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Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs.
Revision 1.173 by root, Thu Aug 7 19:24:56 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).
461		577
462	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
463		579
464	Finally, this is it, the event handler. This function usually is called	580	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	581	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	593	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	594	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.	595	case there are no events and will return after one iteration of the loop.
480		596
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	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	598	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	599	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	600	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	601	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	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
488		604
489	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
490		606
491	* If there are no active watchers (reference count is zero), return.	607	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
		609	- If a fork was detected (by any means), queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
494	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
496	- Calculate for how long to block.	615	- Calculate for how long to sleep or block, if at all
		616	(active idle watchers, EVLOOP_NONBLOCK or not having
		617	any active watchers at all will result in not sleeping).
		618	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
500	- Queue all outstanding timers.	622	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
503	- Queue all check watchers.	625	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	626	- 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	627	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
509		632
510	Example: Queue some jobs and then loop until no events are outsanding	633	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	634	anymore.
512		635
513	... queue jobs here, make sure they register event watchers as long	636	... 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..)	637	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
516	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
517		640
518	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
519		642
520	Can be used to make a call to C<ev_loop> return early (but only after it	643	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	644	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	645	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.	646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		647
		648	This "unloop state" will be cleared when entering C<ev_loop> again.
524		649
525	=item ev_ref (loop)	650	=item ev_ref (loop)
526		651
527	=item ev_unref (loop)	652	=item ev_unref (loop)
528		653
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	658	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	659	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	660	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	661	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	662	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>.	663	libraries. Just remember to I<unref after start> and I<ref before stop>
		664	(but only if the watcher wasn't active before, or was active before,
		665	respectively).
539		666
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	668	running when nothing else is active.
542		669
543	struct ev_signal exitsig;	670	struct ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	672	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	673	evf_unref (loop);
547		674
548	Example: For some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
549		676
550	ev_ref (loop);	677	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	678	ev_signal_stop (loop, &exitsig);
		679
		680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		681
		682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		683
		684	These advanced functions influence the time that libev will spend waiting
		685	for events. Both time intervals are by default C<0>, meaning that libev
		686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
		688
		689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		690	allows libev to delay invocation of I/O and timer/periodic callbacks
		691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
		693
		694	The background is that sometimes your program runs just fast enough to
		695	handle one (or very few) event(s) per loop iteration. While this makes
		696	the program responsive, it also wastes a lot of CPU time to poll for new
		697	events, especially with backends like C<select ()> which have a high
		698	overhead for the actual polling but can deliver many events at once.
		699
		700	By setting a higher I<io collect interval> you allow libev to spend more
		701	time collecting I/O events, so you can handle more events per iteration,
		702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		703	C<ev_timer>) will be not affected. Setting this to a non-null value will
		704	introduce an additional C<ev_sleep ()> call into most loop iterations.
		705
		706	Likewise, by setting a higher I<timeout collect interval> you allow libev
		707	to spend more time collecting timeouts, at the expense of increased
		708	latency (the watcher callback will be called later). C<ev_io> watchers
		709	will not be affected. Setting this to a non-null value will not introduce
		710	any overhead in libev.
		711
		712	Many (busy) programs can usually benefit by setting the I/O collect
		713	interval to a value near C<0.1> or so, which is often enough for
		714	interactive servers (of course not for games), likewise for timeouts. It
		715	usually doesn't make much sense to set it to a lower value than C<0.01>,
		716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
552		735
553	=back	736	=back
554		737
555		738
556	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
557		740
558	A watcher is a structure that you create and register to record your	741	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	742	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:	743	become readable, you would create an C<ev_io> watcher for that:
561		744
562	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
563	{	746	{
564	ev_io_stop (w);	747	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
566	}	749	}
567		750
568	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
569	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
570	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
573	ev_loop (loop, 0);	756	ev_loop (loop, 0);
574		757
575	As you can see, you are responsible for allocating the memory for your	758	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,	759	watcher structures (and it is usually a bad idea to do this on the stack,
577	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
578		761
579	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	763	(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	764	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	765	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	766	is readable and/or writable).
584		767
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	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	769	with arguments specific to this watcher type. There is also a macro
…		…
656	=item C<EV_FORK>	839	=item C<EV_FORK>
657		840
658	The event loop has been resumed in the child process after fork (see	841	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	842	C<ev_fork>).
660		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
661	=item C<EV_ERROR>	848	=item C<EV_ERROR>
662		849
663	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	851	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	852	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	853	problem. You best act on it by reporting the problem and somehow coping
667	with the watcher being stopped.	854	with the watcher being stopped.
668		855
669	Libev will usually signal a few "dummy" events together with an error,	856	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	857	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	858	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	859	with the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	860	programs, though, so beware.
674		861
675	=back	862	=back
676		863
677	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
707	Although some watcher types do not have type-specific arguments	894	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.	895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		896
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		898
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	899	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	900	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
715		902
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		904
718	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
801	to associate arbitrary data with your watcher. If you need more data and	988	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	989	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	990	member, you can also "subclass" the watcher type and provide your own
804	data:	991	data:
805		992
806	struct my_io	993	struct my_io
807	{	994	{
808	struct ev_io io;	995	struct ev_io io;
809	int otherfd;	996	int otherfd;
810	void *somedata;	997	void *somedata;
811	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
812	}	999	}
813		1000
814	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
815	can cast it back to your own type:	1002	can cast it back to your own type:
816		1003
817	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
818	{	1005	{
819	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
820	...	1007	...
821	}	1008	}
822		1009
823	More interesting and less C-conformant ways of casting your callback type	1010	More interesting and less C-conformant ways of casting your callback type
824	instead have been omitted.	1011	instead have been omitted.
825		1012
826	Another common scenario is having some data structure with multiple	1013	Another common scenario is having some data structure with multiple
827	watchers:	1014	watchers:
828		1015
829	struct my_biggy	1016	struct my_biggy
830	{	1017	{
831	int some_data;	1018	int some_data;
832	ev_timer t1;	1019	ev_timer t1;
833	ev_timer t2;	1020	ev_timer t2;
834	}	1021	}
835		1022
836	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
837	you need to use C<offsetof>:	1024	you need to use C<offsetof>:
838		1025
839	#include <stddef.h>	1026	#include <stddef.h>
840		1027
841	static void	1028	static void
842	t1_cb (EV_P_ struct ev_timer *w, int revents)	1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
843	{	1030	{
844	struct my_biggy big = (struct my_biggy *	1031	struct my_biggy big = (struct my_biggy *
845	(((char *)w) - offsetof (struct my_biggy, t1));	1032	(((char *)w) - offsetof (struct my_biggy, t1));
846	}	1033	}
847		1034
848	static void	1035	static void
849	t2_cb (EV_P_ struct ev_timer *w, int revents)	1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
850	{	1037	{
851	struct my_biggy big = (struct my_biggy *	1038	struct my_biggy big = (struct my_biggy *
852	(((char *)w) - offsetof (struct my_biggy, t2));	1039	(((char *)w) - offsetof (struct my_biggy, t2));
853	}	1040	}
854		1041
855		1042
856	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
857		1044
858	This section describes each watcher in detail, but will not repeat	1045	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	1069	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	1070	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	1071	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	1072	required if you know what you are doing).
886		1073
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	1074	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	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
896		1077
897	Another thing you have to watch out for is that it is quite easy to	1078	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	1079	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	1080	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	1081	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	1082	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	1083	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	1084	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.	1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
905		1086
906	If you cannot run the fd in non-blocking mode (for example you should not	1087	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	1088	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	1089	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	1090	such as poll (fortunately in our Xlib example, Xlib already does this on
910	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
911		1092
		1093	=head3 The special problem of disappearing file descriptors
		1094
		1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1096	descriptor (either by calling C<close> explicitly or by any other means,
		1097	such as C<dup>). The reason is that you register interest in some file
		1098	descriptor, but when it goes away, the operating system will silently drop
		1099	this interest. If another file descriptor with the same number then is
		1100	registered with libev, there is no efficient way to see that this is, in
		1101	fact, a different file descriptor.
		1102
		1103	To avoid having to explicitly tell libev about such cases, libev follows
		1104	the following policy: Each time C<ev_io_set> is being called, libev
		1105	will assume that this is potentially a new file descriptor, otherwise
		1106	it is assumed that the file descriptor stays the same. That means that
		1107	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1108	descriptor even if the file descriptor number itself did not change.
		1109
		1110	This is how one would do it normally anyway, the important point is that
		1111	the libev application should not optimise around libev but should leave
		1112	optimisations to libev.
		1113
		1114	=head3 The special problem of dup'ed file descriptors
		1115
		1116	Some backends (e.g. epoll), cannot register events for file descriptors,
		1117	but only events for the underlying file descriptions. That means when you
		1118	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1119	events for them, only one file descriptor might actually receive events.
		1120
		1121	There is no workaround possible except not registering events
		1122	for potentially C<dup ()>'ed file descriptors, or to resort to
		1123	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1124
		1125	=head3 The special problem of fork
		1126
		1127	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1128	useless behaviour. Libev fully supports fork, but needs to be told about
		1129	it in the child.
		1130
		1131	To support fork in your programs, you either have to call
		1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1134	C<EVBACKEND_POLL>.
		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when reading from a pipe whose other end has been closed, your program
		1140	gets send a SIGPIPE, which, by default, aborts your program. For most
		1141	programs this is sensible behaviour, for daemons, this is usually
		1142	undesirable.
		1143
		1144	So when you encounter spurious, unexplained daemon exits, make sure you
		1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1146	somewhere, as that would have given you a big clue).
		1147
		1148
		1149	=head3 Watcher-Specific Functions
		1150
912	=over 4	1151	=over 4
913		1152
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1153	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1154
916	=item ev_io_set (ev_io *, int fd, int events)	1155	=item ev_io_set (ev_io *, int fd, int events)
917		1156
918	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1157	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	1158	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.	1159	C<EV_READ | EV_WRITE> to receive the given events.
921		1160
922	=item int fd [read-only]	1161	=item int fd [read-only]
923		1162
924	The file descriptor being watched.	1163	The file descriptor being watched.
…		…
926	=item int events [read-only]	1165	=item int events [read-only]
927		1166
928	The events being watched.	1167	The events being watched.
929		1168
930	=back	1169	=back
		1170
		1171	=head3 Examples
931		1172
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1173	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	1174	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1175	attempt to read a whole line in the callback.
935		1176
936	static void	1177	static void
937	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
938	{	1179	{
939	ev_io_stop (loop, w);	1180	ev_io_stop (loop, w);
940	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors
941	}	1182	}
942		1183
943	...	1184	...
944	struct ev_loop *loop = ev_default_init (0);	1185	struct ev_loop *loop = ev_default_init (0);
945	struct ev_io stdin_readable;	1186	struct ev_io stdin_readable;
946	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
947	ev_io_start (loop, &stdin_readable);	1188	ev_io_start (loop, &stdin_readable);
948	ev_loop (loop, 0);	1189	ev_loop (loop, 0);
949		1190
950		1191
951	=head2 C<ev_timer> - relative and optionally repeating timeouts	1192	=head2 C<ev_timer> - relative and optionally repeating timeouts
952		1193
953	Timer watchers are simple relative timers that generate an event after a	1194	Timer watchers are simple relative timers that generate an event after a
954	given time, and optionally repeating in regular intervals after that.	1195	given time, and optionally repeating in regular intervals after that.
