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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.
…		…
163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164	recommended ones.	194	recommended ones.
165		195
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, size_t size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
169		199
170	Sets the allocation function to use (the prototype and semantics are	200	Sets the allocation function to use (the prototype is similar - the
171	identical to the realloc C function). It is used to allocate and free	201	semantics is identical - to the realloc C function). It is used to
172	memory (no surprises here). If it returns zero when memory needs to be	202	allocate and free memory (no surprises here). If it returns zero when
173	allocated, the library might abort or take some potentially destructive	203	memory needs to be allocated, the library might abort or take some
174	action. The default is your system realloc function.	204	potentially destructive action. The default is your system realloc
		205	function.
175		206
176	You could override this function in high-availability programs to, say,	207	You could override this function in high-availability programs to, say,
177	free some memory if it cannot allocate memory, to use a special allocator,	208	free some memory if it cannot allocate memory, to use a special allocator,
178	or even to sleep a while and retry until some memory is available.	209	or even to sleep a while and retry until some memory is available.
179		210
…		…
244	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
245		276
246	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
247	function.	278	function.
248		279
		280	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
249	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
250	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
251		293
252	The following flags are supported:	294	The following flags are supported:
253		295
…		…
265	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
266	override the flags completely if it is found in the environment. This is	308	override the flags completely if it is found in the environment. This is
267	useful to try out specific backends to test their performance, or to work	309	useful to try out specific backends to test their performance, or to work
268	around bugs.	310	around bugs.
269		311
		312	=item C<EVFLAG_FORKCHECK>
		313
		314	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		315	a fork, you can also make libev check for a fork in each iteration by
		316	enabling this flag.
		317
		318	This works by calling C<getpid ()> on every iteration of the loop,
		319	and thus this might slow down your event loop if you do a lot of loop
		320	iterations and little real work, but is usually not noticeable (on my
		321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		323	C<pthread_atfork> which is even faster).
		324
		325	The big advantage of this flag is that you can forget about fork (and
		326	forget about forgetting to tell libev about forking) when you use this
		327	flag.
		328
		329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		330	environment variable.
		331
270	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
271		333
272	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
273	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
274	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
275	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
276	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
277		346
278	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
279		348
280	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
281	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
282	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
283	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
284		355
285	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
286		357
287	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
288	but it scales phenomenally better. While poll and select usually scale like	359	but it scales phenomenally better. While poll and select usually scale
289	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	360	like O(total_fds) where n is the total number of fds (or the highest fd),
290	either O(1) or O(active_fds).	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
		362	of shortcomings, such as silently dropping events in some hard-to-detect
		363	cases and requiring a syscall per fd change, no fork support and bad
		364	support for dup.
291		365
292	While stopping and starting an I/O watcher in the same iteration will	366	While stopping, setting and starting an I/O watcher in the same iteration
293	result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
294	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
295	best to avoid that. Also, dup()ed file descriptors might not work very	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
296	well if you register events for both fds.	370	very well if you register events for both fds.
297		371
298	Please note that epoll sometimes generates spurious notifications, so you	372	Please note that epoll sometimes generates spurious notifications, so you
299	need to use non-blocking I/O or other means to avoid blocking when no data	373	need to use non-blocking I/O or other means to avoid blocking when no data
300	(or space) is available.	374	(or space) is available.
301		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
302	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
303		384
304	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
305	was broken on all BSDs except NetBSD (usually it doesn't work with	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
306	anything but sockets and pipes, except on Darwin, where of course its	387	with anything but sockets and pipes, except on Darwin, where of course
307	completely useless). For this reason its not being "autodetected"	388	it's completely useless). For this reason it's not being "autodetected"
308	unless you explicitly specify it explicitly in the flags (i.e. using	389	unless you explicitly specify it explicitly in the flags (i.e. using
309	C<EVBACKEND_KQUEUE>).	390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		391	system like NetBSD.
		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
310		396
311	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
312	kernel is more efficient (which says nothing about its actual speed, of	398	kernel is more efficient (which says nothing about its actual speed, of
313	course). While starting and stopping an I/O watcher does not cause an	399	course). While stopping, setting and starting an I/O watcher does never
314	extra syscall as with epoll, it still adds up to four event changes per	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
315	incident, so its best to avoid that.	401	two event changes per incident, support for C<fork ()> is very bad and it
		402	drops fds silently in similarly hard-to-detect cases.
		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
316		412
317	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
318		414
319	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
320		419
321	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
322		421
323	This uses the Solaris 10 port mechanism. As with everything on Solaris,	422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
324	it's really slow, but it still scales very well (O(active_fds)).	423	it's really slow, but it still scales very well (O(active_fds)).
325		424
326	Please note that solaris ports can result in a lot of spurious	425	Please note that solaris event ports can deliver a lot of spurious
327	notifications, so you need to use non-blocking I/O or other means to avoid	426	notifications, so you need to use non-blocking I/O or other means to avoid
328	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
329		437
330	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
331		439
332	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
333	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
334	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
335		443
		444	It is definitely not recommended to use this flag.
		445
336	=back	446	=back
337		447
338	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
339	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
340	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
341	order of their flag values :)
342		451
343	The most typical usage is like this:	452	The most typical usage is like this:
344		453
345	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
346	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
360		469
361	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
362	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
363	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
364	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
365		478
366	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
367		480
368	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
369	if (!epoller)	482	if (!epoller)
…		…
374	Destroys the default loop again (frees all memory and kernel state	487	Destroys the default loop again (frees all memory and kernel state
375	etc.). None of the active event watchers will be stopped in the normal	488	etc.). None of the active event watchers will be stopped in the normal
376	sense, so e.g. C<ev_is_active> might still return true. It is your	489	sense, so e.g. C<ev_is_active> might still return true. It is your
377	responsibility to either stop all watchers cleanly yoursef I<before>	490	responsibility to either stop all watchers cleanly yoursef I<before>
378	calling this function, or cope with the fact afterwards (which is usually	491	calling this function, or cope with the fact afterwards (which is usually
379	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	492	the easiest thing, you can just ignore the watchers and/or C<free ()> them
380	for example).	493	for example).
		494
		495	Note that certain global state, such as signal state, will not be freed by
		496	this function, and related watchers (such as signal and child watchers)
		497	would need to be stopped manually.
		498
		499	In general it is not advisable to call this function except in the
		500	rare occasion where you really need to free e.g. the signal handling
		501	pipe fds. If you need dynamically allocated loops it is better to use
		502	C<ev_loop_new> and C<ev_loop_destroy>).
381		503
382	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
383		505
384	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
385	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
386		508
387	=item ev_default_fork ()	509	=item ev_default_fork ()
388		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
389	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
390	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
391	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
392	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
393		517
394	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
395	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
396	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
397		521
398	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
399	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
400	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
401		525
402	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
403		527
404	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
405	without calling this function, so if you force one of those backends you
406	do not need to care.
407
408	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
409		529
410	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
411	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
412	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
		537
		538	=item unsigned int ev_loop_count (loop)
		539
		540	Returns the count of loop iterations for the loop, which is identical to
		541	the number of times libev did poll for new events. It starts at C<0> and
		542	happily wraps around with enough iterations.
		543
		544	This value can sometimes be useful as a generation counter of sorts (it
		545	"ticks" the number of loop iterations), as it roughly corresponds with
		546	C<ev_prepare> and C<ev_check> calls.
413		547
414	=item unsigned int ev_backend (loop)	548	=item unsigned int ev_backend (loop)
415		549
416	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	550	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
417	use.	551	use.
…		…
420		554
421	Returns the current "event loop time", which is the time the event loop	555	Returns the current "event loop time", which is the time the event loop
422	received events and started processing them. This timestamp does not	556	received events and started processing them. This timestamp does not
423	change as long as callbacks are being processed, and this is also the base	557	change as long as callbacks are being processed, and this is also the base
424	time used for relative timers. You can treat it as the timestamp of the	558	time used for relative timers. You can treat it as the timestamp of the
425	event occuring (or more correctly, libev finding out about it).	559	event occurring (or more correctly, libev finding out about it).
426		560
427	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
428		562
429	Finally, this is it, the event handler. This function usually is called	563	Finally, this is it, the event handler. This function usually is called
430	after you initialised all your watchers and you want to start handling	564	after you initialised all your watchers and you want to start handling
…		…
451	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
452	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
453		587
454	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
455		589
456	* If there are no active watchers (reference count is zero), return.	590	- Before the first iteration, call any pending watchers.
457	- Queue prepare watchers and then call all outstanding watchers.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
		592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
458	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
459	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
460	- Update the "event loop time".	596	- Update the "event loop time".
461	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
462	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
463	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
464	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
465	- Queue all outstanding timers.	604	- Queue all outstanding timers.
466	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
467	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
468	- Queue all check watchers.	607	- Queue all check watchers.
469	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
470	Signals and child watchers are implemented as I/O watchers, and will	609	Signals and child watchers are implemented as I/O watchers, and will
471	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
472	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
473	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
474		614
475	Example: Queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
476	anymore.	616	anymore.
