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Revision 1.115 by root, Mon Dec 31 01:32:59 2007 UTC vs.
Revision 1.248 by root, Wed Jul 8 04:14:34 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	#include <ev.h>	12	#include <ev.h>
12		13
		14	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_loop's to stop iterating
		32	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_loop to stop iterating
		41	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
		47	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_loop (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
52		68
		69	This document documents the libev software package.
		70
53	The newest version of this document is also available as a html-formatted	71	The newest version of this document is also available as an html-formatted
54	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
55	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
56		84
57	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
58	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
59	these event sources and provide your program with events.	87	these event sources and provide your program with events.
60		88
…		…
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	113	for example).
86		114
87	=head2 CONVENTIONS	115	=head2 CONVENTIONS
88		116
89	Libev is very configurable. In this manual the default configuration will	117	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	118	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	119	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	120	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	121	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	122	name C<loop> (which is always of type C<ev_loop *>) will not have
		123	this argument.
95		124
96	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
97		126
98	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
100	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
101	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
102	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
103	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
104	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
105	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
106		156
107	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
108		158
109	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
110	library in any way.	160	library in any way.
…		…
119		169
120	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
121		171
122	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
123	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
124	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
125		175
126	=item int ev_version_major ()	176	=item int ev_version_major ()
127		177
128	=item int ev_version_minor ()	178	=item int ev_version_minor ()
129		179
…		…
142	not a problem.	192	not a problem.
143		193
144	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
145	version.	195	version.
146		196
147	assert (("libev version mismatch",	197	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
150		200
151	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
152		202
153	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_*>
154	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	206	a description of the set values.
157		207
158	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
159	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
160		210
161	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
163		213
164	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
165		215
166	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
167	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
168	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
169	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
170	(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
171	libev will probe for if you specify no backends explicitly.	221	libev will probe for if you specify no backends explicitly.
172		222
173	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
174		224
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	229	recommended ones.
180		230
181	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
182		232
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
184		234
185	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
186	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
187	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
188	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
189	potentially destructive action. The default is your system realloc	239	or take some potentially destructive action.
190	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.
191		244
192	You could override this function in high-availability programs to, say,	245	You could override this function in high-availability programs to, say,
193	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,
194	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.
195		248
196	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
197	retries).	250	retries (example requires a standards-compliant C<realloc>).
198		251
199	static void *	252	static void *
200	persistent_realloc (void *ptr, size_t size)	253	persistent_realloc (void *ptr, size_t size)
201	{	254	{
202	for (;;)	255	for (;;)
…		…
211	}	264	}
212		265
213	...	266	...
214	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
215		268
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
217		270
218	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
219	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
220	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
221	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
222	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
223	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
224	(such as abort).	277	(such as abort).
225		278
226	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.
…		…
237		290
238	=back	291	=back
239		292
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		294
242	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>
243	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>
244	events, and dynamically created loops which do not.	297	I<function>).
245		298
246	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
247	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
248	create, you also create another event loop. Libev itself does no locking	301	not.
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		302
253	=over 4	303	=over 4
254		304
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		306
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	310	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		311
262	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
263	function.	313	function.
264		314
		315	Note that this function is I<not> thread-safe, so if you want to use it
		316	from multiple threads, you have to lock (note also that this is unlikely,
		317	as loops cannot be shared easily between threads anyway).
		318
		319	The default loop is the only loop that can handle C<ev_signal> and
		320	C<ev_child> watchers, and to do this, it always registers a handler
		321	for C<SIGCHLD>. If this is a problem for your application you can either
		322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		324	C<ev_default_init>.
		325
265	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
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		328
268	The following flags are supported:	329	The following flags are supported:
269		330
…		…
274	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
275	thing, believe me).	336	thing, believe me).
276		337
277	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
278		339
279	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
280	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
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	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
283	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
284	around bugs.	345	around bugs.
…		…
290	enabling this flag.	351	enabling this flag.
291		352
292	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,
293	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
294	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
295	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
296	without a syscall and thus I<very> fast, but my Linux system also has	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
298		359
299	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
300	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
301	flag.	362	flag.
302		363
303	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>
304	environment variable.	365	environment variable.
305		366
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		368
308	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
…		…
310	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
311	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
312	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.
313		374
314	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
315	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
316	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
317	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
318	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
319	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).
320		385
321	=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)
322		387
323	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
324	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
325	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
326	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,
327	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
328	performance tips.	393	performance tips.
329		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
330	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
331		399
332	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,
333	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
334	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),
335	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).
336	of shortcomings, such as silently dropping events in some hard-to-detect	404
337	cases and rewiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
338	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.
339		421
340	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
341	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
342	(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
343	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
344	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
345		427	file descriptors.
346	Please note that epoll sometimes generates spurious notifications, so you
347	need to use non-blocking I/O or other means to avoid blocking when no data
348	(or space) is available.
349		428
350	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
351	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,
352	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.
353		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
354	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
355	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>.
356		446
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		448
359	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
360	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
361	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
362	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
363	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
364	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)
365	system like NetBSD.	457	system like NetBSD.
366		458
367	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
368	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
369	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
370		462
371	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
372	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
373	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
374	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
375	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
376	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
377		470
378	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
379		472
380	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
381	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
382	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
383	(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
384	(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
385	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>.
386		483
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		485
389	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
390	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		492
396	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,
397	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)).
398		495
399	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
400	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
401	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
402		499
403	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
404	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
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	503	might perform better.
407		504
		505	On the positive side, with the exception of the spurious readiness
		506	notifications, this backend actually performed fully to specification
		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>.
		512
408	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
409		514
410	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
411	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
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		518
414	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
415		520
416	=back	521	=back
417		522
418	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
419	backends will be tried (in the reverse order as given here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		526
423	The most typical usage is like this:	527	Example: This is the most typical usage.
424		528
425	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		531
428	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
429	environment settings to be taken into account:	533	environment settings to be taken into account:
430		534
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		536
433	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
434	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
435	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):
436		541
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		543
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		545
441	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
442	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
443	handle signal and child watchers, and attempts to do so will be greeted by	548	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	549	undefined behaviour (or a failed assertion if assertions are enabled).
445		550
		551	Note that this function I<is> thread-safe, and the recommended way to use
		552	libev with threads is indeed to create one loop per thread, and using the
		553	default loop in the "main" or "initial" thread.
		554
446	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.
447		556
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	558	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
451		560
452	=item ev_default_destroy ()	561	=item ev_default_destroy ()
453		562
454	Destroys the default loop again (frees all memory and kernel state	563	Destroys the default loop again (frees all memory and kernel state
455	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
456	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
457	responsibility to either stop all watchers cleanly yoursef I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
458	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
459	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
460	for example).	569	for example).
461		570
462	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
463	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
464	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
465		574
466	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
467	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
468	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
469	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	582	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	583	earlier call to C<ev_loop_new>.
475		584
476	=item ev_default_fork ()	585	=item ev_default_fork ()
477		586
		587	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	588	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	589	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	590	the child process (or both child and parent, but that again makes little
481	again makes little sense).	591	sense). You I<must> call it in the child before using any of the libev
		592	functions, and it will only take effect at the next C<ev_loop> iteration.
482		593
483	You I<must> call this function in the child process after forking if and	594	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	595	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	596	you just fork+exec, you don't have to call it at all.
486		597
487	The function itself is quite fast and it's usually not a problem to call	598	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	599	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	600	quite nicely into a call to C<pthread_atfork>:
490		601
491	pthread_atfork (0, 0, ev_default_fork);	602	pthread_atfork (0, 0, ev_default_fork);
492		603
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
498		605
499	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
500	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
501	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.
		610
		611	=item int ev_is_default_loop (loop)
		612
		613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
502		615
503	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
504		617
505	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
506	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
507	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
508		621
509	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
510	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
511	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.
512		637
513	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
514		639
515	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
516	use.	641	use.
…		…
521	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
522	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
523	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
524	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
525		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
526	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
527		690
528	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
529	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
530	events.	693	events.
…		…
532	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
533	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.
534		697
535	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
536	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
537	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
538	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
539	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.
540		704
541	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
542	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
543	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.
544		709
545	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
546	neccessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
547	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
548	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
549	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
550	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
551	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
552		721
553	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
554		723
555	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
556	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- 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.
558	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
559	- 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.
560	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
561	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
562	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
563	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
564	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
565	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
566	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
567	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
568	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
569	- Queue all outstanding timers.	739	- Queue all expired timers.
570	- Queue all outstanding periodics.	740	- Queue all expired periodics.
571	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
572	- Queue all check watchers.	742	- Queue all check watchers.
573	- 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).
574	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
575	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
576	- 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
…		…
581	anymore.	751	anymore.
582		752
583	... queue jobs here, make sure they register event watchers as long	753	... queue jobs here, make sure they register event watchers as long
584	... 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..)
585	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
586	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
587		757
588	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
589		759
590	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
591	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
592	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
593	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.
594		764
595	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.
596		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
597	=item ev_ref (loop)	769	=item ev_ref (loop)
598		770
599	=item ev_unref (loop)	771	=item ev_unref (loop)
600		772
601	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
602	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
603	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
604	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>
605	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
606	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
607	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
608	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
609	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
610	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
		786	before stop> (but only if the watcher wasn't active before, or was active
		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).
611		790
612	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>
613	running when nothing else is active.	792	running when nothing else is active.
614		793
615	struct ev_signal exitsig;	794	ev_signal exitsig;
616	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
617	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
618	evf_unref (loop);	797	evf_unref (loop);
619		798
620	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
621		800
622	ev_ref (loop);	801	ev_ref (loop);
623	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
624		803
625	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
626		805
627	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
628		807
629	These advanced functions influence the time that libev will spend waiting	808	These advanced functions influence the time that libev will spend waiting
630	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
631	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.
632		812
633	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>)
634	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
635	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
636		817
637	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
638	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
639	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
640	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
641	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.
642		823
643	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
644	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,
645	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
646	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
647	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.
648		831
649	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
650	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
651	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
652	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
653	any overhead in libev.	836	value will not introduce any overhead in libev.
654		837
655	Many (busy) programs can usually benefit by setting the io collect	838	Many (busy) programs can usually benefit by setting the I/O collect
656	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
657	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
658	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>,
659	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.
660		872
661	=back	873	=back
662		874
663		875
664	=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.
665		881
666	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
667	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
668	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:
669		885
670	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)
671	{	887	{
672	ev_io_stop (w);	888	ev_io_stop (w);
673	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
674	}	890	}
675		891
676	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
677	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
678	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
679	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
680	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
681	ev_loop (loop, 0);	900	ev_loop (loop, 0);
682		901
683	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
684	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
685	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).
686		908
687	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
688	(watcher *, callback)>, which expects a callback to be provided. This	910	(watcher *, callback)>, which expects a callback to be provided. This
689	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
690	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
691	is readable and/or writable).	913	is readable and/or writable).
692		914
693	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 *, ...) >>
694	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
695	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<<
696	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
697		919
698	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
699	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
700	*) >>), 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
701	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
702		924
703	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
704	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
705	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
706		928
707	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
708	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
709	third argument.	931	third argument.
710		932
…		…
764	=item C<EV_FORK>	986	=item C<EV_FORK>
765		987
766	The event loop has been resumed in the child process after fork (see	988	The event loop has been resumed in the child process after fork (see
767	C<ev_fork>).	989	C<ev_fork>).
768		990
		991	=item C<EV_ASYNC>
		992
		993	The given async watcher has been asynchronously notified (see C<ev_async>).
		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
769	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
770		1001
771	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
772	happen because the watcher could not be properly started because libev	1003	happen because the watcher could not be properly started because libev
773	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
774	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
775	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.
776		1011
777	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
778	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
779	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
780	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
781	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
782		1018
783	=back	1019	=back
784		1020
785	=head2 GENERIC WATCHER FUNCTIONS	1021	=head2 GENERIC WATCHER FUNCTIONS
786
787	In the following description, C<TYPE> stands for the watcher type,
788	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
789		1022
790	=over 4	1023	=over 4
791		1024
792	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
793		1026
…		…
799	which rolls both calls into one.	1032	which rolls both calls into one.
800		1033
801	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
802	(or never started) and there are no pending events outstanding.	1035	(or never started) and there are no pending events outstanding.
803		1036
804	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,
805	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);
806		1045
807	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
808		1047
809	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
810	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
…		…
813	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
814		1053
815	Although some watcher types do not have type-specific arguments	1054	Although some watcher types do not have type-specific arguments
816	(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.
817		1056
		1057	See C<ev_init>, above, for an example.
		1058
818	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
819		1060
820	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
821	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
822	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);
823		1068
824	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
825		1070
826	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
827	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
828		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
829	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
830		1080
831	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
832	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
833	non-repeating timers are being stopped when they become pending), but	1085	non-repeating timers are being stopped when they become pending - but
834	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
835	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
836	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.
837		1089
838	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
839		1091
840	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
841	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
…		…
867	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>
868	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
869	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
870	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
871		1123
872	This means that priorities are I<only> used for ordering callback
873	invocation after new events have been received. This is useful, for
874	example, to reduce latency after idling, or more often, to bind two
875	watchers on the same event and make sure one is called first.
876
877	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
878	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.
879		1126
880	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
881	pending.	1128	pending.
882		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
883	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
884	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 :).
885		1136
886	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
887	fine, as long as you do not mind that the priority value you query might	1138	priorities.
888	or might not have been adjusted to be within valid range.
889		1139
890	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
891		1141
892	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
893	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
894	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
895		1146
896	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
897		1148
898	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
899	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
900	watcher isn't pending it does nothing and returns C<0>.	1151	watcher isn't pending it does nothing and returns C<0>.
901		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
902	=back	1156	=back
903		1157
904		1158
905	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
906		1160
907	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
908	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
909	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
910	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
911	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
912	data:	1166	data:
913		1167
914	struct my_io	1168	struct my_io
915	{	1169	{
916	struct ev_io io;	1170	ev_io io;
917	int otherfd;	1171	int otherfd;
918	void *somedata;	1172	void *somedata;
919	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
920	}	1174	};
		1175
		1176	...
		1177	struct my_io w;
		1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
921		1179
922	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
923	can cast it back to your own type:	1181	can cast it back to your own type:
924		1182
925	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)
926	{	1184	{
927	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
928	...	1186	...
929	}	1187	}
930		1188
931	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
932	instead have been omitted.	1190	instead have been omitted.
933		1191
934	Another common scenario is having some data structure with multiple	1192	Another common scenario is to use some data structure with multiple
935	watchers:	1193	embedded watchers:
936		1194
937	struct my_biggy	1195	struct my_biggy
938	{	1196	{
939	int some_data;	1197	int some_data;
940	ev_timer t1;	1198	ev_timer t1;
941	ev_timer t2;	1199	ev_timer t2;
942	}	1200	}
943		1201
944	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
945	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):
946		1207
947	#include <stddef.h>	1208	#include <stddef.h>
948		1209
949	static void	1210	static void
950	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
951	{	1212	{
952	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
953	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
954	}	1215	}
955		1216
956	static void	1217	static void
957	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
958	{	1219	{
959	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
960	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
961	}	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.
962		1326
963		1327
964	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
965		1329
966	This section describes each watcher in detail, but will not repeat	1330	This section describes each watcher in detail, but will not repeat
…		…
990	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
991	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
992	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
993	required if you know what you are doing).	1357	required if you know what you are doing).
994		1358
995	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
996	(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
997	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.
998		1364
999	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
1000	receive "spurious" readyness notifications, that is your callback might	1366	receive "spurious" readiness notifications, that is your callback might
1001	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
1002	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
1003	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
1004	this situation even with a relatively standard program structure. Thus	1370	this situation even with a relatively standard program structure. Thus
1005	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
1006	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.
1007		1373
1008	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
1009	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
1010	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
1011	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
1012	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.
1013		1383
1014	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1015		1385
1016	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
1017	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,
1018	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
1019	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
1020	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
1021	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
1022	fact, a different file descriptor.	1392	fact, a different file descriptor.
1023		1393
…		…
1052	To support fork in your programs, you either have to call	1422	To support fork in your programs, you either have to call
1053	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1423	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1054	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1055	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1056		1426
		1427	=head3 The special problem of SIGPIPE
		1428
		1429	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1430	when writing to a pipe whose other end has been closed, your program gets
		1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1432	this is sensible behaviour, for daemons, this is usually undesirable.
		1433
		1434	So when you encounter spurious, unexplained daemon exits, make sure you
		1435	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1436	somewhere, as that would have given you a big clue).