955		1196
956	The timers are based on real time, that is, if you register an event that	1197	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	1198	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	1199	year, it will still time out after (roughly) and hour. "Roughly" because
959	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the
960	monotonic clock option helps a lot here).	1201	monotonic clock option helps a lot here).
961		1202
962	The relative timeouts are calculated relative to the C<ev_now ()>	1203	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	1204	time. This is usually the right thing as this timestamp refers to the time
…		…
965	you suspect event processing to be delayed and you I<need> to base the timeout	1206	you suspect event processing to be delayed and you I<need> to base the timeout
966	on the current time, use something like this to adjust for this:	1207	on the current time, use something like this to adjust for this:
967		1208
968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
969		1210
970	The callback is guarenteed to be invoked only when its timeout has passed,	1211	The callback is guaranteed to be invoked only after its timeout has passed,
971	but if multiple timers become ready during the same loop iteration then	1212	but if multiple timers become ready during the same loop iteration then
972	order of execution is undefined.	1213	order of execution is undefined.
973		1214
		1215	=head3 Watcher-Specific Functions and Data Members
		1216
974	=over 4	1217	=over 4
975		1218
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1219	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1220
978	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1221	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
979		1222
980	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1223	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	1224	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	1225	reached. If it is positive, then the timer will automatically be
983	later, again, and again, until stopped manually.	1226	configured to trigger again C<repeat> seconds later, again, and again,
		1227	until stopped manually.
984		1228
985	The timer itself will do a best-effort at avoiding drift, that is, if you	1229	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	1230	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	1231	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	1232	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.	1233	do stuff) the timer will not fire more than once per event loop iteration.
990		1234
991	=item ev_timer_again (loop)	1235	=item ev_timer_again (loop, ev_timer *)
992		1236
993	This will act as if the timer timed out and restart it again if it is	1237	This will act as if the timer timed out and restart it again if it is
994	repeating. The exact semantics are:	1238	repeating. The exact semantics are:
995		1239
996	If the timer is pending, its pending status is cleared.	1240	If the timer is pending, its pending status is cleared.
997		1241
998	If the timer is started but nonrepeating, stop it (as if it timed out).	1242	If the timer is started but non-repeating, stop it (as if it timed out).
999		1243
1000	If the timer is repeating, either start it if necessary (with the	1244	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.	1245	C<repeat> value), or reset the running timer to the C<repeat> value.
1002		1246
1003	This sounds a bit complicated, but here is a useful and typical	1247	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	1248	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	1249	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	1250	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	1251	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	1252	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	1253	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),	1275	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.	1276	which is also when any modifications are taken into account.
1033		1277
1034	=back	1278	=back
1035		1279
		1280	=head3 Examples
		1281
1036	Example: Create a timer that fires after 60 seconds.	1282	Example: Create a timer that fires after 60 seconds.
1037		1283
1038	static void	1284	static void
1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1040	{	1286	{
1041	.. one minute over, w is actually stopped right here	1287	.. one minute over, w is actually stopped right here
1042	}	1288	}
1043		1289
1044	struct ev_timer mytimer;	1290	struct ev_timer mytimer;
1045	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1046	ev_timer_start (loop, &mytimer);	1292	ev_timer_start (loop, &mytimer);
1047		1293
1048	Example: Create a timeout timer that times out after 10 seconds of	1294	Example: Create a timeout timer that times out after 10 seconds of
1049	inactivity.	1295	inactivity.
1050		1296
1051	static void	1297	static void
1052	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1053	{	1299	{
1054	.. ten seconds without any activity	1300	.. ten seconds without any activity
1055	}	1301	}
1056		1302
1057	struct ev_timer mytimer;	1303	struct ev_timer mytimer;
1058	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1059	ev_timer_again (&mytimer); /* start timer */	1305	ev_timer_again (&mytimer); /* start timer */
1060	ev_loop (loop, 0);	1306	ev_loop (loop, 0);
1061		1307
1062	// and in some piece of code that gets executed on any "activity":	1308	// and in some piece of code that gets executed on any "activity":
1063	// reset the timeout to start ticking again at 10 seconds	1309	// reset the timeout to start ticking again at 10 seconds
1064	ev_timer_again (&mytimer);	1310	ev_timer_again (&mytimer);
1065		1311
1066		1312
1067	=head2 C<ev_periodic> - to cron or not to cron?	1313	=head2 C<ev_periodic> - to cron or not to cron?
1068		1314
1069	Periodic watchers are also timers of a kind, but they are very versatile	1315	Periodic watchers are also timers of a kind, but they are very versatile
1070	(and unfortunately a bit complex).	1316	(and unfortunately a bit complex).
1071		1317
1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1318	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	1319	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	1320	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 ()	1321	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	1322	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1323	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	1324	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	1325	roughly 10 seconds later as it uses a relative timeout).
1079	again).
1080		1326
1081	They can also be used to implement vastly more complex timers, such as	1327	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on eahc midnight, local time.	1328	such as triggering an event on each "midnight, local time", or other
		1329	complicated, rules.
1083		1330
1084	As with timers, the callback is guarenteed to be invoked only when the	1331	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	1332	time (C<at>) has passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1333	during the same loop iteration then order of execution is undefined.
		1334
		1335	=head3 Watcher-Specific Functions and Data Members
1087		1336
1088	=over 4	1337	=over 4
1089		1338
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1340
…		…
1094	Lots of arguments, lets sort it out... There are basically three modes of	1343	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1344	operation, and we will explain them from simplest to complex:
1096		1345
1097	=over 4	1346	=over 4
1098		1347
1099	=item * absolute timer (interval = reschedule_cb = 0)	1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1349
1101	In this configuration the watcher triggers an event at the wallclock time	1350	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,	1351	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	1352	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.	1353	run when the system time reaches or surpasses this time.
1105		1354
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1356
1108	In this mode the watcher will always be scheduled to time out at the next	1357	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	1358	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1359	and then repeat, regardless of any time jumps.
1111		1360
1112	This can be used to create timers that do not drift with respect to system	1361	This can be used to create timers that do not drift with respect to system
1113	time:	1362	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1363	the hour:
1114		1364
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1365	ev_periodic_set (&periodic, 0., 3600., 0);
1116		1366
1117	This doesn't mean there will always be 3600 seconds in between triggers,	1367	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	1368	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	1369	full hour (UTC), or more correctly, when the system time is evenly divisible
1120	by 3600.	1370	by 3600.
1121		1371
1122	Another way to think about it (for the mathematically inclined) is that	1372	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	1373	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.	1374	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1375
		1376	For numerical stability it is preferable that the C<at> value is near
		1377	C<ev_now ()> (the current time), but there is no range requirement for
		1378	this value, and in fact is often specified as zero.
		1379
		1380	Note also that there is an upper limit to how often a timer can fire (CPU
		1381	speed for example), so if C<interval> is very small then timing stability
		1382	will of course deteriorate. Libev itself tries to be exact to be about one
		1383	millisecond (if the OS supports it and the machine is fast enough).
		1384
1126	=item * manual reschedule mode (reschedule_cb = callback)	1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1386
1128	In this mode the values for C<interval> and C<at> are both being	1387	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	1388	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1389	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1390	current time as second argument.
1132		1391
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1392	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,	1393	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		1394
		1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1397	only event loop modification you are allowed to do).
		1398
1138	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1139	ev_tstamp now)>, e.g.:	1400	*w, ev_tstamp now)>, e.g.:
1140		1401
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1142	{	1403	{
1143	return now + 60.;	1404	return now + 60.;
1144	}	1405	}
…		…
1146	It must return the next time to trigger, based on the passed time value	1407	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	1408	(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	1409	will usually be called just before the callback will be triggered, but
1149	might be called at other times, too.	1410	might be called at other times, too.
1150		1411
1151	NOTE: I<< This callback must always return a time that is later than the	1412	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.	1413	equal to the passed C<now> value >>.
1153		1414
1154	This can be used to create very complex timers, such as a timer that	1415	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	1416	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	1417	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	1418	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).	1419	reason I omitted it as an example).
1159		1420
1160	=back	1421	=back
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1425	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1426	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	1427	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1428	program when the crontabs have changed).
1168		1429
		1430	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1431
		1432	When active, returns the absolute time that the watcher is supposed to
		1433	trigger next.
		1434
		1435	=item ev_tstamp offset [read-write]
		1436
		1437	When repeating, this contains the offset value, otherwise this is the
		1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1439
		1440	Can be modified any time, but changes only take effect when the periodic
		1441	timer fires or C<ev_periodic_again> is being called.
		1442
1169	=item ev_tstamp interval [read-write]	1443	=item ev_tstamp interval [read-write]
1170		1444
1171	The current interval value. Can be modified any time, but changes only	1445	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	1446	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1447	called.
…		…
1178	switched off. Can be changed any time, but changes only take effect when	1452	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.	1453	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1454
1181	=back	1455	=back
1182		1456
		1457	=head3 Examples
		1458
1183	Example: Call a callback every hour, or, more precisely, whenever the	1459	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1460	system clock is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1461	potentially a lot of jitter, but good long-term stability.
1186		1462
1187	static void	1463	static void
1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1189	{	1465	{
1190	... its now a full hour (UTC, or TAI or whatever your clock follows)	1466	... its now a full hour (UTC, or TAI or whatever your clock follows)
1191	}	1467	}
1192		1468
1193	struct ev_periodic hourly_tick;	1469	struct ev_periodic hourly_tick;
1194	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1195	ev_periodic_start (loop, &hourly_tick);	1471	ev_periodic_start (loop, &hourly_tick);
1196		1472
1197	Example: The same as above, but use a reschedule callback to do it:	1473	Example: The same as above, but use a reschedule callback to do it:
1198		1474
1199	#include <math.h>	1475	#include <math.h>
1200		1476
1201	static ev_tstamp	1477	static ev_tstamp
1202	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1203	{	1479	{
1204	return fmod (now, 3600.) + 3600.;	1480	return fmod (now, 3600.) + 3600.;
1205	}	1481	}
1206		1482
1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1208		1484
1209	Example: Call a callback every hour, starting now:	1485	Example: Call a callback every hour, starting now:
1210		1486
1211	struct ev_periodic hourly_tick;	1487	struct ev_periodic hourly_tick;
1212	ev_periodic_init (&hourly_tick, clock_cb,	1488	ev_periodic_init (&hourly_tick, clock_cb,
1213	fmod (ev_now (loop), 3600.), 3600., 0);	1489	fmod (ev_now (loop), 3600.), 3600., 0);
1214	ev_periodic_start (loop, &hourly_tick);	1490	ev_periodic_start (loop, &hourly_tick);
1215		1491
1216		1492
1217	=head2 C<ev_signal> - signal me when a signal gets signalled!	1493	=head2 C<ev_signal> - signal me when a signal gets signalled!
1218		1494
1219	Signal watchers will trigger an event when the process receives a specific	1495	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	1502	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	1503	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	1504	watcher for a signal is stopped libev will reset the signal handler to
1229	SIG_DFL (regardless of what it was set to before).	1505	SIG_DFL (regardless of what it was set to before).
1230		1506
		1507	If possible and supported, libev will install its handlers with
		1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1509	interrupted. If you have a problem with system calls getting interrupted by
		1510	signals you can block all signals in an C<ev_check> watcher and unblock
		1511	them in an C<ev_prepare> watcher.
