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Revision 1.139 by root, Wed Apr 2 05:51:40 2008 UTC vs.
Revision 1.232 by root, Thu Apr 16 06:17:26 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
…		…
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
280	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
281	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
283		306
284	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
285	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
286	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
287	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
288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	312	C<ev_default_init>.
290		313
291	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
…		…
300	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
301	thing, believe me).	324	thing, believe me).
302		325
303	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
304		327
305	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
306	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
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	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
309	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
310	around bugs.	333	around bugs.
…		…
317		340
318	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,
319	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
320	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
321	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
322	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
323	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
324		347
325	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
326	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
327	flag.	350	flag.
328		351
329	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>
330	environment variable.	353	environment variable.
331		354
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		356
334	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
…		…
336	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
337	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
338	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.
339		362
340	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
341	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
342	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
343	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
344	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
345	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).
346		373
347	=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)
348		375
349	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
350	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
351	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
352	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,
353	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
354	performance tips.	381	performance tips.
355		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		387
358	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,
359	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
360	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),
361	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).
362	of shortcomings, such as silently dropping events in some hard-to-detect	392
363	cases and rewiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
364	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.
365		409
366	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
367	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
368	(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
369	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
370	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
371		415	file descriptors.
372	Please note that epoll sometimes generates spurious notifications, so you
373	need to use non-blocking I/O or other means to avoid blocking when no data
374	(or space) is available.
375		416
376	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
377	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
378	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.
379		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
380	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
381	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>.
382		434
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		436
385	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
386	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
387	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
388	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
389	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
390	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)
391	system like NetBSD.	445	system like NetBSD.
392		446
393	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
394	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
395	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
396		450
397	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
398	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
399	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
400	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
401	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
402	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
403		458
404	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
405		460
406	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
407	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
408	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
409	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
411	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>.
412		471
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		473
415	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
416	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		480
422	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,
423	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)).
424		483
425	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
426	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
427	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
428		487
429	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
430	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
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	491	might perform better.
433		492
434	On the positive side, ignoring the spurious readyness notifications, this	493	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
436	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>.
437		500
438	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
439		502
440	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
441	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
…		…
443		506
444	It is definitely not recommended to use this flag.	507	It is definitely not recommended to use this flag.
445		508
446	=back	509	=back
447		510
448	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
449	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
450	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
451		514
452	The most typical usage is like this:	515	Example: This is the most typical usage.
453		516
454	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		519
457	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
458	environment settings to be taken into account:	521	environment settings to be taken into account:
459		522
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		524
462	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
463	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
464	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):
465		529
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		531
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		533
470	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
471	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
…		…
476	libev with threads is indeed to create one loop per thread, and using the	540	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	541	default loop in the "main" or "initial" thread.
478		542
479	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.
480		544
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	546	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
484		548
485	=item ev_default_destroy ()	549	=item ev_default_destroy ()
486		550
487	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
488	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
489	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
490	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
491	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
492	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
493	for example).	557	for example).
494		558
495	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
496	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
497	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
498		562
499	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
500	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
501	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
502	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
527		591
528	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
529		593
530	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
531	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
532	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.
533		598
534	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
535		600
536	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.
537		603
538	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
539		605
540	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
541	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
…		…
556	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
557	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
558	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
559	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
560		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
561	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
562		666
563	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
564	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
565	events.	669	events.
…		…
567	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
568	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.
569		673
570	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
571	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
572	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
573	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
574	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.
575		680
576	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
577	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
578	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.
579		685
580	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
581	neccessary) and will handle those and any outstanding ones. It will block	687	necessary) and will handle those and any already outstanding ones. It
582	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
583	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
584	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
585	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
586	usually a better approach for this kind of thing.	696	usually a better approach for this kind of thing.
587		697
588	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
589		699
590	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	701	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- 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.
593	- Queue and call all prepare watchers.	703	- Queue and call all prepare watchers.
594	- 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.
595	- Update the kernel state with all outstanding changes.	706	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	707	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	708	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	709	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	715	- Queue all expired timers.
605	- Queue all outstanding periodics.	716	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	718	- Queue all check watchers.
608	- 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).
609	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
610	be handled here by queueing them when their watcher gets executed.	721	be handled here by queueing them when their watcher gets executed.
611	- 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
…		…
616	anymore.	727	anymore.
617		728
618	... queue jobs here, make sure they register event watchers as long	729	... queue jobs here, make sure they register event watchers as long
619	... 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..)
620	ev_loop (my_loop, 0);	731	ev_loop (my_loop, 0);
621	... jobs done. yeah!	732	... jobs done or somebody called unloop. yeah!
622		733
623	=item ev_unloop (loop, how)	734	=item ev_unloop (loop, how)
624		735
625	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
626	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
627	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
628	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.
629		740
630	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.
631		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
632	=item ev_ref (loop)	745	=item ev_ref (loop)
633		746
634	=item ev_unref (loop)	747	=item ev_unref (loop)
635		748
636	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
637	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
638	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
639	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>
640	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
641	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
642	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
643	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
644	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
645	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
646	(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
647	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).
648		766
649	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>
650	running when nothing else is active.	768	running when nothing else is active.
651		769
652	struct ev_signal exitsig;	770	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	773	evf_unref (loop);
656		774
657	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
658		776
659	ev_ref (loop);	777	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	778	ev_signal_stop (loop, &exitsig);
661		779
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	780	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		781
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	782	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		783
666	These advanced functions influence the time that libev will spend waiting	784	These advanced functions influence the time that libev will spend waiting
667	for events. Both are by default C<0>, meaning that libev will try to	785	for events. Both time intervals are by default C<0>, meaning that libev
668	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.
669		788
670	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>)
671	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
672	increase efficiency of loop iterations.	791	to increase efficiency of loop iterations (or to increase power-saving
		792	opportunities).
673		793
674	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
675	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
676	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
677	events, especially with backends like C<select ()> which have a high	797	events, especially with backends like C<select ()> which have a high
678	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.
679		799
680	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
681	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,
…		…
683	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
684	introduce an additional C<ev_sleep ()> call into most loop iterations.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
685		805
686	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
687	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
689	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
690	any overhead in libev.	810	value will not introduce any overhead in libev.
691		811
692	Many (busy) programs can usually benefit by setting the io collect	812	Many (busy) programs can usually benefit by setting the I/O collect
693	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
694	interactive servers (of course not for games), likewise for timeouts. It	814	interactive servers (of course not for games), likewise for timeouts. It
695	usually doesn't make much sense to set it to a lower value than C<0.01>,	815	usually doesn't make much sense to set it to a lower value than C<0.01>,
696	as this approsaches the timing granularity of most systems.	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.
697		836
698	=back	837	=back
699		838
700		839
701	=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.
702		845
703	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
704	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
705	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:
706		849
707	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)
708	{	851	{
709	ev_io_stop (w);	852	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
711	}	854	}
712		855
713	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
714	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
715	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
718	ev_loop (loop, 0);	864	ev_loop (loop, 0);
719		865
720	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
721	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
722	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).
723		872
724	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
725	(watcher *, callback)>, which expects a callback to be provided. This	874	(watcher *, callback)>, which expects a callback to be provided. This
726	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
727	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
728	is readable and/or writable).	877	is readable and/or writable).
729		878
730	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 *, ...) >>
731	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
732	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<<
733	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
734		883
735	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
736	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
737	*) >>), 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
738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
739		888
740	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
741	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
742	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
743		892
744	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
745	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
746	third argument.	895	third argument.
747		896
…		…
805		954
806	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
807		956
808	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>).
809		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
810	=item C<EV_ERROR>	964	=item C<EV_ERROR>
811		965
812	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
813	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
814	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
815	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
816	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.
817		975
818	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
819	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
820	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
821	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
822	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
823		982
824	=back	983	=back
825		984
826	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
827
828	In the following description, C<TYPE> stands for the watcher type,
829	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
830		986
831	=over 4	987	=over 4
832		988
833	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
834		990
…		…
840	which rolls both calls into one.	996	which rolls both calls into one.
841		997
842	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
843	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
844		1000
845	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,
846	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);
847		1009
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		1011
850	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
851	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
…		…
854	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
855		1017
856	Although some watcher types do not have type-specific arguments	1018	Although some watcher types do not have type-specific arguments
857	(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.
858		1020
		1021	See C<ev_init>, above, for an example.
		1022
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		1024
861	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
862	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
863	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);
864		1032
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		1034
867	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
869		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
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		1044
872	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
873	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	1049	non-repeating timers are being stopped when they become pending - but
875	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
876	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
877	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.
878		1053
879	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
880		1055
881	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
882	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
…		…
908	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
909	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
910	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
911	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
912		1087
		1088	See L<
		1089
913	This means that priorities are I<only> used for ordering callback	1090	This means that priorities are I<only> used for ordering callback
914	invocation after new events have been received. This is useful, for	1091	invocation after new events have been received. This is useful, for
915	example, to reduce latency after idling, or more often, to bind two	1092	example, to reduce latency after idling, or more often, to bind two
916	watchers on the same event and make sure one is called first.	1093	watchers on the same event and make sure one is called first.
917		1094
…		…
924	The default priority used by watchers when no priority has been set is	1101	The default priority used by watchers when no priority has been set is
925	always C<0>, which is supposed to not be too high and not be too low :).	1102	always C<0>, which is supposed to not be too high and not be too low :).
926		1103
927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1104	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
928	fine, as long as you do not mind that the priority value you query might	1105	fine, as long as you do not mind that the priority value you query might
929	or might not have been adjusted to be within valid range.	1106	or might not have been clamped to the valid range.
930		1107
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1108	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1109
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1110	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
934	C<loop> nor C<revents> need to be valid as long as the watcher callback	1111	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1112	can deal with that fact, as both are simply passed through to the
		1113	callback.
936		1114
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1115	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1116
939	If the watcher is pending, this function returns clears its pending status	1117	If the watcher is pending, this function clears its pending status and
940	and returns its C<revents> bitset (as if its callback was invoked). If the	1118	returns its C<revents> bitset (as if its callback was invoked). If the
941	watcher isn't pending it does nothing and returns C<0>.	1119	watcher isn't pending it does nothing and returns C<0>.
942		1120
		1121	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1122	callback to be invoked, which can be accomplished with this function.
		1123
943	=back	1124	=back
944		1125
945		1126
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1127	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1128
948	Each watcher has, by default, a member C<void *data> that you can change	1129	Each watcher has, by default, a member C<void *data> that you can change
949	and read at any time, libev will completely ignore it. This can be used	1130	and read at any time: libev will completely ignore it. This can be used
950	to associate arbitrary data with your watcher. If you need more data and	1131	to associate arbitrary data with your watcher. If you need more data and
951	don't want to allocate memory and store a pointer to it in that data	1132	don't want to allocate memory and store a pointer to it in that data
952	member, you can also "subclass" the watcher type and provide your own	1133	member, you can also "subclass" the watcher type and provide your own
953	data:	1134	data:
954		1135
955	struct my_io	1136	struct my_io
956	{	1137	{
957	struct ev_io io;	1138	ev_io io;
958	int otherfd;	1139	int otherfd;
959	void *somedata;	1140	void *somedata;
960	struct whatever *mostinteresting;	1141	struct whatever *mostinteresting;
961	}	1142	};
		1143
		1144	...
		1145	struct my_io w;
		1146	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1147
963	And since your callback will be called with a pointer to the watcher, you	1148	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1149	can cast it back to your own type:
965		1150
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1151	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1152	{
968	struct my_io *w = (struct my_io *)w_;	1153	struct my_io *w = (struct my_io *)w_;
969	...	1154	...
970	}	1155	}
971		1156
972	More interesting and less C-conformant ways of casting your callback type	1157	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1158	instead have been omitted.
974		1159
975	Another common scenario is having some data structure with multiple	1160	Another common scenario is to use some data structure with multiple
976	watchers:	1161	embedded watchers:
977		1162
978	struct my_biggy	1163	struct my_biggy
979	{	1164	{
980	int some_data;	1165	int some_data;
981	ev_timer t1;	1166	ev_timer t1;
982	ev_timer t2;	1167	ev_timer t2;
983	}	1168	}
984		1169
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1170	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1171	complicated: Either you store the address of your C<my_biggy> struct
		1172	in the C<data> member of the watcher (for woozies), or you need to use
		1173	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1174	programmers):
987		1175
988	#include <stddef.h>	1176	#include <stddef.h>
989		1177
990	static void	1178	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1179	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1180	{
993	struct my_biggy big = (struct my_biggy *	1181	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t1));	1182	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1183	}
996		1184
997	static void	1185	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1186	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1187	{
1000	struct my_biggy big = (struct my_biggy *	1188	struct my_biggy big = (struct my_biggy *
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1189	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1190	}
1003		1191
1004		1192
1005	=head1 WATCHER TYPES	1193	=head1 WATCHER TYPES
1006		1194
1007	This section describes each watcher in detail, but will not repeat	1195	This section describes each watcher in detail, but will not repeat
…		…
1031	In general you can register as many read and/or write event watchers per	1219	In general you can register as many read and/or write event watchers per
1032	fd as you want (as long as you don't confuse yourself). Setting all file	1220	fd as you want (as long as you don't confuse yourself). Setting all file
1033	descriptors to non-blocking mode is also usually a good idea (but not	1221	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1222	required if you know what you are doing).
1035		1223
1036	If you must do this, then force the use of a known-to-be-good backend	1224	If you cannot use non-blocking mode, then force the use of a
1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1225	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1226	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1039		1227
1040	Another thing you have to watch out for is that it is quite easy to	1228	Another thing you have to watch out for is that it is quite easy to
1041	receive "spurious" readyness notifications, that is your callback might	1229	receive "spurious" readiness notifications, that is your callback might
1042	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1230	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1043	because there is no data. Not only are some backends known to create a	1231	because there is no data. Not only are some backends known to create a
1044	lot of those (for example solaris ports), it is very easy to get into	1232	lot of those (for example Solaris ports), it is very easy to get into
1045	this situation even with a relatively standard program structure. Thus	1233	this situation even with a relatively standard program structure. Thus
1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1234	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1235	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1236
1049	If you cannot run the fd in non-blocking mode (for example you should not	1237	If you cannot run the fd in non-blocking mode (for example you should
1050	play around with an Xlib connection), then you have to seperately re-test	1238	not play around with an Xlib connection), then you have to separately
1051	whether a file descriptor is really ready with a known-to-be good interface	1239	re-test whether a file descriptor is really ready with a known-to-be good
1052	such as poll (fortunately in our Xlib example, Xlib already does this on	1240	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1241	does this on its own, so its quite safe to use). Some people additionally
		1242	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1243	indefinitely.
		1244
		1245	But really, best use non-blocking mode.
1054		1246
1055	=head3 The special problem of disappearing file descriptors	1247	=head3 The special problem of disappearing file descriptors
1056		1248
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1249	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1058	descriptor (either by calling C<close> explicitly or by any other means,	1250	descriptor (either due to calling C<close> explicitly or any other means,
1059	such as C<dup>). The reason is that you register interest in some file	1251	such as C<dup2>). The reason is that you register interest in some file
1060	descriptor, but when it goes away, the operating system will silently drop	1252	descriptor, but when it goes away, the operating system will silently drop
1061	this interest. If another file descriptor with the same number then is	1253	this interest. If another file descriptor with the same number then is
1062	registered with libev, there is no efficient way to see that this is, in	1254	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1255	fact, a different file descriptor.
1064		1256
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1287	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1288	C<EVBACKEND_POLL>.
1097		1289
1098	=head3 The special problem of SIGPIPE	1290	=head3 The special problem of SIGPIPE
1099		1291
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1292	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1101	when reading from a pipe whose other end has been closed, your program	1293	when writing to a pipe whose other end has been closed, your program gets
1102	gets send a SIGPIPE, which, by default, aborts your program. For most	1294	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1295	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1296
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1297	So when you encounter spurious, unexplained daemon exits, make sure you
1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1298	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1108	somewhere, as that would have given you a big clue).	1299	somewhere, as that would have given you a big clue).
1109		1300
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1306	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1307
1117	=item ev_io_set (ev_io *, int fd, int events)	1308	=item ev_io_set (ev_io *, int fd, int events)
1118		1309
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1310	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1120	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1311	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1121	C<EV_READ | EV_WRITE> to receive the given events.	1312	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1313
1123	=item int fd [read-only]	1314	=item int fd [read-only]
1124		1315
1125	The file descriptor being watched.	1316	The file descriptor being watched.
1126		1317
…		…
1134		1325
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1326	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1136	readable, but only once. Since it is likely line-buffered, you could	1327	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1328	attempt to read a whole line in the callback.
