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Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs.
Revision 1.177 by root, Mon Sep 8 17:27:42 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	=head1 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 occuring), 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
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
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	=head1 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	=head1 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 such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		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
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
117		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
122	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	170	version of the library your program was compiled against.
127		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
128	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	178	not a problem.
132		179
133	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
134	version.	181	version.
135		182
136	assert (("libev version mismatch",	183	assert (("libev version mismatch",
137	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
138	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
139		186
140	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
141		188
142	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_*>
143	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
145	a description of the set values.	192	a description of the set values.
146		193
147	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
148	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
149		196
150	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
151	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
152		199
153	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
154		201
155	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
156	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
157	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
158	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
159	(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
160	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
161		208
162	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
163		210
…		…
170	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
171		218
172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
173		220
174	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
175	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
176	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
177	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
178	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
179	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.
180		230
181	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
182	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,
183	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.
184		234
185	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
186	retries).	236	retries (example requires a standards-compliant C<realloc>).
187		237
188	static void *	238	static void *
189	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
190	{	240	{
191	for (;;)	241	for (;;)
…		…
202	...	252	...
203	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
204		254
205	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
206		256
207	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
208	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
209	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
210	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
211	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
212	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
213	(such as abort).	263	(such as abort).
214		264
215	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.
…		…
229	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
230		280
231	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
232	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
233	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
234
235	If you use threads, a common model is to run the default event loop
236	in your main thread (or in a separate thread) and for each thread you
237	create, you also create another event loop. Libev itself does no locking
238	whatsoever, so if you mix calls to the same event loop in different
239	threads, make sure you lock (this is usually a bad idea, though, even if
240	done correctly, because it's hideous and inefficient).
241		284
242	=over 4	285	=over 4
243		286
244	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
245		288
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		293
251	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
252	function.	295	function.
253		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
254	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
255	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>).
256		310
257	The following flags are supported:	311	The following flags are supported:
258		312
…		…
263	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
264	thing, believe me).	318	thing, believe me).
265		319
266	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
267		321
268	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
269	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
270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
271	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
272	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
273	around bugs.	327	around bugs.
…		…
279	enabling this flag.	333	enabling this flag.
280		334
281	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,
282	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
283	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
284	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
285	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
286	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
287		341
288	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
289	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
290	flag.	344	flag.
291		345
292	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>
293	environment variable.	347	environment variable.
294		348
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		350
297	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
298	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
299	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
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
302		363
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		365
305	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
309		372
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		374
312	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	377	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
316		382
317	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
319	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	387	very well if you register events for both fds.
322		388
323	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	390	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	391	(or space) is available.
326		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		401
329	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
335		413
336	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
341		429
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		431
344	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
345		436
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		438
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
350		441
351	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
354		454
355	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
356		456
357	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		460
		461	It is definitely not recommended to use this flag.
		462
361	=back	463	=back
362		464
363	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		468
368	The most typical usage is like this:	469	The most typical usage is like this:
369		470
370	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
372		473
373	Restrict libev to the select and poll backends, and do not allow	474	Restrict libev to the select and poll backends, and do not allow
374	environment settings to be taken into account:	475	environment settings to be taken into account:
375		476
376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
377		478
378	Use whatever libev has to offer, but make sure that kqueue is used if	479	Use whatever libev has to offer, but make sure that kqueue is used if
379	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
380	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
381		482
382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
383		484
384	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
385		486
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
387	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
388	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
389	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
390		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
391	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
392		497
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	499	if (!epoller)
395	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
396		501
397	=item ev_default_destroy ()	502	=item ev_default_destroy ()
398		503
399	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
403	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
406		520
407	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
408		522
409	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
411		525
412	=item ev_default_fork ()	526	=item ev_default_fork ()
413		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
417	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
418		534
419	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
422		538
423	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
426		542
427	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
428		544
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
434		546
435	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
438		554
439	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
440		556
441	Returns the count of loop iterations for the loop, which is identical to	557	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		571
456	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
		577
		578	=item ev_now_update (loop)
		579
		580	Establishes the current time by querying the kernel, updating the time
		581	returned by C<ev_now ()> in the progress. This is a costly operation and
		582	is usually done automatically within C<ev_loop ()>.
		583
		584	This function is rarely useful, but when some event callback runs for a
		585	very long time without entering the event loop, updating libev's idea of
		586	the current time is a good idea.
		587
		588	See also "The special problem of time updates" in the C<ev_timer> section.
461		589
462	=item ev_loop (loop, int flags)	590	=item ev_loop (loop, int flags)
463		591
464	Finally, this is it, the event handler. This function usually is called	592	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	593	after you initialised all your watchers and you want to start handling
…		…
477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
478	those events and any outstanding ones, but will not block your process in	606	those events and any outstanding ones, but will not block your process in
479	case there are no events and will return after one iteration of the loop.	607	case there are no events and will return after one iteration of the loop.
480		608
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
482	neccessary) and will handle those and any outstanding ones. It will block	610	necessary) and will handle those and any outstanding ones. It will block
483	your process until at least one new event arrives, and will return after	611	your process until at least one new event arrives, and will return after
484	one iteration of the loop. This is useful if you are waiting for some	612	one iteration of the loop. This is useful if you are waiting for some
485	external event in conjunction with something not expressible using other	613	external event in conjunction with something not expressible using other
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	615	usually a better approach for this kind of thing.
488		616
489	Here are the gory details of what C<ev_loop> does:	617	Here are the gory details of what C<ev_loop> does:
490		618
491	* If there are no active watchers (reference count is zero), return.	619	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	620	* If EVFLAG_FORKCHECK was used, check for a fork.
		621	- If a fork was detected (by any means), queue and call all fork watchers.
		622	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	623	- If we have been forked, detach and recreate the kernel state
		624	as to not disturb the other process.
494	- Update the kernel state with all outstanding changes.	625	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	626	- Update the "event loop time" (ev_now ()).
496	- Calculate for how long to block.	627	- Calculate for how long to sleep or block, if at all
		628	(active idle watchers, EVLOOP_NONBLOCK or not having
		629	any active watchers at all will result in not sleeping).
		630	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	631	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	632	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
500	- Queue all outstanding timers.	634	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	635	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	636	- Unless any events are pending now, queue all idle watchers.
503	- Queue all check watchers.	637	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	638	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	639	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	640	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	642	were used, or there are no active watchers, return, otherwise
		643	continue with step *.
509		644
510	Example: Queue some jobs and then loop until no events are outsanding	645	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	646	anymore.
512		647
513	... queue jobs here, make sure they register event watchers as long	648	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	649	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	650	ev_loop (my_loop, 0);
516	... jobs done. yeah!	651	... jobs done or somebody called unloop. yeah!
517		652
518	=item ev_unloop (loop, how)	653	=item ev_unloop (loop, how)
519		654
520	Can be used to make a call to C<ev_loop> return early (but only after it	655	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	656	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		659
		660	This "unloop state" will be cleared when entering C<ev_loop> again.
524		661
525	=item ev_ref (loop)	662	=item ev_ref (loop)
526		663
527	=item ev_unref (loop)	664	=item ev_unref (loop)
528		665
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	670	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	671	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	672	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	673	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	674	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	675	libraries. Just remember to I<unref after start> and I<ref before stop>
		676	(but only if the watcher wasn't active before, or was active before,
		677	respectively).
539		678
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	680	running when nothing else is active.
542		681
543	struct ev_signal exitsig;	682	struct ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	683	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	684	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	685	evf_unref (loop);
547		686
548	Example: For some weird reason, unregister the above signal handler again.	687	Example: For some weird reason, unregister the above signal handler again.
549		688
550	ev_ref (loop);	689	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	690	ev_signal_stop (loop, &exitsig);
		691
		692	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		693
		694	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		695
		696	These advanced functions influence the time that libev will spend waiting
		697	for events. Both time intervals are by default C<0>, meaning that libev
		698	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		699	latency.
		700
		701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		702	allows libev to delay invocation of I/O and timer/periodic callbacks
		703	to increase efficiency of loop iterations (or to increase power-saving
		704	opportunities).
		705
		706	The background is that sometimes your program runs just fast enough to
		707	handle one (or very few) event(s) per loop iteration. While this makes
		708	the program responsive, it also wastes a lot of CPU time to poll for new
		709	events, especially with backends like C<select ()> which have a high
		710	overhead for the actual polling but can deliver many events at once.
		711
		712	By setting a higher I<io collect interval> you allow libev to spend more
		713	time collecting I/O events, so you can handle more events per iteration,
		714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		715	C<ev_timer>) will be not affected. Setting this to a non-null value will
		716	introduce an additional C<ev_sleep ()> call into most loop iterations.
		717
		718	Likewise, by setting a higher I<timeout collect interval> you allow libev
		719	to spend more time collecting timeouts, at the expense of increased
		720	latency (the watcher callback will be called later). C<ev_io> watchers
		721	will not be affected. Setting this to a non-null value will not introduce
		722	any overhead in libev.
		723
		724	Many (busy) programs can usually benefit by setting the I/O collect
		725	interval to a value near C<0.1> or so, which is often enough for
		726	interactive servers (of course not for games), likewise for timeouts. It
		727	usually doesn't make much sense to set it to a lower value than C<0.01>,
		728	as this approaches the timing granularity of most systems.
		729
		730	Setting the I<timeout collect interval> can improve the opportunity for
		731	saving power, as the program will "bundle" timer callback invocations that
		732	are "near" in time together, by delaying some, thus reducing the number of
		733	times the process sleeps and wakes up again. Another useful technique to
		734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		735	they fire on, say, one-second boundaries only.
		736
		737	=item ev_loop_verify (loop)
		738
		739	This function only does something when C<EV_VERIFY> support has been
		740	compiled in. It tries to go through all internal structures and checks
		741	them for validity. If anything is found to be inconsistent, it will print
		742	an error message to standard error and call C<abort ()>.
		743
		744	This can be used to catch bugs inside libev itself: under normal
		745	circumstances, this function will never abort as of course libev keeps its
		746	data structures consistent.
552		747
553	=back	748	=back
554		749
555		750
556	=head1 ANATOMY OF A WATCHER	751	=head1 ANATOMY OF A WATCHER
557		752
558	A watcher is a structure that you create and register to record your	753	A watcher is a structure that you create and register to record your
559	interest in some event. For instance, if you want to wait for STDIN to	754	interest in some event. For instance, if you want to wait for STDIN to
560	become readable, you would create an C<ev_io> watcher for that:	755	become readable, you would create an C<ev_io> watcher for that:
561		756
562	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
563	{	758	{
564	ev_io_stop (w);	759	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	760	ev_unloop (loop, EVUNLOOP_ALL);
566	}	761	}
567		762
568	struct ev_loop *loop = ev_default_loop (0);	763	struct ev_loop *loop = ev_default_loop (0);
569	struct ev_io stdin_watcher;	764	struct ev_io stdin_watcher;
570	ev_init (&stdin_watcher, my_cb);	765	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	767	ev_io_start (loop, &stdin_watcher);
573	ev_loop (loop, 0);	768	ev_loop (loop, 0);
574		769
575	As you can see, you are responsible for allocating the memory for your	770	As you can see, you are responsible for allocating the memory for your
576	watcher structures (and it is usually a bad idea to do this on the stack,	771	watcher structures (and it is usually a bad idea to do this on the stack,
577	although this can sometimes be quite valid).	772	although this can sometimes be quite valid).
578		773
579	Each watcher structure must be initialised by a call to C<ev_init	774	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	775	(watcher *, callback)>, which expects a callback to be provided. This
581	callback gets invoked each time the event occurs (or, in the case of io	776	callback gets invoked each time the event occurs (or, in the case of I/O
582	watchers, each time the event loop detects that the file descriptor given	777	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	778	is readable and/or writable).
584		779
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
586	with arguments specific to this watcher type. There is also a macro	781	with arguments specific to this watcher type. There is also a macro
…		…
656	=item C<EV_FORK>	851	=item C<EV_FORK>
657		852
658	The event loop has been resumed in the child process after fork (see	853	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	854	C<ev_fork>).
660		855
		856	=item C<EV_ASYNC>
		857
		858	The given async watcher has been asynchronously notified (see C<ev_async>).
		859
661	=item C<EV_ERROR>	860	=item C<EV_ERROR>
662		861
663	An unspecified error has occured, the watcher has been stopped. This might	862	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	863	happen because the watcher could not be properly started because libev
665	ran out of memory, a file descriptor was found to be closed or any other	864	ran out of memory, a file descriptor was found to be closed or any other
666	problem. You best act on it by reporting the problem and somehow coping	865	problem. You best act on it by reporting the problem and somehow coping
667	with the watcher being stopped.	866	with the watcher being stopped.
668		867
669	Libev will usually signal a few "dummy" events together with an error,	868	Libev will usually signal a few "dummy" events together with an error,
670	for example it might indicate that a fd is readable or writable, and if	869	for example it might indicate that a fd is readable or writable, and if
671	your callbacks is well-written it can just attempt the operation and cope	870	your callbacks is well-written it can just attempt the operation and cope
672	with the error from read() or write(). This will not work in multithreaded	871	with the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	872	programs, though, so beware.
674		873
675	=back	874	=back
676		875
677	=head2 GENERIC WATCHER FUNCTIONS	876	=head2 GENERIC WATCHER FUNCTIONS
…		…
707	Although some watcher types do not have type-specific arguments	906	Although some watcher types do not have type-specific arguments
708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		908
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		910
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
713	calls into a single call. This is the most convinient method to initialise	912	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	913	a watcher. The same limitations apply, of course.
715		914
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		916
718	Starts (activates) the given watcher. Only active watchers will receive	917	Starts (activates) the given watcher. Only active watchers will receive
…		…
801	to associate arbitrary data with your watcher. If you need more data and	1000	to associate arbitrary data with your watcher. If you need more data and
802	don't want to allocate memory and store a pointer to it in that data	1001	don't want to allocate memory and store a pointer to it in that data
803	member, you can also "subclass" the watcher type and provide your own	1002	member, you can also "subclass" the watcher type and provide your own
804	data:	1003	data:
805		1004
806	struct my_io	1005	struct my_io
807	{	1006	{
808	struct ev_io io;	1007	struct ev_io io;
809	int otherfd;	1008	int otherfd;
810	void *somedata;	1009	void *somedata;
811	struct whatever *mostinteresting;	1010	struct whatever *mostinteresting;
812	}	1011	}
813		1012
814	And since your callback will be called with a pointer to the watcher, you	1013	And since your callback will be called with a pointer to the watcher, you
815	can cast it back to your own type:	1014	can cast it back to your own type:
816		1015
817	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
818	{	1017	{
819	struct my_io *w = (struct my_io *)w_;	1018	struct my_io *w = (struct my_io *)w_;
820	...	1019	...
821	}	1020	}
822		1021
823	More interesting and less C-conformant ways of casting your callback type	1022	More interesting and less C-conformant ways of casting your callback type
824	instead have been omitted.	1023	instead have been omitted.
