ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.108 by root, Mon Dec 24 10:39:21 2007 UTC vs.
Revision 1.185 by root, Tue Sep 23 09:13:59 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
…		…
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))
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 (;;)
…		…
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));
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
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
265	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
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		310
268	The following flags are supported:	311	The following flags are supported:
269		312
…		…
274	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
275	thing, believe me).	318	thing, believe me).
276		319
277	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
278		321
279	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
280	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
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	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
283	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
284	around bugs.	327	around bugs.
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	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,
293	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
294	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
295	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
296	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
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	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
300	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
301	flag.	344	flag.
302		345
303	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>
304	environment variable.	347	environment variable.
305		348
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		350
308	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
…		…
310	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
311	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
312	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.
313		356
314	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
315	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
316	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
317	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
318	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
319	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).
320		367
321	=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)
322		369
323	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
324	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
325	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
326	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328	performance tips.	375	performance tips.
329		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
330	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
331		381
332	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,
333	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
336	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
337	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
338	support for dup.	388	support for dup.
339		389
340	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
341	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
342	(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
343	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
344	very well if you register events for both fds.	394	very well if you register events for both fds.
345		395
346	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
347	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
348	(or space) is available.	398	(or space) is available.
349		399
350	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
352	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.
353		405
354	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
355	all kernel versions tested so far.	407	all kernel versions tested so far.
356		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		413
359	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
360	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
361	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
362	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
363	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
364	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.
365	system like NetBSD.
366		420
367	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
368	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
369	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
370		424
371	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
372	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
373	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
374	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
375	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
376	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
377		431
378	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
379		433
380	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
381	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
382	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
383	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
385	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>.
386		444
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		446
389	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
390	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		453
396	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,
397	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)).
398		456
399	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
400	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
401	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
402		460
403	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
404	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
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	464	might perform better.
407		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		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>.
		473
408	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
409		475
410	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
411	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
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		479
414	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
415		481
416	=back	482	=back
417		483
418	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
419	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		487
423	The most typical usage is like this:	488	Example: This is the most typical usage.
424		489
425	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		492
428	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
429	environment settings to be taken into account:	494	environment settings to be taken into account:
430		495
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		497
433	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
434	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
435	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
436		502
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		504
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		506
441	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
442	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
443	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
444	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
445		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
446	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.
447		517
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	519	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
451		521
452	=item ev_default_destroy ()	522	=item ev_default_destroy ()
453		523
454	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
458	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
459	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
460	for example).	530	for example).
461		531
462	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
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
475		545
476	=item ev_default_fork ()	546	=item ev_default_fork ()
477		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
481	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
482		554
483	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
486		558
487	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
490		562
491	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
492		564
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
498		566
499	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
500	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
501	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.
502		576
503	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
504		578
505	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
506	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
…		…
521	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
522	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
523	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
524	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
525		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
526	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
527		613
528	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
529	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
530	events.	616	events.
…		…
532	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
533	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.
534		620
535	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
536	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
537	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
538	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
539	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.
540		627
541	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
542	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
543	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.
544		632
545	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
546	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
547	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
548	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
549	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
550	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
551	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
552		644
553	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
554		646
555	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
558	- 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.
559	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
561	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
565	- Queue all outstanding timers.	662	- Queue all expired timers.
566	- Queue all outstanding periodics.	663	- Queue all expired periodics.
567	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
568	- Queue all check watchers.	665	- Queue all check watchers.
569	- 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).
570	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
571	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
572	- 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
573	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
574		672
575	Example: Queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	674	anymore.
577		675
578	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
579	... 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..)
580	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
581	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
582		680
583	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
584		682
585	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
586	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
587	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
588	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.
589		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
590	=item ev_ref (loop)	690	=item ev_ref (loop)
591		691
592	=item ev_unref (loop)	692	=item ev_unref (loop)
593		693
594	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
595	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
596	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
597	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
599	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
600	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
601	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	706	libraries. Just remember to I<unref after start> and I<ref before stop>
		707	(but only if the watcher wasn't active before, or was active before,
		708	respectively).
604		709
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	711	running when nothing else is active.
607		712
608	struct ev_signal exitsig;	713	struct ev_signal exitsig;
609	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
610	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
611	evf_unref (loop);	716	evf_unref (loop);
612		717
613	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
614		719
615	ev_ref (loop);	720	ev_ref (loop);
616	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
617		722
618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619		724
620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621		726
622	These advanced functions influence the time that libev will spend waiting	727	These advanced functions influence the time that libev will spend waiting
623	for events. Both are by default C<0>, meaning that libev will try to	728	for events. Both time intervals are by default C<0>, meaning that libev
624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
625		731
626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	732	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
627	allows libev to delay invocation of I/O and timer/periodic callbacks to	733	allows libev to delay invocation of I/O and timer/periodic callbacks
628	increase efficiency of loop iterations.	734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
629		736
630	The background is that sometimes your program runs just fast enough to	737	The idea is that sometimes your program runs just fast enough to handle
631	handle one (or very few) event(s) per loop iteration. While this makes	738	one (or very few) event(s) per loop iteration. While this makes the
632	the program responsive, it also wastes a lot of CPU time to poll for new	739	program responsive, it also wastes a lot of CPU time to poll for new
633	events, especially with backends like C<select ()> which have a high	740	events, especially with backends like C<select ()> which have a high
634	overhead for the actual polling but can deliver many events at once.	741	overhead for the actual polling but can deliver many events at once.
635		742
636	By setting a higher I<io collect interval> you allow libev to spend more	743	By setting a higher I<io collect interval> you allow libev to spend more
637	time collecting I/O events, so you can handle more events per iteration,	744	time collecting I/O events, so you can handle more events per iteration,
…		…
639	C<ev_timer>) will be not affected. Setting this to a non-null value will	746	C<ev_timer>) will be not affected. Setting this to a non-null value will
640	introduce an additional C<ev_sleep ()> call into most loop iterations.	747	introduce an additional C<ev_sleep ()> call into most loop iterations.
641		748
642	Likewise, by setting a higher I<timeout collect interval> you allow libev	749	Likewise, by setting a higher I<timeout collect interval> you allow libev
643	to spend more time collecting timeouts, at the expense of increased	750	to spend more time collecting timeouts, at the expense of increased
644	latency (the watcher callback will be called later). C<ev_io> watchers	751	latency/jitter/inexactness (the watcher callback will be called
645	will not be affected. Setting this to a non-null value will not introduce	752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
646	any overhead in libev.	753	value will not introduce any overhead in libev.
647		754
648	Many (busy) programs can usually benefit by setting the io collect	755	Many (busy) programs can usually benefit by setting the I/O collect
649	interval to a value near C<0.1> or so, which is often enough for	756	interval to a value near C<0.1> or so, which is often enough for
650	interactive servers (of course not for games), likewise for timeouts. It	757	interactive servers (of course not for games), likewise for timeouts. It
651	usually doesn't make much sense to set it to a lower value than C<0.01>,	758	usually doesn't make much sense to set it to a lower value than C<0.01>,
652	as this approsaches the timing granularity of most systems.	759	as this approaches the timing granularity of most systems.
		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
		768	=item ev_loop_verify (loop)
		769
		770	This function only does something when C<EV_VERIFY> support has been
		771	compiled in. which is the default for non-minimal builds. It tries to go
		772	through all internal structures and checks them for validity. If anything
		773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
		775
		776	This can be used to catch bugs inside libev itself: under normal
		777	circumstances, this function will never abort as of course libev keeps its
		778	data structures consistent.
653		779
654	=back	780	=back
655		781
656		782
657	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
658		784
659	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
660	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
661	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
662		788
663	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
664	{	790	{
665	ev_io_stop (w);	791	ev_io_stop (w);
666	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
667	}	793	}
668		794
669	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
670	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
671	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
672	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
673	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
674	ev_loop (loop, 0);	800	ev_loop (loop, 0);
675		801
676	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
677	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
678	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
679		805
680	Each watcher structure must be initialised by a call to C<ev_init	806	Each watcher structure must be initialised by a call to C<ev_init
681	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
682	callback gets invoked each time the event occurs (or, in the case of io	808	callback gets invoked each time the event occurs (or, in the case of I/O
683	watchers, each time the event loop detects that the file descriptor given	809	watchers, each time the event loop detects that the file descriptor given
684	is readable and/or writable).	810	is readable and/or writable).
685		811
686	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
687	with arguments specific to this watcher type. There is also a macro	813	with arguments specific to this watcher type. There is also a macro
…		…
757	=item C<EV_FORK>	883	=item C<EV_FORK>
758		884
759	The event loop has been resumed in the child process after fork (see	885	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	886	C<ev_fork>).
761		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
762	=item C<EV_ERROR>	892	=item C<EV_ERROR>
763		893
764	An unspecified error has occured, the watcher has been stopped. This might	894	An unspecified error has occurred, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
766	ran out of memory, a file descriptor was found to be closed or any other	896	ran out of memory, a file descriptor was found to be closed or any other
767	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
768	with the watcher being stopped.	898	with the watcher being stopped.
769		899
770	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
771	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
772	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
773	with the error from read() or write(). This will not work in multithreaded	903	the error from read() or write(). This will not work in multi-threaded
774	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
775		906
776	=back	907	=back
777		908
778	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
779		910
…		…
795	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
796		927
797	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
798	int revents)>.	929	int revents)>.
799		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
800	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
801		938
802	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
803	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
804	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
806	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
807		944
808	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
809	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
810		947
		948	See C<ev_init>, above, for an example.
		949
811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
812		951
813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
814	calls into a single call. This is the most convinient method to initialise	953	calls into a single call. This is the most convenient method to initialise
815	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
816		959
817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
818		961
819	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
820	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
821		969
822	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
823		971
824	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
825	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
882		1030
883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
884		1032
885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
886	C<loop> nor C<revents> need to be valid as long as the watcher callback	1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
887	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
888		1037
889	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
890		1039
891	If the watcher is pending, this function returns clears its pending status	1040	If the watcher is pending, this function clears its pending status and
892	and returns its C<revents> bitset (as if its callback was invoked). If the	1041	returns its C<revents> bitset (as if its callback was invoked). If the
893	watcher isn't pending it does nothing and returns C<0>.	1042	watcher isn't pending it does nothing and returns C<0>.
894		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
895	=back	1047	=back
896		1048
897		1049
898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
899		1051
900	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
901	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
902	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
903	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
904	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
905	data:	1057	data:
906		1058
907	struct my_io	1059	struct my_io
908	{	1060	{
909	struct ev_io io;	1061	struct ev_io io;
910	int otherfd;	1062	int otherfd;
911	void *somedata;	1063	void *somedata;
912	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
913	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
914		1070
915	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
916	can cast it back to your own type:	1072	can cast it back to your own type:
917		1073
918	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
919	{	1075	{
920	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
921	...	1077	...
922	}	1078	}
923		1079
924	More interesting and less C-conformant ways of casting your callback type	1080	More interesting and less C-conformant ways of casting your callback type
925	instead have been omitted.	1081	instead have been omitted.
926		1082
927	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
928	watchers:	1084	embedded watchers:
929		1085
930	struct my_biggy	1086	struct my_biggy
931	{	1087	{
932	int some_data;	1088	int some_data;
933	ev_timer t1;	1089	ev_timer t1;
934	ev_timer t2;	1090	ev_timer t2;
935	}	1091	}
936		1092
937	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1093	In this case getting the pointer to C<my_biggy> is a bit more
938	you need to use C<offsetof>:	1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
939		1098
940	#include <stddef.h>	1099	#include <stddef.h>
941		1100
942	static void	1101	static void
943	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
944	{	1103	{
945	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
946	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
947	}	1106	}
948		1107
949	static void	1108	static void
950	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
951	{	1110	{
952	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
953	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
954	}	1113	}
955		1114
956		1115
957	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
958		1117
959	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
983	In general you can register as many read and/or write event watchers per	1142	In general you can register as many read and/or write event watchers per
984	fd as you want (as long as you don't confuse yourself). Setting all file	1143	fd as you want (as long as you don't confuse yourself). Setting all file
985	descriptors to non-blocking mode is also usually a good idea (but not	1144	descriptors to non-blocking mode is also usually a good idea (but not
986	required if you know what you are doing).	1145	required if you know what you are doing).
987		1146
988	You have to be careful with dup'ed file descriptors, though. Some backends	1147	If you cannot use non-blocking mode, then force the use of a
989	(the linux epoll backend is a notable example) cannot handle dup'ed file	1148	known-to-be-good backend (at the time of this writing, this includes only
990	descriptors correctly if you register interest in two or more fds pointing	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
991	to the same underlying file/socket/etc. description (that is, they share
992	the same underlying "file open").
993
994	If you must do this, then force the use of a known-to-be-good backend
995	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996	C<EVBACKEND_POLL>).