1138		1329
1139	static void	1330	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1331	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1332	{
1142	ev_io_stop (loop, w);	1333	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1334	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1335	}
1145		1336
1146	...	1337	...
1147	struct ev_loop *loop = ev_default_init (0);	1338	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1339	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1340	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1341	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1342	ev_loop (loop, 0);
1152		1343
1153		1344
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1345	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1346
1156	Timer watchers are simple relative timers that generate an event after a	1347	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1348	given time, and optionally repeating in regular intervals after that.
1158		1349
1159	The timers are based on real time, that is, if you register an event that	1350	The timers are based on real time, that is, if you register an event that
1160	times out after an hour and you reset your system clock to last years	1351	times out after an hour and you reset your system clock to January last
1161	time, it will still time out after (roughly) and hour. "Roughly" because	1352	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1353	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1354	monotonic clock option helps a lot here).
		1355
		1356	The callback is guaranteed to be invoked only I<after> its timeout has
		1357	passed. If multiple timers become ready during the same loop iteration
		1358	then the ones with earlier time-out values are invoked before ones with
		1359	later time-out values (but this is no longer true when a callback calls
		1360	C<ev_loop> recursively).
		1361
		1362	=head3 Be smart about timeouts
		1363
		1364	Many real-world problems involve some kind of timeout, usually for error
		1365	recovery. A typical example is an HTTP request - if the other side hangs,
		1366	you want to raise some error after a while.
		1367
		1368	What follows are some ways to handle this problem, from obvious and
		1369	inefficient to smart and efficient.
		1370
		1371	In the following, a 60 second activity timeout is assumed - a timeout that
		1372	gets reset to 60 seconds each time there is activity (e.g. each time some
		1373	data or other life sign was received).
		1374
		1375	=over 4
		1376
		1377	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1378
		1379	This is the most obvious, but not the most simple way: In the beginning,
		1380	start the watcher:
		1381
		1382	ev_timer_init (timer, callback, 60., 0.);
		1383	ev_timer_start (loop, timer);
		1384
		1385	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1386	and start it again:
		1387
		1388	ev_timer_stop (loop, timer);
		1389	ev_timer_set (timer, 60., 0.);
		1390	ev_timer_start (loop, timer);
		1391
		1392	This is relatively simple to implement, but means that each time there is
		1393	some activity, libev will first have to remove the timer from its internal
		1394	data structure and then add it again. Libev tries to be fast, but it's
		1395	still not a constant-time operation.
		1396
		1397	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1398
		1399	This is the easiest way, and involves using C<ev_timer_again> instead of
		1400	C<ev_timer_start>.
		1401
		1402	To implement this, configure an C<ev_timer> with a C<repeat> value
		1403	of C<60> and then call C<ev_timer_again> at start and each time you
		1404	successfully read or write some data. If you go into an idle state where
		1405	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1406	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1407
		1408	That means you can ignore both the C<ev_timer_start> function and the
		1409	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1410	member and C<ev_timer_again>.
		1411
		1412	At start:
		1413
		1414	ev_timer_init (timer, callback);
		1415	timer->repeat = 60.;
		1416	ev_timer_again (loop, timer);
		1417
		1418	Each time there is some activity:
		1419
		1420	ev_timer_again (loop, timer);
		1421
		1422	It is even possible to change the time-out on the fly, regardless of
		1423	whether the watcher is active or not:
		1424
		1425	timer->repeat = 30.;
		1426	ev_timer_again (loop, timer);
		1427
		1428	This is slightly more efficient then stopping/starting the timer each time
		1429	you want to modify its timeout value, as libev does not have to completely
		1430	remove and re-insert the timer from/into its internal data structure.
		1431
		1432	It is, however, even simpler than the "obvious" way to do it.
		1433
		1434	=item 3. Let the timer time out, but then re-arm it as required.
		1435
		1436	This method is more tricky, but usually most efficient: Most timeouts are
		1437	relatively long compared to the intervals between other activity - in
		1438	our example, within 60 seconds, there are usually many I/O events with
		1439	associated activity resets.
		1440
		1441	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1442	but remember the time of last activity, and check for a real timeout only
		1443	within the callback:
		1444
		1445	ev_tstamp last_activity; // time of last activity
		1446
		1447	static void
		1448	callback (EV_P_ ev_timer *w, int revents)
		1449	{
		1450	ev_tstamp now = ev_now (EV_A);
		1451	ev_tstamp timeout = last_activity + 60.;
		1452
		1453	// if last_activity + 60. is older than now, we did time out
		1454	if (timeout < now)
		1455	{
		1456	// timeout occured, take action
		1457	}
		1458	else
		1459	{
		1460	// callback was invoked, but there was some activity, re-arm
		1461	// the watcher to fire in last_activity + 60, which is
		1462	// guaranteed to be in the future, so "again" is positive:
		1463	w->repeat = timeout - now;
		1464	ev_timer_again (EV_A_ w);
		1465	}
		1466	}
		1467
		1468	To summarise the callback: first calculate the real timeout (defined
		1469	as "60 seconds after the last activity"), then check if that time has
		1470	been reached, which means something I<did>, in fact, time out. Otherwise
		1471	the callback was invoked too early (C<timeout> is in the future), so
		1472	re-schedule the timer to fire at that future time, to see if maybe we have
		1473	a timeout then.
		1474
		1475	Note how C<ev_timer_again> is used, taking advantage of the
		1476	C<ev_timer_again> optimisation when the timer is already running.
		1477
		1478	This scheme causes more callback invocations (about one every 60 seconds
		1479	minus half the average time between activity), but virtually no calls to
		1480	libev to change the timeout.
		1481
		1482	To start the timer, simply initialise the watcher and set C<last_activity>
		1483	to the current time (meaning we just have some activity :), then call the
		1484	callback, which will "do the right thing" and start the timer:
		1485
		1486	ev_timer_init (timer, callback);
		1487	last_activity = ev_now (loop);
		1488	callback (loop, timer, EV_TIMEOUT);
		1489
		1490	And when there is some activity, simply store the current time in
		1491	C<last_activity>, no libev calls at all:
		1492
		1493	last_actiivty = ev_now (loop);
		1494
		1495	This technique is slightly more complex, but in most cases where the
		1496	time-out is unlikely to be triggered, much more efficient.
		1497
		1498	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1499	callback :) - just change the timeout and invoke the callback, which will
		1500	fix things for you.
		1501
		1502	=item 4. Wee, just use a double-linked list for your timeouts.
		1503
		1504	If there is not one request, but many thousands (millions...), all
		1505	employing some kind of timeout with the same timeout value, then one can
		1506	do even better:
		1507
		1508	When starting the timeout, calculate the timeout value and put the timeout
		1509	at the I<end> of the list.
		1510
		1511	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1512	the list is expected to fire (for example, using the technique #3).
		1513
		1514	When there is some activity, remove the timer from the list, recalculate
		1515	the timeout, append it to the end of the list again, and make sure to
		1516	update the C<ev_timer> if it was taken from the beginning of the list.
		1517
		1518	This way, one can manage an unlimited number of timeouts in O(1) time for
		1519	starting, stopping and updating the timers, at the expense of a major
		1520	complication, and having to use a constant timeout. The constant timeout
		1521	ensures that the list stays sorted.
		1522
		1523	=back
		1524
		1525	So which method the best?
		1526
		1527	Method #2 is a simple no-brain-required solution that is adequate in most
		1528	situations. Method #3 requires a bit more thinking, but handles many cases
		1529	better, and isn't very complicated either. In most case, choosing either
		1530	one is fine, with #3 being better in typical situations.
		1531
		1532	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1533	rather complicated, but extremely efficient, something that really pays
		1534	off after the first million or so of active timers, i.e. it's usually
		1535	overkill :)
		1536
		1537	=head3 The special problem of time updates
		1538
		1539	Establishing the current time is a costly operation (it usually takes at
		1540	least two system calls): EV therefore updates its idea of the current
		1541	time only before and after C<ev_loop> collects new events, which causes a
		1542	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1543	lots of events in one iteration.
1164		1544
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1545	The relative timeouts are calculated relative to the C<ev_now ()>
1166	time. This is usually the right thing as this timestamp refers to the time	1546	time. This is usually the right thing as this timestamp refers to the time
1167	of the event triggering whatever timeout you are modifying/starting. If	1547	of the event triggering whatever timeout you are modifying/starting. If
1168	you suspect event processing to be delayed and you I<need> to base the timeout	1548	you suspect event processing to be delayed and you I<need> to base the
1169	on the current time, use something like this to adjust for this:	1549	timeout on the current time, use something like this to adjust for this:
1170		1550
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1551	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1552
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1553	If the event loop is suspended for a long time, you can also force an
1174	but if multiple timers become ready during the same loop iteration then	1554	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1555	()>.
1176		1556
1177	=head3 Watcher-Specific Functions and Data Members	1557	=head3 Watcher-Specific Functions and Data Members
1178		1558
1179	=over 4	1559	=over 4
1180		1560
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1561	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1562
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1563	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1564
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1565	Configure the timer to trigger after C<after> seconds. If C<repeat>
1186	C<0.>, then it will automatically be stopped. If it is positive, then the	1566	is C<0.>, then it will automatically be stopped once the timeout is
1187	timer will automatically be configured to trigger again C<repeat> seconds	1567	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1568	configured to trigger again C<repeat> seconds later, again, and again,
		1569	until stopped manually.
1189		1570
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1571	The timer itself will do a best-effort at avoiding drift, that is, if
1191	configure a timer to trigger every 10 seconds, then it will trigger at	1572	you configure a timer to trigger every 10 seconds, then it will normally
1192	exactly 10 second intervals. If, however, your program cannot keep up with	1573	trigger at exactly 10 second intervals. If, however, your program cannot
1193	the timer (because it takes longer than those 10 seconds to do stuff) the	1574	keep up with the timer (because it takes longer than those 10 seconds to
1194	timer will not fire more than once per event loop iteration.	1575	do stuff) the timer will not fire more than once per event loop iteration.
1195		1576
1196	=item ev_timer_again (loop, ev_timer *)	1577	=item ev_timer_again (loop, ev_timer *)
1197		1578
1198	This will act as if the timer timed out and restart it again if it is	1579	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1580	repeating. The exact semantics are:
1200		1581
1201	If the timer is pending, its pending status is cleared.	1582	If the timer is pending, its pending status is cleared.
1202		1583
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1584	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1585
1205	If the timer is repeating, either start it if necessary (with the	1586	If the timer is repeating, either start it if necessary (with the
1206	C<repeat> value), or reset the running timer to the C<repeat> value.	1587	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1588
1208	This sounds a bit complicated, but here is a useful and typical	1589	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1209	example: Imagine you have a tcp connection and you want a so-called idle	1590	usage example.
1210	timeout, that is, you want to be called when there have been, say, 60
1211	seconds of inactivity on the socket. The easiest way to do this is to
1212	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1213	C<ev_timer_again> each time you successfully read or write some data. If
1214	you go into an idle state where you do not expect data to travel on the
1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1216	automatically restart it if need be.
1217
1218	That means you can ignore the C<after> value and C<ev_timer_start>
1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1220
1221	ev_timer_init (timer, callback, 0., 5.);
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 17.;
1225	ev_timer_again (loop, timer);
1226	...
1227	timer->again = 10.;
1228	ev_timer_again (loop, timer);
1229
1230	This is more slightly efficient then stopping/starting the timer each time
1231	you want to modify its timeout value.
1232		1591
1233	=item ev_tstamp repeat [read-write]	1592	=item ev_tstamp repeat [read-write]
1234		1593
1235	The current C<repeat> value. Will be used each time the watcher times out	1594	The current C<repeat> value. Will be used each time the watcher times out
1236	or C<ev_timer_again> is called and determines the next timeout (if any),	1595	or C<ev_timer_again> is called, and determines the next timeout (if any),
1237	which is also when any modifications are taken into account.	1596	which is also when any modifications are taken into account.
1238		1597
1239	=back	1598	=back
1240		1599
1241	=head3 Examples	1600	=head3 Examples
1242		1601
1243	Example: Create a timer that fires after 60 seconds.	1602	Example: Create a timer that fires after 60 seconds.
1244		1603
1245	static void	1604	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1605	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1606	{
1248	.. one minute over, w is actually stopped right here	1607	.. one minute over, w is actually stopped right here
1249	}	1608	}
1250		1609
1251	struct ev_timer mytimer;	1610	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1611	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1612	ev_timer_start (loop, &mytimer);
1254		1613
1255	Example: Create a timeout timer that times out after 10 seconds of	1614	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1615	inactivity.
1257		1616
1258	static void	1617	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1618	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1619	{
1261	.. ten seconds without any activity	1620	.. ten seconds without any activity
1262	}	1621	}
1263		1622
1264	struct ev_timer mytimer;	1623	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1624	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1625	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1626	ev_loop (loop, 0);
1268		1627
1269	// and in some piece of code that gets executed on any "activity":	1628	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1629	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1630	ev_timer_again (&mytimer);
1272		1631
1273		1632
1274	=head2 C<ev_periodic> - to cron or not to cron?	1633	=head2 C<ev_periodic> - to cron or not to cron?
1275		1634
1276	Periodic watchers are also timers of a kind, but they are very versatile	1635	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1636	(and unfortunately a bit complex).
1278		1637
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1638	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1280	but on wallclock time (absolute time). You can tell a periodic watcher	1639	relative time, the physical time that passes) but on wall clock time
1281	to trigger "at" some specific point in time. For example, if you tell a	1640	(absolute time, the thing you can read on your calender or clock). The
1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1641	difference is that wall clock time can run faster or slower than real
1283	+ 10.>) and then reset your system clock to the last year, then it will	1642	time, and time jumps are not uncommon (e.g. when you adjust your
1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1643	wrist-watch).
1285	roughly 10 seconds later).
1286		1644
1287	They can also be used to implement vastly more complex timers, such as	1645	You can tell a periodic watcher to trigger after some specific point
1288	triggering an event on each midnight, local time or other, complicated,	1646	in time: for example, if you tell a periodic watcher to trigger "in 10
1289	rules.	1647	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1648	not a delay) and then reset your system clock to January of the previous
		1649	year, then it will take a year or more to trigger the event (unlike an
		1650	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1651	it, as it uses a relative timeout).
1290		1652
		1653	C<ev_periodic> watchers can also be used to implement vastly more complex
		1654	timers, such as triggering an event on each "midnight, local time", or
		1655	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1656	those cannot react to time jumps.
		1657
1291	As with timers, the callback is guarenteed to be invoked only when the	1658	As with timers, the callback is guaranteed to be invoked only when the
1292	time (C<at>) has been passed, but if multiple periodic timers become ready	1659	point in time where it is supposed to trigger has passed. If multiple
1293	during the same loop iteration then order of execution is undefined.	1660	timers become ready during the same loop iteration then the ones with
		1661	earlier time-out values are invoked before ones with later time-out values
		1662	(but this is no longer true when a callback calls C<ev_loop> recursively).
1294		1663
1295	=head3 Watcher-Specific Functions and Data Members	1664	=head3 Watcher-Specific Functions and Data Members
1296		1665
1297	=over 4	1666	=over 4
1298		1667
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1668	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		1669
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1670	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1302		1671
1303	Lots of arguments, lets sort it out... There are basically three modes of	1672	Lots of arguments, let's sort it out... There are basically three modes of
1304	operation, and we will explain them from simplest to complex:	1673	operation, and we will explain them from simplest to most complex:
1305		1674
1306	=over 4	1675	=over 4
1307		1676
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1677	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1309		1678
1310	In this configuration the watcher triggers an event at the wallclock time	1679	In this configuration the watcher triggers an event after the wall clock
1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1680	time C<offset> has passed. It will not repeat and will not adjust when a
1312	that is, if it is to be run at January 1st 2011 then it will run when the	1681	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1313	system time reaches or surpasses this time.	1682	will be stopped and invoked when the system clock reaches or surpasses
		1683	this point in time.
1314		1684
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1685	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1316		1686
1317	In this mode the watcher will always be scheduled to time out at the next	1687	In this mode the watcher will always be scheduled to time out at the next
1318	C<at + N * interval> time (for some integer N, which can also be negative)	1688	C<offset + N * interval> time (for some integer N, which can also be
1319	and then repeat, regardless of any time jumps.	1689	negative) and then repeat, regardless of any time jumps. The C<offset>
		1690	argument is merely an offset into the C<interval> periods.
