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Revision 1.121 by root, Mon Jan 28 12:13:54 2008 UTC vs.
Revision 1.195 by root, Mon Oct 20 17:50:48 2008 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	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	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	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	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	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	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>	107	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.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	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	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	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	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	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	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	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	203	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	204	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	205	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	206	(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.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	215	recommended ones.
180		216
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	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	223	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	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	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,	232	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.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
211	}	250	}
212		251
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
217		256
218	Set the callback function to call on a retryable syscall error (such	257	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	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	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	260	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	261	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	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245		284
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
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
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
257	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
263	function.	295	function.
264		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
265	The default loop is the only loop that can handle C<ev_signal> and	301	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	302	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	303	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	304	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	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	306	C<ev_default_init>.
271		307
272	The flags argument can be used to specify special behaviour or specific	308	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	317	The default flags value. Use this if you have no clue (it's the right
282	thing, believe me).	318	thing, believe me).
283		319
284	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
285		321
286	If this flag bit is ored into the flag value (or the program runs setuid	322	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	323	or setgid) then libev will I<not> look at the environment variable
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	override the flags completely if it is found in the environment. This is	325	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	326	useful to try out specific backends to test their performance, or to work
291	around bugs.	327	around bugs.
…		…
297	enabling this flag.	333	enabling this flag.
298		334
299	This works by calling C<getpid ()> on every iteration of the loop,	335	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	336	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	337	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	338	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	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
304	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
305		341
306	The big advantage of this flag is that you can forget about fork (and	342	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	343	forget about forgetting to tell libev about forking) when you use this
308	flag.	344	flag.
309		345
310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
311	environment variable.	347	environment variable.
312		348
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		350
315	This is your standard select(2) backend. Not I<completely> standard, as	351	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	353	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	354	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.	355	usually the fastest backend for a low number of (low-numbered :) fds.
320		356
321	To get good performance out of this backend you need a high amount of	357	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	358	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	359	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	360	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	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
326	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
327		367
328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
329		369
330	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
331	than select, but handles sparse fds better and has no artificial	371	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	372	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,	373	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	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
335	performance tips.	375	performance tips.
336		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
337	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
338		381
339	For few fds, this backend is a bit little slower than poll and select,	382	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	383	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),	384	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	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
343	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
344	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
345	support for dup.	388	support for dup.
346		389
347	While stopping, setting and starting an I/O watcher in the same iteration	390	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	391	will result in some caching, there is still a system call per such incident
349	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
351	very well if you register events for both fds.	394	very well if you register events for both fds.
352		395
353	Please note that epoll sometimes generates spurious notifications, so you	396	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	397	need to use non-blocking I/O or other means to avoid blocking when no data
355	(or space) is available.	398	(or space) is available.
356		399
357	Best performance from this backend is achieved by not unregistering all	400	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.	401	watchers for a file descriptor until it has been closed, if possible,
359	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
360		405
361	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
362	all kernel versions tested so far.	407	all kernel versions tested so far.
363		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		413
366	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
367	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
368	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
369	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
370	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
372	system like NetBSD.
373		420
374	You still can embed kqueue into a normal poll or select backend and use it	421	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	422	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.	423	the target platform). See C<ev_embed> watchers for more info.
377		424
378	It scales in the same way as the epoll backend, but the interface to the	425	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	426	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	427	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	428	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	429	two event changes per incident. Support for C<fork ()> is very bad and it
383	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
384		431
385	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
386		433
387	While nominally embeddable in other event loops, this doesn't work	434	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	435	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	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
392	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
393		444
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		446
396	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		453
403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	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)).	455	it's really slow, but it still scales very well (O(active_fds)).
405		456
406	Please note that solaris event ports can deliver a lot of spurious	457	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	458	notifications, so you need to use non-blocking I/O or other means to avoid
408	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
409		460
410	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	464	might perform better.
414		465
415	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
417	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
418		473
419	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
420		475
421	Try all backends (even potentially broken ones that wouldn't be tried	476	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	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
424		479
425	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
426		481
427	=back	482	=back
428		483
429	If one or more of these are ored into the flags value, then only these	484	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	485	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.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		487
433	The most typical usage is like this:	488	Example: This is the most typical usage.
434		489
435	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		492
438	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
439	environment settings to be taken into account:	494	environment settings to be taken into account:
440		495
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		497
443	Use whatever libev has to offer, but make sure that kqueue is used if	498	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	499	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):	500	private event loop and only if you know the OS supports your types of
		501	fds):
446		502
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		504
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		506
451	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	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	508	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	509	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).	510	undefined behaviour (or a failed assertion if assertions are enabled).
455		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
456	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
457		517
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	519	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
461		521
462	=item ev_default_destroy ()	522	=item ev_default_destroy ()
463		523
464	Destroys the default loop again (frees all memory and kernel state	524	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	525	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	526	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>	527	responsibility to either stop all watchers cleanly yourself I<before>
468	calling this function, or cope with the fact afterwards (which is usually	528	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	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
470	for example).	530	for example).
471		531
472	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
504		564
505	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
506		566
507	Like C<ev_default_fork>, but acts on an event loop created by	567	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	568	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.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
510		576
511	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
512		578
513	Returns the count of loop iterations for the loop, which is identical to	579	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	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
529	received events and started processing them. This timestamp does not	595	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	596	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	597	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).	598	event occurring (or more correctly, libev finding out about it).
533		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
534	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
535		613
536	Finally, this is it, the event handler. This function usually is called	614	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	615	after you initialised all your watchers and you want to start handling
538	events.	616	events.
…		…
540	If the flags argument is specified as C<0>, it will not return until	618	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.	619	either no event watchers are active anymore or C<ev_unloop> was called.
542		620
543	Please note that an explicit C<ev_unloop> is usually better than	621	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	622	relying on all watchers to be stopped when deciding when a program has
545	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
546	automatically loops as long as it has to and no longer by virtue of	624	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.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
548		627
549	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	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	629	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.	630	process in case there are no events and will return after one iteration of
		631	the loop.
552		632
553	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	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	634	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	635	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	636	be an event internal to libev itself, so there is no guarentee that a
557	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	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	642	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.	643	usually a better approach for this kind of thing.
560		644
561	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
562		646
563	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
566	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
567	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
568	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	662	- Queue all expired timers.
578	- Queue all outstanding periodics.	663	- Queue all expired periodics.
579	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	665	- Queue all check watchers.
581	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- 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	667	Signals and child watchers are implemented as I/O watchers, and will
583	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
589	anymore.	674	anymore.
590		675
591	... queue jobs here, make sure they register event watchers as long	676	... 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..)	677	... as they still have work to do (even an idle watcher will do..)
593	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
594	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
595		680
596	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
597		682
598	Can be used to make a call to C<ev_loop> return early (but only after it	683	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	684	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	685	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.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602		687
603	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
604		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
605	=item ev_ref (loop)	692	=item ev_ref (loop)
606		693
607	=item ev_unref (loop)	694	=item ev_unref (loop)
608		695
609	Ref/unref can be used to add or remove a reference count on the event	696	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	697	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	698	count is nonzero, C<ev_loop> will not return on its own.
		699
612	a watcher you never unregister that should not keep C<ev_loop> from	700	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	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
614	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
615	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
616	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
617	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
618	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
619	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
620	respectively).	710	respectively).
621		711
622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
623	running when nothing else is active.	713	running when nothing else is active.
624		714
625	struct ev_signal exitsig;	715	struct ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	718	evf_unref (loop);
629		719
630	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
631		721
632	ev_ref (loop);	722	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
634		724
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		726
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		728
639	These advanced functions influence the time that libev will spend waiting	729	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	730	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.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
642		733
643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	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	735	allows libev to delay invocation of I/O and timer/periodic callbacks
645	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
646		738
647	The background is that sometimes your program runs just fast enough to	739	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	740	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	741	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	742	events, especially with backends like C<select ()> which have a high
651	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
652		744
653	By setting a higher I<io collect interval> you allow libev to spend more	745	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,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
656	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	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.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
658		750
659	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
660	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
662	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
663	any overhead in libev.	755	value will not introduce any overhead in libev.
664		756
665	Many (busy) programs can usually benefit by setting the io collect	757	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	758	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	759	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>,	760	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.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
670		781
671	=back	782	=back
672		783
673		784
674	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
675		786
676	A watcher is a structure that you create and register to record your	787	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	788	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:	789	become readable, you would create an C<ev_io> watcher for that:
679		790
680	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
681	{	792	{
682	ev_io_stop (w);	793	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
684	}	795	}
685		796
686	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
687	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
688	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
691	ev_loop (loop, 0);	802	ev_loop (loop, 0);
692		803
693	As you can see, you are responsible for allocating the memory for your	804	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,	805	watcher structures (and it is usually a bad idea to do this on the stack,
695	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
696		807
697	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
698	(watcher *, callback)>, which expects a callback to be provided. This	809	(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	810	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	811	watchers, each time the event loop detects that the file descriptor given
701	is readable and/or writable).	812	is readable and/or writable).
702		813
703	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
704	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
774	=item C<EV_FORK>	885	=item C<EV_FORK>
775		886
776	The event loop has been resumed in the child process after fork (see	887	The event loop has been resumed in the child process after fork (see
777	C<ev_fork>).	888	C<ev_fork>).
778		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
779	=item C<EV_ERROR>	894	=item C<EV_ERROR>
780		895
781	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
782	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
783	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
784	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
785	with the watcher being stopped.	900	with the watcher being stopped.
786		901
787	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
788	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
789	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
790	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
791	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
792		908
793	=back	909	=back
794		910
795	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
796		912
…		…
812	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
813		929
814	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
815	int revents)>.	931	int revents)>.
816		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
817	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
818		940
819	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
820	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
821	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
823	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
824		946
825	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
826	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
827		949
		950	See C<ev_init>, above, for an example.
		951
828	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
829		953
830	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
831	calls into a single call. This is the most convinient method to initialise	955	calls into a single call. This is the most convenient method to initialise
832	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
833		961
834	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
835		963
836	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
837	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
838		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
		971
839	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
840		973
841	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher if active, and clears the pending status (whether
		975	the watcher was active or not).
		976
842	status. It is possible that stopped watchers are pending (for example,	977	It is possible that stopped watchers are pending - for example,
843	non-repeating timers are being stopped when they become pending), but	978	non-repeating timers are being stopped when they become pending - but
844	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	979	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
845	you want to free or reuse the memory used by the watcher it is therefore a	980	pending. If you want to free or reuse the memory used by the watcher it is
846	good idea to always call its C<ev_TYPE_stop> function.	981	therefore a good idea to always call its C<ev_TYPE_stop> function.
847		982
848	=item bool ev_is_active (ev_TYPE *watcher)	983	=item bool ev_is_active (ev_TYPE *watcher)
849		984
850	Returns a true value iff the watcher is active (i.e. it has been started	985	Returns a true value iff the watcher is active (i.e. it has been started
851	and not yet been stopped). As long as a watcher is active you must not modify	986	and not yet been stopped). As long as a watcher is active you must not modify
…		…
899		1034
900	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
901		1036
902	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
903	C<loop> nor C<revents> need to be valid as long as the watcher callback	1038	C<loop> nor C<revents> need to be valid as long as the watcher callback
904	can deal with that fact.	1039	can deal with that fact, as both are simply passed through to the
		1040	callback.
905		1041
906	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1042	=item int ev_clear_pending (loop, ev_TYPE *watcher)
907		1043
908	If the watcher is pending, this function returns clears its pending status	1044	If the watcher is pending, this function clears its pending status and
909	and returns its C<revents> bitset (as if its callback was invoked). If the	1045	returns its C<revents> bitset (as if its callback was invoked). If the
910	watcher isn't pending it does nothing and returns C<0>.	1046	watcher isn't pending it does nothing and returns C<0>.
911		1047
		1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1049	callback to be invoked, which can be accomplished with this function.
		1050
912	=back	1051	=back
913		1052
914		1053
915	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
916		1055
917	Each watcher has, by default, a member C<void *data> that you can change	1056	Each watcher has, by default, a member C<void *data> that you can change
918	and read at any time, libev will completely ignore it. This can be used	1057	and read at any time: libev will completely ignore it. This can be used
919	to associate arbitrary data with your watcher. If you need more data and	1058	to associate arbitrary data with your watcher. If you need more data and
920	don't want to allocate memory and store a pointer to it in that data	1059	don't want to allocate memory and store a pointer to it in that data
921	member, you can also "subclass" the watcher type and provide your own	1060	member, you can also "subclass" the watcher type and provide your own
922	data:	1061	data:
923		1062
924	struct my_io	1063	struct my_io
925	{	1064	{
926	struct ev_io io;	1065	struct ev_io io;
927	int otherfd;	1066	int otherfd;
928	void *somedata;	1067	void *somedata;
929	struct whatever *mostinteresting;	1068	struct whatever *mostinteresting;
930	}	1069	};
		1070
		1071	...
		1072	struct my_io w;
		1073	ev_io_init (&w.io, my_cb, fd, EV_READ);
931		1074
932	And since your callback will be called with a pointer to the watcher, you	1075	And since your callback will be called with a pointer to the watcher, you
933	can cast it back to your own type:	1076	can cast it back to your own type:
934		1077
935	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
936	{	1079	{
937	struct my_io *w = (struct my_io *)w_;	1080	struct my_io *w = (struct my_io *)w_;
938	...	1081	...
939	}	1082	}
940		1083
941	More interesting and less C-conformant ways of casting your callback type	1084	More interesting and less C-conformant ways of casting your callback type
942	instead have been omitted.	1085	instead have been omitted.
943		1086
944	Another common scenario is having some data structure with multiple	1087	Another common scenario is to use some data structure with multiple
945	watchers:	1088	embedded watchers:
946		1089
947	struct my_biggy	1090	struct my_biggy
948	{	1091	{
949	int some_data;	1092	int some_data;
950	ev_timer t1;	1093	ev_timer t1;
951	ev_timer t2;	1094	ev_timer t2;
952	}	1095	}
953		1096
954	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1097	In this case getting the pointer to C<my_biggy> is a bit more
955	you need to use C<offsetof>:	1098	complicated: Either you store the address of your C<my_biggy> struct
		1099	in the C<data> member of the watcher (for woozies), or you need to use
		1100	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1101	programmers):
956		1102
957	#include <stddef.h>	1103	#include <stddef.h>
958		1104
959	static void	1105	static void
960	t1_cb (EV_P_ struct ev_timer *w, int revents)	1106	t1_cb (EV_P_ struct ev_timer *w, int revents)
961	{	1107	{
962	struct my_biggy big = (struct my_biggy *	1108	struct my_biggy big = (struct my_biggy *
963	(((char *)w) - offsetof (struct my_biggy, t1));	1109	(((char *)w) - offsetof (struct my_biggy, t1));
964	}	1110	}
965		1111
966	static void	1112	static void
967	t2_cb (EV_P_ struct ev_timer *w, int revents)	1113	t2_cb (EV_P_ struct ev_timer *w, int revents)
968	{	1114	{
969	struct my_biggy big = (struct my_biggy *	1115	struct my_biggy big = (struct my_biggy *
970	(((char *)w) - offsetof (struct my_biggy, t2));	1116	(((char *)w) - offsetof (struct my_biggy, t2));
971	}	1117	}
972		1118
973		1119
974	=head1 WATCHER TYPES	1120	=head1 WATCHER TYPES
975		1121
976	This section describes each watcher in detail, but will not repeat	1122	This section describes each watcher in detail, but will not repeat
…		…
1000	In general you can register as many read and/or write event watchers per	1146	In general you can register as many read and/or write event watchers per
1001	fd as you want (as long as you don't confuse yourself). Setting all file	1147	fd as you want (as long as you don't confuse yourself). Setting all file
1002	descriptors to non-blocking mode is also usually a good idea (but not	1148	descriptors to non-blocking mode is also usually a good idea (but not
1003	required if you know what you are doing).	1149	required if you know what you are doing).
1004		1150
1005	If you must do this, then force the use of a known-to-be-good backend	1151	If you cannot use non-blocking mode, then force the use of a
1006	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1152	known-to-be-good backend (at the time of this writing, this includes only
1007	C<EVBACKEND_POLL>).	1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1008		1154
1009	Another thing you have to watch out for is that it is quite easy to	1155	Another thing you have to watch out for is that it is quite easy to
1010	receive "spurious" readyness notifications, that is your callback might	1156	receive "spurious" readiness notifications, that is your callback might
1011	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1012	because there is no data. Not only are some backends known to create a	1158	because there is no data. Not only are some backends known to create a
1013	lot of those (for example solaris ports), it is very easy to get into	1159	lot of those (for example Solaris ports), it is very easy to get into
1014	this situation even with a relatively standard program structure. Thus	1160	this situation even with a relatively standard program structure. Thus
1015	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1161	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1016	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1162	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1017		1163
1018	If you cannot run the fd in non-blocking mode (for example you should not	1164	If you cannot run the fd in non-blocking mode (for example you should
1019	play around with an Xlib connection), then you have to seperately re-test	1165	not play around with an Xlib connection), then you have to separately
1020	whether a file descriptor is really ready with a known-to-be good interface	1166	re-test whether a file descriptor is really ready with a known-to-be good
1021	such as poll (fortunately in our Xlib example, Xlib already does this on	1167	interface such as poll (fortunately in our Xlib example, Xlib already
1022	its own, so its quite safe to use).	1168	does this on its own, so its quite safe to use). Some people additionally
		1169	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1170	indefinitely.