477		617
478	... queue jobs here, make sure they register event watchers as long	618	... queue jobs here, make sure they register event watchers as long
479	... as they still have work to do (even an idle watcher will do..)	619	... as they still have work to do (even an idle watcher will do..)
480	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
484		624
485	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
486	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
487	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
488	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
489		631
490	=item ev_ref (loop)	632	=item ev_ref (loop)
491		633
492	=item ev_unref (loop)	634	=item ev_unref (loop)
493		635
…		…
498	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
499	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
500	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
501	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
502	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
503	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
504		648
505	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
506	running when nothing else is active.	650	running when nothing else is active.
507		651
508	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
512		656
513	Example: For some weird reason, unregister the above signal handler again.	657	Example: For some weird reason, unregister the above signal handler again.
514		658
515	ev_ref (loop);	659	ev_ref (loop);
516	ev_signal_stop (loop, &exitsig);	660	ev_signal_stop (loop, &exitsig);
		661
		662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		663
		664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		665
		666	These advanced functions influence the time that libev will spend waiting
		667	for events. Both are by default C<0>, meaning that libev will try to
		668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		669
		670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		671	allows libev to delay invocation of I/O and timer/periodic callbacks to
		672	increase efficiency of loop iterations.
		673
		674	The background is that sometimes your program runs just fast enough to
		675	handle one (or very few) event(s) per loop iteration. While this makes
		676	the program responsive, it also wastes a lot of CPU time to poll for new
		677	events, especially with backends like C<select ()> which have a high
		678	overhead for the actual polling but can deliver many events at once.
		679
		680	By setting a higher I<io collect interval> you allow libev to spend more
		681	time collecting I/O events, so you can handle more events per iteration,
		682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
		685
		686	Likewise, by setting a higher I<timeout collect interval> you allow libev
		687	to spend more time collecting timeouts, at the expense of increased
		688	latency (the watcher callback will be called later). C<ev_io> watchers
		689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
		691
		692	Many (busy) programs can usually benefit by setting the io collect
		693	interval to a value near C<0.1> or so, which is often enough for
		694	interactive servers (of course not for games), likewise for timeouts. It
		695	usually doesn't make much sense to set it to a lower value than C<0.01>,
		696	as this approsaches the timing granularity of most systems.
517		697
518	=back	698	=back
519		699
520		700
521	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
…		…
621	=item C<EV_FORK>	801	=item C<EV_FORK>
622		802
623	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
624	C<ev_fork>).	804	C<ev_fork>).
625		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
		809
626	=item C<EV_ERROR>	810	=item C<EV_ERROR>
627		811
628	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
629	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
630	ran out of memory, a file descriptor was found to be closed or any other	814	ran out of memory, a file descriptor was found to be closed or any other
…		…
701	=item bool ev_is_pending (ev_TYPE *watcher)	885	=item bool ev_is_pending (ev_TYPE *watcher)
702		886
703	Returns a true value iff the watcher is pending, (i.e. it has outstanding	887	Returns a true value iff the watcher is pending, (i.e. it has outstanding
704	events but its callback has not yet been invoked). As long as a watcher	888	events but its callback has not yet been invoked). As long as a watcher
705	is pending (but not active) you must not call an init function on it (but	889	is pending (but not active) you must not call an init function on it (but
706	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	890	C<ev_TYPE_set> is safe), you must not change its priority, and you must
707	libev (e.g. you cnanot C<free ()> it).	891	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		892	it).
708		893
709	=item callback ev_cb (ev_TYPE *watcher)	894	=item callback ev_cb (ev_TYPE *watcher)
710		895
711	Returns the callback currently set on the watcher.	896	Returns the callback currently set on the watcher.
712		897
713	=item ev_cb_set (ev_TYPE *watcher, callback)	898	=item ev_cb_set (ev_TYPE *watcher, callback)
714		899
715	Change the callback. You can change the callback at virtually any time	900	Change the callback. You can change the callback at virtually any time
716	(modulo threads).	901	(modulo threads).
		902
		903	=item ev_set_priority (ev_TYPE *watcher, priority)
		904
		905	=item int ev_priority (ev_TYPE *watcher)
		906
		907	Set and query the priority of the watcher. The priority is a small
		908	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		909	(default: C<-2>). Pending watchers with higher priority will be invoked
		910	before watchers with lower priority, but priority will not keep watchers
		911	from being executed (except for C<ev_idle> watchers).
		912
		913	This means that priorities are I<only> used for ordering callback
		914	invocation after new events have been received. This is useful, for
		915	example, to reduce latency after idling, or more often, to bind two
		916	watchers on the same event and make sure one is called first.
		917
		918	If you need to suppress invocation when higher priority events are pending
		919	you need to look at C<ev_idle> watchers, which provide this functionality.
		920
		921	You I<must not> change the priority of a watcher as long as it is active or
		922	pending.
		923
		924	The default priority used by watchers when no priority has been set is
		925	always C<0>, which is supposed to not be too high and not be too low :).
		926
		927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		928	fine, as long as you do not mind that the priority value you query might
		929	or might not have been adjusted to be within valid range.
		930
		931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		932
		933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		934	C<loop> nor C<revents> need to be valid as long as the watcher callback
		935	can deal with that fact.
		936
		937	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		938
		939	If the watcher is pending, this function returns clears its pending status
		940	and returns its C<revents> bitset (as if its callback was invoked). If the
		941	watcher isn't pending it does nothing and returns C<0>.
717		942
718	=back	943	=back
719		944
720		945
721	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
806	In general you can register as many read and/or write event watchers per	1031	In general you can register as many read and/or write event watchers per
807	fd as you want (as long as you don't confuse yourself). Setting all file	1032	fd as you want (as long as you don't confuse yourself). Setting all file
808	descriptors to non-blocking mode is also usually a good idea (but not	1033	descriptors to non-blocking mode is also usually a good idea (but not
809	required if you know what you are doing).	1034	required if you know what you are doing).
810		1035
811	You have to be careful with dup'ed file descriptors, though. Some backends
812	(the linux epoll backend is a notable example) cannot handle dup'ed file
813	descriptors correctly if you register interest in two or more fds pointing
814	to the same underlying file/socket/etc. description (that is, they share
815	the same underlying "file open").
816
817	If you must do this, then force the use of a known-to-be-good backend	1036	If you must do this, then force the use of a known-to-be-good backend
818	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
819	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
820		1039
821	Another thing you have to watch out for is that it is quite easy to	1040	Another thing you have to watch out for is that it is quite easy to
…		…
827	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning
828	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.
829		1048
830	If you cannot run the fd in non-blocking mode (for example you should not	1049	If you cannot run the fd in non-blocking mode (for example you should not
831	play around with an Xlib connection), then you have to seperately re-test	1050	play around with an Xlib connection), then you have to seperately re-test
832	wether a file descriptor is really ready with a known-to-be good interface	1051	whether a file descriptor is really ready with a known-to-be good interface
833	such as poll (fortunately in our Xlib example, Xlib already does this on	1052	such as poll (fortunately in our Xlib example, Xlib already does this on
834	its own, so its quite safe to use).	1053	its own, so its quite safe to use).
		1054
		1055	=head3 The special problem of disappearing file descriptors
		1056
		1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1058	descriptor (either by calling C<close> explicitly or by any other means,
		1059	such as C<dup>). The reason is that you register interest in some file
		1060	descriptor, but when it goes away, the operating system will silently drop
		1061	this interest. If another file descriptor with the same number then is
		1062	registered with libev, there is no efficient way to see that this is, in
		1063	fact, a different file descriptor.
		1064
		1065	To avoid having to explicitly tell libev about such cases, libev follows
		1066	the following policy: Each time C<ev_io_set> is being called, libev
		1067	will assume that this is potentially a new file descriptor, otherwise
		1068	it is assumed that the file descriptor stays the same. That means that
		1069	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1070	descriptor even if the file descriptor number itself did not change.
		1071
		1072	This is how one would do it normally anyway, the important point is that
		1073	the libev application should not optimise around libev but should leave
		1074	optimisations to libev.
		1075
		1076	=head3 The special problem of dup'ed file descriptors
		1077
		1078	Some backends (e.g. epoll), cannot register events for file descriptors,
		1079	but only events for the underlying file descriptions. That means when you
		1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1081	events for them, only one file descriptor might actually receive events.
		1082
		1083	There is no workaround possible except not registering events
		1084	for potentially C<dup ()>'ed file descriptors, or to resort to
		1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1086
		1087	=head3 The special problem of fork
		1088
		1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1090	useless behaviour. Libev fully supports fork, but needs to be told about
		1091	it in the child.
		1092
		1093	To support fork in your programs, you either have to call
		1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1096	C<EVBACKEND_POLL>.