		1437
1057		1438
1058	=head3 Watcher-Specific Functions	1439	=head3 Watcher-Specific Functions
1059		1440
1060	=over 4	1441	=over 4
1061		1442
1062	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1063		1444
1064	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1065		1446
1066	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
1067	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
1068	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.
1069		1450
1070	=item int fd [read-only]	1451	=item int fd [read-only]
1071		1452
1072	The file descriptor being watched.	1453	The file descriptor being watched.
1073		1454
…		…
1081		1462
1082	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
1083	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
1084	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1085		1466
1086	static void	1467	static void
1087	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)
1088	{	1469	{
1089	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1090	.. 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
1091	}	1472	}
1092		1473
1093	...	1474	...
1094	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1095	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1096	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);
1097	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1098	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1099		1480
1100		1481
1101	=head2 C<ev_timer> - relative and optionally repeating timeouts	1482	=head2 C<ev_timer> - relative and optionally repeating timeouts
1102		1483
1103	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
1104	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1105		1486
1106	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
1107	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
1108	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
1109	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1110	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.
1111		1682
1112	The relative timeouts are calculated relative to the C<ev_now ()>	1683	The relative timeouts are calculated relative to the C<ev_now ()>
1113	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
1114	of the event triggering whatever timeout you are modifying/starting. If	1685	of the event triggering whatever timeout you are modifying/starting. If
1115	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
1116	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:
1117		1688
1118	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1119		1690
1120	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
1121	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
1122	order of execution is undefined.	1693	()>.
1123		1694
1124	=head3 Watcher-Specific Functions and Data Members	1695	=head3 Watcher-Specific Functions and Data Members
1125		1696
1126	=over 4	1697	=over 4
1127		1698
1128	=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)
1129		1700
1130	=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)
1131		1702
1132	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>
1133	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
1134	timer will automatically be configured to trigger again C<repeat> seconds	1705	reached. If it is positive, then the timer will automatically be
1135	later, again, and again, until stopped manually.	1706	configured to trigger again C<repeat> seconds later, again, and again,
		1707	until stopped manually.
1136		1708
1137	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
1138	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
1139	exactly 10 second intervals. If, however, your program cannot keep up with	1711	trigger at exactly 10 second intervals. If, however, your program cannot
1140	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
1141	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.
1142		1714
1143	=item ev_timer_again (loop)	1715	=item ev_timer_again (loop, ev_timer *)
1144		1716
1145	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
1146	repeating. The exact semantics are:	1718	repeating. The exact semantics are:
1147		1719
1148	If the timer is pending, its pending status is cleared.	1720	If the timer is pending, its pending status is cleared.
1149		1721
1150	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).
1151		1723
1152	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
1153	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.
1154		1726
1155	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
1156	example: Imagine you have a tcp connection and you want a so-called idle	1728	usage example.
1157	timeout, that is, you want to be called when there have been, say, 60
1158	seconds of inactivity on the socket. The easiest way to do this is to
1159	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1160	C<ev_timer_again> each time you successfully read or write some data. If
1161	you go into an idle state where you do not expect data to travel on the
1162	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1163	automatically restart it if need be.
1164
1165	That means you can ignore the C<after> value and C<ev_timer_start>
1166	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1167
1168	ev_timer_init (timer, callback, 0., 5.);
1169	ev_timer_again (loop, timer);
1170	...
1171	timer->again = 17.;
1172	ev_timer_again (loop, timer);
1173	...
1174	timer->again = 10.;
1175	ev_timer_again (loop, timer);
1176
1177	This is more slightly efficient then stopping/starting the timer each time
1178	you want to modify its timeout value.
1179		1729
1180	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1181		1731
1182	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
1183	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),
1184	which is also when any modifications are taken into account.	1734	which is also when any modifications are taken into account.
1185		1735
1186	=back	1736	=back
1187		1737
1188	=head3 Examples	1738	=head3 Examples
1189		1739
1190	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1191		1741
1192	static void	1742	static void
1193	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)
1194	{	1744	{
1195	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1196	}	1746	}
1197		1747
1198	struct ev_timer mytimer;	1748	ev_timer mytimer;
1199	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1200	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1201		1751
1202	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
1203	inactivity.	1753	inactivity.
1204		1754
1205	static void	1755	static void
1206	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1207	{	1757	{
1208	.. ten seconds without any activity	1758	.. ten seconds without any activity
1209	}	1759	}
1210		1760
1211	struct ev_timer mytimer;	1761	ev_timer mytimer;
1212	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 */
1213	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1214	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1215		1765
1216	// 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":
1217	// reset the timeout to start ticking again at 10 seconds	1767	// reset the timeout to start ticking again at 10 seconds
1218	ev_timer_again (&mytimer);	1768	ev_timer_again (&mytimer);
1219		1769
1220		1770
1221	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1222		1772
1223	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
1224	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1225		1775
1226	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
1227	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
1228	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
1229	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
1230	+ 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
1231	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1781	wrist-watch).
1232	roughly 10 seconds later).
1233		1782
1234	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
1235	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
1236	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).
1237		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
1238	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
1239	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
1240	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).
1241		1801
1242	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1243		1803
1244	=over 4	1804	=over 4
1245		1805
1246	=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)
1247		1807
1248	=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)
1249		1809
1250	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
1251	operation, and we will explain them from simplest to complex:	1811	operation, and we will explain them from simplest to most complex:
1252		1812
1253	=over 4	1813	=over 4
1254		1814
1255	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1256		1816
1257	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
1258	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
1259	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
1260	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.
1261		1822
1262	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1263		1824
1264	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
1265	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
1266	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.
1267		1829
1268	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
1269	time:	1831	system clock, for example, here is an C<ev_periodic> that triggers each
		1832	hour, on the hour (with respect to UTC):
1270		1833
1271	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1272		1835
1273	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,
1274	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
1275	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
1276	by 3600.	1839	by 3600.
1277		1840
1278	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
1279	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
1280	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.
1281		1844
1282	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
1283	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
1284	this value.	1847	this value, and in fact is often specified as zero.
1285		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
1286	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1287		1855
1288	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
1289	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1290	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
1291	current time as second argument.	1859	current time as second argument.
1292		1860
1293	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,
1294	ever, or make any event loop modifications>. If you need to stop it,	1862	or make ANY other event loop modifications whatsoever, unless explicitly
1295	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1863	allowed by documentation here>.
1296	starting an C<ev_prepare> watcher, which is legal).
1297		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
1298	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1299	ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1300		1871
		1872	static ev_tstamp
1301	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1302	{	1874	{
1303	return now + 60.;	1875	return now + 60.;
1304	}	1876	}
1305		1877
1306	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
1307	(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
1308	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
1309	might be called at other times, too.	1881	might be called at other times, too.
1310		1882
1311	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
1312	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1884	equal to the passed C<now> value >>.
1313		1885
1314	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
1315	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
1316	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
1317	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
1318	reason I omitted it as an example).	1890	reason I omitted it as an example).
1319		1891
1320	=back	1892	=back
…		…
1324	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
1325	when you changed some parameters or the reschedule callback would return	1897	when you changed some parameters or the reschedule callback would return
1326	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
1327	program when the crontabs have changed).	1899	program when the crontabs have changed).
1328		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
1329	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1330		1909
1331	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1332	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).
1333		1913
1334	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
1335	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1336		1916
1337	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1338		1918
1339	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
1340	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
1341	called.	1921	called.
1342		1922
1343	=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]
1344		1924
1345	The current reschedule callback, or C<0>, if this functionality is	1925	The current reschedule callback, or C<0>, if this functionality is
1346	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
1347	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.
1348		1928
1349	=item ev_tstamp at [read-only]
1350
1351	When active, contains the absolute time that the watcher is supposed to
1352	trigger next.
1353
1354	=back	1929	=back
1355		1930
1356	=head3 Examples	1931	=head3 Examples
1357		1932
1358	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1359	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1360	potentially a lot of jittering, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1361		1936
1362	static void	1937	static void
1363	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1364	{	1939	{
1365	... 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)
1366	}	1941	}
1367		1942
1368	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1369	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1370	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1371		1946
1372	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:
1373		1948
1374	#include <math.h>	1949	#include <math.h>
1375		1950
1376	static ev_tstamp	1951	static ev_tstamp
1377	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1378	{	1953	{
1379	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1380	}	1955	}
1381		1956
1382	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);
1383		1958
1384	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1385		1960
1386	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1387	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1388	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1389	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1390		1965
1391		1966
1392	=head2 C<ev_signal> - signal me when a signal gets signalled!	1967	=head2 C<ev_signal> - signal me when a signal gets signalled!
1393		1968
1394	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
1395	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
1396	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
1397	normal event processing, like any other event.	1972	normal event processing, like any other event.
1398		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
1399	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
1400	first watcher gets started will libev actually register a signal watcher	1979	first watcher gets started will libev actually register a signal handler
1401	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
1402	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
1403	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
1404	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
		1984
		1985	If possible and supported, libev will install its handlers with
		1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1987	interrupted. If you have a problem with system calls getting interrupted by
		1988	signals you can block all signals in an C<ev_check> watcher and unblock
		1989	them in an C<ev_prepare> watcher.
1405		1990
1406	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1407		1992
1408	=over 4	1993	=over 4
1409		1994
…		…
1418		2003
1419	The signal the watcher watches out for.	2004	The signal the watcher watches out for.
1420		2005
1421	=back	2006	=back
1422		2007
		2008	=head3 Examples
		2009
		2010	Example: Try to exit cleanly on SIGINT.
		2011
		2012	static void
		2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		2014	{
		2015	ev_unloop (loop, EVUNLOOP_ALL);
		2016	}
		2017
		2018	ev_signal signal_watcher;
		2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2020	ev_signal_start (loop, &signal_watcher);
		2021
1423		2022
1424	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1425		2024
1426	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
1427	some child status changes (most typically when a child of yours dies).	2026	some child status changes (most typically when a child of yours dies or
		2027	exits). It is permissible to install a child watcher I<after> the child
		2028	has been forked (which implies it might have already exited), as long
		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.
		2033
		2034	Only the default event loop is capable of handling signals, and therefore
		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 EV_MAXPRI by libev)
		2039
		2040	=head3 Process Interaction
		2041
		2042	Libev grabs C<SIGCHLD> as soon as the default event loop is
		2043	initialised. This is necessary to guarantee proper behaviour even if
		2044	the first child watcher is started after the child exits. The occurrence
		2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		2046	synchronously as part of the event loop processing. Libev always reaps all
		2047	children, even ones not watched.
		2048
		2049	=head3 Overriding the Built-In Processing
		2050
		2051	Libev offers no special support for overriding the built-in child
		2052	processing, but if your application collides with libev's default child
		2053	handler, you can override it easily by installing your own handler for
		2054	C<SIGCHLD> after initialising the default loop, and making sure the
		2055	default loop never gets destroyed. You are encouraged, however, to use an
		2056	event-based approach to child reaping and thus use libev's support for
		2057	that, so other libev users can use C<ev_child> watchers freely.
		2058
		2059	=head3 Stopping the Child Watcher
		2060
		2061	Currently, the child watcher never gets stopped, even when the
		2062	child terminates, so normally one needs to stop the watcher in the
		2063	callback. Future versions of libev might stop the watcher automatically
		2064	when a child exit is detected.
1428		2065
1429	=head3 Watcher-Specific Functions and Data Members	2066	=head3 Watcher-Specific Functions and Data Members
1430		2067
1431	=over 4	2068	=over 4
1432		2069
1433	=item ev_child_init (ev_child *, callback, int pid)	2070	=item ev_child_init (ev_child *, callback, int pid, int trace)
1434		2071
1435	=item ev_child_set (ev_child *, int pid)	2072	=item ev_child_set (ev_child *, int pid, int trace)
1436		2073
1437	Configures the watcher to wait for status changes of process C<pid> (or	2074	Configures the watcher to wait for status changes of process C<pid> (or
1438	I<any> process if C<pid> is specified as C<0>). The callback can look	2075	I<any> process if C<pid> is specified as C<0>). The callback can look
1439	at the C<rstatus> member of the C<ev_child> watcher structure to see	2076	at the C<rstatus> member of the C<ev_child> watcher structure to see
1440	the status word (use the macros from C<sys/wait.h> and see your systems	2077	the status word (use the macros from C<sys/wait.h> and see your systems
1441	C<waitpid> documentation). The C<rpid> member contains the pid of the	2078	C<waitpid> documentation). The C<rpid> member contains the pid of the
1442	process causing the status change.	2079	process causing the status change. C<trace> must be either C<0> (only
		2080	activate the watcher when the process terminates) or C<1> (additionally
		2081	activate the watcher when the process is stopped or continued).
1443		2082
1444	=item int pid [read-only]	2083	=item int pid [read-only]
1445		2084
1446	The process id this watcher watches out for, or C<0>, meaning any process id.	2085	The process id this watcher watches out for, or C<0>, meaning any process id.
1447		2086
…		…
1456		2095
1457	=back	2096	=back
1458		2097
1459	=head3 Examples	2098	=head3 Examples
1460		2099
1461	Example: Try to exit cleanly on SIGINT and SIGTERM.	2100	Example: C<fork()> a new process and install a child handler to wait for
		2101	its completion.
1462		2102
		2103	ev_child cw;
		2104
1463	static void	2105	static void
1464	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2106	child_cb (EV_P_ ev_child *w, int revents)
1465	{	2107	{
1466	ev_unloop (loop, EVUNLOOP_ALL);	2108	ev_child_stop (EV_A_ w);
		2109	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1467	}	2110	}
1468		2111
1469	struct ev_signal signal_watcher;	2112	pid_t pid = fork ();
1470	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2113
1471	ev_signal_start (loop, &sigint_cb);	2114	if (pid < 0)
		2115	// error
		2116	else if (pid == 0)
		2117	{
		2118	// the forked child executes here
		2119	exit (1);
		2120	}
		2121	else
		2122	{
		2123	ev_child_init (&cw, child_cb, pid, 0);
		2124	ev_child_start (EV_DEFAULT_ &cw);
		2125	}
1472		2126
1473		2127
1474	=head2 C<ev_stat> - did the file attributes just change?	2128	=head2 C<ev_stat> - did the file attributes just change?
1475		2129
1476	This watches a filesystem path for attribute changes. That is, it calls	2130	This watches a file system path for attribute changes. That is, it calls
1477	C<stat> regularly (or when the OS says it changed) and sees if it changed	2131	C<stat> on that path in regular intervals (or when the OS says it changed)
1478	compared to the last time, invoking the callback if it did.	2132	and sees if it changed compared to the last time, invoking the callback if
		2133	it did.
1479		2134
1480	The path does not need to exist: changing from "path exists" to "path does	2135	The path does not need to exist: changing from "path exists" to "path does
1481	not exist" is a status change like any other. The condition "path does	2136	not exist" is a status change like any other. The condition "path does not
1482	not exist" is signified by the C<st_nlink> field being zero (which is	2137	exist" (or more correctly "path cannot be stat'ed") is signified by the
1483	otherwise always forced to be at least one) and all the other fields of	2138	C<st_nlink> field being zero (which is otherwise always forced to be at
1484	the stat buffer having unspecified contents.	2139	least one) and all the other fields of the stat buffer having unspecified
		2140	contents.
1485		2141
1486	The path I<should> be absolute and I<must not> end in a slash. If it is	2142	The path I<must not> end in a slash or contain special components such as
		2143	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1487	relative and your working directory changes, the behaviour is undefined.	2144	your working directory changes, then the behaviour is undefined.
1488		2145
1489	Since there is no standard to do this, the portable implementation simply	2146	Since there is no portable change notification interface available, the
1490	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2147	portable implementation simply calls C<stat(2)> regularly on the path
1491	can specify a recommended polling interval for this case. If you specify	2148	to see if it changed somehow. You can specify a recommended polling
1492	a polling interval of C<0> (highly recommended!) then a I<suitable,	2149	interval for this case. If you specify a polling interval of C<0> (highly
1493	unspecified default> value will be used (which you can expect to be around	2150	recommended!) then a I<suitable, unspecified default> value will be used
1494	five seconds, although this might change dynamically). Libev will also	2151	(which you can expect to be around five seconds, although this might
1495	impose a minimum interval which is currently around C<0.1>, but thats	2152	change dynamically). Libev will also impose a minimum interval which is
1496	usually overkill.	2153	currently around C<0.1>, but that's usually overkill.
