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Revision 1.142 by root, Sun Apr 6 09:53:18 2008 UTC vs.
Revision 1.249 by root, Wed Jul 8 04:29:31 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 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	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	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	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	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	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	121	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	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	132	on 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	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
		135
		136	=head1 ERROR HANDLING
		137
		138	Libev knows three classes of errors: operating system errors, usage errors
		139	and internal errors (bugs).
		140
		141	When libev catches an operating system error it cannot handle (for example
		142	a system call indicating a condition libev cannot fix), it calls the callback
		143	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		144	abort. The default is to print a diagnostic message and to call C<abort
		145	()>.
		146
		147	When libev detects a usage error such as a negative timer interval, then
		148	it will print a diagnostic message and abort (via the C<assert> mechanism,
		149	so C<NDEBUG> will disable this checking): these are programming errors in
		150	the libev caller and need to be fixed there.
		151
		152	Libev also has a few internal error-checking C<assert>ions, and also has
		153	extensive consistency checking code. These do not trigger under normal
		154	circumstances, as they indicate either a bug in libev or worse.
		155
121		156
122	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
123		158
124	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
125	library in any way.	160	library in any way.
…		…
134		169
135	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
136		171
137	Sleep for the given interval: The current thread will be blocked until	172	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	173	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
140		175
141	=item int ev_version_major ()	176	=item int ev_version_major ()
142		177
143	=item int ev_version_minor ()	178	=item int ev_version_minor ()
144		179
…		…
157	not a problem.	192	not a problem.
158		193
159	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	195	version.
161		196
162	assert (("libev version mismatch",	197	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
165		200
166	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
167		202
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	206	a description of the set values.
172		207
173	Example: make sure we have the epoll method, because yeah this is cool and	208	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	209	a must have and can we have a torrent of it please!!!11
175		210
176	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
178		213
179	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
180		215
181	Return the set of all backends compiled into this binary of libev and also	216	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	217	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	218	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	219	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	220	(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.	221	libev will probe for if you specify no backends explicitly.
187		222
188	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
189		224
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	229	recommended ones.
195		230
196	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
197		232
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		234
200	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	236	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	237	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	238	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	239	or take some potentially destructive action.
205	function.	240
		241	Since some systems (at least OpenBSD and Darwin) fail to implement
		242	correct C<realloc> semantics, libev will use a wrapper around the system
		243	C<realloc> and C<free> functions by default.
206		244
207	You could override this function in high-availability programs to, say,	245	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,	246	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.	247	or even to sleep a while and retry until some memory is available.
210		248
211	Example: Replace the libev allocator with one that waits a bit and then	249	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	250	retries (example requires a standards-compliant C<realloc>).
213		251
214	static void *	252	static void *
215	persistent_realloc (void *ptr, size_t size)	253	persistent_realloc (void *ptr, size_t size)
216	{	254	{
217	for (;;)	255	for (;;)
…		…
226	}	264	}
227		265
228	...	266	...
229	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
230		268
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		270
233	Set the callback function to call on a retryable syscall error (such	271	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	272	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	273	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	274	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	275	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	276	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	277	(such as abort).
240		278
241	Example: This is basically the same thing that libev does internally, too.	279	Example: This is basically the same thing that libev does internally, too.
…		…
252		290
253	=back	291	=back
254		292
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		294
257	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	297	I<function>).
260		298
261	If you use threads, a common model is to run the default event loop	299	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	300	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	301	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		302
268	=over 4	303	=over 4
269		304
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		306
…		…
277	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
278	function.	313	function.
279		314
280	Note that this function is I<not> thread-safe, so if you want to use it	315	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,	316	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
283		318
284	The default loop is the only loop that can handle C<ev_signal> and	319	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	320	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	321	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	322	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	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	324	C<ev_default_init>.
290		325
291	The flags argument can be used to specify special behaviour or specific	326	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	335	The default flags value. Use this if you have no clue (it's the right
301	thing, believe me).	336	thing, believe me).
302		337
303	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
304		339
305	If this flag bit is ored into the flag value (or the program runs setuid	340	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	341	or setgid) then libev will I<not> look at the environment variable
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	override the flags completely if it is found in the environment. This is	343	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	344	useful to try out specific backends to test their performance, or to work
310	around bugs.	345	around bugs.
…		…
317		352
318	This works by calling C<getpid ()> on every iteration of the loop,	353	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	354	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	355	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	356	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	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
323	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
324		359
325	The big advantage of this flag is that you can forget about fork (and	360	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	361	forget about forgetting to tell libev about forking) when you use this
327	flag.	362	flag.
328		363
329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
330	environment variable.	365	environment variable.
331		366
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		368
334	This is your standard select(2) backend. Not I<completely> standard, as	369	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	371	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	372	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.	373	usually the fastest backend for a low number of (low-numbered :) fds.
339		374
340	To get good performance out of this backend you need a high amount of	375	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	376	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	377	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	378	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	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
345	readyness notifications you get per iteration.	380	readiness notifications you get per iteration.
		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
346		385
347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
348		387
349	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
350	than select, but handles sparse fds better and has no artificial	389	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	390	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,	391	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	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
354	performance tips.	393	performance tips.
355		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		399
358	For few fds, this backend is a bit little slower than poll and select,	400	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	401	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),	402	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	403	epoll scales either O(1) or O(active_fds).
362	of shortcomings, such as silently dropping events in some hard-to-detect	404
363	cases and requiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
364	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
365		421
366	While stopping, setting and starting an I/O watcher in the same iteration	422	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	423	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	424	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	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
370	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
371		427	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		428
376	Best performance from this backend is achieved by not unregistering all	429	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.	430	watchers for a file descriptor until it has been closed, if possible,
378	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
379		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
		440
380	While nominally embeddeble in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
381	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
382		446
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		448
385	Kqueue deserves special mention, as at the time of this writing, it	449	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	450	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	451	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"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	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	455	"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)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
391	system like NetBSD.	457	system like NetBSD.
392		458
393	You still can embed kqueue into a normal poll or select backend and use it	459	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	460	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.	461	the target platform). See C<ev_embed> watchers for more info.
396		462
397	It scales in the same way as the epoll backend, but the interface to the	463	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	464	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	465	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	466	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	467	two event changes per incident. Support for C<fork ()> is very bad (but
402	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
403		470
404	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
405		472
406	While nominally embeddable in other event loops, this doesn't work	473	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	474	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	475	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	476	(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	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
411	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
412		483
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		485
415	This is not implemented yet (and might never be, unless you send me an	486	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	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		492
422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	493	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)).	494	it's really slow, but it still scales very well (O(active_fds)).
424		495
425	Please note that solaris event ports can deliver a lot of spurious	496	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	497	notifications, so you need to use non-blocking I/O or other means to avoid
427	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
428		499
429	While this backend scales well, it requires one system call per active	500	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	501	file descriptor per loop iteration. For small and medium numbers of file
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	503	might perform better.
433		504
434	On the positive side, ignoring the spurious readyness notifications, this	505	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
436	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
437		512
438	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
439		514
440	Try all backends (even potentially broken ones that wouldn't be tried	515	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	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
443		518
444	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
445		520
446	=back	521	=back
447		522
448	If one or more of these are ored into the flags value, then only these	523	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	524	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.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
451		526
452	The most typical usage is like this:	527	Example: This is the most typical usage.
453		528
454	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		531
457	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
458	environment settings to be taken into account:	533	environment settings to be taken into account:
459		534
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		536
462	Use whatever libev has to offer, but make sure that kqueue is used if	537	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	538	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):	539	private event loop and only if you know the OS supports your types of
		540	fds):
465		541
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		543
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		545
470	Similar to C<ev_default_loop>, but always creates a new event loop that is	546	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	547	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	552	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	553	default loop in the "main" or "initial" thread.
478		554
479	Example: Try to create a event loop that uses epoll and nothing else.	555	Example: Try to create a event loop that uses epoll and nothing else.
480		556
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	558	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
484		560
485	=item ev_default_destroy ()	561	=item ev_default_destroy ()
486		562
487	Destroys the default loop again (frees all memory and kernel state	563	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	564	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	565	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>	566	responsibility to either stop all watchers cleanly yourself I<before>
491	calling this function, or cope with the fact afterwards (which is usually	567	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	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
493	for example).	569	for example).
494		570
495	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
496	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
497	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
498		574
499	In general it is not advisable to call this function except in the	575	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	576	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	577	pipe fds. If you need dynamically allocated loops it is better to use
502	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
527		603
528	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
529		605
530	Like C<ev_default_fork>, but acts on an event loop created by	606	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	607	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.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
533		610
534	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
535		612
536	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
537		615
538	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
539		617
540	Returns the count of loop iterations for the loop, which is identical to	618	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	619	the number of times libev did poll for new events. It starts at C<0> and
542	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
543		621
544	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
545	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
546	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
547		637
548	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
549		639
550	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
551	use.	641	use.
…		…
556	received events and started processing them. This timestamp does not	646	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	647	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	648	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).	649	event occurring (or more correctly, libev finding out about it).
560		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
561	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
562		690
563	Finally, this is it, the event handler. This function usually is called	691	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	692	after you initialised all your watchers and you want to start handling
565	events.	693	events.
…		…
567	If the flags argument is specified as C<0>, it will not return until	695	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.	696	either no event watchers are active anymore or C<ev_unloop> was called.
569		697
570	Please note that an explicit C<ev_unloop> is usually better than	698	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	699	relying on all watchers to be stopped when deciding when a program has
572	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
573	automatically loops as long as it has to and no longer by virtue of	701	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.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
575		704
576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	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	706	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.	707	process in case there are no events and will return after one iteration of
		708	the loop.
579		709
580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	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	711	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	712	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	713	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	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	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	719	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.	720	usually a better approach for this kind of thing.
587		721
588	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
589		723
590	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- If a fork was detected, queue and call all fork watchers.	726	- If a fork was detected (by any means), queue and call all fork watchers.
593	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
594	- If we have been forked, recreate the kernel state.	728	- If we have been forked, detach and recreate the kernel state
		729	as to not disturb the other process.
595	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	739	- Queue all expired timers.
605	- Queue all outstanding periodics.	740	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	742	- Queue all check watchers.
608	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- 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	744	Signals and child watchers are implemented as I/O watchers, and will
610	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
616	anymore.	751	anymore.
617		752
618	... queue jobs here, make sure they register event watchers as long	753	... 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..)	754	... as they still have work to do (even an idle watcher will do..)
620	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
621	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
622		757
623	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
624		759
625	Can be used to make a call to C<ev_loop> return early (but only after it	760	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	761	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	762	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.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
629		764
630	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
631		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
632	=item ev_ref (loop)	769	=item ev_ref (loop)
633		770
634	=item ev_unref (loop)	771	=item ev_unref (loop)
635		772
636	Ref/unref can be used to add or remove a reference count on the event	773	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	774	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	775	count is nonzero, C<ev_loop> will not return on its own.
		776
639	a watcher you never unregister that should not keep C<ev_loop> from	777	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	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
641	example, libev itself uses this for its internal signal pipe: It is not	781	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	782	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	783	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	784	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>	785	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,	786	before stop> (but only if the watcher wasn't active before, or was active
647	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
648		790
649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
650	running when nothing else is active.	792	running when nothing else is active.
651		793
652	struct ev_signal exitsig;	794	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	797	evf_unref (loop);
656		798
657	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
658		800
659	ev_ref (loop);	801	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
661		803
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		805
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		807
666	These advanced functions influence the time that libev will spend waiting	808	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	809	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.	810	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		811	latency.
669		812
670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	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	814	allows libev to delay invocation of I/O and timer/periodic callbacks
672	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
673		817
674	The background is that sometimes your program runs just fast enough to	818	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	819	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	820	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	821	events, especially with backends like C<select ()> which have a high
678	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
679		823
680	By setting a higher I<io collect interval> you allow libev to spend more	824	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,	825	time collecting I/O events, so you can handle more events per iteration,
682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
683	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	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.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
685		831
686	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
687	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
689	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
690	any overhead in libev.	836	value will not introduce any overhead in libev.
691		837
692	Many (busy) programs can usually benefit by setting the io collect	838	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	839	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	840	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>,	841	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.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
		847
		848	Setting the I<timeout collect interval> can improve the opportunity for
		849	saving power, as the program will "bundle" timer callback invocations that
		850	are "near" in time together, by delaying some, thus reducing the number of
		851	times the process sleeps and wakes up again. Another useful technique to
		852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		853	they fire on, say, one-second boundaries only.
		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_loop_verify (loop)
		862
		863	This function only does something when C<EV_VERIFY> support has been
		864	compiled in, which is the default for non-minimal builds. It tries to go
		865	through all internal structures and checks them for validity. If anything
		866	is found to be inconsistent, it will print an error message to standard
		867	error and call C<abort ()>.
		868
		869	This can be used to catch bugs inside libev itself: under normal
		870	circumstances, this function will never abort as of course libev keeps its
		871	data structures consistent.
697		872
698	=back	873	=back
699		874
700		875
701	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
702		881
703	A watcher is a structure that you create and register to record your	882	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	883	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:	884	become readable, you would create an C<ev_io> watcher for that:
706		885
707	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
708	{	887	{
709	ev_io_stop (w);	888	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
711	}	890	}
712		891
713	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
714	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
715	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
718	ev_loop (loop, 0);	900	ev_loop (loop, 0);
719		901
720	As you can see, you are responsible for allocating the memory for your	902	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,	903	watcher structures (and it is I<usually> a bad idea to do this on the
722	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
723		908
724	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
725	(watcher *, callback)>, which expects a callback to be provided. This	910	(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	911	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	912	watchers, each time the event loop detects that the file descriptor given
728	is readable and/or writable).	913	is readable and/or writable).
