
		2595	Libev does not offer other language bindings itself, but bindings for a
		2596	numbe rof languages exist in the form of third-party packages. If you know
		2597	any interesting language binding in addition to the ones listed here, drop
		2598	me a note.
		2599
		2600	=over 4
		2601
		2602	=item Perl
		2603
		2604	The EV module implements the full libev API and is actually used to test
		2605	libev. EV is developed together with libev. Apart from the EV core module,
		2606	there are additional modules that implement libev-compatible interfaces
		2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2609
		2610	It can be found and installed via CPAN, its homepage is found at
		2611	L<http://software.schmorp.de/pkg/EV>.
		2612
		2613	=item Ruby
		2614
		2615	Tony Arcieri has written a ruby extension that offers access to a subset
		2616	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2617	more on top of it. It can be found via gem servers. Its homepage is at
		2618	L<http://rev.rubyforge.org/>.
		2619
		2620	=item D
		2621
		2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2624
		2625	=back
2014		2626
2015		2627
2016	=head1 MACRO MAGIC	2628	=head1 MACRO MAGIC
2017		2629
2018	Libev can be compiled with a variety of options, the most fundemantal is	2630	Libev can be compiled with a variety of options, the most fundamantal
2019	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2020	callbacks have an initial C<struct ev_loop *> argument.	2632	functions and callbacks have an initial C<struct ev_loop *> argument.
2021		2633
2022	To make it easier to write programs that cope with either variant, the	2634	To make it easier to write programs that cope with either variant, the
2023	following macros are defined:	2635	following macros are defined:
2024		2636
2025	=over 4	2637	=over 4
…		…
2054		2666
2055	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2056		2668
2057	Similar to the other two macros, this gives you the value of the default	2669	Similar to the other two macros, this gives you the value of the default
2058	loop, if multiple loops are supported ("ev loop default").	2670	loop, if multiple loops are supported ("ev loop default").
		2671
		2672	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2673
		2674	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2675	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2676	is undefined when the default loop has not been initialised by a previous
		2677	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2678
		2679	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2680	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2059		2681
2060	=back	2682	=back
2061		2683
2062	Example: Declare and initialise a check watcher, utilising the above	2684	Example: Declare and initialise a check watcher, utilising the above
2063	macros so it will work regardless of whether multiple loops are supported	2685	macros so it will work regardless of whether multiple loops are supported
…		…
2079	Libev can (and often is) directly embedded into host	2701	Libev can (and often is) directly embedded into host
2080	applications. Examples of applications that embed it include the Deliantra	2702	applications. Examples of applications that embed it include the Deliantra
2081	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2703	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2082	and rxvt-unicode.	2704	and rxvt-unicode.
2083		2705
2084	The goal is to enable you to just copy the neecssary files into your	2706	The goal is to enable you to just copy the necessary files into your
2085	source directory without having to change even a single line in them, so	2707	source directory without having to change even a single line in them, so
2086	you can easily upgrade by simply copying (or having a checked-out copy of	2708	you can easily upgrade by simply copying (or having a checked-out copy of
2087	libev somewhere in your source tree).	2709	libev somewhere in your source tree).
2088		2710
2089	=head2 FILESETS	2711	=head2 FILESETS
…		…
2159		2781
2160	libev.m4	2782	libev.m4
2161		2783
2162	=head2 PREPROCESSOR SYMBOLS/MACROS	2784	=head2 PREPROCESSOR SYMBOLS/MACROS
2163		2785
2164	Libev can be configured via a variety of preprocessor symbols you have to define	2786	Libev can be configured via a variety of preprocessor symbols you have to
2165	before including any of its files. The default is not to build for multiplicity	2787	define before including any of its files. The default in the absense of
2166	and only include the select backend.	2788	autoconf is noted for every option.
