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Revision 1.138 by root, Mon Mar 31 01:14:12 2008 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	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 DESCRIPTION
66		68
67	The newest version of this document is also available as an html-formatted	69	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	70	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		72
71	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
72	file descriptor being readable or a timeout occurring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	75	these event sources and provide your program with events.
74		76
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	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
116	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
117	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
118	it, you should treat it as some floatingpoint value. Unlike the name	120	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	121	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	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
121		144
122	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
123		146
124	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
125	library in any way.	148	library in any way.
…		…
134		157
135	=item ev_sleep (ev_tstamp interval)	158	=item ev_sleep (ev_tstamp interval)
136		159
137	Sleep for the given interval: The current thread will be blocked until	160	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	161	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	162	this is a sub-second-resolution C<sleep ()>.
140		163
141	=item int ev_version_major ()	164	=item int ev_version_major ()
142		165
143	=item int ev_version_minor ()	166	=item int ev_version_minor ()
144		167
…		…
157	not a problem.	180	not a problem.
158		181
159	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
160	version.	183	version.
161		184
162	assert (("libev version mismatch",	185	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
165		188
166	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
167		190
168	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_*>
169	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	194	a description of the set values.
172		195
173	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
174	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
175		198
176	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
178		201
179	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
180		203
181	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
182	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
183	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
184	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
185	(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
186	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
187		210
188	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
189		212
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	217	recommended ones.
195		218
196	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
197		220
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		222
200	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	225	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	226	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
205	function.	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.
206		232
207	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
208	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,
209	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.
210		236
211	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
212	retries).	238	retries (example requires a standards-compliant C<realloc>).
213		239
214	static void *	240	static void *
215	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
216	{	242	{
217	for (;;)	243	for (;;)
…		…
226	}	252	}
227		253
228	...	254	...
229	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
230		256
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		258
233	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
234	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
235	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
236	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
237	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
238	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
239	(such as abort).	265	(such as abort).
240		266
241	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.
…		…
252		278
253	=back	279	=back
254		280
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		282
257	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>
258	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>
259	events, and dynamically created loops which do not.	285	I<function>).
260		286
261	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
262	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
263	create, you also create another event loop. Libev itself does no locking	289	not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		290
268	=over 4	291	=over 4
269		292
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		294
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		299
277	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
278	function.	301	function.
279		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
280	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	312	C<ev_default_init>.
286		313
287	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
…		…
296	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
297	thing, believe me).	324	thing, believe me).
298		325
299	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
300		327
301	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
302	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
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	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
305	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
306	around bugs.	333	around bugs.
…		…
313		340
314	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
320		347
321	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
323	flag.	350	flag.
324		351
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	353	environment variable.
327		354
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		356
330	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
…		…
332	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
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
335		362
336	To get good performance out of this backend you need a high amount of	363	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	364	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	365	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	366	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	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).
342		373
343	=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)
344		375
345	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	378	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	379	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	381	performance tips.
351		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		387
354	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,
355	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	392
359	cases and rewiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	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.
361		409
362	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
363	will 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
364	(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
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
367		415	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		416
372	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	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.
375		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
376	While nominally embeddeble in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	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>.
378		434
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		436
381	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
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's 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
385	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
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	445	system like NetBSD.
388		446
389	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
392		450
393	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
394	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
395	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
399		458
400	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
401		460
402	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	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>.
408		471
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		473
411	This is not implemented yet (and might never be, unless you send me an	474	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		480
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	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)).
420		483
421	Please note that solaris event ports can deliver a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
422	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
423	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
424		487
425	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	491	might perform better.
429		492
430	On the positive side, ignoring the spurious readyness notifications, this	493	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	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>.
433		500
434	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
435		502
436	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
437	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
…		…
439		506
440	It is definitely not recommended to use this flag.	507	It is definitely not recommended to use this flag.
441		508
442	=back	509	=back
443		510
444	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
445	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		514
448	The most typical usage is like this:	515	Example: This is the most typical usage.
449		516
450	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		519
453	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
454	environment settings to be taken into account:	521	environment settings to be taken into account:
455		522
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		524
458	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
459	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
460	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):
461		529
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		531
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		533
466	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
467	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
468	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
469	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
470		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
471	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.
472		544
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	546	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
476		548
477	=item ev_default_destroy ()	549	=item ev_default_destroy ()
478		550
479	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
480	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
481	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
482	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
483	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
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	557	for example).
486		558
487	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
488	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
489	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
490		562
491	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
492	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
493	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
494	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
519		591
520	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
521		593
522	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
523	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
524	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.
525		598
526	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
527		600
528	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
529		603
530	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
531		605
532	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
533	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
548	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
549	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
550	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
551	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
552		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>).
		664
553	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
554		666
555	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
556	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
557	events.	669	events.
…		…
559	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
560	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.
561		673
562	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
563	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
564	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
565	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
566	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.
567		680
568	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
569	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
570	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.
571		685
572	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
573	neccessary) and will handle those and any outstanding ones. It will block	687	necessary) and will handle those and any already outstanding ones. It
574	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
575	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
576	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
577	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
578	usually a better approach for this kind of thing.	696	usually a better approach for this kind of thing.
579		697
580	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
581		699
582	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	701	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	702	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	703	- Queue and call all prepare watchers.
586	- 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.
587	- Update the kernel state with all outstanding changes.	706	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	707	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	708	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	709	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	715	- Queue all expired timers.
597	- Queue all outstanding periodics.	716	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	718	- Queue all check watchers.
600	- 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).
601	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
602	be handled here by queueing them when their watcher gets executed.	721	be handled here by queueing them when their watcher gets executed.
603	- 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
…		…
608	anymore.	727	anymore.
609		728
610	... queue jobs here, make sure they register event watchers as long	729	... queue jobs here, make sure they register event watchers as long
611	... 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..)
612	ev_loop (my_loop, 0);	731	ev_loop (my_loop, 0);
613	... jobs done. yeah!	732	... jobs done or somebody called unloop. yeah!
614		733
615	=item ev_unloop (loop, how)	734	=item ev_unloop (loop, how)
616		735
617	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
618	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
619	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
620	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.
621		740
622	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
623		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
624	=item ev_ref (loop)	745	=item ev_ref (loop)
625		746
626	=item ev_unref (loop)	747	=item ev_unref (loop)
627		748
628	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
629	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
630	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
631	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>
632	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
633	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
634	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
635	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
636	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
637	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
638	(but only if the watcher wasn't active before, or was active before,	762	before stop> (but only if the watcher wasn't active before, or was active
639	respectively).	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).
640		766
641	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>
642	running when nothing else is active.	768	running when nothing else is active.
643		769
644	struct ev_signal exitsig;	770	ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	773	evf_unref (loop);
648		774
649	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
650		776
651	ev_ref (loop);	777	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	778	ev_signal_stop (loop, &exitsig);
653		779
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	780	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		781
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	782	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		783
658	These advanced functions influence the time that libev will spend waiting	784	These advanced functions influence the time that libev will spend waiting
659	for events. Both are by default C<0>, meaning that libev will try to	785	for events. Both time intervals are by default C<0>, meaning that libev
660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	786	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		787	latency.
661		788
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	789	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
663	allows libev to delay invocation of I/O and timer/periodic callbacks to	790	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	791	to increase efficiency of loop iterations (or to increase power-saving
		792	opportunities).
665		793
666	The background is that sometimes your program runs just fast enough to	794	The idea is that sometimes your program runs just fast enough to handle
667	handle one (or very few) event(s) per loop iteration. While this makes	795	one (or very few) event(s) per loop iteration. While this makes the
668	the program responsive, it also wastes a lot of CPU time to poll for new	796	program responsive, it also wastes a lot of CPU time to poll for new
669	events, especially with backends like C<select ()> which have a high	797	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	798	overhead for the actual polling but can deliver many events at once.
671		799
672	By setting a higher I<io collect interval> you allow libev to spend more	800	By setting a higher I<io collect interval> you allow libev to spend more
673	time collecting I/O events, so you can handle more events per iteration,	801	time collecting I/O events, so you can handle more events per iteration,
…		…
675	C<ev_timer>) will be not affected. Setting this to a non-null value will	803	C<ev_timer>) will be not affected. Setting this to a non-null value will
676	introduce an additional C<ev_sleep ()> call into most loop iterations.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
677		805
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	806	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	810	value will not introduce any overhead in libev.
683		811
684	Many (busy) programs can usually benefit by setting the io collect	812	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	813	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	814	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	815	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	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.
689		836
690	=back	837	=back
691		838
692		839
693	=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.
694		845
695	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
696	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
697	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:
698		849
699	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)
700	{	851	{
701	ev_io_stop (w);	852	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
703	}	854	}
704		855
705	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
706	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
707	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
710	ev_loop (loop, 0);	864	ev_loop (loop, 0);
711		865
712	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
713	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
714	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).
715		872
716	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
717	(watcher *, callback)>, which expects a callback to be provided. This	874	(watcher *, callback)>, which expects a callback to be provided. This
718	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
719	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
720	is readable and/or writable).	877	is readable and/or writable).
721		878
722	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 *, ...) >>
723	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
724	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<<
725	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
726		883
727	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
728	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
729	*) >>), 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
730	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
731		888
732	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
733	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
734	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
735		892
736	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
737	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
738	third argument.	895	third argument.
739		896
…		…
797		954
798	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
799		956
800	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
801		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
802	=item C<EV_ERROR>	964	=item C<EV_ERROR>
803		965
804	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
805	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
806	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
807	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
808	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.
809		975
810	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
811	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
812	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
813	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
814	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
815		982
816	=back	983	=back
817		984
818	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
819
820	In the following description, C<TYPE> stands for the watcher type,
821	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
822		986
823	=over 4	987	=over 4
824		988
825	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
826		990
…		…
832	which rolls both calls into one.	996	which rolls both calls into one.
833		997
834	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
835	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
836		1000
837	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,
838	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);
839		1009
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
841		1011
842	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
843	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
…		…
846	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
847		1017
848	Although some watcher types do not have type-specific arguments	1018	Although some watcher types do not have type-specific arguments
849	(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.
850		1020
		1021	See C<ev_init>, above, for an example.
		1022
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		1024
853	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
854	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
855	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);
856		1032
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		1034
859	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
861		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
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
863		1044
864	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
865	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
866	non-repeating timers are being stopped when they become pending), but	1049	non-repeating timers are being stopped when they become pending - but
867	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
868	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
869	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.
870		1053
871	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
872		1055
873	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
874	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
…		…
916	The default priority used by watchers when no priority has been set is	1099	The default priority used by watchers when no priority has been set is
917	always C<0>, which is supposed to not be too high and not be too low :).	1100	always C<0>, which is supposed to not be too high and not be too low :).
918		1101
919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
920	fine, as long as you do not mind that the priority value you query might	1103	fine, as long as you do not mind that the priority value you query might
921	or might not have been adjusted to be within valid range.	1104	or might not have been clamped to the valid range.
922		1105
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1107
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
926	C<loop> nor C<revents> need to be valid as long as the watcher callback	1109	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1110	can deal with that fact, as both are simply passed through to the
		1111	callback.
928		1112
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1113	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1114
931	If the watcher is pending, this function returns clears its pending status	1115	If the watcher is pending, this function clears its pending status and
932	and returns its C<revents> bitset (as if its callback was invoked). If the	1116	returns its C<revents> bitset (as if its callback was invoked). If the
933	watcher isn't pending it does nothing and returns C<0>.	1117	watcher isn't pending it does nothing and returns C<0>.
934		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
935	=back	1122	=back
936		1123
937		1124
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1126
940	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
941	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
942	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
943	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
944	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
945	data:	1132	data:
946		1133
947	struct my_io	1134	struct my_io
948	{	1135	{
949	struct ev_io io;	1136	ev_io io;
950	int otherfd;	1137	int otherfd;
951	void *somedata;	1138	void *somedata;
952	struct whatever *mostinteresting;	1139	struct whatever *mostinteresting;
953	}	1140	};
		1141
		1142	...
		1143	struct my_io w;
		1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1145
955	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
956	can cast it back to your own type:	1147	can cast it back to your own type:
957		1148
958	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)
959	{	1150	{
960	struct my_io *w = (struct my_io *)w_;	1151	struct my_io *w = (struct my_io *)w_;
961	...	1152	...
962	}	1153	}
963		1154
964	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
965	instead have been omitted.	1156	instead have been omitted.