1497		2154
1498	This watcher type is not meant for massive numbers of stat watchers,	2155	This watcher type is not meant for massive numbers of stat watchers,
1499	as even with OS-supported change notifications, this can be	2156	as even with OS-supported change notifications, this can be
1500	resource-intensive.	2157	resource-intensive.
1501		2158
1502	At the time of this writing, only the Linux inotify interface is	2159	At the time of this writing, the only OS-specific interface implemented
1503	implemented (implementing kqueue support is left as an exercise for the	2160	is the Linux inotify interface (implementing kqueue support is left as an
1504	reader). Inotify will be used to give hints only and should not change the	2161	exercise for the reader. Note, however, that the author sees no way of
1505	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2162	implementing C<ev_stat> semantics with kqueue, except as a hint).
1506	to fall back to regular polling again even with inotify, but changes are
1507	usually detected immediately, and if the file exists there will be no
1508	polling.
1509		2163
1510	=head3 Inotify	2164	=head3 ABI Issues (Largefile Support)
1511		2165
		2166	Libev by default (unless the user overrides this) uses the default
		2167	compilation environment, which means that on systems with large file
		2168	support disabled by default, you get the 32 bit version of the stat
		2169	structure. When using the library from programs that change the ABI to
		2170	use 64 bit file offsets the programs will fail. In that case you have to
		2171	compile libev with the same flags to get binary compatibility. This is
		2172	obviously the case with any flags that change the ABI, but the problem is
		2173	most noticeably displayed with ev_stat and large file support.
		2174
		2175	The solution for this is to lobby your distribution maker to make large
		2176	file interfaces available by default (as e.g. FreeBSD does) and not
		2177	optional. Libev cannot simply switch on large file support because it has
		2178	to exchange stat structures with application programs compiled using the
		2179	default compilation environment.
		2180
		2181	=head3 Inotify and Kqueue
		2182
1512	When C<inotify (7)> support has been compiled into libev (generally only	2183	When C<inotify (7)> support has been compiled into libev and present at
1513	available on Linux) and present at runtime, it will be used to speed up	2184	runtime, it will be used to speed up change detection where possible. The
1514	change detection where possible. The inotify descriptor will be created lazily	2185	inotify descriptor will be created lazily when the first C<ev_stat>
1515	when the first C<ev_stat> watcher is being started.	2186	watcher is being started.
1516		2187
1517	Inotify presense does not change the semantics of C<ev_stat> watchers	2188	Inotify presence does not change the semantics of C<ev_stat> watchers
1518	except that changes might be detected earlier, and in some cases, to avoid	2189	except that changes might be detected earlier, and in some cases, to avoid
1519	making regular C<stat> calls. Even in the presense of inotify support	2190	making regular C<stat> calls. Even in the presence of inotify support
1520	there are many cases where libev has to resort to regular C<stat> polling.	2191	there are many cases where libev has to resort to regular C<stat> polling,
		2192	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2193	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2194	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2195	xfs are fully working) libev usually gets away without polling.
1521		2196
1522	(There is no support for kqueue, as apparently it cannot be used to	2197	There is no support for kqueue, as apparently it cannot be used to
1523	implement this functionality, due to the requirement of having a file	2198	implement this functionality, due to the requirement of having a file
1524	descriptor open on the object at all times).	2199	descriptor open on the object at all times, and detecting renames, unlinks
		2200	etc. is difficult.
		2201
		2202	=head3 C<stat ()> is a synchronous operation
		2203
		2204	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2205	the process. The exception are C<ev_stat> watchers - those call C<stat
		2206	()>, which is a synchronous operation.
		2207
		2208	For local paths, this usually doesn't matter: unless the system is very
		2209	busy or the intervals between stat's are large, a stat call will be fast,
		2210	as the path data is usually in memory already (except when starting the
		2211	watcher).
		2212
		2213	For networked file systems, calling C<stat ()> can block an indefinite
		2214	time due to network issues, and even under good conditions, a stat call
		2215	often takes multiple milliseconds.
		2216
		2217	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2218	paths, although this is fully supported by libev.
1525		2219
1526	=head3 The special problem of stat time resolution	2220	=head3 The special problem of stat time resolution
1527		2221
1528	The C<stat ()> syscall only supports full-second resolution portably, and	2222	The C<stat ()> system call only supports full-second resolution portably,
1529	even on systems where the resolution is higher, many filesystems still	2223	and even on systems where the resolution is higher, most file systems
1530	only support whole seconds.	2224	still only support whole seconds.
1531		2225
1532	That means that, if the time is the only thing that changes, you might	2226	That means that, if the time is the only thing that changes, you can
1533	miss updates: on the first update, C<ev_stat> detects a change and calls	2227	easily miss updates: on the first update, C<ev_stat> detects a change and
1534	your callback, which does something. When there is another update within	2228	calls your callback, which does something. When there is another update
1535	the same second, C<ev_stat> will be unable to detect it.	2229	within the same second, C<ev_stat> will be unable to detect unless the
		2230	stat data does change in other ways (e.g. file size).
1536		2231
1537	The solution to this is to delay acting on a change for a second (or till	2232	The solution to this is to delay acting on a change for slightly more
1538	the next second boundary), using a roughly one-second delay C<ev_timer>	2233	than a second (or till slightly after the next full second boundary), using
1539	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2234	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1540	is added to work around small timing inconsistencies of some operating	2235	ev_timer_again (loop, w)>).
1541	systems.	2236
		2237	The C<.02> offset is added to work around small timing inconsistencies
		2238	of some operating systems (where the second counter of the current time
		2239	might be be delayed. One such system is the Linux kernel, where a call to
		2240	C<gettimeofday> might return a timestamp with a full second later than
		2241	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2242	update file times then there will be a small window where the kernel uses
		2243	the previous second to update file times but libev might already execute
		2244	the timer callback).
1542		2245
1543	=head3 Watcher-Specific Functions and Data Members	2246	=head3 Watcher-Specific Functions and Data Members
1544		2247
1545	=over 4	2248	=over 4
1546		2249
…		…
1552	C<path>. The C<interval> is a hint on how quickly a change is expected to	2255	C<path>. The C<interval> is a hint on how quickly a change is expected to
1553	be detected and should normally be specified as C<0> to let libev choose	2256	be detected and should normally be specified as C<0> to let libev choose
1554	a suitable value. The memory pointed to by C<path> must point to the same	2257	a suitable value. The memory pointed to by C<path> must point to the same
1555	path for as long as the watcher is active.	2258	path for as long as the watcher is active.
1556		2259
1557	The callback will be receive C<EV_STAT> when a change was detected,	2260	The callback will receive an C<EV_STAT> event when a change was detected,
1558	relative to the attributes at the time the watcher was started (or the	2261	relative to the attributes at the time the watcher was started (or the
1559	last change was detected).	2262	last change was detected).
1560		2263
1561	=item ev_stat_stat (ev_stat *)	2264	=item ev_stat_stat (loop, ev_stat *)
1562		2265
1563	Updates the stat buffer immediately with new values. If you change the	2266	Updates the stat buffer immediately with new values. If you change the
1564	watched path in your callback, you could call this fucntion to avoid	2267	watched path in your callback, you could call this function to avoid
1565	detecting this change (while introducing a race condition). Can also be	2268	detecting this change (while introducing a race condition if you are not
1566	useful simply to find out the new values.	2269	the only one changing the path). Can also be useful simply to find out the
		2270	new values.
1567		2271
1568	=item ev_statdata attr [read-only]	2272	=item ev_statdata attr [read-only]
1569		2273
1570	The most-recently detected attributes of the file. Although the type is of	2274	The most-recently detected attributes of the file. Although the type is
1571	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2275	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1572	suitable for your system. If the C<st_nlink> member is C<0>, then there	2276	suitable for your system, but you can only rely on the POSIX-standardised
		2277	members to be present. If the C<st_nlink> member is C<0>, then there was
1573	was some error while C<stat>ing the file.	2278	some error while C<stat>ing the file.
1574		2279
1575	=item ev_statdata prev [read-only]	2280	=item ev_statdata prev [read-only]
1576		2281
1577	The previous attributes of the file. The callback gets invoked whenever	2282	The previous attributes of the file. The callback gets invoked whenever
1578	C<prev> != C<attr>.	2283	C<prev> != C<attr>, or, more precisely, one or more of these members
		2284	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2285	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1579		2286
1580	=item ev_tstamp interval [read-only]	2287	=item ev_tstamp interval [read-only]
1581		2288
1582	The specified interval.	2289	The specified interval.
1583		2290
1584	=item const char *path [read-only]	2291	=item const char *path [read-only]
1585		2292
1586	The filesystem path that is being watched.	2293	The file system path that is being watched.
1587		2294
1588	=back	2295	=back
1589		2296
1590	=head3 Examples	2297	=head3 Examples
1591		2298
1592	Example: Watch C</etc/passwd> for attribute changes.	2299	Example: Watch C</etc/passwd> for attribute changes.
1593		2300
1594	static void	2301	static void
1595	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2302	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1596	{	2303	{
1597	/* /etc/passwd changed in some way */	2304	/* /etc/passwd changed in some way */
1598	if (w->attr.st_nlink)	2305	if (w->attr.st_nlink)
1599	{	2306	{
1600	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2307	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1601	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2308	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1602	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2309	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1603	}	2310	}
1604	else	2311	else
1605	/* you shalt not abuse printf for puts */	2312	/* you shalt not abuse printf for puts */
1606	puts ("wow, /etc/passwd is not there, expect problems. "	2313	puts ("wow, /etc/passwd is not there, expect problems. "
1607	"if this is windows, they already arrived\n");	2314	"if this is windows, they already arrived\n");
1608	}	2315	}
1609		2316
1610	...	2317	...
1611	ev_stat passwd;	2318	ev_stat passwd;
1612		2319
1613	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2320	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1614	ev_stat_start (loop, &passwd);	2321	ev_stat_start (loop, &passwd);
1615		2322
1616	Example: Like above, but additionally use a one-second delay so we do not	2323	Example: Like above, but additionally use a one-second delay so we do not
1617	miss updates (however, frequent updates will delay processing, too, so	2324	miss updates (however, frequent updates will delay processing, too, so
1618	one might do the work both on C<ev_stat> callback invocation I<and> on	2325	one might do the work both on C<ev_stat> callback invocation I<and> on
1619	C<ev_timer> callback invocation).	2326	C<ev_timer> callback invocation).
1620		2327
1621	static ev_stat passwd;	2328	static ev_stat passwd;
1622	static ev_timer timer;	2329	static ev_timer timer;
1623		2330
1624	static void	2331	static void
1625	timer_cb (EV_P_ ev_timer *w, int revents)	2332	timer_cb (EV_P_ ev_timer *w, int revents)
1626	{	2333	{
1627	ev_timer_stop (EV_A_ w);	2334	ev_timer_stop (EV_A_ w);
1628		2335
1629	/* now it's one second after the most recent passwd change */	2336	/* now it's one second after the most recent passwd change */
1630	}	2337	}
1631		2338
1632	static void	2339	static void
1633	stat_cb (EV_P_ ev_stat *w, int revents)	2340	stat_cb (EV_P_ ev_stat *w, int revents)
1634	{	2341	{
1635	/* reset the one-second timer */	2342	/* reset the one-second timer */
1636	ev_timer_again (EV_A_ &timer);	2343	ev_timer_again (EV_A_ &timer);
1637	}	2344	}
1638		2345
1639	...	2346	...
1640	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2347	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1641	ev_stat_start (loop, &passwd);	2348	ev_stat_start (loop, &passwd);
1642	ev_timer_init (&timer, timer_cb, 0., 1.01);	2349	ev_timer_init (&timer, timer_cb, 0., 1.02);
1643		2350
1644		2351
1645	=head2 C<ev_idle> - when you've got nothing better to do...	2352	=head2 C<ev_idle> - when you've got nothing better to do...
1646		2353
1647	Idle watchers trigger events when no other events of the same or higher	2354	Idle watchers trigger events when no other events of the same or higher
1648	priority are pending (prepare, check and other idle watchers do not	2355	priority are pending (prepare, check and other idle watchers do not count
1649	count).	2356	as receiving "events").
1650		2357
1651	That is, as long as your process is busy handling sockets or timeouts	2358	That is, as long as your process is busy handling sockets or timeouts
1652	(or even signals, imagine) of the same or higher priority it will not be	2359	(or even signals, imagine) of the same or higher priority it will not be
1653	triggered. But when your process is idle (or only lower-priority watchers	2360	triggered. But when your process is idle (or only lower-priority watchers
1654	are pending), the idle watchers are being called once per event loop	2361	are pending), the idle watchers are being called once per event loop
…		…
1665		2372
1666	=head3 Watcher-Specific Functions and Data Members	2373	=head3 Watcher-Specific Functions and Data Members
1667		2374
1668	=over 4	2375	=over 4
1669		2376
1670	=item ev_idle_init (ev_signal *, callback)	2377	=item ev_idle_init (ev_idle *, callback)
1671		2378
1672	Initialises and configures the idle watcher - it has no parameters of any	2379	Initialises and configures the idle watcher - it has no parameters of any
1673	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2380	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1674	believe me.	2381	believe me.
1675		2382
…		…
1678	=head3 Examples	2385	=head3 Examples
1679		2386
1680	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2387	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1681	callback, free it. Also, use no error checking, as usual.	2388	callback, free it. Also, use no error checking, as usual.
1682		2389
1683	static void	2390	static void
1684	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1685	{	2392	{
1686	free (w);	2393	free (w);
1687	// now do something you wanted to do when the program has	2394	// now do something you wanted to do when the program has
1688	// no longer asnything immediate to do.	2395	// no longer anything immediate to do.
1689	}	2396	}
1690		2397
1691	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1692	ev_idle_init (idle_watcher, idle_cb);	2399	ev_idle_init (idle_watcher, idle_cb);
1693	ev_idle_start (loop, idle_cb);	2400	ev_idle_start (loop, idle_watcher);
1694		2401
1695		2402
1696	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1697		2404
1698	Prepare and check watchers are usually (but not always) used in tandem:	2405	Prepare and check watchers are usually (but not always) used in pairs:
1699	prepare watchers get invoked before the process blocks and check watchers	2406	prepare watchers get invoked before the process blocks and check watchers
1700	afterwards.	2407	afterwards.
1701		2408
1702	You I<must not> call C<ev_loop> or similar functions that enter	2409	You I<must not> call C<ev_loop> or similar functions that enter
1703	the current event loop from either C<ev_prepare> or C<ev_check>	2410	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1706	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1707	C<ev_check> so if you have one watcher of each kind they will always be	2414	C<ev_check> so if you have one watcher of each kind they will always be
1708	called in pairs bracketing the blocking call.	2415	called in pairs bracketing the blocking call.
1709		2416
1710	Their main purpose is to integrate other event mechanisms into libev and	2417	Their main purpose is to integrate other event mechanisms into libev and
1711	their use is somewhat advanced. This could be used, for example, to track	2418	their use is somewhat advanced. They could be used, for example, to track
1712	variable changes, implement your own watchers, integrate net-snmp or a	2419	variable changes, implement your own watchers, integrate net-snmp or a
1713	coroutine library and lots more. They are also occasionally useful if	2420	coroutine library and lots more. They are also occasionally useful if
1714	you cache some data and want to flush it before blocking (for example,	2421	you cache some data and want to flush it before blocking (for example,
1715	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2422	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1716	watcher).	2423	watcher).
1717		2424
1718	This is done by examining in each prepare call which file descriptors need	2425	This is done by examining in each prepare call which file descriptors
1719	to be watched by the other library, registering C<ev_io> watchers for	2426	need to be watched by the other library, registering C<ev_io> watchers
1720	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2427	for them and starting an C<ev_timer> watcher for any timeouts (many
1721	provide just this functionality). Then, in the check watcher you check for	2428	libraries provide exactly this functionality). Then, in the check watcher,
1722	any events that occured (by checking the pending status of all watchers	2429	you check for any events that occurred (by checking the pending status
1723	and stopping them) and call back into the library. The I/O and timer	2430	of all watchers and stopping them) and call back into the library. The
1724	callbacks will never actually be called (but must be valid nevertheless,	2431	I/O and timer callbacks will never actually be called (but must be valid
1725	because you never know, you know?).	2432	nevertheless, because you never know, you know?).