		1512
		1513	=head3 Watcher-Specific Functions and Data Members
		1514
1231	=over 4	1515	=over 4
1232		1516
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1517	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1518
1235	=item ev_signal_set (ev_signal *, int signum)	1519	=item ev_signal_set (ev_signal *, int signum)
…		…
1241		1525
1242	The signal the watcher watches out for.	1526	The signal the watcher watches out for.
1243		1527
1244	=back	1528	=back
1245		1529
		1530	=head3 Examples
		1531
		1532	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1533
		1534	static void
		1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1536	{
		1537	ev_unloop (loop, EVUNLOOP_ALL);
		1538	}
		1539
		1540	struct ev_signal signal_watcher;
		1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1542	ev_signal_start (loop, &sigint_cb);
		1543
1246		1544
1247	=head2 C<ev_child> - watch out for process status changes	1545	=head2 C<ev_child> - watch out for process status changes
1248		1546
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1547	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).	1548	some child status changes (most typically when a child of yours dies). It
		1549	is permissible to install a child watcher I<after> the child has been
		1550	forked (which implies it might have already exited), as long as the event
		1551	loop isn't entered (or is continued from a watcher).
		1552
		1553	Only the default event loop is capable of handling signals, and therefore
		1554	you can only register child watchers in the default event loop.
		1555
		1556	=head3 Process Interaction
		1557
		1558	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1559	initialised. This is necessary to guarantee proper behaviour even if
		1560	the first child watcher is started after the child exits. The occurrence
		1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1562	synchronously as part of the event loop processing. Libev always reaps all
		1563	children, even ones not watched.
		1564
		1565	=head3 Overriding the Built-In Processing
		1566
		1567	Libev offers no special support for overriding the built-in child
		1568	processing, but if your application collides with libev's default child
		1569	handler, you can override it easily by installing your own handler for
		1570	C<SIGCHLD> after initialising the default loop, and making sure the
		1571	default loop never gets destroyed. You are encouraged, however, to use an
		1572	event-based approach to child reaping and thus use libev's support for
		1573	that, so other libev users can use C<ev_child> watchers freely.
		1574
		1575	=head3 Stopping the Child Watcher
		1576
		1577	Currently, the child watcher never gets stopped, even when the
		1578	child terminates, so normally one needs to stop the watcher in the
		1579	callback. Future versions of libev might stop the watcher automatically
		1580	when a child exit is detected.
		1581
		1582	=head3 Watcher-Specific Functions and Data Members
1251		1583
1252	=over 4	1584	=over 4
1253		1585
1254	=item ev_child_init (ev_child *, callback, int pid)	1586	=item ev_child_init (ev_child *, callback, int pid, int trace)
1255		1587
1256	=item ev_child_set (ev_child *, int pid)	1588	=item ev_child_set (ev_child *, int pid, int trace)
1257		1589
1258	Configures the watcher to wait for status changes of process C<pid> (or	1590	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	1591	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	1592	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	1593	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	1594	C<waitpid> documentation). The C<rpid> member contains the pid of the
1263	process causing the status change.	1595	process causing the status change. C<trace> must be either C<0> (only
		1596	activate the watcher when the process terminates) or C<1> (additionally
		1597	activate the watcher when the process is stopped or continued).
1264		1598
1265	=item int pid [read-only]	1599	=item int pid [read-only]
1266		1600
1267	The process id this watcher watches out for, or C<0>, meaning any process id.	1601	The process id this watcher watches out for, or C<0>, meaning any process id.
1268		1602
…		…
1275	The process exit/trace status caused by C<rpid> (see your systems	1609	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1610	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1611
1278	=back	1612	=back
1279		1613
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1614	=head3 Examples
1281		1615
		1616	Example: C<fork()> a new process and install a child handler to wait for
		1617	its completion.
		1618
		1619	ev_child cw;
		1620
1282	static void	1621	static void
1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1622	child_cb (EV_P_ struct ev_child *w, int revents)
1284	{	1623	{
1285	ev_unloop (loop, EVUNLOOP_ALL);	1624	ev_child_stop (EV_A_ w);
		1625	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1286	}	1626	}
1287		1627
1288	struct ev_signal signal_watcher;	1628	pid_t pid = fork ();
1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1629
1290	ev_signal_start (loop, &sigint_cb);	1630	if (pid < 0)
		1631	// error
		1632	else if (pid == 0)
		1633	{
		1634	// the forked child executes here
		1635	exit (1);
		1636	}
		1637	else
		1638	{
		1639	ev_child_init (&cw, child_cb, pid, 0);
		1640	ev_child_start (EV_DEFAULT_ &cw);
		1641	}
1291		1642
1292		1643
1293	=head2 C<ev_stat> - did the file attributes just change?	1644	=head2 C<ev_stat> - did the file attributes just change?
1294		1645
1295	This watches a filesystem path for attribute changes. That is, it calls	1646	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	1647	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.	1648	compared to the last time, invoking the callback if it did.
1298		1649
1299	The path does not need to exist: changing from "path exists" to "path does	1650	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	1651	not exist" is a status change like any other. The condition "path does
…		…
1318	as even with OS-supported change notifications, this can be	1669	as even with OS-supported change notifications, this can be
1319	resource-intensive.	1670	resource-intensive.
1320		1671
1321	At the time of this writing, only the Linux inotify interface is	1672	At the time of this writing, only the Linux inotify interface is
1322	implemented (implementing kqueue support is left as an exercise for the	1673	implemented (implementing kqueue support is left as an exercise for the
		1674	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	1675	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	1676	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	1677	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	1678	but changes are usually detected immediately, and if the file exists there
1327	polling.	1679	will be no polling.
		1680
		1681	=head3 ABI Issues (Largefile Support)
		1682
		1683	Libev by default (unless the user overrides this) uses the default
		1684	compilation environment, which means that on systems with large file
		1685	support disabled by default, you get the 32 bit version of the stat
		1686	structure. When using the library from programs that change the ABI to
		1687	use 64 bit file offsets the programs will fail. In that case you have to
		1688	compile libev with the same flags to get binary compatibility. This is
		1689	obviously the case with any flags that change the ABI, but the problem is
		1690	most noticeably disabled with ev_stat and large file support.
		1691
		1692	The solution for this is to lobby your distribution maker to make large
		1693	file interfaces available by default (as e.g. FreeBSD does) and not
		1694	optional. Libev cannot simply switch on large file support because it has
		1695	to exchange stat structures with application programs compiled using the
		1696	default compilation environment.
		1697
		1698	=head3 Inotify
		1699
		1700	When C<inotify (7)> support has been compiled into libev (generally only
		1701	available on Linux) and present at runtime, it will be used to speed up
		1702	change detection where possible. The inotify descriptor will be created lazily
		1703	when the first C<ev_stat> watcher is being started.
		1704
		1705	Inotify presence does not change the semantics of C<ev_stat> watchers
		1706	except that changes might be detected earlier, and in some cases, to avoid
		1707	making regular C<stat> calls. Even in the presence of inotify support
		1708	there are many cases where libev has to resort to regular C<stat> polling.
		1709
		1710	(There is no support for kqueue, as apparently it cannot be used to
		1711	implement this functionality, due to the requirement of having a file
		1712	descriptor open on the object at all times).
		1713
		1714	=head3 The special problem of stat time resolution
		1715
		1716	The C<stat ()> system call only supports full-second resolution portably, and
		1717	even on systems where the resolution is higher, many file systems still
		1718	only support whole seconds.
		1719
		1720	That means that, if the time is the only thing that changes, you can
		1721	easily miss updates: on the first update, C<ev_stat> detects a change and
		1722	calls your callback, which does something. When there is another update
		1723	within the same second, C<ev_stat> will be unable to detect it as the stat
		1724	data does not change.
		1725
		1726	The solution to this is to delay acting on a change for slightly more
		1727	than a second (or till slightly after the next full second boundary), using
		1728	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1729	ev_timer_again (loop, w)>).
		1730
		1731	The C<.02> offset is added to work around small timing inconsistencies
		1732	of some operating systems (where the second counter of the current time
		1733	might be be delayed. One such system is the Linux kernel, where a call to
		1734	C<gettimeofday> might return a timestamp with a full second later than
		1735	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1736	update file times then there will be a small window where the kernel uses
		1737	the previous second to update file times but libev might already execute
		1738	the timer callback).
		1739
		1740	=head3 Watcher-Specific Functions and Data Members
1328		1741
1329	=over 4	1742	=over 4
1330		1743
1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1744	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1332		1745
…		…
1336	C<path>. The C<interval> is a hint on how quickly a change is expected to	1749	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	1750	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	1751	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.	1752	path for as long as the watcher is active.
1340		1753
1341	The callback will be receive C<EV_STAT> when a change was detected,	1754	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	1755	to the attributes at the time the watcher was started (or the last change
1343	last change was detected).	1756	was detected).
1344		1757
1345	=item ev_stat_stat (ev_stat *)	1758	=item ev_stat_stat (loop, ev_stat *)
1346		1759
1347	Updates the stat buffer immediately with new values. If you change the	1760	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	1761	watched path in your callback, you could call this function to avoid
1349	detecting this change (while introducing a race condition). Can also be	1762	detecting this change (while introducing a race condition if you are not
1350	useful simply to find out the new values.	1763	the only one changing the path). Can also be useful simply to find out the
		1764	new values.
1351		1765
1352	=item ev_statdata attr [read-only]	1766	=item ev_statdata attr [read-only]
1353		1767
1354	The most-recently detected attributes of the file. Although the type is of	1768	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	1769	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	1770	suitable for your system, but you can only rely on the POSIX-standardised
		1771	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.	1772	some error while C<stat>ing the file.
1358		1773
1359	=item ev_statdata prev [read-only]	1774	=item ev_statdata prev [read-only]
1360		1775
1361	The previous attributes of the file. The callback gets invoked whenever	1776	The previous attributes of the file. The callback gets invoked whenever
1362	C<prev> != C<attr>.	1777	C<prev> != C<attr>, or, more precisely, one or more of these members
		1778	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1779	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1363		1780
1364	=item ev_tstamp interval [read-only]	1781	=item ev_tstamp interval [read-only]
1365		1782
1366	The specified interval.	1783	The specified interval.
1367		1784
1368	=item const char *path [read-only]	1785	=item const char *path [read-only]
1369		1786
1370	The filesystem path that is being watched.	1787	The file system path that is being watched.
1371		1788
1372	=back	1789	=back
1373		1790
		1791	=head3 Examples
		1792
1374	Example: Watch C</etc/passwd> for attribute changes.	1793	Example: Watch C</etc/passwd> for attribute changes.
1375		1794
1376	static void	1795	static void
1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1796	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1378	{	1797	{
1379	/* /etc/passwd changed in some way */	1798	/* /etc/passwd changed in some way */
1380	if (w->attr.st_nlink)	1799	if (w->attr.st_nlink)
1381	{	1800	{
1382	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1801	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1383	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1802	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1384	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1803	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1385	}	1804	}
1386	else	1805	else
1387	/* you shalt not abuse printf for puts */	1806	/* you shalt not abuse printf for puts */
1388	puts ("wow, /etc/passwd is not there, expect problems. "	1807	puts ("wow, /etc/passwd is not there, expect problems. "
1389	"if this is windows, they already arrived\n");	1808	"if this is windows, they already arrived\n");
1390	}	1809	}
1391		1810
1392	...	1811	...