		1171
		1172	But really, best use non-blocking mode.
1023		1173
1024	=head3 The special problem of disappearing file descriptors	1174	=head3 The special problem of disappearing file descriptors
1025		1175
1026	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1176	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1027	descriptor (either by calling C<close> explicitly or by any other means,	1177	descriptor (either due to calling C<close> explicitly or any other means,
1028	such as C<dup>). The reason is that you register interest in some file	1178	such as C<dup2>). The reason is that you register interest in some file
1029	descriptor, but when it goes away, the operating system will silently drop	1179	descriptor, but when it goes away, the operating system will silently drop
1030	this interest. If another file descriptor with the same number then is	1180	this interest. If another file descriptor with the same number then is
1031	registered with libev, there is no efficient way to see that this is, in	1181	registered with libev, there is no efficient way to see that this is, in
1032	fact, a different file descriptor.	1182	fact, a different file descriptor.
1033		1183
…		…
1062	To support fork in your programs, you either have to call	1212	To support fork in your programs, you either have to call
1063	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1213	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1064	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1214	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1065	C<EVBACKEND_POLL>.	1215	C<EVBACKEND_POLL>.
1066		1216
		1217	=head3 The special problem of SIGPIPE
		1218
		1219	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1220	when writing to a pipe whose other end has been closed, your program gets
		1221	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1222	this is sensible behaviour, for daemons, this is usually undesirable.
		1223
		1224	So when you encounter spurious, unexplained daemon exits, make sure you
		1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1226	somewhere, as that would have given you a big clue).
		1227
1067		1228
1068	=head3 Watcher-Specific Functions	1229	=head3 Watcher-Specific Functions
1069		1230
1070	=over 4	1231	=over 4
1071		1232
1072	=item ev_io_init (ev_io *, callback, int fd, int events)	1233	=item ev_io_init (ev_io *, callback, int fd, int events)
1073		1234
1074	=item ev_io_set (ev_io *, int fd, int events)	1235	=item ev_io_set (ev_io *, int fd, int events)
1075		1236
1076	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1237	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1077	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1238	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1078	C<EV_READ | EV_WRITE> to receive the given events.	1239	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1079		1240
1080	=item int fd [read-only]	1241	=item int fd [read-only]
1081		1242
1082	The file descriptor being watched.	1243	The file descriptor being watched.
1083		1244
…		…
1091		1252
1092	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1093	readable, but only once. Since it is likely line-buffered, you could	1254	readable, but only once. Since it is likely line-buffered, you could
1094	attempt to read a whole line in the callback.	1255	attempt to read a whole line in the callback.
1095		1256
1096	static void	1257	static void
1097	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1098	{	1259	{
1099	ev_io_stop (loop, w);	1260	ev_io_stop (loop, w);
1100	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1261	.. read from stdin here (or from w->fd) and handle any I/O errors
1101	}	1262	}
1102		1263
1103	...	1264	...
1104	struct ev_loop *loop = ev_default_init (0);	1265	struct ev_loop *loop = ev_default_init (0);
1105	struct ev_io stdin_readable;	1266	struct ev_io stdin_readable;
1106	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1107	ev_io_start (loop, &stdin_readable);	1268	ev_io_start (loop, &stdin_readable);
1108	ev_loop (loop, 0);	1269	ev_loop (loop, 0);
1109		1270
1110		1271
1111	=head2 C<ev_timer> - relative and optionally repeating timeouts	1272	=head2 C<ev_timer> - relative and optionally repeating timeouts
1112		1273
1113	Timer watchers are simple relative timers that generate an event after a	1274	Timer watchers are simple relative timers that generate an event after a
1114	given time, and optionally repeating in regular intervals after that.	1275	given time, and optionally repeating in regular intervals after that.
1115		1276
1116	The timers are based on real time, that is, if you register an event that	1277	The timers are based on real time, that is, if you register an event that
1117	times out after an hour and you reset your system clock to last years	1278	times out after an hour and you reset your system clock to January last
1118	time, it will still time out after (roughly) and hour. "Roughly" because	1279	year, it will still time out after (roughly) one hour. "Roughly" because
1119	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1120	monotonic clock option helps a lot here).	1281	monotonic clock option helps a lot here).
		1282
		1283	The callback is guaranteed to be invoked only I<after> its timeout has
		1284	passed, but if multiple timers become ready during the same loop iteration
		1285	then order of execution is undefined.
		1286
		1287	=head3 The special problem of time updates
		1288
		1289	Establishing the current time is a costly operation (it usually takes at
		1290	least two system calls): EV therefore updates its idea of the current
		1291	time only before and after C<ev_loop> collects new events, which causes a
		1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1293	lots of events in one iteration.
1121		1294
1122	The relative timeouts are calculated relative to the C<ev_now ()>	1295	The relative timeouts are calculated relative to the C<ev_now ()>
1123	time. This is usually the right thing as this timestamp refers to the time	1296	time. This is usually the right thing as this timestamp refers to the time
1124	of the event triggering whatever timeout you are modifying/starting. If	1297	of the event triggering whatever timeout you are modifying/starting. If
1125	you suspect event processing to be delayed and you I<need> to base the timeout	1298	you suspect event processing to be delayed and you I<need> to base the
1126	on the current time, use something like this to adjust for this:	1299	timeout on the current time, use something like this to adjust for this:
1127		1300
1128	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1301	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1129		1302
1130	The callback is guarenteed to be invoked only when its timeout has passed,	1303	If the event loop is suspended for a long time, you can also force an
1131	but if multiple timers become ready during the same loop iteration then	1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1132	order of execution is undefined.	1305	()>.
1133		1306
1134	=head3 Watcher-Specific Functions and Data Members	1307	=head3 Watcher-Specific Functions and Data Members
1135		1308
1136	=over 4	1309	=over 4
1137		1310
1138	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1139		1312
1140	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1313	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1141		1314
1142	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1315	Configure the timer to trigger after C<after> seconds. If C<repeat>
1143	C<0.>, then it will automatically be stopped. If it is positive, then the	1316	is C<0.>, then it will automatically be stopped once the timeout is
1144	timer will automatically be configured to trigger again C<repeat> seconds	1317	reached. If it is positive, then the timer will automatically be
1145	later, again, and again, until stopped manually.	1318	configured to trigger again C<repeat> seconds later, again, and again,
		1319	until stopped manually.
1146		1320
1147	The timer itself will do a best-effort at avoiding drift, that is, if you	1321	The timer itself will do a best-effort at avoiding drift, that is, if
1148	configure a timer to trigger every 10 seconds, then it will trigger at	1322	you configure a timer to trigger every 10 seconds, then it will normally
1149	exactly 10 second intervals. If, however, your program cannot keep up with	1323	trigger at exactly 10 second intervals. If, however, your program cannot
1150	the timer (because it takes longer than those 10 seconds to do stuff) the	1324	keep up with the timer (because it takes longer than those 10 seconds to
1151	timer will not fire more than once per event loop iteration.	1325	do stuff) the timer will not fire more than once per event loop iteration.
1152		1326
1153	=item ev_timer_again (loop)	1327	=item ev_timer_again (loop, ev_timer *)
1154		1328
1155	This will act as if the timer timed out and restart it again if it is	1329	This will act as if the timer timed out and restart it again if it is
1156	repeating. The exact semantics are:	1330	repeating. The exact semantics are:
1157		1331
1158	If the timer is pending, its pending status is cleared.	1332	If the timer is pending, its pending status is cleared.
1159		1333
1160	If the timer is started but nonrepeating, stop it (as if it timed out).	1334	If the timer is started but non-repeating, stop it (as if it timed out).
1161		1335
1162	If the timer is repeating, either start it if necessary (with the	1336	If the timer is repeating, either start it if necessary (with the
1163	C<repeat> value), or reset the running timer to the C<repeat> value.	1337	C<repeat> value), or reset the running timer to the C<repeat> value.
1164		1338
1165	This sounds a bit complicated, but here is a useful and typical	1339	This sounds a bit complicated, but here is a useful and typical
1166	example: Imagine you have a tcp connection and you want a so-called idle	1340	example: Imagine you have a TCP connection and you want a so-called idle
1167	timeout, that is, you want to be called when there have been, say, 60	1341	timeout, that is, you want to be called when there have been, say, 60
1168	seconds of inactivity on the socket. The easiest way to do this is to	1342	seconds of inactivity on the socket. The easiest way to do this is to
1169	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1170	C<ev_timer_again> each time you successfully read or write some data. If	1344	C<ev_timer_again> each time you successfully read or write some data. If
1171	you go into an idle state where you do not expect data to travel on the	1345	you go into an idle state where you do not expect data to travel on the
…		…
1185	ev_timer_again (loop, timer);	1359	ev_timer_again (loop, timer);
1186		1360
1187	This is more slightly efficient then stopping/starting the timer each time	1361	This is more slightly efficient then stopping/starting the timer each time
1188	you want to modify its timeout value.	1362	you want to modify its timeout value.
1189		1363
		1364	Note, however, that it is often even more efficient to remember the
		1365	time of the last activity and let the timer time-out naturally. In the
		1366	callback, you then check whether the time-out is real, or, if there was
		1367	some activity, you reschedule the watcher to time-out in "last_activity +
		1368	timeout - ev_now ()" seconds.
		1369
1190	=item ev_tstamp repeat [read-write]	1370	=item ev_tstamp repeat [read-write]
1191		1371
1192	The current C<repeat> value. Will be used each time the watcher times out	1372	The current C<repeat> value. Will be used each time the watcher times out
1193	or C<ev_timer_again> is called and determines the next timeout (if any),	1373	or C<ev_timer_again> is called, and determines the next timeout (if any),
1194	which is also when any modifications are taken into account.	1374	which is also when any modifications are taken into account.
1195		1375
1196	=back	1376	=back
1197		1377
1198	=head3 Examples	1378	=head3 Examples
1199		1379
1200	Example: Create a timer that fires after 60 seconds.	1380	Example: Create a timer that fires after 60 seconds.
1201		1381
1202	static void	1382	static void
1203	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1204	{	1384	{
1205	.. one minute over, w is actually stopped right here	1385	.. one minute over, w is actually stopped right here
1206	}	1386	}
1207		1387
1208	struct ev_timer mytimer;	1388	struct ev_timer mytimer;
1209	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1210	ev_timer_start (loop, &mytimer);	1390	ev_timer_start (loop, &mytimer);
1211		1391
1212	Example: Create a timeout timer that times out after 10 seconds of	1392	Example: Create a timeout timer that times out after 10 seconds of
1213	inactivity.	1393	inactivity.
1214		1394
1215	static void	1395	static void
1216	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1217	{	1397	{
1218	.. ten seconds without any activity	1398	.. ten seconds without any activity
1219	}	1399	}
1220		1400
1221	struct ev_timer mytimer;	1401	struct ev_timer mytimer;
1222	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1223	ev_timer_again (&mytimer); /* start timer */	1403	ev_timer_again (&mytimer); /* start timer */
1224	ev_loop (loop, 0);	1404	ev_loop (loop, 0);
1225		1405
1226	// and in some piece of code that gets executed on any "activity":	1406	// and in some piece of code that gets executed on any "activity":
1227	// reset the timeout to start ticking again at 10 seconds	1407	// reset the timeout to start ticking again at 10 seconds
1228	ev_timer_again (&mytimer);	1408	ev_timer_again (&mytimer);
1229		1409
1230		1410
1231	=head2 C<ev_periodic> - to cron or not to cron?	1411	=head2 C<ev_periodic> - to cron or not to cron?
1232		1412
1233	Periodic watchers are also timers of a kind, but they are very versatile	1413	Periodic watchers are also timers of a kind, but they are very versatile
1234	(and unfortunately a bit complex).	1414	(and unfortunately a bit complex).
1235		1415
1236	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1237	but on wallclock time (absolute time). You can tell a periodic watcher	1417	but on wall clock time (absolute time). You can tell a periodic watcher
1238	to trigger "at" some specific point in time. For example, if you tell a	1418	to trigger after some specific point in time. For example, if you tell a
1239	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1240	+ 10.>) and then reset your system clock to the last year, then it will	1420	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1421	clock to January of the previous year, then it will take more than year
1241	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1242	roughly 10 seconds later).	1423	roughly 10 seconds later as it uses a relative timeout).
1243		1424
1244	They can also be used to implement vastly more complex timers, such as	1425	C<ev_periodic>s can also be used to implement vastly more complex timers,
1245	triggering an event on each midnight, local time or other, complicated,	1426	such as triggering an event on each "midnight, local time", or other
1246	rules.	1427	complicated rules.
1247		1428
1248	As with timers, the callback is guarenteed to be invoked only when the	1429	As with timers, the callback is guaranteed to be invoked only when the
1249	time (C<at>) has been passed, but if multiple periodic timers become ready	1430	time (C<at>) has passed, but if multiple periodic timers become ready
1250	during the same loop iteration then order of execution is undefined.	1431	during the same loop iteration, then order of execution is undefined.
1251		1432
1252	=head3 Watcher-Specific Functions and Data Members	1433	=head3 Watcher-Specific Functions and Data Members
1253		1434
1254	=over 4	1435	=over 4
1255		1436
1256	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1257		1438
1258	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1259		1440
1260	Lots of arguments, lets sort it out... There are basically three modes of	1441	Lots of arguments, lets sort it out... There are basically three modes of
1261	operation, and we will explain them from simplest to complex:	1442	operation, and we will explain them from simplest to most complex:
1262		1443
1263	=over 4	1444	=over 4
1264		1445
1265	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1266		1447
1267	In this configuration the watcher triggers an event at the wallclock time	1448	In this configuration the watcher triggers an event after the wall clock
1268	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1449	time C<at> has passed. It will not repeat and will not adjust when a time
1269	that is, if it is to be run at January 1st 2011 then it will run when the	1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1270	system time reaches or surpasses this time.	1451	only run when the system clock reaches or surpasses this time.
1271		1452
1272	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1273		1454
1274	In this mode the watcher will always be scheduled to time out at the next	1455	In this mode the watcher will always be scheduled to time out at the next
1275	C<at + N * interval> time (for some integer N, which can also be negative)	1456	C<at + N * interval> time (for some integer N, which can also be negative)
1276	and then repeat, regardless of any time jumps.	1457	and then repeat, regardless of any time jumps.
1277		1458
1278	This can be used to create timers that do not drift with respect to system	1459	This can be used to create timers that do not drift with respect to the
1279	time:	1460	system clock, for example, here is a C<ev_periodic> that triggers each
		1461	hour, on the hour:
1280		1462
1281	ev_periodic_set (&periodic, 0., 3600., 0);	1463	ev_periodic_set (&periodic, 0., 3600., 0);
1282		1464
1283	This doesn't mean there will always be 3600 seconds in between triggers,	1465	This doesn't mean there will always be 3600 seconds in between triggers,
1284	but only that the the callback will be called when the system time shows a	1466	but only that the callback will be called when the system time shows a
1285	full hour (UTC), or more correctly, when the system time is evenly divisible	1467	full hour (UTC), or more correctly, when the system time is evenly divisible
1286	by 3600.	1468	by 3600.
1287		1469
1288	Another way to think about it (for the mathematically inclined) is that	1470	Another way to think about it (for the mathematically inclined) is that
1289	C<ev_periodic> will try to run the callback in this mode at the next possible	1471	C<ev_periodic> will try to run the callback in this mode at the next possible
1290	time where C<time = at (mod interval)>, regardless of any time jumps.	1472	time where C<time = at (mod interval)>, regardless of any time jumps.
1291		1473
1292	For numerical stability it is preferable that the C<at> value is near	1474	For numerical stability it is preferable that the C<at> value is near
1293	C<ev_now ()> (the current time), but there is no range requirement for	1475	C<ev_now ()> (the current time), but there is no range requirement for
1294	this value.	1476	this value, and in fact is often specified as zero.
		1477
		1478	Note also that there is an upper limit to how often a timer can fire (CPU
		1479	speed for example), so if C<interval> is very small then timing stability
		1480	will of course deteriorate. Libev itself tries to be exact to be about one
		1481	millisecond (if the OS supports it and the machine is fast enough).
1295		1482
1296	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1297		1484
1298	In this mode the values for C<interval> and C<at> are both being	1485	In this mode the values for C<interval> and C<at> are both being
1299	ignored. Instead, each time the periodic watcher gets scheduled, the	1486	ignored. Instead, each time the periodic watcher gets scheduled, the
1300	reschedule callback will be called with the watcher as first, and the	1487	reschedule callback will be called with the watcher as first, and the
1301	current time as second argument.	1488	current time as second argument.
