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Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs.
Revision 1.196 by root, Tue Oct 21 20:04:14 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		9	=head2 EXAMPLE PROGRAM
		10
		11	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		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);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
8		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		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://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		70
11	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
12	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
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	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
16	(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
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	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
20	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
21	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
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	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
49	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
50	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
51	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
52		141
53		142
54	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
55		144
56	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
…		…
62		151
63	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	154	you actually want to know.
66		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
		161
67	=item int ev_version_major ()	162	=item int ev_version_major ()
68		163
69	=item int ev_version_minor ()	164	=item int ev_version_minor ()
70		165
71	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	170	version of the library your program was compiled against.
76		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
77	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	178	not a problem.
81		179
82	Example: make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	181	version.
84		182
85	assert (("libev version mismatch",	183	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
88		186
89	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
90		188
91	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
92	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
94	a description of the set values.	192	a description of the set values.
95		193
96	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
97	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
98		196
99	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
100	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
101		199
102	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
103		201
104	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
105	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
106	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
107	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
108	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
109	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
110		208
111	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
112		210
…		…
116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
117	recommended ones.	215	recommended ones.
118		216
119	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
120		218
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
122		220
123	Sets the allocation function to use (the prototype is similar to the	221	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
125	and free memory (no surprises here). If it returns zero when memory	223	used to allocate and free memory (no surprises here). If it returns zero
126	needs to be allocated, the library might abort or take some potentially	224	when memory needs to be allocated (C<size != 0>), the library might abort
127	destructive action. The default is your system realloc function.	225	or take some potentially destructive action.
		226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
128		230
129	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
132		234
133	Example: replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	236	retries (example requires a standards-compliant C<realloc>).
135		237
136	static void *	238	static void *
137	persistent_realloc (void *ptr, long size)	239	persistent_realloc (void *ptr, size_t size)
138	{	240	{
139	for (;;)	241	for (;;)
140	{	242	{
141	void *newptr = realloc (ptr, size);	243	void *newptr = realloc (ptr, size);
142		244
…		…
148	}	250	}
149		251
150	...	252	...
151	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
152		254
153	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
154		256
155	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
156	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
157	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
158	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
159	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	263	(such as abort).
162		264
163	Example: do the same thing as libev does internally:	265	Example: This is basically the same thing that libev does internally, too.
164		266
165	static void	267	static void
166	fatal_error (const char *msg)	268	fatal_error (const char *msg)
167	{	269	{
168	perror (msg);	270	perror (msg);
…		…
178		280
179	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
180	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
181	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
182		284
183	If you use threads, a common model is to run the default event loop
184	in your main thread (or in a separate thread) and for each thread you
185	create, you also create another event loop. Libev itself does no locking
186	whatsoever, so if you mix calls to the same event loop in different
187	threads, make sure you lock (this is usually a bad idea, though, even if
188	done correctly, because it's hideous and inefficient).
189
190	=over 4	285	=over 4
191		286
192	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
193		288
194	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
197	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
198		293
199	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
200	function.	295	function.
201		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
202	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
204		310
205	The following flags are supported:	311	The following flags are supported:
206		312
…		…
211	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
212	thing, believe me).	318	thing, believe me).
213		319
214	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
215		321
216	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
217	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
221	around bugs.	327	around bugs.
222		328
		329	=item C<EVFLAG_FORKCHECK>
		330
		331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		332	a fork, you can also make libev check for a fork in each iteration by
		333	enabling this flag.
		334
		335	This works by calling C<getpid ()> on every iteration of the loop,
		336	and thus this might slow down your event loop if you do a lot of loop
		337	iterations and little real work, but is usually not noticeable (on my
		338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		339	without a system call and thus I<very> fast, but my GNU/Linux system also has
		340	C<pthread_atfork> which is even faster).
		341
		342	The big advantage of this flag is that you can forget about fork (and
		343	forget about forgetting to tell libev about forking) when you use this
		344	flag.
		345
		346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
		347	environment variable.
		348
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		350
225	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
229	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
230		367
231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
232		369
233	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
234	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
235	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
237		379
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		381
240	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	384	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
		386	of shortcomings, such as silently dropping events in some hard-to-detect
		387	cases and requiring a system call per fd change, no fork support and bad
		388	support for dup.
244		389
245	While stopping and starting an I/O watcher in the same iteration will	390	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
247	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	394	very well if you register events for both fds.
250		395
251	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	398	(or space) is available.
254		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		413
257	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
258	was broken on all BSDs except NetBSD (usually it doesn't work with	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
259	anything but sockets and pipes, except on Darwin, where of course its	416	anything but sockets and pipes, except on Darwin, where of course it's
260	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
261	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
262	C<EVBACKEND_KQUEUE>).	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		420
		421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
263		424
264	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
266	course). While starting and stopping an I/O watcher does not cause an	427	course). While stopping, setting and starting an I/O watcher does never
267	extra syscall as with epoll, it still adds up to four event changes per	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
268	incident, so its best to avoid that.	429	two event changes per incident. Support for C<fork ()> is very bad and it
		430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
269		444
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		446
272	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
273		451
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		453
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
278		456
279	Please note that solaris ports can result in a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
282		473
283	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
284		475
285	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288		479
		480	It is definitely not recommended to use this flag.
		481
289	=back	482	=back
290		483
291	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
292	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
293	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
294	order of their flag values :)
295		487
296	The most typical usage is like this:	488	Example: This is the most typical usage.
297		489
298	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
300		492
301	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
302	environment settings to be taken into account:	494	environment settings to be taken into account:
303		495
304	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
305		497
306	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
307	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
308	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
309		502
310	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
311		504
312	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
313		506
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
318		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
319	Example: try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
320		517
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	519	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
324		521
325	=item ev_default_destroy ()	522	=item ev_default_destroy ()
326		523
327	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
328	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
329	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
330	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
331	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	530	for example).
		531
		532	Note that certain global state, such as signal state, will not be freed by
		533	this function, and related watchers (such as signal and child watchers)
		534	would need to be stopped manually.
		535
		536	In general it is not advisable to call this function except in the
		537	rare occasion where you really need to free e.g. the signal handling
		538	pipe fds. If you need dynamically allocated loops it is better to use
		539	C<ev_loop_new> and C<ev_loop_destroy>).
334		540
335	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
336		542
337	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
339		545
340	=item ev_default_fork ()	546	=item ev_default_fork ()
341		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
342	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
343	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
344	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
345	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
346		554
347	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
348	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
349	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
350		558
351	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
352	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
353	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
354		562
355	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
356		564
357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
358	without calling this function, so if you force one of those backends you
359	do not need to care.
360
361	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
362		566
363	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
		576
		577	=item unsigned int ev_loop_count (loop)
		578
		579	Returns the count of loop iterations for the loop, which is identical to
		580	the number of times libev did poll for new events. It starts at C<0> and
		581	happily wraps around with enough iterations.
		582
		583	This value can sometimes be useful as a generation counter of sorts (it
		584	"ticks" the number of loop iterations), as it roughly corresponds with
		585	C<ev_prepare> and C<ev_check> calls.
366		586
367	=item unsigned int ev_backend (loop)	587	=item unsigned int ev_backend (loop)
368		588
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	590	use.
…		…
373		593
374	Returns the current "event loop time", which is the time the event loop	594	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
376	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
377	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
378	event occuring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
379		611
380	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
381		613
382	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
…		…
386	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
387	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
388		620
389	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
390	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
391	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
392	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
393	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
394		627
395	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
396	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
397	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
398		632
399	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
400	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
401	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
402	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
403	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
406		644
407	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
408		646
409	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
410	- Queue prepare watchers and then call all outstanding watchers.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
		649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
411	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
412	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
414	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
415	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
418	- Queue all outstanding timers.	662	- Queue all expired timers.
419	- Queue all outstanding periodics.	663	- Queue all expired periodics.
420	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
421	- Queue all check watchers.	665	- Queue all check watchers.
422	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
423	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
427		672
428	Example: queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
429	anymore.	674	anymore.
430		675
431	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
434	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
435		680
436	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
437		682
438	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
439	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
442		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
443	=item ev_ref (loop)	692	=item ev_ref (loop)
444		693
445	=item ev_unref (loop)	694	=item ev_unref (loop)
446		695
447	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
448	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
449	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
450	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
451	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
452	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
453	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
454	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	708	libraries. Just remember to I<unref after start> and I<ref before stop>
		709	(but only if the watcher wasn't active before, or was active before,
		710	respectively).
457		711
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	713	running when nothing else is active.
460		714
461	struct dv_signal exitsig;	715	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	717	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	718	evf_unref (loop);
465		719
466	Example: for some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
467		721
468	ev_ref (myloop);	722	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
		724
		725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		726
		727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		728
		729	These advanced functions influence the time that libev will spend waiting
		730	for events. Both time intervals are by default C<0>, meaning that libev
		731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
		733
		734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		735	allows libev to delay invocation of I/O and timer/periodic callbacks
		736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
		738
		739	The idea is that sometimes your program runs just fast enough to handle
		740	one (or very few) event(s) per loop iteration. While this makes the
		741	program responsive, it also wastes a lot of CPU time to poll for new
		742	events, especially with backends like C<select ()> which have a high
		743	overhead for the actual polling but can deliver many events at once.
		744
		745	By setting a higher I<io collect interval> you allow libev to spend more
		746	time collecting I/O events, so you can handle more events per iteration,
		747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		748	C<ev_timer>) will be not affected. Setting this to a non-null value will
		749	introduce an additional C<ev_sleep ()> call into most loop iterations.
		750
		751	Likewise, by setting a higher I<timeout collect interval> you allow libev
		752	to spend more time collecting timeouts, at the expense of increased
		753	latency/jitter/inexactness (the watcher callback will be called
		754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		755	value will not introduce any overhead in libev.
		756
		757	Many (busy) programs can usually benefit by setting the I/O collect
		758	interval to a value near C<0.1> or so, which is often enough for
		759	interactive servers (of course not for games), likewise for timeouts. It
		760	usually doesn't make much sense to set it to a lower value than C<0.01>,
		761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
470		781
471	=back	782	=back
472		783
473		784
474	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
475		786
476	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
477	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
478	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
479		790
480	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
481	{	792	{
482	ev_io_stop (w);	793	ev_io_stop (w);
483	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
484	}	795	}
485		796
486	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
487	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
488	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
489	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
490	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
491	ev_loop (loop, 0);	802	ev_loop (loop, 0);
492		803
493	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
494	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
495	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
496		807
497	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
498	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
499	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
500	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
501	is readable and/or writable).	812	is readable and/or writable).
502		813
503	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
504	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	855	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		856
546	=item C<EV_CHILD>	857	=item C<EV_CHILD>
547		858
548	The pid specified in the C<ev_child> watcher has received a status change.	859	The pid specified in the C<ev_child> watcher has received a status change.
		860
		861	=item C<EV_STAT>
		862
		863	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		864
550	=item C<EV_IDLE>	865	=item C<EV_IDLE>
551		866
552	The C<ev_idle> watcher has determined that you have nothing better to do.	867	The C<ev_idle> watcher has determined that you have nothing better to do.
553		868
…		…
561	received events. Callbacks of both watcher types can start and stop as	876	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	877	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	879	C<ev_loop> from blocking).
565		880
		881	=item C<EV_EMBED>
		882
		883	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		884
		885	=item C<EV_FORK>
		886
		887	The event loop has been resumed in the child process after fork (see
		888	C<ev_fork>).
		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
566	=item C<EV_ERROR>	894	=item C<EV_ERROR>
567		895
568	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
571	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
572	with the watcher being stopped.	900	with the watcher being stopped.
573		901
574	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
575	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
576	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
577	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
578	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
579		908
580	=back	909	=back
581		910
582	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
583		912
…		…
599	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
600		929
601	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
602	int revents)>.	931	int revents)>.
603		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
604	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
605		940
606	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
607	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
608	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
610	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
611		946
612	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
613	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
614		949
		950	See C<ev_init>, above, for an example.
		951
615	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
616		953
617	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
618	calls into a single call. This is the most convinient method to initialise	955	calls into a single call. This is the most convenient method to initialise
619	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
620		961
621	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
622		963
623	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
624	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
625		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
		971
626	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
627		973
628	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher if active, and clears the pending status (whether
		975	the watcher was active or not).
		976
629	status. It is possible that stopped watchers are pending (for example,	977	It is possible that stopped watchers are pending - for example,
630	non-repeating timers are being stopped when they become pending), but	978	non-repeating timers are being stopped when they become pending - but
631	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	979	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
632	you want to free or reuse the memory used by the watcher it is therefore a	980	pending. If you want to free or reuse the memory used by the watcher it is
633	good idea to always call its C<ev_TYPE_stop> function.	981	therefore a good idea to always call its C<ev_TYPE_stop> function.
634		982
635	=item bool ev_is_active (ev_TYPE *watcher)	983	=item bool ev_is_active (ev_TYPE *watcher)
636		984
637	Returns a true value iff the watcher is active (i.e. it has been started	985	Returns a true value iff the watcher is active (i.e. it has been started
638	and not yet been stopped). As long as a watcher is active you must not modify	986	and not yet been stopped). As long as a watcher is active you must not modify
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	989	=item bool ev_is_pending (ev_TYPE *watcher)
642		990
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	991	Returns a true value iff the watcher is pending, (i.e. it has outstanding
644	events but its callback has not yet been invoked). As long as a watcher	992	events but its callback has not yet been invoked). As long as a watcher
645	is pending (but not active) you must not call an init function on it (but	993	is pending (but not active) you must not call an init function on it (but
646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	994	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	995	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		996	it).
648		997
649	=item callback = ev_cb (ev_TYPE *watcher)	998	=item callback ev_cb (ev_TYPE *watcher)
650		999
651	Returns the callback currently set on the watcher.	1000	Returns the callback currently set on the watcher.
652		1001
653	=item ev_cb_set (ev_TYPE *watcher, callback)	1002	=item ev_cb_set (ev_TYPE *watcher, callback)
654		1003
655	Change the callback. You can change the callback at virtually any time	1004	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	1005	(modulo threads).
657		1006
		1007	=item ev_set_priority (ev_TYPE *watcher, priority)
		1008
		1009	=item int ev_priority (ev_TYPE *watcher)
		1010
		1011	Set and query the priority of the watcher. The priority is a small
		1012	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1013	(default: C<-2>). Pending watchers with higher priority will be invoked
		1014	before watchers with lower priority, but priority will not keep watchers
		1015	from being executed (except for C<ev_idle> watchers).
		1016
		1017	This means that priorities are I<only> used for ordering callback
		1018	invocation after new events have been received. This is useful, for
		1019	example, to reduce latency after idling, or more often, to bind two
		1020	watchers on the same event and make sure one is called first.
		1021
		1022	If you need to suppress invocation when higher priority events are pending
		1023	you need to look at C<ev_idle> watchers, which provide this functionality.
		1024
		1025	You I<must not> change the priority of a watcher as long as it is active or
		1026	pending.
		1027
		1028	The default priority used by watchers when no priority has been set is
		1029	always C<0>, which is supposed to not be too high and not be too low :).
		1030
		1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1032	fine, as long as you do not mind that the priority value you query might
		1033	or might not have been adjusted to be within valid range.
		1034
		1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1036
		1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1038	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1039	can deal with that fact, as both are simply passed through to the
		1040	callback.
		1041
		1042	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1043
		1044	If the watcher is pending, this function clears its pending status and
		1045	returns its C<revents> bitset (as if its callback was invoked). If the
		1046	watcher isn't pending it does nothing and returns C<0>.
		1047
		1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1049	callback to be invoked, which can be accomplished with this function.
		1050
658	=back	1051	=back
659		1052
660		1053
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
662		1055
663	Each watcher has, by default, a member C<void *data> that you can change	1056	Each watcher has, by default, a member C<void *data> that you can change
664	and read at any time, libev will completely ignore it. This can be used	1057	and read at any time: libev will completely ignore it. This can be used
665	to associate arbitrary data with your watcher. If you need more data and	1058	to associate arbitrary data with your watcher. If you need more data and
666	don't want to allocate memory and store a pointer to it in that data	1059	don't want to allocate memory and store a pointer to it in that data
667	member, you can also "subclass" the watcher type and provide your own	1060	member, you can also "subclass" the watcher type and provide your own
668	data:	1061	data:
669		1062
670	struct my_io	1063	struct my_io
671	{	1064	{
672	struct ev_io io;	1065	struct ev_io io;
673	int otherfd;	1066	int otherfd;
674	void *somedata;	1067	void *somedata;
675	struct whatever *mostinteresting;	1068	struct whatever *mostinteresting;
676	}	1069	};
		1070
		1071	...