1393	ev_stat passwd;	1812	ev_stat passwd;
1394		1813
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1814	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	1815	ev_stat_start (loop, &passwd);
		1816
		1817	Example: Like above, but additionally use a one-second delay so we do not
		1818	miss updates (however, frequent updates will delay processing, too, so
		1819	one might do the work both on C<ev_stat> callback invocation I<and> on
		1820	C<ev_timer> callback invocation).
		1821
		1822	static ev_stat passwd;
		1823	static ev_timer timer;
		1824
		1825	static void
		1826	timer_cb (EV_P_ ev_timer *w, int revents)
		1827	{
		1828	ev_timer_stop (EV_A_ w);
		1829
		1830	/* now it's one second after the most recent passwd change */
		1831	}
		1832
		1833	static void
		1834	stat_cb (EV_P_ ev_stat *w, int revents)
		1835	{
		1836	/* reset the one-second timer */
		1837	ev_timer_again (EV_A_ &timer);
		1838	}
		1839
		1840	...
		1841	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1842	ev_stat_start (loop, &passwd);
		1843	ev_timer_init (&timer, timer_cb, 0., 1.02);
1397		1844
1398		1845
1399	=head2 C<ev_idle> - when you've got nothing better to do...	1846	=head2 C<ev_idle> - when you've got nothing better to do...
1400		1847
1401	Idle watchers trigger events when no other events of the same or higher	1848	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	1862	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	1863	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	1864	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	1865	event loop has handled all outstanding events.
1419		1866
		1867	=head3 Watcher-Specific Functions and Data Members
		1868
1420	=over 4	1869	=over 4
1421		1870
1422	=item ev_idle_init (ev_signal *, callback)	1871	=item ev_idle_init (ev_signal *, callback)
1423		1872
1424	Initialises and configures the idle watcher - it has no parameters of any	1873	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,	1874	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	1875	believe me.
1427		1876
1428	=back	1877	=back
1429		1878
		1879	=head3 Examples
		1880
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1881	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	1882	callback, free it. Also, use no error checking, as usual.
1432		1883
1433	static void	1884	static void
1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1885	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1435	{	1886	{
1436	free (w);	1887	free (w);
1437	// now do something you wanted to do when the program has	1888	// now do something you wanted to do when the program has
1438	// no longer asnything immediate to do.	1889	// no longer anything immediate to do.
1439	}	1890	}
1440		1891
1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1892	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1442	ev_idle_init (idle_watcher, idle_cb);	1893	ev_idle_init (idle_watcher, idle_cb);
1443	ev_idle_start (loop, idle_cb);	1894	ev_idle_start (loop, idle_cb);
1444		1895
1445		1896
1446	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1897	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1447		1898
1448	Prepare and check watchers are usually (but not always) used in tandem:	1899	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1467		1918
1468	This is done by examining in each prepare call which file descriptors need	1919	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	1920	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	1921	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	1922	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	1923	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	1924	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,	1925	callbacks will never actually be called (but must be valid nevertheless,
1475	because you never know, you know?).	1926	because you never know, you know?).
1476		1927
1477	As another example, the Perl Coro module uses these hooks to integrate	1928	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	1932	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	1933	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	1934	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	1935	low-priority coroutines to idle/background tasks).
1485		1936
		1937	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1938	priority, to ensure that they are being run before any other watchers
		1939	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1940	too) should not activate ("feed") events into libev. While libev fully
		1941	supports this, they might get executed before other C<ev_check> watchers
		1942	did their job. As C<ev_check> watchers are often used to embed other
		1943	(non-libev) event loops those other event loops might be in an unusable
		1944	state until their C<ev_check> watcher ran (always remind yourself to
		1945	coexist peacefully with others).
		1946
		1947	=head3 Watcher-Specific Functions and Data Members
		1948
1486	=over 4	1949	=over 4
1487		1950
1488	=item ev_prepare_init (ev_prepare *, callback)	1951	=item ev_prepare_init (ev_prepare *, callback)
1489		1952
1490	=item ev_check_init (ev_check *, callback)	1953	=item ev_check_init (ev_check *, callback)
…		…
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1956	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.	1957	macros, but using them is utterly, utterly and completely pointless.
1495		1958
1496	=back	1959	=back
1497		1960
1498	Example: To include a library such as adns, you would add IO watchers	1961	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	1962
		1963	There are a number of principal ways to embed other event loops or modules
		1964	into libev. Here are some ideas on how to include libadns into libev
		1965	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1966	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1967	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1968	Glib event loop).
		1969
		1970	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	1971	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	1972	is pseudo-code only of course. This requires you to either use a low
		1973	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1974	the callbacks for the IO/timeout watchers might not have been called yet.
1502		1975
1503	static ev_io iow [nfd];	1976	static ev_io iow [nfd];
1504	static ev_timer tw;	1977	static ev_timer tw;
1505		1978
1506	static void	1979	static void
1507	io_cb (ev_loop *loop, ev_io *w, int revents)	1980	io_cb (ev_loop *loop, ev_io *w, int revents)
1508	{	1981	{
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	}	1982	}
1515		1983
1516	// create io watchers for each fd and a timer before blocking	1984	// create io watchers for each fd and a timer before blocking
1517	static void	1985	static void
1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1986	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1519	{	1987	{
1520	int timeout = 3600000;	1988	int timeout = 3600000;
1521	struct pollfd fds [nfd];	1989	struct pollfd fds [nfd];
1522	// actual code will need to loop here and realloc etc.	1990	// actual code will need to loop here and realloc etc.
1523	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1991	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1524		1992
1525	/* the callback is illegal, but won't be called as we stop during check */	1993	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	1994	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	1995	ev_timer_start (loop, &tw);
1528		1996
1529	// create on ev_io per pollfd	1997	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	1998	for (int i = 0; i < nfd; ++i)
1531	{	1999	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	2000	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	2001	((fds [i].events & POLLIN ? EV_READ : 0)
1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2002	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		2003
1536	fds [i].revents = 0;	2004	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	2005	ev_io_start (loop, iow + i);
1539	}	2006	}
1540	}	2007	}
1541		2008
1542	// stop all watchers after blocking	2009	// stop all watchers after blocking
1543	static void	2010	static void
1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2011	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1545	{	2012	{
1546	ev_timer_stop (loop, &tw);	2013	ev_timer_stop (loop, &tw);
1547		2014
1548	for (int i = 0; i < nfd; ++i)	2015	for (int i = 0; i < nfd; ++i)
		2016	{
		2017	// set the relevant poll flags
		2018	// could also call adns_processreadable etc. here
		2019	struct pollfd *fd = fds + i;
		2020	int revents = ev_clear_pending (iow + i);
		2021	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2022	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2023
		2024	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	2025	ev_io_stop (loop, iow + i);
		2026	}
1550		2027
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2028	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1552	}	2029	}
		2030
		2031	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2032	in the prepare watcher and would dispose of the check watcher.
		2033
		2034	Method 3: If the module to be embedded supports explicit event
		2035	notification (libadns does), you can also make use of the actual watcher
		2036	callbacks, and only destroy/create the watchers in the prepare watcher.
		2037
		2038	static void
		2039	timer_cb (EV_P_ ev_timer *w, int revents)
		2040	{
		2041	adns_state ads = (adns_state)w->data;
		2042	update_now (EV_A);
		2043
		2044	adns_processtimeouts (ads, &tv_now);
		2045	}
		2046
		2047	static void
		2048	io_cb (EV_P_ ev_io *w, int revents)
		2049	{
		2050	adns_state ads = (adns_state)w->data;
		2051	update_now (EV_A);
		2052
		2053	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2054	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2055	}
		2056
		2057	// do not ever call adns_afterpoll
		2058
		2059	Method 4: Do not use a prepare or check watcher because the module you
		2060	want to embed is too inflexible to support it. Instead, you can override
		2061	their poll function. The drawback with this solution is that the main
		2062	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2063	this.
		2064
		2065	static gint
		2066	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2067	{
		2068	int got_events = 0;
		2069
		2070	for (n = 0; n < nfds; ++n)
		2071	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2072
		2073	if (timeout >= 0)
		2074	// create/start timer
		2075
		2076	// poll
		2077	ev_loop (EV_A_ 0);
		2078
		2079	// stop timer again
		2080	if (timeout >= 0)
		2081	ev_timer_stop (EV_A_ &to);
		2082
		2083	// stop io watchers again - their callbacks should have set
		2084	for (n = 0; n < nfds; ++n)
		2085	ev_io_stop (EV_A_ iow [n]);
		2086
		2087	return got_events;
		2088	}
1553		2089
1554		2090
1555	=head2 C<ev_embed> - when one backend isn't enough...	2091	=head2 C<ev_embed> - when one backend isn't enough...
1556		2092
1557	This is a rather advanced watcher type that lets you embed one event loop	2093	This is a rather advanced watcher type that lets you embed one event loop
…		…
1599	portable one.	2135	portable one.
1600		2136
1601	So when you want to use this feature you will always have to be prepared	2137	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	2138	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	2139	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:	2140	create it, and if that fails, use the normal loop for everything.
1605		2141
1606	struct ev_loop *loop_hi = ev_default_init (0);	2142	=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		2143
1625	=over 4	2144	=over 4
1626		2145
1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2146	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1628		2147
…		…
1630		2149
1631	Configures the watcher to embed the given loop, which must be	2150	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	2151	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	2152	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,	2153	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).	2154	if you do not want that, you need to temporarily stop the embed watcher).
1636		2155
1637	=item ev_embed_sweep (loop, ev_embed *)	2156	=item ev_embed_sweep (loop, ev_embed *)
1638		2157
1639	Make a single, non-blocking sweep over the embedded loop. This works	2158	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	2159	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.	2160	appropriate way for embedded loops.
1642		2161
1643	=item struct ev_loop *loop [read-only]	2162	=item struct ev_loop *other [read-only]
1644		2163
1645	The embedded event loop.	2164	The embedded event loop.
1646		2165
1647	=back	2166	=back
		2167
		2168	=head3 Examples
		2169
		2170	Example: Try to get an embeddable event loop and embed it into the default
		2171	event loop. If that is not possible, use the default loop. The default
		2172	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2173	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2174	used).
		2175
		2176	struct ev_loop *loop_hi = ev_default_init (0);
		2177	struct ev_loop *loop_lo = 0;
		2178	struct ev_embed embed;
		2179
		2180	// see if there is a chance of getting one that works
		2181	// (remember that a flags value of 0 means autodetection)
		2182	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2183	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2184	: 0;
		2185
		2186	// if we got one, then embed it, otherwise default to loop_hi
		2187	if (loop_lo)
		2188	{
		2189	ev_embed_init (&embed, 0, loop_lo);
		2190	ev_embed_start (loop_hi, &embed);
		2191	}
		2192	else
		2193	loop_lo = loop_hi;
		2194
		2195	Example: Check if kqueue is available but not recommended and create
		2196	a kqueue backend for use with sockets (which usually work with any
		2197	kqueue implementation). Store the kqueue/socket-only event loop in
		2198	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2199
		2200	struct ev_loop *loop = ev_default_init (0);
		2201	struct ev_loop *loop_socket = 0;
		2202	struct ev_embed embed;
		2203
		2204	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2205	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2206	{
		2207	ev_embed_init (&embed, 0, loop_socket);
		2208	ev_embed_start (loop, &embed);
		2209	}
		2210
		2211	if (!loop_socket)
		2212	loop_socket = loop;
		2213
		2214	// now use loop_socket for all sockets, and loop for everything else
1648		2215
1649		2216
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2217	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2218
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2219	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,	2222	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	2223	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	2224	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2225	handlers will be invoked, too, of course.