825		1024
826	Another common scenario is having some data structure with multiple	1025	Another common scenario is having some data structure with multiple
827	watchers:	1026	watchers:
828		1027
829	struct my_biggy	1028	struct my_biggy
830	{	1029	{
831	int some_data;	1030	int some_data;
832	ev_timer t1;	1031	ev_timer t1;
833	ev_timer t2;	1032	ev_timer t2;
834	}	1033	}
835		1034
836	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,
837	you need to use C<offsetof>:	1036	you need to use C<offsetof>:
838		1037
839	#include <stddef.h>	1038	#include <stddef.h>
840		1039
841	static void	1040	static void
842	t1_cb (EV_P_ struct ev_timer *w, int revents)	1041	t1_cb (EV_P_ struct ev_timer *w, int revents)
843	{	1042	{
844	struct my_biggy big = (struct my_biggy *	1043	struct my_biggy big = (struct my_biggy *
845	(((char *)w) - offsetof (struct my_biggy, t1));	1044	(((char *)w) - offsetof (struct my_biggy, t1));
846	}	1045	}
847		1046
848	static void	1047	static void
849	t2_cb (EV_P_ struct ev_timer *w, int revents)	1048	t2_cb (EV_P_ struct ev_timer *w, int revents)
850	{	1049	{
851	struct my_biggy big = (struct my_biggy *	1050	struct my_biggy big = (struct my_biggy *
852	(((char *)w) - offsetof (struct my_biggy, t2));	1051	(((char *)w) - offsetof (struct my_biggy, t2));
853	}	1052	}
854		1053
855		1054
856	=head1 WATCHER TYPES	1055	=head1 WATCHER TYPES
857		1056
858	This section describes each watcher in detail, but will not repeat	1057	This section describes each watcher in detail, but will not repeat
…		…
882	In general you can register as many read and/or write event watchers per	1081	In general you can register as many read and/or write event watchers per
883	fd as you want (as long as you don't confuse yourself). Setting all file	1082	fd as you want (as long as you don't confuse yourself). Setting all file
884	descriptors to non-blocking mode is also usually a good idea (but not	1083	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	1084	required if you know what you are doing).
886		1085
887	You have to be careful with dup'ed file descriptors, though. Some backends
888	(the linux epoll backend is a notable example) cannot handle dup'ed file
889	descriptors correctly if you register interest in two or more fds pointing
890	to the same underlying file/socket/etc. description (that is, they share
891	the same underlying "file open").
892
893	If you must do this, then force the use of a known-to-be-good backend	1086	If you must do this, then force the use of a known-to-be-good backend
894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).	1088	C<EVBACKEND_POLL>).
896		1089
897	Another thing you have to watch out for is that it is quite easy to	1090	Another thing you have to watch out for is that it is quite easy to
898	receive "spurious" readyness notifications, that is your callback might	1091	receive "spurious" readiness notifications, that is your callback might
899	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
900	because there is no data. Not only are some backends known to create a	1093	because there is no data. Not only are some backends known to create a
901	lot of those (for example solaris ports), it is very easy to get into	1094	lot of those (for example Solaris ports), it is very easy to get into
902	this situation even with a relatively standard program structure. Thus	1095	this situation even with a relatively standard program structure. Thus
903	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning
904	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.
905		1098
906	If you cannot run the fd in non-blocking mode (for example you should not	1099	If you cannot run the fd in non-blocking mode (for example you should not
907	play around with an Xlib connection), then you have to seperately re-test	1100	play around with an Xlib connection), then you have to separately re-test
908	whether a file descriptor is really ready with a known-to-be good interface	1101	whether a file descriptor is really ready with a known-to-be good interface
909	such as poll (fortunately in our Xlib example, Xlib already does this on	1102	such as poll (fortunately in our Xlib example, Xlib already does this on
910	its own, so its quite safe to use).	1103	its own, so its quite safe to use).
911		1104
		1105	=head3 The special problem of disappearing file descriptors
		1106
		1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1108	descriptor (either by calling C<close> explicitly or by any other means,
		1109	such as C<dup>). The reason is that you register interest in some file
		1110	descriptor, but when it goes away, the operating system will silently drop
		1111	this interest. If another file descriptor with the same number then is
		1112	registered with libev, there is no efficient way to see that this is, in
		1113	fact, a different file descriptor.
		1114
		1115	To avoid having to explicitly tell libev about such cases, libev follows
		1116	the following policy: Each time C<ev_io_set> is being called, libev
		1117	will assume that this is potentially a new file descriptor, otherwise
		1118	it is assumed that the file descriptor stays the same. That means that
		1119	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1120	descriptor even if the file descriptor number itself did not change.
		1121
		1122	This is how one would do it normally anyway, the important point is that
		1123	the libev application should not optimise around libev but should leave
		1124	optimisations to libev.
		1125
		1126	=head3 The special problem of dup'ed file descriptors
		1127
		1128	Some backends (e.g. epoll), cannot register events for file descriptors,
		1129	but only events for the underlying file descriptions. That means when you
		1130	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1131	events for them, only one file descriptor might actually receive events.
		1132
		1133	There is no workaround possible except not registering events
		1134	for potentially C<dup ()>'ed file descriptors, or to resort to
		1135	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1136
		1137	=head3 The special problem of fork
		1138
		1139	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1140	useless behaviour. Libev fully supports fork, but needs to be told about
		1141	it in the child.
		1142
		1143	To support fork in your programs, you either have to call
		1144	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1146	C<EVBACKEND_POLL>.
		1147
		1148	=head3 The special problem of SIGPIPE
		1149
		1150	While not really specific to libev, it is easy to forget about SIGPIPE:
		1151	when writing to a pipe whose other end has been closed, your program gets
		1152	send a SIGPIPE, which, by default, aborts your program. For most programs
		1153	this is sensible behaviour, for daemons, this is usually undesirable.
		1154
		1155	So when you encounter spurious, unexplained daemon exits, make sure you
		1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1157	somewhere, as that would have given you a big clue).
		1158
		1159
		1160	=head3 Watcher-Specific Functions
		1161
912	=over 4	1162	=over 4
913		1163
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1164	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1165
916	=item ev_io_set (ev_io *, int fd, int events)	1166	=item ev_io_set (ev_io *, int fd, int events)
917		1167
918	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
919	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
920	C<EV_READ | EV_WRITE> to receive the given events.	1170	C<EV_READ | EV_WRITE> to receive the given events.
921		1171
922	=item int fd [read-only]	1172	=item int fd [read-only]
923		1173
924	The file descriptor being watched.	1174	The file descriptor being watched.
…		…
926	=item int events [read-only]	1176	=item int events [read-only]
927		1177
928	The events being watched.	1178	The events being watched.
929		1179
930	=back	1180	=back
		1181
		1182	=head3 Examples
931		1183
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
933	readable, but only once. Since it is likely line-buffered, you could	1185	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1186	attempt to read a whole line in the callback.
935		1187
936	static void	1188	static void
937	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
938	{	1190	{
939	ev_io_stop (loop, w);	1191	ev_io_stop (loop, w);
940	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors
941	}	1193	}
942		1194
943	...	1195	...
944	struct ev_loop *loop = ev_default_init (0);	1196	struct ev_loop *loop = ev_default_init (0);
945	struct ev_io stdin_readable;	1197	struct ev_io stdin_readable;
946	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
947	ev_io_start (loop, &stdin_readable);	1199	ev_io_start (loop, &stdin_readable);
948	ev_loop (loop, 0);	1200	ev_loop (loop, 0);
949		1201
950		1202
951	=head2 C<ev_timer> - relative and optionally repeating timeouts	1203	=head2 C<ev_timer> - relative and optionally repeating timeouts
952		1204
953	Timer watchers are simple relative timers that generate an event after a	1205	Timer watchers are simple relative timers that generate an event after a
954	given time, and optionally repeating in regular intervals after that.	1206	given time, and optionally repeating in regular intervals after that.
955		1207
956	The timers are based on real time, that is, if you register an event that	1208	The timers are based on real time, that is, if you register an event that
957	times out after an hour and you reset your system clock to last years	1209	times out after an hour and you reset your system clock to January last
958	time, it will still time out after (roughly) and hour. "Roughly" because	1210	year, it will still time out after (roughly) and hour. "Roughly" because
959	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the
960	monotonic clock option helps a lot here).	1212	monotonic clock option helps a lot here).
		1213
		1214	The callback is guaranteed to be invoked only after its timeout has passed,
		1215	but if multiple timers become ready during the same loop iteration then
		1216	order of execution is undefined.
		1217
		1218	=head3 The special problem of time updates
		1219
		1220	Establishing the current time is a costly operation (it usually takes at
		1221	least two system calls): EV therefore updates its idea of the current
		1222	time only before and after C<ev_loop> polls for new events, which causes
		1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1224	lots of events.
961		1225
962	The relative timeouts are calculated relative to the C<ev_now ()>	1226	The relative timeouts are calculated relative to the C<ev_now ()>
963	time. This is usually the right thing as this timestamp refers to the time	1227	time. This is usually the right thing as this timestamp refers to the time
964	of the event triggering whatever timeout you are modifying/starting. If	1228	of the event triggering whatever timeout you are modifying/starting. If
965	you suspect event processing to be delayed and you I<need> to base the timeout	1229	you suspect event processing to be delayed and you I<need> to base the
966	on the current time, use something like this to adjust for this:	1230	timeout on the current time, use something like this to adjust for this:
967		1231
968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
969		1233
970	The callback is guarenteed to be invoked only when its timeout has passed,	1234	If the event loop is suspended for a long time, you can also force an
971	but if multiple timers become ready during the same loop iteration then	1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update
972	order of execution is undefined.	1236	()>.
		1237
		1238	=head3 Watcher-Specific Functions and Data Members
973		1239
974	=over 4	1240	=over 4
975		1241
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1242	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1243
978	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1244	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
979		1245
980	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1246	Configure the timer to trigger after C<after> seconds. If C<repeat>
981	C<0.>, then it will automatically be stopped. If it is positive, then the	1247	is C<0.>, then it will automatically be stopped once the timeout is
982	timer will automatically be configured to trigger again C<repeat> seconds	1248	reached. If it is positive, then the timer will automatically be
983	later, again, and again, until stopped manually.	1249	configured to trigger again C<repeat> seconds later, again, and again,
		1250	until stopped manually.
984		1251
985	The timer itself will do a best-effort at avoiding drift, that is, if you	1252	The timer itself will do a best-effort at avoiding drift, that is, if
986	configure a timer to trigger every 10 seconds, then it will trigger at	1253	you configure a timer to trigger every 10 seconds, then it will normally
987	exactly 10 second intervals. If, however, your program cannot keep up with	1254	trigger at exactly 10 second intervals. If, however, your program cannot
988	the timer (because it takes longer than those 10 seconds to do stuff) the	1255	keep up with the timer (because it takes longer than those 10 seconds to
989	timer will not fire more than once per event loop iteration.	1256	do stuff) the timer will not fire more than once per event loop iteration.
990		1257
991	=item ev_timer_again (loop)	1258	=item ev_timer_again (loop, ev_timer *)
992		1259
993	This will act as if the timer timed out and restart it again if it is	1260	This will act as if the timer timed out and restart it again if it is
994	repeating. The exact semantics are:	1261	repeating. The exact semantics are:
995		1262
996	If the timer is pending, its pending status is cleared.	1263	If the timer is pending, its pending status is cleared.
997		1264
998	If the timer is started but nonrepeating, stop it (as if it timed out).	1265	If the timer is started but non-repeating, stop it (as if it timed out).
999		1266
1000	If the timer is repeating, either start it if necessary (with the	1267	If the timer is repeating, either start it if necessary (with the
1001	C<repeat> value), or reset the running timer to the C<repeat> value.	1268	C<repeat> value), or reset the running timer to the C<repeat> value.
1002		1269
1003	This sounds a bit complicated, but here is a useful and typical	1270	This sounds a bit complicated, but here is a useful and typical
1004	example: Imagine you have a tcp connection and you want a so-called idle	1271	example: Imagine you have a TCP connection and you want a so-called idle
1005	timeout, that is, you want to be called when there have been, say, 60	1272	timeout, that is, you want to be called when there have been, say, 60
1006	seconds of inactivity on the socket. The easiest way to do this is to	1273	seconds of inactivity on the socket. The easiest way to do this is to
1007	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1008	C<ev_timer_again> each time you successfully read or write some data. If	1275	C<ev_timer_again> each time you successfully read or write some data. If
1009	you go into an idle state where you do not expect data to travel on the	1276	you go into an idle state where you do not expect data to travel on the
…		…
1031	or C<ev_timer_again> is called and determines the next timeout (if any),	1298	or C<ev_timer_again> is called and determines the next timeout (if any),
1032	which is also when any modifications are taken into account.	1299	which is also when any modifications are taken into account.
1033		1300
1034	=back	1301	=back
1035		1302
		1303	=head3 Examples
		1304
1036	Example: Create a timer that fires after 60 seconds.	1305	Example: Create a timer that fires after 60 seconds.
1037		1306
1038	static void	1307	static void
1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1040	{	1309	{
1041	.. one minute over, w is actually stopped right here	1310	.. one minute over, w is actually stopped right here
1042	}	1311	}
1043		1312
1044	struct ev_timer mytimer;	1313	struct ev_timer mytimer;
1045	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1046	ev_timer_start (loop, &mytimer);	1315	ev_timer_start (loop, &mytimer);
1047		1316
1048	Example: Create a timeout timer that times out after 10 seconds of	1317	Example: Create a timeout timer that times out after 10 seconds of
1049	inactivity.	1318	inactivity.
1050		1319
1051	static void	1320	static void
1052	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1053	{	1322	{
1054	.. ten seconds without any activity	1323	.. ten seconds without any activity
1055	}	1324	}
1056		1325
1057	struct ev_timer mytimer;	1326	struct ev_timer mytimer;
1058	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1059	ev_timer_again (&mytimer); /* start timer */	1328	ev_timer_again (&mytimer); /* start timer */
1060	ev_loop (loop, 0);	1329	ev_loop (loop, 0);
1061		1330
1062	// and in some piece of code that gets executed on any "activity":	1331	// and in some piece of code that gets executed on any "activity":
1063	// reset the timeout to start ticking again at 10 seconds	1332	// reset the timeout to start ticking again at 10 seconds
1064	ev_timer_again (&mytimer);	1333	ev_timer_again (&mytimer);
1065		1334
1066		1335
1067	=head2 C<ev_periodic> - to cron or not to cron?	1336	=head2 C<ev_periodic> - to cron or not to cron?
1068		1337
1069	Periodic watchers are also timers of a kind, but they are very versatile	1338	Periodic watchers are also timers of a kind, but they are very versatile
1070	(and unfortunately a bit complex).	1339	(and unfortunately a bit complex).