997		1150
998	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
999	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
1000	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1001	because there is no data. Not only are some backends known to create a	1154	because there is no data. Not only are some backends known to create a
1002	lot of those (for example solaris ports), it is very easy to get into	1155	lot of those (for example Solaris ports), it is very easy to get into
1003	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1006		1159
1007	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
1008	play around with an Xlib connection), then you have to seperately re-test	1161	not play around with an Xlib connection), then you have to separately
1009	whether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
1010	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
1011	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
1012		1169
1013	=head3 The special problem of disappearing file descriptors	1170	=head3 The special problem of disappearing file descriptors
1014		1171
1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1172	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1016	descriptor (either by calling C<close> explicitly or by any other means,	1173	descriptor (either due to calling C<close> explicitly or any other means,
1017	such as C<dup>). The reason is that you register interest in some file	1174	such as C<dup2>). The reason is that you register interest in some file
1018	descriptor, but when it goes away, the operating system will silently drop	1175	descriptor, but when it goes away, the operating system will silently drop
1019	this interest. If another file descriptor with the same number then is	1176	this interest. If another file descriptor with the same number then is
1020	registered with libev, there is no efficient way to see that this is, in	1177	registered with libev, there is no efficient way to see that this is, in
1021	fact, a different file descriptor.	1178	fact, a different file descriptor.
1022		1179
…		…
1033		1190
1034	=head3 The special problem of dup'ed file descriptors	1191	=head3 The special problem of dup'ed file descriptors
1035		1192
1036	Some backends (e.g. epoll), cannot register events for file descriptors,	1193	Some backends (e.g. epoll), cannot register events for file descriptors,
1037	but only events for the underlying file descriptions. That means when you	1194	but only events for the underlying file descriptions. That means when you
1038	have C<dup ()>'ed file descriptors and register events for them, only one	1195	have C<dup ()>'ed file descriptors or weirder constellations, and register
1039	file descriptor might actually receive events.	1196	events for them, only one file descriptor might actually receive events.
1040		1197
1041	There is no workaround possible except not registering events	1198	There is no workaround possible except not registering events
1042	for potentially C<dup ()>'ed file descriptors, or to resort to	1199	for potentially C<dup ()>'ed file descriptors, or to resort to
1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1200	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044		1201
…		…
1051	To support fork in your programs, you either have to call	1208	To support fork in your programs, you either have to call
1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1054	C<EVBACKEND_POLL>.	1211	C<EVBACKEND_POLL>.
1055		1212
		1213	=head3 The special problem of SIGPIPE
		1214
		1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1216	when writing to a pipe whose other end has been closed, your program gets
		1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1218	this is sensible behaviour, for daemons, this is usually undesirable.
		1219
		1220	So when you encounter spurious, unexplained daemon exits, make sure you
		1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1222	somewhere, as that would have given you a big clue).
		1223
1056		1224
1057	=head3 Watcher-Specific Functions	1225	=head3 Watcher-Specific Functions
1058		1226
1059	=over 4	1227	=over 4
1060		1228
1061	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
1062		1230
1063	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
1064		1232
1065	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1066	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1067	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1068		1236
1069	=item int fd [read-only]	1237	=item int fd [read-only]
1070		1238
1071	The file descriptor being watched.	1239	The file descriptor being watched.
1072		1240
1073	=item int events [read-only]	1241	=item int events [read-only]
1074		1242
1075	The events being watched.	1243	The events being watched.
1076		1244
1077	=back	1245	=back
		1246
		1247	=head3 Examples
1078		1248
1079	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
1081	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
1082		1252
1083	static void	1253	static void
1084	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1085	{	1255	{
1086	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
1087	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
1088	}	1258	}
1089		1259
1090	...	1260	...
1091	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
1092	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
1093	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1094	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
1095	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
1096		1266
1097		1267
1098	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
1099		1269
1100	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
1101	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
1102		1272
1103	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
1104	times out after an hour and you reset your system clock to last years	1274	times out after an hour and you reset your system clock to January last
1105	time, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
1106	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1107	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
1108		1290
1109	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
1110	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
1111	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
1112	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
1113	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
1114		1296
1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1116		1298
1117	The callback is guarenteed to be invoked only when its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
1118	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1119	order of execution is undefined.	1301	()>.
1120		1302
1121	=head3 Watcher-Specific Functions and Data Members	1303	=head3 Watcher-Specific Functions and Data Members
1122		1304
1123	=over 4	1305	=over 4
1124		1306
1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1126		1308
1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1128		1310
1129	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1311	Configure the timer to trigger after C<after> seconds. If C<repeat>
1130	C<0.>, then it will automatically be stopped. If it is positive, then the	1312	is C<0.>, then it will automatically be stopped once the timeout is
1131	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
1132	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
1133		1316
1134	The timer itself will do a best-effort at avoiding drift, that is, if you	1317	The timer itself will do a best-effort at avoiding drift, that is, if
1135	configure a timer to trigger every 10 seconds, then it will trigger at	1318	you configure a timer to trigger every 10 seconds, then it will normally
1136	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
1137	the timer (because it takes longer than those 10 seconds to do stuff) the	1320	keep up with the timer (because it takes longer than those 10 seconds to
1138	timer will not fire more than once per event loop iteration.	1321	do stuff) the timer will not fire more than once per event loop iteration.
1139		1322
1140	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
1141		1324
1142	This will act as if the timer timed out and restart it again if it is	1325	This will act as if the timer timed out and restart it again if it is
1143	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
1144		1327
1145	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
1146		1329
1147	If the timer is started but nonrepeating, stop it (as if it timed out).	1330	If the timer is started but non-repeating, stop it (as if it timed out).
1148		1331
1149	If the timer is repeating, either start it if necessary (with the	1332	If the timer is repeating, either start it if necessary (with the
1150	C<repeat> value), or reset the running timer to the C<repeat> value.	1333	C<repeat> value), or reset the running timer to the C<repeat> value.
1151		1334
1152	This sounds a bit complicated, but here is a useful and typical	1335	This sounds a bit complicated, but here is a useful and typical
1153	example: Imagine you have a tcp connection and you want a so-called idle	1336	example: Imagine you have a TCP connection and you want a so-called idle
1154	timeout, that is, you want to be called when there have been, say, 60	1337	timeout, that is, you want to be called when there have been, say, 60
1155	seconds of inactivity on the socket. The easiest way to do this is to	1338	seconds of inactivity on the socket. The easiest way to do this is to
1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1157	C<ev_timer_again> each time you successfully read or write some data. If	1340	C<ev_timer_again> each time you successfully read or write some data. If
1158	you go into an idle state where you do not expect data to travel on the	1341	you go into an idle state where you do not expect data to travel on the
…		…
1172	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1173		1356
1174	This is more slightly efficient then stopping/starting the timer each time	1357	This is more slightly efficient then stopping/starting the timer each time
1175	you want to modify its timeout value.	1358	you want to modify its timeout value.
1176		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
		1365
1177	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1178		1367
1179	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
1180	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
1181	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1182		1371
1183	=back	1372	=back
1184		1373
		1374	=head3 Examples
		1375
1185	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1186		1377
1187	static void	1378	static void
1188	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189	{	1380	{
1190	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1191	}	1382	}
1192		1383
1193	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1194	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1195	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1196		1387
1197	Example: Create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
1198	inactivity.	1389	inactivity.
1199		1390
1200	static void	1391	static void
1201	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1202	{	1393	{
1203	.. ten seconds without any activity	1394	.. ten seconds without any activity
1204	}	1395	}
1205		1396
1206	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1207	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1208	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1209	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1210		1401
1211	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
1212	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1213	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1214		1405
1215		1406
1216	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1217		1408
1218	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
1219	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1220		1411
1221	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1222	but on wallclock time (absolute time). You can tell a periodic watcher	1413	but on wall clock time (absolute time). You can tell a periodic watcher
1223	to trigger "at" some specific point in time. For example, if you tell a	1414	to trigger after some specific point in time. For example, if you tell a
1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1225	+ 10.>) and then reset your system clock to the last year, then it will	1416	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1417	clock to January of the previous year, then it will take more than year
1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1227	roughly 10 seconds later).	1419	roughly 10 seconds later as it uses a relative timeout).
1228		1420
1229	They can also be used to implement vastly more complex timers, such as	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
1230	triggering an event on each midnight, local time or other, complicated,	1422	such as triggering an event on each "midnight, local time", or other
1231	rules.	1423	complicated rules.
1232		1424
1233	As with timers, the callback is guarenteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
1234	time (C<at>) has been passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
1235	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
1236		1428
1237	=head3 Watcher-Specific Functions and Data Members	1429	=head3 Watcher-Specific Functions and Data Members
1238		1430
1239	=over 4	1431	=over 4
1240		1432
1241	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1242		1434
1243	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1244		1436
1245	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
1246	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1247		1439
1248	=over 4	1440	=over 4
1249		1441
1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1251		1443
1252	In this configuration the watcher triggers an event at the wallclock time	1444	In this configuration the watcher triggers an event after the wall clock
1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1445	time C<at> has passed. It will not repeat and will not adjust when a time
1254	that is, if it is to be run at January 1st 2011 then it will run when the	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1255	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1256		1448
1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258		1450
1259	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
1260	C<at + N * interval> time (for some integer N, which can also be negative)	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1261	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1262		1454
1263	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
1264	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1265		1458
1266	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1267		1460
1268	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1269	but only that the the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
1270	full hour (UTC), or more correctly, when the system time is evenly divisible	1463	full hour (UTC), or more correctly, when the system time is evenly divisible
1271	by 3600.	1464	by 3600.
1272		1465
1273	Another way to think about it (for the mathematically inclined) is that	1466	Another way to think about it (for the mathematically inclined) is that
1274	C<ev_periodic> will try to run the callback in this mode at the next possible	1467	C<ev_periodic> will try to run the callback in this mode at the next possible
1275	time where C<time = at (mod interval)>, regardless of any time jumps.	1468	time where C<time = at (mod interval)>, regardless of any time jumps.
1276		1469
1277	For numerical stability it is preferable that the C<at> value is near	1470	For numerical stability it is preferable that the C<at> value is near
1278	C<ev_now ()> (the current time), but there is no range requirement for	1471	C<ev_now ()> (the current time), but there is no range requirement for
1279	this value.	1472	this value, and in fact is often specified as zero.
		1473
		1474	Note also that there is an upper limit to how often a timer can fire (CPU
		1475	speed for example), so if C<interval> is very small then timing stability
		1476	will of course deteriorate. Libev itself tries to be exact to be about one
		1477	millisecond (if the OS supports it and the machine is fast enough).
1280		1478
1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1282		1480
1283	In this mode the values for C<interval> and C<at> are both being	1481	In this mode the values for C<interval> and C<at> are both being
1284	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1285	reschedule callback will be called with the watcher as first, and the	1483	reschedule callback will be called with the watcher as first, and the
1286	current time as second argument.	1484	current time as second argument.
1287		1485
1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1289	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1291	starting an C<ev_prepare> watcher, which is legal).
1292		1488
		1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1491	only event loop modification you are allowed to do).
		1492
1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1294	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1295		1495
1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1297	{	1497	{
1298	return now + 60.;	1498	return now + 60.;
1299	}	1499	}
…		…
1301	It must return the next time to trigger, based on the passed time value	1501	It must return the next time to trigger, based on the passed time value
1302	(that is, the lowest time value larger than to the second argument). It	1502	(that is, the lowest time value larger than to the second argument). It
1303	will usually be called just before the callback will be triggered, but	1503	will usually be called just before the callback will be triggered, but
1304	might be called at other times, too.	1504	might be called at other times, too.
1305		1505
1306	NOTE: I<< This callback must always return a time that is later than the	1506	NOTE: I<< This callback must always return a time that is higher than or
1307	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1308		1508
1309	This can be used to create very complex timers, such as a timer that	1509	This can be used to create very complex timers, such as a timer that
1310	triggers on each midnight, local time. To do this, you would calculate the	1510	triggers on "next midnight, local time". To do this, you would calculate the
1311	next midnight after C<now> and return the timestamp value for this. How	1511	next midnight after C<now> and return the timestamp value for this. How
1312	you do this is, again, up to you (but it is not trivial, which is the main	1512	you do this is, again, up to you (but it is not trivial, which is the main
1313	reason I omitted it as an example).	1513	reason I omitted it as an example).
1314		1514
1315	=back	1515	=back
…		…
1319	Simply stops and restarts the periodic watcher again. This is only useful	1519	Simply stops and restarts the periodic watcher again. This is only useful
1320	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1321	a different time than the last time it was called (e.g. in a crond like	1521	a different time than the last time it was called (e.g. in a crond like
1322	program when the crontabs have changed).	1522	program when the crontabs have changed).
1323		1523
		1524	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1525
		1526	When active, returns the absolute time that the watcher is supposed to
		1527	trigger next.
		1528
1324	=item ev_tstamp offset [read-write]	1529	=item ev_tstamp offset [read-write]
1325		1530
1326	When repeating, this contains the offset value, otherwise this is the	1531	When repeating, this contains the offset value, otherwise this is the
1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1328		1533
…		…
1339		1544
1340	The current reschedule callback, or C<0>, if this functionality is	1545	The current reschedule callback, or C<0>, if this functionality is
1341	switched off. Can be changed any time, but changes only take effect when	1546	switched off. Can be changed any time, but changes only take effect when
1342	the periodic timer fires or C<ev_periodic_again> is being called.	1547	the periodic timer fires or C<ev_periodic_again> is being called.