1302		1489
1303	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1304	ever, or make any event loop modifications>. If you need to stop it,	1491	ever, or make ANY event loop modifications whatsoever>.
1305	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1306	starting an C<ev_prepare> watcher, which is legal).
1307		1492
		1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1495	only event loop modification you are allowed to do).
		1496
1308	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1309	ev_tstamp now)>, e.g.:	1498	*w, ev_tstamp now)>, e.g.:
1310		1499
1311	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1312	{	1501	{
1313	return now + 60.;	1502	return now + 60.;
1314	}	1503	}
…		…
1316	It must return the next time to trigger, based on the passed time value	1505	It must return the next time to trigger, based on the passed time value
1317	(that is, the lowest time value larger than to the second argument). It	1506	(that is, the lowest time value larger than to the second argument). It
1318	will usually be called just before the callback will be triggered, but	1507	will usually be called just before the callback will be triggered, but
1319	might be called at other times, too.	1508	might be called at other times, too.
1320		1509
1321	NOTE: I<< This callback must always return a time that is later than the	1510	NOTE: I<< This callback must always return a time that is higher than or
1322	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1511	equal to the passed C<now> value >>.
1323		1512
1324	This can be used to create very complex timers, such as a timer that	1513	This can be used to create very complex timers, such as a timer that
1325	triggers on each midnight, local time. To do this, you would calculate the	1514	triggers on "next midnight, local time". To do this, you would calculate the
1326	next midnight after C<now> and return the timestamp value for this. How	1515	next midnight after C<now> and return the timestamp value for this. How
1327	you do this is, again, up to you (but it is not trivial, which is the main	1516	you do this is, again, up to you (but it is not trivial, which is the main
1328	reason I omitted it as an example).	1517	reason I omitted it as an example).
1329		1518
1330	=back	1519	=back
…		…
1334	Simply stops and restarts the periodic watcher again. This is only useful	1523	Simply stops and restarts the periodic watcher again. This is only useful
1335	when you changed some parameters or the reschedule callback would return	1524	when you changed some parameters or the reschedule callback would return
1336	a different time than the last time it was called (e.g. in a crond like	1525	a different time than the last time it was called (e.g. in a crond like
1337	program when the crontabs have changed).	1526	program when the crontabs have changed).
1338		1527
		1528	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1529
		1530	When active, returns the absolute time that the watcher is supposed to
		1531	trigger next.
		1532
1339	=item ev_tstamp offset [read-write]	1533	=item ev_tstamp offset [read-write]
1340		1534
1341	When repeating, this contains the offset value, otherwise this is the	1535	When repeating, this contains the offset value, otherwise this is the
1342	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1343		1537
…		…
1354		1548
1355	The current reschedule callback, or C<0>, if this functionality is	1549	The current reschedule callback, or C<0>, if this functionality is
1356	switched off. Can be changed any time, but changes only take effect when	1550	switched off. Can be changed any time, but changes only take effect when
1357	the periodic timer fires or C<ev_periodic_again> is being called.	1551	the periodic timer fires or C<ev_periodic_again> is being called.
1358		1552
1359	=item ev_tstamp at [read-only]
1360
1361	When active, contains the absolute time that the watcher is supposed to
1362	trigger next.
1363
1364	=back	1553	=back
1365		1554
1366	=head3 Examples	1555	=head3 Examples
1367		1556
1368	Example: Call a callback every hour, or, more precisely, whenever the	1557	Example: Call a callback every hour, or, more precisely, whenever the
1369	system clock is divisible by 3600. The callback invocation times have	1558	system time is divisible by 3600. The callback invocation times have
1370	potentially a lot of jittering, but good long-term stability.	1559	potentially a lot of jitter, but good long-term stability.
1371		1560
1372	static void	1561	static void
1373	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1374	{	1563	{
1375	... its now a full hour (UTC, or TAI or whatever your clock follows)	1564	... its now a full hour (UTC, or TAI or whatever your clock follows)
1376	}	1565	}
1377		1566
1378	struct ev_periodic hourly_tick;	1567	struct ev_periodic hourly_tick;
1379	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1380	ev_periodic_start (loop, &hourly_tick);	1569	ev_periodic_start (loop, &hourly_tick);
1381		1570
1382	Example: The same as above, but use a reschedule callback to do it:	1571	Example: The same as above, but use a reschedule callback to do it:
1383		1572
1384	#include <math.h>	1573	#include <math.h>
1385		1574
1386	static ev_tstamp	1575	static ev_tstamp
1387	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1388	{	1577	{
1389	return fmod (now, 3600.) + 3600.;	1578	return now + (3600. - fmod (now, 3600.));
1390	}	1579	}
1391		1580
1392	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1393		1582
1394	Example: Call a callback every hour, starting now:	1583	Example: Call a callback every hour, starting now:
1395		1584
1396	struct ev_periodic hourly_tick;	1585	struct ev_periodic hourly_tick;
1397	ev_periodic_init (&hourly_tick, clock_cb,	1586	ev_periodic_init (&hourly_tick, clock_cb,
1398	fmod (ev_now (loop), 3600.), 3600., 0);	1587	fmod (ev_now (loop), 3600.), 3600., 0);
1399	ev_periodic_start (loop, &hourly_tick);	1588	ev_periodic_start (loop, &hourly_tick);
1400		1589
1401		1590
1402	=head2 C<ev_signal> - signal me when a signal gets signalled!	1591	=head2 C<ev_signal> - signal me when a signal gets signalled!
1403		1592
1404	Signal watchers will trigger an event when the process receives a specific	1593	Signal watchers will trigger an event when the process receives a specific
1405	signal one or more times. Even though signals are very asynchronous, libev	1594	signal one or more times. Even though signals are very asynchronous, libev
1406	will try it's best to deliver signals synchronously, i.e. as part of the	1595	will try it's best to deliver signals synchronously, i.e. as part of the
1407	normal event processing, like any other event.	1596	normal event processing, like any other event.
1408		1597
		1598	If you want signals asynchronously, just use C<sigaction> as you would
		1599	do without libev and forget about sharing the signal. You can even use
		1600	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1601
1409	You can configure as many watchers as you like per signal. Only when the	1602	You can configure as many watchers as you like per signal. Only when the
1410	first watcher gets started will libev actually register a signal watcher	1603	first watcher gets started will libev actually register a signal handler
1411	with the kernel (thus it coexists with your own signal handlers as long	1604	with the kernel (thus it coexists with your own signal handlers as long as
1412	as you don't register any with libev). Similarly, when the last signal	1605	you don't register any with libev for the same signal). Similarly, when
1413	watcher for a signal is stopped libev will reset the signal handler to	1606	the last signal watcher for a signal is stopped, libev will reset the
1414	SIG_DFL (regardless of what it was set to before).	1607	signal handler to SIG_DFL (regardless of what it was set to before).
		1608
		1609	If possible and supported, libev will install its handlers with
		1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1611	interrupted. If you have a problem with system calls getting interrupted by
		1612	signals you can block all signals in an C<ev_check> watcher and unblock
		1613	them in an C<ev_prepare> watcher.
1415		1614
1416	=head3 Watcher-Specific Functions and Data Members	1615	=head3 Watcher-Specific Functions and Data Members
1417		1616
1418	=over 4	1617	=over 4
1419		1618
…		…
1428		1627
1429	The signal the watcher watches out for.	1628	The signal the watcher watches out for.
1430		1629
1431	=back	1630	=back
1432		1631
		1632	=head3 Examples
		1633
		1634	Example: Try to exit cleanly on SIGINT.
		1635
		1636	static void
		1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1638	{
		1639	ev_unloop (loop, EVUNLOOP_ALL);
		1640	}
		1641
		1642	struct ev_signal signal_watcher;
		1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1644	ev_signal_start (loop, &signal_watcher);
		1645
1433		1646
1434	=head2 C<ev_child> - watch out for process status changes	1647	=head2 C<ev_child> - watch out for process status changes
1435		1648
1436	Child watchers trigger when your process receives a SIGCHLD in response to	1649	Child watchers trigger when your process receives a SIGCHLD in response to
1437	some child status changes (most typically when a child of yours dies).	1650	some child status changes (most typically when a child of yours dies or
		1651	exits). It is permissible to install a child watcher I<after> the child
		1652	has been forked (which implies it might have already exited), as long
		1653	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1654	forking and then immediately registering a watcher for the child is fine,
		1655	but forking and registering a watcher a few event loop iterations later is
		1656	not.
		1657
		1658	Only the default event loop is capable of handling signals, and therefore
		1659	you can only register child watchers in the default event loop.
		1660
		1661	=head3 Process Interaction
		1662
		1663	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1664	initialised. This is necessary to guarantee proper behaviour even if
		1665	the first child watcher is started after the child exits. The occurrence
		1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1667	synchronously as part of the event loop processing. Libev always reaps all
		1668	children, even ones not watched.
		1669
		1670	=head3 Overriding the Built-In Processing
		1671
		1672	Libev offers no special support for overriding the built-in child
		1673	processing, but if your application collides with libev's default child
		1674	handler, you can override it easily by installing your own handler for
		1675	C<SIGCHLD> after initialising the default loop, and making sure the
		1676	default loop never gets destroyed. You are encouraged, however, to use an
		1677	event-based approach to child reaping and thus use libev's support for
		1678	that, so other libev users can use C<ev_child> watchers freely.
		1679
		1680	=head3 Stopping the Child Watcher
		1681
		1682	Currently, the child watcher never gets stopped, even when the
		1683	child terminates, so normally one needs to stop the watcher in the
		1684	callback. Future versions of libev might stop the watcher automatically
		1685	when a child exit is detected.
1438		1686
1439	=head3 Watcher-Specific Functions and Data Members	1687	=head3 Watcher-Specific Functions and Data Members
1440		1688
1441	=over 4	1689	=over 4
1442		1690
…		…
1468		1716
1469	=back	1717	=back
1470		1718
1471	=head3 Examples	1719	=head3 Examples
1472		1720
1473	Example: Try to exit cleanly on SIGINT and SIGTERM.	1721	Example: C<fork()> a new process and install a child handler to wait for
		1722	its completion.
1474		1723
		1724	ev_child cw;
		1725
1475	static void	1726	static void
1476	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1727	child_cb (EV_P_ struct ev_child *w, int revents)
1477	{	1728	{
1478	ev_unloop (loop, EVUNLOOP_ALL);	1729	ev_child_stop (EV_A_ w);
		1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1479	}	1731	}
1480		1732
1481	struct ev_signal signal_watcher;	1733	pid_t pid = fork ();
1482	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1734
1483	ev_signal_start (loop, &sigint_cb);	1735	if (pid < 0)
		1736	// error
		1737	else if (pid == 0)
		1738	{
		1739	// the forked child executes here
		1740	exit (1);
		1741	}
		1742	else
		1743	{
		1744	ev_child_init (&cw, child_cb, pid, 0);
		1745	ev_child_start (EV_DEFAULT_ &cw);
		1746	}
1484		1747
1485		1748
1486	=head2 C<ev_stat> - did the file attributes just change?	1749	=head2 C<ev_stat> - did the file attributes just change?
1487		1750
1488	This watches a filesystem path for attribute changes. That is, it calls	1751	This watches a file system path for attribute changes. That is, it calls
1489	C<stat> regularly (or when the OS says it changed) and sees if it changed	1752	C<stat> regularly (or when the OS says it changed) and sees if it changed
1490	compared to the last time, invoking the callback if it did.	1753	compared to the last time, invoking the callback if it did.
1491		1754
1492	The path does not need to exist: changing from "path exists" to "path does	1755	The path does not need to exist: changing from "path exists" to "path does
1493	not exist" is a status change like any other. The condition "path does	1756	not exist" is a status change like any other. The condition "path does
…		…
1496	the stat buffer having unspecified contents.	1759	the stat buffer having unspecified contents.
1497		1760
1498	The path I<should> be absolute and I<must not> end in a slash. If it is	1761	The path I<should> be absolute and I<must not> end in a slash. If it is
1499	relative and your working directory changes, the behaviour is undefined.	1762	relative and your working directory changes, the behaviour is undefined.
1500		1763
1501	Since there is no standard to do this, the portable implementation simply	1764	Since there is no standard kernel interface to do this, the portable
1502	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1765	implementation simply calls C<stat (2)> regularly on the path to see if
1503	can specify a recommended polling interval for this case. If you specify	1766	it changed somehow. You can specify a recommended polling interval for
1504	a polling interval of C<0> (highly recommended!) then a I<suitable,	1767	this case. If you specify a polling interval of C<0> (highly recommended!)
1505	unspecified default> value will be used (which you can expect to be around	1768	then a I<suitable, unspecified default> value will be used (which
1506	five seconds, although this might change dynamically). Libev will also	1769	you can expect to be around five seconds, although this might change
1507	impose a minimum interval which is currently around C<0.1>, but thats	1770	dynamically). Libev will also impose a minimum interval which is currently
1508	usually overkill.	1771	around C<0.1>, but thats usually overkill.
1509		1772
1510	This watcher type is not meant for massive numbers of stat watchers,	1773	This watcher type is not meant for massive numbers of stat watchers,
1511	as even with OS-supported change notifications, this can be	1774	as even with OS-supported change notifications, this can be
1512	resource-intensive.	1775	resource-intensive.
1513		1776
1514	At the time of this writing, only the Linux inotify interface is	1777	At the time of this writing, the only OS-specific interface implemented
1515	implemented (implementing kqueue support is left as an exercise for the	1778	is the Linux inotify interface (implementing kqueue support is left as
1516	reader). Inotify will be used to give hints only and should not change the	1779	an exercise for the reader. Note, however, that the author sees no way
1517	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1780	of implementing C<ev_stat> semantics with kqueue).
1518	to fall back to regular polling again even with inotify, but changes are
1519	usually detected immediately, and if the file exists there will be no
1520	polling.
1521		1781
1522	=head3 Inotify	1782	=head3 ABI Issues (Largefile Support)
		1783
		1784	Libev by default (unless the user overrides this) uses the default
		1785	compilation environment, which means that on systems with large file
		1786	support disabled by default, you get the 32 bit version of the stat
		1787	structure. When using the library from programs that change the ABI to
		1788	use 64 bit file offsets the programs will fail. In that case you have to
		1789	compile libev with the same flags to get binary compatibility. This is
		1790	obviously the case with any flags that change the ABI, but the problem is
		1791	most noticeably disabled with ev_stat and large file support.
		1792
		1793	The solution for this is to lobby your distribution maker to make large
		1794	file interfaces available by default (as e.g. FreeBSD does) and not
		1795	optional. Libev cannot simply switch on large file support because it has
		1796	to exchange stat structures with application programs compiled using the
		1797	default compilation environment.
		1798
		1799	=head3 Inotify and Kqueue
1523		1800
1524	When C<inotify (7)> support has been compiled into libev (generally only	1801	When C<inotify (7)> support has been compiled into libev (generally only
1525	available on Linux) and present at runtime, it will be used to speed up	1802	available with Linux) and present at runtime, it will be used to speed up
1526	change detection where possible. The inotify descriptor will be created lazily	1803	change detection where possible. The inotify descriptor will be created lazily
1527	when the first C<ev_stat> watcher is being started.	1804	when the first C<ev_stat> watcher is being started.
1528		1805
1529	Inotify presense does not change the semantics of C<ev_stat> watchers	1806	Inotify presence does not change the semantics of C<ev_stat> watchers
1530	except that changes might be detected earlier, and in some cases, to avoid	1807	except that changes might be detected earlier, and in some cases, to avoid
1531	making regular C<stat> calls. Even in the presense of inotify support	1808	making regular C<stat> calls. Even in the presence of inotify support
1532	there are many cases where libev has to resort to regular C<stat> polling.	1809	there are many cases where libev has to resort to regular C<stat> polling,
		1810	but as long as the path exists, libev usually gets away without polling.
1533		1811
1534	(There is no support for kqueue, as apparently it cannot be used to	1812	There is no support for kqueue, as apparently it cannot be used to
1535	implement this functionality, due to the requirement of having a file	1813	implement this functionality, due to the requirement of having a file
1536	descriptor open on the object at all times).	1814	descriptor open on the object at all times, and detecting renames, unlinks
		1815	etc. is difficult.
1537		1816
1538	=head3 The special problem of stat time resolution	1817	=head3 The special problem of stat time resolution
1539		1818
1540	The C<stat ()> syscall only supports full-second resolution portably, and	1819	The C<stat ()> system call only supports full-second resolution portably, and
1541	even on systems where the resolution is higher, many filesystems still	1820	even on systems where the resolution is higher, most file systems still
1542	only support whole seconds.	1821	only support whole seconds.
1543		1822
1544	That means that, if the time is the only thing that changes, you might	1823	That means that, if the time is the only thing that changes, you can
1545	miss updates: on the first update, C<ev_stat> detects a change and calls	1824	easily miss updates: on the first update, C<ev_stat> detects a change and
1546	your callback, which does something. When there is another update within	1825	calls your callback, which does something. When there is another update
1547	the same second, C<ev_stat> will be unable to detect it.	1826	within the same second, C<ev_stat> will be unable to detect unless the
		1827	stat data does change in other ways (e.g. file size).