966		1157
967	Another common scenario is having some data structure with multiple	1158	Another common scenario is to use some data structure with multiple
968	watchers:	1159	embedded watchers:
969		1160
970	struct my_biggy	1161	struct my_biggy
971	{	1162	{
972	int some_data;	1163	int some_data;
973	ev_timer t1;	1164	ev_timer t1;
974	ev_timer t2;	1165	ev_timer t2;
975	}	1166	}
976		1167
977	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
978	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):
979		1173
980	#include <stddef.h>	1174	#include <stddef.h>
981		1175
982	static void	1176	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1177	t1_cb (EV_P_ ev_timer *w, int revents)
984	{	1178	{
985	struct my_biggy big = (struct my_biggy *	1179	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1180	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1181	}
988		1182
989	static void	1183	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1184	t2_cb (EV_P_ ev_timer *w, int revents)
991	{	1185	{
992	struct my_biggy big = (struct my_biggy *	1186	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1187	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1188	}
995		1189
996		1190
997	=head1 WATCHER TYPES	1191	=head1 WATCHER TYPES
998		1192
999	This section describes each watcher in detail, but will not repeat	1193	This section describes each watcher in detail, but will not repeat
…		…
1023	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
1024	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
1025	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
1026	required if you know what you are doing).	1220	required if you know what you are doing).
1027		1221
1028	If you must do this, then force the use of a known-to-be-good backend	1222	If you cannot use non-blocking mode, then force the use of a
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1223	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1031		1225
1032	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
1033	receive "spurious" readyness notifications, that is your callback might	1227	receive "spurious" readiness notifications, that is your callback might
1034	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
1035	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
1036	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
1037	this situation even with a relatively standard program structure. Thus	1231	this situation even with a relatively standard program structure. Thus
1038	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
1039	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.
1040		1234
1041	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
1042	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
1043	whether 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
1044	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
1045	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.
1046		1244
1047	=head3 The special problem of disappearing file descriptors	1245	=head3 The special problem of disappearing file descriptors
1048		1246
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1247	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1050	descriptor (either by calling C<close> explicitly or by any other means,	1248	descriptor (either due to calling C<close> explicitly or any other means,
1051	such as C<dup>). The reason is that you register interest in some file	1249	such as C<dup2>). The reason is that you register interest in some file
1052	descriptor, but when it goes away, the operating system will silently drop	1250	descriptor, but when it goes away, the operating system will silently drop
1053	this interest. If another file descriptor with the same number then is	1251	this interest. If another file descriptor with the same number then is
1054	registered with libev, there is no efficient way to see that this is, in	1252	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1253	fact, a different file descriptor.
1056		1254
…		…
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1286	C<EVBACKEND_POLL>.
1089		1287
1090	=head3 The special problem of SIGPIPE	1288	=head3 The special problem of SIGPIPE
1091		1289
1092	While not really specific to libev, it is easy to forget about SIGPIPE:	1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1093	when reading from a pipe whose other end has been closed, your program	1291	when writing to a pipe whose other end has been closed, your program gets
1094	gets send a SIGPIPE, which, by default, aborts your program. For most	1292	sent a SIGPIPE, which, by default, aborts your program. For most programs
1095	programs this is sensible behaviour, for daemons, this is usually	1293	this is sensible behaviour, for daemons, this is usually undesirable.
1096	undesirable.
1097		1294
1098	So when you encounter spurious, unexplained daemon exits, make sure you	1295	So when you encounter spurious, unexplained daemon exits, make sure you
1099	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1100	somewhere, as that would have given you a big clue).	1297	somewhere, as that would have given you a big clue).
1101		1298
…		…
1107	=item ev_io_init (ev_io *, callback, int fd, int events)	1304	=item ev_io_init (ev_io *, callback, int fd, int events)
1108		1305
1109	=item ev_io_set (ev_io *, int fd, int events)	1306	=item ev_io_set (ev_io *, int fd, int events)
1110		1307
1111	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
1112	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
1113	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.
1114		1311
1115	=item int fd [read-only]	1312	=item int fd [read-only]
1116		1313
1117	The file descriptor being watched.	1314	The file descriptor being watched.
1118		1315
…		…
1126		1323
1127	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
1128	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
1129	attempt to read a whole line in the callback.	1326	attempt to read a whole line in the callback.
1130		1327
1131	static void	1328	static void
1132	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)
1133	{	1330	{
1134	ev_io_stop (loop, w);	1331	ev_io_stop (loop, w);
1135	.. 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
1136	}	1333	}
1137		1334
1138	...	1335	...
1139	struct ev_loop *loop = ev_default_init (0);	1336	struct ev_loop *loop = ev_default_init (0);
1140	struct ev_io stdin_readable;	1337	ev_io stdin_readable;
1141	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);
1142	ev_io_start (loop, &stdin_readable);	1339	ev_io_start (loop, &stdin_readable);
1143	ev_loop (loop, 0);	1340	ev_loop (loop, 0);
1144		1341
1145		1342
1146	=head2 C<ev_timer> - relative and optionally repeating timeouts	1343	=head2 C<ev_timer> - relative and optionally repeating timeouts
1147		1344
1148	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
1149	given time, and optionally repeating in regular intervals after that.	1346	given time, and optionally repeating in regular intervals after that.
1150		1347
1151	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
1152	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
1153	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
1154	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1155	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.
1156		1542
1157	The relative timeouts are calculated relative to the C<ev_now ()>	1543	The relative timeouts are calculated relative to the C<ev_now ()>
1158	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
1159	of the event triggering whatever timeout you are modifying/starting. If	1545	of the event triggering whatever timeout you are modifying/starting. If
1160	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
1161	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:
1162		1548
1163	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1549	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1164		1550
1165	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
1166	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
1167	order of execution is undefined.	1553	()>.
1168		1554
1169	=head3 Watcher-Specific Functions and Data Members	1555	=head3 Watcher-Specific Functions and Data Members
1170		1556
1171	=over 4	1557	=over 4
1172		1558
1173	=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)
1174		1560
1175	=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)
1176		1562
1177	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>
1178	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
1179	timer will automatically be configured to trigger again C<repeat> seconds	1565	reached. If it is positive, then the timer will automatically be
1180	later, again, and again, until stopped manually.	1566	configured to trigger again C<repeat> seconds later, again, and again,
		1567	until stopped manually.
1181		1568
1182	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
1183	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
1184	exactly 10 second intervals. If, however, your program cannot keep up with	1571	trigger at exactly 10 second intervals. If, however, your program cannot
1185	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
1186	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.
1187		1574
1188	=item ev_timer_again (loop, ev_timer *)	1575	=item ev_timer_again (loop, ev_timer *)
1189		1576
1190	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
1191	repeating. The exact semantics are:	1578	repeating. The exact semantics are:
1192		1579
1193	If the timer is pending, its pending status is cleared.	1580	If the timer is pending, its pending status is cleared.
1194		1581
1195	If the timer is started but nonrepeating, stop it (as if it timed out).	1582	If the timer is started but non-repeating, stop it (as if it timed out).
1196		1583
1197	If the timer is repeating, either start it if necessary (with the	1584	If the timer is repeating, either start it if necessary (with the
1198	C<repeat> value), or reset the running timer to the C<repeat> value.	1585	C<repeat> value), or reset the running timer to the C<repeat> value.
1199		1586
1200	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
1201	example: Imagine you have a tcp connection and you want a so-called idle	1588	usage example.
1202	timeout, that is, you want to be called when there have been, say, 60
1203	seconds of inactivity on the socket. The easiest way to do this is to
1204	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1205	C<ev_timer_again> each time you successfully read or write some data. If
1206	you go into an idle state where you do not expect data to travel on the
1207	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1208	automatically restart it if need be.
1209
1210	That means you can ignore the C<after> value and C<ev_timer_start>
1211	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1212
1213	ev_timer_init (timer, callback, 0., 5.);
1214	ev_timer_again (loop, timer);
1215	...
1216	timer->again = 17.;
1217	ev_timer_again (loop, timer);
1218	...
1219	timer->again = 10.;
1220	ev_timer_again (loop, timer);
1221
1222	This is more slightly efficient then stopping/starting the timer each time
1223	you want to modify its timeout value.
1224		1589
1225	=item ev_tstamp repeat [read-write]	1590	=item ev_tstamp repeat [read-write]
1226		1591
1227	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
1228	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),
1229	which is also when any modifications are taken into account.	1594	which is also when any modifications are taken into account.
1230		1595
1231	=back	1596	=back
1232		1597
1233	=head3 Examples	1598	=head3 Examples
1234		1599
1235	Example: Create a timer that fires after 60 seconds.	1600	Example: Create a timer that fires after 60 seconds.
1236		1601
1237	static void	1602	static void
1238	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)
1239	{	1604	{
1240	.. one minute over, w is actually stopped right here	1605	.. one minute over, w is actually stopped right here
1241	}	1606	}
1242		1607
1243	struct ev_timer mytimer;	1608	ev_timer mytimer;
1244	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1609	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1245	ev_timer_start (loop, &mytimer);	1610	ev_timer_start (loop, &mytimer);
1246		1611
1247	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
1248	inactivity.	1613	inactivity.
1249		1614
1250	static void	1615	static void
1251	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1616	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1252	{	1617	{
1253	.. ten seconds without any activity	1618	.. ten seconds without any activity
1254	}	1619	}
1255		1620
1256	struct ev_timer mytimer;	1621	ev_timer mytimer;
1257	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 */
1258	ev_timer_again (&mytimer); /* start timer */	1623	ev_timer_again (&mytimer); /* start timer */
1259	ev_loop (loop, 0);	1624	ev_loop (loop, 0);
1260		1625
1261	// 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":
1262	// reset the timeout to start ticking again at 10 seconds	1627	// reset the timeout to start ticking again at 10 seconds
1263	ev_timer_again (&mytimer);	1628	ev_timer_again (&mytimer);
1264		1629
1265		1630
1266	=head2 C<ev_periodic> - to cron or not to cron?	1631	=head2 C<ev_periodic> - to cron or not to cron?
1267		1632
1268	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
1269	(and unfortunately a bit complex).	1634	(and unfortunately a bit complex).
1270		1635
1271	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
1272	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
1273	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
1274	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
1275	+ 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
1276	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1641	wrist-watch).
1277	roughly 10 seconds later).
1278		1642
1279	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
1280	triggering an event on each midnight, local time or other, complicated,	1644	in time: for example, if you tell a periodic watcher to trigger "in 10
1281	rules.	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).
1282		1650
		1651	C<ev_periodic> watchers can also be used to implement vastly more complex
		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.
		1655
1283	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
1284	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
1285	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).
1286		1661
1287	=head3 Watcher-Specific Functions and Data Members	1662	=head3 Watcher-Specific Functions and Data Members
1288		1663
1289	=over 4	1664	=over 4
1290		1665
1291	=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)
1292		1667
1293	=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)
1294		1669
1295	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
1296	operation, and we will explain them from simplest to complex:	1671	operation, and we will explain them from simplest to most complex:
1297		1672
1298	=over 4	1673	=over 4
1299		1674
1300	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1675	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1301		1676
1302	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
1303	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
1304	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
1305	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.
1306		1682
1307	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1683	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1308		1684
1309	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
1310	C<at + N * interval> time (for some integer N, which can also be negative)	1686	C<offset + N * interval> time (for some integer N, which can also be
1311	and then repeat, regardless 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.
1312		1689
1313	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
1314	time:	1691	system clock, for example, here is an C<ev_periodic> that triggers each
		1692	hour, on the hour (with respect to UTC):
1315		1693
1316	ev_periodic_set (&periodic, 0., 3600., 0);	1694	ev_periodic_set (&periodic, 0., 3600., 0);
1317		1695
1318	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,
1319	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
1320	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
1321	by 3600.	1699	by 3600.
1322		1700
1323	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
1324	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
1325	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.
1326		1704
1327	For numerical stability it is preferable that the C<at> value is near	1705	For numerical stability it is preferable that the C<offset> value is near
1328	C<ev_now ()> (the current time), but there is no range requirement for	1706	C<ev_now ()> (the current time), but there is no range requirement for
1329	this value.	1707	this value, and in fact is often specified as zero.
1330		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
1331	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1714	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1332		1715
1333	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
1334	ignored. Instead, each time the periodic watcher gets scheduled, the	1717	ignored. Instead, each time the periodic watcher gets scheduled, the
1335	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
1336	current time as second argument.	1719	current time as second argument.