2167		2789
2168	=over 4	2790	=over 4
2169		2791
2170	=item EV_STANDALONE	2792	=item EV_STANDALONE
2171		2793
…		…
2179		2801
2180	If defined to be C<1>, libev will try to detect the availability of the	2802	If defined to be C<1>, libev will try to detect the availability of the
2181	monotonic clock option at both compiletime and runtime. Otherwise no use	2803	monotonic clock option at both compiletime and runtime. Otherwise no use
2182	of the monotonic clock option will be attempted. If you enable this, you	2804	of the monotonic clock option will be attempted. If you enable this, you
2183	usually have to link against librt or something similar. Enabling it when	2805	usually have to link against librt or something similar. Enabling it when
2184	the functionality isn't available is safe, though, althoguh you have	2806	the functionality isn't available is safe, though, although you have
2185	to make sure you link against any libraries where the C<clock_gettime>	2807	to make sure you link against any libraries where the C<clock_gettime>
2186	function is hiding in (often F<-lrt>).	2808	function is hiding in (often F<-lrt>).
2187		2809
2188	=item EV_USE_REALTIME	2810	=item EV_USE_REALTIME
2189		2811
2190	If defined to be C<1>, libev will try to detect the availability of the	2812	If defined to be C<1>, libev will try to detect the availability of the
2191	realtime clock option at compiletime (and assume its availability at	2813	realtime clock option at compiletime (and assume its availability at
2192	runtime if successful). Otherwise no use of the realtime clock option will	2814	runtime if successful). Otherwise no use of the realtime clock option will
2193	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2194	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2195	in the description of C<EV_USE_MONOTONIC>, though.	2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2818
		2819	=item EV_USE_NANOSLEEP
		2820
		2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2822	and will use it for delays. Otherwise it will use C<select ()>.
		2823
		2824	=item EV_USE_EVENTFD
		2825
		2826	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2827	available and will probe for kernel support at runtime. This will improve
		2828	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2829	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2830	2.7 or newer, otherwise disabled.
2196		2831
2197	=item EV_USE_SELECT	2832	=item EV_USE_SELECT
2198		2833
2199	If undefined or defined to be C<1>, libev will compile in support for the	2834	If undefined or defined to be C<1>, libev will compile in support for the
2200	C<select>(2) backend. No attempt at autodetection will be done: if no	2835	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2219	be used is the winsock select). This means that it will call	2854	be used is the winsock select). This means that it will call
2220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2855	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2221	it is assumed that all these functions actually work on fds, even	2856	it is assumed that all these functions actually work on fds, even
2222	on win32. Should not be defined on non-win32 platforms.	2857	on win32. Should not be defined on non-win32 platforms.
2223		2858
		2859	=item EV_FD_TO_WIN32_HANDLE
		2860
		2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2862	file descriptors to socket handles. When not defining this symbol (the
		2863	default), then libev will call C<_get_osfhandle>, which is usually
		2864	correct. In some cases, programs use their own file descriptor management,
		2865	in which case they can provide this function to map fds to socket handles.
		2866
2224	=item EV_USE_POLL	2867	=item EV_USE_POLL
2225		2868
2226	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2227	backend. Otherwise it will be enabled on non-win32 platforms. It	2870	backend. Otherwise it will be enabled on non-win32 platforms. It
2228	takes precedence over select.	2871	takes precedence over select.