729		914
730	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	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	916	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	917	is also a macro to combine initialisation and setting in one call: C<<
733	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
734		919
735	To make the watcher actually watch out for events, you have to start it	920	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	921	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	922	*) >>), and you can stop watching for events at any time by calling the
738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
739		924
740	As long as your watcher is active (has been started but not stopped) you	925	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	926	must not touch the values stored in it. Most specifically you must never
742	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
743		928
744	Each and every callback receives the event loop pointer as first, the	929	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	930	registered watcher structure as second, and a bitset of received events as
746	third argument.	931	third argument.
747		932
…		…
805		990
806	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
807		992
808	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
809		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
810	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
811		1001
812	An unspecified error has occured, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
813	happen because the watcher could not be properly started because libev	1003	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	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
815	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
816	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
817		1011
818	Libev will usually signal a few "dummy" events together with an error,	1012	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	1013	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	1014	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	1015	the error from read() or write(). This will not work in multi-threaded
822	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
823		1018
824	=back	1019	=back
825		1020
826	=head2 GENERIC WATCHER FUNCTIONS	1021	=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		1022
831	=over 4	1023	=over 4
832		1024
833	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
834		1026
…		…
840	which rolls both calls into one.	1032	which rolls both calls into one.
841		1033
842	You can reinitialise a watcher at any time as long as it has been stopped	1034	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.	1035	(or never started) and there are no pending events outstanding.
844		1036
845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
846	int revents)>.	1038	int revents)>.
		1039
		1040	Example: Initialise an C<ev_io> watcher in two steps.
		1041
		1042	ev_io w;
		1043	ev_init (&w, my_cb);
		1044	ev_io_set (&w, STDIN_FILENO, EV_READ);
847		1045
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		1047
850	This macro initialises the type-specific parts of a watcher. You need to	1048	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	1049	call C<ev_init> at least once before you call this macro, but you can
…		…
854	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
855		1053
856	Although some watcher types do not have type-specific arguments	1054	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.	1055	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
858		1056
		1057	See C<ev_init>, above, for an example.
		1058
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		1060
861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1061	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	1062	calls into a single call. This is the most convenient method to initialise
863	a watcher. The same limitations apply, of course.	1063	a watcher. The same limitations apply, of course.
		1064
		1065	Example: Initialise and set an C<ev_io> watcher in one step.
		1066
		1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
864		1068
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		1070
867	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
869		1073
		1074	Example: Start the C<ev_io> watcher that is being abused as example in this
		1075	whole section.
		1076
		1077	ev_io_start (EV_DEFAULT_UC, &w);
		1078
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		1080
872	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
873	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	1085	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	1086	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	1087	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.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
878		1089
879	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
880		1091
881	Returns a true value iff the watcher is active (i.e. it has been started	1092	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	1093	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>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
909	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
910	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
911	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
912		1123
913	This means that priorities are I<only> used for ordering callback
914	invocation after new events have been received. This is useful, for
915	example, to reduce latency after idling, or more often, to bind two
916	watchers on the same event and make sure one is called first.
917
918	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
919	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
920		1126
921	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
922	pending.	1128	pending.
923		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
924	The default priority used by watchers when no priority has been set is	1134	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 :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
926		1136
927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
928	fine, as long as you do not mind that the priority value you query might	1138	priorities.
929	or might not have been adjusted to be within valid range.
930		1139
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1141
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	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	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
936		1146
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1148
939	If the watcher is pending, this function returns clears its pending status	1149	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	1150	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>.	1151	watcher isn't pending it does nothing and returns C<0>.
942		1152
		1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1154	callback to be invoked, which can be accomplished with this function.
		1155
943	=back	1156	=back
944		1157
945		1158
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1160
948	Each watcher has, by default, a member C<void *data> that you can change	1161	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	1162	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	1163	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	1164	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	1165	member, you can also "subclass" the watcher type and provide your own
953	data:	1166	data:
954		1167
955	struct my_io	1168	struct my_io
956	{	1169	{
957	struct ev_io io;	1170	ev_io io;
958	int otherfd;	1171	int otherfd;
959	void *somedata;	1172	void *somedata;
960	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
961	}	1174	};
		1175
		1176	...
		1177	struct my_io w;
		1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1179
963	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1181	can cast it back to your own type:
965		1182
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1184	{
968	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
969	...	1186	...
970	}	1187	}
971		1188
972	More interesting and less C-conformant ways of casting your callback type	1189	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1190	instead have been omitted.
974		1191
975	Another common scenario is having some data structure with multiple	1192	Another common scenario is to use some data structure with multiple
976	watchers:	1193	embedded watchers:
977		1194
978	struct my_biggy	1195	struct my_biggy
979	{	1196	{
980	int some_data;	1197	int some_data;
981	ev_timer t1;	1198	ev_timer t1;
982	ev_timer t2;	1199	ev_timer t2;
983	}	1200	}
984		1201
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1202	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1203	complicated: Either you store the address of your C<my_biggy> struct
		1204	in the C<data> member of the watcher (for woozies), or you need to use
		1205	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1206	programmers):
987		1207
988	#include <stddef.h>	1208	#include <stddef.h>
989		1209
990	static void	1210	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1212	{
993	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
994	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1215	}
996		1216
997	static void	1217	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1219	{
1000	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1003		1326
1004		1327
1005	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1006		1329
1007	This section describes each watcher in detail, but will not repeat	1330	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	1354	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	1355	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	1356	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1357	required if you know what you are doing).
1035		1358
1036	If you must do this, then force the use of a known-to-be-good backend	1359	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	1360	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1039		1364
1040	Another thing you have to watch out for is that it is quite easy to	1365	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	1366	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	1367	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	1368	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	1369	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	1370	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	1371	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.	1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1373
1049	If you cannot run the fd in non-blocking mode (for example you should not	1374	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	1375	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	1376	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	1377	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1378	does this on its own, so its quite safe to use). Some people additionally
		1379	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1380	indefinitely.
		1381
		1382	But really, best use non-blocking mode.
1054		1383
1055	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1056		1385
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1386	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,	1387	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	1388	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	1389	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	1390	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	1391	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1392	fact, a different file descriptor.
1064		1393
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1097		1426
1098	=head3 The special problem of SIGPIPE	1427	=head3 The special problem of SIGPIPE
1099		1428
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1429	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	1430	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	1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1432	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1433
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1434	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	1435	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).	1436	somewhere, as that would have given you a big clue).
1109		1437
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1444
1117	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1118		1446
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1447	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	1448	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.	1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1450
1123	=item int fd [read-only]	1451	=item int fd [read-only]
1124		1452
1125	The file descriptor being watched.	1453	The file descriptor being watched.
1126		1454
…		…
1134		1462
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	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	1464	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1138		1466
1139	static void	1467	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1469	{
1142	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1472	}
1145		1473
1146	...	1474	...
1147	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1152		1480
1153		1481
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1482	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1483
1156	Timer watchers are simple relative timers that generate an event after a	1484	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1158		1486
1159	The timers are based on real time, that is, if you register an event that	1487	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	1488	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	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
		1492
		1493	The callback is guaranteed to be invoked only I<after> its timeout has
		1494	passed (not I<at>, so on systems with very low-resolution clocks this
		1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
		1674
		1675	=head3 The special problem of time updates
		1676
		1677	Establishing the current time is a costly operation (it usually takes at
		1678	least two system calls): EV therefore updates its idea of the current
		1679	time only before and after C<ev_loop> collects new events, which causes a
		1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1681	lots of events in one iteration.
1164		1682
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1683	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	1684	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	1685	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	1686	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:	1687	timeout on the current time, use something like this to adjust for this:
1170		1688
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1690
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1691	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	1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1693	()>.
1176		1694
1177	=head3 Watcher-Specific Functions and Data Members	1695	=head3 Watcher-Specific Functions and Data Members
1178		1696
1179	=over 4	1697	=over 4
1180		1698
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1700
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1701	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1702
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1703	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	1704	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	1705	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1706	configured to trigger again C<repeat> seconds later, again, and again,
		1707	until stopped manually.
1189		1708
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1709	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	1710	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	1711	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	1712	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.	1713	do stuff) the timer will not fire more than once per event loop iteration.
1195		1714
1196	=item ev_timer_again (loop, ev_timer *)	1715	=item ev_timer_again (loop, ev_timer *)
1197		1716
1198	This will act as if the timer timed out and restart it again if it is	1717	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1718	repeating. The exact semantics are:
1200		1719
1201	If the timer is pending, its pending status is cleared.	1720	If the timer is pending, its pending status is cleared.
1202		1721
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1723
1205	If the timer is repeating, either start it if necessary (with the	1724	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.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1726
1208	This sounds a bit complicated, but here is a useful and typical	1727	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	1728	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		1729
1233	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1234		1731
1235	The current C<repeat> value. Will be used each time the watcher times out	1732	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),	1733	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.	1734	which is also when any modifications are taken into account.
1238		1735
1239	=back	1736	=back
1240		1737
1241	=head3 Examples	1738	=head3 Examples
1242		1739
1243	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1244		1741
1245	static void	1742	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1744	{
1248	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1249	}	1746	}
1250		1747
1251	struct ev_timer mytimer;	1748	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1254		1751
1255	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1753	inactivity.
1257		1754
1258	static void	1755	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1757	{
1261	.. ten seconds without any activity	1758	.. ten seconds without any activity
1262	}	1759	}
1263		1760
1264	struct ev_timer mytimer;	1761	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1268		1765
1269	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1767	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1768	ev_timer_again (&mytimer);
1272		1769
1273		1770
1274	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1275		1772
1276	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1278		1775
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	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	1777	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	1778	(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 ()	1779	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	1780	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	1781	wrist-watch).
1285	roughly 10 seconds later).
1286		1782
1287	They can also be used to implement vastly more complex timers, such as	1783	You can tell a periodic watcher to trigger after some specific point
1288	triggering an event on each midnight, local time or other, complicated,	1784	in time: for example, if you tell a periodic watcher to trigger "in 10
1289	rules.	1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
1290		1790
		1791	C<ev_periodic> watchers can also be used to implement vastly more complex
		1792	timers, such as triggering an event on each "midnight, local time", or
		1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
		1795
1291	As with timers, the callback is guarenteed to be invoked only when the	1796	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	1797	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.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1294		1801
1295	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1296		1803
1297	=over 4	1804	=over 4
1298		1805
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		1807
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1302		1809
1303	Lots of arguments, lets sort it out... There are basically three modes of	1810	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:	1811	operation, and we will explain them from simplest to most complex:
1305		1812
1306	=over 4	1813	=over 4
1307		1814
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1309		1816
1310	In this configuration the watcher triggers an event at the wallclock time	1817	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,	1818	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	1819	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.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1314		1822
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1316		1824
1317	In this mode the watcher will always be scheduled to time out at the next	1825	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)	1826	C<offset + N * interval> time (for some integer N, which can also be
1319	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1320		1829
1321	This can be used to create timers that do not drift with respect to system	1830	This can be used to create timers that do not drift with respect to the
1322	time:	1831	system clock, for example, here is an C<ev_periodic> that triggers each
		1832	hour, on the hour (with respect to UTC):
1323		1833
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1835
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1836	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	1837	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	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1839	by 3600.
1330		1840
1331	Another way to think about it (for the mathematically inclined) is that	1841	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	1842	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.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1334		1844
1335	For numerical stability it is preferable that the C<at> value is near	1845	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	1846	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1847	this value, and in fact is often specified as zero.
1338		1848
		1849	Note also that there is an upper limit to how often a timer can fire (CPU
		1850	speed for example), so if C<interval> is very small then timing stability
		1851	will of course deteriorate. Libev itself tries to be exact to be about one
		1852	millisecond (if the OS supports it and the machine is fast enough).
		1853
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1340		1855
1341	In this mode the values for C<interval> and C<at> are both being	1856	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	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1859	current time as second argument.
1345		1860
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	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,	1862	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	1863	allowed by documentation here>.
1349	starting an C<ev_prepare> watcher, which is legal).
1350		1864
		1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1867	only event loop modification you are allowed to do).
		1868
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1353		1871
		1872	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1874	{
1356	return now + 60.;	1875	return now + 60.;
1357	}	1876	}
1358		1877
1359	It must return the next time to trigger, based on the passed time value	1878	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	1879	(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	1880	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	1881	might be called at other times, too.
1363		1882
1364	NOTE: I<< This callback must always return a time that is later than the	1883	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.	1884	equal to the passed C<now> value >>.
1366		1885
1367	This can be used to create very complex timers, such as a timer that	1886	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	1887	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	1888	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	1889	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).	1890	reason I omitted it as an example).
1372		1891
1373	=back	1892	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1896	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1897	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	1898	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1899	program when the crontabs have changed).
1381		1900
		1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1902
		1903	When active, returns the absolute time that the watcher is supposed
		1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
		1907
1382	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1383		1909
1384	When repeating, this contains the offset value, otherwise this is the	1910	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>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1386		1913
1387	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1388	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1389		1916
1390	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1391		1918
1392	The current interval value. Can be modified any time, but changes only	1919	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	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	1921	called.
1395		1922
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		1924
1398	The current reschedule callback, or C<0>, if this functionality is	1925	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	1926	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.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1401		1928
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	1929	=back
1408		1930
1409	=head3 Examples	1931	=head3 Examples
1410		1932
1411	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1414		1936
1415	static void	1937	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	1939	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	1941	}
1420		1942
1421	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1424		1946
1425	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1426		1948
1427	#include <math.h>	1949	#include <math.h>
1428		1950
1429	static ev_tstamp	1951	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	1953	{
1432	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1433	}	1955	}
1434		1956
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		1958
1437	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1438		1960
1439	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1443		1965
1444		1966
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	1967	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		1968
1447	Signal watchers will trigger an event when the process receives a specific	1969	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	1970	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	1971	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	1972	normal event processing, like any other event.
1451		1973
		1974	If you want signals asynchronously, just use C<sigaction> as you would
		1975	do without libev and forget about sharing the signal. You can even use
		1976	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1977
1452	You can configure as many watchers as you like per signal. Only when the	1978	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	1979	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	1980	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	1981	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	1982	the last signal watcher for a signal is stopped, libev will reset the
1457	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
1458		1984
1459	If possible and supported, libev will install its handlers with	1985	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1461	interrupted. If you have a problem with syscalls getting interrupted by	1987	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	1988	signals you can block all signals in an C<ev_check> watcher and unblock
1463	them in an C<ev_prepare> watcher.	1989	them in an C<ev_prepare> watcher.