1337		1720
1338	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,
1339	ever, or make any event loop modifications>. If you need to stop it,	1722	or make ANY other event loop modifications whatsoever, unless explicitly
1340	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1723	allowed by documentation here>.
1341	starting an C<ev_prepare> watcher, which is legal).
1342		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
1343	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1729	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1344	ev_tstamp now)>, e.g.:	1730	*w, ev_tstamp now)>, e.g.:
1345		1731
		1732	static ev_tstamp
1346	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1733	my_rescheduler (ev_periodic *w, ev_tstamp now)
1347	{	1734	{
1348	return now + 60.;	1735	return now + 60.;
1349	}	1736	}
1350		1737
1351	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
1352	(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
1353	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
1354	might be called at other times, too.	1741	might be called at other times, too.
1355		1742
1356	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
1357	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1744	equal to the passed C<now> value >>.
1358		1745
1359	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
1360	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
1361	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
1362	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
1363	reason I omitted it as an example).	1750	reason I omitted it as an example).
1364		1751
1365	=back	1752	=back
…		…
1369	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
1370	when you changed some parameters or the reschedule callback would return	1757	when you changed some parameters or the reschedule callback would return
1371	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
1372	program when the crontabs have changed).	1759	program when the crontabs have changed).
1373		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
1374	=item ev_tstamp offset [read-write]	1768	=item ev_tstamp offset [read-write]
1375		1769
1376	When repeating, this contains the offset value, otherwise this is the	1770	When repeating, this contains the offset value, otherwise this is the
1377	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	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).
1378		1773
1379	Can be modified any time, but changes only take effect when the periodic	1774	Can be modified any time, but changes only take effect when the periodic
1380	timer fires or C<ev_periodic_again> is being called.	1775	timer fires or C<ev_periodic_again> is being called.
1381		1776
1382	=item ev_tstamp interval [read-write]	1777	=item ev_tstamp interval [read-write]
1383		1778
1384	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
1385	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
1386	called.	1781	called.
1387		1782
1388	=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]
1389		1784
1390	The current reschedule callback, or C<0>, if this functionality is	1785	The current reschedule callback, or C<0>, if this functionality is
1391	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
1392	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.
1393		1788
1394	=item ev_tstamp at [read-only]
1395
1396	When active, contains the absolute time that the watcher is supposed to
1397	trigger next.
1398
1399	=back	1789	=back
1400		1790
1401	=head3 Examples	1791	=head3 Examples
1402		1792
1403	Example: Call a callback every hour, or, more precisely, whenever the	1793	Example: Call a callback every hour, or, more precisely, whenever the
1404	system clock is divisible by 3600. The callback invocation times have	1794	system time is divisible by 3600. The callback invocation times have
1405	potentially a lot of jittering, but good long-term stability.	1795	potentially a lot of jitter, but good long-term stability.
1406		1796
1407	static void	1797	static void
1408	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1409	{	1799	{
1410	... 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)
1411	}	1801	}
1412		1802
1413	struct ev_periodic hourly_tick;	1803	ev_periodic hourly_tick;
1414	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1804	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1415	ev_periodic_start (loop, &hourly_tick);	1805	ev_periodic_start (loop, &hourly_tick);
1416		1806
1417	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:
1418		1808
1419	#include <math.h>	1809	#include <math.h>
1420		1810
1421	static ev_tstamp	1811	static ev_tstamp
1422	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1812	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1423	{	1813	{
1424	return fmod (now, 3600.) + 3600.;	1814	return now + (3600. - fmod (now, 3600.));
1425	}	1815	}
1426		1816
1427	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);
1428		1818
1429	Example: Call a callback every hour, starting now:	1819	Example: Call a callback every hour, starting now:
1430		1820
1431	struct ev_periodic hourly_tick;	1821	ev_periodic hourly_tick;
1432	ev_periodic_init (&hourly_tick, clock_cb,	1822	ev_periodic_init (&hourly_tick, clock_cb,
1433	fmod (ev_now (loop), 3600.), 3600., 0);	1823	fmod (ev_now (loop), 3600.), 3600., 0);
1434	ev_periodic_start (loop, &hourly_tick);	1824	ev_periodic_start (loop, &hourly_tick);
1435		1825
1436		1826
1437	=head2 C<ev_signal> - signal me when a signal gets signalled!	1827	=head2 C<ev_signal> - signal me when a signal gets signalled!
1438		1828
1439	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
1440	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
1441	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
1442	normal event processing, like any other event.	1832	normal event processing, like any other event.
1443		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
1444	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
1445	first watcher gets started will libev actually register a signal watcher	1839	first watcher gets started will libev actually register a signal handler
1446	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
1447	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
1448	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
1449	SIG_DFL (regardless of what it was set to before).	1843	signal handler to SIG_DFL (regardless of what it was set to before).
1450		1844
1451	If possible and supported, libev will install its handlers with	1845	If possible and supported, libev will install its handlers with
1452	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1453	interrupted. If you have a problem with syscalls getting interrupted by	1847	interrupted. If you have a problem with system calls getting interrupted by
1454	signals you can block all signals in an C<ev_check> watcher and unblock	1848	signals you can block all signals in an C<ev_check> watcher and unblock
1455	them in an C<ev_prepare> watcher.	1849	them in an C<ev_prepare> watcher.
1456		1850
1457	=head3 Watcher-Specific Functions and Data Members	1851	=head3 Watcher-Specific Functions and Data Members
1458		1852
…		…
1471		1865
1472	=back	1866	=back
1473		1867
1474	=head3 Examples	1868	=head3 Examples
1475		1869
1476	Example: Try to exit cleanly on SIGINT and SIGTERM.	1870	Example: Try to exit cleanly on SIGINT.
1477		1871
1478	static void	1872	static void
1479	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1480	{	1874	{
1481	ev_unloop (loop, EVUNLOOP_ALL);	1875	ev_unloop (loop, EVUNLOOP_ALL);
1482	}	1876	}
1483		1877
1484	struct ev_signal signal_watcher;	1878	ev_signal signal_watcher;
1485	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1486	ev_signal_start (loop, &sigint_cb);	1880	ev_signal_start (loop, &signal_watcher);
1487		1881
1488		1882
1489	=head2 C<ev_child> - watch out for process status changes	1883	=head2 C<ev_child> - watch out for process status changes
1490		1884
1491	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
1492	some child status changes (most typically when a child of yours dies). It	1886	some child status changes (most typically when a child of yours dies or
1493	is permissible to install a child watcher I<after> the child has been	1887	exits). It is permissible to install a child watcher I<after> the child
1494	forked (which implies it might have already exited), as long as the event	1888	has been forked (which implies it might have already exited), as long
1495	loop isn't entered (or is continued from a watcher).	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.
1496		1893
1497	Only the default event loop is capable of handling signals, and therefore	1894	Only the default event loop is capable of handling signals, and therefore
1498	you can only rgeister child watchers in the default event loop.	1895	you can only register child watchers in the default event loop.
1499		1896
1500	=head3 Process Interaction	1897	=head3 Process Interaction
1501		1898
1502	Libev grabs C<SIGCHLD> as soon as the default event loop is	1899	Libev grabs C<SIGCHLD> as soon as the default event loop is
1503	initialised. This is necessary to guarantee proper behaviour even if	1900	initialised. This is necessary to guarantee proper behaviour even if
1504	the first child watcher is started after the child exits. The occurance	1901	the first child watcher is started after the child exits. The occurrence
1505	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1506	synchronously as part of the event loop processing. Libev always reaps all	1903	synchronously as part of the event loop processing. Libev always reaps all
1507	children, even ones not watched.	1904	children, even ones not watched.
1508		1905
1509	=head3 Overriding the Built-In Processing	1906	=head3 Overriding the Built-In Processing
…		…
1513	handler, you can override it easily by installing your own handler for	1910	handler, you can override it easily by installing your own handler for
1514	C<SIGCHLD> after initialising the default loop, and making sure the	1911	C<SIGCHLD> after initialising the default loop, and making sure the
1515	default loop never gets destroyed. You are encouraged, however, to use an	1912	default loop never gets destroyed. You are encouraged, however, to use an
1516	event-based approach to child reaping and thus use libev's support for	1913	event-based approach to child reaping and thus use libev's support for
1517	that, so other libev users can use C<ev_child> watchers freely.	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.
1518		1922
1519	=head3 Watcher-Specific Functions and Data Members	1923	=head3 Watcher-Specific Functions and Data Members
1520		1924
1521	=over 4	1925	=over 4
1522		1926
…		…
1551	=head3 Examples	1955	=head3 Examples
1552		1956
1553	Example: C<fork()> a new process and install a child handler to wait for	1957	Example: C<fork()> a new process and install a child handler to wait for
1554	its completion.	1958	its completion.
1555		1959
1556	ev_child cw;	1960	ev_child cw;
1557		1961
1558	static void	1962	static void
1559	child_cb (EV_P_ struct ev_child *w, int revents)	1963	child_cb (EV_P_ ev_child *w, int revents)
1560	{	1964	{
1561	ev_child_stop (EV_A_ w);	1965	ev_child_stop (EV_A_ w);
1562	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1966	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1563	}	1967	}
1564		1968
1565	pid_t pid = fork ();	1969	pid_t pid = fork ();
1566		1970
1567	if (pid < 0)	1971	if (pid < 0)
1568	// error	1972	// error
1569	else if (pid == 0)	1973	else if (pid == 0)
1570	{	1974	{
1571	// the forked child executes here	1975	// the forked child executes here
1572	exit (1);	1976	exit (1);
1573	}	1977	}
1574	else	1978	else
1575	{	1979	{
1576	ev_child_init (&cw, child_cb, pid, 0);	1980	ev_child_init (&cw, child_cb, pid, 0);
1577	ev_child_start (EV_DEFAULT_ &cw);	1981	ev_child_start (EV_DEFAULT_ &cw);
1578	}	1982	}
1579		1983
1580		1984
1581	=head2 C<ev_stat> - did the file attributes just change?	1985	=head2 C<ev_stat> - did the file attributes just change?
1582		1986
1583	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
1584	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)
1585	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.
1586		1991
1587	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
1588	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
1589	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
1590	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
1591	the stat buffer having unspecified contents.	1996	least one) and all the other fields of the stat buffer having unspecified
		1997	contents.
1592		1998
1593	The path I<should> be absolute and I<must not> end in a slash. If it is	1999	The path I<must not> end in a slash or contain special components such as
		2000	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1594	relative and your working directory changes, the behaviour is undefined.	2001	your working directory changes, then the behaviour is undefined.
1595		2002
1596	Since there is no standard to do this, the portable implementation simply	2003	Since there is no portable change notification interface available, the
1597	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2004	portable implementation simply calls C<stat(2)> regularly on the path
1598	can specify a recommended polling interval for this case. If you specify	2005	to see if it changed somehow. You can specify a recommended polling
1599	a polling interval of C<0> (highly recommended!) then a I<suitable,	2006	interval for this case. If you specify a polling interval of C<0> (highly
1600	unspecified default> value will be used (which you can expect to be around	2007	recommended!) then a I<suitable, unspecified default> value will be used
1601	five seconds, although this might change dynamically). Libev will also	2008	(which you can expect to be around five seconds, although this might
1602	impose a minimum interval which is currently around C<0.1>, but thats	2009	change dynamically). Libev will also impose a minimum interval which is
1603	usually overkill.	2010	currently around C<0.1>, but that's usually overkill.
1604		2011
1605	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,
1606	as even with OS-supported change notifications, this can be	2013	as even with OS-supported change notifications, this can be
1607	resource-intensive.	2014	resource-intensive.
1608		2015
1609	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
1610	implemented (implementing kqueue support is left as an exercise for the	2017	is the Linux inotify interface (implementing kqueue support is left as an
1611	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
1612	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2019	implementing C<ev_stat> semantics with kqueue, except as a hint).
1613	to fall back to regular polling again even with inotify, but changes are
1614	usually detected immediately, and if the file exists there will be no
1615	polling.