2229		2872
2230	=item EV_USE_EPOLL	2873	=item EV_USE_EPOLL
2231		2874
2232	If defined to be C<1>, libev will compile in support for the Linux	2875	If defined to be C<1>, libev will compile in support for the Linux
2233	C<epoll>(7) backend. Its availability will be detected at runtime,	2876	C<epoll>(7) backend. Its availability will be detected at runtime,
2234	otherwise another method will be used as fallback. This is the	2877	otherwise another method will be used as fallback. This is the preferred
2235	preferred backend for GNU/Linux systems.	2878	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2879	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2236		2880
2237	=item EV_USE_KQUEUE	2881	=item EV_USE_KQUEUE
2238		2882
2239	If defined to be C<1>, libev will compile in support for the BSD style	2883	If defined to be C<1>, libev will compile in support for the BSD style
2240	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2884	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2259		2903
2260	=item EV_USE_INOTIFY	2904	=item EV_USE_INOTIFY
2261		2905
2262	If defined to be C<1>, libev will compile in support for the Linux inotify	2906	If defined to be C<1>, libev will compile in support for the Linux inotify
2263	interface to speed up C<ev_stat> watchers. Its actual availability will	2907	interface to speed up C<ev_stat> watchers. Its actual availability will
2264	be detected at runtime.	2908	be detected at runtime. If undefined, it will be enabled if the headers
		2909	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2910
		2911	=item EV_ATOMIC_T
		2912
		2913	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2914	access is atomic with respect to other threads or signal contexts. No such
		2915	type is easily found in the C language, so you can provide your own type
		2916	that you know is safe for your purposes. It is used both for signal handler "locking"
		2917	as well as for signal and thread safety in C<ev_async> watchers.
		2918
		2919	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2920	(from F<signal.h>), which is usually good enough on most platforms.
2265		2921
2266	=item EV_H	2922	=item EV_H
2267		2923
2268	The name of the F<ev.h> header file used to include it. The default if	2924	The name of the F<ev.h> header file used to include it. The default if
2269	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2925	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2270	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2926	used to virtually rename the F<ev.h> header file in case of conflicts.
2271		2927
2272	=item EV_CONFIG_H	2928	=item EV_CONFIG_H
2273		2929
2274	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2930	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2275	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2931	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2276	C<EV_H>, above.	2932	C<EV_H>, above.
2277		2933
2278	=item EV_EVENT_H	2934	=item EV_EVENT_H
2279		2935
2280	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2936	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2281	of how the F<event.h> header can be found.	2937	of how the F<event.h> header can be found, the default is C<"event.h">.
2282		2938
2283	=item EV_PROTOTYPES	2939	=item EV_PROTOTYPES
2284		2940
2285	If defined to be C<0>, then F<ev.h> will not define any function	2941	If defined to be C<0>, then F<ev.h> will not define any function
2286	prototypes, but still define all the structs and other symbols. This is	2942	prototypes, but still define all the structs and other symbols. This is
…		…
2337	=item EV_FORK_ENABLE	2993	=item EV_FORK_ENABLE
2338		2994
2339	If undefined or defined to be C<1>, then fork watchers are supported. If	2995	If undefined or defined to be C<1>, then fork watchers are supported. If
2340	defined to be C<0>, then they are not.	2996	defined to be C<0>, then they are not.
2341		2997
		2998	=item EV_ASYNC_ENABLE
		2999
		3000	If undefined or defined to be C<1>, then async watchers are supported. If
		3001	defined to be C<0>, then they are not.
		3002
2342	=item EV_MINIMAL	3003	=item EV_MINIMAL
2343		3004
2344	If you need to shave off some kilobytes of code at the expense of some	3005	If you need to shave off some kilobytes of code at the expense of some
2345	speed, define this symbol to C<1>. Currently only used for gcc to override	3006	speed, define this symbol to C<1>. Currently this is used to override some
2346	some inlining decisions, saves roughly 30% codesize of amd64.	3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		3008	much smaller 2-heap for timer management over the default 4-heap.
2347		3009
2348	=item EV_PID_HASHSIZE	3010	=item EV_PID_HASHSIZE
2349		3011
2350	C<ev_child> watchers use a small hash table to distribute workload by	3012	C<ev_child> watchers use a small hash table to distribute workload by
2351	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2352	than enough. If you need to manage thousands of children you might want to	3014	than enough. If you need to manage thousands of children you might want to
2353	increase this value (I<must> be a power of two).	3015	increase this value (I<must> be a power of two).