		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
		1110
		1111	=head3 Watcher-Specific Functions
835		1112
836	=over 4	1113	=over 4
837		1114
838	=item ev_io_init (ev_io *, callback, int fd, int events)	1115	=item ev_io_init (ev_io *, callback, int fd, int events)
839		1116
…		…
850	=item int events [read-only]	1127	=item int events [read-only]
851		1128
852	The events being watched.	1129	The events being watched.
853		1130
854	=back	1131	=back
		1132
		1133	=head3 Examples
855		1134
856	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
857	readable, but only once. Since it is likely line-buffered, you could	1136	readable, but only once. Since it is likely line-buffered, you could
858	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
859		1138
…		…
893		1172
894	The callback is guarenteed to be invoked only when its timeout has passed,	1173	The callback is guarenteed to be invoked only when its timeout has passed,
895	but if multiple timers become ready during the same loop iteration then	1174	but if multiple timers become ready during the same loop iteration then
896	order of execution is undefined.	1175	order of execution is undefined.
897		1176
		1177	=head3 Watcher-Specific Functions and Data Members
		1178
898	=over 4	1179	=over 4
899		1180
900	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
901		1182
902	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
910	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
911	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
912	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
913	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
914		1195
915	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
916		1197
917	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
918	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
919		1200
		1201	If the timer is pending, its pending status is cleared.
		1202
920	If the timer is started but nonrepeating, stop it.	1203	If the timer is started but nonrepeating, stop it (as if it timed out).
921		1204
922	If the timer is repeating, either start it if necessary (with the repeat	1205	If the timer is repeating, either start it if necessary (with the
923	value), or reset the running timer to the repeat value.	1206	C<repeat> value), or reset the running timer to the C<repeat> value.
924		1207
925	This sounds a bit complicated, but here is a useful and typical	1208	This sounds a bit complicated, but here is a useful and typical
926	example: Imagine you have a tcp connection and you want a so-called	1209	example: Imagine you have a tcp connection and you want a so-called idle
927	idle timeout, that is, you want to be called when there have been,	1210	timeout, that is, you want to be called when there have been, say, 60
928	say, 60 seconds of inactivity on the socket. The easiest way to do	1211	seconds of inactivity on the socket. The easiest way to do this is to
929	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1212	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
930	C<ev_timer_again> each time you successfully read or write some data. If	1213	C<ev_timer_again> each time you successfully read or write some data. If
931	you go into an idle state where you do not expect data to travel on the	1214	you go into an idle state where you do not expect data to travel on the
932	socket, you can stop the timer, and again will automatically restart it if	1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
933	need be.	1216	automatically restart it if need be.
934		1217
935	You can also ignore the C<after> value and C<ev_timer_start> altogether	1218	That means you can ignore the C<after> value and C<ev_timer_start>
936	and only ever use the C<repeat> value:	1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
937		1220
938	ev_timer_init (timer, callback, 0., 5.);	1221	ev_timer_init (timer, callback, 0., 5.);
939	ev_timer_again (loop, timer);	1222	ev_timer_again (loop, timer);
940	...	1223	...
941	timer->again = 17.;	1224	timer->again = 17.;
942	ev_timer_again (loop, timer);	1225	ev_timer_again (loop, timer);
943	...	1226	...
944	timer->again = 10.;	1227	timer->again = 10.;
945	ev_timer_again (loop, timer);	1228	ev_timer_again (loop, timer);
946		1229
947	This is more efficient then stopping/starting the timer eahc time you want	1230	This is more slightly efficient then stopping/starting the timer each time
948	to modify its timeout value.	1231	you want to modify its timeout value.
949		1232
950	=item ev_tstamp repeat [read-write]	1233	=item ev_tstamp repeat [read-write]
951		1234
952	The current C<repeat> value. Will be used each time the watcher times out	1235	The current C<repeat> value. Will be used each time the watcher times out
953	or C<ev_timer_again> is called and determines the next timeout (if any),	1236	or C<ev_timer_again> is called and determines the next timeout (if any),
954	which is also when any modifications are taken into account.	1237	which is also when any modifications are taken into account.
955		1238
956	=back	1239	=back
		1240
		1241	=head3 Examples
957		1242
958	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
959		1244
960	static void	1245	static void
961	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
…		…
995	but on wallclock time (absolute time). You can tell a periodic watcher	1280	but on wallclock time (absolute time). You can tell a periodic watcher
996	to trigger "at" some specific point in time. For example, if you tell a	1281	to trigger "at" some specific point in time. For example, if you tell a
997	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
998	+ 10.>) and then reset your system clock to the last year, then it will	1283	+ 10.>) and then reset your system clock to the last year, then it will
999	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1000	roughly 10 seconds later and of course not if you reset your system time	1285	roughly 10 seconds later).
1001	again).
1002		1286
1003	They can also be used to implement vastly more complex timers, such as	1287	They can also be used to implement vastly more complex timers, such as
1004	triggering an event on eahc midnight, local time.	1288	triggering an event on each midnight, local time or other, complicated,
		1289	rules.
1005		1290
1006	As with timers, the callback is guarenteed to be invoked only when the	1291	As with timers, the callback is guarenteed to be invoked only when the
1007	time (C<at>) has been passed, but if multiple periodic timers become ready	1292	time (C<at>) has been passed, but if multiple periodic timers become ready
1008	during the same loop iteration then order of execution is undefined.	1293	during the same loop iteration then order of execution is undefined.
1009		1294
		1295	=head3 Watcher-Specific Functions and Data Members
		1296
1010	=over 4	1297	=over 4
1011		1298
1012	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1013		1300
1014	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1016	Lots of arguments, lets sort it out... There are basically three modes of	1303	Lots of arguments, lets sort it out... There are basically three modes of
1017	operation, and we will explain them from simplest to complex:	1304	operation, and we will explain them from simplest to complex:
1018		1305
1019	=over 4	1306	=over 4
1020		1307
1021	=item * absolute timer (interval = reschedule_cb = 0)	1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1022		1309
1023	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1024	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1025	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1026	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1027		1314
1028	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1029		1316
1030	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1031	C<at + N * interval> time (for some integer N) and then repeat, regardless	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1032	of any time jumps.	1319	and then repeat, regardless of any time jumps.
1033		1320
1034	This can be used to create timers that do not drift with respect to system	1321	This can be used to create timers that do not drift with respect to system
1035	time:	1322	time:
1036		1323
1037	ev_periodic_set (&periodic, 0., 3600., 0);	1324	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1043		1330
1044	Another way to think about it (for the mathematically inclined) is that	1331	Another way to think about it (for the mathematically inclined) is that
1045	C<ev_periodic> will try to run the callback in this mode at the next possible	1332	C<ev_periodic> will try to run the callback in this mode at the next possible
1046	time where C<time = at (mod interval)>, regardless of any time jumps.	1333	time where C<time = at (mod interval)>, regardless of any time jumps.
1047		1334
		1335	For numerical stability it is preferable that the C<at> value is near
		1336	C<ev_now ()> (the current time), but there is no range requirement for
		1337	this value.
		1338
1048	=item * manual reschedule mode (reschedule_cb = callback)	1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1049		1340
1050	In this mode the values for C<interval> and C<at> are both being	1341	In this mode the values for C<interval> and C<at> are both being
1051	ignored. Instead, each time the periodic watcher gets scheduled, the	1342	ignored. Instead, each time the periodic watcher gets scheduled, the
1052	reschedule callback will be called with the watcher as first, and the	1343	reschedule callback will be called with the watcher as first, and the
1053	current time as second argument.	1344	current time as second argument.
1054		1345
1055	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1056	ever, or make any event loop modifications>. If you need to stop it,	1347	ever, or make any event loop modifications>. If you need to stop it,
1057	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1058	starting a prepare watcher).	1349	starting an C<ev_prepare> watcher, which is legal).
1059		1350
1060	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1061	ev_tstamp now)>, e.g.:	1352	ev_tstamp now)>, e.g.:
1062		1353
1063	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1086	Simply stops and restarts the periodic watcher again. This is only useful	1377	Simply stops and restarts the periodic watcher again. This is only useful
1087	when you changed some parameters or the reschedule callback would return	1378	when you changed some parameters or the reschedule callback would return
1088	a different time than the last time it was called (e.g. in a crond like	1379	a different time than the last time it was called (e.g. in a crond like
1089	program when the crontabs have changed).	1380	program when the crontabs have changed).
1090		1381
		1382	=item ev_tstamp offset [read-write]
		1383
		1384	When repeating, this contains the offset value, otherwise this is the
		1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1386
		1387	Can be modified any time, but changes only take effect when the periodic
		1388	timer fires or C<ev_periodic_again> is being called.
		1389
1091	=item ev_tstamp interval [read-write]	1390	=item ev_tstamp interval [read-write]
1092		1391
1093	The current interval value. Can be modified any time, but changes only	1392	The current interval value. Can be modified any time, but changes only
1094	take effect when the periodic timer fires or C<ev_periodic_again> is being	1393	take effect when the periodic timer fires or C<ev_periodic_again> is being
1095	called.	1394	called.
…		…
1098		1397
1099	The current reschedule callback, or C<0>, if this functionality is	1398	The current reschedule callback, or C<0>, if this functionality is
1100	switched off. Can be changed any time, but changes only take effect when	1399	switched off. Can be changed any time, but changes only take effect when
1101	the periodic timer fires or C<ev_periodic_again> is being called.	1400	the periodic timer fires or C<ev_periodic_again> is being called.