1616		2020
1617	=head3 ABI Issues (Largefile Support)	2021	=head3 ABI Issues (Largefile Support)
1618		2022
1619	Libev by default (unless the user overrides this) uses the default	2023	Libev by default (unless the user overrides this) uses the default
1620	compilation environment, which means that on systems with optionally	2024	compilation environment, which means that on systems with large file
1621	disabled large file support, you get the 32 bit version of the stat	2025	support disabled by default, you get the 32 bit version of the stat
1622	structure. When using the library from programs that change the ABI to	2026	structure. When using the library from programs that change the ABI to
1623	use 64 bit file offsets the programs will fail. In that case you have to	2027	use 64 bit file offsets the programs will fail. In that case you have to
1624	compile libev with the same flags to get binary compatibility. This is	2028	compile libev with the same flags to get binary compatibility. This is
1625	obviously the case with any flags that change the ABI, but the problem is	2029	obviously the case with any flags that change the ABI, but the problem is
1626	most noticably with ev_stat and largefile support.	2030	most noticeably displayed with ev_stat and large file support.
1627		2031
1628	=head3 Inotify	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.
1629		2037
		2038	=head3 Inotify and Kqueue
		2039
1630	When C<inotify (7)> support has been compiled into libev (generally only	2040	When C<inotify (7)> support has been compiled into libev and present at
1631	available on Linux) and present at runtime, it will be used to speed up	2041	runtime, it will be used to speed up change detection where possible. The
1632	change detection where possible. The inotify descriptor will be created lazily	2042	inotify descriptor will be created lazily when the first C<ev_stat>
1633	when the first C<ev_stat> watcher is being started.	2043	watcher is being started.
1634		2044
1635	Inotify presense does not change the semantics of C<ev_stat> watchers	2045	Inotify presence does not change the semantics of C<ev_stat> watchers
1636	except that changes might be detected earlier, and in some cases, to avoid	2046	except that changes might be detected earlier, and in some cases, to avoid
1637	making regular C<stat> calls. Even in the presense of inotify support	2047	making regular C<stat> calls. Even in the presence of inotify support
1638	there are many cases where libev has to resort to regular C<stat> polling.	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.
1639		2053
1640	(There is no support for kqueue, as apparently it cannot be used to	2054	There is no support for kqueue, as apparently it cannot be used to
1641	implement this functionality, due to the requirement of having a file	2055	implement this functionality, due to the requirement of having a file
1642	descriptor open on the object at all times).	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.
1643		2076
1644	=head3 The special problem of stat time resolution	2077	=head3 The special problem of stat time resolution
1645		2078
1646	The C<stat ()> syscall only supports full-second resolution portably, and	2079	The C<stat ()> system call only supports full-second resolution portably,
1647	even on systems where the resolution is higher, many filesystems still	2080	and even on systems where the resolution is higher, most file systems
1648	only support whole seconds.	2081	still only support whole seconds.
1649		2082
1650	That means that, if the time is the only thing that changes, you might	2083	That means that, if the time is the only thing that changes, you can
1651	miss updates: on the first update, C<ev_stat> detects a change and calls	2084	easily miss updates: on the first update, C<ev_stat> detects a change and
1652	your callback, which does something. When there is another update within	2085	calls your callback, which does something. When there is another update
1653	the same second, C<ev_stat> will be unable to detect it.	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).
1654		2088
1655	The solution to this is to delay acting on a change for a second (or till	2089	The solution to this is to delay acting on a change for slightly more
1656	the next second boundary), using a roughly one-second delay C<ev_timer>	2090	than a second (or till slightly after the next full second boundary), using
1657	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2091	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1658	is added to work around small timing inconsistencies of some operating	2092	ev_timer_again (loop, w)>).
1659	systems.	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).
1660		2102
1661	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1662		2104
1663	=over 4	2105	=over 4
1664		2106
…		…
1670	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
1671	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
1672	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
1673	path for as long as the watcher is active.	2115	path for as long as the watcher is active.
1674		2116
1675	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,
1676	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
1677	last change was detected).	2119	last change was detected).
1678		2120
1679	=item ev_stat_stat (loop, ev_stat *)	2121	=item ev_stat_stat (loop, ev_stat *)
1680		2122
1681	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
1682	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
1683	detecting this change (while introducing a race condition). Can also be	2125	detecting this change (while introducing a race condition if you are not
1684	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.
1685		2128
1686	=item ev_statdata attr [read-only]	2129	=item ev_statdata attr [read-only]
1687		2130
1688	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
1689	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
1690	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
1691	was some error while C<stat>ing the file.	2135	some error while C<stat>ing the file.
1692		2136
1693	=item ev_statdata prev [read-only]	2137	=item ev_statdata prev [read-only]
1694		2138
1695	The previous attributes of the file. The callback gets invoked whenever	2139	The previous attributes of the file. The callback gets invoked whenever
1696	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>.
1697		2143
1698	=item ev_tstamp interval [read-only]	2144	=item ev_tstamp interval [read-only]
1699		2145
1700	The specified interval.	2146	The specified interval.
1701		2147
1702	=item const char *path [read-only]	2148	=item const char *path [read-only]
1703		2149
1704	The filesystem path that is being watched.	2150	The file system path that is being watched.
1705		2151
1706	=back	2152	=back
1707		2153
1708	=head3 Examples	2154	=head3 Examples
1709		2155
1710	Example: Watch C</etc/passwd> for attribute changes.	2156	Example: Watch C</etc/passwd> for attribute changes.
1711		2157
1712	static void	2158	static void
1713	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2159	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1714	{	2160	{
1715	/* /etc/passwd changed in some way */	2161	/* /etc/passwd changed in some way */
1716	if (w->attr.st_nlink)	2162	if (w->attr.st_nlink)
1717	{	2163	{
1718	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2164	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1719	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2165	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1720	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2166	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1721	}	2167	}
1722	else	2168	else
1723	/* you shalt not abuse printf for puts */	2169	/* you shalt not abuse printf for puts */
1724	puts ("wow, /etc/passwd is not there, expect problems. "	2170	puts ("wow, /etc/passwd is not there, expect problems. "
1725	"if this is windows, they already arrived\n");	2171	"if this is windows, they already arrived\n");
1726	}	2172	}
1727		2173
1728	...	2174	...
1729	ev_stat passwd;	2175	ev_stat passwd;
1730		2176
1731	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2177	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1732	ev_stat_start (loop, &passwd);	2178	ev_stat_start (loop, &passwd);
1733		2179
1734	Example: Like above, but additionally use a one-second delay so we do not	2180	Example: Like above, but additionally use a one-second delay so we do not
1735	miss updates (however, frequent updates will delay processing, too, so	2181	miss updates (however, frequent updates will delay processing, too, so
1736	one might do the work both on C<ev_stat> callback invocation I<and> on	2182	one might do the work both on C<ev_stat> callback invocation I<and> on
1737	C<ev_timer> callback invocation).	2183	C<ev_timer> callback invocation).
1738		2184
1739	static ev_stat passwd;	2185	static ev_stat passwd;
1740	static ev_timer timer;	2186	static ev_timer timer;
1741		2187
1742	static void	2188	static void
1743	timer_cb (EV_P_ ev_timer *w, int revents)	2189	timer_cb (EV_P_ ev_timer *w, int revents)
1744	{	2190	{
1745	ev_timer_stop (EV_A_ w);	2191	ev_timer_stop (EV_A_ w);
1746		2192
1747	/* now it's one second after the most recent passwd change */	2193	/* now it's one second after the most recent passwd change */
1748	}	2194	}
1749		2195
1750	static void	2196	static void
1751	stat_cb (EV_P_ ev_stat *w, int revents)	2197	stat_cb (EV_P_ ev_stat *w, int revents)
1752	{	2198	{
1753	/* reset the one-second timer */	2199	/* reset the one-second timer */
1754	ev_timer_again (EV_A_ &timer);	2200	ev_timer_again (EV_A_ &timer);
1755	}	2201	}
1756		2202
1757	...	2203	...
1758	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2204	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1759	ev_stat_start (loop, &passwd);	2205	ev_stat_start (loop, &passwd);
1760	ev_timer_init (&timer, timer_cb, 0., 1.01);	2206	ev_timer_init (&timer, timer_cb, 0., 1.02);
1761		2207
1762		2208
1763	=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...
1764		2210
1765	Idle watchers trigger events when no other events of the same or higher	2211	Idle watchers trigger events when no other events of the same or higher
1766	priority are pending (prepare, check and other idle watchers do not	2212	priority are pending (prepare, check and other idle watchers do not count
1767	count).	2213	as receiving "events").
1768		2214
1769	That is, as long as your process is busy handling sockets or timeouts	2215	That is, as long as your process is busy handling sockets or timeouts
1770	(or even signals, imagine) of the same or higher priority it will not be	2216	(or even signals, imagine) of the same or higher priority it will not be
1771	triggered. But when your process is idle (or only lower-priority watchers	2217	triggered. But when your process is idle (or only lower-priority watchers
1772	are pending), the idle watchers are being called once per event loop	2218	are pending), the idle watchers are being called once per event loop
…		…
1783		2229
1784	=head3 Watcher-Specific Functions and Data Members	2230	=head3 Watcher-Specific Functions and Data Members
1785		2231
1786	=over 4	2232	=over 4
1787		2233
1788	=item ev_idle_init (ev_signal *, callback)	2234	=item ev_idle_init (ev_idle *, callback)
1789		2235
1790	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
1791	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,
1792	believe me.	2238	believe me.
1793		2239
…		…
1796	=head3 Examples	2242	=head3 Examples
1797		2243
1798	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
1799	callback, free it. Also, use no error checking, as usual.	2245	callback, free it. Also, use no error checking, as usual.
1800		2246
1801	static void	2247	static void
1802	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2248	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1803	{	2249	{
1804	free (w);	2250	free (w);
1805	// now do something you wanted to do when the program has	2251	// now do something you wanted to do when the program has
1806	// no longer anything immediate to do.	2252	// no longer anything immediate to do.
1807	}	2253	}
1808		2254
1809	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1810	ev_idle_init (idle_watcher, idle_cb);	2256	ev_idle_init (idle_watcher, idle_cb);
1811	ev_idle_start (loop, idle_cb);	2257	ev_idle_start (loop, idle_cb);
1812		2258
1813		2259
1814	=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!
1815		2261
1816	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:
1817	prepare watchers get invoked before the process blocks and check watchers	2263	prepare watchers get invoked before the process blocks and check watchers
1818	afterwards.	2264	afterwards.
1819		2265
1820	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
1821	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>
…		…
1824	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,
1825	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
1826	called in pairs bracketing the blocking call.	2272	called in pairs bracketing the blocking call.
1827		2273
1828	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
1829	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
1830	variable changes, implement your own watchers, integrate net-snmp or a	2276	variable changes, implement your own watchers, integrate net-snmp or a
1831	coroutine library and lots more. They are also occasionally useful if	2277	coroutine library and lots more. They are also occasionally useful if
1832	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,
1833	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>
1834	watcher).	2280	watcher).
1835		2281
1836	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
1837	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
1838	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
1839	provide just this functionality). Then, in the check watcher you check for	2285	libraries provide exactly this functionality). Then, in the check watcher,
1840	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
1841	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
1842	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
1843	because you never know, you know?).	2289	nevertheless, because you never know, you know?).
1844		2290
1845	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
1846	coroutines into libev programs, by yielding to other active coroutines	2292	coroutines into libev programs, by yielding to other active coroutines
1847	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
1848	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
…		…
1851	loop from blocking if lower-priority coroutines are active, thus mapping	2297	loop from blocking if lower-priority coroutines are active, thus mapping
1852	low-priority coroutines to idle/background tasks).	2298	low-priority coroutines to idle/background tasks).
1853		2299
1854	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2300	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1855	priority, to ensure that they are being run before any other watchers	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
1856	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2304	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1857	too) should not activate ("feed") events into libev. While libev fully	2305	activate ("feed") events into libev. While libev fully supports this, they
1858	supports this, they will be called before other C<ev_check> watchers	2306	might get executed before other C<ev_check> watchers did their job. As
1859	did their job. As C<ev_check> watchers are often used to embed other	2307	C<ev_check> watchers are often used to embed other (non-libev) event
1860	(non-libev) event loops those other event loops might be in an unusable	2308	loops those other event loops might be in an unusable state until their
1861	state until their C<ev_check> watcher ran (always remind yourself to	2309	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1862	coexist peacefully with others).	2310	others).
1863		2311
1864	=head3 Watcher-Specific Functions and Data Members	2312	=head3 Watcher-Specific Functions and Data Members
1865		2313
1866	=over 4	2314	=over 4
1867		2315
…		…
1869		2317
1870	=item ev_check_init (ev_check *, callback)	2318	=item ev_check_init (ev_check *, callback)
1871		2319
1872	Initialises and configures the prepare or check watcher - they have no	2320	Initialises and configures the prepare or check watcher - they have no
1873	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>
1874	macros, but using them is utterly, utterly and completely pointless.	2322	macros, but using them is utterly, utterly, utterly and completely
		2323	pointless.
