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Revision 1.257 by root, Wed Jul 15 16:08:24 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
265	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
266	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
267	for C<SIGCHLD>. If this is a problem for your app you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	324	C<ev_default_init>.
271		325
272	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
…		…
281	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
282	thing, believe me).	336	thing, believe me).
283		337
284	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
285		339
286	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
287	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
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	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
290	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
291	around bugs.	345	around bugs.
…		…
297	enabling this flag.	351	enabling this flag.
298		352
299	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,
300	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
301	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
302	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
303	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
304	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
305		359
306	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
307	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
308	flag.	362	flag.
309		363
310	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>
311	environment variable.	365	environment variable.
312		366
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		368
315	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
…		…
317	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
318	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
319	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.
320		374
321	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
322	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
323	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
324	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
325	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
326	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).
327		385
328	=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)
329		387
330	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
331	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
332	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
333	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,
334	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
335	performance tips.	393	performance tips.
336		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
337	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
338		399
339	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,
340	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
341	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),
342	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).
343	of shortcomings, such as silently dropping events in some hard-to-detect	404
344	cases and rewiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
345	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.
346		421
347	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
348	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
349	(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
350	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
351	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
352		427	file descriptors.
353	Please note that epoll sometimes generates spurious notifications, so you
354	need to use non-blocking I/O or other means to avoid blocking when no data
355	(or space) is available.
356		428
357	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
358	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,
359	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.
360		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
361	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
362	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>.
363		446
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		448
366	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
367	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
368	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
369	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
370	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
371	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)
372	system like NetBSD.	457	system like NetBSD.
373		458
374	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
375	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
376	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
377		462
378	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
379	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
380	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
381	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
382	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
383	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
384		470
385	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
386		472
387	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
388	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
389	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
390	(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
391	(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
392	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>.
393		483
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		485
396	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
397	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		492
403	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,
404	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)).
405		495
406	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
407	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
408	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
409		499
410	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
411	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
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	503	might perform better.
414		504
415	On the positive side, ignoring the spurious readyness notifications, this	505	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
417	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
418		512
419	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
420		514
421	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
422	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
…		…
424		518
425	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
426		520
427	=back	521	=back
428		522
429	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
430	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
431	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		526
433	The most typical usage is like this:	527	Example: This is the most typical usage.
434		528
435	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		531
438	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
439	environment settings to be taken into account:	533	environment settings to be taken into account:
440		534
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		536
443	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
444	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
445	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):
446		541
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		543
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		545
451	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
452	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
453	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
454	undefined behaviour (or a failed assertion if assertions are enabled).	549	undefined behaviour (or a failed assertion if assertions are enabled).
455		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
456	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.
457		556
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	558	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
461		560
462	=item ev_default_destroy ()	561	=item ev_default_destroy ()
463		562
464	Destroys the default loop again (frees all memory and kernel state	563	Destroys the default loop again (frees all memory and kernel state
465	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
466	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
467	responsibility to either stop all watchers cleanly yoursef I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
468	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
469	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
470	for example).	569	for example).
471		570
472	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
473	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
474	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
475		574
476	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
477	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
478	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
479	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
504		603
505	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
506		605
507	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
508	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
509	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.
510		615
511	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
512		617
513	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
514	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
515	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
516		621
517	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
518	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
519	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.
520		637
521	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
522		639
523	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
524	use.	641	use.
…		…
529	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
530	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
531	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
532	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
533		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
534	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
535		690
536	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
537	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
538	events.	693	events.
…		…
540	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
541	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.
542		697
543	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
544	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
545	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
546	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
547	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.
548		704
549	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
550	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
551	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.
552		709
553	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
554	neccessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
555	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
556	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
557	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
558	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
559	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
560		721
561	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
562		723
563	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- 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.
566	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
567	- 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.
568	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	739	- Queue all expired timers.
578	- Queue all outstanding periodics.	740	- Queue all expired periodics.
579	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	742	- Queue all check watchers.
581	- 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).
582	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
583	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
584	- 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
…		…
589	anymore.	751	anymore.
590		752
591	... queue jobs here, make sure they register event watchers as long	753	... queue jobs here, make sure they register event watchers as long
592	... 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..)
593	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
594	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
595		757
596	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
597		759
598	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
599	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
600	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
601	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.
602		764
603	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.
604		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
605	=item ev_ref (loop)	769	=item ev_ref (loop)
606		770
607	=item ev_unref (loop)	771	=item ev_unref (loop)
608		772
609	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
610	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
611	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
612	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>
613	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
614	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
615	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
616	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
617	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
618	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
619	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
620	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
621		790
622	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>
623	running when nothing else is active.	792	running when nothing else is active.
624		793
625	struct ev_signal exitsig;	794	ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	797	evf_unref (loop);
629		798
630	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
631		800
632	ev_ref (loop);	801	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
634		803
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		805
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		807
639	These advanced functions influence the time that libev will spend waiting	808	These advanced functions influence the time that libev will spend waiting
640	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
641	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.
642		812
643	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>)
644	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
645	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
646		817
647	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
648	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
649	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
650	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
651	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.
652		823
653	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
654	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,
655	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
656	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
657	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.
658		831
659	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
660	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
662	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
663	any overhead in libev.	836	value will not introduce any overhead in libev.
664		837
665	Many (busy) programs can usually benefit by setting the io collect	838	Many (busy) programs can usually benefit by setting the I/O collect
666	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
667	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
668	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>,
669	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_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
		925
		926	=item ev_loop_verify (loop)
		927
		928	This function only does something when C<EV_VERIFY> support has been
		929	compiled in, which is the default for non-minimal builds. It tries to go
		930	through all internal structures and checks them for validity. If anything
		931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
		933
		934	This can be used to catch bugs inside libev itself: under normal
		935	circumstances, this function will never abort as of course libev keeps its
		936	data structures consistent.
670		937
671	=back	938	=back
672		939
673		940
674	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
		942
		943	In the following description, uppercase C<TYPE> in names stands for the
		944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		945	watchers and C<ev_io_start> for I/O watchers.
675		946
676	A watcher is a structure that you create and register to record your	947	A watcher is a structure that you create and register to record your
677	interest in some event. For instance, if you want to wait for STDIN to	948	interest in some event. For instance, if you want to wait for STDIN to
678	become readable, you would create an C<ev_io> watcher for that:	949	become readable, you would create an C<ev_io> watcher for that:
679		950
680	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
681	{	952	{
682	ev_io_stop (w);	953	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
684	}	955	}
685		956
686	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
687	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
688	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
691	ev_loop (loop, 0);	965	ev_loop (loop, 0);
692		966
693	As you can see, you are responsible for allocating the memory for your	967	As you can see, you are responsible for allocating the memory for your
694	watcher structures (and it is usually a bad idea to do this on the stack,	968	watcher structures (and it is I<usually> a bad idea to do this on the
695	although this can sometimes be quite valid).	969	stack).
		970
		971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
696		973
697	Each watcher structure must be initialised by a call to C<ev_init	974	Each watcher structure must be initialised by a call to C<ev_init
698	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
699	callback gets invoked each time the event occurs (or, in the case of io	976	callback gets invoked each time the event occurs (or, in the case of I/O
700	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
701	is readable and/or writable).	978	is readable and/or writable).
702		979
703	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
704	with arguments specific to this watcher type. There is also a macro	981	macro to configure it, with arguments specific to the watcher type. There
705	to combine initialisation and setting in one call: C<< ev_<type>_init	982	is also a macro to combine initialisation and setting in one call: C<<
706	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
707		984
708	To make the watcher actually watch out for events, you have to start it	985	To make the watcher actually watch out for events, you have to start it
709	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	986	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
710	*) >>), and you can stop watching for events at any time by calling the	987	*) >>), and you can stop watching for events at any time by calling the
711	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
712		989
713	As long as your watcher is active (has been started but not stopped) you	990	As long as your watcher is active (has been started but not stopped) you
714	must not touch the values stored in it. Most specifically you must never	991	must not touch the values stored in it. Most specifically you must never
715	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
716		993
717	Each and every callback receives the event loop pointer as first, the	994	Each and every callback receives the event loop pointer as first, the
718	registered watcher structure as second, and a bitset of received events as	995	registered watcher structure as second, and a bitset of received events as
719	third argument.	996	third argument.
720		997
…		…
778		1055
779	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
780		1057
781	The given async watcher has been asynchronously notified (see C<ev_async>).	1058	The given async watcher has been asynchronously notified (see C<ev_async>).
782		1059
		1060	=item C<EV_CUSTOM>
		1061
		1062	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1063	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1064
783	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
784		1066
785	An unspecified error has occured, the watcher has been stopped. This might	1067	An unspecified error has occurred, the watcher has been stopped. This might
786	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
787	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
788	problem. You best act on it by reporting the problem and somehow coping	1072	You best act on it by reporting the problem and somehow coping with the
789	with the watcher being stopped.	1073	watcher being stopped. Note that well-written programs should not receive
		1074	an error ever, so when your watcher receives it, this usually indicates a
		1075	bug in your program.
790		1076
791	Libev will usually signal a few "dummy" events together with an error,	1077	Libev will usually signal a few "dummy" events together with an error, for
792	for example it might indicate that a fd is readable or writable, and if	1078	example it might indicate that a fd is readable or writable, and if your
793	your callbacks is well-written it can just attempt the operation and cope	1079	callbacks is well-written it can just attempt the operation and cope with
794	with the error from read() or write(). This will not work in multithreaded	1080	the error from read() or write(). This will not work in multi-threaded
795	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
796		1083
797	=back	1084	=back
798		1085
799	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
800
801	In the following description, C<TYPE> stands for the watcher type,
802	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
803		1087
804	=over 4	1088	=over 4
805		1089
806	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
807		1091
…		…
813	which rolls both calls into one.	1097	which rolls both calls into one.
814		1098
815	You can reinitialise a watcher at any time as long as it has been stopped	1099	You can reinitialise a watcher at any time as long as it has been stopped
816	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
817		1101
818	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1102	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
819	int revents)>.	1103	int revents)>.
		1104
		1105	Example: Initialise an C<ev_io> watcher in two steps.
		1106
		1107	ev_io w;
		1108	ev_init (&w, my_cb);
		1109	ev_io_set (&w, STDIN_FILENO, EV_READ);
820		1110
821	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
822		1112
823	This macro initialises the type-specific parts of a watcher. You need to	1113	This macro initialises the type-specific parts of a watcher. You need to
824	call C<ev_init> at least once before you call this macro, but you can	1114	call C<ev_init> at least once before you call this macro, but you can
…		…
827	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
828		1118
829	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
830	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
831		1121
		1122	See C<ev_init>, above, for an example.
		1123
832	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
833		1125
834	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1126	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
835	calls into a single call. This is the most convinient method to initialise	1127	calls into a single call. This is the most convenient method to initialise
836	a watcher. The same limitations apply, of course.	1128	a watcher. The same limitations apply, of course.
		1129
		1130	Example: Initialise and set an C<ev_io> watcher in one step.
		1131
		1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
837		1133
838	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
839		1135
840	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
841	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
842		1138
		1139	Example: Start the C<ev_io> watcher that is being abused as example in this
		1140	whole section.
		1141
		1142	ev_io_start (EV_DEFAULT_UC, &w);
		1143
843	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
844		1145
845	Stops the given watcher again (if active) and clears the pending	1146	Stops the given watcher if active, and clears the pending status (whether
		1147	the watcher was active or not).
		1148
846	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
847	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
848	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
849	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
850	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
851		1154
852	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
853		1156
854	Returns a true value iff the watcher is active (i.e. it has been started	1157	Returns a true value iff the watcher is active (i.e. it has been started
855	and not yet been stopped). As long as a watcher is active you must not modify	1158	and not yet been stopped). As long as a watcher is active you must not modify
…		…
881	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
882	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
883	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
884	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
885		1188
886	This means that priorities are I<only> used for ordering callback
887	invocation after new events have been received. This is useful, for
888	example, to reduce latency after idling, or more often, to bind two
889	watchers on the same event and make sure one is called first.
890
891	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
892	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
893		1191
894	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
895	pending.	1193	pending.
896		1194
		1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1196	fine, as long as you do not mind that the priority value you query might
		1197	or might not have been clamped to the valid range.
		1198
897	The default priority used by watchers when no priority has been set is	1199	The default priority used by watchers when no priority has been set is
898	always C<0>, which is supposed to not be too high and not be too low :).	1200	always C<0>, which is supposed to not be too high and not be too low :).
899		1201
900	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
901	fine, as long as you do not mind that the priority value you query might	1203	priorities.
902	or might not have been adjusted to be within valid range.
903		1204
904	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
905		1206
906	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
907	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
908	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
909		1211
910	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
911		1213
912	If the watcher is pending, this function returns clears its pending status	1214	If the watcher is pending, this function clears its pending status and
913	and returns its C<revents> bitset (as if its callback was invoked). If the	1215	returns its C<revents> bitset (as if its callback was invoked). If the
914	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
915		1217
		1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1219	callback to be invoked, which can be accomplished with this function.
		1220
916	=back	1221	=back
917		1222
918		1223
919	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
920		1225
921	Each watcher has, by default, a member C<void *data> that you can change	1226	Each watcher has, by default, a member C<void *data> that you can change
922	and read at any time, libev will completely ignore it. This can be used	1227	and read at any time: libev will completely ignore it. This can be used
923	to associate arbitrary data with your watcher. If you need more data and	1228	to associate arbitrary data with your watcher. If you need more data and
924	don't want to allocate memory and store a pointer to it in that data	1229	don't want to allocate memory and store a pointer to it in that data
925	member, you can also "subclass" the watcher type and provide your own	1230	member, you can also "subclass" the watcher type and provide your own
926	data:	1231	data:
927		1232
928	struct my_io	1233	struct my_io
929	{	1234	{
930	struct ev_io io;	1235	ev_io io;
931	int otherfd;	1236	int otherfd;
932	void *somedata;	1237	void *somedata;
933	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
934	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
935		1244
936	And since your callback will be called with a pointer to the watcher, you	1245	And since your callback will be called with a pointer to the watcher, you
937	can cast it back to your own type:	1246	can cast it back to your own type:
938		1247
939	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
940	{	1249	{
941	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
942	...	1251	...
943	}	1252	}
944		1253
945	More interesting and less C-conformant ways of casting your callback type	1254	More interesting and less C-conformant ways of casting your callback type
946	instead have been omitted.	1255	instead have been omitted.
947		1256
948	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
949	watchers:	1258	embedded watchers:
950		1259
951	struct my_biggy	1260	struct my_biggy
952	{	1261	{
953	int some_data;	1262	int some_data;
954	ev_timer t1;	1263	ev_timer t1;
955	ev_timer t2;	1264	ev_timer t2;
956	}	1265	}
957		1266
958	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1267	In this case getting the pointer to C<my_biggy> is a bit more
959	you need to use C<offsetof>:	1268	complicated: Either you store the address of your C<my_biggy> struct
		1269	in the C<data> member of the watcher (for woozies), or you need to use
		1270	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1271	programmers):
960		1272
961	#include <stddef.h>	1273	#include <stddef.h>
962		1274
963	static void	1275	static void
964	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
965	{	1277	{
966	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
967	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
968	}	1280	}
969		1281
970	static void	1282	static void
971	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
972	{	1284	{
973	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
974	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
975	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
976		1391
977		1392
978	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
979		1394
980	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1004	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1005	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1006	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1007	required if you know what you are doing).	1422	required if you know what you are doing).
1008		1423
1009	If you must do this, then force the use of a known-to-be-good backend	1424	If you cannot use non-blocking mode, then force the use of a
1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1425	known-to-be-good backend (at the time of this writing, this includes only
1011	C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1012		1429
1013	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1014	receive "spurious" readyness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1015	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1016	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1017	lot of those (for example solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1018	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1019	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1021		1438
1022	If you cannot run the fd in non-blocking mode (for example you should not	1439	If you cannot run the fd in non-blocking mode (for example you should
1023	play around with an Xlib connection), then you have to seperately re-test	1440	not play around with an Xlib connection), then you have to separately
1024	whether a file descriptor is really ready with a known-to-be good interface	1441	re-test whether a file descriptor is really ready with a known-to-be good
1025	such as poll (fortunately in our Xlib example, Xlib already does this on	1442	interface such as poll (fortunately in our Xlib example, Xlib already
1026	its own, so its quite safe to use).	1443	does this on its own, so its quite safe to use). Some people additionally
		1444	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1445	indefinitely.
		1446
		1447	But really, best use non-blocking mode.
1027		1448
1028	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1029		1450
1030	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1451	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1031	descriptor (either by calling C<close> explicitly or by any other means,	1452	descriptor (either due to calling C<close> explicitly or any other means,
1032	such as C<dup>). The reason is that you register interest in some file	1453	such as C<dup2>). The reason is that you register interest in some file
1033	descriptor, but when it goes away, the operating system will silently drop	1454	descriptor, but when it goes away, the operating system will silently drop
1034	this interest. If another file descriptor with the same number then is	1455	this interest. If another file descriptor with the same number then is
1035	registered with libev, there is no efficient way to see that this is, in	1456	registered with libev, there is no efficient way to see that this is, in
1036	fact, a different file descriptor.	1457	fact, a different file descriptor.
1037		1458
…		…
1066	To support fork in your programs, you either have to call	1487	To support fork in your programs, you either have to call
1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1488	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1070		1491
		1492	=head3 The special problem of SIGPIPE
		1493
		1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1495	when writing to a pipe whose other end has been closed, your program gets
		1496	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1497	this is sensible behaviour, for daemons, this is usually undesirable.
		1498
		1499	So when you encounter spurious, unexplained daemon exits, make sure you
		1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1501	somewhere, as that would have given you a big clue).
		1502
1071		1503
1072	=head3 Watcher-Specific Functions	1504	=head3 Watcher-Specific Functions
1073		1505
1074	=over 4	1506	=over 4
1075		1507
1076	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1077		1509
1078	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1079		1511
1080	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1512	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1081	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1513	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1082	C<EV_READ | EV_WRITE> to receive the given events.	1514	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1083		1515
1084	=item int fd [read-only]	1516	=item int fd [read-only]
1085		1517
1086	The file descriptor being watched.	1518	The file descriptor being watched.
1087		1519
…		…
1095		1527
1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1528	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1097	readable, but only once. Since it is likely line-buffered, you could	1529	readable, but only once. Since it is likely line-buffered, you could
1098	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1099		1531
1100	static void	1532	static void
1101	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1533	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1102	{	1534	{
1103	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1104	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1536	.. read from stdin here (or from w->fd) and handle any I/O errors
1105	}	1537	}
1106		1538
1107	...	1539	...
1108	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1109	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1110	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1111	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1112	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1113		1545
1114		1546
1115	=head2 C<ev_timer> - relative and optionally repeating timeouts	1547	=head2 C<ev_timer> - relative and optionally repeating timeouts
1116		1548
1117	Timer watchers are simple relative timers that generate an event after a	1549	Timer watchers are simple relative timers that generate an event after a
1118	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1119		1551
1120	The timers are based on real time, that is, if you register an event that	1552	The timers are based on real time, that is, if you register an event that
1121	times out after an hour and you reset your system clock to last years	1553	times out after an hour and you reset your system clock to January last
1122	time, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1123	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1124	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
		1557
		1558	The callback is guaranteed to be invoked only I<after> its timeout has
		1559	passed (not I<at>, so on systems with very low-resolution clocks this
		1560	might introduce a small delay). If multiple timers become ready during the
		1561	same loop iteration then the ones with earlier time-out values are invoked
		1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
		1564
		1565	=head3 Be smart about timeouts
		1566
		1567	Many real-world problems involve some kind of timeout, usually for error
		1568	recovery. A typical example is an HTTP request - if the other side hangs,
		1569	you want to raise some error after a while.
