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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
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://cvs.schmorp.de/libev/ev.html>.
		70
53	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
54	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
55	these event sources and provide your program with events.	73	these event sources and provide your program with events.
56		74
57	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
58	(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
59	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
61	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
62	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
63	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
64	watcher.	82	watcher.
65		83
66	=head1 FEATURES	84	=head2 FEATURES
67		85
68	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
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	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
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		96
79	It also is quite fast (see this	97	It also is quite fast (see this
80	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
81	for example).	99	for example).
82		100
83	=head1 CONVENTIONS	101	=head2 CONVENTIONS
84		102
85	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
86	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
87	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
88	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
89	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
90	(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.
91		110
92	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
93		112
94	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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
99	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.
100		121
101	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
102		123
103	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
104	library in any way.	125	library in any way.
…		…
109		130
110	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
111	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
112	you actually want to know.	133	you actually want to know.
113		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
114	=item int ev_version_major ()	141	=item int ev_version_major ()
115		142
116	=item int ev_version_minor ()	143	=item int ev_version_minor ()
117		144
118	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
119	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
120	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
121	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
122	version of the library your program was compiled against.	149	version of the library your program was compiled against.
123		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
124	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,
125	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
126	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
127	not a problem.	157	not a problem.
128		158
129	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
130	version.	160	version.
…		…
166	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
167		197
168	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
169		199
170	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
171	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
172	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
173	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
174	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
175	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.
176		209
177	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
178	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,
179	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.
180		213
181	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
182	retries).	215	retries (example requires a standards-compliant C<realloc>).
183		216
184	static void *	217	static void *
185	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
186	{	219	{
187	for (;;)	220	for (;;)
…		…
226		259
227	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
228	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
229	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
230		263
231	If you use threads, a common model is to run the default event loop
232	in your main thread (or in a separate thread) and for each thread you
233	create, you also create another event loop. Libev itself does no locking
234	whatsoever, so if you mix calls to the same event loop in different
235	threads, make sure you lock (this is usually a bad idea, though, even if
236	done correctly, because it's hideous and inefficient).
237
238	=over 4	264	=over 4
239		265
240	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
241		267
242	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
…		…
244	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
245	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
246		272
247	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
248	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>.
249		286
250	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
251	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>).
252		289
253	The following flags are supported:	290	The following flags are supported:
…		…
274	a fork, you can also make libev check for a fork in each iteration by	311	a fork, you can also make libev check for a fork in each iteration by
275	enabling this flag.	312	enabling this flag.
276		313
277	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,
278	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
279	iterations and little real work, but is usually not noticable (on my	316	iterations and little real work, but is usually not noticeable (on my
280	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
281	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
282	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
283		320
284	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
285	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
286	flag.	323	flag.
…		…
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		329
293	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
294	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,
295	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
296	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
297	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
298		342
299	=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)
300		344
301	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
302	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
303	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
304	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.
305		351
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		353
308	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,
309	but it scales phenomenally better. While poll and select usually scale like	355	but it scales phenomenally better. While poll and select usually scale
310	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),
311	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.
312		361
313	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
314	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
315	(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
316	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
317	well if you register events for both fds.	366	very well if you register events for both fds.
318		367
319	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
320	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
321	(or space) is available.	370	(or space) is available.
322		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
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		380
325	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
326	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
327	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
328	completely useless). For this reason its not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
329	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
330	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.
331		392
332	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
333	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
334	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
335	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
336	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.
337		408
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		410
340	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.
341		415
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		417
344	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,
345	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)).
346		420
347	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
348	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
349	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 readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
350		433
351	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
352		435
353	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
354	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
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
356		439
		440	It is definitely not recommended to use this flag.
		441
357	=back	442	=back
358		443
359	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
360	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
361	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
362	order of their flag values :)
363		447
364	The most typical usage is like this:	448	The most typical usage is like this:
365		449
366	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
381		465
382	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
383	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
384	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
385	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.
386		474
387	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.
388		476
389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
390	if (!epoller)	478	if (!epoller)
…		…
395	Destroys the default loop again (frees all memory and kernel state	483	Destroys the default loop again (frees all memory and kernel state
396	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
397	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
398	responsibility to either stop all watchers cleanly yoursef I<before>	486	responsibility to either stop all watchers cleanly yoursef I<before>
399	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
400	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
401	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>).
402		499
403	=item ev_loop_destroy (loop)	500	=item ev_loop_destroy (loop)
404		501
405	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
406	earlier call to C<ev_loop_new>.	503	earlier call to C<ev_loop_new>.
407		504
408	=item ev_default_fork ()	505	=item ev_default_fork ()
409		506
		507	This function sets a flag that causes subsequent C<ev_loop> iterations
410	This function reinitialises the kernel state for backends that have	508	to reinitialise the kernel state for backends that have one. Despite the
411	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
412	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
413	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.
414		513
415	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
416	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
417	fork+exec, you don't have to call it.	516	you just fork+exec, you don't have to call it at all.
418		517
419	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
420	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
421	quite nicely into a call to C<pthread_atfork>:	520	quite nicely into a call to C<pthread_atfork>:
422		521
423	pthread_atfork (0, 0, ev_default_fork);	522	pthread_atfork (0, 0, ev_default_fork);
424		523
425	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
426	without calling this function, so if you force one of those backends you
427	do not need to care.
428
429	=item ev_loop_fork (loop)	524	=item ev_loop_fork (loop)
430		525
431	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
432	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
433	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.
		533
		534	=item unsigned int ev_loop_count (loop)
		535
		536	Returns the count of loop iterations for the loop, which is identical to
		537	the number of times libev did poll for new events. It starts at C<0> and
		538	happily wraps around with enough iterations.
		539
		540	This value can sometimes be useful as a generation counter of sorts (it
		541	"ticks" the number of loop iterations), as it roughly corresponds with
		542	C<ev_prepare> and C<ev_check> calls.
434		543
435	=item unsigned int ev_backend (loop)	544	=item unsigned int ev_backend (loop)
436		545
437	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438	use.	547	use.
…		…
441		550
442	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
443	received events and started processing them. This timestamp does not	552	received events and started processing them. This timestamp does not
444	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
445	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
446	event occuring (or more correctly, libev finding out about it).	555	event occurring (or more correctly, libev finding out about it).
447		556
448	=item ev_loop (loop, int flags)	557	=item ev_loop (loop, int flags)
449		558
450	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
451	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
…		…
472	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
473	usually a better approach for this kind of thing.	582	usually a better approach for this kind of thing.
474		583
475	Here are the gory details of what C<ev_loop> does:	584	Here are the gory details of what C<ev_loop> does:
476		585
477	* If there are no active watchers (reference count is zero), return.	586	- Before the first iteration, call any pending watchers.
478	- Queue prepare watchers and then call all outstanding watchers.	587	* If EVFLAG_FORKCHECK was used, check for a fork.
		588	- If a fork was detected, queue and call all fork watchers.
		589	- Queue and call all prepare watchers.
479	- If we have been forked, recreate the kernel state.	590	- If we have been forked, recreate the kernel state.
480	- Update the kernel state with all outstanding changes.	591	- Update the kernel state with all outstanding changes.
481	- Update the "event loop time".	592	- Update the "event loop time".
482	- 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.
483	- Block the process, waiting for any events.	597	- Block the process, waiting for any events.
484	- Queue all outstanding I/O (fd) events.	598	- Queue all outstanding I/O (fd) events.
485	- Update the "event loop time" and do time jump handling.	599	- Update the "event loop time" and do time jump handling.
486	- Queue all outstanding timers.	600	- Queue all outstanding timers.
487	- Queue all outstanding periodics.	601	- Queue all outstanding periodics.
488	- If no events are pending now, queue all idle watchers.	602	- If no events are pending now, queue all idle watchers.
489	- Queue all check watchers.	603	- Queue all check watchers.
490	- 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).
491	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
492	be handled here by queueing them when their watcher gets executed.	606	be handled here by queueing them when their watcher gets executed.
493	- 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
494	were used, return, otherwise continue with step *.	608	were used, or there are no active watchers, return, otherwise
		609	continue with step *.
495		610
496	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
497	anymore.	612	anymore.
498		613
499	... queue jobs here, make sure they register event watchers as long	614	... queue jobs here, make sure they register event watchers as long
500	... 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..)
501	ev_loop (my_loop, 0);	616	ev_loop (my_loop, 0);
…		…
505		620
506	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
507	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
508	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
509	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.
510		627
511	=item ev_ref (loop)	628	=item ev_ref (loop)
512		629
513	=item ev_unref (loop)	630	=item ev_unref (loop)
514		631
…		…
519	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
520	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
521	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
522	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
523	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
524	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).
525		644
526	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>
527	running when nothing else is active.	646	running when nothing else is active.
528		647
529	struct ev_signal exitsig;	648	struct ev_signal exitsig;
…		…
533		652
534	Example: For some weird reason, unregister the above signal handler again.	653	Example: For some weird reason, unregister the above signal handler again.
535		654
536	ev_ref (loop);	655	ev_ref (loop);
537	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.
538		693
539	=back	694	=back
540		695
541		696
542	=head1 ANATOMY OF A WATCHER	697	=head1 ANATOMY OF A WATCHER
…		…
642	=item C<EV_FORK>	797	=item C<EV_FORK>
643		798
644	The event loop has been resumed in the child process after fork (see	799	The event loop has been resumed in the child process after fork (see
645	C<ev_fork>).	800	C<ev_fork>).
646		801
		802	=item C<EV_ASYNC>
		803
		804	The given async watcher has been asynchronously notified (see C<ev_async>).
		805
647	=item C<EV_ERROR>	806	=item C<EV_ERROR>
648		807
649	An unspecified error has occured, the watcher has been stopped. This might	808	An unspecified error has occured, the watcher has been stopped. This might
650	happen because the watcher could not be properly started because libev	809	happen because the watcher could not be properly started because libev
651	ran out of memory, a file descriptor was found to be closed or any other	810	ran out of memory, a file descriptor was found to be closed or any other
…		…
722	=item bool ev_is_pending (ev_TYPE *watcher)	881	=item bool ev_is_pending (ev_TYPE *watcher)
723		882
724	Returns a true value iff the watcher is pending, (i.e. it has outstanding	883	Returns a true value iff the watcher is pending, (i.e. it has outstanding
725	events but its callback has not yet been invoked). As long as a watcher	884	events but its callback has not yet been invoked). As long as a watcher
726	is pending (but not active) you must not call an init function on it (but	885	is pending (but not active) you must not call an init function on it (but
727	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	886	C<ev_TYPE_set> is safe), you must not change its priority, and you must
728	libev (e.g. you cnanot C<free ()> it).	887	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		888	it).
729		889
730	=item callback ev_cb (ev_TYPE *watcher)	890	=item callback ev_cb (ev_TYPE *watcher)
731		891
732	Returns the callback currently set on the watcher.	892	Returns the callback currently set on the watcher.
733		893
734	=item ev_cb_set (ev_TYPE *watcher, callback)	894	=item ev_cb_set (ev_TYPE *watcher, callback)
735		895
736	Change the callback. You can change the callback at virtually any time	896	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	897	(modulo threads).