1726		2433
1727	As another example, the Perl Coro module uses these hooks to integrate	2434	As another example, the Perl Coro module uses these hooks to integrate
1728	coroutines into libev programs, by yielding to other active coroutines	2435	coroutines into libev programs, by yielding to other active coroutines
1729	during each prepare and only letting the process block if no coroutines	2436	during each prepare and only letting the process block if no coroutines
1730	are ready to run (it's actually more complicated: it only runs coroutines	2437	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1733	loop from blocking if lower-priority coroutines are active, thus mapping	2440	loop from blocking if lower-priority coroutines are active, thus mapping
1734	low-priority coroutines to idle/background tasks).	2441	low-priority coroutines to idle/background tasks).
1735		2442
1736	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2443	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1737	priority, to ensure that they are being run before any other watchers	2444	priority, to ensure that they are being run before any other watchers
		2445	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2446
1738	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2447	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1739	too) should not activate ("feed") events into libev. While libev fully	2448	activate ("feed") events into libev. While libev fully supports this, they
1740	supports this, they will be called before other C<ev_check> watchers	2449	might get executed before other C<ev_check> watchers did their job. As
1741	did their job. As C<ev_check> watchers are often used to embed other	2450	C<ev_check> watchers are often used to embed other (non-libev) event
1742	(non-libev) event loops those other event loops might be in an unusable	2451	loops those other event loops might be in an unusable state until their
1743	state until their C<ev_check> watcher ran (always remind yourself to	2452	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1744	coexist peacefully with others).	2453	others).
1745		2454
1746	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
1747		2456
1748	=over 4	2457	=over 4
1749		2458
…		…
1751		2460
1752	=item ev_check_init (ev_check *, callback)	2461	=item ev_check_init (ev_check *, callback)
1753		2462
1754	Initialises and configures the prepare or check watcher - they have no	2463	Initialises and configures the prepare or check watcher - they have no
1755	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2464	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1756	macros, but using them is utterly, utterly and completely pointless.	2465	macros, but using them is utterly, utterly, utterly and completely
		2466	pointless.
1757		2467
1758	=back	2468	=back
1759		2469
1760	=head3 Examples	2470	=head3 Examples
1761		2471
1762	There are a number of principal ways to embed other event loops or modules	2472	There are a number of principal ways to embed other event loops or modules
1763	into libev. Here are some ideas on how to include libadns into libev	2473	into libev. Here are some ideas on how to include libadns into libev
1764	(there is a Perl module named C<EV::ADNS> that does this, which you could	2474	(there is a Perl module named C<EV::ADNS> that does this, which you could
1765	use for an actually working example. Another Perl module named C<EV::Glib>	2475	use as a working example. Another Perl module named C<EV::Glib> embeds a
1766	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2476	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1767	into the Glib event loop).	2477	Glib event loop).
1768		2478
1769	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2479	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1770	and in a check watcher, destroy them and call into libadns. What follows	2480	and in a check watcher, destroy them and call into libadns. What follows
1771	is pseudo-code only of course. This requires you to either use a low	2481	is pseudo-code only of course. This requires you to either use a low
1772	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2482	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1773	the callbacks for the IO/timeout watchers might not have been called yet.	2483	the callbacks for the IO/timeout watchers might not have been called yet.
1774		2484
1775	static ev_io iow [nfd];	2485	static ev_io iow [nfd];
1776	static ev_timer tw;	2486	static ev_timer tw;
1777		2487
1778	static void	2488	static void
1779	io_cb (ev_loop *loop, ev_io *w, int revents)	2489	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1780	{	2490	{
1781	}	2491	}
1782		2492
1783	// create io watchers for each fd and a timer before blocking	2493	// create io watchers for each fd and a timer before blocking
1784	static void	2494	static void
1785	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2495	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1786	{	2496	{
1787	int timeout = 3600000;	2497	int timeout = 3600000;
1788	struct pollfd fds [nfd];	2498	struct pollfd fds [nfd];
1789	// actual code will need to loop here and realloc etc.	2499	// actual code will need to loop here and realloc etc.
1790	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2500	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1791		2501
1792	/* the callback is illegal, but won't be called as we stop during check */	2502	/* the callback is illegal, but won't be called as we stop during check */
1793	ev_timer_init (&tw, 0, timeout * 1e-3);	2503	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1794	ev_timer_start (loop, &tw);	2504	ev_timer_start (loop, &tw);
1795		2505
1796	// create one ev_io per pollfd	2506	// create one ev_io per pollfd
1797	for (int i = 0; i < nfd; ++i)	2507	for (int i = 0; i < nfd; ++i)
1798	{	2508	{
1799	ev_io_init (iow + i, io_cb, fds [i].fd,	2509	ev_io_init (iow + i, io_cb, fds [i].fd,
1800	((fds [i].events & POLLIN ? EV_READ : 0)	2510	((fds [i].events & POLLIN ? EV_READ : 0)
1801	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2511	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1802		2512
1803	fds [i].revents = 0;	2513	fds [i].revents = 0;
1804	ev_io_start (loop, iow + i);	2514	ev_io_start (loop, iow + i);
1805	}	2515	}
1806	}	2516	}
1807		2517
1808	// stop all watchers after blocking	2518	// stop all watchers after blocking
1809	static void	2519	static void
1810	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2520	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1811	{	2521	{
1812	ev_timer_stop (loop, &tw);	2522	ev_timer_stop (loop, &tw);
1813		2523
1814	for (int i = 0; i < nfd; ++i)	2524	for (int i = 0; i < nfd; ++i)
1815	{	2525	{
1816	// set the relevant poll flags	2526	// set the relevant poll flags
1817	// could also call adns_processreadable etc. here	2527	// could also call adns_processreadable etc. here
1818	struct pollfd *fd = fds + i;	2528	struct pollfd *fd = fds + i;
1819	int revents = ev_clear_pending (iow + i);	2529	int revents = ev_clear_pending (iow + i);
1820	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2530	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1821	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2531	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1822		2532
1823	// now stop the watcher	2533	// now stop the watcher
1824	ev_io_stop (loop, iow + i);	2534	ev_io_stop (loop, iow + i);
1825	}	2535	}
1826		2536
1827	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2537	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1828	}	2538	}
1829		2539
1830	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2540	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1831	in the prepare watcher and would dispose of the check watcher.	2541	in the prepare watcher and would dispose of the check watcher.
1832		2542
1833	Method 3: If the module to be embedded supports explicit event	2543	Method 3: If the module to be embedded supports explicit event
1834	notification (adns does), you can also make use of the actual watcher	2544	notification (libadns does), you can also make use of the actual watcher
1835	callbacks, and only destroy/create the watchers in the prepare watcher.	2545	callbacks, and only destroy/create the watchers in the prepare watcher.
1836		2546
1837	static void	2547	static void
1838	timer_cb (EV_P_ ev_timer *w, int revents)	2548	timer_cb (EV_P_ ev_timer *w, int revents)
1839	{	2549	{
1840	adns_state ads = (adns_state)w->data;	2550	adns_state ads = (adns_state)w->data;
1841	update_now (EV_A);	2551	update_now (EV_A);
1842		2552
1843	adns_processtimeouts (ads, &tv_now);	2553	adns_processtimeouts (ads, &tv_now);
1844	}	2554	}
1845		2555
1846	static void	2556	static void
1847	io_cb (EV_P_ ev_io *w, int revents)	2557	io_cb (EV_P_ ev_io *w, int revents)
1848	{	2558	{
1849	adns_state ads = (adns_state)w->data;	2559	adns_state ads = (adns_state)w->data;
1850	update_now (EV_A);	2560	update_now (EV_A);
1851		2561
1852	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2562	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1853	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2563	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1854	}	2564	}
1855		2565
1856	// do not ever call adns_afterpoll	2566	// do not ever call adns_afterpoll
1857		2567
1858	Method 4: Do not use a prepare or check watcher because the module you	2568	Method 4: Do not use a prepare or check watcher because the module you
1859	want to embed is too inflexible to support it. Instead, youc na override	2569	want to embed is not flexible enough to support it. Instead, you can
1860	their poll function. The drawback with this solution is that the main	2570	override their poll function. The drawback with this solution is that the
1861	loop is now no longer controllable by EV. The C<Glib::EV> module does	2571	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1862	this.	2572	this approach, effectively embedding EV as a client into the horrible
		2573	libglib event loop.
1863		2574
1864	static gint	2575	static gint
1865	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2576	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1866	{	2577	{
1867	int got_events = 0;	2578	int got_events = 0;
1868		2579
1869	for (n = 0; n < nfds; ++n)	2580	for (n = 0; n < nfds; ++n)
1870	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2581	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1871		2582
1872	if (timeout >= 0)	2583	if (timeout >= 0)
1873	// create/start timer	2584	// create/start timer
1874		2585
1875	// poll	2586	// poll
1876	ev_loop (EV_A_ 0);	2587	ev_loop (EV_A_ 0);
1877		2588
1878	// stop timer again	2589	// stop timer again
1879	if (timeout >= 0)	2590	if (timeout >= 0)
1880	ev_timer_stop (EV_A_ &to);	2591	ev_timer_stop (EV_A_ &to);
1881		2592
1882	// stop io watchers again - their callbacks should have set	2593	// stop io watchers again - their callbacks should have set
1883	for (n = 0; n < nfds; ++n)	2594	for (n = 0; n < nfds; ++n)
1884	ev_io_stop (EV_A_ iow [n]);	2595	ev_io_stop (EV_A_ iow [n]);
1885		2596
1886	return got_events;	2597	return got_events;
1887	}	2598	}
1888		2599
1889		2600
1890	=head2 C<ev_embed> - when one backend isn't enough...	2601	=head2 C<ev_embed> - when one backend isn't enough...
1891		2602
1892	This is a rather advanced watcher type that lets you embed one event loop	2603	This is a rather advanced watcher type that lets you embed one event loop
…		…
1898	prioritise I/O.	2609	prioritise I/O.
1899		2610
1900	As an example for a bug workaround, the kqueue backend might only support	2611	As an example for a bug workaround, the kqueue backend might only support
1901	sockets on some platform, so it is unusable as generic backend, but you	2612	sockets on some platform, so it is unusable as generic backend, but you
1902	still want to make use of it because you have many sockets and it scales	2613	still want to make use of it because you have many sockets and it scales
1903	so nicely. In this case, you would create a kqueue-based loop and embed it	2614	so nicely. In this case, you would create a kqueue-based loop and embed
1904	into your default loop (which might use e.g. poll). Overall operation will	2615	it into your default loop (which might use e.g. poll). Overall operation
1905	be a bit slower because first libev has to poll and then call kevent, but	2616	will be a bit slower because first libev has to call C<poll> and then
1906	at least you can use both at what they are best.	2617	C<kevent>, but at least you can use both mechanisms for what they are
		2618	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1907		2619
1908	As for prioritising I/O: rarely you have the case where some fds have	2620	As for prioritising I/O: under rare circumstances you have the case where
1909	to be watched and handled very quickly (with low latency), and even	2621	some fds have to be watched and handled very quickly (with low latency),
1910	priorities and idle watchers might have too much overhead. In this case	2622	and even priorities and idle watchers might have too much overhead. In
1911	you would put all the high priority stuff in one loop and all the rest in	2623	this case you would put all the high priority stuff in one loop and all
1912	a second one, and embed the second one in the first.	2624	the rest in a second one, and embed the second one in the first.
1913		2625
1914	As long as the watcher is active, the callback will be invoked every time	2626	As long as the watcher is active, the callback will be invoked every
1915	there might be events pending in the embedded loop. The callback must then	2627	time there might be events pending in the embedded loop. The callback
1916	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2628	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1917	their callbacks (you could also start an idle watcher to give the embedded	2629	sweep and invoke their callbacks (the callback doesn't need to invoke the
1918	loop strictly lower priority for example). You can also set the callback	2630	C<ev_embed_sweep> function directly, it could also start an idle watcher
1919	to C<0>, in which case the embed watcher will automatically execute the	2631	to give the embedded loop strictly lower priority for example).
1920	embedded loop sweep.
1921		2632
1922	As long as the watcher is started it will automatically handle events. The	2633	You can also set the callback to C<0>, in which case the embed watcher
1923	callback will be invoked whenever some events have been handled. You can	2634	will automatically execute the embedded loop sweep whenever necessary.
1924	set the callback to C<0> to avoid having to specify one if you are not
1925	interested in that.
1926		2635
1927	Also, there have not currently been made special provisions for forking:	2636	Fork detection will be handled transparently while the C<ev_embed> watcher
1928	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2637	is active, i.e., the embedded loop will automatically be forked when the
1929	but you will also have to stop and restart any C<ev_embed> watchers	2638	embedding loop forks. In other cases, the user is responsible for calling
1930	yourself.	2639	C<ev_loop_fork> on the embedded loop.
1931		2640
1932	Unfortunately, not all backends are embeddable, only the ones returned by	2641	Unfortunately, not all backends are embeddable: only the ones returned by
1933	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2642	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1934	portable one.	2643	portable one.
1935		2644
1936	So when you want to use this feature you will always have to be prepared	2645	So when you want to use this feature you will always have to be prepared
1937	that you cannot get an embeddable loop. The recommended way to get around	2646	that you cannot get an embeddable loop. The recommended way to get around
1938	this is to have a separate variables for your embeddable loop, try to	2647	this is to have a separate variables for your embeddable loop, try to
1939	create it, and if that fails, use the normal loop for everything.	2648	create it, and if that fails, use the normal loop for everything.
1940		2649
		2650	=head3 C<ev_embed> and fork
		2651
		2652	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2653	automatically be applied to the embedded loop as well, so no special
		2654	fork handling is required in that case. When the watcher is not running,
		2655	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2656	as applicable.
		2657
1941	=head3 Watcher-Specific Functions and Data Members	2658	=head3 Watcher-Specific Functions and Data Members
1942		2659
1943	=over 4	2660	=over 4
1944		2661
1945	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2662	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1948		2665
1949	Configures the watcher to embed the given loop, which must be	2666	Configures the watcher to embed the given loop, which must be
1950	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2667	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1951	invoked automatically, otherwise it is the responsibility of the callback	2668	invoked automatically, otherwise it is the responsibility of the callback
1952	to invoke it (it will continue to be called until the sweep has been done,	2669	to invoke it (it will continue to be called until the sweep has been done,
1953	if you do not want thta, you need to temporarily stop the embed watcher).	2670	if you do not want that, you need to temporarily stop the embed watcher).
1954		2671
1955	=item ev_embed_sweep (loop, ev_embed *)	2672	=item ev_embed_sweep (loop, ev_embed *)
1956		2673
1957	Make a single, non-blocking sweep over the embedded loop. This works	2674	Make a single, non-blocking sweep over the embedded loop. This works
1958	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2675	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1959	apropriate way for embedded loops.	2676	appropriate way for embedded loops.
1960		2677
1961	=item struct ev_loop *other [read-only]	2678	=item struct ev_loop *other [read-only]
1962		2679
1963	The embedded event loop.	2680	The embedded event loop.
1964		2681
…		…
1966		2683
1967	=head3 Examples	2684	=head3 Examples
1968		2685
1969	Example: Try to get an embeddable event loop and embed it into the default	2686	Example: Try to get an embeddable event loop and embed it into the default
1970	event loop. If that is not possible, use the default loop. The default	2687	event loop. If that is not possible, use the default loop. The default
1971	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2688	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1972	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2689	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1973	used).	2690	used).