1102		1401
		1402	=item ev_tstamp at [read-only]
		1403
		1404	When active, contains the absolute time that the watcher is supposed to
		1405	trigger next.
		1406
1103	=back	1407	=back
		1408
		1409	=head3 Examples
1104		1410
1105	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1106	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1107	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1108		1414
…		…
1148	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1149	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1150	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1151	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1152		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
		1465	=head3 Watcher-Specific Functions and Data Members
		1466
1153	=over 4	1467	=over 4
1154		1468
1155	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
1156		1470
1157	=item ev_signal_set (ev_signal *, int signum)	1471	=item ev_signal_set (ev_signal *, int signum)
…		…
1163		1477
1164	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1165		1479
1166	=back	1480	=back
1167		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1168		1496
1169	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1170		1498
1171	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1172	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
		1526
		1527	=head3 Watcher-Specific Functions and Data Members
1173		1528
1174	=over 4	1529	=over 4
1175		1530
1176	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1177		1532
1178	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1179		1534
1180	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1181	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1182	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1183	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1184	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1185	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1186		1543
1187	=item int pid [read-only]	1544	=item int pid [read-only]
1188		1545
1189	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1190		1547
…		…
1197	The process exit/trace status caused by C<rpid> (see your systems	1554	The process exit/trace status caused by C<rpid> (see your systems
1198	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1199		1556
1200	=back	1557	=back
1201		1558
1202	Example: Try to exit cleanly on SIGINT and SIGTERM.	1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1203		1565
1204	static void	1566	static void
1205	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1206	{	1568	{
1207	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1208	}	1571	}
1209		1572
1210	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1211	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1212	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1213		1587
1214		1588
1215	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1216		1590
1217	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1221	The path does not need to exist: changing from "path exists" to "path does	1595	The path does not need to exist: changing from "path exists" to "path does
1222	not exist" is a status change like any other. The condition "path does	1596	not exist" is a status change like any other. The condition "path does
1223	not exist" is signified by the C<st_nlink> field being zero (which is	1597	not exist" is signified by the C<st_nlink> field being zero (which is
1224	otherwise always forced to be at least one) and all the other fields of	1598	otherwise always forced to be at least one) and all the other fields of
1225	the stat buffer having unspecified contents.	1599	the stat buffer having unspecified contents.
		1600
		1601	The path I<should> be absolute and I<must not> end in a slash. If it is
		1602	relative and your working directory changes, the behaviour is undefined.
1226		1603
1227	Since there is no standard to do this, the portable implementation simply	1604	Since there is no standard to do this, the portable implementation simply
1228	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1229	can specify a recommended polling interval for this case. If you specify	1606	can specify a recommended polling interval for this case. If you specify
1230	a polling interval of C<0> (highly recommended!) then a I<suitable,	1607	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1243	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1244	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1245	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1246	polling.	1623	polling.
1247		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
		1669	=head3 Watcher-Specific Functions and Data Members
		1670
1248	=over 4	1671	=over 4
1249		1672
1250	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1251		1674
1252	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1675	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1259		1682
1260	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1261	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1262	last change was detected).	1685	last change was detected).
1263		1686
1264	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1265		1688
1266	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1267	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1268	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1269	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1287	=item const char *path [read-only]	1710	=item const char *path [read-only]
1288		1711
1289	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1290		1713
1291	=back	1714	=back
		1715
		1716	=head3 Examples
1292		1717
1293	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1294		1719
1295	static void	1720	static void
1296	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1309	}	1734	}
1310		1735
1311	...	1736	...
1312	ev_stat passwd;	1737	ev_stat passwd;
1313		1738
1314	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1315	ev_stat_start (loop, &passwd);	1740	ev_stat_start (loop, &passwd);
1316		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1769
1317		1770
1318	=head2 C<ev_idle> - when you've got nothing better to do...	1771	=head2 C<ev_idle> - when you've got nothing better to do...
1319		1772
1320	Idle watchers trigger events when there are no other events are pending	1773	Idle watchers trigger events when no other events of the same or higher
1321	(prepare, check and other idle watchers do not count). That is, as long	1774	priority are pending (prepare, check and other idle watchers do not
1322	as your process is busy handling sockets or timeouts (or even signals,	1775	count).
1323	imagine) it will not be triggered. But when your process is idle all idle	1776
1324	watchers are being called again and again, once per event loop iteration -	1777	That is, as long as your process is busy handling sockets or timeouts
		1778	(or even signals, imagine) of the same or higher priority it will not be
		1779	triggered. But when your process is idle (or only lower-priority watchers
		1780	are pending), the idle watchers are being called once per event loop
1325	until stopped, that is, or your process receives more events and becomes	1781	iteration - until stopped, that is, or your process receives more events
1326	busy.	1782	and becomes busy again with higher priority stuff.
1327		1783
1328	The most noteworthy effect is that as long as any idle watchers are	1784	The most noteworthy effect is that as long as any idle watchers are
1329	active, the process will not block when waiting for new events.	1785	active, the process will not block when waiting for new events.
1330		1786
1331	Apart from keeping your process non-blocking (which is a useful	1787	Apart from keeping your process non-blocking (which is a useful
1332	effect on its own sometimes), idle watchers are a good place to do	1788	effect on its own sometimes), idle watchers are a good place to do
1333	"pseudo-background processing", or delay processing stuff to after the	1789	"pseudo-background processing", or delay processing stuff to after the
1334	event loop has handled all outstanding events.	1790	event loop has handled all outstanding events.
1335		1791
		1792	=head3 Watcher-Specific Functions and Data Members
		1793
1336	=over 4	1794	=over 4
1337		1795
1338	=item ev_idle_init (ev_signal *, callback)	1796	=item ev_idle_init (ev_signal *, callback)
1339		1797
1340	Initialises and configures the idle watcher - it has no parameters of any	1798	Initialises and configures the idle watcher - it has no parameters of any
1341	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1342	believe me.	1800	believe me.
1343		1801
1344	=back	1802	=back
		1803
		1804	=head3 Examples
1345		1805
1346	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1347	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1348		1808
1349	static void	1809	static void
1350	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1351	{	1811	{
1352	free (w);	1812	free (w);
1353	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1354	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1355	}	1815	}
1356		1816
1357	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1358	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1359	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1397	with priority higher than or equal to the event loop and one coroutine	1857	with priority higher than or equal to the event loop and one coroutine
1398	of lower priority, but only once, using idle watchers to keep the event	1858	of lower priority, but only once, using idle watchers to keep the event
1399	loop from blocking if lower-priority coroutines are active, thus mapping	1859	loop from blocking if lower-priority coroutines are active, thus mapping
1400	low-priority coroutines to idle/background tasks).	1860	low-priority coroutines to idle/background tasks).
1401		1861
		1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1863	priority, to ensure that they are being run before any other watchers
		1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1865	too) should not activate ("feed") events into libev. While libev fully
		1866	supports this, they will be called before other C<ev_check> watchers
		1867	did their job. As C<ev_check> watchers are often used to embed other
		1868	(non-libev) event loops those other event loops might be in an unusable
		1869	state until their C<ev_check> watcher ran (always remind yourself to
		1870	coexist peacefully with others).
		1871
		1872	=head3 Watcher-Specific Functions and Data Members
		1873
1402	=over 4	1874	=over 4
1403		1875
1404	=item ev_prepare_init (ev_prepare *, callback)	1876	=item ev_prepare_init (ev_prepare *, callback)
1405		1877
1406	=item ev_check_init (ev_check *, callback)	1878	=item ev_check_init (ev_check *, callback)
…		…
1409	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1410	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1411		1883
1412	=back	1884	=back
1413		1885
1414	Example: To include a library such as adns, you would add IO watchers	1886	=head3 Examples
1415	and a timeout watcher in a prepare handler, as required by libadns, and	1887
		1888	There are a number of principal ways to embed other event loops or modules
		1889	into libev. Here are some ideas on how to include libadns into libev
		1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1891	use for an actually working example. Another Perl module named C<EV::Glib>
		1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1893	into the Glib event loop).
		1894
		1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1416	in a check watcher, destroy them and call into libadns. What follows is	1896	and in a check watcher, destroy them and call into libadns. What follows
1417	pseudo-code only of course:	1897	is pseudo-code only of course. This requires you to either use a low
		1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1899	the callbacks for the IO/timeout watchers might not have been called yet.
1418		1900
1419	static ev_io iow [nfd];	1901	static ev_io iow [nfd];
1420	static ev_timer tw;	1902	static ev_timer tw;
1421		1903
1422	static void	1904	static void
1423	io_cb (ev_loop *loop, ev_io *w, int revents)	1905	io_cb (ev_loop *loop, ev_io *w, int revents)
1424	{	1906	{
1425	// set the relevant poll flags
1426	// could also call adns_processreadable etc. here
1427	struct pollfd *fd = (struct pollfd *)w->data;
1428	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1429	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1430	}	1907	}
1431		1908
1432	// create io watchers for each fd and a timer before blocking	1909	// create io watchers for each fd and a timer before blocking
1433	static void	1910	static void
1434	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1435	{	1912	{
1436	int timeout = 3600000;truct pollfd fds [nfd];	1913	int timeout = 3600000;
		1914	struct pollfd fds [nfd];
1437	// actual code will need to loop here and realloc etc.	1915	// actual code will need to loop here and realloc etc.