1464		1990
1465	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1466		1992
…		…
1479		2005
1480	=back	2006	=back
1481		2007
1482	=head3 Examples	2008	=head3 Examples
1483		2009
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1485		2011
1486	static void	2012	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	2014	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	2016	}
1491		2017
1492	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1495		2021
1496		2022
1497	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1498		2024
1499	Child watchers trigger when your process receives a SIGCHLD in response to	2025	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	2026	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	2027	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	2028	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2030	forking and then immediately registering a watcher for the child is fine,
		2031	but forking and registering a watcher a few event loop iterations later or
		2032	in the next callback invocation is not.
1504		2033
1505	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2039	libev)
1507		2040
1508	=head3 Process Interaction	2041	=head3 Process Interaction
1509		2042
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	2043	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	2044	initialised. This is necessary to guarantee proper behaviour even if
1512	the first child watcher is started after the child exits. The occurance	2045	the first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2046	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	2047	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	2048	children, even ones not watched.
1516		2049
1517	=head3 Overriding the Built-In Processing	2050	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	2054	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	2055	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	2056	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	2057	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.	2058	that, so other libev users can use C<ev_child> watchers freely.
		2059
		2060	=head3 Stopping the Child Watcher
		2061
		2062	Currently, the child watcher never gets stopped, even when the
		2063	child terminates, so normally one needs to stop the watcher in the
		2064	callback. Future versions of libev might stop the watcher automatically
		2065	when a child exit is detected.
1526		2066
1527	=head3 Watcher-Specific Functions and Data Members	2067	=head3 Watcher-Specific Functions and Data Members
1528		2068
1529	=over 4	2069	=over 4
1530		2070
…		…
1559	=head3 Examples	2099	=head3 Examples
1560		2100
1561	Example: C<fork()> a new process and install a child handler to wait for	2101	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	2102	its completion.
1563		2103
1564	ev_child cw;	2104	ev_child cw;
1565		2105
1566	static void	2106	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	2107	child_cb (EV_P_ ev_child *w, int revents)
1568	{	2108	{
1569	ev_child_stop (EV_A_ w);	2109	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2110	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	2111	}
1572		2112
1573	pid_t pid = fork ();	2113	pid_t pid = fork ();
1574		2114
1575	if (pid < 0)	2115	if (pid < 0)
1576	// error	2116	// error
1577	else if (pid == 0)	2117	else if (pid == 0)
1578	{	2118	{
1579	// the forked child executes here	2119	// the forked child executes here
1580	exit (1);	2120	exit (1);
1581	}	2121	}
1582	else	2122	else
1583	{	2123	{
1584	ev_child_init (&cw, child_cb, pid, 0);	2124	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	2125	ev_child_start (EV_DEFAULT_ &cw);
1586	}	2126	}
1587		2127
1588		2128
1589	=head2 C<ev_stat> - did the file attributes just change?	2129	=head2 C<ev_stat> - did the file attributes just change?
1590		2130
1591	This watches a filesystem path for attribute changes. That is, it calls	2131	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	2132	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.	2133	and sees if it changed compared to the last time, invoking the callback if
		2134	it did.
1594		2135
1595	The path does not need to exist: changing from "path exists" to "path does	2136	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	2137	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	2138	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	2139	C<st_nlink> field being zero (which is otherwise always forced to be at
1599	the stat buffer having unspecified contents.	2140	least one) and all the other fields of the stat buffer having unspecified
		2141	contents.
1600		2142
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	2143	The path I<must not> end in a slash or contain special components such as
		2144	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.	2145	your working directory changes, then the behaviour is undefined.
1603		2146
1604	Since there is no standard to do this, the portable implementation simply	2147	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	2148	portable implementation simply calls C<stat(2)> regularly on the path
1606	can specify a recommended polling interval for this case. If you specify	2149	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,	2150	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	2151	recommended!) then a I<suitable, unspecified default> value will be used
1609	five seconds, although this might change dynamically). Libev will also	2152	(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	2153	change dynamically). Libev will also impose a minimum interval which is
1611	usually overkill.	2154	currently around C<0.1>, but that's usually overkill.
1612		2155
1613	This watcher type is not meant for massive numbers of stat watchers,	2156	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	2157	as even with OS-supported change notifications, this can be
1615	resource-intensive.	2158	resource-intensive.
1616		2159
1617	At the time of this writing, only the Linux inotify interface is	2160	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	2161	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	2162	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	2163	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		2164
1625	=head3 ABI Issues (Largefile Support)	2165	=head3 ABI Issues (Largefile Support)
1626		2166
1627	Libev by default (unless the user overrides this) uses the default	2167	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	2168	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	2169	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	2170	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	2171	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	2172	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	2173	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	2174	most noticeably displayed with ev_stat and large file support.
1635		2175
1636	=head3 Inotify	2176	The solution for this is to lobby your distribution maker to make large
		2177	file interfaces available by default (as e.g. FreeBSD does) and not
		2178	optional. Libev cannot simply switch on large file support because it has
		2179	to exchange stat structures with application programs compiled using the
		2180	default compilation environment.
1637		2181
		2182	=head3 Inotify and Kqueue
		2183
1638	When C<inotify (7)> support has been compiled into libev (generally only	2184	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	2185	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	2186	inotify descriptor will be created lazily when the first C<ev_stat>
1641	when the first C<ev_stat> watcher is being started.	2187	watcher is being started.
1642		2188
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	2189	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	2190	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	2191	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.	2192	there are many cases where libev has to resort to regular C<stat> polling,
		2193	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2194	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2195	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2196	xfs are fully working) libev usually gets away without polling.
1647		2197
1648	(There is no support for kqueue, as apparently it cannot be used to	2198	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	2199	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	2200	descriptor open on the object at all times, and detecting renames, unlinks
		2201	etc. is difficult.
		2202
		2203	=head3 C<stat ()> is a synchronous operation
		2204
		2205	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2206	the process. The exception are C<ev_stat> watchers - those call C<stat
		2207	()>, which is a synchronous operation.
		2208
		2209	For local paths, this usually doesn't matter: unless the system is very
		2210	busy or the intervals between stat's are large, a stat call will be fast,
		2211	as the path data is usually in memory already (except when starting the
		2212	watcher).
		2213
		2214	For networked file systems, calling C<stat ()> can block an indefinite
		2215	time due to network issues, and even under good conditions, a stat call
		2216	often takes multiple milliseconds.
		2217
		2218	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2219	paths, although this is fully supported by libev.
1651		2220
1652	=head3 The special problem of stat time resolution	2221	=head3 The special problem of stat time resolution
1653		2222
1654	The C<stat ()> syscall only supports full-second resolution portably, and	2223	The C<stat ()> system call only supports full-second resolution portably,
1655	even on systems where the resolution is higher, many filesystems still	2224	and even on systems where the resolution is higher, most file systems
1656	only support whole seconds.	2225	still only support whole seconds.
1657		2226
1658	That means that, if the time is the only thing that changes, you might	2227	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	2228	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	2229	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	2230	within the same second, C<ev_stat> will be unable to detect unless the
		2231	stat data does change in other ways (e.g. file size).
1662		2232
1663	The solution to this is to delay acting on a change for a second (or till	2233	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>	2234	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>	2235	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	2236	ev_timer_again (loop, w)>).
1667	systems.	2237
		2238	The C<.02> offset is added to work around small timing inconsistencies
		2239	of some operating systems (where the second counter of the current time
		2240	might be be delayed. One such system is the Linux kernel, where a call to
		2241	C<gettimeofday> might return a timestamp with a full second later than
		2242	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2243	update file times then there will be a small window where the kernel uses
		2244	the previous second to update file times but libev might already execute
		2245	the timer callback).
1668		2246
1669	=head3 Watcher-Specific Functions and Data Members	2247	=head3 Watcher-Specific Functions and Data Members
1670		2248
1671	=over 4	2249	=over 4
1672		2250
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2256	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	2257	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	2258	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.	2259	path for as long as the watcher is active.
1682		2260
1683	The callback will be receive C<EV_STAT> when a change was detected,	2261	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	2262	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2263	last change was detected).
1686		2264
1687	=item ev_stat_stat (loop, ev_stat *)	2265	=item ev_stat_stat (loop, ev_stat *)
1688		2266
1689	Updates the stat buffer immediately with new values. If you change the	2267	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	2268	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2269	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2270	the only one changing the path). Can also be useful simply to find out the
		2271	new values.
1693		2272
1694	=item ev_statdata attr [read-only]	2273	=item ev_statdata attr [read-only]
1695		2274
1696	The most-recently detected attributes of the file. Although the type is of	2275	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	2276	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	2277	suitable for your system, but you can only rely on the POSIX-standardised
		2278	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.	2279	some error while C<stat>ing the file.
1700		2280
1701	=item ev_statdata prev [read-only]	2281	=item ev_statdata prev [read-only]
1702		2282
1703	The previous attributes of the file. The callback gets invoked whenever	2283	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2284	C<prev> != C<attr>, or, more precisely, one or more of these members
		2285	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2286	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2287
1706	=item ev_tstamp interval [read-only]	2288	=item ev_tstamp interval [read-only]
1707		2289
1708	The specified interval.	2290	The specified interval.
1709		2291
1710	=item const char *path [read-only]	2292	=item const char *path [read-only]
1711		2293
1712	The filesystem path that is being watched.	2294	The file system path that is being watched.
1713		2295
1714	=back	2296	=back
1715		2297
1716	=head3 Examples	2298	=head3 Examples
1717		2299
1718	Example: Watch C</etc/passwd> for attribute changes.	2300	Example: Watch C</etc/passwd> for attribute changes.
1719		2301
1720	static void	2302	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2303	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2304	{
1723	/* /etc/passwd changed in some way */	2305	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2306	if (w->attr.st_nlink)
1725	{	2307	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2308	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2309	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2310	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2311	}
1730	else	2312	else
1731	/* you shalt not abuse printf for puts */	2313	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2314	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2315	"if this is windows, they already arrived\n");
1734	}	2316	}
1735		2317
1736	...	2318	...
1737	ev_stat passwd;	2319	ev_stat passwd;
1738		2320
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2321	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2322	ev_stat_start (loop, &passwd);
1741		2323
1742	Example: Like above, but additionally use a one-second delay so we do not	2324	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	2325	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	2326	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2327	C<ev_timer> callback invocation).
1746		2328
1747	static ev_stat passwd;	2329	static ev_stat passwd;
1748	static ev_timer timer;	2330	static ev_timer timer;
1749		2331
1750	static void	2332	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2333	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2334	{
1753	ev_timer_stop (EV_A_ w);	2335	ev_timer_stop (EV_A_ w);
1754		2336
1755	/* now it's one second after the most recent passwd change */	2337	/* now it's one second after the most recent passwd change */
1756	}	2338	}
1757		2339
1758	static void	2340	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2341	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2342	{
1761	/* reset the one-second timer */	2343	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2344	ev_timer_again (EV_A_ &timer);
1763	}	2345	}
1764		2346
1765	...	2347	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2348	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2349	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2350	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2351
1770		2352
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2353	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2354
1773	Idle watchers trigger events when no other events of the same or higher	2355	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	2356	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2357	as receiving "events").
1776		2358
1777	That is, as long as your process is busy handling sockets or timeouts	2359	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	2360	(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	2361	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	2362	are pending), the idle watchers are being called once per event loop
…		…
1791		2373
1792	=head3 Watcher-Specific Functions and Data Members	2374	=head3 Watcher-Specific Functions and Data Members
1793		2375
1794	=over 4	2376	=over 4
1795		2377
1796	=item ev_idle_init (ev_signal *, callback)	2378	=item ev_idle_init (ev_idle *, callback)
1797		2379
1798	Initialises and configures the idle watcher - it has no parameters of any	2380	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,	2381	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1800	believe me.	2382	believe me.
1801		2383
…		…
1804	=head3 Examples	2386	=head3 Examples
1805		2387
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2388	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2389	callback, free it. Also, use no error checking, as usual.
1808		2390
1809	static void	2391	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2392	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2393	{
1812	free (w);	2394	free (w);
1813	// now do something you wanted to do when the program has	2395	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2396	// no longer anything immediate to do.
1815	}	2397	}
1816		2398
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2399	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2400	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2401	ev_idle_start (loop, idle_watcher);
1820		2402
1821		2403
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2404	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2405
1824	Prepare and check watchers are usually (but not always) used in tandem:	2406	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2407	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2408	afterwards.
1827		2409
1828	You I<must not> call C<ev_loop> or similar functions that enter	2410	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>	2411	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,	2414	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	2415	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2416	called in pairs bracketing the blocking call.
1835		2417
1836	Their main purpose is to integrate other event mechanisms into libev and	2418	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	2419	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	2420	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2421	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,	2422	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>	2423	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2424	watcher).
1843		2425
1844	This is done by examining in each prepare call which file descriptors need	2426	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	2427	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	2428	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	2429	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2430	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	2431	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,	2432	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2433	nevertheless, because you never know, you know?).
1852		2434
1853	As another example, the Perl Coro module uses these hooks to integrate	2435	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2436	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2437	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	2438	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	2441	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2442	low-priority coroutines to idle/background tasks).
1861		2443
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2444	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	2445	priority, to ensure that they are being run before any other watchers
		2446	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2447
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2448	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	2449	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2450	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	2451	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	2452	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	2453	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2454	others).
1871		2455
1872	=head3 Watcher-Specific Functions and Data Members	2456	=head3 Watcher-Specific Functions and Data Members
1873		2457
1874	=over 4	2458	=over 4
1875		2459
…		…
1877		2461
1878	=item ev_check_init (ev_check *, callback)	2462	=item ev_check_init (ev_check *, callback)
1879		2463
1880	Initialises and configures the prepare or check watcher - they have no	2464	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>	2465	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.	2466	macros, but using them is utterly, utterly, utterly and completely
		2467	pointless.