1343		1548
1344	=item ev_tstamp at [read-only]
1345
1346	When active, contains the absolute time that the watcher is supposed to
1347	trigger next.
1348
1349	=back	1549	=back
1350		1550
		1551	=head3 Examples
		1552
1351	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1352	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1353	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1354		1556
1355	static void	1557	static void
1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1357	{	1559	{
1358	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1359	}	1561	}
1360		1562
1361	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1363	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1364		1566
1365	Example: The same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1366		1568
1367	#include <math.h>	1569	#include <math.h>
1368		1570
1369	static ev_tstamp	1571	static ev_tstamp
1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1371	{	1573	{
1372	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1373	}	1575	}
1374		1576
1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1376		1578
1377	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1378		1580
1379	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1380	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1381	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1382	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1383		1585
1384		1586
1385	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1386		1588
1387	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1388	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1389	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1390	normal event processing, like any other event.	1592	normal event processing, like any other event.
1391		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1392	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1393	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1394	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1395	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1396	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1397	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
		1604
		1605	If possible and supported, libev will install its handlers with
		1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1607	interrupted. If you have a problem with system calls getting interrupted by
		1608	signals you can block all signals in an C<ev_check> watcher and unblock
		1609	them in an C<ev_prepare> watcher.
1398		1610
1399	=head3 Watcher-Specific Functions and Data Members	1611	=head3 Watcher-Specific Functions and Data Members
1400		1612
1401	=over 4	1613	=over 4
1402		1614
…		…
1411		1623
1412	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1413		1625
1414	=back	1626	=back
1415		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1631
		1632	static void
		1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1634	{
		1635	ev_unloop (loop, EVUNLOOP_ALL);
		1636	}
		1637
		1638	struct ev_signal signal_watcher;
		1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1640	ev_signal_start (loop, &sigint_cb);
		1641
1416		1642
1417	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1418		1644
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1646	some child status changes (most typically when a child of yours dies or
		1647	exits). It is permissible to install a child watcher I<after> the child
		1648	has been forked (which implies it might have already exited), as long
		1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
		1653
		1654	Only the default event loop is capable of handling signals, and therefore
		1655	you can only register child watchers in the default event loop.
		1656
		1657	=head3 Process Interaction
		1658
		1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1660	initialised. This is necessary to guarantee proper behaviour even if
		1661	the first child watcher is started after the child exits. The occurrence
		1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1663	synchronously as part of the event loop processing. Libev always reaps all
		1664	children, even ones not watched.
		1665
		1666	=head3 Overriding the Built-In Processing
		1667
		1668	Libev offers no special support for overriding the built-in child
		1669	processing, but if your application collides with libev's default child
		1670	handler, you can override it easily by installing your own handler for
		1671	C<SIGCHLD> after initialising the default loop, and making sure the
		1672	default loop never gets destroyed. You are encouraged, however, to use an
		1673	event-based approach to child reaping and thus use libev's support for
		1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
1421		1682
1422	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1423		1684
1424	=over 4	1685	=over 4
1425		1686
1426	=item ev_child_init (ev_child *, callback, int pid)	1687	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1688
1428	=item ev_child_set (ev_child *, int pid)	1689	=item ev_child_set (ev_child *, int pid, int trace)
1429		1690
1430	Configures the watcher to wait for status changes of process C<pid> (or	1691	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1692	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1693	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1694	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1695	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1696	process causing the status change. C<trace> must be either C<0> (only
		1697	activate the watcher when the process terminates) or C<1> (additionally
		1698	activate the watcher when the process is stopped or continued).
1436		1699
1437	=item int pid [read-only]	1700	=item int pid [read-only]
1438		1701
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1702	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1703
…		…
1447	The process exit/trace status caused by C<rpid> (see your systems	1710	The process exit/trace status caused by C<rpid> (see your systems
1448	C<waitpid> and C<sys/wait.h> documentation for details).	1711	C<waitpid> and C<sys/wait.h> documentation for details).
1449		1712
1450	=back	1713	=back
1451		1714
1452	Example: Try to exit cleanly on SIGINT and SIGTERM.	1715	=head3 Examples
1453		1716
		1717	Example: C<fork()> a new process and install a child handler to wait for
		1718	its completion.
		1719
		1720	ev_child cw;
		1721
1454	static void	1722	static void
1455	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1456	{	1724	{
1457	ev_unloop (loop, EVUNLOOP_ALL);	1725	ev_child_stop (EV_A_ w);
		1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458	}	1727	}
1459		1728
1460	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1461	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1462	ev_signal_start (loop, &sigint_cb);	1731	if (pid < 0)
		1732	// error
		1733	else if (pid == 0)
		1734	{
		1735	// the forked child executes here
		1736	exit (1);
		1737	}
		1738	else
		1739	{
		1740	ev_child_init (&cw, child_cb, pid, 0);
		1741	ev_child_start (EV_DEFAULT_ &cw);
		1742	}
1463		1743
1464		1744
1465	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1466		1746
1467	This watches a filesystem path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
1468	C<stat> regularly (or when the OS says it changed) and sees if it changed	1748	C<stat> regularly (or when the OS says it changed) and sees if it changed
1469	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1470		1750
1471	The path does not need to exist: changing from "path exists" to "path does	1751	The path does not need to exist: changing from "path exists" to "path does
1472	not exist" is a status change like any other. The condition "path does	1752	not exist" is a status change like any other. The condition "path does
…		…
1475	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1476		1756
1477	The path I<should> be absolute and I<must not> end in a slash. If it is	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1478	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1479		1759
1480	Since there is no standard to do this, the portable implementation simply	1760	Since there is no standard kernel interface to do this, the portable
1481	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1482	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1483	a polling interval of C<0> (highly recommended!) then a I<suitable,	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1484	unspecified default> value will be used (which you can expect to be around	1764	then a I<suitable, unspecified default> value will be used (which
1485	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1486	impose a minimum interval which is currently around C<0.1>, but thats	1766	dynamically). Libev will also impose a minimum interval which is currently
1487	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1488		1768
1489	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1490	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1491	resource-intensive.	1771	resource-intensive.
1492		1772
1493	At the time of this writing, only the Linux inotify interface is	1773	At the time of this writing, the only OS-specific interface implemented
1494	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1495	reader). Inotify will be used to give hints only and should not change the	1775	an exercise for the reader. Note, however, that the author sees no way
1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1497	to fall back to regular polling again even with inotify, but changes are
1498	usually detected immediately, and if the file exists there will be no
1499	polling.
1500		1777
1501	=head3 Inotify	1778	=head3 ABI Issues (Largefile Support)
		1779
		1780	Libev by default (unless the user overrides this) uses the default
		1781	compilation environment, which means that on systems with large file
		1782	support disabled by default, you get the 32 bit version of the stat
		1783	structure. When using the library from programs that change the ABI to
		1784	use 64 bit file offsets the programs will fail. In that case you have to
		1785	compile libev with the same flags to get binary compatibility. This is
		1786	obviously the case with any flags that change the ABI, but the problem is
		1787	most noticeably disabled with ev_stat and large file support.
		1788
		1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
1502		1796
1503	When C<inotify (7)> support has been compiled into libev (generally only	1797	When C<inotify (7)> support has been compiled into libev (generally only
1504	available on Linux) and present at runtime, it will be used to speed up	1798	available with Linux) and present at runtime, it will be used to speed up
1505	change detection where possible. The inotify descriptor will be created lazily	1799	change detection where possible. The inotify descriptor will be created lazily
1506	when the first C<ev_stat> watcher is being started.	1800	when the first C<ev_stat> watcher is being started.
1507		1801
1508	Inotify presense does not change the semantics of C<ev_stat> watchers	1802	Inotify presence does not change the semantics of C<ev_stat> watchers
1509	except that changes might be detected earlier, and in some cases, to avoid	1803	except that changes might be detected earlier, and in some cases, to avoid
1510	making regular C<stat> calls. Even in the presense of inotify support	1804	making regular C<stat> calls. Even in the presence of inotify support
1511	there are many cases where libev has to resort to regular C<stat> polling.	1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
1512		1807
1513	(There is no support for kqueue, as apparently it cannot be used to	1808	There is no support for kqueue, as apparently it cannot be used to
1514	implement this functionality, due to the requirement of having a file	1809	implement this functionality, due to the requirement of having a file
1515	descriptor open on the object at all times).	1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
1516		1812
1517	=head3 The special problem of stat time resolution	1813	=head3 The special problem of stat time resolution
1518		1814
1519	The C<stat ()> syscall only supports full-second resolution portably, and	1815	The C<stat ()> system call only supports full-second resolution portably, and
1520	even on systems where the resolution is higher, many filesystems still	1816	even on systems where the resolution is higher, most file systems still
1521	only support whole seconds.	1817	only support whole seconds.
1522		1818
1523	That means that, if the time is the only thing that changes, you might	1819	That means that, if the time is the only thing that changes, you can
1524	miss updates: on the first update, C<ev_stat> detects a change and calls	1820	easily miss updates: on the first update, C<ev_stat> detects a change and
1525	your callback, which does something. When there is another update within	1821	calls your callback, which does something. When there is another update
1526	the same second, C<ev_stat> will be unable to detect it.	1822	within the same second, C<ev_stat> will be unable to detect unless the
		1823	stat data does change in other ways (e.g. file size).
1527		1824
1528	The solution to this is to delay acting on a change for a second (or till	1825	The solution to this is to delay acting on a change for slightly more
1529	the next second boundary), using a roughly one-second delay C<ev_timer>	1826	than a second (or till slightly after the next full second boundary), using
1530	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1531	is added to work around small timing inconsistencies of some operating	1828	ev_timer_again (loop, w)>).
1532	systems.	1829
		1830	The C<.02> offset is added to work around small timing inconsistencies
		1831	of some operating systems (where the second counter of the current time
		1832	might be be delayed. One such system is the Linux kernel, where a call to
		1833	C<gettimeofday> might return a timestamp with a full second later than
		1834	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1835	update file times then there will be a small window where the kernel uses
		1836	the previous second to update file times but libev might already execute
		1837	the timer callback).
1533		1838
1534	=head3 Watcher-Specific Functions and Data Members	1839	=head3 Watcher-Specific Functions and Data Members
1535		1840
1536	=over 4	1841	=over 4
1537		1842
…		…
1543	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1544	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1545	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1546	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1547		1852
1548	The callback will be receive C<EV_STAT> when a change was detected,	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1549	relative to the attributes at the time the watcher was started (or the	1854	relative to the attributes at the time the watcher was started (or the
1550	last change was detected).	1855	last change was detected).
1551		1856
1552	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1553		1858
1554	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1555	watched path in your callback, you could call this fucntion to avoid	1860	watched path in your callback, you could call this function to avoid
1556	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1557	useful simply to find out the new values.	1862	the only one changing the path). Can also be useful simply to find out the
		1863	new values.
1558		1864
1559	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1560		1866
1561	The most-recently detected attributes of the file. Although the type is of	1867	The most-recently detected attributes of the file. Although the type is
1562	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1868	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1563	suitable for your system. If the C<st_nlink> member is C<0>, then there	1869	suitable for your system, but you can only rely on the POSIX-standardised
		1870	members to be present. If the C<st_nlink> member is C<0>, then there was
1564	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1565		1872
1566	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1567		1874
1568	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1569	C<prev> != C<attr>.	1876	C<prev> != C<attr>, or, more precisely, one or more of these members
		1877	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1878	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1570		1879
1571	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1572		1881
1573	The specified interval.	1882	The specified interval.
1574		1883
1575	=item const char *path [read-only]	1884	=item const char *path [read-only]
1576		1885
1577	The filesystem path that is being watched.	1886	The file system path that is being watched.
1578		1887
1579	=back	1888	=back
1580		1889
1581	=head3 Examples	1890	=head3 Examples
1582		1891
1583	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1584		1893
1585	static void	1894	static void
1586	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1587	{	1896	{
1588	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1589	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1590	{	1899	{
1591	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1592	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1593	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1594	}	1903	}
1595	else	1904	else
1596	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1597	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1598	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1599	}	1908	}
1600		1909
1601	...	1910	...