		1570
		1571	What follows are some ways to handle this problem, from obvious and
		1572	inefficient to smart and efficient.
		1573
		1574	In the following, a 60 second activity timeout is assumed - a timeout that
		1575	gets reset to 60 seconds each time there is activity (e.g. each time some
		1576	data or other life sign was received).
		1577
		1578	=over 4
		1579
		1580	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1581
		1582	This is the most obvious, but not the most simple way: In the beginning,
		1583	start the watcher:
		1584
		1585	ev_timer_init (timer, callback, 60., 0.);
		1586	ev_timer_start (loop, timer);
		1587
		1588	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1589	and start it again:
		1590
		1591	ev_timer_stop (loop, timer);
		1592	ev_timer_set (timer, 60., 0.);
		1593	ev_timer_start (loop, timer);
		1594
		1595	This is relatively simple to implement, but means that each time there is
		1596	some activity, libev will first have to remove the timer from its internal
		1597	data structure and then add it again. Libev tries to be fast, but it's
		1598	still not a constant-time operation.
		1599
		1600	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1601
		1602	This is the easiest way, and involves using C<ev_timer_again> instead of
		1603	C<ev_timer_start>.
		1604
		1605	To implement this, configure an C<ev_timer> with a C<repeat> value
		1606	of C<60> and then call C<ev_timer_again> at start and each time you
		1607	successfully read or write some data. If you go into an idle state where
		1608	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1609	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1610
		1611	That means you can ignore both the C<ev_timer_start> function and the
		1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1613	member and C<ev_timer_again>.
		1614
		1615	At start:
		1616
		1617	ev_init (timer, callback);
		1618	timer->repeat = 60.;
		1619	ev_timer_again (loop, timer);
		1620
		1621	Each time there is some activity:
		1622
		1623	ev_timer_again (loop, timer);
		1624
		1625	It is even possible to change the time-out on the fly, regardless of
		1626	whether the watcher is active or not:
		1627
		1628	timer->repeat = 30.;
		1629	ev_timer_again (loop, timer);
		1630
		1631	This is slightly more efficient then stopping/starting the timer each time
		1632	you want to modify its timeout value, as libev does not have to completely
		1633	remove and re-insert the timer from/into its internal data structure.
		1634
		1635	It is, however, even simpler than the "obvious" way to do it.
		1636
		1637	=item 3. Let the timer time out, but then re-arm it as required.
		1638
		1639	This method is more tricky, but usually most efficient: Most timeouts are
		1640	relatively long compared to the intervals between other activity - in
		1641	our example, within 60 seconds, there are usually many I/O events with
		1642	associated activity resets.
		1643
		1644	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1645	but remember the time of last activity, and check for a real timeout only
		1646	within the callback:
		1647
		1648	ev_tstamp last_activity; // time of last activity
		1649
		1650	static void
		1651	callback (EV_P_ ev_timer *w, int revents)
		1652	{
		1653	ev_tstamp now = ev_now (EV_A);
		1654	ev_tstamp timeout = last_activity + 60.;
		1655
		1656	// if last_activity + 60. is older than now, we did time out
		1657	if (timeout < now)
		1658	{
		1659	// timeout occured, take action
		1660	}
		1661	else
		1662	{
		1663	// callback was invoked, but there was some activity, re-arm
		1664	// the watcher to fire in last_activity + 60, which is
		1665	// guaranteed to be in the future, so "again" is positive:
		1666	w->repeat = timeout - now;
		1667	ev_timer_again (EV_A_ w);
		1668	}
		1669	}
		1670
		1671	To summarise the callback: first calculate the real timeout (defined
		1672	as "60 seconds after the last activity"), then check if that time has
		1673	been reached, which means something I<did>, in fact, time out. Otherwise
		1674	the callback was invoked too early (C<timeout> is in the future), so
		1675	re-schedule the timer to fire at that future time, to see if maybe we have
		1676	a timeout then.
		1677
		1678	Note how C<ev_timer_again> is used, taking advantage of the
		1679	C<ev_timer_again> optimisation when the timer is already running.
		1680
		1681	This scheme causes more callback invocations (about one every 60 seconds
		1682	minus half the average time between activity), but virtually no calls to
		1683	libev to change the timeout.
		1684
		1685	To start the timer, simply initialise the watcher and set C<last_activity>
		1686	to the current time (meaning we just have some activity :), then call the
		1687	callback, which will "do the right thing" and start the timer:
		1688
		1689	ev_init (timer, callback);
		1690	last_activity = ev_now (loop);
		1691	callback (loop, timer, EV_TIMEOUT);
		1692
		1693	And when there is some activity, simply store the current time in
		1694	C<last_activity>, no libev calls at all:
		1695
		1696	last_actiivty = ev_now (loop);
		1697
		1698	This technique is slightly more complex, but in most cases where the
		1699	time-out is unlikely to be triggered, much more efficient.
		1700
		1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1702	callback :) - just change the timeout and invoke the callback, which will
		1703	fix things for you.
		1704
		1705	=item 4. Wee, just use a double-linked list for your timeouts.
		1706
		1707	If there is not one request, but many thousands (millions...), all
		1708	employing some kind of timeout with the same timeout value, then one can
		1709	do even better:
		1710
		1711	When starting the timeout, calculate the timeout value and put the timeout
		1712	at the I<end> of the list.
		1713
		1714	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1715	the list is expected to fire (for example, using the technique #3).
		1716
		1717	When there is some activity, remove the timer from the list, recalculate
		1718	the timeout, append it to the end of the list again, and make sure to
		1719	update the C<ev_timer> if it was taken from the beginning of the list.
		1720
		1721	This way, one can manage an unlimited number of timeouts in O(1) time for
		1722	starting, stopping and updating the timers, at the expense of a major
		1723	complication, and having to use a constant timeout. The constant timeout
		1724	ensures that the list stays sorted.
		1725
		1726	=back
		1727
		1728	So which method the best?
		1729
		1730	Method #2 is a simple no-brain-required solution that is adequate in most
		1731	situations. Method #3 requires a bit more thinking, but handles many cases
		1732	better, and isn't very complicated either. In most case, choosing either
		1733	one is fine, with #3 being better in typical situations.
		1734
		1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1736	rather complicated, but extremely efficient, something that really pays
		1737	off after the first million or so of active timers, i.e. it's usually
		1738	overkill :)
		1739
		1740	=head3 The special problem of time updates
		1741
		1742	Establishing the current time is a costly operation (it usually takes at
		1743	least two system calls): EV therefore updates its idea of the current
		1744	time only before and after C<ev_loop> collects new events, which causes a
		1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1746	lots of events in one iteration.
1125		1747
1126	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1127	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1128	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1129	you suspect event processing to be delayed and you I<need> to base the timeout	1751	you suspect event processing to be delayed and you I<need> to base the
1130	on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1131		1753
1132	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1133		1755
1134	The callback is guarenteed to be invoked only when its timeout has passed,	1756	If the event loop is suspended for a long time, you can also force an
1135	but if multiple timers become ready during the same loop iteration then	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1136	order of execution is undefined.	1758	()>.
		1759
		1760	=head3 The special problems of suspended animation
		1761
		1762	When you leave the server world it is quite customary to hit machines that
		1763	can suspend/hibernate - what happens to the clocks during such a suspend?
		1764
		1765	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1766	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1767	to run until the system is suspended, but they will not advance while the
		1768	system is suspended. That means, on resume, it will be as if the program
		1769	was frozen for a few seconds, but the suspend time will not be counted
		1770	towards C<ev_timer> when a monotonic clock source is used. The real time
		1771	clock advanced as expected, but if it is used as sole clocksource, then a
		1772	long suspend would be detected as a time jump by libev, and timers would
		1773	be adjusted accordingly.
		1774
		1775	I would not be surprised to see different behaviour in different between
		1776	operating systems, OS versions or even different hardware.
		1777
		1778	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1779	time jump in the monotonic clocks and the realtime clock. If the program
		1780	is suspended for a very long time, and monotonic clock sources are in use,
		1781	then you can expect C<ev_timer>s to expire as the full suspension time
		1782	will be counted towards the timers. When no monotonic clock source is in
		1783	use, then libev will again assume a timejump and adjust accordingly.
		1784
		1785	It might be beneficial for this latter case to call C<ev_suspend>
		1786	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1787	deterministic behaviour in this case (you can do nothing against
		1788	C<SIGSTOP>).
1137		1789
1138	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1139		1791
1140	=over 4	1792	=over 4
1141		1793
1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1794	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1143		1795
1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1796	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1145		1797
1146	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1798	Configure the timer to trigger after C<after> seconds. If C<repeat>
1147	C<0.>, then it will automatically be stopped. If it is positive, then the	1799	is C<0.>, then it will automatically be stopped once the timeout is
1148	timer will automatically be configured to trigger again C<repeat> seconds	1800	reached. If it is positive, then the timer will automatically be
1149	later, again, and again, until stopped manually.	1801	configured to trigger again C<repeat> seconds later, again, and again,
		1802	until stopped manually.
1150		1803
1151	The timer itself will do a best-effort at avoiding drift, that is, if you	1804	The timer itself will do a best-effort at avoiding drift, that is, if
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1805	you configure a timer to trigger every 10 seconds, then it will normally
1153	exactly 10 second intervals. If, however, your program cannot keep up with	1806	trigger at exactly 10 second intervals. If, however, your program cannot
1154	the timer (because it takes longer than those 10 seconds to do stuff) the	1807	keep up with the timer (because it takes longer than those 10 seconds to
1155	timer will not fire more than once per event loop iteration.	1808	do stuff) the timer will not fire more than once per event loop iteration.
1156		1809
1157	=item ev_timer_again (loop)	1810	=item ev_timer_again (loop, ev_timer *)
1158		1811
1159	This will act as if the timer timed out and restart it again if it is	1812	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1813	repeating. The exact semantics are:
1161		1814
1162	If the timer is pending, its pending status is cleared.	1815	If the timer is pending, its pending status is cleared.
1163		1816
1164	If the timer is started but nonrepeating, stop it (as if it timed out).	1817	If the timer is started but non-repeating, stop it (as if it timed out).
1165		1818
1166	If the timer is repeating, either start it if necessary (with the	1819	If the timer is repeating, either start it if necessary (with the
1167	C<repeat> value), or reset the running timer to the C<repeat> value.	1820	C<repeat> value), or reset the running timer to the C<repeat> value.
1168		1821
1169	This sounds a bit complicated, but here is a useful and typical	1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1170	example: Imagine you have a tcp connection and you want a so-called idle	1823	usage example.
1171	timeout, that is, you want to be called when there have been, say, 60
1172	seconds of inactivity on the socket. The easiest way to do this is to
1173	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1174	C<ev_timer_again> each time you successfully read or write some data. If
1175	you go into an idle state where you do not expect data to travel on the
1176	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1177	automatically restart it if need be.
1178
1179	That means you can ignore the C<after> value and C<ev_timer_start>
1180	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1181
1182	ev_timer_init (timer, callback, 0., 5.);
1183	ev_timer_again (loop, timer);
1184	...
1185	timer->again = 17.;
1186	ev_timer_again (loop, timer);
1187	...
1188	timer->again = 10.;
1189	ev_timer_again (loop, timer);
1190
1191	This is more slightly efficient then stopping/starting the timer each time
1192	you want to modify its timeout value.
1193		1824
1194	=item ev_tstamp repeat [read-write]	1825	=item ev_tstamp repeat [read-write]
1195		1826
1196	The current C<repeat> value. Will be used each time the watcher times out	1827	The current C<repeat> value. Will be used each time the watcher times out
1197	or C<ev_timer_again> is called and determines the next timeout (if any),	1828	or C<ev_timer_again> is called, and determines the next timeout (if any),
1198	which is also when any modifications are taken into account.	1829	which is also when any modifications are taken into account.
1199		1830
1200	=back	1831	=back
1201		1832
1202	=head3 Examples	1833	=head3 Examples
1203		1834
1204	Example: Create a timer that fires after 60 seconds.	1835	Example: Create a timer that fires after 60 seconds.
1205		1836
1206	static void	1837	static void
1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1838	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1208	{	1839	{
1209	.. one minute over, w is actually stopped right here	1840	.. one minute over, w is actually stopped right here
1210	}	1841	}
1211		1842
1212	struct ev_timer mytimer;	1843	ev_timer mytimer;
1213	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1844	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1214	ev_timer_start (loop, &mytimer);	1845	ev_timer_start (loop, &mytimer);
1215		1846
1216	Example: Create a timeout timer that times out after 10 seconds of	1847	Example: Create a timeout timer that times out after 10 seconds of
1217	inactivity.	1848	inactivity.
1218		1849
1219	static void	1850	static void
1220	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1851	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1221	{	1852	{
1222	.. ten seconds without any activity	1853	.. ten seconds without any activity
1223	}	1854	}
1224		1855
1225	struct ev_timer mytimer;	1856	ev_timer mytimer;
1226	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1227	ev_timer_again (&mytimer); /* start timer */	1858	ev_timer_again (&mytimer); /* start timer */
1228	ev_loop (loop, 0);	1859	ev_loop (loop, 0);
1229		1860
1230	// and in some piece of code that gets executed on any "activity":	1861	// and in some piece of code that gets executed on any "activity":
1231	// reset the timeout to start ticking again at 10 seconds	1862	// reset the timeout to start ticking again at 10 seconds
1232	ev_timer_again (&mytimer);	1863	ev_timer_again (&mytimer);
1233		1864
1234		1865
1235	=head2 C<ev_periodic> - to cron or not to cron?	1866	=head2 C<ev_periodic> - to cron or not to cron?
1236		1867
1237	Periodic watchers are also timers of a kind, but they are very versatile	1868	Periodic watchers are also timers of a kind, but they are very versatile
1238	(and unfortunately a bit complex).	1869	(and unfortunately a bit complex).
1239		1870
1240	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1871	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1241	but on wallclock time (absolute time). You can tell a periodic watcher	1872	relative time, the physical time that passes) but on wall clock time
1242	to trigger "at" some specific point in time. For example, if you tell a	1873	(absolute time, the thing you can read on your calender or clock). The
1243	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1874	difference is that wall clock time can run faster or slower than real
1244	+ 10.>) and then reset your system clock to the last year, then it will	1875	time, and time jumps are not uncommon (e.g. when you adjust your
1245	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1876	wrist-watch).
1246	roughly 10 seconds later).
1247		1877
1248	They can also be used to implement vastly more complex timers, such as	1878	You can tell a periodic watcher to trigger after some specific point
1249	triggering an event on each midnight, local time or other, complicated,	1879	in time: for example, if you tell a periodic watcher to trigger "in 10
1250	rules.	1880	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1881	not a delay) and then reset your system clock to January of the previous
		1882	year, then it will take a year or more to trigger the event (unlike an
		1883	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1884	it, as it uses a relative timeout).
1251		1885
		1886	C<ev_periodic> watchers can also be used to implement vastly more complex
		1887	timers, such as triggering an event on each "midnight, local time", or
		1888	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1889	those cannot react to time jumps.
		1890
1252	As with timers, the callback is guarenteed to be invoked only when the	1891	As with timers, the callback is guaranteed to be invoked only when the
1253	time (C<at>) has been passed, but if multiple periodic timers become ready	1892	point in time where it is supposed to trigger has passed. If multiple
1254	during the same loop iteration then order of execution is undefined.	1893	timers become ready during the same loop iteration then the ones with
		1894	earlier time-out values are invoked before ones with later time-out values
		1895	(but this is no longer true when a callback calls C<ev_loop> recursively).
1255		1896
1256	=head3 Watcher-Specific Functions and Data Members	1897	=head3 Watcher-Specific Functions and Data Members
1257		1898
1258	=over 4	1899	=over 4
1259		1900
1260	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1901	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1261		1902
1262	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1903	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1263		1904
1264	Lots of arguments, lets sort it out... There are basically three modes of	1905	Lots of arguments, let's sort it out... There are basically three modes of
1265	operation, and we will explain them from simplest to complex:	1906	operation, and we will explain them from simplest to most complex:
1266		1907
1267	=over 4	1908	=over 4
1268		1909
1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1910	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1270		1911
1271	In this configuration the watcher triggers an event at the wallclock time	1912	In this configuration the watcher triggers an event after the wall clock
1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1913	time C<offset> has passed. It will not repeat and will not adjust when a
1273	that is, if it is to be run at January 1st 2011 then it will run when the	1914	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1274	system time reaches or surpasses this time.	1915	will be stopped and invoked when the system clock reaches or surpasses
		1916	this point in time.
1275		1917
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1918	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1277		1919
1278	In this mode the watcher will always be scheduled to time out at the next	1920	In this mode the watcher will always be scheduled to time out at the next
1279	C<at + N * interval> time (for some integer N, which can also be negative)	1921	C<offset + N * interval> time (for some integer N, which can also be
1280	and then repeat, regardless of any time jumps.	1922	negative) and then repeat, regardless of any time jumps. The C<offset>
		1923	argument is merely an offset into the C<interval> periods.
1281		1924
1282	This can be used to create timers that do not drift with respect to system	1925	This can be used to create timers that do not drift with respect to the
1283	time:	1926	system clock, for example, here is an C<ev_periodic> that triggers each
		1927	hour, on the hour (with respect to UTC):
1284		1928
1285	ev_periodic_set (&periodic, 0., 3600., 0);	1929	ev_periodic_set (&periodic, 0., 3600., 0);
1286		1930
1287	This doesn't mean there will always be 3600 seconds in between triggers,	1931	This doesn't mean there will always be 3600 seconds in between triggers,
1288	but only that the the callback will be called when the system time shows a	1932	but only that the callback will be called when the system time shows a
1289	full hour (UTC), or more correctly, when the system time is evenly divisible	1933	full hour (UTC), or more correctly, when the system time is evenly divisible
1290	by 3600.	1934	by 3600.
1291		1935
1292	Another way to think about it (for the mathematically inclined) is that	1936	Another way to think about it (for the mathematically inclined) is that
1293	C<ev_periodic> will try to run the callback in this mode at the next possible	1937	C<ev_periodic> will try to run the callback in this mode at the next possible
1294	time where C<time = at (mod interval)>, regardless of any time jumps.	1938	time where C<time = offset (mod interval)>, regardless of any time jumps.
1295		1939
1296	For numerical stability it is preferable that the C<at> value is near	1940	For numerical stability it is preferable that the C<offset> value is near
1297	C<ev_now ()> (the current time), but there is no range requirement for	1941	C<ev_now ()> (the current time), but there is no range requirement for
1298	this value.	1942	this value, and in fact is often specified as zero.
1299		1943
		1944	Note also that there is an upper limit to how often a timer can fire (CPU
		1945	speed for example), so if C<interval> is very small then timing stability
		1946	will of course deteriorate. Libev itself tries to be exact to be about one
		1947	millisecond (if the OS supports it and the machine is fast enough).