1974		2691
1975	struct ev_loop *loop_hi = ev_default_init (0);	2692	struct ev_loop *loop_hi = ev_default_init (0);
1976	struct ev_loop *loop_lo = 0;	2693	struct ev_loop *loop_lo = 0;
1977	struct ev_embed embed;	2694	ev_embed embed;
1978		2695
1979	// see if there is a chance of getting one that works	2696	// see if there is a chance of getting one that works
1980	// (remember that a flags value of 0 means autodetection)	2697	// (remember that a flags value of 0 means autodetection)
1981	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1982	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1983	: 0;	2700	: 0;
1984		2701
1985	// if we got one, then embed it, otherwise default to loop_hi	2702	// if we got one, then embed it, otherwise default to loop_hi
1986	if (loop_lo)	2703	if (loop_lo)
1987	{	2704	{
1988	ev_embed_init (&embed, 0, loop_lo);	2705	ev_embed_init (&embed, 0, loop_lo);
1989	ev_embed_start (loop_hi, &embed);	2706	ev_embed_start (loop_hi, &embed);
1990	}	2707	}
1991	else	2708	else
1992	loop_lo = loop_hi;	2709	loop_lo = loop_hi;
1993		2710
1994	Example: Check if kqueue is available but not recommended and create	2711	Example: Check if kqueue is available but not recommended and create
1995	a kqueue backend for use with sockets (which usually work with any	2712	a kqueue backend for use with sockets (which usually work with any
1996	kqueue implementation). Store the kqueue/socket-only event loop in	2713	kqueue implementation). Store the kqueue/socket-only event loop in
1997	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1998		2715
1999	struct ev_loop *loop = ev_default_init (0);	2716	struct ev_loop *loop = ev_default_init (0);
2000	struct ev_loop *loop_socket = 0;	2717	struct ev_loop *loop_socket = 0;
2001	struct ev_embed embed;	2718	ev_embed embed;
2002		2719
2003	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2004	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2005	{	2722	{
2006	ev_embed_init (&embed, 0, loop_socket);	2723	ev_embed_init (&embed, 0, loop_socket);
2007	ev_embed_start (loop, &embed);	2724	ev_embed_start (loop, &embed);
2008	}	2725	}
2009		2726
2010	if (!loop_socket)	2727	if (!loop_socket)
2011	loop_socket = loop;	2728	loop_socket = loop;
2012		2729
2013	// now use loop_socket for all sockets, and loop for everything else	2730	// now use loop_socket for all sockets, and loop for everything else
2014		2731
2015		2732
2016	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2733	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2017		2734
2018	Fork watchers are called when a C<fork ()> was detected (usually because	2735	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2021	event loop blocks next and before C<ev_check> watchers are being called,	2738	event loop blocks next and before C<ev_check> watchers are being called,
2022	and only in the child after the fork. If whoever good citizen calling	2739	and only in the child after the fork. If whoever good citizen calling
2023	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2024	handlers will be invoked, too, of course.	2741	handlers will be invoked, too, of course.
2025		2742
		2743	=head3 The special problem of life after fork - how is it possible?
		2744
		2745	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2746	up/change the process environment, followed by a call to C<exec()>. This
		2747	sequence should be handled by libev without any problems.
		2748
		2749	This changes when the application actually wants to do event handling
		2750	in the child, or both parent in child, in effect "continuing" after the
		2751	fork.
		2752
		2753	The default mode of operation (for libev, with application help to detect
		2754	forks) is to duplicate all the state in the child, as would be expected
		2755	when I<either> the parent I<or> the child process continues.
		2756
		2757	When both processes want to continue using libev, then this is usually the
		2758	wrong result. In that case, usually one process (typically the parent) is
		2759	supposed to continue with all watchers in place as before, while the other
		2760	process typically wants to start fresh, i.e. without any active watchers.
		2761
		2762	The cleanest and most efficient way to achieve that with libev is to
		2763	simply create a new event loop, which of course will be "empty", and
		2764	use that for new watchers. This has the advantage of not touching more
		2765	memory than necessary, and thus avoiding the copy-on-write, and the
		2766	disadvantage of having to use multiple event loops (which do not support
		2767	signal watchers).
		2768
		2769	When this is not possible, or you want to use the default loop for
		2770	other reasons, then in the process that wants to start "fresh", call
		2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2772	the default loop will "orphan" (not stop) all registered watchers, so you
		2773	have to be careful not to execute code that modifies those watchers. Note
		2774	also that in that case, you have to re-register any signal watchers.
		2775
2026	=head3 Watcher-Specific Functions and Data Members	2776	=head3 Watcher-Specific Functions and Data Members
2027		2777
2028	=over 4	2778	=over 4
2029		2779
2030	=item ev_fork_init (ev_signal *, callback)	2780	=item ev_fork_init (ev_signal *, callback)
…		…
2034	believe me.	2784	believe me.
2035		2785
2036	=back	2786	=back
2037		2787
2038		2788
		2789	=head2 C<ev_async> - how to wake up another event loop
		2790
		2791	In general, you cannot use an C<ev_loop> from multiple threads or other
		2792	asynchronous sources such as signal handlers (as opposed to multiple event
		2793	loops - those are of course safe to use in different threads).
		2794
		2795	Sometimes, however, you need to wake up another event loop you do not
		2796	control, for example because it belongs to another thread. This is what
		2797	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2798	can signal it by calling C<ev_async_send>, which is thread- and signal
		2799	safe.
		2800
		2801	This functionality is very similar to C<ev_signal> watchers, as signals,
		2802	too, are asynchronous in nature, and signals, too, will be compressed
		2803	(i.e. the number of callback invocations may be less than the number of
		2804	C<ev_async_sent> calls).
		2805
		2806	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2807	just the default loop.
		2808
		2809	=head3 Queueing
		2810
		2811	C<ev_async> does not support queueing of data in any way. The reason
		2812	is that the author does not know of a simple (or any) algorithm for a
		2813	multiple-writer-single-reader queue that works in all cases and doesn't
		2814	need elaborate support such as pthreads.
		2815
		2816	That means that if you want to queue data, you have to provide your own
		2817	queue. But at least I can tell you how to implement locking around your
		2818	queue:
		2819
		2820	=over 4
		2821
		2822	=item queueing from a signal handler context
		2823
		2824	To implement race-free queueing, you simply add to the queue in the signal
		2825	handler but you block the signal handler in the watcher callback. Here is
		2826	an example that does that for some fictitious SIGUSR1 handler:
		2827
		2828	static ev_async mysig;
		2829
		2830	static void
		2831	sigusr1_handler (void)
		2832	{
		2833	sometype data;
		2834
		2835	// no locking etc.
		2836	queue_put (data);
		2837	ev_async_send (EV_DEFAULT_ &mysig);
		2838	}
		2839
		2840	static void
		2841	mysig_cb (EV_P_ ev_async *w, int revents)
		2842	{
		2843	sometype data;
		2844	sigset_t block, prev;
		2845
		2846	sigemptyset (&block);
		2847	sigaddset (&block, SIGUSR1);
		2848	sigprocmask (SIG_BLOCK, &block, &prev);
		2849
		2850	while (queue_get (&data))
		2851	process (data);
		2852
		2853	if (sigismember (&prev, SIGUSR1)
		2854	sigprocmask (SIG_UNBLOCK, &block, 0);
		2855	}
		2856
		2857	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2858	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2859	either...).
		2860
		2861	=item queueing from a thread context
		2862
		2863	The strategy for threads is different, as you cannot (easily) block
		2864	threads but you can easily preempt them, so to queue safely you need to
		2865	employ a traditional mutex lock, such as in this pthread example:
		2866
		2867	static ev_async mysig;
		2868	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2869
		2870	static void
		2871	otherthread (void)
		2872	{
		2873	// only need to lock the actual queueing operation
		2874	pthread_mutex_lock (&mymutex);
		2875	queue_put (data);
		2876	pthread_mutex_unlock (&mymutex);
		2877
		2878	ev_async_send (EV_DEFAULT_ &mysig);
		2879	}
		2880
		2881	static void
		2882	mysig_cb (EV_P_ ev_async *w, int revents)
		2883	{
		2884	pthread_mutex_lock (&mymutex);
		2885
		2886	while (queue_get (&data))
		2887	process (data);
		2888
		2889	pthread_mutex_unlock (&mymutex);
		2890	}
		2891
		2892	=back
		2893
		2894
		2895	=head3 Watcher-Specific Functions and Data Members
		2896
		2897	=over 4
		2898
		2899	=item ev_async_init (ev_async *, callback)
		2900
		2901	Initialises and configures the async watcher - it has no parameters of any
		2902	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		2903	trust me.
		2904
		2905	=item ev_async_send (loop, ev_async *)
		2906
		2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2909	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2911	section below on what exactly this means).
		2912
		2913	Note that, as with other watchers in libev, multiple events might get
		2914	compressed into a single callback invocation (another way to look at this
		2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2916	reset when the event loop detects that).
		2917
		2918	This call incurs the overhead of a system call only once per event loop
		2919	iteration, so while the overhead might be noticeable, it doesn't apply to
		2920	repeated calls to C<ev_async_send> for the same event loop.
		2921
		2922	=item bool = ev_async_pending (ev_async *)
		2923
		2924	Returns a non-zero value when C<ev_async_send> has been called on the
		2925	watcher but the event has not yet been processed (or even noted) by the
		2926	event loop.
		2927
		2928	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2929	the loop iterates next and checks for the watcher to have become active,
		2930	it will reset the flag again. C<ev_async_pending> can be used to very
		2931	quickly check whether invoking the loop might be a good idea.
		2932
		2933	Not that this does I<not> check whether the watcher itself is pending,
		2934	only whether it has been requested to make this watcher pending: there
		2935	is a time window between the event loop checking and resetting the async
		2936	notification, and the callback being invoked.
		2937
		2938	=back
		2939
		2940
2039	=head1 OTHER FUNCTIONS	2941	=head1 OTHER FUNCTIONS
2040		2942
2041	There are some other functions of possible interest. Described. Here. Now.	2943	There are some other functions of possible interest. Described. Here. Now.
2042		2944
2043	=over 4	2945	=over 4
2044		2946
2045	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2947	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2046		2948
2047	This function combines a simple timer and an I/O watcher, calls your	2949	This function combines a simple timer and an I/O watcher, calls your
2048	callback on whichever event happens first and automatically stop both	2950	callback on whichever event happens first and automatically stops both
2049	watchers. This is useful if you want to wait for a single event on an fd	2951	watchers. This is useful if you want to wait for a single event on an fd
2050	or timeout without having to allocate/configure/start/stop/free one or	2952	or timeout without having to allocate/configure/start/stop/free one or
2051	more watchers yourself.	2953	more watchers yourself.
2052		2954
2053	If C<fd> is less than 0, then no I/O watcher will be started and events	2955	If C<fd> is less than 0, then no I/O watcher will be started and the
2054	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2956	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2055	C<events> set will be craeted and started.	2957	the given C<fd> and C<events> set will be created and started.
2056		2958
2057	If C<timeout> is less than 0, then no timeout watcher will be	2959	If C<timeout> is less than 0, then no timeout watcher will be
2058	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2059	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2961	repeat = 0) will be started. C<0> is a valid timeout.
2060	dubious value.
2061		2962
2062	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2063	passed an C<revents> set like normal event callbacks (a combination of	2964	passed an C<revents> set like normal event callbacks (a combination of
2064	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2065	value passed to C<ev_once>:	2966	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2967	a timeout and an io event at the same time - you probably should give io
		2968	events precedence.
2066		2969
		2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2971
2067	static void stdin_ready (int revents, void *arg)	2972	static void stdin_ready (int revents, void *arg)
2068	{	2973	{
2069	if (revents & EV_TIMEOUT)
2070	/* doh, nothing entered */;
2071	else if (revents & EV_READ)	2974	if (revents & EV_READ)
2072	/* stdin might have data for us, joy! */;	2975	/* stdin might have data for us, joy! */;
		2976	else if (revents & EV_TIMEOUT)
		2977	/* doh, nothing entered */;
2073	}	2978	}
2074		2979
2075	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2076		2981
2077	=item ev_feed_event (ev_loop *, watcher *, int revents)	2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2078		2983
2079	Feeds the given event set into the event loop, as if the specified event	2984	Feeds the given event set into the event loop, as if the specified event
2080	had happened for the specified watcher (which must be a pointer to an	2985	had happened for the specified watcher (which must be a pointer to an
2081	initialised but not necessarily started event watcher).	2986	initialised but not necessarily started event watcher).
2082		2987
2083	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2084		2989
2085	Feed an event on the given fd, as if a file descriptor backend detected	2990	Feed an event on the given fd, as if a file descriptor backend detected
2086	the given events it.	2991	the given events it.
2087		2992
2088	=item ev_feed_signal_event (ev_loop *loop, int signum)	2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2089		2994
2090	Feed an event as if the given signal occured (C<loop> must be the default	2995	Feed an event as if the given signal occurred (C<loop> must be the default
2091	loop!).	2996	loop!).
2092		2997
2093	=back	2998	=back
2094		2999
2095		3000
…		…
2111		3016
2112	=item * Priorities are not currently supported. Initialising priorities	3017	=item * Priorities are not currently supported. Initialising priorities
2113	will fail and all watchers will have the same priority, even though there	3018	will fail and all watchers will have the same priority, even though there
2114	is an ev_pri field.	3019	is an ev_pri field.
2115		3020
		3021	=item * In libevent, the last base created gets the signals, in libev, the
		3022	first base created (== the default loop) gets the signals.
		3023
2116	=item * Other members are not supported.	3024	=item * Other members are not supported.
2117		3025
2118	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3026	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2119	to use the libev header file and library.	3027	to use the libev header file and library.
2120		3028
2121	=back	3029	=back
2122		3030
2123	=head1 C++ SUPPORT	3031	=head1 C++ SUPPORT
2124		3032
2125	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3033	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2126	you to use some convinience methods to start/stop watchers and also change	3034	you to use some convenience methods to start/stop watchers and also change
2127	the callback model to a model using method callbacks on objects.	3035	the callback model to a model using method callbacks on objects.
2128		3036
2129	To use it,	3037	To use it,
2130		3038
2131	#include <ev++.h>	3039	#include <ev++.h>
2132		3040
2133	This automatically includes F<ev.h> and puts all of its definitions (many	3041	This automatically includes F<ev.h> and puts all of its definitions (many
2134	of them macros) into the global namespace. All C++ specific things are	3042	of them macros) into the global namespace. All C++ specific things are
2135	put into the C<ev> namespace. It should support all the same embedding	3043	put into the C<ev> namespace. It should support all the same embedding
2136	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3044	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2203	your compiler is good :), then the method will be fully inlined into the	3111	your compiler is good :), then the method will be fully inlined into the
2204	thunking function, making it as fast as a direct C callback.	3112	thunking function, making it as fast as a direct C callback.
2205		3113
2206	Example: simple class declaration and watcher initialisation	3114	Example: simple class declaration and watcher initialisation
2207		3115
2208	struct myclass	3116	struct myclass
2209	{	3117	{
2210	void io_cb (ev::io &w, int revents) { }	3118	void io_cb (ev::io &w, int revents) { }
2211	}	3119	}
2212		3120
2213	myclass obj;	3121	myclass obj;
2214	ev::io iow;	3122	ev::io iow;
2215	iow.set <myclass, &myclass::io_cb> (&obj);	3123	iow.set <myclass, &myclass::io_cb> (&obj);
		3124
		3125	=item w->set (object *)
		3126
		3127	This is an B<experimental> feature that might go away in a future version.
		3128
		3129	This is a variation of a method callback - leaving out the method to call
		3130	will default the method to C<operator ()>, which makes it possible to use
		3131	functor objects without having to manually specify the C<operator ()> all
		3132	the time. Incidentally, you can then also leave out the template argument
		3133	list.
		3134
		3135	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3136	int revents)>.
		3137
		3138	See the method-C<set> above for more details.
		3139
		3140	Example: use a functor object as callback.
		3141
		3142	struct myfunctor
		3143	{
		3144	void operator() (ev::io &w, int revents)
		3145	{
		3146	...
		3147	}
		3148	}
		3149
		3150	myfunctor f;
		3151
		3152	ev::io w;
		3153	w.set (&f);
2216		3154
2217	=item w->set<function> (void *data = 0)	3155	=item w->set<function> (void *data = 0)
2218		3156
2219	Also sets a callback, but uses a static method or plain function as	3157	Also sets a callback, but uses a static method or plain function as
2220	callback. The optional C<data> argument will be stored in the watcher's	3158	callback. The optional C<data> argument will be stored in the watcher's
…		…
2222		3160
2223	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3161	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2224		3162
2225	See the method-C<set> above for more details.	3163	See the method-C<set> above for more details.
2226		3164
2227	Example:	3165	Example: Use a plain function as callback.
2228		3166
2229	static void io_cb (ev::io &w, int revents) { }	3167	static void io_cb (ev::io &w, int revents) { }
2230	iow.set <io_cb> ();	3168	iow.set <io_cb> ();
2231		3169
2232	=item w->set (struct ev_loop *)	3170	=item w->set (struct ev_loop *)
2233		3171
2234	Associates a different C<struct ev_loop> with this watcher. You can only	3172	Associates a different C<struct ev_loop> with this watcher. You can only
2235	do this when the watcher is inactive (and not pending either).	3173	do this when the watcher is inactive (and not pending either).