1438	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1439		1917
1440	/* the callback is illegal, but won't be called as we stop during check */	1918	/* the callback is illegal, but won't be called as we stop during check */
1441	ev_timer_init (&tw, 0, timeout * 1e-3);	1919	ev_timer_init (&tw, 0, timeout * 1e-3);
1442	ev_timer_start (loop, &tw);	1920	ev_timer_start (loop, &tw);
1443		1921
1444	// create on ev_io per pollfd	1922	// create one ev_io per pollfd
1445	for (int i = 0; i < nfd; ++i)	1923	for (int i = 0; i < nfd; ++i)
1446	{	1924	{
1447	ev_io_init (iow + i, io_cb, fds [i].fd,	1925	ev_io_init (iow + i, io_cb, fds [i].fd,
1448	((fds [i].events & POLLIN ? EV_READ : 0)	1926	((fds [i].events & POLLIN ? EV_READ : 0)
1449	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1450		1928
1451	fds [i].revents = 0;	1929	fds [i].revents = 0;
1452	iow [i].data = fds + i;
1453	ev_io_start (loop, iow + i);	1930	ev_io_start (loop, iow + i);
1454	}	1931	}
1455	}	1932	}
1456		1933
1457	// stop all watchers after blocking	1934	// stop all watchers after blocking
…		…
1459	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1460	{	1937	{
1461	ev_timer_stop (loop, &tw);	1938	ev_timer_stop (loop, &tw);
1462		1939
1463	for (int i = 0; i < nfd; ++i)	1940	for (int i = 0; i < nfd; ++i)
		1941	{
		1942	// set the relevant poll flags
		1943	// could also call adns_processreadable etc. here
		1944	struct pollfd *fd = fds + i;
		1945	int revents = ev_clear_pending (iow + i);
		1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1948
		1949	// now stop the watcher
1464	ev_io_stop (loop, iow + i);	1950	ev_io_stop (loop, iow + i);
		1951	}
1465		1952
1466	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1954	}
		1955
		1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1957	in the prepare watcher and would dispose of the check watcher.
		1958
		1959	Method 3: If the module to be embedded supports explicit event
		1960	notification (adns does), you can also make use of the actual watcher
		1961	callbacks, and only destroy/create the watchers in the prepare watcher.
		1962
		1963	static void
		1964	timer_cb (EV_P_ ev_timer *w, int revents)
		1965	{
		1966	adns_state ads = (adns_state)w->data;
		1967	update_now (EV_A);
		1968
		1969	adns_processtimeouts (ads, &tv_now);
		1970	}
		1971
		1972	static void
		1973	io_cb (EV_P_ ev_io *w, int revents)
		1974	{
		1975	adns_state ads = (adns_state)w->data;
		1976	update_now (EV_A);
		1977
		1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1980	}
		1981
		1982	// do not ever call adns_afterpoll
		1983
		1984	Method 4: Do not use a prepare or check watcher because the module you
		1985	want to embed is too inflexible to support it. Instead, youc na override
		1986	their poll function. The drawback with this solution is that the main
		1987	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1988	this.
		1989
		1990	static gint
		1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1992	{
		1993	int got_events = 0;
		1994
		1995	for (n = 0; n < nfds; ++n)
		1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1997
		1998	if (timeout >= 0)
		1999	// create/start timer
		2000
		2001	// poll
		2002	ev_loop (EV_A_ 0);
		2003
		2004	// stop timer again
		2005	if (timeout >= 0)
		2006	ev_timer_stop (EV_A_ &to);
		2007
		2008	// stop io watchers again - their callbacks should have set
		2009	for (n = 0; n < nfds; ++n)
		2010	ev_io_stop (EV_A_ iow [n]);
		2011
		2012	return got_events;
1467	}	2013	}
1468		2014
1469		2015
1470	=head2 C<ev_embed> - when one backend isn't enough...	2016	=head2 C<ev_embed> - when one backend isn't enough...
1471		2017
…		…
1514	portable one.	2060	portable one.
1515		2061
1516	So when you want to use this feature you will always have to be prepared	2062	So when you want to use this feature you will always have to be prepared
1517	that you cannot get an embeddable loop. The recommended way to get around	2063	that you cannot get an embeddable loop. The recommended way to get around
1518	this is to have a separate variables for your embeddable loop, try to	2064	this is to have a separate variables for your embeddable loop, try to
1519	create it, and if that fails, use the normal loop for everything:	2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
1520		2100
1521	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1522	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1523	struct ev_embed embed;	2103	struct ev_embed embed;
1524		2104
…		…
1535	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1536	}	2116	}
1537	else	2117	else
1538	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1539		2119
1540	=over 4	2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1541		2124
1542	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
1543		2135
1544	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2136	if (!loop_socket)
		2137	loop_socket = loop;
1545		2138
1546	Configures the watcher to embed the given loop, which must be	2139	// now use loop_socket for all sockets, and loop for everything else
1547	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1548	invoked automatically, otherwise it is the responsibility of the callback
1549	to invoke it (it will continue to be called until the sweep has been done,
1550	if you do not want thta, you need to temporarily stop the embed watcher).
1551
1552	=item ev_embed_sweep (loop, ev_embed *)
1553
1554	Make a single, non-blocking sweep over the embedded loop. This works
1555	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1556	apropriate way for embedded loops.
1557
1558	=item struct ev_loop *loop [read-only]
1559
1560	The embedded event loop.
1561
1562	=back
1563		2140
1564		2141
1565	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1566		2143
1567	Fork watchers are called when a C<fork ()> was detected (usually because	2144	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1570	event loop blocks next and before C<ev_check> watchers are being called,	2147	event loop blocks next and before C<ev_check> watchers are being called,
1571	and only in the child after the fork. If whoever good citizen calling	2148	and only in the child after the fork. If whoever good citizen calling
1572	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1573	handlers will be invoked, too, of course.	2150	handlers will be invoked, too, of course.
1574		2151
		2152	=head3 Watcher-Specific Functions and Data Members
		2153
1575	=over 4	2154	=over 4
1576		2155
1577	=item ev_fork_init (ev_signal *, callback)	2156	=item ev_fork_init (ev_signal *, callback)
1578		2157
1579	Initialises and configures the fork watcher - it has no parameters of any	2158	Initialises and configures the fork watcher - it has no parameters of any
1580	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1581	believe me.	2160	believe me.
		2161
		2162	=back
		2163
		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
1582		2306
1583	=back	2307	=back
1584		2308
1585		2309
1586	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
…		…
1675		2399
1676	To use it,	2400	To use it,
1677		2401
1678	#include <ev++.h>	2402	#include <ev++.h>
1679		2403
1680	(it is not installed by default). This automatically includes F<ev.h>	2404	This automatically includes F<ev.h> and puts all of its definitions (many
1681	and puts all of its definitions (many of them macros) into the global	2405	of them macros) into the global namespace. All C++ specific things are
1682	namespace. All C++ specific things are put into the C<ev> namespace.	2406	put into the C<ev> namespace. It should support all the same embedding
		2407	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1683		2408
1684	It should support all the same embedding options as F<ev.h>, most notably	2409	Care has been taken to keep the overhead low. The only data member the C++
1685	C<EV_MULTIPLICITY>.	2410	classes add (compared to plain C-style watchers) is the event loop pointer
		2411	that the watcher is associated with (or no additional members at all if
		2412	you disable C<EV_MULTIPLICITY> when embedding libev).
		2413
		2414	Currently, functions, and static and non-static member functions can be
		2415	used as callbacks. Other types should be easy to add as long as they only
		2416	need one additional pointer for context. If you need support for other
		2417	types of functors please contact the author (preferably after implementing
		2418	it).
1686		2419
1687	Here is a list of things available in the C<ev> namespace:	2420	Here is a list of things available in the C<ev> namespace:
1688		2421
1689	=over 4	2422	=over 4
1690		2423
…		…
1706		2439
1707	All of those classes have these methods:	2440	All of those classes have these methods:
1708		2441
1709	=over 4	2442	=over 4
1710		2443
1711	=item ev::TYPE::TYPE (object *, object::method *)	2444	=item ev::TYPE::TYPE ()
1712		2445
1713	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2446	=item ev::TYPE::TYPE (struct ev_loop *)
1714		2447
1715	=item ev::TYPE::~TYPE	2448	=item ev::TYPE::~TYPE
1716		2449
1717	The constructor takes a pointer to an object and a method pointer to	2450	The constructor (optionally) takes an event loop to associate the watcher
1718	the event handler callback to call in this class. The constructor calls	2451	with. If it is omitted, it will use C<EV_DEFAULT>.
1719	C<ev_init> for you, which means you have to call the C<set> method	2452
1720	before starting it. If you do not specify a loop then the constructor	2453	The constructor calls C<ev_init> for you, which means you have to call the
1721	automatically associates the default loop with this watcher.	2454	C<set> method before starting it.