1883		2468
1884	=back	2469	=back
1885		2470
1886	=head3 Examples	2471	=head3 Examples
1887		2472
1888	There are a number of principal ways to embed other event loops or modules	2473	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	2474	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	2475	(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>	2476	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	2477	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2478	Glib event loop).
1894		2479
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2480	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	2481	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	2482	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	2483	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.	2484	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2485
1901	static ev_io iow [nfd];	2486	static ev_io iow [nfd];
1902	static ev_timer tw;	2487	static ev_timer tw;
1903		2488
1904	static void	2489	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2490	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2491	{
1907	}	2492	}
1908		2493
1909	// create io watchers for each fd and a timer before blocking	2494	// create io watchers for each fd and a timer before blocking
1910	static void	2495	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2496	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2497	{
1913	int timeout = 3600000;	2498	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2499	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2500	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2501	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2502
1918	/* the callback is illegal, but won't be called as we stop during check */	2503	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2504	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1920	ev_timer_start (loop, &tw);	2505	ev_timer_start (loop, &tw);
1921		2506
1922	// create one ev_io per pollfd	2507	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2508	for (int i = 0; i < nfd; ++i)
1924	{	2509	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2510	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2511	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2512	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2513
1929	fds [i].revents = 0;	2514	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2515	ev_io_start (loop, iow + i);
1931	}	2516	}
1932	}	2517	}
1933		2518
1934	// stop all watchers after blocking	2519	// stop all watchers after blocking
1935	static void	2520	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2521	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2522	{
1938	ev_timer_stop (loop, &tw);	2523	ev_timer_stop (loop, &tw);
1939		2524
1940	for (int i = 0; i < nfd; ++i)	2525	for (int i = 0; i < nfd; ++i)
1941	{	2526	{
1942	// set the relevant poll flags	2527	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2528	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2529	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2530	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2531	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2532	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2533
1949	// now stop the watcher	2534	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2535	ev_io_stop (loop, iow + i);
1951	}	2536	}
1952		2537
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2538	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2539	}
1955		2540
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2541	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.	2542	in the prepare watcher and would dispose of the check watcher.
1958		2543
1959	Method 3: If the module to be embedded supports explicit event	2544	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2545	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2546	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2547
1963	static void	2548	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2549	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2550	{
1966	adns_state ads = (adns_state)w->data;	2551	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2552	update_now (EV_A);
1968		2553
1969	adns_processtimeouts (ads, &tv_now);	2554	adns_processtimeouts (ads, &tv_now);
1970	}	2555	}
1971		2556
1972	static void	2557	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2558	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2559	{
1975	adns_state ads = (adns_state)w->data;	2560	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2561	update_now (EV_A);
1977		2562
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2563	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2564	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2565	}
1981		2566
1982	// do not ever call adns_afterpoll	2567	// do not ever call adns_afterpoll
1983		2568
1984	Method 4: Do not use a prepare or check watcher because the module you	2569	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	2570	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	2571	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	2572	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2573	this approach, effectively embedding EV as a client into the horrible
		2574	libglib event loop.
1989		2575
1990	static gint	2576	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2577	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2578	{
1993	int got_events = 0;	2579	int got_events = 0;
1994		2580
1995	for (n = 0; n < nfds; ++n)	2581	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2582	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2583
1998	if (timeout >= 0)	2584	if (timeout >= 0)
1999	// create/start timer	2585	// create/start timer
2000		2586
2001	// poll	2587	// poll
2002	ev_loop (EV_A_ 0);	2588	ev_loop (EV_A_ 0);
2003		2589
2004	// stop timer again	2590	// stop timer again
2005	if (timeout >= 0)	2591	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2592	ev_timer_stop (EV_A_ &to);
2007		2593
2008	// stop io watchers again - their callbacks should have set	2594	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2595	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2596	ev_io_stop (EV_A_ iow [n]);
2011		2597
2012	return got_events;	2598	return got_events;
2013	}	2599	}
2014		2600
2015		2601
2016	=head2 C<ev_embed> - when one backend isn't enough...	2602	=head2 C<ev_embed> - when one backend isn't enough...
2017		2603
2018	This is a rather advanced watcher type that lets you embed one event loop	2604	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2610	prioritise I/O.
2025		2611
2026	As an example for a bug workaround, the kqueue backend might only support	2612	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	2613	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	2614	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	2615	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	2616	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	2617	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.	2618	C<kevent>, but at least you can use both mechanisms for what they are
		2619	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2620
2034	As for prioritising I/O: rarely you have the case where some fds have	2621	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	2622	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	2623	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	2624	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.	2625	the rest in a second one, and embed the second one in the first.
2039		2626
2040	As long as the watcher is active, the callback will be invoked every time	2627	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	2628	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	2629	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	2630	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	2631	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	2632	to give the embedded loop strictly lower priority for example).
2046	embedded loop sweep.
2047		2633
2048	As long as the watcher is started it will automatically handle events. The	2634	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	2635	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		2636
2053	Also, there have not currently been made special provisions for forking:	2637	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,	2638	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	2639	embedding loop forks. In other cases, the user is responsible for calling
2056	yourself.	2640	C<ev_loop_fork> on the embedded loop.
2057		2641
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2642	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2643	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2644	portable one.
2061		2645
2062	So when you want to use this feature you will always have to be prepared	2646	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	2647	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	2648	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.	2649	create it, and if that fails, use the normal loop for everything.
2066		2650
		2651	=head3 C<ev_embed> and fork
		2652
		2653	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2654	automatically be applied to the embedded loop as well, so no special
		2655	fork handling is required in that case. When the watcher is not running,
		2656	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2657	as applicable.
		2658
2067	=head3 Watcher-Specific Functions and Data Members	2659	=head3 Watcher-Specific Functions and Data Members
2068		2660
2069	=over 4	2661	=over 4
2070		2662
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2663	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2666
2075	Configures the watcher to embed the given loop, which must be	2667	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	2668	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	2669	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,	2670	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).	2671	if you do not want that, you need to temporarily stop the embed watcher).
2080		2672
2081	=item ev_embed_sweep (loop, ev_embed *)	2673	=item ev_embed_sweep (loop, ev_embed *)
2082		2674
2083	Make a single, non-blocking sweep over the embedded loop. This works	2675	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	2676	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2677	appropriate way for embedded loops.
2086		2678
2087	=item struct ev_loop *other [read-only]	2679	=item struct ev_loop *other [read-only]
2088		2680
2089	The embedded event loop.	2681	The embedded event loop.
2090		2682
…		…
2092		2684
2093	=head3 Examples	2685	=head3 Examples
2094		2686
2095	Example: Try to get an embeddable event loop and embed it into the default	2687	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	2688	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	2689	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	2690	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2691	used).
2100		2692
2101	struct ev_loop *loop_hi = ev_default_init (0);	2693	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2694	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2695	ev_embed embed;
2104		2696
2105	// see if there is a chance of getting one that works	2697	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2698	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2699	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2700	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2701	: 0;
2110		2702
2111	// if we got one, then embed it, otherwise default to loop_hi	2703	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2704	if (loop_lo)
2113	{	2705	{
2114	ev_embed_init (&embed, 0, loop_lo);	2706	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2707	ev_embed_start (loop_hi, &embed);
2116	}	2708	}
2117	else	2709	else
2118	loop_lo = loop_hi;	2710	loop_lo = loop_hi;
2119		2711
2120	Example: Check if kqueue is available but not recommended and create	2712	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2713	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2714	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2715	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2716
2125	struct ev_loop *loop = ev_default_init (0);	2717	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2718	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2719	ev_embed embed;
2128		2720
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2721	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2722	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2723	{
2132	ev_embed_init (&embed, 0, loop_socket);	2724	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2725	ev_embed_start (loop, &embed);
2134	}	2726	}
2135		2727
2136	if (!loop_socket)	2728	if (!loop_socket)
2137	loop_socket = loop;	2729	loop_socket = loop;
2138		2730
2139	// now use loop_socket for all sockets, and loop for everything else	2731	// now use loop_socket for all sockets, and loop for everything else
2140		2732
2141		2733
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2734	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2735
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2736	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2147	event loop blocks next and before C<ev_check> watchers are being called,	2739	event loop blocks next and before C<ev_check> watchers are being called,
2148	and only in the child after the fork. If whoever good citizen calling	2740	and only in the child after the fork. If whoever good citizen calling
2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2741	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2150	handlers will be invoked, too, of course.	2742	handlers will be invoked, too, of course.
2151		2743
		2744	=head3 The special problem of life after fork - how is it possible?
		2745
		2746	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2747	up/change the process environment, followed by a call to C<exec()>. This
		2748	sequence should be handled by libev without any problems.
		2749
		2750	This changes when the application actually wants to do event handling
		2751	in the child, or both parent in child, in effect "continuing" after the
		2752	fork.
		2753
		2754	The default mode of operation (for libev, with application help to detect
		2755	forks) is to duplicate all the state in the child, as would be expected
		2756	when I<either> the parent I<or> the child process continues.
		2757
		2758	When both processes want to continue using libev, then this is usually the
		2759	wrong result. In that case, usually one process (typically the parent) is
		2760	supposed to continue with all watchers in place as before, while the other
		2761	process typically wants to start fresh, i.e. without any active watchers.
		2762
		2763	The cleanest and most efficient way to achieve that with libev is to
		2764	simply create a new event loop, which of course will be "empty", and
		2765	use that for new watchers. This has the advantage of not touching more
		2766	memory than necessary, and thus avoiding the copy-on-write, and the
		2767	disadvantage of having to use multiple event loops (which do not support
		2768	signal watchers).
		2769
		2770	When this is not possible, or you want to use the default loop for
		2771	other reasons, then in the process that wants to start "fresh", call
		2772	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2773	the default loop will "orphan" (not stop) all registered watchers, so you
		2774	have to be careful not to execute code that modifies those watchers. Note
		2775	also that in that case, you have to re-register any signal watchers.
		2776
2152	=head3 Watcher-Specific Functions and Data Members	2777	=head3 Watcher-Specific Functions and Data Members
2153		2778
2154	=over 4	2779	=over 4
2155		2780
2156	=item ev_fork_init (ev_signal *, callback)	2781	=item ev_fork_init (ev_signal *, callback)
…		…
2188	is that the author does not know of a simple (or any) algorithm for a	2813	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	2814	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2815	need elaborate support such as pthreads.
2191		2816
2192	That means that if you want to queue data, you have to provide your own	2817	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	2818	queue. But at least I can tell you how to implement locking around your
2194	queue:	2819	queue:
2195		2820
2196	=over 4	2821	=over 4
2197		2822
2198	=item queueing from a signal handler context	2823	=item queueing from a signal handler context
2199		2824
2200	To implement race-free queueing, you simply add to the queue in the signal	2825	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	2826	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2827	an example that does that for some fictitious SIGUSR1 handler:
2203		2828
2204	static ev_async mysig;	2829	static ev_async mysig;
2205		2830
2206	static void	2831	static void
2207	sigusr1_handler (void)	2832	sigusr1_handler (void)
…		…
2273	=over 4	2898	=over 4
2274		2899
2275	=item ev_async_init (ev_async *, callback)	2900	=item ev_async_init (ev_async *, callback)
2276		2901
2277	Initialises and configures the async watcher - it has no parameters of any	2902	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,	2903	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2279	believe me.	2904	trust me.
2280		2905
2281	=item ev_async_send (loop, ev_async *)	2906	=item ev_async_send (loop, ev_async *)
2282		2907
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2908	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	2909	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	2910	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	2911	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	2912	section below on what exactly this means).
2288		2913
		2914	Note that, as with other watchers in libev, multiple events might get
		2915	compressed into a single callback invocation (another way to look at this
		2916	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2917	reset when the event loop detects that).
		2918
2289	This call incurs the overhead of a syscall only once per loop iteration,	2919	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	2920	iteration, so while the overhead might be noticeable, it doesn't apply to
2291	calls to C<ev_async_send>.	2921	repeated calls to C<ev_async_send> for the same event loop.
2292		2922
2293	=item bool = ev_async_pending (ev_async *)	2923	=item bool = ev_async_pending (ev_async *)
2294		2924
2295	Returns a non-zero value when C<ev_async_send> has been called on the	2925	Returns a non-zero value when C<ev_async_send> has been called on the
2296	watcher but the event has not yet been processed (or even noted) by the	2926	watcher but the event has not yet been processed (or even noted) by the
2297	event loop.	2927	event loop.
2298		2928
2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2929	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2300	the loop iterates next and checks for the watcher to have become active,	2930	the loop iterates next and checks for the watcher to have become active,
2301	it will reset the flag again. C<ev_async_pending> can be used to very	2931	it will reset the flag again. C<ev_async_pending> can be used to very
2302	quickly check wether invoking the loop might be a good idea.	2932	quickly check whether invoking the loop might be a good idea.
2303		2933
2304	Not that this does I<not> check wether the watcher itself is pending, only	2934	Not that this does I<not> check whether the watcher itself is pending,
2305	wether it has been requested to make this watcher pending.	2935	only whether it has been requested to make this watcher pending: there
		2936	is a time window between the event loop checking and resetting the async
		2937	notification, and the callback being invoked.
2306		2938
2307	=back	2939	=back
2308		2940
2309		2941
2310	=head1 OTHER FUNCTIONS	2942	=head1 OTHER FUNCTIONS
…		…
2314	=over 4	2946	=over 4
2315		2947
2316	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2948	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2317		2949
2318	This function combines a simple timer and an I/O watcher, calls your	2950	This function combines a simple timer and an I/O watcher, calls your
2319	callback on whichever event happens first and automatically stop both	2951	callback on whichever event happens first and automatically stops both
2320	watchers. This is useful if you want to wait for a single event on an fd	2952	watchers. This is useful if you want to wait for a single event on an fd
2321	or timeout without having to allocate/configure/start/stop/free one or	2953	or timeout without having to allocate/configure/start/stop/free one or
2322	more watchers yourself.	2954	more watchers yourself.