1659		2226
		2227	=head3 Watcher-Specific Functions and Data Members
		2228
1660	=over 4	2229	=over 4
1661		2230
1662	=item ev_fork_init (ev_signal *, callback)	2231	=item ev_fork_init (ev_signal *, callback)
1663		2232
1664	Initialises and configures the fork watcher - it has no parameters of any	2233	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,	2234	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1666	believe me.	2235	believe me.
		2236
		2237	=back
		2238
		2239
		2240	=head2 C<ev_async> - how to wake up another event loop
		2241
		2242	In general, you cannot use an C<ev_loop> from multiple threads or other
		2243	asynchronous sources such as signal handlers (as opposed to multiple event
		2244	loops - those are of course safe to use in different threads).
		2245
		2246	Sometimes, however, you need to wake up another event loop you do not
		2247	control, for example because it belongs to another thread. This is what
		2248	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2249	can signal it by calling C<ev_async_send>, which is thread- and signal
		2250	safe.
		2251
		2252	This functionality is very similar to C<ev_signal> watchers, as signals,
		2253	too, are asynchronous in nature, and signals, too, will be compressed
		2254	(i.e. the number of callback invocations may be less than the number of
		2255	C<ev_async_sent> calls).
		2256
		2257	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2258	just the default loop.
		2259
		2260	=head3 Queueing
		2261
		2262	C<ev_async> does not support queueing of data in any way. The reason
		2263	is that the author does not know of a simple (or any) algorithm for a
		2264	multiple-writer-single-reader queue that works in all cases and doesn't
		2265	need elaborate support such as pthreads.
		2266
		2267	That means that if you want to queue data, you have to provide your own
		2268	queue. But at least I can tell you would implement locking around your
		2269	queue:
		2270
		2271	=over 4
		2272
		2273	=item queueing from a signal handler context
		2274
		2275	To implement race-free queueing, you simply add to the queue in the signal
		2276	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2277	some fictitious SIGUSR1 handler:
		2278
		2279	static ev_async mysig;
		2280
		2281	static void
		2282	sigusr1_handler (void)
		2283	{
		2284	sometype data;
		2285
		2286	// no locking etc.
		2287	queue_put (data);
		2288	ev_async_send (EV_DEFAULT_ &mysig);
		2289	}
		2290
		2291	static void
		2292	mysig_cb (EV_P_ ev_async *w, int revents)
		2293	{
		2294	sometype data;
		2295	sigset_t block, prev;
		2296
		2297	sigemptyset (&block);
		2298	sigaddset (&block, SIGUSR1);
		2299	sigprocmask (SIG_BLOCK, &block, &prev);
		2300
		2301	while (queue_get (&data))
		2302	process (data);
		2303
		2304	if (sigismember (&prev, SIGUSR1)
		2305	sigprocmask (SIG_UNBLOCK, &block, 0);
		2306	}
		2307
		2308	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2309	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2310	either...).
		2311
		2312	=item queueing from a thread context
		2313
		2314	The strategy for threads is different, as you cannot (easily) block
		2315	threads but you can easily preempt them, so to queue safely you need to
		2316	employ a traditional mutex lock, such as in this pthread example:
		2317
		2318	static ev_async mysig;
		2319	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2320
		2321	static void
		2322	otherthread (void)
		2323	{
		2324	// only need to lock the actual queueing operation
		2325	pthread_mutex_lock (&mymutex);
		2326	queue_put (data);
		2327	pthread_mutex_unlock (&mymutex);
		2328
		2329	ev_async_send (EV_DEFAULT_ &mysig);
		2330	}
		2331
		2332	static void
		2333	mysig_cb (EV_P_ ev_async *w, int revents)
		2334	{
		2335	pthread_mutex_lock (&mymutex);
		2336
		2337	while (queue_get (&data))
		2338	process (data);
		2339
		2340	pthread_mutex_unlock (&mymutex);
		2341	}
		2342
		2343	=back
		2344
		2345
		2346	=head3 Watcher-Specific Functions and Data Members
		2347
		2348	=over 4
		2349
		2350	=item ev_async_init (ev_async *, callback)
		2351
		2352	Initialises and configures the async watcher - it has no parameters of any
		2353	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2354	believe me.
		2355
		2356	=item ev_async_send (loop, ev_async *)
		2357
		2358	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2359	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2360	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2361	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2362	section below on what exactly this means).
		2363
		2364	This call incurs the overhead of a system call only once per loop iteration,
		2365	so while the overhead might be noticeable, it doesn't apply to repeated
		2366	calls to C<ev_async_send>.
		2367
		2368	=item bool = ev_async_pending (ev_async *)
		2369
		2370	Returns a non-zero value when C<ev_async_send> has been called on the
		2371	watcher but the event has not yet been processed (or even noted) by the
		2372	event loop.
		2373
		2374	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2375	the loop iterates next and checks for the watcher to have become active,
		2376	it will reset the flag again. C<ev_async_pending> can be used to very
		2377	quickly check whether invoking the loop might be a good idea.
		2378
		2379	Not that this does I<not> check whether the watcher itself is pending, only
		2380	whether it has been requested to make this watcher pending.
1667		2381
1668	=back	2382	=back
1669		2383
1670		2384
1671	=head1 OTHER FUNCTIONS	2385	=head1 OTHER FUNCTIONS
…		…
1682	or timeout without having to allocate/configure/start/stop/free one or	2396	or timeout without having to allocate/configure/start/stop/free one or
1683	more watchers yourself.	2397	more watchers yourself.
1684		2398
1685	If C<fd> is less than 0, then no I/O watcher will be started and events	2399	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	2400	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1687	C<events> set will be craeted and started.	2401	C<events> set will be created and started.
1688		2402
1689	If C<timeout> is less than 0, then no timeout watcher will be	2403	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	2404	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	2405	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1692	dubious value.	2406	dubious value.
…		…
1694	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2408	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	2409	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>	2410	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1697	value passed to C<ev_once>:	2411	value passed to C<ev_once>:
1698		2412
1699	static void stdin_ready (int revents, void *arg)	2413	static void stdin_ready (int revents, void *arg)
1700	{	2414	{
1701	if (revents & EV_TIMEOUT)	2415	if (revents & EV_TIMEOUT)
1702	/* doh, nothing entered */;	2416	/* doh, nothing entered */;
1703	else if (revents & EV_READ)	2417	else if (revents & EV_READ)
1704	/* stdin might have data for us, joy! */;	2418	/* stdin might have data for us, joy! */;
1705	}	2419	}
1706		2420
1707	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2421	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1708		2422
1709	=item ev_feed_event (ev_loop *, watcher *, int revents)	2423	=item ev_feed_event (ev_loop *, watcher *, int revents)
1710		2424
1711	Feeds the given event set into the event loop, as if the specified event	2425	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	2426	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	2431	Feed an event on the given fd, as if a file descriptor backend detected
1718	the given events it.	2432	the given events it.
1719		2433
1720	=item ev_feed_signal_event (ev_loop *loop, int signum)	2434	=item ev_feed_signal_event (ev_loop *loop, int signum)
1721		2435
1722	Feed an event as if the given signal occured (C<loop> must be the default	2436	Feed an event as if the given signal occurred (C<loop> must be the default
1723	loop!).	2437	loop!).
1724		2438
1725	=back	2439	=back
1726		2440
1727		2441
…		…
1743		2457
1744	=item * Priorities are not currently supported. Initialising priorities	2458	=item * Priorities are not currently supported. Initialising priorities
1745	will fail and all watchers will have the same priority, even though there	2459	will fail and all watchers will have the same priority, even though there
1746	is an ev_pri field.	2460	is an ev_pri field.
1747		2461
		2462	=item * In libevent, the last base created gets the signals, in libev, the
		2463	first base created (== the default loop) gets the signals.
		2464
1748	=item * Other members are not supported.	2465	=item * Other members are not supported.
1749		2466
1750	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2467	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1751	to use the libev header file and library.	2468	to use the libev header file and library.
1752		2469
1753	=back	2470	=back
1754		2471
1755	=head1 C++ SUPPORT	2472	=head1 C++ SUPPORT
1756		2473
1757	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2474	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	2475	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.	2476	the callback model to a model using method callbacks on objects.
1760		2477
1761	To use it,	2478	To use it,
1762		2479
1763	#include <ev++.h>	2480	#include <ev++.h>
1764		2481
1765	This automatically includes F<ev.h> and puts all of its definitions (many	2482	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	2483	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	2484	put into the C<ev> namespace. It should support all the same embedding
1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2485	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1835	your compiler is good :), then the method will be fully inlined into the	2552	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.	2553	thunking function, making it as fast as a direct C callback.
1837		2554
1838	Example: simple class declaration and watcher initialisation	2555	Example: simple class declaration and watcher initialisation
1839		2556
1840	struct myclass	2557	struct myclass
1841	{	2558	{
1842	void io_cb (ev::io &w, int revents) { }	2559	void io_cb (ev::io &w, int revents) { }
1843	}	2560	}
1844		2561
1845	myclass obj;	2562	myclass obj;
1846	ev::io iow;	2563	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2564	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2565
1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2566	=item w->set<function> (void *data = 0)
1850		2567
1851	Also sets a callback, but uses a static method or plain function as	2568	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	2569	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2570	C<data> member and is free for you to use.
1854		2571
		2572	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2573
1855	See the method-C<set> above for more details.	2574	See the method-C<set> above for more details.
		2575
		2576	Example:
		2577
		2578	static void io_cb (ev::io &w, int revents) { }
		2579	iow.set <io_cb> ();
1856		2580
1857	=item w->set (struct ev_loop *)	2581	=item w->set (struct ev_loop *)
1858		2582
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2583	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).	2584	do this when the watcher is inactive (and not pending either).
1861		2585
1862	=item w->set ([args])	2586	=item w->set ([arguments])
1863		2587
1864	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2588	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	2589	called at least once. Unlike the C counterpart, an active watcher gets
1866	automatically stopped and restarted when reconfiguring it with this	2590	automatically stopped and restarted when reconfiguring it with this
1867	method.	2591	method.
1868		2592
1869	=item w->start ()	2593	=item w->start ()
…		…
1873		2597
1874	=item w->stop ()	2598	=item w->stop ()
1875		2599
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2600	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2601
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2602	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2603
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2604	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2605	C<ev_TYPE_again> function.
1882		2606
1883	=item w->sweep () C<ev::embed> only	2607	=item w->sweep () (C<ev::embed> only)
1884		2608
1885	Invokes C<ev_embed_sweep>.	2609	Invokes C<ev_embed_sweep>.
1886		2610
1887	=item w->update () C<ev::stat> only	2611	=item w->update () (C<ev::stat> only)
1888		2612
1889	Invokes C<ev_stat_stat>.	2613	Invokes C<ev_stat_stat>.
1890		2614
1891	=back	2615	=back
1892		2616
1893	=back	2617	=back
1894		2618
1895	Example: Define a class with an IO and idle watcher, start one of them in	2619	Example: Define a class with an IO and idle watcher, start one of them in
1896	the constructor.	2620	the constructor.