		2455
		2456	It will not set a callback, however: You have to call the templated C<set>
		2457	method to set a callback before you can start the watcher.
		2458
		2459	(The reason why you have to use a method is a limitation in C++ which does
		2460	not allow explicit template arguments for constructors).
1722		2461
1723	The destructor automatically stops the watcher if it is active.	2462	The destructor automatically stops the watcher if it is active.
		2463
		2464	=item w->set<class, &class::method> (object *)
		2465
		2466	This method sets the callback method to call. The method has to have a
		2467	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2468	first argument and the C<revents> as second. The object must be given as
		2469	parameter and is stored in the C<data> member of the watcher.
		2470
		2471	This method synthesizes efficient thunking code to call your method from
		2472	the C callback that libev requires. If your compiler can inline your
		2473	callback (i.e. it is visible to it at the place of the C<set> call and
		2474	your compiler is good :), then the method will be fully inlined into the
		2475	thunking function, making it as fast as a direct C callback.
		2476
		2477	Example: simple class declaration and watcher initialisation
		2478
		2479	struct myclass
		2480	{
		2481	void io_cb (ev::io &w, int revents) { }
		2482	}
		2483
		2484	myclass obj;
		2485	ev::io iow;
		2486	iow.set <myclass, &myclass::io_cb> (&obj);
		2487
		2488	=item w->set<function> (void *data = 0)
		2489
		2490	Also sets a callback, but uses a static method or plain function as
		2491	callback. The optional C<data> argument will be stored in the watcher's
		2492	C<data> member and is free for you to use.
		2493
		2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2495
		2496	See the method-C<set> above for more details.
		2497
		2498	Example:
		2499
		2500	static void io_cb (ev::io &w, int revents) { }
		2501	iow.set <io_cb> ();
1724		2502
1725	=item w->set (struct ev_loop *)	2503	=item w->set (struct ev_loop *)
1726		2504
1727	Associates a different C<struct ev_loop> with this watcher. You can only	2505	Associates a different C<struct ev_loop> with this watcher. You can only
1728	do this when the watcher is inactive (and not pending either).	2506	do this when the watcher is inactive (and not pending either).
1729		2507
1730	=item w->set ([args])	2508	=item w->set ([args])
1731		2509
1732	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2510	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1733	called at least once. Unlike the C counterpart, an active watcher gets	2511	called at least once. Unlike the C counterpart, an active watcher gets
1734	automatically stopped and restarted.	2512	automatically stopped and restarted when reconfiguring it with this
		2513	method.
1735		2514
1736	=item w->start ()	2515	=item w->start ()
1737		2516
1738	Starts the watcher. Note that there is no C<loop> argument as the	2517	Starts the watcher. Note that there is no C<loop> argument, as the
1739	constructor already takes the loop.	2518	constructor already stores the event loop.
1740		2519
1741	=item w->stop ()	2520	=item w->stop ()
1742		2521
1743	Stops the watcher if it is active. Again, no C<loop> argument.	2522	Stops the watcher if it is active. Again, no C<loop> argument.
1744		2523
1745	=item w->again () C<ev::timer>, C<ev::periodic> only	2524	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1746		2525
1747	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2526	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1748	C<ev_TYPE_again> function.	2527	C<ev_TYPE_again> function.
1749		2528
1750	=item w->sweep () C<ev::embed> only	2529	=item w->sweep () (C<ev::embed> only)
1751		2530
1752	Invokes C<ev_embed_sweep>.	2531	Invokes C<ev_embed_sweep>.
1753		2532
1754	=item w->update () C<ev::stat> only	2533	=item w->update () (C<ev::stat> only)
1755		2534
1756	Invokes C<ev_stat_stat>.	2535	Invokes C<ev_stat_stat>.
1757		2536
1758	=back	2537	=back
1759		2538
…		…
1762	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
1763	the constructor.	2542	the constructor.
1764		2543
1765	class myclass	2544	class myclass
1766	{	2545	{
1767	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
1768	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
1769		2548
1770	myclass ();	2549	myclass (int fd)
1771	}
1772
1773	myclass::myclass (int fd)
1774	: io (this, &myclass::io_cb),
1775	idle (this, &myclass::idle_cb)
1776	{	2550	{
		2551	io .set <myclass, &myclass::io_cb > (this);
		2552	idle.set <myclass, &myclass::idle_cb> (this);
		2553
1777	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
1778	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
1779		2592
1780		2593
1781	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
1782		2595
1783	Libev can be compiled with a variety of options, the most fundemantal is	2596	Libev can be compiled with a variety of options, the most fundamantal
1784	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1785	callbacks have an initial C<struct ev_loop *> argument.	2598	functions and callbacks have an initial C<struct ev_loop *> argument.
1786		2599
1787	To make it easier to write programs that cope with either variant, the	2600	To make it easier to write programs that cope with either variant, the
1788	following macros are defined:	2601	following macros are defined:
1789		2602
1790	=over 4	2603	=over 4
…		…
1822	Similar to the other two macros, this gives you the value of the default	2635	Similar to the other two macros, this gives you the value of the default
1823	loop, if multiple loops are supported ("ev loop default").	2636	loop, if multiple loops are supported ("ev loop default").
1824		2637
1825	=back	2638	=back
1826		2639
1827	Example: Declare and initialise a check watcher, working regardless of	2640	Example: Declare and initialise a check watcher, utilising the above
1828	wether multiple loops are supported or not.	2641	macros so it will work regardless of whether multiple loops are supported
		2642	or not.
1829		2643
1830	static void	2644	static void
1831	check_cb (EV_P_ ev_timer *w, int revents)	2645	check_cb (EV_P_ ev_timer *w, int revents)
1832	{	2646	{
1833	ev_check_stop (EV_A_ w);	2647	ev_check_stop (EV_A_ w);
…		…
1836	ev_check check;	2650	ev_check check;
1837	ev_check_init (&check, check_cb);	2651	ev_check_init (&check, check_cb);
1838	ev_check_start (EV_DEFAULT_ &check);	2652	ev_check_start (EV_DEFAULT_ &check);
1839	ev_loop (EV_DEFAULT_ 0);	2653	ev_loop (EV_DEFAULT_ 0);
1840		2654
1841
1842	=head1 EMBEDDING	2655	=head1 EMBEDDING
1843		2656
1844	Libev can (and often is) directly embedded into host	2657	Libev can (and often is) directly embedded into host
1845	applications. Examples of applications that embed it include the Deliantra	2658	applications. Examples of applications that embed it include the Deliantra
1846	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2659	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1847	and rxvt-unicode.	2660	and rxvt-unicode.
1848		2661
1849	The goal is to enable you to just copy the neecssary files into your	2662	The goal is to enable you to just copy the necessary files into your
1850	source directory without having to change even a single line in them, so	2663	source directory without having to change even a single line in them, so
1851	you can easily upgrade by simply copying (or having a checked-out copy of	2664	you can easily upgrade by simply copying (or having a checked-out copy of
1852	libev somewhere in your source tree).	2665	libev somewhere in your source tree).
1853		2666
1854	=head2 FILESETS	2667	=head2 FILESETS
…		…
1885	ev_vars.h	2698	ev_vars.h
1886	ev_wrap.h	2699	ev_wrap.h
1887		2700
1888	ev_win32.c required on win32 platforms only	2701	ev_win32.c required on win32 platforms only
1889		2702
1890	ev_select.c only when select backend is enabled (which is by default)	2703	ev_select.c only when select backend is enabled (which is enabled by default)
1891	ev_poll.c only when poll backend is enabled (disabled by default)	2704	ev_poll.c only when poll backend is enabled (disabled by default)
1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2705	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2706	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1894	ev_port.c only when the solaris port backend is enabled (disabled by default)	2707	ev_port.c only when the solaris port backend is enabled (disabled by default)
1895		2708
…		…
1924		2737
1925	libev.m4	2738	libev.m4
1926		2739
1927	=head2 PREPROCESSOR SYMBOLS/MACROS	2740	=head2 PREPROCESSOR SYMBOLS/MACROS
1928		2741
1929	Libev can be configured via a variety of preprocessor symbols you have to define	2742	Libev can be configured via a variety of preprocessor symbols you have to
1930	before including any of its files. The default is not to build for multiplicity	2743	define before including any of its files. The default in the absense of
1931	and only include the select backend.	2744	autoconf is noted for every option.
1932		2745
1933	=over 4	2746	=over 4
1934		2747
1935	=item EV_STANDALONE	2748	=item EV_STANDALONE
1936		2749
…		…
1944		2757
1945	If defined to be C<1>, libev will try to detect the availability of the	2758	If defined to be C<1>, libev will try to detect the availability of the
1946	monotonic clock option at both compiletime and runtime. Otherwise no use	2759	monotonic clock option at both compiletime and runtime. Otherwise no use
1947	of the monotonic clock option will be attempted. If you enable this, you	2760	of the monotonic clock option will be attempted. If you enable this, you
1948	usually have to link against librt or something similar. Enabling it when	2761	usually have to link against librt or something similar. Enabling it when
1949	the functionality isn't available is safe, though, althoguh you have	2762	the functionality isn't available is safe, though, although you have
1950	to make sure you link against any libraries where the C<clock_gettime>	2763	to make sure you link against any libraries where the C<clock_gettime>
1951	function is hiding in (often F<-lrt>).	2764	function is hiding in (often F<-lrt>).