1548		1828
1549	The solution to this is to delay acting on a change for a second (or till	1829	The solution to this is to delay acting on a change for slightly more
1550	the next second boundary), using a roughly one-second delay C<ev_timer>	1830	than a second (or till slightly after the next full second boundary), using
1551	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1831	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1552	is added to work around small timing inconsistencies of some operating	1832	ev_timer_again (loop, w)>).
1553	systems.	1833
		1834	The C<.02> offset is added to work around small timing inconsistencies
		1835	of some operating systems (where the second counter of the current time
		1836	might be be delayed. One such system is the Linux kernel, where a call to
		1837	C<gettimeofday> might return a timestamp with a full second later than
		1838	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1839	update file times then there will be a small window where the kernel uses
		1840	the previous second to update file times but libev might already execute
		1841	the timer callback).
1554		1842
1555	=head3 Watcher-Specific Functions and Data Members	1843	=head3 Watcher-Specific Functions and Data Members
1556		1844
1557	=over 4	1845	=over 4
1558		1846
…		…
1564	C<path>. The C<interval> is a hint on how quickly a change is expected to	1852	C<path>. The C<interval> is a hint on how quickly a change is expected to
1565	be detected and should normally be specified as C<0> to let libev choose	1853	be detected and should normally be specified as C<0> to let libev choose
1566	a suitable value. The memory pointed to by C<path> must point to the same	1854	a suitable value. The memory pointed to by C<path> must point to the same
1567	path for as long as the watcher is active.	1855	path for as long as the watcher is active.
1568		1856
1569	The callback will be receive C<EV_STAT> when a change was detected,	1857	The callback will receive an C<EV_STAT> event when a change was detected,
1570	relative to the attributes at the time the watcher was started (or the	1858	relative to the attributes at the time the watcher was started (or the
1571	last change was detected).	1859	last change was detected).
1572		1860
1573	=item ev_stat_stat (ev_stat *)	1861	=item ev_stat_stat (loop, ev_stat *)
1574		1862
1575	Updates the stat buffer immediately with new values. If you change the	1863	Updates the stat buffer immediately with new values. If you change the
1576	watched path in your callback, you could call this fucntion to avoid	1864	watched path in your callback, you could call this function to avoid
1577	detecting this change (while introducing a race condition). Can also be	1865	detecting this change (while introducing a race condition if you are not
1578	useful simply to find out the new values.	1866	the only one changing the path). Can also be useful simply to find out the
		1867	new values.
1579		1868
1580	=item ev_statdata attr [read-only]	1869	=item ev_statdata attr [read-only]
1581		1870
1582	The most-recently detected attributes of the file. Although the type is of	1871	The most-recently detected attributes of the file. Although the type is
1583	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1872	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1584	suitable for your system. If the C<st_nlink> member is C<0>, then there	1873	suitable for your system, but you can only rely on the POSIX-standardised
		1874	members to be present. If the C<st_nlink> member is C<0>, then there was
1585	was some error while C<stat>ing the file.	1875	some error while C<stat>ing the file.
1586		1876
1587	=item ev_statdata prev [read-only]	1877	=item ev_statdata prev [read-only]
1588		1878
1589	The previous attributes of the file. The callback gets invoked whenever	1879	The previous attributes of the file. The callback gets invoked whenever
1590	C<prev> != C<attr>.	1880	C<prev> != C<attr>, or, more precisely, one or more of these members
		1881	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1882	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1591		1883
1592	=item ev_tstamp interval [read-only]	1884	=item ev_tstamp interval [read-only]
1593		1885
1594	The specified interval.	1886	The specified interval.
1595		1887
1596	=item const char *path [read-only]	1888	=item const char *path [read-only]
1597		1889
1598	The filesystem path that is being watched.	1890	The file system path that is being watched.
1599		1891
1600	=back	1892	=back
1601		1893
1602	=head3 Examples	1894	=head3 Examples
1603		1895
1604	Example: Watch C</etc/passwd> for attribute changes.	1896	Example: Watch C</etc/passwd> for attribute changes.
1605		1897
1606	static void	1898	static void
1607	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1899	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1608	{	1900	{
1609	/* /etc/passwd changed in some way */	1901	/* /etc/passwd changed in some way */
1610	if (w->attr.st_nlink)	1902	if (w->attr.st_nlink)
1611	{	1903	{
1612	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1904	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1613	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1905	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1614	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1906	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1615	}	1907	}
1616	else	1908	else
1617	/* you shalt not abuse printf for puts */	1909	/* you shalt not abuse printf for puts */
1618	puts ("wow, /etc/passwd is not there, expect problems. "	1910	puts ("wow, /etc/passwd is not there, expect problems. "
1619	"if this is windows, they already arrived\n");	1911	"if this is windows, they already arrived\n");
1620	}	1912	}
1621		1913
1622	...	1914	...
1623	ev_stat passwd;	1915	ev_stat passwd;
1624		1916
1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1917	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1626	ev_stat_start (loop, &passwd);	1918	ev_stat_start (loop, &passwd);
1627		1919
1628	Example: Like above, but additionally use a one-second delay so we do not	1920	Example: Like above, but additionally use a one-second delay so we do not
1629	miss updates (however, frequent updates will delay processing, too, so	1921	miss updates (however, frequent updates will delay processing, too, so
1630	one might do the work both on C<ev_stat> callback invocation I<and> on	1922	one might do the work both on C<ev_stat> callback invocation I<and> on
1631	C<ev_timer> callback invocation).	1923	C<ev_timer> callback invocation).
1632		1924
1633	static ev_stat passwd;	1925	static ev_stat passwd;
1634	static ev_timer timer;	1926	static ev_timer timer;
1635		1927
1636	static void	1928	static void
1637	timer_cb (EV_P_ ev_timer *w, int revents)	1929	timer_cb (EV_P_ ev_timer *w, int revents)
1638	{	1930	{
1639	ev_timer_stop (EV_A_ w);	1931	ev_timer_stop (EV_A_ w);
1640		1932
1641	/* now it's one second after the most recent passwd change */	1933	/* now it's one second after the most recent passwd change */
1642	}	1934	}
1643		1935
1644	static void	1936	static void
1645	stat_cb (EV_P_ ev_stat *w, int revents)	1937	stat_cb (EV_P_ ev_stat *w, int revents)
1646	{	1938	{
1647	/* reset the one-second timer */	1939	/* reset the one-second timer */
1648	ev_timer_again (EV_A_ &timer);	1940	ev_timer_again (EV_A_ &timer);
1649	}	1941	}
1650		1942
1651	...	1943	...
1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1944	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1653	ev_stat_start (loop, &passwd);	1945	ev_stat_start (loop, &passwd);
1654	ev_timer_init (&timer, timer_cb, 0., 1.01);	1946	ev_timer_init (&timer, timer_cb, 0., 1.02);
1655		1947
1656		1948
1657	=head2 C<ev_idle> - when you've got nothing better to do...	1949	=head2 C<ev_idle> - when you've got nothing better to do...
1658		1950
1659	Idle watchers trigger events when no other events of the same or higher	1951	Idle watchers trigger events when no other events of the same or higher
1660	priority are pending (prepare, check and other idle watchers do not	1952	priority are pending (prepare, check and other idle watchers do not count
1661	count).	1953	as receiving "events").
1662		1954
1663	That is, as long as your process is busy handling sockets or timeouts	1955	That is, as long as your process is busy handling sockets or timeouts
1664	(or even signals, imagine) of the same or higher priority it will not be	1956	(or even signals, imagine) of the same or higher priority it will not be
1665	triggered. But when your process is idle (or only lower-priority watchers	1957	triggered. But when your process is idle (or only lower-priority watchers
1666	are pending), the idle watchers are being called once per event loop	1958	are pending), the idle watchers are being called once per event loop
…		…
1690	=head3 Examples	1982	=head3 Examples
1691		1983
1692	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1984	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1693	callback, free it. Also, use no error checking, as usual.	1985	callback, free it. Also, use no error checking, as usual.
1694		1986
1695	static void	1987	static void
1696	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1988	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1697	{	1989	{
1698	free (w);	1990	free (w);
1699	// now do something you wanted to do when the program has	1991	// now do something you wanted to do when the program has
1700	// no longer anything immediate to do.	1992	// no longer anything immediate to do.
1701	}	1993	}
1702		1994
1703	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1995	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1704	ev_idle_init (idle_watcher, idle_cb);	1996	ev_idle_init (idle_watcher, idle_cb);
1705	ev_idle_start (loop, idle_cb);	1997	ev_idle_start (loop, idle_cb);
1706		1998
1707		1999
1708	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2000	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1709		2001
1710	Prepare and check watchers are usually (but not always) used in tandem:	2002	Prepare and check watchers are usually (but not always) used in pairs:
1711	prepare watchers get invoked before the process blocks and check watchers	2003	prepare watchers get invoked before the process blocks and check watchers
1712	afterwards.	2004	afterwards.
1713		2005
1714	You I<must not> call C<ev_loop> or similar functions that enter	2006	You I<must not> call C<ev_loop> or similar functions that enter
1715	the current event loop from either C<ev_prepare> or C<ev_check>	2007	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1718	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2010	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1719	C<ev_check> so if you have one watcher of each kind they will always be	2011	C<ev_check> so if you have one watcher of each kind they will always be
1720	called in pairs bracketing the blocking call.	2012	called in pairs bracketing the blocking call.
1721		2013
1722	Their main purpose is to integrate other event mechanisms into libev and	2014	Their main purpose is to integrate other event mechanisms into libev and
1723	their use is somewhat advanced. This could be used, for example, to track	2015	their use is somewhat advanced. They could be used, for example, to track
1724	variable changes, implement your own watchers, integrate net-snmp or a	2016	variable changes, implement your own watchers, integrate net-snmp or a
1725	coroutine library and lots more. They are also occasionally useful if	2017	coroutine library and lots more. They are also occasionally useful if
1726	you cache some data and want to flush it before blocking (for example,	2018	you cache some data and want to flush it before blocking (for example,
1727	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2019	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1728	watcher).	2020	watcher).
1729		2021
1730	This is done by examining in each prepare call which file descriptors need	2022	This is done by examining in each prepare call which file descriptors
1731	to be watched by the other library, registering C<ev_io> watchers for	2023	need to be watched by the other library, registering C<ev_io> watchers
1732	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2024	for them and starting an C<ev_timer> watcher for any timeouts (many
1733	provide just this functionality). Then, in the check watcher you check for	2025	libraries provide exactly this functionality). Then, in the check watcher,
1734	any events that occured (by checking the pending status of all watchers	2026	you check for any events that occurred (by checking the pending status
1735	and stopping them) and call back into the library. The I/O and timer	2027	of all watchers and stopping them) and call back into the library. The
1736	callbacks will never actually be called (but must be valid nevertheless,	2028	I/O and timer callbacks will never actually be called (but must be valid
1737	because you never know, you know?).	2029	nevertheless, because you never know, you know?).
1738		2030
1739	As another example, the Perl Coro module uses these hooks to integrate	2031	As another example, the Perl Coro module uses these hooks to integrate
1740	coroutines into libev programs, by yielding to other active coroutines	2032	coroutines into libev programs, by yielding to other active coroutines
1741	during each prepare and only letting the process block if no coroutines	2033	during each prepare and only letting the process block if no coroutines
1742	are ready to run (it's actually more complicated: it only runs coroutines	2034	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1745	loop from blocking if lower-priority coroutines are active, thus mapping	2037	loop from blocking if lower-priority coroutines are active, thus mapping
1746	low-priority coroutines to idle/background tasks).	2038	low-priority coroutines to idle/background tasks).
1747		2039
1748	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2040	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1749	priority, to ensure that they are being run before any other watchers	2041	priority, to ensure that they are being run before any other watchers
		2042	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2043
1750	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2044	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1751	too) should not activate ("feed") events into libev. While libev fully	2045	activate ("feed") events into libev. While libev fully supports this, they
1752	supports this, they will be called before other C<ev_check> watchers	2046	might get executed before other C<ev_check> watchers did their job. As
1753	did their job. As C<ev_check> watchers are often used to embed other	2047	C<ev_check> watchers are often used to embed other (non-libev) event
1754	(non-libev) event loops those other event loops might be in an unusable	2048	loops those other event loops might be in an unusable state until their
1755	state until their C<ev_check> watcher ran (always remind yourself to	2049	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1756	coexist peacefully with others).	2050	others).
1757		2051
1758	=head3 Watcher-Specific Functions and Data Members	2052	=head3 Watcher-Specific Functions and Data Members
1759		2053
1760	=over 4	2054	=over 4
1761		2055
…		…
1763		2057
1764	=item ev_check_init (ev_check *, callback)	2058	=item ev_check_init (ev_check *, callback)
1765		2059
1766	Initialises and configures the prepare or check watcher - they have no	2060	Initialises and configures the prepare or check watcher - they have no
1767	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2061	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1768	macros, but using them is utterly, utterly and completely pointless.	2062	macros, but using them is utterly, utterly, utterly and completely
		2063	pointless.
1769		2064
1770	=back	2065	=back
1771		2066
1772	=head3 Examples	2067	=head3 Examples
1773		2068
1774	There are a number of principal ways to embed other event loops or modules	2069	There are a number of principal ways to embed other event loops or modules
1775	into libev. Here are some ideas on how to include libadns into libev	2070	into libev. Here are some ideas on how to include libadns into libev
1776	(there is a Perl module named C<EV::ADNS> that does this, which you could	2071	(there is a Perl module named C<EV::ADNS> that does this, which you could
1777	use for an actually working example. Another Perl module named C<EV::Glib>	2072	use as a working example. Another Perl module named C<EV::Glib> embeds a
1778	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2073	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1779	into the Glib event loop).	2074	Glib event loop).
1780		2075
1781	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2076	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1782	and in a check watcher, destroy them and call into libadns. What follows	2077	and in a check watcher, destroy them and call into libadns. What follows
1783	is pseudo-code only of course. This requires you to either use a low	2078	is pseudo-code only of course. This requires you to either use a low
1784	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2079	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1785	the callbacks for the IO/timeout watchers might not have been called yet.	2080	the callbacks for the IO/timeout watchers might not have been called yet.
1786		2081
1787	static ev_io iow [nfd];	2082	static ev_io iow [nfd];
1788	static ev_timer tw;	2083	static ev_timer tw;
1789		2084
1790	static void	2085	static void
1791	io_cb (ev_loop *loop, ev_io *w, int revents)	2086	io_cb (ev_loop *loop, ev_io *w, int revents)
1792	{	2087	{
1793	}	2088	}
1794		2089
1795	// create io watchers for each fd and a timer before blocking	2090	// create io watchers for each fd and a timer before blocking
1796	static void	2091	static void
1797	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2092	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1798	{	2093	{
1799	int timeout = 3600000;	2094	int timeout = 3600000;
1800	struct pollfd fds [nfd];	2095	struct pollfd fds [nfd];
1801	// actual code will need to loop here and realloc etc.	2096	// actual code will need to loop here and realloc etc.
1802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2097	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1803		2098
1804	/* the callback is illegal, but won't be called as we stop during check */	2099	/* the callback is illegal, but won't be called as we stop during check */
1805	ev_timer_init (&tw, 0, timeout * 1e-3);	2100	ev_timer_init (&tw, 0, timeout * 1e-3);
1806	ev_timer_start (loop, &tw);	2101	ev_timer_start (loop, &tw);
1807		2102
1808	// create one ev_io per pollfd	2103	// create one ev_io per pollfd
1809	for (int i = 0; i < nfd; ++i)	2104	for (int i = 0; i < nfd; ++i)
1810	{	2105	{
1811	ev_io_init (iow + i, io_cb, fds [i].fd,	2106	ev_io_init (iow + i, io_cb, fds [i].fd,
1812	((fds [i].events & POLLIN ? EV_READ : 0)	2107	((fds [i].events & POLLIN ? EV_READ : 0)
1813	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2108	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1814		2109
1815	fds [i].revents = 0;	2110	fds [i].revents = 0;
1816	ev_io_start (loop, iow + i);	2111	ev_io_start (loop, iow + i);
1817	}	2112	}
1818	}	2113	}
1819		2114
1820	// stop all watchers after blocking	2115	// stop all watchers after blocking
1821	static void	2116	static void
1822	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2117	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1823	{	2118	{
1824	ev_timer_stop (loop, &tw);	2119	ev_timer_stop (loop, &tw);
1825		2120
1826	for (int i = 0; i < nfd; ++i)	2121	for (int i = 0; i < nfd; ++i)
1827	{	2122	{
1828	// set the relevant poll flags	2123	// set the relevant poll flags
1829	// could also call adns_processreadable etc. here	2124	// could also call adns_processreadable etc. here
1830	struct pollfd *fd = fds + i;	2125	struct pollfd *fd = fds + i;
1831	int revents = ev_clear_pending (iow + i);	2126	int revents = ev_clear_pending (iow + i);
1832	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2127	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1833	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2128	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1834		2129
1835	// now stop the watcher	2130	// now stop the watcher
1836	ev_io_stop (loop, iow + i);	2131	ev_io_stop (loop, iow + i);
1837	}	2132	}
1838		2133
1839	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2134	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1840	}	2135	}
1841		2136
1842	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2137	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1843	in the prepare watcher and would dispose of the check watcher.	2138	in the prepare watcher and would dispose of the check watcher.