2323		2955
2324	If C<fd> is less than 0, then no I/O watcher will be started and events	2956	If C<fd> is less than 0, then no I/O watcher will be started and the
2325	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2957	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2326	C<events> set will be craeted and started.	2958	the given C<fd> and C<events> set will be created and started.
2327		2959
2328	If C<timeout> is less than 0, then no timeout watcher will be	2960	If C<timeout> is less than 0, then no timeout watcher will be
2329	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2961	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2330	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2962	repeat = 0) will be started. C<0> is a valid timeout.
2331	dubious value.
2332		2963
2333	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2964	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2334	passed an C<revents> set like normal event callbacks (a combination of	2965	passed an C<revents> set like normal event callbacks (a combination of
2335	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2966	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2336	value passed to C<ev_once>:	2967	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2968	a timeout and an io event at the same time - you probably should give io
		2969	events precedence.
2337		2970
		2971	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2972
2338	static void stdin_ready (int revents, void *arg)	2973	static void stdin_ready (int revents, void *arg)
2339	{	2974	{
2340	if (revents & EV_TIMEOUT)
2341	/* doh, nothing entered */;
2342	else if (revents & EV_READ)	2975	if (revents & EV_READ)
2343	/* stdin might have data for us, joy! */;	2976	/* stdin might have data for us, joy! */;
		2977	else if (revents & EV_TIMEOUT)
		2978	/* doh, nothing entered */;
2344	}	2979	}
2345		2980
2346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2981	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2347		2982
2348	=item ev_feed_event (ev_loop *, watcher *, int revents)	2983	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2349		2984
2350	Feeds the given event set into the event loop, as if the specified event	2985	Feeds the given event set into the event loop, as if the specified event
2351	had happened for the specified watcher (which must be a pointer to an	2986	had happened for the specified watcher (which must be a pointer to an
2352	initialised but not necessarily started event watcher).	2987	initialised but not necessarily started event watcher).
2353		2988
2354	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2989	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2355		2990
2356	Feed an event on the given fd, as if a file descriptor backend detected	2991	Feed an event on the given fd, as if a file descriptor backend detected
2357	the given events it.	2992	the given events it.
2358		2993
2359	=item ev_feed_signal_event (ev_loop *loop, int signum)	2994	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2360		2995
2361	Feed an event as if the given signal occured (C<loop> must be the default	2996	Feed an event as if the given signal occurred (C<loop> must be the default
2362	loop!).	2997	loop!).
2363		2998
2364	=back	2999	=back
2365		3000
2366		3001
…		…
2382		3017
2383	=item * Priorities are not currently supported. Initialising priorities	3018	=item * Priorities are not currently supported. Initialising priorities
2384	will fail and all watchers will have the same priority, even though there	3019	will fail and all watchers will have the same priority, even though there
2385	is an ev_pri field.	3020	is an ev_pri field.
2386		3021
		3022	=item * In libevent, the last base created gets the signals, in libev, the
		3023	first base created (== the default loop) gets the signals.
		3024
2387	=item * Other members are not supported.	3025	=item * Other members are not supported.
2388		3026
2389	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3027	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2390	to use the libev header file and library.	3028	to use the libev header file and library.
2391		3029
2392	=back	3030	=back
2393		3031
2394	=head1 C++ SUPPORT	3032	=head1 C++ SUPPORT
2395		3033
2396	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3034	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2397	you to use some convinience methods to start/stop watchers and also change	3035	you to use some convenience methods to start/stop watchers and also change
2398	the callback model to a model using method callbacks on objects.	3036	the callback model to a model using method callbacks on objects.
2399		3037
2400	To use it,	3038	To use it,
2401		3039
2402	#include <ev++.h>	3040	#include <ev++.h>
2403		3041
2404	This automatically includes F<ev.h> and puts all of its definitions (many	3042	This automatically includes F<ev.h> and puts all of its definitions (many
2405	of them macros) into the global namespace. All C++ specific things are	3043	of them macros) into the global namespace. All C++ specific things are
2406	put into the C<ev> namespace. It should support all the same embedding	3044	put into the C<ev> namespace. It should support all the same embedding
2407	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3045	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2474	your compiler is good :), then the method will be fully inlined into the	3112	your compiler is good :), then the method will be fully inlined into the
2475	thunking function, making it as fast as a direct C callback.	3113	thunking function, making it as fast as a direct C callback.
2476		3114
2477	Example: simple class declaration and watcher initialisation	3115	Example: simple class declaration and watcher initialisation
2478		3116
2479	struct myclass	3117	struct myclass
2480	{	3118	{
2481	void io_cb (ev::io &w, int revents) { }	3119	void io_cb (ev::io &w, int revents) { }
2482	}	3120	}
2483		3121
2484	myclass obj;	3122	myclass obj;
2485	ev::io iow;	3123	ev::io iow;
2486	iow.set <myclass, &myclass::io_cb> (&obj);	3124	iow.set <myclass, &myclass::io_cb> (&obj);
		3125
		3126	=item w->set (object *)
		3127
		3128	This is an B<experimental> feature that might go away in a future version.
		3129
		3130	This is a variation of a method callback - leaving out the method to call
		3131	will default the method to C<operator ()>, which makes it possible to use
		3132	functor objects without having to manually specify the C<operator ()> all
		3133	the time. Incidentally, you can then also leave out the template argument
		3134	list.
		3135
		3136	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3137	int revents)>.
		3138
		3139	See the method-C<set> above for more details.
		3140
		3141	Example: use a functor object as callback.
		3142
		3143	struct myfunctor
		3144	{
		3145	void operator() (ev::io &w, int revents)
		3146	{
		3147	...
		3148	}
		3149	}
		3150
		3151	myfunctor f;
		3152
		3153	ev::io w;
		3154	w.set (&f);
2487		3155
2488	=item w->set<function> (void *data = 0)	3156	=item w->set<function> (void *data = 0)
2489		3157
2490	Also sets a callback, but uses a static method or plain function as	3158	Also sets a callback, but uses a static method or plain function as
2491	callback. The optional C<data> argument will be stored in the watcher's	3159	callback. The optional C<data> argument will be stored in the watcher's
…		…
2493		3161
2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3162	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2495		3163
2496	See the method-C<set> above for more details.	3164	See the method-C<set> above for more details.
2497		3165
2498	Example:	3166	Example: Use a plain function as callback.
2499		3167
2500	static void io_cb (ev::io &w, int revents) { }	3168	static void io_cb (ev::io &w, int revents) { }
2501	iow.set <io_cb> ();	3169	iow.set <io_cb> ();
2502		3170
2503	=item w->set (struct ev_loop *)	3171	=item w->set (struct ev_loop *)
2504		3172
2505	Associates a different C<struct ev_loop> with this watcher. You can only	3173	Associates a different C<struct ev_loop> with this watcher. You can only
2506	do this when the watcher is inactive (and not pending either).	3174	do this when the watcher is inactive (and not pending either).
2507		3175
2508	=item w->set ([args])	3176	=item w->set ([arguments])
2509		3177
2510	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3178	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2511	called at least once. Unlike the C counterpart, an active watcher gets	3179	called at least once. Unlike the C counterpart, an active watcher gets
2512	automatically stopped and restarted when reconfiguring it with this	3180	automatically stopped and restarted when reconfiguring it with this
2513	method.	3181	method.
2514		3182
2515	=item w->start ()	3183	=item w->start ()
…		…
2539	=back	3207	=back
2540		3208
2541	Example: Define a class with an IO and idle watcher, start one of them in	3209	Example: Define a class with an IO and idle watcher, start one of them in
2542	the constructor.	3210	the constructor.
2543		3211
2544	class myclass	3212	class myclass
2545	{	3213	{
2546	ev::io io; void io_cb (ev::io &w, int revents);	3214	ev::io io ; void io_cb (ev::io &w, int revents);
2547	ev:idle idle void idle_cb (ev::idle &w, int revents);	3215	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2548		3216
2549	myclass (int fd)	3217	myclass (int fd)
2550	{	3218	{
2551	io .set <myclass, &myclass::io_cb > (this);	3219	io .set <myclass, &myclass::io_cb > (this);
2552	idle.set <myclass, &myclass::idle_cb> (this);	3220	idle.set <myclass, &myclass::idle_cb> (this);
2553		3221
2554	io.start (fd, ev::READ);	3222	io.start (fd, ev::READ);
2555	}	3223	}
2556	};	3224	};
2557		3225
2558		3226
2559	=head1 OTHER LANGUAGE BINDINGS	3227	=head1 OTHER LANGUAGE BINDINGS
2560		3228
2561	Libev does not offer other language bindings itself, but bindings for a	3229	Libev does not offer other language bindings itself, but bindings for a
2562	numbe rof languages exist in the form of third-party packages. If you know	3230	number of languages exist in the form of third-party packages. If you know
2563	any interesting language binding in addition to the ones listed here, drop	3231	any interesting language binding in addition to the ones listed here, drop
2564	me a note.	3232	me a note.
2565		3233
2566	=over 4	3234	=over 4
2567		3235
2568	=item Perl	3236	=item Perl
2569		3237
2570	The EV module implements the full libev API and is actually used to test	3238	The EV module implements the full libev API and is actually used to test
2571	libev. EV is developed together with libev. Apart from the EV core module,	3239	libev. EV is developed together with libev. Apart from the EV core module,
2572	there are additional modules that implement libev-compatible interfaces	3240	there are additional modules that implement libev-compatible interfaces
2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3241	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3242	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3243	and C<EV::Glib>).
2575		3244
2576	It can be found and installed via CPAN, its homepage is found at	3245	It can be found and installed via CPAN, its homepage is at
2577	L<http://software.schmorp.de/pkg/EV>.	3246	L<http://software.schmorp.de/pkg/EV>.
2578		3247
		3248	=item Python
		3249
		3250	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3251	seems to be quite complete and well-documented.
		3252
2579	=item Ruby	3253	=item Ruby
2580		3254
2581	Tony Arcieri has written a ruby extension that offers access to a subset	3255	Tony Arcieri has written a ruby extension that offers access to a subset
2582	of the libev API and adds filehandle abstractions, asynchronous DNS and	3256	of the libev API and adds file handle abstractions, asynchronous DNS and
2583	more on top of it. It can be found via gem servers. Its homepage is at	3257	more on top of it. It can be found via gem servers. Its homepage is at
2584	L<http://rev.rubyforge.org/>.	3258	L<http://rev.rubyforge.org/>.
2585		3259
		3260	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3261	makes rev work even on mingw.
		3262
		3263	=item Haskell
		3264
		3265	A haskell binding to libev is available at
		3266	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3267
2586	=item D	3268	=item D
2587		3269
2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3270	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3271	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3272
		3273	=item Ocaml
		3274
		3275	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3276	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2590		3277
2591	=back	3278	=back
2592		3279
2593		3280
2594	=head1 MACRO MAGIC	3281	=head1 MACRO MAGIC
2595		3282
2596	Libev can be compiled with a variety of options, the most fundamantal	3283	Libev can be compiled with a variety of options, the most fundamental
2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3284	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2598	functions and callbacks have an initial C<struct ev_loop *> argument.	3285	functions and callbacks have an initial C<struct ev_loop *> argument.
2599		3286
2600	To make it easier to write programs that cope with either variant, the	3287	To make it easier to write programs that cope with either variant, the
2601	following macros are defined:	3288	following macros are defined:
…		…
2606		3293
2607	This provides the loop I<argument> for functions, if one is required ("ev	3294	This provides the loop I<argument> for functions, if one is required ("ev
2608	loop argument"). The C<EV_A> form is used when this is the sole argument,	3295	loop argument"). The C<EV_A> form is used when this is the sole argument,
2609	C<EV_A_> is used when other arguments are following. Example:	3296	C<EV_A_> is used when other arguments are following. Example:
2610		3297
2611	ev_unref (EV_A);	3298	ev_unref (EV_A);
2612	ev_timer_add (EV_A_ watcher);	3299	ev_timer_add (EV_A_ watcher);
2613	ev_loop (EV_A_ 0);	3300	ev_loop (EV_A_ 0);
2614		3301
2615	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3302	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2616	which is often provided by the following macro.	3303	which is often provided by the following macro.
2617		3304
2618	=item C<EV_P>, C<EV_P_>	3305	=item C<EV_P>, C<EV_P_>
2619		3306
2620	This provides the loop I<parameter> for functions, if one is required ("ev	3307	This provides the loop I<parameter> for functions, if one is required ("ev
2621	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3308	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2622	C<EV_P_> is used when other parameters are following. Example:	3309	C<EV_P_> is used when other parameters are following. Example:
2623		3310
2624	// this is how ev_unref is being declared	3311	// this is how ev_unref is being declared
2625	static void ev_unref (EV_P);	3312	static void ev_unref (EV_P);
2626		3313
2627	// this is how you can declare your typical callback	3314	// this is how you can declare your typical callback
2628	static void cb (EV_P_ ev_timer *w, int revents)	3315	static void cb (EV_P_ ev_timer *w, int revents)
2629		3316
2630	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3317	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2631	suitable for use with C<EV_A>.	3318	suitable for use with C<EV_A>.
2632		3319
2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3320	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2634		3321
2635	Similar to the other two macros, this gives you the value of the default	3322	Similar to the other two macros, this gives you the value of the default
2636	loop, if multiple loops are supported ("ev loop default").	3323	loop, if multiple loops are supported ("ev loop default").
		3324
		3325	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3326
		3327	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3328	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3329	is undefined when the default loop has not been initialised by a previous
		3330	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3331
		3332	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3333	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2637		3334
2638	=back	3335	=back
2639		3336
2640	Example: Declare and initialise a check watcher, utilising the above	3337	Example: Declare and initialise a check watcher, utilising the above
2641	macros so it will work regardless of whether multiple loops are supported	3338	macros so it will work regardless of whether multiple loops are supported
2642	or not.	3339	or not.