1952		2765
1953	=item EV_USE_REALTIME	2766	=item EV_USE_REALTIME
1954		2767
1955	If defined to be C<1>, libev will try to detect the availability of the	2768	If defined to be C<1>, libev will try to detect the availability of the
1956	realtime clock option at compiletime (and assume its availability at	2769	realtime clock option at compiletime (and assume its availability at
1957	runtime if successful). Otherwise no use of the realtime clock option will	2770	runtime if successful). Otherwise no use of the realtime clock option will
1958	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1959	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1960	in the description of C<EV_USE_MONOTONIC>, though.	2773	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2774
		2775	=item EV_USE_NANOSLEEP
		2776
		2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2778	and will use it for delays. Otherwise it will use C<select ()>.
		2779
		2780	=item EV_USE_EVENTFD
		2781
		2782	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2783	available and will probe for kernel support at runtime. This will improve
		2784	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2785	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2786	2.7 or newer, otherwise disabled.
1961		2787
1962	=item EV_USE_SELECT	2788	=item EV_USE_SELECT
1963		2789
1964	If undefined or defined to be C<1>, libev will compile in support for the	2790	If undefined or defined to be C<1>, libev will compile in support for the
1965	C<select>(2) backend. No attempt at autodetection will be done: if no	2791	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1984	be used is the winsock select). This means that it will call	2810	be used is the winsock select). This means that it will call
1985	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2811	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1986	it is assumed that all these functions actually work on fds, even	2812	it is assumed that all these functions actually work on fds, even
1987	on win32. Should not be defined on non-win32 platforms.	2813	on win32. Should not be defined on non-win32 platforms.
1988		2814
		2815	=item EV_FD_TO_WIN32_HANDLE
		2816
		2817	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2818	file descriptors to socket handles. When not defining this symbol (the
		2819	default), then libev will call C<_get_osfhandle>, which is usually
		2820	correct. In some cases, programs use their own file descriptor management,
		2821	in which case they can provide this function to map fds to socket handles.
		2822
1989	=item EV_USE_POLL	2823	=item EV_USE_POLL
1990		2824
1991	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2825	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1992	backend. Otherwise it will be enabled on non-win32 platforms. It	2826	backend. Otherwise it will be enabled on non-win32 platforms. It
1993	takes precedence over select.	2827	takes precedence over select.
1994		2828
1995	=item EV_USE_EPOLL	2829	=item EV_USE_EPOLL
1996		2830
1997	If defined to be C<1>, libev will compile in support for the Linux	2831	If defined to be C<1>, libev will compile in support for the Linux
1998	C<epoll>(7) backend. Its availability will be detected at runtime,	2832	C<epoll>(7) backend. Its availability will be detected at runtime,
1999	otherwise another method will be used as fallback. This is the	2833	otherwise another method will be used as fallback. This is the preferred
2000	preferred backend for GNU/Linux systems.	2834	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2835	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2001		2836
2002	=item EV_USE_KQUEUE	2837	=item EV_USE_KQUEUE
2003		2838
2004	If defined to be C<1>, libev will compile in support for the BSD style	2839	If defined to be C<1>, libev will compile in support for the BSD style
2005	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2840	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2024		2859
2025	=item EV_USE_INOTIFY	2860	=item EV_USE_INOTIFY
2026		2861
2027	If defined to be C<1>, libev will compile in support for the Linux inotify	2862	If defined to be C<1>, libev will compile in support for the Linux inotify
2028	interface to speed up C<ev_stat> watchers. Its actual availability will	2863	interface to speed up C<ev_stat> watchers. Its actual availability will
2029	be detected at runtime.	2864	be detected at runtime. If undefined, it will be enabled if the headers
		2865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2866
		2867	=item EV_ATOMIC_T
		2868
		2869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2870	access is atomic with respect to other threads or signal contexts. No such
		2871	type is easily found in the C language, so you can provide your own type
		2872	that you know is safe for your purposes. It is used both for signal handler "locking"
		2873	as well as for signal and thread safety in C<ev_async> watchers.
		2874
		2875	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2876	(from F<signal.h>), which is usually good enough on most platforms.
2030		2877
2031	=item EV_H	2878	=item EV_H
2032		2879
2033	The name of the F<ev.h> header file used to include it. The default if	2880	The name of the F<ev.h> header file used to include it. The default if
2034	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2035	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2882	used to virtually rename the F<ev.h> header file in case of conflicts.
2036		2883
2037	=item EV_CONFIG_H	2884	=item EV_CONFIG_H
2038		2885
2039	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2886	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2040	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2887	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2041	C<EV_H>, above.	2888	C<EV_H>, above.
2042		2889
2043	=item EV_EVENT_H	2890	=item EV_EVENT_H
2044		2891
2045	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2892	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2046	of how the F<event.h> header can be found.	2893	of how the F<event.h> header can be found, the default is C<"event.h">.
2047		2894
2048	=item EV_PROTOTYPES	2895	=item EV_PROTOTYPES
2049		2896
2050	If defined to be C<0>, then F<ev.h> will not define any function	2897	If defined to be C<0>, then F<ev.h> will not define any function
2051	prototypes, but still define all the structs and other symbols. This is	2898	prototypes, but still define all the structs and other symbols. This is
…		…
2058	will have the C<struct ev_loop *> as first argument, and you can create	2905	will have the C<struct ev_loop *> as first argument, and you can create
2059	additional independent event loops. Otherwise there will be no support	2906	additional independent event loops. Otherwise there will be no support
2060	for multiple event loops and there is no first event loop pointer	2907	for multiple event loops and there is no first event loop pointer
2061	argument. Instead, all functions act on the single default loop.	2908	argument. Instead, all functions act on the single default loop.
2062		2909
		2910	=item EV_MINPRI
		2911
		2912	=item EV_MAXPRI
		2913
		2914	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2915	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2916	provide for more priorities by overriding those symbols (usually defined
		2917	to be C<-2> and C<2>, respectively).
		2918
		2919	When doing priority-based operations, libev usually has to linearly search
		2920	all the priorities, so having many of them (hundreds) uses a lot of space
		2921	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2922	fine.
		2923
		2924	If your embedding app does not need any priorities, defining these both to
		2925	C<0> will save some memory and cpu.
		2926
2063	=item EV_PERIODIC_ENABLE	2927	=item EV_PERIODIC_ENABLE
2064		2928
2065	If undefined or defined to be C<1>, then periodic timers are supported. If	2929	If undefined or defined to be C<1>, then periodic timers are supported. If
2066	defined to be C<0>, then they are not. Disabling them saves a few kB of	2930	defined to be C<0>, then they are not. Disabling them saves a few kB of
2067	code.	2931	code.
2068		2932
		2933	=item EV_IDLE_ENABLE
		2934
		2935	If undefined or defined to be C<1>, then idle watchers are supported. If
		2936	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2937	code.
		2938
2069	=item EV_EMBED_ENABLE	2939	=item EV_EMBED_ENABLE
2070		2940
2071	If undefined or defined to be C<1>, then embed watchers are supported. If	2941	If undefined or defined to be C<1>, then embed watchers are supported. If
2072	defined to be C<0>, then they are not.	2942	defined to be C<0>, then they are not.
2073		2943
…		…
2077	defined to be C<0>, then they are not.	2947	defined to be C<0>, then they are not.
2078		2948
2079	=item EV_FORK_ENABLE	2949	=item EV_FORK_ENABLE
2080		2950
2081	If undefined or defined to be C<1>, then fork watchers are supported. If	2951	If undefined or defined to be C<1>, then fork watchers are supported. If
		2952	defined to be C<0>, then they are not.
		2953
		2954	=item EV_ASYNC_ENABLE
		2955
		2956	If undefined or defined to be C<1>, then async watchers are supported. If
2082	defined to be C<0>, then they are not.	2957	defined to be C<0>, then they are not.
2083		2958
2084	=item EV_MINIMAL	2959	=item EV_MINIMAL
2085		2960
2086	If you need to shave off some kilobytes of code at the expense of some	2961	If you need to shave off some kilobytes of code at the expense of some
…		…
2094	than enough. If you need to manage thousands of children you might want to	2969	than enough. If you need to manage thousands of children you might want to
2095	increase this value (I<must> be a power of two).	2970	increase this value (I<must> be a power of two).
2096		2971
2097	=item EV_INOTIFY_HASHSIZE	2972	=item EV_INOTIFY_HASHSIZE
2098		2973
2099	C<ev_staz> watchers use a small hash table to distribute workload by	2974	C<ev_stat> watchers use a small hash table to distribute workload by
2100	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2975	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2101	usually more than enough. If you need to manage thousands of C<ev_stat>	2976	usually more than enough. If you need to manage thousands of C<ev_stat>
2102	watchers you might want to increase this value (I<must> be a power of	2977	watchers you might want to increase this value (I<must> be a power of
2103	two).	2978	two).