1897		2621
1898	class myclass	2622	class myclass
1899	{	2623	{
1900	ev_io io; void io_cb (ev::io &w, int revents);	2624	ev::io io; void io_cb (ev::io &w, int revents);
1901	ev_idle idle void idle_cb (ev::idle &w, int revents);	2625	ev:idle idle void idle_cb (ev::idle &w, int revents);
1902		2626
1903	myclass ();	2627	myclass (int fd)
1904	}	2628	{
1905
1906	myclass::myclass (int fd)
1907	{
1908	io .set <myclass, &myclass::io_cb > (this);	2629	io .set <myclass, &myclass::io_cb > (this);
1909	idle.set <myclass, &myclass::idle_cb> (this);	2630	idle.set <myclass, &myclass::idle_cb> (this);
1910		2631
1911	io.start (fd, ev::READ);	2632	io.start (fd, ev::READ);
		2633	}
1912	}	2634	};
		2635
		2636
		2637	=head1 OTHER LANGUAGE BINDINGS
		2638
		2639	Libev does not offer other language bindings itself, but bindings for a
		2640	number of languages exist in the form of third-party packages. If you know
		2641	any interesting language binding in addition to the ones listed here, drop
		2642	me a note.
		2643
		2644	=over 4
		2645
		2646	=item Perl
		2647
		2648	The EV module implements the full libev API and is actually used to test
		2649	libev. EV is developed together with libev. Apart from the EV core module,
		2650	there are additional modules that implement libev-compatible interfaces
		2651	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2652	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2653
		2654	It can be found and installed via CPAN, its homepage is at
		2655	L<http://software.schmorp.de/pkg/EV>.
		2656
		2657	=item Python
		2658
		2659	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2660	seems to be quite complete and well-documented. Note, however, that the
		2661	patch they require for libev is outright dangerous as it breaks the ABI
		2662	for everybody else, and therefore, should never be applied in an installed
		2663	libev (if python requires an incompatible ABI then it needs to embed
		2664	libev).
		2665
		2666	=item Ruby
		2667
		2668	Tony Arcieri has written a ruby extension that offers access to a subset
		2669	of the libev API and adds file handle abstractions, asynchronous DNS and
		2670	more on top of it. It can be found via gem servers. Its homepage is at
		2671	L<http://rev.rubyforge.org/>.
		2672
		2673	=item D
		2674
		2675	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2676	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2677
		2678	=back
1913		2679
1914		2680
1915	=head1 MACRO MAGIC	2681	=head1 MACRO MAGIC
1916		2682
1917	Libev can be compiled with a variety of options, the most fundemantal is	2683	Libev can be compiled with a variety of options, the most fundamental
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2684	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2685	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2686
1921	To make it easier to write programs that cope with either variant, the	2687	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2688	following macros are defined:
1923		2689
1924	=over 4	2690	=over 4
…		…
1927		2693
1928	This provides the loop I<argument> for functions, if one is required ("ev	2694	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,	2695	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:	2696	C<EV_A_> is used when other arguments are following. Example:
1931		2697
1932	ev_unref (EV_A);	2698	ev_unref (EV_A);
1933	ev_timer_add (EV_A_ watcher);	2699	ev_timer_add (EV_A_ watcher);
1934	ev_loop (EV_A_ 0);	2700	ev_loop (EV_A_ 0);
1935		2701
1936	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2702	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1937	which is often provided by the following macro.	2703	which is often provided by the following macro.
1938		2704
1939	=item C<EV_P>, C<EV_P_>	2705	=item C<EV_P>, C<EV_P_>
1940		2706
1941	This provides the loop I<parameter> for functions, if one is required ("ev	2707	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,	2708	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:	2709	C<EV_P_> is used when other parameters are following. Example:
1944		2710
1945	// this is how ev_unref is being declared	2711	// this is how ev_unref is being declared
1946	static void ev_unref (EV_P);	2712	static void ev_unref (EV_P);
1947		2713
1948	// this is how you can declare your typical callback	2714	// this is how you can declare your typical callback
1949	static void cb (EV_P_ ev_timer *w, int revents)	2715	static void cb (EV_P_ ev_timer *w, int revents)
1950		2716
1951	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2717	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1952	suitable for use with C<EV_A>.	2718	suitable for use with C<EV_A>.
1953		2719
1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2720	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1955		2721
1956	Similar to the other two macros, this gives you the value of the default	2722	Similar to the other two macros, this gives you the value of the default
1957	loop, if multiple loops are supported ("ev loop default").	2723	loop, if multiple loops are supported ("ev loop default").
		2724
		2725	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2726
		2727	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2728	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2729	is undefined when the default loop has not been initialised by a previous
		2730	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2731
		2732	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2733	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1958		2734
1959	=back	2735	=back
1960		2736
1961	Example: Declare and initialise a check watcher, utilising the above	2737	Example: Declare and initialise a check watcher, utilising the above
1962	macros so it will work regardless of whether multiple loops are supported	2738	macros so it will work regardless of whether multiple loops are supported
1963	or not.	2739	or not.
1964		2740
1965	static void	2741	static void
1966	check_cb (EV_P_ ev_timer *w, int revents)	2742	check_cb (EV_P_ ev_timer *w, int revents)
1967	{	2743	{
1968	ev_check_stop (EV_A_ w);	2744	ev_check_stop (EV_A_ w);
1969	}	2745	}
1970		2746
1971	ev_check check;	2747	ev_check check;
1972	ev_check_init (&check, check_cb);	2748	ev_check_init (&check, check_cb);
1973	ev_check_start (EV_DEFAULT_ &check);	2749	ev_check_start (EV_DEFAULT_ &check);
1974	ev_loop (EV_DEFAULT_ 0);	2750	ev_loop (EV_DEFAULT_ 0);
1975		2751
1976	=head1 EMBEDDING	2752	=head1 EMBEDDING
1977		2753
1978	Libev can (and often is) directly embedded into host	2754	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	2755	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2756	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	2757	and rxvt-unicode.
1982		2758
1983	The goal is to enable you to just copy the neecssary files into your	2759	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	2760	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	2761	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	2762	libev somewhere in your source tree).
1987		2763
1988	=head2 FILESETS	2764	=head2 FILESETS
1989		2765
1990	Depending on what features you need you need to include one or more sets of files	2766	Depending on what features you need you need to include one or more sets of files
1991	in your app.	2767	in your application.
1992		2768
1993	=head3 CORE EVENT LOOP	2769	=head3 CORE EVENT LOOP
1994		2770
1995	To include only the libev core (all the C<ev_*> functions), with manual	2771	To include only the libev core (all the C<ev_*> functions), with manual
1996	configuration (no autoconf):	2772	configuration (no autoconf):
1997		2773
1998	#define EV_STANDALONE 1	2774	#define EV_STANDALONE 1
1999	#include "ev.c"	2775	#include "ev.c"
2000		2776
2001	This will automatically include F<ev.h>, too, and should be done in a	2777	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	2778	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	2779	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	2780	done by writing a wrapper around F<ev.h> that you can include instead and
2005	where you can put other configuration options):	2781	where you can put other configuration options):
2006		2782
2007	#define EV_STANDALONE 1	2783	#define EV_STANDALONE 1
2008	#include "ev.h"	2784	#include "ev.h"
2009		2785
2010	Both header files and implementation files can be compiled with a C++	2786	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	2787	compiler (at least, thats a stated goal, and breakage will be treated
2012	as a bug).	2788	as a bug).
2013		2789
2014	You need the following files in your source tree, or in a directory	2790	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):	2791	in your include path (e.g. in libev/ when using -Ilibev):
2016		2792
2017	ev.h	2793	ev.h
2018	ev.c	2794	ev.c
2019	ev_vars.h	2795	ev_vars.h
2020	ev_wrap.h	2796	ev_wrap.h
2021		2797
2022	ev_win32.c required on win32 platforms only	2798	ev_win32.c required on win32 platforms only
2023		2799
2024	ev_select.c only when select backend is enabled (which is enabled by default)	2800	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)	2801	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)	2802	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)	2803	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)	2804	ev_port.c only when the solaris port backend is enabled (disabled by default)
2029		2805
2030	F<ev.c> includes the backend files directly when enabled, so you only need	2806	F<ev.c> includes the backend files directly when enabled, so you only need
2031	to compile this single file.	2807	to compile this single file.
2032		2808
2033	=head3 LIBEVENT COMPATIBILITY API	2809	=head3 LIBEVENT COMPATIBILITY API
2034		2810
2035	To include the libevent compatibility API, also include:	2811	To include the libevent compatibility API, also include:
2036		2812
2037	#include "event.c"	2813	#include "event.c"
2038		2814
2039	in the file including F<ev.c>, and:	2815	in the file including F<ev.c>, and:
2040		2816
2041	#include "event.h"	2817	#include "event.h"
2042		2818
2043	in the files that want to use the libevent API. This also includes F<ev.h>.	2819	in the files that want to use the libevent API. This also includes F<ev.h>.
2044		2820
2045	You need the following additional files for this:	2821	You need the following additional files for this:
2046		2822
2047	event.h	2823	event.h
2048	event.c	2824	event.c
2049		2825
2050	=head3 AUTOCONF SUPPORT	2826	=head3 AUTOCONF SUPPORT
2051		2827
2052	Instead of using C<EV_STANDALONE=1> and providing your config in	2828	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	2829	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	2830	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2055	include F<config.h> and configure itself accordingly.	2831	include F<config.h> and configure itself accordingly.
2056		2832
2057	For this of course you need the m4 file:	2833	For this of course you need the m4 file:
2058		2834
2059	libev.m4	2835	libev.m4
2060		2836
2061	=head2 PREPROCESSOR SYMBOLS/MACROS	2837	=head2 PREPROCESSOR SYMBOLS/MACROS
2062		2838
2063	Libev can be configured via a variety of preprocessor symbols you have to define	2839	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	2840	define before including any of its files. The default in the absence of
2065	and only include the select backend.	2841	autoconf is noted for every option.
2066		2842
2067	=over 4	2843	=over 4
2068		2844
2069	=item EV_STANDALONE	2845	=item EV_STANDALONE
2070		2846
…		…
2075	F<event.h> that are not directly supported by the libev core alone.	2851	F<event.h> that are not directly supported by the libev core alone.
2076		2852
2077	=item EV_USE_MONOTONIC	2853	=item EV_USE_MONOTONIC
2078		2854
2079	If defined to be C<1>, libev will try to detect the availability of the	2855	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	2856	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	2857	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	2858	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	2859	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>	2860	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	2861	function is hiding in (often F<-lrt>).
2086		2862
2087	=item EV_USE_REALTIME	2863	=item EV_USE_REALTIME
2088		2864
2089	If defined to be C<1>, libev will try to detect the availability of the	2865	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	2866	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	2867	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	2868	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	2869	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	2870	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2871
		2872	=item EV_USE_NANOSLEEP
		2873
		2874	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2875	and will use it for delays. Otherwise it will use C<select ()>.
		2876
		2877	=item EV_USE_EVENTFD
		2878
		2879	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2880	available and will probe for kernel support at runtime. This will improve
		2881	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2882	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2883	2.7 or newer, otherwise disabled.
2095		2884
2096	=item EV_USE_SELECT	2885	=item EV_USE_SELECT
2097		2886
2098	If undefined or defined to be C<1>, libev will compile in support for the	2887	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	2888	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	2889	other method takes over, select will be it. Otherwise the select backend
2101	will not be compiled in.	2890	will not be compiled in.
2102		2891
2103	=item EV_SELECT_USE_FD_SET	2892	=item EV_SELECT_USE_FD_SET
2104		2893
2105	If defined to C<1>, then the select backend will use the system C<fd_set>	2894	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	2895	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	2896	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	2897	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	2898	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	2899	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2111	influence the size of the C<fd_set> used.	2900	influence the size of the C<fd_set> used.