		1948
1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1949	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1301		1950
1302	In this mode the values for C<interval> and C<at> are both being	1951	In this mode the values for C<interval> and C<offset> are both being
1303	ignored. Instead, each time the periodic watcher gets scheduled, the	1952	ignored. Instead, each time the periodic watcher gets scheduled, the
1304	reschedule callback will be called with the watcher as first, and the	1953	reschedule callback will be called with the watcher as first, and the
1305	current time as second argument.	1954	current time as second argument.
1306		1955
1307	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1956	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1308	ever, or make any event loop modifications>. If you need to stop it,	1957	or make ANY other event loop modifications whatsoever, unless explicitly
1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1958	allowed by documentation here>.
1310	starting an C<ev_prepare> watcher, which is legal).
1311		1959
		1960	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1961	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1962	only event loop modification you are allowed to do).
		1963
1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1964	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1313	ev_tstamp now)>, e.g.:	1965	*w, ev_tstamp now)>, e.g.:
1314		1966
		1967	static ev_tstamp
1315	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1968	my_rescheduler (ev_periodic *w, ev_tstamp now)
1316	{	1969	{
1317	return now + 60.;	1970	return now + 60.;
1318	}	1971	}
1319		1972
1320	It must return the next time to trigger, based on the passed time value	1973	It must return the next time to trigger, based on the passed time value
1321	(that is, the lowest time value larger than to the second argument). It	1974	(that is, the lowest time value larger than to the second argument). It
1322	will usually be called just before the callback will be triggered, but	1975	will usually be called just before the callback will be triggered, but
1323	might be called at other times, too.	1976	might be called at other times, too.
1324		1977
1325	NOTE: I<< This callback must always return a time that is later than the	1978	NOTE: I<< This callback must always return a time that is higher than or
1326	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1979	equal to the passed C<now> value >>.
1327		1980
1328	This can be used to create very complex timers, such as a timer that	1981	This can be used to create very complex timers, such as a timer that
1329	triggers on each midnight, local time. To do this, you would calculate the	1982	triggers on "next midnight, local time". To do this, you would calculate the
1330	next midnight after C<now> and return the timestamp value for this. How	1983	next midnight after C<now> and return the timestamp value for this. How
1331	you do this is, again, up to you (but it is not trivial, which is the main	1984	you do this is, again, up to you (but it is not trivial, which is the main
1332	reason I omitted it as an example).	1985	reason I omitted it as an example).
1333		1986
1334	=back	1987	=back
…		…
1338	Simply stops and restarts the periodic watcher again. This is only useful	1991	Simply stops and restarts the periodic watcher again. This is only useful
1339	when you changed some parameters or the reschedule callback would return	1992	when you changed some parameters or the reschedule callback would return
1340	a different time than the last time it was called (e.g. in a crond like	1993	a different time than the last time it was called (e.g. in a crond like
1341	program when the crontabs have changed).	1994	program when the crontabs have changed).
1342		1995
		1996	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1997
		1998	When active, returns the absolute time that the watcher is supposed
		1999	to trigger next. This is not the same as the C<offset> argument to
		2000	C<ev_periodic_set>, but indeed works even in interval and manual
		2001	rescheduling modes.
		2002
1343	=item ev_tstamp offset [read-write]	2003	=item ev_tstamp offset [read-write]
1344		2004
1345	When repeating, this contains the offset value, otherwise this is the	2005	When repeating, this contains the offset value, otherwise this is the
1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2006	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2007	although libev might modify this value for better numerical stability).
1347		2008
1348	Can be modified any time, but changes only take effect when the periodic	2009	Can be modified any time, but changes only take effect when the periodic
1349	timer fires or C<ev_periodic_again> is being called.	2010	timer fires or C<ev_periodic_again> is being called.
1350		2011
1351	=item ev_tstamp interval [read-write]	2012	=item ev_tstamp interval [read-write]
1352		2013
1353	The current interval value. Can be modified any time, but changes only	2014	The current interval value. Can be modified any time, but changes only
1354	take effect when the periodic timer fires or C<ev_periodic_again> is being	2015	take effect when the periodic timer fires or C<ev_periodic_again> is being
1355	called.	2016	called.
1356		2017
1357	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2018	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1358		2019
1359	The current reschedule callback, or C<0>, if this functionality is	2020	The current reschedule callback, or C<0>, if this functionality is
1360	switched off. Can be changed any time, but changes only take effect when	2021	switched off. Can be changed any time, but changes only take effect when
1361	the periodic timer fires or C<ev_periodic_again> is being called.	2022	the periodic timer fires or C<ev_periodic_again> is being called.
1362		2023
1363	=item ev_tstamp at [read-only]
1364
1365	When active, contains the absolute time that the watcher is supposed to
1366	trigger next.
1367
1368	=back	2024	=back
1369		2025
1370	=head3 Examples	2026	=head3 Examples
1371		2027
1372	Example: Call a callback every hour, or, more precisely, whenever the	2028	Example: Call a callback every hour, or, more precisely, whenever the
1373	system clock is divisible by 3600. The callback invocation times have	2029	system time is divisible by 3600. The callback invocation times have
1374	potentially a lot of jittering, but good long-term stability.	2030	potentially a lot of jitter, but good long-term stability.
1375		2031
1376	static void	2032	static void
1377	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2033	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1378	{	2034	{
1379	... its now a full hour (UTC, or TAI or whatever your clock follows)	2035	... its now a full hour (UTC, or TAI or whatever your clock follows)
1380	}	2036	}
1381		2037
1382	struct ev_periodic hourly_tick;	2038	ev_periodic hourly_tick;
1383	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1384	ev_periodic_start (loop, &hourly_tick);	2040	ev_periodic_start (loop, &hourly_tick);
1385		2041
1386	Example: The same as above, but use a reschedule callback to do it:	2042	Example: The same as above, but use a reschedule callback to do it:
1387		2043
1388	#include <math.h>	2044	#include <math.h>
1389		2045
1390	static ev_tstamp	2046	static ev_tstamp
1391	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2047	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1392	{	2048	{
1393	return fmod (now, 3600.) + 3600.;	2049	return now + (3600. - fmod (now, 3600.));
1394	}	2050	}
1395		2051
1396	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1397		2053
1398	Example: Call a callback every hour, starting now:	2054	Example: Call a callback every hour, starting now:
1399		2055
1400	struct ev_periodic hourly_tick;	2056	ev_periodic hourly_tick;
1401	ev_periodic_init (&hourly_tick, clock_cb,	2057	ev_periodic_init (&hourly_tick, clock_cb,
1402	fmod (ev_now (loop), 3600.), 3600., 0);	2058	fmod (ev_now (loop), 3600.), 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	2059	ev_periodic_start (loop, &hourly_tick);
1404		2060
1405		2061
1406	=head2 C<ev_signal> - signal me when a signal gets signalled!	2062	=head2 C<ev_signal> - signal me when a signal gets signalled!
1407		2063
1408	Signal watchers will trigger an event when the process receives a specific	2064	Signal watchers will trigger an event when the process receives a specific
1409	signal one or more times. Even though signals are very asynchronous, libev	2065	signal one or more times. Even though signals are very asynchronous, libev
1410	will try it's best to deliver signals synchronously, i.e. as part of the	2066	will try it's best to deliver signals synchronously, i.e. as part of the
1411	normal event processing, like any other event.	2067	normal event processing, like any other event.
1412		2068
		2069	If you want signals asynchronously, just use C<sigaction> as you would
		2070	do without libev and forget about sharing the signal. You can even use
		2071	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2072
1413	You can configure as many watchers as you like per signal. Only when the	2073	You can configure as many watchers as you like per signal. Only when the
1414	first watcher gets started will libev actually register a signal watcher	2074	first watcher gets started will libev actually register a signal handler
1415	with the kernel (thus it coexists with your own signal handlers as long	2075	with the kernel (thus it coexists with your own signal handlers as long as
1416	as you don't register any with libev). Similarly, when the last signal	2076	you don't register any with libev for the same signal). Similarly, when
1417	watcher for a signal is stopped libev will reset the signal handler to	2077	the last signal watcher for a signal is stopped, libev will reset the
1418	SIG_DFL (regardless of what it was set to before).	2078	signal handler to SIG_DFL (regardless of what it was set to before).
		2079
		2080	If possible and supported, libev will install its handlers with
		2081	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		2082	interrupted. If you have a problem with system calls getting interrupted by
		2083	signals you can block all signals in an C<ev_check> watcher and unblock
		2084	them in an C<ev_prepare> watcher.
1419		2085
1420	=head3 Watcher-Specific Functions and Data Members	2086	=head3 Watcher-Specific Functions and Data Members
1421		2087
1422	=over 4	2088	=over 4
1423		2089
…		…
1432		2098
1433	The signal the watcher watches out for.	2099	The signal the watcher watches out for.
1434		2100
1435	=back	2101	=back
1436		2102
		2103	=head3 Examples
		2104
		2105	Example: Try to exit cleanly on SIGINT.
		2106
		2107	static void
		2108	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		2109	{
		2110	ev_unloop (loop, EVUNLOOP_ALL);
		2111	}
		2112
		2113	ev_signal signal_watcher;
		2114	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2115	ev_signal_start (loop, &signal_watcher);
		2116
1437		2117
1438	=head2 C<ev_child> - watch out for process status changes	2118	=head2 C<ev_child> - watch out for process status changes
1439		2119
1440	Child watchers trigger when your process receives a SIGCHLD in response to	2120	Child watchers trigger when your process receives a SIGCHLD in response to
1441	some child status changes (most typically when a child of yours dies).	2121	some child status changes (most typically when a child of yours dies or
		2122	exits). It is permissible to install a child watcher I<after> the child
		2123	has been forked (which implies it might have already exited), as long
		2124	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2125	forking and then immediately registering a watcher for the child is fine,
		2126	but forking and registering a watcher a few event loop iterations later or
		2127	in the next callback invocation is not.
		2128
		2129	Only the default event loop is capable of handling signals, and therefore
		2130	you can only register child watchers in the default event loop.
		2131
		2132	Due to some design glitches inside libev, child watchers will always be
		2133	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2134	libev)
		2135
		2136	=head3 Process Interaction
		2137
		2138	Libev grabs C<SIGCHLD> as soon as the default event loop is
		2139	initialised. This is necessary to guarantee proper behaviour even if
		2140	the first child watcher is started after the child exits. The occurrence
		2141	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		2142	synchronously as part of the event loop processing. Libev always reaps all
		2143	children, even ones not watched.
		2144
		2145	=head3 Overriding the Built-In Processing
		2146
		2147	Libev offers no special support for overriding the built-in child
		2148	processing, but if your application collides with libev's default child
		2149	handler, you can override it easily by installing your own handler for
		2150	C<SIGCHLD> after initialising the default loop, and making sure the
		2151	default loop never gets destroyed. You are encouraged, however, to use an
		2152	event-based approach to child reaping and thus use libev's support for
		2153	that, so other libev users can use C<ev_child> watchers freely.
		2154
		2155	=head3 Stopping the Child Watcher
		2156
		2157	Currently, the child watcher never gets stopped, even when the
		2158	child terminates, so normally one needs to stop the watcher in the
		2159	callback. Future versions of libev might stop the watcher automatically
		2160	when a child exit is detected.
1442		2161
1443	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1444		2163
1445	=over 4	2164	=over 4
1446		2165
…		…
1472		2191
1473	=back	2192	=back
1474		2193
1475	=head3 Examples	2194	=head3 Examples
1476		2195
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	2196	Example: C<fork()> a new process and install a child handler to wait for
		2197	its completion.
1478		2198
		2199	ev_child cw;
		2200
1479	static void	2201	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2202	child_cb (EV_P_ ev_child *w, int revents)
1481	{	2203	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	2204	ev_child_stop (EV_A_ w);
		2205	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	2206	}
1484		2207
1485	struct ev_signal signal_watcher;	2208	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2209
1487	ev_signal_start (loop, &sigint_cb);	2210	if (pid < 0)
		2211	// error
		2212	else if (pid == 0)
		2213	{
		2214	// the forked child executes here
		2215	exit (1);
		2216	}
		2217	else
		2218	{
		2219	ev_child_init (&cw, child_cb, pid, 0);
		2220	ev_child_start (EV_DEFAULT_ &cw);
		2221	}
1488		2222
1489		2223
1490	=head2 C<ev_stat> - did the file attributes just change?	2224	=head2 C<ev_stat> - did the file attributes just change?
1491		2225
1492	This watches a filesystem path for attribute changes. That is, it calls	2226	This watches a file system path for attribute changes. That is, it calls
1493	C<stat> regularly (or when the OS says it changed) and sees if it changed	2227	C<stat> on that path in regular intervals (or when the OS says it changed)
1494	compared to the last time, invoking the callback if it did.	2228	and sees if it changed compared to the last time, invoking the callback if
		2229	it did.
1495		2230
1496	The path does not need to exist: changing from "path exists" to "path does	2231	The path does not need to exist: changing from "path exists" to "path does
1497	not exist" is a status change like any other. The condition "path does	2232	not exist" is a status change like any other. The condition "path does not
1498	not exist" is signified by the C<st_nlink> field being zero (which is	2233	exist" (or more correctly "path cannot be stat'ed") is signified by the
1499	otherwise always forced to be at least one) and all the other fields of	2234	C<st_nlink> field being zero (which is otherwise always forced to be at
1500	the stat buffer having unspecified contents.	2235	least one) and all the other fields of the stat buffer having unspecified
		2236	contents.
1501		2237
1502	The path I<should> be absolute and I<must not> end in a slash. If it is	2238	The path I<must not> end in a slash or contain special components such as
		2239	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1503	relative and your working directory changes, the behaviour is undefined.	2240	your working directory changes, then the behaviour is undefined.
1504		2241
1505	Since there is no standard to do this, the portable implementation simply	2242	Since there is no portable change notification interface available, the
1506	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2243	portable implementation simply calls C<stat(2)> regularly on the path
1507	can specify a recommended polling interval for this case. If you specify	2244	to see if it changed somehow. You can specify a recommended polling
1508	a polling interval of C<0> (highly recommended!) then a I<suitable,	2245	interval for this case. If you specify a polling interval of C<0> (highly
1509	unspecified default> value will be used (which you can expect to be around	2246	recommended!) then a I<suitable, unspecified default> value will be used
1510	five seconds, although this might change dynamically). Libev will also	2247	(which you can expect to be around five seconds, although this might
1511	impose a minimum interval which is currently around C<0.1>, but thats	2248	change dynamically). Libev will also impose a minimum interval which is
1512	usually overkill.	2249	currently around C<0.1>, but that's usually overkill.
1513		2250
1514	This watcher type is not meant for massive numbers of stat watchers,	2251	This watcher type is not meant for massive numbers of stat watchers,
1515	as even with OS-supported change notifications, this can be	2252	as even with OS-supported change notifications, this can be
1516	resource-intensive.	2253	resource-intensive.
1517		2254
1518	At the time of this writing, only the Linux inotify interface is	2255	At the time of this writing, the only OS-specific interface implemented
1519	implemented (implementing kqueue support is left as an exercise for the	2256	is the Linux inotify interface (implementing kqueue support is left as an
1520	reader). Inotify will be used to give hints only and should not change the	2257	exercise for the reader. Note, however, that the author sees no way of
1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2258	implementing C<ev_stat> semantics with kqueue, except as a hint).
1522	to fall back to regular polling again even with inotify, but changes are
1523	usually detected immediately, and if the file exists there will be no
1524	polling.
1525		2259
1526	=head3 Inotify	2260	=head3 ABI Issues (Largefile Support)
1527		2261
		2262	Libev by default (unless the user overrides this) uses the default
		2263	compilation environment, which means that on systems with large file
		2264	support disabled by default, you get the 32 bit version of the stat
		2265	structure. When using the library from programs that change the ABI to
		2266	use 64 bit file offsets the programs will fail. In that case you have to
		2267	compile libev with the same flags to get binary compatibility. This is
		2268	obviously the case with any flags that change the ABI, but the problem is
		2269	most noticeably displayed with ev_stat and large file support.
		2270
		2271	The solution for this is to lobby your distribution maker to make large
		2272	file interfaces available by default (as e.g. FreeBSD does) and not
		2273	optional. Libev cannot simply switch on large file support because it has
		2274	to exchange stat structures with application programs compiled using the
		2275	default compilation environment.
		2276
		2277	=head3 Inotify and Kqueue
		2278
1528	When C<inotify (7)> support has been compiled into libev (generally only	2279	When C<inotify (7)> support has been compiled into libev and present at
1529	available on Linux) and present at runtime, it will be used to speed up	2280	runtime, it will be used to speed up change detection where possible. The
1530	change detection where possible. The inotify descriptor will be created lazily	2281	inotify descriptor will be created lazily when the first C<ev_stat>
1531	when the first C<ev_stat> watcher is being started.	2282	watcher is being started.
1532		2283
1533	Inotify presense does not change the semantics of C<ev_stat> watchers	2284	Inotify presence does not change the semantics of C<ev_stat> watchers
1534	except that changes might be detected earlier, and in some cases, to avoid	2285	except that changes might be detected earlier, and in some cases, to avoid
1535	making regular C<stat> calls. Even in the presense of inotify support	2286	making regular C<stat> calls. Even in the presence of inotify support
1536	there are many cases where libev has to resort to regular C<stat> polling.	2287	there are many cases where libev has to resort to regular C<stat> polling,
		2288	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2289	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2290	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2291	xfs are fully working) libev usually gets away without polling.
1537		2292
1538	(There is no support for kqueue, as apparently it cannot be used to	2293	There is no support for kqueue, as apparently it cannot be used to
1539	implement this functionality, due to the requirement of having a file	2294	implement this functionality, due to the requirement of having a file
1540	descriptor open on the object at all times).	2295	descriptor open on the object at all times, and detecting renames, unlinks
		2296	etc. is difficult.
		2297
		2298	=head3 C<stat ()> is a synchronous operation
		2299
		2300	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2301	the process. The exception are C<ev_stat> watchers - those call C<stat
		2302	()>, which is a synchronous operation.
		2303
		2304	For local paths, this usually doesn't matter: unless the system is very
		2305	busy or the intervals between stat's are large, a stat call will be fast,
		2306	as the path data is usually in memory already (except when starting the
		2307	watcher).
		2308
		2309	For networked file systems, calling C<stat ()> can block an indefinite
		2310	time due to network issues, and even under good conditions, a stat call
		2311	often takes multiple milliseconds.
		2312
		2313	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2314	paths, although this is fully supported by libev.
1541		2315
1542	=head3 The special problem of stat time resolution	2316	=head3 The special problem of stat time resolution
1543		2317
1544	The C<stat ()> syscall only supports full-second resolution portably, and	2318	The C<stat ()> system call only supports full-second resolution portably,
1545	even on systems where the resolution is higher, many filesystems still	2319	and even on systems where the resolution is higher, most file systems
1546	only support whole seconds.	2320	still only support whole seconds.
1547		2321
1548	That means that, if the time is the only thing that changes, you might	2322	That means that, if the time is the only thing that changes, you can
1549	miss updates: on the first update, C<ev_stat> detects a change and calls	2323	easily miss updates: on the first update, C<ev_stat> detects a change and
1550	your callback, which does something. When there is another update within	2324	calls your callback, which does something. When there is another update
1551	the same second, C<ev_stat> will be unable to detect it.	2325	within the same second, C<ev_stat> will be unable to detect unless the
		2326	stat data does change in other ways (e.g. file size).