1320		1691
1321	This can be used to create timers that do not drift with respect to system	1692	This can be used to create timers that do not drift with respect to the
1322	time:	1693	system clock, for example, here is an C<ev_periodic> that triggers each
		1694	hour, on the hour (with respect to UTC):
1323		1695
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1696	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1697
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1698	This doesn't mean there will always be 3600 seconds in between triggers,
1327	but only that the the callback will be called when the system time shows a	1699	but only that the callback will be called when the system time shows a
1328	full hour (UTC), or more correctly, when the system time is evenly divisible	1700	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1701	by 3600.
1330		1702
1331	Another way to think about it (for the mathematically inclined) is that	1703	Another way to think about it (for the mathematically inclined) is that
1332	C<ev_periodic> will try to run the callback in this mode at the next possible	1704	C<ev_periodic> will try to run the callback in this mode at the next possible
1333	time where C<time = at (mod interval)>, regardless of any time jumps.	1705	time where C<time = offset (mod interval)>, regardless of any time jumps.
1334		1706
1335	For numerical stability it is preferable that the C<at> value is near	1707	For numerical stability it is preferable that the C<offset> value is near
1336	C<ev_now ()> (the current time), but there is no range requirement for	1708	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1709	this value, and in fact is often specified as zero.
1338		1710
		1711	Note also that there is an upper limit to how often a timer can fire (CPU
		1712	speed for example), so if C<interval> is very small then timing stability
		1713	will of course deteriorate. Libev itself tries to be exact to be about one
		1714	millisecond (if the OS supports it and the machine is fast enough).
		1715
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1716	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1340		1717
1341	In this mode the values for C<interval> and C<at> are both being	1718	In this mode the values for C<interval> and C<offset> are both being
1342	ignored. Instead, each time the periodic watcher gets scheduled, the	1719	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1720	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1721	current time as second argument.
1345		1722
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1723	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1347	ever, or make any event loop modifications>. If you need to stop it,	1724	or make ANY other event loop modifications whatsoever, unless explicitly
1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1725	allowed by documentation here>.
1349	starting an C<ev_prepare> watcher, which is legal).
1350		1726
		1727	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1728	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1729	only event loop modification you are allowed to do).
		1730
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1731	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1732	*w, ev_tstamp now)>, e.g.:
1353		1733
		1734	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1735	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1736	{
1356	return now + 60.;	1737	return now + 60.;
1357	}	1738	}
1358		1739
1359	It must return the next time to trigger, based on the passed time value	1740	It must return the next time to trigger, based on the passed time value
1360	(that is, the lowest time value larger than to the second argument). It	1741	(that is, the lowest time value larger than to the second argument). It
1361	will usually be called just before the callback will be triggered, but	1742	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	1743	might be called at other times, too.
1363		1744
1364	NOTE: I<< This callback must always return a time that is later than the	1745	NOTE: I<< This callback must always return a time that is higher than or
1365	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1746	equal to the passed C<now> value >>.
1366		1747
1367	This can be used to create very complex timers, such as a timer that	1748	This can be used to create very complex timers, such as a timer that
1368	triggers on each midnight, local time. To do this, you would calculate the	1749	triggers on "next midnight, local time". To do this, you would calculate the
1369	next midnight after C<now> and return the timestamp value for this. How	1750	next midnight after C<now> and return the timestamp value for this. How
1370	you do this is, again, up to you (but it is not trivial, which is the main	1751	you do this is, again, up to you (but it is not trivial, which is the main
1371	reason I omitted it as an example).	1752	reason I omitted it as an example).
1372		1753
1373	=back	1754	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1758	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1759	when you changed some parameters or the reschedule callback would return
1379	a different time than the last time it was called (e.g. in a crond like	1760	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1761	program when the crontabs have changed).
1381		1762
		1763	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1764
		1765	When active, returns the absolute time that the watcher is supposed
		1766	to trigger next. This is not the same as the C<offset> argument to
		1767	C<ev_periodic_set>, but indeed works even in interval and manual
		1768	rescheduling modes.
		1769
1382	=item ev_tstamp offset [read-write]	1770	=item ev_tstamp offset [read-write]
1383		1771
1384	When repeating, this contains the offset value, otherwise this is the	1772	When repeating, this contains the offset value, otherwise this is the
1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1773	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1774	although libev might modify this value for better numerical stability).
1386		1775
1387	Can be modified any time, but changes only take effect when the periodic	1776	Can be modified any time, but changes only take effect when the periodic
1388	timer fires or C<ev_periodic_again> is being called.	1777	timer fires or C<ev_periodic_again> is being called.
1389		1778
1390	=item ev_tstamp interval [read-write]	1779	=item ev_tstamp interval [read-write]
1391		1780
1392	The current interval value. Can be modified any time, but changes only	1781	The current interval value. Can be modified any time, but changes only
1393	take effect when the periodic timer fires or C<ev_periodic_again> is being	1782	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	1783	called.
1395		1784
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1785	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		1786
1398	The current reschedule callback, or C<0>, if this functionality is	1787	The current reschedule callback, or C<0>, if this functionality is
1399	switched off. Can be changed any time, but changes only take effect when	1788	switched off. Can be changed any time, but changes only take effect when
1400	the periodic timer fires or C<ev_periodic_again> is being called.	1789	the periodic timer fires or C<ev_periodic_again> is being called.
1401		1790
1402	=item ev_tstamp at [read-only]
1403
1404	When active, contains the absolute time that the watcher is supposed to
1405	trigger next.
1406
1407	=back	1791	=back
1408		1792
1409	=head3 Examples	1793	=head3 Examples
1410		1794
1411	Example: Call a callback every hour, or, more precisely, whenever the	1795	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	1796	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	1797	potentially a lot of jitter, but good long-term stability.
1414		1798
1415	static void	1799	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1800	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	1801	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	1802	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	1803	}
1420		1804
1421	struct ev_periodic hourly_tick;	1805	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1806	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	1807	ev_periodic_start (loop, &hourly_tick);
1424		1808
1425	Example: The same as above, but use a reschedule callback to do it:	1809	Example: The same as above, but use a reschedule callback to do it:
1426		1810
1427	#include <math.h>	1811	#include <math.h>
1428		1812
1429	static ev_tstamp	1813	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1814	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	1815	{
1432	return fmod (now, 3600.) + 3600.;	1816	return now + (3600. - fmod (now, 3600.));
1433	}	1817	}
1434		1818
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1819	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		1820
1437	Example: Call a callback every hour, starting now:	1821	Example: Call a callback every hour, starting now:
1438		1822
1439	struct ev_periodic hourly_tick;	1823	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	1824	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	1825	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	1826	ev_periodic_start (loop, &hourly_tick);
1443		1827
1444		1828
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	1829	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		1830
1447	Signal watchers will trigger an event when the process receives a specific	1831	Signal watchers will trigger an event when the process receives a specific
1448	signal one or more times. Even though signals are very asynchronous, libev	1832	signal one or more times. Even though signals are very asynchronous, libev
1449	will try it's best to deliver signals synchronously, i.e. as part of the	1833	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	1834	normal event processing, like any other event.
1451		1835
		1836	If you want signals asynchronously, just use C<sigaction> as you would
		1837	do without libev and forget about sharing the signal. You can even use
		1838	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1839
1452	You can configure as many watchers as you like per signal. Only when the	1840	You can configure as many watchers as you like per signal. Only when the
1453	first watcher gets started will libev actually register a signal watcher	1841	first watcher gets started will libev actually register a signal handler
1454	with the kernel (thus it coexists with your own signal handlers as long	1842	with the kernel (thus it coexists with your own signal handlers as long as
1455	as you don't register any with libev). Similarly, when the last signal	1843	you don't register any with libev for the same signal). Similarly, when
1456	watcher for a signal is stopped libev will reset the signal handler to	1844	the last signal watcher for a signal is stopped, libev will reset the
1457	SIG_DFL (regardless of what it was set to before).	1845	signal handler to SIG_DFL (regardless of what it was set to before).
1458		1846
1459	If possible and supported, libev will install its handlers with	1847	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1848	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1461	interrupted. If you have a problem with syscalls getting interrupted by	1849	interrupted. If you have a problem with system calls getting interrupted by
1462	signals you can block all signals in an C<ev_check> watcher and unblock	1850	signals you can block all signals in an C<ev_check> watcher and unblock
1463	them in an C<ev_prepare> watcher.	1851	them in an C<ev_prepare> watcher.
1464		1852
1465	=head3 Watcher-Specific Functions and Data Members	1853	=head3 Watcher-Specific Functions and Data Members
1466		1854
…		…
1479		1867
1480	=back	1868	=back
1481		1869
1482	=head3 Examples	1870	=head3 Examples
1483		1871
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	1872	Example: Try to exit cleanly on SIGINT.
1485		1873
1486	static void	1874	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1875	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	1876	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	1877	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	1878	}
1491		1879
1492	struct ev_signal signal_watcher;	1880	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1881	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	1882	ev_signal_start (loop, &signal_watcher);
1495		1883
1496		1884
1497	=head2 C<ev_child> - watch out for process status changes	1885	=head2 C<ev_child> - watch out for process status changes
1498		1886
1499	Child watchers trigger when your process receives a SIGCHLD in response to	1887	Child watchers trigger when your process receives a SIGCHLD in response to
1500	some child status changes (most typically when a child of yours dies). It	1888	some child status changes (most typically when a child of yours dies or
1501	is permissible to install a child watcher I<after> the child has been	1889	exits). It is permissible to install a child watcher I<after> the child
1502	forked (which implies it might have already exited), as long as the event	1890	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	1891	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1892	forking and then immediately registering a watcher for the child is fine,
		1893	but forking and registering a watcher a few event loop iterations later is
		1894	not.
1504		1895
1505	Only the default event loop is capable of handling signals, and therefore	1896	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	1897	you can only register child watchers in the default event loop.
1507		1898
1508	=head3 Process Interaction	1899	=head3 Process Interaction
1509		1900
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	1901	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	1902	initialised. This is necessary to guarantee proper behaviour even if
1512	the first child watcher is started after the child exits. The occurance	1903	the first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1904	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	1905	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	1906	children, even ones not watched.
1516		1907
1517	=head3 Overriding the Built-In Processing	1908	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	1912	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	1913	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	1914	default loop never gets destroyed. You are encouraged, however, to use an
1524	event-based approach to child reaping and thus use libev's support for	1915	event-based approach to child reaping and thus use libev's support for
1525	that, so other libev users can use C<ev_child> watchers freely.	1916	that, so other libev users can use C<ev_child> watchers freely.
		1917
		1918	=head3 Stopping the Child Watcher
		1919
		1920	Currently, the child watcher never gets stopped, even when the
		1921	child terminates, so normally one needs to stop the watcher in the
		1922	callback. Future versions of libev might stop the watcher automatically
		1923	when a child exit is detected.
1526		1924
1527	=head3 Watcher-Specific Functions and Data Members	1925	=head3 Watcher-Specific Functions and Data Members
1528		1926
1529	=over 4	1927	=over 4
1530		1928
…		…
1559	=head3 Examples	1957	=head3 Examples
1560		1958
1561	Example: C<fork()> a new process and install a child handler to wait for	1959	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	1960	its completion.
1563		1961
1564	ev_child cw;	1962	ev_child cw;
1565		1963
1566	static void	1964	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	1965	child_cb (EV_P_ ev_child *w, int revents)
1568	{	1966	{
1569	ev_child_stop (EV_A_ w);	1967	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1968	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	1969	}
1572		1970
1573	pid_t pid = fork ();	1971	pid_t pid = fork ();
1574		1972
1575	if (pid < 0)	1973	if (pid < 0)
1576	// error	1974	// error
1577	else if (pid == 0)	1975	else if (pid == 0)
1578	{	1976	{
1579	// the forked child executes here	1977	// the forked child executes here
1580	exit (1);	1978	exit (1);
1581	}	1979	}
1582	else	1980	else
1583	{	1981	{
1584	ev_child_init (&cw, child_cb, pid, 0);	1982	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	1983	ev_child_start (EV_DEFAULT_ &cw);
1586	}	1984	}
1587		1985
1588		1986
1589	=head2 C<ev_stat> - did the file attributes just change?	1987	=head2 C<ev_stat> - did the file attributes just change?
1590		1988
1591	This watches a filesystem path for attribute changes. That is, it calls	1989	This watches a file system path for attribute changes. That is, it calls
1592	C<stat> regularly (or when the OS says it changed) and sees if it changed	1990	C<stat> on that path in regular intervals (or when the OS says it changed)
1593	compared to the last time, invoking the callback if it did.	1991	and sees if it changed compared to the last time, invoking the callback if
		1992	it did.
1594		1993
1595	The path does not need to exist: changing from "path exists" to "path does	1994	The path does not need to exist: changing from "path exists" to "path does
1596	not exist" is a status change like any other. The condition "path does	1995	not exist" is a status change like any other. The condition "path does not
1597	not exist" is signified by the C<st_nlink> field being zero (which is	1996	exist" (or more correctly "path cannot be stat'ed") is signified by the
1598	otherwise always forced to be at least one) and all the other fields of	1997	C<st_nlink> field being zero (which is otherwise always forced to be at
1599	the stat buffer having unspecified contents.	1998	least one) and all the other fields of the stat buffer having unspecified
		1999	contents.
1600		2000
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	2001	The path I<must not> end in a slash or contain special components such as
		2002	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1602	relative and your working directory changes, the behaviour is undefined.	2003	your working directory changes, then the behaviour is undefined.
1603		2004
1604	Since there is no standard to do this, the portable implementation simply	2005	Since there is no portable change notification interface available, the
1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2006	portable implementation simply calls C<stat(2)> regularly on the path
1606	can specify a recommended polling interval for this case. If you specify	2007	to see if it changed somehow. You can specify a recommended polling
1607	a polling interval of C<0> (highly recommended!) then a I<suitable,	2008	interval for this case. If you specify a polling interval of C<0> (highly
1608	unspecified default> value will be used (which you can expect to be around	2009	recommended!) then a I<suitable, unspecified default> value will be used
1609	five seconds, although this might change dynamically). Libev will also	2010	(which you can expect to be around five seconds, although this might
1610	impose a minimum interval which is currently around C<0.1>, but thats	2011	change dynamically). Libev will also impose a minimum interval which is
1611	usually overkill.	2012	currently around C<0.1>, but that's usually overkill.
1612		2013
1613	This watcher type is not meant for massive numbers of stat watchers,	2014	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	2015	as even with OS-supported change notifications, this can be
1615	resource-intensive.	2016	resource-intensive.
1616		2017
1617	At the time of this writing, only the Linux inotify interface is	2018	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	2019	is the Linux inotify interface (implementing kqueue support is left as an
1619	reader). Inotify will be used to give hints only and should not change the	2020	exercise for the reader. Note, however, that the author sees no way of
1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2021	implementing C<ev_stat> semantics with kqueue, except as a hint).
1621	to fall back to regular polling again even with inotify, but changes are
1622	usually detected immediately, and if the file exists there will be no
1623	polling.
1624		2022
1625	=head3 ABI Issues (Largefile Support)	2023	=head3 ABI Issues (Largefile Support)
1626		2024
1627	Libev by default (unless the user overrides this) uses the default	2025	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	2026	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	2027	support disabled by default, you get the 32 bit version of the stat
1630	structure. When using the library from programs that change the ABI to	2028	structure. When using the library from programs that change the ABI to
1631	use 64 bit file offsets the programs will fail. In that case you have to	2029	use 64 bit file offsets the programs will fail. In that case you have to
1632	compile libev with the same flags to get binary compatibility. This is	2030	compile libev with the same flags to get binary compatibility. This is
1633	obviously the case with any flags that change the ABI, but the problem is	2031	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	2032	most noticeably displayed with ev_stat and large file support.
1635		2033
1636	=head3 Inotify	2034	The solution for this is to lobby your distribution maker to make large
		2035	file interfaces available by default (as e.g. FreeBSD does) and not
		2036	optional. Libev cannot simply switch on large file support because it has
		2037	to exchange stat structures with application programs compiled using the
		2038	default compilation environment.
1637		2039
		2040	=head3 Inotify and Kqueue
		2041
1638	When C<inotify (7)> support has been compiled into libev (generally only	2042	When C<inotify (7)> support has been compiled into libev and present at
1639	available on Linux) and present at runtime, it will be used to speed up	2043	runtime, it will be used to speed up change detection where possible. The
1640	change detection where possible. The inotify descriptor will be created lazily	2044	inotify descriptor will be created lazily when the first C<ev_stat>
1641	when the first C<ev_stat> watcher is being started.	2045	watcher is being started.