2112		2901
…		…
2118	be used is the winsock select). This means that it will call	2907	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,	2908	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	2909	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	2910	on win32. Should not be defined on non-win32 platforms.
2122		2911
		2912	=item EV_FD_TO_WIN32_HANDLE
		2913
		2914	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2915	file descriptors to socket handles. When not defining this symbol (the
		2916	default), then libev will call C<_get_osfhandle>, which is usually
		2917	correct. In some cases, programs use their own file descriptor management,
		2918	in which case they can provide this function to map fds to socket handles.
		2919
2123	=item EV_USE_POLL	2920	=item EV_USE_POLL
2124		2921
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2922	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	2923	backend. Otherwise it will be enabled on non-win32 platforms. It
2127	takes precedence over select.	2924	takes precedence over select.
2128		2925
2129	=item EV_USE_EPOLL	2926	=item EV_USE_EPOLL
2130		2927
2131	If defined to be C<1>, libev will compile in support for the Linux	2928	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,	2929	C<epoll>(7) backend. Its availability will be detected at runtime,
2133	otherwise another method will be used as fallback. This is the	2930	otherwise another method will be used as fallback. This is the preferred
2134	preferred backend for GNU/Linux systems.	2931	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2932	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2135		2933
2136	=item EV_USE_KQUEUE	2934	=item EV_USE_KQUEUE
2137		2935
2138	If defined to be C<1>, libev will compile in support for the BSD style	2936	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,	2937	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	2950	otherwise another method will be used as fallback. This is the preferred
2153	backend for Solaris 10 systems.	2951	backend for Solaris 10 systems.
2154		2952
2155	=item EV_USE_DEVPOLL	2953	=item EV_USE_DEVPOLL
2156		2954
2157	reserved for future expansion, works like the USE symbols above.	2955	Reserved for future expansion, works like the USE symbols above.
2158		2956
2159	=item EV_USE_INOTIFY	2957	=item EV_USE_INOTIFY
2160		2958
2161	If defined to be C<1>, libev will compile in support for the Linux inotify	2959	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	2960	interface to speed up C<ev_stat> watchers. Its actual availability will
2163	be detected at runtime.	2961	be detected at runtime. If undefined, it will be enabled if the headers
		2962	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2963
		2964	=item EV_ATOMIC_T
		2965
		2966	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2967	access is atomic with respect to other threads or signal contexts. No such
		2968	type is easily found in the C language, so you can provide your own type
		2969	that you know is safe for your purposes. It is used both for signal handler "locking"
		2970	as well as for signal and thread safety in C<ev_async> watchers.
		2971
		2972	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2973	(from F<signal.h>), which is usually good enough on most platforms.
2164		2974
2165	=item EV_H	2975	=item EV_H
2166		2976
2167	The name of the F<ev.h> header file used to include it. The default if	2977	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	2978	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.	2979	used to virtually rename the F<ev.h> header file in case of conflicts.
2170		2980
2171	=item EV_CONFIG_H	2981	=item EV_CONFIG_H
2172		2982
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2983	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	2984	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	2985	C<EV_H>, above.
2176		2986
2177	=item EV_EVENT_H	2987	=item EV_EVENT_H
2178		2988
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2989	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.	2990	of how the F<event.h> header can be found, the default is C<"event.h">.
2181		2991
2182	=item EV_PROTOTYPES	2992	=item EV_PROTOTYPES
2183		2993
2184	If defined to be C<0>, then F<ev.h> will not define any function	2994	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	2995	prototypes, but still define all the structs and other symbols. This is
…		…
2206	When doing priority-based operations, libev usually has to linearly search	3016	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	3017	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	3018	and time, so using the defaults of five priorities (-2 .. +2) is usually
2209	fine.	3019	fine.
2210		3020
2211	If your embedding app does not need any priorities, defining these both to	3021	If your embedding application does not need any priorities, defining these both to
2212	C<0> will save some memory and cpu.	3022	C<0> will save some memory and CPU.
2213		3023
2214	=item EV_PERIODIC_ENABLE	3024	=item EV_PERIODIC_ENABLE
2215		3025
2216	If undefined or defined to be C<1>, then periodic timers are supported. If	3026	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	3027	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2236	=item EV_FORK_ENABLE	3046	=item EV_FORK_ENABLE
2237		3047
2238	If undefined or defined to be C<1>, then fork watchers are supported. If	3048	If undefined or defined to be C<1>, then fork watchers are supported. If
2239	defined to be C<0>, then they are not.	3049	defined to be C<0>, then they are not.
2240		3050
		3051	=item EV_ASYNC_ENABLE
		3052
		3053	If undefined or defined to be C<1>, then async watchers are supported. If
		3054	defined to be C<0>, then they are not.
		3055
2241	=item EV_MINIMAL	3056	=item EV_MINIMAL
2242		3057
2243	If you need to shave off some kilobytes of code at the expense of some	3058	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	3059	speed, define this symbol to C<1>. Currently this is used to override some
2245	some inlining decisions, saves roughly 30% codesize of amd64.	3060	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3061	much smaller 2-heap for timer management over the default 4-heap.
2246		3062
2247	=item EV_PID_HASHSIZE	3063	=item EV_PID_HASHSIZE
2248		3064
2249	C<ev_child> watchers use a small hash table to distribute workload by	3065	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	3066	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	3067	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).	3068	increase this value (I<must> be a power of two).
2253		3069
2254	=item EV_INOTIFY_HASHSIZE	3070	=item EV_INOTIFY_HASHSIZE
2255		3071
2256	C<ev_staz> watchers use a small hash table to distribute workload by	3072	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>),	3073	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>	3074	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	3075	watchers you might want to increase this value (I<must> be a power of
2260	two).	3076	two).
2261		3077
		3078	=item EV_USE_4HEAP
		3079
		3080	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3081	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3082	to C<1>. The 4-heap uses more complicated (longer) code but has
		3083	noticeably faster performance with many (thousands) of watchers.
		3084
		3085	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3086	(disabled).
		3087
		3088	=item EV_HEAP_CACHE_AT
		3089
		3090	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3091	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3092	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3093	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3094	but avoids random read accesses on heap changes. This improves performance
		3095	noticeably with with many (hundreds) of watchers.
		3096
		3097	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3098	(disabled).
		3099
		3100	=item EV_VERIFY
		3101
		3102	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3103	be done: If set to C<0>, no internal verification code will be compiled
		3104	in. If set to C<1>, then verification code will be compiled in, but not
		3105	called. If set to C<2>, then the internal verification code will be
		3106	called once per loop, which can slow down libev. If set to C<3>, then the
		3107	verification code will be called very frequently, which will slow down
		3108	libev considerably.
		3109
		3110	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3111	C<0.>
		3112
2262	=item EV_COMMON	3113	=item EV_COMMON
2263		3114
2264	By default, all watchers have a C<void *data> member. By redefining	3115	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	3116	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,	3117	members. You have to define it each time you include one of the files,
2267	though, and it must be identical each time.	3118	though, and it must be identical each time.
2268		3119
2269	For example, the perl EV module uses something like this:	3120	For example, the perl EV module uses something like this:
2270		3121
2271	#define EV_COMMON \	3122	#define EV_COMMON \
2272	SV *self; /* contains this struct */ \	3123	SV *self; /* contains this struct */ \
2273	SV *cb_sv, *fh /* note no trailing ";" */	3124	SV *cb_sv, *fh /* note no trailing ";" */
2274		3125
2275	=item EV_CB_DECLARE (type)	3126	=item EV_CB_DECLARE (type)
2276		3127
2277	=item EV_CB_INVOKE (watcher, revents)	3128	=item EV_CB_INVOKE (watcher, revents)
2278		3129
2279	=item ev_set_cb (ev, cb)	3130	=item ev_set_cb (ev, cb)
2280		3131
2281	Can be used to change the callback member declaration in each watcher,	3132	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	3133	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	3134	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	3135	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	3136	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++.	3137	method calls instead of plain function calls in C++.
		3138
		3139	=head2 EXPORTED API SYMBOLS
		3140
		3141	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3142	exported symbols, you can use the provided F<Symbol.*> files which list
		3143	all public symbols, one per line:
		3144
		3145	Symbols.ev for libev proper
		3146	Symbols.event for the libevent emulation
		3147
		3148	This can also be used to rename all public symbols to avoid clashes with
		3149	multiple versions of libev linked together (which is obviously bad in
		3150	itself, but sometimes it is inconvenient to avoid this).
		3151
		3152	A sed command like this will create wrapper C<#define>'s that you need to
		3153	include before including F<ev.h>:
		3154
		3155	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3156
		3157	This would create a file F<wrap.h> which essentially looks like this:
		3158
		3159	#define ev_backend myprefix_ev_backend
		3160	#define ev_check_start myprefix_ev_check_start
		3161	#define ev_check_stop myprefix_ev_check_stop
		3162	...
2287		3163
2288	=head2 EXAMPLES	3164	=head2 EXAMPLES
2289		3165
2290	For a real-world example of a program the includes libev	3166	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	3167	verbatim, you can have a look at the EV perl module
…		…
2296	file.	3172	file.
2297		3173
2298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3174	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:	3175	that everybody includes and which overrides some configure choices:
2300		3176
2301	#define EV_MINIMAL 1	3177	#define EV_MINIMAL 1
2302	#define EV_USE_POLL 0	3178	#define EV_USE_POLL 0
2303	#define EV_MULTIPLICITY 0	3179	#define EV_MULTIPLICITY 0
2304	#define EV_PERIODIC_ENABLE 0	3180	#define EV_PERIODIC_ENABLE 0
2305	#define EV_STAT_ENABLE 0	3181	#define EV_STAT_ENABLE 0
2306	#define EV_FORK_ENABLE 0	3182	#define EV_FORK_ENABLE 0
2307	#define EV_CONFIG_H <config.h>	3183	#define EV_CONFIG_H <config.h>
2308	#define EV_MINPRI 0	3184	#define EV_MINPRI 0
2309	#define EV_MAXPRI 0	3185	#define EV_MAXPRI 0
2310		3186
2311	#include "ev++.h"	3187	#include "ev++.h"
2312		3188
2313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3189	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2314		3190
2315	#include "ev_cpp.h"	3191	#include "ev_cpp.h"
2316	#include "ev.c"	3192	#include "ev.c"
		3193
		3194
		3195	=head1 THREADS AND COROUTINES
		3196
		3197	=head2 THREADS
		3198
		3199	Libev itself is completely thread-safe, but it uses no locking. This
		3200	means that you can use as many loops as you want in parallel, as long as
		3201	only one thread ever calls into one libev function with the same loop
		3202	parameter.
		3203
		3204	Or put differently: calls with different loop parameters can be done in
		3205	parallel from multiple threads, calls with the same loop parameter must be
		3206	done serially (but can be done from different threads, as long as only one
		3207	thread ever is inside a call at any point in time, e.g. by using a mutex
		3208	per loop).
		3209
		3210	If you want to know which design (one loop, locking, or multiple loops
		3211	without or something else still) is best for your problem, then I cannot
		3212	help you. I can give some generic advice however:
		3213
		3214	=over 4
		3215
		3216	=item * most applications have a main thread: use the default libev loop
		3217	in that thread, or create a separate thread running only the default loop.
		3218
		3219	This helps integrating other libraries or software modules that use libev
		3220	themselves and don't care/know about threading.
		3221
		3222	=item * one loop per thread is usually a good model.
		3223
		3224	Doing this is almost never wrong, sometimes a better-performance model
		3225	exists, but it is always a good start.