		898
		899	=item ev_set_priority (ev_TYPE *watcher, priority)
		900
		901	=item int ev_priority (ev_TYPE *watcher)
		902
		903	Set and query the priority of the watcher. The priority is a small
		904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		905	(default: C<-2>). Pending watchers with higher priority will be invoked
		906	before watchers with lower priority, but priority will not keep watchers
		907	from being executed (except for C<ev_idle> watchers).
		908
		909	This means that priorities are I<only> used for ordering callback
		910	invocation after new events have been received. This is useful, for
		911	example, to reduce latency after idling, or more often, to bind two
		912	watchers on the same event and make sure one is called first.
		913
		914	If you need to suppress invocation when higher priority events are pending
		915	you need to look at C<ev_idle> watchers, which provide this functionality.
		916
		917	You I<must not> change the priority of a watcher as long as it is active or
		918	pending.
		919
		920	The default priority used by watchers when no priority has been set is
		921	always C<0>, which is supposed to not be too high and not be too low :).
		922
		923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		924	fine, as long as you do not mind that the priority value you query might
		925	or might not have been adjusted to be within valid range.
		926
		927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		928
		929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		930	C<loop> nor C<revents> need to be valid as long as the watcher callback
		931	can deal with that fact.
		932
		933	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		934
		935	If the watcher is pending, this function returns clears its pending status
		936	and returns its C<revents> bitset (as if its callback was invoked). If the
		937	watcher isn't pending it does nothing and returns C<0>.
738		938
739	=back	939	=back
740		940
741		941
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
827	In general you can register as many read and/or write event watchers per	1027	In general you can register as many read and/or write event watchers per
828	fd as you want (as long as you don't confuse yourself). Setting all file	1028	fd as you want (as long as you don't confuse yourself). Setting all file
829	descriptors to non-blocking mode is also usually a good idea (but not	1029	descriptors to non-blocking mode is also usually a good idea (but not
830	required if you know what you are doing).	1030	required if you know what you are doing).
831		1031
832	You have to be careful with dup'ed file descriptors, though. Some backends
833	(the linux epoll backend is a notable example) cannot handle dup'ed file
834	descriptors correctly if you register interest in two or more fds pointing
835	to the same underlying file/socket/etc. description (that is, they share
836	the same underlying "file open").
837
838	If you must do this, then force the use of a known-to-be-good backend	1032	If you must do this, then force the use of a known-to-be-good backend
839	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
840	C<EVBACKEND_POLL>).	1034	C<EVBACKEND_POLL>).
841		1035
842	Another thing you have to watch out for is that it is quite easy to	1036	Another thing you have to watch out for is that it is quite easy to
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning
849	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		1044
851	If you cannot run the fd in non-blocking mode (for example you should not	1045	If you cannot run the fd in non-blocking mode (for example you should not
852	play around with an Xlib connection), then you have to seperately re-test	1046	play around with an Xlib connection), then you have to seperately re-test
853	wether a file descriptor is really ready with a known-to-be good interface	1047	whether a file descriptor is really ready with a known-to-be good interface
854	such as poll (fortunately in our Xlib example, Xlib already does this on	1048	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	1049	its own, so its quite safe to use).
		1050
		1051	=head3 The special problem of disappearing file descriptors
		1052
		1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1054	descriptor (either by calling C<close> explicitly or by any other means,
		1055	such as C<dup>). The reason is that you register interest in some file
		1056	descriptor, but when it goes away, the operating system will silently drop
		1057	this interest. If another file descriptor with the same number then is
		1058	registered with libev, there is no efficient way to see that this is, in
		1059	fact, a different file descriptor.
		1060
		1061	To avoid having to explicitly tell libev about such cases, libev follows
		1062	the following policy: Each time C<ev_io_set> is being called, libev
		1063	will assume that this is potentially a new file descriptor, otherwise
		1064	it is assumed that the file descriptor stays the same. That means that
		1065	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1066	descriptor even if the file descriptor number itself did not change.
		1067
		1068	This is how one would do it normally anyway, the important point is that
		1069	the libev application should not optimise around libev but should leave
		1070	optimisations to libev.
		1071
		1072	=head3 The special problem of dup'ed file descriptors
		1073
		1074	Some backends (e.g. epoll), cannot register events for file descriptors,
		1075	but only events for the underlying file descriptions. That means when you
		1076	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1077	events for them, only one file descriptor might actually receive events.
		1078
		1079	There is no workaround possible except not registering events
		1080	for potentially C<dup ()>'ed file descriptors, or to resort to
		1081	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1082
		1083	=head3 The special problem of fork
		1084
		1085	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1086	useless behaviour. Libev fully supports fork, but needs to be told about
		1087	it in the child.
		1088
		1089	To support fork in your programs, you either have to call
		1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1092	C<EVBACKEND_POLL>.
		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
		1106
		1107	=head3 Watcher-Specific Functions
856		1108
857	=over 4	1109	=over 4
858		1110
859	=item ev_io_init (ev_io *, callback, int fd, int events)	1111	=item ev_io_init (ev_io *, callback, int fd, int events)
860		1112
…		…
871	=item int events [read-only]	1123	=item int events [read-only]
872		1124
873	The events being watched.	1125	The events being watched.
874		1126
875	=back	1127	=back
		1128
		1129	=head3 Examples
876		1130
877	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
878	readable, but only once. Since it is likely line-buffered, you could	1132	readable, but only once. Since it is likely line-buffered, you could
879	attempt to read a whole line in the callback.	1133	attempt to read a whole line in the callback.
880		1134
…		…
914		1168
915	The callback is guarenteed to be invoked only when its timeout has passed,	1169	The callback is guarenteed to be invoked only when its timeout has passed,
916	but if multiple timers become ready during the same loop iteration then	1170	but if multiple timers become ready during the same loop iteration then
917	order of execution is undefined.	1171	order of execution is undefined.
918		1172
		1173	=head3 Watcher-Specific Functions and Data Members
		1174
919	=over 4	1175	=over 4
920		1176
921	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
922		1178
923	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
931	configure a timer to trigger every 10 seconds, then it will trigger at	1187	configure a timer to trigger every 10 seconds, then it will trigger at
932	exactly 10 second intervals. If, however, your program cannot keep up with	1188	exactly 10 second intervals. If, however, your program cannot keep up with
933	the timer (because it takes longer than those 10 seconds to do stuff) the	1189	the timer (because it takes longer than those 10 seconds to do stuff) the
934	timer will not fire more than once per event loop iteration.	1190	timer will not fire more than once per event loop iteration.
935		1191
936	=item ev_timer_again (loop)	1192	=item ev_timer_again (loop, ev_timer *)
937		1193
938	This will act as if the timer timed out and restart it again if it is	1194	This will act as if the timer timed out and restart it again if it is
939	repeating. The exact semantics are:	1195	repeating. The exact semantics are:
940		1196
941	If the timer is pending, its pending status is cleared.	1197	If the timer is pending, its pending status is cleared.
…		…
976	or C<ev_timer_again> is called and determines the next timeout (if any),	1232	or C<ev_timer_again> is called and determines the next timeout (if any),
977	which is also when any modifications are taken into account.	1233	which is also when any modifications are taken into account.
978		1234
979	=back	1235	=back
980		1236
		1237	=head3 Examples
		1238
981	Example: Create a timer that fires after 60 seconds.	1239	Example: Create a timer that fires after 60 seconds.
982		1240
983	static void	1241	static void
984	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
985	{	1243	{
…		…
1018	but on wallclock time (absolute time). You can tell a periodic watcher	1276	but on wallclock time (absolute time). You can tell a periodic watcher
1019	to trigger "at" some specific point in time. For example, if you tell a	1277	to trigger "at" some specific point in time. For example, if you tell a
1020	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1021	+ 10.>) and then reset your system clock to the last year, then it will	1279	+ 10.>) and then reset your system clock to the last year, then it will
1022	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1023	roughly 10 seconds later and of course not if you reset your system time	1281	roughly 10 seconds later).
1024	again).
1025		1282
1026	They can also be used to implement vastly more complex timers, such as	1283	They can also be used to implement vastly more complex timers, such as
1027	triggering an event on eahc midnight, local time.	1284	triggering an event on each midnight, local time or other, complicated,
		1285	rules.
1028		1286
1029	As with timers, the callback is guarenteed to be invoked only when the	1287	As with timers, the callback is guarenteed to be invoked only when the
1030	time (C<at>) has been passed, but if multiple periodic timers become ready	1288	time (C<at>) has been passed, but if multiple periodic timers become ready
1031	during the same loop iteration then order of execution is undefined.	1289	during the same loop iteration then order of execution is undefined.
1032		1290
		1291	=head3 Watcher-Specific Functions and Data Members
		1292
1033	=over 4	1293	=over 4
1034		1294
1035	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1036		1296
1037	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1039	Lots of arguments, lets sort it out... There are basically three modes of	1299	Lots of arguments, lets sort it out... There are basically three modes of
1040	operation, and we will explain them from simplest to complex:	1300	operation, and we will explain them from simplest to complex:
1041		1301
1042	=over 4	1302	=over 4
1043		1303
1044	=item * absolute timer (interval = reschedule_cb = 0)	1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1045		1305
1046	In this configuration the watcher triggers an event at the wallclock time	1306	In this configuration the watcher triggers an event at the wallclock time
1047	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1048	that is, if it is to be run at January 1st 2011 then it will run when the	1308	that is, if it is to be run at January 1st 2011 then it will run when the
1049	system time reaches or surpasses this time.	1309	system time reaches or surpasses this time.
1050		1310
1051	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1052		1312
1053	In this mode the watcher will always be scheduled to time out at the next	1313	In this mode the watcher will always be scheduled to time out at the next
1054	C<at + N * interval> time (for some integer N) and then repeat, regardless	1314	C<at + N * interval> time (for some integer N, which can also be negative)
1055	of any time jumps.	1315	and then repeat, regardless of any time jumps.
1056		1316
1057	This can be used to create timers that do not drift with respect to system	1317	This can be used to create timers that do not drift with respect to system
1058	time:	1318	time:
1059		1319
1060	ev_periodic_set (&periodic, 0., 3600., 0);	1320	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1066		1326
1067	Another way to think about it (for the mathematically inclined) is that	1327	Another way to think about it (for the mathematically inclined) is that
1068	C<ev_periodic> will try to run the callback in this mode at the next possible	1328	C<ev_periodic> will try to run the callback in this mode at the next possible
1069	time where C<time = at (mod interval)>, regardless of any time jumps.	1329	time where C<time = at (mod interval)>, regardless of any time jumps.
1070		1330
		1331	For numerical stability it is preferable that the C<at> value is near
		1332	C<ev_now ()> (the current time), but there is no range requirement for
		1333	this value.