		1072	struct my_io w;
		1073	ev_io_init (&w.io, my_cb, fd, EV_READ);
677		1074
678	And since your callback will be called with a pointer to the watcher, you	1075	And since your callback will be called with a pointer to the watcher, you
679	can cast it back to your own type:	1076	can cast it back to your own type:
680		1077
681	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
682	{	1079	{
683	struct my_io *w = (struct my_io *)w_;	1080	struct my_io *w = (struct my_io *)w_;
684	...	1081	...
685	}	1082	}
686		1083
687	More interesting and less C-conformant ways of catsing your callback type	1084	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	1085	instead have been omitted.
		1086
		1087	Another common scenario is to use some data structure with multiple
		1088	embedded watchers:
		1089
		1090	struct my_biggy
		1091	{
		1092	int some_data;
		1093	ev_timer t1;
		1094	ev_timer t2;
		1095	}
		1096
		1097	In this case getting the pointer to C<my_biggy> is a bit more
		1098	complicated: Either you store the address of your C<my_biggy> struct
		1099	in the C<data> member of the watcher (for woozies), or you need to use
		1100	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1101	programmers):
		1102
		1103	#include <stddef.h>
		1104
		1105	static void
		1106	t1_cb (EV_P_ struct ev_timer *w, int revents)
		1107	{
		1108	struct my_biggy big = (struct my_biggy *
		1109	(((char *)w) - offsetof (struct my_biggy, t1));
		1110	}
		1111
		1112	static void
		1113	t2_cb (EV_P_ struct ev_timer *w, int revents)
		1114	{
		1115	struct my_biggy big = (struct my_biggy *
		1116	(((char *)w) - offsetof (struct my_biggy, t2));
		1117	}
689		1118
690		1119
691	=head1 WATCHER TYPES	1120	=head1 WATCHER TYPES
692		1121
693	This section describes each watcher in detail, but will not repeat	1122	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	1123	information given in the last section. Any initialisation/set macros,
		1124	functions and members specific to the watcher type are explained.
		1125
		1126	Members are additionally marked with either I<[read-only]>, meaning that,
		1127	while the watcher is active, you can look at the member and expect some
		1128	sensible content, but you must not modify it (you can modify it while the
		1129	watcher is stopped to your hearts content), or I<[read-write]>, which
		1130	means you can expect it to have some sensible content while the watcher
		1131	is active, but you can also modify it. Modifying it may not do something
		1132	sensible or take immediate effect (or do anything at all), but libev will
		1133	not crash or malfunction in any way.
695		1134
696		1135
697	=head2 C<ev_io> - is this file descriptor readable or writable?	1136	=head2 C<ev_io> - is this file descriptor readable or writable?
698		1137
699	I/O watchers check whether a file descriptor is readable or writable	1138	I/O watchers check whether a file descriptor is readable or writable
…		…
707	In general you can register as many read and/or write event watchers per	1146	In general you can register as many read and/or write event watchers per
708	fd as you want (as long as you don't confuse yourself). Setting all file	1147	fd as you want (as long as you don't confuse yourself). Setting all file
709	descriptors to non-blocking mode is also usually a good idea (but not	1148	descriptors to non-blocking mode is also usually a good idea (but not
710	required if you know what you are doing).	1149	required if you know what you are doing).
711		1150
712	You have to be careful with dup'ed file descriptors, though. Some backends	1151	If you cannot use non-blocking mode, then force the use of a
713	(the linux epoll backend is a notable example) cannot handle dup'ed file	1152	known-to-be-good backend (at the time of this writing, this includes only
714	descriptors correctly if you register interest in two or more fds pointing	1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
715	to the same underlying file/socket/etc. description (that is, they share
716	the same underlying "file open").
717
718	If you must do this, then force the use of a known-to-be-good backend
719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
720	C<EVBACKEND_POLL>).
721		1154
722	Another thing you have to watch out for is that it is quite easy to	1155	Another thing you have to watch out for is that it is quite easy to
723	receive "spurious" readyness notifications, that is your callback might	1156	receive "spurious" readiness notifications, that is your callback might
724	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
725	because there is no data. Not only are some backends known to create a	1158	because there is no data. Not only are some backends known to create a
726	lot of those (for example solaris ports), it is very easy to get into	1159	lot of those (for example Solaris ports), it is very easy to get into
727	this situation even with a relatively standard program structure. Thus	1160	this situation even with a relatively standard program structure. Thus
728	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1161	it is best to always use non-blocking I/O: An extra C<read>(2) returning
729	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1162	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		1163
731	If you cannot run the fd in non-blocking mode (for example you should not	1164	If you cannot run the fd in non-blocking mode (for example you should
732	play around with an Xlib connection), then you have to seperately re-test	1165	not play around with an Xlib connection), then you have to separately
733	wether a file descriptor is really ready with a known-to-be good interface	1166	re-test whether a file descriptor is really ready with a known-to-be good
734	such as poll (fortunately in our Xlib example, Xlib already does this on	1167	interface such as poll (fortunately in our Xlib example, Xlib already
735	its own, so its quite safe to use).	1168	does this on its own, so its quite safe to use). Some people additionally
		1169	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1170	indefinitely.
		1171
		1172	But really, best use non-blocking mode.
		1173
		1174	=head3 The special problem of disappearing file descriptors
		1175
		1176	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1177	descriptor (either due to calling C<close> explicitly or any other means,
		1178	such as C<dup2>). The reason is that you register interest in some file
		1179	descriptor, but when it goes away, the operating system will silently drop
		1180	this interest. If another file descriptor with the same number then is
		1181	registered with libev, there is no efficient way to see that this is, in
		1182	fact, a different file descriptor.
		1183
		1184	To avoid having to explicitly tell libev about such cases, libev follows
		1185	the following policy: Each time C<ev_io_set> is being called, libev
		1186	will assume that this is potentially a new file descriptor, otherwise
		1187	it is assumed that the file descriptor stays the same. That means that
		1188	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1189	descriptor even if the file descriptor number itself did not change.
		1190
		1191	This is how one would do it normally anyway, the important point is that
		1192	the libev application should not optimise around libev but should leave
		1193	optimisations to libev.
		1194
		1195	=head3 The special problem of dup'ed file descriptors
		1196
		1197	Some backends (e.g. epoll), cannot register events for file descriptors,
		1198	but only events for the underlying file descriptions. That means when you
		1199	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1200	events for them, only one file descriptor might actually receive events.
		1201
		1202	There is no workaround possible except not registering events
		1203	for potentially C<dup ()>'ed file descriptors, or to resort to
		1204	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1205
		1206	=head3 The special problem of fork
		1207
		1208	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1209	useless behaviour. Libev fully supports fork, but needs to be told about
		1210	it in the child.
		1211
		1212	To support fork in your programs, you either have to call
		1213	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1214	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1215	C<EVBACKEND_POLL>.
		1216
		1217	=head3 The special problem of SIGPIPE
		1218
		1219	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1220	when writing to a pipe whose other end has been closed, your program gets
		1221	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1222	this is sensible behaviour, for daemons, this is usually undesirable.
		1223
		1224	So when you encounter spurious, unexplained daemon exits, make sure you
		1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1226	somewhere, as that would have given you a big clue).
		1227
		1228
		1229	=head3 Watcher-Specific Functions
736		1230
737	=over 4	1231	=over 4
738		1232
739	=item ev_io_init (ev_io *, callback, int fd, int events)	1233	=item ev_io_init (ev_io *, callback, int fd, int events)
740		1234
741	=item ev_io_set (ev_io *, int fd, int events)	1235	=item ev_io_set (ev_io *, int fd, int events)
742		1236
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1237	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1238	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ | EV_WRITE> to receive the given events.	1239	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
		1240
		1241	=item int fd [read-only]
		1242
		1243	The file descriptor being watched.
		1244
		1245	=item int events [read-only]
		1246
		1247	The events being watched.
746		1248
747	=back	1249	=back
748		1250
		1251	=head3 Examples
		1252
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	1254	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	1255	attempt to read a whole line in the callback.
752		1256
753	static void	1257	static void
754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
755	{	1259	{
756	ev_io_stop (loop, w);	1260	ev_io_stop (loop, w);
757	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1261	.. read from stdin here (or from w->fd) and handle any I/O errors
758	}	1262	}
759		1263
760	...	1264	...
761	struct ev_loop *loop = ev_default_init (0);	1265	struct ev_loop *loop = ev_default_init (0);
762	struct ev_io stdin_readable;	1266	struct ev_io stdin_readable;
763	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
764	ev_io_start (loop, &stdin_readable);	1268	ev_io_start (loop, &stdin_readable);
765	ev_loop (loop, 0);	1269	ev_loop (loop, 0);
766		1270
767		1271
768	=head2 C<ev_timer> - relative and optionally repeating timeouts	1272	=head2 C<ev_timer> - relative and optionally repeating timeouts
769		1273
770	Timer watchers are simple relative timers that generate an event after a	1274	Timer watchers are simple relative timers that generate an event after a
771	given time, and optionally repeating in regular intervals after that.	1275	given time, and optionally repeating in regular intervals after that.
772		1276
773	The timers are based on real time, that is, if you register an event that	1277	The timers are based on real time, that is, if you register an event that
774	times out after an hour and you reset your system clock to last years	1278	times out after an hour and you reset your system clock to January last
775	time, it will still time out after (roughly) and hour. "Roughly" because	1279	year, it will still time out after (roughly) one hour. "Roughly" because
776	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the
777	monotonic clock option helps a lot here).	1281	monotonic clock option helps a lot here).
		1282
		1283	The callback is guaranteed to be invoked only I<after> its timeout has
		1284	passed, but if multiple timers become ready during the same loop iteration
		1285	then order of execution is undefined.
		1286
		1287	=head3 The special problem of time updates
		1288
		1289	Establishing the current time is a costly operation (it usually takes at
		1290	least two system calls): EV therefore updates its idea of the current
		1291	time only before and after C<ev_loop> collects new events, which causes a
		1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1293	lots of events in one iteration.
778		1294
779	The relative timeouts are calculated relative to the C<ev_now ()>	1295	The relative timeouts are calculated relative to the C<ev_now ()>
780	time. This is usually the right thing as this timestamp refers to the time	1296	time. This is usually the right thing as this timestamp refers to the time
781	of the event triggering whatever timeout you are modifying/starting. If	1297	of the event triggering whatever timeout you are modifying/starting. If
782	you suspect event processing to be delayed and you I<need> to base the timeout	1298	you suspect event processing to be delayed and you I<need> to base the
783	on the current time, use something like this to adjust for this:	1299	timeout on the current time, use something like this to adjust for this:
784		1300
785	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1301	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
786		1302
787	The callback is guarenteed to be invoked only when its timeout has passed,	1303	If the event loop is suspended for a long time, you can also force an
788	but if multiple timers become ready during the same loop iteration then	1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update
789	order of execution is undefined.	1305	()>.
		1306
		1307	=head3 Watcher-Specific Functions and Data Members
790		1308
791	=over 4	1309	=over 4
792		1310
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1312
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1313	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
796		1314
797	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1315	Configure the timer to trigger after C<after> seconds. If C<repeat>
798	C<0.>, then it will automatically be stopped. If it is positive, then the	1316	is C<0.>, then it will automatically be stopped once the timeout is
799	timer will automatically be configured to trigger again C<repeat> seconds	1317	reached. If it is positive, then the timer will automatically be
800	later, again, and again, until stopped manually.	1318	configured to trigger again C<repeat> seconds later, again, and again,
		1319	until stopped manually.
801		1320
802	The timer itself will do a best-effort at avoiding drift, that is, if you	1321	The timer itself will do a best-effort at avoiding drift, that is, if
803	configure a timer to trigger every 10 seconds, then it will trigger at	1322	you configure a timer to trigger every 10 seconds, then it will normally
804	exactly 10 second intervals. If, however, your program cannot keep up with	1323	trigger at exactly 10 second intervals. If, however, your program cannot
805	the timer (because it takes longer than those 10 seconds to do stuff) the	1324	keep up with the timer (because it takes longer than those 10 seconds to
806	timer will not fire more than once per event loop iteration.	1325	do stuff) the timer will not fire more than once per event loop iteration.
807		1326
808	=item ev_timer_again (loop)	1327	=item ev_timer_again (loop, ev_timer *)
809		1328
810	This will act as if the timer timed out and restart it again if it is	1329	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1330	repeating. The exact semantics are:
812		1331
		1332	If the timer is pending, its pending status is cleared.
		1333
813	If the timer is started but nonrepeating, stop it.	1334	If the timer is started but non-repeating, stop it (as if it timed out).
814		1335
815	If the timer is repeating, either start it if necessary (with the repeat	1336	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1337	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1338
818	This sounds a bit complicated, but here is a useful and typical	1339	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1340	example: Imagine you have a TCP connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1341	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1342	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1344	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1345	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1347	automatically restart it if need be.
		1348
		1349	That means you can ignore the C<after> value and C<ev_timer_start>
		1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1351
		1352	ev_timer_init (timer, callback, 0., 5.);
		1353	ev_timer_again (loop, timer);
		1354	...
		1355	timer->again = 17.;
		1356	ev_timer_again (loop, timer);
		1357	...
		1358	timer->again = 10.;
		1359	ev_timer_again (loop, timer);
		1360
		1361	This is more slightly efficient then stopping/starting the timer each time
		1362	you want to modify its timeout value.
		1363
		1364	Note, however, that it is often even more efficient to remember the
		1365	time of the last activity and let the timer time-out naturally. In the
		1366	callback, you then check whether the time-out is real, or, if there was
		1367	some activity, you reschedule the watcher to time-out in "last_activity +
		1368	timeout - ev_now ()" seconds.
		1369
		1370	=item ev_tstamp repeat [read-write]
		1371
		1372	The current C<repeat> value. Will be used each time the watcher times out
		1373	or C<ev_timer_again> is called, and determines the next timeout (if any),
		1374	which is also when any modifications are taken into account.
826		1375
827	=back	1376	=back
828		1377
		1378	=head3 Examples
		1379
829	Example: create a timer that fires after 60 seconds.	1380	Example: Create a timer that fires after 60 seconds.
830		1381
831	static void	1382	static void
832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
833	{	1384	{
834	.. one minute over, w is actually stopped right here	1385	.. one minute over, w is actually stopped right here
835	}	1386	}
836		1387
837	struct ev_timer mytimer;	1388	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1390	ev_timer_start (loop, &mytimer);
840		1391
841	Example: create a timeout timer that times out after 10 seconds of	1392	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1393	inactivity.
843		1394
844	static void	1395	static void
845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
846	{	1397	{
847	.. ten seconds without any activity	1398	.. ten seconds without any activity
848	}	1399	}
849		1400
850	struct ev_timer mytimer;	1401	struct ev_timer mytimer;
851	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
852	ev_timer_again (&mytimer); /* start timer */	1403	ev_timer_again (&mytimer); /* start timer */
853	ev_loop (loop, 0);	1404	ev_loop (loop, 0);
854		1405
855	// and in some piece of code that gets executed on any "activity":	1406	// and in some piece of code that gets executed on any "activity":
856	// reset the timeout to start ticking again at 10 seconds	1407	// reset the timeout to start ticking again at 10 seconds
857	ev_timer_again (&mytimer);	1408	ev_timer_again (&mytimer);
858		1409
859		1410
860	=head2 C<ev_periodic> - to cron or not to cron?	1411	=head2 C<ev_periodic> - to cron or not to cron?
861		1412
862	Periodic watchers are also timers of a kind, but they are very versatile	1413	Periodic watchers are also timers of a kind, but they are very versatile
863	(and unfortunately a bit complex).	1414	(and unfortunately a bit complex).
864		1415
865	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
866	but on wallclock time (absolute time). You can tell a periodic watcher	1417	but on wall clock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1418	to trigger after some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1420	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1421	clock to January of the previous year, then it will take more than year
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
871	roughly 10 seconds later and of course not if you reset your system time	1423	roughly 10 seconds later as it uses a relative timeout).
872	again).
873		1424
874	They can also be used to implement vastly more complex timers, such as	1425	C<ev_periodic>s can also be used to implement vastly more complex timers,
875	triggering an event on eahc midnight, local time.	1426	such as triggering an event on each "midnight, local time", or other
		1427	complicated rules.
876		1428
877	As with timers, the callback is guarenteed to be invoked only when the	1429	As with timers, the callback is guaranteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1430	time (C<at>) has passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1431	during the same loop iteration, then order of execution is undefined.
		1432
		1433	=head3 Watcher-Specific Functions and Data Members
880		1434
881	=over 4	1435	=over 4
882		1436
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1438
885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
886		1440
887	Lots of arguments, lets sort it out... There are basically three modes of	1441	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1442	operation, and we will explain them from simplest to most complex:
889		1443
890	=over 4	1444	=over 4
891		1445
892	=item * absolute timer (interval = reschedule_cb = 0)	1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1447
894	In this configuration the watcher triggers an event at the wallclock time	1448	In this configuration the watcher triggers an event after the wall clock
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1449	time C<at> has passed. It will not repeat and will not adjust when a time
896	that is, if it is to be run at January 1st 2011 then it will run when the	1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will
897	system time reaches or surpasses this time.	1451	only run when the system clock reaches or surpasses this time.
898		1452
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1454
901	In this mode the watcher will always be scheduled to time out at the next	1455	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1456	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1457	and then repeat, regardless of any time jumps.
904		1458
905	This can be used to create timers that do not drift with respect to system	1459	This can be used to create timers that do not drift with respect to the
906	time:	1460	system clock, for example, here is a C<ev_periodic> that triggers each
		1461	hour, on the hour:
907		1462
908	ev_periodic_set (&periodic, 0., 3600., 0);	1463	ev_periodic_set (&periodic, 0., 3600., 0);
909		1464
910	This doesn't mean there will always be 3600 seconds in between triggers,	1465	This doesn't mean there will always be 3600 seconds in between triggers,
911	but only that the the callback will be called when the system time shows a	1466	but only that the callback will be called when the system time shows a
912	full hour (UTC), or more correctly, when the system time is evenly divisible	1467	full hour (UTC), or more correctly, when the system time is evenly divisible
913	by 3600.	1468	by 3600.
914		1469
915	Another way to think about it (for the mathematically inclined) is that	1470	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1471	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1472	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1473
		1474	For numerical stability it is preferable that the C<at> value is near
		1475	C<ev_now ()> (the current time), but there is no range requirement for
		1476	this value, and in fact is often specified as zero.
		1477
		1478	Note also that there is an upper limit to how often a timer can fire (CPU
		1479	speed for example), so if C<interval> is very small then timing stability
		1480	will of course deteriorate. Libev itself tries to be exact to be about one
		1481	millisecond (if the OS supports it and the machine is fast enough).
		1482
919	=item * manual reschedule mode (reschedule_cb = callback)	1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1484
921	In this mode the values for C<interval> and C<at> are both being	1485	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1486	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1487	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1488	current time as second argument.
925		1489
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1491	ever, or make ANY event loop modifications whatsoever>.
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).
930		1492
		1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1495	only event loop modification you are allowed to do).
		1496
931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
932	ev_tstamp now)>, e.g.:	1498	*w, ev_tstamp now)>, e.g.:
933		1499
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
935	{	1501	{
936	return now + 60.;	1502	return now + 60.;
937	}	1503	}
…		…
939	It must return the next time to trigger, based on the passed time value	1505	It must return the next time to trigger, based on the passed time value
940	(that is, the lowest time value larger than to the second argument). It	1506	(that is, the lowest time value larger than to the second argument). It
941	will usually be called just before the callback will be triggered, but	1507	will usually be called just before the callback will be triggered, but
942	might be called at other times, too.	1508	might be called at other times, too.
943		1509
944	NOTE: I<< This callback must always return a time that is later than the	1510	NOTE: I<< This callback must always return a time that is higher than or
945	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1511	equal to the passed C<now> value >>.
946		1512
947	This can be used to create very complex timers, such as a timer that	1513	This can be used to create very complex timers, such as a timer that
948	triggers on each midnight, local time. To do this, you would calculate the	1514	triggers on "next midnight, local time". To do this, you would calculate the
949	next midnight after C<now> and return the timestamp value for this. How	1515	next midnight after C<now> and return the timestamp value for this. How
950	you do this is, again, up to you (but it is not trivial, which is the main	1516	you do this is, again, up to you (but it is not trivial, which is the main
951	reason I omitted it as an example).	1517	reason I omitted it as an example).
952		1518
953	=back	1519	=back
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1523	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1524	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1525	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1526	program when the crontabs have changed).
961		1527
		1528	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1529
		1530	When active, returns the absolute time that the watcher is supposed to
		1531	trigger next.
		1532
		1533	=item ev_tstamp offset [read-write]
		1534
		1535	When repeating, this contains the offset value, otherwise this is the
		1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1537
		1538	Can be modified any time, but changes only take effect when the periodic
		1539	timer fires or C<ev_periodic_again> is being called.
		1540
		1541	=item ev_tstamp interval [read-write]
		1542
		1543	The current interval value. Can be modified any time, but changes only
		1544	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1545	called.
		1546
		1547	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1548
		1549	The current reschedule callback, or C<0>, if this functionality is
		1550	switched off. Can be changed any time, but changes only take effect when
		1551	the periodic timer fires or C<ev_periodic_again> is being called.
		1552
962	=back	1553	=back
963		1554
		1555	=head3 Examples
		1556
964	Example: call a callback every hour, or, more precisely, whenever the	1557	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1558	system time is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1559	potentially a lot of jitter, but good long-term stability.
967		1560
968	static void	1561	static void
969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
970	{	1563	{
971	... its now a full hour (UTC, or TAI or whatever your clock follows)	1564	... its now a full hour (UTC, or TAI or whatever your clock follows)
972	}	1565	}
973		1566
974	struct ev_periodic hourly_tick;	1567	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1569	ev_periodic_start (loop, &hourly_tick);
977		1570
978	Example: the same as above, but use a reschedule callback to do it:	1571	Example: The same as above, but use a reschedule callback to do it:
979		1572
980	#include <math.h>	1573	#include <math.h>
981		1574
982	static ev_tstamp	1575	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
984	{	1577	{
985	return fmod (now, 3600.) + 3600.;	1578	return now + (3600. - fmod (now, 3600.));
986	}	1579	}
987		1580
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1582
990	Example: call a callback every hour, starting now:	1583	Example: Call a callback every hour, starting now:
991		1584
992	struct ev_periodic hourly_tick;	1585	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1586	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1587	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1588	ev_periodic_start (loop, &hourly_tick);
996		1589
997		1590
998	=head2 C<ev_signal> - signal me when a signal gets signalled!	1591	=head2 C<ev_signal> - signal me when a signal gets signalled!
999		1592
1000	Signal watchers will trigger an event when the process receives a specific	1593	Signal watchers will trigger an event when the process receives a specific
1001	signal one or more times. Even though signals are very asynchronous, libev	1594	signal one or more times. Even though signals are very asynchronous, libev
1002	will try it's best to deliver signals synchronously, i.e. as part of the	1595	will try it's best to deliver signals synchronously, i.e. as part of the
1003	normal event processing, like any other event.	1596	normal event processing, like any other event.
1004		1597
		1598	If you want signals asynchronously, just use C<sigaction> as you would
		1599	do without libev and forget about sharing the signal. You can even use
		1600	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1601
1005	You can configure as many watchers as you like per signal. Only when the	1602	You can configure as many watchers as you like per signal. Only when the
1006	first watcher gets started will libev actually register a signal watcher	1603	first watcher gets started will libev actually register a signal handler
1007	with the kernel (thus it coexists with your own signal handlers as long	1604	with the kernel (thus it coexists with your own signal handlers as long as
1008	as you don't register any with libev). Similarly, when the last signal	1605	you don't register any with libev for the same signal). Similarly, when
1009	watcher for a signal is stopped libev will reset the signal handler to	1606	the last signal watcher for a signal is stopped, libev will reset the
1010	SIG_DFL (regardless of what it was set to before).	1607	signal handler to SIG_DFL (regardless of what it was set to before).
		1608
		1609	If possible and supported, libev will install its handlers with
		1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1611	interrupted. If you have a problem with system calls getting interrupted by
		1612	signals you can block all signals in an C<ev_check> watcher and unblock
		1613	them in an C<ev_prepare> watcher.
		1614
		1615	=head3 Watcher-Specific Functions and Data Members
1011		1616
1012	=over 4	1617	=over 4
1013		1618
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1619	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1620
1016	=item ev_signal_set (ev_signal *, int signum)	1621	=item ev_signal_set (ev_signal *, int signum)
1017		1622
1018	Configures the watcher to trigger on the given signal number (usually one	1623	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1624	of the C<SIGxxx> constants).
1020		1625
		1626	=item int signum [read-only]
		1627
		1628	The signal the watcher watches out for.
		1629
1021	=back	1630	=back
1022		1631
		1632	=head3 Examples
		1633
		1634	Example: Try to exit cleanly on SIGINT.
		1635
		1636	static void
		1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1638	{
		1639	ev_unloop (loop, EVUNLOOP_ALL);
		1640	}
		1641
		1642	struct ev_signal signal_watcher;
		1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1644	ev_signal_start (loop, &signal_watcher);
		1645
1023		1646
1024	=head2 C<ev_child> - watch out for process status changes	1647	=head2 C<ev_child> - watch out for process status changes
1025		1648
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1649	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1650	some child status changes (most typically when a child of yours dies or
		1651	exits). It is permissible to install a child watcher I<after> the child
		1652	has been forked (which implies it might have already exited), as long
		1653	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1654	forking and then immediately registering a watcher for the child is fine,
		1655	but forking and registering a watcher a few event loop iterations later is
		1656	not.
		1657
		1658	Only the default event loop is capable of handling signals, and therefore
		1659	you can only register child watchers in the default event loop.
		1660
		1661	=head3 Process Interaction
		1662
		1663	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1664	initialised. This is necessary to guarantee proper behaviour even if
		1665	the first child watcher is started after the child exits. The occurrence
		1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1667	synchronously as part of the event loop processing. Libev always reaps all
		1668	children, even ones not watched.
		1669
		1670	=head3 Overriding the Built-In Processing
		1671
		1672	Libev offers no special support for overriding the built-in child
		1673	processing, but if your application collides with libev's default child
		1674	handler, you can override it easily by installing your own handler for
		1675	C<SIGCHLD> after initialising the default loop, and making sure the
		1676	default loop never gets destroyed. You are encouraged, however, to use an
		1677	event-based approach to child reaping and thus use libev's support for
		1678	that, so other libev users can use C<ev_child> watchers freely.
		1679
		1680	=head3 Stopping the Child Watcher
		1681
		1682	Currently, the child watcher never gets stopped, even when the
		1683	child terminates, so normally one needs to stop the watcher in the
		1684	callback. Future versions of libev might stop the watcher automatically
		1685	when a child exit is detected.
		1686
		1687	=head3 Watcher-Specific Functions and Data Members
1028		1688
1029	=over 4	1689	=over 4
1030		1690
1031	=item ev_child_init (ev_child *, callback, int pid)	1691	=item ev_child_init (ev_child *, callback, int pid, int trace)
1032		1692
1033	=item ev_child_set (ev_child *, int pid)	1693	=item ev_child_set (ev_child *, int pid, int trace)
1034		1694
1035	Configures the watcher to wait for status changes of process C<pid> (or	1695	Configures the watcher to wait for status changes of process C<pid> (or
1036	I<any> process if C<pid> is specified as C<0>). The callback can look	1696	I<any> process if C<pid> is specified as C<0>). The callback can look
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1697	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1698	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1699	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1700	process causing the status change. C<trace> must be either C<0> (only
		1701	activate the watcher when the process terminates) or C<1> (additionally
		1702	activate the watcher when the process is stopped or continued).
		1703
		1704	=item int pid [read-only]
		1705
		1706	The process id this watcher watches out for, or C<0>, meaning any process id.
		1707
		1708	=item int rpid [read-write]
		1709
		1710	The process id that detected a status change.
		1711
		1712	=item int rstatus [read-write]
		1713
		1714	The process exit/trace status caused by C<rpid> (see your systems
		1715	C<waitpid> and C<sys/wait.h> documentation for details).
1041		1716
1042	=back	1717	=back
1043		1718
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1719	=head3 Examples
1045		1720
		1721	Example: C<fork()> a new process and install a child handler to wait for
		1722	its completion.
		1723
		1724	ev_child cw;
		1725
1046	static void	1726	static void
1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1727	child_cb (EV_P_ struct ev_child *w, int revents)
1048	{	1728	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1729	ev_child_stop (EV_A_ w);
		1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1050	}	1731	}
1051		1732
1052	struct ev_signal signal_watcher;	1733	pid_t pid = fork ();
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1734
1054	ev_signal_start (loop, &sigint_cb);	1735	if (pid < 0)
		1736	// error
		1737	else if (pid == 0)
		1738	{
		1739	// the forked child executes here
		1740	exit (1);
		1741	}
		1742	else
		1743	{
		1744	ev_child_init (&cw, child_cb, pid, 0);
		1745	ev_child_start (EV_DEFAULT_ &cw);
		1746	}
		1747
		1748
		1749	=head2 C<ev_stat> - did the file attributes just change?
		1750
		1751	This watches a file system path for attribute changes. That is, it calls
		1752	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1753	compared to the last time, invoking the callback if it did.
		1754
		1755	The path does not need to exist: changing from "path exists" to "path does
		1756	not exist" is a status change like any other. The condition "path does
		1757	not exist" is signified by the C<st_nlink> field being zero (which is
		1758	otherwise always forced to be at least one) and all the other fields of
		1759	the stat buffer having unspecified contents.
		1760
		1761	The path I<should> be absolute and I<must not> end in a slash. If it is
		1762	relative and your working directory changes, the behaviour is undefined.
		1763
		1764	Since there is no standard kernel interface to do this, the portable
		1765	implementation simply calls C<stat (2)> regularly on the path to see if
		1766	it changed somehow. You can specify a recommended polling interval for
		1767	this case. If you specify a polling interval of C<0> (highly recommended!)
		1768	then a I<suitable, unspecified default> value will be used (which
		1769	you can expect to be around five seconds, although this might change
		1770	dynamically). Libev will also impose a minimum interval which is currently
		1771	around C<0.1>, but thats usually overkill.
		1772
		1773	This watcher type is not meant for massive numbers of stat watchers,
		1774	as even with OS-supported change notifications, this can be
		1775	resource-intensive.
		1776
		1777	At the time of this writing, the only OS-specific interface implemented
		1778	is the Linux inotify interface (implementing kqueue support is left as
		1779	an exercise for the reader. Note, however, that the author sees no way
		1780	of implementing C<ev_stat> semantics with kqueue).
		1781
		1782	=head3 ABI Issues (Largefile Support)
		1783
		1784	Libev by default (unless the user overrides this) uses the default
		1785	compilation environment, which means that on systems with large file
		1786	support disabled by default, you get the 32 bit version of the stat
		1787	structure. When using the library from programs that change the ABI to
		1788	use 64 bit file offsets the programs will fail. In that case you have to
		1789	compile libev with the same flags to get binary compatibility. This is
		1790	obviously the case with any flags that change the ABI, but the problem is
		1791	most noticeably disabled with ev_stat and large file support.
		1792
		1793	The solution for this is to lobby your distribution maker to make large
		1794	file interfaces available by default (as e.g. FreeBSD does) and not
		1795	optional. Libev cannot simply switch on large file support because it has
		1796	to exchange stat structures with application programs compiled using the
		1797	default compilation environment.
		1798
		1799	=head3 Inotify and Kqueue
		1800
		1801	When C<inotify (7)> support has been compiled into libev (generally
		1802	only available with Linux 2.6.25 or above due to bugs in earlier
		1803	implementations) and present at runtime, it will be used to speed up
		1804	change detection where possible. The inotify descriptor will be created
		1805	lazily when the first C<ev_stat> watcher is being started.
		1806
		1807	Inotify presence does not change the semantics of C<ev_stat> watchers
		1808	except that changes might be detected earlier, and in some cases, to avoid
		1809	making regular C<stat> calls. Even in the presence of inotify support
		1810	there are many cases where libev has to resort to regular C<stat> polling,
		1811	but as long as the path exists, libev usually gets away without polling.
		1812
		1813	There is no support for kqueue, as apparently it cannot be used to
		1814	implement this functionality, due to the requirement of having a file
		1815	descriptor open on the object at all times, and detecting renames, unlinks
		1816	etc. is difficult.
		1817
		1818	=head3 The special problem of stat time resolution
		1819
		1820	The C<stat ()> system call only supports full-second resolution portably, and
		1821	even on systems where the resolution is higher, most file systems still
		1822	only support whole seconds.
		1823
		1824	That means that, if the time is the only thing that changes, you can
		1825	easily miss updates: on the first update, C<ev_stat> detects a change and
		1826	calls your callback, which does something. When there is another update
		1827	within the same second, C<ev_stat> will be unable to detect unless the
		1828	stat data does change in other ways (e.g. file size).
		1829
		1830	The solution to this is to delay acting on a change for slightly more
		1831	than a second (or till slightly after the next full second boundary), using
		1832	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1833	ev_timer_again (loop, w)>).
		1834
		1835	The C<.02> offset is added to work around small timing inconsistencies
		1836	of some operating systems (where the second counter of the current time
		1837	might be be delayed. One such system is the Linux kernel, where a call to
		1838	C<gettimeofday> might return a timestamp with a full second later than
		1839	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1840	update file times then there will be a small window where the kernel uses
		1841	the previous second to update file times but libev might already execute
		1842	the timer callback).
		1843
		1844	=head3 Watcher-Specific Functions and Data Members
		1845
		1846	=over 4
		1847
		1848	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1849
		1850	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1851
		1852	Configures the watcher to wait for status changes of the given
		1853	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1854	be detected and should normally be specified as C<0> to let libev choose
		1855	a suitable value. The memory pointed to by C<path> must point to the same
		1856	path for as long as the watcher is active.
		1857
		1858	The callback will receive an C<EV_STAT> event when a change was detected,
		1859	relative to the attributes at the time the watcher was started (or the
		1860	last change was detected).
		1861
		1862	=item ev_stat_stat (loop, ev_stat *)
		1863
		1864	Updates the stat buffer immediately with new values. If you change the
		1865	watched path in your callback, you could call this function to avoid
		1866	detecting this change (while introducing a race condition if you are not
		1867	the only one changing the path). Can also be useful simply to find out the
		1868	new values.
		1869
		1870	=item ev_statdata attr [read-only]
		1871
		1872	The most-recently detected attributes of the file. Although the type is
		1873	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1874	suitable for your system, but you can only rely on the POSIX-standardised
		1875	members to be present. If the C<st_nlink> member is C<0>, then there was
		1876	some error while C<stat>ing the file.
		1877
		1878	=item ev_statdata prev [read-only]
		1879
		1880	The previous attributes of the file. The callback gets invoked whenever
		1881	C<prev> != C<attr>, or, more precisely, one or more of these members
		1882	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1883	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
		1884
		1885	=item ev_tstamp interval [read-only]
		1886
		1887	The specified interval.
		1888
		1889	=item const char *path [read-only]
		1890
		1891	The file system path that is being watched.
		1892
		1893	=back
		1894
		1895	=head3 Examples
		1896
		1897	Example: Watch C</etc/passwd> for attribute changes.
		1898
		1899	static void
		1900	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1901	{
		1902	/* /etc/passwd changed in some way */
		1903	if (w->attr.st_nlink)
		1904	{
		1905	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1906	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1907	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1908	}
		1909	else
		1910	/* you shalt not abuse printf for puts */
		1911	puts ("wow, /etc/passwd is not there, expect problems. "
		1912	"if this is windows, they already arrived\n");
		1913	}
		1914
		1915	...
		1916	ev_stat passwd;
		1917
		1918	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1919	ev_stat_start (loop, &passwd);
		1920
		1921	Example: Like above, but additionally use a one-second delay so we do not
		1922	miss updates (however, frequent updates will delay processing, too, so
		1923	one might do the work both on C<ev_stat> callback invocation I<and> on
		1924	C<ev_timer> callback invocation).
		1925
		1926	static ev_stat passwd;
		1927	static ev_timer timer;
		1928
		1929	static void
		1930	timer_cb (EV_P_ ev_timer *w, int revents)
		1931	{
		1932	ev_timer_stop (EV_A_ w);
		1933
		1934	/* now it's one second after the most recent passwd change */
		1935	}
		1936
		1937	static void
		1938	stat_cb (EV_P_ ev_stat *w, int revents)
		1939	{
		1940	/* reset the one-second timer */
		1941	ev_timer_again (EV_A_ &timer);
		1942	}
		1943
		1944	...
		1945	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1946	ev_stat_start (loop, &passwd);
		1947	ev_timer_init (&timer, timer_cb, 0., 1.02);
1055		1948
1056		1949
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1950	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1951
1059	Idle watchers trigger events when there are no other events are pending	1952	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1953	priority are pending (prepare, check and other idle watchers do not count
1061	as your process is busy handling sockets or timeouts (or even signals,	1954	as receiving "events").
1062	imagine) it will not be triggered. But when your process is idle all idle	1955
1063	watchers are being called again and again, once per event loop iteration -	1956	That is, as long as your process is busy handling sockets or timeouts
		1957	(or even signals, imagine) of the same or higher priority it will not be
		1958	triggered. But when your process is idle (or only lower-priority watchers
		1959	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1960	iteration - until stopped, that is, or your process receives more events
1065	busy.	1961	and becomes busy again with higher priority stuff.
1066		1962
1067	The most noteworthy effect is that as long as any idle watchers are	1963	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1964	active, the process will not block when waiting for new events.
1069		1965
1070	Apart from keeping your process non-blocking (which is a useful	1966	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1967	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1968	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1969	event loop has handled all outstanding events.
1074		1970
		1971	=head3 Watcher-Specific Functions and Data Members
		1972
1075	=over 4	1973	=over 4
1076		1974
1077	=item ev_idle_init (ev_signal *, callback)	1975	=item ev_idle_init (ev_signal *, callback)
1078		1976
1079	Initialises and configures the idle watcher - it has no parameters of any	1977	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1978	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1979	believe me.
1082		1980
1083	=back	1981	=back
1084		1982
		1983	=head3 Examples
		1984
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1985	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1986	callback, free it. Also, use no error checking, as usual.
1087		1987
1088	static void	1988	static void
1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1989	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090	{	1990	{
1091	free (w);	1991	free (w);
1092	// now do something you wanted to do when the program has	1992	// now do something you wanted to do when the program has
1093	// no longer asnything immediate to do.	1993	// no longer anything immediate to do.
1094	}	1994	}
1095		1995
1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1996	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1097	ev_idle_init (idle_watcher, idle_cb);	1997	ev_idle_init (idle_watcher, idle_cb);
1098	ev_idle_start (loop, idle_cb);	1998	ev_idle_start (loop, idle_cb);
1099		1999
1100		2000
1101	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1102		2002
1103	Prepare and check watchers are usually (but not always) used in tandem:	2003	Prepare and check watchers are usually (but not always) used in pairs:
1104	prepare watchers get invoked before the process blocks and check watchers	2004	prepare watchers get invoked before the process blocks and check watchers
1105	afterwards.	2005	afterwards.
1106		2006
1107	You I<must not> call C<ev_loop> or similar functions that enter	2007	You I<must not> call C<ev_loop> or similar functions that enter
1108	the current event loop from either C<ev_prepare> or C<ev_check>	2008	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1111	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2011	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1112	C<ev_check> so if you have one watcher of each kind they will always be	2012	C<ev_check> so if you have one watcher of each kind they will always be
1113	called in pairs bracketing the blocking call.	2013	called in pairs bracketing the blocking call.
1114		2014
1115	Their main purpose is to integrate other event mechanisms into libev and	2015	Their main purpose is to integrate other event mechanisms into libev and
1116	their use is somewhat advanced. This could be used, for example, to track	2016	their use is somewhat advanced. They could be used, for example, to track
1117	variable changes, implement your own watchers, integrate net-snmp or a	2017	variable changes, implement your own watchers, integrate net-snmp or a
1118	coroutine library and lots more. They are also occasionally useful if	2018	coroutine library and lots more. They are also occasionally useful if
1119	you cache some data and want to flush it before blocking (for example,	2019	you cache some data and want to flush it before blocking (for example,
1120	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2020	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1121	watcher).	2021	watcher).
1122		2022
1123	This is done by examining in each prepare call which file descriptors need	2023	This is done by examining in each prepare call which file descriptors
1124	to be watched by the other library, registering C<ev_io> watchers for	2024	need to be watched by the other library, registering C<ev_io> watchers
1125	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2025	for them and starting an C<ev_timer> watcher for any timeouts (many
1126	provide just this functionality). Then, in the check watcher you check for	2026	libraries provide exactly this functionality). Then, in the check watcher,
1127	any events that occured (by checking the pending status of all watchers	2027	you check for any events that occurred (by checking the pending status
1128	and stopping them) and call back into the library. The I/O and timer	2028	of all watchers and stopping them) and call back into the library. The
1129	callbacks will never actually be called (but must be valid nevertheless,	2029	I/O and timer callbacks will never actually be called (but must be valid
1130	because you never know, you know?).	2030	nevertheless, because you never know, you know?).
1131		2031
1132	As another example, the Perl Coro module uses these hooks to integrate	2032	As another example, the Perl Coro module uses these hooks to integrate
1133	coroutines into libev programs, by yielding to other active coroutines	2033	coroutines into libev programs, by yielding to other active coroutines
1134	during each prepare and only letting the process block if no coroutines	2034	during each prepare and only letting the process block if no coroutines
1135	are ready to run (it's actually more complicated: it only runs coroutines	2035	are ready to run (it's actually more complicated: it only runs coroutines
1136	with priority higher than or equal to the event loop and one coroutine	2036	with priority higher than or equal to the event loop and one coroutine
1137	of lower priority, but only once, using idle watchers to keep the event	2037	of lower priority, but only once, using idle watchers to keep the event
1138	loop from blocking if lower-priority coroutines are active, thus mapping	2038	loop from blocking if lower-priority coroutines are active, thus mapping
1139	low-priority coroutines to idle/background tasks).	2039	low-priority coroutines to idle/background tasks).
1140		2040
		2041	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2042	priority, to ensure that they are being run before any other watchers
		2043	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2044
		2045	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2046	activate ("feed") events into libev. While libev fully supports this, they
		2047	might get executed before other C<ev_check> watchers did their job. As
		2048	C<ev_check> watchers are often used to embed other (non-libev) event
		2049	loops those other event loops might be in an unusable state until their
		2050	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2051	others).
		2052
		2053	=head3 Watcher-Specific Functions and Data Members
		2054
1141	=over 4	2055	=over 4
1142		2056
1143	=item ev_prepare_init (ev_prepare *, callback)	2057	=item ev_prepare_init (ev_prepare *, callback)
1144		2058
1145	=item ev_check_init (ev_check *, callback)	2059	=item ev_check_init (ev_check *, callback)
1146		2060
1147	Initialises and configures the prepare or check watcher - they have no	2061	Initialises and configures the prepare or check watcher - they have no
1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2062	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1149	macros, but using them is utterly, utterly and completely pointless.	2063	macros, but using them is utterly, utterly, utterly and completely
		2064	pointless.
1150		2065
1151	=back	2066	=back
1152		2067
1153	Example: To include a library such as adns, you would add IO watchers	2068	=head3 Examples
1154	and a timeout watcher in a prepare handler, as required by libadns, and	2069
		2070	There are a number of principal ways to embed other event loops or modules
		2071	into libev. Here are some ideas on how to include libadns into libev
		2072	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2073	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2074	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2075	Glib event loop).
		2076
		2077	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1155	in a check watcher, destroy them and call into libadns. What follows is	2078	and in a check watcher, destroy them and call into libadns. What follows
1156	pseudo-code only of course:	2079	is pseudo-code only of course. This requires you to either use a low
		2080	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2081	the callbacks for the IO/timeout watchers might not have been called yet.
1157		2082
1158	static ev_io iow [nfd];	2083	static ev_io iow [nfd];
1159	static ev_timer tw;	2084	static ev_timer tw;
1160		2085
1161	static void	2086	static void
1162	io_cb (ev_loop *loop, ev_io *w, int revents)	2087	io_cb (ev_loop *loop, ev_io *w, int revents)
1163	{	2088	{
1164	// set the relevant poll flags
1165	// could also call adns_processreadable etc. here
1166	struct pollfd *fd = (struct pollfd *)w->data;
1167	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1168	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1169	}	2089	}
1170		2090
1171	// create io watchers for each fd and a timer before blocking	2091	// create io watchers for each fd and a timer before blocking
1172	static void	2092	static void
1173	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2093	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1174	{	2094	{
1175	int timeout = 3600000;truct pollfd fds [nfd];	2095	int timeout = 3600000;
		2096	struct pollfd fds [nfd];
1176	// actual code will need to loop here and realloc etc.	2097	// actual code will need to loop here and realloc etc.
1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2098	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1178		2099
1179	/* the callback is illegal, but won't be called as we stop during check */	2100	/* the callback is illegal, but won't be called as we stop during check */
1180	ev_timer_init (&tw, 0, timeout * 1e-3);	2101	ev_timer_init (&tw, 0, timeout * 1e-3);
1181	ev_timer_start (loop, &tw);	2102	ev_timer_start (loop, &tw);
1182		2103
1183	// create on ev_io per pollfd	2104	// create one ev_io per pollfd
1184	for (int i = 0; i < nfd; ++i)	2105	for (int i = 0; i < nfd; ++i)
1185	{	2106	{
1186	ev_io_init (iow + i, io_cb, fds [i].fd,	2107	ev_io_init (iow + i, io_cb, fds [i].fd,
1187	((fds [i].events & POLLIN ? EV_READ : 0)	2108	((fds [i].events & POLLIN ? EV_READ : 0)
1188	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2109	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1189		2110
1190	fds [i].revents = 0;	2111	fds [i].revents = 0;
1191	iow [i].data = fds + i;
1192	ev_io_start (loop, iow + i);	2112	ev_io_start (loop, iow + i);
1193	}	2113	}
1194	}	2114	}
1195		2115
1196	// stop all watchers after blocking	2116	// stop all watchers after blocking
1197	static void	2117	static void
1198	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2118	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1199	{	2119	{
1200	ev_timer_stop (loop, &tw);	2120	ev_timer_stop (loop, &tw);
1201		2121
1202	for (int i = 0; i < nfd; ++i)	2122	for (int i = 0; i < nfd; ++i)
		2123	{
		2124	// set the relevant poll flags
		2125	// could also call adns_processreadable etc. here
		2126	struct pollfd *fd = fds + i;
		2127	int revents = ev_clear_pending (iow + i);
		2128	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2129	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2130
		2131	// now stop the watcher
1203	ev_io_stop (loop, iow + i);	2132	ev_io_stop (loop, iow + i);
		2133	}
1204		2134
1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2135	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1206	}	2136	}
		2137
		2138	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2139	in the prepare watcher and would dispose of the check watcher.
		2140
		2141	Method 3: If the module to be embedded supports explicit event
		2142	notification (libadns does), you can also make use of the actual watcher
		2143	callbacks, and only destroy/create the watchers in the prepare watcher.
		2144
		2145	static void
		2146	timer_cb (EV_P_ ev_timer *w, int revents)
		2147	{
		2148	adns_state ads = (adns_state)w->data;
		2149	update_now (EV_A);
		2150
		2151	adns_processtimeouts (ads, &tv_now);
		2152	}
		2153
		2154	static void
		2155	io_cb (EV_P_ ev_io *w, int revents)
		2156	{
		2157	adns_state ads = (adns_state)w->data;
		2158	update_now (EV_A);
		2159
		2160	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2161	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2162	}
		2163
		2164	// do not ever call adns_afterpoll
		2165
		2166	Method 4: Do not use a prepare or check watcher because the module you
		2167	want to embed is not flexible enough to support it. Instead, you can
		2168	override their poll function. The drawback with this solution is that the
		2169	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2170	this approach, effectively embedding EV as a client into the horrible
		2171	libglib event loop.
		2172
		2173	static gint
		2174	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2175	{
		2176	int got_events = 0;
		2177
		2178	for (n = 0; n < nfds; ++n)
		2179	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2180
		2181	if (timeout >= 0)
		2182	// create/start timer
		2183
		2184	// poll
		2185	ev_loop (EV_A_ 0);
		2186
		2187	// stop timer again
		2188	if (timeout >= 0)
		2189	ev_timer_stop (EV_A_ &to);
		2190
		2191	// stop io watchers again - their callbacks should have set
		2192	for (n = 0; n < nfds; ++n)
		2193	ev_io_stop (EV_A_ iow [n]);
		2194
		2195	return got_events;
		2196	}
1207		2197
1208		2198
1209	=head2 C<ev_embed> - when one backend isn't enough...	2199	=head2 C<ev_embed> - when one backend isn't enough...
1210		2200
1211	This is a rather advanced watcher type that lets you embed one event loop	2201	This is a rather advanced watcher type that lets you embed one event loop
…		…
1217	prioritise I/O.	2207	prioritise I/O.
1218		2208
1219	As an example for a bug workaround, the kqueue backend might only support	2209	As an example for a bug workaround, the kqueue backend might only support
1220	sockets on some platform, so it is unusable as generic backend, but you	2210	sockets on some platform, so it is unusable as generic backend, but you
1221	still want to make use of it because you have many sockets and it scales	2211	still want to make use of it because you have many sockets and it scales
1222	so nicely. In this case, you would create a kqueue-based loop and embed it	2212	so nicely. In this case, you would create a kqueue-based loop and embed
1223	into your default loop (which might use e.g. poll). Overall operation will	2213	it into your default loop (which might use e.g. poll). Overall operation
1224	be a bit slower because first libev has to poll and then call kevent, but	2214	will be a bit slower because first libev has to call C<poll> and then
1225	at least you can use both at what they are best.	2215	C<kevent>, but at least you can use both mechanisms for what they are
		2216	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1226		2217
1227	As for prioritising I/O: rarely you have the case where some fds have	2218	As for prioritising I/O: under rare circumstances you have the case where
1228	to be watched and handled very quickly (with low latency), and even	2219	some fds have to be watched and handled very quickly (with low latency),
1229	priorities and idle watchers might have too much overhead. In this case	2220	and even priorities and idle watchers might have too much overhead. In
1230	you would put all the high priority stuff in one loop and all the rest in	2221	this case you would put all the high priority stuff in one loop and all
1231	a second one, and embed the second one in the first.	2222	the rest in a second one, and embed the second one in the first.
1232		2223
1233	As long as the watcher is active, the callback will be invoked every time	2224	As long as the watcher is active, the callback will be invoked every time
1234	there might be events pending in the embedded loop. The callback must then	2225	there might be events pending in the embedded loop. The callback must then
1235	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1236	their callbacks (you could also start an idle watcher to give the embedded	2227	their callbacks (you could also start an idle watcher to give the embedded
…		…
1244	interested in that.	2235	interested in that.
1245		2236
1246	Also, there have not currently been made special provisions for forking:	2237	Also, there have not currently been made special provisions for forking:
1247	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1248	but you will also have to stop and restart any C<ev_embed> watchers	2239	but you will also have to stop and restart any C<ev_embed> watchers
1249	yourself.	2240	yourself - but you can use a fork watcher to handle this automatically,
		2241	and future versions of libev might do just that.
1250		2242
1251	Unfortunately, not all backends are embeddable, only the ones returned by	2243	Unfortunately, not all backends are embeddable: only the ones returned by
1252	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1253	portable one.	2245	portable one.
1254		2246
1255	So when you want to use this feature you will always have to be prepared	2247	So when you want to use this feature you will always have to be prepared
1256	that you cannot get an embeddable loop. The recommended way to get around	2248	that you cannot get an embeddable loop. The recommended way to get around
1257	this is to have a separate variables for your embeddable loop, try to	2249	this is to have a separate variables for your embeddable loop, try to
1258	create it, and if that fails, use the normal loop for everything:	2250	create it, and if that fails, use the normal loop for everything.
1259		2251
1260	struct ev_loop *loop_hi = ev_default_init (0);	2252	=head3 C<ev_embed> and fork
1261	struct ev_loop *loop_lo = 0;
1262	struct ev_embed embed;
1263
1264	// see if there is a chance of getting one that works
1265	// (remember that a flags value of 0 means autodetection)
1266	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1267	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1268	: 0;
1269		2253
1270	// if we got one, then embed it, otherwise default to loop_hi	2254	While the C<ev_embed> watcher is running, forks in the embedding loop will
1271	if (loop_lo)	2255	automatically be applied to the embedded loop as well, so no special
1272	{	2256	fork handling is required in that case. When the watcher is not running,
1273	ev_embed_init (&embed, 0, loop_lo);	2257	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1274	ev_embed_start (loop_hi, &embed);	2258	as applicable.
1275	}	2259
1276	else	2260	=head3 Watcher-Specific Functions and Data Members
1277	loop_lo = loop_hi;
1278		2261
1279	=over 4	2262	=over 4
1280		2263
1281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2264	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1282		2265
…		…
1284		2267
1285	Configures the watcher to embed the given loop, which must be	2268	Configures the watcher to embed the given loop, which must be
1286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2269	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1287	invoked automatically, otherwise it is the responsibility of the callback	2270	invoked automatically, otherwise it is the responsibility of the callback
1288	to invoke it (it will continue to be called until the sweep has been done,	2271	to invoke it (it will continue to be called until the sweep has been done,
1289	if you do not want thta, you need to temporarily stop the embed watcher).	2272	if you do not want that, you need to temporarily stop the embed watcher).
1290		2273
1291	=item ev_embed_sweep (loop, ev_embed *)	2274	=item ev_embed_sweep (loop, ev_embed *)
1292		2275
1293	Make a single, non-blocking sweep over the embedded loop. This works	2276	Make a single, non-blocking sweep over the embedded loop. This works
1294	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2277	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1295	apropriate way for embedded loops.	2278	appropriate way for embedded loops.
		2279
		2280	=item struct ev_loop *other [read-only]
		2281
		2282	The embedded event loop.
1296		2283
1297	=back	2284	=back
1298		2285
		2286	=head3 Examples
		2287
		2288	Example: Try to get an embeddable event loop and embed it into the default
		2289	event loop. If that is not possible, use the default loop. The default
		2290	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2291	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2292	used).
		2293
		2294	struct ev_loop *loop_hi = ev_default_init (0);
		2295	struct ev_loop *loop_lo = 0;
		2296	struct ev_embed embed;
		2297
		2298	// see if there is a chance of getting one that works
		2299	// (remember that a flags value of 0 means autodetection)
		2300	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2301	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2302	: 0;
		2303
		2304	// if we got one, then embed it, otherwise default to loop_hi
		2305	if (loop_lo)
		2306	{
		2307	ev_embed_init (&embed, 0, loop_lo);
		2308	ev_embed_start (loop_hi, &embed);
		2309	}
		2310	else
		2311	loop_lo = loop_hi;
		2312
		2313	Example: Check if kqueue is available but not recommended and create
		2314	a kqueue backend for use with sockets (which usually work with any
		2315	kqueue implementation). Store the kqueue/socket-only event loop in
		2316	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2317
		2318	struct ev_loop *loop = ev_default_init (0);
		2319	struct ev_loop *loop_socket = 0;
		2320	struct ev_embed embed;
		2321
		2322	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2323	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2324	{
		2325	ev_embed_init (&embed, 0, loop_socket);
		2326	ev_embed_start (loop, &embed);
		2327	}
		2328
		2329	if (!loop_socket)
		2330	loop_socket = loop;
		2331
		2332	// now use loop_socket for all sockets, and loop for everything else
		2333
		2334
		2335	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2336
		2337	Fork watchers are called when a C<fork ()> was detected (usually because
		2338	whoever is a good citizen cared to tell libev about it by calling
		2339	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2340	event loop blocks next and before C<ev_check> watchers are being called,
		2341	and only in the child after the fork. If whoever good citizen calling
		2342	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2343	handlers will be invoked, too, of course.
		2344
		2345	=head3 Watcher-Specific Functions and Data Members
		2346
		2347	=over 4
		2348
		2349	=item ev_fork_init (ev_signal *, callback)
		2350
		2351	Initialises and configures the fork watcher - it has no parameters of any
		2352	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2353	believe me.
		2354
		2355	=back
		2356
		2357
		2358	=head2 C<ev_async> - how to wake up another event loop
		2359
		2360	In general, you cannot use an C<ev_loop> from multiple threads or other
		2361	asynchronous sources such as signal handlers (as opposed to multiple event
		2362	loops - those are of course safe to use in different threads).
		2363
		2364	Sometimes, however, you need to wake up another event loop you do not
		2365	control, for example because it belongs to another thread. This is what
		2366	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2367	can signal it by calling C<ev_async_send>, which is thread- and signal
		2368	safe.
		2369
		2370	This functionality is very similar to C<ev_signal> watchers, as signals,
		2371	too, are asynchronous in nature, and signals, too, will be compressed
		2372	(i.e. the number of callback invocations may be less than the number of
		2373	C<ev_async_sent> calls).
		2374
		2375	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2376	just the default loop.
		2377
		2378	=head3 Queueing
		2379
		2380	C<ev_async> does not support queueing of data in any way. The reason
		2381	is that the author does not know of a simple (or any) algorithm for a
		2382	multiple-writer-single-reader queue that works in all cases and doesn't
		2383	need elaborate support such as pthreads.
		2384
		2385	That means that if you want to queue data, you have to provide your own
		2386	queue. But at least I can tell you how to implement locking around your
		2387	queue:
		2388
		2389	=over 4
		2390
		2391	=item queueing from a signal handler context
		2392
		2393	To implement race-free queueing, you simply add to the queue in the signal
		2394	handler but you block the signal handler in the watcher callback. Here is
		2395	an example that does that for some fictitious SIGUSR1 handler:
		2396
		2397	static ev_async mysig;
		2398
		2399	static void
		2400	sigusr1_handler (void)
		2401	{
		2402	sometype data;
		2403
		2404	// no locking etc.
		2405	queue_put (data);
		2406	ev_async_send (EV_DEFAULT_ &mysig);
		2407	}
		2408
		2409	static void
		2410	mysig_cb (EV_P_ ev_async *w, int revents)
		2411	{
		2412	sometype data;
		2413	sigset_t block, prev;
		2414
		2415	sigemptyset (&block);
		2416	sigaddset (&block, SIGUSR1);
		2417	sigprocmask (SIG_BLOCK, &block, &prev);
		2418
		2419	while (queue_get (&data))
		2420	process (data);
		2421
		2422	if (sigismember (&prev, SIGUSR1)
		2423	sigprocmask (SIG_UNBLOCK, &block, 0);
		2424	}
		2425
		2426	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2427	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2428	either...).
		2429
		2430	=item queueing from a thread context
		2431
		2432	The strategy for threads is different, as you cannot (easily) block
		2433	threads but you can easily preempt them, so to queue safely you need to
		2434	employ a traditional mutex lock, such as in this pthread example:
		2435
		2436	static ev_async mysig;
		2437	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2438
		2439	static void
		2440	otherthread (void)
		2441	{
		2442	// only need to lock the actual queueing operation
		2443	pthread_mutex_lock (&mymutex);
		2444	queue_put (data);
		2445	pthread_mutex_unlock (&mymutex);
		2446
		2447	ev_async_send (EV_DEFAULT_ &mysig);
		2448	}
		2449
		2450	static void
		2451	mysig_cb (EV_P_ ev_async *w, int revents)
		2452	{
		2453	pthread_mutex_lock (&mymutex);
		2454
		2455	while (queue_get (&data))
		2456	process (data);
		2457
		2458	pthread_mutex_unlock (&mymutex);
		2459	}
		2460
		2461	=back
		2462
		2463
		2464	=head3 Watcher-Specific Functions and Data Members
		2465
		2466	=over 4
		2467
		2468	=item ev_async_init (ev_async *, callback)
		2469
		2470	Initialises and configures the async watcher - it has no parameters of any
		2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2472	trust me.
		2473
		2474	=item ev_async_send (loop, ev_async *)
		2475
		2476	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2477	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2478	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2480	section below on what exactly this means).
		2481
		2482	This call incurs the overhead of a system call only once per loop iteration,
		2483	so while the overhead might be noticeable, it doesn't apply to repeated
		2484	calls to C<ev_async_send>.
		2485
		2486	=item bool = ev_async_pending (ev_async *)
		2487
		2488	Returns a non-zero value when C<ev_async_send> has been called on the
		2489	watcher but the event has not yet been processed (or even noted) by the
		2490	event loop.
		2491
		2492	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2493	the loop iterates next and checks for the watcher to have become active,
		2494	it will reset the flag again. C<ev_async_pending> can be used to very
		2495	quickly check whether invoking the loop might be a good idea.
		2496
		2497	Not that this does I<not> check whether the watcher itself is pending, only
		2498	whether it has been requested to make this watcher pending.
		2499
		2500	=back
		2501
1299		2502
1300	=head1 OTHER FUNCTIONS	2503	=head1 OTHER FUNCTIONS
1301		2504
1302	There are some other functions of possible interest. Described. Here. Now.	2505	There are some other functions of possible interest. Described. Here. Now.
1303		2506
1304	=over 4	2507	=over 4
1305		2508
1306	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2509	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1307		2510
1308	This function combines a simple timer and an I/O watcher, calls your	2511	This function combines a simple timer and an I/O watcher, calls your
1309	callback on whichever event happens first and automatically stop both	2512	callback on whichever event happens first and automatically stops both
1310	watchers. This is useful if you want to wait for a single event on an fd	2513	watchers. This is useful if you want to wait for a single event on an fd
1311	or timeout without having to allocate/configure/start/stop/free one or	2514	or timeout without having to allocate/configure/start/stop/free one or
1312	more watchers yourself.	2515	more watchers yourself.
1313		2516
1314	If C<fd> is less than 0, then no I/O watcher will be started and events	2517	If C<fd> is less than 0, then no I/O watcher will be started and the
1315	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2518	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1316	C<events> set will be craeted and started.	2519	the given C<fd> and C<events> set will be created and started.
1317		2520
1318	If C<timeout> is less than 0, then no timeout watcher will be	2521	If C<timeout> is less than 0, then no timeout watcher will be
1319	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2522	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1320	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2523	repeat = 0) will be started. C<0> is a valid timeout.
1321	dubious value.
1322		2524
1323	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2525	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1324	passed an C<revents> set like normal event callbacks (a combination of	2526	passed an C<revents> set like normal event callbacks (a combination of
1325	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2527	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1326	value passed to C<ev_once>:	2528	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2529	a timeout and an io event at the same time - you probably should give io
		2530	events precedence.
1327		2531
		2532	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2533
1328	static void stdin_ready (int revents, void *arg)	2534	static void stdin_ready (int revents, void *arg)
1329	{	2535	{
1330	if (revents & EV_TIMEOUT)
1331	/* doh, nothing entered */;
1332	else if (revents & EV_READ)	2536	if (revents & EV_READ)
1333	/* stdin might have data for us, joy! */;	2537	/* stdin might have data for us, joy! */;
		2538	else if (revents & EV_TIMEOUT)
		2539	/* doh, nothing entered */;
1334	}	2540	}
1335		2541
1336	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1337		2543
1338	=item ev_feed_event (ev_loop *, watcher *, int revents)	2544	=item ev_feed_event (ev_loop *, watcher *, int revents)
1339		2545
1340	Feeds the given event set into the event loop, as if the specified event	2546	Feeds the given event set into the event loop, as if the specified event
1341	had happened for the specified watcher (which must be a pointer to an	2547	had happened for the specified watcher (which must be a pointer to an
…		…
1346	Feed an event on the given fd, as if a file descriptor backend detected	2552	Feed an event on the given fd, as if a file descriptor backend detected
1347	the given events it.	2553	the given events it.
1348		2554
1349	=item ev_feed_signal_event (ev_loop *loop, int signum)	2555	=item ev_feed_signal_event (ev_loop *loop, int signum)
1350		2556
1351	Feed an event as if the given signal occured (C<loop> must be the default	2557	Feed an event as if the given signal occurred (C<loop> must be the default
1352	loop!).	2558	loop!).
1353		2559
1354	=back	2560	=back
1355		2561
1356		2562
…		…
1372		2578
1373	=item * Priorities are not currently supported. Initialising priorities	2579	=item * Priorities are not currently supported. Initialising priorities
1374	will fail and all watchers will have the same priority, even though there	2580	will fail and all watchers will have the same priority, even though there
1375	is an ev_pri field.	2581	is an ev_pri field.
1376		2582
		2583	=item * In libevent, the last base created gets the signals, in libev, the
		2584	first base created (== the default loop) gets the signals.
		2585
1377	=item * Other members are not supported.	2586	=item * Other members are not supported.
1378		2587
1379	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2588	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1380	to use the libev header file and library.	2589	to use the libev header file and library.
1381		2590
1382	=back	2591	=back
1383		2592
1384	=head1 C++ SUPPORT	2593	=head1 C++ SUPPORT
1385		2594
1386	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2595	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1387	you to use some convinience methods to start/stop watchers and also change	2596	you to use some convenience methods to start/stop watchers and also change
1388	the callback model to a model using method callbacks on objects.	2597	the callback model to a model using method callbacks on objects.
1389		2598
1390	To use it,	2599	To use it,
1391		2600
1392	#include <ev++.h>	2601	#include <ev++.h>
1393		2602
1394	(it is not installed by default). This automatically includes F<ev.h>	2603	This automatically includes F<ev.h> and puts all of its definitions (many
1395	and puts all of its definitions (many of them macros) into the global	2604	of them macros) into the global namespace. All C++ specific things are
1396	namespace. All C++ specific things are put into the C<ev> namespace.	2605	put into the C<ev> namespace. It should support all the same embedding
		2606	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1397		2607
1398	It should support all the same embedding options as F<ev.h>, most notably	2608	Care has been taken to keep the overhead low. The only data member the C++
1399	C<EV_MULTIPLICITY>.	2609	classes add (compared to plain C-style watchers) is the event loop pointer
		2610	that the watcher is associated with (or no additional members at all if
		2611	you disable C<EV_MULTIPLICITY> when embedding libev).
		2612
		2613	Currently, functions, and static and non-static member functions can be
		2614	used as callbacks. Other types should be easy to add as long as they only
		2615	need one additional pointer for context. If you need support for other
		2616	types of functors please contact the author (preferably after implementing
		2617	it).
1400		2618
1401	Here is a list of things available in the C<ev> namespace:	2619	Here is a list of things available in the C<ev> namespace:
1402		2620
1403	=over 4	2621	=over 4
1404		2622
…		…
1420		2638
1421	All of those classes have these methods:	2639	All of those classes have these methods:
1422		2640
1423	=over 4	2641	=over 4
1424		2642
1425	=item ev::TYPE::TYPE (object *, object::method *)	2643	=item ev::TYPE::TYPE ()
1426		2644
1427	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2645	=item ev::TYPE::TYPE (struct ev_loop *)
1428		2646
1429	=item ev::TYPE::~TYPE	2647	=item ev::TYPE::~TYPE
1430		2648
1431	The constructor takes a pointer to an object and a method pointer to	2649	The constructor (optionally) takes an event loop to associate the watcher
1432	the event handler callback to call in this class. The constructor calls	2650	with. If it is omitted, it will use C<EV_DEFAULT>.
1433	C<ev_init> for you, which means you have to call the C<set> method	2651
1434	before starting it. If you do not specify a loop then the constructor	2652	The constructor calls C<ev_init> for you, which means you have to call the
1435	automatically associates the default loop with this watcher.	2653	C<set> method before starting it.
		2654
		2655	It will not set a callback, however: You have to call the templated C<set>
		2656	method to set a callback before you can start the watcher.
		2657
		2658	(The reason why you have to use a method is a limitation in C++ which does
		2659	not allow explicit template arguments for constructors).
1436		2660
1437	The destructor automatically stops the watcher if it is active.	2661	The destructor automatically stops the watcher if it is active.
		2662
		2663	=item w->set<class, &class::method> (object *)
		2664
		2665	This method sets the callback method to call. The method has to have a
		2666	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2667	first argument and the C<revents> as second. The object must be given as
		2668	parameter and is stored in the C<data> member of the watcher.
		2669
		2670	This method synthesizes efficient thunking code to call your method from
		2671	the C callback that libev requires. If your compiler can inline your
		2672	callback (i.e. it is visible to it at the place of the C<set> call and
		2673	your compiler is good :), then the method will be fully inlined into the
		2674	thunking function, making it as fast as a direct C callback.
		2675
		2676	Example: simple class declaration and watcher initialisation
		2677
		2678	struct myclass
		2679	{
		2680	void io_cb (ev::io &w, int revents) { }
		2681	}
		2682
		2683	myclass obj;
		2684	ev::io iow;
		2685	iow.set <myclass, &myclass::io_cb> (&obj);
		2686
		2687	=item w->set<function> (void *data = 0)
		2688
		2689	Also sets a callback, but uses a static method or plain function as
		2690	callback. The optional C<data> argument will be stored in the watcher's
		2691	C<data> member and is free for you to use.
		2692
		2693	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2694
		2695	See the method-C<set> above for more details.
		2696
		2697	Example: Use a plain function as callback.
		2698
		2699	static void io_cb (ev::io &w, int revents) { }
		2700	iow.set <io_cb> ();
1438		2701
1439	=item w->set (struct ev_loop *)	2702	=item w->set (struct ev_loop *)
1440		2703
1441	Associates a different C<struct ev_loop> with this watcher. You can only	2704	Associates a different C<struct ev_loop> with this watcher. You can only
1442	do this when the watcher is inactive (and not pending either).	2705	do this when the watcher is inactive (and not pending either).
1443		2706
1444	=item w->set ([args])	2707	=item w->set ([arguments])
1445		2708
1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2709	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1447	called at least once. Unlike the C counterpart, an active watcher gets	2710	called at least once. Unlike the C counterpart, an active watcher gets
1448	automatically stopped and restarted.	2711	automatically stopped and restarted when reconfiguring it with this
		2712	method.
1449		2713
1450	=item w->start ()	2714	=item w->start ()
1451		2715
1452	Starts the watcher. Note that there is no C<loop> argument as the	2716	Starts the watcher. Note that there is no C<loop> argument, as the
1453	constructor already takes the loop.	2717	constructor already stores the event loop.
1454		2718
1455	=item w->stop ()	2719	=item w->stop ()
1456		2720
1457	Stops the watcher if it is active. Again, no C<loop> argument.	2721	Stops the watcher if it is active. Again, no C<loop> argument.
1458		2722
1459	=item w->again () C<ev::timer>, C<ev::periodic> only	2723	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1460		2724
1461	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2725	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1462	C<ev_TYPE_again> function.	2726	C<ev_TYPE_again> function.
1463		2727
1464	=item w->sweep () C<ev::embed> only	2728	=item w->sweep () (C<ev::embed> only)
1465		2729
1466	Invokes C<ev_embed_sweep>.	2730	Invokes C<ev_embed_sweep>.
		2731
		2732	=item w->update () (C<ev::stat> only)
		2733
		2734	Invokes C<ev_stat_stat>.
1467		2735
1468	=back	2736	=back
1469		2737
1470	=back	2738	=back
1471		2739
1472	Example: Define a class with an IO and idle watcher, start one of them in	2740	Example: Define a class with an IO and idle watcher, start one of them in
1473	the constructor.	2741	the constructor.
1474		2742
1475	class myclass	2743	class myclass
1476	{	2744	{
1477	ev_io io; void io_cb (ev::io &w, int revents);	2745	ev::io io ; void io_cb (ev::io &w, int revents);
1478	ev_idle idle void idle_cb (ev::idle &w, int revents);	2746	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1479		2747
1480	myclass ();	2748	myclass (int fd)
1481	}	2749	{
		2750	io .set <myclass, &myclass::io_cb > (this);
		2751	idle.set <myclass, &myclass::idle_cb> (this);
1482		2752
1483	myclass::myclass (int fd)
1484	: io (this, &myclass::io_cb),
1485	idle (this, &myclass::idle_cb)
1486	{
1487	io.start (fd, ev::READ);	2753	io.start (fd, ev::READ);
		2754	}
		2755	};
		2756
		2757
		2758	=head1 OTHER LANGUAGE BINDINGS
		2759
		2760	Libev does not offer other language bindings itself, but bindings for a
		2761	number of languages exist in the form of third-party packages. If you know
		2762	any interesting language binding in addition to the ones listed here, drop
		2763	me a note.
		2764
		2765	=over 4
		2766
		2767	=item Perl
		2768
		2769	The EV module implements the full libev API and is actually used to test
		2770	libev. EV is developed together with libev. Apart from the EV core module,
		2771	there are additional modules that implement libev-compatible interfaces
		2772	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2773	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2774	and C<EV::Glib>).
		2775
		2776	It can be found and installed via CPAN, its homepage is at
		2777	L<http://software.schmorp.de/pkg/EV>.
		2778
		2779	=item Python
		2780
		2781	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2782	seems to be quite complete and well-documented. Note, however, that the
		2783	patch they require for libev is outright dangerous as it breaks the ABI
		2784	for everybody else, and therefore, should never be applied in an installed
		2785	libev (if python requires an incompatible ABI then it needs to embed
		2786	libev).
		2787
		2788	=item Ruby
		2789
		2790	Tony Arcieri has written a ruby extension that offers access to a subset
		2791	of the libev API and adds file handle abstractions, asynchronous DNS and
		2792	more on top of it. It can be found via gem servers. Its homepage is at
		2793	L<http://rev.rubyforge.org/>.
		2794
		2795	=item D
		2796
		2797	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2799
		2800	=back
		2801
		2802
		2803	=head1 MACRO MAGIC
		2804
		2805	Libev can be compiled with a variety of options, the most fundamental
		2806	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2807	functions and callbacks have an initial C<struct ev_loop *> argument.
		2808
		2809	To make it easier to write programs that cope with either variant, the
		2810	following macros are defined:
		2811
		2812	=over 4
		2813
		2814	=item C<EV_A>, C<EV_A_>
		2815
		2816	This provides the loop I<argument> for functions, if one is required ("ev
		2817	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2818	C<EV_A_> is used when other arguments are following. Example:
		2819
		2820	ev_unref (EV_A);
		2821	ev_timer_add (EV_A_ watcher);
		2822	ev_loop (EV_A_ 0);
		2823
		2824	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2825	which is often provided by the following macro.
		2826
		2827	=item C<EV_P>, C<EV_P_>
		2828
		2829	This provides the loop I<parameter> for functions, if one is required ("ev
		2830	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2831	C<EV_P_> is used when other parameters are following. Example:
		2832
		2833	// this is how ev_unref is being declared
		2834	static void ev_unref (EV_P);
		2835
		2836	// this is how you can declare your typical callback
		2837	static void cb (EV_P_ ev_timer *w, int revents)
		2838
		2839	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2840	suitable for use with C<EV_A>.
		2841
		2842	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2843
		2844	Similar to the other two macros, this gives you the value of the default
		2845	loop, if multiple loops are supported ("ev loop default").
		2846
		2847	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2848
		2849	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2850	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2851	is undefined when the default loop has not been initialised by a previous
		2852	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2853
		2854	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2855	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2856
		2857	=back
		2858
		2859	Example: Declare and initialise a check watcher, utilising the above
		2860	macros so it will work regardless of whether multiple loops are supported
		2861	or not.
		2862
		2863	static void
		2864	check_cb (EV_P_ ev_timer *w, int revents)
		2865	{
		2866	ev_check_stop (EV_A_ w);
1488	}	2867	}
		2868
		2869	ev_check check;
		2870	ev_check_init (&check, check_cb);
		2871	ev_check_start (EV_DEFAULT_ &check);
		2872	ev_loop (EV_DEFAULT_ 0);
1489		2873
1490	=head1 EMBEDDING	2874	=head1 EMBEDDING
1491		2875
1492	Libev can (and often is) directly embedded into host	2876	Libev can (and often is) directly embedded into host
1493	applications. Examples of applications that embed it include the Deliantra	2877	applications. Examples of applications that embed it include the Deliantra
1494	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2878	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1495	and rxvt-unicode.	2879	and rxvt-unicode.
1496		2880
1497	The goal is to enable you to just copy the neecssary files into your	2881	The goal is to enable you to just copy the necessary files into your
1498	source directory without having to change even a single line in them, so	2882	source directory without having to change even a single line in them, so
1499	you can easily upgrade by simply copying (or having a checked-out copy of	2883	you can easily upgrade by simply copying (or having a checked-out copy of
1500	libev somewhere in your source tree).	2884	libev somewhere in your source tree).
1501		2885
1502	=head2 FILESETS	2886	=head2 FILESETS
1503		2887
1504	Depending on what features you need you need to include one or more sets of files	2888	Depending on what features you need you need to include one or more sets of files
1505	in your app.	2889	in your application.
1506		2890
1507	=head3 CORE EVENT LOOP	2891	=head3 CORE EVENT LOOP
1508		2892
1509	To include only the libev core (all the C<ev_*> functions), with manual	2893	To include only the libev core (all the C<ev_*> functions), with manual
1510	configuration (no autoconf):	2894	configuration (no autoconf):
1511		2895
1512	#define EV_STANDALONE 1	2896	#define EV_STANDALONE 1
1513	#include "ev.c"	2897	#include "ev.c"
1514		2898
1515	This will automatically include F<ev.h>, too, and should be done in a	2899	This will automatically include F<ev.h>, too, and should be done in a
1516	single C source file only to provide the function implementations. To use	2900	single C source file only to provide the function implementations. To use
1517	it, do the same for F<ev.h> in all files wishing to use this API (best	2901	it, do the same for F<ev.h> in all files wishing to use this API (best
1518	done by writing a wrapper around F<ev.h> that you can include instead and	2902	done by writing a wrapper around F<ev.h> that you can include instead and
1519	where you can put other configuration options):	2903	where you can put other configuration options):
1520		2904
1521	#define EV_STANDALONE 1	2905	#define EV_STANDALONE 1
1522	#include "ev.h"	2906	#include "ev.h"
1523		2907
1524	Both header files and implementation files can be compiled with a C++	2908	Both header files and implementation files can be compiled with a C++
1525	compiler (at least, thats a stated goal, and breakage will be treated	2909	compiler (at least, thats a stated goal, and breakage will be treated
1526	as a bug).	2910	as a bug).
1527		2911
1528	You need the following files in your source tree, or in a directory	2912	You need the following files in your source tree, or in a directory
1529	in your include path (e.g. in libev/ when using -Ilibev):	2913	in your include path (e.g. in libev/ when using -Ilibev):
1530		2914
1531	ev.h	2915	ev.h
1532	ev.c	2916	ev.c
1533	ev_vars.h	2917	ev_vars.h
1534	ev_wrap.h	2918	ev_wrap.h
1535		2919
1536	ev_win32.c required on win32 platforms only	2920	ev_win32.c required on win32 platforms only
1537		2921
1538	ev_select.c only when select backend is enabled (which is by default)	2922	ev_select.c only when select backend is enabled (which is enabled by default)
1539	ev_poll.c only when poll backend is enabled (disabled by default)	2923	ev_poll.c only when poll backend is enabled (disabled by default)
1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2924	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2925	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542	ev_port.c only when the solaris port backend is enabled (disabled by default)	2926	ev_port.c only when the solaris port backend is enabled (disabled by default)
1543		2927
1544	F<ev.c> includes the backend files directly when enabled, so you only need	2928	F<ev.c> includes the backend files directly when enabled, so you only need
1545	to compile this single file.	2929	to compile this single file.
1546		2930
1547	=head3 LIBEVENT COMPATIBILITY API	2931	=head3 LIBEVENT COMPATIBILITY API
1548		2932
1549	To include the libevent compatibility API, also include:	2933	To include the libevent compatibility API, also include:
1550		2934
1551	#include "event.c"	2935	#include "event.c"
1552		2936
1553	in the file including F<ev.c>, and:	2937	in the file including F<ev.c>, and:
1554		2938
1555	#include "event.h"	2939	#include "event.h"
1556		2940
1557	in the files that want to use the libevent API. This also includes F<ev.h>.	2941	in the files that want to use the libevent API. This also includes F<ev.h>.
1558		2942
1559	You need the following additional files for this:	2943	You need the following additional files for this:
1560		2944
1561	event.h	2945	event.h
1562	event.c	2946	event.c
1563		2947
1564	=head3 AUTOCONF SUPPORT	2948	=head3 AUTOCONF SUPPORT
1565		2949
1566	Instead of using C<EV_STANDALONE=1> and providing your config in	2950	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1567	whatever way you want, you can also C<m4_include([libev.m4])> in your	2951	whatever way you want, you can also C<m4_include([libev.m4])> in your
1568	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2952	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1569	include F<config.h> and configure itself accordingly.	2953	include F<config.h> and configure itself accordingly.
1570		2954
1571	For this of course you need the m4 file:	2955	For this of course you need the m4 file:
1572		2956
1573	libev.m4	2957	libev.m4
1574		2958
1575	=head2 PREPROCESSOR SYMBOLS/MACROS	2959	=head2 PREPROCESSOR SYMBOLS/MACROS
1576		2960
1577	Libev can be configured via a variety of preprocessor symbols you have to define	2961	Libev can be configured via a variety of preprocessor symbols you have to
1578	before including any of its files. The default is not to build for multiplicity	2962	define before including any of its files. The default in the absence of
1579	and only include the select backend.	2963	autoconf is documented for every option.
1580		2964
1581	=over 4	2965	=over 4
1582		2966
1583	=item EV_STANDALONE	2967	=item EV_STANDALONE
1584		2968
…		…
1589	F<event.h> that are not directly supported by the libev core alone.	2973	F<event.h> that are not directly supported by the libev core alone.
1590		2974
1591	=item EV_USE_MONOTONIC	2975	=item EV_USE_MONOTONIC
1592		2976
1593	If defined to be C<1>, libev will try to detect the availability of the	2977	If defined to be C<1>, libev will try to detect the availability of the
1594	monotonic clock option at both compiletime and runtime. Otherwise no use	2978	monotonic clock option at both compile time and runtime. Otherwise no use
1595	of the monotonic clock option will be attempted. If you enable this, you	2979	of the monotonic clock option will be attempted. If you enable this, you
1596	usually have to link against librt or something similar. Enabling it when	2980	usually have to link against librt or something similar. Enabling it when
1597	the functionality isn't available is safe, though, althoguh you have	2981	the functionality isn't available is safe, though, although you have
1598	to make sure you link against any libraries where the C<clock_gettime>	2982	to make sure you link against any libraries where the C<clock_gettime>
1599	function is hiding in (often F<-lrt>).	2983	function is hiding in (often F<-lrt>).
1600		2984
1601	=item EV_USE_REALTIME	2985	=item EV_USE_REALTIME
1602		2986
1603	If defined to be C<1>, libev will try to detect the availability of the	2987	If defined to be C<1>, libev will try to detect the availability of the
1604	realtime clock option at compiletime (and assume its availability at	2988	real-time clock option at compile time (and assume its availability at
1605	runtime if successful). Otherwise no use of the realtime clock option will	2989	runtime if successful). Otherwise no use of the real-time clock option will
1606	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2990	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1607	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2991	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1608	in the description of C<EV_USE_MONOTONIC>, though.	2992	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2993
		2994	=item EV_USE_NANOSLEEP
		2995
		2996	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2997	and will use it for delays. Otherwise it will use C<select ()>.
		2998
		2999	=item EV_USE_EVENTFD
		3000
		3001	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3002	available and will probe for kernel support at runtime. This will improve
		3003	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3004	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3005	2.7 or newer, otherwise disabled.
1609		3006
1610	=item EV_USE_SELECT	3007	=item EV_USE_SELECT
1611		3008
1612	If undefined or defined to be C<1>, libev will compile in support for the	3009	If undefined or defined to be C<1>, libev will compile in support for the
1613	C<select>(2) backend. No attempt at autodetection will be done: if no	3010	C<select>(2) backend. No attempt at auto-detection will be done: if no
1614	other method takes over, select will be it. Otherwise the select backend	3011	other method takes over, select will be it. Otherwise the select backend
1615	will not be compiled in.	3012	will not be compiled in.
1616		3013
1617	=item EV_SELECT_USE_FD_SET	3014	=item EV_SELECT_USE_FD_SET
1618		3015
1619	If defined to C<1>, then the select backend will use the system C<fd_set>	3016	If defined to C<1>, then the select backend will use the system C<fd_set>
1620	structure. This is useful if libev doesn't compile due to a missing	3017	structure. This is useful if libev doesn't compile due to a missing
1621	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3018	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
1622	exotic systems. This usually limits the range of file descriptors to some	3019	exotic systems. This usually limits the range of file descriptors to some
1623	low limit such as 1024 or might have other limitations (winsocket only	3020	low limit such as 1024 or might have other limitations (winsocket only
1624	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3021	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1625	influence the size of the C<fd_set> used.	3022	influence the size of the C<fd_set> used.
1626		3023
…		…
1632	be used is the winsock select). This means that it will call	3029	be used is the winsock select). This means that it will call
1633	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3030	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1634	it is assumed that all these functions actually work on fds, even	3031	it is assumed that all these functions actually work on fds, even
1635	on win32. Should not be defined on non-win32 platforms.	3032	on win32. Should not be defined on non-win32 platforms.
1636		3033
		3034	=item EV_FD_TO_WIN32_HANDLE
		3035
		3036	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3037	file descriptors to socket handles. When not defining this symbol (the
		3038	default), then libev will call C<_get_osfhandle>, which is usually
		3039	correct. In some cases, programs use their own file descriptor management,
		3040	in which case they can provide this function to map fds to socket handles.
		3041
1637	=item EV_USE_POLL	3042	=item EV_USE_POLL
1638		3043
1639	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3044	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1640	backend. Otherwise it will be enabled on non-win32 platforms. It	3045	backend. Otherwise it will be enabled on non-win32 platforms. It
1641	takes precedence over select.	3046	takes precedence over select.
1642		3047
1643	=item EV_USE_EPOLL	3048	=item EV_USE_EPOLL
1644		3049
1645	If defined to be C<1>, libev will compile in support for the Linux	3050	If defined to be C<1>, libev will compile in support for the Linux
1646	C<epoll>(7) backend. Its availability will be detected at runtime,	3051	C<epoll>(7) backend. Its availability will be detected at runtime,
1647	otherwise another method will be used as fallback. This is the	3052	otherwise another method will be used as fallback. This is the preferred
1648	preferred backend for GNU/Linux systems.	3053	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3054	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
1649		3055
1650	=item EV_USE_KQUEUE	3056	=item EV_USE_KQUEUE
1651		3057
1652	If defined to be C<1>, libev will compile in support for the BSD style	3058	If defined to be C<1>, libev will compile in support for the BSD style
1653	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3059	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
1666	otherwise another method will be used as fallback. This is the preferred	3072	otherwise another method will be used as fallback. This is the preferred
1667	backend for Solaris 10 systems.	3073	backend for Solaris 10 systems.
1668		3074
1669	=item EV_USE_DEVPOLL	3075	=item EV_USE_DEVPOLL
1670		3076
1671	reserved for future expansion, works like the USE symbols above.	3077	Reserved for future expansion, works like the USE symbols above.
		3078
		3079	=item EV_USE_INOTIFY
		3080
		3081	If defined to be C<1>, libev will compile in support for the Linux inotify
		3082	interface to speed up C<ev_stat> watchers. Its actual availability will
		3083	be detected at runtime. If undefined, it will be enabled if the headers
		3084	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3085
		3086	=item EV_ATOMIC_T
		3087
		3088	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3089	access is atomic with respect to other threads or signal contexts. No such
		3090	type is easily found in the C language, so you can provide your own type
		3091	that you know is safe for your purposes. It is used both for signal handler "locking"
		3092	as well as for signal and thread safety in C<ev_async> watchers.
		3093
		3094	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3095	(from F<signal.h>), which is usually good enough on most platforms.
1672		3096
1673	=item EV_H	3097	=item EV_H
1674		3098
1675	The name of the F<ev.h> header file used to include it. The default if	3099	The name of the F<ev.h> header file used to include it. The default if
1676	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3100	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1677	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3101	used to virtually rename the F<ev.h> header file in case of conflicts.
1678		3102
1679	=item EV_CONFIG_H	3103	=item EV_CONFIG_H
1680		3104
1681	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3105	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1682	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3106	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1683	C<EV_H>, above.	3107	C<EV_H>, above.
1684		3108
1685	=item EV_EVENT_H	3109	=item EV_EVENT_H
1686		3110
1687	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3111	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1688	of how the F<event.h> header can be found.	3112	of how the F<event.h> header can be found, the default is C<"event.h">.
1689		3113
1690	=item EV_PROTOTYPES	3114	=item EV_PROTOTYPES
1691		3115
1692	If defined to be C<0>, then F<ev.h> will not define any function	3116	If defined to be C<0>, then F<ev.h> will not define any function
1693	prototypes, but still define all the structs and other symbols. This is	3117	prototypes, but still define all the structs and other symbols. This is
…		…
1700	will have the C<struct ev_loop *> as first argument, and you can create	3124	will have the C<struct ev_loop *> as first argument, and you can create
1701	additional independent event loops. Otherwise there will be no support	3125	additional independent event loops. Otherwise there will be no support
1702	for multiple event loops and there is no first event loop pointer	3126	for multiple event loops and there is no first event loop pointer
1703	argument. Instead, all functions act on the single default loop.	3127	argument. Instead, all functions act on the single default loop.
1704		3128
		3129	=item EV_MINPRI
		3130
		3131	=item EV_MAXPRI
		3132
		3133	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3134	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3135	provide for more priorities by overriding those symbols (usually defined
		3136	to be C<-2> and C<2>, respectively).
		3137
		3138	When doing priority-based operations, libev usually has to linearly search
		3139	all the priorities, so having many of them (hundreds) uses a lot of space
		3140	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3141	fine.
		3142
		3143	If your embedding application does not need any priorities, defining these
		3144	both to C<0> will save some memory and CPU.
		3145
1705	=item EV_PERIODICS	3146	=item EV_PERIODIC_ENABLE
1706		3147
1707	If undefined or defined to be C<1>, then periodic timers are supported,	3148	If undefined or defined to be C<1>, then periodic timers are supported. If
1708	otherwise not. This saves a few kb of code.	3149	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3150	code.
		3151
		3152	=item EV_IDLE_ENABLE
		3153
		3154	If undefined or defined to be C<1>, then idle watchers are supported. If
		3155	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3156	code.
		3157
		3158	=item EV_EMBED_ENABLE
		3159
		3160	If undefined or defined to be C<1>, then embed watchers are supported. If
		3161	defined to be C<0>, then they are not. Embed watchers rely on most other
		3162	watcher types, which therefore must not be disabled.
		3163
		3164	=item EV_STAT_ENABLE
		3165
		3166	If undefined or defined to be C<1>, then stat watchers are supported. If
		3167	defined to be C<0>, then they are not.
		3168
		3169	=item EV_FORK_ENABLE
		3170
		3171	If undefined or defined to be C<1>, then fork watchers are supported. If
		3172	defined to be C<0>, then they are not.
		3173
		3174	=item EV_ASYNC_ENABLE
		3175
		3176	If undefined or defined to be C<1>, then async watchers are supported. If
		3177	defined to be C<0>, then they are not.
		3178
		3179	=item EV_MINIMAL
		3180
		3181	If you need to shave off some kilobytes of code at the expense of some
		3182	speed, define this symbol to C<1>. Currently this is used to override some
		3183	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3184	much smaller 2-heap for timer management over the default 4-heap.
		3185
		3186	=item EV_PID_HASHSIZE
		3187
		3188	C<ev_child> watchers use a small hash table to distribute workload by
		3189	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		3190	than enough. If you need to manage thousands of children you might want to
		3191	increase this value (I<must> be a power of two).
		3192
		3193	=item EV_INOTIFY_HASHSIZE
		3194
		3195	C<ev_stat> watchers use a small hash table to distribute workload by
		3196	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3197	usually more than enough. If you need to manage thousands of C<ev_stat>
		3198	watchers you might want to increase this value (I<must> be a power of
		3199	two).
		3200
		3201	=item EV_USE_4HEAP
		3202
		3203	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3204	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3205	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3206	faster performance with many (thousands) of watchers.
		3207
		3208	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3209	(disabled).
		3210
		3211	=item EV_HEAP_CACHE_AT
		3212
		3213	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3214	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3215	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3216	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3217	but avoids random read accesses on heap changes. This improves performance
		3218	noticeably with many (hundreds) of watchers.
		3219
		3220	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3221	(disabled).
		3222
		3223	=item EV_VERIFY
		3224
		3225	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3226	be done: If set to C<0>, no internal verification code will be compiled
		3227	in. If set to C<1>, then verification code will be compiled in, but not
		3228	called. If set to C<2>, then the internal verification code will be
		3229	called once per loop, which can slow down libev. If set to C<3>, then the
		3230	verification code will be called very frequently, which will slow down
		3231	libev considerably.
		3232
		3233	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3234	C<0>.
1709		3235
1710	=item EV_COMMON	3236	=item EV_COMMON
1711		3237
1712	By default, all watchers have a C<void *data> member. By redefining	3238	By default, all watchers have a C<void *data> member. By redefining
1713	this macro to a something else you can include more and other types of	3239	this macro to a something else you can include more and other types of
1714	members. You have to define it each time you include one of the files,	3240	members. You have to define it each time you include one of the files,
1715	though, and it must be identical each time.	3241	though, and it must be identical each time.
1716		3242
1717	For example, the perl EV module uses something like this:	3243	For example, the perl EV module uses something like this:
1718		3244
1719	#define EV_COMMON \	3245	#define EV_COMMON \
1720	SV *self; /* contains this struct */ \	3246	SV *self; /* contains this struct */ \
1721	SV *cb_sv, *fh /* note no trailing ";" */	3247	SV *cb_sv, *fh /* note no trailing ";" */
1722		3248
1723	=item EV_CB_DECLARE (type)	3249	=item EV_CB_DECLARE (type)
1724		3250
1725	=item EV_CB_INVOKE (watcher, revents)	3251	=item EV_CB_INVOKE (watcher, revents)
1726		3252
1727	=item ev_set_cb (ev, cb)	3253	=item ev_set_cb (ev, cb)
1728		3254
1729	Can be used to change the callback member declaration in each watcher,	3255	Can be used to change the callback member declaration in each watcher,
1730	and the way callbacks are invoked and set. Must expand to a struct member	3256	and the way callbacks are invoked and set. Must expand to a struct member
1731	definition and a statement, respectively. See the F<ev.v> header file for	3257	definition and a statement, respectively. See the F<ev.h> header file for
1732	their default definitions. One possible use for overriding these is to	3258	their default definitions. One possible use for overriding these is to
1733	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3259	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1734	method calls instead of plain function calls in C++.	3260	method calls instead of plain function calls in C++.
		3261
		3262	=back
		3263
		3264	=head2 EXPORTED API SYMBOLS
		3265
		3266	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3267	exported symbols, you can use the provided F<Symbol.*> files which list
		3268	all public symbols, one per line:
		3269
		3270	Symbols.ev for libev proper
		3271	Symbols.event for the libevent emulation
		3272
		3273	This can also be used to rename all public symbols to avoid clashes with
		3274	multiple versions of libev linked together (which is obviously bad in
		3275	itself, but sometimes it is inconvenient to avoid this).
		3276
		3277	A sed command like this will create wrapper C<#define>'s that you need to
		3278	include before including F<ev.h>:
		3279
		3280	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3281
		3282	This would create a file F<wrap.h> which essentially looks like this:
		3283
		3284	#define ev_backend myprefix_ev_backend
		3285	#define ev_check_start myprefix_ev_check_start
		3286	#define ev_check_stop myprefix_ev_check_stop
		3287	...
1735		3288
1736	=head2 EXAMPLES	3289	=head2 EXAMPLES
1737		3290
1738	For a real-world example of a program the includes libev	3291	For a real-world example of a program the includes libev
1739	verbatim, you can have a look at the EV perl module	3292	verbatim, you can have a look at the EV perl module
…		…
1742	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3295	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1743	will be compiled. It is pretty complex because it provides its own header	3296	will be compiled. It is pretty complex because it provides its own header
1744	file.	3297	file.
1745		3298
1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3299	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1747	that everybody includes and which overrides some autoconf choices:	3300	that everybody includes and which overrides some configure choices:
1748		3301
		3302	#define EV_MINIMAL 1
1749	#define EV_USE_POLL 0	3303	#define EV_USE_POLL 0
1750	#define EV_MULTIPLICITY 0	3304	#define EV_MULTIPLICITY 0
1751	#define EV_PERIODICS 0	3305	#define EV_PERIODIC_ENABLE 0
		3306	#define EV_STAT_ENABLE 0
		3307	#define EV_FORK_ENABLE 0
1752	#define EV_CONFIG_H <config.h>	3308	#define EV_CONFIG_H <config.h>
		3309	#define EV_MINPRI 0
		3310	#define EV_MAXPRI 0
1753		3311
1754	#include "ev++.h"	3312	#include "ev++.h"
1755		3313
1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3314	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1757		3315
1758	#include "ev_cpp.h"	3316	#include "ev_cpp.h"
1759	#include "ev.c"	3317	#include "ev.c"
1760		3318
		3319	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
1761		3320
		3321	=head2 THREADS AND COROUTINES
		3322
		3323	=head3 THREADS
		3324
		3325	All libev functions are reentrant and thread-safe unless explicitly
		3326	documented otherwise, but libev implements no locking itself. This means
		3327	that you can use as many loops as you want in parallel, as long as there
		3328	are no concurrent calls into any libev function with the same loop
		3329	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3330	of course): libev guarantees that different event loops share no data
		3331	structures that need any locking.
		3332
		3333	Or to put it differently: calls with different loop parameters can be done
		3334	concurrently from multiple threads, calls with the same loop parameter
		3335	must be done serially (but can be done from different threads, as long as
		3336	only one thread ever is inside a call at any point in time, e.g. by using
		3337	a mutex per loop).
		3338
		3339	Specifically to support threads (and signal handlers), libev implements
		3340	so-called C<ev_async> watchers, which allow some limited form of
		3341	concurrency on the same event loop, namely waking it up "from the
		3342	outside".
		3343
		3344	If you want to know which design (one loop, locking, or multiple loops
		3345	without or something else still) is best for your problem, then I cannot
		3346	help you, but here is some generic advice:
		3347
		3348	=over 4
		3349
		3350	=item * most applications have a main thread: use the default libev loop
		3351	in that thread, or create a separate thread running only the default loop.
		3352
		3353	This helps integrating other libraries or software modules that use libev
		3354	themselves and don't care/know about threading.
		3355
		3356	=item * one loop per thread is usually a good model.
		3357
		3358	Doing this is almost never wrong, sometimes a better-performance model
		3359	exists, but it is always a good start.
		3360
		3361	=item * other models exist, such as the leader/follower pattern, where one
		3362	loop is handed through multiple threads in a kind of round-robin fashion.
		3363
		3364	Choosing a model is hard - look around, learn, know that usually you can do
		3365	better than you currently do :-)
		3366
		3367	=item * often you need to talk to some other thread which blocks in the
		3368	event loop.
		3369
		3370	C<ev_async> watchers can be used to wake them up from other threads safely
		3371	(or from signal contexts...).
		3372
		3373	An example use would be to communicate signals or other events that only
		3374	work in the default loop by registering the signal watcher with the
		3375	default loop and triggering an C<ev_async> watcher from the default loop
		3376	watcher callback into the event loop interested in the signal.
		3377
		3378	=back
		3379
		3380	=head3 COROUTINES
		3381
		3382	Libev is very accommodating to coroutines ("cooperative threads"):
		3383	libev fully supports nesting calls to its functions from different
		3384	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3385	different coroutines, and switch freely between both coroutines running the
		3386	loop, as long as you don't confuse yourself). The only exception is that
		3387	you must not do this from C<ev_periodic> reschedule callbacks.
		3388
		3389	Care has been taken to ensure that libev does not keep local state inside
		3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3391	they do not clal any callbacks.
		3392
		3393	=head2 COMPILER WARNINGS
		3394
		3395	Depending on your compiler and compiler settings, you might get no or a
		3396	lot of warnings when compiling libev code. Some people are apparently
		3397	scared by this.
		3398
		3399	However, these are unavoidable for many reasons. For one, each compiler
		3400	has different warnings, and each user has different tastes regarding
		3401	warning options. "Warn-free" code therefore cannot be a goal except when
		3402	targeting a specific compiler and compiler-version.
		3403
		3404	Another reason is that some compiler warnings require elaborate
		3405	workarounds, or other changes to the code that make it less clear and less
		3406	maintainable.
		3407
		3408	And of course, some compiler warnings are just plain stupid, or simply
		3409	wrong (because they don't actually warn about the condition their message
		3410	seems to warn about). For example, certain older gcc versions had some
		3411	warnings that resulted an extreme number of false positives. These have
		3412	been fixed, but some people still insist on making code warn-free with
		3413	such buggy versions.
		3414
		3415	While libev is written to generate as few warnings as possible,
		3416	"warn-free" code is not a goal, and it is recommended not to build libev
		3417	with any compiler warnings enabled unless you are prepared to cope with
		3418	them (e.g. by ignoring them). Remember that warnings are just that:
		3419	warnings, not errors, or proof of bugs.
		3420
		3421
		3422	=head2 VALGRIND
		3423
		3424	Valgrind has a special section here because it is a popular tool that is
		3425	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3426
		3427	If you think you found a bug (memory leak, uninitialised data access etc.)
		3428	in libev, then check twice: If valgrind reports something like:
		3429
		3430	==2274== definitely lost: 0 bytes in 0 blocks.
		3431	==2274== possibly lost: 0 bytes in 0 blocks.
		3432	==2274== still reachable: 256 bytes in 1 blocks.
		3433
		3434	Then there is no memory leak, just as memory accounted to global variables
		3435	is not a memleak - the memory is still being refernced, and didn't leak.
		3436
		3437	Similarly, under some circumstances, valgrind might report kernel bugs
		3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3439	although an acceptable workaround has been found here), or it might be
		3440	confused.
		3441
		3442	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3443	make it into some kind of religion.
		3444
		3445	If you are unsure about something, feel free to contact the mailing list
		3446	with the full valgrind report and an explanation on why you think this
		3447	is a bug in libev (best check the archives, too :). However, don't be
		3448	annoyed when you get a brisk "this is no bug" answer and take the chance
		3449	of learning how to interpret valgrind properly.
		3450
		3451	If you need, for some reason, empty reports from valgrind for your project
		3452	I suggest using suppression lists.
		3453
		3454
		3455	=head1 PORTABILITY NOTES
		3456
		3457	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3458
		3459	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3460	requires, and its I/O model is fundamentally incompatible with the POSIX
		3461	model. Libev still offers limited functionality on this platform in
		3462	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3463	descriptors. This only applies when using Win32 natively, not when using
		3464	e.g. cygwin.
		3465
		3466	Lifting these limitations would basically require the full
		3467	re-implementation of the I/O system. If you are into these kinds of
		3468	things, then note that glib does exactly that for you in a very portable
		3469	way (note also that glib is the slowest event library known to man).
		3470
		3471	There is no supported compilation method available on windows except
		3472	embedding it into other applications.
		3473
		3474	Not a libev limitation but worth mentioning: windows apparently doesn't
		3475	accept large writes: instead of resulting in a partial write, windows will
		3476	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3477	so make sure you only write small amounts into your sockets (less than a
		3478	megabyte seems safe, but this apparently depends on the amount of memory
		3479	available).
		3480
		3481	Due to the many, low, and arbitrary limits on the win32 platform and
		3482	the abysmal performance of winsockets, using a large number of sockets
		3483	is not recommended (and not reasonable). If your program needs to use
		3484	more than a hundred or so sockets, then likely it needs to use a totally
		3485	different implementation for windows, as libev offers the POSIX readiness
		3486	notification model, which cannot be implemented efficiently on windows
		3487	(Microsoft monopoly games).
		3488
		3489	A typical way to use libev under windows is to embed it (see the embedding
		3490	section for details) and use the following F<evwrap.h> header file instead
		3491	of F<ev.h>:
		3492
		3493	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3494	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3495
		3496	#include "ev.h"
		3497
		3498	And compile the following F<evwrap.c> file into your project (make sure
		3499	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3500
		3501	#include "evwrap.h"
		3502	#include "ev.c"
		3503
		3504	=over 4
		3505
		3506	=item The winsocket select function
		3507
		3508	The winsocket C<select> function doesn't follow POSIX in that it
		3509	requires socket I<handles> and not socket I<file descriptors> (it is
		3510	also extremely buggy). This makes select very inefficient, and also
		3511	requires a mapping from file descriptors to socket handles (the Microsoft
		3512	C runtime provides the function C<_open_osfhandle> for this). See the
		3513	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3514	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3515
		3516	The configuration for a "naked" win32 using the Microsoft runtime
		3517	libraries and raw winsocket select is:
		3518
		3519	#define EV_USE_SELECT 1
		3520	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3521
		3522	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3523	complexity in the O(n²) range when using win32.
		3524
		3525	=item Limited number of file descriptors
		3526
		3527	Windows has numerous arbitrary (and low) limits on things.
		3528
		3529	Early versions of winsocket's select only supported waiting for a maximum
		3530	of C<64> handles (probably owning to the fact that all windows kernels
		3531	can only wait for C<64> things at the same time internally; Microsoft
		3532	recommends spawning a chain of threads and wait for 63 handles and the
		3533	previous thread in each. Great).
		3534
		3535	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3536	to some high number (e.g. C<2048>) before compiling the winsocket select
		3537	call (which might be in libev or elsewhere, for example, perl does its own
		3538	select emulation on windows).
		3539
		3540	Another limit is the number of file descriptors in the Microsoft runtime
		3541	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3542	or something like this inside Microsoft). You can increase this by calling
		3543	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3544	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3545	libraries.
		3546
		3547	This might get you to about C<512> or C<2048> sockets (depending on
		3548	windows version and/or the phase of the moon). To get more, you need to
		3549	wrap all I/O functions and provide your own fd management, but the cost of
		3550	calling select (O(n²)) will likely make this unworkable.
		3551
		3552	=back
		3553
		3554	=head2 PORTABILITY REQUIREMENTS
		3555
		3556	In addition to a working ISO-C implementation and of course the
		3557	backend-specific APIs, libev relies on a few additional extensions:
		3558
		3559	=over 4
		3560
		3561	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3562	calling conventions regardless of C<ev_watcher_type *>.
		3563
		3564	Libev assumes not only that all watcher pointers have the same internal
		3565	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3566	assumes that the same (machine) code can be used to call any watcher
		3567	callback: The watcher callbacks have different type signatures, but libev
		3568	calls them using an C<ev_watcher *> internally.
		3569
		3570	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3571
		3572	The type C<sig_atomic_t volatile> (or whatever is defined as
		3573	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3574	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3575	believed to be sufficiently portable.
		3576
		3577	=item C<sigprocmask> must work in a threaded environment
		3578
		3579	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3580	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3581	pthread implementations will either allow C<sigprocmask> in the "main
		3582	thread" or will block signals process-wide, both behaviours would
		3583	be compatible with libev. Interaction between C<sigprocmask> and
		3584	C<pthread_sigmask> could complicate things, however.
		3585
		3586	The most portable way to handle signals is to block signals in all threads
		3587	except the initial one, and run the default loop in the initial thread as
		3588	well.
		3589
		3590	=item C<long> must be large enough for common memory allocation sizes
		3591
		3592	To improve portability and simplify its API, libev uses C<long> internally
		3593	instead of C<size_t> when allocating its data structures. On non-POSIX
		3594	systems (Microsoft...) this might be unexpectedly low, but is still at
		3595	least 31 bits everywhere, which is enough for hundreds of millions of
		3596	watchers.
		3597
		3598	=item C<double> must hold a time value in seconds with enough accuracy
		3599
		3600	The type C<double> is used to represent timestamps. It is required to
		3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3602	enough for at least into the year 4000. This requirement is fulfilled by
		3603	implementations implementing IEEE 754 (basically all existing ones).
		3604
		3605	=back
		3606
		3607	If you know of other additional requirements drop me a note.
		3608
		3609
1762	=head1 COMPLEXITIES	3610	=head1 ALGORITHMIC COMPLEXITIES
1763		3611
1764	In this section the complexities of (many of) the algorithms used inside	3612	In this section the complexities of (many of) the algorithms used inside
1765	libev will be explained. For complexity discussions about backends see the	3613	libev will be documented. For complexity discussions about backends see
1766	documentation for C<ev_default_init>.	3614	the documentation for C<ev_default_init>.
		3615
		3616	All of the following are about amortised time: If an array needs to be
		3617	extended, libev needs to realloc and move the whole array, but this
		3618	happens asymptotically rarer with higher number of elements, so O(1) might
		3619	mean that libev does a lengthy realloc operation in rare cases, but on
		3620	average it is much faster and asymptotically approaches constant time.
1767		3621
1768	=over 4	3622	=over 4
1769		3623
1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3624	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1771		3625
		3626	This means that, when you have a watcher that triggers in one hour and
		3627	there are 100 watchers that would trigger before that, then inserting will
		3628	have to skip roughly seven (C<ld 100>) of these watchers.
		3629
1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3630	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
1773		3631
		3632	That means that changing a timer costs less than removing/adding them,
		3633	as only the relative motion in the event queue has to be paid for.
		3634
1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3635	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
1775		3636
		3637	These just add the watcher into an array or at the head of a list.
		3638
1776	=item Stopping check/prepare/idle watchers: O(1)	3639	=item Stopping check/prepare/idle/fork/async watchers: O(1)
1777		3640
1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	3641	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
1779		3642
		3643	These watchers are stored in lists, so they need to be walked to find the
		3644	correct watcher to remove. The lists are usually short (you don't usually
		3645	have many watchers waiting for the same fd or signal: one is typical, two
		3646	is rare).
		3647
1780	=item Finding the next timer per loop iteration: O(1)	3648	=item Finding the next timer in each loop iteration: O(1)
		3649
		3650	By virtue of using a binary or 4-heap, the next timer is always found at a
		3651	fixed position in the storage array.
1781		3652
1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3653	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1783		3654
1784	=item Activating one watcher: O(1)	3655	A change means an I/O watcher gets started or stopped, which requires
		3656	libev to recalculate its status (and possibly tell the kernel, depending
		3657	on backend and whether C<ev_io_set> was used).
		3658
		3659	=item Activating one watcher (putting it into the pending state): O(1)
		3660
		3661	=item Priority handling: O(number_of_priorities)
		3662
		3663	Priorities are implemented by allocating some space for each
		3664	priority. When doing priority-based operations, libev usually has to
		3665	linearly search all the priorities, but starting/stopping and activating
		3666	watchers becomes O(1) with respect to priority handling.
		3667
		3668	=item Sending an ev_async: O(1)
		3669
		3670	=item Processing ev_async_send: O(number_of_async_watchers)
		3671
		3672	=item Processing signals: O(max_signal_number)
		3673
		3674	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3675	calls in the current loop iteration. Checking for async and signal events
		3676	involves iterating over all running async watchers or all signal numbers.
1785		3677
1786	=back	3678	=back
1787		3679
1788		3680
1789	=head1 AUTHOR	3681	=head1 AUTHOR

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