2354		3016
2355	=item EV_INOTIFY_HASHSIZE	3017	=item EV_INOTIFY_HASHSIZE
2356		3018
2357	C<ev_staz> watchers use a small hash table to distribute workload by	3019	C<ev_stat> watchers use a small hash table to distribute workload by
2358	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3020	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2359	usually more than enough. If you need to manage thousands of C<ev_stat>	3021	usually more than enough. If you need to manage thousands of C<ev_stat>
2360	watchers you might want to increase this value (I<must> be a power of	3022	watchers you might want to increase this value (I<must> be a power of
2361	two).	3023	two).
2362		3024
		3025	=item EV_USE_4HEAP
		3026
		3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3029	to C<1>. The 4-heap uses more complicated (longer) code but has
		3030	noticably faster performance with many (thousands) of watchers.
		3031
		3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3033	(disabled).
		3034
		3035	=item EV_HEAP_CACHE_AT
		3036
		3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3038	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3041	but avoids random read accesses on heap changes. This improves performance
		3042	noticably with with many (hundreds) of watchers.
		3043
		3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3045	(disabled).
		3046
		3047	=item EV_VERIFY
		3048
		3049	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3050	be done: If set to C<0>, no internal verification code will be compiled
		3051	in. If set to C<1>, then verification code will be compiled in, but not
		3052	called. If set to C<2>, then the internal verification code will be
		3053	called once per loop, which can slow down libev. If set to C<3>, then the
		3054	verification code will be called very frequently, which will slow down
		3055	libev considerably.
		3056
		3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3058	C<0.>
		3059
2363	=item EV_COMMON	3060	=item EV_COMMON
2364		3061
2365	By default, all watchers have a C<void *data> member. By redefining	3062	By default, all watchers have a C<void *data> member. By redefining
2366	this macro to a something else you can include more and other types of	3063	this macro to a something else you can include more and other types of
2367	members. You have to define it each time you include one of the files,	3064	members. You have to define it each time you include one of the files,
…		…
2379		3076
2380	=item ev_set_cb (ev, cb)	3077	=item ev_set_cb (ev, cb)
2381		3078
2382	Can be used to change the callback member declaration in each watcher,	3079	Can be used to change the callback member declaration in each watcher,
2383	and the way callbacks are invoked and set. Must expand to a struct member	3080	and the way callbacks are invoked and set. Must expand to a struct member
2384	definition and a statement, respectively. See the F<ev.v> header file for	3081	definition and a statement, respectively. See the F<ev.h> header file for
2385	their default definitions. One possible use for overriding these is to	3082	their default definitions. One possible use for overriding these is to
2386	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2387	method calls instead of plain function calls in C++.	3084	method calls instead of plain function calls in C++.
		3085
		3086	=head2 EXPORTED API SYMBOLS
		3087
		3088	If you need to re-export the API (e.g. via a dll) and you need a list of
		3089	exported symbols, you can use the provided F<Symbol.*> files which list
		3090	all public symbols, one per line:
		3091
		3092	Symbols.ev for libev proper
		3093	Symbols.event for the libevent emulation
		3094
		3095	This can also be used to rename all public symbols to avoid clashes with
		3096	multiple versions of libev linked together (which is obviously bad in
		3097	itself, but sometimes it is inconvinient to avoid this).
		3098
		3099	A sed command like this will create wrapper C<#define>'s that you need to
		3100	include before including F<ev.h>:
		3101
		3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3103
		3104	This would create a file F<wrap.h> which essentially looks like this:
		3105
		3106	#define ev_backend myprefix_ev_backend
		3107	#define ev_check_start myprefix_ev_check_start
		3108	#define ev_check_stop myprefix_ev_check_stop
		3109	...