1642		2046
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	2047	Inotify presence does not change the semantics of C<ev_stat> watchers
1644	except that changes might be detected earlier, and in some cases, to avoid	2048	except that changes might be detected earlier, and in some cases, to avoid
1645	making regular C<stat> calls. Even in the presense of inotify support	2049	making regular C<stat> calls. Even in the presence of inotify support
1646	there are many cases where libev has to resort to regular C<stat> polling.	2050	there are many cases where libev has to resort to regular C<stat> polling,
		2051	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2052	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2053	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2054	xfs are fully working) libev usually gets away without polling.
1647		2055
1648	(There is no support for kqueue, as apparently it cannot be used to	2056	There is no support for kqueue, as apparently it cannot be used to
1649	implement this functionality, due to the requirement of having a file	2057	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	2058	descriptor open on the object at all times, and detecting renames, unlinks
		2059	etc. is difficult.
		2060
		2061	=head3 C<stat ()> is a synchronous operation
		2062
		2063	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2064	the process. The exception are C<ev_stat> watchers - those call C<stat
		2065	()>, which is a synchronous operation.
		2066
		2067	For local paths, this usually doesn't matter: unless the system is very
		2068	busy or the intervals between stat's are large, a stat call will be fast,
		2069	as the path data is usually in memory already (except when starting the
		2070	watcher).
		2071
		2072	For networked file systems, calling C<stat ()> can block an indefinite
		2073	time due to network issues, and even under good conditions, a stat call
		2074	often takes multiple milliseconds.
		2075
		2076	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2077	paths, although this is fully supported by libev.
1651		2078
1652	=head3 The special problem of stat time resolution	2079	=head3 The special problem of stat time resolution
1653		2080
1654	The C<stat ()> syscall only supports full-second resolution portably, and	2081	The C<stat ()> system call only supports full-second resolution portably,
1655	even on systems where the resolution is higher, many filesystems still	2082	and even on systems where the resolution is higher, most file systems
1656	only support whole seconds.	2083	still only support whole seconds.
1657		2084
1658	That means that, if the time is the only thing that changes, you might	2085	That means that, if the time is the only thing that changes, you can
1659	miss updates: on the first update, C<ev_stat> detects a change and calls	2086	easily miss updates: on the first update, C<ev_stat> detects a change and
1660	your callback, which does something. When there is another update within	2087	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	2088	within the same second, C<ev_stat> will be unable to detect unless the
		2089	stat data does change in other ways (e.g. file size).
1662		2090
1663	The solution to this is to delay acting on a change for a second (or till	2091	The solution to this is to delay acting on a change for slightly more
1664	the next second boundary), using a roughly one-second delay C<ev_timer>	2092	than a second (or till slightly after the next full second boundary), using
1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2093	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1666	is added to work around small timing inconsistencies of some operating	2094	ev_timer_again (loop, w)>).
1667	systems.	2095
		2096	The C<.02> offset is added to work around small timing inconsistencies
		2097	of some operating systems (where the second counter of the current time
		2098	might be be delayed. One such system is the Linux kernel, where a call to
		2099	C<gettimeofday> might return a timestamp with a full second later than
		2100	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2101	update file times then there will be a small window where the kernel uses
		2102	the previous second to update file times but libev might already execute
		2103	the timer callback).
1668		2104
1669	=head3 Watcher-Specific Functions and Data Members	2105	=head3 Watcher-Specific Functions and Data Members
1670		2106
1671	=over 4	2107	=over 4
1672		2108
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2114	C<path>. The C<interval> is a hint on how quickly a change is expected to
1679	be detected and should normally be specified as C<0> to let libev choose	2115	be detected and should normally be specified as C<0> to let libev choose
1680	a suitable value. The memory pointed to by C<path> must point to the same	2116	a suitable value. The memory pointed to by C<path> must point to the same
1681	path for as long as the watcher is active.	2117	path for as long as the watcher is active.
1682		2118
1683	The callback will be receive C<EV_STAT> when a change was detected,	2119	The callback will receive an C<EV_STAT> event when a change was detected,
1684	relative to the attributes at the time the watcher was started (or the	2120	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2121	last change was detected).
1686		2122
1687	=item ev_stat_stat (loop, ev_stat *)	2123	=item ev_stat_stat (loop, ev_stat *)
1688		2124
1689	Updates the stat buffer immediately with new values. If you change the	2125	Updates the stat buffer immediately with new values. If you change the
1690	watched path in your callback, you could call this fucntion to avoid	2126	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2127	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2128	the only one changing the path). Can also be useful simply to find out the
		2129	new values.
1693		2130
1694	=item ev_statdata attr [read-only]	2131	=item ev_statdata attr [read-only]
1695		2132
1696	The most-recently detected attributes of the file. Although the type is of	2133	The most-recently detected attributes of the file. Although the type is
1697	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2134	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1698	suitable for your system. If the C<st_nlink> member is C<0>, then there	2135	suitable for your system, but you can only rely on the POSIX-standardised
		2136	members to be present. If the C<st_nlink> member is C<0>, then there was
1699	was some error while C<stat>ing the file.	2137	some error while C<stat>ing the file.
1700		2138
1701	=item ev_statdata prev [read-only]	2139	=item ev_statdata prev [read-only]
1702		2140
1703	The previous attributes of the file. The callback gets invoked whenever	2141	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2142	C<prev> != C<attr>, or, more precisely, one or more of these members
		2143	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2144	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2145
1706	=item ev_tstamp interval [read-only]	2146	=item ev_tstamp interval [read-only]
1707		2147
1708	The specified interval.	2148	The specified interval.
1709		2149
1710	=item const char *path [read-only]	2150	=item const char *path [read-only]
1711		2151
1712	The filesystem path that is being watched.	2152	The file system path that is being watched.
1713		2153
1714	=back	2154	=back
1715		2155
1716	=head3 Examples	2156	=head3 Examples
1717		2157
1718	Example: Watch C</etc/passwd> for attribute changes.	2158	Example: Watch C</etc/passwd> for attribute changes.
1719		2159
1720	static void	2160	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2161	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2162	{
1723	/* /etc/passwd changed in some way */	2163	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2164	if (w->attr.st_nlink)
1725	{	2165	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2166	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2167	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2168	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2169	}
1730	else	2170	else
1731	/* you shalt not abuse printf for puts */	2171	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2172	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2173	"if this is windows, they already arrived\n");
1734	}	2174	}
1735		2175
1736	...	2176	...
1737	ev_stat passwd;	2177	ev_stat passwd;
1738		2178
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2179	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2180	ev_stat_start (loop, &passwd);
1741		2181
1742	Example: Like above, but additionally use a one-second delay so we do not	2182	Example: Like above, but additionally use a one-second delay so we do not
1743	miss updates (however, frequent updates will delay processing, too, so	2183	miss updates (however, frequent updates will delay processing, too, so
1744	one might do the work both on C<ev_stat> callback invocation I<and> on	2184	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2185	C<ev_timer> callback invocation).
1746		2186
1747	static ev_stat passwd;	2187	static ev_stat passwd;
1748	static ev_timer timer;	2188	static ev_timer timer;
1749		2189
1750	static void	2190	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2191	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2192	{
1753	ev_timer_stop (EV_A_ w);	2193	ev_timer_stop (EV_A_ w);
1754		2194
1755	/* now it's one second after the most recent passwd change */	2195	/* now it's one second after the most recent passwd change */
1756	}	2196	}
1757		2197
1758	static void	2198	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2199	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2200	{
1761	/* reset the one-second timer */	2201	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2202	ev_timer_again (EV_A_ &timer);
1763	}	2203	}
1764		2204
1765	...	2205	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2206	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2207	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2208	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2209
1770		2210
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2211	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2212
1773	Idle watchers trigger events when no other events of the same or higher	2213	Idle watchers trigger events when no other events of the same or higher
1774	priority are pending (prepare, check and other idle watchers do not	2214	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2215	as receiving "events").
1776		2216
1777	That is, as long as your process is busy handling sockets or timeouts	2217	That is, as long as your process is busy handling sockets or timeouts
1778	(or even signals, imagine) of the same or higher priority it will not be	2218	(or even signals, imagine) of the same or higher priority it will not be
1779	triggered. But when your process is idle (or only lower-priority watchers	2219	triggered. But when your process is idle (or only lower-priority watchers
1780	are pending), the idle watchers are being called once per event loop	2220	are pending), the idle watchers are being called once per event loop
…		…
1791		2231
1792	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1793		2233
1794	=over 4	2234	=over 4
1795		2235
1796	=item ev_idle_init (ev_signal *, callback)	2236	=item ev_idle_init (ev_idle *, callback)
1797		2237
1798	Initialises and configures the idle watcher - it has no parameters of any	2238	Initialises and configures the idle watcher - it has no parameters of any
1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2239	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1800	believe me.	2240	believe me.
1801		2241
…		…
1804	=head3 Examples	2244	=head3 Examples
1805		2245
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2246	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2247	callback, free it. Also, use no error checking, as usual.
1808		2248
1809	static void	2249	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2250	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2251	{
1812	free (w);	2252	free (w);
1813	// now do something you wanted to do when the program has	2253	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2254	// no longer anything immediate to do.
1815	}	2255	}
1816		2256
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2257	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2258	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2259	ev_idle_start (loop, idle_cb);
1820		2260
1821		2261
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2262	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2263
1824	Prepare and check watchers are usually (but not always) used in tandem:	2264	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2265	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2266	afterwards.
1827		2267
1828	You I<must not> call C<ev_loop> or similar functions that enter	2268	You I<must not> call C<ev_loop> or similar functions that enter
1829	the current event loop from either C<ev_prepare> or C<ev_check>	2269	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1832	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2272	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1833	C<ev_check> so if you have one watcher of each kind they will always be	2273	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2274	called in pairs bracketing the blocking call.
1835		2275
1836	Their main purpose is to integrate other event mechanisms into libev and	2276	Their main purpose is to integrate other event mechanisms into libev and
1837	their use is somewhat advanced. This could be used, for example, to track	2277	their use is somewhat advanced. They could be used, for example, to track
1838	variable changes, implement your own watchers, integrate net-snmp or a	2278	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2279	coroutine library and lots more. They are also occasionally useful if
1840	you cache some data and want to flush it before blocking (for example,	2280	you cache some data and want to flush it before blocking (for example,
1841	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2281	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2282	watcher).
1843		2283
1844	This is done by examining in each prepare call which file descriptors need	2284	This is done by examining in each prepare call which file descriptors
1845	to be watched by the other library, registering C<ev_io> watchers for	2285	need to be watched by the other library, registering C<ev_io> watchers
1846	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2286	for them and starting an C<ev_timer> watcher for any timeouts (many
1847	provide just this functionality). Then, in the check watcher you check for	2287	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2288	you check for any events that occurred (by checking the pending status
1849	and stopping them) and call back into the library. The I/O and timer	2289	of all watchers and stopping them) and call back into the library. The
1850	callbacks will never actually be called (but must be valid nevertheless,	2290	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2291	nevertheless, because you never know, you know?).
1852		2292
1853	As another example, the Perl Coro module uses these hooks to integrate	2293	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2294	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2295	during each prepare and only letting the process block if no coroutines
1856	are ready to run (it's actually more complicated: it only runs coroutines	2296	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1859	loop from blocking if lower-priority coroutines are active, thus mapping	2299	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2300	low-priority coroutines to idle/background tasks).
1861		2301
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2302	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1863	priority, to ensure that they are being run before any other watchers	2303	priority, to ensure that they are being run before any other watchers
		2304	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2305
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2306	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1865	too) should not activate ("feed") events into libev. While libev fully	2307	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2308	might get executed before other C<ev_check> watchers did their job. As
1867	did their job. As C<ev_check> watchers are often used to embed other	2309	C<ev_check> watchers are often used to embed other (non-libev) event
1868	(non-libev) event loops those other event loops might be in an unusable	2310	loops those other event loops might be in an unusable state until their
1869	state until their C<ev_check> watcher ran (always remind yourself to	2311	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2312	others).
1871		2313
1872	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1873		2315
1874	=over 4	2316	=over 4
1875		2317
…		…
1877		2319
1878	=item ev_check_init (ev_check *, callback)	2320	=item ev_check_init (ev_check *, callback)
1879		2321
1880	Initialises and configures the prepare or check watcher - they have no	2322	Initialises and configures the prepare or check watcher - they have no
1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2323	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1882	macros, but using them is utterly, utterly and completely pointless.	2324	macros, but using them is utterly, utterly, utterly and completely
		2325	pointless.
1883		2326
1884	=back	2327	=back
1885		2328
1886	=head3 Examples	2329	=head3 Examples
1887		2330
1888	There are a number of principal ways to embed other event loops or modules	2331	There are a number of principal ways to embed other event loops or modules
1889	into libev. Here are some ideas on how to include libadns into libev	2332	into libev. Here are some ideas on how to include libadns into libev
1890	(there is a Perl module named C<EV::ADNS> that does this, which you could	2333	(there is a Perl module named C<EV::ADNS> that does this, which you could
1891	use for an actually working example. Another Perl module named C<EV::Glib>	2334	use as a working example. Another Perl module named C<EV::Glib> embeds a
1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2335	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2336	Glib event loop).
1894		2337
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2338	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1896	and in a check watcher, destroy them and call into libadns. What follows	2339	and in a check watcher, destroy them and call into libadns. What follows
1897	is pseudo-code only of course. This requires you to either use a low	2340	is pseudo-code only of course. This requires you to either use a low
1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2341	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1899	the callbacks for the IO/timeout watchers might not have been called yet.	2342	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2343
1901	static ev_io iow [nfd];	2344	static ev_io iow [nfd];
1902	static ev_timer tw;	2345	static ev_timer tw;
1903		2346
1904	static void	2347	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2348	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2349	{
1907	}	2350	}
1908		2351
1909	// create io watchers for each fd and a timer before blocking	2352	// create io watchers for each fd and a timer before blocking
1910	static void	2353	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2354	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2355	{
1913	int timeout = 3600000;	2356	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2357	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2358	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2360
1918	/* the callback is illegal, but won't be called as we stop during check */	2361	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2362	ev_timer_init (&tw, 0, timeout * 1e-3);
1920	ev_timer_start (loop, &tw);	2363	ev_timer_start (loop, &tw);
1921		2364
1922	// create one ev_io per pollfd	2365	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2366	for (int i = 0; i < nfd; ++i)
1924	{	2367	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2368	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2369	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2370	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2371
1929	fds [i].revents = 0;	2372	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2373	ev_io_start (loop, iow + i);
1931	}	2374	}
1932	}	2375	}
1933		2376
1934	// stop all watchers after blocking	2377	// stop all watchers after blocking
1935	static void	2378	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2379	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2380	{
1938	ev_timer_stop (loop, &tw);	2381	ev_timer_stop (loop, &tw);
1939		2382
1940	for (int i = 0; i < nfd; ++i)	2383	for (int i = 0; i < nfd; ++i)
1941	{	2384	{
1942	// set the relevant poll flags	2385	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2386	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2387	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2388	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2389	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2390	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2391
1949	// now stop the watcher	2392	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2393	ev_io_stop (loop, iow + i);
1951	}	2394	}
1952		2395
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2396	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2397	}
1955		2398
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2399	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1957	in the prepare watcher and would dispose of the check watcher.	2400	in the prepare watcher and would dispose of the check watcher.
1958		2401
1959	Method 3: If the module to be embedded supports explicit event	2402	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2403	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2404	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2405
1963	static void	2406	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2407	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2408	{
1966	adns_state ads = (adns_state)w->data;	2409	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2410	update_now (EV_A);
1968		2411
1969	adns_processtimeouts (ads, &tv_now);	2412	adns_processtimeouts (ads, &tv_now);
1970	}	2413	}
1971		2414
1972	static void	2415	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2416	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2417	{
1975	adns_state ads = (adns_state)w->data;	2418	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2419	update_now (EV_A);
1977		2420
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2421	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2422	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2423	}
1981		2424
1982	// do not ever call adns_afterpoll	2425	// do not ever call adns_afterpoll
1983		2426
1984	Method 4: Do not use a prepare or check watcher because the module you	2427	Method 4: Do not use a prepare or check watcher because the module you
1985	want to embed is too inflexible to support it. Instead, youc na override	2428	want to embed is not flexible enough to support it. Instead, you can
1986	their poll function. The drawback with this solution is that the main	2429	override their poll function. The drawback with this solution is that the
1987	loop is now no longer controllable by EV. The C<Glib::EV> module does	2430	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2431	this approach, effectively embedding EV as a client into the horrible
		2432	libglib event loop.