1875		2324
1876	=back	2325	=back
1877		2326
1878	=head3 Examples	2327	=head3 Examples
1879		2328
1880	There are a number of principal ways to embed other event loops or modules	2329	There are a number of principal ways to embed other event loops or modules
1881	into libev. Here are some ideas on how to include libadns into libev	2330	into libev. Here are some ideas on how to include libadns into libev
1882	(there is a Perl module named C<EV::ADNS> that does this, which you could	2331	(there is a Perl module named C<EV::ADNS> that does this, which you could
1883	use for an actually working example. Another Perl module named C<EV::Glib>	2332	use as a working example. Another Perl module named C<EV::Glib> embeds a
1884	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2333	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1885	into the Glib event loop).	2334	Glib event loop).
1886		2335
1887	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2336	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1888	and in a check watcher, destroy them and call into libadns. What follows	2337	and in a check watcher, destroy them and call into libadns. What follows
1889	is pseudo-code only of course. This requires you to either use a low	2338	is pseudo-code only of course. This requires you to either use a low
1890	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2339	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1891	the callbacks for the IO/timeout watchers might not have been called yet.	2340	the callbacks for the IO/timeout watchers might not have been called yet.
1892		2341
1893	static ev_io iow [nfd];	2342	static ev_io iow [nfd];
1894	static ev_timer tw;	2343	static ev_timer tw;
1895		2344
1896	static void	2345	static void
1897	io_cb (ev_loop *loop, ev_io *w, int revents)	2346	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1898	{	2347	{
1899	}	2348	}
1900		2349
1901	// create io watchers for each fd and a timer before blocking	2350	// create io watchers for each fd and a timer before blocking
1902	static void	2351	static void
1903	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2352	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1904	{	2353	{
1905	int timeout = 3600000;	2354	int timeout = 3600000;
1906	struct pollfd fds [nfd];	2355	struct pollfd fds [nfd];
1907	// actual code will need to loop here and realloc etc.	2356	// actual code will need to loop here and realloc etc.
1908	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1909		2358
1910	/* 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 */
1911	ev_timer_init (&tw, 0, timeout * 1e-3);	2360	ev_timer_init (&tw, 0, timeout * 1e-3);
1912	ev_timer_start (loop, &tw);	2361	ev_timer_start (loop, &tw);
1913		2362
1914	// create one ev_io per pollfd	2363	// create one ev_io per pollfd
1915	for (int i = 0; i < nfd; ++i)	2364	for (int i = 0; i < nfd; ++i)
1916	{	2365	{
1917	ev_io_init (iow + i, io_cb, fds [i].fd,	2366	ev_io_init (iow + i, io_cb, fds [i].fd,
1918	((fds [i].events & POLLIN ? EV_READ : 0)	2367	((fds [i].events & POLLIN ? EV_READ : 0)
1919	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2368	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1920		2369
1921	fds [i].revents = 0;	2370	fds [i].revents = 0;
1922	ev_io_start (loop, iow + i);	2371	ev_io_start (loop, iow + i);
1923	}	2372	}
1924	}	2373	}
1925		2374
1926	// stop all watchers after blocking	2375	// stop all watchers after blocking
1927	static void	2376	static void
1928	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2377	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1929	{	2378	{
1930	ev_timer_stop (loop, &tw);	2379	ev_timer_stop (loop, &tw);
1931		2380
1932	for (int i = 0; i < nfd; ++i)	2381	for (int i = 0; i < nfd; ++i)
1933	{	2382	{
1934	// set the relevant poll flags	2383	// set the relevant poll flags
1935	// could also call adns_processreadable etc. here	2384	// could also call adns_processreadable etc. here
1936	struct pollfd *fd = fds + i;	2385	struct pollfd *fd = fds + i;
1937	int revents = ev_clear_pending (iow + i);	2386	int revents = ev_clear_pending (iow + i);
1938	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2387	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1939	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2388	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1940		2389
1941	// now stop the watcher	2390	// now stop the watcher
1942	ev_io_stop (loop, iow + i);	2391	ev_io_stop (loop, iow + i);
1943	}	2392	}
1944		2393
1945	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2394	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1946	}	2395	}
1947		2396
1948	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2397	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1949	in the prepare watcher and would dispose of the check watcher.	2398	in the prepare watcher and would dispose of the check watcher.
1950		2399
1951	Method 3: If the module to be embedded supports explicit event	2400	Method 3: If the module to be embedded supports explicit event
1952	notification (adns does), you can also make use of the actual watcher	2401	notification (libadns does), you can also make use of the actual watcher
1953	callbacks, and only destroy/create the watchers in the prepare watcher.	2402	callbacks, and only destroy/create the watchers in the prepare watcher.
1954		2403
1955	static void	2404	static void
1956	timer_cb (EV_P_ ev_timer *w, int revents)	2405	timer_cb (EV_P_ ev_timer *w, int revents)
1957	{	2406	{
1958	adns_state ads = (adns_state)w->data;	2407	adns_state ads = (adns_state)w->data;
1959	update_now (EV_A);	2408	update_now (EV_A);
1960		2409
1961	adns_processtimeouts (ads, &tv_now);	2410	adns_processtimeouts (ads, &tv_now);
1962	}	2411	}
1963		2412
1964	static void	2413	static void
1965	io_cb (EV_P_ ev_io *w, int revents)	2414	io_cb (EV_P_ ev_io *w, int revents)
1966	{	2415	{
1967	adns_state ads = (adns_state)w->data;	2416	adns_state ads = (adns_state)w->data;
1968	update_now (EV_A);	2417	update_now (EV_A);
1969		2418
1970	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2419	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1971	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2420	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1972	}	2421	}
1973		2422
1974	// do not ever call adns_afterpoll	2423	// do not ever call adns_afterpoll
1975		2424
1976	Method 4: Do not use a prepare or check watcher because the module you	2425	Method 4: Do not use a prepare or check watcher because the module you
1977	want to embed is too inflexible to support it. Instead, youc na override	2426	want to embed is not flexible enough to support it. Instead, you can
1978	their poll function. The drawback with this solution is that the main	2427	override their poll function. The drawback with this solution is that the
1979	loop is now no longer controllable by EV. The C<Glib::EV> module does	2428	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1980	this.	2429	this approach, effectively embedding EV as a client into the horrible
		2430	libglib event loop.
1981		2431
1982	static gint	2432	static gint
1983	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2433	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1984	{	2434	{
1985	int got_events = 0;	2435	int got_events = 0;
1986		2436
1987	for (n = 0; n < nfds; ++n)	2437	for (n = 0; n < nfds; ++n)
1988	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2438	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1989		2439
1990	if (timeout >= 0)	2440	if (timeout >= 0)
1991	// create/start timer	2441	// create/start timer
1992		2442
1993	// poll	2443	// poll
1994	ev_loop (EV_A_ 0);	2444	ev_loop (EV_A_ 0);
1995		2445
1996	// stop timer again	2446	// stop timer again
1997	if (timeout >= 0)	2447	if (timeout >= 0)
1998	ev_timer_stop (EV_A_ &to);	2448	ev_timer_stop (EV_A_ &to);
1999		2449
2000	// stop io watchers again - their callbacks should have set	2450	// stop io watchers again - their callbacks should have set
2001	for (n = 0; n < nfds; ++n)	2451	for (n = 0; n < nfds; ++n)
2002	ev_io_stop (EV_A_ iow [n]);	2452	ev_io_stop (EV_A_ iow [n]);
2003		2453
2004	return got_events;	2454	return got_events;
2005	}	2455	}
2006		2456
2007		2457
2008	=head2 C<ev_embed> - when one backend isn't enough...	2458	=head2 C<ev_embed> - when one backend isn't enough...
2009		2459
2010	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
…		…
2016	prioritise I/O.	2466	prioritise I/O.
2017		2467
2018	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
2019	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
2020	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
2021	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
2022	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
2023	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
2024	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 :)
2025		2476
2026	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
2027	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),
2028	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
2029	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
2030	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.
2031		2482
2032	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
2033	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
2034	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
2035	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
2036	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
2037	to C<0>, in which case the embed watcher will automatically execute the	2488	to give the embedded loop strictly lower priority for example).
2038	embedded loop sweep.
2039		2489
2040	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
2041	callback will be invoked whenever some events have been handled. You can	2491	will automatically execute the embedded loop sweep whenever necessary.
2042	set the callback to C<0> to avoid having to specify one if you are not
2043	interested in that.
2044		2492
2045	Also, there have not currently been made special provisions for forking:	2493	Fork detection will be handled transparently while the C<ev_embed> watcher
2046	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
2047	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
2048	yourself.	2496	C<ev_loop_fork> on the embedded loop.
2049		2497
2050	Unfortunately, not all backends are embeddable, only the ones returned by	2498	Unfortunately, not all backends are embeddable: only the ones returned by
2051	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2499	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2052	portable one.	2500	portable one.
2053		2501
2054	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
2055	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
2056	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
2057	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.
2058		2506
		2507	=head3 C<ev_embed> and fork
		2508
		2509	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2510	automatically be applied to the embedded loop as well, so no special
		2511	fork handling is required in that case. When the watcher is not running,
		2512	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2513	as applicable.
		2514
2059	=head3 Watcher-Specific Functions and Data Members	2515	=head3 Watcher-Specific Functions and Data Members
2060		2516
2061	=over 4	2517	=over 4
2062		2518
2063	=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)
…		…
2066		2522
2067	Configures the watcher to embed the given loop, which must be	2523	Configures the watcher to embed the given loop, which must be
2068	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
2069	invoked automatically, otherwise it is the responsibility of the callback	2525	invoked automatically, otherwise it is the responsibility of the callback
2070	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,
2071	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).
2072		2528
2073	=item ev_embed_sweep (loop, ev_embed *)	2529	=item ev_embed_sweep (loop, ev_embed *)
2074		2530
2075	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
2076	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
2077	apropriate way for embedded loops.	2533	appropriate way for embedded loops.
2078		2534
2079	=item struct ev_loop *other [read-only]	2535	=item struct ev_loop *other [read-only]
2080		2536
2081	The embedded event loop.	2537	The embedded event loop.
2082		2538
…		…
2084		2540
2085	=head3 Examples	2541	=head3 Examples
2086		2542
2087	Example: Try to get an embeddable event loop and embed it into the default	2543	Example: Try to get an embeddable event loop and embed it into the default
2088	event loop. If that is not possible, use the default loop. The default	2544	event loop. If that is not possible, use the default loop. The default
2089	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2545	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2090	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2546	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2091	used).	2547	used).
2092		2548
2093	struct ev_loop *loop_hi = ev_default_init (0);	2549	struct ev_loop *loop_hi = ev_default_init (0);
2094	struct ev_loop *loop_lo = 0;	2550	struct ev_loop *loop_lo = 0;
2095	struct ev_embed embed;	2551	ev_embed embed;
2096		2552
2097	// see if there is a chance of getting one that works	2553	// see if there is a chance of getting one that works
2098	// (remember that a flags value of 0 means autodetection)	2554	// (remember that a flags value of 0 means autodetection)
2099	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2555	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2100	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2556	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2101	: 0;	2557	: 0;
2102		2558
2103	// if we got one, then embed it, otherwise default to loop_hi	2559	// if we got one, then embed it, otherwise default to loop_hi
2104	if (loop_lo)	2560	if (loop_lo)
2105	{	2561	{
2106	ev_embed_init (&embed, 0, loop_lo);	2562	ev_embed_init (&embed, 0, loop_lo);
2107	ev_embed_start (loop_hi, &embed);	2563	ev_embed_start (loop_hi, &embed);
2108	}	2564	}
2109	else	2565	else
2110	loop_lo = loop_hi;	2566	loop_lo = loop_hi;
2111		2567
2112	Example: Check if kqueue is available but not recommended and create	2568	Example: Check if kqueue is available but not recommended and create
2113	a kqueue backend for use with sockets (which usually work with any	2569	a kqueue backend for use with sockets (which usually work with any
2114	kqueue implementation). Store the kqueue/socket-only event loop in	2570	kqueue implementation). Store the kqueue/socket-only event loop in
2115	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2571	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2116		2572
2117	struct ev_loop *loop = ev_default_init (0);	2573	struct ev_loop *loop = ev_default_init (0);
2118	struct ev_loop *loop_socket = 0;	2574	struct ev_loop *loop_socket = 0;
2119	struct ev_embed embed;	2575	ev_embed embed;
2120		2576
2121	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2577	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2122	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2578	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2123	{	2579	{
2124	ev_embed_init (&embed, 0, loop_socket);	2580	ev_embed_init (&embed, 0, loop_socket);
2125	ev_embed_start (loop, &embed);	2581	ev_embed_start (loop, &embed);
2126	}	2582	}
2127		2583
2128	if (!loop_socket)	2584	if (!loop_socket)
2129	loop_socket = loop;	2585	loop_socket = loop;
2130		2586
2131	// now use loop_socket for all sockets, and loop for everything else	2587	// now use loop_socket for all sockets, and loop for everything else
2132		2588
2133		2589
2134	=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
2135		2591
2136	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
…		…
2180	is that the author does not know of a simple (or any) algorithm for a	2636	is that the author does not know of a simple (or any) algorithm for a
2181	multiple-writer-single-reader queue that works in all cases and doesn't	2637	multiple-writer-single-reader queue that works in all cases and doesn't
2182	need elaborate support such as pthreads.	2638	need elaborate support such as pthreads.