		1334
1071	=item * manual reschedule mode (reschedule_cb = callback)	1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1072		1336
1073	In this mode the values for C<interval> and C<at> are both being	1337	In this mode the values for C<interval> and C<at> are both being
1074	ignored. Instead, each time the periodic watcher gets scheduled, the	1338	ignored. Instead, each time the periodic watcher gets scheduled, the
1075	reschedule callback will be called with the watcher as first, and the	1339	reschedule callback will be called with the watcher as first, and the
1076	current time as second argument.	1340	current time as second argument.
1077		1341
1078	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1079	ever, or make any event loop modifications>. If you need to stop it,	1343	ever, or make any event loop modifications>. If you need to stop it,
1080	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1081	starting a prepare watcher).	1345	starting an C<ev_prepare> watcher, which is legal).
1082		1346
1083	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1084	ev_tstamp now)>, e.g.:	1348	ev_tstamp now)>, e.g.:
1085		1349
1086	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1109	Simply stops and restarts the periodic watcher again. This is only useful	1373	Simply stops and restarts the periodic watcher again. This is only useful
1110	when you changed some parameters or the reschedule callback would return	1374	when you changed some parameters or the reschedule callback would return
1111	a different time than the last time it was called (e.g. in a crond like	1375	a different time than the last time it was called (e.g. in a crond like
1112	program when the crontabs have changed).	1376	program when the crontabs have changed).
1113		1377
		1378	=item ev_tstamp offset [read-write]
		1379
		1380	When repeating, this contains the offset value, otherwise this is the
		1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1382
		1383	Can be modified any time, but changes only take effect when the periodic
		1384	timer fires or C<ev_periodic_again> is being called.
		1385
1114	=item ev_tstamp interval [read-write]	1386	=item ev_tstamp interval [read-write]
1115		1387
1116	The current interval value. Can be modified any time, but changes only	1388	The current interval value. Can be modified any time, but changes only
1117	take effect when the periodic timer fires or C<ev_periodic_again> is being	1389	take effect when the periodic timer fires or C<ev_periodic_again> is being
1118	called.	1390	called.
…		…
1121		1393
1122	The current reschedule callback, or C<0>, if this functionality is	1394	The current reschedule callback, or C<0>, if this functionality is
1123	switched off. Can be changed any time, but changes only take effect when	1395	switched off. Can be changed any time, but changes only take effect when
1124	the periodic timer fires or C<ev_periodic_again> is being called.	1396	the periodic timer fires or C<ev_periodic_again> is being called.
1125		1397
		1398	=item ev_tstamp at [read-only]
		1399
		1400	When active, contains the absolute time that the watcher is supposed to
		1401	trigger next.
		1402
1126	=back	1403	=back
		1404
		1405	=head3 Examples
1127		1406
1128	Example: Call a callback every hour, or, more precisely, whenever the	1407	Example: Call a callback every hour, or, more precisely, whenever the
1129	system clock is divisible by 3600. The callback invocation times have	1408	system clock is divisible by 3600. The callback invocation times have
1130	potentially a lot of jittering, but good long-term stability.	1409	potentially a lot of jittering, but good long-term stability.
1131		1410
…		…
1171	with the kernel (thus it coexists with your own signal handlers as long	1450	with the kernel (thus it coexists with your own signal handlers as long
1172	as you don't register any with libev). Similarly, when the last signal	1451	as you don't register any with libev). Similarly, when the last signal
1173	watcher for a signal is stopped libev will reset the signal handler to	1452	watcher for a signal is stopped libev will reset the signal handler to
1174	SIG_DFL (regardless of what it was set to before).	1453	SIG_DFL (regardless of what it was set to before).
1175		1454
		1455	If possible and supported, libev will install its handlers with
		1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1457	interrupted. If you have a problem with syscalls getting interrupted by
		1458	signals you can block all signals in an C<ev_check> watcher and unblock
		1459	them in an C<ev_prepare> watcher.
		1460
		1461	=head3 Watcher-Specific Functions and Data Members
		1462
1176	=over 4	1463	=over 4
1177		1464
1178	=item ev_signal_init (ev_signal *, callback, int signum)	1465	=item ev_signal_init (ev_signal *, callback, int signum)
1179		1466
1180	=item ev_signal_set (ev_signal *, int signum)	1467	=item ev_signal_set (ev_signal *, int signum)
…		…
1186		1473
1187	The signal the watcher watches out for.	1474	The signal the watcher watches out for.
1188		1475
1189	=back	1476	=back
1190		1477
		1478	=head3 Examples
		1479
		1480	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1481
		1482	static void
		1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1484	{
		1485	ev_unloop (loop, EVUNLOOP_ALL);
		1486	}
		1487
		1488	struct ev_signal signal_watcher;
		1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1490	ev_signal_start (loop, &sigint_cb);
		1491
1191		1492
1192	=head2 C<ev_child> - watch out for process status changes	1493	=head2 C<ev_child> - watch out for process status changes
1193		1494
1194	Child watchers trigger when your process receives a SIGCHLD in response to	1495	Child watchers trigger when your process receives a SIGCHLD in response to
1195	some child status changes (most typically when a child of yours dies).	1496	some child status changes (most typically when a child of yours dies). It
		1497	is permissible to install a child watcher I<after> the child has been
		1498	forked (which implies it might have already exited), as long as the event
		1499	loop isn't entered (or is continued from a watcher).
		1500
		1501	Only the default event loop is capable of handling signals, and therefore
		1502	you can only rgeister child watchers in the default event loop.
		1503
		1504	=head3 Process Interaction
		1505
		1506	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1507	initialised. This is necessary to guarantee proper behaviour even if
		1508	the first child watcher is started after the child exits. The occurance
		1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1510	synchronously as part of the event loop processing. Libev always reaps all
		1511	children, even ones not watched.
		1512
		1513	=head3 Overriding the Built-In Processing
		1514
		1515	Libev offers no special support for overriding the built-in child
		1516	processing, but if your application collides with libev's default child
		1517	handler, you can override it easily by installing your own handler for
		1518	C<SIGCHLD> after initialising the default loop, and making sure the
		1519	default loop never gets destroyed. You are encouraged, however, to use an
		1520	event-based approach to child reaping and thus use libev's support for
		1521	that, so other libev users can use C<ev_child> watchers freely.
		1522
		1523	=head3 Watcher-Specific Functions and Data Members
1196		1524
1197	=over 4	1525	=over 4
1198		1526
1199	=item ev_child_init (ev_child *, callback, int pid)	1527	=item ev_child_init (ev_child *, callback, int pid, int trace)
1200		1528
1201	=item ev_child_set (ev_child *, int pid)	1529	=item ev_child_set (ev_child *, int pid, int trace)
1202		1530
1203	Configures the watcher to wait for status changes of process C<pid> (or	1531	Configures the watcher to wait for status changes of process C<pid> (or
1204	I<any> process if C<pid> is specified as C<0>). The callback can look	1532	I<any> process if C<pid> is specified as C<0>). The callback can look
1205	at the C<rstatus> member of the C<ev_child> watcher structure to see	1533	at the C<rstatus> member of the C<ev_child> watcher structure to see
1206	the status word (use the macros from C<sys/wait.h> and see your systems	1534	the status word (use the macros from C<sys/wait.h> and see your systems
1207	C<waitpid> documentation). The C<rpid> member contains the pid of the	1535	C<waitpid> documentation). The C<rpid> member contains the pid of the
1208	process causing the status change.	1536	process causing the status change. C<trace> must be either C<0> (only
		1537	activate the watcher when the process terminates) or C<1> (additionally
		1538	activate the watcher when the process is stopped or continued).
1209		1539
1210	=item int pid [read-only]	1540	=item int pid [read-only]
1211		1541
1212	The process id this watcher watches out for, or C<0>, meaning any process id.	1542	The process id this watcher watches out for, or C<0>, meaning any process id.
1213		1543
…		…
1220	The process exit/trace status caused by C<rpid> (see your systems	1550	The process exit/trace status caused by C<rpid> (see your systems
1221	C<waitpid> and C<sys/wait.h> documentation for details).	1551	C<waitpid> and C<sys/wait.h> documentation for details).
1222		1552
1223	=back	1553	=back
1224		1554
1225	Example: Try to exit cleanly on SIGINT and SIGTERM.	1555	=head3 Examples
		1556
		1557	Example: C<fork()> a new process and install a child handler to wait for
		1558	its completion.
		1559
		1560	ev_child cw;
1226		1561
1227	static void	1562	static void
1228	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1563	child_cb (EV_P_ struct ev_child *w, int revents)
1229	{	1564	{
1230	ev_unloop (loop, EVUNLOOP_ALL);	1565	ev_child_stop (EV_A_ w);
		1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1231	}	1567	}
1232		1568
1233	struct ev_signal signal_watcher;	1569	pid_t pid = fork ();
1234	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1570
1235	ev_signal_start (loop, &sigint_cb);	1571	if (pid < 0)
		1572	// error
		1573	else if (pid == 0)
		1574	{
		1575	// the forked child executes here
		1576	exit (1);
		1577	}
		1578	else
		1579	{
		1580	ev_child_init (&cw, child_cb, pid, 0);
		1581	ev_child_start (EV_DEFAULT_ &cw);
		1582	}
1236		1583
1237		1584
1238	=head2 C<ev_stat> - did the file attributes just change?	1585	=head2 C<ev_stat> - did the file attributes just change?
1239		1586
1240	This watches a filesystem path for attribute changes. That is, it calls	1587	This watches a filesystem path for attribute changes. That is, it calls
…		…
1269	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270	to fall back to regular polling again even with inotify, but changes are	1617	to fall back to regular polling again even with inotify, but changes are
1271	usually detected immediately, and if the file exists there will be no	1618	usually detected immediately, and if the file exists there will be no
1272	polling.	1619	polling.
1273		1620
		1621	=head3 ABI Issues (Largefile Support)
		1622
		1623	Libev by default (unless the user overrides this) uses the default
		1624	compilation environment, which means that on systems with optionally
		1625	disabled large file support, you get the 32 bit version of the stat
		1626	structure. When using the library from programs that change the ABI to
		1627	use 64 bit file offsets the programs will fail. In that case you have to
		1628	compile libev with the same flags to get binary compatibility. This is
		1629	obviously the case with any flags that change the ABI, but the problem is
		1630	most noticably with ev_stat and largefile support.
		1631
		1632	=head3 Inotify
		1633
		1634	When C<inotify (7)> support has been compiled into libev (generally only
		1635	available on Linux) and present at runtime, it will be used to speed up
		1636	change detection where possible. The inotify descriptor will be created lazily
		1637	when the first C<ev_stat> watcher is being started.
		1638
		1639	Inotify presence does not change the semantics of C<ev_stat> watchers
		1640	except that changes might be detected earlier, and in some cases, to avoid
		1641	making regular C<stat> calls. Even in the presence of inotify support
		1642	there are many cases where libev has to resort to regular C<stat> polling.
		1643
		1644	(There is no support for kqueue, as apparently it cannot be used to
		1645	implement this functionality, due to the requirement of having a file
		1646	descriptor open on the object at all times).