1989		2433
1990	static gint	2434	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2435	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2436	{
1993	int got_events = 0;	2437	int got_events = 0;
1994		2438
1995	for (n = 0; n < nfds; ++n)	2439	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2440	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2441
1998	if (timeout >= 0)	2442	if (timeout >= 0)
1999	// create/start timer	2443	// create/start timer
2000		2444
2001	// poll	2445	// poll
2002	ev_loop (EV_A_ 0);	2446	ev_loop (EV_A_ 0);
2003		2447
2004	// stop timer again	2448	// stop timer again
2005	if (timeout >= 0)	2449	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2450	ev_timer_stop (EV_A_ &to);
2007		2451
2008	// stop io watchers again - their callbacks should have set	2452	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2453	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2454	ev_io_stop (EV_A_ iow [n]);
2011		2455
2012	return got_events;	2456	return got_events;
2013	}	2457	}
2014		2458
2015		2459
2016	=head2 C<ev_embed> - when one backend isn't enough...	2460	=head2 C<ev_embed> - when one backend isn't enough...
2017		2461
2018	This is a rather advanced watcher type that lets you embed one event loop	2462	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2468	prioritise I/O.
2025		2469
2026	As an example for a bug workaround, the kqueue backend might only support	2470	As an example for a bug workaround, the kqueue backend might only support
2027	sockets on some platform, so it is unusable as generic backend, but you	2471	sockets on some platform, so it is unusable as generic backend, but you
2028	still want to make use of it because you have many sockets and it scales	2472	still want to make use of it because you have many sockets and it scales
2029	so nicely. In this case, you would create a kqueue-based loop and embed it	2473	so nicely. In this case, you would create a kqueue-based loop and embed
2030	into your default loop (which might use e.g. poll). Overall operation will	2474	it into your default loop (which might use e.g. poll). Overall operation
2031	be a bit slower because first libev has to poll and then call kevent, but	2475	will be a bit slower because first libev has to call C<poll> and then
2032	at least you can use both at what they are best.	2476	C<kevent>, but at least you can use both mechanisms for what they are
		2477	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2478
2034	As for prioritising I/O: rarely you have the case where some fds have	2479	As for prioritising I/O: under rare circumstances you have the case where
2035	to be watched and handled very quickly (with low latency), and even	2480	some fds have to be watched and handled very quickly (with low latency),
2036	priorities and idle watchers might have too much overhead. In this case	2481	and even priorities and idle watchers might have too much overhead. In
2037	you would put all the high priority stuff in one loop and all the rest in	2482	this case you would put all the high priority stuff in one loop and all
2038	a second one, and embed the second one in the first.	2483	the rest in a second one, and embed the second one in the first.
2039		2484
2040	As long as the watcher is active, the callback will be invoked every time	2485	As long as the watcher is active, the callback will be invoked every
2041	there might be events pending in the embedded loop. The callback must then	2486	time there might be events pending in the embedded loop. The callback
2042	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2487	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2043	their callbacks (you could also start an idle watcher to give the embedded	2488	sweep and invoke their callbacks (the callback doesn't need to invoke the
2044	loop strictly lower priority for example). You can also set the callback	2489	C<ev_embed_sweep> function directly, it could also start an idle watcher
2045	to C<0>, in which case the embed watcher will automatically execute the	2490	to give the embedded loop strictly lower priority for example).
2046	embedded loop sweep.
2047		2491
2048	As long as the watcher is started it will automatically handle events. The	2492	You can also set the callback to C<0>, in which case the embed watcher
2049	callback will be invoked whenever some events have been handled. You can	2493	will automatically execute the embedded loop sweep whenever necessary.
2050	set the callback to C<0> to avoid having to specify one if you are not
2051	interested in that.
2052		2494
2053	Also, there have not currently been made special provisions for forking:	2495	Fork detection will be handled transparently while the C<ev_embed> watcher
2054	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2496	is active, i.e., the embedded loop will automatically be forked when the
2055	but you will also have to stop and restart any C<ev_embed> watchers	2497	embedding loop forks. In other cases, the user is responsible for calling
2056	yourself.	2498	C<ev_loop_fork> on the embedded loop.
2057		2499
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2500	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2501	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2502	portable one.
2061		2503
2062	So when you want to use this feature you will always have to be prepared	2504	So when you want to use this feature you will always have to be prepared
2063	that you cannot get an embeddable loop. The recommended way to get around	2505	that you cannot get an embeddable loop. The recommended way to get around
2064	this is to have a separate variables for your embeddable loop, try to	2506	this is to have a separate variables for your embeddable loop, try to
2065	create it, and if that fails, use the normal loop for everything.	2507	create it, and if that fails, use the normal loop for everything.
2066		2508
		2509	=head3 C<ev_embed> and fork
		2510
		2511	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2512	automatically be applied to the embedded loop as well, so no special
		2513	fork handling is required in that case. When the watcher is not running,
		2514	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2515	as applicable.
		2516
2067	=head3 Watcher-Specific Functions and Data Members	2517	=head3 Watcher-Specific Functions and Data Members
2068		2518
2069	=over 4	2519	=over 4
2070		2520
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2521	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2524
2075	Configures the watcher to embed the given loop, which must be	2525	Configures the watcher to embed the given loop, which must be
2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2526	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2077	invoked automatically, otherwise it is the responsibility of the callback	2527	invoked automatically, otherwise it is the responsibility of the callback
2078	to invoke it (it will continue to be called until the sweep has been done,	2528	to invoke it (it will continue to be called until the sweep has been done,
2079	if you do not want thta, you need to temporarily stop the embed watcher).	2529	if you do not want that, you need to temporarily stop the embed watcher).
2080		2530
2081	=item ev_embed_sweep (loop, ev_embed *)	2531	=item ev_embed_sweep (loop, ev_embed *)
2082		2532
2083	Make a single, non-blocking sweep over the embedded loop. This works	2533	Make a single, non-blocking sweep over the embedded loop. This works
2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2534	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2535	appropriate way for embedded loops.
2086		2536
2087	=item struct ev_loop *other [read-only]	2537	=item struct ev_loop *other [read-only]
2088		2538
2089	The embedded event loop.	2539	The embedded event loop.
2090		2540
…		…
2092		2542
2093	=head3 Examples	2543	=head3 Examples
2094		2544
2095	Example: Try to get an embeddable event loop and embed it into the default	2545	Example: Try to get an embeddable event loop and embed it into the default
2096	event loop. If that is not possible, use the default loop. The default	2546	event loop. If that is not possible, use the default loop. The default
2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2547	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2548	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2549	used).
2100		2550
2101	struct ev_loop *loop_hi = ev_default_init (0);	2551	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2552	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2553	ev_embed embed;
2104		2554
2105	// see if there is a chance of getting one that works	2555	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2556	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2557	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2558	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2559	: 0;
2110		2560
2111	// if we got one, then embed it, otherwise default to loop_hi	2561	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2562	if (loop_lo)
2113	{	2563	{
2114	ev_embed_init (&embed, 0, loop_lo);	2564	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2565	ev_embed_start (loop_hi, &embed);
2116	}	2566	}
2117	else	2567	else
2118	loop_lo = loop_hi;	2568	loop_lo = loop_hi;
2119		2569
2120	Example: Check if kqueue is available but not recommended and create	2570	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2571	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2572	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2573	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2574
2125	struct ev_loop *loop = ev_default_init (0);	2575	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2576	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2577	ev_embed embed;
2128		2578
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2579	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2580	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2581	{
2132	ev_embed_init (&embed, 0, loop_socket);	2582	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2583	ev_embed_start (loop, &embed);
2134	}	2584	}
2135		2585
2136	if (!loop_socket)	2586	if (!loop_socket)
2137	loop_socket = loop;	2587	loop_socket = loop;
2138		2588
2139	// now use loop_socket for all sockets, and loop for everything else	2589	// now use loop_socket for all sockets, and loop for everything else
2140		2590
2141		2591
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2592	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2593
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2594	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2188	is that the author does not know of a simple (or any) algorithm for a	2638	is that the author does not know of a simple (or any) algorithm for a
2189	multiple-writer-single-reader queue that works in all cases and doesn't	2639	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2640	need elaborate support such as pthreads.
2191		2641
2192	That means that if you want to queue data, you have to provide your own	2642	That means that if you want to queue data, you have to provide your own
2193	queue. But at least I can tell you would implement locking around your	2643	queue. But at least I can tell you how to implement locking around your
2194	queue:	2644	queue:
2195		2645
2196	=over 4	2646	=over 4
2197		2647
2198	=item queueing from a signal handler context	2648	=item queueing from a signal handler context
2199		2649
2200	To implement race-free queueing, you simply add to the queue in the signal	2650	To implement race-free queueing, you simply add to the queue in the signal
2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2651	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2652	an example that does that for some fictitious SIGUSR1 handler:
2203		2653
2204	static ev_async mysig;	2654	static ev_async mysig;
2205		2655
2206	static void	2656	static void
2207	sigusr1_handler (void)	2657	sigusr1_handler (void)
…		…
2273	=over 4	2723	=over 4
2274		2724
2275	=item ev_async_init (ev_async *, callback)	2725	=item ev_async_init (ev_async *, callback)
2276		2726
2277	Initialises and configures the async watcher - it has no parameters of any	2727	Initialises and configures the async watcher - it has no parameters of any
2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2728	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2279	believe me.	2729	trust me.
2280		2730
2281	=item ev_async_send (loop, ev_async *)	2731	=item ev_async_send (loop, ev_async *)
2282		2732
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2733	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2734	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2285	C<ev_feed_event>, this call is safe to do in other threads, signal or	2735	C<ev_feed_event>, this call is safe to do from other threads, signal or
2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2736	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	2737	section below on what exactly this means).
2288		2738
		2739	Note that, as with other watchers in libev, multiple events might get
		2740	compressed into a single callback invocation (another way to look at this
		2741	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2742	reset when the event loop detects that).
		2743
2289	This call incurs the overhead of a syscall only once per loop iteration,	2744	This call incurs the overhead of a system call only once per event loop
2290	so while the overhead might be noticable, it doesn't apply to repeated	2745	iteration, so while the overhead might be noticeable, it doesn't apply to
2291	calls to C<ev_async_send>.	2746	repeated calls to C<ev_async_send> for the same event loop.
		2747
		2748	=item bool = ev_async_pending (ev_async *)
		2749
		2750	Returns a non-zero value when C<ev_async_send> has been called on the
		2751	watcher but the event has not yet been processed (or even noted) by the
		2752	event loop.
		2753
		2754	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2755	the loop iterates next and checks for the watcher to have become active,
		2756	it will reset the flag again. C<ev_async_pending> can be used to very
		2757	quickly check whether invoking the loop might be a good idea.
		2758
		2759	Not that this does I<not> check whether the watcher itself is pending,
		2760	only whether it has been requested to make this watcher pending: there
		2761	is a time window between the event loop checking and resetting the async
		2762	notification, and the callback being invoked.
2292		2763
2293	=back	2764	=back
2294		2765
2295		2766
2296	=head1 OTHER FUNCTIONS	2767	=head1 OTHER FUNCTIONS
…		…
2300	=over 4	2771	=over 4
2301		2772
2302	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2773	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2303		2774
2304	This function combines a simple timer and an I/O watcher, calls your	2775	This function combines a simple timer and an I/O watcher, calls your
2305	callback on whichever event happens first and automatically stop both	2776	callback on whichever event happens first and automatically stops both
2306	watchers. This is useful if you want to wait for a single event on an fd	2777	watchers. This is useful if you want to wait for a single event on an fd
2307	or timeout without having to allocate/configure/start/stop/free one or	2778	or timeout without having to allocate/configure/start/stop/free one or
2308	more watchers yourself.	2779	more watchers yourself.
2309		2780
2310	If C<fd> is less than 0, then no I/O watcher will be started and events	2781	If C<fd> is less than 0, then no I/O watcher will be started and the
2311	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2782	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2312	C<events> set will be craeted and started.	2783	the given C<fd> and C<events> set will be created and started.
2313		2784
2314	If C<timeout> is less than 0, then no timeout watcher will be	2785	If C<timeout> is less than 0, then no timeout watcher will be
2315	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2786	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2316	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2787	repeat = 0) will be started. C<0> is a valid timeout.
2317	dubious value.
2318		2788
2319	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2789	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2320	passed an C<revents> set like normal event callbacks (a combination of	2790	passed an C<revents> set like normal event callbacks (a combination of
2321	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2791	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2322	value passed to C<ev_once>:	2792	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2793	a timeout and an io event at the same time - you probably should give io
		2794	events precedence.
2323		2795
		2796	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2797
2324	static void stdin_ready (int revents, void *arg)	2798	static void stdin_ready (int revents, void *arg)
2325	{	2799	{
2326	if (revents & EV_TIMEOUT)
2327	/* doh, nothing entered */;
2328	else if (revents & EV_READ)	2800	if (revents & EV_READ)
2329	/* stdin might have data for us, joy! */;	2801	/* stdin might have data for us, joy! */;
		2802	else if (revents & EV_TIMEOUT)
		2803	/* doh, nothing entered */;
2330	}	2804	}
2331		2805
2332	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2806	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2333		2807
2334	=item ev_feed_event (ev_loop *, watcher *, int revents)	2808	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2335		2809
2336	Feeds the given event set into the event loop, as if the specified event	2810	Feeds the given event set into the event loop, as if the specified event
2337	had happened for the specified watcher (which must be a pointer to an	2811	had happened for the specified watcher (which must be a pointer to an
2338	initialised but not necessarily started event watcher).	2812	initialised but not necessarily started event watcher).
2339		2813
2340	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2814	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2341		2815
2342	Feed an event on the given fd, as if a file descriptor backend detected	2816	Feed an event on the given fd, as if a file descriptor backend detected
2343	the given events it.	2817	the given events it.
2344		2818
2345	=item ev_feed_signal_event (ev_loop *loop, int signum)	2819	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2346		2820
2347	Feed an event as if the given signal occured (C<loop> must be the default	2821	Feed an event as if the given signal occurred (C<loop> must be the default
2348	loop!).	2822	loop!).
2349		2823
2350	=back	2824	=back
2351		2825
2352		2826
…		…
2368		2842
2369	=item * Priorities are not currently supported. Initialising priorities	2843	=item * Priorities are not currently supported. Initialising priorities
2370	will fail and all watchers will have the same priority, even though there	2844	will fail and all watchers will have the same priority, even though there
2371	is an ev_pri field.	2845	is an ev_pri field.
2372		2846
		2847	=item * In libevent, the last base created gets the signals, in libev, the
		2848	first base created (== the default loop) gets the signals.
		2849
2373	=item * Other members are not supported.	2850	=item * Other members are not supported.
2374		2851
2375	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2852	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2376	to use the libev header file and library.	2853	to use the libev header file and library.
2377		2854
2378	=back	2855	=back
2379		2856
2380	=head1 C++ SUPPORT	2857	=head1 C++ SUPPORT
2381		2858
2382	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2859	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2383	you to use some convinience methods to start/stop watchers and also change	2860	you to use some convenience methods to start/stop watchers and also change
2384	the callback model to a model using method callbacks on objects.	2861	the callback model to a model using method callbacks on objects.
2385		2862
2386	To use it,	2863	To use it,
2387		2864
2388	#include <ev++.h>	2865	#include <ev++.h>
2389		2866
2390	This automatically includes F<ev.h> and puts all of its definitions (many	2867	This automatically includes F<ev.h> and puts all of its definitions (many
2391	of them macros) into the global namespace. All C++ specific things are	2868	of them macros) into the global namespace. All C++ specific things are
2392	put into the C<ev> namespace. It should support all the same embedding	2869	put into the C<ev> namespace. It should support all the same embedding
2393	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2870	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2460	your compiler is good :), then the method will be fully inlined into the	2937	your compiler is good :), then the method will be fully inlined into the
2461	thunking function, making it as fast as a direct C callback.	2938	thunking function, making it as fast as a direct C callback.
2462		2939
2463	Example: simple class declaration and watcher initialisation	2940	Example: simple class declaration and watcher initialisation
2464		2941
2465	struct myclass	2942	struct myclass
2466	{	2943	{
2467	void io_cb (ev::io &w, int revents) { }	2944	void io_cb (ev::io &w, int revents) { }
2468	}	2945	}
2469		2946
2470	myclass obj;	2947	myclass obj;
2471	ev::io iow;	2948	ev::io iow;
2472	iow.set <myclass, &myclass::io_cb> (&obj);	2949	iow.set <myclass, &myclass::io_cb> (&obj);
		2950
		2951	=item w->set (object *)
		2952
		2953	This is an B<experimental> feature that might go away in a future version.
		2954
		2955	This is a variation of a method callback - leaving out the method to call
		2956	will default the method to C<operator ()>, which makes it possible to use
		2957	functor objects without having to manually specify the C<operator ()> all
		2958	the time. Incidentally, you can then also leave out the template argument
		2959	list.