1844		2139
1845	Method 3: If the module to be embedded supports explicit event	2140	Method 3: If the module to be embedded supports explicit event
1846	notification (adns does), you can also make use of the actual watcher	2141	notification (libadns does), you can also make use of the actual watcher
1847	callbacks, and only destroy/create the watchers in the prepare watcher.	2142	callbacks, and only destroy/create the watchers in the prepare watcher.
1848		2143
1849	static void	2144	static void
1850	timer_cb (EV_P_ ev_timer *w, int revents)	2145	timer_cb (EV_P_ ev_timer *w, int revents)
1851	{	2146	{
1852	adns_state ads = (adns_state)w->data;	2147	adns_state ads = (adns_state)w->data;
1853	update_now (EV_A);	2148	update_now (EV_A);
1854		2149
1855	adns_processtimeouts (ads, &tv_now);	2150	adns_processtimeouts (ads, &tv_now);
1856	}	2151	}
1857		2152
1858	static void	2153	static void
1859	io_cb (EV_P_ ev_io *w, int revents)	2154	io_cb (EV_P_ ev_io *w, int revents)
1860	{	2155	{
1861	adns_state ads = (adns_state)w->data;	2156	adns_state ads = (adns_state)w->data;
1862	update_now (EV_A);	2157	update_now (EV_A);
1863		2158
1864	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2159	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1865	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2160	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1866	}	2161	}
1867		2162
1868	// do not ever call adns_afterpoll	2163	// do not ever call adns_afterpoll
1869		2164
1870	Method 4: Do not use a prepare or check watcher because the module you	2165	Method 4: Do not use a prepare or check watcher because the module you
1871	want to embed is too inflexible to support it. Instead, youc na override	2166	want to embed is not flexible enough to support it. Instead, you can
1872	their poll function. The drawback with this solution is that the main	2167	override their poll function. The drawback with this solution is that the
1873	loop is now no longer controllable by EV. The C<Glib::EV> module does	2168	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1874	this.	2169	this approach, effectively embedding EV as a client into the horrible
		2170	libglib event loop.
1875		2171
1876	static gint	2172	static gint
1877	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2173	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1878	{	2174	{
1879	int got_events = 0;	2175	int got_events = 0;
1880		2176
1881	for (n = 0; n < nfds; ++n)	2177	for (n = 0; n < nfds; ++n)
1882	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2178	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1883		2179
1884	if (timeout >= 0)	2180	if (timeout >= 0)
1885	// create/start timer	2181	// create/start timer
1886		2182
1887	// poll	2183	// poll
1888	ev_loop (EV_A_ 0);	2184	ev_loop (EV_A_ 0);
1889		2185
1890	// stop timer again	2186	// stop timer again
1891	if (timeout >= 0)	2187	if (timeout >= 0)
1892	ev_timer_stop (EV_A_ &to);	2188	ev_timer_stop (EV_A_ &to);
1893		2189
1894	// stop io watchers again - their callbacks should have set	2190	// stop io watchers again - their callbacks should have set
1895	for (n = 0; n < nfds; ++n)	2191	for (n = 0; n < nfds; ++n)
1896	ev_io_stop (EV_A_ iow [n]);	2192	ev_io_stop (EV_A_ iow [n]);
1897		2193
1898	return got_events;	2194	return got_events;
1899	}	2195	}
1900		2196
1901		2197
1902	=head2 C<ev_embed> - when one backend isn't enough...	2198	=head2 C<ev_embed> - when one backend isn't enough...
1903		2199
1904	This is a rather advanced watcher type that lets you embed one event loop	2200	This is a rather advanced watcher type that lets you embed one event loop
…		…
1910	prioritise I/O.	2206	prioritise I/O.
1911		2207
1912	As an example for a bug workaround, the kqueue backend might only support	2208	As an example for a bug workaround, the kqueue backend might only support
1913	sockets on some platform, so it is unusable as generic backend, but you	2209	sockets on some platform, so it is unusable as generic backend, but you
1914	still want to make use of it because you have many sockets and it scales	2210	still want to make use of it because you have many sockets and it scales
1915	so nicely. In this case, you would create a kqueue-based loop and embed it	2211	so nicely. In this case, you would create a kqueue-based loop and embed
1916	into your default loop (which might use e.g. poll). Overall operation will	2212	it into your default loop (which might use e.g. poll). Overall operation
1917	be a bit slower because first libev has to poll and then call kevent, but	2213	will be a bit slower because first libev has to call C<poll> and then
1918	at least you can use both at what they are best.	2214	C<kevent>, but at least you can use both mechanisms for what they are
		2215	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1919		2216
1920	As for prioritising I/O: rarely you have the case where some fds have	2217	As for prioritising I/O: under rare circumstances you have the case where
1921	to be watched and handled very quickly (with low latency), and even	2218	some fds have to be watched and handled very quickly (with low latency),
1922	priorities and idle watchers might have too much overhead. In this case	2219	and even priorities and idle watchers might have too much overhead. In
1923	you would put all the high priority stuff in one loop and all the rest in	2220	this case you would put all the high priority stuff in one loop and all
1924	a second one, and embed the second one in the first.	2221	the rest in a second one, and embed the second one in the first.
1925		2222
1926	As long as the watcher is active, the callback will be invoked every time	2223	As long as the watcher is active, the callback will be invoked every time
1927	there might be events pending in the embedded loop. The callback must then	2224	there might be events pending in the embedded loop. The callback must then
1928	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2225	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1929	their callbacks (you could also start an idle watcher to give the embedded	2226	their callbacks (you could also start an idle watcher to give the embedded
…		…
1937	interested in that.	2234	interested in that.
1938		2235
1939	Also, there have not currently been made special provisions for forking:	2236	Also, there have not currently been made special provisions for forking:
1940	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2237	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1941	but you will also have to stop and restart any C<ev_embed> watchers	2238	but you will also have to stop and restart any C<ev_embed> watchers
1942	yourself.	2239	yourself - but you can use a fork watcher to handle this automatically,
		2240	and future versions of libev might do just that.
1943		2241
1944	Unfortunately, not all backends are embeddable, only the ones returned by	2242	Unfortunately, not all backends are embeddable: only the ones returned by
1945	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2243	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1946	portable one.	2244	portable one.
1947		2245
1948	So when you want to use this feature you will always have to be prepared	2246	So when you want to use this feature you will always have to be prepared
1949	that you cannot get an embeddable loop. The recommended way to get around	2247	that you cannot get an embeddable loop. The recommended way to get around
1950	this is to have a separate variables for your embeddable loop, try to	2248	this is to have a separate variables for your embeddable loop, try to
1951	create it, and if that fails, use the normal loop for everything.	2249	create it, and if that fails, use the normal loop for everything.
1952		2250
		2251	=head3 C<ev_embed> and fork
		2252
		2253	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2254	automatically be applied to the embedded loop as well, so no special
		2255	fork handling is required in that case. When the watcher is not running,
		2256	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2257	as applicable.
		2258
1953	=head3 Watcher-Specific Functions and Data Members	2259	=head3 Watcher-Specific Functions and Data Members
1954		2260
1955	=over 4	2261	=over 4
1956		2262
1957	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2263	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1960		2266
1961	Configures the watcher to embed the given loop, which must be	2267	Configures the watcher to embed the given loop, which must be
1962	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2268	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1963	invoked automatically, otherwise it is the responsibility of the callback	2269	invoked automatically, otherwise it is the responsibility of the callback
1964	to invoke it (it will continue to be called until the sweep has been done,	2270	to invoke it (it will continue to be called until the sweep has been done,
1965	if you do not want thta, you need to temporarily stop the embed watcher).	2271	if you do not want that, you need to temporarily stop the embed watcher).
1966		2272
1967	=item ev_embed_sweep (loop, ev_embed *)	2273	=item ev_embed_sweep (loop, ev_embed *)
1968		2274
1969	Make a single, non-blocking sweep over the embedded loop. This works	2275	Make a single, non-blocking sweep over the embedded loop. This works
1970	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2276	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1971	apropriate way for embedded loops.	2277	appropriate way for embedded loops.
1972		2278
1973	=item struct ev_loop *other [read-only]	2279	=item struct ev_loop *other [read-only]
1974		2280
1975	The embedded event loop.	2281	The embedded event loop.
1976		2282
…		…
1978		2284
1979	=head3 Examples	2285	=head3 Examples
1980		2286
1981	Example: Try to get an embeddable event loop and embed it into the default	2287	Example: Try to get an embeddable event loop and embed it into the default
1982	event loop. If that is not possible, use the default loop. The default	2288	event loop. If that is not possible, use the default loop. The default
1983	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2289	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1984	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2290	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1985	used).	2291	used).
1986		2292
1987	struct ev_loop *loop_hi = ev_default_init (0);	2293	struct ev_loop *loop_hi = ev_default_init (0);
1988	struct ev_loop *loop_lo = 0;	2294	struct ev_loop *loop_lo = 0;
1989	struct ev_embed embed;	2295	struct ev_embed embed;
1990		2296
1991	// see if there is a chance of getting one that works	2297	// see if there is a chance of getting one that works
1992	// (remember that a flags value of 0 means autodetection)	2298	// (remember that a flags value of 0 means autodetection)
1993	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2299	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1994	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2300	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1995	: 0;	2301	: 0;
1996		2302
1997	// if we got one, then embed it, otherwise default to loop_hi	2303	// if we got one, then embed it, otherwise default to loop_hi
1998	if (loop_lo)	2304	if (loop_lo)
1999	{	2305	{
2000	ev_embed_init (&embed, 0, loop_lo);	2306	ev_embed_init (&embed, 0, loop_lo);
2001	ev_embed_start (loop_hi, &embed);	2307	ev_embed_start (loop_hi, &embed);
2002	}	2308	}
2003	else	2309	else
2004	loop_lo = loop_hi;	2310	loop_lo = loop_hi;
2005		2311
2006	Example: Check if kqueue is available but not recommended and create	2312	Example: Check if kqueue is available but not recommended and create
2007	a kqueue backend for use with sockets (which usually work with any	2313	a kqueue backend for use with sockets (which usually work with any
2008	kqueue implementation). Store the kqueue/socket-only event loop in	2314	kqueue implementation). Store the kqueue/socket-only event loop in
2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2315	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2010		2316
2011	struct ev_loop *loop = ev_default_init (0);	2317	struct ev_loop *loop = ev_default_init (0);
2012	struct ev_loop *loop_socket = 0;	2318	struct ev_loop *loop_socket = 0;
2013	struct ev_embed embed;	2319	struct ev_embed embed;
2014		2320
2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2321	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2322	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2017	{	2323	{
2018	ev_embed_init (&embed, 0, loop_socket);	2324	ev_embed_init (&embed, 0, loop_socket);
2019	ev_embed_start (loop, &embed);	2325	ev_embed_start (loop, &embed);
2020	}	2326	}
2021		2327
2022	if (!loop_socket)	2328	if (!loop_socket)
2023	loop_socket = loop;	2329	loop_socket = loop;
2024		2330
2025	// now use loop_socket for all sockets, and loop for everything else	2331	// now use loop_socket for all sockets, and loop for everything else
2026		2332
2027		2333
2028	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2334	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2029		2335
2030	Fork watchers are called when a C<fork ()> was detected (usually because	2336	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2046	believe me.	2352	believe me.
2047		2353
2048	=back	2354	=back
2049		2355
2050		2356
		2357	=head2 C<ev_async> - how to wake up another event loop
		2358
		2359	In general, you cannot use an C<ev_loop> from multiple threads or other
		2360	asynchronous sources such as signal handlers (as opposed to multiple event
		2361	loops - those are of course safe to use in different threads).
		2362
		2363	Sometimes, however, you need to wake up another event loop you do not
		2364	control, for example because it belongs to another thread. This is what
		2365	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2366	can signal it by calling C<ev_async_send>, which is thread- and signal
		2367	safe.
		2368
		2369	This functionality is very similar to C<ev_signal> watchers, as signals,
		2370	too, are asynchronous in nature, and signals, too, will be compressed
		2371	(i.e. the number of callback invocations may be less than the number of
		2372	C<ev_async_sent> calls).
		2373
		2374	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2375	just the default loop.
		2376
		2377	=head3 Queueing
		2378
		2379	C<ev_async> does not support queueing of data in any way. The reason
		2380	is that the author does not know of a simple (or any) algorithm for a
		2381	multiple-writer-single-reader queue that works in all cases and doesn't
		2382	need elaborate support such as pthreads.
		2383
		2384	That means that if you want to queue data, you have to provide your own
		2385	queue. But at least I can tell you how to implement locking around your
		2386	queue:
		2387
		2388	=over 4
		2389
		2390	=item queueing from a signal handler context
		2391
		2392	To implement race-free queueing, you simply add to the queue in the signal
		2393	handler but you block the signal handler in the watcher callback. Here is
		2394	an example that does that for some fictitious SIGUSR1 handler:
		2395
		2396	static ev_async mysig;
		2397
		2398	static void
		2399	sigusr1_handler (void)
		2400	{
		2401	sometype data;
		2402
		2403	// no locking etc.
		2404	queue_put (data);
		2405	ev_async_send (EV_DEFAULT_ &mysig);
		2406	}
		2407
		2408	static void
		2409	mysig_cb (EV_P_ ev_async *w, int revents)
		2410	{
		2411	sometype data;
		2412	sigset_t block, prev;
		2413
		2414	sigemptyset (&block);
		2415	sigaddset (&block, SIGUSR1);
		2416	sigprocmask (SIG_BLOCK, &block, &prev);
		2417
		2418	while (queue_get (&data))
		2419	process (data);
		2420
		2421	if (sigismember (&prev, SIGUSR1)
		2422	sigprocmask (SIG_UNBLOCK, &block, 0);
		2423	}
		2424
		2425	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2426	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2427	either...).
		2428
		2429	=item queueing from a thread context
		2430
		2431	The strategy for threads is different, as you cannot (easily) block
		2432	threads but you can easily preempt them, so to queue safely you need to
		2433	employ a traditional mutex lock, such as in this pthread example:
		2434
		2435	static ev_async mysig;
		2436	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2437
		2438	static void
		2439	otherthread (void)
		2440	{
		2441	// only need to lock the actual queueing operation
		2442	pthread_mutex_lock (&mymutex);
		2443	queue_put (data);
		2444	pthread_mutex_unlock (&mymutex);
		2445
		2446	ev_async_send (EV_DEFAULT_ &mysig);
		2447	}
		2448
		2449	static void
		2450	mysig_cb (EV_P_ ev_async *w, int revents)
		2451	{
		2452	pthread_mutex_lock (&mymutex);
		2453
		2454	while (queue_get (&data))
		2455	process (data);
		2456
		2457	pthread_mutex_unlock (&mymutex);
		2458	}
		2459
		2460	=back
		2461
		2462
		2463	=head3 Watcher-Specific Functions and Data Members
		2464
		2465	=over 4
		2466
		2467	=item ev_async_init (ev_async *, callback)
		2468
		2469	Initialises and configures the async watcher - it has no parameters of any
		2470	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2471	trust me.
		2472
		2473	=item ev_async_send (loop, ev_async *)
		2474
		2475	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2476	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2477	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2478	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2479	section below on what exactly this means).
		2480
		2481	This call incurs the overhead of a system call only once per loop iteration,
		2482	so while the overhead might be noticeable, it doesn't apply to repeated
		2483	calls to C<ev_async_send>.
		2484
		2485	=item bool = ev_async_pending (ev_async *)
		2486
		2487	Returns a non-zero value when C<ev_async_send> has been called on the
		2488	watcher but the event has not yet been processed (or even noted) by the
		2489	event loop.
		2490
		2491	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2492	the loop iterates next and checks for the watcher to have become active,
		2493	it will reset the flag again. C<ev_async_pending> can be used to very
		2494	quickly check whether invoking the loop might be a good idea.
		2495
		2496	Not that this does I<not> check whether the watcher itself is pending, only
		2497	whether it has been requested to make this watcher pending.
		2498
		2499	=back
		2500
		2501
2051	=head1 OTHER FUNCTIONS	2502	=head1 OTHER FUNCTIONS
2052		2503
2053	There are some other functions of possible interest. Described. Here. Now.	2504	There are some other functions of possible interest. Described. Here. Now.
2054		2505
2055	=over 4	2506	=over 4
2056		2507
2057	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2508	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2058		2509
2059	This function combines a simple timer and an I/O watcher, calls your	2510	This function combines a simple timer and an I/O watcher, calls your
2060	callback on whichever event happens first and automatically stop both	2511	callback on whichever event happens first and automatically stops both
2061	watchers. This is useful if you want to wait for a single event on an fd	2512	watchers. This is useful if you want to wait for a single event on an fd
2062	or timeout without having to allocate/configure/start/stop/free one or	2513	or timeout without having to allocate/configure/start/stop/free one or
2063	more watchers yourself.	2514	more watchers yourself.