		1647
		1648	=head3 The special problem of stat time resolution
		1649
		1650	The C<stat ()> syscall only supports full-second resolution portably, and
		1651	even on systems where the resolution is higher, many filesystems still
		1652	only support whole seconds.
		1653
		1654	That means that, if the time is the only thing that changes, you might
		1655	miss updates: on the first update, C<ev_stat> detects a change and calls
		1656	your callback, which does something. When there is another update within
		1657	the same second, C<ev_stat> will be unable to detect it.
		1658
		1659	The solution to this is to delay acting on a change for a second (or till
		1660	the next second boundary), using a roughly one-second delay C<ev_timer>
		1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1662	is added to work around small timing inconsistencies of some operating
		1663	systems.
		1664
		1665	=head3 Watcher-Specific Functions and Data Members
		1666
1274	=over 4	1667	=over 4
1275		1668
1276	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1669	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1277		1670
1278	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1671	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1285		1678
1286	The callback will be receive C<EV_STAT> when a change was detected,	1679	The callback will be receive C<EV_STAT> when a change was detected,
1287	relative to the attributes at the time the watcher was started (or the	1680	relative to the attributes at the time the watcher was started (or the
1288	last change was detected).	1681	last change was detected).
1289		1682
1290	=item ev_stat_stat (ev_stat *)	1683	=item ev_stat_stat (loop, ev_stat *)
1291		1684
1292	Updates the stat buffer immediately with new values. If you change the	1685	Updates the stat buffer immediately with new values. If you change the
1293	watched path in your callback, you could call this fucntion to avoid	1686	watched path in your callback, you could call this fucntion to avoid
1294	detecting this change (while introducing a race condition). Can also be	1687	detecting this change (while introducing a race condition). Can also be
1295	useful simply to find out the new values.	1688	useful simply to find out the new values.
…		…
1313	=item const char *path [read-only]	1706	=item const char *path [read-only]
1314		1707
1315	The filesystem path that is being watched.	1708	The filesystem path that is being watched.
1316		1709
1317	=back	1710	=back
		1711
		1712	=head3 Examples
1318		1713
1319	Example: Watch C</etc/passwd> for attribute changes.	1714	Example: Watch C</etc/passwd> for attribute changes.
1320		1715
1321	static void	1716	static void
1322	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1335	}	1730	}
1336		1731
1337	...	1732	...
1338	ev_stat passwd;	1733	ev_stat passwd;
1339		1734
1340	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1341	ev_stat_start (loop, &passwd);	1736	ev_stat_start (loop, &passwd);
1342		1737
		1738	Example: Like above, but additionally use a one-second delay so we do not
		1739	miss updates (however, frequent updates will delay processing, too, so
		1740	one might do the work both on C<ev_stat> callback invocation I<and> on
		1741	C<ev_timer> callback invocation).
		1742
		1743	static ev_stat passwd;
		1744	static ev_timer timer;
		1745
		1746	static void
		1747	timer_cb (EV_P_ ev_timer *w, int revents)
		1748	{
		1749	ev_timer_stop (EV_A_ w);
		1750
		1751	/* now it's one second after the most recent passwd change */
		1752	}
		1753
		1754	static void
		1755	stat_cb (EV_P_ ev_stat *w, int revents)
		1756	{
		1757	/* reset the one-second timer */
		1758	ev_timer_again (EV_A_ &timer);
		1759	}
		1760
		1761	...
		1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1763	ev_stat_start (loop, &passwd);
		1764	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1765
1343		1766
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1767	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1768
1346	Idle watchers trigger events when there are no other events are pending	1769	Idle watchers trigger events when no other events of the same or higher
1347	(prepare, check and other idle watchers do not count). That is, as long	1770	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1771	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1772
1350	watchers are being called again and again, once per event loop iteration -	1773	That is, as long as your process is busy handling sockets or timeouts
		1774	(or even signals, imagine) of the same or higher priority it will not be
		1775	triggered. But when your process is idle (or only lower-priority watchers
		1776	are pending), the idle watchers are being called once per event loop
1351	until stopped, that is, or your process receives more events and becomes	1777	iteration - until stopped, that is, or your process receives more events
1352	busy.	1778	and becomes busy again with higher priority stuff.
1353		1779
1354	The most noteworthy effect is that as long as any idle watchers are	1780	The most noteworthy effect is that as long as any idle watchers are
1355	active, the process will not block when waiting for new events.	1781	active, the process will not block when waiting for new events.
1356		1782
1357	Apart from keeping your process non-blocking (which is a useful	1783	Apart from keeping your process non-blocking (which is a useful
1358	effect on its own sometimes), idle watchers are a good place to do	1784	effect on its own sometimes), idle watchers are a good place to do
1359	"pseudo-background processing", or delay processing stuff to after the	1785	"pseudo-background processing", or delay processing stuff to after the
1360	event loop has handled all outstanding events.	1786	event loop has handled all outstanding events.
1361		1787
		1788	=head3 Watcher-Specific Functions and Data Members
		1789
1362	=over 4	1790	=over 4
1363		1791
1364	=item ev_idle_init (ev_signal *, callback)	1792	=item ev_idle_init (ev_signal *, callback)
1365		1793
1366	Initialises and configures the idle watcher - it has no parameters of any	1794	Initialises and configures the idle watcher - it has no parameters of any
1367	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1368	believe me.	1796	believe me.
1369		1797
1370	=back	1798	=back
		1799
		1800	=head3 Examples
1371		1801
1372	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1373	callback, free it. Also, use no error checking, as usual.	1803	callback, free it. Also, use no error checking, as usual.
1374		1804
1375	static void	1805	static void
1376	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1377	{	1807	{
1378	free (w);	1808	free (w);
1379	// now do something you wanted to do when the program has	1809	// now do something you wanted to do when the program has
1380	// no longer asnything immediate to do.	1810	// no longer anything immediate to do.
1381	}	1811	}
1382		1812
1383	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1384	ev_idle_init (idle_watcher, idle_cb);	1814	ev_idle_init (idle_watcher, idle_cb);
1385	ev_idle_start (loop, idle_cb);	1815	ev_idle_start (loop, idle_cb);
…		…
1423	with priority higher than or equal to the event loop and one coroutine	1853	with priority higher than or equal to the event loop and one coroutine
1424	of lower priority, but only once, using idle watchers to keep the event	1854	of lower priority, but only once, using idle watchers to keep the event
1425	loop from blocking if lower-priority coroutines are active, thus mapping	1855	loop from blocking if lower-priority coroutines are active, thus mapping
1426	low-priority coroutines to idle/background tasks).	1856	low-priority coroutines to idle/background tasks).
1427		1857
		1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1859	priority, to ensure that they are being run before any other watchers
		1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1861	too) should not activate ("feed") events into libev. While libev fully
		1862	supports this, they will be called before other C<ev_check> watchers
		1863	did their job. As C<ev_check> watchers are often used to embed other
		1864	(non-libev) event loops those other event loops might be in an unusable
		1865	state until their C<ev_check> watcher ran (always remind yourself to
		1866	coexist peacefully with others).
		1867
		1868	=head3 Watcher-Specific Functions and Data Members
		1869
1428	=over 4	1870	=over 4
1429		1871
1430	=item ev_prepare_init (ev_prepare *, callback)	1872	=item ev_prepare_init (ev_prepare *, callback)
1431		1873
1432	=item ev_check_init (ev_check *, callback)	1874	=item ev_check_init (ev_check *, callback)
…		…
1435	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1436	macros, but using them is utterly, utterly and completely pointless.	1878	macros, but using them is utterly, utterly and completely pointless.
1437		1879
1438	=back	1880	=back
1439		1881
1440	Example: To include a library such as adns, you would add IO watchers	1882	=head3 Examples
1441	and a timeout watcher in a prepare handler, as required by libadns, and	1883
		1884	There are a number of principal ways to embed other event loops or modules
		1885	into libev. Here are some ideas on how to include libadns into libev
		1886	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1887	use for an actually working example. Another Perl module named C<EV::Glib>
		1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1889	into the Glib event loop).
		1890
		1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1442	in a check watcher, destroy them and call into libadns. What follows is	1892	and in a check watcher, destroy them and call into libadns. What follows
1443	pseudo-code only of course:	1893	is pseudo-code only of course. This requires you to either use a low
		1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1895	the callbacks for the IO/timeout watchers might not have been called yet.
1444		1896
1445	static ev_io iow [nfd];	1897	static ev_io iow [nfd];
1446	static ev_timer tw;	1898	static ev_timer tw;
1447		1899
1448	static void	1900	static void
1449	io_cb (ev_loop *loop, ev_io *w, int revents)	1901	io_cb (ev_loop *loop, ev_io *w, int revents)
1450	{	1902	{
1451	// set the relevant poll flags
1452	// could also call adns_processreadable etc. here
1453	struct pollfd *fd = (struct pollfd *)w->data;
1454	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1455	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1456	}	1903	}
1457		1904
1458	// create io watchers for each fd and a timer before blocking	1905	// create io watchers for each fd and a timer before blocking
1459	static void	1906	static void
1460	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1461	{	1908	{
1462	int timeout = 3600000;truct pollfd fds [nfd];	1909	int timeout = 3600000;
		1910	struct pollfd fds [nfd];
1463	// actual code will need to loop here and realloc etc.	1911	// actual code will need to loop here and realloc etc.
1464	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1465		1913
1466	/* the callback is illegal, but won't be called as we stop during check */	1914	/* the callback is illegal, but won't be called as we stop during check */
1467	ev_timer_init (&tw, 0, timeout * 1e-3);	1915	ev_timer_init (&tw, 0, timeout * 1e-3);
1468	ev_timer_start (loop, &tw);	1916	ev_timer_start (loop, &tw);
1469		1917
1470	// create on ev_io per pollfd	1918	// create one ev_io per pollfd
1471	for (int i = 0; i < nfd; ++i)	1919	for (int i = 0; i < nfd; ++i)
1472	{	1920	{
1473	ev_io_init (iow + i, io_cb, fds [i].fd,	1921	ev_io_init (iow + i, io_cb, fds [i].fd,
1474	((fds [i].events & POLLIN ? EV_READ : 0)	1922	((fds [i].events & POLLIN ? EV_READ : 0)
1475	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1476		1924
1477	fds [i].revents = 0;	1925	fds [i].revents = 0;
1478	iow [i].data = fds + i;
1479	ev_io_start (loop, iow + i);	1926	ev_io_start (loop, iow + i);
1480	}	1927	}
1481	}	1928	}
1482		1929
1483	// stop all watchers after blocking	1930	// stop all watchers after blocking
…		…
1485	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1486	{	1933	{
1487	ev_timer_stop (loop, &tw);	1934	ev_timer_stop (loop, &tw);
1488		1935
1489	for (int i = 0; i < nfd; ++i)	1936	for (int i = 0; i < nfd; ++i)
		1937	{
		1938	// set the relevant poll flags
		1939	// could also call adns_processreadable etc. here
		1940	struct pollfd *fd = fds + i;
		1941	int revents = ev_clear_pending (iow + i);
		1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1944
		1945	// now stop the watcher
1490	ev_io_stop (loop, iow + i);	1946	ev_io_stop (loop, iow + i);
		1947	}
1491		1948
1492	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1950	}
		1951
		1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1953	in the prepare watcher and would dispose of the check watcher.