1071		1340
1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1073	but on wallclock time (absolute time). You can tell a periodic watcher	1342	but on wall clock time (absolute time). You can tell a periodic watcher
1074	to trigger "at" some specific point in time. For example, if you tell a	1343	to trigger after some specific point in time. For example, if you tell a
1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1076	+ 10.>) and then reset your system clock to the last year, then it will	1345	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1346	clock to January of the previous year, then it will take more than year
1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1078	roughly 10 seconds later and of course not if you reset your system time	1348	roughly 10 seconds later as it uses a relative timeout).
1079	again).
1080		1349
1081	They can also be used to implement vastly more complex timers, such as	1350	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on eahc midnight, local time.	1351	such as triggering an event on each "midnight, local time", or other
		1352	complicated, rules.
1083		1353
1084	As with timers, the callback is guarenteed to be invoked only when the	1354	As with timers, the callback is guaranteed to be invoked only when the
1085	time (C<at>) has been passed, but if multiple periodic timers become ready	1355	time (C<at>) has passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1356	during the same loop iteration then order of execution is undefined.
		1357
		1358	=head3 Watcher-Specific Functions and Data Members
1087		1359
1088	=over 4	1360	=over 4
1089		1361
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1362	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1363
…		…
1094	Lots of arguments, lets sort it out... There are basically three modes of	1366	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1367	operation, and we will explain them from simplest to complex:
1096		1368
1097	=over 4	1369	=over 4
1098		1370
1099	=item * absolute timer (interval = reschedule_cb = 0)	1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1372
1101	In this configuration the watcher triggers an event at the wallclock time	1373	In this configuration the watcher triggers an event after the wall clock
1102	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1374	time C<at> has passed and doesn't repeat. It will not adjust when a time
1103	that is, if it is to be run at January 1st 2011 then it will run when the	1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1104	system time reaches or surpasses this time.	1376	run when the system time reaches or surpasses this time.
1105		1377
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1379
1108	In this mode the watcher will always be scheduled to time out at the next	1380	In this mode the watcher will always be scheduled to time out at the next
1109	C<at + N * interval> time (for some integer N) and then repeat, regardless	1381	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1382	and then repeat, regardless of any time jumps.
1111		1383
1112	This can be used to create timers that do not drift with respect to system	1384	This can be used to create timers that do not drift with respect to system
1113	time:	1385	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1386	the hour:
1114		1387
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1388	ev_periodic_set (&periodic, 0., 3600., 0);
1116		1389
1117	This doesn't mean there will always be 3600 seconds in between triggers,	1390	This doesn't mean there will always be 3600 seconds in between triggers,
1118	but only that the the callback will be called when the system time shows a	1391	but only that the callback will be called when the system time shows a
1119	full hour (UTC), or more correctly, when the system time is evenly divisible	1392	full hour (UTC), or more correctly, when the system time is evenly divisible
1120	by 3600.	1393	by 3600.
1121		1394
1122	Another way to think about it (for the mathematically inclined) is that	1395	Another way to think about it (for the mathematically inclined) is that
1123	C<ev_periodic> will try to run the callback in this mode at the next possible	1396	C<ev_periodic> will try to run the callback in this mode at the next possible
1124	time where C<time = at (mod interval)>, regardless of any time jumps.	1397	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1398
		1399	For numerical stability it is preferable that the C<at> value is near
		1400	C<ev_now ()> (the current time), but there is no range requirement for
		1401	this value, and in fact is often specified as zero.
		1402
		1403	Note also that there is an upper limit to how often a timer can fire (CPU
		1404	speed for example), so if C<interval> is very small then timing stability
		1405	will of course deteriorate. Libev itself tries to be exact to be about one
		1406	millisecond (if the OS supports it and the machine is fast enough).
		1407
1126	=item * manual reschedule mode (reschedule_cb = callback)	1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1409
1128	In this mode the values for C<interval> and C<at> are both being	1410	In this mode the values for C<interval> and C<at> are both being
1129	ignored. Instead, each time the periodic watcher gets scheduled, the	1411	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1412	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1413	current time as second argument.
1132		1414
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1134	ever, or make any event loop modifications>. If you need to stop it,	1416	ever, or make ANY event loop modifications whatsoever>.
1135	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1136	starting a prepare watcher).
1137		1417
		1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1420	only event loop modification you are allowed to do).
		1421
1138	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1139	ev_tstamp now)>, e.g.:	1423	*w, ev_tstamp now)>, e.g.:
1140		1424
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1142	{	1426	{
1143	return now + 60.;	1427	return now + 60.;
1144	}	1428	}
…		…
1146	It must return the next time to trigger, based on the passed time value	1430	It must return the next time to trigger, based on the passed time value
1147	(that is, the lowest time value larger than to the second argument). It	1431	(that is, the lowest time value larger than to the second argument). It
1148	will usually be called just before the callback will be triggered, but	1432	will usually be called just before the callback will be triggered, but
1149	might be called at other times, too.	1433	might be called at other times, too.
1150		1434
1151	NOTE: I<< This callback must always return a time that is later than the	1435	NOTE: I<< This callback must always return a time that is higher than or
1152	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1436	equal to the passed C<now> value >>.
1153		1437
1154	This can be used to create very complex timers, such as a timer that	1438	This can be used to create very complex timers, such as a timer that
1155	triggers on each midnight, local time. To do this, you would calculate the	1439	triggers on "next midnight, local time". To do this, you would calculate the
1156	next midnight after C<now> and return the timestamp value for this. How	1440	next midnight after C<now> and return the timestamp value for this. How
1157	you do this is, again, up to you (but it is not trivial, which is the main	1441	you do this is, again, up to you (but it is not trivial, which is the main
1158	reason I omitted it as an example).	1442	reason I omitted it as an example).
1159		1443
1160	=back	1444	=back
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1448	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1449	when you changed some parameters or the reschedule callback would return
1166	a different time than the last time it was called (e.g. in a crond like	1450	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1451	program when the crontabs have changed).
1168		1452
		1453	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1454
		1455	When active, returns the absolute time that the watcher is supposed to
		1456	trigger next.
		1457
		1458	=item ev_tstamp offset [read-write]
		1459
		1460	When repeating, this contains the offset value, otherwise this is the
		1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1462
		1463	Can be modified any time, but changes only take effect when the periodic
		1464	timer fires or C<ev_periodic_again> is being called.
		1465
1169	=item ev_tstamp interval [read-write]	1466	=item ev_tstamp interval [read-write]
1170		1467
1171	The current interval value. Can be modified any time, but changes only	1468	The current interval value. Can be modified any time, but changes only
1172	take effect when the periodic timer fires or C<ev_periodic_again> is being	1469	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1470	called.
…		…
1178	switched off. Can be changed any time, but changes only take effect when	1475	switched off. Can be changed any time, but changes only take effect when
1179	the periodic timer fires or C<ev_periodic_again> is being called.	1476	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1477
1181	=back	1478	=back
1182		1479
		1480	=head3 Examples
		1481
1183	Example: Call a callback every hour, or, more precisely, whenever the	1482	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1483	system clock is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1484	potentially a lot of jitter, but good long-term stability.
1186		1485
1187	static void	1486	static void
1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1189	{	1488	{
1190	... its now a full hour (UTC, or TAI or whatever your clock follows)	1489	... its now a full hour (UTC, or TAI or whatever your clock follows)
1191	}	1490	}
1192		1491
1193	struct ev_periodic hourly_tick;	1492	struct ev_periodic hourly_tick;
1194	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1195	ev_periodic_start (loop, &hourly_tick);	1494	ev_periodic_start (loop, &hourly_tick);
1196		1495
1197	Example: The same as above, but use a reschedule callback to do it:	1496	Example: The same as above, but use a reschedule callback to do it:
1198		1497
1199	#include <math.h>	1498	#include <math.h>
1200		1499
1201	static ev_tstamp	1500	static ev_tstamp
1202	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1203	{	1502	{
1204	return fmod (now, 3600.) + 3600.;	1503	return fmod (now, 3600.) + 3600.;
1205	}	1504	}
1206		1505
1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1208		1507
1209	Example: Call a callback every hour, starting now:	1508	Example: Call a callback every hour, starting now:
1210		1509
1211	struct ev_periodic hourly_tick;	1510	struct ev_periodic hourly_tick;
1212	ev_periodic_init (&hourly_tick, clock_cb,	1511	ev_periodic_init (&hourly_tick, clock_cb,
1213	fmod (ev_now (loop), 3600.), 3600., 0);	1512	fmod (ev_now (loop), 3600.), 3600., 0);
1214	ev_periodic_start (loop, &hourly_tick);	1513	ev_periodic_start (loop, &hourly_tick);
1215		1514
1216		1515
1217	=head2 C<ev_signal> - signal me when a signal gets signalled!	1516	=head2 C<ev_signal> - signal me when a signal gets signalled!
1218		1517
1219	Signal watchers will trigger an event when the process receives a specific	1518	Signal watchers will trigger an event when the process receives a specific
…		…
1226	with the kernel (thus it coexists with your own signal handlers as long	1525	with the kernel (thus it coexists with your own signal handlers as long
1227	as you don't register any with libev). Similarly, when the last signal	1526	as you don't register any with libev). Similarly, when the last signal
1228	watcher for a signal is stopped libev will reset the signal handler to	1527	watcher for a signal is stopped libev will reset the signal handler to
1229	SIG_DFL (regardless of what it was set to before).	1528	SIG_DFL (regardless of what it was set to before).
1230		1529
		1530	If possible and supported, libev will install its handlers with
		1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1532	interrupted. If you have a problem with system calls getting interrupted by
		1533	signals you can block all signals in an C<ev_check> watcher and unblock
		1534	them in an C<ev_prepare> watcher.
		1535
		1536	=head3 Watcher-Specific Functions and Data Members
		1537
1231	=over 4	1538	=over 4
1232		1539
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1540	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1541
1235	=item ev_signal_set (ev_signal *, int signum)	1542	=item ev_signal_set (ev_signal *, int signum)
…		…
1241		1548
1242	The signal the watcher watches out for.	1549	The signal the watcher watches out for.
1243		1550
1244	=back	1551	=back
1245		1552
		1553	=head3 Examples
		1554
		1555	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1556
		1557	static void
		1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1559	{
		1560	ev_unloop (loop, EVUNLOOP_ALL);
		1561	}
		1562
		1563	struct ev_signal signal_watcher;
		1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1565	ev_signal_start (loop, &sigint_cb);
		1566
1246		1567
1247	=head2 C<ev_child> - watch out for process status changes	1568	=head2 C<ev_child> - watch out for process status changes
1248		1569
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1570	Child watchers trigger when your process receives a SIGCHLD in response to
1250	some child status changes (most typically when a child of yours dies).	1571	some child status changes (most typically when a child of yours dies). It
		1572	is permissible to install a child watcher I<after> the child has been
		1573	forked (which implies it might have already exited), as long as the event
		1574	loop isn't entered (or is continued from a watcher).
		1575
		1576	Only the default event loop is capable of handling signals, and therefore
		1577	you can only register child watchers in the default event loop.
		1578
		1579	=head3 Process Interaction
		1580
		1581	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1582	initialised. This is necessary to guarantee proper behaviour even if
		1583	the first child watcher is started after the child exits. The occurrence
		1584	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1585	synchronously as part of the event loop processing. Libev always reaps all
		1586	children, even ones not watched.
		1587
		1588	=head3 Overriding the Built-In Processing
		1589
		1590	Libev offers no special support for overriding the built-in child
		1591	processing, but if your application collides with libev's default child
		1592	handler, you can override it easily by installing your own handler for
		1593	C<SIGCHLD> after initialising the default loop, and making sure the
		1594	default loop never gets destroyed. You are encouraged, however, to use an
		1595	event-based approach to child reaping and thus use libev's support for
		1596	that, so other libev users can use C<ev_child> watchers freely.
		1597
		1598	=head3 Stopping the Child Watcher
		1599
		1600	Currently, the child watcher never gets stopped, even when the
		1601	child terminates, so normally one needs to stop the watcher in the
		1602	callback. Future versions of libev might stop the watcher automatically
		1603	when a child exit is detected.
		1604
		1605	=head3 Watcher-Specific Functions and Data Members
1251		1606
1252	=over 4	1607	=over 4
1253		1608
1254	=item ev_child_init (ev_child *, callback, int pid)	1609	=item ev_child_init (ev_child *, callback, int pid, int trace)
1255		1610
1256	=item ev_child_set (ev_child *, int pid)	1611	=item ev_child_set (ev_child *, int pid, int trace)
1257		1612
1258	Configures the watcher to wait for status changes of process C<pid> (or	1613	Configures the watcher to wait for status changes of process C<pid> (or
1259	I<any> process if C<pid> is specified as C<0>). The callback can look	1614	I<any> process if C<pid> is specified as C<0>). The callback can look
1260	at the C<rstatus> member of the C<ev_child> watcher structure to see	1615	at the C<rstatus> member of the C<ev_child> watcher structure to see
1261	the status word (use the macros from C<sys/wait.h> and see your systems	1616	the status word (use the macros from C<sys/wait.h> and see your systems
1262	C<waitpid> documentation). The C<rpid> member contains the pid of the	1617	C<waitpid> documentation). The C<rpid> member contains the pid of the
1263	process causing the status change.	1618	process causing the status change. C<trace> must be either C<0> (only
		1619	activate the watcher when the process terminates) or C<1> (additionally
		1620	activate the watcher when the process is stopped or continued).
1264		1621
1265	=item int pid [read-only]	1622	=item int pid [read-only]
1266		1623
1267	The process id this watcher watches out for, or C<0>, meaning any process id.	1624	The process id this watcher watches out for, or C<0>, meaning any process id.
1268		1625
…		…
1275	The process exit/trace status caused by C<rpid> (see your systems	1632	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1633	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1634
1278	=back	1635	=back
1279		1636
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1637	=head3 Examples
1281		1638
		1639	Example: C<fork()> a new process and install a child handler to wait for
		1640	its completion.
		1641
		1642	ev_child cw;
		1643
1282	static void	1644	static void
1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1645	child_cb (EV_P_ struct ev_child *w, int revents)
1284	{	1646	{
1285	ev_unloop (loop, EVUNLOOP_ALL);	1647	ev_child_stop (EV_A_ w);
		1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1286	}	1649	}
1287		1650
1288	struct ev_signal signal_watcher;	1651	pid_t pid = fork ();
1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1652
1290	ev_signal_start (loop, &sigint_cb);	1653	if (pid < 0)
		1654	// error
		1655	else if (pid == 0)
		1656	{
		1657	// the forked child executes here
		1658	exit (1);
		1659	}
		1660	else
		1661	{
		1662	ev_child_init (&cw, child_cb, pid, 0);
		1663	ev_child_start (EV_DEFAULT_ &cw);
		1664	}
1291		1665
1292		1666
1293	=head2 C<ev_stat> - did the file attributes just change?	1667	=head2 C<ev_stat> - did the file attributes just change?