1602	ev_stat passwd;	1911	ev_stat passwd;
1603		1912
1604	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1605	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
1606		1915
1607	Example: Like above, but additionally use a one-second delay so we do not	1916	Example: Like above, but additionally use a one-second delay so we do not
1608	miss updates (however, frequent updates will delay processing, too, so	1917	miss updates (however, frequent updates will delay processing, too, so
1609	one might do the work both on C<ev_stat> callback invocation I<and> on	1918	one might do the work both on C<ev_stat> callback invocation I<and> on
1610	C<ev_timer> callback invocation).	1919	C<ev_timer> callback invocation).
1611		1920
1612	static ev_stat passwd;	1921	static ev_stat passwd;
1613	static ev_timer timer;	1922	static ev_timer timer;
1614		1923
1615	static void	1924	static void
1616	timer_cb (EV_P_ ev_timer *w, int revents)	1925	timer_cb (EV_P_ ev_timer *w, int revents)
1617	{	1926	{
1618	ev_timer_stop (EV_A_ w);	1927	ev_timer_stop (EV_A_ w);
1619		1928
1620	/* now it's one second after the most recent passwd change */	1929	/* now it's one second after the most recent passwd change */
1621	}	1930	}
1622		1931
1623	static void	1932	static void
1624	stat_cb (EV_P_ ev_stat *w, int revents)	1933	stat_cb (EV_P_ ev_stat *w, int revents)
1625	{	1934	{
1626	/* reset the one-second timer */	1935	/* reset the one-second timer */
1627	ev_timer_again (EV_A_ &timer);	1936	ev_timer_again (EV_A_ &timer);
1628	}	1937	}
1629		1938
1630	...	1939	...
1631	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1632	ev_stat_start (loop, &passwd);	1941	ev_stat_start (loop, &passwd);
1633	ev_timer_init (&timer, timer_cb, 0., 1.01);	1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1634		1943
1635		1944
1636	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1637		1946
1638	Idle watchers trigger events when no other events of the same or higher	1947	Idle watchers trigger events when no other events of the same or higher
1639	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1640	count).	1949	as receiving "events").
1641		1950
1642	That is, as long as your process is busy handling sockets or timeouts	1951	That is, as long as your process is busy handling sockets or timeouts
1643	(or even signals, imagine) of the same or higher priority it will not be	1952	(or even signals, imagine) of the same or higher priority it will not be
1644	triggered. But when your process is idle (or only lower-priority watchers	1953	triggered. But when your process is idle (or only lower-priority watchers
1645	are pending), the idle watchers are being called once per event loop	1954	are pending), the idle watchers are being called once per event loop
…		…
1664	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1665	believe me.	1974	believe me.
1666		1975
1667	=back	1976	=back
1668		1977
		1978	=head3 Examples
		1979
1669	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1670	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1671		1982
1672	static void	1983	static void
1673	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1674	{	1985	{
1675	free (w);	1986	free (w);
1676	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1677	// no longer asnything immediate to do.	1988	// no longer anything immediate to do.
1678	}	1989	}
1679		1990
1680	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1681	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1682	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1683		1994
1684		1995
1685	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1686		1997
1687	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1688	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1689	afterwards.	2000	afterwards.
1690		2001
1691	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1692	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1695	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1696	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1697	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1698		2009
1699	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1700	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1701	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1702	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1703	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1704	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1705	watcher).	2016	watcher).
1706		2017
1707	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1708	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1709	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1710	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1711	any events that occured (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1712	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1713	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1714	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1715		2026
1716	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1717	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1718	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1719	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1722	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1723	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1724		2035
1725	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1726	priority, to ensure that they are being run before any other watchers	2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
1727	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1728	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1729	supports this, they will be called before other C<ev_check> watchers	2042	might get executed before other C<ev_check> watchers did their job. As
1730	did their job. As C<ev_check> watchers are often used to embed other	2043	C<ev_check> watchers are often used to embed other (non-libev) event
1731	(non-libev) event loops those other event loops might be in an unusable	2044	loops those other event loops might be in an unusable state until their
1732	state until their C<ev_check> watcher ran (always remind yourself to	2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1733	coexist peacefully with others).	2046	others).
1734		2047
1735	=head3 Watcher-Specific Functions and Data Members	2048	=head3 Watcher-Specific Functions and Data Members
1736		2049
1737	=over 4	2050	=over 4
1738		2051
…		…
1740		2053
1741	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1742		2055
1743	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1744	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1745	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1746		2060
1747	=back	2061	=back
		2062
		2063	=head3 Examples
1748		2064
1749	There are a number of principal ways to embed other event loops or modules	2065	There are a number of principal ways to embed other event loops or modules
1750	into libev. Here are some ideas on how to include libadns into libev	2066	into libev. Here are some ideas on how to include libadns into libev
1751	(there is a Perl module named C<EV::ADNS> that does this, which you could	2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
1752	use for an actually working example. Another Perl module named C<EV::Glib>	2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
1753	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1754	into the Glib event loop).	2070	Glib event loop).
1755		2071
1756	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1757	and in a check watcher, destroy them and call into libadns. What follows	2073	and in a check watcher, destroy them and call into libadns. What follows
1758	is pseudo-code only of course. This requires you to either use a low	2074	is pseudo-code only of course. This requires you to either use a low
1759	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1760	the callbacks for the IO/timeout watchers might not have been called yet.	2076	the callbacks for the IO/timeout watchers might not have been called yet.
1761		2077
1762	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1763	static ev_timer tw;	2079	static ev_timer tw;
1764		2080
1765	static void	2081	static void
1766	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1767	{	2083	{
1768	}	2084	}
1769		2085
1770	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1771	static void	2087	static void
1772	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1773	{	2089	{
1774	int timeout = 3600000;	2090	int timeout = 3600000;
1775	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1776	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1777	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1778		2094
1779	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1780	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1781	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1782		2098
1783	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1784	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1785	{	2101	{
1786	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1787	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1788	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1789		2105
1790	fds [i].revents = 0;	2106	fds [i].revents = 0;
1791	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1792	}	2108	}
1793	}	2109	}
1794		2110
1795	// stop all watchers after blocking	2111	// stop all watchers after blocking
1796	static void	2112	static void
1797	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1798	{	2114	{
1799	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1800		2116
1801	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1802	{	2118	{
1803	// set the relevant poll flags	2119	// set the relevant poll flags
1804	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1805	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1806	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1807	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1808	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1809		2125
1810	// now stop the watcher	2126	// now stop the watcher
1811	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
1812	}	2128	}
1813		2129
1814	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1815	}	2131	}
1816		2132
1817	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1818	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
1819		2135
1820	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
1821	notification (adns does), you can also make use of the actual watcher	2137	notification (libadns does), you can also make use of the actual watcher
1822	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
1823		2139
1824	static void	2140	static void
1825	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
1826	{	2142	{
1827	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
1828	update_now (EV_A);	2144	update_now (EV_A);
1829		2145
1830	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
1831	}	2147	}
1832		2148
1833	static void	2149	static void
1834	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
1835	{	2151	{
1836	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1837	update_now (EV_A);	2153	update_now (EV_A);
1838		2154
1839	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1840	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1841	}	2157	}
1842		2158
1843	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
1844		2160
1845	Method 4: Do not use a prepare or check watcher because the module you	2161	Method 4: Do not use a prepare or check watcher because the module you
1846	want to embed is too inflexible to support it. Instead, youc na override	2162	want to embed is not flexible enough to support it. Instead, you can
1847	their poll function. The drawback with this solution is that the main	2163	override their poll function. The drawback with this solution is that the
1848	loop is now no longer controllable by EV. The C<Glib::EV> module does	2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1849	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
1850		2167
1851	static gint	2168	static gint
1852	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1853	{	2170	{
1854	int got_events = 0;	2171	int got_events = 0;
1855		2172
1856	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
1857	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1858		2175
1859	if (timeout >= 0)	2176	if (timeout >= 0)
1860	// create/start timer	2177	// create/start timer
1861		2178
1862	// poll	2179	// poll
1863	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
1864		2181
1865	// stop timer again	2182	// stop timer again
1866	if (timeout >= 0)	2183	if (timeout >= 0)
1867	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
1868		2185
1869	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
1870	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
1871	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
1872		2189
1873	return got_events;	2190	return got_events;
1874	}	2191	}
1875		2192
1876		2193
1877	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1878		2195
1879	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
…		…
1885	prioritise I/O.	2202	prioritise I/O.
1886		2203
1887	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
1888	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
1889	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
1890	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
1891	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
1892	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
1893	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1894		2212
1895	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
1896	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
1897	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
1898	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
1899	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
1900		2218
1901	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
1902	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
1903	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1904	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
1912	interested in that.	2230	interested in that.
1913		2231
1914	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1915	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1916	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
1917	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1918		2237
1919	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
1920	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1921	portable one.	2240	portable one.
1922		2241
1923	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
1924	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
1925	this is to have a separate variables for your embeddable loop, try to	2244	this is to have a separate variables for your embeddable loop, try to
1926	create it, and if that fails, use the normal loop for everything:	2245	create it, and if that fails, use the normal loop for everything.
1927
1928	struct ev_loop *loop_hi = ev_default_init (0);
1929	struct ev_loop *loop_lo = 0;
1930	struct ev_embed embed;
1931
1932	// see if there is a chance of getting one that works
1933	// (remember that a flags value of 0 means autodetection)
1934	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1935	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1936	: 0;
1937
1938	// if we got one, then embed it, otherwise default to loop_hi
1939	if (loop_lo)
1940	{
1941	ev_embed_init (&embed, 0, loop_lo);
1942	ev_embed_start (loop_hi, &embed);
1943	}
1944	else
1945	loop_lo = loop_hi;
1946		2246
1947	=head3 Watcher-Specific Functions and Data Members	2247	=head3 Watcher-Specific Functions and Data Members
1948		2248
1949	=over 4	2249	=over 4
1950		2250
…		…
1954		2254
1955	Configures the watcher to embed the given loop, which must be	2255	Configures the watcher to embed the given loop, which must be
1956	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2256	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1957	invoked automatically, otherwise it is the responsibility of the callback	2257	invoked automatically, otherwise it is the responsibility of the callback
1958	to invoke it (it will continue to be called until the sweep has been done,	2258	to invoke it (it will continue to be called until the sweep has been done,
1959	if you do not want thta, you need to temporarily stop the embed watcher).	2259	if you do not want that, you need to temporarily stop the embed watcher).
1960		2260
1961	=item ev_embed_sweep (loop, ev_embed *)	2261	=item ev_embed_sweep (loop, ev_embed *)
1962		2262
1963	Make a single, non-blocking sweep over the embedded loop. This works	2263	Make a single, non-blocking sweep over the embedded loop. This works
1964	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2264	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1965	apropriate way for embedded loops.	2265	appropriate way for embedded loops.
1966		2266
1967	=item struct ev_loop *other [read-only]	2267	=item struct ev_loop *other [read-only]
1968		2268
1969	The embedded event loop.	2269	The embedded event loop.
1970		2270
1971	=back	2271	=back
		2272
		2273	=head3 Examples
		2274
		2275	Example: Try to get an embeddable event loop and embed it into the default
		2276	event loop. If that is not possible, use the default loop. The default
		2277	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2279	used).
		2280
		2281	struct ev_loop *loop_hi = ev_default_init (0);
		2282	struct ev_loop *loop_lo = 0;
		2283	struct ev_embed embed;
		2284
		2285	// see if there is a chance of getting one that works
		2286	// (remember that a flags value of 0 means autodetection)
		2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2289	: 0;
		2290
		2291	// if we got one, then embed it, otherwise default to loop_hi
		2292	if (loop_lo)
		2293	{
		2294	ev_embed_init (&embed, 0, loop_lo);
		2295	ev_embed_start (loop_hi, &embed);
		2296	}
		2297	else
		2298	loop_lo = loop_hi;
		2299
		2300	Example: Check if kqueue is available but not recommended and create
		2301	a kqueue backend for use with sockets (which usually work with any
		2302	kqueue implementation). Store the kqueue/socket-only event loop in
		2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2304
		2305	struct ev_loop *loop = ev_default_init (0);
		2306	struct ev_loop *loop_socket = 0;
		2307	struct ev_embed embed;
		2308
		2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2311	{
		2312	ev_embed_init (&embed, 0, loop_socket);
		2313	ev_embed_start (loop, &embed);
		2314	}
		2315
		2316	if (!loop_socket)
		2317	loop_socket = loop;
		2318
		2319	// now use loop_socket for all sockets, and loop for everything else
1972		2320
1973		2321
1974	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2322	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1975		2323
1976	Fork watchers are called when a C<fork ()> was detected (usually because	2324	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1992	believe me.	2340	believe me.
1993		2341
1994	=back	2342	=back
1995		2343
1996		2344
		2345	=head2 C<ev_async> - how to wake up another event loop
		2346
		2347	In general, you cannot use an C<ev_loop> from multiple threads or other
		2348	asynchronous sources such as signal handlers (as opposed to multiple event
		2349	loops - those are of course safe to use in different threads).
		2350
		2351	Sometimes, however, you need to wake up another event loop you do not
		2352	control, for example because it belongs to another thread. This is what
		2353	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2354	can signal it by calling C<ev_async_send>, which is thread- and signal
		2355	safe.
		2356
		2357	This functionality is very similar to C<ev_signal> watchers, as signals,
		2358	too, are asynchronous in nature, and signals, too, will be compressed
		2359	(i.e. the number of callback invocations may be less than the number of
		2360	C<ev_async_sent> calls).
		2361
		2362	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2363	just the default loop.
		2364
		2365	=head3 Queueing
		2366
		2367	C<ev_async> does not support queueing of data in any way. The reason
		2368	is that the author does not know of a simple (or any) algorithm for a
		2369	multiple-writer-single-reader queue that works in all cases and doesn't
		2370	need elaborate support such as pthreads.