2104		2979
…		…
2121		2996
2122	=item ev_set_cb (ev, cb)	2997	=item ev_set_cb (ev, cb)
2123		2998
2124	Can be used to change the callback member declaration in each watcher,	2999	Can be used to change the callback member declaration in each watcher,
2125	and the way callbacks are invoked and set. Must expand to a struct member	3000	and the way callbacks are invoked and set. Must expand to a struct member
2126	definition and a statement, respectively. See the F<ev.v> header file for	3001	definition and a statement, respectively. See the F<ev.h> header file for
2127	their default definitions. One possible use for overriding these is to	3002	their default definitions. One possible use for overriding these is to
2128	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3003	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2129	method calls instead of plain function calls in C++.	3004	method calls instead of plain function calls in C++.
		3005
		3006	=head2 EXPORTED API SYMBOLS
		3007
		3008	If you need to re-export the API (e.g. via a dll) and you need a list of
		3009	exported symbols, you can use the provided F<Symbol.*> files which list
		3010	all public symbols, one per line:
		3011
		3012	Symbols.ev for libev proper
		3013	Symbols.event for the libevent emulation
		3014
		3015	This can also be used to rename all public symbols to avoid clashes with
		3016	multiple versions of libev linked together (which is obviously bad in
		3017	itself, but sometimes it is inconvinient to avoid this).
		3018
		3019	A sed command like this will create wrapper C<#define>'s that you need to
		3020	include before including F<ev.h>:
		3021
		3022	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3023
		3024	This would create a file F<wrap.h> which essentially looks like this:
		3025
		3026	#define ev_backend myprefix_ev_backend
		3027	#define ev_check_start myprefix_ev_check_start
		3028	#define ev_check_stop myprefix_ev_check_stop
		3029	...
2130		3030
2131	=head2 EXAMPLES	3031	=head2 EXAMPLES
2132		3032
2133	For a real-world example of a program the includes libev	3033	For a real-world example of a program the includes libev
2134	verbatim, you can have a look at the EV perl module	3034	verbatim, you can have a look at the EV perl module
…		…
2137	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3037	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2138	will be compiled. It is pretty complex because it provides its own header	3038	will be compiled. It is pretty complex because it provides its own header
2139	file.	3039	file.
2140		3040
2141	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3041	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2142	that everybody includes and which overrides some autoconf choices:	3042	that everybody includes and which overrides some configure choices:
2143		3043
		3044	#define EV_MINIMAL 1
2144	#define EV_USE_POLL 0	3045	#define EV_USE_POLL 0
2145	#define EV_MULTIPLICITY 0	3046	#define EV_MULTIPLICITY 0
2146	#define EV_PERIODICS 0	3047	#define EV_PERIODIC_ENABLE 0
		3048	#define EV_STAT_ENABLE 0
		3049	#define EV_FORK_ENABLE 0
2147	#define EV_CONFIG_H <config.h>	3050	#define EV_CONFIG_H <config.h>
		3051	#define EV_MINPRI 0
		3052	#define EV_MAXPRI 0
2148		3053
2149	#include "ev++.h"	3054	#include "ev++.h"
2150		3055
2151	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3056	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2152		3057
…		…
2158		3063
2159	In this section the complexities of (many of) the algorithms used inside	3064	In this section the complexities of (many of) the algorithms used inside
2160	libev will be explained. For complexity discussions about backends see the	3065	libev will be explained. For complexity discussions about backends see the
2161	documentation for C<ev_default_init>.	3066	documentation for C<ev_default_init>.
2162		3067
		3068	All of the following are about amortised time: If an array needs to be
		3069	extended, libev needs to realloc and move the whole array, but this
		3070	happens asymptotically never with higher number of elements, so O(1) might
		3071	mean it might do a lengthy realloc operation in rare cases, but on average
		3072	it is much faster and asymptotically approaches constant time.
		3073
2163	=over 4	3074	=over 4
2164		3075
2165	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3076	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2166		3077
		3078	This means that, when you have a watcher that triggers in one hour and
		3079	there are 100 watchers that would trigger before that then inserting will
		3080	have to skip roughly seven (C<ld 100>) of these watchers.
		3081
2167	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3082	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2168		3083
		3084	That means that changing a timer costs less than removing/adding them
		3085	as only the relative motion in the event queue has to be paid for.
		3086
2169	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3087	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2170		3088
		3089	These just add the watcher into an array or at the head of a list.
		3090
2171	=item Stopping check/prepare/idle watchers: O(1)	3091	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2172		3092
2173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3093	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2174		3094
		3095	These watchers are stored in lists then need to be walked to find the
		3096	correct watcher to remove. The lists are usually short (you don't usually
		3097	have many watchers waiting for the same fd or signal).
		3098
2175	=item Finding the next timer per loop iteration: O(1)	3099	=item Finding the next timer in each loop iteration: O(1)
		3100
		3101	By virtue of using a binary heap, the next timer is always found at the
		3102	beginning of the storage array.
2176		3103
2177	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3104	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2178		3105
2179	=item Activating one watcher: O(1)	3106	A change means an I/O watcher gets started or stopped, which requires
		3107	libev to recalculate its status (and possibly tell the kernel, depending
		3108	on backend and wether C<ev_io_set> was used).
		3109
		3110	=item Activating one watcher (putting it into the pending state): O(1)
		3111
		3112	=item Priority handling: O(number_of_priorities)
		3113
		3114	Priorities are implemented by allocating some space for each
		3115	priority. When doing priority-based operations, libev usually has to
		3116	linearly search all the priorities, but starting/stopping and activating
		3117	watchers becomes O(1) w.r.t. priority handling.
		3118
		3119	=item Sending an ev_async: O(1)
		3120
		3121	=item Processing ev_async_send: O(number_of_async_watchers)
		3122
		3123	=item Processing signals: O(max_signal_number)
		3124
		3125	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3126	calls in the current loop iteration. Checking for async and signal events
		3127	involves iterating over all running async watchers or all signal numbers.
2180		3128
2181	=back	3129	=back
2182		3130
2183		3131
		3132	=head1 Win32 platform limitations and workarounds
		3133
		3134	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3135	requires, and its I/O model is fundamentally incompatible with the POSIX
		3136	model. Libev still offers limited functionality on this platform in
		3137	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3138	descriptors. This only applies when using Win32 natively, not when using
		3139	e.g. cygwin.
		3140
		3141	There is no supported compilation method available on windows except
		3142	embedding it into other applications.
		3143
		3144	Due to the many, low, and arbitrary limits on the win32 platform and the
		3145	abysmal performance of winsockets, using a large number of sockets is not
		3146	recommended (and not reasonable). If your program needs to use more than
		3147	a hundred or so sockets, then likely it needs to use a totally different
		3148	implementation for windows, as libev offers the POSIX model, which cannot
		3149	be implemented efficiently on windows (microsoft monopoly games).
		3150
		3151	=over 4
		3152
		3153	=item The winsocket select function
		3154
		3155	The winsocket C<select> function doesn't follow POSIX in that it requires
		3156	socket I<handles> and not socket I<file descriptors>. This makes select
		3157	very inefficient, and also requires a mapping from file descriptors
		3158	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3159	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3160	symbols for more info.
		3161
		3162	The configuration for a "naked" win32 using the microsoft runtime
		3163	libraries and raw winsocket select is:
		3164
		3165	#define EV_USE_SELECT 1
		3166	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3167
		3168	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3169	complexity in the O(n²) range when using win32.
		3170
		3171	=item Limited number of file descriptors
		3172
		3173	Windows has numerous arbitrary (and low) limits on things. Early versions
		3174	of winsocket's select only supported waiting for a max. of C<64> handles
		3175	(probably owning to the fact that all windows kernels can only wait for
		3176	C<64> things at the same time internally; microsoft recommends spawning a
		3177	chain of threads and wait for 63 handles and the previous thread in each).
		3178
		3179	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3180	to some high number (e.g. C<2048>) before compiling the winsocket select
		3181	call (which might be in libev or elsewhere, for example, perl does its own
		3182	select emulation on windows).
		3183
		3184	Another limit is the number of file descriptors in the microsoft runtime
		3185	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3186	or something like this inside microsoft). You can increase this by calling
		3187	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3188	arbitrary limit), but is broken in many versions of the microsoft runtime
		3189	libraries.
		3190
		3191	This might get you to about C<512> or C<2048> sockets (depending on
		3192	windows version and/or the phase of the moon). To get more, you need to
		3193	wrap all I/O functions and provide your own fd management, but the cost of
		3194	calling select (O(n²)) will likely make this unworkable.
		3195
		3196	=back
		3197
		3198
2184	=head1 AUTHOR	3199	=head1 AUTHOR
2185		3200
2186	Marc Lehmann <libev@schmorp.de>.	3201	Marc Lehmann <libev@schmorp.de>.
2187		3202

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