1294		1668
1295	This watches a filesystem path for attribute changes. That is, it calls	1669	This watches a file system path for attribute changes. That is, it calls
1296	C<stat> regularly (or when the OS says it changed) and sees if it changed	1670	C<stat> regularly (or when the OS says it changed) and sees if it changed
1297	compared to the last time, invoking the callback if it did.	1671	compared to the last time, invoking the callback if it did.
1298		1672
1299	The path does not need to exist: changing from "path exists" to "path does	1673	The path does not need to exist: changing from "path exists" to "path does
1300	not exist" is a status change like any other. The condition "path does	1674	not exist" is a status change like any other. The condition "path does
…		…
1318	as even with OS-supported change notifications, this can be	1692	as even with OS-supported change notifications, this can be
1319	resource-intensive.	1693	resource-intensive.
1320		1694
1321	At the time of this writing, only the Linux inotify interface is	1695	At the time of this writing, only the Linux inotify interface is
1322	implemented (implementing kqueue support is left as an exercise for the	1696	implemented (implementing kqueue support is left as an exercise for the
		1697	reader, note, however, that the author sees no way of implementing ev_stat
1323	reader). Inotify will be used to give hints only and should not change the	1698	semantics with kqueue). Inotify will be used to give hints only and should
1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1699	not change the semantics of C<ev_stat> watchers, which means that libev
1325	to fall back to regular polling again even with inotify, but changes are	1700	sometimes needs to fall back to regular polling again even with inotify,
1326	usually detected immediately, and if the file exists there will be no	1701	but changes are usually detected immediately, and if the file exists there
1327	polling.	1702	will be no polling.
		1703
		1704	=head3 ABI Issues (Largefile Support)
		1705
		1706	Libev by default (unless the user overrides this) uses the default
		1707	compilation environment, which means that on systems with large file
		1708	support disabled by default, you get the 32 bit version of the stat
		1709	structure. When using the library from programs that change the ABI to
		1710	use 64 bit file offsets the programs will fail. In that case you have to
		1711	compile libev with the same flags to get binary compatibility. This is
		1712	obviously the case with any flags that change the ABI, but the problem is
		1713	most noticeably disabled with ev_stat and large file support.
		1714
		1715	The solution for this is to lobby your distribution maker to make large
		1716	file interfaces available by default (as e.g. FreeBSD does) and not
		1717	optional. Libev cannot simply switch on large file support because it has
		1718	to exchange stat structures with application programs compiled using the
		1719	default compilation environment.
		1720
		1721	=head3 Inotify
		1722
		1723	When C<inotify (7)> support has been compiled into libev (generally only
		1724	available on Linux) and present at runtime, it will be used to speed up
		1725	change detection where possible. The inotify descriptor will be created lazily
		1726	when the first C<ev_stat> watcher is being started.
		1727
		1728	Inotify presence does not change the semantics of C<ev_stat> watchers
		1729	except that changes might be detected earlier, and in some cases, to avoid
		1730	making regular C<stat> calls. Even in the presence of inotify support
		1731	there are many cases where libev has to resort to regular C<stat> polling.
		1732
		1733	(There is no support for kqueue, as apparently it cannot be used to
		1734	implement this functionality, due to the requirement of having a file
		1735	descriptor open on the object at all times).
		1736
		1737	=head3 The special problem of stat time resolution
		1738
		1739	The C<stat ()> system call only supports full-second resolution portably, and
		1740	even on systems where the resolution is higher, many file systems still
		1741	only support whole seconds.
		1742
		1743	That means that, if the time is the only thing that changes, you can
		1744	easily miss updates: on the first update, C<ev_stat> detects a change and
		1745	calls your callback, which does something. When there is another update
		1746	within the same second, C<ev_stat> will be unable to detect it as the stat
		1747	data does not change.
		1748
		1749	The solution to this is to delay acting on a change for slightly more
		1750	than a second (or till slightly after the next full second boundary), using
		1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1752	ev_timer_again (loop, w)>).
		1753
		1754	The C<.02> offset is added to work around small timing inconsistencies
		1755	of some operating systems (where the second counter of the current time
		1756	might be be delayed. One such system is the Linux kernel, where a call to
		1757	C<gettimeofday> might return a timestamp with a full second later than
		1758	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1759	update file times then there will be a small window where the kernel uses
		1760	the previous second to update file times but libev might already execute
		1761	the timer callback).
		1762
		1763	=head3 Watcher-Specific Functions and Data Members
1328		1764
1329	=over 4	1765	=over 4
1330		1766
1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1767	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1332		1768
…		…
1336	C<path>. The C<interval> is a hint on how quickly a change is expected to	1772	C<path>. The C<interval> is a hint on how quickly a change is expected to
1337	be detected and should normally be specified as C<0> to let libev choose	1773	be detected and should normally be specified as C<0> to let libev choose
1338	a suitable value. The memory pointed to by C<path> must point to the same	1774	a suitable value. The memory pointed to by C<path> must point to the same
1339	path for as long as the watcher is active.	1775	path for as long as the watcher is active.
1340		1776
1341	The callback will be receive C<EV_STAT> when a change was detected,	1777	The callback will receive C<EV_STAT> when a change was detected, relative
1342	relative to the attributes at the time the watcher was started (or the	1778	to the attributes at the time the watcher was started (or the last change
1343	last change was detected).	1779	was detected).
1344		1780
1345	=item ev_stat_stat (ev_stat *)	1781	=item ev_stat_stat (loop, ev_stat *)
1346		1782
1347	Updates the stat buffer immediately with new values. If you change the	1783	Updates the stat buffer immediately with new values. If you change the
1348	watched path in your callback, you could call this fucntion to avoid	1784	watched path in your callback, you could call this function to avoid
1349	detecting this change (while introducing a race condition). Can also be	1785	detecting this change (while introducing a race condition if you are not
1350	useful simply to find out the new values.	1786	the only one changing the path). Can also be useful simply to find out the
		1787	new values.
1351		1788
1352	=item ev_statdata attr [read-only]	1789	=item ev_statdata attr [read-only]
1353		1790
1354	The most-recently detected attributes of the file. Although the type is of	1791	The most-recently detected attributes of the file. Although the type is
1355	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1792	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1356	suitable for your system. If the C<st_nlink> member is C<0>, then there	1793	suitable for your system, but you can only rely on the POSIX-standardised
		1794	members to be present. If the C<st_nlink> member is C<0>, then there was
1357	was some error while C<stat>ing the file.	1795	some error while C<stat>ing the file.
1358		1796
1359	=item ev_statdata prev [read-only]	1797	=item ev_statdata prev [read-only]
1360		1798
1361	The previous attributes of the file. The callback gets invoked whenever	1799	The previous attributes of the file. The callback gets invoked whenever
1362	C<prev> != C<attr>.	1800	C<prev> != C<attr>, or, more precisely, one or more of these members
		1801	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1802	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1363		1803
1364	=item ev_tstamp interval [read-only]	1804	=item ev_tstamp interval [read-only]
1365		1805
1366	The specified interval.	1806	The specified interval.
1367		1807
1368	=item const char *path [read-only]	1808	=item const char *path [read-only]
1369		1809
1370	The filesystem path that is being watched.	1810	The file system path that is being watched.
1371		1811
1372	=back	1812	=back
1373		1813
		1814	=head3 Examples
		1815
1374	Example: Watch C</etc/passwd> for attribute changes.	1816	Example: Watch C</etc/passwd> for attribute changes.
1375		1817
1376	static void	1818	static void
1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1819	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1378	{	1820	{
1379	/* /etc/passwd changed in some way */	1821	/* /etc/passwd changed in some way */
1380	if (w->attr.st_nlink)	1822	if (w->attr.st_nlink)
1381	{	1823	{
1382	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1824	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1383	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1825	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1384	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1826	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1385	}	1827	}
1386	else	1828	else
1387	/* you shalt not abuse printf for puts */	1829	/* you shalt not abuse printf for puts */
1388	puts ("wow, /etc/passwd is not there, expect problems. "	1830	puts ("wow, /etc/passwd is not there, expect problems. "
1389	"if this is windows, they already arrived\n");	1831	"if this is windows, they already arrived\n");
1390	}	1832	}
1391		1833
1392	...	1834	...
1393	ev_stat passwd;	1835	ev_stat passwd;
1394		1836
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1837	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	1838	ev_stat_start (loop, &passwd);
		1839
		1840	Example: Like above, but additionally use a one-second delay so we do not
		1841	miss updates (however, frequent updates will delay processing, too, so
		1842	one might do the work both on C<ev_stat> callback invocation I<and> on
		1843	C<ev_timer> callback invocation).
		1844
		1845	static ev_stat passwd;
		1846	static ev_timer timer;
		1847
		1848	static void
		1849	timer_cb (EV_P_ ev_timer *w, int revents)
		1850	{
		1851	ev_timer_stop (EV_A_ w);
		1852
		1853	/* now it's one second after the most recent passwd change */
		1854	}
		1855
		1856	static void
		1857	stat_cb (EV_P_ ev_stat *w, int revents)
		1858	{
		1859	/* reset the one-second timer */
		1860	ev_timer_again (EV_A_ &timer);
		1861	}
		1862
		1863	...
		1864	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1865	ev_stat_start (loop, &passwd);
		1866	ev_timer_init (&timer, timer_cb, 0., 1.02);
1397		1867
1398		1868
1399	=head2 C<ev_idle> - when you've got nothing better to do...	1869	=head2 C<ev_idle> - when you've got nothing better to do...
1400		1870
1401	Idle watchers trigger events when no other events of the same or higher	1871	Idle watchers trigger events when no other events of the same or higher
…		…
1415	Apart from keeping your process non-blocking (which is a useful	1885	Apart from keeping your process non-blocking (which is a useful
1416	effect on its own sometimes), idle watchers are a good place to do	1886	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	1887	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	1888	event loop has handled all outstanding events.
1419		1889
		1890	=head3 Watcher-Specific Functions and Data Members
		1891
1420	=over 4	1892	=over 4
1421		1893
1422	=item ev_idle_init (ev_signal *, callback)	1894	=item ev_idle_init (ev_signal *, callback)
1423		1895
1424	Initialises and configures the idle watcher - it has no parameters of any	1896	Initialises and configures the idle watcher - it has no parameters of any
1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	1898	believe me.
1427		1899
1428	=back	1900	=back
1429		1901
		1902	=head3 Examples
		1903
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	1905	callback, free it. Also, use no error checking, as usual.
1432		1906
1433	static void	1907	static void
1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1435	{	1909	{
1436	free (w);	1910	free (w);
1437	// now do something you wanted to do when the program has	1911	// now do something you wanted to do when the program has
1438	// no longer asnything immediate to do.	1912	// no longer anything immediate to do.
1439	}	1913	}
1440		1914
1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1442	ev_idle_init (idle_watcher, idle_cb);	1916	ev_idle_init (idle_watcher, idle_cb);
1443	ev_idle_start (loop, idle_cb);	1917	ev_idle_start (loop, idle_cb);
1444		1918
1445		1919
1446	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1447		1921
1448	Prepare and check watchers are usually (but not always) used in tandem:	1922	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1467		1941
1468	This is done by examining in each prepare call which file descriptors need	1942	This is done by examining in each prepare call which file descriptors need
1469	to be watched by the other library, registering C<ev_io> watchers for	1943	to be watched by the other library, registering C<ev_io> watchers for
1470	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1471	provide just this functionality). Then, in the check watcher you check for	1945	provide just this functionality). Then, in the check watcher you check for
1472	any events that occured (by checking the pending status of all watchers	1946	any events that occurred (by checking the pending status of all watchers
1473	and stopping them) and call back into the library. The I/O and timer	1947	and stopping them) and call back into the library. The I/O and timer
1474	callbacks will never actually be called (but must be valid nevertheless,	1948	callbacks will never actually be called (but must be valid nevertheless,
1475	because you never know, you know?).	1949	because you never know, you know?).
1476		1950
1477	As another example, the Perl Coro module uses these hooks to integrate	1951	As another example, the Perl Coro module uses these hooks to integrate
…		…
1481	with priority higher than or equal to the event loop and one coroutine	1955	with priority higher than or equal to the event loop and one coroutine
1482	of lower priority, but only once, using idle watchers to keep the event	1956	of lower priority, but only once, using idle watchers to keep the event
1483	loop from blocking if lower-priority coroutines are active, thus mapping	1957	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	1958	low-priority coroutines to idle/background tasks).
1485		1959
		1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1961	priority, to ensure that they are being run before any other watchers
		1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1963	too) should not activate ("feed") events into libev. While libev fully
		1964	supports this, they might get executed before other C<ev_check> watchers
		1965	did their job. As C<ev_check> watchers are often used to embed other
		1966	(non-libev) event loops those other event loops might be in an unusable
		1967	state until their C<ev_check> watcher ran (always remind yourself to
		1968	coexist peacefully with others).
		1969
		1970	=head3 Watcher-Specific Functions and Data Members
		1971
1486	=over 4	1972	=over 4
1487		1973
1488	=item ev_prepare_init (ev_prepare *, callback)	1974	=item ev_prepare_init (ev_prepare *, callback)
1489		1975
1490	=item ev_check_init (ev_check *, callback)	1976	=item ev_check_init (ev_check *, callback)
…		…
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1494	macros, but using them is utterly, utterly and completely pointless.	1980	macros, but using them is utterly, utterly and completely pointless.
1495		1981
1496	=back	1982	=back
1497		1983
1498	Example: To include a library such as adns, you would add IO watchers	1984	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	1985
		1986	There are a number of principal ways to embed other event loops or modules
		1987	into libev. Here are some ideas on how to include libadns into libev
		1988	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1989	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1990	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1991	Glib event loop).
		1992
		1993	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1500	in a check watcher, destroy them and call into libadns. What follows is	1994	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	1995	is pseudo-code only of course. This requires you to either use a low
		1996	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1997	the callbacks for the IO/timeout watchers might not have been called yet.
1502		1998
1503	static ev_io iow [nfd];	1999	static ev_io iow [nfd];
1504	static ev_timer tw;	2000	static ev_timer tw;
1505		2001
1506	static void	2002	static void
1507	io_cb (ev_loop *loop, ev_io *w, int revents)	2003	io_cb (ev_loop *loop, ev_io *w, int revents)
1508	{	2004	{
1509	// set the relevant poll flags
1510	// could also call adns_processreadable etc. here
1511	struct pollfd *fd = (struct pollfd *)w->data;
1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1514	}	2005	}
1515		2006
1516	// create io watchers for each fd and a timer before blocking	2007	// create io watchers for each fd and a timer before blocking
1517	static void	2008	static void
1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1519	{	2010	{
1520	int timeout = 3600000;	2011	int timeout = 3600000;
1521	struct pollfd fds [nfd];	2012	struct pollfd fds [nfd];
1522	// actual code will need to loop here and realloc etc.	2013	// actual code will need to loop here and realloc etc.