2643		3340
2644	static void	3341	static void
2645	check_cb (EV_P_ ev_timer *w, int revents)	3342	check_cb (EV_P_ ev_timer *w, int revents)
2646	{	3343	{
2647	ev_check_stop (EV_A_ w);	3344	ev_check_stop (EV_A_ w);
2648	}	3345	}
2649		3346
2650	ev_check check;	3347	ev_check check;
2651	ev_check_init (&check, check_cb);	3348	ev_check_init (&check, check_cb);
2652	ev_check_start (EV_DEFAULT_ &check);	3349	ev_check_start (EV_DEFAULT_ &check);
2653	ev_loop (EV_DEFAULT_ 0);	3350	ev_loop (EV_DEFAULT_ 0);
2654		3351
2655	=head1 EMBEDDING	3352	=head1 EMBEDDING
2656		3353
2657	Libev can (and often is) directly embedded into host	3354	Libev can (and often is) directly embedded into host
2658	applications. Examples of applications that embed it include the Deliantra	3355	applications. Examples of applications that embed it include the Deliantra
…		…
2665	libev somewhere in your source tree).	3362	libev somewhere in your source tree).
2666		3363
2667	=head2 FILESETS	3364	=head2 FILESETS
2668		3365
2669	Depending on what features you need you need to include one or more sets of files	3366	Depending on what features you need you need to include one or more sets of files
2670	in your app.	3367	in your application.
2671		3368
2672	=head3 CORE EVENT LOOP	3369	=head3 CORE EVENT LOOP
2673		3370
2674	To include only the libev core (all the C<ev_*> functions), with manual	3371	To include only the libev core (all the C<ev_*> functions), with manual
2675	configuration (no autoconf):	3372	configuration (no autoconf):
2676		3373
2677	#define EV_STANDALONE 1	3374	#define EV_STANDALONE 1
2678	#include "ev.c"	3375	#include "ev.c"
2679		3376
2680	This will automatically include F<ev.h>, too, and should be done in a	3377	This will automatically include F<ev.h>, too, and should be done in a
2681	single C source file only to provide the function implementations. To use	3378	single C source file only to provide the function implementations. To use
2682	it, do the same for F<ev.h> in all files wishing to use this API (best	3379	it, do the same for F<ev.h> in all files wishing to use this API (best
2683	done by writing a wrapper around F<ev.h> that you can include instead and	3380	done by writing a wrapper around F<ev.h> that you can include instead and
2684	where you can put other configuration options):	3381	where you can put other configuration options):
2685		3382
2686	#define EV_STANDALONE 1	3383	#define EV_STANDALONE 1
2687	#include "ev.h"	3384	#include "ev.h"
2688		3385
2689	Both header files and implementation files can be compiled with a C++	3386	Both header files and implementation files can be compiled with a C++
2690	compiler (at least, thats a stated goal, and breakage will be treated	3387	compiler (at least, that's a stated goal, and breakage will be treated
2691	as a bug).	3388	as a bug).
2692		3389
2693	You need the following files in your source tree, or in a directory	3390	You need the following files in your source tree, or in a directory
2694	in your include path (e.g. in libev/ when using -Ilibev):	3391	in your include path (e.g. in libev/ when using -Ilibev):
2695		3392
2696	ev.h	3393	ev.h
2697	ev.c	3394	ev.c
2698	ev_vars.h	3395	ev_vars.h
2699	ev_wrap.h	3396	ev_wrap.h
2700		3397
2701	ev_win32.c required on win32 platforms only	3398	ev_win32.c required on win32 platforms only
2702		3399
2703	ev_select.c only when select backend is enabled (which is enabled by default)	3400	ev_select.c only when select backend is enabled (which is enabled by default)
2704	ev_poll.c only when poll backend is enabled (disabled by default)	3401	ev_poll.c only when poll backend is enabled (disabled by default)
2705	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3402	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2706	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3403	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2707	ev_port.c only when the solaris port backend is enabled (disabled by default)	3404	ev_port.c only when the solaris port backend is enabled (disabled by default)
2708		3405
2709	F<ev.c> includes the backend files directly when enabled, so you only need	3406	F<ev.c> includes the backend files directly when enabled, so you only need
2710	to compile this single file.	3407	to compile this single file.
2711		3408
2712	=head3 LIBEVENT COMPATIBILITY API	3409	=head3 LIBEVENT COMPATIBILITY API
2713		3410
2714	To include the libevent compatibility API, also include:	3411	To include the libevent compatibility API, also include:
2715		3412
2716	#include "event.c"	3413	#include "event.c"
2717		3414
2718	in the file including F<ev.c>, and:	3415	in the file including F<ev.c>, and:
2719		3416
2720	#include "event.h"	3417	#include "event.h"
2721		3418
2722	in the files that want to use the libevent API. This also includes F<ev.h>.	3419	in the files that want to use the libevent API. This also includes F<ev.h>.
2723		3420
2724	You need the following additional files for this:	3421	You need the following additional files for this:
2725		3422
2726	event.h	3423	event.h
2727	event.c	3424	event.c
2728		3425
2729	=head3 AUTOCONF SUPPORT	3426	=head3 AUTOCONF SUPPORT
2730		3427
2731	Instead of using C<EV_STANDALONE=1> and providing your config in	3428	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2732	whatever way you want, you can also C<m4_include([libev.m4])> in your	3429	whatever way you want, you can also C<m4_include([libev.m4])> in your
2733	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3430	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2734	include F<config.h> and configure itself accordingly.	3431	include F<config.h> and configure itself accordingly.
2735		3432
2736	For this of course you need the m4 file:	3433	For this of course you need the m4 file:
2737		3434
2738	libev.m4	3435	libev.m4
2739		3436
2740	=head2 PREPROCESSOR SYMBOLS/MACROS	3437	=head2 PREPROCESSOR SYMBOLS/MACROS
2741		3438
2742	Libev can be configured via a variety of preprocessor symbols you have to	3439	Libev can be configured via a variety of preprocessor symbols you have to
2743	define before including any of its files. The default in the absense of	3440	define before including any of its files. The default in the absence of
2744	autoconf is noted for every option.	3441	autoconf is documented for every option.
2745		3442
2746	=over 4	3443	=over 4
2747		3444
2748	=item EV_STANDALONE	3445	=item EV_STANDALONE
2749		3446
…		…
2751	keeps libev from including F<config.h>, and it also defines dummy	3448	keeps libev from including F<config.h>, and it also defines dummy
2752	implementations for some libevent functions (such as logging, which is not	3449	implementations for some libevent functions (such as logging, which is not
2753	supported). It will also not define any of the structs usually found in	3450	supported). It will also not define any of the structs usually found in
2754	F<event.h> that are not directly supported by the libev core alone.	3451	F<event.h> that are not directly supported by the libev core alone.
2755		3452
		3453	In stanbdalone mode, libev will still try to automatically deduce the
		3454	configuration, but has to be more conservative.
		3455
2756	=item EV_USE_MONOTONIC	3456	=item EV_USE_MONOTONIC
2757		3457
2758	If defined to be C<1>, libev will try to detect the availability of the	3458	If defined to be C<1>, libev will try to detect the availability of the
2759	monotonic clock option at both compiletime and runtime. Otherwise no use	3459	monotonic clock option at both compile time and runtime. Otherwise no
2760	of the monotonic clock option will be attempted. If you enable this, you	3460	use of the monotonic clock option will be attempted. If you enable this,
2761	usually have to link against librt or something similar. Enabling it when	3461	you usually have to link against librt or something similar. Enabling it
2762	the functionality isn't available is safe, though, although you have	3462	when the functionality isn't available is safe, though, although you have
2763	to make sure you link against any libraries where the C<clock_gettime>	3463	to make sure you link against any libraries where the C<clock_gettime>
2764	function is hiding in (often F<-lrt>).	3464	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2765		3465
2766	=item EV_USE_REALTIME	3466	=item EV_USE_REALTIME
2767		3467
2768	If defined to be C<1>, libev will try to detect the availability of the	3468	If defined to be C<1>, libev will try to detect the availability of the
2769	realtime clock option at compiletime (and assume its availability at	3469	real-time clock option at compile time (and assume its availability
2770	runtime if successful). Otherwise no use of the realtime clock option will	3470	at runtime if successful). Otherwise no use of the real-time clock
2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3471	option will be attempted. This effectively replaces C<gettimeofday>
2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3472	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2773	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3473	correctness. See the note about libraries in the description of
		3474	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3475	C<EV_USE_CLOCK_SYSCALL>.
		3476
		3477	=item EV_USE_CLOCK_SYSCALL
		3478
		3479	If defined to be C<1>, libev will try to use a direct syscall instead
		3480	of calling the system-provided C<clock_gettime> function. This option
		3481	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3482	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3483	programs needlessly. Using a direct syscall is slightly slower (in
		3484	theory), because no optimised vdso implementation can be used, but avoids
		3485	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3486	higher, as it simplifies linking (no need for C<-lrt>).
2774		3487
2775	=item EV_USE_NANOSLEEP	3488	=item EV_USE_NANOSLEEP
2776		3489
2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3490	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2778	and will use it for delays. Otherwise it will use C<select ()>.	3491	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2786	2.7 or newer, otherwise disabled.	3499	2.7 or newer, otherwise disabled.
2787		3500
2788	=item EV_USE_SELECT	3501	=item EV_USE_SELECT
2789		3502
2790	If undefined or defined to be C<1>, libev will compile in support for the	3503	If undefined or defined to be C<1>, libev will compile in support for the
2791	C<select>(2) backend. No attempt at autodetection will be done: if no	3504	C<select>(2) backend. No attempt at auto-detection will be done: if no
2792	other method takes over, select will be it. Otherwise the select backend	3505	other method takes over, select will be it. Otherwise the select backend
2793	will not be compiled in.	3506	will not be compiled in.
2794		3507
2795	=item EV_SELECT_USE_FD_SET	3508	=item EV_SELECT_USE_FD_SET
2796		3509
2797	If defined to C<1>, then the select backend will use the system C<fd_set>	3510	If defined to C<1>, then the select backend will use the system C<fd_set>
2798	structure. This is useful if libev doesn't compile due to a missing	3511	structure. This is useful if libev doesn't compile due to a missing
2799	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3512	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2800	exotic systems. This usually limits the range of file descriptors to some	3513	on exotic systems. This usually limits the range of file descriptors to
2801	low limit such as 1024 or might have other limitations (winsocket only	3514	some low limit such as 1024 or might have other limitations (winsocket
2802	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3515	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2803	influence the size of the C<fd_set> used.	3516	configures the maximum size of the C<fd_set>.
2804		3517
2805	=item EV_SELECT_IS_WINSOCKET	3518	=item EV_SELECT_IS_WINSOCKET
2806		3519
2807	When defined to C<1>, the select backend will assume that	3520	When defined to C<1>, the select backend will assume that
2808	select/socket/connect etc. don't understand file descriptors but	3521	select/socket/connect etc. don't understand file descriptors but
…		…
2853	otherwise another method will be used as fallback. This is the preferred	3566	otherwise another method will be used as fallback. This is the preferred
2854	backend for Solaris 10 systems.	3567	backend for Solaris 10 systems.
2855		3568
2856	=item EV_USE_DEVPOLL	3569	=item EV_USE_DEVPOLL
2857		3570
2858	reserved for future expansion, works like the USE symbols above.	3571	Reserved for future expansion, works like the USE symbols above.
2859		3572
2860	=item EV_USE_INOTIFY	3573	=item EV_USE_INOTIFY
2861		3574
2862	If defined to be C<1>, libev will compile in support for the Linux inotify	3575	If defined to be C<1>, libev will compile in support for the Linux inotify
2863	interface to speed up C<ev_stat> watchers. Its actual availability will	3576	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2870	access is atomic with respect to other threads or signal contexts. No such	3583	access is atomic with respect to other threads or signal contexts. No such
2871	type is easily found in the C language, so you can provide your own type	3584	type is easily found in the C language, so you can provide your own type
2872	that you know is safe for your purposes. It is used both for signal handler "locking"	3585	that you know is safe for your purposes. It is used both for signal handler "locking"
2873	as well as for signal and thread safety in C<ev_async> watchers.	3586	as well as for signal and thread safety in C<ev_async> watchers.
2874		3587
2875	In the absense of this define, libev will use C<sig_atomic_t volatile>	3588	In the absence of this define, libev will use C<sig_atomic_t volatile>
2876	(from F<signal.h>), which is usually good enough on most platforms.	3589	(from F<signal.h>), which is usually good enough on most platforms.
2877		3590
2878	=item EV_H	3591	=item EV_H
2879		3592
2880	The name of the F<ev.h> header file used to include it. The default if	3593	The name of the F<ev.h> header file used to include it. The default if
…		…
2919	When doing priority-based operations, libev usually has to linearly search	3632	When doing priority-based operations, libev usually has to linearly search
2920	all the priorities, so having many of them (hundreds) uses a lot of space	3633	all the priorities, so having many of them (hundreds) uses a lot of space
2921	and time, so using the defaults of five priorities (-2 .. +2) is usually	3634	and time, so using the defaults of five priorities (-2 .. +2) is usually
2922	fine.	3635	fine.
2923		3636
2924	If your embedding app does not need any priorities, defining these both to	3637	If your embedding application does not need any priorities, defining these
2925	C<0> will save some memory and cpu.	3638	both to C<0> will save some memory and CPU.
2926		3639
2927	=item EV_PERIODIC_ENABLE	3640	=item EV_PERIODIC_ENABLE
2928		3641
2929	If undefined or defined to be C<1>, then periodic timers are supported. If	3642	If undefined or defined to be C<1>, then periodic timers are supported. If
2930	defined to be C<0>, then they are not. Disabling them saves a few kB of	3643	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2937	code.	3650	code.