2236		3174
2237	=item w->set ([args])	3175	=item w->set ([arguments])
2238		3176
2239	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3177	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2240	called at least once. Unlike the C counterpart, an active watcher gets	3178	called at least once. Unlike the C counterpart, an active watcher gets
2241	automatically stopped and restarted when reconfiguring it with this	3179	automatically stopped and restarted when reconfiguring it with this
2242	method.	3180	method.
2243		3181
2244	=item w->start ()	3182	=item w->start ()
…		…
2268	=back	3206	=back
2269		3207
2270	Example: Define a class with an IO and idle watcher, start one of them in	3208	Example: Define a class with an IO and idle watcher, start one of them in
2271	the constructor.	3209	the constructor.
2272		3210
2273	class myclass	3211	class myclass
2274	{	3212	{
2275	ev_io io; void io_cb (ev::io &w, int revents);	3213	ev::io io ; void io_cb (ev::io &w, int revents);
2276	ev_idle idle void idle_cb (ev::idle &w, int revents);	3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2277		3215
2278	myclass ();	3216	myclass (int fd)
2279	}	3217	{
2280
2281	myclass::myclass (int fd)
2282	{
2283	io .set <myclass, &myclass::io_cb > (this);	3218	io .set <myclass, &myclass::io_cb > (this);
2284	idle.set <myclass, &myclass::idle_cb> (this);	3219	idle.set <myclass, &myclass::idle_cb> (this);
2285		3220
2286	io.start (fd, ev::READ);	3221	io.start (fd, ev::READ);
		3222	}
2287	}	3223	};
		3224
		3225
		3226	=head1 OTHER LANGUAGE BINDINGS
		3227
		3228	Libev does not offer other language bindings itself, but bindings for a
		3229	number of languages exist in the form of third-party packages. If you know
		3230	any interesting language binding in addition to the ones listed here, drop
		3231	me a note.
		3232
		3233	=over 4
		3234
		3235	=item Perl
		3236
		3237	The EV module implements the full libev API and is actually used to test
		3238	libev. EV is developed together with libev. Apart from the EV core module,
		3239	there are additional modules that implement libev-compatible interfaces
		3240	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3241	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3242	and C<EV::Glib>).
		3243
		3244	It can be found and installed via CPAN, its homepage is at
		3245	L<http://software.schmorp.de/pkg/EV>.
		3246
		3247	=item Python
		3248
		3249	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3250	seems to be quite complete and well-documented.
		3251
		3252	=item Ruby
		3253
		3254	Tony Arcieri has written a ruby extension that offers access to a subset
		3255	of the libev API and adds file handle abstractions, asynchronous DNS and
		3256	more on top of it. It can be found via gem servers. Its homepage is at
		3257	L<http://rev.rubyforge.org/>.
		3258
		3259	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3260	makes rev work even on mingw.
		3261
		3262	=item Haskell
		3263
		3264	A haskell binding to libev is available at
		3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3266
		3267	=item D
		3268
		3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3271
		3272	=item Ocaml
		3273
		3274	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3276
		3277	=back
2288		3278
2289		3279
2290	=head1 MACRO MAGIC	3280	=head1 MACRO MAGIC
2291		3281
2292	Libev can be compiled with a variety of options, the most fundamantal	3282	Libev can be compiled with a variety of options, the most fundamental
2293	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3283	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2294	functions and callbacks have an initial C<struct ev_loop *> argument.	3284	functions and callbacks have an initial C<struct ev_loop *> argument.
2295		3285
2296	To make it easier to write programs that cope with either variant, the	3286	To make it easier to write programs that cope with either variant, the
2297	following macros are defined:	3287	following macros are defined:
…		…
2302		3292
2303	This provides the loop I<argument> for functions, if one is required ("ev	3293	This provides the loop I<argument> for functions, if one is required ("ev
2304	loop argument"). The C<EV_A> form is used when this is the sole argument,	3294	loop argument"). The C<EV_A> form is used when this is the sole argument,
2305	C<EV_A_> is used when other arguments are following. Example:	3295	C<EV_A_> is used when other arguments are following. Example:
2306		3296
2307	ev_unref (EV_A);	3297	ev_unref (EV_A);
2308	ev_timer_add (EV_A_ watcher);	3298	ev_timer_add (EV_A_ watcher);
2309	ev_loop (EV_A_ 0);	3299	ev_loop (EV_A_ 0);
2310		3300
2311	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3301	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2312	which is often provided by the following macro.	3302	which is often provided by the following macro.
2313		3303
2314	=item C<EV_P>, C<EV_P_>	3304	=item C<EV_P>, C<EV_P_>
2315		3305
2316	This provides the loop I<parameter> for functions, if one is required ("ev	3306	This provides the loop I<parameter> for functions, if one is required ("ev
2317	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3307	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2318	C<EV_P_> is used when other parameters are following. Example:	3308	C<EV_P_> is used when other parameters are following. Example:
2319		3309
2320	// this is how ev_unref is being declared	3310	// this is how ev_unref is being declared
2321	static void ev_unref (EV_P);	3311	static void ev_unref (EV_P);
2322		3312
2323	// this is how you can declare your typical callback	3313	// this is how you can declare your typical callback
2324	static void cb (EV_P_ ev_timer *w, int revents)	3314	static void cb (EV_P_ ev_timer *w, int revents)
2325		3315
2326	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3316	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2327	suitable for use with C<EV_A>.	3317	suitable for use with C<EV_A>.
2328		3318
2329	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3319	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2330		3320
2331	Similar to the other two macros, this gives you the value of the default	3321	Similar to the other two macros, this gives you the value of the default
2332	loop, if multiple loops are supported ("ev loop default").	3322	loop, if multiple loops are supported ("ev loop default").
		3323
		3324	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3325
		3326	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3327	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3328	is undefined when the default loop has not been initialised by a previous
		3329	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3330
		3331	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3332	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2333		3333
2334	=back	3334	=back
2335		3335
2336	Example: Declare and initialise a check watcher, utilising the above	3336	Example: Declare and initialise a check watcher, utilising the above
2337	macros so it will work regardless of whether multiple loops are supported	3337	macros so it will work regardless of whether multiple loops are supported
2338	or not.	3338	or not.
2339		3339
2340	static void	3340	static void
2341	check_cb (EV_P_ ev_timer *w, int revents)	3341	check_cb (EV_P_ ev_timer *w, int revents)
2342	{	3342	{
2343	ev_check_stop (EV_A_ w);	3343	ev_check_stop (EV_A_ w);
2344	}	3344	}
2345		3345
2346	ev_check check;	3346	ev_check check;
2347	ev_check_init (&check, check_cb);	3347	ev_check_init (&check, check_cb);
2348	ev_check_start (EV_DEFAULT_ &check);	3348	ev_check_start (EV_DEFAULT_ &check);
2349	ev_loop (EV_DEFAULT_ 0);	3349	ev_loop (EV_DEFAULT_ 0);
2350		3350
2351	=head1 EMBEDDING	3351	=head1 EMBEDDING
2352		3352
2353	Libev can (and often is) directly embedded into host	3353	Libev can (and often is) directly embedded into host
2354	applications. Examples of applications that embed it include the Deliantra	3354	applications. Examples of applications that embed it include the Deliantra
…		…
2361	libev somewhere in your source tree).	3361	libev somewhere in your source tree).
2362		3362
2363	=head2 FILESETS	3363	=head2 FILESETS
2364		3364
2365	Depending on what features you need you need to include one or more sets of files	3365	Depending on what features you need you need to include one or more sets of files
2366	in your app.	3366	in your application.
2367		3367
2368	=head3 CORE EVENT LOOP	3368	=head3 CORE EVENT LOOP
2369		3369
2370	To include only the libev core (all the C<ev_*> functions), with manual	3370	To include only the libev core (all the C<ev_*> functions), with manual
2371	configuration (no autoconf):	3371	configuration (no autoconf):
2372		3372
2373	#define EV_STANDALONE 1	3373	#define EV_STANDALONE 1
2374	#include "ev.c"	3374	#include "ev.c"
2375		3375
2376	This will automatically include F<ev.h>, too, and should be done in a	3376	This will automatically include F<ev.h>, too, and should be done in a
2377	single C source file only to provide the function implementations. To use	3377	single C source file only to provide the function implementations. To use
2378	it, do the same for F<ev.h> in all files wishing to use this API (best	3378	it, do the same for F<ev.h> in all files wishing to use this API (best
2379	done by writing a wrapper around F<ev.h> that you can include instead and	3379	done by writing a wrapper around F<ev.h> that you can include instead and
2380	where you can put other configuration options):	3380	where you can put other configuration options):
2381		3381
2382	#define EV_STANDALONE 1	3382	#define EV_STANDALONE 1
2383	#include "ev.h"	3383	#include "ev.h"
2384		3384
2385	Both header files and implementation files can be compiled with a C++	3385	Both header files and implementation files can be compiled with a C++
2386	compiler (at least, thats a stated goal, and breakage will be treated	3386	compiler (at least, that's a stated goal, and breakage will be treated
2387	as a bug).	3387	as a bug).
2388		3388
2389	You need the following files in your source tree, or in a directory	3389	You need the following files in your source tree, or in a directory
2390	in your include path (e.g. in libev/ when using -Ilibev):	3390	in your include path (e.g. in libev/ when using -Ilibev):
2391		3391
2392	ev.h	3392	ev.h
2393	ev.c	3393	ev.c
2394	ev_vars.h	3394	ev_vars.h
2395	ev_wrap.h	3395	ev_wrap.h
2396		3396
2397	ev_win32.c required on win32 platforms only	3397	ev_win32.c required on win32 platforms only
2398		3398
2399	ev_select.c only when select backend is enabled (which is enabled by default)	3399	ev_select.c only when select backend is enabled (which is enabled by default)
2400	ev_poll.c only when poll backend is enabled (disabled by default)	3400	ev_poll.c only when poll backend is enabled (disabled by default)
2401	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3401	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2402	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3402	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2403	ev_port.c only when the solaris port backend is enabled (disabled by default)	3403	ev_port.c only when the solaris port backend is enabled (disabled by default)
2404		3404
2405	F<ev.c> includes the backend files directly when enabled, so you only need	3405	F<ev.c> includes the backend files directly when enabled, so you only need
2406	to compile this single file.	3406	to compile this single file.
2407		3407
2408	=head3 LIBEVENT COMPATIBILITY API	3408	=head3 LIBEVENT COMPATIBILITY API
2409		3409
2410	To include the libevent compatibility API, also include:	3410	To include the libevent compatibility API, also include:
2411		3411
2412	#include "event.c"	3412	#include "event.c"
2413		3413
2414	in the file including F<ev.c>, and:	3414	in the file including F<ev.c>, and:
2415		3415
2416	#include "event.h"	3416	#include "event.h"
2417		3417
2418	in the files that want to use the libevent API. This also includes F<ev.h>.	3418	in the files that want to use the libevent API. This also includes F<ev.h>.
2419		3419
2420	You need the following additional files for this:	3420	You need the following additional files for this:
2421		3421
2422	event.h	3422	event.h
2423	event.c	3423	event.c
2424		3424
2425	=head3 AUTOCONF SUPPORT	3425	=head3 AUTOCONF SUPPORT
2426		3426
2427	Instead of using C<EV_STANDALONE=1> and providing your config in	3427	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2428	whatever way you want, you can also C<m4_include([libev.m4])> in your	3428	whatever way you want, you can also C<m4_include([libev.m4])> in your
2429	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3429	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2430	include F<config.h> and configure itself accordingly.	3430	include F<config.h> and configure itself accordingly.
2431		3431
2432	For this of course you need the m4 file:	3432	For this of course you need the m4 file:
2433		3433
2434	libev.m4	3434	libev.m4
2435		3435
2436	=head2 PREPROCESSOR SYMBOLS/MACROS	3436	=head2 PREPROCESSOR SYMBOLS/MACROS
2437		3437
2438	Libev can be configured via a variety of preprocessor symbols you have to define	3438	Libev can be configured via a variety of preprocessor symbols you have to
2439	before including any of its files. The default is not to build for multiplicity	3439	define before including any of its files. The default in the absence of
2440	and only include the select backend.	3440	autoconf is documented for every option.
2441		3441
2442	=over 4	3442	=over 4
2443		3443
2444	=item EV_STANDALONE	3444	=item EV_STANDALONE
2445		3445
…		…
2447	keeps libev from including F<config.h>, and it also defines dummy	3447	keeps libev from including F<config.h>, and it also defines dummy
2448	implementations for some libevent functions (such as logging, which is not	3448	implementations for some libevent functions (such as logging, which is not
2449	supported). It will also not define any of the structs usually found in	3449	supported). It will also not define any of the structs usually found in
2450	F<event.h> that are not directly supported by the libev core alone.	3450	F<event.h> that are not directly supported by the libev core alone.
2451		3451
		3452	In stanbdalone mode, libev will still try to automatically deduce the
		3453	configuration, but has to be more conservative.
		3454
2452	=item EV_USE_MONOTONIC	3455	=item EV_USE_MONOTONIC
2453		3456
2454	If defined to be C<1>, libev will try to detect the availability of the	3457	If defined to be C<1>, libev will try to detect the availability of the
2455	monotonic clock option at both compiletime and runtime. Otherwise no use	3458	monotonic clock option at both compile time and runtime. Otherwise no
2456	of the monotonic clock option will be attempted. If you enable this, you	3459	use of the monotonic clock option will be attempted. If you enable this,
2457	usually have to link against librt or something similar. Enabling it when	3460	you usually have to link against librt or something similar. Enabling it
2458	the functionality isn't available is safe, though, although you have	3461	when the functionality isn't available is safe, though, although you have
2459	to make sure you link against any libraries where the C<clock_gettime>	3462	to make sure you link against any libraries where the C<clock_gettime>
2460	function is hiding in (often F<-lrt>).	3463	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2461		3464
2462	=item EV_USE_REALTIME	3465	=item EV_USE_REALTIME
2463		3466
2464	If defined to be C<1>, libev will try to detect the availability of the	3467	If defined to be C<1>, libev will try to detect the availability of the
2465	realtime clock option at compiletime (and assume its availability at	3468	real-time clock option at compile time (and assume its availability
2466	runtime if successful). Otherwise no use of the realtime clock option will	3469	at runtime if successful). Otherwise no use of the real-time clock
2467	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3470	option will be attempted. This effectively replaces C<gettimeofday>
2468	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3471	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2469	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3472	correctness. See the note about libraries in the description of
		3473	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3474	C<EV_USE_CLOCK_SYSCALL>.
		3475
		3476	=item EV_USE_CLOCK_SYSCALL
		3477
		3478	If defined to be C<1>, libev will try to use a direct syscall instead
		3479	of calling the system-provided C<clock_gettime> function. This option
		3480	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3481	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3482	programs needlessly. Using a direct syscall is slightly slower (in
		3483	theory), because no optimised vdso implementation can be used, but avoids
		3484	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3485	higher, as it simplifies linking (no need for C<-lrt>).
2470		3486
2471	=item EV_USE_NANOSLEEP	3487	=item EV_USE_NANOSLEEP
2472		3488
2473	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3489	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2474	and will use it for delays. Otherwise it will use C<select ()>.	3490	and will use it for delays. Otherwise it will use C<select ()>.
2475		3491
		3492	=item EV_USE_EVENTFD
		3493
		3494	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3495	available and will probe for kernel support at runtime. This will improve
		3496	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3497	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3498	2.7 or newer, otherwise disabled.
		3499
2476	=item EV_USE_SELECT	3500	=item EV_USE_SELECT
2477		3501
2478	If undefined or defined to be C<1>, libev will compile in support for the	3502	If undefined or defined to be C<1>, libev will compile in support for the
2479	C<select>(2) backend. No attempt at autodetection will be done: if no	3503	C<select>(2) backend. No attempt at auto-detection will be done: if no
2480	other method takes over, select will be it. Otherwise the select backend	3504	other method takes over, select will be it. Otherwise the select backend
2481	will not be compiled in.	3505	will not be compiled in.
2482		3506
2483	=item EV_SELECT_USE_FD_SET	3507	=item EV_SELECT_USE_FD_SET
2484		3508
2485	If defined to C<1>, then the select backend will use the system C<fd_set>	3509	If defined to C<1>, then the select backend will use the system C<fd_set>
2486	structure. This is useful if libev doesn't compile due to a missing	3510	structure. This is useful if libev doesn't compile due to a missing
2487	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3511	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2488	exotic systems. This usually limits the range of file descriptors to some	3512	on exotic systems. This usually limits the range of file descriptors to
2489	low limit such as 1024 or might have other limitations (winsocket only	3513	some low limit such as 1024 or might have other limitations (winsocket
2490	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3514	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2491	influence the size of the C<fd_set> used.	3515	configures the maximum size of the C<fd_set>.