		2371
		2372	That means that if you want to queue data, you have to provide your own
		2373	queue. But at least I can tell you how to implement locking around your
		2374	queue:
		2375
		2376	=over 4
		2377
		2378	=item queueing from a signal handler context
		2379
		2380	To implement race-free queueing, you simply add to the queue in the signal
		2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2382	some fictitious SIGUSR1 handler:
		2383
		2384	static ev_async mysig;
		2385
		2386	static void
		2387	sigusr1_handler (void)
		2388	{
		2389	sometype data;
		2390
		2391	// no locking etc.
		2392	queue_put (data);
		2393	ev_async_send (EV_DEFAULT_ &mysig);
		2394	}
		2395
		2396	static void
		2397	mysig_cb (EV_P_ ev_async *w, int revents)
		2398	{
		2399	sometype data;
		2400	sigset_t block, prev;
		2401
		2402	sigemptyset (&block);
		2403	sigaddset (&block, SIGUSR1);
		2404	sigprocmask (SIG_BLOCK, &block, &prev);
		2405
		2406	while (queue_get (&data))
		2407	process (data);
		2408
		2409	if (sigismember (&prev, SIGUSR1)
		2410	sigprocmask (SIG_UNBLOCK, &block, 0);
		2411	}
		2412
		2413	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2414	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2415	either...).
		2416
		2417	=item queueing from a thread context
		2418
		2419	The strategy for threads is different, as you cannot (easily) block
		2420	threads but you can easily preempt them, so to queue safely you need to
		2421	employ a traditional mutex lock, such as in this pthread example:
		2422
		2423	static ev_async mysig;
		2424	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2425
		2426	static void
		2427	otherthread (void)
		2428	{
		2429	// only need to lock the actual queueing operation
		2430	pthread_mutex_lock (&mymutex);
		2431	queue_put (data);
		2432	pthread_mutex_unlock (&mymutex);
		2433
		2434	ev_async_send (EV_DEFAULT_ &mysig);
		2435	}
		2436
		2437	static void
		2438	mysig_cb (EV_P_ ev_async *w, int revents)
		2439	{
		2440	pthread_mutex_lock (&mymutex);
		2441
		2442	while (queue_get (&data))
		2443	process (data);
		2444
		2445	pthread_mutex_unlock (&mymutex);
		2446	}
		2447
		2448	=back
		2449
		2450
		2451	=head3 Watcher-Specific Functions and Data Members
		2452
		2453	=over 4
		2454
		2455	=item ev_async_init (ev_async *, callback)
		2456
		2457	Initialises and configures the async watcher - it has no parameters of any
		2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2459	trust me.
		2460
		2461	=item ev_async_send (loop, ev_async *)
		2462
		2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2465	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2467	section below on what exactly this means).
		2468
		2469	This call incurs the overhead of a system call only once per loop iteration,
		2470	so while the overhead might be noticeable, it doesn't apply to repeated
		2471	calls to C<ev_async_send>.
		2472
		2473	=item bool = ev_async_pending (ev_async *)
		2474
		2475	Returns a non-zero value when C<ev_async_send> has been called on the
		2476	watcher but the event has not yet been processed (or even noted) by the
		2477	event loop.
		2478
		2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2480	the loop iterates next and checks for the watcher to have become active,
		2481	it will reset the flag again. C<ev_async_pending> can be used to very
		2482	quickly check whether invoking the loop might be a good idea.
		2483
		2484	Not that this does I<not> check whether the watcher itself is pending, only
		2485	whether it has been requested to make this watcher pending.
		2486
		2487	=back
		2488
		2489
1997	=head1 OTHER FUNCTIONS	2490	=head1 OTHER FUNCTIONS
1998		2491
1999	There are some other functions of possible interest. Described. Here. Now.	2492	There are some other functions of possible interest. Described. Here. Now.
2000		2493
2001	=over 4	2494	=over 4
…		…
2008	or timeout without having to allocate/configure/start/stop/free one or	2501	or timeout without having to allocate/configure/start/stop/free one or
2009	more watchers yourself.	2502	more watchers yourself.
2010		2503
2011	If C<fd> is less than 0, then no I/O watcher will be started and events	2504	If C<fd> is less than 0, then no I/O watcher will be started and events
2012	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2013	C<events> set will be craeted and started.	2506	C<events> set will be created and started.
2014		2507
2015	If C<timeout> is less than 0, then no timeout watcher will be	2508	If C<timeout> is less than 0, then no timeout watcher will be
2016	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2017	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2018	dubious value.	2511	dubious value.
…		…
2020	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2021	passed an C<revents> set like normal event callbacks (a combination of	2514	passed an C<revents> set like normal event callbacks (a combination of
2022	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2023	value passed to C<ev_once>:	2516	value passed to C<ev_once>:
2024		2517
2025	static void stdin_ready (int revents, void *arg)	2518	static void stdin_ready (int revents, void *arg)
2026	{	2519	{
2027	if (revents & EV_TIMEOUT)	2520	if (revents & EV_TIMEOUT)
2028	/* doh, nothing entered */;	2521	/* doh, nothing entered */;
2029	else if (revents & EV_READ)	2522	else if (revents & EV_READ)
2030	/* stdin might have data for us, joy! */;	2523	/* stdin might have data for us, joy! */;
2031	}	2524	}
2032		2525
2033	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2034		2527
2035	=item ev_feed_event (ev_loop *, watcher *, int revents)	2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2036		2529
2037	Feeds the given event set into the event loop, as if the specified event	2530	Feeds the given event set into the event loop, as if the specified event
2038	had happened for the specified watcher (which must be a pointer to an	2531	had happened for the specified watcher (which must be a pointer to an
…		…
2043	Feed an event on the given fd, as if a file descriptor backend detected	2536	Feed an event on the given fd, as if a file descriptor backend detected
2044	the given events it.	2537	the given events it.
2045		2538
2046	=item ev_feed_signal_event (ev_loop *loop, int signum)	2539	=item ev_feed_signal_event (ev_loop *loop, int signum)
2047		2540
2048	Feed an event as if the given signal occured (C<loop> must be the default	2541	Feed an event as if the given signal occurred (C<loop> must be the default
2049	loop!).	2542	loop!).
2050		2543
2051	=back	2544	=back
2052		2545
2053		2546
…		…
2069		2562
2070	=item * Priorities are not currently supported. Initialising priorities	2563	=item * Priorities are not currently supported. Initialising priorities
2071	will fail and all watchers will have the same priority, even though there	2564	will fail and all watchers will have the same priority, even though there
2072	is an ev_pri field.	2565	is an ev_pri field.
2073		2566
		2567	=item * In libevent, the last base created gets the signals, in libev, the
		2568	first base created (== the default loop) gets the signals.
		2569
2074	=item * Other members are not supported.	2570	=item * Other members are not supported.
2075		2571
2076	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2572	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2077	to use the libev header file and library.	2573	to use the libev header file and library.
2078		2574
2079	=back	2575	=back
2080		2576
2081	=head1 C++ SUPPORT	2577	=head1 C++ SUPPORT
2082		2578
2083	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2579	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2084	you to use some convinience methods to start/stop watchers and also change	2580	you to use some convenience methods to start/stop watchers and also change
2085	the callback model to a model using method callbacks on objects.	2581	the callback model to a model using method callbacks on objects.
2086		2582
2087	To use it,	2583	To use it,
2088		2584
2089	#include <ev++.h>	2585	#include <ev++.h>
2090		2586
2091	This automatically includes F<ev.h> and puts all of its definitions (many	2587	This automatically includes F<ev.h> and puts all of its definitions (many
2092	of them macros) into the global namespace. All C++ specific things are	2588	of them macros) into the global namespace. All C++ specific things are
2093	put into the C<ev> namespace. It should support all the same embedding	2589	put into the C<ev> namespace. It should support all the same embedding
2094	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2590	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2161	your compiler is good :), then the method will be fully inlined into the	2657	your compiler is good :), then the method will be fully inlined into the
2162	thunking function, making it as fast as a direct C callback.	2658	thunking function, making it as fast as a direct C callback.
2163		2659
2164	Example: simple class declaration and watcher initialisation	2660	Example: simple class declaration and watcher initialisation
2165		2661
2166	struct myclass	2662	struct myclass
2167	{	2663	{
2168	void io_cb (ev::io &w, int revents) { }	2664	void io_cb (ev::io &w, int revents) { }
2169	}	2665	}
2170		2666
2171	myclass obj;	2667	myclass obj;
2172	ev::io iow;	2668	ev::io iow;
2173	iow.set <myclass, &myclass::io_cb> (&obj);	2669	iow.set <myclass, &myclass::io_cb> (&obj);
2174		2670
2175	=item w->set<function> (void *data = 0)	2671	=item w->set<function> (void *data = 0)
2176		2672
2177	Also sets a callback, but uses a static method or plain function as	2673	Also sets a callback, but uses a static method or plain function as
2178	callback. The optional C<data> argument will be stored in the watcher's	2674	callback. The optional C<data> argument will be stored in the watcher's
…		…
2180		2676
2181	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2182		2678
2183	See the method-C<set> above for more details.	2679	See the method-C<set> above for more details.
2184		2680
2185	Example:	2681	Example: Use a plain function as callback.
2186		2682
2187	static void io_cb (ev::io &w, int revents) { }	2683	static void io_cb (ev::io &w, int revents) { }
2188	iow.set <io_cb> ();	2684	iow.set <io_cb> ();
2189		2685
2190	=item w->set (struct ev_loop *)	2686	=item w->set (struct ev_loop *)
2191		2687
2192	Associates a different C<struct ev_loop> with this watcher. You can only	2688	Associates a different C<struct ev_loop> with this watcher. You can only
2193	do this when the watcher is inactive (and not pending either).	2689	do this when the watcher is inactive (and not pending either).
2194		2690
2195	=item w->set ([args])	2691	=item w->set ([arguments])
2196		2692
2197	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2693	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2198	called at least once. Unlike the C counterpart, an active watcher gets	2694	called at least once. Unlike the C counterpart, an active watcher gets
2199	automatically stopped and restarted when reconfiguring it with this	2695	automatically stopped and restarted when reconfiguring it with this
2200	method.	2696	method.
2201		2697
2202	=item w->start ()	2698	=item w->start ()
…		…
2226	=back	2722	=back
2227		2723
2228	Example: Define a class with an IO and idle watcher, start one of them in	2724	Example: Define a class with an IO and idle watcher, start one of them in
2229	the constructor.	2725	the constructor.
2230		2726
2231	class myclass	2727	class myclass
2232	{	2728	{
2233	ev_io io; void io_cb (ev::io &w, int revents);	2729	ev::io io ; void io_cb (ev::io &w, int revents);
2234	ev_idle idle void idle_cb (ev::idle &w, int revents);	2730	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2235		2731
2236	myclass ();	2732	myclass (int fd)
2237	}	2733	{
2238
2239	myclass::myclass (int fd)
2240	{
2241	io .set <myclass, &myclass::io_cb > (this);	2734	io .set <myclass, &myclass::io_cb > (this);
2242	idle.set <myclass, &myclass::idle_cb> (this);	2735	idle.set <myclass, &myclass::idle_cb> (this);
2243		2736
2244	io.start (fd, ev::READ);	2737	io.start (fd, ev::READ);
		2738	}
2245	}	2739	};
		2740
		2741
		2742	=head1 OTHER LANGUAGE BINDINGS
		2743
		2744	Libev does not offer other language bindings itself, but bindings for a
		2745	number of languages exist in the form of third-party packages. If you know
		2746	any interesting language binding in addition to the ones listed here, drop
		2747	me a note.
		2748
		2749	=over 4
		2750
		2751	=item Perl
		2752
		2753	The EV module implements the full libev API and is actually used to test
		2754	libev. EV is developed together with libev. Apart from the EV core module,
		2755	there are additional modules that implement libev-compatible interfaces
		2756	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2757	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2758	and C<EV::Glib>).
		2759
		2760	It can be found and installed via CPAN, its homepage is at
		2761	L<http://software.schmorp.de/pkg/EV>.
		2762
		2763	=item Python
		2764
		2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2766	seems to be quite complete and well-documented. Note, however, that the
		2767	patch they require for libev is outright dangerous as it breaks the ABI
		2768	for everybody else, and therefore, should never be applied in an installed
		2769	libev (if python requires an incompatible ABI then it needs to embed
		2770	libev).
		2771
		2772	=item Ruby
		2773
		2774	Tony Arcieri has written a ruby extension that offers access to a subset
		2775	of the libev API and adds file handle abstractions, asynchronous DNS and
		2776	more on top of it. It can be found via gem servers. Its homepage is at
		2777	L<http://rev.rubyforge.org/>.
		2778
		2779	=item D
		2780
		2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2783
		2784	=back
2246		2785
2247		2786
2248	=head1 MACRO MAGIC	2787	=head1 MACRO MAGIC
2249		2788
2250	Libev can be compiled with a variety of options, the most fundamantal	2789	Libev can be compiled with a variety of options, the most fundamental
2251	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2790	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2252	functions and callbacks have an initial C<struct ev_loop *> argument.	2791	functions and callbacks have an initial C<struct ev_loop *> argument.