2938		3651
2939	=item EV_EMBED_ENABLE	3652	=item EV_EMBED_ENABLE
2940		3653
2941	If undefined or defined to be C<1>, then embed watchers are supported. If	3654	If undefined or defined to be C<1>, then embed watchers are supported. If
2942	defined to be C<0>, then they are not.	3655	defined to be C<0>, then they are not. Embed watchers rely on most other
		3656	watcher types, which therefore must not be disabled.
2943		3657
2944	=item EV_STAT_ENABLE	3658	=item EV_STAT_ENABLE
2945		3659
2946	If undefined or defined to be C<1>, then stat watchers are supported. If	3660	If undefined or defined to be C<1>, then stat watchers are supported. If
2947	defined to be C<0>, then they are not.	3661	defined to be C<0>, then they are not.
…		…
2957	defined to be C<0>, then they are not.	3671	defined to be C<0>, then they are not.
2958		3672
2959	=item EV_MINIMAL	3673	=item EV_MINIMAL
2960		3674
2961	If you need to shave off some kilobytes of code at the expense of some	3675	If you need to shave off some kilobytes of code at the expense of some
2962	speed, define this symbol to C<1>. Currently only used for gcc to override	3676	speed, define this symbol to C<1>. Currently this is used to override some
2963	some inlining decisions, saves roughly 30% codesize of amd64.	3677	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3678	much smaller 2-heap for timer management over the default 4-heap.
2964		3679
2965	=item EV_PID_HASHSIZE	3680	=item EV_PID_HASHSIZE
2966		3681
2967	C<ev_child> watchers use a small hash table to distribute workload by	3682	C<ev_child> watchers use a small hash table to distribute workload by
2968	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3683	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2975	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3690	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2976	usually more than enough. If you need to manage thousands of C<ev_stat>	3691	usually more than enough. If you need to manage thousands of C<ev_stat>
2977	watchers you might want to increase this value (I<must> be a power of	3692	watchers you might want to increase this value (I<must> be a power of
2978	two).	3693	two).
2979		3694
		3695	=item EV_USE_4HEAP
		3696
		3697	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3698	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3699	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3700	faster performance with many (thousands) of watchers.
		3701
		3702	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3703	(disabled).
		3704
		3705	=item EV_HEAP_CACHE_AT
		3706
		3707	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3708	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3709	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3710	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3711	but avoids random read accesses on heap changes. This improves performance
		3712	noticeably with many (hundreds) of watchers.
		3713
		3714	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3715	(disabled).
		3716
		3717	=item EV_VERIFY
		3718
		3719	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3720	be done: If set to C<0>, no internal verification code will be compiled
		3721	in. If set to C<1>, then verification code will be compiled in, but not
		3722	called. If set to C<2>, then the internal verification code will be
		3723	called once per loop, which can slow down libev. If set to C<3>, then the
		3724	verification code will be called very frequently, which will slow down
		3725	libev considerably.
		3726
		3727	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3728	C<0>.
		3729
2980	=item EV_COMMON	3730	=item EV_COMMON
2981		3731
2982	By default, all watchers have a C<void *data> member. By redefining	3732	By default, all watchers have a C<void *data> member. By redefining
2983	this macro to a something else you can include more and other types of	3733	this macro to a something else you can include more and other types of
2984	members. You have to define it each time you include one of the files,	3734	members. You have to define it each time you include one of the files,
2985	though, and it must be identical each time.	3735	though, and it must be identical each time.
2986		3736
2987	For example, the perl EV module uses something like this:	3737	For example, the perl EV module uses something like this:
2988		3738
2989	#define EV_COMMON \	3739	#define EV_COMMON \
2990	SV *self; /* contains this struct */ \	3740	SV *self; /* contains this struct */ \
2991	SV *cb_sv, *fh /* note no trailing ";" */	3741	SV *cb_sv, *fh /* note no trailing ";" */
2992		3742
2993	=item EV_CB_DECLARE (type)	3743	=item EV_CB_DECLARE (type)
2994		3744
2995	=item EV_CB_INVOKE (watcher, revents)	3745	=item EV_CB_INVOKE (watcher, revents)
2996		3746
…		…
3001	definition and a statement, respectively. See the F<ev.h> header file for	3751	definition and a statement, respectively. See the F<ev.h> header file for
3002	their default definitions. One possible use for overriding these is to	3752	their default definitions. One possible use for overriding these is to
3003	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3753	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3004	method calls instead of plain function calls in C++.	3754	method calls instead of plain function calls in C++.
3005		3755
		3756	=back
		3757
3006	=head2 EXPORTED API SYMBOLS	3758	=head2 EXPORTED API SYMBOLS
3007		3759
3008	If you need to re-export the API (e.g. via a dll) and you need a list of	3760	If you need to re-export the API (e.g. via a DLL) and you need a list of
3009	exported symbols, you can use the provided F<Symbol.*> files which list	3761	exported symbols, you can use the provided F<Symbol.*> files which list
3010	all public symbols, one per line:	3762	all public symbols, one per line:
3011		3763
3012	Symbols.ev for libev proper	3764	Symbols.ev for libev proper
3013	Symbols.event for the libevent emulation	3765	Symbols.event for the libevent emulation
3014		3766
3015	This can also be used to rename all public symbols to avoid clashes with	3767	This can also be used to rename all public symbols to avoid clashes with
3016	multiple versions of libev linked together (which is obviously bad in	3768	multiple versions of libev linked together (which is obviously bad in
3017	itself, but sometimes it is inconvinient to avoid this).	3769	itself, but sometimes it is inconvenient to avoid this).
3018		3770
3019	A sed command like this will create wrapper C<#define>'s that you need to	3771	A sed command like this will create wrapper C<#define>'s that you need to
3020	include before including F<ev.h>:	3772	include before including F<ev.h>:
3021		3773
3022	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3774	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3039	file.	3791	file.
3040		3792
3041	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3793	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3042	that everybody includes and which overrides some configure choices:	3794	that everybody includes and which overrides some configure choices:
3043		3795
3044	#define EV_MINIMAL 1	3796	#define EV_MINIMAL 1
3045	#define EV_USE_POLL 0	3797	#define EV_USE_POLL 0
3046	#define EV_MULTIPLICITY 0	3798	#define EV_MULTIPLICITY 0
3047	#define EV_PERIODIC_ENABLE 0	3799	#define EV_PERIODIC_ENABLE 0
3048	#define EV_STAT_ENABLE 0	3800	#define EV_STAT_ENABLE 0
3049	#define EV_FORK_ENABLE 0	3801	#define EV_FORK_ENABLE 0
3050	#define EV_CONFIG_H <config.h>	3802	#define EV_CONFIG_H <config.h>
3051	#define EV_MINPRI 0	3803	#define EV_MINPRI 0
3052	#define EV_MAXPRI 0	3804	#define EV_MAXPRI 0
3053		3805
3054	#include "ev++.h"	3806	#include "ev++.h"
3055		3807
3056	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3808	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3057		3809
3058	#include "ev_cpp.h"	3810	#include "ev_cpp.h"
3059	#include "ev.c"	3811	#include "ev.c"
3060		3812
		3813	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3061		3814
3062	=head1 COMPLEXITIES	3815	=head2 THREADS AND COROUTINES
3063		3816
3064	In this section the complexities of (many of) the algorithms used inside	3817	=head3 THREADS
3065	libev will be explained. For complexity discussions about backends see the
3066	documentation for C<ev_default_init>.
3067		3818
3068	All of the following are about amortised time: If an array needs to be	3819	All libev functions are reentrant and thread-safe unless explicitly
3069	extended, libev needs to realloc and move the whole array, but this	3820	documented otherwise, but libev implements no locking itself. This means
3070	happens asymptotically never with higher number of elements, so O(1) might	3821	that you can use as many loops as you want in parallel, as long as there
3071	mean it might do a lengthy realloc operation in rare cases, but on average	3822	are no concurrent calls into any libev function with the same loop
3072	it is much faster and asymptotically approaches constant time.	3823	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3824	of course): libev guarantees that different event loops share no data
		3825	structures that need any locking.
		3826
		3827	Or to put it differently: calls with different loop parameters can be done
		3828	concurrently from multiple threads, calls with the same loop parameter
		3829	must be done serially (but can be done from different threads, as long as
		3830	only one thread ever is inside a call at any point in time, e.g. by using
		3831	a mutex per loop).
		3832
		3833	Specifically to support threads (and signal handlers), libev implements
		3834	so-called C<ev_async> watchers, which allow some limited form of
		3835	concurrency on the same event loop, namely waking it up "from the
		3836	outside".
		3837
		3838	If you want to know which design (one loop, locking, or multiple loops
		3839	without or something else still) is best for your problem, then I cannot
		3840	help you, but here is some generic advice:
3073		3841
3074	=over 4	3842	=over 4
3075		3843
3076	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3844	=item * most applications have a main thread: use the default libev loop
		3845	in that thread, or create a separate thread running only the default loop.
3077		3846
3078	This means that, when you have a watcher that triggers in one hour and	3847	This helps integrating other libraries or software modules that use libev
3079	there are 100 watchers that would trigger before that then inserting will	3848	themselves and don't care/know about threading.
3080	have to skip roughly seven (C<ld 100>) of these watchers.
3081		3849
3082	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3850	=item * one loop per thread is usually a good model.
3083		3851
3084	That means that changing a timer costs less than removing/adding them	3852	Doing this is almost never wrong, sometimes a better-performance model
3085	as only the relative motion in the event queue has to be paid for.	3853	exists, but it is always a good start.
3086		3854
3087	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3855	=item * other models exist, such as the leader/follower pattern, where one
		3856	loop is handed through multiple threads in a kind of round-robin fashion.
3088		3857
3089	These just add the watcher into an array or at the head of a list.	3858	Choosing a model is hard - look around, learn, know that usually you can do
		3859	better than you currently do :-)
3090		3860
3091	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3861	=item * often you need to talk to some other thread which blocks in the
		3862	event loop.
3092		3863
3093	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3864	C<ev_async> watchers can be used to wake them up from other threads safely
		3865	(or from signal contexts...).
3094		3866
3095	These watchers are stored in lists then need to be walked to find the	3867	An example use would be to communicate signals or other events that only
3096	correct watcher to remove. The lists are usually short (you don't usually	3868	work in the default loop by registering the signal watcher with the
3097	have many watchers waiting for the same fd or signal).	3869	default loop and triggering an C<ev_async> watcher from the default loop
3098		3870	watcher callback into the event loop interested in the signal.
3099	=item Finding the next timer in each loop iteration: O(1)
3100
3101	By virtue of using a binary heap, the next timer is always found at the
3102	beginning of the storage array.
3103
3104	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3105
3106	A change means an I/O watcher gets started or stopped, which requires
3107	libev to recalculate its status (and possibly tell the kernel, depending
3108	on backend and wether C<ev_io_set> was used).
3109
3110	=item Activating one watcher (putting it into the pending state): O(1)
3111
3112	=item Priority handling: O(number_of_priorities)
3113
3114	Priorities are implemented by allocating some space for each
3115	priority. When doing priority-based operations, libev usually has to
3116	linearly search all the priorities, but starting/stopping and activating
3117	watchers becomes O(1) w.r.t. priority handling.
3118
3119	=item Sending an ev_async: O(1)
3120
3121	=item Processing ev_async_send: O(number_of_async_watchers)
3122
3123	=item Processing signals: O(max_signal_number)
3124
3125	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3126	calls in the current loop iteration. Checking for async and signal events
3127	involves iterating over all running async watchers or all signal numbers.
3128		3871
3129	=back	3872	=back
3130		3873
		3874	=head3 COROUTINES
3131		3875
3132	=head1 Win32 platform limitations and workarounds	3876	Libev is very accommodating to coroutines ("cooperative threads"):
		3877	libev fully supports nesting calls to its functions from different
		3878	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3879	different coroutines, and switch freely between both coroutines running the
		3880	loop, as long as you don't confuse yourself). The only exception is that
		3881	you must not do this from C<ev_periodic> reschedule callbacks.
		3882
		3883	Care has been taken to ensure that libev does not keep local state inside
		3884	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3885	they do not call any callbacks.
		3886
		3887	=head2 COMPILER WARNINGS
		3888
		3889	Depending on your compiler and compiler settings, you might get no or a
		3890	lot of warnings when compiling libev code. Some people are apparently
		3891	scared by this.
		3892
		3893	However, these are unavoidable for many reasons. For one, each compiler
		3894	has different warnings, and each user has different tastes regarding
		3895	warning options. "Warn-free" code therefore cannot be a goal except when
		3896	targeting a specific compiler and compiler-version.
		3897
		3898	Another reason is that some compiler warnings require elaborate
		3899	workarounds, or other changes to the code that make it less clear and less
		3900	maintainable.
		3901
		3902	And of course, some compiler warnings are just plain stupid, or simply
		3903	wrong (because they don't actually warn about the condition their message
		3904	seems to warn about). For example, certain older gcc versions had some
		3905	warnings that resulted an extreme number of false positives. These have
		3906	been fixed, but some people still insist on making code warn-free with
		3907	such buggy versions.
		3908
		3909	While libev is written to generate as few warnings as possible,
		3910	"warn-free" code is not a goal, and it is recommended not to build libev
		3911	with any compiler warnings enabled unless you are prepared to cope with
		3912	them (e.g. by ignoring them). Remember that warnings are just that:
		3913	warnings, not errors, or proof of bugs.
		3914
		3915
		3916	=head2 VALGRIND
		3917
		3918	Valgrind has a special section here because it is a popular tool that is
		3919	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3920
		3921	If you think you found a bug (memory leak, uninitialised data access etc.)
		3922	in libev, then check twice: If valgrind reports something like:
		3923
		3924	==2274== definitely lost: 0 bytes in 0 blocks.
		3925	==2274== possibly lost: 0 bytes in 0 blocks.
		3926	==2274== still reachable: 256 bytes in 1 blocks.
		3927
		3928	Then there is no memory leak, just as memory accounted to global variables
		3929	is not a memleak - the memory is still being referenced, and didn't leak.