1552		2327
1553	The solution to this is to delay acting on a change for a second (or till	2328	The solution to this is to delay acting on a change for slightly more
1554	the next second boundary), using a roughly one-second delay C<ev_timer>	2329	than a second (or till slightly after the next full second boundary), using
1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2330	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1556	is added to work around small timing inconsistencies of some operating	2331	ev_timer_again (loop, w)>).
1557	systems.	2332
		2333	The C<.02> offset is added to work around small timing inconsistencies
		2334	of some operating systems (where the second counter of the current time
		2335	might be be delayed. One such system is the Linux kernel, where a call to
		2336	C<gettimeofday> might return a timestamp with a full second later than
		2337	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2338	update file times then there will be a small window where the kernel uses
		2339	the previous second to update file times but libev might already execute
		2340	the timer callback).
1558		2341
1559	=head3 Watcher-Specific Functions and Data Members	2342	=head3 Watcher-Specific Functions and Data Members
1560		2343
1561	=over 4	2344	=over 4
1562		2345
…		…
1568	C<path>. The C<interval> is a hint on how quickly a change is expected to	2351	C<path>. The C<interval> is a hint on how quickly a change is expected to
1569	be detected and should normally be specified as C<0> to let libev choose	2352	be detected and should normally be specified as C<0> to let libev choose
1570	a suitable value. The memory pointed to by C<path> must point to the same	2353	a suitable value. The memory pointed to by C<path> must point to the same
1571	path for as long as the watcher is active.	2354	path for as long as the watcher is active.
1572		2355
1573	The callback will be receive C<EV_STAT> when a change was detected,	2356	The callback will receive an C<EV_STAT> event when a change was detected,
1574	relative to the attributes at the time the watcher was started (or the	2357	relative to the attributes at the time the watcher was started (or the
1575	last change was detected).	2358	last change was detected).
1576		2359
1577	=item ev_stat_stat (ev_stat *)	2360	=item ev_stat_stat (loop, ev_stat *)
1578		2361
1579	Updates the stat buffer immediately with new values. If you change the	2362	Updates the stat buffer immediately with new values. If you change the
1580	watched path in your callback, you could call this fucntion to avoid	2363	watched path in your callback, you could call this function to avoid
1581	detecting this change (while introducing a race condition). Can also be	2364	detecting this change (while introducing a race condition if you are not
1582	useful simply to find out the new values.	2365	the only one changing the path). Can also be useful simply to find out the
		2366	new values.
1583		2367
1584	=item ev_statdata attr [read-only]	2368	=item ev_statdata attr [read-only]
1585		2369
1586	The most-recently detected attributes of the file. Although the type is of	2370	The most-recently detected attributes of the file. Although the type is
1587	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2371	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1588	suitable for your system. If the C<st_nlink> member is C<0>, then there	2372	suitable for your system, but you can only rely on the POSIX-standardised
		2373	members to be present. If the C<st_nlink> member is C<0>, then there was
1589	was some error while C<stat>ing the file.	2374	some error while C<stat>ing the file.
1590		2375
1591	=item ev_statdata prev [read-only]	2376	=item ev_statdata prev [read-only]
1592		2377
1593	The previous attributes of the file. The callback gets invoked whenever	2378	The previous attributes of the file. The callback gets invoked whenever
1594	C<prev> != C<attr>.	2379	C<prev> != C<attr>, or, more precisely, one or more of these members
		2380	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2381	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1595		2382
1596	=item ev_tstamp interval [read-only]	2383	=item ev_tstamp interval [read-only]
1597		2384
1598	The specified interval.	2385	The specified interval.
1599		2386
1600	=item const char *path [read-only]	2387	=item const char *path [read-only]
1601		2388
1602	The filesystem path that is being watched.	2389	The file system path that is being watched.
1603		2390
1604	=back	2391	=back
1605		2392
1606	=head3 Examples	2393	=head3 Examples
1607		2394
1608	Example: Watch C</etc/passwd> for attribute changes.	2395	Example: Watch C</etc/passwd> for attribute changes.
1609		2396
1610	static void	2397	static void
1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2398	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1612	{	2399	{
1613	/* /etc/passwd changed in some way */	2400	/* /etc/passwd changed in some way */
1614	if (w->attr.st_nlink)	2401	if (w->attr.st_nlink)
1615	{	2402	{
1616	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2403	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1617	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2404	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1618	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2405	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1619	}	2406	}
1620	else	2407	else
1621	/* you shalt not abuse printf for puts */	2408	/* you shalt not abuse printf for puts */
1622	puts ("wow, /etc/passwd is not there, expect problems. "	2409	puts ("wow, /etc/passwd is not there, expect problems. "
1623	"if this is windows, they already arrived\n");	2410	"if this is windows, they already arrived\n");
1624	}	2411	}
1625		2412
1626	...	2413	...
1627	ev_stat passwd;	2414	ev_stat passwd;
1628		2415
1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2416	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1630	ev_stat_start (loop, &passwd);	2417	ev_stat_start (loop, &passwd);
1631		2418
1632	Example: Like above, but additionally use a one-second delay so we do not	2419	Example: Like above, but additionally use a one-second delay so we do not
1633	miss updates (however, frequent updates will delay processing, too, so	2420	miss updates (however, frequent updates will delay processing, too, so
1634	one might do the work both on C<ev_stat> callback invocation I<and> on	2421	one might do the work both on C<ev_stat> callback invocation I<and> on
1635	C<ev_timer> callback invocation).	2422	C<ev_timer> callback invocation).
1636		2423
1637	static ev_stat passwd;	2424	static ev_stat passwd;
1638	static ev_timer timer;	2425	static ev_timer timer;
1639		2426
1640	static void	2427	static void
1641	timer_cb (EV_P_ ev_timer *w, int revents)	2428	timer_cb (EV_P_ ev_timer *w, int revents)
1642	{	2429	{
1643	ev_timer_stop (EV_A_ w);	2430	ev_timer_stop (EV_A_ w);
1644		2431
1645	/* now it's one second after the most recent passwd change */	2432	/* now it's one second after the most recent passwd change */
1646	}	2433	}
1647		2434
1648	static void	2435	static void
1649	stat_cb (EV_P_ ev_stat *w, int revents)	2436	stat_cb (EV_P_ ev_stat *w, int revents)
1650	{	2437	{
1651	/* reset the one-second timer */	2438	/* reset the one-second timer */
1652	ev_timer_again (EV_A_ &timer);	2439	ev_timer_again (EV_A_ &timer);
1653	}	2440	}
1654		2441
1655	...	2442	...
1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2443	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657	ev_stat_start (loop, &passwd);	2444	ev_stat_start (loop, &passwd);
1658	ev_timer_init (&timer, timer_cb, 0., 1.01);	2445	ev_timer_init (&timer, timer_cb, 0., 1.02);
1659		2446
1660		2447
1661	=head2 C<ev_idle> - when you've got nothing better to do...	2448	=head2 C<ev_idle> - when you've got nothing better to do...
1662		2449
1663	Idle watchers trigger events when no other events of the same or higher	2450	Idle watchers trigger events when no other events of the same or higher
1664	priority are pending (prepare, check and other idle watchers do not	2451	priority are pending (prepare, check and other idle watchers do not count
1665	count).	2452	as receiving "events").
1666		2453
1667	That is, as long as your process is busy handling sockets or timeouts	2454	That is, as long as your process is busy handling sockets or timeouts
1668	(or even signals, imagine) of the same or higher priority it will not be	2455	(or even signals, imagine) of the same or higher priority it will not be
1669	triggered. But when your process is idle (or only lower-priority watchers	2456	triggered. But when your process is idle (or only lower-priority watchers
1670	are pending), the idle watchers are being called once per event loop	2457	are pending), the idle watchers are being called once per event loop
…		…
1681		2468
1682	=head3 Watcher-Specific Functions and Data Members	2469	=head3 Watcher-Specific Functions and Data Members
1683		2470
1684	=over 4	2471	=over 4
1685		2472
1686	=item ev_idle_init (ev_signal *, callback)	2473	=item ev_idle_init (ev_idle *, callback)
1687		2474
1688	Initialises and configures the idle watcher - it has no parameters of any	2475	Initialises and configures the idle watcher - it has no parameters of any
1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2476	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1690	believe me.	2477	believe me.
1691		2478
…		…
1694	=head3 Examples	2481	=head3 Examples
1695		2482
1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2483	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1697	callback, free it. Also, use no error checking, as usual.	2484	callback, free it. Also, use no error checking, as usual.
1698		2485
1699	static void	2486	static void
1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2487	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1701	{	2488	{
1702	free (w);	2489	free (w);
1703	// now do something you wanted to do when the program has	2490	// now do something you wanted to do when the program has
1704	// no longer anything immediate to do.	2491	// no longer anything immediate to do.
1705	}	2492	}
1706		2493
1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2494	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1708	ev_idle_init (idle_watcher, idle_cb);	2495	ev_idle_init (idle_watcher, idle_cb);
1709	ev_idle_start (loop, idle_cb);	2496	ev_idle_start (loop, idle_watcher);
1710		2497
1711		2498
1712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2499	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1713		2500
1714	Prepare and check watchers are usually (but not always) used in tandem:	2501	Prepare and check watchers are usually (but not always) used in pairs:
1715	prepare watchers get invoked before the process blocks and check watchers	2502	prepare watchers get invoked before the process blocks and check watchers
1716	afterwards.	2503	afterwards.
1717		2504
1718	You I<must not> call C<ev_loop> or similar functions that enter	2505	You I<must not> call C<ev_loop> or similar functions that enter
1719	the current event loop from either C<ev_prepare> or C<ev_check>	2506	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1722	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2509	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1723	C<ev_check> so if you have one watcher of each kind they will always be	2510	C<ev_check> so if you have one watcher of each kind they will always be
1724	called in pairs bracketing the blocking call.	2511	called in pairs bracketing the blocking call.
1725		2512
1726	Their main purpose is to integrate other event mechanisms into libev and	2513	Their main purpose is to integrate other event mechanisms into libev and
1727	their use is somewhat advanced. This could be used, for example, to track	2514	their use is somewhat advanced. They could be used, for example, to track
1728	variable changes, implement your own watchers, integrate net-snmp or a	2515	variable changes, implement your own watchers, integrate net-snmp or a
1729	coroutine library and lots more. They are also occasionally useful if	2516	coroutine library and lots more. They are also occasionally useful if
1730	you cache some data and want to flush it before blocking (for example,	2517	you cache some data and want to flush it before blocking (for example,
1731	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2518	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1732	watcher).	2519	watcher).
1733		2520
1734	This is done by examining in each prepare call which file descriptors need	2521	This is done by examining in each prepare call which file descriptors
1735	to be watched by the other library, registering C<ev_io> watchers for	2522	need to be watched by the other library, registering C<ev_io> watchers
1736	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2523	for them and starting an C<ev_timer> watcher for any timeouts (many
1737	provide just this functionality). Then, in the check watcher you check for	2524	libraries provide exactly this functionality). Then, in the check watcher,
1738	any events that occured (by checking the pending status of all watchers	2525	you check for any events that occurred (by checking the pending status
1739	and stopping them) and call back into the library. The I/O and timer	2526	of all watchers and stopping them) and call back into the library. The
1740	callbacks will never actually be called (but must be valid nevertheless,	2527	I/O and timer callbacks will never actually be called (but must be valid
1741	because you never know, you know?).	2528	nevertheless, because you never know, you know?).
1742		2529
1743	As another example, the Perl Coro module uses these hooks to integrate	2530	As another example, the Perl Coro module uses these hooks to integrate
1744	coroutines into libev programs, by yielding to other active coroutines	2531	coroutines into libev programs, by yielding to other active coroutines
1745	during each prepare and only letting the process block if no coroutines	2532	during each prepare and only letting the process block if no coroutines
1746	are ready to run (it's actually more complicated: it only runs coroutines	2533	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1749	loop from blocking if lower-priority coroutines are active, thus mapping	2536	loop from blocking if lower-priority coroutines are active, thus mapping
1750	low-priority coroutines to idle/background tasks).	2537	low-priority coroutines to idle/background tasks).
1751		2538
1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2539	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1753	priority, to ensure that they are being run before any other watchers	2540	priority, to ensure that they are being run before any other watchers
		2541	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2542
1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2543	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1755	too) should not activate ("feed") events into libev. While libev fully	2544	activate ("feed") events into libev. While libev fully supports this, they
1756	supports this, they will be called before other C<ev_check> watchers	2545	might get executed before other C<ev_check> watchers did their job. As
1757	did their job. As C<ev_check> watchers are often used to embed other	2546	C<ev_check> watchers are often used to embed other (non-libev) event
1758	(non-libev) event loops those other event loops might be in an unusable	2547	loops those other event loops might be in an unusable state until their
1759	state until their C<ev_check> watcher ran (always remind yourself to	2548	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1760	coexist peacefully with others).	2549	others).
1761		2550
1762	=head3 Watcher-Specific Functions and Data Members	2551	=head3 Watcher-Specific Functions and Data Members
1763		2552
1764	=over 4	2553	=over 4
1765		2554
…		…
1767		2556
1768	=item ev_check_init (ev_check *, callback)	2557	=item ev_check_init (ev_check *, callback)
1769		2558
1770	Initialises and configures the prepare or check watcher - they have no	2559	Initialises and configures the prepare or check watcher - they have no
1771	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2560	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1772	macros, but using them is utterly, utterly and completely pointless.	2561	macros, but using them is utterly, utterly, utterly and completely
		2562	pointless.
1773		2563
1774	=back	2564	=back
1775		2565
1776	=head3 Examples	2566	=head3 Examples
1777		2567
1778	There are a number of principal ways to embed other event loops or modules	2568	There are a number of principal ways to embed other event loops or modules
1779	into libev. Here are some ideas on how to include libadns into libev	2569	into libev. Here are some ideas on how to include libadns into libev
1780	(there is a Perl module named C<EV::ADNS> that does this, which you could	2570	(there is a Perl module named C<EV::ADNS> that does this, which you could
1781	use for an actually working example. Another Perl module named C<EV::Glib>	2571	use as a working example. Another Perl module named C<EV::Glib> embeds a
1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2572	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1783	into the Glib event loop).	2573	Glib event loop).
1784		2574
1785	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2575	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1786	and in a check watcher, destroy them and call into libadns. What follows	2576	and in a check watcher, destroy them and call into libadns. What follows
1787	is pseudo-code only of course. This requires you to either use a low	2577	is pseudo-code only of course. This requires you to either use a low
1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2578	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1789	the callbacks for the IO/timeout watchers might not have been called yet.	2579	the callbacks for the IO/timeout watchers might not have been called yet.
1790		2580
1791	static ev_io iow [nfd];	2581	static ev_io iow [nfd];
1792	static ev_timer tw;	2582	static ev_timer tw;
1793		2583
1794	static void	2584	static void
1795	io_cb (ev_loop *loop, ev_io *w, int revents)	2585	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1796	{	2586	{
1797	}	2587	}
1798		2588
1799	// create io watchers for each fd and a timer before blocking	2589	// create io watchers for each fd and a timer before blocking
1800	static void	2590	static void
1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2591	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1802	{	2592	{
1803	int timeout = 3600000;	2593	int timeout = 3600000;
1804	struct pollfd fds [nfd];	2594	struct pollfd fds [nfd];
1805	// actual code will need to loop here and realloc etc.	2595	// actual code will need to loop here and realloc etc.
1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2596	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1807		2597
1808	/* the callback is illegal, but won't be called as we stop during check */	2598	/* the callback is illegal, but won't be called as we stop during check */
1809	ev_timer_init (&tw, 0, timeout * 1e-3);	2599	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1810	ev_timer_start (loop, &tw);	2600	ev_timer_start (loop, &tw);
1811		2601
1812	// create one ev_io per pollfd	2602	// create one ev_io per pollfd
1813	for (int i = 0; i < nfd; ++i)	2603	for (int i = 0; i < nfd; ++i)
1814	{	2604	{
1815	ev_io_init (iow + i, io_cb, fds [i].fd,	2605	ev_io_init (iow + i, io_cb, fds [i].fd,
1816	((fds [i].events & POLLIN ? EV_READ : 0)	2606	((fds [i].events & POLLIN ? EV_READ : 0)
1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2607	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1818		2608
1819	fds [i].revents = 0;	2609	fds [i].revents = 0;
1820	ev_io_start (loop, iow + i);	2610	ev_io_start (loop, iow + i);
1821	}	2611	}
1822	}	2612	}
1823		2613
1824	// stop all watchers after blocking	2614	// stop all watchers after blocking
1825	static void	2615	static void
1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2616	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1827	{	2617	{
1828	ev_timer_stop (loop, &tw);	2618	ev_timer_stop (loop, &tw);
1829		2619
1830	for (int i = 0; i < nfd; ++i)	2620	for (int i = 0; i < nfd; ++i)
1831	{	2621	{
1832	// set the relevant poll flags	2622	// set the relevant poll flags
1833	// could also call adns_processreadable etc. here	2623	// could also call adns_processreadable etc. here
1834	struct pollfd *fd = fds + i;	2624	struct pollfd *fd = fds + i;
1835	int revents = ev_clear_pending (iow + i);	2625	int revents = ev_clear_pending (iow + i);
1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2626	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2627	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1838		2628
1839	// now stop the watcher	2629	// now stop the watcher
1840	ev_io_stop (loop, iow + i);	2630	ev_io_stop (loop, iow + i);
1841	}	2631	}
1842		2632
1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2633	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1844	}	2634	}
1845		2635
1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2636	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1847	in the prepare watcher and would dispose of the check watcher.	2637	in the prepare watcher and would dispose of the check watcher.
1848		2638
1849	Method 3: If the module to be embedded supports explicit event	2639	Method 3: If the module to be embedded supports explicit event
1850	notification (adns does), you can also make use of the actual watcher	2640	notification (libadns does), you can also make use of the actual watcher
1851	callbacks, and only destroy/create the watchers in the prepare watcher.	2641	callbacks, and only destroy/create the watchers in the prepare watcher.
1852		2642
1853	static void	2643	static void
1854	timer_cb (EV_P_ ev_timer *w, int revents)	2644	timer_cb (EV_P_ ev_timer *w, int revents)
1855	{	2645	{
1856	adns_state ads = (adns_state)w->data;	2646	adns_state ads = (adns_state)w->data;
1857	update_now (EV_A);	2647	update_now (EV_A);
1858		2648
1859	adns_processtimeouts (ads, &tv_now);	2649	adns_processtimeouts (ads, &tv_now);
1860	}	2650	}
1861		2651
1862	static void	2652	static void
1863	io_cb (EV_P_ ev_io *w, int revents)	2653	io_cb (EV_P_ ev_io *w, int revents)
1864	{	2654	{
1865	adns_state ads = (adns_state)w->data;	2655	adns_state ads = (adns_state)w->data;
1866	update_now (EV_A);	2656	update_now (EV_A);
1867		2657
1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2658	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2659	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1870	}	2660	}
1871		2661
1872	// do not ever call adns_afterpoll	2662	// do not ever call adns_afterpoll
1873		2663
1874	Method 4: Do not use a prepare or check watcher because the module you	2664	Method 4: Do not use a prepare or check watcher because the module you
1875	want to embed is too inflexible to support it. Instead, youc na override	2665	want to embed is not flexible enough to support it. Instead, you can
1876	their poll function. The drawback with this solution is that the main	2666	override their poll function. The drawback with this solution is that the
1877	loop is now no longer controllable by EV. The C<Glib::EV> module does	2667	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1878	this.	2668	this approach, effectively embedding EV as a client into the horrible
		2669	libglib event loop.