2388		3110
2389	=head2 EXAMPLES	3111	=head2 EXAMPLES
2390		3112
2391	For a real-world example of a program the includes libev	3113	For a real-world example of a program the includes libev
2392	verbatim, you can have a look at the EV perl module	3114	verbatim, you can have a look at the EV perl module
…		…
2415		3137
2416	#include "ev_cpp.h"	3138	#include "ev_cpp.h"
2417	#include "ev.c"	3139	#include "ev.c"
2418		3140
2419		3141
		3142	=head1 THREADS AND COROUTINES
		3143
		3144	=head2 THREADS
		3145
		3146	Libev itself is completely threadsafe, but it uses no locking. This
		3147	means that you can use as many loops as you want in parallel, as long as
		3148	only one thread ever calls into one libev function with the same loop
		3149	parameter.
		3150
		3151	Or put differently: calls with different loop parameters can be done in
		3152	parallel from multiple threads, calls with the same loop parameter must be
		3153	done serially (but can be done from different threads, as long as only one
		3154	thread ever is inside a call at any point in time, e.g. by using a mutex
		3155	per loop).
		3156
		3157	If you want to know which design is best for your problem, then I cannot
		3158	help you but by giving some generic advice:
		3159
		3160	=over 4
		3161
		3162	=item * most applications have a main thread: use the default libev loop
		3163	in that thread, or create a seperate thread running only the default loop.
		3164
		3165	This helps integrating other libraries or software modules that use libev
		3166	themselves and don't care/know about threading.
		3167
		3168	=item * one loop per thread is usually a good model.
		3169
		3170	Doing this is almost never wrong, sometimes a better-performance model
		3171	exists, but it is always a good start.
		3172
		3173	=item * other models exist, such as the leader/follower pattern, where one
		3174	loop is handed through multiple threads in a kind of round-robbin fashion.
		3175
		3176	Chosing a model is hard - look around, learn, know that usually you cna do
		3177	better than you currently do :-)
		3178
		3179	=item * often you need to talk to some other thread which blocks in the
		3180	event loop - C<ev_async> watchers can be used to wake them up from other
		3181	threads safely (or from signal contexts...).
		3182
		3183	=back
		3184
		3185	=head2 COROUTINES
		3186
		3187	Libev is much more accomodating to coroutines ("cooperative threads"):
		3188	libev fully supports nesting calls to it's functions from different
		3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3190	different coroutines and switch freely between both coroutines running the
		3191	loop, as long as you don't confuse yourself). The only exception is that
		3192	you must not do this from C<ev_periodic> reschedule callbacks.
		3193
		3194	Care has been invested into making sure that libev does not keep local
		3195	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3196	switches.
		3197
		3198
2420	=head1 COMPLEXITIES	3199	=head1 COMPLEXITIES
2421		3200
2422	In this section the complexities of (many of) the algorithms used inside	3201	In this section the complexities of (many of) the algorithms used inside
2423	libev will be explained. For complexity discussions about backends see the	3202	libev will be explained. For complexity discussions about backends see the
2424	documentation for C<ev_default_init>.	3203	documentation for C<ev_default_init>.
…		…
2433		3212
2434	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2435		3214
2436	This means that, when you have a watcher that triggers in one hour and	3215	This means that, when you have a watcher that triggers in one hour and
2437	there are 100 watchers that would trigger before that then inserting will	3216	there are 100 watchers that would trigger before that then inserting will
2438	have to skip those 100 watchers.	3217	have to skip roughly seven (C<ld 100>) of these watchers.
2439		3218
2440	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2441		3220
2442	That means that for changing a timer costs less than removing/adding them	3221	That means that changing a timer costs less than removing/adding them
2443	as only the relative motion in the event queue has to be paid for.	3222	as only the relative motion in the event queue has to be paid for.
2444		3223
2445	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2446		3225
2447	These just add the watcher into an array or at the head of a list.	3226	These just add the watcher into an array or at the head of a list.