2183		2639
2184	That means that if you want to queue data, you have to provide your own	2640	That means that if you want to queue data, you have to provide your own
2185	queue. But at least I can tell you would implement locking around your	2641	queue. But at least I can tell you how to implement locking around your
2186	queue:	2642	queue:
2187		2643
2188	=over 4	2644	=over 4
2189		2645
2190	=item queueing from a signal handler context	2646	=item queueing from a signal handler context
2191		2647
2192	To implement race-free queueing, you simply add to the queue in the signal	2648	To implement race-free queueing, you simply add to the queue in the signal
2193	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2649	handler but you block the signal handler in the watcher callback. Here is
2194	some fictitiuous SIGUSR1 handler:	2650	an example that does that for some fictitious SIGUSR1 handler:
2195		2651
2196	static ev_async mysig;	2652	static ev_async mysig;
2197		2653
2198	static void	2654	static void
2199	sigusr1_handler (void)	2655	sigusr1_handler (void)
…		…
2265	=over 4	2721	=over 4
2266		2722
2267	=item ev_async_init (ev_async *, callback)	2723	=item ev_async_init (ev_async *, callback)
2268		2724
2269	Initialises and configures the async watcher - it has no parameters of any	2725	Initialises and configures the async watcher - it has no parameters of any
2270	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2726	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2271	believe me.	2727	trust me.
2272		2728
2273	=item ev_async_send (loop, ev_async *)	2729	=item ev_async_send (loop, ev_async *)
2274		2730
2275	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2276	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2277	C<ev_feed_event>, this call is safe to do in other threads, signal or	2733	C<ev_feed_event>, this call is safe to do from other threads, signal or
2278	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2279	section below on what exactly this means).	2735	section below on what exactly this means).
2280		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
2281	This call incurs the overhead of a syscall only once per loop iteration,	2742	This call incurs the overhead of a system call only once per event loop
2282	so while the overhead might be noticable, it doesn't apply to repeated	2743	iteration, so while the overhead might be noticeable, it doesn't apply to
2283	calls to C<ev_async_send>.	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.
2284		2761
2285	=back	2762	=back
2286		2763
2287		2764
2288	=head1 OTHER FUNCTIONS	2765	=head1 OTHER FUNCTIONS
…		…
2292	=over 4	2769	=over 4
2293		2770
2294	=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)
2295		2772
2296	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
2297	callback on whichever event happens first and automatically stop both	2774	callback on whichever event happens first and automatically stops both
2298	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
2299	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
2300	more watchers yourself.	2777	more watchers yourself.
2301		2778
2302	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
2303	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
2304	C<events> set will be craeted and started.	2781	the given C<fd> and C<events> set will be created and started.
2305		2782
2306	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
2307	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
2308	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.
2309	dubious value.
2310		2786
2311	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
2312	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
2313	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>
2314	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.
2315		2793
		2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2795
2316	static void stdin_ready (int revents, void *arg)	2796	static void stdin_ready (int revents, void *arg)
2317	{	2797	{
2318	if (revents & EV_TIMEOUT)
2319	/* doh, nothing entered */;
2320	else if (revents & EV_READ)	2798	if (revents & EV_READ)
2321	/* 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 */;
2322	}	2802	}
2323		2803
2324	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2325		2805
2326	=item ev_feed_event (ev_loop *, watcher *, int revents)	2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2327		2807
2328	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
2329	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
2330	initialised but not necessarily started event watcher).	2810	initialised but not necessarily started event watcher).
2331		2811
2332	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2333		2813
2334	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
2335	the given events it.	2815	the given events it.
2336		2816
2337	=item ev_feed_signal_event (ev_loop *loop, int signum)	2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2338		2818
2339	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
2340	loop!).	2820	loop!).
2341		2821
2342	=back	2822	=back
2343		2823
2344		2824
…		…
2360		2840
2361	=item * Priorities are not currently supported. Initialising priorities	2841	=item * Priorities are not currently supported. Initialising priorities
2362	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
2363	is an ev_pri field.	2843	is an ev_pri field.
2364		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
2365	=item * Other members are not supported.	2848	=item * Other members are not supported.
2366		2849
2367	=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
2368	to use the libev header file and library.	2851	to use the libev header file and library.
2369		2852
2370	=back	2853	=back
2371		2854
2372	=head1 C++ SUPPORT	2855	=head1 C++ SUPPORT
2373		2856
2374	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
2375	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
2376	the callback model to a model using method callbacks on objects.	2859	the callback model to a model using method callbacks on objects.
2377		2860
2378	To use it,	2861	To use it,
2379		2862
2380	#include <ev++.h>	2863	#include <ev++.h>
2381		2864
2382	This automatically includes F<ev.h> and puts all of its definitions (many	2865	This automatically includes F<ev.h> and puts all of its definitions (many
2383	of them macros) into the global namespace. All C++ specific things are	2866	of them macros) into the global namespace. All C++ specific things are
2384	put into the C<ev> namespace. It should support all the same embedding	2867	put into the C<ev> namespace. It should support all the same embedding
2385	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2868	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2452	your compiler is good :), then the method will be fully inlined into the	2935	your compiler is good :), then the method will be fully inlined into the
2453	thunking function, making it as fast as a direct C callback.	2936	thunking function, making it as fast as a direct C callback.
2454		2937
2455	Example: simple class declaration and watcher initialisation	2938	Example: simple class declaration and watcher initialisation
2456		2939
2457	struct myclass	2940	struct myclass
2458	{	2941	{
2459	void io_cb (ev::io &w, int revents) { }	2942	void io_cb (ev::io &w, int revents) { }
2460	}	2943	}
2461		2944
2462	myclass obj;	2945	myclass obj;
2463	ev::io iow;	2946	ev::io iow;
2464	iow.set <myclass, &myclass::io_cb> (&obj);	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);
2465		2978
2466	=item w->set<function> (void *data = 0)	2979	=item w->set<function> (void *data = 0)
2467		2980
2468	Also sets a callback, but uses a static method or plain function as	2981	Also sets a callback, but uses a static method or plain function as
2469	callback. The optional C<data> argument will be stored in the watcher's	2982	callback. The optional C<data> argument will be stored in the watcher's
…		…
2471		2984
2472	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2985	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2473		2986
2474	See the method-C<set> above for more details.	2987	See the method-C<set> above for more details.
2475		2988
2476	Example:	2989	Example: Use a plain function as callback.
2477		2990
2478	static void io_cb (ev::io &w, int revents) { }	2991	static void io_cb (ev::io &w, int revents) { }
2479	iow.set <io_cb> ();	2992	iow.set <io_cb> ();
2480		2993
2481	=item w->set (struct ev_loop *)	2994	=item w->set (struct ev_loop *)
2482		2995
2483	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
2484	do this when the watcher is inactive (and not pending either).	2997	do this when the watcher is inactive (and not pending either).
2485		2998
2486	=item w->set ([args])	2999	=item w->set ([arguments])
2487		3000
2488	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
2489	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
2490	automatically stopped and restarted when reconfiguring it with this	3003	automatically stopped and restarted when reconfiguring it with this
2491	method.	3004	method.
2492		3005
2493	=item w->start ()	3006	=item w->start ()
…		…
2517	=back	3030	=back
2518		3031
2519	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
2520	the constructor.	3033	the constructor.
2521		3034
2522	class myclass	3035	class myclass
2523	{	3036	{
2524	ev::io io; void io_cb (ev::io &w, int revents);	3037	ev::io io ; void io_cb (ev::io &w, int revents);
2525	ev:idle idle void idle_cb (ev::idle &w, int revents);	3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2526		3039
2527	myclass (int fd)	3040	myclass (int fd)
2528	{	3041	{
2529	io .set <myclass, &myclass::io_cb > (this);	3042	io .set <myclass, &myclass::io_cb > (this);
2530	idle.set <myclass, &myclass::idle_cb> (this);	3043	idle.set <myclass, &myclass::idle_cb> (this);
2531		3044
2532	io.start (fd, ev::READ);	3045	io.start (fd, ev::READ);
2533	}	3046	}
2534	};	3047	};
2535		3048
2536		3049
2537	=head1 OTHER LANGUAGE BINDINGS	3050	=head1 OTHER LANGUAGE BINDINGS
2538		3051
2539	Libev does not offer other language bindings itself, but bindings for a	3052	Libev does not offer other language bindings itself, but bindings for a
2540	numbe rof languages exist in the form of third-party packages. If you know	3053	number of languages exist in the form of third-party packages. If you know
2541	any interesting language binding in addition to the ones listed here, drop	3054	any interesting language binding in addition to the ones listed here, drop
2542	me a note.	3055	me a note.
2543		3056
2544	=over 4	3057	=over 4
2545		3058
2546	=item Perl	3059	=item Perl
2547		3060
2548	The EV module implements the full libev API and is actually used to test	3061	The EV module implements the full libev API and is actually used to test
2549	libev. EV is developed together with libev. Apart from the EV core module,	3062	libev. EV is developed together with libev. Apart from the EV core module,
2550	there are additional modules that implement libev-compatible interfaces	3063	there are additional modules that implement libev-compatible interfaces
2551	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3064	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2552	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3065	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3066	and C<EV::Glib>).
2553		3067
2554	It can be found and installed via CPAN, its homepage is found at	3068	It can be found and installed via CPAN, its homepage is at
2555	L<http://software.schmorp.de/pkg/EV>.	3069	L<http://software.schmorp.de/pkg/EV>.
2556		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
2557	=item Ruby	3076	=item Ruby
2558		3077
2559	Tony Arcieri has written a ruby extension that offers access to a subset	3078	Tony Arcieri has written a ruby extension that offers access to a subset
2560	of the libev API and adds filehandle abstractions, asynchronous DNS and	3079	of the libev API and adds file handle abstractions, asynchronous DNS and
2561	more on top of it. It can be found via gem servers. Its homepage is at	3080	more on top of it. It can be found via gem servers. Its homepage is at
2562	L<http://rev.rubyforge.org/>.	3081	L<http://rev.rubyforge.org/>.
2563		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
2564	=item D	3091	=item D
2565		3092
2566	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2567	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	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/>.
2568		3100
2569	=back	3101	=back
2570		3102
2571		3103
2572	=head1 MACRO MAGIC	3104	=head1 MACRO MAGIC
2573		3105
2574	Libev can be compiled with a variety of options, the most fundamantal	3106	Libev can be compiled with a variety of options, the most fundamental
2575	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3107	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2576	functions and callbacks have an initial C<struct ev_loop *> argument.	3108	functions and callbacks have an initial C<struct ev_loop *> argument.
2577		3109
2578	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
2579	following macros are defined:	3111	following macros are defined:
…		…
2584		3116
2585	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
2586	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,
2587	C<EV_A_> is used when other arguments are following. Example:	3119	C<EV_A_> is used when other arguments are following. Example:
2588		3120
2589	ev_unref (EV_A);	3121	ev_unref (EV_A);
2590	ev_timer_add (EV_A_ watcher);	3122	ev_timer_add (EV_A_ watcher);
2591	ev_loop (EV_A_ 0);	3123	ev_loop (EV_A_ 0);
2592		3124
2593	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,
2594	which is often provided by the following macro.	3126	which is often provided by the following macro.