1879		2670
1880	static gint	2671	static gint
1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1882	{	2673	{
1883	int got_events = 0;	2674	int got_events = 0;
1884		2675
1885	for (n = 0; n < nfds; ++n)	2676	for (n = 0; n < nfds; ++n)
1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1887		2678
1888	if (timeout >= 0)	2679	if (timeout >= 0)
1889	// create/start timer	2680	// create/start timer
1890		2681
1891	// poll	2682	// poll
1892	ev_loop (EV_A_ 0);	2683	ev_loop (EV_A_ 0);
1893		2684
1894	// stop timer again	2685	// stop timer again
1895	if (timeout >= 0)	2686	if (timeout >= 0)
1896	ev_timer_stop (EV_A_ &to);	2687	ev_timer_stop (EV_A_ &to);
1897		2688
1898	// stop io watchers again - their callbacks should have set	2689	// stop io watchers again - their callbacks should have set
1899	for (n = 0; n < nfds; ++n)	2690	for (n = 0; n < nfds; ++n)
1900	ev_io_stop (EV_A_ iow [n]);	2691	ev_io_stop (EV_A_ iow [n]);
1901		2692
1902	return got_events;	2693	return got_events;
1903	}	2694	}
1904		2695
1905		2696
1906	=head2 C<ev_embed> - when one backend isn't enough...	2697	=head2 C<ev_embed> - when one backend isn't enough...
1907		2698
1908	This is a rather advanced watcher type that lets you embed one event loop	2699	This is a rather advanced watcher type that lets you embed one event loop
…		…
1914	prioritise I/O.	2705	prioritise I/O.
1915		2706
1916	As an example for a bug workaround, the kqueue backend might only support	2707	As an example for a bug workaround, the kqueue backend might only support
1917	sockets on some platform, so it is unusable as generic backend, but you	2708	sockets on some platform, so it is unusable as generic backend, but you
1918	still want to make use of it because you have many sockets and it scales	2709	still want to make use of it because you have many sockets and it scales
1919	so nicely. In this case, you would create a kqueue-based loop and embed it	2710	so nicely. In this case, you would create a kqueue-based loop and embed
1920	into your default loop (which might use e.g. poll). Overall operation will	2711	it into your default loop (which might use e.g. poll). Overall operation
1921	be a bit slower because first libev has to poll and then call kevent, but	2712	will be a bit slower because first libev has to call C<poll> and then
1922	at least you can use both at what they are best.	2713	C<kevent>, but at least you can use both mechanisms for what they are
		2714	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1923		2715
1924	As for prioritising I/O: rarely you have the case where some fds have	2716	As for prioritising I/O: under rare circumstances you have the case where
1925	to be watched and handled very quickly (with low latency), and even	2717	some fds have to be watched and handled very quickly (with low latency),
1926	priorities and idle watchers might have too much overhead. In this case	2718	and even priorities and idle watchers might have too much overhead. In
1927	you would put all the high priority stuff in one loop and all the rest in	2719	this case you would put all the high priority stuff in one loop and all
1928	a second one, and embed the second one in the first.	2720	the rest in a second one, and embed the second one in the first.
1929		2721
1930	As long as the watcher is active, the callback will be invoked every time	2722	As long as the watcher is active, the callback will be invoked every
1931	there might be events pending in the embedded loop. The callback must then	2723	time there might be events pending in the embedded loop. The callback
1932	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2724	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1933	their callbacks (you could also start an idle watcher to give the embedded	2725	sweep and invoke their callbacks (the callback doesn't need to invoke the
1934	loop strictly lower priority for example). You can also set the callback	2726	C<ev_embed_sweep> function directly, it could also start an idle watcher
1935	to C<0>, in which case the embed watcher will automatically execute the	2727	to give the embedded loop strictly lower priority for example).
1936	embedded loop sweep.
1937		2728
1938	As long as the watcher is started it will automatically handle events. The	2729	You can also set the callback to C<0>, in which case the embed watcher
1939	callback will be invoked whenever some events have been handled. You can	2730	will automatically execute the embedded loop sweep whenever necessary.
1940	set the callback to C<0> to avoid having to specify one if you are not
1941	interested in that.
1942		2731
1943	Also, there have not currently been made special provisions for forking:	2732	Fork detection will be handled transparently while the C<ev_embed> watcher
1944	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2733	is active, i.e., the embedded loop will automatically be forked when the
1945	but you will also have to stop and restart any C<ev_embed> watchers	2734	embedding loop forks. In other cases, the user is responsible for calling
1946	yourself.	2735	C<ev_loop_fork> on the embedded loop.
1947		2736
1948	Unfortunately, not all backends are embeddable, only the ones returned by	2737	Unfortunately, not all backends are embeddable: only the ones returned by
1949	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2738	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1950	portable one.	2739	portable one.
1951		2740
1952	So when you want to use this feature you will always have to be prepared	2741	So when you want to use this feature you will always have to be prepared
1953	that you cannot get an embeddable loop. The recommended way to get around	2742	that you cannot get an embeddable loop. The recommended way to get around
1954	this is to have a separate variables for your embeddable loop, try to	2743	this is to have a separate variables for your embeddable loop, try to
1955	create it, and if that fails, use the normal loop for everything.	2744	create it, and if that fails, use the normal loop for everything.
1956		2745
		2746	=head3 C<ev_embed> and fork
		2747
		2748	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2749	automatically be applied to the embedded loop as well, so no special
		2750	fork handling is required in that case. When the watcher is not running,
		2751	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2752	as applicable.
		2753
1957	=head3 Watcher-Specific Functions and Data Members	2754	=head3 Watcher-Specific Functions and Data Members
1958		2755
1959	=over 4	2756	=over 4
1960		2757
1961	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2758	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1964		2761
1965	Configures the watcher to embed the given loop, which must be	2762	Configures the watcher to embed the given loop, which must be
1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2763	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967	invoked automatically, otherwise it is the responsibility of the callback	2764	invoked automatically, otherwise it is the responsibility of the callback
1968	to invoke it (it will continue to be called until the sweep has been done,	2765	to invoke it (it will continue to be called until the sweep has been done,
1969	if you do not want thta, you need to temporarily stop the embed watcher).	2766	if you do not want that, you need to temporarily stop the embed watcher).
1970		2767
1971	=item ev_embed_sweep (loop, ev_embed *)	2768	=item ev_embed_sweep (loop, ev_embed *)
1972		2769
1973	Make a single, non-blocking sweep over the embedded loop. This works	2770	Make a single, non-blocking sweep over the embedded loop. This works
1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2771	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975	apropriate way for embedded loops.	2772	appropriate way for embedded loops.
1976		2773
1977	=item struct ev_loop *other [read-only]	2774	=item struct ev_loop *other [read-only]
1978		2775
1979	The embedded event loop.	2776	The embedded event loop.
1980		2777
…		…
1982		2779
1983	=head3 Examples	2780	=head3 Examples
1984		2781
1985	Example: Try to get an embeddable event loop and embed it into the default	2782	Example: Try to get an embeddable event loop and embed it into the default
1986	event loop. If that is not possible, use the default loop. The default	2783	event loop. If that is not possible, use the default loop. The default
1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2784	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2785	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1989	used).	2786	used).
1990		2787
1991	struct ev_loop *loop_hi = ev_default_init (0);	2788	struct ev_loop *loop_hi = ev_default_init (0);
1992	struct ev_loop *loop_lo = 0;	2789	struct ev_loop *loop_lo = 0;
1993	struct ev_embed embed;	2790	ev_embed embed;
1994		2791
1995	// see if there is a chance of getting one that works	2792	// see if there is a chance of getting one that works
1996	// (remember that a flags value of 0 means autodetection)	2793	// (remember that a flags value of 0 means autodetection)
1997	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2794	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1998	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2795	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1999	: 0;	2796	: 0;
2000		2797
2001	// if we got one, then embed it, otherwise default to loop_hi	2798	// if we got one, then embed it, otherwise default to loop_hi
2002	if (loop_lo)	2799	if (loop_lo)
2003	{	2800	{
2004	ev_embed_init (&embed, 0, loop_lo);	2801	ev_embed_init (&embed, 0, loop_lo);
2005	ev_embed_start (loop_hi, &embed);	2802	ev_embed_start (loop_hi, &embed);
2006	}	2803	}
2007	else	2804	else
2008	loop_lo = loop_hi;	2805	loop_lo = loop_hi;
2009		2806
2010	Example: Check if kqueue is available but not recommended and create	2807	Example: Check if kqueue is available but not recommended and create
2011	a kqueue backend for use with sockets (which usually work with any	2808	a kqueue backend for use with sockets (which usually work with any
2012	kqueue implementation). Store the kqueue/socket-only event loop in	2809	kqueue implementation). Store the kqueue/socket-only event loop in
2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2810	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2014		2811
2015	struct ev_loop *loop = ev_default_init (0);	2812	struct ev_loop *loop = ev_default_init (0);
2016	struct ev_loop *loop_socket = 0;	2813	struct ev_loop *loop_socket = 0;
2017	struct ev_embed embed;	2814	ev_embed embed;
2018		2815
2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2816	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2817	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021	{	2818	{
2022	ev_embed_init (&embed, 0, loop_socket);	2819	ev_embed_init (&embed, 0, loop_socket);
2023	ev_embed_start (loop, &embed);	2820	ev_embed_start (loop, &embed);
2024	}	2821	}
2025		2822
2026	if (!loop_socket)	2823	if (!loop_socket)
2027	loop_socket = loop;	2824	loop_socket = loop;
2028		2825
2029	// now use loop_socket for all sockets, and loop for everything else	2826	// now use loop_socket for all sockets, and loop for everything else
2030		2827
2031		2828
2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2829	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2033		2830
2034	Fork watchers are called when a C<fork ()> was detected (usually because	2831	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2037	event loop blocks next and before C<ev_check> watchers are being called,	2834	event loop blocks next and before C<ev_check> watchers are being called,
2038	and only in the child after the fork. If whoever good citizen calling	2835	and only in the child after the fork. If whoever good citizen calling
2039	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2836	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2040	handlers will be invoked, too, of course.	2837	handlers will be invoked, too, of course.
2041		2838
		2839	=head3 The special problem of life after fork - how is it possible?
		2840
		2841	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2842	up/change the process environment, followed by a call to C<exec()>. This
		2843	sequence should be handled by libev without any problems.
		2844
		2845	This changes when the application actually wants to do event handling
		2846	in the child, or both parent in child, in effect "continuing" after the
		2847	fork.
		2848
		2849	The default mode of operation (for libev, with application help to detect
		2850	forks) is to duplicate all the state in the child, as would be expected
		2851	when I<either> the parent I<or> the child process continues.
		2852
		2853	When both processes want to continue using libev, then this is usually the
		2854	wrong result. In that case, usually one process (typically the parent) is
		2855	supposed to continue with all watchers in place as before, while the other
		2856	process typically wants to start fresh, i.e. without any active watchers.
		2857
		2858	The cleanest and most efficient way to achieve that with libev is to
		2859	simply create a new event loop, which of course will be "empty", and
		2860	use that for new watchers. This has the advantage of not touching more
		2861	memory than necessary, and thus avoiding the copy-on-write, and the
		2862	disadvantage of having to use multiple event loops (which do not support
		2863	signal watchers).
		2864
		2865	When this is not possible, or you want to use the default loop for
		2866	other reasons, then in the process that wants to start "fresh", call
		2867	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2868	the default loop will "orphan" (not stop) all registered watchers, so you
		2869	have to be careful not to execute code that modifies those watchers. Note
		2870	also that in that case, you have to re-register any signal watchers.
		2871
2042	=head3 Watcher-Specific Functions and Data Members	2872	=head3 Watcher-Specific Functions and Data Members
2043		2873
2044	=over 4	2874	=over 4
2045		2875
2046	=item ev_fork_init (ev_signal *, callback)	2876	=item ev_fork_init (ev_signal *, callback)
…		…
2078	is that the author does not know of a simple (or any) algorithm for a	2908	is that the author does not know of a simple (or any) algorithm for a
2079	multiple-writer-single-reader queue that works in all cases and doesn't	2909	multiple-writer-single-reader queue that works in all cases and doesn't
2080	need elaborate support such as pthreads.	2910	need elaborate support such as pthreads.
2081		2911
2082	That means that if you want to queue data, you have to provide your own	2912	That means that if you want to queue data, you have to provide your own
2083	queue. But at least I can tell you would implement locking around your	2913	queue. But at least I can tell you how to implement locking around your
2084	queue:	2914	queue:
2085		2915
2086	=over 4	2916	=over 4
2087		2917
2088	=item queueing from a signal handler context	2918	=item queueing from a signal handler context
2089		2919
2090	To implement race-free queueing, you simply add to the queue in the signal	2920	To implement race-free queueing, you simply add to the queue in the signal
2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2921	handler but you block the signal handler in the watcher callback. Here is
2092	some fictitiuous SIGUSR1 handler:	2922	an example that does that for some fictitious SIGUSR1 handler:
2093		2923
2094	static ev_async mysig;	2924	static ev_async mysig;
2095		2925
2096	static void	2926	static void
2097	sigusr1_handler (void)	2927	sigusr1_handler (void)
2098	{	2928	{
2099	sometype data;	2929	sometype data;
2100		2930
2101	// no locking etc.	2931	// no locking etc.
2102	queue_put (data);	2932	queue_put (data);
2103	ev_async_send (DEFAULT_ &mysig);	2933	ev_async_send (EV_DEFAULT_ &mysig);
2104	}	2934	}
2105		2935
2106	static void	2936	static void
2107	mysig_cb (EV_P_ ev_async *w, int revents)	2937	mysig_cb (EV_P_ ev_async *w, int revents)
2108	{	2938	{
…		…
2139	// only need to lock the actual queueing operation	2969	// only need to lock the actual queueing operation
2140	pthread_mutex_lock (&mymutex);	2970	pthread_mutex_lock (&mymutex);
2141	queue_put (data);	2971	queue_put (data);
2142	pthread_mutex_unlock (&mymutex);	2972	pthread_mutex_unlock (&mymutex);
2143		2973
2144	ev_async_send (DEFAULT_ &mysig);	2974	ev_async_send (EV_DEFAULT_ &mysig);
2145	}	2975	}
2146		2976
2147	static void	2977	static void
2148	mysig_cb (EV_P_ ev_async *w, int revents)	2978	mysig_cb (EV_P_ ev_async *w, int revents)
2149	{	2979	{
…		…
2163	=over 4	2993	=over 4
2164		2994
2165	=item ev_async_init (ev_async *, callback)	2995	=item ev_async_init (ev_async *, callback)
2166		2996
2167	Initialises and configures the async watcher - it has no parameters of any	2997	Initialises and configures the async watcher - it has no parameters of any
2168	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2998	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2169	believe me.	2999	trust me.
2170		3000
2171	=item ev_async_send (loop, ev_async *)	3001	=item ev_async_send (loop, ev_async *)
2172		3002
2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3003	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3004	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2175	C<ev_feed_event>, this call is safe to do in other threads, signal or	3005	C<ev_feed_event>, this call is safe to do from other threads, signal or
2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3006	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2177	section below on what exactly this means).	3007	section below on what exactly this means).
2178		3008
		3009	Note that, as with other watchers in libev, multiple events might get
		3010	compressed into a single callback invocation (another way to look at this
		3011	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3012	reset when the event loop detects that).
		3013
2179	This call incurs the overhead of a syscall only once per loop iteration,	3014	This call incurs the overhead of a system call only once per event loop
2180	so while the overhead might be noticable, it doesn't apply to repeated	3015	iteration, so while the overhead might be noticeable, it doesn't apply to
2181	calls to C<ev_async_send>.	3016	repeated calls to C<ev_async_send> for the same event loop.
		3017
		3018	=item bool = ev_async_pending (ev_async *)
		3019
		3020	Returns a non-zero value when C<ev_async_send> has been called on the
		3021	watcher but the event has not yet been processed (or even noted) by the
		3022	event loop.
		3023
		3024	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		3025	the loop iterates next and checks for the watcher to have become active,
		3026	it will reset the flag again. C<ev_async_pending> can be used to very
		3027	quickly check whether invoking the loop might be a good idea.
		3028
		3029	Not that this does I<not> check whether the watcher itself is pending,
		3030	only whether it has been requested to make this watcher pending: there
		3031	is a time window between the event loop checking and resetting the async
		3032	notification, and the callback being invoked.
2182		3033
2183	=back	3034	=back
2184		3035
2185		3036
2186	=head1 OTHER FUNCTIONS	3037	=head1 OTHER FUNCTIONS
…		…
2190	=over 4	3041	=over 4
2191		3042
2192	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3043	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2193		3044
2194	This function combines a simple timer and an I/O watcher, calls your	3045	This function combines a simple timer and an I/O watcher, calls your
2195	callback on whichever event happens first and automatically stop both	3046	callback on whichever event happens first and automatically stops both
2196	watchers. This is useful if you want to wait for a single event on an fd	3047	watchers. This is useful if you want to wait for a single event on an fd
2197	or timeout without having to allocate/configure/start/stop/free one or	3048	or timeout without having to allocate/configure/start/stop/free one or
2198	more watchers yourself.	3049	more watchers yourself.
2199		3050
2200	If C<fd> is less than 0, then no I/O watcher will be started and events	3051	If C<fd> is less than 0, then no I/O watcher will be started and the
2201	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3052	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2202	C<events> set will be craeted and started.	3053	the given C<fd> and C<events> set will be created and started.
2203		3054
2204	If C<timeout> is less than 0, then no timeout watcher will be	3055	If C<timeout> is less than 0, then no timeout watcher will be
2205	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3056	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2206	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3057	repeat = 0) will be started. C<0> is a valid timeout.
2207	dubious value.
2208		3058
2209	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3059	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2210	passed an C<revents> set like normal event callbacks (a combination of	3060	passed an C<revents> set like normal event callbacks (a combination of
2211	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3061	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2212	value passed to C<ev_once>:	3062	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3063	a timeout and an io event at the same time - you probably should give io
		3064	events precedence.
2213		3065
		3066	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3067
2214	static void stdin_ready (int revents, void *arg)	3068	static void stdin_ready (int revents, void *arg)
2215	{	3069	{
2216	if (revents & EV_TIMEOUT)
2217	/* doh, nothing entered */;
2218	else if (revents & EV_READ)	3070	if (revents & EV_READ)
2219	/* stdin might have data for us, joy! */;	3071	/* stdin might have data for us, joy! */;
		3072	else if (revents & EV_TIMEOUT)
		3073	/* doh, nothing entered */;
2220	}	3074	}
2221		3075
2222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3076	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2223		3077
2224	=item ev_feed_event (ev_loop *, watcher *, int revents)	3078	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2225		3079
2226	Feeds the given event set into the event loop, as if the specified event	3080	Feeds the given event set into the event loop, as if the specified event
2227	had happened for the specified watcher (which must be a pointer to an	3081	had happened for the specified watcher (which must be a pointer to an
2228	initialised but not necessarily started event watcher).	3082	initialised but not necessarily started event watcher).
2229		3083
2230	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3084	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2231		3085
2232	Feed an event on the given fd, as if a file descriptor backend detected	3086	Feed an event on the given fd, as if a file descriptor backend detected
2233	the given events it.	3087	the given events it.