		1954
		1955	Method 3: If the module to be embedded supports explicit event
		1956	notification (adns does), you can also make use of the actual watcher
		1957	callbacks, and only destroy/create the watchers in the prepare watcher.
		1958
		1959	static void
		1960	timer_cb (EV_P_ ev_timer *w, int revents)
		1961	{
		1962	adns_state ads = (adns_state)w->data;
		1963	update_now (EV_A);
		1964
		1965	adns_processtimeouts (ads, &tv_now);
		1966	}
		1967
		1968	static void
		1969	io_cb (EV_P_ ev_io *w, int revents)
		1970	{
		1971	adns_state ads = (adns_state)w->data;
		1972	update_now (EV_A);
		1973
		1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1976	}
		1977
		1978	// do not ever call adns_afterpoll
		1979
		1980	Method 4: Do not use a prepare or check watcher because the module you
		1981	want to embed is too inflexible to support it. Instead, youc na override
		1982	their poll function. The drawback with this solution is that the main
		1983	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1984	this.
		1985
		1986	static gint
		1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1988	{
		1989	int got_events = 0;
		1990
		1991	for (n = 0; n < nfds; ++n)
		1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1993
		1994	if (timeout >= 0)
		1995	// create/start timer
		1996
		1997	// poll
		1998	ev_loop (EV_A_ 0);
		1999
		2000	// stop timer again
		2001	if (timeout >= 0)
		2002	ev_timer_stop (EV_A_ &to);
		2003
		2004	// stop io watchers again - their callbacks should have set
		2005	for (n = 0; n < nfds; ++n)
		2006	ev_io_stop (EV_A_ iow [n]);
		2007
		2008	return got_events;
1493	}	2009	}
1494		2010
1495		2011
1496	=head2 C<ev_embed> - when one backend isn't enough...	2012	=head2 C<ev_embed> - when one backend isn't enough...
1497		2013
…		…
1540	portable one.	2056	portable one.
1541		2057
1542	So when you want to use this feature you will always have to be prepared	2058	So when you want to use this feature you will always have to be prepared
1543	that you cannot get an embeddable loop. The recommended way to get around	2059	that you cannot get an embeddable loop. The recommended way to get around
1544	this is to have a separate variables for your embeddable loop, try to	2060	this is to have a separate variables for your embeddable loop, try to
1545	create it, and if that fails, use the normal loop for everything:	2061	create it, and if that fails, use the normal loop for everything.
		2062
		2063	=head3 Watcher-Specific Functions and Data Members
		2064
		2065	=over 4
		2066
		2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2068
		2069	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2070
		2071	Configures the watcher to embed the given loop, which must be
		2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2073	invoked automatically, otherwise it is the responsibility of the callback
		2074	to invoke it (it will continue to be called until the sweep has been done,
		2075	if you do not want thta, you need to temporarily stop the embed watcher).
		2076
		2077	=item ev_embed_sweep (loop, ev_embed *)
		2078
		2079	Make a single, non-blocking sweep over the embedded loop. This works
		2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2081	apropriate way for embedded loops.
		2082
		2083	=item struct ev_loop *other [read-only]
		2084
		2085	The embedded event loop.
		2086
		2087	=back
		2088
		2089	=head3 Examples
		2090
		2091	Example: Try to get an embeddable event loop and embed it into the default
		2092	event loop. If that is not possible, use the default loop. The default
		2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2095	used).
1546		2096
1547	struct ev_loop *loop_hi = ev_default_init (0);	2097	struct ev_loop *loop_hi = ev_default_init (0);
1548	struct ev_loop *loop_lo = 0;	2098	struct ev_loop *loop_lo = 0;
1549	struct ev_embed embed;	2099	struct ev_embed embed;
1550		2100
…		…
1561	ev_embed_start (loop_hi, &embed);	2111	ev_embed_start (loop_hi, &embed);
1562	}	2112	}
1563	else	2113	else
1564	loop_lo = loop_hi;	2114	loop_lo = loop_hi;
1565		2115
1566	=over 4	2116	Example: Check if kqueue is available but not recommended and create
		2117	a kqueue backend for use with sockets (which usually work with any
		2118	kqueue implementation). Store the kqueue/socket-only event loop in
		2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1567		2120
1568	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2121	struct ev_loop *loop = ev_default_init (0);
		2122	struct ev_loop *loop_socket = 0;
		2123	struct ev_embed embed;
		2124
		2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2127	{
		2128	ev_embed_init (&embed, 0, loop_socket);
		2129	ev_embed_start (loop, &embed);
		2130	}
1569		2131
1570	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2132	if (!loop_socket)
		2133	loop_socket = loop;
1571		2134
1572	Configures the watcher to embed the given loop, which must be	2135	// now use loop_socket for all sockets, and loop for everything else
1573	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1574	invoked automatically, otherwise it is the responsibility of the callback
1575	to invoke it (it will continue to be called until the sweep has been done,
1576	if you do not want thta, you need to temporarily stop the embed watcher).
1577
1578	=item ev_embed_sweep (loop, ev_embed *)
1579
1580	Make a single, non-blocking sweep over the embedded loop. This works
1581	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1582	apropriate way for embedded loops.
1583
1584	=item struct ev_loop *loop [read-only]
1585
1586	The embedded event loop.
1587
1588	=back
1589		2136
1590		2137
1591	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1592		2139
1593	Fork watchers are called when a C<fork ()> was detected (usually because	2140	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1596	event loop blocks next and before C<ev_check> watchers are being called,	2143	event loop blocks next and before C<ev_check> watchers are being called,
1597	and only in the child after the fork. If whoever good citizen calling	2144	and only in the child after the fork. If whoever good citizen calling
1598	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2145	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1599	handlers will be invoked, too, of course.	2146	handlers will be invoked, too, of course.
1600		2147
		2148	=head3 Watcher-Specific Functions and Data Members
		2149
1601	=over 4	2150	=over 4
1602		2151
1603	=item ev_fork_init (ev_signal *, callback)	2152	=item ev_fork_init (ev_signal *, callback)
1604		2153
1605	Initialises and configures the fork watcher - it has no parameters of any	2154	Initialises and configures the fork watcher - it has no parameters of any
1606	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2155	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1607	believe me.	2156	believe me.
		2157
		2158	=back
		2159
		2160
		2161	=head2 C<ev_async> - how to wake up another event loop
		2162
		2163	In general, you cannot use an C<ev_loop> from multiple threads or other
		2164	asynchronous sources such as signal handlers (as opposed to multiple event
		2165	loops - those are of course safe to use in different threads).
		2166
		2167	Sometimes, however, you need to wake up another event loop you do not
		2168	control, for example because it belongs to another thread. This is what
		2169	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2170	can signal it by calling C<ev_async_send>, which is thread- and signal
		2171	safe.
		2172
		2173	This functionality is very similar to C<ev_signal> watchers, as signals,
		2174	too, are asynchronous in nature, and signals, too, will be compressed
		2175	(i.e. the number of callback invocations may be less than the number of
		2176	C<ev_async_sent> calls).
		2177
		2178	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2179	just the default loop.
		2180
		2181	=head3 Queueing
		2182
		2183	C<ev_async> does not support queueing of data in any way. The reason
		2184	is that the author does not know of a simple (or any) algorithm for a
		2185	multiple-writer-single-reader queue that works in all cases and doesn't
		2186	need elaborate support such as pthreads.
		2187
		2188	That means that if you want to queue data, you have to provide your own
		2189	queue. But at least I can tell you would implement locking around your
		2190	queue:
		2191
		2192	=over 4
		2193
		2194	=item queueing from a signal handler context
		2195
		2196	To implement race-free queueing, you simply add to the queue in the signal
		2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2198	some fictitiuous SIGUSR1 handler:
		2199
		2200	static ev_async mysig;
		2201
		2202	static void
		2203	sigusr1_handler (void)
		2204	{
		2205	sometype data;
		2206
		2207	// no locking etc.
		2208	queue_put (data);
		2209	ev_async_send (EV_DEFAULT_ &mysig);
		2210	}
		2211
		2212	static void
		2213	mysig_cb (EV_P_ ev_async *w, int revents)
		2214	{
		2215	sometype data;
		2216	sigset_t block, prev;
		2217
		2218	sigemptyset (&block);
		2219	sigaddset (&block, SIGUSR1);
		2220	sigprocmask (SIG_BLOCK, &block, &prev);
		2221
		2222	while (queue_get (&data))
		2223	process (data);
		2224
		2225	if (sigismember (&prev, SIGUSR1)
		2226	sigprocmask (SIG_UNBLOCK, &block, 0);
		2227	}
		2228
		2229	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2230	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2231	either...).
		2232
		2233	=item queueing from a thread context
		2234
		2235	The strategy for threads is different, as you cannot (easily) block
		2236	threads but you can easily preempt them, so to queue safely you need to
		2237	employ a traditional mutex lock, such as in this pthread example:
		2238
		2239	static ev_async mysig;
		2240	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2241
		2242	static void
		2243	otherthread (void)
		2244	{
		2245	// only need to lock the actual queueing operation
		2246	pthread_mutex_lock (&mymutex);
		2247	queue_put (data);
		2248	pthread_mutex_unlock (&mymutex);
		2249
		2250	ev_async_send (EV_DEFAULT_ &mysig);
		2251	}
		2252
		2253	static void
		2254	mysig_cb (EV_P_ ev_async *w, int revents)
		2255	{
		2256	pthread_mutex_lock (&mymutex);
		2257
		2258	while (queue_get (&data))
		2259	process (data);
		2260
		2261	pthread_mutex_unlock (&mymutex);
		2262	}
		2263
		2264	=back
		2265
		2266
		2267	=head3 Watcher-Specific Functions and Data Members
		2268
		2269	=over 4
		2270
		2271	=item ev_async_init (ev_async *, callback)
		2272
		2273	Initialises and configures the async watcher - it has no parameters of any
		2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2275	believe me.
		2276
		2277	=item ev_async_send (loop, ev_async *)
		2278
		2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2281	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2283	section below on what exactly this means).
		2284
		2285	This call incurs the overhead of a syscall only once per loop iteration,
		2286	so while the overhead might be noticable, it doesn't apply to repeated
		2287	calls to C<ev_async_send>.
		2288
		2289	=item bool = ev_async_pending (ev_async *)
		2290
		2291	Returns a non-zero value when C<ev_async_send> has been called on the
		2292	watcher but the event has not yet been processed (or even noted) by the
		2293	event loop.
		2294
		2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2296	the loop iterates next and checks for the watcher to have become active,
		2297	it will reset the flag again. C<ev_async_pending> can be used to very
		2298	quickly check wether invoking the loop might be a good idea.