		3227
2448	=item Stopping check/prepare/idle watchers: O(1)	3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2449		3229
2450	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2451		3231
2452	These watchers are stored in lists then need to be walked to find the	3232	These watchers are stored in lists then need to be walked to find the
2453	correct watcher to remove. The lists are usually short (you don't usually	3233	correct watcher to remove. The lists are usually short (you don't usually
2454	have many watchers waiting for the same fd or signal).	3234	have many watchers waiting for the same fd or signal).
2455		3235
2456	=item Finding the next timer per loop iteration: O(1)	3236	=item Finding the next timer in each loop iteration: O(1)
		3237
		3238	By virtue of using a binary or 4-heap, the next timer is always found at a
		3239	fixed position in the storage array.
2457		3240
2458	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2459		3242
2460	A change means an I/O watcher gets started or stopped, which requires	3243	A change means an I/O watcher gets started or stopped, which requires
2461	libev to recalculate its status (and possibly tell the kernel).	3244	libev to recalculate its status (and possibly tell the kernel, depending
		3245	on backend and wether C<ev_io_set> was used).
2462		3246
2463	=item Activating one watcher: O(1)	3247	=item Activating one watcher (putting it into the pending state): O(1)
2464		3248
2465	=item Priority handling: O(number_of_priorities)	3249	=item Priority handling: O(number_of_priorities)
2466		3250
2467	Priorities are implemented by allocating some space for each	3251	Priorities are implemented by allocating some space for each
2468	priority. When doing priority-based operations, libev usually has to	3252	priority. When doing priority-based operations, libev usually has to
2469	linearly search all the priorities.	3253	linearly search all the priorities, but starting/stopping and activating
		3254	watchers becomes O(1) w.r.t. priority handling.
		3255
		3256	=item Sending an ev_async: O(1)
		3257
		3258	=item Processing ev_async_send: O(number_of_async_watchers)
		3259
		3260	=item Processing signals: O(max_signal_number)
		3261
		3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3263	calls in the current loop iteration. Checking for async and signal events
		3264	involves iterating over all running async watchers or all signal numbers.
2470		3265
2471	=back	3266	=back
2472		3267
2473		3268
		3269	=head1 Win32 platform limitations and workarounds
		3270
		3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3272	requires, and its I/O model is fundamentally incompatible with the POSIX
		3273	model. Libev still offers limited functionality on this platform in
		3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3275	descriptors. This only applies when using Win32 natively, not when using
		3276	e.g. cygwin.
		3277
		3278	Lifting these limitations would basically require the full
		3279	re-implementation of the I/O system. If you are into these kinds of
		3280	things, then note that glib does exactly that for you in a very portable
		3281	way (note also that glib is the slowest event library known to man).
		3282
		3283	There is no supported compilation method available on windows except
		3284	embedding it into other applications.
		3285
		3286	Due to the many, low, and arbitrary limits on the win32 platform and
		3287	the abysmal performance of winsockets, using a large number of sockets
		3288	is not recommended (and not reasonable). If your program needs to use
		3289	more than a hundred or so sockets, then likely it needs to use a totally
		3290	different implementation for windows, as libev offers the POSIX readiness
		3291	notification model, which cannot be implemented efficiently on windows
		3292	(microsoft monopoly games).
		3293
		3294	=over 4
		3295
		3296	=item The winsocket select function
		3297
		3298	The winsocket C<select> function doesn't follow POSIX in that it requires
		3299	socket I<handles> and not socket I<file descriptors>. This makes select
		3300	very inefficient, and also requires a mapping from file descriptors
		3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3303	symbols for more info.
		3304
		3305	The configuration for a "naked" win32 using the microsoft runtime
		3306	libraries and raw winsocket select is:
		3307
		3308	#define EV_USE_SELECT 1
		3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3310
		3311	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3312	complexity in the O(n²) range when using win32.
		3313
		3314	=item Limited number of file descriptors
		3315
		3316	Windows has numerous arbitrary (and low) limits on things.
		3317
		3318	Early versions of winsocket's select only supported waiting for a maximum
		3319	of C<64> handles (probably owning to the fact that all windows kernels
		3320	can only wait for C<64> things at the same time internally; microsoft
		3321	recommends spawning a chain of threads and wait for 63 handles and the
		3322	previous thread in each. Great).