2234		3088
2235	=item ev_feed_signal_event (ev_loop *loop, int signum)	3089	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2236		3090
2237	Feed an event as if the given signal occured (C<loop> must be the default	3091	Feed an event as if the given signal occurred (C<loop> must be the default
2238	loop!).	3092	loop!).
2239		3093
2240	=back	3094	=back
2241		3095
2242		3096
…		…
2258		3112
2259	=item * Priorities are not currently supported. Initialising priorities	3113	=item * Priorities are not currently supported. Initialising priorities
2260	will fail and all watchers will have the same priority, even though there	3114	will fail and all watchers will have the same priority, even though there
2261	is an ev_pri field.	3115	is an ev_pri field.
2262		3116
		3117	=item * In libevent, the last base created gets the signals, in libev, the
		3118	first base created (== the default loop) gets the signals.
		3119
2263	=item * Other members are not supported.	3120	=item * Other members are not supported.
2264		3121
2265	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3122	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2266	to use the libev header file and library.	3123	to use the libev header file and library.
2267		3124
2268	=back	3125	=back
2269		3126
2270	=head1 C++ SUPPORT	3127	=head1 C++ SUPPORT
2271		3128
2272	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3129	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2273	you to use some convinience methods to start/stop watchers and also change	3130	you to use some convenience methods to start/stop watchers and also change
2274	the callback model to a model using method callbacks on objects.	3131	the callback model to a model using method callbacks on objects.
2275		3132
2276	To use it,	3133	To use it,
2277		3134
2278	#include <ev++.h>	3135	#include <ev++.h>
2279		3136
2280	This automatically includes F<ev.h> and puts all of its definitions (many	3137	This automatically includes F<ev.h> and puts all of its definitions (many
2281	of them macros) into the global namespace. All C++ specific things are	3138	of them macros) into the global namespace. All C++ specific things are
2282	put into the C<ev> namespace. It should support all the same embedding	3139	put into the C<ev> namespace. It should support all the same embedding
2283	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3140	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2350	your compiler is good :), then the method will be fully inlined into the	3207	your compiler is good :), then the method will be fully inlined into the
2351	thunking function, making it as fast as a direct C callback.	3208	thunking function, making it as fast as a direct C callback.
2352		3209
2353	Example: simple class declaration and watcher initialisation	3210	Example: simple class declaration and watcher initialisation
2354		3211
2355	struct myclass	3212	struct myclass
2356	{	3213	{
2357	void io_cb (ev::io &w, int revents) { }	3214	void io_cb (ev::io &w, int revents) { }
2358	}	3215	}
2359		3216
2360	myclass obj;	3217	myclass obj;
2361	ev::io iow;	3218	ev::io iow;
2362	iow.set <myclass, &myclass::io_cb> (&obj);	3219	iow.set <myclass, &myclass::io_cb> (&obj);
		3220
		3221	=item w->set (object *)
		3222
		3223	This is an B<experimental> feature that might go away in a future version.
		3224
		3225	This is a variation of a method callback - leaving out the method to call
		3226	will default the method to C<operator ()>, which makes it possible to use
		3227	functor objects without having to manually specify the C<operator ()> all
		3228	the time. Incidentally, you can then also leave out the template argument
		3229	list.
		3230
		3231	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3232	int revents)>.
		3233
		3234	See the method-C<set> above for more details.
		3235
		3236	Example: use a functor object as callback.
		3237
		3238	struct myfunctor
		3239	{
		3240	void operator() (ev::io &w, int revents)
		3241	{
		3242	...
		3243	}
		3244	}
		3245
		3246	myfunctor f;
		3247
		3248	ev::io w;
		3249	w.set (&f);
2363		3250
2364	=item w->set<function> (void *data = 0)	3251	=item w->set<function> (void *data = 0)
2365		3252
2366	Also sets a callback, but uses a static method or plain function as	3253	Also sets a callback, but uses a static method or plain function as
2367	callback. The optional C<data> argument will be stored in the watcher's	3254	callback. The optional C<data> argument will be stored in the watcher's
…		…
2369		3256
2370	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3257	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2371		3258
2372	See the method-C<set> above for more details.	3259	See the method-C<set> above for more details.
2373		3260
2374	Example:	3261	Example: Use a plain function as callback.
2375		3262
2376	static void io_cb (ev::io &w, int revents) { }	3263	static void io_cb (ev::io &w, int revents) { }
2377	iow.set <io_cb> ();	3264	iow.set <io_cb> ();
2378		3265
2379	=item w->set (struct ev_loop *)	3266	=item w->set (struct ev_loop *)
2380		3267
2381	Associates a different C<struct ev_loop> with this watcher. You can only	3268	Associates a different C<struct ev_loop> with this watcher. You can only
2382	do this when the watcher is inactive (and not pending either).	3269	do this when the watcher is inactive (and not pending either).
2383		3270
2384	=item w->set ([args])	3271	=item w->set ([arguments])
2385		3272
2386	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3273	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2387	called at least once. Unlike the C counterpart, an active watcher gets	3274	called at least once. Unlike the C counterpart, an active watcher gets
2388	automatically stopped and restarted when reconfiguring it with this	3275	automatically stopped and restarted when reconfiguring it with this
2389	method.	3276	method.
2390		3277
2391	=item w->start ()	3278	=item w->start ()
…		…
2415	=back	3302	=back
2416		3303
2417	Example: Define a class with an IO and idle watcher, start one of them in	3304	Example: Define a class with an IO and idle watcher, start one of them in
2418	the constructor.	3305	the constructor.
2419		3306
2420	class myclass	3307	class myclass
2421	{	3308	{
2422	ev::io io; void io_cb (ev::io &w, int revents);	3309	ev::io io ; void io_cb (ev::io &w, int revents);
2423	ev:idle idle void idle_cb (ev::idle &w, int revents);	3310	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2424		3311
2425	myclass (int fd)	3312	myclass (int fd)
2426	{	3313	{
2427	io .set <myclass, &myclass::io_cb > (this);	3314	io .set <myclass, &myclass::io_cb > (this);
2428	idle.set <myclass, &myclass::idle_cb> (this);	3315	idle.set <myclass, &myclass::idle_cb> (this);
2429		3316
2430	io.start (fd, ev::READ);	3317	io.start (fd, ev::READ);
2431	}	3318	}
2432	};	3319	};
		3320
		3321
		3322	=head1 OTHER LANGUAGE BINDINGS
		3323
		3324	Libev does not offer other language bindings itself, but bindings for a
		3325	number of languages exist in the form of third-party packages. If you know
		3326	any interesting language binding in addition to the ones listed here, drop
		3327	me a note.
		3328
		3329	=over 4
		3330
		3331	=item Perl
		3332
		3333	The EV module implements the full libev API and is actually used to test
		3334	libev. EV is developed together with libev. Apart from the EV core module,
		3335	there are additional modules that implement libev-compatible interfaces
		3336	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3337	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3338	and C<EV::Glib>).
		3339
		3340	It can be found and installed via CPAN, its homepage is at
		3341	L<http://software.schmorp.de/pkg/EV>.
		3342
		3343	=item Python
		3344
		3345	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3346	seems to be quite complete and well-documented.
		3347
		3348	=item Ruby
		3349
		3350	Tony Arcieri has written a ruby extension that offers access to a subset
		3351	of the libev API and adds file handle abstractions, asynchronous DNS and
		3352	more on top of it. It can be found via gem servers. Its homepage is at
		3353	L<http://rev.rubyforge.org/>.
		3354
		3355	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3356	makes rev work even on mingw.
		3357
		3358	=item Haskell
		3359
		3360	A haskell binding to libev is available at
		3361	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3362
		3363	=item D
		3364
		3365	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3366	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3367
		3368	=item Ocaml
		3369
		3370	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3371	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3372
		3373	=back
2433		3374
2434		3375
2435	=head1 MACRO MAGIC	3376	=head1 MACRO MAGIC
2436		3377
2437	Libev can be compiled with a variety of options, the most fundamantal	3378	Libev can be compiled with a variety of options, the most fundamental
2438	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3379	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2439	functions and callbacks have an initial C<struct ev_loop *> argument.	3380	functions and callbacks have an initial C<struct ev_loop *> argument.
2440		3381
2441	To make it easier to write programs that cope with either variant, the	3382	To make it easier to write programs that cope with either variant, the
2442	following macros are defined:	3383	following macros are defined:
…		…
2447		3388
2448	This provides the loop I<argument> for functions, if one is required ("ev	3389	This provides the loop I<argument> for functions, if one is required ("ev
2449	loop argument"). The C<EV_A> form is used when this is the sole argument,	3390	loop argument"). The C<EV_A> form is used when this is the sole argument,
2450	C<EV_A_> is used when other arguments are following. Example:	3391	C<EV_A_> is used when other arguments are following. Example:
2451		3392
2452	ev_unref (EV_A);	3393	ev_unref (EV_A);
2453	ev_timer_add (EV_A_ watcher);	3394	ev_timer_add (EV_A_ watcher);
2454	ev_loop (EV_A_ 0);	3395	ev_loop (EV_A_ 0);
2455		3396
2456	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3397	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2457	which is often provided by the following macro.	3398	which is often provided by the following macro.
2458		3399
2459	=item C<EV_P>, C<EV_P_>	3400	=item C<EV_P>, C<EV_P_>
2460		3401
2461	This provides the loop I<parameter> for functions, if one is required ("ev	3402	This provides the loop I<parameter> for functions, if one is required ("ev
2462	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3403	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2463	C<EV_P_> is used when other parameters are following. Example:	3404	C<EV_P_> is used when other parameters are following. Example:
2464		3405
2465	// this is how ev_unref is being declared	3406	// this is how ev_unref is being declared
2466	static void ev_unref (EV_P);	3407	static void ev_unref (EV_P);
2467		3408
2468	// this is how you can declare your typical callback	3409	// this is how you can declare your typical callback
2469	static void cb (EV_P_ ev_timer *w, int revents)	3410	static void cb (EV_P_ ev_timer *w, int revents)
2470		3411
2471	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3412	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2472	suitable for use with C<EV_A>.	3413	suitable for use with C<EV_A>.
2473		3414
2474	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3415	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2475		3416
2476	Similar to the other two macros, this gives you the value of the default	3417	Similar to the other two macros, this gives you the value of the default
2477	loop, if multiple loops are supported ("ev loop default").	3418	loop, if multiple loops are supported ("ev loop default").
		3419
		3420	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3421
		3422	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3423	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3424	is undefined when the default loop has not been initialised by a previous
		3425	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3426
		3427	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3428	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2478		3429
2479	=back	3430	=back
2480		3431
2481	Example: Declare and initialise a check watcher, utilising the above	3432	Example: Declare and initialise a check watcher, utilising the above
2482	macros so it will work regardless of whether multiple loops are supported	3433	macros so it will work regardless of whether multiple loops are supported
2483	or not.	3434	or not.
2484		3435
2485	static void	3436	static void
2486	check_cb (EV_P_ ev_timer *w, int revents)	3437	check_cb (EV_P_ ev_timer *w, int revents)
2487	{	3438	{
2488	ev_check_stop (EV_A_ w);	3439	ev_check_stop (EV_A_ w);
2489	}	3440	}
2490		3441
2491	ev_check check;	3442	ev_check check;
2492	ev_check_init (&check, check_cb);	3443	ev_check_init (&check, check_cb);
2493	ev_check_start (EV_DEFAULT_ &check);	3444	ev_check_start (EV_DEFAULT_ &check);
2494	ev_loop (EV_DEFAULT_ 0);	3445	ev_loop (EV_DEFAULT_ 0);
2495		3446
2496	=head1 EMBEDDING	3447	=head1 EMBEDDING
2497		3448
2498	Libev can (and often is) directly embedded into host	3449	Libev can (and often is) directly embedded into host
2499	applications. Examples of applications that embed it include the Deliantra	3450	applications. Examples of applications that embed it include the Deliantra
…		…
2506	libev somewhere in your source tree).	3457	libev somewhere in your source tree).
2507		3458
2508	=head2 FILESETS	3459	=head2 FILESETS
2509		3460
2510	Depending on what features you need you need to include one or more sets of files	3461	Depending on what features you need you need to include one or more sets of files
2511	in your app.	3462	in your application.
2512		3463
2513	=head3 CORE EVENT LOOP	3464	=head3 CORE EVENT LOOP
2514		3465
2515	To include only the libev core (all the C<ev_*> functions), with manual	3466	To include only the libev core (all the C<ev_*> functions), with manual
2516	configuration (no autoconf):	3467	configuration (no autoconf):
2517		3468
2518	#define EV_STANDALONE 1	3469	#define EV_STANDALONE 1
2519	#include "ev.c"	3470	#include "ev.c"
2520		3471
2521	This will automatically include F<ev.h>, too, and should be done in a	3472	This will automatically include F<ev.h>, too, and should be done in a
2522	single C source file only to provide the function implementations. To use	3473	single C source file only to provide the function implementations. To use
2523	it, do the same for F<ev.h> in all files wishing to use this API (best	3474	it, do the same for F<ev.h> in all files wishing to use this API (best
2524	done by writing a wrapper around F<ev.h> that you can include instead and	3475	done by writing a wrapper around F<ev.h> that you can include instead and
2525	where you can put other configuration options):	3476	where you can put other configuration options):
2526		3477
2527	#define EV_STANDALONE 1	3478	#define EV_STANDALONE 1
2528	#include "ev.h"	3479	#include "ev.h"
2529		3480
2530	Both header files and implementation files can be compiled with a C++	3481	Both header files and implementation files can be compiled with a C++
2531	compiler (at least, thats a stated goal, and breakage will be treated	3482	compiler (at least, that's a stated goal, and breakage will be treated
2532	as a bug).	3483	as a bug).
2533		3484
2534	You need the following files in your source tree, or in a directory	3485	You need the following files in your source tree, or in a directory
2535	in your include path (e.g. in libev/ when using -Ilibev):	3486	in your include path (e.g. in libev/ when using -Ilibev):
2536		3487
2537	ev.h	3488	ev.h
2538	ev.c	3489	ev.c
2539	ev_vars.h	3490	ev_vars.h
2540	ev_wrap.h	3491	ev_wrap.h
2541		3492
2542	ev_win32.c required on win32 platforms only	3493	ev_win32.c required on win32 platforms only
2543		3494
2544	ev_select.c only when select backend is enabled (which is enabled by default)	3495	ev_select.c only when select backend is enabled (which is enabled by default)
2545	ev_poll.c only when poll backend is enabled (disabled by default)	3496	ev_poll.c only when poll backend is enabled (disabled by default)
2546	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3497	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2547	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3498	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2548	ev_port.c only when the solaris port backend is enabled (disabled by default)	3499	ev_port.c only when the solaris port backend is enabled (disabled by default)
2549		3500
2550	F<ev.c> includes the backend files directly when enabled, so you only need	3501	F<ev.c> includes the backend files directly when enabled, so you only need
2551	to compile this single file.	3502	to compile this single file.
2552		3503
2553	=head3 LIBEVENT COMPATIBILITY API	3504	=head3 LIBEVENT COMPATIBILITY API
2554		3505
2555	To include the libevent compatibility API, also include:	3506	To include the libevent compatibility API, also include:
2556		3507
2557	#include "event.c"	3508	#include "event.c"
2558		3509
2559	in the file including F<ev.c>, and:	3510	in the file including F<ev.c>, and:
2560		3511
2561	#include "event.h"	3512	#include "event.h"
2562		3513
2563	in the files that want to use the libevent API. This also includes F<ev.h>.	3514	in the files that want to use the libevent API. This also includes F<ev.h>.
2564		3515
2565	You need the following additional files for this:	3516	You need the following additional files for this:
2566		3517
2567	event.h	3518	event.h
2568	event.c	3519	event.c
2569		3520
2570	=head3 AUTOCONF SUPPORT	3521	=head3 AUTOCONF SUPPORT
2571		3522
2572	Instead of using C<EV_STANDALONE=1> and providing your config in	3523	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2573	whatever way you want, you can also C<m4_include([libev.m4])> in your	3524	whatever way you want, you can also C<m4_include([libev.m4])> in your
2574	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3525	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2575	include F<config.h> and configure itself accordingly.	3526	include F<config.h> and configure itself accordingly.
2576		3527
2577	For this of course you need the m4 file:	3528	For this of course you need the m4 file:
2578		3529
2579	libev.m4	3530	libev.m4
2580		3531
2581	=head2 PREPROCESSOR SYMBOLS/MACROS	3532	=head2 PREPROCESSOR SYMBOLS/MACROS
2582		3533
2583	Libev can be configured via a variety of preprocessor symbols you have to define	3534	Libev can be configured via a variety of preprocessor symbols you have to
2584	before including any of its files. The default is not to build for multiplicity	3535	define before including any of its files. The default in the absence of
2585	and only include the select backend.	3536	autoconf is documented for every option.
2586		3537
2587	=over 4	3538	=over 4
2588		3539
2589	=item EV_STANDALONE	3540	=item EV_STANDALONE
2590		3541
…		…
2592	keeps libev from including F<config.h>, and it also defines dummy	3543	keeps libev from including F<config.h>, and it also defines dummy
2593	implementations for some libevent functions (such as logging, which is not	3544	implementations for some libevent functions (such as logging, which is not
2594	supported). It will also not define any of the structs usually found in	3545	supported). It will also not define any of the structs usually found in
2595	F<event.h> that are not directly supported by the libev core alone.	3546	F<event.h> that are not directly supported by the libev core alone.
2596		3547
		3548	In stanbdalone mode, libev will still try to automatically deduce the
		3549	configuration, but has to be more conservative.
		3550
2597	=item EV_USE_MONOTONIC	3551	=item EV_USE_MONOTONIC
2598		3552
2599	If defined to be C<1>, libev will try to detect the availability of the	3553	If defined to be C<1>, libev will try to detect the availability of the
2600	monotonic clock option at both compiletime and runtime. Otherwise no use	3554	monotonic clock option at both compile time and runtime. Otherwise no
2601	of the monotonic clock option will be attempted. If you enable this, you	3555	use of the monotonic clock option will be attempted. If you enable this,
2602	usually have to link against librt or something similar. Enabling it when	3556	you usually have to link against librt or something similar. Enabling it
2603	the functionality isn't available is safe, though, although you have	3557	when the functionality isn't available is safe, though, although you have
2604	to make sure you link against any libraries where the C<clock_gettime>	3558	to make sure you link against any libraries where the C<clock_gettime>
2605	function is hiding in (often F<-lrt>).	3559	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2606		3560
2607	=item EV_USE_REALTIME	3561	=item EV_USE_REALTIME
2608		3562
2609	If defined to be C<1>, libev will try to detect the availability of the	3563	If defined to be C<1>, libev will try to detect the availability of the
2610	realtime clock option at compiletime (and assume its availability at	3564	real-time clock option at compile time (and assume its availability
2611	runtime if successful). Otherwise no use of the realtime clock option will	3565	at runtime if successful). Otherwise no use of the real-time clock
2612	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3566	option will be attempted. This effectively replaces C<gettimeofday>
2613	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3567	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2614	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3568	correctness. See the note about libraries in the description of
		3569	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3570	C<EV_USE_CLOCK_SYSCALL>.
		3571
		3572	=item EV_USE_CLOCK_SYSCALL
		3573
		3574	If defined to be C<1>, libev will try to use a direct syscall instead
		3575	of calling the system-provided C<clock_gettime> function. This option
		3576	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3577	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3578	programs needlessly. Using a direct syscall is slightly slower (in
		3579	theory), because no optimised vdso implementation can be used, but avoids
		3580	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3581	higher, as it simplifies linking (no need for C<-lrt>).