		2299
		2300	Not that this does I<not> check wether the watcher itself is pending, only
		2301	wether it has been requested to make this watcher pending.
1608		2302
1609	=back	2303	=back
1610		2304
1611		2305
1612	=head1 OTHER FUNCTIONS	2306	=head1 OTHER FUNCTIONS
…		…
1684		2378
1685	=item * Priorities are not currently supported. Initialising priorities	2379	=item * Priorities are not currently supported. Initialising priorities
1686	will fail and all watchers will have the same priority, even though there	2380	will fail and all watchers will have the same priority, even though there
1687	is an ev_pri field.	2381	is an ev_pri field.
1688		2382
		2383	=item * In libevent, the last base created gets the signals, in libev, the
		2384	first base created (== the default loop) gets the signals.
		2385
1689	=item * Other members are not supported.	2386	=item * Other members are not supported.
1690		2387
1691	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2388	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1692	to use the libev header file and library.	2389	to use the libev header file and library.
1693		2390
…		…
1701		2398
1702	To use it,	2399	To use it,
1703		2400
1704	#include <ev++.h>	2401	#include <ev++.h>
1705		2402
1706	(it is not installed by default). This automatically includes F<ev.h>	2403	This automatically includes F<ev.h> and puts all of its definitions (many
1707	and puts all of its definitions (many of them macros) into the global	2404	of them macros) into the global namespace. All C++ specific things are
1708	namespace. All C++ specific things are put into the C<ev> namespace.	2405	put into the C<ev> namespace. It should support all the same embedding
		2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1709		2407
1710	It should support all the same embedding options as F<ev.h>, most notably	2408	Care has been taken to keep the overhead low. The only data member the C++
1711	C<EV_MULTIPLICITY>.	2409	classes add (compared to plain C-style watchers) is the event loop pointer
		2410	that the watcher is associated with (or no additional members at all if
		2411	you disable C<EV_MULTIPLICITY> when embedding libev).
		2412
		2413	Currently, functions, and static and non-static member functions can be
		2414	used as callbacks. Other types should be easy to add as long as they only
		2415	need one additional pointer for context. If you need support for other
		2416	types of functors please contact the author (preferably after implementing
		2417	it).
1712		2418
1713	Here is a list of things available in the C<ev> namespace:	2419	Here is a list of things available in the C<ev> namespace:
1714		2420
1715	=over 4	2421	=over 4
1716		2422
…		…
1732		2438
1733	All of those classes have these methods:	2439	All of those classes have these methods:
1734		2440
1735	=over 4	2441	=over 4
1736		2442
1737	=item ev::TYPE::TYPE (object *, object::method *)	2443	=item ev::TYPE::TYPE ()
1738		2444
1739	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2445	=item ev::TYPE::TYPE (struct ev_loop *)
1740		2446
1741	=item ev::TYPE::~TYPE	2447	=item ev::TYPE::~TYPE
1742		2448
1743	The constructor takes a pointer to an object and a method pointer to	2449	The constructor (optionally) takes an event loop to associate the watcher
1744	the event handler callback to call in this class. The constructor calls	2450	with. If it is omitted, it will use C<EV_DEFAULT>.
1745	C<ev_init> for you, which means you have to call the C<set> method	2451
1746	before starting it. If you do not specify a loop then the constructor	2452	The constructor calls C<ev_init> for you, which means you have to call the
1747	automatically associates the default loop with this watcher.	2453	C<set> method before starting it.
		2454
		2455	It will not set a callback, however: You have to call the templated C<set>
		2456	method to set a callback before you can start the watcher.
		2457
		2458	(The reason why you have to use a method is a limitation in C++ which does
		2459	not allow explicit template arguments for constructors).
1748		2460
1749	The destructor automatically stops the watcher if it is active.	2461	The destructor automatically stops the watcher if it is active.
		2462
		2463	=item w->set<class, &class::method> (object *)
		2464
		2465	This method sets the callback method to call. The method has to have a
		2466	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2467	first argument and the C<revents> as second. The object must be given as
		2468	parameter and is stored in the C<data> member of the watcher.
		2469
		2470	This method synthesizes efficient thunking code to call your method from
		2471	the C callback that libev requires. If your compiler can inline your
		2472	callback (i.e. it is visible to it at the place of the C<set> call and
		2473	your compiler is good :), then the method will be fully inlined into the
		2474	thunking function, making it as fast as a direct C callback.
		2475
		2476	Example: simple class declaration and watcher initialisation
		2477
		2478	struct myclass
		2479	{
		2480	void io_cb (ev::io &w, int revents) { }
		2481	}
		2482
		2483	myclass obj;
		2484	ev::io iow;
		2485	iow.set <myclass, &myclass::io_cb> (&obj);
		2486
		2487	=item w->set<function> (void *data = 0)
		2488
		2489	Also sets a callback, but uses a static method or plain function as
		2490	callback. The optional C<data> argument will be stored in the watcher's
		2491	C<data> member and is free for you to use.
		2492
		2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2494
		2495	See the method-C<set> above for more details.
		2496
		2497	Example:
		2498
		2499	static void io_cb (ev::io &w, int revents) { }
		2500	iow.set <io_cb> ();
1750		2501
1751	=item w->set (struct ev_loop *)	2502	=item w->set (struct ev_loop *)
1752		2503
1753	Associates a different C<struct ev_loop> with this watcher. You can only	2504	Associates a different C<struct ev_loop> with this watcher. You can only
1754	do this when the watcher is inactive (and not pending either).	2505	do this when the watcher is inactive (and not pending either).
1755		2506
1756	=item w->set ([args])	2507	=item w->set ([args])
1757		2508
1758	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1759	called at least once. Unlike the C counterpart, an active watcher gets	2510	called at least once. Unlike the C counterpart, an active watcher gets
1760	automatically stopped and restarted.	2511	automatically stopped and restarted when reconfiguring it with this
		2512	method.
1761		2513
1762	=item w->start ()	2514	=item w->start ()
1763		2515
1764	Starts the watcher. Note that there is no C<loop> argument as the	2516	Starts the watcher. Note that there is no C<loop> argument, as the
1765	constructor already takes the loop.	2517	constructor already stores the event loop.
1766		2518
1767	=item w->stop ()	2519	=item w->stop ()
1768		2520
1769	Stops the watcher if it is active. Again, no C<loop> argument.	2521	Stops the watcher if it is active. Again, no C<loop> argument.
1770		2522
1771	=item w->again () C<ev::timer>, C<ev::periodic> only	2523	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1772		2524
1773	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2525	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1774	C<ev_TYPE_again> function.	2526	C<ev_TYPE_again> function.
1775		2527
1776	=item w->sweep () C<ev::embed> only	2528	=item w->sweep () (C<ev::embed> only)
1777		2529
1778	Invokes C<ev_embed_sweep>.	2530	Invokes C<ev_embed_sweep>.
1779		2531
1780	=item w->update () C<ev::stat> only	2532	=item w->update () (C<ev::stat> only)
1781		2533
1782	Invokes C<ev_stat_stat>.	2534	Invokes C<ev_stat_stat>.
1783		2535
1784	=back	2536	=back
1785		2537
…		…
1788	Example: Define a class with an IO and idle watcher, start one of them in	2540	Example: Define a class with an IO and idle watcher, start one of them in
1789	the constructor.	2541	the constructor.
1790		2542
1791	class myclass	2543	class myclass
1792	{	2544	{
1793	ev_io io; void io_cb (ev::io &w, int revents);	2545	ev::io io; void io_cb (ev::io &w, int revents);
1794	ev_idle idle void idle_cb (ev::idle &w, int revents);	2546	ev:idle idle void idle_cb (ev::idle &w, int revents);
1795		2547
1796	myclass ();	2548	myclass (int fd)
1797	}
1798
1799	myclass::myclass (int fd)
1800	: io (this, &myclass::io_cb),
1801	idle (this, &myclass::idle_cb)
1802	{	2549	{
		2550	io .set <myclass, &myclass::io_cb > (this);
		2551	idle.set <myclass, &myclass::idle_cb> (this);
		2552
1803	io.start (fd, ev::READ);	2553	io.start (fd, ev::READ);
		2554	}
1804	}	2555	};
		2556
		2557
		2558	=head1 OTHER LANGUAGE BINDINGS
		2559
		2560	Libev does not offer other language bindings itself, but bindings for a
		2561	numbe rof languages exist in the form of third-party packages. If you know
		2562	any interesting language binding in addition to the ones listed here, drop
		2563	me a note.
		2564
		2565	=over 4
		2566
		2567	=item Perl
		2568
		2569	The EV module implements the full libev API and is actually used to test
		2570	libev. EV is developed together with libev. Apart from the EV core module,
		2571	there are additional modules that implement libev-compatible interfaces
		2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2574
		2575	It can be found and installed via CPAN, its homepage is found at
		2576	L<http://software.schmorp.de/pkg/EV>.
		2577
		2578	=item Ruby
		2579
		2580	Tony Arcieri has written a ruby extension that offers access to a subset
		2581	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2582	more on top of it. It can be found via gem servers. Its homepage is at
		2583	L<http://rev.rubyforge.org/>.
		2584
		2585	=item D
		2586
		2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2589
		2590	=back
1805		2591
1806		2592
1807	=head1 MACRO MAGIC	2593	=head1 MACRO MAGIC
1808		2594
1809	Libev can be compiled with a variety of options, the most fundemantal is	2595	Libev can be compiled with a variety of options, the most fundamantal
1810	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1811	callbacks have an initial C<struct ev_loop *> argument.	2597	functions and callbacks have an initial C<struct ev_loop *> argument.
1812		2598
1813	To make it easier to write programs that cope with either variant, the	2599	To make it easier to write programs that cope with either variant, the
1814	following macros are defined:	2600	following macros are defined:
1815		2601
1816	=over 4	2602	=over 4
…		…
1846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1847		2633
1848	Similar to the other two macros, this gives you the value of the default	2634	Similar to the other two macros, this gives you the value of the default
1849	loop, if multiple loops are supported ("ev loop default").	2635	loop, if multiple loops are supported ("ev loop default").
1850		2636
		2637	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2638
		2639	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2640	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2641	is undefined when the default loop has not been initialised by a previous
		2642	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2643
		2644	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2645	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2646
1851	=back	2647	=back
1852		2648
1853	Example: Declare and initialise a check watcher, utilising the above	2649	Example: Declare and initialise a check watcher, utilising the above
1854	macros so it will work regardless of wether multiple loops are supported	2650	macros so it will work regardless of whether multiple loops are supported
1855	or not.	2651	or not.
1856		2652
1857	static void	2653	static void
1858	check_cb (EV_P_ ev_timer *w, int revents)	2654	check_cb (EV_P_ ev_timer *w, int revents)
1859	{	2655	{
…		…
1870	Libev can (and often is) directly embedded into host	2666	Libev can (and often is) directly embedded into host
1871	applications. Examples of applications that embed it include the Deliantra	2667	applications. Examples of applications that embed it include the Deliantra
1872	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2668	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1873	and rxvt-unicode.	2669	and rxvt-unicode.