		3930
		3931	Similarly, under some circumstances, valgrind might report kernel bugs
		3932	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3933	although an acceptable workaround has been found here), or it might be
		3934	confused.
		3935
		3936	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3937	make it into some kind of religion.
		3938
		3939	If you are unsure about something, feel free to contact the mailing list
		3940	with the full valgrind report and an explanation on why you think this
		3941	is a bug in libev (best check the archives, too :). However, don't be
		3942	annoyed when you get a brisk "this is no bug" answer and take the chance
		3943	of learning how to interpret valgrind properly.
		3944
		3945	If you need, for some reason, empty reports from valgrind for your project
		3946	I suggest using suppression lists.
		3947
		3948
		3949	=head1 PORTABILITY NOTES
		3950
		3951	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3133		3952
3134	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3953	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3135	requires, and its I/O model is fundamentally incompatible with the POSIX	3954	requires, and its I/O model is fundamentally incompatible with the POSIX
3136	model. Libev still offers limited functionality on this platform in	3955	model. Libev still offers limited functionality on this platform in
3137	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3956	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3138	descriptors. This only applies when using Win32 natively, not when using	3957	descriptors. This only applies when using Win32 natively, not when using
3139	e.g. cygwin.	3958	e.g. cygwin.
3140		3959
		3960	Lifting these limitations would basically require the full
		3961	re-implementation of the I/O system. If you are into these kinds of
		3962	things, then note that glib does exactly that for you in a very portable
		3963	way (note also that glib is the slowest event library known to man).
		3964
3141	There is no supported compilation method available on windows except	3965	There is no supported compilation method available on windows except
3142	embedding it into other applications.	3966	embedding it into other applications.
3143		3967
		3968	Sensible signal handling is officially unsupported by Microsoft - libev
		3969	tries its best, but under most conditions, signals will simply not work.
		3970
		3971	Not a libev limitation but worth mentioning: windows apparently doesn't
		3972	accept large writes: instead of resulting in a partial write, windows will
		3973	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3974	so make sure you only write small amounts into your sockets (less than a
		3975	megabyte seems safe, but this apparently depends on the amount of memory
		3976	available).
		3977
3144	Due to the many, low, and arbitrary limits on the win32 platform and the	3978	Due to the many, low, and arbitrary limits on the win32 platform and
3145	abysmal performance of winsockets, using a large number of sockets is not	3979	the abysmal performance of winsockets, using a large number of sockets
3146	recommended (and not reasonable). If your program needs to use more than	3980	is not recommended (and not reasonable). If your program needs to use
3147	a hundred or so sockets, then likely it needs to use a totally different	3981	more than a hundred or so sockets, then likely it needs to use a totally
3148	implementation for windows, as libev offers the POSIX model, which cannot	3982	different implementation for windows, as libev offers the POSIX readiness
3149	be implemented efficiently on windows (microsoft monopoly games).	3983	notification model, which cannot be implemented efficiently on windows
		3984	(due to Microsoft monopoly games).
		3985
		3986	A typical way to use libev under windows is to embed it (see the embedding
		3987	section for details) and use the following F<evwrap.h> header file instead
		3988	of F<ev.h>:
		3989
		3990	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3991	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3992
		3993	#include "ev.h"
		3994
		3995	And compile the following F<evwrap.c> file into your project (make sure
		3996	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3997
		3998	#include "evwrap.h"
		3999	#include "ev.c"
3150		4000
3151	=over 4	4001	=over 4
3152		4002
3153	=item The winsocket select function	4003	=item The winsocket select function
3154		4004
3155	The winsocket C<select> function doesn't follow POSIX in that it requires	4005	The winsocket C<select> function doesn't follow POSIX in that it
3156	socket I<handles> and not socket I<file descriptors>. This makes select	4006	requires socket I<handles> and not socket I<file descriptors> (it is
3157	very inefficient, and also requires a mapping from file descriptors	4007	also extremely buggy). This makes select very inefficient, and also
3158	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4008	requires a mapping from file descriptors to socket handles (the Microsoft
3159	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4009	C runtime provides the function C<_open_osfhandle> for this). See the
3160	symbols for more info.	4010	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4011	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3161		4012
3162	The configuration for a "naked" win32 using the microsoft runtime	4013	The configuration for a "naked" win32 using the Microsoft runtime
3163	libraries and raw winsocket select is:	4014	libraries and raw winsocket select is:
3164		4015
3165	#define EV_USE_SELECT 1	4016	#define EV_USE_SELECT 1
3166	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4017	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3167		4018
3168	Note that winsockets handling of fd sets is O(n), so you can easily get a	4019	Note that winsockets handling of fd sets is O(n), so you can easily get a
3169	complexity in the O(n²) range when using win32.	4020	complexity in the O(n²) range when using win32.
3170		4021
3171	=item Limited number of file descriptors	4022	=item Limited number of file descriptors
3172		4023
3173	Windows has numerous arbitrary (and low) limits on things. Early versions	4024	Windows has numerous arbitrary (and low) limits on things.
3174	of winsocket's select only supported waiting for a max. of C<64> handles	4025
		4026	Early versions of winsocket's select only supported waiting for a maximum
3175	(probably owning to the fact that all windows kernels can only wait for	4027	of C<64> handles (probably owning to the fact that all windows kernels
3176	C<64> things at the same time internally; microsoft recommends spawning a	4028	can only wait for C<64> things at the same time internally; Microsoft
3177	chain of threads and wait for 63 handles and the previous thread in each).	4029	recommends spawning a chain of threads and wait for 63 handles and the
		4030	previous thread in each. Sounds great!).
3178		4031
3179	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4032	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3180	to some high number (e.g. C<2048>) before compiling the winsocket select	4033	to some high number (e.g. C<2048>) before compiling the winsocket select
3181	call (which might be in libev or elsewhere, for example, perl does its own	4034	call (which might be in libev or elsewhere, for example, perl and many
3182	select emulation on windows).	4035	other interpreters do their own select emulation on windows).
3183		4036
3184	Another limit is the number of file descriptors in the microsoft runtime	4037	Another limit is the number of file descriptors in the Microsoft runtime
3185	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4038	libraries, which by default is C<64> (there must be a hidden I<64>
3186	or something like this inside microsoft). You can increase this by calling	4039	fetish or something like this inside Microsoft). You can increase this
3187	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4040	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3188	arbitrary limit), but is broken in many versions of the microsoft runtime	4041	(another arbitrary limit), but is broken in many versions of the Microsoft
3189	libraries.
3190
3191	This might get you to about C<512> or C<2048> sockets (depending on	4042	runtime libraries. This might get you to about C<512> or C<2048> sockets
3192	windows version and/or the phase of the moon). To get more, you need to	4043	(depending on windows version and/or the phase of the moon). To get more,
3193	wrap all I/O functions and provide your own fd management, but the cost of	4044	you need to wrap all I/O functions and provide your own fd management, but
3194	calling select (O(n²)) will likely make this unworkable.	4045	the cost of calling select (O(n²)) will likely make this unworkable.
3195		4046
3196	=back	4047	=back
3197		4048
		4049	=head2 PORTABILITY REQUIREMENTS
		4050
		4051	In addition to a working ISO-C implementation and of course the
		4052	backend-specific APIs, libev relies on a few additional extensions:
		4053
		4054	=over 4
		4055
		4056	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4057	calling conventions regardless of C<ev_watcher_type *>.
		4058
		4059	Libev assumes not only that all watcher pointers have the same internal
		4060	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4061	assumes that the same (machine) code can be used to call any watcher
		4062	callback: The watcher callbacks have different type signatures, but libev
		4063	calls them using an C<ev_watcher *> internally.
		4064
		4065	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4066
		4067	The type C<sig_atomic_t volatile> (or whatever is defined as
		4068	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4069	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4070	believed to be sufficiently portable.
		4071
		4072	=item C<sigprocmask> must work in a threaded environment
		4073
		4074	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4075	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4076	pthread implementations will either allow C<sigprocmask> in the "main
		4077	thread" or will block signals process-wide, both behaviours would
		4078	be compatible with libev. Interaction between C<sigprocmask> and
		4079	C<pthread_sigmask> could complicate things, however.
		4080
		4081	The most portable way to handle signals is to block signals in all threads
		4082	except the initial one, and run the default loop in the initial thread as
		4083	well.
		4084
		4085	=item C<long> must be large enough for common memory allocation sizes
		4086
		4087	To improve portability and simplify its API, libev uses C<long> internally
		4088	instead of C<size_t> when allocating its data structures. On non-POSIX
		4089	systems (Microsoft...) this might be unexpectedly low, but is still at
		4090	least 31 bits everywhere, which is enough for hundreds of millions of
		4091	watchers.
		4092
		4093	=item C<double> must hold a time value in seconds with enough accuracy
		4094
		4095	The type C<double> is used to represent timestamps. It is required to
		4096	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4097	enough for at least into the year 4000. This requirement is fulfilled by
		4098	implementations implementing IEEE 754, which is basically all existing
		4099	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4100	2200.
		4101
		4102	=back
		4103
		4104	If you know of other additional requirements drop me a note.
		4105
		4106
		4107	=head1 ALGORITHMIC COMPLEXITIES
		4108
		4109	In this section the complexities of (many of) the algorithms used inside
		4110	libev will be documented. For complexity discussions about backends see
		4111	the documentation for C<ev_default_init>.
		4112
		4113	All of the following are about amortised time: If an array needs to be
		4114	extended, libev needs to realloc and move the whole array, but this
		4115	happens asymptotically rarer with higher number of elements, so O(1) might
		4116	mean that libev does a lengthy realloc operation in rare cases, but on
		4117	average it is much faster and asymptotically approaches constant time.
		4118
		4119	=over 4
		4120
		4121	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4122
		4123	This means that, when you have a watcher that triggers in one hour and
		4124	there are 100 watchers that would trigger before that, then inserting will
		4125	have to skip roughly seven (C<ld 100>) of these watchers.
		4126
		4127	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4128
		4129	That means that changing a timer costs less than removing/adding them,
		4130	as only the relative motion in the event queue has to be paid for.
		4131
		4132	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4133
		4134	These just add the watcher into an array or at the head of a list.
		4135
		4136	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4137
		4138	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4139
		4140	These watchers are stored in lists, so they need to be walked to find the
		4141	correct watcher to remove. The lists are usually short (you don't usually
		4142	have many watchers waiting for the same fd or signal: one is typical, two
		4143	is rare).
		4144
		4145	=item Finding the next timer in each loop iteration: O(1)
		4146
		4147	By virtue of using a binary or 4-heap, the next timer is always found at a
		4148	fixed position in the storage array.
		4149
		4150	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4151
		4152	A change means an I/O watcher gets started or stopped, which requires
		4153	libev to recalculate its status (and possibly tell the kernel, depending
		4154	on backend and whether C<ev_io_set> was used).
		4155
		4156	=item Activating one watcher (putting it into the pending state): O(1)
		4157
		4158	=item Priority handling: O(number_of_priorities)
		4159
		4160	Priorities are implemented by allocating some space for each
		4161	priority. When doing priority-based operations, libev usually has to
		4162	linearly search all the priorities, but starting/stopping and activating
		4163	watchers becomes O(1) with respect to priority handling.
		4164
		4165	=item Sending an ev_async: O(1)
		4166
		4167	=item Processing ev_async_send: O(number_of_async_watchers)
		4168
		4169	=item Processing signals: O(max_signal_number)
		4170
		4171	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4172	calls in the current loop iteration. Checking for async and signal events
		4173	involves iterating over all running async watchers or all signal numbers.
		4174
		4175	=back
		4176
		4177
		4178	=head1 GLOSSARY
		4179
		4180	=over 4
		4181
		4182	=item active
		4183
		4184	A watcher is active as long as it has been started (has been attached to
		4185	an event loop) but not yet stopped (disassociated from the event loop).
		4186
		4187	=item application
		4188
		4189	In this document, an application is whatever is using libev.
		4190
		4191	=item callback
		4192
		4193	The address of a function that is called when some event has been
		4194	detected. Callbacks are being passed the event loop, the watcher that
		4195	received the event, and the actual event bitset.
		4196
		4197	=item callback invocation
		4198
		4199	The act of calling the callback associated with a watcher.
		4200
		4201	=item event
		4202
		4203	A change of state of some external event, such as data now being available
		4204	for reading on a file descriptor, time having passed or simply not having
		4205	any other events happening anymore.
		4206
		4207	In libev, events are represented as single bits (such as C<EV_READ> or
		4208	C<EV_TIMEOUT>).
		4209
		4210	=item event library
		4211
		4212	A software package implementing an event model and loop.
		4213
		4214	=item event loop
		4215
		4216	An entity that handles and processes external events and converts them
		4217	into callback invocations.
		4218
		4219	=item event model
		4220
		4221	The model used to describe how an event loop handles and processes
		4222	watchers and events.
		4223
		4224	=item pending
		4225
		4226	A watcher is pending as soon as the corresponding event has been detected,
		4227	and stops being pending as soon as the watcher will be invoked or its
		4228	pending status is explicitly cleared by the application.
		4229
		4230	A watcher can be pending, but not active. Stopping a watcher also clears
		4231	its pending status.
		4232
		4233	=item real time
		4234
		4235	The physical time that is observed. It is apparently strictly monotonic :)
		4236
		4237	=item wall-clock time
		4238
		4239	The time and date as shown on clocks. Unlike real time, it can actually
		4240	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4241	clock.
		4242
		4243	=item watcher
		4244
		4245	A data structure that describes interest in certain events. Watchers need
		4246	to be started (attached to an event loop) before they can receive events.
		4247
		4248	=item watcher invocation
		4249
		4250	The act of calling the callback associated with a watcher.
		4251
		4252	=back
3198		4253
3199	=head1 AUTHOR	4254	=head1 AUTHOR
3200		4255
3201	Marc Lehmann <libev@schmorp.de>.	4256	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3202		4257

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