2064		2515
2065	If C<fd> is less than 0, then no I/O watcher will be started and events	2516	If C<fd> is less than 0, then no I/O watcher will be started and the
2066	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2517	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2067	C<events> set will be craeted and started.	2518	the given C<fd> and C<events> set will be created and started.
2068		2519
2069	If C<timeout> is less than 0, then no timeout watcher will be	2520	If C<timeout> is less than 0, then no timeout watcher will be
2070	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2521	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2071	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2522	repeat = 0) will be started. C<0> is a valid timeout.
2072	dubious value.
2073		2523
2074	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2524	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2075	passed an C<revents> set like normal event callbacks (a combination of	2525	passed an C<revents> set like normal event callbacks (a combination of
2076	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2526	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2077	value passed to C<ev_once>:	2527	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2528	a timeout and an io event at the same time - you probably should give io
		2529	events precedence.
2078		2530
		2531	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2532
2079	static void stdin_ready (int revents, void *arg)	2533	static void stdin_ready (int revents, void *arg)
2080	{	2534	{
2081	if (revents & EV_TIMEOUT)
2082	/* doh, nothing entered */;
2083	else if (revents & EV_READ)	2535	if (revents & EV_READ)
2084	/* stdin might have data for us, joy! */;	2536	/* stdin might have data for us, joy! */;
		2537	else if (revents & EV_TIMEOUT)
		2538	/* doh, nothing entered */;
2085	}	2539	}
2086		2540
2087	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2541	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2088		2542
2089	=item ev_feed_event (ev_loop *, watcher *, int revents)	2543	=item ev_feed_event (ev_loop *, watcher *, int revents)
2090		2544
2091	Feeds the given event set into the event loop, as if the specified event	2545	Feeds the given event set into the event loop, as if the specified event
2092	had happened for the specified watcher (which must be a pointer to an	2546	had happened for the specified watcher (which must be a pointer to an
…		…
2097	Feed an event on the given fd, as if a file descriptor backend detected	2551	Feed an event on the given fd, as if a file descriptor backend detected
2098	the given events it.	2552	the given events it.
2099		2553
2100	=item ev_feed_signal_event (ev_loop *loop, int signum)	2554	=item ev_feed_signal_event (ev_loop *loop, int signum)
2101		2555
2102	Feed an event as if the given signal occured (C<loop> must be the default	2556	Feed an event as if the given signal occurred (C<loop> must be the default
2103	loop!).	2557	loop!).
2104		2558
2105	=back	2559	=back
2106		2560
2107		2561
…		…
2123		2577
2124	=item * Priorities are not currently supported. Initialising priorities	2578	=item * Priorities are not currently supported. Initialising priorities
2125	will fail and all watchers will have the same priority, even though there	2579	will fail and all watchers will have the same priority, even though there
2126	is an ev_pri field.	2580	is an ev_pri field.
2127		2581
		2582	=item * In libevent, the last base created gets the signals, in libev, the
		2583	first base created (== the default loop) gets the signals.
		2584
2128	=item * Other members are not supported.	2585	=item * Other members are not supported.
2129		2586
2130	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2587	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2131	to use the libev header file and library.	2588	to use the libev header file and library.
2132		2589
2133	=back	2590	=back
2134		2591
2135	=head1 C++ SUPPORT	2592	=head1 C++ SUPPORT
2136		2593
2137	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2594	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2138	you to use some convinience methods to start/stop watchers and also change	2595	you to use some convenience methods to start/stop watchers and also change
2139	the callback model to a model using method callbacks on objects.	2596	the callback model to a model using method callbacks on objects.
2140		2597
2141	To use it,	2598	To use it,
2142		2599
2143	#include <ev++.h>	2600	#include <ev++.h>
2144		2601
2145	This automatically includes F<ev.h> and puts all of its definitions (many	2602	This automatically includes F<ev.h> and puts all of its definitions (many
2146	of them macros) into the global namespace. All C++ specific things are	2603	of them macros) into the global namespace. All C++ specific things are
2147	put into the C<ev> namespace. It should support all the same embedding	2604	put into the C<ev> namespace. It should support all the same embedding
2148	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2605	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2215	your compiler is good :), then the method will be fully inlined into the	2672	your compiler is good :), then the method will be fully inlined into the
2216	thunking function, making it as fast as a direct C callback.	2673	thunking function, making it as fast as a direct C callback.
2217		2674
2218	Example: simple class declaration and watcher initialisation	2675	Example: simple class declaration and watcher initialisation
2219		2676
2220	struct myclass	2677	struct myclass
2221	{	2678	{
2222	void io_cb (ev::io &w, int revents) { }	2679	void io_cb (ev::io &w, int revents) { }
2223	}	2680	}
2224		2681
2225	myclass obj;	2682	myclass obj;
2226	ev::io iow;	2683	ev::io iow;
2227	iow.set <myclass, &myclass::io_cb> (&obj);	2684	iow.set <myclass, &myclass::io_cb> (&obj);
2228		2685
2229	=item w->set<function> (void *data = 0)	2686	=item w->set<function> (void *data = 0)
2230		2687
2231	Also sets a callback, but uses a static method or plain function as	2688	Also sets a callback, but uses a static method or plain function as
2232	callback. The optional C<data> argument will be stored in the watcher's	2689	callback. The optional C<data> argument will be stored in the watcher's
…		…
2234		2691
2235	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2692	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2236		2693
2237	See the method-C<set> above for more details.	2694	See the method-C<set> above for more details.
2238		2695
2239	Example:	2696	Example: Use a plain function as callback.
2240		2697
2241	static void io_cb (ev::io &w, int revents) { }	2698	static void io_cb (ev::io &w, int revents) { }
2242	iow.set <io_cb> ();	2699	iow.set <io_cb> ();
2243		2700
2244	=item w->set (struct ev_loop *)	2701	=item w->set (struct ev_loop *)
2245		2702
2246	Associates a different C<struct ev_loop> with this watcher. You can only	2703	Associates a different C<struct ev_loop> with this watcher. You can only
2247	do this when the watcher is inactive (and not pending either).	2704	do this when the watcher is inactive (and not pending either).
2248		2705
2249	=item w->set ([args])	2706	=item w->set ([arguments])
2250		2707
2251	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2708	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2252	called at least once. Unlike the C counterpart, an active watcher gets	2709	called at least once. Unlike the C counterpart, an active watcher gets
2253	automatically stopped and restarted when reconfiguring it with this	2710	automatically stopped and restarted when reconfiguring it with this
2254	method.	2711	method.
2255		2712
2256	=item w->start ()	2713	=item w->start ()
…		…
2280	=back	2737	=back
2281		2738
2282	Example: Define a class with an IO and idle watcher, start one of them in	2739	Example: Define a class with an IO and idle watcher, start one of them in
2283	the constructor.	2740	the constructor.
2284		2741
2285	class myclass	2742	class myclass
2286	{	2743	{
2287	ev::io io; void io_cb (ev::io &w, int revents);	2744	ev::io io ; void io_cb (ev::io &w, int revents);
2288	ev:idle idle void idle_cb (ev::idle &w, int revents);	2745	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2289		2746
2290	myclass (int fd)	2747	myclass (int fd)
2291	{	2748	{
2292	io .set <myclass, &myclass::io_cb > (this);	2749	io .set <myclass, &myclass::io_cb > (this);
2293	idle.set <myclass, &myclass::idle_cb> (this);	2750	idle.set <myclass, &myclass::idle_cb> (this);
2294		2751
2295	io.start (fd, ev::READ);	2752	io.start (fd, ev::READ);
2296	}	2753	}
2297	};	2754	};
		2755
		2756
		2757	=head1 OTHER LANGUAGE BINDINGS
		2758
		2759	Libev does not offer other language bindings itself, but bindings for a
		2760	number of languages exist in the form of third-party packages. If you know
		2761	any interesting language binding in addition to the ones listed here, drop
		2762	me a note.
		2763
		2764	=over 4
		2765
		2766	=item Perl
		2767
		2768	The EV module implements the full libev API and is actually used to test
		2769	libev. EV is developed together with libev. Apart from the EV core module,
		2770	there are additional modules that implement libev-compatible interfaces
		2771	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2772	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2773	and C<EV::Glib>).
		2774
		2775	It can be found and installed via CPAN, its homepage is at
		2776	L<http://software.schmorp.de/pkg/EV>.
		2777
		2778	=item Python
		2779
		2780	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2781	seems to be quite complete and well-documented. Note, however, that the
		2782	patch they require for libev is outright dangerous as it breaks the ABI
		2783	for everybody else, and therefore, should never be applied in an installed
		2784	libev (if python requires an incompatible ABI then it needs to embed
		2785	libev).
		2786
		2787	=item Ruby
		2788
		2789	Tony Arcieri has written a ruby extension that offers access to a subset
		2790	of the libev API and adds file handle abstractions, asynchronous DNS and
		2791	more on top of it. It can be found via gem servers. Its homepage is at
		2792	L<http://rev.rubyforge.org/>.
		2793
		2794	=item D
		2795
		2796	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2797	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2798
		2799	=back
2298		2800
2299		2801
2300	=head1 MACRO MAGIC	2802	=head1 MACRO MAGIC
2301		2803
2302	Libev can be compiled with a variety of options, the most fundamantal	2804	Libev can be compiled with a variety of options, the most fundamental
2303	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2805	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2304	functions and callbacks have an initial C<struct ev_loop *> argument.	2806	functions and callbacks have an initial C<struct ev_loop *> argument.
2305		2807
2306	To make it easier to write programs that cope with either variant, the	2808	To make it easier to write programs that cope with either variant, the
2307	following macros are defined:	2809	following macros are defined:
…		…
2312		2814
2313	This provides the loop I<argument> for functions, if one is required ("ev	2815	This provides the loop I<argument> for functions, if one is required ("ev
2314	loop argument"). The C<EV_A> form is used when this is the sole argument,	2816	loop argument"). The C<EV_A> form is used when this is the sole argument,
2315	C<EV_A_> is used when other arguments are following. Example:	2817	C<EV_A_> is used when other arguments are following. Example:
2316		2818
2317	ev_unref (EV_A);	2819	ev_unref (EV_A);
2318	ev_timer_add (EV_A_ watcher);	2820	ev_timer_add (EV_A_ watcher);
2319	ev_loop (EV_A_ 0);	2821	ev_loop (EV_A_ 0);
2320		2822
2321	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2823	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2322	which is often provided by the following macro.	2824	which is often provided by the following macro.
2323		2825
2324	=item C<EV_P>, C<EV_P_>	2826	=item C<EV_P>, C<EV_P_>
2325		2827
2326	This provides the loop I<parameter> for functions, if one is required ("ev	2828	This provides the loop I<parameter> for functions, if one is required ("ev
2327	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2829	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2328	C<EV_P_> is used when other parameters are following. Example:	2830	C<EV_P_> is used when other parameters are following. Example:
2329		2831
2330	// this is how ev_unref is being declared	2832	// this is how ev_unref is being declared
2331	static void ev_unref (EV_P);	2833	static void ev_unref (EV_P);
2332		2834
2333	// this is how you can declare your typical callback	2835	// this is how you can declare your typical callback
2334	static void cb (EV_P_ ev_timer *w, int revents)	2836	static void cb (EV_P_ ev_timer *w, int revents)
2335		2837
2336	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2838	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2337	suitable for use with C<EV_A>.	2839	suitable for use with C<EV_A>.
2338		2840
2339	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2841	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2340		2842
2341	Similar to the other two macros, this gives you the value of the default	2843	Similar to the other two macros, this gives you the value of the default
2342	loop, if multiple loops are supported ("ev loop default").	2844	loop, if multiple loops are supported ("ev loop default").
		2845
		2846	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2847
		2848	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2849	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2850	is undefined when the default loop has not been initialised by a previous
		2851	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2852
		2853	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2854	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2343		2855
2344	=back	2856	=back
2345		2857
2346	Example: Declare and initialise a check watcher, utilising the above	2858	Example: Declare and initialise a check watcher, utilising the above
2347	macros so it will work regardless of whether multiple loops are supported	2859	macros so it will work regardless of whether multiple loops are supported
2348	or not.	2860	or not.
2349		2861
2350	static void	2862	static void
2351	check_cb (EV_P_ ev_timer *w, int revents)	2863	check_cb (EV_P_ ev_timer *w, int revents)
2352	{	2864	{
2353	ev_check_stop (EV_A_ w);	2865	ev_check_stop (EV_A_ w);
2354	}	2866	}
2355		2867
2356	ev_check check;	2868	ev_check check;
2357	ev_check_init (&check, check_cb);	2869	ev_check_init (&check, check_cb);
2358	ev_check_start (EV_DEFAULT_ &check);	2870	ev_check_start (EV_DEFAULT_ &check);
2359	ev_loop (EV_DEFAULT_ 0);	2871	ev_loop (EV_DEFAULT_ 0);
2360		2872
2361	=head1 EMBEDDING	2873	=head1 EMBEDDING
2362		2874
2363	Libev can (and often is) directly embedded into host	2875	Libev can (and often is) directly embedded into host
2364	applications. Examples of applications that embed it include the Deliantra	2876	applications. Examples of applications that embed it include the Deliantra
…		…
2371	libev somewhere in your source tree).	2883	libev somewhere in your source tree).
2372		2884
2373	=head2 FILESETS	2885	=head2 FILESETS
2374		2886
2375	Depending on what features you need you need to include one or more sets of files	2887	Depending on what features you need you need to include one or more sets of files
2376	in your app.	2888	in your application.
2377		2889
2378	=head3 CORE EVENT LOOP	2890	=head3 CORE EVENT LOOP
2379		2891
2380	To include only the libev core (all the C<ev_*> functions), with manual	2892	To include only the libev core (all the C<ev_*> functions), with manual
2381	configuration (no autoconf):	2893	configuration (no autoconf):
2382		2894
2383	#define EV_STANDALONE 1	2895	#define EV_STANDALONE 1
2384	#include "ev.c"	2896	#include "ev.c"
2385		2897
2386	This will automatically include F<ev.h>, too, and should be done in a	2898	This will automatically include F<ev.h>, too, and should be done in a
2387	single C source file only to provide the function implementations. To use	2899	single C source file only to provide the function implementations. To use
2388	it, do the same for F<ev.h> in all files wishing to use this API (best	2900	it, do the same for F<ev.h> in all files wishing to use this API (best
2389	done by writing a wrapper around F<ev.h> that you can include instead and	2901	done by writing a wrapper around F<ev.h> that you can include instead and
2390	where you can put other configuration options):	2902	where you can put other configuration options):
2391		2903
2392	#define EV_STANDALONE 1	2904	#define EV_STANDALONE 1
2393	#include "ev.h"	2905	#include "ev.h"
2394		2906
2395	Both header files and implementation files can be compiled with a C++	2907	Both header files and implementation files can be compiled with a C++
2396	compiler (at least, thats a stated goal, and breakage will be treated	2908	compiler (at least, thats a stated goal, and breakage will be treated
2397	as a bug).	2909	as a bug).
2398		2910
2399	You need the following files in your source tree, or in a directory	2911	You need the following files in your source tree, or in a directory
2400	in your include path (e.g. in libev/ when using -Ilibev):	2912	in your include path (e.g. in libev/ when using -Ilibev):
2401		2913
2402	ev.h	2914	ev.h
2403	ev.c	2915	ev.c
2404	ev_vars.h	2916	ev_vars.h
2405	ev_wrap.h	2917	ev_wrap.h
2406		2918
2407	ev_win32.c required on win32 platforms only	2919	ev_win32.c required on win32 platforms only
2408		2920
2409	ev_select.c only when select backend is enabled (which is enabled by default)	2921	ev_select.c only when select backend is enabled (which is enabled by default)
2410	ev_poll.c only when poll backend is enabled (disabled by default)	2922	ev_poll.c only when poll backend is enabled (disabled by default)
2411	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2923	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2412	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2924	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2413	ev_port.c only when the solaris port backend is enabled (disabled by default)	2925	ev_port.c only when the solaris port backend is enabled (disabled by default)
2414		2926
2415	F<ev.c> includes the backend files directly when enabled, so you only need	2927	F<ev.c> includes the backend files directly when enabled, so you only need
2416	to compile this single file.	2928	to compile this single file.
2417		2929
2418	=head3 LIBEVENT COMPATIBILITY API	2930	=head3 LIBEVENT COMPATIBILITY API
2419		2931
2420	To include the libevent compatibility API, also include:	2932	To include the libevent compatibility API, also include:
2421		2933
2422	#include "event.c"	2934	#include "event.c"
2423		2935
2424	in the file including F<ev.c>, and:	2936	in the file including F<ev.c>, and:
2425		2937
2426	#include "event.h"	2938	#include "event.h"
2427		2939
2428	in the files that want to use the libevent API. This also includes F<ev.h>.	2940	in the files that want to use the libevent API. This also includes F<ev.h>.