2253		2792
2254	To make it easier to write programs that cope with either variant, the	2793	To make it easier to write programs that cope with either variant, the
2255	following macros are defined:	2794	following macros are defined:
…		…
2260		2799
2261	This provides the loop I<argument> for functions, if one is required ("ev	2800	This provides the loop I<argument> for functions, if one is required ("ev
2262	loop argument"). The C<EV_A> form is used when this is the sole argument,	2801	loop argument"). The C<EV_A> form is used when this is the sole argument,
2263	C<EV_A_> is used when other arguments are following. Example:	2802	C<EV_A_> is used when other arguments are following. Example:
2264		2803
2265	ev_unref (EV_A);	2804	ev_unref (EV_A);
2266	ev_timer_add (EV_A_ watcher);	2805	ev_timer_add (EV_A_ watcher);
2267	ev_loop (EV_A_ 0);	2806	ev_loop (EV_A_ 0);
2268		2807
2269	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2808	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2270	which is often provided by the following macro.	2809	which is often provided by the following macro.
2271		2810
2272	=item C<EV_P>, C<EV_P_>	2811	=item C<EV_P>, C<EV_P_>
2273		2812
2274	This provides the loop I<parameter> for functions, if one is required ("ev	2813	This provides the loop I<parameter> for functions, if one is required ("ev
2275	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2814	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2276	C<EV_P_> is used when other parameters are following. Example:	2815	C<EV_P_> is used when other parameters are following. Example:
2277		2816
2278	// this is how ev_unref is being declared	2817	// this is how ev_unref is being declared
2279	static void ev_unref (EV_P);	2818	static void ev_unref (EV_P);
2280		2819
2281	// this is how you can declare your typical callback	2820	// this is how you can declare your typical callback
2282	static void cb (EV_P_ ev_timer *w, int revents)	2821	static void cb (EV_P_ ev_timer *w, int revents)
2283		2822
2284	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2823	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2285	suitable for use with C<EV_A>.	2824	suitable for use with C<EV_A>.
2286		2825
2287	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2826	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2288		2827
2289	Similar to the other two macros, this gives you the value of the default	2828	Similar to the other two macros, this gives you the value of the default
2290	loop, if multiple loops are supported ("ev loop default").	2829	loop, if multiple loops are supported ("ev loop default").
		2830
		2831	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2832
		2833	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2834	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2835	is undefined when the default loop has not been initialised by a previous
		2836	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2837
		2838	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2839	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2291		2840
2292	=back	2841	=back
2293		2842
2294	Example: Declare and initialise a check watcher, utilising the above	2843	Example: Declare and initialise a check watcher, utilising the above
2295	macros so it will work regardless of whether multiple loops are supported	2844	macros so it will work regardless of whether multiple loops are supported
2296	or not.	2845	or not.
2297		2846
2298	static void	2847	static void
2299	check_cb (EV_P_ ev_timer *w, int revents)	2848	check_cb (EV_P_ ev_timer *w, int revents)
2300	{	2849	{
2301	ev_check_stop (EV_A_ w);	2850	ev_check_stop (EV_A_ w);
2302	}	2851	}
2303		2852
2304	ev_check check;	2853	ev_check check;
2305	ev_check_init (&check, check_cb);	2854	ev_check_init (&check, check_cb);
2306	ev_check_start (EV_DEFAULT_ &check);	2855	ev_check_start (EV_DEFAULT_ &check);
2307	ev_loop (EV_DEFAULT_ 0);	2856	ev_loop (EV_DEFAULT_ 0);
2308		2857
2309	=head1 EMBEDDING	2858	=head1 EMBEDDING
2310		2859
2311	Libev can (and often is) directly embedded into host	2860	Libev can (and often is) directly embedded into host
2312	applications. Examples of applications that embed it include the Deliantra	2861	applications. Examples of applications that embed it include the Deliantra
…		…
2319	libev somewhere in your source tree).	2868	libev somewhere in your source tree).
2320		2869
2321	=head2 FILESETS	2870	=head2 FILESETS
2322		2871
2323	Depending on what features you need you need to include one or more sets of files	2872	Depending on what features you need you need to include one or more sets of files
2324	in your app.	2873	in your application.
2325		2874
2326	=head3 CORE EVENT LOOP	2875	=head3 CORE EVENT LOOP
2327		2876
2328	To include only the libev core (all the C<ev_*> functions), with manual	2877	To include only the libev core (all the C<ev_*> functions), with manual
2329	configuration (no autoconf):	2878	configuration (no autoconf):
2330		2879
2331	#define EV_STANDALONE 1	2880	#define EV_STANDALONE 1
2332	#include "ev.c"	2881	#include "ev.c"
2333		2882
2334	This will automatically include F<ev.h>, too, and should be done in a	2883	This will automatically include F<ev.h>, too, and should be done in a
2335	single C source file only to provide the function implementations. To use	2884	single C source file only to provide the function implementations. To use
2336	it, do the same for F<ev.h> in all files wishing to use this API (best	2885	it, do the same for F<ev.h> in all files wishing to use this API (best
2337	done by writing a wrapper around F<ev.h> that you can include instead and	2886	done by writing a wrapper around F<ev.h> that you can include instead and
2338	where you can put other configuration options):	2887	where you can put other configuration options):
2339		2888
2340	#define EV_STANDALONE 1	2889	#define EV_STANDALONE 1
2341	#include "ev.h"	2890	#include "ev.h"
2342		2891
2343	Both header files and implementation files can be compiled with a C++	2892	Both header files and implementation files can be compiled with a C++
2344	compiler (at least, thats a stated goal, and breakage will be treated	2893	compiler (at least, thats a stated goal, and breakage will be treated
2345	as a bug).	2894	as a bug).
2346		2895
2347	You need the following files in your source tree, or in a directory	2896	You need the following files in your source tree, or in a directory
2348	in your include path (e.g. in libev/ when using -Ilibev):	2897	in your include path (e.g. in libev/ when using -Ilibev):
2349		2898
2350	ev.h	2899	ev.h
2351	ev.c	2900	ev.c
2352	ev_vars.h	2901	ev_vars.h
2353	ev_wrap.h	2902	ev_wrap.h
2354		2903
2355	ev_win32.c required on win32 platforms only	2904	ev_win32.c required on win32 platforms only
2356		2905
2357	ev_select.c only when select backend is enabled (which is enabled by default)	2906	ev_select.c only when select backend is enabled (which is enabled by default)
2358	ev_poll.c only when poll backend is enabled (disabled by default)	2907	ev_poll.c only when poll backend is enabled (disabled by default)
2359	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2908	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2360	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2909	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2361	ev_port.c only when the solaris port backend is enabled (disabled by default)	2910	ev_port.c only when the solaris port backend is enabled (disabled by default)
2362		2911
2363	F<ev.c> includes the backend files directly when enabled, so you only need	2912	F<ev.c> includes the backend files directly when enabled, so you only need
2364	to compile this single file.	2913	to compile this single file.
2365		2914
2366	=head3 LIBEVENT COMPATIBILITY API	2915	=head3 LIBEVENT COMPATIBILITY API
2367		2916
2368	To include the libevent compatibility API, also include:	2917	To include the libevent compatibility API, also include:
2369		2918
2370	#include "event.c"	2919	#include "event.c"
2371		2920
2372	in the file including F<ev.c>, and:	2921	in the file including F<ev.c>, and:
2373		2922
2374	#include "event.h"	2923	#include "event.h"
2375		2924
2376	in the files that want to use the libevent API. This also includes F<ev.h>.	2925	in the files that want to use the libevent API. This also includes F<ev.h>.
2377		2926
2378	You need the following additional files for this:	2927	You need the following additional files for this:
2379		2928
2380	event.h	2929	event.h
2381	event.c	2930	event.c
2382		2931
2383	=head3 AUTOCONF SUPPORT	2932	=head3 AUTOCONF SUPPORT
2384		2933
2385	Instead of using C<EV_STANDALONE=1> and providing your config in	2934	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2386	whatever way you want, you can also C<m4_include([libev.m4])> in your	2935	whatever way you want, you can also C<m4_include([libev.m4])> in your
2387	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2936	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2388	include F<config.h> and configure itself accordingly.	2937	include F<config.h> and configure itself accordingly.
2389		2938
2390	For this of course you need the m4 file:	2939	For this of course you need the m4 file:
2391		2940
2392	libev.m4	2941	libev.m4
2393		2942
2394	=head2 PREPROCESSOR SYMBOLS/MACROS	2943	=head2 PREPROCESSOR SYMBOLS/MACROS
2395		2944
2396	Libev can be configured via a variety of preprocessor symbols you have to define	2945	Libev can be configured via a variety of preprocessor symbols you have to
2397	before including any of its files. The default is not to build for multiplicity	2946	define before including any of its files. The default in the absence of
2398	and only include the select backend.	2947	autoconf is documented for every option.
2399		2948
2400	=over 4	2949	=over 4
2401		2950
2402	=item EV_STANDALONE	2951	=item EV_STANDALONE
2403		2952
…		…
2408	F<event.h> that are not directly supported by the libev core alone.	2957	F<event.h> that are not directly supported by the libev core alone.
2409		2958
2410	=item EV_USE_MONOTONIC	2959	=item EV_USE_MONOTONIC
2411		2960
2412	If defined to be C<1>, libev will try to detect the availability of the	2961	If defined to be C<1>, libev will try to detect the availability of the
2413	monotonic clock option at both compiletime and runtime. Otherwise no use	2962	monotonic clock option at both compile time and runtime. Otherwise no use
2414	of the monotonic clock option will be attempted. If you enable this, you	2963	of the monotonic clock option will be attempted. If you enable this, you
2415	usually have to link against librt or something similar. Enabling it when	2964	usually have to link against librt or something similar. Enabling it when
2416	the functionality isn't available is safe, though, although you have	2965	the functionality isn't available is safe, though, although you have
2417	to make sure you link against any libraries where the C<clock_gettime>	2966	to make sure you link against any libraries where the C<clock_gettime>
2418	function is hiding in (often F<-lrt>).	2967	function is hiding in (often F<-lrt>).
2419		2968
2420	=item EV_USE_REALTIME	2969	=item EV_USE_REALTIME
2421		2970
2422	If defined to be C<1>, libev will try to detect the availability of the	2971	If defined to be C<1>, libev will try to detect the availability of the
2423	realtime clock option at compiletime (and assume its availability at	2972	real-time clock option at compile time (and assume its availability at
2424	runtime if successful). Otherwise no use of the realtime clock option will	2973	runtime if successful). Otherwise no use of the real-time clock option will
2425	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2426	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2427	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2428		2977
2429	=item EV_USE_NANOSLEEP	2978	=item EV_USE_NANOSLEEP
2430		2979
2431	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2432	and will use it for delays. Otherwise it will use C<select ()>.	2981	and will use it for delays. Otherwise it will use C<select ()>.
2433		2982
		2983	=item EV_USE_EVENTFD
		2984
		2985	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2986	available and will probe for kernel support at runtime. This will improve
		2987	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2988	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2989	2.7 or newer, otherwise disabled.
		2990
2434	=item EV_USE_SELECT	2991	=item EV_USE_SELECT
2435		2992
2436	If undefined or defined to be C<1>, libev will compile in support for the	2993	If undefined or defined to be C<1>, libev will compile in support for the
2437	C<select>(2) backend. No attempt at autodetection will be done: if no	2994	C<select>(2) backend. No attempt at auto-detection will be done: if no
2438	other method takes over, select will be it. Otherwise the select backend	2995	other method takes over, select will be it. Otherwise the select backend
2439	will not be compiled in.	2996	will not be compiled in.
2440		2997
2441	=item EV_SELECT_USE_FD_SET	2998	=item EV_SELECT_USE_FD_SET
2442		2999
2443	If defined to C<1>, then the select backend will use the system C<fd_set>	3000	If defined to C<1>, then the select backend will use the system C<fd_set>
2444	structure. This is useful if libev doesn't compile due to a missing	3001	structure. This is useful if libev doesn't compile due to a missing
2445	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2446	exotic systems. This usually limits the range of file descriptors to some	3003	exotic systems. This usually limits the range of file descriptors to some
2447	low limit such as 1024 or might have other limitations (winsocket only	3004	low limit such as 1024 or might have other limitations (winsocket only
2448	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2449	influence the size of the C<fd_set> used.	3006	influence the size of the C<fd_set> used.
2450		3007
…		…
2456	be used is the winsock select). This means that it will call	3013	be used is the winsock select). This means that it will call
2457	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3014	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2458	it is assumed that all these functions actually work on fds, even	3015	it is assumed that all these functions actually work on fds, even
2459	on win32. Should not be defined on non-win32 platforms.	3016	on win32. Should not be defined on non-win32 platforms.