		3226
		3227	=item * other models exist, such as the leader/follower pattern, where one
		3228	loop is handed through multiple threads in a kind of round-robin fashion.
		3229
		3230	Choosing a model is hard - look around, learn, know that usually you can do
		3231	better than you currently do :-)
		3232
		3233	=item * often you need to talk to some other thread which blocks in the
		3234	event loop - C<ev_async> watchers can be used to wake them up from other
		3235	threads safely (or from signal contexts...).
		3236
		3237	=back
		3238
		3239	=head2 COROUTINES
		3240
		3241	Libev is much more accommodating to coroutines ("cooperative threads"):
		3242	libev fully supports nesting calls to it's functions from different
		3243	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3244	different coroutines and switch freely between both coroutines running the
		3245	loop, as long as you don't confuse yourself). The only exception is that
		3246	you must not do this from C<ev_periodic> reschedule callbacks.
		3247
		3248	Care has been invested into making sure that libev does not keep local
		3249	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3250	switches.
2317		3251
2318		3252
2319	=head1 COMPLEXITIES	3253	=head1 COMPLEXITIES
2320		3254
2321	In this section the complexities of (many of) the algorithms used inside	3255	In this section the complexities of (many of) the algorithms used inside
…		…
2332		3266
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3267	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		3268
2335	This means that, when you have a watcher that triggers in one hour and	3269	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	3270	there are 100 watchers that would trigger before that then inserting will
2337	have to skip those 100 watchers.	3271	have to skip roughly seven (C<ld 100>) of these watchers.
2338		3272
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3273	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		3274
2341	That means that for changing a timer costs less than removing/adding them	3275	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.	3276	as only the relative motion in the event queue has to be paid for.
2343		3277
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3278	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2345		3279
2346	These just add the watcher into an array or at the head of a list.	3280	These just add the watcher into an array or at the head of a list.
		3281
2347	=item Stopping check/prepare/idle watchers: O(1)	3282	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2348		3283
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		3285
2351	These watchers are stored in lists then need to be walked to find the	3286	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	3287	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	3288	have many watchers waiting for the same fd or signal).
2354		3289
2355	=item Finding the next timer per loop iteration: O(1)	3290	=item Finding the next timer in each loop iteration: O(1)
		3291
		3292	By virtue of using a binary or 4-heap, the next timer is always found at a
		3293	fixed position in the storage array.
2356		3294
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3295	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		3296
2359	A change means an I/O watcher gets started or stopped, which requires	3297	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	3298	libev to recalculate its status (and possibly tell the kernel, depending
		3299	on backend and whether C<ev_io_set> was used).
2361		3300
2362	=item Activating one watcher: O(1)	3301	=item Activating one watcher (putting it into the pending state): O(1)
2363		3302
2364	=item Priority handling: O(number_of_priorities)	3303	=item Priority handling: O(number_of_priorities)
2365		3304
2366	Priorities are implemented by allocating some space for each	3305	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	3306	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	3307	linearly search all the priorities, but starting/stopping and activating
		3308	watchers becomes O(1) w.r.t. priority handling.
		3309
		3310	=item Sending an ev_async: O(1)
		3311
		3312	=item Processing ev_async_send: O(number_of_async_watchers)
		3313
		3314	=item Processing signals: O(max_signal_number)
		3315
		3316	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3317	calls in the current loop iteration. Checking for async and signal events
		3318	involves iterating over all running async watchers or all signal numbers.
2369		3319
2370	=back	3320	=back
2371		3321
2372		3322
		3323	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3324
		3325	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3326	requires, and its I/O model is fundamentally incompatible with the POSIX
		3327	model. Libev still offers limited functionality on this platform in
		3328	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3329	descriptors. This only applies when using Win32 natively, not when using
		3330	e.g. cygwin.
		3331
		3332	Lifting these limitations would basically require the full
		3333	re-implementation of the I/O system. If you are into these kinds of
		3334	things, then note that glib does exactly that for you in a very portable
		3335	way (note also that glib is the slowest event library known to man).
		3336
		3337	There is no supported compilation method available on windows except
		3338	embedding it into other applications.
		3339
		3340	Not a libev limitation but worth mentioning: windows apparently doesn't
		3341	accept large writes: instead of resulting in a partial write, windows will
		3342	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3343	so make sure you only write small amounts into your sockets (less than a
		3344	megabyte seems safe, but thsi apparently depends on the amount of memory
		3345	available).
		3346
		3347	Due to the many, low, and arbitrary limits on the win32 platform and
		3348	the abysmal performance of winsockets, using a large number of sockets
		3349	is not recommended (and not reasonable). If your program needs to use
		3350	more than a hundred or so sockets, then likely it needs to use a totally
		3351	different implementation for windows, as libev offers the POSIX readiness
		3352	notification model, which cannot be implemented efficiently on windows
		3353	(Microsoft monopoly games).
		3354
		3355	A typical way to use libev under windows is to embed it (see the embedding
		3356	section for details) and use the following F<evwrap.h> header file instead
		3357	of F<ev.h>:
		3358
		3359	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3360	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3361
		3362	#include "ev.h"
		3363
		3364	And compile the following F<evwrap.c> file into your project (make sure
		3365	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3366
		3367	#include "evwrap.h"
		3368	#include "ev.c"
		3369
		3370	=over 4
		3371
		3372	=item The winsocket select function
		3373
		3374	The winsocket C<select> function doesn't follow POSIX in that it
		3375	requires socket I<handles> and not socket I<file descriptors> (it is
		3376	also extremely buggy). This makes select very inefficient, and also
		3377	requires a mapping from file descriptors to socket handles (the Microsoft
		3378	C runtime provides the function C<_open_osfhandle> for this). See the
		3379	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3380	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3381
		3382	The configuration for a "naked" win32 using the Microsoft runtime
		3383	libraries and raw winsocket select is:
		3384
		3385	#define EV_USE_SELECT 1
		3386	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3387
		3388	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3389	complexity in the O(n²) range when using win32.
		3390
		3391	=item Limited number of file descriptors
		3392
		3393	Windows has numerous arbitrary (and low) limits on things.
		3394
		3395	Early versions of winsocket's select only supported waiting for a maximum
		3396	of C<64> handles (probably owning to the fact that all windows kernels
		3397	can only wait for C<64> things at the same time internally; Microsoft
		3398	recommends spawning a chain of threads and wait for 63 handles and the
		3399	previous thread in each. Great).
		3400
		3401	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3402	to some high number (e.g. C<2048>) before compiling the winsocket select
		3403	call (which might be in libev or elsewhere, for example, perl does its own
		3404	select emulation on windows).
		3405
		3406	Another limit is the number of file descriptors in the Microsoft runtime
		3407	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3408	or something like this inside Microsoft). You can increase this by calling
		3409	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3410	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3411	libraries.
		3412
		3413	This might get you to about C<512> or C<2048> sockets (depending on
		3414	windows version and/or the phase of the moon). To get more, you need to
		3415	wrap all I/O functions and provide your own fd management, but the cost of
		3416	calling select (O(n²)) will likely make this unworkable.
		3417
		3418	=back
		3419
		3420
		3421	=head1 PORTABILITY REQUIREMENTS
		3422
		3423	In addition to a working ISO-C implementation, libev relies on a few
		3424	additional extensions:
		3425
		3426	=over 4
		3427
		3428	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3429	calling conventions regardless of C<ev_watcher_type *>.
		3430
		3431	Libev assumes not only that all watcher pointers have the same internal
		3432	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3433	assumes that the same (machine) code can be used to call any watcher
		3434	callback: The watcher callbacks have different type signatures, but libev
		3435	calls them using an C<ev_watcher *> internally.
		3436
		3437	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3438
		3439	The type C<sig_atomic_t volatile> (or whatever is defined as
		3440	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3441	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3442	believed to be sufficiently portable.
		3443
		3444	=item C<sigprocmask> must work in a threaded environment
		3445
		3446	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3447	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3448	pthread implementations will either allow C<sigprocmask> in the "main
		3449	thread" or will block signals process-wide, both behaviours would
		3450	be compatible with libev. Interaction between C<sigprocmask> and
		3451	C<pthread_sigmask> could complicate things, however.
		3452
		3453	The most portable way to handle signals is to block signals in all threads
		3454	except the initial one, and run the default loop in the initial thread as
		3455	well.
		3456
		3457	=item C<long> must be large enough for common memory allocation sizes
		3458
		3459	To improve portability and simplify using libev, libev uses C<long>
		3460	internally instead of C<size_t> when allocating its data structures. On
		3461	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3462	is still at least 31 bits everywhere, which is enough for hundreds of
		3463	millions of watchers.
		3464
		3465	=item C<double> must hold a time value in seconds with enough accuracy
		3466
		3467	The type C<double> is used to represent timestamps. It is required to
		3468	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3469	enough for at least into the year 4000. This requirement is fulfilled by
		3470	implementations implementing IEEE 754 (basically all existing ones).
		3471
		3472	=back
		3473
		3474	If you know of other additional requirements drop me a note.
		3475
		3476
		3477	=head1 COMPILER WARNINGS
		3478
		3479	Depending on your compiler and compiler settings, you might get no or a
		3480	lot of warnings when compiling libev code. Some people are apparently
		3481	scared by this.
		3482
		3483	However, these are unavoidable for many reasons. For one, each compiler
		3484	has different warnings, and each user has different tastes regarding
		3485	warning options. "Warn-free" code therefore cannot be a goal except when
		3486	targeting a specific compiler and compiler-version.
		3487
		3488	Another reason is that some compiler warnings require elaborate
		3489	workarounds, or other changes to the code that make it less clear and less
		3490	maintainable.
		3491
		3492	And of course, some compiler warnings are just plain stupid, or simply
		3493	wrong (because they don't actually warn about the condition their message
		3494	seems to warn about).
		3495
		3496	While libev is written to generate as few warnings as possible,
		3497	"warn-free" code is not a goal, and it is recommended not to build libev
		3498	with any compiler warnings enabled unless you are prepared to cope with
		3499	them (e.g. by ignoring them). Remember that warnings are just that:
		3500	warnings, not errors, or proof of bugs.
		3501
		3502
		3503	=head1 VALGRIND
		3504
		3505	Valgrind has a special section here because it is a popular tool that is
		3506	highly useful, but valgrind reports are very hard to interpret.
		3507
		3508	If you think you found a bug (memory leak, uninitialised data access etc.)
		3509	in libev, then check twice: If valgrind reports something like:
		3510
		3511	==2274== definitely lost: 0 bytes in 0 blocks.
		3512	==2274== possibly lost: 0 bytes in 0 blocks.
		3513	==2274== still reachable: 256 bytes in 1 blocks.
		3514
		3515	Then there is no memory leak. Similarly, under some circumstances,
		3516	valgrind might report kernel bugs as if it were a bug in libev, or it
		3517	might be confused (it is a very good tool, but only a tool).
		3518
		3519	If you are unsure about something, feel free to contact the mailing list
		3520	with the full valgrind report and an explanation on why you think this is
		3521	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3522	no bug" answer and take the chance of learning how to interpret valgrind
		3523	properly.
		3524
		3525	If you need, for some reason, empty reports from valgrind for your project
		3526	I suggest using suppression lists.
		3527
		3528
2373	=head1 AUTHOR	3529	=head1 AUTHOR
2374		3530
2375	Marc Lehmann <libev@schmorp.de>.	3531	Marc Lehmann <libev@schmorp.de>.
2376		3532

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