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Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 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		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_loop's to stop iterating
		32	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_loop to stop iterating
		41	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
		47	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_loop (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 DESCRIPTION
52		68
		69	The newest version of this document is also available as an html-formatted
		70	web page you might find easier to navigate when reading it for the first
		71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		72
53	Libev is an event loop: you register interest in certain events (such as a	73	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
55	these event sources and provide your program with events.	75	these event sources and provide your program with events.
56		76
57	To do this, it must take more or less complete control over your process	77	To do this, it must take more or less complete control over your process
58	(or thread) by executing the I<event loop> handler, and will then	78	(or thread) by executing the I<event loop> handler, and will then
59	communicate events via a callback mechanism.	79	communicate events via a callback mechanism.
…		…
61	You register interest in certain events by registering so-called I<event	81	You register interest in certain events by registering so-called I<event
62	watchers>, which are relatively small C structures you initialise with the	82	watchers>, which are relatively small C structures you initialise with the
63	details of the event, and then hand it over to libev by I<starting> the	83	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	84	watcher.
65		85
66	=head1 FEATURES	86	=head2 FEATURES
67		87
68	Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the	88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	bsd-specific C<kqueue> and the solaris-specific event port mechanisms	89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),	90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
		91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous	92	with customised rescheduling (C<ev_periodic>), synchronous signals
72	signals (C<ev_signal>), process status change events (C<ev_child>), and	93	(C<ev_signal>), process status change events (C<ev_child>), and event
73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,	94	watchers dealing with the event loop mechanism itself (C<ev_idle>,
74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75	file watchers (C<ev_stat>) and even limited support for fork events	96	file watchers (C<ev_stat>) and even limited support for fork events
76	(C<ev_fork>).	97	(C<ev_fork>).
77		98
78	It also is quite fast (see this	99	It also is quite fast (see this
79	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
80	for example).	101	for example).
81		102
82	=head1 CONVENTIONS	103	=head2 CONVENTIONS
83		104
84	Libev is very configurable. In this manual the default configuration will	105	Libev is very configurable. In this manual the default (and most common)
85	be described, which supports multiple event loops. For more info about	106	configuration will be described, which supports multiple event loops. For
86	various configuration options please have a look at B<EMBED> section in	107	more info about various configuration options please have a look at
87	this manual. If libev was configured without support for multiple event	108	B<EMBED> section in this manual. If libev was configured without support
88	loops, then all functions taking an initial argument of name C<loop>	109	for multiple event loops, then all functions taking an initial argument of
89	(which is always of type C<struct ev_loop *>) will not have this argument.	110	name C<loop> (which is always of type C<ev_loop *>) will not have
		111	this argument.
90		112
91	=head1 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
92		114
93	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
94	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
95	the beginning of 1970, details are complicated, don't ask). This type is	117	the beginning of 1970, details are complicated, don't ask). This type is
96	called C<ev_tstamp>, which is what you should use too. It usually aliases	118	called C<ev_tstamp>, which is what you should use too. It usually aliases
97	to the C<double> type in C, and when you need to do any calculations on	119	to the C<double> type in C, and when you need to do any calculations on
98	it, you should treat it as such.	120	it, you should treat it as some floating point value. Unlike the name
		121	component C<stamp> might indicate, it is also used for time differences
		122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
99		144
100	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
101		146
102	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
103	library in any way.	148	library in any way.
…		…
108		153
109	Returns the current time as libev would use it. Please note that the	154	Returns the current time as libev would use it. Please note that the
110	C<ev_now> function is usually faster and also often returns the timestamp	155	C<ev_now> function is usually faster and also often returns the timestamp
111	you actually want to know.	156	you actually want to know.
112		157
		158	=item ev_sleep (ev_tstamp interval)
		159
		160	Sleep for the given interval: The current thread will be blocked until
		161	either it is interrupted or the given time interval has passed. Basically
		162	this is a sub-second-resolution C<sleep ()>.
		163
113	=item int ev_version_major ()	164	=item int ev_version_major ()
114		165
115	=item int ev_version_minor ()	166	=item int ev_version_minor ()
116		167
117	You can find out the major and minor version numbers of the library	168	You can find out the major and minor ABI version numbers of the library
118	you linked against by calling the functions C<ev_version_major> and	169	you linked against by calling the functions C<ev_version_major> and
119	C<ev_version_minor>. If you want, you can compare against the global	170	C<ev_version_minor>. If you want, you can compare against the global
120	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	171	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
121	version of the library your program was compiled against.	172	version of the library your program was compiled against.
122		173
		174	These version numbers refer to the ABI version of the library, not the
		175	release version.
		176
123	Usually, it's a good idea to terminate if the major versions mismatch,	177	Usually, it's a good idea to terminate if the major versions mismatch,
124	as this indicates an incompatible change. Minor versions are usually	178	as this indicates an incompatible change. Minor versions are usually
125	compatible to older versions, so a larger minor version alone is usually	179	compatible to older versions, so a larger minor version alone is usually
126	not a problem.	180	not a problem.
127		181
128	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
129	version.	183	version.
130		184
131	assert (("libev version mismatch",	185	assert (("libev version mismatch",
132	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
133	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
134		188
135	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
136		190
137	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
138	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
140	a description of the set values.	194	a description of the set values.
141		195
142	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
143	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
144		198
145	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
146	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
147		201
148	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
149		203
150	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
151	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
152	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
153	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
154	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
155	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
156		210
157	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
158		212
…		…
162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163	recommended ones.	217	recommended ones.
164		218
165	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
166		220
167	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
168		222
169	Sets the allocation function to use (the prototype and semantics are	223	Sets the allocation function to use (the prototype is similar - the
170	identical to the realloc C function). It is used to allocate and free	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
171	memory (no surprises here). If it returns zero when memory needs to be	225	used to allocate and free memory (no surprises here). If it returns zero
172	allocated, the library might abort or take some potentially destructive	226	when memory needs to be allocated (C<size != 0>), the library might abort
173	action. The default is your system realloc function.	227	or take some potentially destructive action.
		228
		229	Since some systems (at least OpenBSD and Darwin) fail to implement
		230	correct C<realloc> semantics, libev will use a wrapper around the system
		231	C<realloc> and C<free> functions by default.
174		232
175	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
176	free some memory if it cannot allocate memory, to use a special allocator,	234	free some memory if it cannot allocate memory, to use a special allocator,
177	or even to sleep a while and retry until some memory is available.	235	or even to sleep a while and retry until some memory is available.
178		236
179	Example: Replace the libev allocator with one that waits a bit and then	237	Example: Replace the libev allocator with one that waits a bit and then
180	retries).	238	retries (example requires a standards-compliant C<realloc>).
181		239
182	static void *	240	static void *
183	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
184	{	242	{
185	for (;;)	243	for (;;)
…		…
194	}	252	}
195		253
196	...	254	...
197	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
198		256
199	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
200		258
201	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
202	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
203	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
204	callback is set, then libev will expect it to remedy the sitution, no	262	callback is set, then libev will expect it to remedy the situation, no
205	matter what, when it returns. That is, libev will generally retry the	263	matter what, when it returns. That is, libev will generally retry the
206	requested operation, or, if the condition doesn't go away, do bad stuff	264	requested operation, or, if the condition doesn't go away, do bad stuff
207	(such as abort).	265	(such as abort).
208		266
209	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
220		278
221	=back	279	=back
222		280
223	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
224		282
225	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
226	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
227	events, and dynamically created loops which do not.	285	I<function>).
228		286
229	If you use threads, a common model is to run the default event loop	287	The library knows two types of such loops, the I<default> loop, which
230	in your main thread (or in a separate thread) and for each thread you	288	supports signals and child events, and dynamically created loops which do
231	create, you also create another event loop. Libev itself does no locking	289	not.
232	whatsoever, so if you mix calls to the same event loop in different
233	threads, make sure you lock (this is usually a bad idea, though, even if
234	done correctly, because it's hideous and inefficient).
235		290
236	=over 4	291	=over 4
237		292
238	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
239		294
…		…
243	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
244		299
245	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
246	function.	301	function.
247		302
		303	Note that this function is I<not> thread-safe, so if you want to use it
		304	from multiple threads, you have to lock (note also that this is unlikely,
		305	as loops cannot be shared easily between threads anyway).
		306
		307	The default loop is the only loop that can handle C<ev_signal> and
		308	C<ev_child> watchers, and to do this, it always registers a handler
		309	for C<SIGCHLD>. If this is a problem for your application you can either
		310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		312	C<ev_default_init>.
		313
248	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
249	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
250		316
251	The following flags are supported:	317	The following flags are supported:
252		318
…		…
257	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
258	thing, believe me).	324	thing, believe me).
259		325
260	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
261		327
262	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
263	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
266	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
267	around bugs.	333	around bugs.
268		334
		335	=item C<EVFLAG_FORKCHECK>
		336
		337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		338	a fork, you can also make libev check for a fork in each iteration by
		339	enabling this flag.
		340
		341	This works by calling C<getpid ()> on every iteration of the loop,
		342	and thus this might slow down your event loop if you do a lot of loop
		343	iterations and little real work, but is usually not noticeable (on my
		344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		345	without a system call and thus I<very> fast, but my GNU/Linux system also has
		346	C<pthread_atfork> which is even faster).
		347
		348	The big advantage of this flag is that you can forget about fork (and
		349	forget about forgetting to tell libev about forking) when you use this
		350	flag.
		351
		352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
		353	environment variable.
		354
269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270		356
271	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
272	libev tries to roll its own fd_set with no limits on the number of fds,	358	libev tries to roll its own fd_set with no limits on the number of fds,
273	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
274	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
275	the fastest backend for a low number of fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
		362
		363	To get good performance out of this backend you need a high amount of
		364	parallelism (most of the file descriptors should be busy). If you are
		365	writing a server, you should C<accept ()> in a loop to accept as many
		366	connections as possible during one iteration. You might also want to have
		367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
276		373
277	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
278		375
279	And this is your standard poll(2) backend. It's more complicated than	376	And this is your standard poll(2) backend. It's more complicated
280	select, but handles sparse fds better and has no artificial limit on the	377	than select, but handles sparse fds better and has no artificial
281	number of fds you can use (except it will slow down considerably with a	378	limit on the number of fds you can use (except it will slow down
282	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	379	considerably with a lot of inactive fds). It scales similarly to select,
		380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		381	performance tips.
		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
283		385
284	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
285		387
286	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
287	but it scales phenomenally better. While poll and select usually scale like	389	but it scales phenomenally better. While poll and select usually scale
288	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	390	like O(total_fds) where n is the total number of fds (or the highest fd),
289	either O(1) or O(active_fds).	391	epoll scales either O(1) or O(active_fds).
290		392
		393	The epoll mechanism deserves honorable mention as the most misdesigned
		394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
		409
291	While stopping and starting an I/O watcher in the same iteration will	410	While stopping, setting and starting an I/O watcher in the same iteration
292	result in some caching, there is still a syscall per such incident	411	will result in some caching, there is still a system call per such
293	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
294	best to avoid that. Also, dup()ed file descriptors might not work very	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
295	well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
		415	file descriptors.
296		416
297	Please note that epoll sometimes generates spurious notifications, so you	417	Best performance from this backend is achieved by not unregistering all
298	need to use non-blocking I/O or other means to avoid blocking when no data	418	watchers for a file descriptor until it has been closed, if possible,
299	(or space) is available.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
		429	While nominally embeddable in other event loops, this feature is broken in
		430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
300		434
301	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
302		436
303	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
304	was broken on all BSDs except NetBSD (usually it doesn't work with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
305	anything but sockets and pipes, except on Darwin, where of course its	439	with anything but sockets and pipes, except on Darwin, where of course
306	completely useless). For this reason its not being "autodetected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
307	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
308	C<EVBACKEND_KQUEUE>).	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
		446
		447	You still can embed kqueue into a normal poll or select backend and use it
		448	only for sockets (after having made sure that sockets work with kqueue on
		449	the target platform). See C<ev_embed> watchers for more info.
309		450
310	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
311	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
312	course). While starting and stopping an I/O watcher does not cause an	453	course). While stopping, setting and starting an I/O watcher does never
313	extra syscall as with epoll, it still adds up to four event changes per	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
314	incident, so its best to avoid that.	455	two event changes per incident. Support for C<fork ()> is very bad (but
		456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
		458
		459	This backend usually performs well under most conditions.
		460
		461	While nominally embeddable in other event loops, this doesn't work
		462	everywhere, so you might need to test for this. And since it is broken
		463	almost everywhere, you should only use it when you have a lot of sockets
		464	(for which it usually works), by embedding it into another event loop
		465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
		466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
315		471
316	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
317		473
318	This is not implemented yet (and might never be).	474	This is not implemented yet (and might never be, unless you send me an
		475	implementation). According to reports, C</dev/poll> only supports sockets
		476	and is not embeddable, which would limit the usefulness of this backend
		477	immensely.
319		478
320	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
321		480
322	This uses the Solaris 10 port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
323	it's really slow, but it still scales very well (O(active_fds)).	482	it's really slow, but it still scales very well (O(active_fds)).
324		483
325	Please note that solaris ports can result in a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
326	notifications, so you need to use non-blocking I/O or other means to avoid	485	notifications, so you need to use non-blocking I/O or other means to avoid
327	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
		487
		488	While this backend scales well, it requires one system call per active
		489	file descriptor per loop iteration. For small and medium numbers of file
		490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		491	might perform better.
		492
		493	On the positive side, with the exception of the spurious readiness
		494	notifications, this backend actually performed fully to specification
		495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
328		500
329	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
330		502
331	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
332	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
333	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
334		506
		507	It is definitely not recommended to use this flag.
		508
335	=back	509	=back
336		510
337	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
338	backends will be tried (in the reverse order as given here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
339	specified, most compiled-in backend will be tried, usually in reverse	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
340	order of their flag values :)
341		514
342	The most typical usage is like this:	515	Example: This is the most typical usage.
343		516
344	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
345	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
346		519
347	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
348	environment settings to be taken into account:	521	environment settings to be taken into account:
349		522
350	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
351		524
352	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
353	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
354	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
355		529
356	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
357		531
358	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
359		533
360	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
361	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
362	handle signal and child watchers, and attempts to do so will be greeted by	536	handle signal and child watchers, and attempts to do so will be greeted by
363	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
364		538
		539	Note that this function I<is> thread-safe, and the recommended way to use
		540	libev with threads is indeed to create one loop per thread, and using the
		541	default loop in the "main" or "initial" thread.
		542
365	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
366		544
367	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
368	if (!epoller)	546	if (!epoller)
369	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
370		548
371	=item ev_default_destroy ()	549	=item ev_default_destroy ()
372		550
373	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
374	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
375	sense, so e.g. C<ev_is_active> might still return true. It is your	553	sense, so e.g. C<ev_is_active> might still return true. It is your
376	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
377	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
378	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
379	for example).	557	for example).
		558
		559	Note that certain global state, such as signal state (and installed signal
		560	handlers), will not be freed by this function, and related watchers (such
		561	as signal and child watchers) would need to be stopped manually.
		562
		563	In general it is not advisable to call this function except in the
		564	rare occasion where you really need to free e.g. the signal handling
		565	pipe fds. If you need dynamically allocated loops it is better to use
		566	C<ev_loop_new> and C<ev_loop_destroy>).
380		567
381	=item ev_loop_destroy (loop)	568	=item ev_loop_destroy (loop)
382		569
383	Like C<ev_default_destroy>, but destroys an event loop created by an	570	Like C<ev_default_destroy>, but destroys an event loop created by an
384	earlier call to C<ev_loop_new>.	571	earlier call to C<ev_loop_new>.
385		572
386	=item ev_default_fork ()	573	=item ev_default_fork ()
387		574
		575	This function sets a flag that causes subsequent C<ev_loop> iterations
388	This function reinitialises the kernel state for backends that have	576	to reinitialise the kernel state for backends that have one. Despite the
389	one. Despite the name, you can call it anytime, but it makes most sense	577	name, you can call it anytime, but it makes most sense after forking, in
390	after forking, in either the parent or child process (or both, but that	578	the child process (or both child and parent, but that again makes little
391	again makes little sense).	579	sense). You I<must> call it in the child before using any of the libev
		580	functions, and it will only take effect at the next C<ev_loop> iteration.
392		581
393	You I<must> call this function in the child process after forking if and	582	On the other hand, you only need to call this function in the child
394	only if you want to use the event library in both processes. If you just	583	process if and only if you want to use the event library in the child. If
395	fork+exec, you don't have to call it.	584	you just fork+exec, you don't have to call it at all.
396		585
397	The function itself is quite fast and it's usually not a problem to call	586	The function itself is quite fast and it's usually not a problem to call
398	it just in case after a fork. To make this easy, the function will fit in	587	it just in case after a fork. To make this easy, the function will fit in
399	quite nicely into a call to C<pthread_atfork>:	588	quite nicely into a call to C<pthread_atfork>:
400		589
401	pthread_atfork (0, 0, ev_default_fork);	590	pthread_atfork (0, 0, ev_default_fork);
402		591
403	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
404	without calling this function, so if you force one of those backends you
405	do not need to care.
406
407	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
408		593
409	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
410	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
411	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
		598
		599	=item int ev_is_default_loop (loop)
		600
		601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
		603
		604	=item unsigned int ev_loop_count (loop)
		605
		606	Returns the count of loop iterations for the loop, which is identical to
		607	the number of times libev did poll for new events. It starts at C<0> and
		608	happily wraps around with enough iterations.
		609
		610	This value can sometimes be useful as a generation counter of sorts (it
		611	"ticks" the number of loop iterations), as it roughly corresponds with
		612	C<ev_prepare> and C<ev_check> calls.
412		613
413	=item unsigned int ev_backend (loop)	614	=item unsigned int ev_backend (loop)
414		615
415	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
416	use.	617	use.
…		…
419		620
420	Returns the current "event loop time", which is the time the event loop	621	Returns the current "event loop time", which is the time the event loop
421	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
422	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
423	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
424	event occuring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
425		664
426	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
427		666
428	Finally, this is it, the event handler. This function usually is called	667	Finally, this is it, the event handler. This function usually is called
429	after you initialised all your watchers and you want to start handling	668	after you initialised all your watchers and you want to start handling
…		…
432	If the flags argument is specified as C<0>, it will not return until	671	If the flags argument is specified as C<0>, it will not return until
433	either no event watchers are active anymore or C<ev_unloop> was called.	672	either no event watchers are active anymore or C<ev_unloop> was called.
434		673
435	Please note that an explicit C<ev_unloop> is usually better than	674	Please note that an explicit C<ev_unloop> is usually better than
436	relying on all watchers to be stopped when deciding when a program has	675	relying on all watchers to be stopped when deciding when a program has
437	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
438	automatically loops as long as it has to and no longer by virtue of	677	that automatically loops as long as it has to and no longer by virtue
439	relying on its watchers stopping correctly is a thing of beauty.	678	of relying on its watchers stopping correctly, that is truly a thing of
		679	beauty.
440		680
441	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
442	those events and any outstanding ones, but will not block your process in	682	those events and any already outstanding ones, but will not block your
443	case there are no events and will return after one iteration of the loop.	683	process in case there are no events and will return after one iteration of
		684	the loop.
444		685
445	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
446	neccessary) and will handle those and any outstanding ones. It will block	687	necessary) and will handle those and any already outstanding ones. It
447	your process until at least one new event arrives, and will return after	688	will block your process until at least one new event arrives (which could
448	one iteration of the loop. This is useful if you are waiting for some	689	be an event internal to libev itself, so there is no guarantee that a
449	external event in conjunction with something not expressible using other	690	user-registered callback will be called), and will return after one
		691	iteration of the loop.
		692
		693	This is useful if you are waiting for some external event in conjunction
		694	with something not expressible using other libev watchers (i.e. "roll your
450	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
451	usually a better approach for this kind of thing.	696	usually a better approach for this kind of thing.
452		697
453	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
454		699
455	* If there are no active watchers (reference count is zero), return.	700	- Before the first iteration, call any pending watchers.
456	- Queue prepare watchers and then call all outstanding watchers.	701	* If EVFLAG_FORKCHECK was used, check for a fork.
		702	- If a fork was detected (by any means), queue and call all fork watchers.
		703	- Queue and call all prepare watchers.
457	- If we have been forked, recreate the kernel state.	704	- If we have been forked, detach and recreate the kernel state
		705	as to not disturb the other process.
458	- Update the kernel state with all outstanding changes.	706	- Update the kernel state with all outstanding changes.
459	- Update the "event loop time".	707	- Update the "event loop time" (ev_now ()).
460	- Calculate for how long to block.	708	- Calculate for how long to sleep or block, if at all
		709	(active idle watchers, EVLOOP_NONBLOCK or not having
		710	any active watchers at all will result in not sleeping).
		711	- Sleep if the I/O and timer collect interval say so.
461	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
462	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
463	- Update the "event loop time" and do time jump handling.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
464	- Queue all outstanding timers.	715	- Queue all expired timers.
465	- Queue all outstanding periodics.	716	- Queue all expired periodics.
466	- If no events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
467	- Queue all check watchers.	718	- Queue all check watchers.
468	- Call all queued watchers in reverse order (i.e. check watchers first).	719	- Call all queued watchers in reverse order (i.e. check watchers first).
469	Signals and child watchers are implemented as I/O watchers, and will	720	Signals and child watchers are implemented as I/O watchers, and will
470	be handled here by queueing them when their watcher gets executed.	721	be handled here by queueing them when their watcher gets executed.
471	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
472	were used, return, otherwise continue with step *.	723	were used, or there are no active watchers, return, otherwise
		724	continue with step *.
473		725
474	Example: Queue some jobs and then loop until no events are outsanding	726	Example: Queue some jobs and then loop until no events are outstanding
475	anymore.	727	anymore.
476		728
477	... queue jobs here, make sure they register event watchers as long	729	... queue jobs here, make sure they register event watchers as long
478	... as they still have work to do (even an idle watcher will do..)	730	... as they still have work to do (even an idle watcher will do..)
479	ev_loop (my_loop, 0);	731	ev_loop (my_loop, 0);
480	... jobs done. yeah!	732	... jobs done or somebody called unloop. yeah!
481		733
482	=item ev_unloop (loop, how)	734	=item ev_unloop (loop, how)
483		735
484	Can be used to make a call to C<ev_loop> return early (but only after it	736	Can be used to make a call to C<ev_loop> return early (but only after it
485	has processed all outstanding events). The C<how> argument must be either	737	has processed all outstanding events). The C<how> argument must be either
486	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
487	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
488		740
		741	This "unloop state" will be cleared when entering C<ev_loop> again.
		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
489	=item ev_ref (loop)	745	=item ev_ref (loop)
490		746
491	=item ev_unref (loop)	747	=item ev_unref (loop)
492		748
493	Ref/unref can be used to add or remove a reference count on the event	749	Ref/unref can be used to add or remove a reference count on the event
494	loop: Every watcher keeps one reference, and as long as the reference	750	loop: Every watcher keeps one reference, and as long as the reference
495	count is nonzero, C<ev_loop> will not return on its own. If you have	751	count is nonzero, C<ev_loop> will not return on its own.
		752
496	a watcher you never unregister that should not keep C<ev_loop> from	753	If you have a watcher you never unregister that should not keep C<ev_loop>
497	returning, ev_unref() after starting, and ev_ref() before stopping it. For	754	from returning, call ev_unref() after starting, and ev_ref() before
		755	stopping it.
		756
498	example, libev itself uses this for its internal signal pipe: It is not	757	As an example, libev itself uses this for its internal signal pipe: It
499	visible to the libev user and should not keep C<ev_loop> from exiting if	758	is not visible to the libev user and should not keep C<ev_loop> from
500	no event watchers registered by it are active. It is also an excellent	759	exiting if no event watchers registered by it are active. It is also an
501	way to do this for generic recurring timers or from within third-party	760	excellent way to do this for generic recurring timers or from within
502	libraries. Just remember to I<unref after start> and I<ref before stop>.	761	third-party libraries. Just remember to I<unref after start> and I<ref
		762	before stop> (but only if the watcher wasn't active before, or was active
		763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
503		766
504	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
505	running when nothing else is active.	768	running when nothing else is active.
506		769
507	struct ev_signal exitsig;	770	ev_signal exitsig;
508	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
509	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
510	evf_unref (loop);	773	evf_unref (loop);
511		774
512	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
513		776
514	ev_ref (loop);	777	ev_ref (loop);
515	ev_signal_stop (loop, &exitsig);	778	ev_signal_stop (loop, &exitsig);
		779
		780	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		781
		782	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		783
		784	These advanced functions influence the time that libev will spend waiting
		785	for events. Both time intervals are by default C<0>, meaning that libev
		786	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		787	latency.
		788
		789	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		790	allows libev to delay invocation of I/O and timer/periodic callbacks
		791	to increase efficiency of loop iterations (or to increase power-saving
		792	opportunities).
		793
		794	The idea is that sometimes your program runs just fast enough to handle
		795	one (or very few) event(s) per loop iteration. While this makes the
		796	program responsive, it also wastes a lot of CPU time to poll for new
		797	events, especially with backends like C<select ()> which have a high
		798	overhead for the actual polling but can deliver many events at once.
		799
		800	By setting a higher I<io collect interval> you allow libev to spend more
		801	time collecting I/O events, so you can handle more events per iteration,
		802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		803	C<ev_timer>) will be not affected. Setting this to a non-null value will
		804	introduce an additional C<ev_sleep ()> call into most loop iterations.
		805
		806	Likewise, by setting a higher I<timeout collect interval> you allow libev
		807	to spend more time collecting timeouts, at the expense of increased
		808	latency/jitter/inexactness (the watcher callback will be called
		809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		810	value will not introduce any overhead in libev.
		811
		812	Many (busy) programs can usually benefit by setting the I/O collect
		813	interval to a value near C<0.1> or so, which is often enough for
		814	interactive servers (of course not for games), likewise for timeouts. It
		815	usually doesn't make much sense to set it to a lower value than C<0.01>,
		816	as this approaches the timing granularity of most systems.
		817
		818	Setting the I<timeout collect interval> can improve the opportunity for
		819	saving power, as the program will "bundle" timer callback invocations that
		820	are "near" in time together, by delaying some, thus reducing the number of
		821	times the process sleeps and wakes up again. Another useful technique to
		822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		823	they fire on, say, one-second boundaries only.
		824
		825	=item ev_loop_verify (loop)
		826
		827	This function only does something when C<EV_VERIFY> support has been
		828	compiled in, which is the default for non-minimal builds. It tries to go
		829	through all internal structures and checks them for validity. If anything
		830	is found to be inconsistent, it will print an error message to standard
		831	error and call C<abort ()>.
		832
		833	This can be used to catch bugs inside libev itself: under normal
		834	circumstances, this function will never abort as of course libev keeps its
		835	data structures consistent.
516		836
517	=back	837	=back
518		838
519		839
520	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
521		845
522	A watcher is a structure that you create and register to record your	846	A watcher is a structure that you create and register to record your
523	interest in some event. For instance, if you want to wait for STDIN to	847	interest in some event. For instance, if you want to wait for STDIN to
524	become readable, you would create an C<ev_io> watcher for that:	848	become readable, you would create an C<ev_io> watcher for that:
525		849
526	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
527	{	851	{
528	ev_io_stop (w);	852	ev_io_stop (w);
529	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
530	}	854	}
531		855
532	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
533	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
534	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
535	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
536	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
537	ev_loop (loop, 0);	864	ev_loop (loop, 0);
538		865
539	As you can see, you are responsible for allocating the memory for your	866	As you can see, you are responsible for allocating the memory for your
540	watcher structures (and it is usually a bad idea to do this on the stack,	867	watcher structures (and it is I<usually> a bad idea to do this on the
541	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
542		872
543	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
544	(watcher *, callback)>, which expects a callback to be provided. This	874	(watcher *, callback)>, which expects a callback to be provided. This
545	callback gets invoked each time the event occurs (or, in the case of io	875	callback gets invoked each time the event occurs (or, in the case of I/O
546	watchers, each time the event loop detects that the file descriptor given	876	watchers, each time the event loop detects that the file descriptor given
547	is readable and/or writable).	877	is readable and/or writable).
548		878
549	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
550	with arguments specific to this watcher type. There is also a macro	880	macro to configure it, with arguments specific to the watcher type. There
551	to combine initialisation and setting in one call: C<< ev_<type>_init	881	is also a macro to combine initialisation and setting in one call: C<<
552	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
553		883
554	To make the watcher actually watch out for events, you have to start it	884	To make the watcher actually watch out for events, you have to start it
555	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	885	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
556	*) >>), and you can stop watching for events at any time by calling the	886	*) >>), and you can stop watching for events at any time by calling the
557	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
558		888
559	As long as your watcher is active (has been started but not stopped) you	889	As long as your watcher is active (has been started but not stopped) you
560	must not touch the values stored in it. Most specifically you must never	890	must not touch the values stored in it. Most specifically you must never
561	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
562		892
563	Each and every callback receives the event loop pointer as first, the	893	Each and every callback receives the event loop pointer as first, the
564	registered watcher structure as second, and a bitset of received events as	894	registered watcher structure as second, and a bitset of received events as
565	third argument.	895	third argument.
566		896
…		…
620	=item C<EV_FORK>	950	=item C<EV_FORK>
621		951
622	The event loop has been resumed in the child process after fork (see	952	The event loop has been resumed in the child process after fork (see
623	C<ev_fork>).	953	C<ev_fork>).
624		954
		955	=item C<EV_ASYNC>
		956
		957	The given async watcher has been asynchronously notified (see C<ev_async>).
		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
625	=item C<EV_ERROR>	964	=item C<EV_ERROR>
626		965
627	An unspecified error has occured, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
628	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
629	ran out of memory, a file descriptor was found to be closed or any other	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
630	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
631	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
632		975
633	Libev will usually signal a few "dummy" events together with an error,	976	Libev will usually signal a few "dummy" events together with an error, for
634	for example it might indicate that a fd is readable or writable, and if	977	example it might indicate that a fd is readable or writable, and if your
635	your callbacks is well-written it can just attempt the operation and cope	978	callbacks is well-written it can just attempt the operation and cope with
636	with the error from read() or write(). This will not work in multithreaded	979	the error from read() or write(). This will not work in multi-threaded
637	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
638		982
639	=back	983	=back
640		984
641	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
642
643	In the following description, C<TYPE> stands for the watcher type,
644	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
645		986
646	=over 4	987	=over 4
647		988
648	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
649		990
…		…
655	which rolls both calls into one.	996	which rolls both calls into one.
656		997
657	You can reinitialise a watcher at any time as long as it has been stopped	998	You can reinitialise a watcher at any time as long as it has been stopped
658	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
659		1000
660	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
661	int revents)>.	1002	int revents)>.
		1003
		1004	Example: Initialise an C<ev_io> watcher in two steps.
		1005
		1006	ev_io w;
		1007	ev_init (&w, my_cb);
		1008	ev_io_set (&w, STDIN_FILENO, EV_READ);
662		1009
663	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
664		1011
665	This macro initialises the type-specific parts of a watcher. You need to	1012	This macro initialises the type-specific parts of a watcher. You need to
666	call C<ev_init> at least once before you call this macro, but you can	1013	call C<ev_init> at least once before you call this macro, but you can
…		…
669	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
670		1017
671	Although some watcher types do not have type-specific arguments	1018	Although some watcher types do not have type-specific arguments
672	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1019	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
673		1020
		1021	See C<ev_init>, above, for an example.
		1022
674	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
675		1024
676	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1025	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
677	calls into a single call. This is the most convinient method to initialise	1026	calls into a single call. This is the most convenient method to initialise
678	a watcher. The same limitations apply, of course.	1027	a watcher. The same limitations apply, of course.
		1028
		1029	Example: Initialise and set an C<ev_io> watcher in one step.
		1030
		1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
679		1032
680	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
681		1034
682	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
683	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
684		1037
		1038	Example: Start the C<ev_io> watcher that is being abused as example in this
		1039	whole section.
		1040
		1041	ev_io_start (EV_DEFAULT_UC, &w);
		1042
685	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
686		1044
687	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
688	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
689	non-repeating timers are being stopped when they become pending), but	1049	non-repeating timers are being stopped when they become pending - but
690	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1050	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
691	you want to free or reuse the memory used by the watcher it is therefore a	1051	pending. If you want to free or reuse the memory used by the watcher it is
692	good idea to always call its C<ev_TYPE_stop> function.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
693		1053
694	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
695		1055
696	Returns a true value iff the watcher is active (i.e. it has been started	1056	Returns a true value iff the watcher is active (i.e. it has been started
697	and not yet been stopped). As long as a watcher is active you must not modify	1057	and not yet been stopped). As long as a watcher is active you must not modify
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	1060	=item bool ev_is_pending (ev_TYPE *watcher)
701		1061
702	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1062	Returns a true value iff the watcher is pending, (i.e. it has outstanding
703	events but its callback has not yet been invoked). As long as a watcher	1063	events but its callback has not yet been invoked). As long as a watcher
704	is pending (but not active) you must not call an init function on it (but	1064	is pending (but not active) you must not call an init function on it (but
705	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	1065	C<ev_TYPE_set> is safe), you must not change its priority, and you must
706	libev (e.g. you cnanot C<free ()> it).	1066	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1067	it).
707		1068
708	=item callback ev_cb (ev_TYPE *watcher)	1069	=item callback ev_cb (ev_TYPE *watcher)
709		1070
710	Returns the callback currently set on the watcher.	1071	Returns the callback currently set on the watcher.
711		1072
712	=item ev_cb_set (ev_TYPE *watcher, callback)	1073	=item ev_cb_set (ev_TYPE *watcher, callback)
713		1074
714	Change the callback. You can change the callback at virtually any time	1075	Change the callback. You can change the callback at virtually any time
715	(modulo threads).	1076	(modulo threads).
716		1077
		1078	=item ev_set_priority (ev_TYPE *watcher, priority)
		1079
		1080	=item int ev_priority (ev_TYPE *watcher)
		1081
		1082	Set and query the priority of the watcher. The priority is a small
		1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1084	(default: C<-2>). Pending watchers with higher priority will be invoked
		1085	before watchers with lower priority, but priority will not keep watchers
		1086	from being executed (except for C<ev_idle> watchers).
		1087
		1088	This means that priorities are I<only> used for ordering callback
		1089	invocation after new events have been received. This is useful, for
		1090	example, to reduce latency after idling, or more often, to bind two
		1091	watchers on the same event and make sure one is called first.
		1092
		1093	If you need to suppress invocation when higher priority events are pending
		1094	you need to look at C<ev_idle> watchers, which provide this functionality.
		1095
		1096	You I<must not> change the priority of a watcher as long as it is active or
		1097	pending.
		1098
		1099	The default priority used by watchers when no priority has been set is
		1100	always C<0>, which is supposed to not be too high and not be too low :).
		1101
		1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1103	fine, as long as you do not mind that the priority value you query might
		1104	or might not have been clamped to the valid range.
		1105
		1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1107
		1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1109	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1110	can deal with that fact, as both are simply passed through to the
		1111	callback.
		1112
		1113	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1114
		1115	If the watcher is pending, this function clears its pending status and
		1116	returns its C<revents> bitset (as if its callback was invoked). If the
		1117	watcher isn't pending it does nothing and returns C<0>.
		1118
		1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1120	callback to be invoked, which can be accomplished with this function.
		1121
717	=back	1122	=back
718		1123
719		1124
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
721		1126
722	Each watcher has, by default, a member C<void *data> that you can change	1127	Each watcher has, by default, a member C<void *data> that you can change
723	and read at any time, libev will completely ignore it. This can be used	1128	and read at any time: libev will completely ignore it. This can be used
724	to associate arbitrary data with your watcher. If you need more data and	1129	to associate arbitrary data with your watcher. If you need more data and
725	don't want to allocate memory and store a pointer to it in that data	1130	don't want to allocate memory and store a pointer to it in that data
726	member, you can also "subclass" the watcher type and provide your own	1131	member, you can also "subclass" the watcher type and provide your own
727	data:	1132	data:
728		1133
729	struct my_io	1134	struct my_io
730	{	1135	{
731	struct ev_io io;	1136	ev_io io;
732	int otherfd;	1137	int otherfd;
733	void *somedata;	1138	void *somedata;
734	struct whatever *mostinteresting;	1139	struct whatever *mostinteresting;
735	}	1140	};
		1141
		1142	...
		1143	struct my_io w;
		1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
736		1145
737	And since your callback will be called with a pointer to the watcher, you	1146	And since your callback will be called with a pointer to the watcher, you
738	can cast it back to your own type:	1147	can cast it back to your own type:
739		1148
740	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
741	{	1150	{
742	struct my_io *w = (struct my_io *)w_;	1151	struct my_io *w = (struct my_io *)w_;
743	...	1152	...
744	}	1153	}
745		1154
746	More interesting and less C-conformant ways of casting your callback type	1155	More interesting and less C-conformant ways of casting your callback type
747	instead have been omitted.	1156	instead have been omitted.
748		1157
749	Another common scenario is having some data structure with multiple	1158	Another common scenario is to use some data structure with multiple
750	watchers:	1159	embedded watchers:
751		1160
752	struct my_biggy	1161	struct my_biggy
753	{	1162	{
754	int some_data;	1163	int some_data;
755	ev_timer t1;	1164	ev_timer t1;
756	ev_timer t2;	1165	ev_timer t2;
757	}	1166	}
758		1167
759	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1168	In this case getting the pointer to C<my_biggy> is a bit more
760	you need to use C<offsetof>:	1169	complicated: Either you store the address of your C<my_biggy> struct
		1170	in the C<data> member of the watcher (for woozies), or you need to use
		1171	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1172	programmers):
761		1173
762	#include <stddef.h>	1174	#include <stddef.h>
763		1175
764	static void	1176	static void
765	t1_cb (EV_P_ struct ev_timer *w, int revents)	1177	t1_cb (EV_P_ ev_timer *w, int revents)
766	{	1178	{
767	struct my_biggy big = (struct my_biggy *	1179	struct my_biggy big = (struct my_biggy *
768	(((char *)w) - offsetof (struct my_biggy, t1));	1180	(((char *)w) - offsetof (struct my_biggy, t1));
769	}	1181	}
770		1182
771	static void	1183	static void
772	t2_cb (EV_P_ struct ev_timer *w, int revents)	1184	t2_cb (EV_P_ ev_timer *w, int revents)
773	{	1185	{
774	struct my_biggy big = (struct my_biggy *	1186	struct my_biggy big = (struct my_biggy *
775	(((char *)w) - offsetof (struct my_biggy, t2));	1187	(((char *)w) - offsetof (struct my_biggy, t2));
776	}	1188	}
777		1189
778		1190
779	=head1 WATCHER TYPES	1191	=head1 WATCHER TYPES
780		1192
781	This section describes each watcher in detail, but will not repeat	1193	This section describes each watcher in detail, but will not repeat
…		…
805	In general you can register as many read and/or write event watchers per	1217	In general you can register as many read and/or write event watchers per
806	fd as you want (as long as you don't confuse yourself). Setting all file	1218	fd as you want (as long as you don't confuse yourself). Setting all file
807	descriptors to non-blocking mode is also usually a good idea (but not	1219	descriptors to non-blocking mode is also usually a good idea (but not
808	required if you know what you are doing).	1220	required if you know what you are doing).
809		1221
810	You have to be careful with dup'ed file descriptors, though. Some backends	1222	If you cannot use non-blocking mode, then force the use of a
811	(the linux epoll backend is a notable example) cannot handle dup'ed file	1223	known-to-be-good backend (at the time of this writing, this includes only
812	descriptors correctly if you register interest in two or more fds pointing	1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
813	to the same underlying file/socket/etc. description (that is, they share
814	the same underlying "file open").
815
816	If you must do this, then force the use of a known-to-be-good backend
817	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
818	C<EVBACKEND_POLL>).
819		1225
820	Another thing you have to watch out for is that it is quite easy to	1226	Another thing you have to watch out for is that it is quite easy to
821	receive "spurious" readyness notifications, that is your callback might	1227	receive "spurious" readiness notifications, that is your callback might
822	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
823	because there is no data. Not only are some backends known to create a	1229	because there is no data. Not only are some backends known to create a
824	lot of those (for example solaris ports), it is very easy to get into	1230	lot of those (for example Solaris ports), it is very easy to get into
825	this situation even with a relatively standard program structure. Thus	1231	this situation even with a relatively standard program structure. Thus
826	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1232	it is best to always use non-blocking I/O: An extra C<read>(2) returning
827	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1233	C<EAGAIN> is far preferable to a program hanging until some data arrives.
828		1234
829	If you cannot run the fd in non-blocking mode (for example you should not	1235	If you cannot run the fd in non-blocking mode (for example you should
830	play around with an Xlib connection), then you have to seperately re-test	1236	not play around with an Xlib connection), then you have to separately
831	wether a file descriptor is really ready with a known-to-be good interface	1237	re-test whether a file descriptor is really ready with a known-to-be good
832	such as poll (fortunately in our Xlib example, Xlib already does this on	1238	interface such as poll (fortunately in our Xlib example, Xlib already
833	its own, so its quite safe to use).	1239	does this on its own, so its quite safe to use). Some people additionally
		1240	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1241	indefinitely.
		1242
		1243	But really, best use non-blocking mode.
		1244
		1245	=head3 The special problem of disappearing file descriptors
		1246
		1247	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1248	descriptor (either due to calling C<close> explicitly or any other means,
		1249	such as C<dup2>). The reason is that you register interest in some file
		1250	descriptor, but when it goes away, the operating system will silently drop
		1251	this interest. If another file descriptor with the same number then is
		1252	registered with libev, there is no efficient way to see that this is, in
		1253	fact, a different file descriptor.
		1254
		1255	To avoid having to explicitly tell libev about such cases, libev follows
		1256	the following policy: Each time C<ev_io_set> is being called, libev
		1257	will assume that this is potentially a new file descriptor, otherwise
		1258	it is assumed that the file descriptor stays the same. That means that
		1259	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1260	descriptor even if the file descriptor number itself did not change.
		1261
		1262	This is how one would do it normally anyway, the important point is that
		1263	the libev application should not optimise around libev but should leave
		1264	optimisations to libev.
		1265
		1266	=head3 The special problem of dup'ed file descriptors
		1267
		1268	Some backends (e.g. epoll), cannot register events for file descriptors,
		1269	but only events for the underlying file descriptions. That means when you
		1270	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1271	events for them, only one file descriptor might actually receive events.
		1272
		1273	There is no workaround possible except not registering events
		1274	for potentially C<dup ()>'ed file descriptors, or to resort to
		1275	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1276
		1277	=head3 The special problem of fork
		1278
		1279	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1280	useless behaviour. Libev fully supports fork, but needs to be told about
		1281	it in the child.
		1282
		1283	To support fork in your programs, you either have to call
		1284	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1286	C<EVBACKEND_POLL>.