2460		3017
		3018	=item EV_FD_TO_WIN32_HANDLE
		3019
		3020	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3021	file descriptors to socket handles. When not defining this symbol (the
		3022	default), then libev will call C<_get_osfhandle>, which is usually
		3023	correct. In some cases, programs use their own file descriptor management,
		3024	in which case they can provide this function to map fds to socket handles.
		3025
2461	=item EV_USE_POLL	3026	=item EV_USE_POLL
2462		3027
2463	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3028	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2464	backend. Otherwise it will be enabled on non-win32 platforms. It	3029	backend. Otherwise it will be enabled on non-win32 platforms. It
2465	takes precedence over select.	3030	takes precedence over select.
2466		3031
2467	=item EV_USE_EPOLL	3032	=item EV_USE_EPOLL
2468		3033
2469	If defined to be C<1>, libev will compile in support for the Linux	3034	If defined to be C<1>, libev will compile in support for the Linux
2470	C<epoll>(7) backend. Its availability will be detected at runtime,	3035	C<epoll>(7) backend. Its availability will be detected at runtime,
2471	otherwise another method will be used as fallback. This is the	3036	otherwise another method will be used as fallback. This is the preferred
2472	preferred backend for GNU/Linux systems.	3037	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3038	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2473		3039
2474	=item EV_USE_KQUEUE	3040	=item EV_USE_KQUEUE
2475		3041
2476	If defined to be C<1>, libev will compile in support for the BSD style	3042	If defined to be C<1>, libev will compile in support for the BSD style
2477	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3043	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2490	otherwise another method will be used as fallback. This is the preferred	3056	otherwise another method will be used as fallback. This is the preferred
2491	backend for Solaris 10 systems.	3057	backend for Solaris 10 systems.
2492		3058
2493	=item EV_USE_DEVPOLL	3059	=item EV_USE_DEVPOLL
2494		3060
2495	reserved for future expansion, works like the USE symbols above.	3061	Reserved for future expansion, works like the USE symbols above.
2496		3062
2497	=item EV_USE_INOTIFY	3063	=item EV_USE_INOTIFY
2498		3064
2499	If defined to be C<1>, libev will compile in support for the Linux inotify	3065	If defined to be C<1>, libev will compile in support for the Linux inotify
2500	interface to speed up C<ev_stat> watchers. Its actual availability will	3066	interface to speed up C<ev_stat> watchers. Its actual availability will
2501	be detected at runtime.	3067	be detected at runtime. If undefined, it will be enabled if the headers
		3068	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3069
		3070	=item EV_ATOMIC_T
		3071
		3072	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3073	access is atomic with respect to other threads or signal contexts. No such
		3074	type is easily found in the C language, so you can provide your own type
		3075	that you know is safe for your purposes. It is used both for signal handler "locking"
		3076	as well as for signal and thread safety in C<ev_async> watchers.
		3077
		3078	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3079	(from F<signal.h>), which is usually good enough on most platforms.
2502		3080
2503	=item EV_H	3081	=item EV_H
2504		3082
2505	The name of the F<ev.h> header file used to include it. The default if	3083	The name of the F<ev.h> header file used to include it. The default if
2506	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3084	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2507	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3085	used to virtually rename the F<ev.h> header file in case of conflicts.
2508		3086
2509	=item EV_CONFIG_H	3087	=item EV_CONFIG_H
2510		3088
2511	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3089	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2512	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3090	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2513	C<EV_H>, above.	3091	C<EV_H>, above.
2514		3092
2515	=item EV_EVENT_H	3093	=item EV_EVENT_H
2516		3094
2517	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3095	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2518	of how the F<event.h> header can be found.	3096	of how the F<event.h> header can be found, the default is C<"event.h">.
2519		3097
2520	=item EV_PROTOTYPES	3098	=item EV_PROTOTYPES
2521		3099
2522	If defined to be C<0>, then F<ev.h> will not define any function	3100	If defined to be C<0>, then F<ev.h> will not define any function
2523	prototypes, but still define all the structs and other symbols. This is	3101	prototypes, but still define all the structs and other symbols. This is
…		…
2544	When doing priority-based operations, libev usually has to linearly search	3122	When doing priority-based operations, libev usually has to linearly search
2545	all the priorities, so having many of them (hundreds) uses a lot of space	3123	all the priorities, so having many of them (hundreds) uses a lot of space
2546	and time, so using the defaults of five priorities (-2 .. +2) is usually	3124	and time, so using the defaults of five priorities (-2 .. +2) is usually
2547	fine.	3125	fine.
2548		3126
2549	If your embedding app does not need any priorities, defining these both to	3127	If your embedding application does not need any priorities, defining these
2550	C<0> will save some memory and cpu.	3128	both to C<0> will save some memory and CPU.
2551		3129
2552	=item EV_PERIODIC_ENABLE	3130	=item EV_PERIODIC_ENABLE
2553		3131
2554	If undefined or defined to be C<1>, then periodic timers are supported. If	3132	If undefined or defined to be C<1>, then periodic timers are supported. If
2555	defined to be C<0>, then they are not. Disabling them saves a few kB of	3133	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2562	code.	3140	code.
2563		3141
2564	=item EV_EMBED_ENABLE	3142	=item EV_EMBED_ENABLE
2565		3143
2566	If undefined or defined to be C<1>, then embed watchers are supported. If	3144	If undefined or defined to be C<1>, then embed watchers are supported. If
2567	defined to be C<0>, then they are not.	3145	defined to be C<0>, then they are not. Embed watchers rely on most other
		3146	watcher types, which therefore must not be disabled.
2568		3147
2569	=item EV_STAT_ENABLE	3148	=item EV_STAT_ENABLE
2570		3149
2571	If undefined or defined to be C<1>, then stat watchers are supported. If	3150	If undefined or defined to be C<1>, then stat watchers are supported. If
2572	defined to be C<0>, then they are not.	3151	defined to be C<0>, then they are not.
…		…
2574	=item EV_FORK_ENABLE	3153	=item EV_FORK_ENABLE
2575		3154
2576	If undefined or defined to be C<1>, then fork watchers are supported. If	3155	If undefined or defined to be C<1>, then fork watchers are supported. If
2577	defined to be C<0>, then they are not.	3156	defined to be C<0>, then they are not.
2578		3157
		3158	=item EV_ASYNC_ENABLE
		3159
		3160	If undefined or defined to be C<1>, then async watchers are supported. If
		3161	defined to be C<0>, then they are not.
		3162
2579	=item EV_MINIMAL	3163	=item EV_MINIMAL
2580		3164
2581	If you need to shave off some kilobytes of code at the expense of some	3165	If you need to shave off some kilobytes of code at the expense of some
2582	speed, define this symbol to C<1>. Currently only used for gcc to override	3166	speed, define this symbol to C<1>. Currently this is used to override some
2583	some inlining decisions, saves roughly 30% codesize of amd64.	3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3168	much smaller 2-heap for timer management over the default 4-heap.
2584		3169
2585	=item EV_PID_HASHSIZE	3170	=item EV_PID_HASHSIZE
2586		3171
2587	C<ev_child> watchers use a small hash table to distribute workload by	3172	C<ev_child> watchers use a small hash table to distribute workload by
2588	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2595	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2596	usually more than enough. If you need to manage thousands of C<ev_stat>	3181	usually more than enough. If you need to manage thousands of C<ev_stat>
2597	watchers you might want to increase this value (I<must> be a power of	3182	watchers you might want to increase this value (I<must> be a power of
2598	two).	3183	two).
2599		3184
		3185	=item EV_USE_4HEAP
		3186
		3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3190	faster performance with many (thousands) of watchers.
		3191
		3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3193	(disabled).
		3194
		3195	=item EV_HEAP_CACHE_AT
		3196
		3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3201	but avoids random read accesses on heap changes. This improves performance
		3202	noticeably with many (hundreds) of watchers.
		3203
		3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3205	(disabled).
		3206
		3207	=item EV_VERIFY
		3208
		3209	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3210	be done: If set to C<0>, no internal verification code will be compiled
		3211	in. If set to C<1>, then verification code will be compiled in, but not
		3212	called. If set to C<2>, then the internal verification code will be
		3213	called once per loop, which can slow down libev. If set to C<3>, then the
		3214	verification code will be called very frequently, which will slow down
		3215	libev considerably.
		3216
		3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3218	C<0>.
		3219
2600	=item EV_COMMON	3220	=item EV_COMMON
2601		3221
2602	By default, all watchers have a C<void *data> member. By redefining	3222	By default, all watchers have a C<void *data> member. By redefining
2603	this macro to a something else you can include more and other types of	3223	this macro to a something else you can include more and other types of
2604	members. You have to define it each time you include one of the files,	3224	members. You have to define it each time you include one of the files,
2605	though, and it must be identical each time.	3225	though, and it must be identical each time.
2606		3226
2607	For example, the perl EV module uses something like this:	3227	For example, the perl EV module uses something like this:
2608		3228
2609	#define EV_COMMON \	3229	#define EV_COMMON \
2610	SV *self; /* contains this struct */ \	3230	SV *self; /* contains this struct */ \
2611	SV *cb_sv, *fh /* note no trailing ";" */	3231	SV *cb_sv, *fh /* note no trailing ";" */
2612		3232
2613	=item EV_CB_DECLARE (type)	3233	=item EV_CB_DECLARE (type)
2614		3234
2615	=item EV_CB_INVOKE (watcher, revents)	3235	=item EV_CB_INVOKE (watcher, revents)
2616		3236
…		…
2621	definition and a statement, respectively. See the F<ev.h> header file for	3241	definition and a statement, respectively. See the F<ev.h> header file for
2622	their default definitions. One possible use for overriding these is to	3242	their default definitions. One possible use for overriding these is to
2623	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2624	method calls instead of plain function calls in C++.	3244	method calls instead of plain function calls in C++.
2625		3245
		3246	=back
		3247
2626	=head2 EXPORTED API SYMBOLS	3248	=head2 EXPORTED API SYMBOLS
2627		3249
2628	If you need to re-export the API (e.g. via a dll) and you need a list of	3250	If you need to re-export the API (e.g. via a DLL) and you need a list of
2629	exported symbols, you can use the provided F<Symbol.*> files which list	3251	exported symbols, you can use the provided F<Symbol.*> files which list
2630	all public symbols, one per line:	3252	all public symbols, one per line:
2631		3253
2632	Symbols.ev for libev proper	3254	Symbols.ev for libev proper
2633	Symbols.event for the libevent emulation	3255	Symbols.event for the libevent emulation
2634		3256
2635	This can also be used to rename all public symbols to avoid clashes with	3257	This can also be used to rename all public symbols to avoid clashes with
2636	multiple versions of libev linked together (which is obviously bad in	3258	multiple versions of libev linked together (which is obviously bad in
2637	itself, but sometimes it is inconvinient to avoid this).	3259	itself, but sometimes it is inconvenient to avoid this).
2638		3260
2639	A sed command like this will create wrapper C<#define>'s that you need to	3261	A sed command like this will create wrapper C<#define>'s that you need to
2640	include before including F<ev.h>:	3262	include before including F<ev.h>:
2641		3263
2642	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3264	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2659	file.	3281	file.
2660		3282
2661	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3283	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2662	that everybody includes and which overrides some configure choices:	3284	that everybody includes and which overrides some configure choices:
2663		3285
2664	#define EV_MINIMAL 1	3286	#define EV_MINIMAL 1
2665	#define EV_USE_POLL 0	3287	#define EV_USE_POLL 0
2666	#define EV_MULTIPLICITY 0	3288	#define EV_MULTIPLICITY 0
2667	#define EV_PERIODIC_ENABLE 0	3289	#define EV_PERIODIC_ENABLE 0
2668	#define EV_STAT_ENABLE 0	3290	#define EV_STAT_ENABLE 0
2669	#define EV_FORK_ENABLE 0	3291	#define EV_FORK_ENABLE 0
2670	#define EV_CONFIG_H <config.h>	3292	#define EV_CONFIG_H <config.h>
2671	#define EV_MINPRI 0	3293	#define EV_MINPRI 0
2672	#define EV_MAXPRI 0	3294	#define EV_MAXPRI 0
2673		3295
2674	#include "ev++.h"	3296	#include "ev++.h"
2675		3297
2676	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2677		3299
2678	#include "ev_cpp.h"	3300	#include "ev_cpp.h"
2679	#include "ev.c"	3301	#include "ev.c"
		3302
		3303
		3304	=head1 THREADS AND COROUTINES
		3305
		3306	=head2 THREADS
		3307
		3308	Libev itself is thread-safe (unless the opposite is specifically
		3309	documented for a function), but it uses no locking itself. This means that
		3310	you can use as many loops as you want in parallel, as long as only one
		3311	thread ever calls into one libev function with the same loop parameter:
		3312	libev guarantees that different event loops share no data structures that
		3313	need locking.
		3314
		3315	Or to put it differently: calls with different loop parameters can be done
		3316	concurrently from multiple threads, calls with the same loop parameter
		3317	must be done serially (but can be done from different threads, as long as
		3318	only one thread ever is inside a call at any point in time, e.g. by using
		3319	a mutex per loop).
		3320
		3321	Specifically to support threads (and signal handlers), libev implements
		3322	so-called C<ev_async> watchers, which allow some limited form of
		3323	concurrency on the same event loop.