1523	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1524		2015
1525	/* the callback is illegal, but won't be called as we stop during check */	2016	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	2017	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	2018	ev_timer_start (loop, &tw);
1528		2019
1529	// create on ev_io per pollfd	2020	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	2021	for (int i = 0; i < nfd; ++i)
1531	{	2022	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	2023	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	2024	((fds [i].events & POLLIN ? EV_READ : 0)
1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2025	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		2026
1536	fds [i].revents = 0;	2027	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	2028	ev_io_start (loop, iow + i);
1539	}	2029	}
1540	}	2030	}
1541		2031
1542	// stop all watchers after blocking	2032	// stop all watchers after blocking
1543	static void	2033	static void
1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1545	{	2035	{
1546	ev_timer_stop (loop, &tw);	2036	ev_timer_stop (loop, &tw);
1547		2037
1548	for (int i = 0; i < nfd; ++i)	2038	for (int i = 0; i < nfd; ++i)
		2039	{
		2040	// set the relevant poll flags
		2041	// could also call adns_processreadable etc. here
		2042	struct pollfd *fd = fds + i;
		2043	int revents = ev_clear_pending (iow + i);
		2044	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2045	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2046
		2047	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	2048	ev_io_stop (loop, iow + i);
		2049	}
1550		2050
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2051	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1552	}	2052	}
		2053
		2054	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2055	in the prepare watcher and would dispose of the check watcher.
		2056
		2057	Method 3: If the module to be embedded supports explicit event
		2058	notification (libadns does), you can also make use of the actual watcher
		2059	callbacks, and only destroy/create the watchers in the prepare watcher.
		2060
		2061	static void
		2062	timer_cb (EV_P_ ev_timer *w, int revents)
		2063	{
		2064	adns_state ads = (adns_state)w->data;
		2065	update_now (EV_A);
		2066
		2067	adns_processtimeouts (ads, &tv_now);
		2068	}
		2069
		2070	static void
		2071	io_cb (EV_P_ ev_io *w, int revents)
		2072	{
		2073	adns_state ads = (adns_state)w->data;
		2074	update_now (EV_A);
		2075
		2076	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2077	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2078	}
		2079
		2080	// do not ever call adns_afterpoll
		2081
		2082	Method 4: Do not use a prepare or check watcher because the module you
		2083	want to embed is too inflexible to support it. Instead, you can override
		2084	their poll function. The drawback with this solution is that the main
		2085	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2086	this.
		2087
		2088	static gint
		2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2090	{
		2091	int got_events = 0;
		2092
		2093	for (n = 0; n < nfds; ++n)
		2094	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2095
		2096	if (timeout >= 0)
		2097	// create/start timer
		2098
		2099	// poll
		2100	ev_loop (EV_A_ 0);
		2101
		2102	// stop timer again
		2103	if (timeout >= 0)
		2104	ev_timer_stop (EV_A_ &to);
		2105
		2106	// stop io watchers again - their callbacks should have set
		2107	for (n = 0; n < nfds; ++n)
		2108	ev_io_stop (EV_A_ iow [n]);
		2109
		2110	return got_events;
		2111	}
1553		2112
1554		2113
1555	=head2 C<ev_embed> - when one backend isn't enough...	2114	=head2 C<ev_embed> - when one backend isn't enough...
1556		2115
1557	This is a rather advanced watcher type that lets you embed one event loop	2116	This is a rather advanced watcher type that lets you embed one event loop
…		…
1599	portable one.	2158	portable one.
1600		2159
1601	So when you want to use this feature you will always have to be prepared	2160	So when you want to use this feature you will always have to be prepared
1602	that you cannot get an embeddable loop. The recommended way to get around	2161	that you cannot get an embeddable loop. The recommended way to get around
1603	this is to have a separate variables for your embeddable loop, try to	2162	this is to have a separate variables for your embeddable loop, try to
1604	create it, and if that fails, use the normal loop for everything:	2163	create it, and if that fails, use the normal loop for everything.
1605		2164
1606	struct ev_loop *loop_hi = ev_default_init (0);	2165	=head3 Watcher-Specific Functions and Data Members
1607	struct ev_loop *loop_lo = 0;
1608	struct ev_embed embed;
1609
1610	// see if there is a chance of getting one that works
1611	// (remember that a flags value of 0 means autodetection)
1612	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1613	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1614	: 0;
1615
1616	// if we got one, then embed it, otherwise default to loop_hi
1617	if (loop_lo)
1618	{
1619	ev_embed_init (&embed, 0, loop_lo);
1620	ev_embed_start (loop_hi, &embed);
1621	}
1622	else
1623	loop_lo = loop_hi;
1624		2166
1625	=over 4	2167	=over 4
1626		2168
1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2169	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1628		2170
…		…
1630		2172
1631	Configures the watcher to embed the given loop, which must be	2173	Configures the watcher to embed the given loop, which must be
1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2174	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1633	invoked automatically, otherwise it is the responsibility of the callback	2175	invoked automatically, otherwise it is the responsibility of the callback
1634	to invoke it (it will continue to be called until the sweep has been done,	2176	to invoke it (it will continue to be called until the sweep has been done,
1635	if you do not want thta, you need to temporarily stop the embed watcher).	2177	if you do not want that, you need to temporarily stop the embed watcher).
1636		2178
1637	=item ev_embed_sweep (loop, ev_embed *)	2179	=item ev_embed_sweep (loop, ev_embed *)
1638		2180
1639	Make a single, non-blocking sweep over the embedded loop. This works	2181	Make a single, non-blocking sweep over the embedded loop. This works
1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2182	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.	2183	appropriate way for embedded loops.
1642		2184
1643	=item struct ev_loop *loop [read-only]	2185	=item struct ev_loop *other [read-only]
1644		2186
1645	The embedded event loop.	2187	The embedded event loop.
1646		2188
1647	=back	2189	=back
		2190
		2191	=head3 Examples
		2192
		2193	Example: Try to get an embeddable event loop and embed it into the default
		2194	event loop. If that is not possible, use the default loop. The default
		2195	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2197	used).
		2198
		2199	struct ev_loop *loop_hi = ev_default_init (0);
		2200	struct ev_loop *loop_lo = 0;
		2201	struct ev_embed embed;
		2202
		2203	// see if there is a chance of getting one that works
		2204	// (remember that a flags value of 0 means autodetection)
		2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2207	: 0;
		2208
		2209	// if we got one, then embed it, otherwise default to loop_hi
		2210	if (loop_lo)
		2211	{
		2212	ev_embed_init (&embed, 0, loop_lo);
		2213	ev_embed_start (loop_hi, &embed);
		2214	}
		2215	else
		2216	loop_lo = loop_hi;
		2217
		2218	Example: Check if kqueue is available but not recommended and create
		2219	a kqueue backend for use with sockets (which usually work with any
		2220	kqueue implementation). Store the kqueue/socket-only event loop in
		2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2222
		2223	struct ev_loop *loop = ev_default_init (0);
		2224	struct ev_loop *loop_socket = 0;
		2225	struct ev_embed embed;
		2226
		2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2229	{
		2230	ev_embed_init (&embed, 0, loop_socket);
		2231	ev_embed_start (loop, &embed);
		2232	}
		2233
		2234	if (!loop_socket)
		2235	loop_socket = loop;
		2236
		2237	// now use loop_socket for all sockets, and loop for everything else
1648		2238
1649		2239
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2240	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2241
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2242	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1655	event loop blocks next and before C<ev_check> watchers are being called,	2245	event loop blocks next and before C<ev_check> watchers are being called,
1656	and only in the child after the fork. If whoever good citizen calling	2246	and only in the child after the fork. If whoever good citizen calling
1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2247	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2248	handlers will be invoked, too, of course.
1659		2249
		2250	=head3 Watcher-Specific Functions and Data Members
		2251
1660	=over 4	2252	=over 4
1661		2253
1662	=item ev_fork_init (ev_signal *, callback)	2254	=item ev_fork_init (ev_signal *, callback)
1663		2255
1664	Initialises and configures the fork watcher - it has no parameters of any	2256	Initialises and configures the fork watcher - it has no parameters of any
1665	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2257	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1666	believe me.	2258	believe me.
		2259
		2260	=back
		2261
		2262
		2263	=head2 C<ev_async> - how to wake up another event loop
		2264
		2265	In general, you cannot use an C<ev_loop> from multiple threads or other
		2266	asynchronous sources such as signal handlers (as opposed to multiple event
		2267	loops - those are of course safe to use in different threads).
		2268
		2269	Sometimes, however, you need to wake up another event loop you do not
		2270	control, for example because it belongs to another thread. This is what
		2271	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2272	can signal it by calling C<ev_async_send>, which is thread- and signal
		2273	safe.
		2274
		2275	This functionality is very similar to C<ev_signal> watchers, as signals,
		2276	too, are asynchronous in nature, and signals, too, will be compressed
		2277	(i.e. the number of callback invocations may be less than the number of
		2278	C<ev_async_sent> calls).
		2279
		2280	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2281	just the default loop.
		2282
		2283	=head3 Queueing
		2284
		2285	C<ev_async> does not support queueing of data in any way. The reason
		2286	is that the author does not know of a simple (or any) algorithm for a
		2287	multiple-writer-single-reader queue that works in all cases and doesn't
		2288	need elaborate support such as pthreads.
		2289
		2290	That means that if you want to queue data, you have to provide your own
		2291	queue. But at least I can tell you would implement locking around your
		2292	queue:
		2293
		2294	=over 4
		2295
		2296	=item queueing from a signal handler context
		2297
		2298	To implement race-free queueing, you simply add to the queue in the signal
		2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2300	some fictitious SIGUSR1 handler:
		2301
		2302	static ev_async mysig;
		2303
		2304	static void
		2305	sigusr1_handler (void)
		2306	{
		2307	sometype data;
		2308
		2309	// no locking etc.
		2310	queue_put (data);
		2311	ev_async_send (EV_DEFAULT_ &mysig);
		2312	}
		2313
		2314	static void
		2315	mysig_cb (EV_P_ ev_async *w, int revents)
		2316	{
		2317	sometype data;
		2318	sigset_t block, prev;
		2319
		2320	sigemptyset (&block);
		2321	sigaddset (&block, SIGUSR1);
		2322	sigprocmask (SIG_BLOCK, &block, &prev);
		2323
		2324	while (queue_get (&data))
		2325	process (data);
		2326
		2327	if (sigismember (&prev, SIGUSR1)
		2328	sigprocmask (SIG_UNBLOCK, &block, 0);
		2329	}
		2330
		2331	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2332	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2333	either...).
		2334
		2335	=item queueing from a thread context
		2336
		2337	The strategy for threads is different, as you cannot (easily) block
		2338	threads but you can easily preempt them, so to queue safely you need to
		2339	employ a traditional mutex lock, such as in this pthread example:
		2340
		2341	static ev_async mysig;
		2342	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2343
		2344	static void
		2345	otherthread (void)
		2346	{
		2347	// only need to lock the actual queueing operation
		2348	pthread_mutex_lock (&mymutex);
		2349	queue_put (data);
		2350	pthread_mutex_unlock (&mymutex);
		2351
		2352	ev_async_send (EV_DEFAULT_ &mysig);
		2353	}
		2354
		2355	static void
		2356	mysig_cb (EV_P_ ev_async *w, int revents)
		2357	{
		2358	pthread_mutex_lock (&mymutex);
		2359
		2360	while (queue_get (&data))
		2361	process (data);
		2362
		2363	pthread_mutex_unlock (&mymutex);
		2364	}
		2365
		2366	=back
		2367
		2368
		2369	=head3 Watcher-Specific Functions and Data Members
		2370
		2371	=over 4
		2372
		2373	=item ev_async_init (ev_async *, callback)
		2374
		2375	Initialises and configures the async watcher - it has no parameters of any
		2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2377	believe me.
		2378
		2379	=item ev_async_send (loop, ev_async *)
		2380
		2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2383	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2385	section below on what exactly this means).
		2386
		2387	This call incurs the overhead of a system call only once per loop iteration,
		2388	so while the overhead might be noticeable, it doesn't apply to repeated
		2389	calls to C<ev_async_send>.
		2390
		2391	=item bool = ev_async_pending (ev_async *)
		2392
		2393	Returns a non-zero value when C<ev_async_send> has been called on the
		2394	watcher but the event has not yet been processed (or even noted) by the
		2395	event loop.
		2396
		2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2398	the loop iterates next and checks for the watcher to have become active,
		2399	it will reset the flag again. C<ev_async_pending> can be used to very
		2400	quickly check whether invoking the loop might be a good idea.
		2401
		2402	Not that this does I<not> check whether the watcher itself is pending, only
		2403	whether it has been requested to make this watcher pending.
1667		2404
1668	=back	2405	=back
1669		2406
1670		2407
1671	=head1 OTHER FUNCTIONS	2408	=head1 OTHER FUNCTIONS
…		…
1682	or timeout without having to allocate/configure/start/stop/free one or	2419	or timeout without having to allocate/configure/start/stop/free one or
1683	more watchers yourself.	2420	more watchers yourself.
1684		2421
1685	If C<fd> is less than 0, then no I/O watcher will be started and events	2422	If C<fd> is less than 0, then no I/O watcher will be started and events
1686	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1687	C<events> set will be craeted and started.	2424	C<events> set will be created and started.
1688		2425
1689	If C<timeout> is less than 0, then no timeout watcher will be	2426	If C<timeout> is less than 0, then no timeout watcher will be
1690	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1691	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1692	dubious value.	2429	dubious value.
…		…
1694	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1695	passed an C<revents> set like normal event callbacks (a combination of	2432	passed an C<revents> set like normal event callbacks (a combination of
1696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1697	value passed to C<ev_once>:	2434	value passed to C<ev_once>:
1698		2435
1699	static void stdin_ready (int revents, void *arg)	2436	static void stdin_ready (int revents, void *arg)
1700	{	2437	{
1701	if (revents & EV_TIMEOUT)	2438	if (revents & EV_TIMEOUT)
1702	/* doh, nothing entered */;	2439	/* doh, nothing entered */;
1703	else if (revents & EV_READ)	2440	else if (revents & EV_READ)
1704	/* stdin might have data for us, joy! */;	2441	/* stdin might have data for us, joy! */;
1705	}	2442	}
1706		2443
1707	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1708		2445
1709	=item ev_feed_event (ev_loop *, watcher *, int revents)	2446	=item ev_feed_event (ev_loop *, watcher *, int revents)
1710		2447
1711	Feeds the given event set into the event loop, as if the specified event	2448	Feeds the given event set into the event loop, as if the specified event
1712	had happened for the specified watcher (which must be a pointer to an	2449	had happened for the specified watcher (which must be a pointer to an
…		…
1717	Feed an event on the given fd, as if a file descriptor backend detected	2454	Feed an event on the given fd, as if a file descriptor backend detected
1718	the given events it.	2455	the given events it.
1719		2456
1720	=item ev_feed_signal_event (ev_loop *loop, int signum)	2457	=item ev_feed_signal_event (ev_loop *loop, int signum)
1721		2458
1722	Feed an event as if the given signal occured (C<loop> must be the default	2459	Feed an event as if the given signal occurred (C<loop> must be the default
1723	loop!).	2460	loop!).
1724		2461
1725	=back	2462	=back
1726		2463
1727		2464
…		…
1743		2480
1744	=item * Priorities are not currently supported. Initialising priorities	2481	=item * Priorities are not currently supported. Initialising priorities
1745	will fail and all watchers will have the same priority, even though there	2482	will fail and all watchers will have the same priority, even though there
1746	is an ev_pri field.	2483	is an ev_pri field.
1747		2484
		2485	=item * In libevent, the last base created gets the signals, in libev, the
		2486	first base created (== the default loop) gets the signals.
		2487
1748	=item * Other members are not supported.	2488	=item * Other members are not supported.
1749		2489
1750	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2490	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1751	to use the libev header file and library.	2491	to use the libev header file and library.
1752		2492
1753	=back	2493	=back
1754		2494
1755	=head1 C++ SUPPORT	2495	=head1 C++ SUPPORT
1756		2496
1757	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2497	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1758	you to use some convinience methods to start/stop watchers and also change	2498	you to use some convenience methods to start/stop watchers and also change
1759	the callback model to a model using method callbacks on objects.	2499	the callback model to a model using method callbacks on objects.
1760		2500
1761	To use it,	2501	To use it,
1762		2502
1763	#include <ev++.h>	2503	#include <ev++.h>
1764		2504
1765	This automatically includes F<ev.h> and puts all of its definitions (many	2505	This automatically includes F<ev.h> and puts all of its definitions (many
1766	of them macros) into the global namespace. All C++ specific things are	2506	of them macros) into the global namespace. All C++ specific things are
1767	put into the C<ev> namespace. It should support all the same embedding	2507	put into the C<ev> namespace. It should support all the same embedding
1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2508	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1835	your compiler is good :), then the method will be fully inlined into the	2575	your compiler is good :), then the method will be fully inlined into the
1836	thunking function, making it as fast as a direct C callback.	2576	thunking function, making it as fast as a direct C callback.
1837		2577
1838	Example: simple class declaration and watcher initialisation	2578	Example: simple class declaration and watcher initialisation
1839		2579
1840	struct myclass	2580	struct myclass
1841	{	2581	{
1842	void io_cb (ev::io &w, int revents) { }	2582	void io_cb (ev::io &w, int revents) { }
1843	}	2583	}
1844		2584
1845	myclass obj;	2585	myclass obj;
1846	ev::io iow;	2586	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2587	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2588
1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2589	=item w->set<function> (void *data = 0)
1850		2590
1851	Also sets a callback, but uses a static method or plain function as	2591	Also sets a callback, but uses a static method or plain function as
1852	callback. The optional C<data> argument will be stored in the watcher's	2592	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2593	C<data> member and is free for you to use.
1854		2594
		2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2596
1855	See the method-C<set> above for more details.	2597	See the method-C<set> above for more details.
		2598
		2599	Example:
		2600
		2601	static void io_cb (ev::io &w, int revents) { }
		2602	iow.set <io_cb> ();
1856		2603
1857	=item w->set (struct ev_loop *)	2604	=item w->set (struct ev_loop *)
1858		2605
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2606	Associates a different C<struct ev_loop> with this watcher. You can only
1860	do this when the watcher is inactive (and not pending either).	2607	do this when the watcher is inactive (and not pending either).
1861		2608
1862	=item w->set ([args])	2609	=item w->set ([arguments])
1863		2610
1864	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2611	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1865	called at least once. Unlike the C counterpart, an active watcher gets	2612	called at least once. Unlike the C counterpart, an active watcher gets
1866	automatically stopped and restarted when reconfiguring it with this	2613	automatically stopped and restarted when reconfiguring it with this
1867	method.	2614	method.
1868		2615
1869	=item w->start ()	2616	=item w->start ()
…		…
1873		2620
1874	=item w->stop ()	2621	=item w->stop ()
1875		2622
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2623	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2624
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2625	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2626
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2627	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2628	C<ev_TYPE_again> function.
1882		2629
1883	=item w->sweep () C<ev::embed> only	2630	=item w->sweep () (C<ev::embed> only)
1884		2631
1885	Invokes C<ev_embed_sweep>.	2632	Invokes C<ev_embed_sweep>.
1886		2633
1887	=item w->update () C<ev::stat> only	2634	=item w->update () (C<ev::stat> only)
1888		2635
1889	Invokes C<ev_stat_stat>.	2636	Invokes C<ev_stat_stat>.
1890		2637
1891	=back	2638	=back
1892		2639
1893	=back	2640	=back
1894		2641
1895	Example: Define a class with an IO and idle watcher, start one of them in	2642	Example: Define a class with an IO and idle watcher, start one of them in
1896	the constructor.	2643	the constructor.
1897		2644
1898	class myclass	2645	class myclass
1899	{	2646	{
1900	ev_io io; void io_cb (ev::io &w, int revents);	2647	ev::io io; void io_cb (ev::io &w, int revents);
1901	ev_idle idle void idle_cb (ev::idle &w, int revents);	2648	ev:idle idle void idle_cb (ev::idle &w, int revents);
1902		2649
1903	myclass ();	2650	myclass (int fd)
1904	}	2651	{
1905
1906	myclass::myclass (int fd)
1907	{
1908	io .set <myclass, &myclass::io_cb > (this);	2652	io .set <myclass, &myclass::io_cb > (this);
1909	idle.set <myclass, &myclass::idle_cb> (this);	2653	idle.set <myclass, &myclass::idle_cb> (this);
1910		2654
1911	io.start (fd, ev::READ);	2655	io.start (fd, ev::READ);
		2656	}
1912	}	2657	};
		2658
		2659
		2660	=head1 OTHER LANGUAGE BINDINGS
		2661
		2662	Libev does not offer other language bindings itself, but bindings for a
		2663	number of languages exist in the form of third-party packages. If you know
		2664	any interesting language binding in addition to the ones listed here, drop
		2665	me a note.
		2666
		2667	=over 4
		2668
		2669	=item Perl
		2670
		2671	The EV module implements the full libev API and is actually used to test
		2672	libev. EV is developed together with libev. Apart from the EV core module,
		2673	there are additional modules that implement libev-compatible interfaces
		2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2676
		2677	It can be found and installed via CPAN, its homepage is at
		2678	L<http://software.schmorp.de/pkg/EV>.
		2679
		2680	=item Python
		2681
		2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2683	seems to be quite complete and well-documented. Note, however, that the
		2684	patch they require for libev is outright dangerous as it breaks the ABI
		2685	for everybody else, and therefore, should never be applied in an installed
		2686	libev (if python requires an incompatible ABI then it needs to embed
		2687	libev).
		2688
		2689	=item Ruby
		2690
		2691	Tony Arcieri has written a ruby extension that offers access to a subset
		2692	of the libev API and adds file handle abstractions, asynchronous DNS and
		2693	more on top of it. It can be found via gem servers. Its homepage is at
		2694	L<http://rev.rubyforge.org/>.
		2695
		2696	=item D
		2697
		2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2700
		2701	=back
1913		2702
1914		2703
1915	=head1 MACRO MAGIC	2704	=head1 MACRO MAGIC
1916		2705
1917	Libev can be compiled with a variety of options, the most fundemantal is	2706	Libev can be compiled with a variety of options, the most fundamental
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2707	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2708	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2709
1921	To make it easier to write programs that cope with either variant, the	2710	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2711	following macros are defined:
1923		2712
1924	=over 4	2713	=over 4
…		…
1927		2716
1928	This provides the loop I<argument> for functions, if one is required ("ev	2717	This provides the loop I<argument> for functions, if one is required ("ev
1929	loop argument"). The C<EV_A> form is used when this is the sole argument,	2718	loop argument"). The C<EV_A> form is used when this is the sole argument,
1930	C<EV_A_> is used when other arguments are following. Example:	2719	C<EV_A_> is used when other arguments are following. Example:
1931		2720
1932	ev_unref (EV_A);	2721	ev_unref (EV_A);
1933	ev_timer_add (EV_A_ watcher);	2722	ev_timer_add (EV_A_ watcher);
1934	ev_loop (EV_A_ 0);	2723	ev_loop (EV_A_ 0);
1935		2724
1936	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2725	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1937	which is often provided by the following macro.	2726	which is often provided by the following macro.
1938		2727
1939	=item C<EV_P>, C<EV_P_>	2728	=item C<EV_P>, C<EV_P_>
1940		2729
1941	This provides the loop I<parameter> for functions, if one is required ("ev	2730	This provides the loop I<parameter> for functions, if one is required ("ev
1942	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2731	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1943	C<EV_P_> is used when other parameters are following. Example:	2732	C<EV_P_> is used when other parameters are following. Example:
1944		2733
1945	// this is how ev_unref is being declared	2734	// this is how ev_unref is being declared
1946	static void ev_unref (EV_P);	2735	static void ev_unref (EV_P);
1947		2736
1948	// this is how you can declare your typical callback	2737	// this is how you can declare your typical callback
1949	static void cb (EV_P_ ev_timer *w, int revents)	2738	static void cb (EV_P_ ev_timer *w, int revents)
1950		2739
1951	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2740	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1952	suitable for use with C<EV_A>.	2741	suitable for use with C<EV_A>.
1953		2742
1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2743	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1955		2744
1956	Similar to the other two macros, this gives you the value of the default	2745	Similar to the other two macros, this gives you the value of the default
1957	loop, if multiple loops are supported ("ev loop default").	2746	loop, if multiple loops are supported ("ev loop default").
		2747
		2748	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2749
		2750	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2751	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2752	is undefined when the default loop has not been initialised by a previous
		2753	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2754
		2755	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2756	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1958		2757
1959	=back	2758	=back
1960		2759
1961	Example: Declare and initialise a check watcher, utilising the above	2760	Example: Declare and initialise a check watcher, utilising the above
1962	macros so it will work regardless of whether multiple loops are supported	2761	macros so it will work regardless of whether multiple loops are supported
1963	or not.	2762	or not.
1964		2763
1965	static void	2764	static void
1966	check_cb (EV_P_ ev_timer *w, int revents)	2765	check_cb (EV_P_ ev_timer *w, int revents)
1967	{	2766	{
1968	ev_check_stop (EV_A_ w);	2767	ev_check_stop (EV_A_ w);
1969	}	2768	}
1970		2769
1971	ev_check check;	2770	ev_check check;
1972	ev_check_init (&check, check_cb);	2771	ev_check_init (&check, check_cb);
1973	ev_check_start (EV_DEFAULT_ &check);	2772	ev_check_start (EV_DEFAULT_ &check);
1974	ev_loop (EV_DEFAULT_ 0);	2773	ev_loop (EV_DEFAULT_ 0);
1975		2774
1976	=head1 EMBEDDING	2775	=head1 EMBEDDING
1977		2776
1978	Libev can (and often is) directly embedded into host	2777	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	2778	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2779	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	2780	and rxvt-unicode.
1982		2781
1983	The goal is to enable you to just copy the neecssary files into your	2782	The goal is to enable you to just copy the necessary files into your
1984	source directory without having to change even a single line in them, so	2783	source directory without having to change even a single line in them, so
1985	you can easily upgrade by simply copying (or having a checked-out copy of	2784	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	2785	libev somewhere in your source tree).
1987		2786
1988	=head2 FILESETS	2787	=head2 FILESETS
1989		2788
1990	Depending on what features you need you need to include one or more sets of files	2789	Depending on what features you need you need to include one or more sets of files
1991	in your app.	2790	in your application.
1992		2791
1993	=head3 CORE EVENT LOOP	2792	=head3 CORE EVENT LOOP
1994		2793
1995	To include only the libev core (all the C<ev_*> functions), with manual	2794	To include only the libev core (all the C<ev_*> functions), with manual
1996	configuration (no autoconf):	2795	configuration (no autoconf):
1997		2796
1998	#define EV_STANDALONE 1	2797	#define EV_STANDALONE 1
1999	#include "ev.c"	2798	#include "ev.c"
2000		2799
2001	This will automatically include F<ev.h>, too, and should be done in a	2800	This will automatically include F<ev.h>, too, and should be done in a
2002	single C source file only to provide the function implementations. To use	2801	single C source file only to provide the function implementations. To use
2003	it, do the same for F<ev.h> in all files wishing to use this API (best	2802	it, do the same for F<ev.h> in all files wishing to use this API (best
2004	done by writing a wrapper around F<ev.h> that you can include instead and	2803	done by writing a wrapper around F<ev.h> that you can include instead and
2005	where you can put other configuration options):	2804	where you can put other configuration options):
2006		2805
2007	#define EV_STANDALONE 1	2806	#define EV_STANDALONE 1
2008	#include "ev.h"	2807	#include "ev.h"
2009		2808
2010	Both header files and implementation files can be compiled with a C++	2809	Both header files and implementation files can be compiled with a C++
2011	compiler (at least, thats a stated goal, and breakage will be treated	2810	compiler (at least, thats a stated goal, and breakage will be treated
2012	as a bug).	2811	as a bug).
2013		2812
2014	You need the following files in your source tree, or in a directory	2813	You need the following files in your source tree, or in a directory
2015	in your include path (e.g. in libev/ when using -Ilibev):	2814	in your include path (e.g. in libev/ when using -Ilibev):
2016		2815
2017	ev.h	2816	ev.h
2018	ev.c	2817	ev.c
2019	ev_vars.h	2818	ev_vars.h
2020	ev_wrap.h	2819	ev_wrap.h
2021		2820
2022	ev_win32.c required on win32 platforms only	2821	ev_win32.c required on win32 platforms only
2023		2822
2024	ev_select.c only when select backend is enabled (which is enabled by default)	2823	ev_select.c only when select backend is enabled (which is enabled by default)
2025	ev_poll.c only when poll backend is enabled (disabled by default)	2824	ev_poll.c only when poll backend is enabled (disabled by default)
2026	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2825	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2027	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2826	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2028	ev_port.c only when the solaris port backend is enabled (disabled by default)	2827	ev_port.c only when the solaris port backend is enabled (disabled by default)
2029		2828
2030	F<ev.c> includes the backend files directly when enabled, so you only need	2829	F<ev.c> includes the backend files directly when enabled, so you only need
2031	to compile this single file.	2830	to compile this single file.
2032		2831
2033	=head3 LIBEVENT COMPATIBILITY API	2832	=head3 LIBEVENT COMPATIBILITY API
2034		2833
2035	To include the libevent compatibility API, also include:	2834	To include the libevent compatibility API, also include:
2036		2835
2037	#include "event.c"	2836	#include "event.c"
2038		2837
2039	in the file including F<ev.c>, and:	2838	in the file including F<ev.c>, and:
2040		2839
2041	#include "event.h"	2840	#include "event.h"
2042		2841
2043	in the files that want to use the libevent API. This also includes F<ev.h>.	2842	in the files that want to use the libevent API. This also includes F<ev.h>.
2044		2843
2045	You need the following additional files for this:	2844	You need the following additional files for this:
2046		2845
2047	event.h	2846	event.h
2048	event.c	2847	event.c
2049		2848
2050	=head3 AUTOCONF SUPPORT	2849	=head3 AUTOCONF SUPPORT
2051		2850
2052	Instead of using C<EV_STANDALONE=1> and providing your config in	2851	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2053	whatever way you want, you can also C<m4_include([libev.m4])> in your	2852	whatever way you want, you can also C<m4_include([libev.m4])> in your
2054	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2853	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2055	include F<config.h> and configure itself accordingly.	2854	include F<config.h> and configure itself accordingly.
2056		2855
2057	For this of course you need the m4 file:	2856	For this of course you need the m4 file:
2058		2857
2059	libev.m4	2858	libev.m4
2060		2859
2061	=head2 PREPROCESSOR SYMBOLS/MACROS	2860	=head2 PREPROCESSOR SYMBOLS/MACROS
2062		2861
2063	Libev can be configured via a variety of preprocessor symbols you have to define	2862	Libev can be configured via a variety of preprocessor symbols you have to
2064	before including any of its files. The default is not to build for multiplicity	2863	define before including any of its files. The default in the absence of
2065	and only include the select backend.	2864	autoconf is noted for every option.
2066		2865
2067	=over 4	2866	=over 4
2068		2867
2069	=item EV_STANDALONE	2868	=item EV_STANDALONE
2070		2869
…		…
2075	F<event.h> that are not directly supported by the libev core alone.	2874	F<event.h> that are not directly supported by the libev core alone.
2076		2875
2077	=item EV_USE_MONOTONIC	2876	=item EV_USE_MONOTONIC
2078		2877
2079	If defined to be C<1>, libev will try to detect the availability of the	2878	If defined to be C<1>, libev will try to detect the availability of the
2080	monotonic clock option at both compiletime and runtime. Otherwise no use	2879	monotonic clock option at both compile time and runtime. Otherwise no use
2081	of the monotonic clock option will be attempted. If you enable this, you	2880	of the monotonic clock option will be attempted. If you enable this, you
2082	usually have to link against librt or something similar. Enabling it when	2881	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	2882	the functionality isn't available is safe, though, although you have
2084	to make sure you link against any libraries where the C<clock_gettime>	2883	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	2884	function is hiding in (often F<-lrt>).
2086		2885
2087	=item EV_USE_REALTIME	2886	=item EV_USE_REALTIME
2088		2887
2089	If defined to be C<1>, libev will try to detect the availability of the	2888	If defined to be C<1>, libev will try to detect the availability of the
2090	realtime clock option at compiletime (and assume its availability at	2889	real-time clock option at compile time (and assume its availability at
2091	runtime if successful). Otherwise no use of the realtime clock option will	2890	runtime if successful). Otherwise no use of the real-time clock option will
2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2894
		2895	=item EV_USE_NANOSLEEP
		2896
		2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2898	and will use it for delays. Otherwise it will use C<select ()>.
		2899
		2900	=item EV_USE_EVENTFD
		2901
		2902	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2903	available and will probe for kernel support at runtime. This will improve
		2904	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2905	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2906	2.7 or newer, otherwise disabled.
2095		2907
2096	=item EV_USE_SELECT	2908	=item EV_USE_SELECT
2097		2909
2098	If undefined or defined to be C<1>, libev will compile in support for the	2910	If undefined or defined to be C<1>, libev will compile in support for the
2099	C<select>(2) backend. No attempt at autodetection will be done: if no	2911	C<select>(2) backend. No attempt at auto-detection will be done: if no
2100	other method takes over, select will be it. Otherwise the select backend	2912	other method takes over, select will be it. Otherwise the select backend
2101	will not be compiled in.	2913	will not be compiled in.
2102		2914
2103	=item EV_SELECT_USE_FD_SET	2915	=item EV_SELECT_USE_FD_SET
2104		2916
2105	If defined to C<1>, then the select backend will use the system C<fd_set>	2917	If defined to C<1>, then the select backend will use the system C<fd_set>
2106	structure. This is useful if libev doesn't compile due to a missing	2918	structure. This is useful if libev doesn't compile due to a missing
2107	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2108	exotic systems. This usually limits the range of file descriptors to some	2920	exotic systems. This usually limits the range of file descriptors to some
2109	low limit such as 1024 or might have other limitations (winsocket only	2921	low limit such as 1024 or might have other limitations (winsocket only
2110	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2111	influence the size of the C<fd_set> used.	2923	influence the size of the C<fd_set> used.
2112		2924
…		…
2118	be used is the winsock select). This means that it will call	2930	be used is the winsock select). This means that it will call
2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2931	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2120	it is assumed that all these functions actually work on fds, even	2932	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	2933	on win32. Should not be defined on non-win32 platforms.
2122		2934
		2935	=item EV_FD_TO_WIN32_HANDLE
		2936
		2937	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2938	file descriptors to socket handles. When not defining this symbol (the
		2939	default), then libev will call C<_get_osfhandle>, which is usually
		2940	correct. In some cases, programs use their own file descriptor management,
		2941	in which case they can provide this function to map fds to socket handles.
		2942
2123	=item EV_USE_POLL	2943	=item EV_USE_POLL
2124		2944
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2945	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2126	backend. Otherwise it will be enabled on non-win32 platforms. It	2946	backend. Otherwise it will be enabled on non-win32 platforms. It
2127	takes precedence over select.	2947	takes precedence over select.
2128		2948
2129	=item EV_USE_EPOLL	2949	=item EV_USE_EPOLL
2130		2950
2131	If defined to be C<1>, libev will compile in support for the Linux	2951	If defined to be C<1>, libev will compile in support for the Linux
2132	C<epoll>(7) backend. Its availability will be detected at runtime,	2952	C<epoll>(7) backend. Its availability will be detected at runtime,
2133	otherwise another method will be used as fallback. This is the	2953	otherwise another method will be used as fallback. This is the preferred
2134	preferred backend for GNU/Linux systems.	2954	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2955	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2135		2956
2136	=item EV_USE_KQUEUE	2957	=item EV_USE_KQUEUE
2137		2958
2138	If defined to be C<1>, libev will compile in support for the BSD style	2959	If defined to be C<1>, libev will compile in support for the BSD style
2139	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2960	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2152	otherwise another method will be used as fallback. This is the preferred	2973	otherwise another method will be used as fallback. This is the preferred
2153	backend for Solaris 10 systems.	2974	backend for Solaris 10 systems.
2154		2975
2155	=item EV_USE_DEVPOLL	2976	=item EV_USE_DEVPOLL
2156		2977
2157	reserved for future expansion, works like the USE symbols above.	2978	Reserved for future expansion, works like the USE symbols above.
2158		2979
2159	=item EV_USE_INOTIFY	2980	=item EV_USE_INOTIFY
2160		2981
2161	If defined to be C<1>, libev will compile in support for the Linux inotify	2982	If defined to be C<1>, libev will compile in support for the Linux inotify
2162	interface to speed up C<ev_stat> watchers. Its actual availability will	2983	interface to speed up C<ev_stat> watchers. Its actual availability will
2163	be detected at runtime.	2984	be detected at runtime. If undefined, it will be enabled if the headers
		2985	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2986
		2987	=item EV_ATOMIC_T
		2988
		2989	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2990	access is atomic with respect to other threads or signal contexts. No such
		2991	type is easily found in the C language, so you can provide your own type
		2992	that you know is safe for your purposes. It is used both for signal handler "locking"
		2993	as well as for signal and thread safety in C<ev_async> watchers.
		2994
		2995	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2996	(from F<signal.h>), which is usually good enough on most platforms.
2164		2997
2165	=item EV_H	2998	=item EV_H
2166		2999
2167	The name of the F<ev.h> header file used to include it. The default if	3000	The name of the F<ev.h> header file used to include it. The default if
2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3001	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3002	used to virtually rename the F<ev.h> header file in case of conflicts.
2170		3003
2171	=item EV_CONFIG_H	3004	=item EV_CONFIG_H
2172		3005
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3006	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3007	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	3008	C<EV_H>, above.
2176		3009
2177	=item EV_EVENT_H	3010	=item EV_EVENT_H
2178		3011
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3012	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2180	of how the F<event.h> header can be found.	3013	of how the F<event.h> header can be found, the default is C<"event.h">.
2181		3014
2182	=item EV_PROTOTYPES	3015	=item EV_PROTOTYPES
2183		3016
2184	If defined to be C<0>, then F<ev.h> will not define any function	3017	If defined to be C<0>, then F<ev.h> will not define any function
2185	prototypes, but still define all the structs and other symbols. This is	3018	prototypes, but still define all the structs and other symbols. This is
…		…
2206	When doing priority-based operations, libev usually has to linearly search	3039	When doing priority-based operations, libev usually has to linearly search
2207	all the priorities, so having many of them (hundreds) uses a lot of space	3040	all the priorities, so having many of them (hundreds) uses a lot of space
2208	and time, so using the defaults of five priorities (-2 .. +2) is usually	3041	and time, so using the defaults of five priorities (-2 .. +2) is usually
2209	fine.	3042	fine.
2210		3043
2211	If your embedding app does not need any priorities, defining these both to	3044	If your embedding application does not need any priorities, defining these both to
2212	C<0> will save some memory and cpu.	3045	C<0> will save some memory and CPU.
2213		3046
2214	=item EV_PERIODIC_ENABLE	3047	=item EV_PERIODIC_ENABLE
2215		3048
2216	If undefined or defined to be C<1>, then periodic timers are supported. If	3049	If undefined or defined to be C<1>, then periodic timers are supported. If
2217	defined to be C<0>, then they are not. Disabling them saves a few kB of	3050	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2236	=item EV_FORK_ENABLE	3069	=item EV_FORK_ENABLE
2237		3070
2238	If undefined or defined to be C<1>, then fork watchers are supported. If	3071	If undefined or defined to be C<1>, then fork watchers are supported. If
2239	defined to be C<0>, then they are not.	3072	defined to be C<0>, then they are not.
2240		3073
		3074	=item EV_ASYNC_ENABLE
		3075
		3076	If undefined or defined to be C<1>, then async watchers are supported. If
		3077	defined to be C<0>, then they are not.
		3078
2241	=item EV_MINIMAL	3079	=item EV_MINIMAL
2242		3080
2243	If you need to shave off some kilobytes of code at the expense of some	3081	If you need to shave off some kilobytes of code at the expense of some
2244	speed, define this symbol to C<1>. Currently only used for gcc to override	3082	speed, define this symbol to C<1>. Currently this is used to override some
2245	some inlining decisions, saves roughly 30% codesize of amd64.	3083	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3084	much smaller 2-heap for timer management over the default 4-heap.
2246		3085
2247	=item EV_PID_HASHSIZE	3086	=item EV_PID_HASHSIZE
2248		3087
2249	C<ev_child> watchers use a small hash table to distribute workload by	3088	C<ev_child> watchers use a small hash table to distribute workload by
2250	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3089	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2251	than enough. If you need to manage thousands of children you might want to	3090	than enough. If you need to manage thousands of children you might want to
2252	increase this value (I<must> be a power of two).	3091	increase this value (I<must> be a power of two).
2253		3092
2254	=item EV_INOTIFY_HASHSIZE	3093	=item EV_INOTIFY_HASHSIZE
2255		3094
2256	C<ev_staz> watchers use a small hash table to distribute workload by	3095	C<ev_stat> watchers use a small hash table to distribute workload by
2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3096	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2258	usually more than enough. If you need to manage thousands of C<ev_stat>	3097	usually more than enough. If you need to manage thousands of C<ev_stat>
2259	watchers you might want to increase this value (I<must> be a power of	3098	watchers you might want to increase this value (I<must> be a power of
2260	two).	3099	two).
2261		3100
		3101	=item EV_USE_4HEAP
		3102
		3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3105	to C<1>. The 4-heap uses more complicated (longer) code but has
		3106	noticeably faster performance with many (thousands) of watchers.
		3107
		3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3109	(disabled).
		3110
		3111	=item EV_HEAP_CACHE_AT
		3112
		3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3114	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3117	but avoids random read accesses on heap changes. This improves performance
		3118	noticeably with with many (hundreds) of watchers.
		3119
		3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3121	(disabled).
		3122
		3123	=item EV_VERIFY
		3124
		3125	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3126	be done: If set to C<0>, no internal verification code will be compiled
		3127	in. If set to C<1>, then verification code will be compiled in, but not
		3128	called. If set to C<2>, then the internal verification code will be
		3129	called once per loop, which can slow down libev. If set to C<3>, then the
		3130	verification code will be called very frequently, which will slow down
		3131	libev considerably.
		3132
		3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3134	C<0.>
		3135
2262	=item EV_COMMON	3136	=item EV_COMMON
2263		3137
2264	By default, all watchers have a C<void *data> member. By redefining	3138	By default, all watchers have a C<void *data> member. By redefining
2265	this macro to a something else you can include more and other types of	3139	this macro to a something else you can include more and other types of
2266	members. You have to define it each time you include one of the files,	3140	members. You have to define it each time you include one of the files,
2267	though, and it must be identical each time.	3141	though, and it must be identical each time.
2268		3142
2269	For example, the perl EV module uses something like this:	3143	For example, the perl EV module uses something like this:
2270		3144
2271	#define EV_COMMON \	3145	#define EV_COMMON \
2272	SV *self; /* contains this struct */ \	3146	SV *self; /* contains this struct */ \
2273	SV *cb_sv, *fh /* note no trailing ";" */	3147	SV *cb_sv, *fh /* note no trailing ";" */
2274		3148
2275	=item EV_CB_DECLARE (type)	3149	=item EV_CB_DECLARE (type)
2276		3150
2277	=item EV_CB_INVOKE (watcher, revents)	3151	=item EV_CB_INVOKE (watcher, revents)
2278		3152
2279	=item ev_set_cb (ev, cb)	3153	=item ev_set_cb (ev, cb)
2280		3154
2281	Can be used to change the callback member declaration in each watcher,	3155	Can be used to change the callback member declaration in each watcher,
2282	and the way callbacks are invoked and set. Must expand to a struct member	3156	and the way callbacks are invoked and set. Must expand to a struct member
2283	definition and a statement, respectively. See the F<ev.v> header file for	3157	definition and a statement, respectively. See the F<ev.h> header file for
2284	their default definitions. One possible use for overriding these is to	3158	their default definitions. One possible use for overriding these is to
2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2286	method calls instead of plain function calls in C++.	3160	method calls instead of plain function calls in C++.
		3161
		3162	=head2 EXPORTED API SYMBOLS
		3163
		3164	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3165	exported symbols, you can use the provided F<Symbol.*> files which list
		3166	all public symbols, one per line:
		3167
		3168	Symbols.ev for libev proper
		3169	Symbols.event for the libevent emulation
		3170
		3171	This can also be used to rename all public symbols to avoid clashes with
		3172	multiple versions of libev linked together (which is obviously bad in
		3173	itself, but sometimes it is inconvenient to avoid this).