		1287
		1288	=head3 The special problem of SIGPIPE
		1289
		1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1291	when writing to a pipe whose other end has been closed, your program gets
		1292	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1293	this is sensible behaviour, for daemons, this is usually undesirable.
		1294
		1295	So when you encounter spurious, unexplained daemon exits, make sure you
		1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1297	somewhere, as that would have given you a big clue).
		1298
		1299
		1300	=head3 Watcher-Specific Functions
834		1301
835	=over 4	1302	=over 4
836		1303
837	=item ev_io_init (ev_io *, callback, int fd, int events)	1304	=item ev_io_init (ev_io *, callback, int fd, int events)
838		1305
839	=item ev_io_set (ev_io *, int fd, int events)	1306	=item ev_io_set (ev_io *, int fd, int events)
840		1307
841	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1308	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
842	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1309	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
843	C<EV_READ | EV_WRITE> to receive the given events.	1310	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
844		1311
845	=item int fd [read-only]	1312	=item int fd [read-only]
846		1313
847	The file descriptor being watched.	1314	The file descriptor being watched.
848		1315
849	=item int events [read-only]	1316	=item int events [read-only]
850		1317
851	The events being watched.	1318	The events being watched.
852		1319
853	=back	1320	=back
		1321
		1322	=head3 Examples
854		1323
855	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1324	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
856	readable, but only once. Since it is likely line-buffered, you could	1325	readable, but only once. Since it is likely line-buffered, you could
857	attempt to read a whole line in the callback.	1326	attempt to read a whole line in the callback.
858		1327
859	static void	1328	static void
860	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1329	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
861	{	1330	{
862	ev_io_stop (loop, w);	1331	ev_io_stop (loop, w);
863	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1332	.. read from stdin here (or from w->fd) and handle any I/O errors
864	}	1333	}
865		1334
866	...	1335	...
867	struct ev_loop *loop = ev_default_init (0);	1336	struct ev_loop *loop = ev_default_init (0);
868	struct ev_io stdin_readable;	1337	ev_io stdin_readable;
869	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
870	ev_io_start (loop, &stdin_readable);	1339	ev_io_start (loop, &stdin_readable);
871	ev_loop (loop, 0);	1340	ev_loop (loop, 0);
872		1341
873		1342
874	=head2 C<ev_timer> - relative and optionally repeating timeouts	1343	=head2 C<ev_timer> - relative and optionally repeating timeouts
875		1344
876	Timer watchers are simple relative timers that generate an event after a	1345	Timer watchers are simple relative timers that generate an event after a
877	given time, and optionally repeating in regular intervals after that.	1346	given time, and optionally repeating in regular intervals after that.
878		1347
879	The timers are based on real time, that is, if you register an event that	1348	The timers are based on real time, that is, if you register an event that
880	times out after an hour and you reset your system clock to last years	1349	times out after an hour and you reset your system clock to January last
881	time, it will still time out after (roughly) and hour. "Roughly" because	1350	year, it will still time out after (roughly) one hour. "Roughly" because
882	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the
883	monotonic clock option helps a lot here).	1352	monotonic clock option helps a lot here).
		1353
		1354	The callback is guaranteed to be invoked only I<after> its timeout has
		1355	passed. If multiple timers become ready during the same loop iteration
		1356	then the ones with earlier time-out values are invoked before ones with
		1357	later time-out values (but this is no longer true when a callback calls
		1358	C<ev_loop> recursively).
		1359
		1360	=head3 Be smart about timeouts
		1361
		1362	Many real-world problems involve some kind of timeout, usually for error
		1363	recovery. A typical example is an HTTP request - if the other side hangs,
		1364	you want to raise some error after a while.
		1365
		1366	What follows are some ways to handle this problem, from obvious and
		1367	inefficient to smart and efficient.
		1368
		1369	In the following, a 60 second activity timeout is assumed - a timeout that
		1370	gets reset to 60 seconds each time there is activity (e.g. each time some
		1371	data or other life sign was received).
		1372
		1373	=over 4
		1374
		1375	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1376
		1377	This is the most obvious, but not the most simple way: In the beginning,
		1378	start the watcher:
		1379
		1380	ev_timer_init (timer, callback, 60., 0.);
		1381	ev_timer_start (loop, timer);
		1382
		1383	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1384	and start it again:
		1385
		1386	ev_timer_stop (loop, timer);
		1387	ev_timer_set (timer, 60., 0.);
		1388	ev_timer_start (loop, timer);
		1389
		1390	This is relatively simple to implement, but means that each time there is
		1391	some activity, libev will first have to remove the timer from its internal
		1392	data structure and then add it again. Libev tries to be fast, but it's
		1393	still not a constant-time operation.
		1394
		1395	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1396
		1397	This is the easiest way, and involves using C<ev_timer_again> instead of
		1398	C<ev_timer_start>.
		1399
		1400	To implement this, configure an C<ev_timer> with a C<repeat> value
		1401	of C<60> and then call C<ev_timer_again> at start and each time you
		1402	successfully read or write some data. If you go into an idle state where
		1403	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1404	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1405
		1406	That means you can ignore both the C<ev_timer_start> function and the
		1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1408	member and C<ev_timer_again>.
		1409
		1410	At start:
		1411
		1412	ev_timer_init (timer, callback);
		1413	timer->repeat = 60.;
		1414	ev_timer_again (loop, timer);
		1415
		1416	Each time there is some activity:
		1417
		1418	ev_timer_again (loop, timer);
		1419
		1420	It is even possible to change the time-out on the fly, regardless of
		1421	whether the watcher is active or not:
		1422
		1423	timer->repeat = 30.;
		1424	ev_timer_again (loop, timer);
		1425
		1426	This is slightly more efficient then stopping/starting the timer each time
		1427	you want to modify its timeout value, as libev does not have to completely
		1428	remove and re-insert the timer from/into its internal data structure.
		1429
		1430	It is, however, even simpler than the "obvious" way to do it.
		1431
		1432	=item 3. Let the timer time out, but then re-arm it as required.
		1433
		1434	This method is more tricky, but usually most efficient: Most timeouts are
		1435	relatively long compared to the intervals between other activity - in
		1436	our example, within 60 seconds, there are usually many I/O events with
		1437	associated activity resets.
		1438
		1439	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1440	but remember the time of last activity, and check for a real timeout only
		1441	within the callback:
		1442
		1443	ev_tstamp last_activity; // time of last activity
		1444
		1445	static void
		1446	callback (EV_P_ ev_timer *w, int revents)
		1447	{
		1448	ev_tstamp now = ev_now (EV_A);
		1449	ev_tstamp timeout = last_activity + 60.;
		1450
		1451	// if last_activity + 60. is older than now, we did time out
		1452	if (timeout < now)
		1453	{
		1454	// timeout occured, take action
		1455	}
		1456	else
		1457	{
		1458	// callback was invoked, but there was some activity, re-arm
		1459	// the watcher to fire in last_activity + 60, which is
		1460	// guaranteed to be in the future, so "again" is positive:
		1461	w->repeat = timeout - now;
		1462	ev_timer_again (EV_A_ w);
		1463	}
		1464	}
		1465
		1466	To summarise the callback: first calculate the real timeout (defined
		1467	as "60 seconds after the last activity"), then check if that time has
		1468	been reached, which means something I<did>, in fact, time out. Otherwise
		1469	the callback was invoked too early (C<timeout> is in the future), so
		1470	re-schedule the timer to fire at that future time, to see if maybe we have
		1471	a timeout then.
		1472
		1473	Note how C<ev_timer_again> is used, taking advantage of the
		1474	C<ev_timer_again> optimisation when the timer is already running.
		1475
		1476	This scheme causes more callback invocations (about one every 60 seconds
		1477	minus half the average time between activity), but virtually no calls to
		1478	libev to change the timeout.
		1479
		1480	To start the timer, simply initialise the watcher and set C<last_activity>
		1481	to the current time (meaning we just have some activity :), then call the
		1482	callback, which will "do the right thing" and start the timer:
		1483
		1484	ev_timer_init (timer, callback);
		1485	last_activity = ev_now (loop);
		1486	callback (loop, timer, EV_TIMEOUT);
		1487
		1488	And when there is some activity, simply store the current time in
		1489	C<last_activity>, no libev calls at all:
		1490
		1491	last_actiivty = ev_now (loop);
		1492
		1493	This technique is slightly more complex, but in most cases where the
		1494	time-out is unlikely to be triggered, much more efficient.
		1495
		1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1497	callback :) - just change the timeout and invoke the callback, which will
		1498	fix things for you.
		1499
		1500	=item 4. Wee, just use a double-linked list for your timeouts.
		1501
		1502	If there is not one request, but many thousands (millions...), all
		1503	employing some kind of timeout with the same timeout value, then one can
		1504	do even better:
		1505
		1506	When starting the timeout, calculate the timeout value and put the timeout
		1507	at the I<end> of the list.
		1508
		1509	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1510	the list is expected to fire (for example, using the technique #3).
		1511
		1512	When there is some activity, remove the timer from the list, recalculate
		1513	the timeout, append it to the end of the list again, and make sure to
		1514	update the C<ev_timer> if it was taken from the beginning of the list.
		1515
		1516	This way, one can manage an unlimited number of timeouts in O(1) time for
		1517	starting, stopping and updating the timers, at the expense of a major
		1518	complication, and having to use a constant timeout. The constant timeout
		1519	ensures that the list stays sorted.
		1520
		1521	=back
		1522
		1523	So which method the best?
		1524
		1525	Method #2 is a simple no-brain-required solution that is adequate in most
		1526	situations. Method #3 requires a bit more thinking, but handles many cases
		1527	better, and isn't very complicated either. In most case, choosing either
		1528	one is fine, with #3 being better in typical situations.
		1529
		1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1531	rather complicated, but extremely efficient, something that really pays
		1532	off after the first million or so of active timers, i.e. it's usually
		1533	overkill :)
		1534
		1535	=head3 The special problem of time updates
		1536
		1537	Establishing the current time is a costly operation (it usually takes at
		1538	least two system calls): EV therefore updates its idea of the current
		1539	time only before and after C<ev_loop> collects new events, which causes a
		1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1541	lots of events in one iteration.
884		1542
885	The relative timeouts are calculated relative to the C<ev_now ()>	1543	The relative timeouts are calculated relative to the C<ev_now ()>
886	time. This is usually the right thing as this timestamp refers to the time	1544	time. This is usually the right thing as this timestamp refers to the time
887	of the event triggering whatever timeout you are modifying/starting. If	1545	of the event triggering whatever timeout you are modifying/starting. If
888	you suspect event processing to be delayed and you I<need> to base the timeout	1546	you suspect event processing to be delayed and you I<need> to base the
889	on the current time, use something like this to adjust for this:	1547	timeout on the current time, use something like this to adjust for this:
890		1548
891	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1549	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
892		1550
893	The callback is guarenteed to be invoked only when its timeout has passed,	1551	If the event loop is suspended for a long time, you can also force an
894	but if multiple timers become ready during the same loop iteration then	1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update
895	order of execution is undefined.	1553	()>.
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
896		1556
897	=over 4	1557	=over 4
898		1558
899	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
900		1560
901	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1561	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
902		1562
903	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1563	Configure the timer to trigger after C<after> seconds. If C<repeat>
904	C<0.>, then it will automatically be stopped. If it is positive, then the	1564	is C<0.>, then it will automatically be stopped once the timeout is
905	timer will automatically be configured to trigger again C<repeat> seconds	1565	reached. If it is positive, then the timer will automatically be
906	later, again, and again, until stopped manually.	1566	configured to trigger again C<repeat> seconds later, again, and again,
		1567	until stopped manually.
907		1568
908	The timer itself will do a best-effort at avoiding drift, that is, if you	1569	The timer itself will do a best-effort at avoiding drift, that is, if
909	configure a timer to trigger every 10 seconds, then it will trigger at	1570	you configure a timer to trigger every 10 seconds, then it will normally
910	exactly 10 second intervals. If, however, your program cannot keep up with	1571	trigger at exactly 10 second intervals. If, however, your program cannot
911	the timer (because it takes longer than those 10 seconds to do stuff) the	1572	keep up with the timer (because it takes longer than those 10 seconds to
912	timer will not fire more than once per event loop iteration.	1573	do stuff) the timer will not fire more than once per event loop iteration.
913		1574
914	=item ev_timer_again (loop)	1575	=item ev_timer_again (loop, ev_timer *)
915		1576
916	This will act as if the timer timed out and restart it again if it is	1577	This will act as if the timer timed out and restart it again if it is
917	repeating. The exact semantics are:	1578	repeating. The exact semantics are:
918		1579
		1580	If the timer is pending, its pending status is cleared.
		1581
919	If the timer is started but nonrepeating, stop it.	1582	If the timer is started but non-repeating, stop it (as if it timed out).
920		1583
921	If the timer is repeating, either start it if necessary (with the repeat	1584	If the timer is repeating, either start it if necessary (with the
922	value), or reset the running timer to the repeat value.	1585	C<repeat> value), or reset the running timer to the C<repeat> value.
923		1586
924	This sounds a bit complicated, but here is a useful and typical	1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a
925	example: Imagine you have a tcp connection and you want a so-called	1588	usage example.
926	idle timeout, that is, you want to be called when there have been,
927	say, 60 seconds of inactivity on the socket. The easiest way to do
928	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
929	C<ev_timer_again> each time you successfully read or write some data. If
930	you go into an idle state where you do not expect data to travel on the
931	socket, you can stop the timer, and again will automatically restart it if
932	need be.
933
934	You can also ignore the C<after> value and C<ev_timer_start> altogether
935	and only ever use the C<repeat> value:
936
937	ev_timer_init (timer, callback, 0., 5.);
938	ev_timer_again (loop, timer);
939	...
940	timer->again = 17.;
941	ev_timer_again (loop, timer);
942	...
943	timer->again = 10.;
944	ev_timer_again (loop, timer);
945
946	This is more efficient then stopping/starting the timer eahc time you want
947	to modify its timeout value.
948		1589
949	=item ev_tstamp repeat [read-write]	1590	=item ev_tstamp repeat [read-write]
950		1591
951	The current C<repeat> value. Will be used each time the watcher times out	1592	The current C<repeat> value. Will be used each time the watcher times out
952	or C<ev_timer_again> is called and determines the next timeout (if any),	1593	or C<ev_timer_again> is called, and determines the next timeout (if any),
953	which is also when any modifications are taken into account.	1594	which is also when any modifications are taken into account.
954		1595
955	=back	1596	=back
956		1597
		1598	=head3 Examples
		1599
957	Example: Create a timer that fires after 60 seconds.	1600	Example: Create a timer that fires after 60 seconds.
958		1601
959	static void	1602	static void
960	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1603	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
961	{	1604	{
962	.. one minute over, w is actually stopped right here	1605	.. one minute over, w is actually stopped right here
963	}	1606	}
964		1607
965	struct ev_timer mytimer;	1608	ev_timer mytimer;
966	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1609	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
967	ev_timer_start (loop, &mytimer);	1610	ev_timer_start (loop, &mytimer);
968		1611
969	Example: Create a timeout timer that times out after 10 seconds of	1612	Example: Create a timeout timer that times out after 10 seconds of
970	inactivity.	1613	inactivity.
971		1614
972	static void	1615	static void
973	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1616	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
974	{	1617	{
975	.. ten seconds without any activity	1618	.. ten seconds without any activity
976	}	1619	}
977		1620
978	struct ev_timer mytimer;	1621	ev_timer mytimer;
979	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
980	ev_timer_again (&mytimer); /* start timer */	1623	ev_timer_again (&mytimer); /* start timer */
981	ev_loop (loop, 0);	1624	ev_loop (loop, 0);
982		1625
983	// and in some piece of code that gets executed on any "activity":	1626	// and in some piece of code that gets executed on any "activity":
984	// reset the timeout to start ticking again at 10 seconds	1627	// reset the timeout to start ticking again at 10 seconds
985	ev_timer_again (&mytimer);	1628	ev_timer_again (&mytimer);
986		1629
987		1630
988	=head2 C<ev_periodic> - to cron or not to cron?	1631	=head2 C<ev_periodic> - to cron or not to cron?
989		1632
990	Periodic watchers are also timers of a kind, but they are very versatile	1633	Periodic watchers are also timers of a kind, but they are very versatile
991	(and unfortunately a bit complex).	1634	(and unfortunately a bit complex).
992		1635
993	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1636	Unlike C<ev_timer>, periodic watchers are not based on real time (or
994	but on wallclock time (absolute time). You can tell a periodic watcher	1637	relative time, the physical time that passes) but on wall clock time
995	to trigger "at" some specific point in time. For example, if you tell a	1638	(absolute time, the thing you can read on your calender or clock). The
996	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1639	difference is that wall clock time can run faster or slower than real
997	+ 10.>) and then reset your system clock to the last year, then it will	1640	time, and time jumps are not uncommon (e.g. when you adjust your
998	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1641	wrist-watch).
999	roughly 10 seconds later and of course not if you reset your system time
1000	again).
1001		1642
1002	They can also be used to implement vastly more complex timers, such as	1643	You can tell a periodic watcher to trigger after some specific point
		1644	in time: for example, if you tell a periodic watcher to trigger "in 10
		1645	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1646	not a delay) and then reset your system clock to January of the previous
		1647	year, then it will take a year or more to trigger the event (unlike an
		1648	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1649	it, as it uses a relative timeout).
		1650
		1651	C<ev_periodic> watchers can also be used to implement vastly more complex
1003	triggering an event on eahc midnight, local time.	1652	timers, such as triggering an event on each "midnight, local time", or
		1653	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1654	those cannot react to time jumps.
1004		1655
1005	As with timers, the callback is guarenteed to be invoked only when the	1656	As with timers, the callback is guaranteed to be invoked only when the
1006	time (C<at>) has been passed, but if multiple periodic timers become ready	1657	point in time where it is supposed to trigger has passed. If multiple
1007	during the same loop iteration then order of execution is undefined.	1658	timers become ready during the same loop iteration then the ones with
		1659	earlier time-out values are invoked before ones with later time-out values
		1660	(but this is no longer true when a callback calls C<ev_loop> recursively).
		1661
		1662	=head3 Watcher-Specific Functions and Data Members
1008		1663
1009	=over 4	1664	=over 4
1010		1665
1011	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1666	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1012		1667
1013	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1668	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1014		1669
1015	Lots of arguments, lets sort it out... There are basically three modes of	1670	Lots of arguments, let's sort it out... There are basically three modes of
1016	operation, and we will explain them from simplest to complex:	1671	operation, and we will explain them from simplest to most complex:
1017		1672
1018	=over 4	1673	=over 4
1019		1674
1020	=item * absolute timer (interval = reschedule_cb = 0)	1675	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1021		1676
1022	In this configuration the watcher triggers an event at the wallclock time	1677	In this configuration the watcher triggers an event after the wall clock
1023	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1678	time C<offset> has passed. It will not repeat and will not adjust when a
1024	that is, if it is to be run at January 1st 2011 then it will run when the	1679	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1025	system time reaches or surpasses this time.	1680	will be stopped and invoked when the system clock reaches or surpasses
		1681	this point in time.
1026		1682
1027	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1683	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1028		1684
1029	In this mode the watcher will always be scheduled to time out at the next	1685	In this mode the watcher will always be scheduled to time out at the next
1030	C<at + N * interval> time (for some integer N) and then repeat, regardless	1686	C<offset + N * interval> time (for some integer N, which can also be
1031	of any time jumps.	1687	negative) and then repeat, regardless of any time jumps. The C<offset>
		1688	argument is merely an offset into the C<interval> periods.
1032		1689
1033	This can be used to create timers that do not drift with respect to system	1690	This can be used to create timers that do not drift with respect to the
1034	time:	1691	system clock, for example, here is an C<ev_periodic> that triggers each
		1692	hour, on the hour (with respect to UTC):
1035		1693
1036	ev_periodic_set (&periodic, 0., 3600., 0);	1694	ev_periodic_set (&periodic, 0., 3600., 0);
1037		1695
1038	This doesn't mean there will always be 3600 seconds in between triggers,	1696	This doesn't mean there will always be 3600 seconds in between triggers,
1039	but only that the the callback will be called when the system time shows a	1697	but only that the callback will be called when the system time shows a
1040	full hour (UTC), or more correctly, when the system time is evenly divisible	1698	full hour (UTC), or more correctly, when the system time is evenly divisible
1041	by 3600.	1699	by 3600.
1042		1700
1043	Another way to think about it (for the mathematically inclined) is that	1701	Another way to think about it (for the mathematically inclined) is that
1044	C<ev_periodic> will try to run the callback in this mode at the next possible	1702	C<ev_periodic> will try to run the callback in this mode at the next possible
1045	time where C<time = at (mod interval)>, regardless of any time jumps.	1703	time where C<time = offset (mod interval)>, regardless of any time jumps.
1046		1704
		1705	For numerical stability it is preferable that the C<offset> value is near
		1706	C<ev_now ()> (the current time), but there is no range requirement for
		1707	this value, and in fact is often specified as zero.
		1708
		1709	Note also that there is an upper limit to how often a timer can fire (CPU
		1710	speed for example), so if C<interval> is very small then timing stability
		1711	will of course deteriorate. Libev itself tries to be exact to be about one
		1712	millisecond (if the OS supports it and the machine is fast enough).
		1713
1047	=item * manual reschedule mode (reschedule_cb = callback)	1714	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1048		1715
1049	In this mode the values for C<interval> and C<at> are both being	1716	In this mode the values for C<interval> and C<offset> are both being
1050	ignored. Instead, each time the periodic watcher gets scheduled, the	1717	ignored. Instead, each time the periodic watcher gets scheduled, the
1051	reschedule callback will be called with the watcher as first, and the	1718	reschedule callback will be called with the watcher as first, and the
1052	current time as second argument.	1719	current time as second argument.
1053		1720
1054	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1721	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1055	ever, or make any event loop modifications>. If you need to stop it,	1722	or make ANY other event loop modifications whatsoever, unless explicitly
1056	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1723	allowed by documentation here>.
1057	starting a prepare watcher).
1058		1724
		1725	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1726	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1727	only event loop modification you are allowed to do).
		1728
1059	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1729	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1060	ev_tstamp now)>, e.g.:	1730	*w, ev_tstamp now)>, e.g.:
1061		1731
		1732	static ev_tstamp
1062	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1733	my_rescheduler (ev_periodic *w, ev_tstamp now)
1063	{	1734	{
1064	return now + 60.;	1735	return now + 60.;
1065	}	1736	}
1066		1737
1067	It must return the next time to trigger, based on the passed time value	1738	It must return the next time to trigger, based on the passed time value
1068	(that is, the lowest time value larger than to the second argument). It	1739	(that is, the lowest time value larger than to the second argument). It
1069	will usually be called just before the callback will be triggered, but	1740	will usually be called just before the callback will be triggered, but
1070	might be called at other times, too.	1741	might be called at other times, too.
1071		1742
1072	NOTE: I<< This callback must always return a time that is later than the	1743	NOTE: I<< This callback must always return a time that is higher than or
1073	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1744	equal to the passed C<now> value >>.
1074		1745
1075	This can be used to create very complex timers, such as a timer that	1746	This can be used to create very complex timers, such as a timer that
1076	triggers on each midnight, local time. To do this, you would calculate the	1747	triggers on "next midnight, local time". To do this, you would calculate the
1077	next midnight after C<now> and return the timestamp value for this. How	1748	next midnight after C<now> and return the timestamp value for this. How
1078	you do this is, again, up to you (but it is not trivial, which is the main	1749	you do this is, again, up to you (but it is not trivial, which is the main
1079	reason I omitted it as an example).	1750	reason I omitted it as an example).
1080		1751
1081	=back	1752	=back
…		…
1085	Simply stops and restarts the periodic watcher again. This is only useful	1756	Simply stops and restarts the periodic watcher again. This is only useful
1086	when you changed some parameters or the reschedule callback would return	1757	when you changed some parameters or the reschedule callback would return
1087	a different time than the last time it was called (e.g. in a crond like	1758	a different time than the last time it was called (e.g. in a crond like
1088	program when the crontabs have changed).	1759	program when the crontabs have changed).
1089		1760
		1761	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1762
		1763	When active, returns the absolute time that the watcher is supposed
		1764	to trigger next. This is not the same as the C<offset> argument to
		1765	C<ev_periodic_set>, but indeed works even in interval and manual
		1766	rescheduling modes.
		1767
		1768	=item ev_tstamp offset [read-write]
		1769
		1770	When repeating, this contains the offset value, otherwise this is the
		1771	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1772	although libev might modify this value for better numerical stability).
		1773
		1774	Can be modified any time, but changes only take effect when the periodic
		1775	timer fires or C<ev_periodic_again> is being called.
		1776
1090	=item ev_tstamp interval [read-write]	1777	=item ev_tstamp interval [read-write]
1091		1778
1092	The current interval value. Can be modified any time, but changes only	1779	The current interval value. Can be modified any time, but changes only
1093	take effect when the periodic timer fires or C<ev_periodic_again> is being	1780	take effect when the periodic timer fires or C<ev_periodic_again> is being
1094	called.	1781	called.
1095		1782
1096	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1783	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1097		1784
1098	The current reschedule callback, or C<0>, if this functionality is	1785	The current reschedule callback, or C<0>, if this functionality is
1099	switched off. Can be changed any time, but changes only take effect when	1786	switched off. Can be changed any time, but changes only take effect when
1100	the periodic timer fires or C<ev_periodic_again> is being called.	1787	the periodic timer fires or C<ev_periodic_again> is being called.
1101		1788
1102	=back	1789	=back
1103		1790
		1791	=head3 Examples
		1792
1104	Example: Call a callback every hour, or, more precisely, whenever the	1793	Example: Call a callback every hour, or, more precisely, whenever the
1105	system clock is divisible by 3600. The callback invocation times have	1794	system time is divisible by 3600. The callback invocation times have
1106	potentially a lot of jittering, but good long-term stability.	1795	potentially a lot of jitter, but good long-term stability.
1107		1796
1108	static void	1797	static void
1109	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1110	{	1799	{
1111	... its now a full hour (UTC, or TAI or whatever your clock follows)	1800	... its now a full hour (UTC, or TAI or whatever your clock follows)
1112	}	1801	}
1113		1802
1114	struct ev_periodic hourly_tick;	1803	ev_periodic hourly_tick;
1115	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1804	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1116	ev_periodic_start (loop, &hourly_tick);	1805	ev_periodic_start (loop, &hourly_tick);
1117		1806
1118	Example: The same as above, but use a reschedule callback to do it:	1807	Example: The same as above, but use a reschedule callback to do it:
1119		1808
1120	#include <math.h>	1809	#include <math.h>
1121		1810
1122	static ev_tstamp	1811	static ev_tstamp
1123	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1812	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1124	{	1813	{
1125	return fmod (now, 3600.) + 3600.;	1814	return now + (3600. - fmod (now, 3600.));
1126	}	1815	}
1127		1816
1128	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1817	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1129		1818
1130	Example: Call a callback every hour, starting now:	1819	Example: Call a callback every hour, starting now:
1131		1820
1132	struct ev_periodic hourly_tick;	1821	ev_periodic hourly_tick;
1133	ev_periodic_init (&hourly_tick, clock_cb,	1822	ev_periodic_init (&hourly_tick, clock_cb,
1134	fmod (ev_now (loop), 3600.), 3600., 0);	1823	fmod (ev_now (loop), 3600.), 3600., 0);
1135	ev_periodic_start (loop, &hourly_tick);	1824	ev_periodic_start (loop, &hourly_tick);
1136		1825
1137		1826
1138	=head2 C<ev_signal> - signal me when a signal gets signalled!	1827	=head2 C<ev_signal> - signal me when a signal gets signalled!
1139		1828
1140	Signal watchers will trigger an event when the process receives a specific	1829	Signal watchers will trigger an event when the process receives a specific
1141	signal one or more times. Even though signals are very asynchronous, libev	1830	signal one or more times. Even though signals are very asynchronous, libev
1142	will try it's best to deliver signals synchronously, i.e. as part of the	1831	will try it's best to deliver signals synchronously, i.e. as part of the
1143	normal event processing, like any other event.	1832	normal event processing, like any other event.
1144		1833
		1834	If you want signals asynchronously, just use C<sigaction> as you would
		1835	do without libev and forget about sharing the signal. You can even use
		1836	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1837
1145	You can configure as many watchers as you like per signal. Only when the	1838	You can configure as many watchers as you like per signal. Only when the
1146	first watcher gets started will libev actually register a signal watcher	1839	first watcher gets started will libev actually register a signal handler
1147	with the kernel (thus it coexists with your own signal handlers as long	1840	with the kernel (thus it coexists with your own signal handlers as long as
1148	as you don't register any with libev). Similarly, when the last signal	1841	you don't register any with libev for the same signal). Similarly, when
1149	watcher for a signal is stopped libev will reset the signal handler to	1842	the last signal watcher for a signal is stopped, libev will reset the
1150	SIG_DFL (regardless of what it was set to before).	1843	signal handler to SIG_DFL (regardless of what it was set to before).
		1844
		1845	If possible and supported, libev will install its handlers with
		1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1847	interrupted. If you have a problem with system calls getting interrupted by
		1848	signals you can block all signals in an C<ev_check> watcher and unblock
		1849	them in an C<ev_prepare> watcher.
		1850
		1851	=head3 Watcher-Specific Functions and Data Members
1151		1852
1152	=over 4	1853	=over 4
1153		1854
1154	=item ev_signal_init (ev_signal *, callback, int signum)	1855	=item ev_signal_init (ev_signal *, callback, int signum)
1155		1856
…		…
1162		1863
1163	The signal the watcher watches out for.	1864	The signal the watcher watches out for.
1164		1865
1165	=back	1866	=back
1166		1867
		1868	=head3 Examples
		1869
		1870	Example: Try to exit cleanly on SIGINT.
		1871
		1872	static void
		1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1874	{
		1875	ev_unloop (loop, EVUNLOOP_ALL);
		1876	}
		1877
		1878	ev_signal signal_watcher;
		1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1880	ev_signal_start (loop, &signal_watcher);
		1881
1167		1882
1168	=head2 C<ev_child> - watch out for process status changes	1883	=head2 C<ev_child> - watch out for process status changes
1169		1884
1170	Child watchers trigger when your process receives a SIGCHLD in response to	1885	Child watchers trigger when your process receives a SIGCHLD in response to
1171	some child status changes (most typically when a child of yours dies).	1886	some child status changes (most typically when a child of yours dies or
		1887	exits). It is permissible to install a child watcher I<after> the child
		1888	has been forked (which implies it might have already exited), as long
		1889	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1890	forking and then immediately registering a watcher for the child is fine,
		1891	but forking and registering a watcher a few event loop iterations later is
		1892	not.
		1893
		1894	Only the default event loop is capable of handling signals, and therefore
		1895	you can only register child watchers in the default event loop.
		1896
		1897	=head3 Process Interaction
		1898
		1899	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1900	initialised. This is necessary to guarantee proper behaviour even if
		1901	the first child watcher is started after the child exits. The occurrence
		1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1903	synchronously as part of the event loop processing. Libev always reaps all
		1904	children, even ones not watched.
		1905
		1906	=head3 Overriding the Built-In Processing
		1907
		1908	Libev offers no special support for overriding the built-in child
		1909	processing, but if your application collides with libev's default child
		1910	handler, you can override it easily by installing your own handler for
		1911	C<SIGCHLD> after initialising the default loop, and making sure the
		1912	default loop never gets destroyed. You are encouraged, however, to use an
		1913	event-based approach to child reaping and thus use libev's support for
		1914	that, so other libev users can use C<ev_child> watchers freely.
		1915
		1916	=head3 Stopping the Child Watcher
		1917
		1918	Currently, the child watcher never gets stopped, even when the
		1919	child terminates, so normally one needs to stop the watcher in the
		1920	callback. Future versions of libev might stop the watcher automatically
		1921	when a child exit is detected.
		1922
		1923	=head3 Watcher-Specific Functions and Data Members
1172		1924
1173	=over 4	1925	=over 4
1174		1926
1175	=item ev_child_init (ev_child *, callback, int pid)	1927	=item ev_child_init (ev_child *, callback, int pid, int trace)
1176		1928
1177	=item ev_child_set (ev_child *, int pid)	1929	=item ev_child_set (ev_child *, int pid, int trace)
1178		1930
1179	Configures the watcher to wait for status changes of process C<pid> (or	1931	Configures the watcher to wait for status changes of process C<pid> (or
1180	I<any> process if C<pid> is specified as C<0>). The callback can look	1932	I<any> process if C<pid> is specified as C<0>). The callback can look
1181	at the C<rstatus> member of the C<ev_child> watcher structure to see	1933	at the C<rstatus> member of the C<ev_child> watcher structure to see
1182	the status word (use the macros from C<sys/wait.h> and see your systems	1934	the status word (use the macros from C<sys/wait.h> and see your systems
1183	C<waitpid> documentation). The C<rpid> member contains the pid of the	1935	C<waitpid> documentation). The C<rpid> member contains the pid of the
1184	process causing the status change.	1936	process causing the status change. C<trace> must be either C<0> (only
		1937	activate the watcher when the process terminates) or C<1> (additionally
		1938	activate the watcher when the process is stopped or continued).
1185		1939
1186	=item int pid [read-only]	1940	=item int pid [read-only]
1187		1941
1188	The process id this watcher watches out for, or C<0>, meaning any process id.	1942	The process id this watcher watches out for, or C<0>, meaning any process id.
1189		1943
…		…
1196	The process exit/trace status caused by C<rpid> (see your systems	1950	The process exit/trace status caused by C<rpid> (see your systems
1197	C<waitpid> and C<sys/wait.h> documentation for details).	1951	C<waitpid> and C<sys/wait.h> documentation for details).
1198		1952
1199	=back	1953	=back
1200		1954
1201	Example: Try to exit cleanly on SIGINT and SIGTERM.	1955	=head3 Examples
1202		1956
		1957	Example: C<fork()> a new process and install a child handler to wait for
		1958	its completion.
		1959
		1960	ev_child cw;
		1961
1203	static void	1962	static void
1204	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1963	child_cb (EV_P_ ev_child *w, int revents)
1205	{	1964	{
1206	ev_unloop (loop, EVUNLOOP_ALL);	1965	ev_child_stop (EV_A_ w);
		1966	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1207	}	1967	}
1208		1968
1209	struct ev_signal signal_watcher;	1969	pid_t pid = fork ();
1210	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1970
1211	ev_signal_start (loop, &sigint_cb);	1971	if (pid < 0)
		1972	// error
		1973	else if (pid == 0)
		1974	{
		1975	// the forked child executes here
		1976	exit (1);
		1977	}
		1978	else
		1979	{
		1980	ev_child_init (&cw, child_cb, pid, 0);
		1981	ev_child_start (EV_DEFAULT_ &cw);
		1982	}
1212		1983
1213		1984
1214	=head2 C<ev_stat> - did the file attributes just change?	1985	=head2 C<ev_stat> - did the file attributes just change?
1215		1986
1216	This watches a filesystem path for attribute changes. That is, it calls	1987	This watches a file system path for attribute changes. That is, it calls
1217	C<stat> regularly (or when the OS says it changed) and sees if it changed	1988	C<stat> on that path in regular intervals (or when the OS says it changed)
1218	compared to the last time, invoking the callback if it did.	1989	and sees if it changed compared to the last time, invoking the callback if
		1990	it did.
1219		1991
1220	The path does not need to exist: changing from "path exists" to "path does	1992	The path does not need to exist: changing from "path exists" to "path does
1221	not exist" is a status change like any other. The condition "path does	1993	not exist" is a status change like any other. The condition "path does not
1222	not exist" is signified by the C<st_nlink> field being zero (which is	1994	exist" (or more correctly "path cannot be stat'ed") is signified by the
1223	otherwise always forced to be at least one) and all the other fields of	1995	C<st_nlink> field being zero (which is otherwise always forced to be at
1224	the stat buffer having unspecified contents.	1996	least one) and all the other fields of the stat buffer having unspecified
		1997	contents.
1225		1998
1226	Since there is no standard to do this, the portable implementation simply	1999	The path I<must not> end in a slash or contain special components such as
1227	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2000	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1228	can specify a recommended polling interval for this case. If you specify	2001	your working directory changes, then the behaviour is undefined.
1229	a polling interval of C<0> (highly recommended!) then a I<suitable,	2002
1230	unspecified default> value will be used (which you can expect to be around	2003	Since there is no portable change notification interface available, the
1231	five seconds, although this might change dynamically). Libev will also	2004	portable implementation simply calls C<stat(2)> regularly on the path
1232	impose a minimum interval which is currently around C<0.1>, but thats	2005	to see if it changed somehow. You can specify a recommended polling
1233	usually overkill.	2006	interval for this case. If you specify a polling interval of C<0> (highly
		2007	recommended!) then a I<suitable, unspecified default> value will be used
		2008	(which you can expect to be around five seconds, although this might
		2009	change dynamically). Libev will also impose a minimum interval which is
		2010	currently around C<0.1>, but that's usually overkill.
1234		2011
1235	This watcher type is not meant for massive numbers of stat watchers,	2012	This watcher type is not meant for massive numbers of stat watchers,
1236	as even with OS-supported change notifications, this can be	2013	as even with OS-supported change notifications, this can be
1237	resource-intensive.	2014	resource-intensive.
1238		2015
1239	At the time of this writing, only the Linux inotify interface is	2016	At the time of this writing, the only OS-specific interface implemented
1240	implemented (implementing kqueue support is left as an exercise for the	2017	is the Linux inotify interface (implementing kqueue support is left as an
1241	reader). Inotify will be used to give hints only and should not change the	2018	exercise for the reader. Note, however, that the author sees no way of
1242	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2019	implementing C<ev_stat> semantics with kqueue, except as a hint).
1243	to fall back to regular polling again even with inotify, but changes are	2020
1244	usually detected immediately, and if the file exists there will be no	2021	=head3 ABI Issues (Largefile Support)
1245	polling.	2022
		2023	Libev by default (unless the user overrides this) uses the default
		2024	compilation environment, which means that on systems with large file
		2025	support disabled by default, you get the 32 bit version of the stat
		2026	structure. When using the library from programs that change the ABI to
		2027	use 64 bit file offsets the programs will fail. In that case you have to
		2028	compile libev with the same flags to get binary compatibility. This is
		2029	obviously the case with any flags that change the ABI, but the problem is
		2030	most noticeably displayed with ev_stat and large file support.
		2031
		2032	The solution for this is to lobby your distribution maker to make large
		2033	file interfaces available by default (as e.g. FreeBSD does) and not
		2034	optional. Libev cannot simply switch on large file support because it has
		2035	to exchange stat structures with application programs compiled using the
		2036	default compilation environment.
		2037
		2038	=head3 Inotify and Kqueue
		2039
		2040	When C<inotify (7)> support has been compiled into libev and present at
		2041	runtime, it will be used to speed up change detection where possible. The
		2042	inotify descriptor will be created lazily when the first C<ev_stat>
		2043	watcher is being started.
		2044
		2045	Inotify presence does not change the semantics of C<ev_stat> watchers
		2046	except that changes might be detected earlier, and in some cases, to avoid
		2047	making regular C<stat> calls. Even in the presence of inotify support
		2048	there are many cases where libev has to resort to regular C<stat> polling,
		2049	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2050	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2051	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2052	xfs are fully working) libev usually gets away without polling.
		2053
		2054	There is no support for kqueue, as apparently it cannot be used to
		2055	implement this functionality, due to the requirement of having a file
		2056	descriptor open on the object at all times, and detecting renames, unlinks
		2057	etc. is difficult.
		2058
		2059	=head3 C<stat ()> is a synchronous operation
		2060
		2061	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2062	the process. The exception are C<ev_stat> watchers - those call C<stat
		2063	()>, which is a synchronous operation.
		2064
		2065	For local paths, this usually doesn't matter: unless the system is very
		2066	busy or the intervals between stat's are large, a stat call will be fast,
		2067	as the path data is usually in memory already (except when starting the
		2068	watcher).
		2069
		2070	For networked file systems, calling C<stat ()> can block an indefinite
		2071	time due to network issues, and even under good conditions, a stat call
		2072	often takes multiple milliseconds.
		2073
		2074	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2075	paths, although this is fully supported by libev.
		2076
		2077	=head3 The special problem of stat time resolution
		2078
		2079	The C<stat ()> system call only supports full-second resolution portably,
		2080	and even on systems where the resolution is higher, most file systems
		2081	still only support whole seconds.
		2082
		2083	That means that, if the time is the only thing that changes, you can
		2084	easily miss updates: on the first update, C<ev_stat> detects a change and
		2085	calls your callback, which does something. When there is another update
		2086	within the same second, C<ev_stat> will be unable to detect unless the
		2087	stat data does change in other ways (e.g. file size).
		2088
		2089	The solution to this is to delay acting on a change for slightly more
		2090	than a second (or till slightly after the next full second boundary), using
		2091	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		2092	ev_timer_again (loop, w)>).
		2093
		2094	The C<.02> offset is added to work around small timing inconsistencies
		2095	of some operating systems (where the second counter of the current time
		2096	might be be delayed. One such system is the Linux kernel, where a call to
		2097	C<gettimeofday> might return a timestamp with a full second later than
		2098	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2099	update file times then there will be a small window where the kernel uses
		2100	the previous second to update file times but libev might already execute
		2101	the timer callback).
		2102
		2103	=head3 Watcher-Specific Functions and Data Members
1246		2104
1247	=over 4	2105	=over 4
1248		2106
1249	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	2107	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1250		2108
…		…
1254	C<path>. The C<interval> is a hint on how quickly a change is expected to	2112	C<path>. The C<interval> is a hint on how quickly a change is expected to
1255	be detected and should normally be specified as C<0> to let libev choose	2113	be detected and should normally be specified as C<0> to let libev choose
1256	a suitable value. The memory pointed to by C<path> must point to the same	2114	a suitable value. The memory pointed to by C<path> must point to the same
1257	path for as long as the watcher is active.	2115	path for as long as the watcher is active.
1258		2116
1259	The callback will be receive C<EV_STAT> when a change was detected,	2117	The callback will receive an C<EV_STAT> event when a change was detected,
1260	relative to the attributes at the time the watcher was started (or the	2118	relative to the attributes at the time the watcher was started (or the
1261	last change was detected).	2119	last change was detected).
1262		2120
1263	=item ev_stat_stat (ev_stat *)	2121	=item ev_stat_stat (loop, ev_stat *)
1264		2122
1265	Updates the stat buffer immediately with new values. If you change the	2123	Updates the stat buffer immediately with new values. If you change the
1266	watched path in your callback, you could call this fucntion to avoid	2124	watched path in your callback, you could call this function to avoid
1267	detecting this change (while introducing a race condition). Can also be	2125	detecting this change (while introducing a race condition if you are not
1268	useful simply to find out the new values.	2126	the only one changing the path). Can also be useful simply to find out the
		2127	new values.
1269		2128
1270	=item ev_statdata attr [read-only]	2129	=item ev_statdata attr [read-only]
1271		2130
1272	The most-recently detected attributes of the file. Although the type is of	2131	The most-recently detected attributes of the file. Although the type is
1273	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2132	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1274	suitable for your system. If the C<st_nlink> member is C<0>, then there	2133	suitable for your system, but you can only rely on the POSIX-standardised
		2134	members to be present. If the C<st_nlink> member is C<0>, then there was
1275	was some error while C<stat>ing the file.	2135	some error while C<stat>ing the file.
1276		2136
1277	=item ev_statdata prev [read-only]	2137	=item ev_statdata prev [read-only]
1278		2138
1279	The previous attributes of the file. The callback gets invoked whenever	2139	The previous attributes of the file. The callback gets invoked whenever
1280	C<prev> != C<attr>.	2140	C<prev> != C<attr>, or, more precisely, one or more of these members
		2141	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2142	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1281		2143
1282	=item ev_tstamp interval [read-only]	2144	=item ev_tstamp interval [read-only]
1283		2145
1284	The specified interval.	2146	The specified interval.
1285		2147
1286	=item const char *path [read-only]	2148	=item const char *path [read-only]
1287		2149
1288	The filesystem path that is being watched.	2150	The file system path that is being watched.
1289		2151
1290	=back	2152	=back
1291		2153
		2154	=head3 Examples
		2155
1292	Example: Watch C</etc/passwd> for attribute changes.	2156	Example: Watch C</etc/passwd> for attribute changes.
1293		2157
1294	static void	2158	static void
1295	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2159	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1296	{	2160	{
1297	/* /etc/passwd changed in some way */	2161	/* /etc/passwd changed in some way */
1298	if (w->attr.st_nlink)	2162	if (w->attr.st_nlink)
1299	{	2163	{
1300	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2164	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1301	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2165	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1302	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2166	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1303	}	2167	}
1304	else	2168	else
1305	/* you shalt not abuse printf for puts */	2169	/* you shalt not abuse printf for puts */
1306	puts ("wow, /etc/passwd is not there, expect problems. "	2170	puts ("wow, /etc/passwd is not there, expect problems. "
1307	"if this is windows, they already arrived\n");	2171	"if this is windows, they already arrived\n");
1308	}	2172	}
1309		2173
1310	...	2174	...
1311	ev_stat passwd;	2175	ev_stat passwd;
1312		2176
1313	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2177	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1314	ev_stat_start (loop, &passwd);	2178	ev_stat_start (loop, &passwd);
		2179
		2180	Example: Like above, but additionally use a one-second delay so we do not
		2181	miss updates (however, frequent updates will delay processing, too, so
		2182	one might do the work both on C<ev_stat> callback invocation I<and> on
		2183	C<ev_timer> callback invocation).
		2184
		2185	static ev_stat passwd;
		2186	static ev_timer timer;
		2187
		2188	static void
		2189	timer_cb (EV_P_ ev_timer *w, int revents)
		2190	{
		2191	ev_timer_stop (EV_A_ w);
		2192
		2193	/* now it's one second after the most recent passwd change */
		2194	}
		2195
		2196	static void
		2197	stat_cb (EV_P_ ev_stat *w, int revents)
		2198	{
		2199	/* reset the one-second timer */
		2200	ev_timer_again (EV_A_ &timer);
		2201	}
		2202
		2203	...
		2204	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2205	ev_stat_start (loop, &passwd);
		2206	ev_timer_init (&timer, timer_cb, 0., 1.02);
1315		2207
1316		2208
1317	=head2 C<ev_idle> - when you've got nothing better to do...	2209	=head2 C<ev_idle> - when you've got nothing better to do...
1318		2210
1319	Idle watchers trigger events when there are no other events are pending	2211	Idle watchers trigger events when no other events of the same or higher
1320	(prepare, check and other idle watchers do not count). That is, as long	2212	priority are pending (prepare, check and other idle watchers do not count
1321	as your process is busy handling sockets or timeouts (or even signals,	2213	as receiving "events").
1322	imagine) it will not be triggered. But when your process is idle all idle	2214
1323	watchers are being called again and again, once per event loop iteration -	2215	That is, as long as your process is busy handling sockets or timeouts
		2216	(or even signals, imagine) of the same or higher priority it will not be
		2217	triggered. But when your process is idle (or only lower-priority watchers
		2218	are pending), the idle watchers are being called once per event loop
1324	until stopped, that is, or your process receives more events and becomes	2219	iteration - until stopped, that is, or your process receives more events
1325	busy.	2220	and becomes busy again with higher priority stuff.
1326		2221
1327	The most noteworthy effect is that as long as any idle watchers are	2222	The most noteworthy effect is that as long as any idle watchers are
1328	active, the process will not block when waiting for new events.	2223	active, the process will not block when waiting for new events.
1329		2224
1330	Apart from keeping your process non-blocking (which is a useful	2225	Apart from keeping your process non-blocking (which is a useful
1331	effect on its own sometimes), idle watchers are a good place to do	2226	effect on its own sometimes), idle watchers are a good place to do
1332	"pseudo-background processing", or delay processing stuff to after the	2227	"pseudo-background processing", or delay processing stuff to after the
1333	event loop has handled all outstanding events.	2228	event loop has handled all outstanding events.
1334		2229
		2230	=head3 Watcher-Specific Functions and Data Members
		2231
1335	=over 4	2232	=over 4
1336		2233
1337	=item ev_idle_init (ev_signal *, callback)	2234	=item ev_idle_init (ev_idle *, callback)
1338		2235
1339	Initialises and configures the idle watcher - it has no parameters of any	2236	Initialises and configures the idle watcher - it has no parameters of any
1340	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2237	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1341	believe me.	2238	believe me.
1342		2239
1343	=back	2240	=back
1344		2241
		2242	=head3 Examples
		2243
1345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2244	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1346	callback, free it. Also, use no error checking, as usual.	2245	callback, free it. Also, use no error checking, as usual.
1347		2246
1348	static void	2247	static void
1349	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2248	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1350	{	2249	{
1351	free (w);	2250	free (w);
1352	// now do something you wanted to do when the program has	2251	// now do something you wanted to do when the program has
1353	// no longer asnything immediate to do.	2252	// no longer anything immediate to do.
1354	}	2253	}
1355		2254
1356	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1357	ev_idle_init (idle_watcher, idle_cb);	2256	ev_idle_init (idle_watcher, idle_cb);
1358	ev_idle_start (loop, idle_cb);	2257	ev_idle_start (loop, idle_cb);
1359		2258
1360		2259
1361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1362		2261
1363	Prepare and check watchers are usually (but not always) used in tandem:	2262	Prepare and check watchers are usually (but not always) used in pairs:
1364	prepare watchers get invoked before the process blocks and check watchers	2263	prepare watchers get invoked before the process blocks and check watchers
1365	afterwards.	2264	afterwards.
1366		2265
1367	You I<must not> call C<ev_loop> or similar functions that enter	2266	You I<must not> call C<ev_loop> or similar functions that enter
1368	the current event loop from either C<ev_prepare> or C<ev_check>	2267	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1371	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1372	C<ev_check> so if you have one watcher of each kind they will always be	2271	C<ev_check> so if you have one watcher of each kind they will always be
1373	called in pairs bracketing the blocking call.	2272	called in pairs bracketing the blocking call.
1374		2273
1375	Their main purpose is to integrate other event mechanisms into libev and	2274	Their main purpose is to integrate other event mechanisms into libev and
1376	their use is somewhat advanced. This could be used, for example, to track	2275	their use is somewhat advanced. They could be used, for example, to track
1377	variable changes, implement your own watchers, integrate net-snmp or a	2276	variable changes, implement your own watchers, integrate net-snmp or a
1378	coroutine library and lots more. They are also occasionally useful if	2277	coroutine library and lots more. They are also occasionally useful if
1379	you cache some data and want to flush it before blocking (for example,	2278	you cache some data and want to flush it before blocking (for example,
1380	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2279	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1381	watcher).	2280	watcher).
1382		2281
1383	This is done by examining in each prepare call which file descriptors need	2282	This is done by examining in each prepare call which file descriptors
1384	to be watched by the other library, registering C<ev_io> watchers for	2283	need to be watched by the other library, registering C<ev_io> watchers
1385	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2284	for them and starting an C<ev_timer> watcher for any timeouts (many
1386	provide just this functionality). Then, in the check watcher you check for	2285	libraries provide exactly this functionality). Then, in the check watcher,
1387	any events that occured (by checking the pending status of all watchers	2286	you check for any events that occurred (by checking the pending status
1388	and stopping them) and call back into the library. The I/O and timer	2287	of all watchers and stopping them) and call back into the library. The
1389	callbacks will never actually be called (but must be valid nevertheless,	2288	I/O and timer callbacks will never actually be called (but must be valid
1390	because you never know, you know?).	2289	nevertheless, because you never know, you know?).
1391		2290
1392	As another example, the Perl Coro module uses these hooks to integrate	2291	As another example, the Perl Coro module uses these hooks to integrate
1393	coroutines into libev programs, by yielding to other active coroutines	2292	coroutines into libev programs, by yielding to other active coroutines
1394	during each prepare and only letting the process block if no coroutines	2293	during each prepare and only letting the process block if no coroutines
1395	are ready to run (it's actually more complicated: it only runs coroutines	2294	are ready to run (it's actually more complicated: it only runs coroutines
1396	with priority higher than or equal to the event loop and one coroutine	2295	with priority higher than or equal to the event loop and one coroutine
1397	of lower priority, but only once, using idle watchers to keep the event	2296	of lower priority, but only once, using idle watchers to keep the event
1398	loop from blocking if lower-priority coroutines are active, thus mapping	2297	loop from blocking if lower-priority coroutines are active, thus mapping
1399	low-priority coroutines to idle/background tasks).	2298	low-priority coroutines to idle/background tasks).
1400		2299
		2300	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2301	priority, to ensure that they are being run before any other watchers
		2302	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2303
		2304	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2305	activate ("feed") events into libev. While libev fully supports this, they
		2306	might get executed before other C<ev_check> watchers did their job. As
		2307	C<ev_check> watchers are often used to embed other (non-libev) event
		2308	loops those other event loops might be in an unusable state until their
		2309	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2310	others).
		2311
		2312	=head3 Watcher-Specific Functions and Data Members
		2313
1401	=over 4	2314	=over 4
1402		2315
1403	=item ev_prepare_init (ev_prepare *, callback)	2316	=item ev_prepare_init (ev_prepare *, callback)
1404		2317
1405	=item ev_check_init (ev_check *, callback)	2318	=item ev_check_init (ev_check *, callback)
1406		2319
1407	Initialises and configures the prepare or check watcher - they have no	2320	Initialises and configures the prepare or check watcher - they have no
1408	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2321	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1409	macros, but using them is utterly, utterly and completely pointless.	2322	macros, but using them is utterly, utterly, utterly and completely
		2323	pointless.
1410		2324
1411	=back	2325	=back
1412		2326
1413	Example: To include a library such as adns, you would add IO watchers	2327	=head3 Examples
1414	and a timeout watcher in a prepare handler, as required by libadns, and	2328
		2329	There are a number of principal ways to embed other event loops or modules
		2330	into libev. Here are some ideas on how to include libadns into libev
		2331	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2332	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2333	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2334	Glib event loop).
		2335
		2336	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1415	in a check watcher, destroy them and call into libadns. What follows is	2337	and in a check watcher, destroy them and call into libadns. What follows
1416	pseudo-code only of course:	2338	is pseudo-code only of course. This requires you to either use a low
		2339	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2340	the callbacks for the IO/timeout watchers might not have been called yet.
1417		2341
1418	static ev_io iow [nfd];	2342	static ev_io iow [nfd];
1419	static ev_timer tw;	2343	static ev_timer tw;
1420		2344
1421	static void	2345	static void
1422	io_cb (ev_loop *loop, ev_io *w, int revents)	2346	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1423	{	2347	{
1424	// set the relevant poll flags
1425	// could also call adns_processreadable etc. here
1426	struct pollfd *fd = (struct pollfd *)w->data;
1427	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1428	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1429	}	2348	}
1430		2349
1431	// create io watchers for each fd and a timer before blocking	2350	// create io watchers for each fd and a timer before blocking
1432	static void	2351	static void
1433	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2352	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1434	{	2353	{
1435	int timeout = 3600000;truct pollfd fds [nfd];	2354	int timeout = 3600000;
		2355	struct pollfd fds [nfd];
1436	// actual code will need to loop here and realloc etc.	2356	// actual code will need to loop here and realloc etc.
1437	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1438		2358
1439	/* the callback is illegal, but won't be called as we stop during check */	2359	/* the callback is illegal, but won't be called as we stop during check */
1440	ev_timer_init (&tw, 0, timeout * 1e-3);	2360	ev_timer_init (&tw, 0, timeout * 1e-3);
1441	ev_timer_start (loop, &tw);	2361	ev_timer_start (loop, &tw);
1442		2362
1443	// create on ev_io per pollfd	2363	// create one ev_io per pollfd
1444	for (int i = 0; i < nfd; ++i)	2364	for (int i = 0; i < nfd; ++i)
1445	{	2365	{
1446	ev_io_init (iow + i, io_cb, fds [i].fd,	2366	ev_io_init (iow + i, io_cb, fds [i].fd,
1447	((fds [i].events & POLLIN ? EV_READ : 0)	2367	((fds [i].events & POLLIN ? EV_READ : 0)
1448	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2368	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1449		2369
1450	fds [i].revents = 0;	2370	fds [i].revents = 0;
1451	iow [i].data = fds + i;
1452	ev_io_start (loop, iow + i);	2371	ev_io_start (loop, iow + i);
1453	}	2372	}
1454	}	2373	}
1455		2374
1456	// stop all watchers after blocking	2375	// stop all watchers after blocking
1457	static void	2376	static void
1458	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2377	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1459	{	2378	{
1460	ev_timer_stop (loop, &tw);	2379	ev_timer_stop (loop, &tw);
1461		2380
1462	for (int i = 0; i < nfd; ++i)	2381	for (int i = 0; i < nfd; ++i)
		2382	{
		2383	// set the relevant poll flags
		2384	// could also call adns_processreadable etc. here
		2385	struct pollfd *fd = fds + i;
		2386	int revents = ev_clear_pending (iow + i);
		2387	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2388	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2389
		2390	// now stop the watcher
1463	ev_io_stop (loop, iow + i);	2391	ev_io_stop (loop, iow + i);
		2392	}
1464		2393
1465	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2394	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1466	}	2395	}
		2396
		2397	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2398	in the prepare watcher and would dispose of the check watcher.
		2399
		2400	Method 3: If the module to be embedded supports explicit event
		2401	notification (libadns does), you can also make use of the actual watcher
		2402	callbacks, and only destroy/create the watchers in the prepare watcher.
		2403
		2404	static void
		2405	timer_cb (EV_P_ ev_timer *w, int revents)
		2406	{
		2407	adns_state ads = (adns_state)w->data;
		2408	update_now (EV_A);
		2409
		2410	adns_processtimeouts (ads, &tv_now);
		2411	}
		2412
		2413	static void
		2414	io_cb (EV_P_ ev_io *w, int revents)
		2415	{
		2416	adns_state ads = (adns_state)w->data;
		2417	update_now (EV_A);
		2418
		2419	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2420	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2421	}
		2422
		2423	// do not ever call adns_afterpoll
		2424
		2425	Method 4: Do not use a prepare or check watcher because the module you
		2426	want to embed is not flexible enough to support it. Instead, you can
		2427	override their poll function. The drawback with this solution is that the
		2428	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2429	this approach, effectively embedding EV as a client into the horrible
		2430	libglib event loop.
		2431
		2432	static gint
		2433	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2434	{
		2435	int got_events = 0;
		2436
		2437	for (n = 0; n < nfds; ++n)
		2438	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2439
		2440	if (timeout >= 0)
		2441	// create/start timer
		2442
		2443	// poll
		2444	ev_loop (EV_A_ 0);
		2445
		2446	// stop timer again
		2447	if (timeout >= 0)
		2448	ev_timer_stop (EV_A_ &to);
		2449
		2450	// stop io watchers again - their callbacks should have set
		2451	for (n = 0; n < nfds; ++n)
		2452	ev_io_stop (EV_A_ iow [n]);
		2453
		2454	return got_events;
		2455	}
1467		2456
1468		2457
1469	=head2 C<ev_embed> - when one backend isn't enough...	2458	=head2 C<ev_embed> - when one backend isn't enough...
1470		2459
1471	This is a rather advanced watcher type that lets you embed one event loop	2460	This is a rather advanced watcher type that lets you embed one event loop
…		…
1477	prioritise I/O.	2466	prioritise I/O.
1478		2467
1479	As an example for a bug workaround, the kqueue backend might only support	2468	As an example for a bug workaround, the kqueue backend might only support
1480	sockets on some platform, so it is unusable as generic backend, but you	2469	sockets on some platform, so it is unusable as generic backend, but you
1481	still want to make use of it because you have many sockets and it scales	2470	still want to make use of it because you have many sockets and it scales
1482	so nicely. In this case, you would create a kqueue-based loop and embed it	2471	so nicely. In this case, you would create a kqueue-based loop and embed
1483	into your default loop (which might use e.g. poll). Overall operation will	2472	it into your default loop (which might use e.g. poll). Overall operation
1484	be a bit slower because first libev has to poll and then call kevent, but	2473	will be a bit slower because first libev has to call C<poll> and then
1485	at least you can use both at what they are best.	2474	C<kevent>, but at least you can use both mechanisms for what they are
		2475	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1486		2476
1487	As for prioritising I/O: rarely you have the case where some fds have	2477	As for prioritising I/O: under rare circumstances you have the case where
1488	to be watched and handled very quickly (with low latency), and even	2478	some fds have to be watched and handled very quickly (with low latency),
1489	priorities and idle watchers might have too much overhead. In this case	2479	and even priorities and idle watchers might have too much overhead. In
1490	you would put all the high priority stuff in one loop and all the rest in	2480	this case you would put all the high priority stuff in one loop and all
1491	a second one, and embed the second one in the first.	2481	the rest in a second one, and embed the second one in the first.
1492		2482
1493	As long as the watcher is active, the callback will be invoked every time	2483	As long as the watcher is active, the callback will be invoked every
1494	there might be events pending in the embedded loop. The callback must then	2484	time there might be events pending in the embedded loop. The callback
1495	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2485	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1496	their callbacks (you could also start an idle watcher to give the embedded	2486	sweep and invoke their callbacks (the callback doesn't need to invoke the
1497	loop strictly lower priority for example). You can also set the callback	2487	C<ev_embed_sweep> function directly, it could also start an idle watcher
1498	to C<0>, in which case the embed watcher will automatically execute the	2488	to give the embedded loop strictly lower priority for example).
1499	embedded loop sweep.
1500		2489
1501	As long as the watcher is started it will automatically handle events. The	2490	You can also set the callback to C<0>, in which case the embed watcher
1502	callback will be invoked whenever some events have been handled. You can	2491	will automatically execute the embedded loop sweep whenever necessary.
1503	set the callback to C<0> to avoid having to specify one if you are not
1504	interested in that.
1505		2492
1506	Also, there have not currently been made special provisions for forking:	2493	Fork detection will be handled transparently while the C<ev_embed> watcher
1507	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2494	is active, i.e., the embedded loop will automatically be forked when the
1508	but you will also have to stop and restart any C<ev_embed> watchers	2495	embedding loop forks. In other cases, the user is responsible for calling
1509	yourself.	2496	C<ev_loop_fork> on the embedded loop.
1510		2497
1511	Unfortunately, not all backends are embeddable, only the ones returned by	2498	Unfortunately, not all backends are embeddable: only the ones returned by
1512	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2499	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1513	portable one.	2500	portable one.
1514		2501
1515	So when you want to use this feature you will always have to be prepared	2502	So when you want to use this feature you will always have to be prepared
1516	that you cannot get an embeddable loop. The recommended way to get around	2503	that you cannot get an embeddable loop. The recommended way to get around
1517	this is to have a separate variables for your embeddable loop, try to	2504	this is to have a separate variables for your embeddable loop, try to
1518	create it, and if that fails, use the normal loop for everything:	2505	create it, and if that fails, use the normal loop for everything.
1519		2506
1520	struct ev_loop *loop_hi = ev_default_init (0);	2507	=head3 C<ev_embed> and fork
1521	struct ev_loop *loop_lo = 0;
1522	struct ev_embed embed;
1523
1524	// see if there is a chance of getting one that works
1525	// (remember that a flags value of 0 means autodetection)
1526	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1527	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1528	: 0;
1529		2508
1530	// if we got one, then embed it, otherwise default to loop_hi	2509	While the C<ev_embed> watcher is running, forks in the embedding loop will
1531	if (loop_lo)	2510	automatically be applied to the embedded loop as well, so no special
1532	{	2511	fork handling is required in that case. When the watcher is not running,
1533	ev_embed_init (&embed, 0, loop_lo);	2512	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1534	ev_embed_start (loop_hi, &embed);	2513	as applicable.
1535	}	2514
1536	else	2515	=head3 Watcher-Specific Functions and Data Members
1537	loop_lo = loop_hi;
1538		2516
1539	=over 4	2517	=over 4
1540		2518
1541	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2519	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1542		2520
…		…
1544		2522
1545	Configures the watcher to embed the given loop, which must be	2523	Configures the watcher to embed the given loop, which must be
1546	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2524	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1547	invoked automatically, otherwise it is the responsibility of the callback	2525	invoked automatically, otherwise it is the responsibility of the callback
1548	to invoke it (it will continue to be called until the sweep has been done,	2526	to invoke it (it will continue to be called until the sweep has been done,
1549	if you do not want thta, you need to temporarily stop the embed watcher).	2527	if you do not want that, you need to temporarily stop the embed watcher).
1550		2528
1551	=item ev_embed_sweep (loop, ev_embed *)	2529	=item ev_embed_sweep (loop, ev_embed *)
1552		2530
1553	Make a single, non-blocking sweep over the embedded loop. This works	2531	Make a single, non-blocking sweep over the embedded loop. This works
1554	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1555	apropriate way for embedded loops.	2533	appropriate way for embedded loops.
1556		2534
1557	=item struct ev_loop *loop [read-only]	2535	=item struct ev_loop *other [read-only]
1558		2536
1559	The embedded event loop.	2537	The embedded event loop.
1560		2538
1561	=back	2539	=back
		2540
		2541	=head3 Examples
		2542
		2543	Example: Try to get an embeddable event loop and embed it into the default
		2544	event loop. If that is not possible, use the default loop. The default
		2545	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2546	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2547	used).
		2548
		2549	struct ev_loop *loop_hi = ev_default_init (0);
		2550	struct ev_loop *loop_lo = 0;
		2551	ev_embed embed;
		2552
		2553	// see if there is a chance of getting one that works
		2554	// (remember that a flags value of 0 means autodetection)
		2555	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2556	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2557	: 0;
		2558
		2559	// if we got one, then embed it, otherwise default to loop_hi
		2560	if (loop_lo)
		2561	{
		2562	ev_embed_init (&embed, 0, loop_lo);
		2563	ev_embed_start (loop_hi, &embed);
		2564	}
		2565	else
		2566	loop_lo = loop_hi;
		2567
		2568	Example: Check if kqueue is available but not recommended and create
		2569	a kqueue backend for use with sockets (which usually work with any
		2570	kqueue implementation). Store the kqueue/socket-only event loop in
		2571	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2572
		2573	struct ev_loop *loop = ev_default_init (0);
		2574	struct ev_loop *loop_socket = 0;
		2575	ev_embed embed;
		2576
		2577	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2578	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2579	{
		2580	ev_embed_init (&embed, 0, loop_socket);
		2581	ev_embed_start (loop, &embed);
		2582	}
		2583
		2584	if (!loop_socket)
		2585	loop_socket = loop;
		2586
		2587	// now use loop_socket for all sockets, and loop for everything else
1562		2588
1563		2589
1564	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2590	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1565		2591
1566	Fork watchers are called when a C<fork ()> was detected (usually because	2592	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1569	event loop blocks next and before C<ev_check> watchers are being called,	2595	event loop blocks next and before C<ev_check> watchers are being called,
1570	and only in the child after the fork. If whoever good citizen calling	2596	and only in the child after the fork. If whoever good citizen calling
1571	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1572	handlers will be invoked, too, of course.	2598	handlers will be invoked, too, of course.
1573		2599
		2600	=head3 Watcher-Specific Functions and Data Members
		2601
1574	=over 4	2602	=over 4
1575		2603
1576	=item ev_fork_init (ev_signal *, callback)	2604	=item ev_fork_init (ev_signal *, callback)
1577		2605
1578	Initialises and configures the fork watcher - it has no parameters of any	2606	Initialises and configures the fork watcher - it has no parameters of any
…		…
1580	believe me.	2608	believe me.
1581		2609
1582	=back	2610	=back
1583		2611
1584		2612
		2613	=head2 C<ev_async> - how to wake up another event loop
		2614
		2615	In general, you cannot use an C<ev_loop> from multiple threads or other
		2616	asynchronous sources such as signal handlers (as opposed to multiple event
		2617	loops - those are of course safe to use in different threads).
		2618
		2619	Sometimes, however, you need to wake up another event loop you do not
		2620	control, for example because it belongs to another thread. This is what
		2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2622	can signal it by calling C<ev_async_send>, which is thread- and signal
		2623	safe.
		2624
		2625	This functionality is very similar to C<ev_signal> watchers, as signals,
		2626	too, are asynchronous in nature, and signals, too, will be compressed
		2627	(i.e. the number of callback invocations may be less than the number of
		2628	C<ev_async_sent> calls).
		2629
		2630	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2631	just the default loop.
		2632
		2633	=head3 Queueing
		2634
		2635	C<ev_async> does not support queueing of data in any way. The reason
		2636	is that the author does not know of a simple (or any) algorithm for a
		2637	multiple-writer-single-reader queue that works in all cases and doesn't
		2638	need elaborate support such as pthreads.
		2639
		2640	That means that if you want to queue data, you have to provide your own
		2641	queue. But at least I can tell you how to implement locking around your
		2642	queue:
		2643
		2644	=over 4
		2645
		2646	=item queueing from a signal handler context
		2647
		2648	To implement race-free queueing, you simply add to the queue in the signal
		2649	handler but you block the signal handler in the watcher callback. Here is
		2650	an example that does that for some fictitious SIGUSR1 handler:
		2651
		2652	static ev_async mysig;
		2653
		2654	static void
		2655	sigusr1_handler (void)
		2656	{
		2657	sometype data;
		2658
		2659	// no locking etc.
		2660	queue_put (data);
		2661	ev_async_send (EV_DEFAULT_ &mysig);
		2662	}
		2663
		2664	static void
		2665	mysig_cb (EV_P_ ev_async *w, int revents)
		2666	{
		2667	sometype data;
		2668	sigset_t block, prev;
		2669
		2670	sigemptyset (&block);
		2671	sigaddset (&block, SIGUSR1);
		2672	sigprocmask (SIG_BLOCK, &block, &prev);
		2673
		2674	while (queue_get (&data))
		2675	process (data);
		2676
		2677	if (sigismember (&prev, SIGUSR1)
		2678	sigprocmask (SIG_UNBLOCK, &block, 0);
		2679	}
		2680
		2681	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2682	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2683	either...).
		2684
		2685	=item queueing from a thread context
		2686
		2687	The strategy for threads is different, as you cannot (easily) block
		2688	threads but you can easily preempt them, so to queue safely you need to
		2689	employ a traditional mutex lock, such as in this pthread example:
		2690
		2691	static ev_async mysig;
		2692	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2693
		2694	static void
		2695	otherthread (void)
		2696	{
		2697	// only need to lock the actual queueing operation
		2698	pthread_mutex_lock (&mymutex);
		2699	queue_put (data);
		2700	pthread_mutex_unlock (&mymutex);
		2701
		2702	ev_async_send (EV_DEFAULT_ &mysig);
		2703	}
		2704
		2705	static void
		2706	mysig_cb (EV_P_ ev_async *w, int revents)
		2707	{
		2708	pthread_mutex_lock (&mymutex);
		2709
		2710	while (queue_get (&data))
		2711	process (data);
		2712
		2713	pthread_mutex_unlock (&mymutex);
		2714	}
		2715
		2716	=back
		2717
		2718
		2719	=head3 Watcher-Specific Functions and Data Members
		2720
		2721	=over 4
		2722
		2723	=item ev_async_init (ev_async *, callback)
		2724
		2725	Initialises and configures the async watcher - it has no parameters of any
		2726	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		2727	trust me.
		2728
		2729	=item ev_async_send (loop, ev_async *)
		2730
		2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2733	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2735	section below on what exactly this means).
		2736
		2737	Note that, as with other watchers in libev, multiple events might get
		2738	compressed into a single callback invocation (another way to look at this
		2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2740	reset when the event loop detects that).
		2741
		2742	This call incurs the overhead of a system call only once per event loop
		2743	iteration, so while the overhead might be noticeable, it doesn't apply to
		2744	repeated calls to C<ev_async_send> for the same event loop.
		2745
		2746	=item bool = ev_async_pending (ev_async *)
		2747
		2748	Returns a non-zero value when C<ev_async_send> has been called on the
		2749	watcher but the event has not yet been processed (or even noted) by the
		2750	event loop.
		2751
		2752	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2753	the loop iterates next and checks for the watcher to have become active,
		2754	it will reset the flag again. C<ev_async_pending> can be used to very
		2755	quickly check whether invoking the loop might be a good idea.
		2756
		2757	Not that this does I<not> check whether the watcher itself is pending,
		2758	only whether it has been requested to make this watcher pending: there
		2759	is a time window between the event loop checking and resetting the async
		2760	notification, and the callback being invoked.
		2761
		2762	=back
		2763
		2764
1585	=head1 OTHER FUNCTIONS	2765	=head1 OTHER FUNCTIONS
1586		2766
1587	There are some other functions of possible interest. Described. Here. Now.	2767	There are some other functions of possible interest. Described. Here. Now.
1588		2768
1589	=over 4	2769	=over 4
1590		2770
1591	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2771	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1592		2772
1593	This function combines a simple timer and an I/O watcher, calls your	2773	This function combines a simple timer and an I/O watcher, calls your
1594	callback on whichever event happens first and automatically stop both	2774	callback on whichever event happens first and automatically stops both
1595	watchers. This is useful if you want to wait for a single event on an fd	2775	watchers. This is useful if you want to wait for a single event on an fd
1596	or timeout without having to allocate/configure/start/stop/free one or	2776	or timeout without having to allocate/configure/start/stop/free one or
1597	more watchers yourself.	2777	more watchers yourself.
1598		2778
1599	If C<fd> is less than 0, then no I/O watcher will be started and events	2779	If C<fd> is less than 0, then no I/O watcher will be started and the
1600	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2780	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1601	C<events> set will be craeted and started.	2781	the given C<fd> and C<events> set will be created and started.
1602		2782
1603	If C<timeout> is less than 0, then no timeout watcher will be	2783	If C<timeout> is less than 0, then no timeout watcher will be
1604	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1605	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2785	repeat = 0) will be started. C<0> is a valid timeout.
1606	dubious value.
1607		2786
1608	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2787	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1609	passed an C<revents> set like normal event callbacks (a combination of	2788	passed an C<revents> set like normal event callbacks (a combination of
1610	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1611	value passed to C<ev_once>:	2790	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2791	a timeout and an io event at the same time - you probably should give io
		2792	events precedence.
1612		2793
		2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2795
1613	static void stdin_ready (int revents, void *arg)	2796	static void stdin_ready (int revents, void *arg)
1614	{	2797	{
1615	if (revents & EV_TIMEOUT)
1616	/* doh, nothing entered */;
1617	else if (revents & EV_READ)	2798	if (revents & EV_READ)
1618	/* stdin might have data for us, joy! */;	2799	/* stdin might have data for us, joy! */;
		2800	else if (revents & EV_TIMEOUT)
		2801	/* doh, nothing entered */;
1619	}	2802	}
1620		2803
1621	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1622		2805
1623	=item ev_feed_event (ev_loop *, watcher *, int revents)	2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1624		2807
1625	Feeds the given event set into the event loop, as if the specified event	2808	Feeds the given event set into the event loop, as if the specified event
1626	had happened for the specified watcher (which must be a pointer to an	2809	had happened for the specified watcher (which must be a pointer to an
1627	initialised but not necessarily started event watcher).	2810	initialised but not necessarily started event watcher).
1628		2811
1629	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1630		2813
1631	Feed an event on the given fd, as if a file descriptor backend detected	2814	Feed an event on the given fd, as if a file descriptor backend detected
1632	the given events it.	2815	the given events it.
1633		2816
1634	=item ev_feed_signal_event (ev_loop *loop, int signum)	2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1635		2818
1636	Feed an event as if the given signal occured (C<loop> must be the default	2819	Feed an event as if the given signal occurred (C<loop> must be the default
1637	loop!).	2820	loop!).
1638		2821
1639	=back	2822	=back
1640		2823
1641		2824
…		…
1657		2840
1658	=item * Priorities are not currently supported. Initialising priorities	2841	=item * Priorities are not currently supported. Initialising priorities
1659	will fail and all watchers will have the same priority, even though there	2842	will fail and all watchers will have the same priority, even though there
1660	is an ev_pri field.	2843	is an ev_pri field.
1661		2844
		2845	=item * In libevent, the last base created gets the signals, in libev, the
		2846	first base created (== the default loop) gets the signals.
		2847
1662	=item * Other members are not supported.	2848	=item * Other members are not supported.
1663		2849
1664	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1665	to use the libev header file and library.	2851	to use the libev header file and library.
1666		2852
1667	=back	2853	=back
1668		2854
1669	=head1 C++ SUPPORT	2855	=head1 C++ SUPPORT
1670		2856
1671	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2857	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1672	you to use some convinience methods to start/stop watchers and also change	2858	you to use some convenience methods to start/stop watchers and also change
1673	the callback model to a model using method callbacks on objects.	2859	the callback model to a model using method callbacks on objects.
1674		2860
1675	To use it,	2861	To use it,
1676		2862
1677	#include <ev++.h>	2863	#include <ev++.h>
1678		2864
1679	(it is not installed by default). This automatically includes F<ev.h>	2865	This automatically includes F<ev.h> and puts all of its definitions (many
1680	and puts all of its definitions (many of them macros) into the global	2866	of them macros) into the global namespace. All C++ specific things are
1681	namespace. All C++ specific things are put into the C<ev> namespace.	2867	put into the C<ev> namespace. It should support all the same embedding
		2868	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1682		2869
1683	It should support all the same embedding options as F<ev.h>, most notably	2870	Care has been taken to keep the overhead low. The only data member the C++
1684	C<EV_MULTIPLICITY>.	2871	classes add (compared to plain C-style watchers) is the event loop pointer
		2872	that the watcher is associated with (or no additional members at all if
		2873	you disable C<EV_MULTIPLICITY> when embedding libev).
		2874
		2875	Currently, functions, and static and non-static member functions can be
		2876	used as callbacks. Other types should be easy to add as long as they only
		2877	need one additional pointer for context. If you need support for other
		2878	types of functors please contact the author (preferably after implementing
		2879	it).
1685		2880
1686	Here is a list of things available in the C<ev> namespace:	2881	Here is a list of things available in the C<ev> namespace:
1687		2882
1688	=over 4	2883	=over 4
1689		2884
…		…
1705		2900
1706	All of those classes have these methods:	2901	All of those classes have these methods:
1707		2902
1708	=over 4	2903	=over 4
1709		2904
1710	=item ev::TYPE::TYPE (object *, object::method *)	2905	=item ev::TYPE::TYPE ()
1711		2906
1712	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2907	=item ev::TYPE::TYPE (struct ev_loop *)
1713		2908
1714	=item ev::TYPE::~TYPE	2909	=item ev::TYPE::~TYPE
1715		2910
1716	The constructor takes a pointer to an object and a method pointer to	2911	The constructor (optionally) takes an event loop to associate the watcher
1717	the event handler callback to call in this class. The constructor calls	2912	with. If it is omitted, it will use C<EV_DEFAULT>.
1718	C<ev_init> for you, which means you have to call the C<set> method	2913
1719	before starting it. If you do not specify a loop then the constructor	2914	The constructor calls C<ev_init> for you, which means you have to call the
1720	automatically associates the default loop with this watcher.	2915	C<set> method before starting it.
		2916
		2917	It will not set a callback, however: You have to call the templated C<set>
		2918	method to set a callback before you can start the watcher.
		2919
		2920	(The reason why you have to use a method is a limitation in C++ which does
		2921	not allow explicit template arguments for constructors).
1721		2922
1722	The destructor automatically stops the watcher if it is active.	2923	The destructor automatically stops the watcher if it is active.
		2924
		2925	=item w->set<class, &class::method> (object *)
		2926
		2927	This method sets the callback method to call. The method has to have a
		2928	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2929	first argument and the C<revents> as second. The object must be given as
		2930	parameter and is stored in the C<data> member of the watcher.
		2931
		2932	This method synthesizes efficient thunking code to call your method from
		2933	the C callback that libev requires. If your compiler can inline your
		2934	callback (i.e. it is visible to it at the place of the C<set> call and
		2935	your compiler is good :), then the method will be fully inlined into the
		2936	thunking function, making it as fast as a direct C callback.
		2937
		2938	Example: simple class declaration and watcher initialisation
		2939
		2940	struct myclass
		2941	{
		2942	void io_cb (ev::io &w, int revents) { }
		2943	}
		2944
		2945	myclass obj;
		2946	ev::io iow;
		2947	iow.set <myclass, &myclass::io_cb> (&obj);
		2948
		2949	=item w->set (object *)
		2950
		2951	This is an B<experimental> feature that might go away in a future version.
		2952
		2953	This is a variation of a method callback - leaving out the method to call
		2954	will default the method to C<operator ()>, which makes it possible to use
		2955	functor objects without having to manually specify the C<operator ()> all
		2956	the time. Incidentally, you can then also leave out the template argument
		2957	list.
		2958
		2959	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2960	int revents)>.
		2961
		2962	See the method-C<set> above for more details.
		2963
		2964	Example: use a functor object as callback.
		2965
		2966	struct myfunctor
		2967	{
		2968	void operator() (ev::io &w, int revents)
		2969	{
		2970	...
		2971	}
		2972	}
		2973
		2974	myfunctor f;
		2975
		2976	ev::io w;
		2977	w.set (&f);
		2978
		2979	=item w->set<function> (void *data = 0)
		2980
		2981	Also sets a callback, but uses a static method or plain function as
		2982	callback. The optional C<data> argument will be stored in the watcher's
		2983	C<data> member and is free for you to use.
		2984
		2985	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2986
		2987	See the method-C<set> above for more details.
		2988
		2989	Example: Use a plain function as callback.
		2990
		2991	static void io_cb (ev::io &w, int revents) { }
		2992	iow.set <io_cb> ();
1723		2993
1724	=item w->set (struct ev_loop *)	2994	=item w->set (struct ev_loop *)
1725		2995
1726	Associates a different C<struct ev_loop> with this watcher. You can only	2996	Associates a different C<struct ev_loop> with this watcher. You can only
1727	do this when the watcher is inactive (and not pending either).	2997	do this when the watcher is inactive (and not pending either).
1728		2998
1729	=item w->set ([args])	2999	=item w->set ([arguments])
1730		3000
1731	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1732	called at least once. Unlike the C counterpart, an active watcher gets	3002	called at least once. Unlike the C counterpart, an active watcher gets
1733	automatically stopped and restarted.	3003	automatically stopped and restarted when reconfiguring it with this
		3004	method.
1734		3005
1735	=item w->start ()	3006	=item w->start ()
1736		3007
1737	Starts the watcher. Note that there is no C<loop> argument as the	3008	Starts the watcher. Note that there is no C<loop> argument, as the
1738	constructor already takes the loop.	3009	constructor already stores the event loop.
1739		3010
1740	=item w->stop ()	3011	=item w->stop ()
1741		3012
1742	Stops the watcher if it is active. Again, no C<loop> argument.	3013	Stops the watcher if it is active. Again, no C<loop> argument.
1743		3014
1744	=item w->again () C<ev::timer>, C<ev::periodic> only	3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1745		3016
1746	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	3017	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1747	C<ev_TYPE_again> function.	3018	C<ev_TYPE_again> function.
1748		3019
1749	=item w->sweep () C<ev::embed> only	3020	=item w->sweep () (C<ev::embed> only)
1750		3021
1751	Invokes C<ev_embed_sweep>.	3022	Invokes C<ev_embed_sweep>.
1752		3023
1753	=item w->update () C<ev::stat> only	3024	=item w->update () (C<ev::stat> only)
1754		3025
1755	Invokes C<ev_stat_stat>.	3026	Invokes C<ev_stat_stat>.
1756		3027
1757	=back	3028	=back
1758		3029
1759	=back	3030	=back
1760		3031
1761	Example: Define a class with an IO and idle watcher, start one of them in	3032	Example: Define a class with an IO and idle watcher, start one of them in
1762	the constructor.	3033	the constructor.
1763		3034
1764	class myclass	3035	class myclass
1765	{	3036	{
1766	ev_io io; void io_cb (ev::io &w, int revents);	3037	ev::io io ; void io_cb (ev::io &w, int revents);
1767	ev_idle idle void idle_cb (ev::idle &w, int revents);	3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1768		3039
1769	myclass ();	3040	myclass (int fd)
1770	}	3041	{
		3042	io .set <myclass, &myclass::io_cb > (this);
		3043	idle.set <myclass, &myclass::idle_cb> (this);
1771		3044
1772	myclass::myclass (int fd)
1773	: io (this, &myclass::io_cb),
1774	idle (this, &myclass::idle_cb)
1775	{
1776	io.start (fd, ev::READ);	3045	io.start (fd, ev::READ);
		3046	}
1777	}	3047	};
		3048
		3049
		3050	=head1 OTHER LANGUAGE BINDINGS
		3051
		3052	Libev does not offer other language bindings itself, but bindings for a
		3053	number of languages exist in the form of third-party packages. If you know
		3054	any interesting language binding in addition to the ones listed here, drop
		3055	me a note.
		3056
		3057	=over 4
		3058
		3059	=item Perl
		3060
		3061	The EV module implements the full libev API and is actually used to test
		3062	libev. EV is developed together with libev. Apart from the EV core module,
		3063	there are additional modules that implement libev-compatible interfaces
		3064	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3065	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3066	and C<EV::Glib>).
		3067
		3068	It can be found and installed via CPAN, its homepage is at
		3069	L<http://software.schmorp.de/pkg/EV>.
		3070
		3071	=item Python
		3072
		3073	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3074	seems to be quite complete and well-documented.
		3075
		3076	=item Ruby
		3077
		3078	Tony Arcieri has written a ruby extension that offers access to a subset
		3079	of the libev API and adds file handle abstractions, asynchronous DNS and
		3080	more on top of it. It can be found via gem servers. Its homepage is at
		3081	L<http://rev.rubyforge.org/>.
		3082
		3083	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3084	makes rev work even on mingw.
		3085
		3086	=item Haskell
		3087
		3088	A haskell binding to libev is available at
		3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3090
		3091	=item D
		3092
		3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3095
		3096	=item Ocaml
		3097
		3098	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3100
		3101	=back
1778		3102
1779		3103
1780	=head1 MACRO MAGIC	3104	=head1 MACRO MAGIC
1781		3105
1782	Libev can be compiled with a variety of options, the most fundemantal is	3106	Libev can be compiled with a variety of options, the most fundamental
1783	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	3107	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1784	callbacks have an initial C<struct ev_loop *> argument.	3108	functions and callbacks have an initial C<struct ev_loop *> argument.
1785		3109
1786	To make it easier to write programs that cope with either variant, the	3110	To make it easier to write programs that cope with either variant, the
1787	following macros are defined:	3111	following macros are defined:
1788		3112
1789	=over 4	3113	=over 4
…		…
1792		3116
1793	This provides the loop I<argument> for functions, if one is required ("ev	3117	This provides the loop I<argument> for functions, if one is required ("ev
1794	loop argument"). The C<EV_A> form is used when this is the sole argument,	3118	loop argument"). The C<EV_A> form is used when this is the sole argument,
1795	C<EV_A_> is used when other arguments are following. Example:	3119	C<EV_A_> is used when other arguments are following. Example:
1796		3120
1797	ev_unref (EV_A);	3121	ev_unref (EV_A);
1798	ev_timer_add (EV_A_ watcher);	3122	ev_timer_add (EV_A_ watcher);
1799	ev_loop (EV_A_ 0);	3123	ev_loop (EV_A_ 0);
1800		3124
1801	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1802	which is often provided by the following macro.	3126	which is often provided by the following macro.
1803		3127
1804	=item C<EV_P>, C<EV_P_>	3128	=item C<EV_P>, C<EV_P_>
1805		3129
1806	This provides the loop I<parameter> for functions, if one is required ("ev	3130	This provides the loop I<parameter> for functions, if one is required ("ev
1807	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3131	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1808	C<EV_P_> is used when other parameters are following. Example:	3132	C<EV_P_> is used when other parameters are following. Example:
1809		3133
1810	// this is how ev_unref is being declared	3134	// this is how ev_unref is being declared
1811	static void ev_unref (EV_P);	3135	static void ev_unref (EV_P);
1812		3136
1813	// this is how you can declare your typical callback	3137	// this is how you can declare your typical callback
1814	static void cb (EV_P_ ev_timer *w, int revents)	3138	static void cb (EV_P_ ev_timer *w, int revents)
1815		3139
1816	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3140	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1817	suitable for use with C<EV_A>.	3141	suitable for use with C<EV_A>.
1818		3142
1819	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3143	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1820		3144
1821	Similar to the other two macros, this gives you the value of the default	3145	Similar to the other two macros, this gives you the value of the default
1822	loop, if multiple loops are supported ("ev loop default").	3146	loop, if multiple loops are supported ("ev loop default").
1823		3147
		3148	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3149
		3150	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3151	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3152	is undefined when the default loop has not been initialised by a previous
		3153	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3154
		3155	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3156	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		3157
1824	=back	3158	=back
1825		3159
1826	Example: Declare and initialise a check watcher, working regardless of	3160	Example: Declare and initialise a check watcher, utilising the above
1827	wether multiple loops are supported or not.	3161	macros so it will work regardless of whether multiple loops are supported
		3162	or not.
1828		3163
1829	static void	3164	static void
1830	check_cb (EV_P_ ev_timer *w, int revents)	3165	check_cb (EV_P_ ev_timer *w, int revents)
1831	{	3166	{
1832	ev_check_stop (EV_A_ w);	3167	ev_check_stop (EV_A_ w);
1833	}	3168	}
1834		3169
1835	ev_check check;	3170	ev_check check;
1836	ev_check_init (&check, check_cb);	3171	ev_check_init (&check, check_cb);
1837	ev_check_start (EV_DEFAULT_ &check);	3172	ev_check_start (EV_DEFAULT_ &check);
1838	ev_loop (EV_DEFAULT_ 0);	3173	ev_loop (EV_DEFAULT_ 0);
1839
1840		3174
1841	=head1 EMBEDDING	3175	=head1 EMBEDDING
1842		3176
1843	Libev can (and often is) directly embedded into host	3177	Libev can (and often is) directly embedded into host
1844	applications. Examples of applications that embed it include the Deliantra	3178	applications. Examples of applications that embed it include the Deliantra
1845	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3179	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1846	and rxvt-unicode.	3180	and rxvt-unicode.
1847		3181
1848	The goal is to enable you to just copy the neecssary files into your	3182	The goal is to enable you to just copy the necessary files into your
1849	source directory without having to change even a single line in them, so	3183	source directory without having to change even a single line in them, so
1850	you can easily upgrade by simply copying (or having a checked-out copy of	3184	you can easily upgrade by simply copying (or having a checked-out copy of
1851	libev somewhere in your source tree).	3185	libev somewhere in your source tree).
1852		3186
1853	=head2 FILESETS	3187	=head2 FILESETS
1854		3188
1855	Depending on what features you need you need to include one or more sets of files	3189	Depending on what features you need you need to include one or more sets of files
1856	in your app.	3190	in your application.
1857		3191
1858	=head3 CORE EVENT LOOP	3192	=head3 CORE EVENT LOOP
1859		3193
1860	To include only the libev core (all the C<ev_*> functions), with manual	3194	To include only the libev core (all the C<ev_*> functions), with manual
1861	configuration (no autoconf):	3195	configuration (no autoconf):
1862		3196
1863	#define EV_STANDALONE 1	3197	#define EV_STANDALONE 1
1864	#include "ev.c"	3198	#include "ev.c"
1865		3199
1866	This will automatically include F<ev.h>, too, and should be done in a	3200	This will automatically include F<ev.h>, too, and should be done in a
1867	single C source file only to provide the function implementations. To use	3201	single C source file only to provide the function implementations. To use
1868	it, do the same for F<ev.h> in all files wishing to use this API (best	3202	it, do the same for F<ev.h> in all files wishing to use this API (best
1869	done by writing a wrapper around F<ev.h> that you can include instead and	3203	done by writing a wrapper around F<ev.h> that you can include instead and
1870	where you can put other configuration options):	3204	where you can put other configuration options):
1871		3205
1872	#define EV_STANDALONE 1	3206	#define EV_STANDALONE 1
1873	#include "ev.h"	3207	#include "ev.h"
1874		3208
1875	Both header files and implementation files can be compiled with a C++	3209	Both header files and implementation files can be compiled with a C++
1876	compiler (at least, thats a stated goal, and breakage will be treated	3210	compiler (at least, that's a stated goal, and breakage will be treated
1877	as a bug).	3211	as a bug).
1878		3212
1879	You need the following files in your source tree, or in a directory	3213	You need the following files in your source tree, or in a directory
1880	in your include path (e.g. in libev/ when using -Ilibev):	3214	in your include path (e.g. in libev/ when using -Ilibev):
1881		3215
1882	ev.h	3216	ev.h
1883	ev.c	3217	ev.c
1884	ev_vars.h	3218	ev_vars.h
1885	ev_wrap.h	3219	ev_wrap.h
1886		3220
1887	ev_win32.c required on win32 platforms only	3221	ev_win32.c required on win32 platforms only
1888		3222
1889	ev_select.c only when select backend is enabled (which is by default)	3223	ev_select.c only when select backend is enabled (which is enabled by default)
1890	ev_poll.c only when poll backend is enabled (disabled by default)	3224	ev_poll.c only when poll backend is enabled (disabled by default)
1891	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3225	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1892	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3226	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1893	ev_port.c only when the solaris port backend is enabled (disabled by default)	3227	ev_port.c only when the solaris port backend is enabled (disabled by default)
1894		3228
1895	F<ev.c> includes the backend files directly when enabled, so you only need	3229	F<ev.c> includes the backend files directly when enabled, so you only need
1896	to compile this single file.	3230	to compile this single file.
1897		3231
1898	=head3 LIBEVENT COMPATIBILITY API	3232	=head3 LIBEVENT COMPATIBILITY API
1899		3233
1900	To include the libevent compatibility API, also include:	3234	To include the libevent compatibility API, also include:
1901		3235
1902	#include "event.c"	3236	#include "event.c"
1903		3237
1904	in the file including F<ev.c>, and:	3238	in the file including F<ev.c>, and:
1905		3239
1906	#include "event.h"	3240	#include "event.h"
1907		3241
1908	in the files that want to use the libevent API. This also includes F<ev.h>.	3242	in the files that want to use the libevent API. This also includes F<ev.h>.
1909		3243
1910	You need the following additional files for this:	3244	You need the following additional files for this:
1911		3245
1912	event.h	3246	event.h
1913	event.c	3247	event.c
1914		3248
1915	=head3 AUTOCONF SUPPORT	3249	=head3 AUTOCONF SUPPORT
1916		3250
1917	Instead of using C<EV_STANDALONE=1> and providing your config in	3251	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1918	whatever way you want, you can also C<m4_include([libev.m4])> in your	3252	whatever way you want, you can also C<m4_include([libev.m4])> in your
1919	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3253	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1920	include F<config.h> and configure itself accordingly.	3254	include F<config.h> and configure itself accordingly.
1921		3255
1922	For this of course you need the m4 file:	3256	For this of course you need the m4 file:
1923		3257
1924	libev.m4	3258	libev.m4
1925		3259
1926	=head2 PREPROCESSOR SYMBOLS/MACROS	3260	=head2 PREPROCESSOR SYMBOLS/MACROS
1927		3261
1928	Libev can be configured via a variety of preprocessor symbols you have to define	3262	Libev can be configured via a variety of preprocessor symbols you have to
1929	before including any of its files. The default is not to build for multiplicity	3263	define before including any of its files. The default in the absence of
1930	and only include the select backend.	3264	autoconf is documented for every option.
1931		3265
1932	=over 4	3266	=over 4
1933		3267
1934	=item EV_STANDALONE	3268	=item EV_STANDALONE
1935		3269
…		…
1937	keeps libev from including F<config.h>, and it also defines dummy	3271	keeps libev from including F<config.h>, and it also defines dummy
1938	implementations for some libevent functions (such as logging, which is not	3272	implementations for some libevent functions (such as logging, which is not
1939	supported). It will also not define any of the structs usually found in	3273	supported). It will also not define any of the structs usually found in
1940	F<event.h> that are not directly supported by the libev core alone.	3274	F<event.h> that are not directly supported by the libev core alone.
1941		3275
		3276	In stanbdalone mode, libev will still try to automatically deduce the
		3277	configuration, but has to be more conservative.
		3278
1942	=item EV_USE_MONOTONIC	3279	=item EV_USE_MONOTONIC
1943		3280
1944	If defined to be C<1>, libev will try to detect the availability of the	3281	If defined to be C<1>, libev will try to detect the availability of the
1945	monotonic clock option at both compiletime and runtime. Otherwise no use	3282	monotonic clock option at both compile time and runtime. Otherwise no
1946	of the monotonic clock option will be attempted. If you enable this, you	3283	use of the monotonic clock option will be attempted. If you enable this,
1947	usually have to link against librt or something similar. Enabling it when	3284	you usually have to link against librt or something similar. Enabling it
1948	the functionality isn't available is safe, though, althoguh you have	3285	when the functionality isn't available is safe, though, although you have
1949	to make sure you link against any libraries where the C<clock_gettime>	3286	to make sure you link against any libraries where the C<clock_gettime>
1950	function is hiding in (often F<-lrt>).	3287	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
1951		3288
1952	=item EV_USE_REALTIME	3289	=item EV_USE_REALTIME
1953		3290
1954	If defined to be C<1>, libev will try to detect the availability of the	3291	If defined to be C<1>, libev will try to detect the availability of the
1955	realtime clock option at compiletime (and assume its availability at	3292	real-time clock option at compile time (and assume its availability
1956	runtime if successful). Otherwise no use of the realtime clock option will	3293	at runtime if successful). Otherwise no use of the real-time clock
1957	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3294	option will be attempted. This effectively replaces C<gettimeofday>
1958	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3295	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
1959	in the description of C<EV_USE_MONOTONIC>, though.	3296	correctness. See the note about libraries in the description of
		3297	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3298	C<EV_USE_CLOCK_SYSCALL>.
		3299
		3300	=item EV_USE_CLOCK_SYSCALL
		3301
		3302	If defined to be C<1>, libev will try to use a direct syscall instead
		3303	of calling the system-provided C<clock_gettime> function. This option
		3304	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3305	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3306	programs needlessly. Using a direct syscall is slightly slower (in
		3307	theory), because no optimised vdso implementation can be used, but avoids
		3308	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3309	higher, as it simplifies linking (no need for C<-lrt>).
		3310
		3311	=item EV_USE_NANOSLEEP
		3312
		3313	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3314	and will use it for delays. Otherwise it will use C<select ()>.
		3315
		3316	=item EV_USE_EVENTFD
		3317
		3318	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3319	available and will probe for kernel support at runtime. This will improve
		3320	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3321	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3322	2.7 or newer, otherwise disabled.
1960		3323
1961	=item EV_USE_SELECT	3324	=item EV_USE_SELECT
1962		3325
1963	If undefined or defined to be C<1>, libev will compile in support for the	3326	If undefined or defined to be C<1>, libev will compile in support for the
1964	C<select>(2) backend. No attempt at autodetection will be done: if no	3327	C<select>(2) backend. No attempt at auto-detection will be done: if no
1965	other method takes over, select will be it. Otherwise the select backend	3328	other method takes over, select will be it. Otherwise the select backend
1966	will not be compiled in.	3329	will not be compiled in.
1967		3330
1968	=item EV_SELECT_USE_FD_SET	3331	=item EV_SELECT_USE_FD_SET
1969		3332
1970	If defined to C<1>, then the select backend will use the system C<fd_set>	3333	If defined to C<1>, then the select backend will use the system C<fd_set>
1971	structure. This is useful if libev doesn't compile due to a missing	3334	structure. This is useful if libev doesn't compile due to a missing
1972	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3335	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
1973	exotic systems. This usually limits the range of file descriptors to some	3336	on exotic systems. This usually limits the range of file descriptors to
1974	low limit such as 1024 or might have other limitations (winsocket only	3337	some low limit such as 1024 or might have other limitations (winsocket
1975	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3338	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
1976	influence the size of the C<fd_set> used.	3339	configures the maximum size of the C<fd_set>.
1977		3340
1978	=item EV_SELECT_IS_WINSOCKET	3341	=item EV_SELECT_IS_WINSOCKET
1979		3342
1980	When defined to C<1>, the select backend will assume that	3343	When defined to C<1>, the select backend will assume that
1981	select/socket/connect etc. don't understand file descriptors but	3344	select/socket/connect etc. don't understand file descriptors but
…		…
1983	be used is the winsock select). This means that it will call	3346	be used is the winsock select). This means that it will call
1984	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1985	it is assumed that all these functions actually work on fds, even	3348	it is assumed that all these functions actually work on fds, even
1986	on win32. Should not be defined on non-win32 platforms.	3349	on win32. Should not be defined on non-win32 platforms.
1987		3350
		3351	=item EV_FD_TO_WIN32_HANDLE
		3352
		3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3354	file descriptors to socket handles. When not defining this symbol (the
		3355	default), then libev will call C<_get_osfhandle>, which is usually
		3356	correct. In some cases, programs use their own file descriptor management,
		3357	in which case they can provide this function to map fds to socket handles.
		3358
1988	=item EV_USE_POLL	3359	=item EV_USE_POLL
1989		3360
1990	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1991	backend. Otherwise it will be enabled on non-win32 platforms. It	3362	backend. Otherwise it will be enabled on non-win32 platforms. It
1992	takes precedence over select.	3363	takes precedence over select.
1993		3364
1994	=item EV_USE_EPOLL	3365	=item EV_USE_EPOLL
1995		3366
1996	If defined to be C<1>, libev will compile in support for the Linux	3367	If defined to be C<1>, libev will compile in support for the Linux
1997	C<epoll>(7) backend. Its availability will be detected at runtime,	3368	C<epoll>(7) backend. Its availability will be detected at runtime,
1998	otherwise another method will be used as fallback. This is the	3369	otherwise another method will be used as fallback. This is the preferred
1999	preferred backend for GNU/Linux systems.	3370	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3371	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2000		3372
2001	=item EV_USE_KQUEUE	3373	=item EV_USE_KQUEUE
2002		3374
2003	If defined to be C<1>, libev will compile in support for the BSD style	3375	If defined to be C<1>, libev will compile in support for the BSD style
2004	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3376	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2017	otherwise another method will be used as fallback. This is the preferred	3389	otherwise another method will be used as fallback. This is the preferred
2018	backend for Solaris 10 systems.	3390	backend for Solaris 10 systems.
2019		3391
2020	=item EV_USE_DEVPOLL	3392	=item EV_USE_DEVPOLL
2021		3393
2022	reserved for future expansion, works like the USE symbols above.	3394	Reserved for future expansion, works like the USE symbols above.
2023		3395
2024	=item EV_USE_INOTIFY	3396	=item EV_USE_INOTIFY
2025		3397
2026	If defined to be C<1>, libev will compile in support for the Linux inotify	3398	If defined to be C<1>, libev will compile in support for the Linux inotify
2027	interface to speed up C<ev_stat> watchers. Its actual availability will	3399	interface to speed up C<ev_stat> watchers. Its actual availability will
2028	be detected at runtime.	3400	be detected at runtime. If undefined, it will be enabled if the headers
		3401	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3402
		3403	=item EV_ATOMIC_T
		3404
		3405	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3406	access is atomic with respect to other threads or signal contexts. No such
		3407	type is easily found in the C language, so you can provide your own type
		3408	that you know is safe for your purposes. It is used both for signal handler "locking"
		3409	as well as for signal and thread safety in C<ev_async> watchers.
		3410
		3411	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3412	(from F<signal.h>), which is usually good enough on most platforms.
2029		3413
2030	=item EV_H	3414	=item EV_H
2031		3415
2032	The name of the F<ev.h> header file used to include it. The default if	3416	The name of the F<ev.h> header file used to include it. The default if
2033	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2034	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3418	used to virtually rename the F<ev.h> header file in case of conflicts.
2035		3419
2036	=item EV_CONFIG_H	3420	=item EV_CONFIG_H
2037		3421
2038	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2039	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2040	C<EV_H>, above.	3424	C<EV_H>, above.
2041		3425
2042	=item EV_EVENT_H	3426	=item EV_EVENT_H
2043		3427
2044	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2045	of how the F<event.h> header can be found.	3429	of how the F<event.h> header can be found, the default is C<"event.h">.
2046		3430
2047	=item EV_PROTOTYPES	3431	=item EV_PROTOTYPES
2048		3432
2049	If defined to be C<0>, then F<ev.h> will not define any function	3433	If defined to be C<0>, then F<ev.h> will not define any function
2050	prototypes, but still define all the structs and other symbols. This is	3434	prototypes, but still define all the structs and other symbols. This is
…		…
2057	will have the C<struct ev_loop *> as first argument, and you can create	3441	will have the C<struct ev_loop *> as first argument, and you can create
2058	additional independent event loops. Otherwise there will be no support	3442	additional independent event loops. Otherwise there will be no support
2059	for multiple event loops and there is no first event loop pointer	3443	for multiple event loops and there is no first event loop pointer
2060	argument. Instead, all functions act on the single default loop.	3444	argument. Instead, all functions act on the single default loop.
2061		3445
		3446	=item EV_MINPRI
		3447
		3448	=item EV_MAXPRI
		3449
		3450	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3451	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3452	provide for more priorities by overriding those symbols (usually defined
		3453	to be C<-2> and C<2>, respectively).
		3454
		3455	When doing priority-based operations, libev usually has to linearly search
		3456	all the priorities, so having many of them (hundreds) uses a lot of space
		3457	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3458	fine.
		3459
		3460	If your embedding application does not need any priorities, defining these
		3461	both to C<0> will save some memory and CPU.
		3462
2062	=item EV_PERIODIC_ENABLE	3463	=item EV_PERIODIC_ENABLE
2063		3464
2064	If undefined or defined to be C<1>, then periodic timers are supported. If	3465	If undefined or defined to be C<1>, then periodic timers are supported. If
2065	defined to be C<0>, then they are not. Disabling them saves a few kB of	3466	defined to be C<0>, then they are not. Disabling them saves a few kB of
2066	code.	3467	code.
2067		3468
		3469	=item EV_IDLE_ENABLE
		3470
		3471	If undefined or defined to be C<1>, then idle watchers are supported. If
		3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3473	code.
		3474
2068	=item EV_EMBED_ENABLE	3475	=item EV_EMBED_ENABLE
2069		3476
2070	If undefined or defined to be C<1>, then embed watchers are supported. If	3477	If undefined or defined to be C<1>, then embed watchers are supported. If
2071	defined to be C<0>, then they are not.	3478	defined to be C<0>, then they are not. Embed watchers rely on most other
		3479	watcher types, which therefore must not be disabled.
2072		3480
2073	=item EV_STAT_ENABLE	3481	=item EV_STAT_ENABLE
2074		3482
2075	If undefined or defined to be C<1>, then stat watchers are supported. If	3483	If undefined or defined to be C<1>, then stat watchers are supported. If
2076	defined to be C<0>, then they are not.	3484	defined to be C<0>, then they are not.
…		…
2078	=item EV_FORK_ENABLE	3486	=item EV_FORK_ENABLE
2079		3487
2080	If undefined or defined to be C<1>, then fork watchers are supported. If	3488	If undefined or defined to be C<1>, then fork watchers are supported. If
2081	defined to be C<0>, then they are not.	3489	defined to be C<0>, then they are not.
2082		3490
		3491	=item EV_ASYNC_ENABLE
		3492
		3493	If undefined or defined to be C<1>, then async watchers are supported. If
		3494	defined to be C<0>, then they are not.
		3495
2083	=item EV_MINIMAL	3496	=item EV_MINIMAL
2084		3497
2085	If you need to shave off some kilobytes of code at the expense of some	3498	If you need to shave off some kilobytes of code at the expense of some
2086	speed, define this symbol to C<1>. Currently only used for gcc to override	3499	speed, define this symbol to C<1>. Currently this is used to override some
2087	some inlining decisions, saves roughly 30% codesize of amd64.	3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3501	much smaller 2-heap for timer management over the default 4-heap.
2088		3502
2089	=item EV_PID_HASHSIZE	3503	=item EV_PID_HASHSIZE
2090		3504
2091	C<ev_child> watchers use a small hash table to distribute workload by	3505	C<ev_child> watchers use a small hash table to distribute workload by
2092	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2093	than enough. If you need to manage thousands of children you might want to	3507	than enough. If you need to manage thousands of children you might want to
2094	increase this value (I<must> be a power of two).	3508	increase this value (I<must> be a power of two).
2095		3509
2096	=item EV_INOTIFY_HASHSIZE	3510	=item EV_INOTIFY_HASHSIZE
2097		3511
2098	C<ev_staz> watchers use a small hash table to distribute workload by	3512	C<ev_stat> watchers use a small hash table to distribute workload by
2099	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2100	usually more than enough. If you need to manage thousands of C<ev_stat>	3514	usually more than enough. If you need to manage thousands of C<ev_stat>
2101	watchers you might want to increase this value (I<must> be a power of	3515	watchers you might want to increase this value (I<must> be a power of
2102	two).	3516	two).
2103		3517
		3518	=item EV_USE_4HEAP
		3519
		3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3523	faster performance with many (thousands) of watchers.
		3524
		3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3526	(disabled).
		3527
		3528	=item EV_HEAP_CACHE_AT
		3529
		3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3534	but avoids random read accesses on heap changes. This improves performance
		3535	noticeably with many (hundreds) of watchers.
		3536
		3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3538	(disabled).
		3539
		3540	=item EV_VERIFY
		3541
		3542	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3543	be done: If set to C<0>, no internal verification code will be compiled
		3544	in. If set to C<1>, then verification code will be compiled in, but not
		3545	called. If set to C<2>, then the internal verification code will be
		3546	called once per loop, which can slow down libev. If set to C<3>, then the
		3547	verification code will be called very frequently, which will slow down
		3548	libev considerably.
		3549
		3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3551	C<0>.
		3552
2104	=item EV_COMMON	3553	=item EV_COMMON
2105		3554
2106	By default, all watchers have a C<void *data> member. By redefining	3555	By default, all watchers have a C<void *data> member. By redefining
2107	this macro to a something else you can include more and other types of	3556	this macro to a something else you can include more and other types of
2108	members. You have to define it each time you include one of the files,	3557	members. You have to define it each time you include one of the files,
2109	though, and it must be identical each time.	3558	though, and it must be identical each time.
2110		3559
2111	For example, the perl EV module uses something like this:	3560	For example, the perl EV module uses something like this:
2112		3561
2113	#define EV_COMMON \	3562	#define EV_COMMON \
2114	SV *self; /* contains this struct */ \	3563	SV *self; /* contains this struct */ \
2115	SV *cb_sv, *fh /* note no trailing ";" */	3564	SV *cb_sv, *fh /* note no trailing ";" */
2116		3565
2117	=item EV_CB_DECLARE (type)	3566	=item EV_CB_DECLARE (type)
2118		3567
2119	=item EV_CB_INVOKE (watcher, revents)	3568	=item EV_CB_INVOKE (watcher, revents)
2120		3569
2121	=item ev_set_cb (ev, cb)	3570	=item ev_set_cb (ev, cb)
2122		3571
2123	Can be used to change the callback member declaration in each watcher,	3572	Can be used to change the callback member declaration in each watcher,
2124	and the way callbacks are invoked and set. Must expand to a struct member	3573	and the way callbacks are invoked and set. Must expand to a struct member
2125	definition and a statement, respectively. See the F<ev.v> header file for	3574	definition and a statement, respectively. See the F<ev.h> header file for
2126	their default definitions. One possible use for overriding these is to	3575	their default definitions. One possible use for overriding these is to
2127	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3576	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2128	method calls instead of plain function calls in C++.	3577	method calls instead of plain function calls in C++.
		3578
		3579	=back
		3580
		3581	=head2 EXPORTED API SYMBOLS
		3582
		3583	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3584	exported symbols, you can use the provided F<Symbol.*> files which list
		3585	all public symbols, one per line:
		3586
		3587	Symbols.ev for libev proper
		3588	Symbols.event for the libevent emulation
		3589
		3590	This can also be used to rename all public symbols to avoid clashes with
		3591	multiple versions of libev linked together (which is obviously bad in
		3592	itself, but sometimes it is inconvenient to avoid this).
		3593
		3594	A sed command like this will create wrapper C<#define>'s that you need to
		3595	include before including F<ev.h>:
		3596
		3597	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3598
		3599	This would create a file F<wrap.h> which essentially looks like this:
		3600
		3601	#define ev_backend myprefix_ev_backend
		3602	#define ev_check_start myprefix_ev_check_start
		3603	#define ev_check_stop myprefix_ev_check_stop
		3604	...
2129		3605
2130	=head2 EXAMPLES	3606	=head2 EXAMPLES
2131		3607
2132	For a real-world example of a program the includes libev	3608	For a real-world example of a program the includes libev
2133	verbatim, you can have a look at the EV perl module	3609	verbatim, you can have a look at the EV perl module
…		…
2136	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3612	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2137	will be compiled. It is pretty complex because it provides its own header	3613	will be compiled. It is pretty complex because it provides its own header
2138	file.	3614	file.
2139		3615
2140	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2141	that everybody includes and which overrides some autoconf choices:	3617	that everybody includes and which overrides some configure choices:
2142		3618
		3619	#define EV_MINIMAL 1
2143	#define EV_USE_POLL 0	3620	#define EV_USE_POLL 0
2144	#define EV_MULTIPLICITY 0	3621	#define EV_MULTIPLICITY 0
2145	#define EV_PERIODICS 0	3622	#define EV_PERIODIC_ENABLE 0
		3623	#define EV_STAT_ENABLE 0
		3624	#define EV_FORK_ENABLE 0
2146	#define EV_CONFIG_H <config.h>	3625	#define EV_CONFIG_H <config.h>
		3626	#define EV_MINPRI 0
		3627	#define EV_MAXPRI 0
2147		3628
2148	#include "ev++.h"	3629	#include "ev++.h"
2149		3630
2150	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2151		3632
2152	#include "ev_cpp.h"	3633	#include "ev_cpp.h"
2153	#include "ev.c"	3634	#include "ev.c"
2154		3635
		3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2155		3637
		3638	=head2 THREADS AND COROUTINES
		3639
		3640	=head3 THREADS
		3641
		3642	All libev functions are reentrant and thread-safe unless explicitly
		3643	documented otherwise, but libev implements no locking itself. This means
		3644	that you can use as many loops as you want in parallel, as long as there
		3645	are no concurrent calls into any libev function with the same loop
		3646	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3647	of course): libev guarantees that different event loops share no data
		3648	structures that need any locking.
		3649
		3650	Or to put it differently: calls with different loop parameters can be done
		3651	concurrently from multiple threads, calls with the same loop parameter
		3652	must be done serially (but can be done from different threads, as long as
		3653	only one thread ever is inside a call at any point in time, e.g. by using
		3654	a mutex per loop).
		3655
		3656	Specifically to support threads (and signal handlers), libev implements
		3657	so-called C<ev_async> watchers, which allow some limited form of
		3658	concurrency on the same event loop, namely waking it up "from the
		3659	outside".
		3660
		3661	If you want to know which design (one loop, locking, or multiple loops
		3662	without or something else still) is best for your problem, then I cannot
		3663	help you, but here is some generic advice:
		3664
		3665	=over 4
		3666
		3667	=item * most applications have a main thread: use the default libev loop
		3668	in that thread, or create a separate thread running only the default loop.
		3669
		3670	This helps integrating other libraries or software modules that use libev
		3671	themselves and don't care/know about threading.
		3672
		3673	=item * one loop per thread is usually a good model.
		3674
		3675	Doing this is almost never wrong, sometimes a better-performance model
		3676	exists, but it is always a good start.
		3677
		3678	=item * other models exist, such as the leader/follower pattern, where one
		3679	loop is handed through multiple threads in a kind of round-robin fashion.
		3680
		3681	Choosing a model is hard - look around, learn, know that usually you can do
		3682	better than you currently do :-)
		3683
		3684	=item * often you need to talk to some other thread which blocks in the
		3685	event loop.
		3686
		3687	C<ev_async> watchers can be used to wake them up from other threads safely
		3688	(or from signal contexts...).
		3689
		3690	An example use would be to communicate signals or other events that only
		3691	work in the default loop by registering the signal watcher with the
		3692	default loop and triggering an C<ev_async> watcher from the default loop
		3693	watcher callback into the event loop interested in the signal.
		3694
		3695	=back
		3696
		3697	=head3 COROUTINES
		3698
		3699	Libev is very accommodating to coroutines ("cooperative threads"):
		3700	libev fully supports nesting calls to its functions from different
		3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3702	different coroutines, and switch freely between both coroutines running the
		3703	loop, as long as you don't confuse yourself). The only exception is that
		3704	you must not do this from C<ev_periodic> reschedule callbacks.
		3705
		3706	Care has been taken to ensure that libev does not keep local state inside
		3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3708	they do not call any callbacks.
		3709
		3710	=head2 COMPILER WARNINGS
		3711
		3712	Depending on your compiler and compiler settings, you might get no or a
		3713	lot of warnings when compiling libev code. Some people are apparently
		3714	scared by this.
		3715
		3716	However, these are unavoidable for many reasons. For one, each compiler
		3717	has different warnings, and each user has different tastes regarding
		3718	warning options. "Warn-free" code therefore cannot be a goal except when
		3719	targeting a specific compiler and compiler-version.
		3720
		3721	Another reason is that some compiler warnings require elaborate
		3722	workarounds, or other changes to the code that make it less clear and less
		3723	maintainable.
		3724
		3725	And of course, some compiler warnings are just plain stupid, or simply
		3726	wrong (because they don't actually warn about the condition their message
		3727	seems to warn about). For example, certain older gcc versions had some
		3728	warnings that resulted an extreme number of false positives. These have
		3729	been fixed, but some people still insist on making code warn-free with
		3730	such buggy versions.
		3731
		3732	While libev is written to generate as few warnings as possible,
		3733	"warn-free" code is not a goal, and it is recommended not to build libev
		3734	with any compiler warnings enabled unless you are prepared to cope with
		3735	them (e.g. by ignoring them). Remember that warnings are just that:
		3736	warnings, not errors, or proof of bugs.
		3737
		3738
		3739	=head2 VALGRIND
		3740
		3741	Valgrind has a special section here because it is a popular tool that is
		3742	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3743
		3744	If you think you found a bug (memory leak, uninitialised data access etc.)
		3745	in libev, then check twice: If valgrind reports something like:
		3746
		3747	==2274== definitely lost: 0 bytes in 0 blocks.
		3748	==2274== possibly lost: 0 bytes in 0 blocks.
		3749	==2274== still reachable: 256 bytes in 1 blocks.
		3750
		3751	Then there is no memory leak, just as memory accounted to global variables
		3752	is not a memleak - the memory is still being referenced, and didn't leak.
		3753
		3754	Similarly, under some circumstances, valgrind might report kernel bugs
		3755	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3756	although an acceptable workaround has been found here), or it might be
		3757	confused.
		3758
		3759	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3760	make it into some kind of religion.
		3761
		3762	If you are unsure about something, feel free to contact the mailing list
		3763	with the full valgrind report and an explanation on why you think this
		3764	is a bug in libev (best check the archives, too :). However, don't be
		3765	annoyed when you get a brisk "this is no bug" answer and take the chance
		3766	of learning how to interpret valgrind properly.
		3767
		3768	If you need, for some reason, empty reports from valgrind for your project
		3769	I suggest using suppression lists.
		3770
		3771
		3772	=head1 PORTABILITY NOTES
		3773
		3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3775
		3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3777	requires, and its I/O model is fundamentally incompatible with the POSIX
		3778	model. Libev still offers limited functionality on this platform in
		3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3780	descriptors. This only applies when using Win32 natively, not when using
		3781	e.g. cygwin.
		3782
		3783	Lifting these limitations would basically require the full
		3784	re-implementation of the I/O system. If you are into these kinds of
		3785	things, then note that glib does exactly that for you in a very portable
		3786	way (note also that glib is the slowest event library known to man).
		3787
		3788	There is no supported compilation method available on windows except
		3789	embedding it into other applications.
		3790
		3791	Not a libev limitation but worth mentioning: windows apparently doesn't
		3792	accept large writes: instead of resulting in a partial write, windows will
		3793	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3794	so make sure you only write small amounts into your sockets (less than a
		3795	megabyte seems safe, but this apparently depends on the amount of memory
		3796	available).
		3797
		3798	Due to the many, low, and arbitrary limits on the win32 platform and
		3799	the abysmal performance of winsockets, using a large number of sockets
		3800	is not recommended (and not reasonable). If your program needs to use
		3801	more than a hundred or so sockets, then likely it needs to use a totally
		3802	different implementation for windows, as libev offers the POSIX readiness
		3803	notification model, which cannot be implemented efficiently on windows
		3804	(Microsoft monopoly games).
		3805
		3806	A typical way to use libev under windows is to embed it (see the embedding
		3807	section for details) and use the following F<evwrap.h> header file instead
		3808	of F<ev.h>:
		3809
		3810	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3811	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3812
		3813	#include "ev.h"
		3814
		3815	And compile the following F<evwrap.c> file into your project (make sure
		3816	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3817
		3818	#include "evwrap.h"
		3819	#include "ev.c"
		3820
		3821	=over 4
		3822
		3823	=item The winsocket select function
		3824
		3825	The winsocket C<select> function doesn't follow POSIX in that it
		3826	requires socket I<handles> and not socket I<file descriptors> (it is
		3827	also extremely buggy). This makes select very inefficient, and also
		3828	requires a mapping from file descriptors to socket handles (the Microsoft
		3829	C runtime provides the function C<_open_osfhandle> for this). See the
		3830	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3831	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3832
		3833	The configuration for a "naked" win32 using the Microsoft runtime
		3834	libraries and raw winsocket select is:
		3835
		3836	#define EV_USE_SELECT 1
		3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3838
		3839	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3840	complexity in the O(n²) range when using win32.
		3841
		3842	=item Limited number of file descriptors
		3843
		3844	Windows has numerous arbitrary (and low) limits on things.
		3845
		3846	Early versions of winsocket's select only supported waiting for a maximum
		3847	of C<64> handles (probably owning to the fact that all windows kernels
		3848	can only wait for C<64> things at the same time internally; Microsoft
		3849	recommends spawning a chain of threads and wait for 63 handles and the
		3850	previous thread in each. Great).
		3851
		3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3853	to some high number (e.g. C<2048>) before compiling the winsocket select
		3854	call (which might be in libev or elsewhere, for example, perl does its own
		3855	select emulation on windows).
		3856
		3857	Another limit is the number of file descriptors in the Microsoft runtime
		3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3859	or something like this inside Microsoft). You can increase this by calling
		3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3861	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3862	libraries.
		3863
		3864	This might get you to about C<512> or C<2048> sockets (depending on
		3865	windows version and/or the phase of the moon). To get more, you need to
		3866	wrap all I/O functions and provide your own fd management, but the cost of
		3867	calling select (O(n²)) will likely make this unworkable.
		3868
		3869	=back
		3870
		3871	=head2 PORTABILITY REQUIREMENTS
		3872
		3873	In addition to a working ISO-C implementation and of course the
		3874	backend-specific APIs, libev relies on a few additional extensions:
		3875
		3876	=over 4
		3877
		3878	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3879	calling conventions regardless of C<ev_watcher_type *>.
		3880
		3881	Libev assumes not only that all watcher pointers have the same internal
		3882	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3883	assumes that the same (machine) code can be used to call any watcher
		3884	callback: The watcher callbacks have different type signatures, but libev
		3885	calls them using an C<ev_watcher *> internally.
		3886
		3887	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3888
		3889	The type C<sig_atomic_t volatile> (or whatever is defined as
		3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3891	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3892	believed to be sufficiently portable.
		3893
		3894	=item C<sigprocmask> must work in a threaded environment
		3895
		3896	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3897	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3898	pthread implementations will either allow C<sigprocmask> in the "main
		3899	thread" or will block signals process-wide, both behaviours would
		3900	be compatible with libev. Interaction between C<sigprocmask> and
		3901	C<pthread_sigmask> could complicate things, however.
		3902
		3903	The most portable way to handle signals is to block signals in all threads
		3904	except the initial one, and run the default loop in the initial thread as
		3905	well.
		3906
		3907	=item C<long> must be large enough for common memory allocation sizes
		3908
		3909	To improve portability and simplify its API, libev uses C<long> internally
		3910	instead of C<size_t> when allocating its data structures. On non-POSIX
		3911	systems (Microsoft...) this might be unexpectedly low, but is still at
		3912	least 31 bits everywhere, which is enough for hundreds of millions of
		3913	watchers.
		3914
		3915	=item C<double> must hold a time value in seconds with enough accuracy
		3916
		3917	The type C<double> is used to represent timestamps. It is required to
		3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3919	enough for at least into the year 4000. This requirement is fulfilled by
		3920	implementations implementing IEEE 754 (basically all existing ones).
		3921
		3922	=back
		3923
		3924	If you know of other additional requirements drop me a note.
		3925
		3926
2156	=head1 COMPLEXITIES	3927	=head1 ALGORITHMIC COMPLEXITIES
2157		3928
2158	In this section the complexities of (many of) the algorithms used inside	3929	In this section the complexities of (many of) the algorithms used inside
2159	libev will be explained. For complexity discussions about backends see the	3930	libev will be documented. For complexity discussions about backends see
2160	documentation for C<ev_default_init>.	3931	the documentation for C<ev_default_init>.
		3932
		3933	All of the following are about amortised time: If an array needs to be
		3934	extended, libev needs to realloc and move the whole array, but this
		3935	happens asymptotically rarer with higher number of elements, so O(1) might
		3936	mean that libev does a lengthy realloc operation in rare cases, but on
		3937	average it is much faster and asymptotically approaches constant time.
2161		3938
2162	=over 4	3939	=over 4
2163		3940
2164	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3941	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2165		3942
		3943	This means that, when you have a watcher that triggers in one hour and
		3944	there are 100 watchers that would trigger before that, then inserting will
		3945	have to skip roughly seven (C<ld 100>) of these watchers.
		3946
2166	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3947	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2167		3948
		3949	That means that changing a timer costs less than removing/adding them,
		3950	as only the relative motion in the event queue has to be paid for.
		3951
2168	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3952	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2169		3953
		3954	These just add the watcher into an array or at the head of a list.
		3955
2170	=item Stopping check/prepare/idle watchers: O(1)	3956	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2171		3957
2172	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3958	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2173		3959
		3960	These watchers are stored in lists, so they need to be walked to find the
		3961	correct watcher to remove. The lists are usually short (you don't usually
		3962	have many watchers waiting for the same fd or signal: one is typical, two
		3963	is rare).
		3964
2174	=item Finding the next timer per loop iteration: O(1)	3965	=item Finding the next timer in each loop iteration: O(1)
		3966
		3967	By virtue of using a binary or 4-heap, the next timer is always found at a
		3968	fixed position in the storage array.
2175		3969
2176	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3970	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2177		3971
2178	=item Activating one watcher: O(1)	3972	A change means an I/O watcher gets started or stopped, which requires
		3973	libev to recalculate its status (and possibly tell the kernel, depending
		3974	on backend and whether C<ev_io_set> was used).
		3975
		3976	=item Activating one watcher (putting it into the pending state): O(1)
		3977
		3978	=item Priority handling: O(number_of_priorities)
		3979
		3980	Priorities are implemented by allocating some space for each
		3981	priority. When doing priority-based operations, libev usually has to
		3982	linearly search all the priorities, but starting/stopping and activating
		3983	watchers becomes O(1) with respect to priority handling.
		3984
		3985	=item Sending an ev_async: O(1)
		3986
		3987	=item Processing ev_async_send: O(number_of_async_watchers)
		3988
		3989	=item Processing signals: O(max_signal_number)
		3990
		3991	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3992	calls in the current loop iteration. Checking for async and signal events
		3993	involves iterating over all running async watchers or all signal numbers.
2179		3994
2180	=back	3995	=back
2181		3996
2182		3997
2183	=head1 AUTHOR	3998	=head1 AUTHOR
2184		3999
2185	Marc Lehmann <libev@schmorp.de>.	4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2186		4001

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