2615		3582
2616	=item EV_USE_NANOSLEEP	3583	=item EV_USE_NANOSLEEP
2617		3584
2618	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3585	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2619	and will use it for delays. Otherwise it will use C<select ()>.	3586	and will use it for delays. Otherwise it will use C<select ()>.
2620		3587
		3588	=item EV_USE_EVENTFD
		3589
		3590	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3591	available and will probe for kernel support at runtime. This will improve
		3592	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3593	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3594	2.7 or newer, otherwise disabled.
		3595
2621	=item EV_USE_SELECT	3596	=item EV_USE_SELECT
2622		3597
2623	If undefined or defined to be C<1>, libev will compile in support for the	3598	If undefined or defined to be C<1>, libev will compile in support for the
2624	C<select>(2) backend. No attempt at autodetection will be done: if no	3599	C<select>(2) backend. No attempt at auto-detection will be done: if no
2625	other method takes over, select will be it. Otherwise the select backend	3600	other method takes over, select will be it. Otherwise the select backend
2626	will not be compiled in.	3601	will not be compiled in.
2627		3602
2628	=item EV_SELECT_USE_FD_SET	3603	=item EV_SELECT_USE_FD_SET
2629		3604
2630	If defined to C<1>, then the select backend will use the system C<fd_set>	3605	If defined to C<1>, then the select backend will use the system C<fd_set>
2631	structure. This is useful if libev doesn't compile due to a missing	3606	structure. This is useful if libev doesn't compile due to a missing
2632	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3607	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2633	exotic systems. This usually limits the range of file descriptors to some	3608	on exotic systems. This usually limits the range of file descriptors to
2634	low limit such as 1024 or might have other limitations (winsocket only	3609	some low limit such as 1024 or might have other limitations (winsocket
2635	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3610	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2636	influence the size of the C<fd_set> used.	3611	configures the maximum size of the C<fd_set>.
2637		3612
2638	=item EV_SELECT_IS_WINSOCKET	3613	=item EV_SELECT_IS_WINSOCKET
2639		3614
2640	When defined to C<1>, the select backend will assume that	3615	When defined to C<1>, the select backend will assume that
2641	select/socket/connect etc. don't understand file descriptors but	3616	select/socket/connect etc. don't understand file descriptors but
…		…
2661		3636
2662	=item EV_USE_EPOLL	3637	=item EV_USE_EPOLL
2663		3638
2664	If defined to be C<1>, libev will compile in support for the Linux	3639	If defined to be C<1>, libev will compile in support for the Linux
2665	C<epoll>(7) backend. Its availability will be detected at runtime,	3640	C<epoll>(7) backend. Its availability will be detected at runtime,
2666	otherwise another method will be used as fallback. This is the	3641	otherwise another method will be used as fallback. This is the preferred
2667	preferred backend for GNU/Linux systems.	3642	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3643	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2668		3644
2669	=item EV_USE_KQUEUE	3645	=item EV_USE_KQUEUE
2670		3646
2671	If defined to be C<1>, libev will compile in support for the BSD style	3647	If defined to be C<1>, libev will compile in support for the BSD style
2672	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3648	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2685	otherwise another method will be used as fallback. This is the preferred	3661	otherwise another method will be used as fallback. This is the preferred
2686	backend for Solaris 10 systems.	3662	backend for Solaris 10 systems.
2687		3663
2688	=item EV_USE_DEVPOLL	3664	=item EV_USE_DEVPOLL
2689		3665
2690	reserved for future expansion, works like the USE symbols above.	3666	Reserved for future expansion, works like the USE symbols above.
2691		3667
2692	=item EV_USE_INOTIFY	3668	=item EV_USE_INOTIFY
2693		3669
2694	If defined to be C<1>, libev will compile in support for the Linux inotify	3670	If defined to be C<1>, libev will compile in support for the Linux inotify
2695	interface to speed up C<ev_stat> watchers. Its actual availability will	3671	interface to speed up C<ev_stat> watchers. Its actual availability will
2696	be detected at runtime.	3672	be detected at runtime. If undefined, it will be enabled if the headers
		3673	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2697		3674
2698	=item EV_ATOMIC_T	3675	=item EV_ATOMIC_T
2699		3676
2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3677	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2701	access is atomic with respect to other threads or signal contexts. No such	3678	access is atomic with respect to other threads or signal contexts. No such
2702	type is easily found in the C language, so you can provide your own type	3679	type is easily found in the C language, so you can provide your own type
2703	that you know is safe for your purposes. It is used both for signal handler "locking"	3680	that you know is safe for your purposes. It is used both for signal handler "locking"
2704	as well as for signal and thread safety in C<ev_async> watchers.	3681	as well as for signal and thread safety in C<ev_async> watchers.
2705		3682
2706	In the absense of this define, libev will use C<sig_atomic_t volatile>	3683	In the absence of this define, libev will use C<sig_atomic_t volatile>
2707	(from F<signal.h>), which is usually good enough on most platforms.	3684	(from F<signal.h>), which is usually good enough on most platforms.
2708		3685
2709	=item EV_H	3686	=item EV_H
2710		3687
2711	The name of the F<ev.h> header file used to include it. The default if	3688	The name of the F<ev.h> header file used to include it. The default if
…		…
2750	When doing priority-based operations, libev usually has to linearly search	3727	When doing priority-based operations, libev usually has to linearly search
2751	all the priorities, so having many of them (hundreds) uses a lot of space	3728	all the priorities, so having many of them (hundreds) uses a lot of space
2752	and time, so using the defaults of five priorities (-2 .. +2) is usually	3729	and time, so using the defaults of five priorities (-2 .. +2) is usually
2753	fine.	3730	fine.
2754		3731
2755	If your embedding app does not need any priorities, defining these both to	3732	If your embedding application does not need any priorities, defining these
2756	C<0> will save some memory and cpu.	3733	both to C<0> will save some memory and CPU.
2757		3734
2758	=item EV_PERIODIC_ENABLE	3735	=item EV_PERIODIC_ENABLE
2759		3736
2760	If undefined or defined to be C<1>, then periodic timers are supported. If	3737	If undefined or defined to be C<1>, then periodic timers are supported. If
2761	defined to be C<0>, then they are not. Disabling them saves a few kB of	3738	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2768	code.	3745	code.
2769		3746
2770	=item EV_EMBED_ENABLE	3747	=item EV_EMBED_ENABLE
2771		3748
2772	If undefined or defined to be C<1>, then embed watchers are supported. If	3749	If undefined or defined to be C<1>, then embed watchers are supported. If
2773	defined to be C<0>, then they are not.	3750	defined to be C<0>, then they are not. Embed watchers rely on most other
		3751	watcher types, which therefore must not be disabled.
2774		3752
2775	=item EV_STAT_ENABLE	3753	=item EV_STAT_ENABLE
2776		3754
2777	If undefined or defined to be C<1>, then stat watchers are supported. If	3755	If undefined or defined to be C<1>, then stat watchers are supported. If
2778	defined to be C<0>, then they are not.	3756	defined to be C<0>, then they are not.
…		…
2788	defined to be C<0>, then they are not.	3766	defined to be C<0>, then they are not.
2789		3767
2790	=item EV_MINIMAL	3768	=item EV_MINIMAL
2791		3769
2792	If you need to shave off some kilobytes of code at the expense of some	3770	If you need to shave off some kilobytes of code at the expense of some
2793	speed, define this symbol to C<1>. Currently only used for gcc to override	3771	speed (but with the full API), define this symbol to C<1>. Currently this
2794	some inlining decisions, saves roughly 30% codesize of amd64.	3772	is used to override some inlining decisions, saves roughly 30% code size
		3773	on amd64. It also selects a much smaller 2-heap for timer management over
		3774	the default 4-heap.
		3775
		3776	You can save even more by disabling watcher types you do not need
		3777	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3778	(C<-DNDEBUG>) will usually reduce code size a lot.
		3779
		3780	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3781	provide a bare-bones event library. See C<ev.h> for details on what parts
		3782	of the API are still available, and do not complain if this subset changes
		3783	over time.
2795		3784
2796	=item EV_PID_HASHSIZE	3785	=item EV_PID_HASHSIZE
2797		3786
2798	C<ev_child> watchers use a small hash table to distribute workload by	3787	C<ev_child> watchers use a small hash table to distribute workload by
2799	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3788	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2806	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3795	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2807	usually more than enough. If you need to manage thousands of C<ev_stat>	3796	usually more than enough. If you need to manage thousands of C<ev_stat>
2808	watchers you might want to increase this value (I<must> be a power of	3797	watchers you might want to increase this value (I<must> be a power of
2809	two).	3798	two).
2810		3799
		3800	=item EV_USE_4HEAP
		3801
		3802	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3803	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3804	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3805	faster performance with many (thousands) of watchers.
		3806
		3807	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3808	(disabled).
		3809
		3810	=item EV_HEAP_CACHE_AT
		3811
		3812	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3813	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3814	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3815	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3816	but avoids random read accesses on heap changes. This improves performance
		3817	noticeably with many (hundreds) of watchers.
		3818
		3819	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3820	(disabled).
		3821
		3822	=item EV_VERIFY
		3823
		3824	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3825	be done: If set to C<0>, no internal verification code will be compiled
		3826	in. If set to C<1>, then verification code will be compiled in, but not
		3827	called. If set to C<2>, then the internal verification code will be
		3828	called once per loop, which can slow down libev. If set to C<3>, then the
		3829	verification code will be called very frequently, which will slow down
		3830	libev considerably.
		3831
		3832	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3833	C<0>.
		3834
2811	=item EV_COMMON	3835	=item EV_COMMON
2812		3836
2813	By default, all watchers have a C<void *data> member. By redefining	3837	By default, all watchers have a C<void *data> member. By redefining
2814	this macro to a something else you can include more and other types of	3838	this macro to a something else you can include more and other types of
2815	members. You have to define it each time you include one of the files,	3839	members. You have to define it each time you include one of the files,
2816	though, and it must be identical each time.	3840	though, and it must be identical each time.
2817		3841
2818	For example, the perl EV module uses something like this:	3842	For example, the perl EV module uses something like this:
2819		3843
2820	#define EV_COMMON \	3844	#define EV_COMMON \
2821	SV *self; /* contains this struct */ \	3845	SV *self; /* contains this struct */ \
2822	SV *cb_sv, *fh /* note no trailing ";" */	3846	SV *cb_sv, *fh /* note no trailing ";" */
2823		3847
2824	=item EV_CB_DECLARE (type)	3848	=item EV_CB_DECLARE (type)
2825		3849
2826	=item EV_CB_INVOKE (watcher, revents)	3850	=item EV_CB_INVOKE (watcher, revents)
2827		3851
…		…
2832	definition and a statement, respectively. See the F<ev.h> header file for	3856	definition and a statement, respectively. See the F<ev.h> header file for
2833	their default definitions. One possible use for overriding these is to	3857	their default definitions. One possible use for overriding these is to
2834	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3858	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2835	method calls instead of plain function calls in C++.	3859	method calls instead of plain function calls in C++.
2836		3860
		3861	=back
		3862
2837	=head2 EXPORTED API SYMBOLS	3863	=head2 EXPORTED API SYMBOLS
2838		3864
2839	If you need to re-export the API (e.g. via a dll) and you need a list of	3865	If you need to re-export the API (e.g. via a DLL) and you need a list of
2840	exported symbols, you can use the provided F<Symbol.*> files which list	3866	exported symbols, you can use the provided F<Symbol.*> files which list
2841	all public symbols, one per line:	3867	all public symbols, one per line:
2842		3868
2843	Symbols.ev for libev proper	3869	Symbols.ev for libev proper
2844	Symbols.event for the libevent emulation	3870	Symbols.event for the libevent emulation
2845		3871
2846	This can also be used to rename all public symbols to avoid clashes with	3872	This can also be used to rename all public symbols to avoid clashes with
2847	multiple versions of libev linked together (which is obviously bad in	3873	multiple versions of libev linked together (which is obviously bad in
2848	itself, but sometimes it is inconvinient to avoid this).	3874	itself, but sometimes it is inconvenient to avoid this).
2849		3875
2850	A sed command like this will create wrapper C<#define>'s that you need to	3876	A sed command like this will create wrapper C<#define>'s that you need to
2851	include before including F<ev.h>:	3877	include before including F<ev.h>:
2852		3878
2853	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3879	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2870	file.	3896	file.
2871		3897
2872	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3898	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2873	that everybody includes and which overrides some configure choices:	3899	that everybody includes and which overrides some configure choices:
2874		3900
2875	#define EV_MINIMAL 1	3901	#define EV_MINIMAL 1
2876	#define EV_USE_POLL 0	3902	#define EV_USE_POLL 0
2877	#define EV_MULTIPLICITY 0	3903	#define EV_MULTIPLICITY 0
2878	#define EV_PERIODIC_ENABLE 0	3904	#define EV_PERIODIC_ENABLE 0
2879	#define EV_STAT_ENABLE 0	3905	#define EV_STAT_ENABLE 0
2880	#define EV_FORK_ENABLE 0	3906	#define EV_FORK_ENABLE 0
2881	#define EV_CONFIG_H <config.h>	3907	#define EV_CONFIG_H <config.h>
2882	#define EV_MINPRI 0	3908	#define EV_MINPRI 0
2883	#define EV_MAXPRI 0	3909	#define EV_MAXPRI 0
2884		3910
2885	#include "ev++.h"	3911	#include "ev++.h"
2886		3912
2887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3913	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2888		3914
2889	#include "ev_cpp.h"	3915	#include "ev_cpp.h"
2890	#include "ev.c"	3916	#include "ev.c"
2891		3917
		3918	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2892		3919
2893	=head1 COMPLEXITIES	3920	=head2 THREADS AND COROUTINES
2894		3921
2895	In this section the complexities of (many of) the algorithms used inside	3922	=head3 THREADS
2896	libev will be explained. For complexity discussions about backends see the
2897	documentation for C<ev_default_init>.
2898		3923
2899	All of the following are about amortised time: If an array needs to be	3924	All libev functions are reentrant and thread-safe unless explicitly
2900	extended, libev needs to realloc and move the whole array, but this	3925	documented otherwise, but libev implements no locking itself. This means
2901	happens asymptotically never with higher number of elements, so O(1) might	3926	that you can use as many loops as you want in parallel, as long as there
2902	mean it might do a lengthy realloc operation in rare cases, but on average	3927	are no concurrent calls into any libev function with the same loop
2903	it is much faster and asymptotically approaches constant time.	3928	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3929	of course): libev guarantees that different event loops share no data
		3930	structures that need any locking.
		3931
		3932	Or to put it differently: calls with different loop parameters can be done
		3933	concurrently from multiple threads, calls with the same loop parameter
		3934	must be done serially (but can be done from different threads, as long as
		3935	only one thread ever is inside a call at any point in time, e.g. by using
		3936	a mutex per loop).
		3937
		3938	Specifically to support threads (and signal handlers), libev implements
		3939	so-called C<ev_async> watchers, which allow some limited form of
		3940	concurrency on the same event loop, namely waking it up "from the
		3941	outside".
		3942
		3943	If you want to know which design (one loop, locking, or multiple loops
		3944	without or something else still) is best for your problem, then I cannot
		3945	help you, but here is some generic advice:
2904		3946
2905	=over 4	3947	=over 4
2906		3948
2907	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3949	=item * most applications have a main thread: use the default libev loop
		3950	in that thread, or create a separate thread running only the default loop.
2908		3951
2909	This means that, when you have a watcher that triggers in one hour and	3952	This helps integrating other libraries or software modules that use libev
2910	there are 100 watchers that would trigger before that then inserting will	3953	themselves and don't care/know about threading.
2911	have to skip roughly seven (C<ld 100>) of these watchers.
2912		3954
2913	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3955	=item * one loop per thread is usually a good model.
2914		3956
2915	That means that changing a timer costs less than removing/adding them	3957	Doing this is almost never wrong, sometimes a better-performance model
2916	as only the relative motion in the event queue has to be paid for.	3958	exists, but it is always a good start.
2917		3959
2918	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3960	=item * other models exist, such as the leader/follower pattern, where one
		3961	loop is handed through multiple threads in a kind of round-robin fashion.
2919		3962
2920	These just add the watcher into an array or at the head of a list.	3963	Choosing a model is hard - look around, learn, know that usually you can do
		3964	better than you currently do :-)
2921		3965
2922	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3966	=item * often you need to talk to some other thread which blocks in the
		3967	event loop.
2923		3968
2924	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3969	C<ev_async> watchers can be used to wake them up from other threads safely
		3970	(or from signal contexts...).
2925		3971
2926	These watchers are stored in lists then need to be walked to find the	3972	An example use would be to communicate signals or other events that only
2927	correct watcher to remove. The lists are usually short (you don't usually	3973	work in the default loop by registering the signal watcher with the
2928	have many watchers waiting for the same fd or signal).	3974	default loop and triggering an C<ev_async> watcher from the default loop
2929		3975	watcher callback into the event loop interested in the signal.
2930	=item Finding the next timer in each loop iteration: O(1)
2931
2932	By virtue of using a binary heap, the next timer is always found at the
2933	beginning of the storage array.
2934
2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2936
2937	A change means an I/O watcher gets started or stopped, which requires
2938	libev to recalculate its status (and possibly tell the kernel, depending
2939	on backend and wether C<ev_io_set> was used).
2940
2941	=item Activating one watcher (putting it into the pending state): O(1)
2942
2943	=item Priority handling: O(number_of_priorities)
2944
2945	Priorities are implemented by allocating some space for each
2946	priority. When doing priority-based operations, libev usually has to
2947	linearly search all the priorities, but starting/stopping and activating
2948	watchers becomes O(1) w.r.t. priority handling.
2949
2950	=item Sending an ev_async: O(1)
2951
2952	=item Processing ev_async_send: O(number_of_async_watchers)
2953
2954	=item Processing signals: O(max_signal_number)
2955
2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>
2957	calls in the current loop iteration. Checking for async and signal events
2958	involves iterating over all running async watchers or all signal numbers.
2959		3976
2960	=back	3977	=back
2961		3978
		3979	=head4 THREAD LOCKING EXAMPLE
2962		3980
2963	=head1 Win32 platform limitations and workarounds	3981	Here is a fictitious example of how to run an event loop in a different
		3982	thread than where callbacks are being invoked and watchers are
		3983	created/added/removed.
		3984
		3985	For a real-world example, see the C<EV::Loop::Async> perl module,
		3986	which uses exactly this technique (which is suited for many high-level
		3987	languages).
		3988
		3989	The example uses a pthread mutex to protect the loop data, a condition
		3990	variable to wait for callback invocations, an async watcher to notify the
		3991	event loop thread and an unspecified mechanism to wake up the main thread.
		3992
		3993	First, you need to associate some data with the event loop:
		3994
		3995	typedef struct {
		3996	mutex_t lock; /* global loop lock */
		3997	ev_async async_w;
		3998	thread_t tid;
		3999	cond_t invoke_cv;
		4000	} userdata;
		4001
		4002	void prepare_loop (EV_P)
		4003	{
		4004	// for simplicity, we use a static userdata struct.