		3174
		3175	A sed command like this will create wrapper C<#define>'s that you need to
		3176	include before including F<ev.h>:
		3177
		3178	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3179
		3180	This would create a file F<wrap.h> which essentially looks like this:
		3181
		3182	#define ev_backend myprefix_ev_backend
		3183	#define ev_check_start myprefix_ev_check_start
		3184	#define ev_check_stop myprefix_ev_check_stop
		3185	...
2287		3186
2288	=head2 EXAMPLES	3187	=head2 EXAMPLES
2289		3188
2290	For a real-world example of a program the includes libev	3189	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	3190	verbatim, you can have a look at the EV perl module
…		…
2296	file.	3195	file.
2297		3196
2298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3197	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2299	that everybody includes and which overrides some configure choices:	3198	that everybody includes and which overrides some configure choices:
2300		3199
2301	#define EV_MINIMAL 1	3200	#define EV_MINIMAL 1
2302	#define EV_USE_POLL 0	3201	#define EV_USE_POLL 0
2303	#define EV_MULTIPLICITY 0	3202	#define EV_MULTIPLICITY 0
2304	#define EV_PERIODIC_ENABLE 0	3203	#define EV_PERIODIC_ENABLE 0
2305	#define EV_STAT_ENABLE 0	3204	#define EV_STAT_ENABLE 0
2306	#define EV_FORK_ENABLE 0	3205	#define EV_FORK_ENABLE 0
2307	#define EV_CONFIG_H <config.h>	3206	#define EV_CONFIG_H <config.h>
2308	#define EV_MINPRI 0	3207	#define EV_MINPRI 0
2309	#define EV_MAXPRI 0	3208	#define EV_MAXPRI 0
2310		3209
2311	#include "ev++.h"	3210	#include "ev++.h"
2312		3211
2313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2314		3213
2315	#include "ev_cpp.h"	3214	#include "ev_cpp.h"
2316	#include "ev.c"	3215	#include "ev.c"
		3216
		3217
		3218	=head1 THREADS AND COROUTINES
		3219
		3220	=head2 THREADS
		3221
		3222	Libev itself is completely thread-safe, but it uses no locking. This
		3223	means that you can use as many loops as you want in parallel, as long as
		3224	only one thread ever calls into one libev function with the same loop
		3225	parameter.
		3226
		3227	Or put differently: calls with different loop parameters can be done in
		3228	parallel from multiple threads, calls with the same loop parameter must be
		3229	done serially (but can be done from different threads, as long as only one
		3230	thread ever is inside a call at any point in time, e.g. by using a mutex
		3231	per loop).
		3232
		3233	If you want to know which design (one loop, locking, or multiple loops
		3234	without or something else still) is best for your problem, then I cannot
		3235	help you. I can give some generic advice however:
		3236
		3237	=over 4
		3238
		3239	=item * most applications have a main thread: use the default libev loop
		3240	in that thread, or create a separate thread running only the default loop.
		3241
		3242	This helps integrating other libraries or software modules that use libev
		3243	themselves and don't care/know about threading.
		3244
		3245	=item * one loop per thread is usually a good model.
		3246
		3247	Doing this is almost never wrong, sometimes a better-performance model
		3248	exists, but it is always a good start.
		3249
		3250	=item * other models exist, such as the leader/follower pattern, where one
		3251	loop is handed through multiple threads in a kind of round-robin fashion.
		3252
		3253	Choosing a model is hard - look around, learn, know that usually you can do
		3254	better than you currently do :-)
		3255
		3256	=item * often you need to talk to some other thread which blocks in the
		3257	event loop - C<ev_async> watchers can be used to wake them up from other
		3258	threads safely (or from signal contexts...).
		3259
		3260	=back
		3261
		3262	=head2 COROUTINES
		3263
		3264	Libev is much more accommodating to coroutines ("cooperative threads"):
		3265	libev fully supports nesting calls to it's functions from different
		3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3267	different coroutines and switch freely between both coroutines running the
		3268	loop, as long as you don't confuse yourself). The only exception is that
		3269	you must not do this from C<ev_periodic> reschedule callbacks.
		3270
		3271	Care has been invested into making sure that libev does not keep local
		3272	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3273	switches.
2317		3274
2318		3275
2319	=head1 COMPLEXITIES	3276	=head1 COMPLEXITIES
2320		3277
2321	In this section the complexities of (many of) the algorithms used inside	3278	In this section the complexities of (many of) the algorithms used inside
…		…
2332		3289
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		3291
2335	This means that, when you have a watcher that triggers in one hour and	3292	This means that, when you have a watcher that triggers in one hour and
2336	there are 100 watchers that would trigger before that then inserting will	3293	there are 100 watchers that would trigger before that then inserting will
2337	have to skip those 100 watchers.	3294	have to skip roughly seven (C<ld 100>) of these watchers.
2338		3295
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		3297
2341	That means that for changing a timer costs less than removing/adding them	3298	That means that changing a timer costs less than removing/adding them
2342	as only the relative motion in the event queue has to be paid for.	3299	as only the relative motion in the event queue has to be paid for.
2343		3300
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2345		3302
2346	These just add the watcher into an array or at the head of a list.	3303	These just add the watcher into an array or at the head of a list.
		3304
2347	=item Stopping check/prepare/idle watchers: O(1)	3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2348		3306
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		3308
2351	These watchers are stored in lists then need to be walked to find the	3309	These watchers are stored in lists then need to be walked to find the
2352	correct watcher to remove. The lists are usually short (you don't usually	3310	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	3311	have many watchers waiting for the same fd or signal).
2354		3312
2355	=item Finding the next timer per loop iteration: O(1)	3313	=item Finding the next timer in each loop iteration: O(1)
		3314
		3315	By virtue of using a binary or 4-heap, the next timer is always found at a
		3316	fixed position in the storage array.
2356		3317
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		3319
2359	A change means an I/O watcher gets started or stopped, which requires	3320	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	3321	libev to recalculate its status (and possibly tell the kernel, depending
		3322	on backend and whether C<ev_io_set> was used).
2361		3323
2362	=item Activating one watcher: O(1)	3324	=item Activating one watcher (putting it into the pending state): O(1)
2363		3325
2364	=item Priority handling: O(number_of_priorities)	3326	=item Priority handling: O(number_of_priorities)
2365		3327
2366	Priorities are implemented by allocating some space for each	3328	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	3329	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	3330	linearly search all the priorities, but starting/stopping and activating
		3331	watchers becomes O(1) w.r.t. priority handling.
		3332
		3333	=item Sending an ev_async: O(1)
		3334
		3335	=item Processing ev_async_send: O(number_of_async_watchers)
		3336
		3337	=item Processing signals: O(max_signal_number)
		3338
		3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3340	calls in the current loop iteration. Checking for async and signal events
		3341	involves iterating over all running async watchers or all signal numbers.
2369		3342
2370	=back	3343	=back
2371		3344
2372		3345
		3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3347
		3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3349	requires, and its I/O model is fundamentally incompatible with the POSIX
		3350	model. Libev still offers limited functionality on this platform in
		3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3352	descriptors. This only applies when using Win32 natively, not when using
		3353	e.g. cygwin.
		3354
		3355	Lifting these limitations would basically require the full
		3356	re-implementation of the I/O system. If you are into these kinds of
		3357	things, then note that glib does exactly that for you in a very portable
		3358	way (note also that glib is the slowest event library known to man).
		3359
		3360	There is no supported compilation method available on windows except
		3361	embedding it into other applications.
		3362
		3363	Not a libev limitation but worth mentioning: windows apparently doesn't
		3364	accept large writes: instead of resulting in a partial write, windows will
		3365	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3366	so make sure you only write small amounts into your sockets (less than a
		3367	megabyte seems safe, but thsi apparently depends on the amount of memory
		3368	available).
		3369
		3370	Due to the many, low, and arbitrary limits on the win32 platform and
		3371	the abysmal performance of winsockets, using a large number of sockets
		3372	is not recommended (and not reasonable). If your program needs to use
		3373	more than a hundred or so sockets, then likely it needs to use a totally
		3374	different implementation for windows, as libev offers the POSIX readiness
		3375	notification model, which cannot be implemented efficiently on windows
		3376	(Microsoft monopoly games).
		3377
		3378	A typical way to use libev under windows is to embed it (see the embedding
		3379	section for details) and use the following F<evwrap.h> header file instead
		3380	of F<ev.h>:
		3381
		3382	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3384
		3385	#include "ev.h"
		3386
		3387	And compile the following F<evwrap.c> file into your project (make sure
		3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3389
		3390	#include "evwrap.h"
		3391	#include "ev.c"
		3392
		3393	=over 4
		3394
		3395	=item The winsocket select function
		3396
		3397	The winsocket C<select> function doesn't follow POSIX in that it
		3398	requires socket I<handles> and not socket I<file descriptors> (it is
		3399	also extremely buggy). This makes select very inefficient, and also
		3400	requires a mapping from file descriptors to socket handles (the Microsoft
		3401	C runtime provides the function C<_open_osfhandle> for this). See the
		3402	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3403	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3404
		3405	The configuration for a "naked" win32 using the Microsoft runtime
		3406	libraries and raw winsocket select is:
		3407
		3408	#define EV_USE_SELECT 1
		3409	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3410
		3411	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3412	complexity in the O(n²) range when using win32.
		3413
		3414	=item Limited number of file descriptors
		3415
		3416	Windows has numerous arbitrary (and low) limits on things.
		3417
		3418	Early versions of winsocket's select only supported waiting for a maximum
		3419	of C<64> handles (probably owning to the fact that all windows kernels
		3420	can only wait for C<64> things at the same time internally; Microsoft
		3421	recommends spawning a chain of threads and wait for 63 handles and the
		3422	previous thread in each. Great).
		3423
		3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3425	to some high number (e.g. C<2048>) before compiling the winsocket select
		3426	call (which might be in libev or elsewhere, for example, perl does its own
		3427	select emulation on windows).
		3428
		3429	Another limit is the number of file descriptors in the Microsoft runtime
		3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3431	or something like this inside Microsoft). You can increase this by calling
		3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3433	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3434	libraries.
		3435
		3436	This might get you to about C<512> or C<2048> sockets (depending on
		3437	windows version and/or the phase of the moon). To get more, you need to
		3438	wrap all I/O functions and provide your own fd management, but the cost of
		3439	calling select (O(n²)) will likely make this unworkable.
		3440
		3441	=back
		3442
		3443
		3444	=head1 PORTABILITY REQUIREMENTS
		3445
		3446	In addition to a working ISO-C implementation, libev relies on a few
		3447	additional extensions:
		3448
		3449	=over 4
		3450
		3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3452	calling conventions regardless of C<ev_watcher_type *>.
		3453
		3454	Libev assumes not only that all watcher pointers have the same internal
		3455	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3456	assumes that the same (machine) code can be used to call any watcher
		3457	callback: The watcher callbacks have different type signatures, but libev
		3458	calls them using an C<ev_watcher *> internally.
		3459
		3460	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3461
		3462	The type C<sig_atomic_t volatile> (or whatever is defined as
		3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3464	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3465	believed to be sufficiently portable.
		3466
		3467	=item C<sigprocmask> must work in a threaded environment
		3468
		3469	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3470	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3471	pthread implementations will either allow C<sigprocmask> in the "main
		3472	thread" or will block signals process-wide, both behaviours would
		3473	be compatible with libev. Interaction between C<sigprocmask> and
		3474	C<pthread_sigmask> could complicate things, however.
		3475
		3476	The most portable way to handle signals is to block signals in all threads
		3477	except the initial one, and run the default loop in the initial thread as
		3478	well.
		3479
		3480	=item C<long> must be large enough for common memory allocation sizes
		3481
		3482	To improve portability and simplify using libev, libev uses C<long>
		3483	internally instead of C<size_t> when allocating its data structures. On
		3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3485	is still at least 31 bits everywhere, which is enough for hundreds of
		3486	millions of watchers.
		3487
		3488	=item C<double> must hold a time value in seconds with enough accuracy
		3489
		3490	The type C<double> is used to represent timestamps. It is required to
		3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3492	enough for at least into the year 4000. This requirement is fulfilled by
		3493	implementations implementing IEEE 754 (basically all existing ones).
		3494
		3495	=back
		3496
		3497	If you know of other additional requirements drop me a note.
		3498
		3499
		3500	=head1 COMPILER WARNINGS
		3501
		3502	Depending on your compiler and compiler settings, you might get no or a
		3503	lot of warnings when compiling libev code. Some people are apparently
		3504	scared by this.
		3505
		3506	However, these are unavoidable for many reasons. For one, each compiler
		3507	has different warnings, and each user has different tastes regarding
		3508	warning options. "Warn-free" code therefore cannot be a goal except when
		3509	targeting a specific compiler and compiler-version.
		3510
		3511	Another reason is that some compiler warnings require elaborate
		3512	workarounds, or other changes to the code that make it less clear and less
		3513	maintainable.
		3514
		3515	And of course, some compiler warnings are just plain stupid, or simply
		3516	wrong (because they don't actually warn about the condition their message
		3517	seems to warn about).
		3518
		3519	While libev is written to generate as few warnings as possible,
		3520	"warn-free" code is not a goal, and it is recommended not to build libev
		3521	with any compiler warnings enabled unless you are prepared to cope with
		3522	them (e.g. by ignoring them). Remember that warnings are just that:
		3523	warnings, not errors, or proof of bugs.
		3524
		3525
		3526	=head1 VALGRIND
		3527
		3528	Valgrind has a special section here because it is a popular tool that is
		3529	highly useful, but valgrind reports are very hard to interpret.
		3530
		3531	If you think you found a bug (memory leak, uninitialised data access etc.)
		3532	in libev, then check twice: If valgrind reports something like:
		3533
		3534	==2274== definitely lost: 0 bytes in 0 blocks.
		3535	==2274== possibly lost: 0 bytes in 0 blocks.
		3536	==2274== still reachable: 256 bytes in 1 blocks.
		3537
		3538	Then there is no memory leak. Similarly, under some circumstances,
		3539	valgrind might report kernel bugs as if it were a bug in libev, or it
		3540	might be confused (it is a very good tool, but only a tool).
		3541
		3542	If you are unsure about something, feel free to contact the mailing list
		3543	with the full valgrind report and an explanation on why you think this is
		3544	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3545	no bug" answer and take the chance of learning how to interpret valgrind
		3546	properly.
		3547
		3548	If you need, for some reason, empty reports from valgrind for your project
		3549	I suggest using suppression lists.
		3550
		3551
2373	=head1 AUTHOR	3552	=head1 AUTHOR
2374		3553
2375	Marc Lehmann <libev@schmorp.de>.	3554	Marc Lehmann <libev@schmorp.de>.
2376		3555

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