		2960
		2961	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2962	int revents)>.
		2963
		2964	See the method-C<set> above for more details.
		2965
		2966	Example: use a functor object as callback.
		2967
		2968	struct myfunctor
		2969	{
		2970	void operator() (ev::io &w, int revents)
		2971	{
		2972	...
		2973	}
		2974	}
		2975
		2976	myfunctor f;
		2977
		2978	ev::io w;
		2979	w.set (&f);
2473		2980
2474	=item w->set<function> (void *data = 0)	2981	=item w->set<function> (void *data = 0)
2475		2982
2476	Also sets a callback, but uses a static method or plain function as	2983	Also sets a callback, but uses a static method or plain function as
2477	callback. The optional C<data> argument will be stored in the watcher's	2984	callback. The optional C<data> argument will be stored in the watcher's
…		…
2479		2986
2480	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2987	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2481		2988
2482	See the method-C<set> above for more details.	2989	See the method-C<set> above for more details.
2483		2990
2484	Example:	2991	Example: Use a plain function as callback.
2485		2992
2486	static void io_cb (ev::io &w, int revents) { }	2993	static void io_cb (ev::io &w, int revents) { }
2487	iow.set <io_cb> ();	2994	iow.set <io_cb> ();
2488		2995
2489	=item w->set (struct ev_loop *)	2996	=item w->set (struct ev_loop *)
2490		2997
2491	Associates a different C<struct ev_loop> with this watcher. You can only	2998	Associates a different C<struct ev_loop> with this watcher. You can only
2492	do this when the watcher is inactive (and not pending either).	2999	do this when the watcher is inactive (and not pending either).
2493		3000
2494	=item w->set ([args])	3001	=item w->set ([arguments])
2495		3002
2496	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3003	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2497	called at least once. Unlike the C counterpart, an active watcher gets	3004	called at least once. Unlike the C counterpart, an active watcher gets
2498	automatically stopped and restarted when reconfiguring it with this	3005	automatically stopped and restarted when reconfiguring it with this
2499	method.	3006	method.
2500		3007
2501	=item w->start ()	3008	=item w->start ()
…		…
2525	=back	3032	=back
2526		3033
2527	Example: Define a class with an IO and idle watcher, start one of them in	3034	Example: Define a class with an IO and idle watcher, start one of them in
2528	the constructor.	3035	the constructor.
2529		3036
2530	class myclass	3037	class myclass
2531	{	3038	{
2532	ev::io io; void io_cb (ev::io &w, int revents);	3039	ev::io io ; void io_cb (ev::io &w, int revents);
2533	ev:idle idle void idle_cb (ev::idle &w, int revents);	3040	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2534		3041
2535	myclass (int fd)	3042	myclass (int fd)
2536	{	3043	{
2537	io .set <myclass, &myclass::io_cb > (this);	3044	io .set <myclass, &myclass::io_cb > (this);
2538	idle.set <myclass, &myclass::idle_cb> (this);	3045	idle.set <myclass, &myclass::idle_cb> (this);
2539		3046
2540	io.start (fd, ev::READ);	3047	io.start (fd, ev::READ);
2541	}	3048	}
2542	};	3049	};
2543		3050
2544		3051
2545	=head1 OTHER LANGUAGE BINDINGS	3052	=head1 OTHER LANGUAGE BINDINGS
2546		3053
2547	Libev does not offer other language bindings itself, but bindings for a	3054	Libev does not offer other language bindings itself, but bindings for a
2548	numbe rof languages exist in the form of third-party packages. If you know	3055	number of languages exist in the form of third-party packages. If you know
2549	any interesting language binding in addition to the ones listed here, drop	3056	any interesting language binding in addition to the ones listed here, drop
2550	me a note.	3057	me a note.
2551		3058
2552	=over 4	3059	=over 4
2553		3060
2554	=item Perl	3061	=item Perl
2555		3062
2556	The EV module implements the full libev API and is actually used to test	3063	The EV module implements the full libev API and is actually used to test
2557	libev. EV is developed together with libev. Apart from the EV core module,	3064	libev. EV is developed together with libev. Apart from the EV core module,
2558	there are additional modules that implement libev-compatible interfaces	3065	there are additional modules that implement libev-compatible interfaces
2559	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3066	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2560	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3067	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3068	and C<EV::Glib>).
2561		3069
2562	It can be found and installed via CPAN, its homepage is found at	3070	It can be found and installed via CPAN, its homepage is at
2563	L<http://software.schmorp.de/pkg/EV>.	3071	L<http://software.schmorp.de/pkg/EV>.
2564		3072
		3073	=item Python
		3074
		3075	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3076	seems to be quite complete and well-documented.
		3077
2565	=item Ruby	3078	=item Ruby
2566		3079
2567	Tony Arcieri has written a ruby extension that offers access to a subset	3080	Tony Arcieri has written a ruby extension that offers access to a subset
2568	of the libev API and adds filehandle abstractions, asynchronous DNS and	3081	of the libev API and adds file handle abstractions, asynchronous DNS and
2569	more on top of it. It can be found via gem servers. Its homepage is at	3082	more on top of it. It can be found via gem servers. Its homepage is at
2570	L<http://rev.rubyforge.org/>.	3083	L<http://rev.rubyforge.org/>.
2571		3084
		3085	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3086	makes rev work even on mingw.
		3087
		3088	=item Haskell
		3089
		3090	A haskell binding to libev is available at
		3091	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3092
2572	=item D	3093	=item D
2573		3094
2574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3095	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2575	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3096	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3097
		3098	=item Ocaml
		3099
		3100	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3101	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2576		3102
2577	=back	3103	=back
2578		3104
2579		3105
2580	=head1 MACRO MAGIC	3106	=head1 MACRO MAGIC
2581		3107
2582	Libev can be compiled with a variety of options, the most fundamantal	3108	Libev can be compiled with a variety of options, the most fundamental
2583	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3109	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2584	functions and callbacks have an initial C<struct ev_loop *> argument.	3110	functions and callbacks have an initial C<struct ev_loop *> argument.
2585		3111
2586	To make it easier to write programs that cope with either variant, the	3112	To make it easier to write programs that cope with either variant, the
2587	following macros are defined:	3113	following macros are defined:
…		…
2592		3118
2593	This provides the loop I<argument> for functions, if one is required ("ev	3119	This provides the loop I<argument> for functions, if one is required ("ev
2594	loop argument"). The C<EV_A> form is used when this is the sole argument,	3120	loop argument"). The C<EV_A> form is used when this is the sole argument,
2595	C<EV_A_> is used when other arguments are following. Example:	3121	C<EV_A_> is used when other arguments are following. Example:
2596		3122
2597	ev_unref (EV_A);	3123	ev_unref (EV_A);
2598	ev_timer_add (EV_A_ watcher);	3124	ev_timer_add (EV_A_ watcher);
2599	ev_loop (EV_A_ 0);	3125	ev_loop (EV_A_ 0);
2600		3126
2601	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3127	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2602	which is often provided by the following macro.	3128	which is often provided by the following macro.
2603		3129
2604	=item C<EV_P>, C<EV_P_>	3130	=item C<EV_P>, C<EV_P_>
2605		3131
2606	This provides the loop I<parameter> for functions, if one is required ("ev	3132	This provides the loop I<parameter> for functions, if one is required ("ev
2607	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3133	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2608	C<EV_P_> is used when other parameters are following. Example:	3134	C<EV_P_> is used when other parameters are following. Example:
2609		3135
2610	// this is how ev_unref is being declared	3136	// this is how ev_unref is being declared
2611	static void ev_unref (EV_P);	3137	static void ev_unref (EV_P);
2612		3138
2613	// this is how you can declare your typical callback	3139	// this is how you can declare your typical callback
2614	static void cb (EV_P_ ev_timer *w, int revents)	3140	static void cb (EV_P_ ev_timer *w, int revents)
2615		3141
2616	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3142	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2617	suitable for use with C<EV_A>.	3143	suitable for use with C<EV_A>.
2618		3144
2619	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3145	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2620		3146
2621	Similar to the other two macros, this gives you the value of the default	3147	Similar to the other two macros, this gives you the value of the default
2622	loop, if multiple loops are supported ("ev loop default").	3148	loop, if multiple loops are supported ("ev loop default").
		3149
		3150	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3151
		3152	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3153	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3154	is undefined when the default loop has not been initialised by a previous
		3155	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3156
		3157	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3158	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2623		3159
2624	=back	3160	=back
2625		3161
2626	Example: Declare and initialise a check watcher, utilising the above	3162	Example: Declare and initialise a check watcher, utilising the above
2627	macros so it will work regardless of whether multiple loops are supported	3163	macros so it will work regardless of whether multiple loops are supported
2628	or not.	3164	or not.
2629		3165
2630	static void	3166	static void
2631	check_cb (EV_P_ ev_timer *w, int revents)	3167	check_cb (EV_P_ ev_timer *w, int revents)
2632	{	3168	{
2633	ev_check_stop (EV_A_ w);	3169	ev_check_stop (EV_A_ w);
2634	}	3170	}
2635		3171
2636	ev_check check;	3172	ev_check check;
2637	ev_check_init (&check, check_cb);	3173	ev_check_init (&check, check_cb);
2638	ev_check_start (EV_DEFAULT_ &check);	3174	ev_check_start (EV_DEFAULT_ &check);
2639	ev_loop (EV_DEFAULT_ 0);	3175	ev_loop (EV_DEFAULT_ 0);
2640		3176
2641	=head1 EMBEDDING	3177	=head1 EMBEDDING
2642		3178
2643	Libev can (and often is) directly embedded into host	3179	Libev can (and often is) directly embedded into host
2644	applications. Examples of applications that embed it include the Deliantra	3180	applications. Examples of applications that embed it include the Deliantra
…		…
2651	libev somewhere in your source tree).	3187	libev somewhere in your source tree).
2652		3188
2653	=head2 FILESETS	3189	=head2 FILESETS
2654		3190
2655	Depending on what features you need you need to include one or more sets of files	3191	Depending on what features you need you need to include one or more sets of files
2656	in your app.	3192	in your application.
2657		3193
2658	=head3 CORE EVENT LOOP	3194	=head3 CORE EVENT LOOP
2659		3195
2660	To include only the libev core (all the C<ev_*> functions), with manual	3196	To include only the libev core (all the C<ev_*> functions), with manual
2661	configuration (no autoconf):	3197	configuration (no autoconf):
2662		3198
2663	#define EV_STANDALONE 1	3199	#define EV_STANDALONE 1
2664	#include "ev.c"	3200	#include "ev.c"
2665		3201
2666	This will automatically include F<ev.h>, too, and should be done in a	3202	This will automatically include F<ev.h>, too, and should be done in a
2667	single C source file only to provide the function implementations. To use	3203	single C source file only to provide the function implementations. To use
2668	it, do the same for F<ev.h> in all files wishing to use this API (best	3204	it, do the same for F<ev.h> in all files wishing to use this API (best
2669	done by writing a wrapper around F<ev.h> that you can include instead and	3205	done by writing a wrapper around F<ev.h> that you can include instead and
2670	where you can put other configuration options):	3206	where you can put other configuration options):
2671		3207
2672	#define EV_STANDALONE 1	3208	#define EV_STANDALONE 1
2673	#include "ev.h"	3209	#include "ev.h"
2674		3210
2675	Both header files and implementation files can be compiled with a C++	3211	Both header files and implementation files can be compiled with a C++
2676	compiler (at least, thats a stated goal, and breakage will be treated	3212	compiler (at least, that's a stated goal, and breakage will be treated
2677	as a bug).	3213	as a bug).
2678		3214
2679	You need the following files in your source tree, or in a directory	3215	You need the following files in your source tree, or in a directory
2680	in your include path (e.g. in libev/ when using -Ilibev):	3216	in your include path (e.g. in libev/ when using -Ilibev):
2681		3217
2682	ev.h	3218	ev.h
2683	ev.c	3219	ev.c
2684	ev_vars.h	3220	ev_vars.h
2685	ev_wrap.h	3221	ev_wrap.h
2686		3222
2687	ev_win32.c required on win32 platforms only	3223	ev_win32.c required on win32 platforms only
2688		3224
2689	ev_select.c only when select backend is enabled (which is enabled by default)	3225	ev_select.c only when select backend is enabled (which is enabled by default)
2690	ev_poll.c only when poll backend is enabled (disabled by default)	3226	ev_poll.c only when poll backend is enabled (disabled by default)
2691	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3227	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2692	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3228	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2693	ev_port.c only when the solaris port backend is enabled (disabled by default)	3229	ev_port.c only when the solaris port backend is enabled (disabled by default)
2694		3230
2695	F<ev.c> includes the backend files directly when enabled, so you only need	3231	F<ev.c> includes the backend files directly when enabled, so you only need
2696	to compile this single file.	3232	to compile this single file.
2697		3233
2698	=head3 LIBEVENT COMPATIBILITY API	3234	=head3 LIBEVENT COMPATIBILITY API
2699		3235
2700	To include the libevent compatibility API, also include:	3236	To include the libevent compatibility API, also include:
2701		3237
2702	#include "event.c"	3238	#include "event.c"
2703		3239
2704	in the file including F<ev.c>, and:	3240	in the file including F<ev.c>, and:
2705		3241
2706	#include "event.h"	3242	#include "event.h"
2707		3243
2708	in the files that want to use the libevent API. This also includes F<ev.h>.	3244	in the files that want to use the libevent API. This also includes F<ev.h>.
2709		3245
2710	You need the following additional files for this:	3246	You need the following additional files for this:
2711		3247
2712	event.h	3248	event.h
2713	event.c	3249	event.c
2714		3250
2715	=head3 AUTOCONF SUPPORT	3251	=head3 AUTOCONF SUPPORT
2716		3252
2717	Instead of using C<EV_STANDALONE=1> and providing your config in	3253	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2718	whatever way you want, you can also C<m4_include([libev.m4])> in your	3254	whatever way you want, you can also C<m4_include([libev.m4])> in your
2719	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3255	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2720	include F<config.h> and configure itself accordingly.	3256	include F<config.h> and configure itself accordingly.
2721		3257
2722	For this of course you need the m4 file:	3258	For this of course you need the m4 file:
2723		3259
2724	libev.m4	3260	libev.m4
2725		3261
2726	=head2 PREPROCESSOR SYMBOLS/MACROS	3262	=head2 PREPROCESSOR SYMBOLS/MACROS
2727		3263
2728	Libev can be configured via a variety of preprocessor symbols you have to define	3264	Libev can be configured via a variety of preprocessor symbols you have to
2729	before including any of its files. The default is not to build for multiplicity	3265	define before including any of its files. The default in the absence of
2730	and only include the select backend.	3266	autoconf is documented for every option.
2731		3267
2732	=over 4	3268	=over 4
2733		3269
2734	=item EV_STANDALONE	3270	=item EV_STANDALONE
2735		3271
…		…
2737	keeps libev from including F<config.h>, and it also defines dummy	3273	keeps libev from including F<config.h>, and it also defines dummy
2738	implementations for some libevent functions (such as logging, which is not	3274	implementations for some libevent functions (such as logging, which is not
2739	supported). It will also not define any of the structs usually found in	3275	supported). It will also not define any of the structs usually found in
2740	F<event.h> that are not directly supported by the libev core alone.	3276	F<event.h> that are not directly supported by the libev core alone.
2741		3277
		3278	In stanbdalone mode, libev will still try to automatically deduce the
		3279	configuration, but has to be more conservative.