2492		3516
2493	=item EV_SELECT_IS_WINSOCKET	3517	=item EV_SELECT_IS_WINSOCKET
2494		3518
2495	When defined to C<1>, the select backend will assume that	3519	When defined to C<1>, the select backend will assume that
2496	select/socket/connect etc. don't understand file descriptors but	3520	select/socket/connect etc. don't understand file descriptors but
…		…
2516		3540
2517	=item EV_USE_EPOLL	3541	=item EV_USE_EPOLL
2518		3542
2519	If defined to be C<1>, libev will compile in support for the Linux	3543	If defined to be C<1>, libev will compile in support for the Linux
2520	C<epoll>(7) backend. Its availability will be detected at runtime,	3544	C<epoll>(7) backend. Its availability will be detected at runtime,
2521	otherwise another method will be used as fallback. This is the	3545	otherwise another method will be used as fallback. This is the preferred
2522	preferred backend for GNU/Linux systems.	3546	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3547	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2523		3548
2524	=item EV_USE_KQUEUE	3549	=item EV_USE_KQUEUE
2525		3550
2526	If defined to be C<1>, libev will compile in support for the BSD style	3551	If defined to be C<1>, libev will compile in support for the BSD style
2527	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3552	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2540	otherwise another method will be used as fallback. This is the preferred	3565	otherwise another method will be used as fallback. This is the preferred
2541	backend for Solaris 10 systems.	3566	backend for Solaris 10 systems.
2542		3567
2543	=item EV_USE_DEVPOLL	3568	=item EV_USE_DEVPOLL
2544		3569
2545	reserved for future expansion, works like the USE symbols above.	3570	Reserved for future expansion, works like the USE symbols above.
2546		3571
2547	=item EV_USE_INOTIFY	3572	=item EV_USE_INOTIFY
2548		3573
2549	If defined to be C<1>, libev will compile in support for the Linux inotify	3574	If defined to be C<1>, libev will compile in support for the Linux inotify
2550	interface to speed up C<ev_stat> watchers. Its actual availability will	3575	interface to speed up C<ev_stat> watchers. Its actual availability will
2551	be detected at runtime.	3576	be detected at runtime. If undefined, it will be enabled if the headers
		3577	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3578
		3579	=item EV_ATOMIC_T
		3580
		3581	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3582	access is atomic with respect to other threads or signal contexts. No such
		3583	type is easily found in the C language, so you can provide your own type
		3584	that you know is safe for your purposes. It is used both for signal handler "locking"
		3585	as well as for signal and thread safety in C<ev_async> watchers.
		3586
		3587	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3588	(from F<signal.h>), which is usually good enough on most platforms.
2552		3589
2553	=item EV_H	3590	=item EV_H
2554		3591
2555	The name of the F<ev.h> header file used to include it. The default if	3592	The name of the F<ev.h> header file used to include it. The default if
2556	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	3593	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2557	virtually rename the F<ev.h> header file in case of conflicts.	3594	used to virtually rename the F<ev.h> header file in case of conflicts.
2558		3595
2559	=item EV_CONFIG_H	3596	=item EV_CONFIG_H
2560		3597
2561	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3598	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2562	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3599	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2563	C<EV_H>, above.	3600	C<EV_H>, above.
2564		3601
2565	=item EV_EVENT_H	3602	=item EV_EVENT_H
2566		3603
2567	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3604	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2568	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	3605	of how the F<event.h> header can be found, the default is C<"event.h">.
2569		3606
2570	=item EV_PROTOTYPES	3607	=item EV_PROTOTYPES
2571		3608
2572	If defined to be C<0>, then F<ev.h> will not define any function	3609	If defined to be C<0>, then F<ev.h> will not define any function
2573	prototypes, but still define all the structs and other symbols. This is	3610	prototypes, but still define all the structs and other symbols. This is
…		…
2594	When doing priority-based operations, libev usually has to linearly search	3631	When doing priority-based operations, libev usually has to linearly search
2595	all the priorities, so having many of them (hundreds) uses a lot of space	3632	all the priorities, so having many of them (hundreds) uses a lot of space
2596	and time, so using the defaults of five priorities (-2 .. +2) is usually	3633	and time, so using the defaults of five priorities (-2 .. +2) is usually
2597	fine.	3634	fine.
2598		3635
2599	If your embedding app does not need any priorities, defining these both to	3636	If your embedding application does not need any priorities, defining these
2600	C<0> will save some memory and cpu.	3637	both to C<0> will save some memory and CPU.
2601		3638
2602	=item EV_PERIODIC_ENABLE	3639	=item EV_PERIODIC_ENABLE
2603		3640
2604	If undefined or defined to be C<1>, then periodic timers are supported. If	3641	If undefined or defined to be C<1>, then periodic timers are supported. If
2605	defined to be C<0>, then they are not. Disabling them saves a few kB of	3642	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2612	code.	3649	code.
2613		3650
2614	=item EV_EMBED_ENABLE	3651	=item EV_EMBED_ENABLE
2615		3652
2616	If undefined or defined to be C<1>, then embed watchers are supported. If	3653	If undefined or defined to be C<1>, then embed watchers are supported. If
2617	defined to be C<0>, then they are not.	3654	defined to be C<0>, then they are not. Embed watchers rely on most other
		3655	watcher types, which therefore must not be disabled.
2618		3656
2619	=item EV_STAT_ENABLE	3657	=item EV_STAT_ENABLE
2620		3658
2621	If undefined or defined to be C<1>, then stat watchers are supported. If	3659	If undefined or defined to be C<1>, then stat watchers are supported. If
2622	defined to be C<0>, then they are not.	3660	defined to be C<0>, then they are not.
…		…
2624	=item EV_FORK_ENABLE	3662	=item EV_FORK_ENABLE
2625		3663
2626	If undefined or defined to be C<1>, then fork watchers are supported. If	3664	If undefined or defined to be C<1>, then fork watchers are supported. If
2627	defined to be C<0>, then they are not.	3665	defined to be C<0>, then they are not.
2628		3666
		3667	=item EV_ASYNC_ENABLE
		3668
		3669	If undefined or defined to be C<1>, then async watchers are supported. If
		3670	defined to be C<0>, then they are not.
		3671
2629	=item EV_MINIMAL	3672	=item EV_MINIMAL
2630		3673
2631	If you need to shave off some kilobytes of code at the expense of some	3674	If you need to shave off some kilobytes of code at the expense of some
2632	speed, define this symbol to C<1>. Currently only used for gcc to override	3675	speed, define this symbol to C<1>. Currently this is used to override some
2633	some inlining decisions, saves roughly 30% codesize of amd64.	3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3677	much smaller 2-heap for timer management over the default 4-heap.
2634		3678
2635	=item EV_PID_HASHSIZE	3679	=item EV_PID_HASHSIZE
2636		3680
2637	C<ev_child> watchers use a small hash table to distribute workload by	3681	C<ev_child> watchers use a small hash table to distribute workload by
2638	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2645	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3689	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2646	usually more than enough. If you need to manage thousands of C<ev_stat>	3690	usually more than enough. If you need to manage thousands of C<ev_stat>
2647	watchers you might want to increase this value (I<must> be a power of	3691	watchers you might want to increase this value (I<must> be a power of
2648	two).	3692	two).
2649		3693
		3694	=item EV_USE_4HEAP
		3695
		3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3699	faster performance with many (thousands) of watchers.
		3700
		3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3702	(disabled).
		3703
		3704	=item EV_HEAP_CACHE_AT
		3705
		3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3710	but avoids random read accesses on heap changes. This improves performance
		3711	noticeably with many (hundreds) of watchers.
		3712
		3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3714	(disabled).
		3715
		3716	=item EV_VERIFY
		3717
		3718	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3719	be done: If set to C<0>, no internal verification code will be compiled
		3720	in. If set to C<1>, then verification code will be compiled in, but not
		3721	called. If set to C<2>, then the internal verification code will be
		3722	called once per loop, which can slow down libev. If set to C<3>, then the
		3723	verification code will be called very frequently, which will slow down
		3724	libev considerably.
		3725
		3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3727	C<0>.
		3728
2650	=item EV_COMMON	3729	=item EV_COMMON
2651		3730
2652	By default, all watchers have a C<void *data> member. By redefining	3731	By default, all watchers have a C<void *data> member. By redefining
2653	this macro to a something else you can include more and other types of	3732	this macro to a something else you can include more and other types of
2654	members. You have to define it each time you include one of the files,	3733	members. You have to define it each time you include one of the files,
2655	though, and it must be identical each time.	3734	though, and it must be identical each time.
2656		3735
2657	For example, the perl EV module uses something like this:	3736	For example, the perl EV module uses something like this:
2658		3737
2659	#define EV_COMMON \	3738	#define EV_COMMON \
2660	SV *self; /* contains this struct */ \	3739	SV *self; /* contains this struct */ \
2661	SV *cb_sv, *fh /* note no trailing ";" */	3740	SV *cb_sv, *fh /* note no trailing ";" */
2662		3741
2663	=item EV_CB_DECLARE (type)	3742	=item EV_CB_DECLARE (type)
2664		3743
2665	=item EV_CB_INVOKE (watcher, revents)	3744	=item EV_CB_INVOKE (watcher, revents)
2666		3745
…		…
2671	definition and a statement, respectively. See the F<ev.h> header file for	3750	definition and a statement, respectively. See the F<ev.h> header file for
2672	their default definitions. One possible use for overriding these is to	3751	their default definitions. One possible use for overriding these is to
2673	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3752	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2674	method calls instead of plain function calls in C++.	3753	method calls instead of plain function calls in C++.
2675		3754
		3755	=back
		3756
2676	=head2 EXPORTED API SYMBOLS	3757	=head2 EXPORTED API SYMBOLS
2677		3758
2678	If you need to re-export the API (e.g. via a dll) and you need a list of	3759	If you need to re-export the API (e.g. via a DLL) and you need a list of
2679	exported symbols, you can use the provided F<Symbol.*> files which list	3760	exported symbols, you can use the provided F<Symbol.*> files which list
2680	all public symbols, one per line:	3761	all public symbols, one per line:
2681		3762
2682	Symbols.ev for libev proper	3763	Symbols.ev for libev proper
2683	Symbols.event for the libevent emulation	3764	Symbols.event for the libevent emulation
2684		3765
2685	This can also be used to rename all public symbols to avoid clashes with	3766	This can also be used to rename all public symbols to avoid clashes with
2686	multiple versions of libev linked together (which is obviously bad in	3767	multiple versions of libev linked together (which is obviously bad in
2687	itself, but sometimes it is inconvinient to avoid this).	3768	itself, but sometimes it is inconvenient to avoid this).
2688		3769
2689	A sed command like this will create wrapper C<#define>'s that you need to	3770	A sed command like this will create wrapper C<#define>'s that you need to
2690	include before including F<ev.h>:	3771	include before including F<ev.h>:
2691		3772
2692	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3773	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2709	file.	3790	file.
2710		3791
2711	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3792	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2712	that everybody includes and which overrides some configure choices:	3793	that everybody includes and which overrides some configure choices:
2713		3794
2714	#define EV_MINIMAL 1	3795	#define EV_MINIMAL 1
2715	#define EV_USE_POLL 0	3796	#define EV_USE_POLL 0
2716	#define EV_MULTIPLICITY 0	3797	#define EV_MULTIPLICITY 0
2717	#define EV_PERIODIC_ENABLE 0	3798	#define EV_PERIODIC_ENABLE 0
2718	#define EV_STAT_ENABLE 0	3799	#define EV_STAT_ENABLE 0
2719	#define EV_FORK_ENABLE 0	3800	#define EV_FORK_ENABLE 0
2720	#define EV_CONFIG_H <config.h>	3801	#define EV_CONFIG_H <config.h>
2721	#define EV_MINPRI 0	3802	#define EV_MINPRI 0
2722	#define EV_MAXPRI 0	3803	#define EV_MAXPRI 0
2723		3804
2724	#include "ev++.h"	3805	#include "ev++.h"
2725		3806
2726	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2727		3808
2728	#include "ev_cpp.h"	3809	#include "ev_cpp.h"
2729	#include "ev.c"	3810	#include "ev.c"
2730		3811
		3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2731		3813
2732	=head1 COMPLEXITIES	3814	=head2 THREADS AND COROUTINES
2733		3815
2734	In this section the complexities of (many of) the algorithms used inside	3816	=head3 THREADS
2735	libev will be explained. For complexity discussions about backends see the
2736	documentation for C<ev_default_init>.
2737		3817
2738	All of the following are about amortised time: If an array needs to be	3818	All libev functions are reentrant and thread-safe unless explicitly
2739	extended, libev needs to realloc and move the whole array, but this	3819	documented otherwise, but libev implements no locking itself. This means
2740	happens asymptotically never with higher number of elements, so O(1) might	3820	that you can use as many loops as you want in parallel, as long as there
2741	mean it might do a lengthy realloc operation in rare cases, but on average	3821	are no concurrent calls into any libev function with the same loop
2742	it is much faster and asymptotically approaches constant time.	3822	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3823	of course): libev guarantees that different event loops share no data
		3824	structures that need any locking.
		3825
		3826	Or to put it differently: calls with different loop parameters can be done
		3827	concurrently from multiple threads, calls with the same loop parameter
		3828	must be done serially (but can be done from different threads, as long as
		3829	only one thread ever is inside a call at any point in time, e.g. by using
		3830	a mutex per loop).
		3831
		3832	Specifically to support threads (and signal handlers), libev implements
		3833	so-called C<ev_async> watchers, which allow some limited form of
		3834	concurrency on the same event loop, namely waking it up "from the
		3835	outside".
		3836
		3837	If you want to know which design (one loop, locking, or multiple loops
		3838	without or something else still) is best for your problem, then I cannot
		3839	help you, but here is some generic advice:
2743		3840
2744	=over 4	3841	=over 4
2745		3842
2746	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3843	=item * most applications have a main thread: use the default libev loop
		3844	in that thread, or create a separate thread running only the default loop.
2747		3845
2748	This means that, when you have a watcher that triggers in one hour and	3846	This helps integrating other libraries or software modules that use libev
2749	there are 100 watchers that would trigger before that then inserting will	3847	themselves and don't care/know about threading.
2750	have to skip roughly seven (C<ld 100>) of these watchers.
2751		3848
2752	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3849	=item * one loop per thread is usually a good model.
2753		3850
2754	That means that changing a timer costs less than removing/adding them	3851	Doing this is almost never wrong, sometimes a better-performance model
2755	as only the relative motion in the event queue has to be paid for.	3852	exists, but it is always a good start.
2756		3853
2757	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3854	=item * other models exist, such as the leader/follower pattern, where one
		3855	loop is handed through multiple threads in a kind of round-robin fashion.
2758		3856
2759	These just add the watcher into an array or at the head of a list.	3857	Choosing a model is hard - look around, learn, know that usually you can do
		3858	better than you currently do :-)
2760		3859
2761	=item Stopping check/prepare/idle watchers: O(1)	3860	=item * often you need to talk to some other thread which blocks in the
		3861	event loop.
2762		3862
2763	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3863	C<ev_async> watchers can be used to wake them up from other threads safely
		3864	(or from signal contexts...).
2764		3865
2765	These watchers are stored in lists then need to be walked to find the	3866	An example use would be to communicate signals or other events that only
2766	correct watcher to remove. The lists are usually short (you don't usually	3867	work in the default loop by registering the signal watcher with the
2767	have many watchers waiting for the same fd or signal).	3868	default loop and triggering an C<ev_async> watcher from the default loop
2768		3869	watcher callback into the event loop interested in the signal.
2769	=item Finding the next timer in each loop iteration: O(1)
2770
2771	By virtue of using a binary heap, the next timer is always found at the
2772	beginning of the storage array.
2773
2774	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2775
2776	A change means an I/O watcher gets started or stopped, which requires
2777	libev to recalculate its status (and possibly tell the kernel, depending
2778	on backend and wether C<ev_io_set> was used).
2779
2780	=item Activating one watcher (putting it into the pending state): O(1)
2781
2782	=item Priority handling: O(number_of_priorities)
2783
2784	Priorities are implemented by allocating some space for each
2785	priority. When doing priority-based operations, libev usually has to
2786	linearly search all the priorities, but starting/stopping and activating
2787	watchers becomes O(1) w.r.t. prioritiy handling.