2595		3127
2596	=item C<EV_P>, C<EV_P_>	3128	=item C<EV_P>, C<EV_P_>
2597		3129
2598	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
2599	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,
2600	C<EV_P_> is used when other parameters are following. Example:	3132	C<EV_P_> is used when other parameters are following. Example:
2601		3133
2602	// this is how ev_unref is being declared	3134	// this is how ev_unref is being declared
2603	static void ev_unref (EV_P);	3135	static void ev_unref (EV_P);
2604		3136
2605	// this is how you can declare your typical callback	3137	// this is how you can declare your typical callback
2606	static void cb (EV_P_ ev_timer *w, int revents)	3138	static void cb (EV_P_ ev_timer *w, int revents)
2607		3139
2608	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
2609	suitable for use with C<EV_A>.	3141	suitable for use with C<EV_A>.
2610		3142
2611	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3143	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2612		3144
2613	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
2614	loop, if multiple loops are supported ("ev loop default").	3146	loop, if multiple loops are supported ("ev loop default").
		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.
2615		3157
2616	=back	3158	=back
2617		3159
2618	Example: Declare and initialise a check watcher, utilising the above	3160	Example: Declare and initialise a check watcher, utilising the above
2619	macros so it will work regardless of whether multiple loops are supported	3161	macros so it will work regardless of whether multiple loops are supported
2620	or not.	3162	or not.
2621		3163
2622	static void	3164	static void
2623	check_cb (EV_P_ ev_timer *w, int revents)	3165	check_cb (EV_P_ ev_timer *w, int revents)
2624	{	3166	{
2625	ev_check_stop (EV_A_ w);	3167	ev_check_stop (EV_A_ w);
2626	}	3168	}
2627		3169
2628	ev_check check;	3170	ev_check check;
2629	ev_check_init (&check, check_cb);	3171	ev_check_init (&check, check_cb);
2630	ev_check_start (EV_DEFAULT_ &check);	3172	ev_check_start (EV_DEFAULT_ &check);
2631	ev_loop (EV_DEFAULT_ 0);	3173	ev_loop (EV_DEFAULT_ 0);
2632		3174
2633	=head1 EMBEDDING	3175	=head1 EMBEDDING
2634		3176
2635	Libev can (and often is) directly embedded into host	3177	Libev can (and often is) directly embedded into host
2636	applications. Examples of applications that embed it include the Deliantra	3178	applications. Examples of applications that embed it include the Deliantra
…		…
2643	libev somewhere in your source tree).	3185	libev somewhere in your source tree).
2644		3186
2645	=head2 FILESETS	3187	=head2 FILESETS
2646		3188
2647	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
2648	in your app.	3190	in your application.
2649		3191
2650	=head3 CORE EVENT LOOP	3192	=head3 CORE EVENT LOOP
2651		3193
2652	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
2653	configuration (no autoconf):	3195	configuration (no autoconf):
2654		3196
2655	#define EV_STANDALONE 1	3197	#define EV_STANDALONE 1
2656	#include "ev.c"	3198	#include "ev.c"
2657		3199
2658	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
2659	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
2660	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
2661	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
2662	where you can put other configuration options):	3204	where you can put other configuration options):
2663		3205
2664	#define EV_STANDALONE 1	3206	#define EV_STANDALONE 1
2665	#include "ev.h"	3207	#include "ev.h"
2666		3208
2667	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++
2668	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
2669	as a bug).	3211	as a bug).
2670		3212
2671	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
2672	in your include path (e.g. in libev/ when using -Ilibev):	3214	in your include path (e.g. in libev/ when using -Ilibev):
2673		3215
2674	ev.h	3216	ev.h
2675	ev.c	3217	ev.c
2676	ev_vars.h	3218	ev_vars.h
2677	ev_wrap.h	3219	ev_wrap.h
2678		3220
2679	ev_win32.c required on win32 platforms only	3221	ev_win32.c required on win32 platforms only
2680		3222
2681	ev_select.c only when select backend is enabled (which is enabled by default)	3223	ev_select.c only when select backend is enabled (which is enabled by default)
2682	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)
2683	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)
2684	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)
2685	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)
2686		3228
2687	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
2688	to compile this single file.	3230	to compile this single file.
2689		3231
2690	=head3 LIBEVENT COMPATIBILITY API	3232	=head3 LIBEVENT COMPATIBILITY API
2691		3233
2692	To include the libevent compatibility API, also include:	3234	To include the libevent compatibility API, also include:
2693		3235
2694	#include "event.c"	3236	#include "event.c"
2695		3237
2696	in the file including F<ev.c>, and:	3238	in the file including F<ev.c>, and:
2697		3239
2698	#include "event.h"	3240	#include "event.h"
2699		3241
2700	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>.
2701		3243
2702	You need the following additional files for this:	3244	You need the following additional files for this:
2703		3245
2704	event.h	3246	event.h
2705	event.c	3247	event.c
2706		3248
2707	=head3 AUTOCONF SUPPORT	3249	=head3 AUTOCONF SUPPORT
2708		3250
2709	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
2710	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
2711	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
2712	include F<config.h> and configure itself accordingly.	3254	include F<config.h> and configure itself accordingly.
2713		3255
2714	For this of course you need the m4 file:	3256	For this of course you need the m4 file:
2715		3257
2716	libev.m4	3258	libev.m4
2717		3259
2718	=head2 PREPROCESSOR SYMBOLS/MACROS	3260	=head2 PREPROCESSOR SYMBOLS/MACROS
2719		3261
2720	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
2721	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
2722	and only include the select backend.	3264	autoconf is documented for every option.
2723		3265
2724	=over 4	3266	=over 4
2725		3267
2726	=item EV_STANDALONE	3268	=item EV_STANDALONE
2727		3269
…		…
2729	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
2730	implementations for some libevent functions (such as logging, which is not	3272	implementations for some libevent functions (such as logging, which is not
2731	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
2732	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.
2733		3275
		3276	In stanbdalone mode, libev will still try to automatically deduce the
		3277	configuration, but has to be more conservative.
		3278
2734	=item EV_USE_MONOTONIC	3279	=item EV_USE_MONOTONIC
2735		3280
2736	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
2737	monotonic clock option at both compiletime and runtime. Otherwise no use	3282	monotonic clock option at both compile time and runtime. Otherwise no
2738	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,
2739	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
2740	the functionality isn't available is safe, though, although you have	3285	when the functionality isn't available is safe, though, although you have
2741	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>
2742	function is hiding in (often F<-lrt>).	3287	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2743		3288
2744	=item EV_USE_REALTIME	3289	=item EV_USE_REALTIME
2745		3290
2746	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
2747	realtime clock option at compiletime (and assume its availability at	3292	real-time clock option at compile time (and assume its availability
2748	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
2749	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3294	option will be attempted. This effectively replaces C<gettimeofday>
2750	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3295	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2751	note about libraries 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>).
2752		3310
2753	=item EV_USE_NANOSLEEP	3311	=item EV_USE_NANOSLEEP
2754		3312
2755	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3313	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2756	and will use it for delays. Otherwise it will use C<select ()>.	3314	and will use it for delays. Otherwise it will use C<select ()>.
2757		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.
		3323
2758	=item EV_USE_SELECT	3324	=item EV_USE_SELECT
2759		3325
2760	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
2761	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
2762	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
2763	will not be compiled in.	3329	will not be compiled in.
2764		3330
2765	=item EV_SELECT_USE_FD_SET	3331	=item EV_SELECT_USE_FD_SET
2766		3332
2767	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>
2768	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
2769	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
2770	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
2771	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
2772	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,
2773	influence the size of the C<fd_set> used.	3339	configures the maximum size of the C<fd_set>.
2774		3340
2775	=item EV_SELECT_IS_WINSOCKET	3341	=item EV_SELECT_IS_WINSOCKET
2776		3342
2777	When defined to C<1>, the select backend will assume that	3343	When defined to C<1>, the select backend will assume that
2778	select/socket/connect etc. don't understand file descriptors but	3344	select/socket/connect etc. don't understand file descriptors but
…		…
2798		3364
2799	=item EV_USE_EPOLL	3365	=item EV_USE_EPOLL
2800		3366
2801	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
2802	C<epoll>(7) backend. Its availability will be detected at runtime,	3368	C<epoll>(7) backend. Its availability will be detected at runtime,
2803	otherwise another method will be used as fallback. This is the	3369	otherwise another method will be used as fallback. This is the preferred
2804	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.
2805		3372
2806	=item EV_USE_KQUEUE	3373	=item EV_USE_KQUEUE
2807		3374
2808	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
2809	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,
…		…
2822	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
2823	backend for Solaris 10 systems.	3390	backend for Solaris 10 systems.
2824		3391
2825	=item EV_USE_DEVPOLL	3392	=item EV_USE_DEVPOLL
2826		3393
2827	reserved for future expansion, works like the USE symbols above.	3394	Reserved for future expansion, works like the USE symbols above.
2828		3395
2829	=item EV_USE_INOTIFY	3396	=item EV_USE_INOTIFY
2830		3397
2831	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
2832	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
2833	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.
2834		3402
2835	=item EV_ATOMIC_T	3403	=item EV_ATOMIC_T
2836		3404
2837	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3405	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2838	access is atomic with respect to other threads or signal contexts. No such	3406	access is atomic with respect to other threads or signal contexts. No such
2839	type is easily found in the C language, so you can provide your own type	3407	type is easily found in the C language, so you can provide your own type
2840	that you know is safe for your purposes. It is used both for signal handler "locking"	3408	that you know is safe for your purposes. It is used both for signal handler "locking"
2841	as well as for signal and thread safety in C<ev_async> watchers.	3409	as well as for signal and thread safety in C<ev_async> watchers.
2842		3410
2843	In the absense of this define, libev will use C<sig_atomic_t volatile>	3411	In the absence of this define, libev will use C<sig_atomic_t volatile>
2844	(from F<signal.h>), which is usually good enough on most platforms.	3412	(from F<signal.h>), which is usually good enough on most platforms.
2845		3413
2846	=item EV_H	3414	=item EV_H
2847		3415
2848	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
…		…
2887	When doing priority-based operations, libev usually has to linearly search	3455	When doing priority-based operations, libev usually has to linearly search
2888	all the priorities, so having many of them (hundreds) uses a lot of space	3456	all the priorities, so having many of them (hundreds) uses a lot of space
2889	and time, so using the defaults of five priorities (-2 .. +2) is usually	3457	and time, so using the defaults of five priorities (-2 .. +2) is usually
2890	fine.	3458	fine.
2891		3459
2892	If your embedding app does not need any priorities, defining these both to	3460	If your embedding application does not need any priorities, defining these
2893	C<0> will save some memory and cpu.	3461	both to C<0> will save some memory and CPU.
2894		3462
2895	=item EV_PERIODIC_ENABLE	3463	=item EV_PERIODIC_ENABLE
2896		3464
2897	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
2898	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
…		…
2905	code.	3473	code.
2906		3474
2907	=item EV_EMBED_ENABLE	3475	=item EV_EMBED_ENABLE
2908		3476
2909	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
2910	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.
2911		3480
2912	=item EV_STAT_ENABLE	3481	=item EV_STAT_ENABLE
2913		3482
2914	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
2915	defined to be C<0>, then they are not.	3484	defined to be C<0>, then they are not.
…		…
2925	defined to be C<0>, then they are not.	3494	defined to be C<0>, then they are not.
2926		3495
2927	=item EV_MINIMAL	3496	=item EV_MINIMAL
2928		3497
2929	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
2930	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
2931	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.
2932		3502
2933	=item EV_PID_HASHSIZE	3503	=item EV_PID_HASHSIZE
2934		3504
2935	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
2936	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
…		…
2943	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>),
2944	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>
2945	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
2946	two).	3516	two).
2947		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
2948	=item EV_COMMON	3553	=item EV_COMMON
2949		3554
2950	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
2951	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
2952	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,
2953	though, and it must be identical each time.	3558	though, and it must be identical each time.