1874		2670
1875	The goal is to enable you to just copy the neecssary files into your	2671	The goal is to enable you to just copy the necessary files into your
1876	source directory without having to change even a single line in them, so	2672	source directory without having to change even a single line in them, so
1877	you can easily upgrade by simply copying (or having a checked-out copy of	2673	you can easily upgrade by simply copying (or having a checked-out copy of
1878	libev somewhere in your source tree).	2674	libev somewhere in your source tree).
1879		2675
1880	=head2 FILESETS	2676	=head2 FILESETS
…		…
1950		2746
1951	libev.m4	2747	libev.m4
1952		2748
1953	=head2 PREPROCESSOR SYMBOLS/MACROS	2749	=head2 PREPROCESSOR SYMBOLS/MACROS
1954		2750
1955	Libev can be configured via a variety of preprocessor symbols you have to define	2751	Libev can be configured via a variety of preprocessor symbols you have to
1956	before including any of its files. The default is not to build for multiplicity	2752	define before including any of its files. The default in the absense of
1957	and only include the select backend.	2753	autoconf is noted for every option.
1958		2754
1959	=over 4	2755	=over 4
1960		2756
1961	=item EV_STANDALONE	2757	=item EV_STANDALONE
1962		2758
…		…
1970		2766
1971	If defined to be C<1>, libev will try to detect the availability of the	2767	If defined to be C<1>, libev will try to detect the availability of the
1972	monotonic clock option at both compiletime and runtime. Otherwise no use	2768	monotonic clock option at both compiletime and runtime. Otherwise no use
1973	of the monotonic clock option will be attempted. If you enable this, you	2769	of the monotonic clock option will be attempted. If you enable this, you
1974	usually have to link against librt or something similar. Enabling it when	2770	usually have to link against librt or something similar. Enabling it when
1975	the functionality isn't available is safe, though, althoguh you have	2771	the functionality isn't available is safe, though, although you have
1976	to make sure you link against any libraries where the C<clock_gettime>	2772	to make sure you link against any libraries where the C<clock_gettime>
1977	function is hiding in (often F<-lrt>).	2773	function is hiding in (often F<-lrt>).
1978		2774
1979	=item EV_USE_REALTIME	2775	=item EV_USE_REALTIME
1980		2776
1981	If defined to be C<1>, libev will try to detect the availability of the	2777	If defined to be C<1>, libev will try to detect the availability of the
1982	realtime clock option at compiletime (and assume its availability at	2778	realtime clock option at compiletime (and assume its availability at
1983	runtime if successful). Otherwise no use of the realtime clock option will	2779	runtime if successful). Otherwise no use of the realtime clock option will
1984	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1985	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1986	in the description of C<EV_USE_MONOTONIC>, though.	2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2783
		2784	=item EV_USE_NANOSLEEP
		2785
		2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2787	and will use it for delays. Otherwise it will use C<select ()>.
		2788
		2789	=item EV_USE_EVENTFD
		2790
		2791	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2792	available and will probe for kernel support at runtime. This will improve
		2793	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2794	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2795	2.7 or newer, otherwise disabled.
1987		2796
1988	=item EV_USE_SELECT	2797	=item EV_USE_SELECT
1989		2798
1990	If undefined or defined to be C<1>, libev will compile in support for the	2799	If undefined or defined to be C<1>, libev will compile in support for the
1991	C<select>(2) backend. No attempt at autodetection will be done: if no	2800	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2010	be used is the winsock select). This means that it will call	2819	be used is the winsock select). This means that it will call
2011	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2820	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2012	it is assumed that all these functions actually work on fds, even	2821	it is assumed that all these functions actually work on fds, even
2013	on win32. Should not be defined on non-win32 platforms.	2822	on win32. Should not be defined on non-win32 platforms.
2014		2823
		2824	=item EV_FD_TO_WIN32_HANDLE
		2825
		2826	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2827	file descriptors to socket handles. When not defining this symbol (the
		2828	default), then libev will call C<_get_osfhandle>, which is usually
		2829	correct. In some cases, programs use their own file descriptor management,
		2830	in which case they can provide this function to map fds to socket handles.
		2831
2015	=item EV_USE_POLL	2832	=item EV_USE_POLL
2016		2833
2017	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2834	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2018	backend. Otherwise it will be enabled on non-win32 platforms. It	2835	backend. Otherwise it will be enabled on non-win32 platforms. It
2019	takes precedence over select.	2836	takes precedence over select.
2020		2837
2021	=item EV_USE_EPOLL	2838	=item EV_USE_EPOLL
2022		2839
2023	If defined to be C<1>, libev will compile in support for the Linux	2840	If defined to be C<1>, libev will compile in support for the Linux
2024	C<epoll>(7) backend. Its availability will be detected at runtime,	2841	C<epoll>(7) backend. Its availability will be detected at runtime,
2025	otherwise another method will be used as fallback. This is the	2842	otherwise another method will be used as fallback. This is the preferred
2026	preferred backend for GNU/Linux systems.	2843	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2844	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2027		2845
2028	=item EV_USE_KQUEUE	2846	=item EV_USE_KQUEUE
2029		2847
2030	If defined to be C<1>, libev will compile in support for the BSD style	2848	If defined to be C<1>, libev will compile in support for the BSD style
2031	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2849	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2050		2868
2051	=item EV_USE_INOTIFY	2869	=item EV_USE_INOTIFY
2052		2870
2053	If defined to be C<1>, libev will compile in support for the Linux inotify	2871	If defined to be C<1>, libev will compile in support for the Linux inotify
2054	interface to speed up C<ev_stat> watchers. Its actual availability will	2872	interface to speed up C<ev_stat> watchers. Its actual availability will
2055	be detected at runtime.	2873	be detected at runtime. If undefined, it will be enabled if the headers
		2874	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2875
		2876	=item EV_ATOMIC_T
		2877
		2878	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2879	access is atomic with respect to other threads or signal contexts. No such
		2880	type is easily found in the C language, so you can provide your own type
		2881	that you know is safe for your purposes. It is used both for signal handler "locking"
		2882	as well as for signal and thread safety in C<ev_async> watchers.
		2883
		2884	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2885	(from F<signal.h>), which is usually good enough on most platforms.
2056		2886
2057	=item EV_H	2887	=item EV_H
2058		2888
2059	The name of the F<ev.h> header file used to include it. The default if	2889	The name of the F<ev.h> header file used to include it. The default if
2060	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2890	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2061	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2891	used to virtually rename the F<ev.h> header file in case of conflicts.
2062		2892
2063	=item EV_CONFIG_H	2893	=item EV_CONFIG_H
2064		2894
2065	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2895	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2066	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2896	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2067	C<EV_H>, above.	2897	C<EV_H>, above.
2068		2898
2069	=item EV_EVENT_H	2899	=item EV_EVENT_H
2070		2900
2071	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2901	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2072	of how the F<event.h> header can be found.	2902	of how the F<event.h> header can be found, the default is C<"event.h">.
2073		2903
2074	=item EV_PROTOTYPES	2904	=item EV_PROTOTYPES
2075		2905
2076	If defined to be C<0>, then F<ev.h> will not define any function	2906	If defined to be C<0>, then F<ev.h> will not define any function
2077	prototypes, but still define all the structs and other symbols. This is	2907	prototypes, but still define all the structs and other symbols. This is
…		…
2084	will have the C<struct ev_loop *> as first argument, and you can create	2914	will have the C<struct ev_loop *> as first argument, and you can create
2085	additional independent event loops. Otherwise there will be no support	2915	additional independent event loops. Otherwise there will be no support
2086	for multiple event loops and there is no first event loop pointer	2916	for multiple event loops and there is no first event loop pointer
2087	argument. Instead, all functions act on the single default loop.	2917	argument. Instead, all functions act on the single default loop.
2088		2918
		2919	=item EV_MINPRI
		2920
		2921	=item EV_MAXPRI
		2922
		2923	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2924	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2925	provide for more priorities by overriding those symbols (usually defined
		2926	to be C<-2> and C<2>, respectively).
		2927
		2928	When doing priority-based operations, libev usually has to linearly search
		2929	all the priorities, so having many of them (hundreds) uses a lot of space
		2930	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2931	fine.
		2932
		2933	If your embedding app does not need any priorities, defining these both to
		2934	C<0> will save some memory and cpu.
		2935
2089	=item EV_PERIODIC_ENABLE	2936	=item EV_PERIODIC_ENABLE
2090		2937
2091	If undefined or defined to be C<1>, then periodic timers are supported. If	2938	If undefined or defined to be C<1>, then periodic timers are supported. If
2092	defined to be C<0>, then they are not. Disabling them saves a few kB of	2939	defined to be C<0>, then they are not. Disabling them saves a few kB of
2093	code.	2940	code.
2094		2941
		2942	=item EV_IDLE_ENABLE
		2943
		2944	If undefined or defined to be C<1>, then idle watchers are supported. If
		2945	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2946	code.
		2947
2095	=item EV_EMBED_ENABLE	2948	=item EV_EMBED_ENABLE
2096		2949
2097	If undefined or defined to be C<1>, then embed watchers are supported. If	2950	If undefined or defined to be C<1>, then embed watchers are supported. If
2098	defined to be C<0>, then they are not.	2951	defined to be C<0>, then they are not.
2099		2952
…		…
2103	defined to be C<0>, then they are not.	2956	defined to be C<0>, then they are not.
2104		2957
2105	=item EV_FORK_ENABLE	2958	=item EV_FORK_ENABLE
2106		2959
2107	If undefined or defined to be C<1>, then fork watchers are supported. If	2960	If undefined or defined to be C<1>, then fork watchers are supported. If
		2961	defined to be C<0>, then they are not.
		2962
		2963	=item EV_ASYNC_ENABLE
		2964
		2965	If undefined or defined to be C<1>, then async watchers are supported. If
2108	defined to be C<0>, then they are not.	2966	defined to be C<0>, then they are not.
2109		2967
2110	=item EV_MINIMAL	2968	=item EV_MINIMAL
2111		2969
2112	If you need to shave off some kilobytes of code at the expense of some	2970	If you need to shave off some kilobytes of code at the expense of some
…		…
2120	than enough. If you need to manage thousands of children you might want to	2978	than enough. If you need to manage thousands of children you might want to
2121	increase this value (I<must> be a power of two).	2979	increase this value (I<must> be a power of two).
2122		2980
2123	=item EV_INOTIFY_HASHSIZE	2981	=item EV_INOTIFY_HASHSIZE
2124		2982
2125	C<ev_staz> watchers use a small hash table to distribute workload by	2983	C<ev_stat> watchers use a small hash table to distribute workload by
2126	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2127	usually more than enough. If you need to manage thousands of C<ev_stat>	2985	usually more than enough. If you need to manage thousands of C<ev_stat>
2128	watchers you might want to increase this value (I<must> be a power of	2986	watchers you might want to increase this value (I<must> be a power of
2129	two).	2987	two).