		3280
2742	=item EV_USE_MONOTONIC	3281	=item EV_USE_MONOTONIC
2743		3282
2744	If defined to be C<1>, libev will try to detect the availability of the	3283	If defined to be C<1>, libev will try to detect the availability of the
2745	monotonic clock option at both compiletime and runtime. Otherwise no use	3284	monotonic clock option at both compile time and runtime. Otherwise no
2746	of the monotonic clock option will be attempted. If you enable this, you	3285	use of the monotonic clock option will be attempted. If you enable this,
2747	usually have to link against librt or something similar. Enabling it when	3286	you usually have to link against librt or something similar. Enabling it
2748	the functionality isn't available is safe, though, although you have	3287	when the functionality isn't available is safe, though, although you have
2749	to make sure you link against any libraries where the C<clock_gettime>	3288	to make sure you link against any libraries where the C<clock_gettime>
2750	function is hiding in (often F<-lrt>).	3289	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2751		3290
2752	=item EV_USE_REALTIME	3291	=item EV_USE_REALTIME
2753		3292
2754	If defined to be C<1>, libev will try to detect the availability of the	3293	If defined to be C<1>, libev will try to detect the availability of the
2755	realtime clock option at compiletime (and assume its availability at	3294	real-time clock option at compile time (and assume its availability
2756	runtime if successful). Otherwise no use of the realtime clock option will	3295	at runtime if successful). Otherwise no use of the real-time clock
2757	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3296	option will be attempted. This effectively replaces C<gettimeofday>
2758	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3297	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2759	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3298	correctness. See the note about libraries in the description of
		3299	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3300	C<EV_USE_CLOCK_SYSCALL>.
		3301
		3302	=item EV_USE_CLOCK_SYSCALL
		3303
		3304	If defined to be C<1>, libev will try to use a direct syscall instead
		3305	of calling the system-provided C<clock_gettime> function. This option
		3306	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3307	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3308	programs needlessly. Using a direct syscall is slightly slower (in
		3309	theory), because no optimised vdso implementation can be used, but avoids
		3310	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3311	higher, as it simplifies linking (no need for C<-lrt>).
2760		3312
2761	=item EV_USE_NANOSLEEP	3313	=item EV_USE_NANOSLEEP
2762		3314
2763	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3315	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2764	and will use it for delays. Otherwise it will use C<select ()>.	3316	and will use it for delays. Otherwise it will use C<select ()>.
2765		3317
		3318	=item EV_USE_EVENTFD
		3319
		3320	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3321	available and will probe for kernel support at runtime. This will improve
		3322	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3323	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3324	2.7 or newer, otherwise disabled.
		3325
2766	=item EV_USE_SELECT	3326	=item EV_USE_SELECT
2767		3327
2768	If undefined or defined to be C<1>, libev will compile in support for the	3328	If undefined or defined to be C<1>, libev will compile in support for the
2769	C<select>(2) backend. No attempt at autodetection will be done: if no	3329	C<select>(2) backend. No attempt at auto-detection will be done: if no
2770	other method takes over, select will be it. Otherwise the select backend	3330	other method takes over, select will be it. Otherwise the select backend
2771	will not be compiled in.	3331	will not be compiled in.
2772		3332
2773	=item EV_SELECT_USE_FD_SET	3333	=item EV_SELECT_USE_FD_SET
2774		3334
2775	If defined to C<1>, then the select backend will use the system C<fd_set>	3335	If defined to C<1>, then the select backend will use the system C<fd_set>
2776	structure. This is useful if libev doesn't compile due to a missing	3336	structure. This is useful if libev doesn't compile due to a missing
2777	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3337	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2778	exotic systems. This usually limits the range of file descriptors to some	3338	on exotic systems. This usually limits the range of file descriptors to
2779	low limit such as 1024 or might have other limitations (winsocket only	3339	some low limit such as 1024 or might have other limitations (winsocket
2780	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3340	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2781	influence the size of the C<fd_set> used.	3341	configures the maximum size of the C<fd_set>.
2782		3342
2783	=item EV_SELECT_IS_WINSOCKET	3343	=item EV_SELECT_IS_WINSOCKET
2784		3344
2785	When defined to C<1>, the select backend will assume that	3345	When defined to C<1>, the select backend will assume that
2786	select/socket/connect etc. don't understand file descriptors but	3346	select/socket/connect etc. don't understand file descriptors but
…		…
2806		3366
2807	=item EV_USE_EPOLL	3367	=item EV_USE_EPOLL
2808		3368
2809	If defined to be C<1>, libev will compile in support for the Linux	3369	If defined to be C<1>, libev will compile in support for the Linux
2810	C<epoll>(7) backend. Its availability will be detected at runtime,	3370	C<epoll>(7) backend. Its availability will be detected at runtime,
2811	otherwise another method will be used as fallback. This is the	3371	otherwise another method will be used as fallback. This is the preferred
2812	preferred backend for GNU/Linux systems.	3372	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3373	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2813		3374
2814	=item EV_USE_KQUEUE	3375	=item EV_USE_KQUEUE
2815		3376
2816	If defined to be C<1>, libev will compile in support for the BSD style	3377	If defined to be C<1>, libev will compile in support for the BSD style
2817	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3378	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2830	otherwise another method will be used as fallback. This is the preferred	3391	otherwise another method will be used as fallback. This is the preferred
2831	backend for Solaris 10 systems.	3392	backend for Solaris 10 systems.
2832		3393
2833	=item EV_USE_DEVPOLL	3394	=item EV_USE_DEVPOLL
2834		3395
2835	reserved for future expansion, works like the USE symbols above.	3396	Reserved for future expansion, works like the USE symbols above.
2836		3397
2837	=item EV_USE_INOTIFY	3398	=item EV_USE_INOTIFY
2838		3399
2839	If defined to be C<1>, libev will compile in support for the Linux inotify	3400	If defined to be C<1>, libev will compile in support for the Linux inotify
2840	interface to speed up C<ev_stat> watchers. Its actual availability will	3401	interface to speed up C<ev_stat> watchers. Its actual availability will
2841	be detected at runtime.	3402	be detected at runtime. If undefined, it will be enabled if the headers
		3403	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2842		3404
2843	=item EV_ATOMIC_T	3405	=item EV_ATOMIC_T
2844		3406
2845	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3407	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2846	access is atomic with respect to other threads or signal contexts. No such	3408	access is atomic with respect to other threads or signal contexts. No such
2847	type is easily found in the C language, so you can provide your own type	3409	type is easily found in the C language, so you can provide your own type
2848	that you know is safe for your purposes. It is used both for signal handler "locking"	3410	that you know is safe for your purposes. It is used both for signal handler "locking"
2849	as well as for signal and thread safety in C<ev_async> watchers.	3411	as well as for signal and thread safety in C<ev_async> watchers.
2850		3412
2851	In the absense of this define, libev will use C<sig_atomic_t volatile>	3413	In the absence of this define, libev will use C<sig_atomic_t volatile>
2852	(from F<signal.h>), which is usually good enough on most platforms.	3414	(from F<signal.h>), which is usually good enough on most platforms.
2853		3415
2854	=item EV_H	3416	=item EV_H
2855		3417
2856	The name of the F<ev.h> header file used to include it. The default if	3418	The name of the F<ev.h> header file used to include it. The default if
…		…
2895	When doing priority-based operations, libev usually has to linearly search	3457	When doing priority-based operations, libev usually has to linearly search
2896	all the priorities, so having many of them (hundreds) uses a lot of space	3458	all the priorities, so having many of them (hundreds) uses a lot of space
2897	and time, so using the defaults of five priorities (-2 .. +2) is usually	3459	and time, so using the defaults of five priorities (-2 .. +2) is usually
2898	fine.	3460	fine.
2899		3461
2900	If your embedding app does not need any priorities, defining these both to	3462	If your embedding application does not need any priorities, defining these
2901	C<0> will save some memory and cpu.	3463	both to C<0> will save some memory and CPU.
2902		3464
2903	=item EV_PERIODIC_ENABLE	3465	=item EV_PERIODIC_ENABLE
2904		3466
2905	If undefined or defined to be C<1>, then periodic timers are supported. If	3467	If undefined or defined to be C<1>, then periodic timers are supported. If
2906	defined to be C<0>, then they are not. Disabling them saves a few kB of	3468	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2913	code.	3475	code.
2914		3476
2915	=item EV_EMBED_ENABLE	3477	=item EV_EMBED_ENABLE
2916		3478
2917	If undefined or defined to be C<1>, then embed watchers are supported. If	3479	If undefined or defined to be C<1>, then embed watchers are supported. If
2918	defined to be C<0>, then they are not.	3480	defined to be C<0>, then they are not. Embed watchers rely on most other
		3481	watcher types, which therefore must not be disabled.
2919		3482
2920	=item EV_STAT_ENABLE	3483	=item EV_STAT_ENABLE
2921		3484
2922	If undefined or defined to be C<1>, then stat watchers are supported. If	3485	If undefined or defined to be C<1>, then stat watchers are supported. If
2923	defined to be C<0>, then they are not.	3486	defined to be C<0>, then they are not.
…		…
2933	defined to be C<0>, then they are not.	3496	defined to be C<0>, then they are not.
2934		3497
2935	=item EV_MINIMAL	3498	=item EV_MINIMAL
2936		3499
2937	If you need to shave off some kilobytes of code at the expense of some	3500	If you need to shave off some kilobytes of code at the expense of some
2938	speed, define this symbol to C<1>. Currently only used for gcc to override	3501	speed, define this symbol to C<1>. Currently this is used to override some
2939	some inlining decisions, saves roughly 30% codesize of amd64.	3502	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3503	much smaller 2-heap for timer management over the default 4-heap.
2940		3504
2941	=item EV_PID_HASHSIZE	3505	=item EV_PID_HASHSIZE
2942		3506
2943	C<ev_child> watchers use a small hash table to distribute workload by	3507	C<ev_child> watchers use a small hash table to distribute workload by
2944	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3508	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2951	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3515	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2952	usually more than enough. If you need to manage thousands of C<ev_stat>	3516	usually more than enough. If you need to manage thousands of C<ev_stat>
2953	watchers you might want to increase this value (I<must> be a power of	3517	watchers you might want to increase this value (I<must> be a power of
2954	two).	3518	two).
2955		3519
		3520	=item EV_USE_4HEAP
		3521
		3522	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3523	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3524	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3525	faster performance with many (thousands) of watchers.
		3526
		3527	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3528	(disabled).
		3529
		3530	=item EV_HEAP_CACHE_AT
		3531
		3532	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3533	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3534	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3535	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3536	but avoids random read accesses on heap changes. This improves performance
		3537	noticeably with many (hundreds) of watchers.
		3538
		3539	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3540	(disabled).
		3541
		3542	=item EV_VERIFY
		3543
		3544	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3545	be done: If set to C<0>, no internal verification code will be compiled
		3546	in. If set to C<1>, then verification code will be compiled in, but not
		3547	called. If set to C<2>, then the internal verification code will be
		3548	called once per loop, which can slow down libev. If set to C<3>, then the
		3549	verification code will be called very frequently, which will slow down
		3550	libev considerably.
		3551
		3552	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3553	C<0>.
		3554
2956	=item EV_COMMON	3555	=item EV_COMMON
2957		3556
2958	By default, all watchers have a C<void *data> member. By redefining	3557	By default, all watchers have a C<void *data> member. By redefining
2959	this macro to a something else you can include more and other types of	3558	this macro to a something else you can include more and other types of
2960	members. You have to define it each time you include one of the files,	3559	members. You have to define it each time you include one of the files,
2961	though, and it must be identical each time.	3560	though, and it must be identical each time.
2962		3561
2963	For example, the perl EV module uses something like this:	3562	For example, the perl EV module uses something like this:
2964		3563
2965	#define EV_COMMON \	3564	#define EV_COMMON \
2966	SV *self; /* contains this struct */ \	3565	SV *self; /* contains this struct */ \
2967	SV *cb_sv, *fh /* note no trailing ";" */	3566	SV *cb_sv, *fh /* note no trailing ";" */
2968		3567
2969	=item EV_CB_DECLARE (type)	3568	=item EV_CB_DECLARE (type)
2970		3569
2971	=item EV_CB_INVOKE (watcher, revents)	3570	=item EV_CB_INVOKE (watcher, revents)
2972		3571
…		…
2977	definition and a statement, respectively. See the F<ev.h> header file for	3576	definition and a statement, respectively. See the F<ev.h> header file for
2978	their default definitions. One possible use for overriding these is to	3577	their default definitions. One possible use for overriding these is to
2979	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3578	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2980	method calls instead of plain function calls in C++.	3579	method calls instead of plain function calls in C++.
2981		3580
		3581	=back
		3582
2982	=head2 EXPORTED API SYMBOLS	3583	=head2 EXPORTED API SYMBOLS
2983		3584
2984	If you need to re-export the API (e.g. via a dll) and you need a list of	3585	If you need to re-export the API (e.g. via a DLL) and you need a list of
2985	exported symbols, you can use the provided F<Symbol.*> files which list	3586	exported symbols, you can use the provided F<Symbol.*> files which list
2986	all public symbols, one per line:	3587	all public symbols, one per line:
2987		3588
2988	Symbols.ev for libev proper	3589	Symbols.ev for libev proper
2989	Symbols.event for the libevent emulation	3590	Symbols.event for the libevent emulation
2990		3591
2991	This can also be used to rename all public symbols to avoid clashes with	3592	This can also be used to rename all public symbols to avoid clashes with
2992	multiple versions of libev linked together (which is obviously bad in	3593	multiple versions of libev linked together (which is obviously bad in
2993	itself, but sometimes it is inconvinient to avoid this).	3594	itself, but sometimes it is inconvenient to avoid this).
2994		3595
2995	A sed command like this will create wrapper C<#define>'s that you need to	3596	A sed command like this will create wrapper C<#define>'s that you need to
2996	include before including F<ev.h>:	3597	include before including F<ev.h>:
2997		3598
2998	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3599	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3015	file.	3616	file.
3016		3617
3017	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3618	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3018	that everybody includes and which overrides some configure choices:	3619	that everybody includes and which overrides some configure choices:
3019		3620
3020	#define EV_MINIMAL 1	3621	#define EV_MINIMAL 1
3021	#define EV_USE_POLL 0	3622	#define EV_USE_POLL 0
3022	#define EV_MULTIPLICITY 0	3623	#define EV_MULTIPLICITY 0
3023	#define EV_PERIODIC_ENABLE 0	3624	#define EV_PERIODIC_ENABLE 0
3024	#define EV_STAT_ENABLE 0	3625	#define EV_STAT_ENABLE 0
3025	#define EV_FORK_ENABLE 0	3626	#define EV_FORK_ENABLE 0
3026	#define EV_CONFIG_H <config.h>	3627	#define EV_CONFIG_H <config.h>
3027	#define EV_MINPRI 0	3628	#define EV_MINPRI 0
3028	#define EV_MAXPRI 0	3629	#define EV_MAXPRI 0
3029		3630
3030	#include "ev++.h"	3631	#include "ev++.h"
3031		3632
3032	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3633	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3033		3634
3034	#include "ev_cpp.h"	3635	#include "ev_cpp.h"
3035	#include "ev.c"	3636	#include "ev.c"
3036		3637
		3638	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3037		3639
3038	=head1 COMPLEXITIES	3640	=head2 THREADS AND COROUTINES
3039		3641
3040	In this section the complexities of (many of) the algorithms used inside	3642	=head3 THREADS
3041	libev will be explained. For complexity discussions about backends see the
3042	documentation for C<ev_default_init>.
3043		3643
3044	All of the following are about amortised time: If an array needs to be	3644	All libev functions are reentrant and thread-safe unless explicitly
3045	extended, libev needs to realloc and move the whole array, but this	3645	documented otherwise, but libev implements no locking itself. This means
3046	happens asymptotically never with higher number of elements, so O(1) might	3646	that you can use as many loops as you want in parallel, as long as there
3047	mean it might do a lengthy realloc operation in rare cases, but on average	3647	are no concurrent calls into any libev function with the same loop
3048	it is much faster and asymptotically approaches constant time.	3648	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3649	of course): libev guarantees that different event loops share no data
		3650	structures that need any locking.
		3651
		3652	Or to put it differently: calls with different loop parameters can be done
		3653	concurrently from multiple threads, calls with the same loop parameter
		3654	must be done serially (but can be done from different threads, as long as
		3655	only one thread ever is inside a call at any point in time, e.g. by using
		3656	a mutex per loop).
		3657
		3658	Specifically to support threads (and signal handlers), libev implements
		3659	so-called C<ev_async> watchers, which allow some limited form of
		3660	concurrency on the same event loop, namely waking it up "from the
		3661	outside".
		3662
		3663	If you want to know which design (one loop, locking, or multiple loops
		3664	without or something else still) is best for your problem, then I cannot
		3665	help you, but here is some generic advice:
3049		3666
3050	=over 4	3667	=over 4
3051		3668
3052	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3669	=item * most applications have a main thread: use the default libev loop
		3670	in that thread, or create a separate thread running only the default loop.