2954		3559
2955	For example, the perl EV module uses something like this:	3560	For example, the perl EV module uses something like this:
2956		3561
2957	#define EV_COMMON \	3562	#define EV_COMMON \
2958	SV *self; /* contains this struct */ \	3563	SV *self; /* contains this struct */ \
2959	SV *cb_sv, *fh /* note no trailing ";" */	3564	SV *cb_sv, *fh /* note no trailing ";" */
2960		3565
2961	=item EV_CB_DECLARE (type)	3566	=item EV_CB_DECLARE (type)
2962		3567
2963	=item EV_CB_INVOKE (watcher, revents)	3568	=item EV_CB_INVOKE (watcher, revents)
2964		3569
…		…
2969	definition and a statement, respectively. See the F<ev.h> header file for	3574	definition and a statement, respectively. See the F<ev.h> header file for
2970	their default definitions. One possible use for overriding these is to	3575	their default definitions. One possible use for overriding these is to
2971	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
2972	method calls instead of plain function calls in C++.	3577	method calls instead of plain function calls in C++.
2973		3578
		3579	=back
		3580
2974	=head2 EXPORTED API SYMBOLS	3581	=head2 EXPORTED API SYMBOLS
2975		3582
2976	If you need to re-export the API (e.g. via a dll) and you need a list of	3583	If you need to re-export the API (e.g. via a DLL) and you need a list of
2977	exported symbols, you can use the provided F<Symbol.*> files which list	3584	exported symbols, you can use the provided F<Symbol.*> files which list
2978	all public symbols, one per line:	3585	all public symbols, one per line:
2979		3586
2980	Symbols.ev for libev proper	3587	Symbols.ev for libev proper
2981	Symbols.event for the libevent emulation	3588	Symbols.event for the libevent emulation
2982		3589
2983	This can also be used to rename all public symbols to avoid clashes with	3590	This can also be used to rename all public symbols to avoid clashes with
2984	multiple versions of libev linked together (which is obviously bad in	3591	multiple versions of libev linked together (which is obviously bad in
2985	itself, but sometimes it is inconvinient to avoid this).	3592	itself, but sometimes it is inconvenient to avoid this).
2986		3593
2987	A sed command like this will create wrapper C<#define>'s that you need to	3594	A sed command like this will create wrapper C<#define>'s that you need to
2988	include before including F<ev.h>:	3595	include before including F<ev.h>:
2989		3596
2990	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3597	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3007	file.	3614	file.
3008		3615
3009	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
3010	that everybody includes and which overrides some configure choices:	3617	that everybody includes and which overrides some configure choices:
3011		3618
3012	#define EV_MINIMAL 1	3619	#define EV_MINIMAL 1
3013	#define EV_USE_POLL 0	3620	#define EV_USE_POLL 0
3014	#define EV_MULTIPLICITY 0	3621	#define EV_MULTIPLICITY 0
3015	#define EV_PERIODIC_ENABLE 0	3622	#define EV_PERIODIC_ENABLE 0
3016	#define EV_STAT_ENABLE 0	3623	#define EV_STAT_ENABLE 0
3017	#define EV_FORK_ENABLE 0	3624	#define EV_FORK_ENABLE 0
3018	#define EV_CONFIG_H <config.h>	3625	#define EV_CONFIG_H <config.h>
3019	#define EV_MINPRI 0	3626	#define EV_MINPRI 0
3020	#define EV_MAXPRI 0	3627	#define EV_MAXPRI 0
3021		3628
3022	#include "ev++.h"	3629	#include "ev++.h"
3023		3630
3024	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:
3025		3632
3026	#include "ev_cpp.h"	3633	#include "ev_cpp.h"
3027	#include "ev.c"	3634	#include "ev.c"
3028		3635
		3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3029		3637
3030	=head1 COMPLEXITIES	3638	=head2 THREADS AND COROUTINES
3031		3639
3032	In this section the complexities of (many of) the algorithms used inside	3640	=head3 THREADS
3033	libev will be explained. For complexity discussions about backends see the
3034	documentation for C<ev_default_init>.
3035		3641
3036	All of the following are about amortised time: If an array needs to be	3642	All libev functions are reentrant and thread-safe unless explicitly
3037	extended, libev needs to realloc and move the whole array, but this	3643	documented otherwise, but libev implements no locking itself. This means
3038	happens asymptotically never with higher number of elements, so O(1) might	3644	that you can use as many loops as you want in parallel, as long as there
3039	mean it might do a lengthy realloc operation in rare cases, but on average	3645	are no concurrent calls into any libev function with the same loop
3040	it is much faster and asymptotically approaches constant time.	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:
3041		3664
3042	=over 4	3665	=over 4
3043		3666
3044	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	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.
3045		3669
3046	This means that, when you have a watcher that triggers in one hour and	3670	This helps integrating other libraries or software modules that use libev
3047	there are 100 watchers that would trigger before that then inserting will	3671	themselves and don't care/know about threading.
3048	have to skip roughly seven (C<ld 100>) of these watchers.
3049		3672
3050	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3673	=item * one loop per thread is usually a good model.
3051		3674
3052	That means that changing a timer costs less than removing/adding them	3675	Doing this is almost never wrong, sometimes a better-performance model
3053	as only the relative motion in the event queue has to be paid for.	3676	exists, but it is always a good start.
3054		3677
3055	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	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.
3056		3680
3057	These just add the watcher into an array or at the head of a list.	3681	Choosing a model is hard - look around, learn, know that usually you can do
		3682	better than you currently do :-)
3058		3683
3059	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3684	=item * often you need to talk to some other thread which blocks in the
		3685	event loop.
3060		3686
3061	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3687	C<ev_async> watchers can be used to wake them up from other threads safely
		3688	(or from signal contexts...).
3062		3689
3063	These watchers are stored in lists then need to be walked to find the	3690	An example use would be to communicate signals or other events that only
3064	correct watcher to remove. The lists are usually short (you don't usually	3691	work in the default loop by registering the signal watcher with the
3065	have many watchers waiting for the same fd or signal).	3692	default loop and triggering an C<ev_async> watcher from the default loop
3066		3693	watcher callback into the event loop interested in the signal.
3067	=item Finding the next timer in each loop iteration: O(1)
3068
3069	By virtue of using a binary heap, the next timer is always found at the
3070	beginning of the storage array.
3071
3072	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3073
3074	A change means an I/O watcher gets started or stopped, which requires
3075	libev to recalculate its status (and possibly tell the kernel, depending
3076	on backend and wether C<ev_io_set> was used).
3077
3078	=item Activating one watcher (putting it into the pending state): O(1)
3079
3080	=item Priority handling: O(number_of_priorities)
3081
3082	Priorities are implemented by allocating some space for each
3083	priority. When doing priority-based operations, libev usually has to
3084	linearly search all the priorities, but starting/stopping and activating
3085	watchers becomes O(1) w.r.t. priority handling.
3086
3087	=item Sending an ev_async: O(1)
3088
3089	=item Processing ev_async_send: O(number_of_async_watchers)
3090
3091	=item Processing signals: O(max_signal_number)
3092
3093	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3094	calls in the current loop iteration. Checking for async and signal events
3095	involves iterating over all running async watchers or all signal numbers.
3096		3694
3097	=back	3695	=back
3098		3696
		3697	=head3 COROUTINES
3099		3698
3100	=head1 Win32 platform limitations and workarounds	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
3101		3775
3102	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3103	requires, and its I/O model is fundamentally incompatible with the POSIX	3777	requires, and its I/O model is fundamentally incompatible with the POSIX
3104	model. Libev still offers limited functionality on this platform in	3778	model. Libev still offers limited functionality on this platform in
3105	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3106	descriptors. This only applies when using Win32 natively, not when using	3780	descriptors. This only applies when using Win32 natively, not when using
3107	e.g. cygwin.	3781	e.g. cygwin.
3108		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
3109	There is no supported compilation method available on windows except	3788	There is no supported compilation method available on windows except
3110	embedding it into other applications.	3789	embedding it into other applications.
3111		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
3112	Due to the many, low, and arbitrary limits on the win32 platform and the	3798	Due to the many, low, and arbitrary limits on the win32 platform and
3113	abysmal performance of winsockets, using a large number of sockets is not	3799	the abysmal performance of winsockets, using a large number of sockets
3114	recommended (and not reasonable). If your program needs to use more than	3800	is not recommended (and not reasonable). If your program needs to use
3115	a hundred or so sockets, then likely it needs to use a totally different	3801	more than a hundred or so sockets, then likely it needs to use a totally
3116	implementation for windows, as libev offers the POSIX model, which cannot	3802	different implementation for windows, as libev offers the POSIX readiness
3117	be implemented efficiently on windows (microsoft monopoly games).	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"
3118		3820
3119	=over 4	3821	=over 4
3120		3822
3121	=item The winsocket select function	3823	=item The winsocket select function
3122		3824
3123	The winsocket C<select> function doesn't follow POSIX in that it requires	3825	The winsocket C<select> function doesn't follow POSIX in that it
3124	socket I<handles> and not socket I<file descriptors>. This makes select	3826	requires socket I<handles> and not socket I<file descriptors> (it is
3125	very inefficient, and also requires a mapping from file descriptors	3827	also extremely buggy). This makes select very inefficient, and also
3126	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3828	requires a mapping from file descriptors to socket handles (the Microsoft
3127	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3829	C runtime provides the function C<_open_osfhandle> for this). See the
3128	symbols for more info.	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.
3129		3832
3130	The configuration for a "naked" win32 using the microsoft runtime	3833	The configuration for a "naked" win32 using the Microsoft runtime
3131	libraries and raw winsocket select is:	3834	libraries and raw winsocket select is:
3132		3835
3133	#define EV_USE_SELECT 1	3836	#define EV_USE_SELECT 1
3134	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3135		3838
3136	Note that winsockets handling of fd sets is O(n), so you can easily get a	3839	Note that winsockets handling of fd sets is O(n), so you can easily get a
3137	complexity in the O(n²) range when using win32.	3840	complexity in the O(n²) range when using win32.
3138		3841
3139	=item Limited number of file descriptors	3842	=item Limited number of file descriptors
3140		3843
3141	Windows has numerous arbitrary (and low) limits on things. Early versions	3844	Windows has numerous arbitrary (and low) limits on things.
3142	of winsocket's select only supported waiting for a max. of C<64> handles	3845
		3846	Early versions of winsocket's select only supported waiting for a maximum
3143	(probably owning to the fact that all windows kernels can only wait for	3847	of C<64> handles (probably owning to the fact that all windows kernels
3144	C<64> things at the same time internally; microsoft recommends spawning a	3848	can only wait for C<64> things at the same time internally; Microsoft
3145	chain of threads and wait for 63 handles and the previous thread in each).	3849	recommends spawning a chain of threads and wait for 63 handles and the
		3850	previous thread in each. Great).
3146		3851
3147	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3148	to some high number (e.g. C<2048>) before compiling the winsocket select	3853	to some high number (e.g. C<2048>) before compiling the winsocket select
3149	call (which might be in libev or elsewhere, for example, perl does its own	3854	call (which might be in libev or elsewhere, for example, perl does its own
3150	select emulation on windows).	3855	select emulation on windows).
3151		3856
3152	Another limit is the number of file descriptors in the microsoft runtime	3857	Another limit is the number of file descriptors in the Microsoft runtime
3153	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3154	or something like this inside microsoft). You can increase this by calling	3859	or something like this inside Microsoft). You can increase this by calling
3155	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3156	arbitrary limit), but is broken in many versions of the microsoft runtime	3861	arbitrary limit), but is broken in many versions of the Microsoft runtime
3157	libraries.	3862	libraries.
3158		3863
3159	This might get you to about C<512> or C<2048> sockets (depending on	3864	This might get you to about C<512> or C<2048> sockets (depending on
3160	windows version and/or the phase of the moon). To get more, you need to	3865	windows version and/or the phase of the moon). To get more, you need to
3161	wrap all I/O functions and provide your own fd management, but the cost of	3866	wrap all I/O functions and provide your own fd management, but the cost of
3162	calling select (O(n²)) will likely make this unworkable.	3867	calling select (O(n²)) will likely make this unworkable.
3163		3868
3164	=back	3869	=back
3165		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
		3927	=head1 ALGORITHMIC COMPLEXITIES
		3928
		3929	In this section the complexities of (many of) the algorithms used inside
		3930	libev will be documented. For complexity discussions about backends see
		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.
		3938
		3939	=over 4
		3940
		3941	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		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
		3947	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		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
		3952	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3953
		3954	These just add the watcher into an array or at the head of a list.
		3955
		3956	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3957
		3958	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		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
		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.
		3969
		3970	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3971
		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.
		3994
		3995	=back
		3996
3166		3997
3167	=head1 AUTHOR	3998	=head1 AUTHOR
3168		3999
3169	Marc Lehmann <libev@schmorp.de>.	4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3170		4001

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