		4005	static userdata u;
		4006
		4007	ev_async_init (&u->async_w, async_cb);
		4008	ev_async_start (EV_A_ &u->async_w);
		4009
		4010	pthread_mutex_init (&u->lock, 0);
		4011	pthread_cond_init (&u->invoke_cv, 0);
		4012
		4013	// now associate this with the loop
		4014	ev_set_userdata (EV_A_ u);
		4015	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4016	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4017
		4018	// then create the thread running ev_loop
		4019	pthread_create (&u->tid, 0, l_run, EV_A);
		4020	}
		4021
		4022	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4023	solely to wake up the event loop so it takes notice of any new watchers
		4024	that might have been added:
		4025
		4026	static void
		4027	async_cb (EV_P_ ev_async *w, int revents)
		4028	{
		4029	// just used for the side effects
		4030	}
		4031
		4032	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4033	protecting the loop data, respectively.
		4034
		4035	static void
		4036	l_release (EV_P)
		4037	{
		4038	userdata *u = ev_userdata (EV_A);
		4039	pthread_mutex_unlock (&u->lock);
		4040	}
		4041
		4042	static void
		4043	l_acquire (EV_P)
		4044	{
		4045	userdata *u = ev_userdata (EV_A);
		4046	pthread_mutex_lock (&u->lock);
		4047	}
		4048
		4049	The event loop thread first acquires the mutex, and then jumps straight
		4050	into C<ev_loop>:
		4051
		4052	void *
		4053	l_run (void *thr_arg)
		4054	{
		4055	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4056
		4057	l_acquire (EV_A);
		4058	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4059	ev_loop (EV_A_ 0);
		4060	l_release (EV_A);
		4061
		4062	return 0;
		4063	}
		4064
		4065	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4066	signal the main thread via some unspecified mechanism (signals? pipe
		4067	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4068	have been called (in a while loop because a) spurious wakeups are possible
		4069	and b) skipping inter-thread-communication when there are no pending
		4070	watchers is very beneficial):
		4071
		4072	static void
		4073	l_invoke (EV_P)
		4074	{
		4075	userdata *u = ev_userdata (EV_A);
		4076
		4077	while (ev_pending_count (EV_A))
		4078	{
		4079	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4080	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4081	}
		4082	}
		4083
		4084	Now, whenever the main thread gets told to invoke pending watchers, it
		4085	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4086	thread to continue:
		4087
		4088	static void
		4089	real_invoke_pending (EV_P)
		4090	{
		4091	userdata *u = ev_userdata (EV_A);
		4092
		4093	pthread_mutex_lock (&u->lock);
		4094	ev_invoke_pending (EV_A);
		4095	pthread_cond_signal (&u->invoke_cv);
		4096	pthread_mutex_unlock (&u->lock);
		4097	}
		4098
		4099	Whenever you want to start/stop a watcher or do other modifications to an
		4100	event loop, you will now have to lock:
		4101
		4102	ev_timer timeout_watcher;
		4103	userdata *u = ev_userdata (EV_A);
		4104
		4105	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4106
		4107	pthread_mutex_lock (&u->lock);
		4108	ev_timer_start (EV_A_ &timeout_watcher);
		4109	ev_async_send (EV_A_ &u->async_w);
		4110	pthread_mutex_unlock (&u->lock);
		4111
		4112	Note that sending the C<ev_async> watcher is required because otherwise
		4113	an event loop currently blocking in the kernel will have no knowledge
		4114	about the newly added timer. By waking up the loop it will pick up any new
		4115	watchers in the next event loop iteration.
		4116
		4117	=head3 COROUTINES
		4118
		4119	Libev is very accommodating to coroutines ("cooperative threads"):
		4120	libev fully supports nesting calls to its functions from different
		4121	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		4122	different coroutines, and switch freely between both coroutines running
		4123	the loop, as long as you don't confuse yourself). The only exception is
		4124	that you must not do this from C<ev_periodic> reschedule callbacks.
		4125
		4126	Care has been taken to ensure that libev does not keep local state inside
		4127	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4128	they do not call any callbacks.
		4129
		4130	=head2 COMPILER WARNINGS
		4131
		4132	Depending on your compiler and compiler settings, you might get no or a
		4133	lot of warnings when compiling libev code. Some people are apparently
		4134	scared by this.
		4135
		4136	However, these are unavoidable for many reasons. For one, each compiler
		4137	has different warnings, and each user has different tastes regarding
		4138	warning options. "Warn-free" code therefore cannot be a goal except when
		4139	targeting a specific compiler and compiler-version.
		4140
		4141	Another reason is that some compiler warnings require elaborate
		4142	workarounds, or other changes to the code that make it less clear and less
		4143	maintainable.
		4144
		4145	And of course, some compiler warnings are just plain stupid, or simply
		4146	wrong (because they don't actually warn about the condition their message
		4147	seems to warn about). For example, certain older gcc versions had some
		4148	warnings that resulted an extreme number of false positives. These have
		4149	been fixed, but some people still insist on making code warn-free with
		4150	such buggy versions.
		4151
		4152	While libev is written to generate as few warnings as possible,
		4153	"warn-free" code is not a goal, and it is recommended not to build libev
		4154	with any compiler warnings enabled unless you are prepared to cope with
		4155	them (e.g. by ignoring them). Remember that warnings are just that:
		4156	warnings, not errors, or proof of bugs.
		4157
		4158
		4159	=head2 VALGRIND
		4160
		4161	Valgrind has a special section here because it is a popular tool that is
		4162	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4163
		4164	If you think you found a bug (memory leak, uninitialised data access etc.)
		4165	in libev, then check twice: If valgrind reports something like:
		4166
		4167	==2274== definitely lost: 0 bytes in 0 blocks.
		4168	==2274== possibly lost: 0 bytes in 0 blocks.
		4169	==2274== still reachable: 256 bytes in 1 blocks.
		4170
		4171	Then there is no memory leak, just as memory accounted to global variables
		4172	is not a memleak - the memory is still being referenced, and didn't leak.
		4173
		4174	Similarly, under some circumstances, valgrind might report kernel bugs
		4175	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4176	although an acceptable workaround has been found here), or it might be
		4177	confused.
		4178
		4179	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4180	make it into some kind of religion.
		4181
		4182	If you are unsure about something, feel free to contact the mailing list
		4183	with the full valgrind report and an explanation on why you think this
		4184	is a bug in libev (best check the archives, too :). However, don't be
		4185	annoyed when you get a brisk "this is no bug" answer and take the chance
		4186	of learning how to interpret valgrind properly.
		4187
		4188	If you need, for some reason, empty reports from valgrind for your project
		4189	I suggest using suppression lists.
		4190
		4191
		4192	=head1 PORTABILITY NOTES
		4193
		4194	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2964		4195
2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4196	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2966	requires, and its I/O model is fundamentally incompatible with the POSIX	4197	requires, and its I/O model is fundamentally incompatible with the POSIX
2967	model. Libev still offers limited functionality on this platform in	4198	model. Libev still offers limited functionality on this platform in
2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2969	descriptors. This only applies when using Win32 natively, not when using	4200	descriptors. This only applies when using Win32 natively, not when using
2970	e.g. cygwin.	4201	e.g. cygwin.
2971		4202
		4203	Lifting these limitations would basically require the full
		4204	re-implementation of the I/O system. If you are into these kinds of
		4205	things, then note that glib does exactly that for you in a very portable
		4206	way (note also that glib is the slowest event library known to man).
		4207
2972	There is no supported compilation method available on windows except	4208	There is no supported compilation method available on windows except
2973	embedding it into other applications.	4209	embedding it into other applications.
2974		4210
		4211	Sensible signal handling is officially unsupported by Microsoft - libev
		4212	tries its best, but under most conditions, signals will simply not work.
		4213
		4214	Not a libev limitation but worth mentioning: windows apparently doesn't
		4215	accept large writes: instead of resulting in a partial write, windows will
		4216	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4217	so make sure you only write small amounts into your sockets (less than a
		4218	megabyte seems safe, but this apparently depends on the amount of memory
		4219	available).
		4220
2975	Due to the many, low, and arbitrary limits on the win32 platform and the	4221	Due to the many, low, and arbitrary limits on the win32 platform and
2976	abysmal performance of winsockets, using a large number of sockets is not	4222	the abysmal performance of winsockets, using a large number of sockets
2977	recommended (and not reasonable). If your program needs to use more than	4223	is not recommended (and not reasonable). If your program needs to use
2978	a hundred or so sockets, then likely it needs to use a totally different	4224	more than a hundred or so sockets, then likely it needs to use a totally
2979	implementation for windows, as libev offers the POSIX model, which cannot	4225	different implementation for windows, as libev offers the POSIX readiness
2980	be implemented efficiently on windows (microsoft monopoly games).	4226	notification model, which cannot be implemented efficiently on windows
		4227	(due to Microsoft monopoly games).
		4228
		4229	A typical way to use libev under windows is to embed it (see the embedding
		4230	section for details) and use the following F<evwrap.h> header file instead
		4231	of F<ev.h>:
		4232
		4233	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4234	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4235
		4236	#include "ev.h"
		4237
		4238	And compile the following F<evwrap.c> file into your project (make sure
		4239	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4240
		4241	#include "evwrap.h"
		4242	#include "ev.c"
2981		4243
2982	=over 4	4244	=over 4
2983		4245
2984	=item The winsocket select function	4246	=item The winsocket select function
2985		4247
2986	The winsocket C<select> function doesn't follow POSIX in that it requires	4248	The winsocket C<select> function doesn't follow POSIX in that it
2987	socket I<handles> and not socket I<file descriptors>. This makes select	4249	requires socket I<handles> and not socket I<file descriptors> (it is
2988	very inefficient, and also requires a mapping from file descriptors	4250	also extremely buggy). This makes select very inefficient, and also
2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4251	requires a mapping from file descriptors to socket handles (the Microsoft
2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4252	C runtime provides the function C<_open_osfhandle> for this). See the
2991	symbols for more info.	4253	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4254	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2992		4255
2993	The configuration for a "naked" win32 using the microsoft runtime	4256	The configuration for a "naked" win32 using the Microsoft runtime
2994	libraries and raw winsocket select is:	4257	libraries and raw winsocket select is:
2995		4258
2996	#define EV_USE_SELECT 1	4259	#define EV_USE_SELECT 1
2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4260	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2998		4261
2999	Note that winsockets handling of fd sets is O(n), so you can easily get a	4262	Note that winsockets handling of fd sets is O(n), so you can easily get a
3000	complexity in the O(n²) range when using win32.	4263	complexity in the O(n²) range when using win32.
3001		4264
3002	=item Limited number of file descriptors	4265	=item Limited number of file descriptors
3003		4266
3004	Windows has numerous arbitrary (and low) limits on things. Early versions	4267	Windows has numerous arbitrary (and low) limits on things.
3005	of winsocket's select only supported waiting for a max. of C<64> handles	4268
		4269	Early versions of winsocket's select only supported waiting for a maximum
3006	(probably owning to the fact that all windows kernels can only wait for	4270	of C<64> handles (probably owning to the fact that all windows kernels
3007	C<64> things at the same time internally; microsoft recommends spawning a	4271	can only wait for C<64> things at the same time internally; Microsoft
3008	chain of threads and wait for 63 handles and the previous thread in each).	4272	recommends spawning a chain of threads and wait for 63 handles and the
		4273	previous thread in each. Sounds great!).
3009		4274
3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4275	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3011	to some high number (e.g. C<2048>) before compiling the winsocket select	4276	to some high number (e.g. C<2048>) before compiling the winsocket select
3012	call (which might be in libev or elsewhere, for example, perl does its own	4277	call (which might be in libev or elsewhere, for example, perl and many
3013	select emulation on windows).	4278	other interpreters do their own select emulation on windows).
3014		4279
3015	Another limit is the number of file descriptors in the microsoft runtime	4280	Another limit is the number of file descriptors in the Microsoft runtime
3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4281	libraries, which by default is C<64> (there must be a hidden I<64>
3017	or something like this inside microsoft). You can increase this by calling	4282	fetish or something like this inside Microsoft). You can increase this
3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4283	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3019	arbitrary limit), but is broken in many versions of the microsoft runtime	4284	(another arbitrary limit), but is broken in many versions of the Microsoft
3020	libraries.
3021
3022	This might get you to about C<512> or C<2048> sockets (depending on	4285	runtime libraries. This might get you to about C<512> or C<2048> sockets
3023	windows version and/or the phase of the moon). To get more, you need to	4286	(depending on windows version and/or the phase of the moon). To get more,
3024	wrap all I/O functions and provide your own fd management, but the cost of	4287	you need to wrap all I/O functions and provide your own fd management, but
3025	calling select (O(n²)) will likely make this unworkable.	4288	the cost of calling select (O(n²)) will likely make this unworkable.
3026		4289
3027	=back	4290	=back
3028		4291
		4292	=head2 PORTABILITY REQUIREMENTS
		4293
		4294	In addition to a working ISO-C implementation and of course the
		4295	backend-specific APIs, libev relies on a few additional extensions:
		4296
		4297	=over 4
		4298
		4299	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4300	calling conventions regardless of C<ev_watcher_type *>.
		4301
		4302	Libev assumes not only that all watcher pointers have the same internal
		4303	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4304	assumes that the same (machine) code can be used to call any watcher
		4305	callback: The watcher callbacks have different type signatures, but libev
		4306	calls them using an C<ev_watcher *> internally.
		4307
		4308	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4309
		4310	The type C<sig_atomic_t volatile> (or whatever is defined as
		4311	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4312	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4313	believed to be sufficiently portable.
		4314
		4315	=item C<sigprocmask> must work in a threaded environment
		4316
		4317	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4318	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4319	pthread implementations will either allow C<sigprocmask> in the "main
		4320	thread" or will block signals process-wide, both behaviours would
		4321	be compatible with libev. Interaction between C<sigprocmask> and
		4322	C<pthread_sigmask> could complicate things, however.
		4323
		4324	The most portable way to handle signals is to block signals in all threads
		4325	except the initial one, and run the default loop in the initial thread as
		4326	well.
		4327
		4328	=item C<long> must be large enough for common memory allocation sizes
		4329
		4330	To improve portability and simplify its API, libev uses C<long> internally
		4331	instead of C<size_t> when allocating its data structures. On non-POSIX
		4332	systems (Microsoft...) this might be unexpectedly low, but is still at
		4333	least 31 bits everywhere, which is enough for hundreds of millions of
		4334	watchers.
		4335
		4336	=item C<double> must hold a time value in seconds with enough accuracy
		4337
		4338	The type C<double> is used to represent timestamps. It is required to
		4339	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4340	enough for at least into the year 4000. This requirement is fulfilled by
		4341	implementations implementing IEEE 754, which is basically all existing
		4342	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4343	2200.
		4344
		4345	=back
		4346
		4347	If you know of other additional requirements drop me a note.
		4348
		4349
		4350	=head1 ALGORITHMIC COMPLEXITIES
		4351
		4352	In this section the complexities of (many of) the algorithms used inside
		4353	libev will be documented. For complexity discussions about backends see
		4354	the documentation for C<ev_default_init>.
		4355
		4356	All of the following are about amortised time: If an array needs to be
		4357	extended, libev needs to realloc and move the whole array, but this
		4358	happens asymptotically rarer with higher number of elements, so O(1) might
		4359	mean that libev does a lengthy realloc operation in rare cases, but on
		4360	average it is much faster and asymptotically approaches constant time.
		4361
		4362	=over 4
		4363
		4364	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4365
		4366	This means that, when you have a watcher that triggers in one hour and
		4367	there are 100 watchers that would trigger before that, then inserting will
		4368	have to skip roughly seven (C<ld 100>) of these watchers.
		4369
		4370	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4371
		4372	That means that changing a timer costs less than removing/adding them,
		4373	as only the relative motion in the event queue has to be paid for.
		4374
		4375	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4376
		4377	These just add the watcher into an array or at the head of a list.
		4378
		4379	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4380
		4381	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4382
		4383	These watchers are stored in lists, so they need to be walked to find the
		4384	correct watcher to remove. The lists are usually short (you don't usually
		4385	have many watchers waiting for the same fd or signal: one is typical, two
		4386	is rare).
		4387
		4388	=item Finding the next timer in each loop iteration: O(1)
		4389
		4390	By virtue of using a binary or 4-heap, the next timer is always found at a
		4391	fixed position in the storage array.
		4392
		4393	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4394
		4395	A change means an I/O watcher gets started or stopped, which requires
		4396	libev to recalculate its status (and possibly tell the kernel, depending
		4397	on backend and whether C<ev_io_set> was used).
		4398
		4399	=item Activating one watcher (putting it into the pending state): O(1)
		4400
		4401	=item Priority handling: O(number_of_priorities)
		4402
		4403	Priorities are implemented by allocating some space for each
		4404	priority. When doing priority-based operations, libev usually has to
		4405	linearly search all the priorities, but starting/stopping and activating
		4406	watchers becomes O(1) with respect to priority handling.
		4407
		4408	=item Sending an ev_async: O(1)
		4409
		4410	=item Processing ev_async_send: O(number_of_async_watchers)
		4411
		4412	=item Processing signals: O(max_signal_number)
		4413
		4414	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4415	calls in the current loop iteration. Checking for async and signal events
		4416	involves iterating over all running async watchers or all signal numbers.
		4417
		4418	=back
		4419
		4420
		4421	=head1 GLOSSARY
		4422
		4423	=over 4
		4424
		4425	=item active
		4426
		4427	A watcher is active as long as it has been started (has been attached to
		4428	an event loop) but not yet stopped (disassociated from the event loop).
		4429
		4430	=item application
		4431
		4432	In this document, an application is whatever is using libev.
		4433
		4434	=item callback
		4435
		4436	The address of a function that is called when some event has been
		4437	detected. Callbacks are being passed the event loop, the watcher that
		4438	received the event, and the actual event bitset.
		4439
		4440	=item callback invocation
		4441
		4442	The act of calling the callback associated with a watcher.
		4443
		4444	=item event
		4445
		4446	A change of state of some external event, such as data now being available
		4447	for reading on a file descriptor, time having passed or simply not having
		4448	any other events happening anymore.
		4449
		4450	In libev, events are represented as single bits (such as C<EV_READ> or
		4451	C<EV_TIMEOUT>).
		4452
		4453	=item event library
		4454
		4455	A software package implementing an event model and loop.
		4456
		4457	=item event loop
		4458
		4459	An entity that handles and processes external events and converts them
		4460	into callback invocations.
		4461
		4462	=item event model
		4463
		4464	The model used to describe how an event loop handles and processes
		4465	watchers and events.
		4466
		4467	=item pending
		4468
		4469	A watcher is pending as soon as the corresponding event has been detected,
		4470	and stops being pending as soon as the watcher will be invoked or its
		4471	pending status is explicitly cleared by the application.
		4472
		4473	A watcher can be pending, but not active. Stopping a watcher also clears
		4474	its pending status.
		4475
		4476	=item real time
		4477
		4478	The physical time that is observed. It is apparently strictly monotonic :)
		4479
		4480	=item wall-clock time
		4481
		4482	The time and date as shown on clocks. Unlike real time, it can actually
		4483	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4484	clock.
		4485
		4486	=item watcher
		4487
		4488	A data structure that describes interest in certain events. Watchers need
		4489	to be started (attached to an event loop) before they can receive events.
		4490
		4491	=item watcher invocation
		4492
		4493	The act of calling the callback associated with a watcher.
		4494
		4495	=back
3029		4496
3030	=head1 AUTHOR	4497	=head1 AUTHOR
3031		4498
3032	Marc Lehmann <libev@schmorp.de>.	4499	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3033		4500

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