		3323
		3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3325	to some high number (e.g. C<2048>) before compiling the winsocket select
		3326	call (which might be in libev or elsewhere, for example, perl does its own
		3327	select emulation on windows).
		3328
		3329	Another limit is the number of file descriptors in the microsoft runtime
		3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3331	or something like this inside microsoft). You can increase this by calling
		3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3333	arbitrary limit), but is broken in many versions of the microsoft runtime
		3334	libraries.
		3335
		3336	This might get you to about C<512> or C<2048> sockets (depending on
		3337	windows version and/or the phase of the moon). To get more, you need to
		3338	wrap all I/O functions and provide your own fd management, but the cost of
		3339	calling select (O(n²)) will likely make this unworkable.
		3340
		3341	=back
		3342
		3343
		3344	=head1 PORTABILITY REQUIREMENTS
		3345
		3346	In addition to a working ISO-C implementation, libev relies on a few
		3347	additional extensions:
		3348
		3349	=over 4
		3350
		3351	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3352
		3353	The type C<sig_atomic_t volatile> (or whatever is defined as
		3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3355	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3356	believed to be sufficiently portable.
		3357
		3358	=item C<sigprocmask> must work in a threaded environment
		3359
		3360	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3361	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3362	pthread implementations will either allow C<sigprocmask> in the "main
		3363	thread" or will block signals process-wide, both behaviours would
		3364	be compatible with libev. Interaction between C<sigprocmask> and
		3365	C<pthread_sigmask> could complicate things, however.
		3366
		3367	The most portable way to handle signals is to block signals in all threads
		3368	except the initial one, and run the default loop in the initial thread as
		3369	well.
		3370
		3371	=item C<long> must be large enough for common memory allocation sizes
		3372
		3373	To improve portability and simplify using libev, libev uses C<long>
		3374	internally instead of C<size_t> when allocating its data structures. On
		3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3376	is still at least 31 bits everywhere, which is enough for hundreds of
		3377	millions of watchers.
		3378
		3379	=item C<double> must hold a time value in seconds with enough accuracy
		3380
		3381	The type C<double> is used to represent timestamps. It is required to
		3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3383	enough for at least into the year 4000. This requirement is fulfilled by
		3384	implementations implementing IEEE 754 (basically all existing ones).
		3385
		3386	=back
		3387
		3388	If you know of other additional requirements drop me a note.
		3389
		3390
		3391	=head1 VALGRIND
		3392
		3393	Valgrind has a special section here because it is a popular tool that is
		3394	highly useful, but valgrind reports are very hard to interpret.
		3395
		3396	If you think you found a bug (memory leak, uninitialised data access etc.)
		3397	in libev, then check twice: If valgrind reports something like:
		3398
		3399	==2274== definitely lost: 0 bytes in 0 blocks.
		3400	==2274== possibly lost: 0 bytes in 0 blocks.
		3401	==2274== still reachable: 256 bytes in 1 blocks.
		3402
		3403	then there is no memory leak. Similarly, under some circumstances,
		3404	valgrind might report kernel bugs as if it were a bug in libev, or it
		3405	might be confused (it is a very good tool, but only a tool).
		3406
		3407	If you are unsure about something, feel free to contact the mailing list
		3408	with the full valgrind report and an explanation on why you think this is
		3409	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3410	no bug" answer and take the chance of learning how to interpret valgrind
		3411	properly.
		3412
		3413	If you need, for some reason, empty reports from valgrind for your project
		3414	I suggest using suppression lists.
		3415
		3416
2474	=head1 AUTHOR	3417	=head1 AUTHOR
2475		3418
2476	Marc Lehmann <libev@schmorp.de>.	3419	Marc Lehmann <libev@schmorp.de>.
2477		3420

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