2429		2941
2430	You need the following additional files for this:	2942	You need the following additional files for this:
2431		2943
2432	event.h	2944	event.h
2433	event.c	2945	event.c
2434		2946
2435	=head3 AUTOCONF SUPPORT	2947	=head3 AUTOCONF SUPPORT
2436		2948
2437	Instead of using C<EV_STANDALONE=1> and providing your config in	2949	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2438	whatever way you want, you can also C<m4_include([libev.m4])> in your	2950	whatever way you want, you can also C<m4_include([libev.m4])> in your
2439	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2951	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2440	include F<config.h> and configure itself accordingly.	2952	include F<config.h> and configure itself accordingly.
2441		2953
2442	For this of course you need the m4 file:	2954	For this of course you need the m4 file:
2443		2955
2444	libev.m4	2956	libev.m4
2445		2957
2446	=head2 PREPROCESSOR SYMBOLS/MACROS	2958	=head2 PREPROCESSOR SYMBOLS/MACROS
2447		2959
2448	Libev can be configured via a variety of preprocessor symbols you have to define	2960	Libev can be configured via a variety of preprocessor symbols you have to
2449	before including any of its files. The default is not to build for multiplicity	2961	define before including any of its files. The default in the absence of
2450	and only include the select backend.	2962	autoconf is documented for every option.
2451		2963
2452	=over 4	2964	=over 4
2453		2965
2454	=item EV_STANDALONE	2966	=item EV_STANDALONE
2455		2967
…		…
2460	F<event.h> that are not directly supported by the libev core alone.	2972	F<event.h> that are not directly supported by the libev core alone.
2461		2973
2462	=item EV_USE_MONOTONIC	2974	=item EV_USE_MONOTONIC
2463		2975
2464	If defined to be C<1>, libev will try to detect the availability of the	2976	If defined to be C<1>, libev will try to detect the availability of the
2465	monotonic clock option at both compiletime and runtime. Otherwise no use	2977	monotonic clock option at both compile time and runtime. Otherwise no use
2466	of the monotonic clock option will be attempted. If you enable this, you	2978	of the monotonic clock option will be attempted. If you enable this, you
2467	usually have to link against librt or something similar. Enabling it when	2979	usually have to link against librt or something similar. Enabling it when
2468	the functionality isn't available is safe, though, although you have	2980	the functionality isn't available is safe, though, although you have
2469	to make sure you link against any libraries where the C<clock_gettime>	2981	to make sure you link against any libraries where the C<clock_gettime>
2470	function is hiding in (often F<-lrt>).	2982	function is hiding in (often F<-lrt>).
2471		2983
2472	=item EV_USE_REALTIME	2984	=item EV_USE_REALTIME
2473		2985
2474	If defined to be C<1>, libev will try to detect the availability of the	2986	If defined to be C<1>, libev will try to detect the availability of the
2475	realtime clock option at compiletime (and assume its availability at	2987	real-time clock option at compile time (and assume its availability at
2476	runtime if successful). Otherwise no use of the realtime clock option will	2988	runtime if successful). Otherwise no use of the real-time clock option will
2477	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2989	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2478	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2990	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2479	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2991	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2480		2992
2481	=item EV_USE_NANOSLEEP	2993	=item EV_USE_NANOSLEEP
2482		2994
2483	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2995	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2484	and will use it for delays. Otherwise it will use C<select ()>.	2996	and will use it for delays. Otherwise it will use C<select ()>.
2485		2997
		2998	=item EV_USE_EVENTFD
		2999
		3000	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3001	available and will probe for kernel support at runtime. This will improve
		3002	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3003	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3004	2.7 or newer, otherwise disabled.
		3005
2486	=item EV_USE_SELECT	3006	=item EV_USE_SELECT
2487		3007
2488	If undefined or defined to be C<1>, libev will compile in support for the	3008	If undefined or defined to be C<1>, libev will compile in support for the
2489	C<select>(2) backend. No attempt at autodetection will be done: if no	3009	C<select>(2) backend. No attempt at auto-detection will be done: if no
2490	other method takes over, select will be it. Otherwise the select backend	3010	other method takes over, select will be it. Otherwise the select backend
2491	will not be compiled in.	3011	will not be compiled in.
2492		3012
2493	=item EV_SELECT_USE_FD_SET	3013	=item EV_SELECT_USE_FD_SET
2494		3014
2495	If defined to C<1>, then the select backend will use the system C<fd_set>	3015	If defined to C<1>, then the select backend will use the system C<fd_set>
2496	structure. This is useful if libev doesn't compile due to a missing	3016	structure. This is useful if libev doesn't compile due to a missing
2497	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3017	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2498	exotic systems. This usually limits the range of file descriptors to some	3018	exotic systems. This usually limits the range of file descriptors to some
2499	low limit such as 1024 or might have other limitations (winsocket only	3019	low limit such as 1024 or might have other limitations (winsocket only
2500	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3020	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2501	influence the size of the C<fd_set> used.	3021	influence the size of the C<fd_set> used.
2502		3022
…		…
2526		3046
2527	=item EV_USE_EPOLL	3047	=item EV_USE_EPOLL
2528		3048
2529	If defined to be C<1>, libev will compile in support for the Linux	3049	If defined to be C<1>, libev will compile in support for the Linux
2530	C<epoll>(7) backend. Its availability will be detected at runtime,	3050	C<epoll>(7) backend. Its availability will be detected at runtime,
2531	otherwise another method will be used as fallback. This is the	3051	otherwise another method will be used as fallback. This is the preferred
2532	preferred backend for GNU/Linux systems.	3052	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3053	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2533		3054
2534	=item EV_USE_KQUEUE	3055	=item EV_USE_KQUEUE
2535		3056
2536	If defined to be C<1>, libev will compile in support for the BSD style	3057	If defined to be C<1>, libev will compile in support for the BSD style
2537	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3058	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2550	otherwise another method will be used as fallback. This is the preferred	3071	otherwise another method will be used as fallback. This is the preferred
2551	backend for Solaris 10 systems.	3072	backend for Solaris 10 systems.
2552		3073
2553	=item EV_USE_DEVPOLL	3074	=item EV_USE_DEVPOLL
2554		3075
2555	reserved for future expansion, works like the USE symbols above.	3076	Reserved for future expansion, works like the USE symbols above.
2556		3077
2557	=item EV_USE_INOTIFY	3078	=item EV_USE_INOTIFY
2558		3079
2559	If defined to be C<1>, libev will compile in support for the Linux inotify	3080	If defined to be C<1>, libev will compile in support for the Linux inotify
2560	interface to speed up C<ev_stat> watchers. Its actual availability will	3081	interface to speed up C<ev_stat> watchers. Its actual availability will
2561	be detected at runtime.	3082	be detected at runtime. If undefined, it will be enabled if the headers
		3083	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3084
		3085	=item EV_ATOMIC_T
		3086
		3087	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3088	access is atomic with respect to other threads or signal contexts. No such
		3089	type is easily found in the C language, so you can provide your own type
		3090	that you know is safe for your purposes. It is used both for signal handler "locking"
		3091	as well as for signal and thread safety in C<ev_async> watchers.
		3092
		3093	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3094	(from F<signal.h>), which is usually good enough on most platforms.
2562		3095
2563	=item EV_H	3096	=item EV_H
2564		3097
2565	The name of the F<ev.h> header file used to include it. The default if	3098	The name of the F<ev.h> header file used to include it. The default if
2566	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3099	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
2604	When doing priority-based operations, libev usually has to linearly search	3137	When doing priority-based operations, libev usually has to linearly search
2605	all the priorities, so having many of them (hundreds) uses a lot of space	3138	all the priorities, so having many of them (hundreds) uses a lot of space
2606	and time, so using the defaults of five priorities (-2 .. +2) is usually	3139	and time, so using the defaults of five priorities (-2 .. +2) is usually
2607	fine.	3140	fine.
2608		3141
2609	If your embedding app does not need any priorities, defining these both to	3142	If your embedding application does not need any priorities, defining these
2610	C<0> will save some memory and cpu.	3143	both to C<0> will save some memory and CPU.
2611		3144
2612	=item EV_PERIODIC_ENABLE	3145	=item EV_PERIODIC_ENABLE
2613		3146
2614	If undefined or defined to be C<1>, then periodic timers are supported. If	3147	If undefined or defined to be C<1>, then periodic timers are supported. If
2615	defined to be C<0>, then they are not. Disabling them saves a few kB of	3148	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2622	code.	3155	code.
2623		3156
2624	=item EV_EMBED_ENABLE	3157	=item EV_EMBED_ENABLE
2625		3158
2626	If undefined or defined to be C<1>, then embed watchers are supported. If	3159	If undefined or defined to be C<1>, then embed watchers are supported. If
2627	defined to be C<0>, then they are not.	3160	defined to be C<0>, then they are not. Embed watchers rely on most other
		3161	watcher types, which therefore must not be disabled.
2628		3162
2629	=item EV_STAT_ENABLE	3163	=item EV_STAT_ENABLE
2630		3164
2631	If undefined or defined to be C<1>, then stat watchers are supported. If	3165	If undefined or defined to be C<1>, then stat watchers are supported. If
2632	defined to be C<0>, then they are not.	3166	defined to be C<0>, then they are not.
…		…
2634	=item EV_FORK_ENABLE	3168	=item EV_FORK_ENABLE
2635		3169
2636	If undefined or defined to be C<1>, then fork watchers are supported. If	3170	If undefined or defined to be C<1>, then fork watchers are supported. If
2637	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
2638		3172
		3173	=item EV_ASYNC_ENABLE
		3174
		3175	If undefined or defined to be C<1>, then async watchers are supported. If
		3176	defined to be C<0>, then they are not.
		3177
2639	=item EV_MINIMAL	3178	=item EV_MINIMAL
2640		3179
2641	If you need to shave off some kilobytes of code at the expense of some	3180	If you need to shave off some kilobytes of code at the expense of some
2642	speed, define this symbol to C<1>. Currently only used for gcc to override	3181	speed, define this symbol to C<1>. Currently this is used to override some
2643	some inlining decisions, saves roughly 30% codesize of amd64.	3182	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3183	much smaller 2-heap for timer management over the default 4-heap.
2644		3184
2645	=item EV_PID_HASHSIZE	3185	=item EV_PID_HASHSIZE
2646		3186
2647	C<ev_child> watchers use a small hash table to distribute workload by	3187	C<ev_child> watchers use a small hash table to distribute workload by
2648	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3188	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2655	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3195	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2656	usually more than enough. If you need to manage thousands of C<ev_stat>	3196	usually more than enough. If you need to manage thousands of C<ev_stat>
2657	watchers you might want to increase this value (I<must> be a power of	3197	watchers you might want to increase this value (I<must> be a power of
2658	two).	3198	two).
2659		3199
		3200	=item EV_USE_4HEAP
		3201
		3202	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3203	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3204	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3205	faster performance with many (thousands) of watchers.
		3206
		3207	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3208	(disabled).
		3209
		3210	=item EV_HEAP_CACHE_AT
		3211
		3212	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3213	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3214	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3215	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3216	but avoids random read accesses on heap changes. This improves performance
		3217	noticeably with many (hundreds) of watchers.
		3218
		3219	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3220	(disabled).
		3221
		3222	=item EV_VERIFY
		3223
		3224	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3225	be done: If set to C<0>, no internal verification code will be compiled
		3226	in. If set to C<1>, then verification code will be compiled in, but not
		3227	called. If set to C<2>, then the internal verification code will be
		3228	called once per loop, which can slow down libev. If set to C<3>, then the
		3229	verification code will be called very frequently, which will slow down
		3230	libev considerably.
		3231
		3232	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3233	C<0>.
		3234
2660	=item EV_COMMON	3235	=item EV_COMMON
2661		3236
2662	By default, all watchers have a C<void *data> member. By redefining	3237	By default, all watchers have a C<void *data> member. By redefining
2663	this macro to a something else you can include more and other types of	3238	this macro to a something else you can include more and other types of
2664	members. You have to define it each time you include one of the files,	3239	members. You have to define it each time you include one of the files,
2665	though, and it must be identical each time.	3240	though, and it must be identical each time.
2666		3241
2667	For example, the perl EV module uses something like this:	3242	For example, the perl EV module uses something like this:
2668		3243
2669	#define EV_COMMON \	3244	#define EV_COMMON \
2670	SV *self; /* contains this struct */ \	3245	SV *self; /* contains this struct */ \
2671	SV *cb_sv, *fh /* note no trailing ";" */	3246	SV *cb_sv, *fh /* note no trailing ";" */
2672		3247
2673	=item EV_CB_DECLARE (type)	3248	=item EV_CB_DECLARE (type)
2674		3249
2675	=item EV_CB_INVOKE (watcher, revents)	3250	=item EV_CB_INVOKE (watcher, revents)
2676		3251
…		…
2681	definition and a statement, respectively. See the F<ev.h> header file for	3256	definition and a statement, respectively. See the F<ev.h> header file for
2682	their default definitions. One possible use for overriding these is to	3257	their default definitions. One possible use for overriding these is to
2683	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3258	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2684	method calls instead of plain function calls in C++.	3259	method calls instead of plain function calls in C++.
2685		3260
		3261	=back
		3262
2686	=head2 EXPORTED API SYMBOLS	3263	=head2 EXPORTED API SYMBOLS
2687		3264
2688	If you need to re-export the API (e.g. via a dll) and you need a list of	3265	If you need to re-export the API (e.g. via a DLL) and you need a list of
2689	exported symbols, you can use the provided F<Symbol.*> files which list	3266	exported symbols, you can use the provided F<Symbol.*> files which list
2690	all public symbols, one per line:	3267	all public symbols, one per line:
2691		3268
2692	Symbols.ev for libev proper	3269	Symbols.ev for libev proper
2693	Symbols.event for the libevent emulation	3270	Symbols.event for the libevent emulation
2694		3271
2695	This can also be used to rename all public symbols to avoid clashes with	3272	This can also be used to rename all public symbols to avoid clashes with
2696	multiple versions of libev linked together (which is obviously bad in	3273	multiple versions of libev linked together (which is obviously bad in
2697	itself, but sometimes it is inconvinient to avoid this).	3274	itself, but sometimes it is inconvenient to avoid this).
2698		3275
2699	A sed command like this will create wrapper C<#define>'s that you need to	3276	A sed command like this will create wrapper C<#define>'s that you need to
2700	include before including F<ev.h>:	3277	include before including F<ev.h>:
2701		3278
2702	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3279	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2719	file.	3296	file.
2720		3297
2721	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2722	that everybody includes and which overrides some configure choices:	3299	that everybody includes and which overrides some configure choices:
2723		3300
2724	#define EV_MINIMAL 1	3301	#define EV_MINIMAL 1
2725	#define EV_USE_POLL 0	3302	#define EV_USE_POLL 0
2726	#define EV_MULTIPLICITY 0	3303	#define EV_MULTIPLICITY 0
2727	#define EV_PERIODIC_ENABLE 0	3304	#define EV_PERIODIC_ENABLE 0
2728	#define EV_STAT_ENABLE 0	3305	#define EV_STAT_ENABLE 0
2729	#define EV_FORK_ENABLE 0	3306	#define EV_FORK_ENABLE 0
2730	#define EV_CONFIG_H <config.h>	3307	#define EV_CONFIG_H <config.h>
2731	#define EV_MINPRI 0	3308	#define EV_MINPRI 0
2732	#define EV_MAXPRI 0	3309	#define EV_MAXPRI 0
2733		3310
2734	#include "ev++.h"	3311	#include "ev++.h"
2735		3312
2736	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2737		3314
2738	#include "ev_cpp.h"	3315	#include "ev_cpp.h"
2739	#include "ev.c"	3316	#include "ev.c"
2740		3317
		3318	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2741		3319
2742	=head1 COMPLEXITIES	3320	=head2 THREADS AND COROUTINES
2743		3321
2744	In this section the complexities of (many of) the algorithms used inside	3322	=head3 THREADS
2745	libev will be explained. For complexity discussions about backends see the
2746	documentation for C<ev_default_init>.
2747		3323
2748	All of the following are about amortised time: If an array needs to be	3324	All libev functions are reentrant and thread-safe unless explicitly
2749	extended, libev needs to realloc and move the whole array, but this	3325	documented otherwise, but libev implements no locking itself. This means
2750	happens asymptotically never with higher number of elements, so O(1) might	3326	that you can use as many loops as you want in parallel, as long as there
2751	mean it might do a lengthy realloc operation in rare cases, but on average	3327	are no concurrent calls into any libev function with the same loop
2752	it is much faster and asymptotically approaches constant time.	3328	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3329	of course): libev guarantees that different event loops share no data
		3330	structures that need any locking.
		3331
		3332	Or to put it differently: calls with different loop parameters can be done
		3333	concurrently from multiple threads, calls with the same loop parameter
		3334	must be done serially (but can be done from different threads, as long as
		3335	only one thread ever is inside a call at any point in time, e.g. by using
		3336	a mutex per loop).