2130		2988
…		…
2147		3005
2148	=item ev_set_cb (ev, cb)	3006	=item ev_set_cb (ev, cb)
2149		3007
2150	Can be used to change the callback member declaration in each watcher,	3008	Can be used to change the callback member declaration in each watcher,
2151	and the way callbacks are invoked and set. Must expand to a struct member	3009	and the way callbacks are invoked and set. Must expand to a struct member
2152	definition and a statement, respectively. See the F<ev.v> header file for	3010	definition and a statement, respectively. See the F<ev.h> header file for
2153	their default definitions. One possible use for overriding these is to	3011	their default definitions. One possible use for overriding these is to
2154	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2155	method calls instead of plain function calls in C++.	3013	method calls instead of plain function calls in C++.
		3014
		3015	=head2 EXPORTED API SYMBOLS
		3016
		3017	If you need to re-export the API (e.g. via a dll) and you need a list of
		3018	exported symbols, you can use the provided F<Symbol.*> files which list
		3019	all public symbols, one per line:
		3020
		3021	Symbols.ev for libev proper
		3022	Symbols.event for the libevent emulation
		3023
		3024	This can also be used to rename all public symbols to avoid clashes with
		3025	multiple versions of libev linked together (which is obviously bad in
		3026	itself, but sometimes it is inconvinient to avoid this).
		3027
		3028	A sed command like this will create wrapper C<#define>'s that you need to
		3029	include before including F<ev.h>:
		3030
		3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3032
		3033	This would create a file F<wrap.h> which essentially looks like this:
		3034
		3035	#define ev_backend myprefix_ev_backend
		3036	#define ev_check_start myprefix_ev_check_start
		3037	#define ev_check_stop myprefix_ev_check_stop
		3038	...
2156		3039
2157	=head2 EXAMPLES	3040	=head2 EXAMPLES
2158		3041
2159	For a real-world example of a program the includes libev	3042	For a real-world example of a program the includes libev
2160	verbatim, you can have a look at the EV perl module	3043	verbatim, you can have a look at the EV perl module
…		…
2183		3066
2184	#include "ev_cpp.h"	3067	#include "ev_cpp.h"
2185	#include "ev.c"	3068	#include "ev.c"
2186		3069
2187		3070
		3071	=head1 THREADS AND COROUTINES
		3072
		3073	=head2 THREADS
		3074
		3075	Libev itself is completely threadsafe, but it uses no locking. This
		3076	means that you can use as many loops as you want in parallel, as long as
		3077	only one thread ever calls into one libev function with the same loop
		3078	parameter.
		3079
		3080	Or put differently: calls with different loop parameters can be done in
		3081	parallel from multiple threads, calls with the same loop parameter must be
		3082	done serially (but can be done from different threads, as long as only one
		3083	thread ever is inside a call at any point in time, e.g. by using a mutex
		3084	per loop).
		3085
		3086	If you want to know which design is best for your problem, then I cannot
		3087	help you but by giving some generic advice:
		3088
		3089	=over 4
		3090
		3091	=item * most applications have a main thread: use the default libev loop
		3092	in that thread, or create a seperate thread running only the default loop.
		3093
		3094	This helps integrating other libraries or software modules that use libev
		3095	themselves and don't care/know about threading.
		3096
		3097	=item * one loop per thread is usually a good model.
		3098
		3099	Doing this is almost never wrong, sometimes a better-performance model
		3100	exists, but it is always a good start.
		3101
		3102	=item * other models exist, such as the leader/follower pattern, where one
		3103	loop is handed through multiple threads in a kind of round-robbin fashion.
		3104
		3105	Chosing a model is hard - look around, learn, know that usually you cna do
		3106	better than you currently do :-)
		3107
		3108	=item * often you need to talk to some other thread which blocks in the
		3109	event loop - C<ev_async> watchers can be used to wake them up from other
		3110	threads safely (or from signal contexts...).
		3111
		3112	=back
		3113
		3114	=head2 COROUTINES
		3115
		3116	Libev is much more accomodating to coroutines ("cooperative threads"):
		3117	libev fully supports nesting calls to it's functions from different
		3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3119	different coroutines and switch freely between both coroutines running the
		3120	loop, as long as you don't confuse yourself). The only exception is that
		3121	you must not do this from C<ev_periodic> reschedule callbacks.
		3122
		3123	Care has been invested into making sure that libev does not keep local
		3124	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3125	switches.
		3126
		3127
2188	=head1 COMPLEXITIES	3128	=head1 COMPLEXITIES
2189		3129
2190	In this section the complexities of (many of) the algorithms used inside	3130	In this section the complexities of (many of) the algorithms used inside
2191	libev will be explained. For complexity discussions about backends see the	3131	libev will be explained. For complexity discussions about backends see the
2192	documentation for C<ev_default_init>.	3132	documentation for C<ev_default_init>.
2193		3133
		3134	All of the following are about amortised time: If an array needs to be
		3135	extended, libev needs to realloc and move the whole array, but this
		3136	happens asymptotically never with higher number of elements, so O(1) might
		3137	mean it might do a lengthy realloc operation in rare cases, but on average
		3138	it is much faster and asymptotically approaches constant time.
		3139
2194	=over 4	3140	=over 4
2195		3141
2196	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2197		3143
		3144	This means that, when you have a watcher that triggers in one hour and
		3145	there are 100 watchers that would trigger before that then inserting will
		3146	have to skip roughly seven (C<ld 100>) of these watchers.
		3147
2198	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2199		3149
		3150	That means that changing a timer costs less than removing/adding them
		3151	as only the relative motion in the event queue has to be paid for.
		3152
2200	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2201		3154
		3155	These just add the watcher into an array or at the head of a list.
		3156
2202	=item Stopping check/prepare/idle watchers: O(1)	3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2203		3158
2204	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2205		3160
		3161	These watchers are stored in lists then need to be walked to find the
		3162	correct watcher to remove. The lists are usually short (you don't usually
		3163	have many watchers waiting for the same fd or signal).
		3164
2206	=item Finding the next timer per loop iteration: O(1)	3165	=item Finding the next timer in each loop iteration: O(1)
		3166
		3167	By virtue of using a binary heap, the next timer is always found at the
		3168	beginning of the storage array.
2207		3169
2208	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2209		3171
2210	=item Activating one watcher: O(1)	3172	A change means an I/O watcher gets started or stopped, which requires
		3173	libev to recalculate its status (and possibly tell the kernel, depending
		3174	on backend and wether C<ev_io_set> was used).
		3175
		3176	=item Activating one watcher (putting it into the pending state): O(1)
		3177
		3178	=item Priority handling: O(number_of_priorities)
		3179
		3180	Priorities are implemented by allocating some space for each
		3181	priority. When doing priority-based operations, libev usually has to
		3182	linearly search all the priorities, but starting/stopping and activating
		3183	watchers becomes O(1) w.r.t. priority handling.
		3184
		3185	=item Sending an ev_async: O(1)
		3186
		3187	=item Processing ev_async_send: O(number_of_async_watchers)
		3188
		3189	=item Processing signals: O(max_signal_number)
		3190
		3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3192	calls in the current loop iteration. Checking for async and signal events
		3193	involves iterating over all running async watchers or all signal numbers.
2211		3194
2212	=back	3195	=back
2213		3196
2214		3197
		3198	=head1 Win32 platform limitations and workarounds
		3199
		3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3201	requires, and its I/O model is fundamentally incompatible with the POSIX
		3202	model. Libev still offers limited functionality on this platform in
		3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3204	descriptors. This only applies when using Win32 natively, not when using
		3205	e.g. cygwin.
		3206
		3207	There is no supported compilation method available on windows except
		3208	embedding it into other applications.
		3209
		3210	Due to the many, low, and arbitrary limits on the win32 platform and the
		3211	abysmal performance of winsockets, using a large number of sockets is not
		3212	recommended (and not reasonable). If your program needs to use more than
		3213	a hundred or so sockets, then likely it needs to use a totally different
		3214	implementation for windows, as libev offers the POSIX model, which cannot
		3215	be implemented efficiently on windows (microsoft monopoly games).
		3216
		3217	=over 4
		3218
		3219	=item The winsocket select function
		3220
		3221	The winsocket C<select> function doesn't follow POSIX in that it requires
		3222	socket I<handles> and not socket I<file descriptors>. This makes select
		3223	very inefficient, and also requires a mapping from file descriptors
		3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3226	symbols for more info.
		3227
		3228	The configuration for a "naked" win32 using the microsoft runtime
		3229	libraries and raw winsocket select is:
		3230
		3231	#define EV_USE_SELECT 1
		3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3233
		3234	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3235	complexity in the O(n²) range when using win32.
		3236
		3237	=item Limited number of file descriptors
		3238
		3239	Windows has numerous arbitrary (and low) limits on things. Early versions
		3240	of winsocket's select only supported waiting for a max. of C<64> handles
		3241	(probably owning to the fact that all windows kernels can only wait for
		3242	C<64> things at the same time internally; microsoft recommends spawning a
		3243	chain of threads and wait for 63 handles and the previous thread in each).
		3244
		3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3246	to some high number (e.g. C<2048>) before compiling the winsocket select
		3247	call (which might be in libev or elsewhere, for example, perl does its own
		3248	select emulation on windows).
		3249
		3250	Another limit is the number of file descriptors in the microsoft runtime
		3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3252	or something like this inside microsoft). You can increase this by calling
		3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3254	arbitrary limit), but is broken in many versions of the microsoft runtime
		3255	libraries.
		3256
		3257	This might get you to about C<512> or C<2048> sockets (depending on
		3258	windows version and/or the phase of the moon). To get more, you need to
		3259	wrap all I/O functions and provide your own fd management, but the cost of
		3260	calling select (O(n²)) will likely make this unworkable.
		3261
		3262	=back
		3263
		3264
		3265	=head1 PORTABILITY REQUIREMENTS
		3266
		3267	In addition to a working ISO-C implementation, libev relies on a few
		3268	additional extensions:
		3269
		3270	=over 4
		3271
		3272	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3273
		3274	The type C<sig_atomic_t volatile> (or whatever is defined as
		3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3276	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3277	believed to be sufficiently portable.
		3278
		3279	=item C<sigprocmask> must work in a threaded environment
		3280
		3281	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3282	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3283	pthread implementations will either allow C<sigprocmask> in the "main
		3284	thread" or will block signals process-wide, both behaviours would
		3285	be compatible with libev. Interaction between C<sigprocmask> and
		3286	C<pthread_sigmask> could complicate things, however.
		3287
		3288	The most portable way to handle signals is to block signals in all threads
		3289	except the initial one, and run the default loop in the initial thread as
		3290	well.
		3291
		3292	=back
		3293
		3294	If you know of other additional requirements drop me a note.
		3295
		3296
2215	=head1 AUTHOR	3297	=head1 AUTHOR
2216		3298
2217	Marc Lehmann <libev@schmorp.de>.	3299	Marc Lehmann <libev@schmorp.de>.
2218		3300

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