3053		3671
3054	This means that, when you have a watcher that triggers in one hour and	3672	This helps integrating other libraries or software modules that use libev
3055	there are 100 watchers that would trigger before that then inserting will	3673	themselves and don't care/know about threading.
3056	have to skip roughly seven (C<ld 100>) of these watchers.
3057		3674
3058	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3675	=item * one loop per thread is usually a good model.
3059		3676
3060	That means that changing a timer costs less than removing/adding them	3677	Doing this is almost never wrong, sometimes a better-performance model
3061	as only the relative motion in the event queue has to be paid for.	3678	exists, but it is always a good start.
3062		3679
3063	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3680	=item * other models exist, such as the leader/follower pattern, where one
		3681	loop is handed through multiple threads in a kind of round-robin fashion.
3064		3682
3065	These just add the watcher into an array or at the head of a list.	3683	Choosing a model is hard - look around, learn, know that usually you can do
		3684	better than you currently do :-)
3066		3685
3067	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3686	=item * often you need to talk to some other thread which blocks in the
		3687	event loop.
3068		3688
3069	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3689	C<ev_async> watchers can be used to wake them up from other threads safely
		3690	(or from signal contexts...).
3070		3691
3071	These watchers are stored in lists then need to be walked to find the	3692	An example use would be to communicate signals or other events that only
3072	correct watcher to remove. The lists are usually short (you don't usually	3693	work in the default loop by registering the signal watcher with the
3073	have many watchers waiting for the same fd or signal).	3694	default loop and triggering an C<ev_async> watcher from the default loop
3074		3695	watcher callback into the event loop interested in the signal.
3075	=item Finding the next timer in each loop iteration: O(1)
3076
3077	By virtue of using a binary heap, the next timer is always found at the
3078	beginning of the storage array.
3079
3080	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3081
3082	A change means an I/O watcher gets started or stopped, which requires
3083	libev to recalculate its status (and possibly tell the kernel, depending
3084	on backend and wether C<ev_io_set> was used).
3085
3086	=item Activating one watcher (putting it into the pending state): O(1)
3087
3088	=item Priority handling: O(number_of_priorities)
3089
3090	Priorities are implemented by allocating some space for each
3091	priority. When doing priority-based operations, libev usually has to
3092	linearly search all the priorities, but starting/stopping and activating
3093	watchers becomes O(1) w.r.t. priority handling.
3094
3095	=item Sending an ev_async: O(1)
3096
3097	=item Processing ev_async_send: O(number_of_async_watchers)
3098
3099	=item Processing signals: O(max_signal_number)
3100
3101	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3102	calls in the current loop iteration. Checking for async and signal events
3103	involves iterating over all running async watchers or all signal numbers.
3104		3696
3105	=back	3697	=back
3106		3698
		3699	=head3 COROUTINES
3107		3700
3108	=head1 Win32 platform limitations and workarounds	3701	Libev is very accommodating to coroutines ("cooperative threads"):
		3702	libev fully supports nesting calls to its functions from different
		3703	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3704	different coroutines, and switch freely between both coroutines running the
		3705	loop, as long as you don't confuse yourself). The only exception is that
		3706	you must not do this from C<ev_periodic> reschedule callbacks.
		3707
		3708	Care has been taken to ensure that libev does not keep local state inside
		3709	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3710	they do not call any callbacks.
		3711
		3712	=head2 COMPILER WARNINGS
		3713
		3714	Depending on your compiler and compiler settings, you might get no or a
		3715	lot of warnings when compiling libev code. Some people are apparently
		3716	scared by this.
		3717
		3718	However, these are unavoidable for many reasons. For one, each compiler
		3719	has different warnings, and each user has different tastes regarding
		3720	warning options. "Warn-free" code therefore cannot be a goal except when
		3721	targeting a specific compiler and compiler-version.
		3722
		3723	Another reason is that some compiler warnings require elaborate
		3724	workarounds, or other changes to the code that make it less clear and less
		3725	maintainable.
		3726
		3727	And of course, some compiler warnings are just plain stupid, or simply
		3728	wrong (because they don't actually warn about the condition their message
		3729	seems to warn about). For example, certain older gcc versions had some
		3730	warnings that resulted an extreme number of false positives. These have
		3731	been fixed, but some people still insist on making code warn-free with
		3732	such buggy versions.
		3733
		3734	While libev is written to generate as few warnings as possible,
		3735	"warn-free" code is not a goal, and it is recommended not to build libev
		3736	with any compiler warnings enabled unless you are prepared to cope with
		3737	them (e.g. by ignoring them). Remember that warnings are just that:
		3738	warnings, not errors, or proof of bugs.
		3739
		3740
		3741	=head2 VALGRIND
		3742
		3743	Valgrind has a special section here because it is a popular tool that is
		3744	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3745
		3746	If you think you found a bug (memory leak, uninitialised data access etc.)
		3747	in libev, then check twice: If valgrind reports something like:
		3748
		3749	==2274== definitely lost: 0 bytes in 0 blocks.
		3750	==2274== possibly lost: 0 bytes in 0 blocks.
		3751	==2274== still reachable: 256 bytes in 1 blocks.
		3752
		3753	Then there is no memory leak, just as memory accounted to global variables
		3754	is not a memleak - the memory is still being referenced, and didn't leak.
		3755
		3756	Similarly, under some circumstances, valgrind might report kernel bugs
		3757	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3758	although an acceptable workaround has been found here), or it might be
		3759	confused.
		3760
		3761	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3762	make it into some kind of religion.
		3763
		3764	If you are unsure about something, feel free to contact the mailing list
		3765	with the full valgrind report and an explanation on why you think this
		3766	is a bug in libev (best check the archives, too :). However, don't be
		3767	annoyed when you get a brisk "this is no bug" answer and take the chance
		3768	of learning how to interpret valgrind properly.
		3769
		3770	If you need, for some reason, empty reports from valgrind for your project
		3771	I suggest using suppression lists.
		3772
		3773
		3774	=head1 PORTABILITY NOTES
		3775
		3776	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3109		3777
3110	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3778	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3111	requires, and its I/O model is fundamentally incompatible with the POSIX	3779	requires, and its I/O model is fundamentally incompatible with the POSIX
3112	model. Libev still offers limited functionality on this platform in	3780	model. Libev still offers limited functionality on this platform in
3113	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3781	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3114	descriptors. This only applies when using Win32 natively, not when using	3782	descriptors. This only applies when using Win32 natively, not when using
3115	e.g. cygwin.	3783	e.g. cygwin.
3116		3784
		3785	Lifting these limitations would basically require the full
		3786	re-implementation of the I/O system. If you are into these kinds of
		3787	things, then note that glib does exactly that for you in a very portable
		3788	way (note also that glib is the slowest event library known to man).
		3789
3117	There is no supported compilation method available on windows except	3790	There is no supported compilation method available on windows except
3118	embedding it into other applications.	3791	embedding it into other applications.
3119		3792
		3793	Not a libev limitation but worth mentioning: windows apparently doesn't
		3794	accept large writes: instead of resulting in a partial write, windows will
		3795	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3796	so make sure you only write small amounts into your sockets (less than a
		3797	megabyte seems safe, but this apparently depends on the amount of memory
		3798	available).
		3799
3120	Due to the many, low, and arbitrary limits on the win32 platform and the	3800	Due to the many, low, and arbitrary limits on the win32 platform and
3121	abysmal performance of winsockets, using a large number of sockets is not	3801	the abysmal performance of winsockets, using a large number of sockets
3122	recommended (and not reasonable). If your program needs to use more than	3802	is not recommended (and not reasonable). If your program needs to use
3123	a hundred or so sockets, then likely it needs to use a totally different	3803	more than a hundred or so sockets, then likely it needs to use a totally
3124	implementation for windows, as libev offers the POSIX model, which cannot	3804	different implementation for windows, as libev offers the POSIX readiness
3125	be implemented efficiently on windows (microsoft monopoly games).	3805	notification model, which cannot be implemented efficiently on windows
		3806	(Microsoft monopoly games).
		3807
		3808	A typical way to use libev under windows is to embed it (see the embedding
		3809	section for details) and use the following F<evwrap.h> header file instead
		3810	of F<ev.h>:
		3811
		3812	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3813	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3814
		3815	#include "ev.h"
		3816
		3817	And compile the following F<evwrap.c> file into your project (make sure
		3818	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3819
		3820	#include "evwrap.h"
		3821	#include "ev.c"
3126		3822
3127	=over 4	3823	=over 4
3128		3824
3129	=item The winsocket select function	3825	=item The winsocket select function
3130		3826
3131	The winsocket C<select> function doesn't follow POSIX in that it requires	3827	The winsocket C<select> function doesn't follow POSIX in that it
3132	socket I<handles> and not socket I<file descriptors>. This makes select	3828	requires socket I<handles> and not socket I<file descriptors> (it is
3133	very inefficient, and also requires a mapping from file descriptors	3829	also extremely buggy). This makes select very inefficient, and also
3134	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3830	requires a mapping from file descriptors to socket handles (the Microsoft
3135	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3831	C runtime provides the function C<_open_osfhandle> for this). See the
3136	symbols for more info.	3832	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3833	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3137		3834
3138	The configuration for a "naked" win32 using the microsoft runtime	3835	The configuration for a "naked" win32 using the Microsoft runtime
3139	libraries and raw winsocket select is:	3836	libraries and raw winsocket select is:
3140		3837
3141	#define EV_USE_SELECT 1	3838	#define EV_USE_SELECT 1
3142	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3839	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3143		3840
3144	Note that winsockets handling of fd sets is O(n), so you can easily get a	3841	Note that winsockets handling of fd sets is O(n), so you can easily get a
3145	complexity in the O(n²) range when using win32.	3842	complexity in the O(n²) range when using win32.
3146		3843
3147	=item Limited number of file descriptors	3844	=item Limited number of file descriptors
3148		3845
3149	Windows has numerous arbitrary (and low) limits on things. Early versions	3846	Windows has numerous arbitrary (and low) limits on things.
3150	of winsocket's select only supported waiting for a max. of C<64> handles	3847
		3848	Early versions of winsocket's select only supported waiting for a maximum
3151	(probably owning to the fact that all windows kernels can only wait for	3849	of C<64> handles (probably owning to the fact that all windows kernels
3152	C<64> things at the same time internally; microsoft recommends spawning a	3850	can only wait for C<64> things at the same time internally; Microsoft
3153	chain of threads and wait for 63 handles and the previous thread in each).	3851	recommends spawning a chain of threads and wait for 63 handles and the
		3852	previous thread in each. Great).
3154		3853
3155	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3854	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3156	to some high number (e.g. C<2048>) before compiling the winsocket select	3855	to some high number (e.g. C<2048>) before compiling the winsocket select
3157	call (which might be in libev or elsewhere, for example, perl does its own	3856	call (which might be in libev or elsewhere, for example, perl does its own
3158	select emulation on windows).	3857	select emulation on windows).
3159		3858
3160	Another limit is the number of file descriptors in the microsoft runtime	3859	Another limit is the number of file descriptors in the Microsoft runtime
3161	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3860	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3162	or something like this inside microsoft). You can increase this by calling	3861	or something like this inside Microsoft). You can increase this by calling
3163	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3862	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3164	arbitrary limit), but is broken in many versions of the microsoft runtime	3863	arbitrary limit), but is broken in many versions of the Microsoft runtime
3165	libraries.	3864	libraries.
3166		3865
3167	This might get you to about C<512> or C<2048> sockets (depending on	3866	This might get you to about C<512> or C<2048> sockets (depending on
3168	windows version and/or the phase of the moon). To get more, you need to	3867	windows version and/or the phase of the moon). To get more, you need to
3169	wrap all I/O functions and provide your own fd management, but the cost of	3868	wrap all I/O functions and provide your own fd management, but the cost of
3170	calling select (O(n²)) will likely make this unworkable.	3869	calling select (O(n²)) will likely make this unworkable.
3171		3870
3172	=back	3871	=back
3173		3872
		3873	=head2 PORTABILITY REQUIREMENTS
		3874
		3875	In addition to a working ISO-C implementation and of course the
		3876	backend-specific APIs, libev relies on a few additional extensions:
		3877
		3878	=over 4
		3879
		3880	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3881	calling conventions regardless of C<ev_watcher_type *>.
		3882
		3883	Libev assumes not only that all watcher pointers have the same internal
		3884	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3885	assumes that the same (machine) code can be used to call any watcher
		3886	callback: The watcher callbacks have different type signatures, but libev
		3887	calls them using an C<ev_watcher *> internally.
		3888
		3889	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3890
		3891	The type C<sig_atomic_t volatile> (or whatever is defined as
		3892	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3893	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3894	believed to be sufficiently portable.
		3895
		3896	=item C<sigprocmask> must work in a threaded environment
		3897
		3898	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3899	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3900	pthread implementations will either allow C<sigprocmask> in the "main
		3901	thread" or will block signals process-wide, both behaviours would
		3902	be compatible with libev. Interaction between C<sigprocmask> and
		3903	C<pthread_sigmask> could complicate things, however.
		3904
		3905	The most portable way to handle signals is to block signals in all threads
		3906	except the initial one, and run the default loop in the initial thread as
		3907	well.
		3908
		3909	=item C<long> must be large enough for common memory allocation sizes
		3910
		3911	To improve portability and simplify its API, libev uses C<long> internally
		3912	instead of C<size_t> when allocating its data structures. On non-POSIX
		3913	systems (Microsoft...) this might be unexpectedly low, but is still at
		3914	least 31 bits everywhere, which is enough for hundreds of millions of
		3915	watchers.
		3916
		3917	=item C<double> must hold a time value in seconds with enough accuracy
		3918
		3919	The type C<double> is used to represent timestamps. It is required to
		3920	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3921	enough for at least into the year 4000. This requirement is fulfilled by
		3922	implementations implementing IEEE 754 (basically all existing ones).
		3923
		3924	=back
		3925
		3926	If you know of other additional requirements drop me a note.
		3927
		3928
		3929	=head1 ALGORITHMIC COMPLEXITIES
		3930
		3931	In this section the complexities of (many of) the algorithms used inside
		3932	libev will be documented. For complexity discussions about backends see
		3933	the documentation for C<ev_default_init>.
		3934
		3935	All of the following are about amortised time: If an array needs to be
		3936	extended, libev needs to realloc and move the whole array, but this
		3937	happens asymptotically rarer with higher number of elements, so O(1) might
		3938	mean that libev does a lengthy realloc operation in rare cases, but on
		3939	average it is much faster and asymptotically approaches constant time.
		3940
		3941	=over 4
		3942
		3943	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3944
		3945	This means that, when you have a watcher that triggers in one hour and
		3946	there are 100 watchers that would trigger before that, then inserting will
		3947	have to skip roughly seven (C<ld 100>) of these watchers.
		3948
		3949	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3950
		3951	That means that changing a timer costs less than removing/adding them,
		3952	as only the relative motion in the event queue has to be paid for.
		3953
		3954	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3955
		3956	These just add the watcher into an array or at the head of a list.
		3957
		3958	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3959
		3960	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3961
		3962	These watchers are stored in lists, so they need to be walked to find the
		3963	correct watcher to remove. The lists are usually short (you don't usually
		3964	have many watchers waiting for the same fd or signal: one is typical, two
		3965	is rare).
		3966
		3967	=item Finding the next timer in each loop iteration: O(1)
		3968
		3969	By virtue of using a binary or 4-heap, the next timer is always found at a
		3970	fixed position in the storage array.
		3971
		3972	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3973
		3974	A change means an I/O watcher gets started or stopped, which requires
		3975	libev to recalculate its status (and possibly tell the kernel, depending
		3976	on backend and whether C<ev_io_set> was used).
		3977
		3978	=item Activating one watcher (putting it into the pending state): O(1)
		3979
		3980	=item Priority handling: O(number_of_priorities)
		3981
		3982	Priorities are implemented by allocating some space for each
		3983	priority. When doing priority-based operations, libev usually has to
		3984	linearly search all the priorities, but starting/stopping and activating
		3985	watchers becomes O(1) with respect to priority handling.
		3986
		3987	=item Sending an ev_async: O(1)
		3988
		3989	=item Processing ev_async_send: O(number_of_async_watchers)
		3990
		3991	=item Processing signals: O(max_signal_number)
		3992
		3993	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3994	calls in the current loop iteration. Checking for async and signal events
		3995	involves iterating over all running async watchers or all signal numbers.
		3996
		3997	=back
		3998
3174		3999
3175	=head1 AUTHOR	4000	=head1 AUTHOR
3176		4001
3177	Marc Lehmann <libev@schmorp.de>.	4002	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3178		4003

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