		3337
		3338	Specifically to support threads (and signal handlers), libev implements
		3339	so-called C<ev_async> watchers, which allow some limited form of
		3340	concurrency on the same event loop, namely waking it up "from the
		3341	outside".
		3342
		3343	If you want to know which design (one loop, locking, or multiple loops
		3344	without or something else still) is best for your problem, then I cannot
		3345	help you, but here is some generic advice:
2753		3346
2754	=over 4	3347	=over 4
2755		3348
2756	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3349	=item * most applications have a main thread: use the default libev loop
		3350	in that thread, or create a separate thread running only the default loop.
2757		3351
2758	This means that, when you have a watcher that triggers in one hour and	3352	This helps integrating other libraries or software modules that use libev
2759	there are 100 watchers that would trigger before that then inserting will	3353	themselves and don't care/know about threading.
2760	have to skip roughly seven (C<ld 100>) of these watchers.
2761		3354
2762	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3355	=item * one loop per thread is usually a good model.
2763		3356
2764	That means that changing a timer costs less than removing/adding them	3357	Doing this is almost never wrong, sometimes a better-performance model
2765	as only the relative motion in the event queue has to be paid for.	3358	exists, but it is always a good start.
2766		3359
2767	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3360	=item * other models exist, such as the leader/follower pattern, where one
		3361	loop is handed through multiple threads in a kind of round-robin fashion.
2768		3362
2769	These just add the watcher into an array or at the head of a list.	3363	Choosing a model is hard - look around, learn, know that usually you can do
		3364	better than you currently do :-)
2770		3365
2771	=item Stopping check/prepare/idle watchers: O(1)	3366	=item * often you need to talk to some other thread which blocks in the
		3367	event loop.
2772		3368
2773	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3369	C<ev_async> watchers can be used to wake them up from other threads safely
		3370	(or from signal contexts...).
2774		3371
2775	These watchers are stored in lists then need to be walked to find the	3372	An example use would be to communicate signals or other events that only
2776	correct watcher to remove. The lists are usually short (you don't usually	3373	work in the default loop by registering the signal watcher with the
2777	have many watchers waiting for the same fd or signal).	3374	default loop and triggering an C<ev_async> watcher from the default loop
2778		3375	watcher callback into the event loop interested in the signal.
2779	=item Finding the next timer in each loop iteration: O(1)
2780
2781	By virtue of using a binary heap, the next timer is always found at the
2782	beginning of the storage array.
2783
2784	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2785
2786	A change means an I/O watcher gets started or stopped, which requires
2787	libev to recalculate its status (and possibly tell the kernel, depending
2788	on backend and wether C<ev_io_set> was used).
2789
2790	=item Activating one watcher (putting it into the pending state): O(1)
2791
2792	=item Priority handling: O(number_of_priorities)
2793
2794	Priorities are implemented by allocating some space for each
2795	priority. When doing priority-based operations, libev usually has to
2796	linearly search all the priorities, but starting/stopping and activating
2797	watchers becomes O(1) w.r.t. prioritiy handling.
2798		3376
2799	=back	3377	=back
2800		3378
		3379	=head3 COROUTINES
2801		3380
2802	=head1 Win32 platform limitations and workarounds	3381	Libev is very accommodating to coroutines ("cooperative threads"):
		3382	libev fully supports nesting calls to its functions from different
		3383	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3384	different coroutines, and switch freely between both coroutines running the
		3385	loop, as long as you don't confuse yourself). The only exception is that
		3386	you must not do this from C<ev_periodic> reschedule callbacks.
		3387
		3388	Care has been taken to ensure that libev does not keep local state inside
		3389	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3390	they do not clal any callbacks.
		3391
		3392	=head2 COMPILER WARNINGS
		3393
		3394	Depending on your compiler and compiler settings, you might get no or a
		3395	lot of warnings when compiling libev code. Some people are apparently
		3396	scared by this.
		3397
		3398	However, these are unavoidable for many reasons. For one, each compiler
		3399	has different warnings, and each user has different tastes regarding
		3400	warning options. "Warn-free" code therefore cannot be a goal except when
		3401	targeting a specific compiler and compiler-version.
		3402
		3403	Another reason is that some compiler warnings require elaborate
		3404	workarounds, or other changes to the code that make it less clear and less
		3405	maintainable.
		3406
		3407	And of course, some compiler warnings are just plain stupid, or simply
		3408	wrong (because they don't actually warn about the condition their message
		3409	seems to warn about). For example, certain older gcc versions had some
		3410	warnings that resulted an extreme number of false positives. These have
		3411	been fixed, but some people still insist on making code warn-free with
		3412	such buggy versions.
		3413
		3414	While libev is written to generate as few warnings as possible,
		3415	"warn-free" code is not a goal, and it is recommended not to build libev
		3416	with any compiler warnings enabled unless you are prepared to cope with
		3417	them (e.g. by ignoring them). Remember that warnings are just that:
		3418	warnings, not errors, or proof of bugs.
		3419
		3420
		3421	=head2 VALGRIND
		3422
		3423	Valgrind has a special section here because it is a popular tool that is
		3424	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3425
		3426	If you think you found a bug (memory leak, uninitialised data access etc.)
		3427	in libev, then check twice: If valgrind reports something like:
		3428
		3429	==2274== definitely lost: 0 bytes in 0 blocks.
		3430	==2274== possibly lost: 0 bytes in 0 blocks.
		3431	==2274== still reachable: 256 bytes in 1 blocks.
		3432
		3433	Then there is no memory leak, just as memory accounted to global variables
		3434	is not a memleak - the memory is still being refernced, and didn't leak.
		3435
		3436	Similarly, under some circumstances, valgrind might report kernel bugs
		3437	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3438	although an acceptable workaround has been found here), or it might be
		3439	confused.
		3440
		3441	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3442	make it into some kind of religion.
		3443
		3444	If you are unsure about something, feel free to contact the mailing list
		3445	with the full valgrind report and an explanation on why you think this
		3446	is a bug in libev (best check the archives, too :). However, don't be
		3447	annoyed when you get a brisk "this is no bug" answer and take the chance
		3448	of learning how to interpret valgrind properly.
		3449
		3450	If you need, for some reason, empty reports from valgrind for your project
		3451	I suggest using suppression lists.
		3452
		3453
		3454	=head1 PORTABILITY NOTES
		3455
		3456	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2803		3457
2804	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3458	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2805	requires, and its I/O model is fundamentally incompatible with the POSIX	3459	requires, and its I/O model is fundamentally incompatible with the POSIX
2806	model. Libev still offers limited functionality on this platform in	3460	model. Libev still offers limited functionality on this platform in
2807	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3461	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2808	descriptors. This only applies when using Win32 natively, not when using	3462	descriptors. This only applies when using Win32 natively, not when using
2809	e.g. cygwin.	3463	e.g. cygwin.
2810		3464
		3465	Lifting these limitations would basically require the full
		3466	re-implementation of the I/O system. If you are into these kinds of
		3467	things, then note that glib does exactly that for you in a very portable
		3468	way (note also that glib is the slowest event library known to man).
		3469
2811	There is no supported compilation method available on windows except	3470	There is no supported compilation method available on windows except
2812	embedding it into other applications.	3471	embedding it into other applications.
2813		3472
		3473	Not a libev limitation but worth mentioning: windows apparently doesn't
		3474	accept large writes: instead of resulting in a partial write, windows will
		3475	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3476	so make sure you only write small amounts into your sockets (less than a
		3477	megabyte seems safe, but this apparently depends on the amount of memory
		3478	available).
		3479
2814	Due to the many, low, and arbitrary limits on the win32 platform and the	3480	Due to the many, low, and arbitrary limits on the win32 platform and
2815	abysmal performance of winsockets, using a large number of sockets is not	3481	the abysmal performance of winsockets, using a large number of sockets
2816	recommended (and not reasonable). If your program needs to use more than	3482	is not recommended (and not reasonable). If your program needs to use
2817	a hundred or so sockets, then likely it needs to use a totally different	3483	more than a hundred or so sockets, then likely it needs to use a totally
2818	implementation for windows, as libev offers the POSIX model, which cannot	3484	different implementation for windows, as libev offers the POSIX readiness
2819	be implemented efficiently on windows (microsoft monopoly games).	3485	notification model, which cannot be implemented efficiently on windows
		3486	(Microsoft monopoly games).
		3487
		3488	A typical way to use libev under windows is to embed it (see the embedding
		3489	section for details) and use the following F<evwrap.h> header file instead
		3490	of F<ev.h>:
		3491
		3492	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3493	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3494
		3495	#include "ev.h"
		3496
		3497	And compile the following F<evwrap.c> file into your project (make sure
		3498	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3499
		3500	#include "evwrap.h"
		3501	#include "ev.c"
2820		3502
2821	=over 4	3503	=over 4
2822		3504
2823	=item The winsocket select function	3505	=item The winsocket select function
2824		3506
2825	The winsocket C<select> function doesn't follow POSIX in that it requires	3507	The winsocket C<select> function doesn't follow POSIX in that it
2826	socket I<handles> and not socket I<file descriptors>. This makes select	3508	requires socket I<handles> and not socket I<file descriptors> (it is
2827	very inefficient, and also requires a mapping from file descriptors	3509	also extremely buggy). This makes select very inefficient, and also
2828	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3510	requires a mapping from file descriptors to socket handles (the Microsoft
2829	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3511	C runtime provides the function C<_open_osfhandle> for this). See the
2830	symbols for more info.	3512	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3513	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2831		3514
2832	The configuration for a "naked" win32 using the microsoft runtime	3515	The configuration for a "naked" win32 using the Microsoft runtime
2833	libraries and raw winsocket select is:	3516	libraries and raw winsocket select is:
2834		3517
2835	#define EV_USE_SELECT 1	3518	#define EV_USE_SELECT 1
2836	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3519	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2837		3520
2838	Note that winsockets handling of fd sets is O(n), so you can easily get a	3521	Note that winsockets handling of fd sets is O(n), so you can easily get a
2839	complexity in the O(n²) range when using win32.	3522	complexity in the O(n²) range when using win32.
2840		3523
2841	=item Limited number of file descriptors	3524	=item Limited number of file descriptors
2842		3525
2843	Windows has numerous arbitrary (and low) limits on things. Early versions	3526	Windows has numerous arbitrary (and low) limits on things.
2844	of winsocket's select only supported waiting for a max. of C<64> handles	3527
		3528	Early versions of winsocket's select only supported waiting for a maximum
2845	(probably owning to the fact that all windows kernels can only wait for	3529	of C<64> handles (probably owning to the fact that all windows kernels
2846	C<64> things at the same time internally; microsoft recommends spawning a	3530	can only wait for C<64> things at the same time internally; Microsoft
2847	chain of threads and wait for 63 handles and the previous thread in each).	3531	recommends spawning a chain of threads and wait for 63 handles and the
		3532	previous thread in each. Great).
2848		3533
2849	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3534	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2850	to some high number (e.g. C<2048>) before compiling the winsocket select	3535	to some high number (e.g. C<2048>) before compiling the winsocket select
2851	call (which might be in libev or elsewhere, for example, perl does its own	3536	call (which might be in libev or elsewhere, for example, perl does its own
2852	select emulation on windows).	3537	select emulation on windows).
2853		3538
2854	Another limit is the number of file descriptors in the microsoft runtime	3539	Another limit is the number of file descriptors in the Microsoft runtime
2855	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3540	libraries, which by default is C<64> (there must be a hidden I<64> fetish
2856	or something like this inside microsoft). You can increase this by calling	3541	or something like this inside Microsoft). You can increase this by calling
2857	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3542	C<_setmaxstdio>, which can increase this limit to C<2048> (another
2858	arbitrary limit), but is broken in many versions of the microsoft runtime	3543	arbitrary limit), but is broken in many versions of the Microsoft runtime
2859	libraries.	3544	libraries.
2860		3545
2861	This might get you to about C<512> or C<2048> sockets (depending on	3546	This might get you to about C<512> or C<2048> sockets (depending on
2862	windows version and/or the phase of the moon). To get more, you need to	3547	windows version and/or the phase of the moon). To get more, you need to
2863	wrap all I/O functions and provide your own fd management, but the cost of	3548	wrap all I/O functions and provide your own fd management, but the cost of
2864	calling select (O(n²)) will likely make this unworkable.	3549	calling select (O(n²)) will likely make this unworkable.
2865		3550
2866	=back	3551	=back
2867		3552
		3553	=head2 PORTABILITY REQUIREMENTS
		3554
		3555	In addition to a working ISO-C implementation and of course the
		3556	backend-specific APIs, libev relies on a few additional extensions:
		3557
		3558	=over 4
		3559
		3560	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3561	calling conventions regardless of C<ev_watcher_type *>.
		3562
		3563	Libev assumes not only that all watcher pointers have the same internal
		3564	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3565	assumes that the same (machine) code can be used to call any watcher
		3566	callback: The watcher callbacks have different type signatures, but libev
		3567	calls them using an C<ev_watcher *> internally.
		3568
		3569	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3570
		3571	The type C<sig_atomic_t volatile> (or whatever is defined as
		3572	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3573	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3574	believed to be sufficiently portable.
		3575
		3576	=item C<sigprocmask> must work in a threaded environment
		3577
		3578	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3579	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3580	pthread implementations will either allow C<sigprocmask> in the "main
		3581	thread" or will block signals process-wide, both behaviours would
		3582	be compatible with libev. Interaction between C<sigprocmask> and
		3583	C<pthread_sigmask> could complicate things, however.
		3584
		3585	The most portable way to handle signals is to block signals in all threads
		3586	except the initial one, and run the default loop in the initial thread as
		3587	well.
		3588
		3589	=item C<long> must be large enough for common memory allocation sizes
		3590
		3591	To improve portability and simplify its API, libev uses C<long> internally
		3592	instead of C<size_t> when allocating its data structures. On non-POSIX
		3593	systems (Microsoft...) this might be unexpectedly low, but is still at
		3594	least 31 bits everywhere, which is enough for hundreds of millions of
		3595	watchers.
		3596
		3597	=item C<double> must hold a time value in seconds with enough accuracy
		3598
		3599	The type C<double> is used to represent timestamps. It is required to
		3600	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3601	enough for at least into the year 4000. This requirement is fulfilled by
		3602	implementations implementing IEEE 754 (basically all existing ones).
		3603
		3604	=back
		3605
		3606	If you know of other additional requirements drop me a note.
		3607
		3608
		3609	=head1 ALGORITHMIC COMPLEXITIES
		3610
		3611	In this section the complexities of (many of) the algorithms used inside
		3612	libev will be documented. For complexity discussions about backends see
		3613	the documentation for C<ev_default_init>.
		3614
		3615	All of the following are about amortised time: If an array needs to be
		3616	extended, libev needs to realloc and move the whole array, but this
		3617	happens asymptotically rarer with higher number of elements, so O(1) might
		3618	mean that libev does a lengthy realloc operation in rare cases, but on
		3619	average it is much faster and asymptotically approaches constant time.
		3620
		3621	=over 4
		3622
		3623	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3624
		3625	This means that, when you have a watcher that triggers in one hour and
		3626	there are 100 watchers that would trigger before that, then inserting will
		3627	have to skip roughly seven (C<ld 100>) of these watchers.
		3628
		3629	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3630
		3631	That means that changing a timer costs less than removing/adding them,
		3632	as only the relative motion in the event queue has to be paid for.
		3633
		3634	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3635
		3636	These just add the watcher into an array or at the head of a list.
		3637
		3638	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3639
		3640	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3641
		3642	These watchers are stored in lists, so they need to be walked to find the
		3643	correct watcher to remove. The lists are usually short (you don't usually
		3644	have many watchers waiting for the same fd or signal: one is typical, two
		3645	is rare).
		3646
		3647	=item Finding the next timer in each loop iteration: O(1)
		3648
		3649	By virtue of using a binary or 4-heap, the next timer is always found at a
		3650	fixed position in the storage array.
		3651
		3652	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3653
		3654	A change means an I/O watcher gets started or stopped, which requires
		3655	libev to recalculate its status (and possibly tell the kernel, depending
		3656	on backend and whether C<ev_io_set> was used).
		3657
		3658	=item Activating one watcher (putting it into the pending state): O(1)
		3659
		3660	=item Priority handling: O(number_of_priorities)
		3661
		3662	Priorities are implemented by allocating some space for each
		3663	priority. When doing priority-based operations, libev usually has to
		3664	linearly search all the priorities, but starting/stopping and activating
		3665	watchers becomes O(1) with respect to priority handling.
		3666
		3667	=item Sending an ev_async: O(1)
		3668
		3669	=item Processing ev_async_send: O(number_of_async_watchers)
		3670
		3671	=item Processing signals: O(max_signal_number)
		3672
		3673	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3674	calls in the current loop iteration. Checking for async and signal events
		3675	involves iterating over all running async watchers or all signal numbers.
		3676
		3677	=back
		3678
2868		3679
2869	=head1 AUTHOR	3680	=head1 AUTHOR
2870		3681
2871	Marc Lehmann <libev@schmorp.de>.	3682	Marc Lehmann <libev@schmorp.de>.
2872		3683

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