2788		3870
2789	=back	3871	=back
2790		3872
		3873	=head3 COROUTINES
2791		3874
2792	=head1 Win32 platform limitations and workarounds	3875	Libev is very accommodating to coroutines ("cooperative threads"):
		3876	libev fully supports nesting calls to its functions from different
		3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3878	different coroutines, and switch freely between both coroutines running the
		3879	loop, as long as you don't confuse yourself). The only exception is that
		3880	you must not do this from C<ev_periodic> reschedule callbacks.
		3881
		3882	Care has been taken to ensure that libev does not keep local state inside
		3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3884	they do not call any callbacks.
		3885
		3886	=head2 COMPILER WARNINGS
		3887
		3888	Depending on your compiler and compiler settings, you might get no or a
		3889	lot of warnings when compiling libev code. Some people are apparently
		3890	scared by this.
		3891
		3892	However, these are unavoidable for many reasons. For one, each compiler
		3893	has different warnings, and each user has different tastes regarding
		3894	warning options. "Warn-free" code therefore cannot be a goal except when
		3895	targeting a specific compiler and compiler-version.
		3896
		3897	Another reason is that some compiler warnings require elaborate
		3898	workarounds, or other changes to the code that make it less clear and less
		3899	maintainable.
		3900
		3901	And of course, some compiler warnings are just plain stupid, or simply
		3902	wrong (because they don't actually warn about the condition their message
		3903	seems to warn about). For example, certain older gcc versions had some
		3904	warnings that resulted an extreme number of false positives. These have
		3905	been fixed, but some people still insist on making code warn-free with
		3906	such buggy versions.
		3907
		3908	While libev is written to generate as few warnings as possible,
		3909	"warn-free" code is not a goal, and it is recommended not to build libev
		3910	with any compiler warnings enabled unless you are prepared to cope with
		3911	them (e.g. by ignoring them). Remember that warnings are just that:
		3912	warnings, not errors, or proof of bugs.
		3913
		3914
		3915	=head2 VALGRIND
		3916
		3917	Valgrind has a special section here because it is a popular tool that is
		3918	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3919
		3920	If you think you found a bug (memory leak, uninitialised data access etc.)
		3921	in libev, then check twice: If valgrind reports something like:
		3922
		3923	==2274== definitely lost: 0 bytes in 0 blocks.
		3924	==2274== possibly lost: 0 bytes in 0 blocks.
		3925	==2274== still reachable: 256 bytes in 1 blocks.
		3926
		3927	Then there is no memory leak, just as memory accounted to global variables
		3928	is not a memleak - the memory is still being referenced, and didn't leak.
		3929
		3930	Similarly, under some circumstances, valgrind might report kernel bugs
		3931	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3932	although an acceptable workaround has been found here), or it might be
		3933	confused.
		3934
		3935	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3936	make it into some kind of religion.
		3937
		3938	If you are unsure about something, feel free to contact the mailing list
		3939	with the full valgrind report and an explanation on why you think this
		3940	is a bug in libev (best check the archives, too :). However, don't be
		3941	annoyed when you get a brisk "this is no bug" answer and take the chance
		3942	of learning how to interpret valgrind properly.
		3943
		3944	If you need, for some reason, empty reports from valgrind for your project
		3945	I suggest using suppression lists.
		3946
		3947
		3948	=head1 PORTABILITY NOTES
		3949
		3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2793		3951
2794	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2795	requires, and its I/O model is fundamentally incompatible with the POSIX	3953	requires, and its I/O model is fundamentally incompatible with the POSIX
2796	model. Libev still offers limited functionality on this platform in	3954	model. Libev still offers limited functionality on this platform in
2797	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2798	descriptors. This only applies when using Win32 natively, not when using	3956	descriptors. This only applies when using Win32 natively, not when using
2799	e.g. cygwin.	3957	e.g. cygwin.
2800		3958
		3959	Lifting these limitations would basically require the full
		3960	re-implementation of the I/O system. If you are into these kinds of
		3961	things, then note that glib does exactly that for you in a very portable
		3962	way (note also that glib is the slowest event library known to man).
		3963
2801	There is no supported compilation method available on windows except	3964	There is no supported compilation method available on windows except
2802	embedding it into other applications.	3965	embedding it into other applications.
2803		3966
		3967	Sensible signal handling is officially unsupported by Microsoft - libev
		3968	tries its best, but under most conditions, signals will simply not work.
		3969
		3970	Not a libev limitation but worth mentioning: windows apparently doesn't
		3971	accept large writes: instead of resulting in a partial write, windows will
		3972	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3973	so make sure you only write small amounts into your sockets (less than a
		3974	megabyte seems safe, but this apparently depends on the amount of memory
		3975	available).
		3976
2804	Due to the many, low, and arbitrary limits on the win32 platform and the	3977	Due to the many, low, and arbitrary limits on the win32 platform and
2805	abysmal performance of winsockets, using a large number of sockets is not	3978	the abysmal performance of winsockets, using a large number of sockets
2806	recommended (and not reasonable). If your program needs to use more than	3979	is not recommended (and not reasonable). If your program needs to use
2807	a hundred or so sockets, then likely it needs to use a totally different	3980	more than a hundred or so sockets, then likely it needs to use a totally
2808	implementation for windows, as libev offers the POSIX model, which cannot	3981	different implementation for windows, as libev offers the POSIX readiness
2809	be implemented efficiently on windows (microsoft monopoly games).	3982	notification model, which cannot be implemented efficiently on windows
		3983	(due to Microsoft monopoly games).
		3984
		3985	A typical way to use libev under windows is to embed it (see the embedding
		3986	section for details) and use the following F<evwrap.h> header file instead
		3987	of F<ev.h>:
		3988
		3989	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3990	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3991
		3992	#include "ev.h"
		3993
		3994	And compile the following F<evwrap.c> file into your project (make sure
		3995	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3996
		3997	#include "evwrap.h"
		3998	#include "ev.c"
2810		3999
2811	=over 4	4000	=over 4
2812		4001
2813	=item The winsocket select function	4002	=item The winsocket select function
2814		4003
2815	The winsocket C<select> function doesn't follow POSIX in that it requires	4004	The winsocket C<select> function doesn't follow POSIX in that it
2816	socket I<handles> and not socket I<file descriptors>. This makes select	4005	requires socket I<handles> and not socket I<file descriptors> (it is
2817	very inefficient, and also requires a mapping from file descriptors	4006	also extremely buggy). This makes select very inefficient, and also
2818	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4007	requires a mapping from file descriptors to socket handles (the Microsoft
2819	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4008	C runtime provides the function C<_open_osfhandle> for this). See the
2820	symbols for more info.	4009	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4010	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2821		4011
2822	The configuration for a "naked" win32 using the microsoft runtime	4012	The configuration for a "naked" win32 using the Microsoft runtime
2823	libraries and raw winsocket select is:	4013	libraries and raw winsocket select is:
2824		4014
2825	#define EV_USE_SELECT 1	4015	#define EV_USE_SELECT 1
2826	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4016	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2827		4017
2828	Note that winsockets handling of fd sets is O(n), so you can easily get a	4018	Note that winsockets handling of fd sets is O(n), so you can easily get a
2829	complexity in the O(n²) range when using win32.	4019	complexity in the O(n²) range when using win32.
2830		4020
2831	=item Limited number of file descriptors	4021	=item Limited number of file descriptors
2832		4022
2833	Windows has numerous arbitrary (and low) limits on things. Early versions	4023	Windows has numerous arbitrary (and low) limits on things.
2834	of winsocket's select only supported waiting for a max. of C<64> handles	4024
		4025	Early versions of winsocket's select only supported waiting for a maximum
2835	(probably owning to the fact that all windows kernels can only wait for	4026	of C<64> handles (probably owning to the fact that all windows kernels
2836	C<64> things at the same time internally; microsoft recommends spawning a	4027	can only wait for C<64> things at the same time internally; Microsoft
2837	chain of threads and wait for 63 handles and the previous thread in each).	4028	recommends spawning a chain of threads and wait for 63 handles and the
		4029	previous thread in each. Sounds great!).
2838		4030
2839	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4031	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2840	to some high number (e.g. C<2048>) before compiling the winsocket select	4032	to some high number (e.g. C<2048>) before compiling the winsocket select
2841	call (which might be in libev or elsewhere, for example, perl does its own	4033	call (which might be in libev or elsewhere, for example, perl and many
2842	select emulation on windows).	4034	other interpreters do their own select emulation on windows).
2843		4035
2844	Another limit is the number of file descriptors in the microsoft runtime	4036	Another limit is the number of file descriptors in the Microsoft runtime
2845	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4037	libraries, which by default is C<64> (there must be a hidden I<64>
2846	or something like this inside microsoft). You can increase this by calling	4038	fetish or something like this inside Microsoft). You can increase this
2847	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4039	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
2848	arbitrary limit), but is broken in many versions of the microsoft runtime	4040	(another arbitrary limit), but is broken in many versions of the Microsoft
2849	libraries.
2850
2851	This might get you to about C<512> or C<2048> sockets (depending on	4041	runtime libraries. This might get you to about C<512> or C<2048> sockets
2852	windows version and/or the phase of the moon). To get more, you need to	4042	(depending on windows version and/or the phase of the moon). To get more,
2853	wrap all I/O functions and provide your own fd management, but the cost of	4043	you need to wrap all I/O functions and provide your own fd management, but
2854	calling select (O(n²)) will likely make this unworkable.	4044	the cost of calling select (O(n²)) will likely make this unworkable.
2855		4045
2856	=back	4046	=back
2857		4047
		4048	=head2 PORTABILITY REQUIREMENTS
		4049
		4050	In addition to a working ISO-C implementation and of course the
		4051	backend-specific APIs, libev relies on a few additional extensions:
		4052
		4053	=over 4
		4054
		4055	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4056	calling conventions regardless of C<ev_watcher_type *>.
		4057
		4058	Libev assumes not only that all watcher pointers have the same internal
		4059	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4060	assumes that the same (machine) code can be used to call any watcher
		4061	callback: The watcher callbacks have different type signatures, but libev
		4062	calls them using an C<ev_watcher *> internally.
		4063
		4064	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4065
		4066	The type C<sig_atomic_t volatile> (or whatever is defined as
		4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4068	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4069	believed to be sufficiently portable.
		4070
		4071	=item C<sigprocmask> must work in a threaded environment
		4072
		4073	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4074	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4075	pthread implementations will either allow C<sigprocmask> in the "main
		4076	thread" or will block signals process-wide, both behaviours would
		4077	be compatible with libev. Interaction between C<sigprocmask> and
		4078	C<pthread_sigmask> could complicate things, however.
		4079
		4080	The most portable way to handle signals is to block signals in all threads
		4081	except the initial one, and run the default loop in the initial thread as
		4082	well.
		4083
		4084	=item C<long> must be large enough for common memory allocation sizes
		4085
		4086	To improve portability and simplify its API, libev uses C<long> internally
		4087	instead of C<size_t> when allocating its data structures. On non-POSIX
		4088	systems (Microsoft...) this might be unexpectedly low, but is still at
		4089	least 31 bits everywhere, which is enough for hundreds of millions of
		4090	watchers.
		4091
		4092	=item C<double> must hold a time value in seconds with enough accuracy
		4093
		4094	The type C<double> is used to represent timestamps. It is required to
		4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4096	enough for at least into the year 4000. This requirement is fulfilled by
		4097	implementations implementing IEEE 754, which is basically all existing
		4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4099	2200.
		4100
		4101	=back
		4102
		4103	If you know of other additional requirements drop me a note.
		4104
		4105
		4106	=head1 ALGORITHMIC COMPLEXITIES
		4107
		4108	In this section the complexities of (many of) the algorithms used inside
		4109	libev will be documented. For complexity discussions about backends see
		4110	the documentation for C<ev_default_init>.
		4111
		4112	All of the following are about amortised time: If an array needs to be
		4113	extended, libev needs to realloc and move the whole array, but this
		4114	happens asymptotically rarer with higher number of elements, so O(1) might
		4115	mean that libev does a lengthy realloc operation in rare cases, but on
		4116	average it is much faster and asymptotically approaches constant time.
		4117
		4118	=over 4
		4119
		4120	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4121
		4122	This means that, when you have a watcher that triggers in one hour and
		4123	there are 100 watchers that would trigger before that, then inserting will
		4124	have to skip roughly seven (C<ld 100>) of these watchers.
		4125
		4126	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4127
		4128	That means that changing a timer costs less than removing/adding them,
		4129	as only the relative motion in the event queue has to be paid for.
		4130
		4131	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4132
		4133	These just add the watcher into an array or at the head of a list.
		4134
		4135	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4136
		4137	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4138
		4139	These watchers are stored in lists, so they need to be walked to find the
		4140	correct watcher to remove. The lists are usually short (you don't usually
		4141	have many watchers waiting for the same fd or signal: one is typical, two
		4142	is rare).
		4143
		4144	=item Finding the next timer in each loop iteration: O(1)
		4145
		4146	By virtue of using a binary or 4-heap, the next timer is always found at a
		4147	fixed position in the storage array.
		4148
		4149	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4150
		4151	A change means an I/O watcher gets started or stopped, which requires
		4152	libev to recalculate its status (and possibly tell the kernel, depending
		4153	on backend and whether C<ev_io_set> was used).
		4154
		4155	=item Activating one watcher (putting it into the pending state): O(1)
		4156
		4157	=item Priority handling: O(number_of_priorities)
		4158
		4159	Priorities are implemented by allocating some space for each
		4160	priority. When doing priority-based operations, libev usually has to
		4161	linearly search all the priorities, but starting/stopping and activating
		4162	watchers becomes O(1) with respect to priority handling.
		4163
		4164	=item Sending an ev_async: O(1)
		4165
		4166	=item Processing ev_async_send: O(number_of_async_watchers)
		4167
		4168	=item Processing signals: O(max_signal_number)
		4169
		4170	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4171	calls in the current loop iteration. Checking for async and signal events
		4172	involves iterating over all running async watchers or all signal numbers.
		4173
		4174	=back
		4175
		4176
		4177	=head1 GLOSSARY
		4178
		4179	=over 4
		4180
		4181	=item active
		4182
		4183	A watcher is active as long as it has been started (has been attached to
		4184	an event loop) but not yet stopped (disassociated from the event loop).
		4185
		4186	=item application
		4187
		4188	In this document, an application is whatever is using libev.
		4189
		4190	=item callback
		4191
		4192	The address of a function that is called when some event has been
		4193	detected. Callbacks are being passed the event loop, the watcher that
		4194	received the event, and the actual event bitset.
		4195
		4196	=item callback invocation
		4197
		4198	The act of calling the callback associated with a watcher.
		4199
		4200	=item event
		4201
		4202	A change of state of some external event, such as data now being available
		4203	for reading on a file descriptor, time having passed or simply not having
		4204	any other events happening anymore.
		4205
		4206	In libev, events are represented as single bits (such as C<EV_READ> or
		4207	C<EV_TIMEOUT>).
		4208
		4209	=item event library
		4210
		4211	A software package implementing an event model and loop.
		4212
		4213	=item event loop
		4214
		4215	An entity that handles and processes external events and converts them
		4216	into callback invocations.
		4217
		4218	=item event model
		4219
		4220	The model used to describe how an event loop handles and processes
		4221	watchers and events.
		4222
		4223	=item pending
		4224
		4225	A watcher is pending as soon as the corresponding event has been detected,
		4226	and stops being pending as soon as the watcher will be invoked or its
		4227	pending status is explicitly cleared by the application.
		4228
		4229	A watcher can be pending, but not active. Stopping a watcher also clears
		4230	its pending status.
		4231
		4232	=item real time
		4233
		4234	The physical time that is observed. It is apparently strictly monotonic :)
		4235
		4236	=item wall-clock time
		4237
		4238	The time and date as shown on clocks. Unlike real time, it can actually
		4239	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4240	clock.
		4241
		4242	=item watcher
		4243
		4244	A data structure that describes interest in certain events. Watchers need
		4245	to be started (attached to an event loop) before they can receive events.
		4246
		4247	=item watcher invocation
		4248
		4249	The act of calling the callback associated with a watcher.
		4250
		4251	=back
2858		4252
2859	=head1 AUTHOR	4253	=head1 AUTHOR
2860		4254
2861	Marc Lehmann <libev@schmorp.de>.	4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2862		4256

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