		3324
		3325	If you want to know which design (one loop, locking, or multiple loops
		3326	without or something else still) is best for your problem, then I cannot
		3327	help you. I can give some generic advice however:
		3328
		3329	=over 4
		3330
		3331	=item * most applications have a main thread: use the default libev loop
		3332	in that thread, or create a separate thread running only the default loop.
		3333
		3334	This helps integrating other libraries or software modules that use libev
		3335	themselves and don't care/know about threading.
		3336
		3337	=item * one loop per thread is usually a good model.
		3338
		3339	Doing this is almost never wrong, sometimes a better-performance model
		3340	exists, but it is always a good start.
		3341
		3342	=item * other models exist, such as the leader/follower pattern, where one
		3343	loop is handed through multiple threads in a kind of round-robin fashion.
		3344
		3345	Choosing a model is hard - look around, learn, know that usually you can do
		3346	better than you currently do :-)
		3347
		3348	=item * often you need to talk to some other thread which blocks in the
		3349	event loop.
		3350
		3351	C<ev_async> watchers can be used to wake them up from other threads safely
		3352	(or from signal contexts...).
		3353
		3354	An example use would be to communicate signals or other events that only
		3355	work in the default loop by registering the signal watcher with the
		3356	default loop and triggering an C<ev_async> watcher from the default loop
		3357	watcher callback into the event loop interested in the signal.
		3358
		3359	=back
		3360
		3361	=head2 COROUTINES
		3362
		3363	Libev is much more accommodating to coroutines ("cooperative threads"):
		3364	libev fully supports nesting calls to it's functions from different
		3365	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3366	different coroutines and switch freely between both coroutines running the
		3367	loop, as long as you don't confuse yourself). The only exception is that
		3368	you must not do this from C<ev_periodic> reschedule callbacks.
		3369
		3370	Care has been taken to ensure that libev does not keep local state inside
		3371	C<ev_loop>, and other calls do not usually allow coroutine switches.
2680		3372
2681		3373
2682	=head1 COMPLEXITIES	3374	=head1 COMPLEXITIES
2683		3375
2684	In this section the complexities of (many of) the algorithms used inside	3376	In this section the complexities of (many of) the algorithms used inside
…		…
2702	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3394	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2703		3395
2704	That means that changing a timer costs less than removing/adding them	3396	That means that changing a timer costs less than removing/adding them
2705	as only the relative motion in the event queue has to be paid for.	3397	as only the relative motion in the event queue has to be paid for.
2706		3398
2707	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3399	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2708		3400
2709	These just add the watcher into an array or at the head of a list.	3401	These just add the watcher into an array or at the head of a list.
2710		3402
2711	=item Stopping check/prepare/idle watchers: O(1)	3403	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2712		3404
2713	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3405	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2714		3406
2715	These watchers are stored in lists then need to be walked to find the	3407	These watchers are stored in lists then need to be walked to find the
2716	correct watcher to remove. The lists are usually short (you don't usually	3408	correct watcher to remove. The lists are usually short (you don't usually
2717	have many watchers waiting for the same fd or signal).	3409	have many watchers waiting for the same fd or signal).
2718		3410
2719	=item Finding the next timer in each loop iteration: O(1)	3411	=item Finding the next timer in each loop iteration: O(1)
2720		3412
2721	By virtue of using a binary heap, the next timer is always found at the	3413	By virtue of using a binary or 4-heap, the next timer is always found at a
2722	beginning of the storage array.	3414	fixed position in the storage array.
2723		3415
2724	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3416	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2725		3417
2726	A change means an I/O watcher gets started or stopped, which requires	3418	A change means an I/O watcher gets started or stopped, which requires
2727	libev to recalculate its status (and possibly tell the kernel, depending	3419	libev to recalculate its status (and possibly tell the kernel, depending
2728	on backend and wether C<ev_io_set> was used).	3420	on backend and whether C<ev_io_set> was used).
2729		3421
2730	=item Activating one watcher (putting it into the pending state): O(1)	3422	=item Activating one watcher (putting it into the pending state): O(1)
2731		3423
2732	=item Priority handling: O(number_of_priorities)	3424	=item Priority handling: O(number_of_priorities)
2733		3425
2734	Priorities are implemented by allocating some space for each	3426	Priorities are implemented by allocating some space for each
2735	priority. When doing priority-based operations, libev usually has to	3427	priority. When doing priority-based operations, libev usually has to
2736	linearly search all the priorities, but starting/stopping and activating	3428	linearly search all the priorities, but starting/stopping and activating
2737	watchers becomes O(1) w.r.t. prioritiy handling.	3429	watchers becomes O(1) with respect to priority handling.
		3430
		3431	=item Sending an ev_async: O(1)
		3432
		3433	=item Processing ev_async_send: O(number_of_async_watchers)
		3434
		3435	=item Processing signals: O(max_signal_number)
		3436
		3437	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3438	calls in the current loop iteration. Checking for async and signal events
		3439	involves iterating over all running async watchers or all signal numbers.
2738		3440
2739	=back	3441	=back
2740		3442
2741		3443
		3444	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3445
		3446	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3447	requires, and its I/O model is fundamentally incompatible with the POSIX
		3448	model. Libev still offers limited functionality on this platform in
		3449	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3450	descriptors. This only applies when using Win32 natively, not when using
		3451	e.g. cygwin.
		3452
		3453	Lifting these limitations would basically require the full
		3454	re-implementation of the I/O system. If you are into these kinds of
		3455	things, then note that glib does exactly that for you in a very portable
		3456	way (note also that glib is the slowest event library known to man).
		3457
		3458	There is no supported compilation method available on windows except
		3459	embedding it into other applications.
		3460
		3461	Not a libev limitation but worth mentioning: windows apparently doesn't
		3462	accept large writes: instead of resulting in a partial write, windows will
		3463	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3464	so make sure you only write small amounts into your sockets (less than a
		3465	megabyte seems safe, but this apparently depends on the amount of memory
		3466	available).
		3467
		3468	Due to the many, low, and arbitrary limits on the win32 platform and
		3469	the abysmal performance of winsockets, using a large number of sockets
		3470	is not recommended (and not reasonable). If your program needs to use
		3471	more than a hundred or so sockets, then likely it needs to use a totally
		3472	different implementation for windows, as libev offers the POSIX readiness
		3473	notification model, which cannot be implemented efficiently on windows
		3474	(Microsoft monopoly games).
		3475
		3476	A typical way to use libev under windows is to embed it (see the embedding
		3477	section for details) and use the following F<evwrap.h> header file instead
		3478	of F<ev.h>:
		3479
		3480	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3481	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3482
		3483	#include "ev.h"
		3484
		3485	And compile the following F<evwrap.c> file into your project (make sure
		3486	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3487
		3488	#include "evwrap.h"
		3489	#include "ev.c"
		3490
		3491	=over 4
		3492
		3493	=item The winsocket select function
		3494
		3495	The winsocket C<select> function doesn't follow POSIX in that it
		3496	requires socket I<handles> and not socket I<file descriptors> (it is
		3497	also extremely buggy). This makes select very inefficient, and also
		3498	requires a mapping from file descriptors to socket handles (the Microsoft
		3499	C runtime provides the function C<_open_osfhandle> for this). See the
		3500	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3501	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3502
		3503	The configuration for a "naked" win32 using the Microsoft runtime
		3504	libraries and raw winsocket select is:
		3505
		3506	#define EV_USE_SELECT 1
		3507	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3508
		3509	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3510	complexity in the O(n²) range when using win32.
		3511
		3512	=item Limited number of file descriptors
		3513
		3514	Windows has numerous arbitrary (and low) limits on things.
		3515
		3516	Early versions of winsocket's select only supported waiting for a maximum
		3517	of C<64> handles (probably owning to the fact that all windows kernels
		3518	can only wait for C<64> things at the same time internally; Microsoft
		3519	recommends spawning a chain of threads and wait for 63 handles and the
		3520	previous thread in each. Great).
		3521
		3522	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3523	to some high number (e.g. C<2048>) before compiling the winsocket select
		3524	call (which might be in libev or elsewhere, for example, perl does its own
		3525	select emulation on windows).
		3526
		3527	Another limit is the number of file descriptors in the Microsoft runtime
		3528	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3529	or something like this inside Microsoft). You can increase this by calling
		3530	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3531	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3532	libraries.
		3533
		3534	This might get you to about C<512> or C<2048> sockets (depending on
		3535	windows version and/or the phase of the moon). To get more, you need to
		3536	wrap all I/O functions and provide your own fd management, but the cost of
		3537	calling select (O(n²)) will likely make this unworkable.
		3538
		3539	=back
		3540
		3541
		3542	=head1 PORTABILITY REQUIREMENTS
		3543
		3544	In addition to a working ISO-C implementation, libev relies on a few
		3545	additional extensions:
		3546
		3547	=over 4
		3548
		3549	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3550	calling conventions regardless of C<ev_watcher_type *>.
		3551
		3552	Libev assumes not only that all watcher pointers have the same internal
		3553	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3554	assumes that the same (machine) code can be used to call any watcher
		3555	callback: The watcher callbacks have different type signatures, but libev
		3556	calls them using an C<ev_watcher *> internally.
		3557
		3558	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3559
		3560	The type C<sig_atomic_t volatile> (or whatever is defined as
		3561	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3562	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3563	believed to be sufficiently portable.
		3564
		3565	=item C<sigprocmask> must work in a threaded environment
		3566
		3567	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3568	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3569	pthread implementations will either allow C<sigprocmask> in the "main
		3570	thread" or will block signals process-wide, both behaviours would
		3571	be compatible with libev. Interaction between C<sigprocmask> and
		3572	C<pthread_sigmask> could complicate things, however.
		3573
		3574	The most portable way to handle signals is to block signals in all threads
		3575	except the initial one, and run the default loop in the initial thread as
		3576	well.
		3577
		3578	=item C<long> must be large enough for common memory allocation sizes
		3579
		3580	To improve portability and simplify using libev, libev uses C<long>
		3581	internally instead of C<size_t> when allocating its data structures. On
		3582	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3583	is still at least 31 bits everywhere, which is enough for hundreds of
		3584	millions of watchers.
		3585
		3586	=item C<double> must hold a time value in seconds with enough accuracy
		3587
		3588	The type C<double> is used to represent timestamps. It is required to
		3589	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3590	enough for at least into the year 4000. This requirement is fulfilled by
		3591	implementations implementing IEEE 754 (basically all existing ones).
		3592
		3593	=back
		3594
		3595	If you know of other additional requirements drop me a note.
		3596
		3597
		3598	=head1 COMPILER WARNINGS
		3599
		3600	Depending on your compiler and compiler settings, you might get no or a
		3601	lot of warnings when compiling libev code. Some people are apparently
		3602	scared by this.
		3603
		3604	However, these are unavoidable for many reasons. For one, each compiler
		3605	has different warnings, and each user has different tastes regarding
		3606	warning options. "Warn-free" code therefore cannot be a goal except when
		3607	targeting a specific compiler and compiler-version.
		3608
		3609	Another reason is that some compiler warnings require elaborate
		3610	workarounds, or other changes to the code that make it less clear and less
		3611	maintainable.
		3612
		3613	And of course, some compiler warnings are just plain stupid, or simply
		3614	wrong (because they don't actually warn about the condition their message
		3615	seems to warn about).
		3616
		3617	While libev is written to generate as few warnings as possible,
		3618	"warn-free" code is not a goal, and it is recommended not to build libev
		3619	with any compiler warnings enabled unless you are prepared to cope with
		3620	them (e.g. by ignoring them). Remember that warnings are just that:
		3621	warnings, not errors, or proof of bugs.
		3622
		3623
		3624	=head1 VALGRIND
		3625
		3626	Valgrind has a special section here because it is a popular tool that is
		3627	highly useful, but valgrind reports are very hard to interpret.
		3628
		3629	If you think you found a bug (memory leak, uninitialised data access etc.)
		3630	in libev, then check twice: If valgrind reports something like:
		3631
		3632	==2274== definitely lost: 0 bytes in 0 blocks.
		3633	==2274== possibly lost: 0 bytes in 0 blocks.
		3634	==2274== still reachable: 256 bytes in 1 blocks.
		3635
		3636	Then there is no memory leak. Similarly, under some circumstances,
		3637	valgrind might report kernel bugs as if it were a bug in libev, or it
		3638	might be confused (it is a very good tool, but only a tool).
		3639
		3640	If you are unsure about something, feel free to contact the mailing list
		3641	with the full valgrind report and an explanation on why you think this is
		3642	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3643	no bug" answer and take the chance of learning how to interpret valgrind
		3644	properly.
		3645
		3646	If you need, for some reason, empty reports from valgrind for your project
		3647	I suggest using suppression lists.
		3648
		3649
2742	=head1 AUTHOR	3650	=head1 AUTHOR
2743		3651
2744	Marc Lehmann <libev@schmorp.de>.	3652	Marc Lehmann <libev@schmorp.de>.
2745		3653

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines