ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.89 by root, Wed Dec 19 01:59:29 2007 UTC vs.
Revision 1.164 by root, Sat May 31 23:22:23 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 some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
114	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
115		151
116	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
117	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
118	you actually want to know.	154	you actually want to know.
		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 ()>.
119		161
120	=item int ev_version_major ()	162	=item int ev_version_major ()
121		163
122	=item int ev_version_minor ()	164	=item int ev_version_minor ()
123		165
…		…
136	not a problem.	178	not a problem.
137		179
138	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
139	version.	181	version.
140		182
141	assert (("libev version mismatch",	183	assert (("libev version mismatch",
142	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
143	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
144		186
145	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
146		188
147	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_*>
148	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
150	a description of the set values.	192	a description of the set values.
151		193
152	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
153	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
154		196
155	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
156	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
157		199
158	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
159		201
160	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
161	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
162	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
163	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
164	(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
165	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
166		208
167	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
168		210
…		…
175	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
176		218
177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
178		220
179	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
180	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
181	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
182	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
183	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
184	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.
185		230
186	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
187	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,
188	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.
189		234
190	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
191	retries).	236	retries (example requires a standards-compliant C<realloc>).
192		237
193	static void *	238	static void *
194	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
195	{	240	{
196	for (;;)	241	for (;;)
…		…
207	...	252	...
208	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
209		254
210	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
211		256
212	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
213	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
214	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
215	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
216	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
217	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
218	(such as abort).	263	(such as abort).
219		264
220	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.
…		…
234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
235		280
236	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
237	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
238	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
239
240	If you use threads, a common model is to run the default event loop
241	in your main thread (or in a separate thread) and for each thread you
242	create, you also create another event loop. Libev itself does no locking
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246		284
247	=over 4	285	=over 4
248		286
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		288
…		…
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		293
256	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
257	function.	295	function.
258		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
259	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
260	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>).
261		310
262	The following flags are supported:	311	The following flags are supported:
263		312
…		…
268	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
269	thing, believe me).	318	thing, believe me).
270		319
271	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
272		321
273	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
274	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
275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
276	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
277	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
278	around bugs.	327	around bugs.
…		…
284	enabling this flag.	333	enabling this flag.
285		334
286	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,
287	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
288	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
289	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
290	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
291	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
292		341
293	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
294	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
295	flag.	344	flag.
296		345
297	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>
298	environment variable.	347	environment variable.
299		348
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		350
302	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
303	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,
304	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
305	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
306	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.
307		363
308	=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)
309		365
310	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
311	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
312	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
313	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.
314		372
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		374
317	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,
318	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
319	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),
320	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.
321		382
322	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
323	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
324	(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
325	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
326	well if you register events for both fds.	387	very well if you register events for both fds.
327		388
328	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
329	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
330	(or space) is available.	391	(or space) is available.
331		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
332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
333		401
334	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
335	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
336	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
337	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
338	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
339	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.
340		413
341	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
342	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
343	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
344	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
345	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.
346		429
347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
348		431
349	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.
350		436
351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
352		438
353	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,
354	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)).
355		441
356	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
357	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
358	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.
359		454
360	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
361		456
362	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
363	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
364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
365		460
		461	It is definitely not recommended to use this flag.
		462
366	=back	463	=back
367		464
368	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
369	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
370	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
371	order of their flag values :)
372		468
373	The most typical usage is like this:	469	The most typical usage is like this:
374		470
375	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
377		473
378	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
379	environment settings to be taken into account:	475	environment settings to be taken into account:
380		476
381	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
382		478
383	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
384	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
385	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):
386		482
387	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
388		484
389	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
390		486
391	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
392	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
393	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
394	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
395		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
396	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.
397		497
398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
399	if (!epoller)	499	if (!epoller)
400	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
401		501
402	=item ev_default_destroy ()	502	=item ev_default_destroy ()
403		503
404	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
405	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
406	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
407	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
408	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
409	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
410	for example).	510	for example).
411		511
412	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
423	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
424	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
425		525
426	=item ev_default_fork ()	526	=item ev_default_fork ()
427		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
428	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
429	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
430	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
431	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.
432		534
433	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
434	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
435	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
436		538
437	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
438	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
439	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
440		542
441	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
442		544
443	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
444	without calling this function, so if you force one of those backends you
445	do not need to care.
446
447	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
448		546
449	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
450	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
451	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.
452		554
453	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
454		556
455	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
456	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
…		…
469		571
470	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
471	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
472	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
473	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
474	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
475		577
476	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
477		579
478	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
479	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
…		…
491	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
492	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
493	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.
494		596
495	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
496	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
497	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
498	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
499	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
500	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
501	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
502		604
503	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
504		606
505	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
506	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
507	- Queue all prepare watchers and then call all outstanding watchers.	609	- If a fork was detected, queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
508	- If we have been forked, recreate the kernel state.	611	- If we have been forked, recreate the kernel state.
509	- Update the kernel state with all outstanding changes.	612	- Update the kernel state with all outstanding changes.
510	- Update the "event loop time".	613	- Update the "event loop time".
511	- Calculate for how long to block.	614	- Calculate for how long to sleep or block, if at all
		615	(active idle watchers, EVLOOP_NONBLOCK or not having
		616	any active watchers at all will result in not sleeping).
		617	- Sleep if the I/O and timer collect interval say so.
512	- Block the process, waiting for any events.	618	- Block the process, waiting for any events.
513	- Queue all outstanding I/O (fd) events.	619	- Queue all outstanding I/O (fd) events.
514	- Update the "event loop time" and do time jump handling.	620	- Update the "event loop time" and do time jump handling.
515	- Queue all outstanding timers.	621	- Queue all outstanding timers.
516	- Queue all outstanding periodics.	622	- Queue all outstanding periodics.
517	- If no events are pending now, queue all idle watchers.	623	- If no events are pending now, queue all idle watchers.
518	- Queue all check watchers.	624	- Queue all check watchers.
519	- Call all queued watchers in reverse order (i.e. check watchers first).	625	- Call all queued watchers in reverse order (i.e. check watchers first).
520	Signals and child watchers are implemented as I/O watchers, and will	626	Signals and child watchers are implemented as I/O watchers, and will
521	be handled here by queueing them when their watcher gets executed.	627	be handled here by queueing them when their watcher gets executed.
522	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
523	were used, return, otherwise continue with step *.	629	were used, or there are no active watchers, return, otherwise
		630	continue with step *.
524		631
525	Example: Queue some jobs and then loop until no events are outsanding	632	Example: Queue some jobs and then loop until no events are outstanding
526	anymore.	633	anymore.
527		634
528	... queue jobs here, make sure they register event watchers as long	635	... queue jobs here, make sure they register event watchers as long
529	... as they still have work to do (even an idle watcher will do..)	636	... as they still have work to do (even an idle watcher will do..)
530	ev_loop (my_loop, 0);	637	ev_loop (my_loop, 0);
…		…
534		641
535	Can be used to make a call to C<ev_loop> return early (but only after it	642	Can be used to make a call to C<ev_loop> return early (but only after it
536	has processed all outstanding events). The C<how> argument must be either	643	has processed all outstanding events). The C<how> argument must be either
537	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
538	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		646
		647	This "unloop state" will be cleared when entering C<ev_loop> again.
539		648
540	=item ev_ref (loop)	649	=item ev_ref (loop)
541		650
542	=item ev_unref (loop)	651	=item ev_unref (loop)
543		652
…		…
548	returning, ev_unref() after starting, and ev_ref() before stopping it. For	657	returning, ev_unref() after starting, and ev_ref() before stopping it. For
549	example, libev itself uses this for its internal signal pipe: It is not	658	example, libev itself uses this for its internal signal pipe: It is not
550	visible to the libev user and should not keep C<ev_loop> from exiting if	659	visible to the libev user and should not keep C<ev_loop> from exiting if
551	no event watchers registered by it are active. It is also an excellent	660	no event watchers registered by it are active. It is also an excellent
552	way to do this for generic recurring timers or from within third-party	661	way to do this for generic recurring timers or from within third-party
553	libraries. Just remember to I<unref after start> and I<ref before stop>.	662	libraries. Just remember to I<unref after start> and I<ref before stop>
		663	(but only if the watcher wasn't active before, or was active before,
		664	respectively).
554		665
555	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
556	running when nothing else is active.	667	running when nothing else is active.
557		668
558	struct ev_signal exitsig;	669	struct ev_signal exitsig;
559	ev_signal_init (&exitsig, sig_cb, SIGINT);	670	ev_signal_init (&exitsig, sig_cb, SIGINT);
560	ev_signal_start (loop, &exitsig);	671	ev_signal_start (loop, &exitsig);
561	evf_unref (loop);	672	evf_unref (loop);
562		673
563	Example: For some weird reason, unregister the above signal handler again.	674	Example: For some weird reason, unregister the above signal handler again.
564		675
565	ev_ref (loop);	676	ev_ref (loop);
566	ev_signal_stop (loop, &exitsig);	677	ev_signal_stop (loop, &exitsig);
		678
		679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		680
		681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		682
		683	These advanced functions influence the time that libev will spend waiting
		684	for events. Both are by default C<0>, meaning that libev will try to
		685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		686
		687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		688	allows libev to delay invocation of I/O and timer/periodic callbacks to
		689	increase efficiency of loop iterations.
		690
		691	The background is that sometimes your program runs just fast enough to
		692	handle one (or very few) event(s) per loop iteration. While this makes
		693	the program responsive, it also wastes a lot of CPU time to poll for new
		694	events, especially with backends like C<select ()> which have a high
		695	overhead for the actual polling but can deliver many events at once.
		696
		697	By setting a higher I<io collect interval> you allow libev to spend more
		698	time collecting I/O events, so you can handle more events per iteration,
		699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		700	C<ev_timer>) will be not affected. Setting this to a non-null value will
		701	introduce an additional C<ev_sleep ()> call into most loop iterations.
		702
		703	Likewise, by setting a higher I<timeout collect interval> you allow libev
		704	to spend more time collecting timeouts, at the expense of increased
		705	latency (the watcher callback will be called later). C<ev_io> watchers
		706	will not be affected. Setting this to a non-null value will not introduce
		707	any overhead in libev.
		708
		709	Many (busy) programs can usually benefit by setting the I/O collect
		710	interval to a value near C<0.1> or so, which is often enough for
		711	interactive servers (of course not for games), likewise for timeouts. It
		712	usually doesn't make much sense to set it to a lower value than C<0.01>,
		713	as this approaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
567		725
568	=back	726	=back
569		727
570		728
571	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
572		730
573	A watcher is a structure that you create and register to record your	731	A watcher is a structure that you create and register to record your
574	interest in some event. For instance, if you want to wait for STDIN to	732	interest in some event. For instance, if you want to wait for STDIN to
575	become readable, you would create an C<ev_io> watcher for that:	733	become readable, you would create an C<ev_io> watcher for that:
576		734
577	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
578	{	736	{
579	ev_io_stop (w);	737	ev_io_stop (w);
580	ev_unloop (loop, EVUNLOOP_ALL);	738	ev_unloop (loop, EVUNLOOP_ALL);
581	}	739	}
582		740
583	struct ev_loop *loop = ev_default_loop (0);	741	struct ev_loop *loop = ev_default_loop (0);
584	struct ev_io stdin_watcher;	742	struct ev_io stdin_watcher;
585	ev_init (&stdin_watcher, my_cb);	743	ev_init (&stdin_watcher, my_cb);
586	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
587	ev_io_start (loop, &stdin_watcher);	745	ev_io_start (loop, &stdin_watcher);
588	ev_loop (loop, 0);	746	ev_loop (loop, 0);
589		747
590	As you can see, you are responsible for allocating the memory for your	748	As you can see, you are responsible for allocating the memory for your
591	watcher structures (and it is usually a bad idea to do this on the stack,	749	watcher structures (and it is usually a bad idea to do this on the stack,
592	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
593		751
594	Each watcher structure must be initialised by a call to C<ev_init	752	Each watcher structure must be initialised by a call to C<ev_init
595	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
596	callback gets invoked each time the event occurs (or, in the case of io	754	callback gets invoked each time the event occurs (or, in the case of I/O
597	watchers, each time the event loop detects that the file descriptor given	755	watchers, each time the event loop detects that the file descriptor given
598	is readable and/or writable).	756	is readable and/or writable).
599		757
600	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
601	with arguments specific to this watcher type. There is also a macro	759	with arguments specific to this watcher type. There is also a macro
…		…
671	=item C<EV_FORK>	829	=item C<EV_FORK>
672		830
673	The event loop has been resumed in the child process after fork (see	831	The event loop has been resumed in the child process after fork (see
674	C<ev_fork>).	832	C<ev_fork>).
675		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
		837
676	=item C<EV_ERROR>	838	=item C<EV_ERROR>
677		839
678	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occurred, the watcher has been stopped. This might
679	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
680	ran out of memory, a file descriptor was found to be closed or any other	842	ran out of memory, a file descriptor was found to be closed or any other
681	problem. You best act on it by reporting the problem and somehow coping	843	problem. You best act on it by reporting the problem and somehow coping
682	with the watcher being stopped.	844	with the watcher being stopped.
683		845
684	Libev will usually signal a few "dummy" events together with an error,	846	Libev will usually signal a few "dummy" events together with an error,
685	for example it might indicate that a fd is readable or writable, and if	847	for example it might indicate that a fd is readable or writable, and if
686	your callbacks is well-written it can just attempt the operation and cope	848	your callbacks is well-written it can just attempt the operation and cope
687	with the error from read() or write(). This will not work in multithreaded	849	with the error from read() or write(). This will not work in multi-threaded
688	programs, though, so beware.	850	programs, though, so beware.
689		851
690	=back	852	=back
691		853
692	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
722	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
723	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
724		886
725	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
726		888
727	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
728	calls into a single call. This is the most convinient method to initialise	890	calls into a single call. This is the most convenient method to initialise
729	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
730		892
731	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
732		894
733	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
816	to associate arbitrary data with your watcher. If you need more data and	978	to associate arbitrary data with your watcher. If you need more data and
817	don't want to allocate memory and store a pointer to it in that data	979	don't want to allocate memory and store a pointer to it in that data
818	member, you can also "subclass" the watcher type and provide your own	980	member, you can also "subclass" the watcher type and provide your own
819	data:	981	data:
820		982
821	struct my_io	983	struct my_io
822	{	984	{
823	struct ev_io io;	985	struct ev_io io;
824	int otherfd;	986	int otherfd;
825	void *somedata;	987	void *somedata;
826	struct whatever *mostinteresting;	988	struct whatever *mostinteresting;
827	}	989	}
828		990
829	And since your callback will be called with a pointer to the watcher, you	991	And since your callback will be called with a pointer to the watcher, you
830	can cast it back to your own type:	992	can cast it back to your own type:
831		993
832	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
833	{	995	{
834	struct my_io *w = (struct my_io *)w_;	996	struct my_io *w = (struct my_io *)w_;
835	...	997	...
836	}	998	}
837		999
838	More interesting and less C-conformant ways of casting your callback type	1000	More interesting and less C-conformant ways of casting your callback type
839	instead have been omitted.	1001	instead have been omitted.
840		1002
841	Another common scenario is having some data structure with multiple	1003	Another common scenario is having some data structure with multiple
842	watchers:	1004	watchers:
843		1005
844	struct my_biggy	1006	struct my_biggy
845	{	1007	{
846	int some_data;	1008	int some_data;
847	ev_timer t1;	1009	ev_timer t1;
848	ev_timer t2;	1010	ev_timer t2;
849	}	1011	}
850		1012
851	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,
852	you need to use C<offsetof>:	1014	you need to use C<offsetof>:
853		1015
854	#include <stddef.h>	1016	#include <stddef.h>
855		1017
856	static void	1018	static void
857	t1_cb (EV_P_ struct ev_timer *w, int revents)	1019	t1_cb (EV_P_ struct ev_timer *w, int revents)
858	{	1020	{
859	struct my_biggy big = (struct my_biggy *	1021	struct my_biggy big = (struct my_biggy *
860	(((char *)w) - offsetof (struct my_biggy, t1));	1022	(((char *)w) - offsetof (struct my_biggy, t1));
861	}	1023	}
862		1024
863	static void	1025	static void
864	t2_cb (EV_P_ struct ev_timer *w, int revents)	1026	t2_cb (EV_P_ struct ev_timer *w, int revents)
865	{	1027	{
866	struct my_biggy big = (struct my_biggy *	1028	struct my_biggy big = (struct my_biggy *
867	(((char *)w) - offsetof (struct my_biggy, t2));	1029	(((char *)w) - offsetof (struct my_biggy, t2));
868	}	1030	}
869		1031
870		1032
871	=head1 WATCHER TYPES	1033	=head1 WATCHER TYPES
872		1034
873	This section describes each watcher in detail, but will not repeat	1035	This section describes each watcher in detail, but will not repeat
…		…
897	In general you can register as many read and/or write event watchers per	1059	In general you can register as many read and/or write event watchers per
898	fd as you want (as long as you don't confuse yourself). Setting all file	1060	fd as you want (as long as you don't confuse yourself). Setting all file
899	descriptors to non-blocking mode is also usually a good idea (but not	1061	descriptors to non-blocking mode is also usually a good idea (but not
900	required if you know what you are doing).	1062	required if you know what you are doing).
901		1063
902	You have to be careful with dup'ed file descriptors, though. Some backends
903	(the linux epoll backend is a notable example) cannot handle dup'ed file
904	descriptors correctly if you register interest in two or more fds pointing
905	to the same underlying file/socket/etc. description (that is, they share
906	the same underlying "file open").
907
908	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
909	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
910	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
911		1067
912	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
913	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
914	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
915	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
916	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example Solaris ports), it is very easy to get into
917	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
918	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
919	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.
920		1076
921	If you cannot run the fd in non-blocking mode (for example you should not	1077	If you cannot run the fd in non-blocking mode (for example you should not
922	play around with an Xlib connection), then you have to seperately re-test	1078	play around with an Xlib connection), then you have to separately re-test
923	whether a file descriptor is really ready with a known-to-be good interface	1079	whether a file descriptor is really ready with a known-to-be good interface
924	such as poll (fortunately in our Xlib example, Xlib already does this on	1080	such as poll (fortunately in our Xlib example, Xlib already does this on
925	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
926		1082
927	=head3 The special problem of disappearing file descriptors	1083	=head3 The special problem of disappearing file descriptors
928		1084
929	Some backends (e.g kqueue, epoll) need to be told about closing a file	1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file
930	descriptor (either by calling C<close> explicitly or by any other means,	1086	descriptor (either by calling C<close> explicitly or by any other means,
931	such as C<dup>). The reason is that you register interest in some file	1087	such as C<dup>). The reason is that you register interest in some file
932	descriptor, but when it goes away, the operating system will silently drop	1088	descriptor, but when it goes away, the operating system will silently drop
933	this interest. If another file descriptor with the same number then is	1089	this interest. If another file descriptor with the same number then is
934	registered with libev, there is no efficient way to see that this is, in	1090	registered with libev, there is no efficient way to see that this is, in
…		…
943		1099
944	This is how one would do it normally anyway, the important point is that	1100	This is how one would do it normally anyway, the important point is that
945	the libev application should not optimise around libev but should leave	1101	the libev application should not optimise around libev but should leave
946	optimisations to libev.	1102	optimisations to libev.
947		1103
		1104	=head3 The special problem of dup'ed file descriptors
		1105
		1106	Some backends (e.g. epoll), cannot register events for file descriptors,
		1107	but only events for the underlying file descriptions. That means when you
		1108	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1109	events for them, only one file descriptor might actually receive events.
		1110
		1111	There is no workaround possible except not registering events
		1112	for potentially C<dup ()>'ed file descriptors, or to resort to
		1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1114
		1115	=head3 The special problem of fork
		1116
		1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1118	useless behaviour. Libev fully supports fork, but needs to be told about
		1119	it in the child.
		1120
		1121	To support fork in your programs, you either have to call
		1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1124	C<EVBACKEND_POLL>.
		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
948		1138
949	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
950		1140
951	=over 4	1141	=over 4
952		1142
953	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
954		1144
955	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
956		1146
957	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
958	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
959	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
960		1150
961	=item int fd [read-only]	1151	=item int fd [read-only]
962		1152
963	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
965	=item int events [read-only]	1155	=item int events [read-only]
966		1156
967	The events being watched.	1157	The events being watched.
968		1158
969	=back	1159	=back
		1160
		1161	=head3 Examples
970		1162
971	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
972	readable, but only once. Since it is likely line-buffered, you could	1164	readable, but only once. Since it is likely line-buffered, you could
973	attempt to read a whole line in the callback.	1165	attempt to read a whole line in the callback.
974		1166
975	static void	1167	static void
976	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
977	{	1169	{
978	ev_io_stop (loop, w);	1170	ev_io_stop (loop, w);
979	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors
980	}	1172	}
981		1173
982	...	1174	...
983	struct ev_loop *loop = ev_default_init (0);	1175	struct ev_loop *loop = ev_default_init (0);
984	struct ev_io stdin_readable;	1176	struct ev_io stdin_readable;
985	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
986	ev_io_start (loop, &stdin_readable);	1178	ev_io_start (loop, &stdin_readable);
987	ev_loop (loop, 0);	1179	ev_loop (loop, 0);
988		1180
989		1181
990	=head2 C<ev_timer> - relative and optionally repeating timeouts	1182	=head2 C<ev_timer> - relative and optionally repeating timeouts
991		1183
992	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
993	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
994		1186
995	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
996	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to January last
997	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
998	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
999	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1000		1192
1001	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1002	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1004	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1005	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1006		1198
1007	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1008		1200
1009	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guaranteed to be invoked only after its timeout has passed,
1010	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1011	order of execution is undefined.	1203	order of execution is undefined.
1012		1204
1013	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1014		1206
…		…
1016		1208
1017	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1018		1210
1019	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1020		1212
1021	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1022	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1023	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1024	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1025		1218
1026	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1027	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1028	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1029	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1030	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1031		1224
1032	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
1033		1226
1034	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1035	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1036		1229
1037	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
1038		1231
1039	If the timer is started but nonrepeating, stop it (as if it timed out).	1232	If the timer is started but non-repeating, stop it (as if it timed out).
1040		1233
1041	If the timer is repeating, either start it if necessary (with the	1234	If the timer is repeating, either start it if necessary (with the
1042	C<repeat> value), or reset the running timer to the C<repeat> value.	1235	C<repeat> value), or reset the running timer to the C<repeat> value.
1043		1236
1044	This sounds a bit complicated, but here is a useful and typical	1237	This sounds a bit complicated, but here is a useful and typical
1045	example: Imagine you have a tcp connection and you want a so-called idle	1238	example: Imagine you have a TCP connection and you want a so-called idle
1046	timeout, that is, you want to be called when there have been, say, 60	1239	timeout, that is, you want to be called when there have been, say, 60
1047	seconds of inactivity on the socket. The easiest way to do this is to	1240	seconds of inactivity on the socket. The easiest way to do this is to
1048	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1049	C<ev_timer_again> each time you successfully read or write some data. If	1242	C<ev_timer_again> each time you successfully read or write some data. If
1050	you go into an idle state where you do not expect data to travel on the	1243	you go into an idle state where you do not expect data to travel on the
…		…
1072	or C<ev_timer_again> is called and determines the next timeout (if any),	1265	or C<ev_timer_again> is called and determines the next timeout (if any),
1073	which is also when any modifications are taken into account.	1266	which is also when any modifications are taken into account.
1074		1267
1075	=back	1268	=back
1076		1269
		1270	=head3 Examples
		1271
1077	Example: Create a timer that fires after 60 seconds.	1272	Example: Create a timer that fires after 60 seconds.
1078		1273
1079	static void	1274	static void
1080	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1081	{	1276	{
1082	.. one minute over, w is actually stopped right here	1277	.. one minute over, w is actually stopped right here
1083	}	1278	}
1084		1279
1085	struct ev_timer mytimer;	1280	struct ev_timer mytimer;
1086	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1087	ev_timer_start (loop, &mytimer);	1282	ev_timer_start (loop, &mytimer);
1088		1283
1089	Example: Create a timeout timer that times out after 10 seconds of	1284	Example: Create a timeout timer that times out after 10 seconds of
1090	inactivity.	1285	inactivity.
1091		1286
1092	static void	1287	static void
1093	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1094	{	1289	{
1095	.. ten seconds without any activity	1290	.. ten seconds without any activity
1096	}	1291	}
1097		1292
1098	struct ev_timer mytimer;	1293	struct ev_timer mytimer;
1099	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1100	ev_timer_again (&mytimer); /* start timer */	1295	ev_timer_again (&mytimer); /* start timer */
1101	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1102		1297
1103	// and in some piece of code that gets executed on any "activity":	1298	// and in some piece of code that gets executed on any "activity":
1104	// reset the timeout to start ticking again at 10 seconds	1299	// reset the timeout to start ticking again at 10 seconds
1105	ev_timer_again (&mytimer);	1300	ev_timer_again (&mytimer);
1106		1301
1107		1302
1108	=head2 C<ev_periodic> - to cron or not to cron?	1303	=head2 C<ev_periodic> - to cron or not to cron?
1109		1304
1110	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1111	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1112		1307
1113	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1114	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wall clock time (absolute time). You can tell a periodic watcher
1115	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1116	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1117	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to January of the previous year, then it will take more than year
1118	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1119	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1120		1316
1121	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1122	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1123	rules.	1319	complicated, rules.
1124		1320
1125	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guaranteed to be invoked only when the
1126	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1127	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1128		1324
1129	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1130		1326
1131	=over 4	1327	=over 4
…		…
1139		1335
1140	=over 4	1336	=over 4
1141		1337
1142	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1143		1339
1144	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wall clock
1145	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1146	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1147	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1148		1344
1149	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1150		1346
1151	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1152	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1153	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1154		1350
1155	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1156	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1157		1354
1158	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1159		1356
1160	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1161	but only that the the callback will be called when the system time shows a	1358	but only that the callback will be called when the system time shows a
1162	full hour (UTC), or more correctly, when the system time is evenly divisible	1359	full hour (UTC), or more correctly, when the system time is evenly divisible
1163	by 3600.	1360	by 3600.
1164		1361
1165	Another way to think about it (for the mathematically inclined) is that	1362	Another way to think about it (for the mathematically inclined) is that
1166	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1167	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1168		1365
1169	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1170	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1171	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (CPU
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course deteriorate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1172		1374
1173	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1174		1376
1175	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1176	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1177	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1178	current time as second argument.	1380	current time as second argument.
1179		1381
1180	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1181	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1182	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1183	starting an C<ev_prepare> watcher, which is legal).
1184		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1185	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1186	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1187		1391
1188	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1189	{	1393	{
1190	return now + 60.;	1394	return now + 60.;
1191	}	1395	}
…		…
1193	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1194	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1195	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1196	might be called at other times, too.	1400	might be called at other times, too.
1197		1401
1198	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1199	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1200		1404
1201	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1202	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1203	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1204	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1205	reason I omitted it as an example).	1409	reason I omitted it as an example).
1206		1410
1207	=back	1411	=back
…		…
1211	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1212	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1213	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1214	program when the crontabs have changed).	1418	program when the crontabs have changed).
1215		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1216	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1217		1426
1218	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1219	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1220		1429
…		…
1231		1440
1232	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1233	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1234	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1235		1444
1236	=item ev_tstamp at [read-only]
1237
1238	When active, contains the absolute time that the watcher is supposed to
1239	trigger next.
1240
1241	=back	1445	=back
		1446
		1447	=head3 Examples
1242		1448
1243	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1244	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1245	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1246		1452
1247	static void	1453	static void
1248	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1249	{	1455	{
1250	... its now a full hour (UTC, or TAI or whatever your clock follows)	1456	... its now a full hour (UTC, or TAI or whatever your clock follows)
1251	}	1457	}
1252		1458
1253	struct ev_periodic hourly_tick;	1459	struct ev_periodic hourly_tick;
1254	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1255	ev_periodic_start (loop, &hourly_tick);	1461	ev_periodic_start (loop, &hourly_tick);
1256		1462
1257	Example: The same as above, but use a reschedule callback to do it:	1463	Example: The same as above, but use a reschedule callback to do it:
1258		1464
1259	#include <math.h>	1465	#include <math.h>
1260		1466
1261	static ev_tstamp	1467	static ev_tstamp
1262	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1263	{	1469	{
1264	return fmod (now, 3600.) + 3600.;	1470	return fmod (now, 3600.) + 3600.;
1265	}	1471	}
1266		1472
1267	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1268		1474
1269	Example: Call a callback every hour, starting now:	1475	Example: Call a callback every hour, starting now:
1270		1476
1271	struct ev_periodic hourly_tick;	1477	struct ev_periodic hourly_tick;
1272	ev_periodic_init (&hourly_tick, clock_cb,	1478	ev_periodic_init (&hourly_tick, clock_cb,
1273	fmod (ev_now (loop), 3600.), 3600., 0);	1479	fmod (ev_now (loop), 3600.), 3600., 0);
1274	ev_periodic_start (loop, &hourly_tick);	1480	ev_periodic_start (loop, &hourly_tick);
1275		1481
1276		1482
1277	=head2 C<ev_signal> - signal me when a signal gets signalled!	1483	=head2 C<ev_signal> - signal me when a signal gets signalled!
1278		1484
1279	Signal watchers will trigger an event when the process receives a specific	1485	Signal watchers will trigger an event when the process receives a specific
…		…
1286	with the kernel (thus it coexists with your own signal handlers as long	1492	with the kernel (thus it coexists with your own signal handlers as long
1287	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1288	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1289	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1290		1496
		1497	If possible and supported, libev will install its handlers with
		1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1499	interrupted. If you have a problem with system calls getting interrupted by
		1500	signals you can block all signals in an C<ev_check> watcher and unblock
		1501	them in an C<ev_prepare> watcher.
		1502
1291	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1292		1504
1293	=over 4	1505	=over 4
1294		1506
1295	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1303		1515
1304	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1305		1517
1306	=back	1518	=back
1307		1519
		1520	=head3 Examples
		1521
		1522	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1523
		1524	static void
		1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1526	{
		1527	ev_unloop (loop, EVUNLOOP_ALL);
		1528	}
		1529
		1530	struct ev_signal signal_watcher;
		1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1532	ev_signal_start (loop, &sigint_cb);
		1533
1308		1534
1309	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1310		1536
1311	Child watchers trigger when your process receives a SIGCHLD in response to	1537	Child watchers trigger when your process receives a SIGCHLD in response to
1312	some child status changes (most typically when a child of yours dies).	1538	some child status changes (most typically when a child of yours dies). It
		1539	is permissible to install a child watcher I<after> the child has been
		1540	forked (which implies it might have already exited), as long as the event
		1541	loop isn't entered (or is continued from a watcher).
		1542
		1543	Only the default event loop is capable of handling signals, and therefore
		1544	you can only register child watchers in the default event loop.
		1545
		1546	=head3 Process Interaction
		1547
		1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1549	initialised. This is necessary to guarantee proper behaviour even if
		1550	the first child watcher is started after the child exits. The occurrence
		1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1552	synchronously as part of the event loop processing. Libev always reaps all
		1553	children, even ones not watched.
		1554
		1555	=head3 Overriding the Built-In Processing
		1556
		1557	Libev offers no special support for overriding the built-in child
		1558	processing, but if your application collides with libev's default child
		1559	handler, you can override it easily by installing your own handler for
		1560	C<SIGCHLD> after initialising the default loop, and making sure the
		1561	default loop never gets destroyed. You are encouraged, however, to use an
		1562	event-based approach to child reaping and thus use libev's support for
		1563	that, so other libev users can use C<ev_child> watchers freely.
1313		1564
1314	=head3 Watcher-Specific Functions and Data Members	1565	=head3 Watcher-Specific Functions and Data Members
1315		1566
1316	=over 4	1567	=over 4
1317		1568
1318	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1319		1570
1320	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1321		1572
1322	Configures the watcher to wait for status changes of process C<pid> (or	1573	Configures the watcher to wait for status changes of process C<pid> (or
1323	I<any> process if C<pid> is specified as C<0>). The callback can look	1574	I<any> process if C<pid> is specified as C<0>). The callback can look
1324	at the C<rstatus> member of the C<ev_child> watcher structure to see	1575	at the C<rstatus> member of the C<ev_child> watcher structure to see
1325	the status word (use the macros from C<sys/wait.h> and see your systems	1576	the status word (use the macros from C<sys/wait.h> and see your systems
1326	C<waitpid> documentation). The C<rpid> member contains the pid of the	1577	C<waitpid> documentation). The C<rpid> member contains the pid of the
1327	process causing the status change.	1578	process causing the status change. C<trace> must be either C<0> (only
		1579	activate the watcher when the process terminates) or C<1> (additionally
		1580	activate the watcher when the process is stopped or continued).
1328		1581
1329	=item int pid [read-only]	1582	=item int pid [read-only]
1330		1583
1331	The process id this watcher watches out for, or C<0>, meaning any process id.	1584	The process id this watcher watches out for, or C<0>, meaning any process id.
1332		1585
…		…
1339	The process exit/trace status caused by C<rpid> (see your systems	1592	The process exit/trace status caused by C<rpid> (see your systems
1340	C<waitpid> and C<sys/wait.h> documentation for details).	1593	C<waitpid> and C<sys/wait.h> documentation for details).
1341		1594
1342	=back	1595	=back
1343		1596
1344	Example: Try to exit cleanly on SIGINT and SIGTERM.	1597	=head3 Examples
1345		1598
		1599	Example: C<fork()> a new process and install a child handler to wait for
		1600	its completion.
		1601
		1602	ev_child cw;
		1603
1346	static void	1604	static void
1347	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1348	{	1606	{
1349	ev_unloop (loop, EVUNLOOP_ALL);	1607	ev_child_stop (EV_A_ w);
		1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1350	}	1609	}
1351		1610
1352	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1354	ev_signal_start (loop, &sigint_cb);	1613	if (pid < 0)
		1614	// error
		1615	else if (pid == 0)
		1616	{
		1617	// the forked child executes here
		1618	exit (1);
		1619	}
		1620	else
		1621	{
		1622	ev_child_init (&cw, child_cb, pid, 0);
		1623	ev_child_start (EV_DEFAULT_ &cw);
		1624	}
1355		1625
1356		1626
1357	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1358		1628
1359	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a file system path for attribute changes. That is, it calls
1360	C<stat> regularly (or when the OS says it changed) and sees if it changed	1630	C<stat> regularly (or when the OS says it changed) and sees if it changed
1361	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1362		1632
1363	The path does not need to exist: changing from "path exists" to "path does	1633	The path does not need to exist: changing from "path exists" to "path does
1364	not exist" is a status change like any other. The condition "path does	1634	not exist" is a status change like any other. The condition "path does
…		…
1382	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1383	resource-intensive.	1653	resource-intensive.
1384		1654
1385	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1386	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1387	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1388	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1389	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1390	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1391	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with optionally
		1668	disabled large file support, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticeably with ev_stat and large file support.
		1674
		1675	=head3 Inotify
		1676
		1677	When C<inotify (7)> support has been compiled into libev (generally only
		1678	available on Linux) and present at runtime, it will be used to speed up
		1679	change detection where possible. The inotify descriptor will be created lazily
		1680	when the first C<ev_stat> watcher is being started.
		1681
		1682	Inotify presence does not change the semantics of C<ev_stat> watchers
		1683	except that changes might be detected earlier, and in some cases, to avoid
		1684	making regular C<stat> calls. Even in the presence of inotify support
		1685	there are many cases where libev has to resort to regular C<stat> polling.
		1686
		1687	(There is no support for kqueue, as apparently it cannot be used to
		1688	implement this functionality, due to the requirement of having a file
		1689	descriptor open on the object at all times).
		1690
		1691	=head3 The special problem of stat time resolution
		1692
		1693	The C<stat ()> system call only supports full-second resolution portably, and
		1694	even on systems where the resolution is higher, many file systems still
		1695	only support whole seconds.
		1696
		1697	That means that, if the time is the only thing that changes, you can
		1698	easily miss updates: on the first update, C<ev_stat> detects a change and
		1699	calls your callback, which does something. When there is another update
		1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
		1702
		1703	The solution to this is to delay acting on a change for slightly more
		1704	than a second (or till slightly after the next full second boundary), using
		1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1706	ev_timer_again (loop, w)>).
		1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
1392		1716
1393	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1394		1718
1395	=over 4	1719	=over 4
1396		1720
…		…
1402	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1403	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1404	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1405	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1406		1730
1407	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1408	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1409	last change was detected).	1733	was detected).
1410		1734
1411	=item ev_stat_stat (ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1412		1736
1413	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1414	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1415	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1416	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1417		1742
1418	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1419		1744
1420	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1421	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1422	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1423	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1424		1750
1425	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1426		1752
1427	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1428	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1429		1757
1430	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1431		1759
1432	The specified interval.	1760	The specified interval.
1433		1761
1434	=item const char *path [read-only]	1762	=item const char *path [read-only]
1435		1763
1436	The filesystem path that is being watched.	1764	The file system path that is being watched.
1437		1765
1438	=back	1766	=back
1439		1767
		1768	=head3 Examples
		1769
1440	Example: Watch C</etc/passwd> for attribute changes.	1770	Example: Watch C</etc/passwd> for attribute changes.
1441		1771
1442	static void	1772	static void
1443	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1444	{	1774	{
1445	/* /etc/passwd changed in some way */	1775	/* /etc/passwd changed in some way */
1446	if (w->attr.st_nlink)	1776	if (w->attr.st_nlink)
1447	{	1777	{
1448	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1449	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1450	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1451	}	1781	}
1452	else	1782	else
1453	/* you shalt not abuse printf for puts */	1783	/* you shalt not abuse printf for puts */
1454	puts ("wow, /etc/passwd is not there, expect problems. "	1784	puts ("wow, /etc/passwd is not there, expect problems. "
1455	"if this is windows, they already arrived\n");	1785	"if this is windows, they already arrived\n");
1456	}	1786	}
1457		1787
1458	...	1788	...
1459	ev_stat passwd;	1789	ev_stat passwd;
1460		1790
1461	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1462	ev_stat_start (loop, &passwd);	1792	ev_stat_start (loop, &passwd);
		1793
		1794	Example: Like above, but additionally use a one-second delay so we do not
		1795	miss updates (however, frequent updates will delay processing, too, so
		1796	one might do the work both on C<ev_stat> callback invocation I<and> on
		1797	C<ev_timer> callback invocation).
		1798
		1799	static ev_stat passwd;
		1800	static ev_timer timer;
		1801
		1802	static void
		1803	timer_cb (EV_P_ ev_timer *w, int revents)
		1804	{
		1805	ev_timer_stop (EV_A_ w);
		1806
		1807	/* now it's one second after the most recent passwd change */
		1808	}
		1809
		1810	static void
		1811	stat_cb (EV_P_ ev_stat *w, int revents)
		1812	{
		1813	/* reset the one-second timer */
		1814	ev_timer_again (EV_A_ &timer);
		1815	}
		1816
		1817	...
		1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1819	ev_stat_start (loop, &passwd);
		1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1463		1821
1464		1822
1465	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1466		1824
1467	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1493	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1494	believe me.	1852	believe me.
1495		1853
1496	=back	1854	=back
1497		1855
		1856	=head3 Examples
		1857
1498	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1499	callback, free it. Also, use no error checking, as usual.	1859	callback, free it. Also, use no error checking, as usual.
1500		1860
1501	static void	1861	static void
1502	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1503	{	1863	{
1504	free (w);	1864	free (w);
1505	// now do something you wanted to do when the program has	1865	// now do something you wanted to do when the program has
1506	// no longer asnything immediate to do.	1866	// no longer anything immediate to do.
1507	}	1867	}
1508		1868
1509	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1510	ev_idle_init (idle_watcher, idle_cb);	1870	ev_idle_init (idle_watcher, idle_cb);
1511	ev_idle_start (loop, idle_cb);	1871	ev_idle_start (loop, idle_cb);
1512		1872
1513		1873
1514	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1515		1875
1516	Prepare and check watchers are usually (but not always) used in tandem:	1876	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1535		1895
1536	This is done by examining in each prepare call which file descriptors need	1896	This is done by examining in each prepare call which file descriptors need
1537	to be watched by the other library, registering C<ev_io> watchers for	1897	to be watched by the other library, registering C<ev_io> watchers for
1538	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1539	provide just this functionality). Then, in the check watcher you check for	1899	provide just this functionality). Then, in the check watcher you check for
1540	any events that occured (by checking the pending status of all watchers	1900	any events that occurred (by checking the pending status of all watchers
1541	and stopping them) and call back into the library. The I/O and timer	1901	and stopping them) and call back into the library. The I/O and timer
1542	callbacks will never actually be called (but must be valid nevertheless,	1902	callbacks will never actually be called (but must be valid nevertheless,
1543	because you never know, you know?).	1903	because you never know, you know?).
1544		1904
1545	As another example, the Perl Coro module uses these hooks to integrate	1905	As another example, the Perl Coro module uses these hooks to integrate
…		…
1553		1913
1554	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1555	priority, to ensure that they are being run before any other watchers	1915	priority, to ensure that they are being run before any other watchers
1556	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1557	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1558	supports this, they will be called before other C<ev_check> watchers did	1918	supports this, they might get executed before other C<ev_check> watchers
1559	their job. As C<ev_check> watchers are often used to embed other event	1919	did their job. As C<ev_check> watchers are often used to embed other
1560	loops those other event loops might be in an unusable state until their	1920	(non-libev) event loops those other event loops might be in an unusable
1561	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1921	state until their C<ev_check> watcher ran (always remind yourself to
1562	others).	1922	coexist peacefully with others).
1563		1923
1564	=head3 Watcher-Specific Functions and Data Members	1924	=head3 Watcher-Specific Functions and Data Members
1565		1925
1566	=over 4	1926	=over 4
1567		1927
…		…
1573	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1574	macros, but using them is utterly, utterly and completely pointless.	1934	macros, but using them is utterly, utterly and completely pointless.
1575		1935
1576	=back	1936	=back
1577		1937
		1938	=head3 Examples
		1939
1578	There are a number of principal ways to embed other event loops or modules	1940	There are a number of principal ways to embed other event loops or modules
1579	into libev. Here are some ideas on how to include libadns into libev	1941	into libev. Here are some ideas on how to include libadns into libev
1580	(there is a Perl module named C<EV::ADNS> that does this, which you could	1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
1581	use for an actually working example. Another Perl module named C<EV::Glib>	1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
1582	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1583	into the Glib event loop).	1945	Glib event loop).
1584		1946
1585	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1586	and in a check watcher, destroy them and call into libadns. What follows	1948	and in a check watcher, destroy them and call into libadns. What follows
1587	is pseudo-code only of course. This requires you to either use a low	1949	is pseudo-code only of course. This requires you to either use a low
1588	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1589	the callbacks for the IO/timeout watchers might not have been called yet.	1951	the callbacks for the IO/timeout watchers might not have been called yet.
1590		1952
1591	static ev_io iow [nfd];	1953	static ev_io iow [nfd];
1592	static ev_timer tw;	1954	static ev_timer tw;
1593		1955
1594	static void	1956	static void
1595	io_cb (ev_loop *loop, ev_io *w, int revents)	1957	io_cb (ev_loop *loop, ev_io *w, int revents)
1596	{	1958	{
1597	}	1959	}
1598		1960
1599	// create io watchers for each fd and a timer before blocking	1961	// create io watchers for each fd and a timer before blocking
1600	static void	1962	static void
1601	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1602	{	1964	{
1603	int timeout = 3600000;	1965	int timeout = 3600000;
1604	struct pollfd fds [nfd];	1966	struct pollfd fds [nfd];
1605	// actual code will need to loop here and realloc etc.	1967	// actual code will need to loop here and realloc etc.
1606	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1607		1969
1608	/* the callback is illegal, but won't be called as we stop during check */	1970	/* the callback is illegal, but won't be called as we stop during check */
1609	ev_timer_init (&tw, 0, timeout * 1e-3);	1971	ev_timer_init (&tw, 0, timeout * 1e-3);
1610	ev_timer_start (loop, &tw);	1972	ev_timer_start (loop, &tw);
1611		1973
1612	// create one ev_io per pollfd	1974	// create one ev_io per pollfd
1613	for (int i = 0; i < nfd; ++i)	1975	for (int i = 0; i < nfd; ++i)
1614	{	1976	{
1615	ev_io_init (iow + i, io_cb, fds [i].fd,	1977	ev_io_init (iow + i, io_cb, fds [i].fd,
1616	((fds [i].events & POLLIN ? EV_READ : 0)	1978	((fds [i].events & POLLIN ? EV_READ : 0)
1617	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1618		1980
1619	fds [i].revents = 0;	1981	fds [i].revents = 0;
1620	ev_io_start (loop, iow + i);	1982	ev_io_start (loop, iow + i);
1621	}	1983	}
1622	}	1984	}
1623		1985
1624	// stop all watchers after blocking	1986	// stop all watchers after blocking
1625	static void	1987	static void
1626	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1627	{	1989	{
1628	ev_timer_stop (loop, &tw);	1990	ev_timer_stop (loop, &tw);
1629		1991
1630	for (int i = 0; i < nfd; ++i)	1992	for (int i = 0; i < nfd; ++i)
1631	{	1993	{
1632	// set the relevant poll flags	1994	// set the relevant poll flags
1633	// could also call adns_processreadable etc. here	1995	// could also call adns_processreadable etc. here
1634	struct pollfd *fd = fds + i;	1996	struct pollfd *fd = fds + i;
1635	int revents = ev_clear_pending (iow + i);	1997	int revents = ev_clear_pending (iow + i);
1636	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1637	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1638		2000
1639	// now stop the watcher	2001	// now stop the watcher
1640	ev_io_stop (loop, iow + i);	2002	ev_io_stop (loop, iow + i);
1641	}	2003	}
1642		2004
1643	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1644	}	2006	}
1645		2007
1646	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1647	in the prepare watcher and would dispose of the check watcher.	2009	in the prepare watcher and would dispose of the check watcher.
1648		2010
1649	Method 3: If the module to be embedded supports explicit event	2011	Method 3: If the module to be embedded supports explicit event
1650	notification (adns does), you can also make use of the actual watcher	2012	notification (libadns does), you can also make use of the actual watcher
1651	callbacks, and only destroy/create the watchers in the prepare watcher.	2013	callbacks, and only destroy/create the watchers in the prepare watcher.
1652		2014
1653	static void	2015	static void
1654	timer_cb (EV_P_ ev_timer *w, int revents)	2016	timer_cb (EV_P_ ev_timer *w, int revents)
1655	{	2017	{
1656	adns_state ads = (adns_state)w->data;	2018	adns_state ads = (adns_state)w->data;
1657	update_now (EV_A);	2019	update_now (EV_A);
1658		2020
1659	adns_processtimeouts (ads, &tv_now);	2021	adns_processtimeouts (ads, &tv_now);
1660	}	2022	}
1661		2023
1662	static void	2024	static void
1663	io_cb (EV_P_ ev_io *w, int revents)	2025	io_cb (EV_P_ ev_io *w, int revents)
1664	{	2026	{
1665	adns_state ads = (adns_state)w->data;	2027	adns_state ads = (adns_state)w->data;
1666	update_now (EV_A);	2028	update_now (EV_A);
1667		2029
1668	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1669	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1670	}	2032	}
1671		2033
1672	// do not ever call adns_afterpoll	2034	// do not ever call adns_afterpoll
1673		2035
1674	Method 4: Do not use a prepare or check watcher because the module you	2036	Method 4: Do not use a prepare or check watcher because the module you
1675	want to embed is too inflexible to support it. Instead, youc na override	2037	want to embed is too inflexible to support it. Instead, you can override
1676	their poll function. The drawback with this solution is that the main	2038	their poll function. The drawback with this solution is that the main
1677	loop is now no longer controllable by EV. The C<Glib::EV> module does	2039	loop is now no longer controllable by EV. The C<Glib::EV> module does
1678	this.	2040	this.
1679		2041
1680	static gint	2042	static gint
1681	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1682	{	2044	{
1683	int got_events = 0;	2045	int got_events = 0;
1684		2046
1685	for (n = 0; n < nfds; ++n)	2047	for (n = 0; n < nfds; ++n)
1686	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1687		2049
1688	if (timeout >= 0)	2050	if (timeout >= 0)
1689	// create/start timer	2051	// create/start timer
1690		2052
1691	// poll	2053	// poll
1692	ev_loop (EV_A_ 0);	2054	ev_loop (EV_A_ 0);
1693		2055
1694	// stop timer again	2056	// stop timer again
1695	if (timeout >= 0)	2057	if (timeout >= 0)
1696	ev_timer_stop (EV_A_ &to);	2058	ev_timer_stop (EV_A_ &to);
1697		2059
1698	// stop io watchers again - their callbacks should have set	2060	// stop io watchers again - their callbacks should have set
1699	for (n = 0; n < nfds; ++n)	2061	for (n = 0; n < nfds; ++n)
1700	ev_io_stop (EV_A_ iow [n]);	2062	ev_io_stop (EV_A_ iow [n]);
1701		2063
1702	return got_events;	2064	return got_events;
1703	}	2065	}
1704		2066
1705		2067
1706	=head2 C<ev_embed> - when one backend isn't enough...	2068	=head2 C<ev_embed> - when one backend isn't enough...
1707		2069
1708	This is a rather advanced watcher type that lets you embed one event loop	2070	This is a rather advanced watcher type that lets you embed one event loop
…		…
1750	portable one.	2112	portable one.
1751		2113
1752	So when you want to use this feature you will always have to be prepared	2114	So when you want to use this feature you will always have to be prepared
1753	that you cannot get an embeddable loop. The recommended way to get around	2115	that you cannot get an embeddable loop. The recommended way to get around
1754	this is to have a separate variables for your embeddable loop, try to	2116	this is to have a separate variables for your embeddable loop, try to
1755	create it, and if that fails, use the normal loop for everything:	2117	create it, and if that fails, use the normal loop for everything.
1756
1757	struct ev_loop *loop_hi = ev_default_init (0);
1758	struct ev_loop *loop_lo = 0;
1759	struct ev_embed embed;
1760
1761	// see if there is a chance of getting one that works
1762	// (remember that a flags value of 0 means autodetection)
1763	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1764	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1765	: 0;
1766
1767	// if we got one, then embed it, otherwise default to loop_hi
1768	if (loop_lo)
1769	{
1770	ev_embed_init (&embed, 0, loop_lo);
1771	ev_embed_start (loop_hi, &embed);
1772	}
1773	else
1774	loop_lo = loop_hi;
1775		2118
1776	=head3 Watcher-Specific Functions and Data Members	2119	=head3 Watcher-Specific Functions and Data Members
1777		2120
1778	=over 4	2121	=over 4
1779		2122
…		…
1783		2126
1784	Configures the watcher to embed the given loop, which must be	2127	Configures the watcher to embed the given loop, which must be
1785	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2128	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1786	invoked automatically, otherwise it is the responsibility of the callback	2129	invoked automatically, otherwise it is the responsibility of the callback
1787	to invoke it (it will continue to be called until the sweep has been done,	2130	to invoke it (it will continue to be called until the sweep has been done,
1788	if you do not want thta, you need to temporarily stop the embed watcher).	2131	if you do not want that, you need to temporarily stop the embed watcher).
1789		2132
1790	=item ev_embed_sweep (loop, ev_embed *)	2133	=item ev_embed_sweep (loop, ev_embed *)
1791		2134
1792	Make a single, non-blocking sweep over the embedded loop. This works	2135	Make a single, non-blocking sweep over the embedded loop. This works
1793	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1794	apropriate way for embedded loops.	2137	appropriate way for embedded loops.
1795		2138
1796	=item struct ev_loop *loop [read-only]	2139	=item struct ev_loop *other [read-only]
1797		2140
1798	The embedded event loop.	2141	The embedded event loop.
1799		2142
1800	=back	2143	=back
		2144
		2145	=head3 Examples
		2146
		2147	Example: Try to get an embeddable event loop and embed it into the default
		2148	event loop. If that is not possible, use the default loop. The default
		2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2151	used).
		2152
		2153	struct ev_loop *loop_hi = ev_default_init (0);
		2154	struct ev_loop *loop_lo = 0;
		2155	struct ev_embed embed;
		2156
		2157	// see if there is a chance of getting one that works
		2158	// (remember that a flags value of 0 means autodetection)
		2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2161	: 0;
		2162
		2163	// if we got one, then embed it, otherwise default to loop_hi
		2164	if (loop_lo)
		2165	{
		2166	ev_embed_init (&embed, 0, loop_lo);
		2167	ev_embed_start (loop_hi, &embed);
		2168	}
		2169	else
		2170	loop_lo = loop_hi;
		2171
		2172	Example: Check if kqueue is available but not recommended and create
		2173	a kqueue backend for use with sockets (which usually work with any
		2174	kqueue implementation). Store the kqueue/socket-only event loop in
		2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2176
		2177	struct ev_loop *loop = ev_default_init (0);
		2178	struct ev_loop *loop_socket = 0;
		2179	struct ev_embed embed;
		2180
		2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2183	{
		2184	ev_embed_init (&embed, 0, loop_socket);
		2185	ev_embed_start (loop, &embed);
		2186	}
		2187
		2188	if (!loop_socket)
		2189	loop_socket = loop;
		2190
		2191	// now use loop_socket for all sockets, and loop for everything else
1801		2192
1802		2193
1803	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1804		2195
1805	Fork watchers are called when a C<fork ()> was detected (usually because	2196	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1821	believe me.	2212	believe me.
1822		2213
1823	=back	2214	=back
1824		2215
1825		2216
		2217	=head2 C<ev_async> - how to wake up another event loop
		2218
		2219	In general, you cannot use an C<ev_loop> from multiple threads or other
		2220	asynchronous sources such as signal handlers (as opposed to multiple event
		2221	loops - those are of course safe to use in different threads).
		2222
		2223	Sometimes, however, you need to wake up another event loop you do not
		2224	control, for example because it belongs to another thread. This is what
		2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2226	can signal it by calling C<ev_async_send>, which is thread- and signal
		2227	safe.
		2228
		2229	This functionality is very similar to C<ev_signal> watchers, as signals,
		2230	too, are asynchronous in nature, and signals, too, will be compressed
		2231	(i.e. the number of callback invocations may be less than the number of
		2232	C<ev_async_sent> calls).
		2233
		2234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2235	just the default loop.
		2236
		2237	=head3 Queueing
		2238
		2239	C<ev_async> does not support queueing of data in any way. The reason
		2240	is that the author does not know of a simple (or any) algorithm for a
		2241	multiple-writer-single-reader queue that works in all cases and doesn't
		2242	need elaborate support such as pthreads.
		2243
		2244	That means that if you want to queue data, you have to provide your own
		2245	queue. But at least I can tell you would implement locking around your
		2246	queue:
		2247
		2248	=over 4
		2249
		2250	=item queueing from a signal handler context
		2251
		2252	To implement race-free queueing, you simply add to the queue in the signal
		2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2254	some fictitious SIGUSR1 handler:
		2255
		2256	static ev_async mysig;
		2257
		2258	static void
		2259	sigusr1_handler (void)
		2260	{
		2261	sometype data;
		2262
		2263	// no locking etc.
		2264	queue_put (data);
		2265	ev_async_send (EV_DEFAULT_ &mysig);
		2266	}
		2267
		2268	static void
		2269	mysig_cb (EV_P_ ev_async *w, int revents)
		2270	{
		2271	sometype data;
		2272	sigset_t block, prev;
		2273
		2274	sigemptyset (&block);
		2275	sigaddset (&block, SIGUSR1);
		2276	sigprocmask (SIG_BLOCK, &block, &prev);
		2277
		2278	while (queue_get (&data))
		2279	process (data);
		2280
		2281	if (sigismember (&prev, SIGUSR1)
		2282	sigprocmask (SIG_UNBLOCK, &block, 0);
		2283	}
		2284
		2285	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2286	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2287	either...).
		2288
		2289	=item queueing from a thread context
		2290
		2291	The strategy for threads is different, as you cannot (easily) block
		2292	threads but you can easily preempt them, so to queue safely you need to
		2293	employ a traditional mutex lock, such as in this pthread example:
		2294
		2295	static ev_async mysig;
		2296	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2297
		2298	static void
		2299	otherthread (void)
		2300	{
		2301	// only need to lock the actual queueing operation
		2302	pthread_mutex_lock (&mymutex);
		2303	queue_put (data);
		2304	pthread_mutex_unlock (&mymutex);
		2305
		2306	ev_async_send (EV_DEFAULT_ &mysig);
		2307	}
		2308
		2309	static void
		2310	mysig_cb (EV_P_ ev_async *w, int revents)
		2311	{
		2312	pthread_mutex_lock (&mymutex);
		2313
		2314	while (queue_get (&data))
		2315	process (data);
		2316
		2317	pthread_mutex_unlock (&mymutex);
		2318	}
		2319
		2320	=back
		2321
		2322
		2323	=head3 Watcher-Specific Functions and Data Members
		2324
		2325	=over 4
		2326
		2327	=item ev_async_init (ev_async *, callback)
		2328
		2329	Initialises and configures the async watcher - it has no parameters of any
		2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2331	believe me.
		2332
		2333	=item ev_async_send (loop, ev_async *)
		2334
		2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2337	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2339	section below on what exactly this means).
		2340
		2341	This call incurs the overhead of a system call only once per loop iteration,
		2342	so while the overhead might be noticeable, it doesn't apply to repeated
		2343	calls to C<ev_async_send>.
		2344
		2345	=item bool = ev_async_pending (ev_async *)
		2346
		2347	Returns a non-zero value when C<ev_async_send> has been called on the
		2348	watcher but the event has not yet been processed (or even noted) by the
		2349	event loop.
		2350
		2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2352	the loop iterates next and checks for the watcher to have become active,
		2353	it will reset the flag again. C<ev_async_pending> can be used to very
		2354	quickly check whether invoking the loop might be a good idea.
		2355
		2356	Not that this does I<not> check whether the watcher itself is pending, only
		2357	whether it has been requested to make this watcher pending.
		2358
		2359	=back
		2360
		2361
1826	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
1827		2363
1828	There are some other functions of possible interest. Described. Here. Now.	2364	There are some other functions of possible interest. Described. Here. Now.
1829		2365
1830	=over 4	2366	=over 4
…		…
1837	or timeout without having to allocate/configure/start/stop/free one or	2373	or timeout without having to allocate/configure/start/stop/free one or
1838	more watchers yourself.	2374	more watchers yourself.
1839		2375
1840	If C<fd> is less than 0, then no I/O watcher will be started and events	2376	If C<fd> is less than 0, then no I/O watcher will be started and events
1841	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1842	C<events> set will be craeted and started.	2378	C<events> set will be created and started.
1843		2379
1844	If C<timeout> is less than 0, then no timeout watcher will be	2380	If C<timeout> is less than 0, then no timeout watcher will be
1845	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1846	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1847	dubious value.	2383	dubious value.
…		…
1849	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1850	passed an C<revents> set like normal event callbacks (a combination of	2386	passed an C<revents> set like normal event callbacks (a combination of
1851	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1852	value passed to C<ev_once>:	2388	value passed to C<ev_once>:
1853		2389
1854	static void stdin_ready (int revents, void *arg)	2390	static void stdin_ready (int revents, void *arg)
1855	{	2391	{
1856	if (revents & EV_TIMEOUT)	2392	if (revents & EV_TIMEOUT)
1857	/* doh, nothing entered */;	2393	/* doh, nothing entered */;
1858	else if (revents & EV_READ)	2394	else if (revents & EV_READ)
1859	/* stdin might have data for us, joy! */;	2395	/* stdin might have data for us, joy! */;
1860	}	2396	}
1861		2397
1862	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1863		2399
1864	=item ev_feed_event (ev_loop *, watcher *, int revents)	2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
1865		2401
1866	Feeds the given event set into the event loop, as if the specified event	2402	Feeds the given event set into the event loop, as if the specified event
1867	had happened for the specified watcher (which must be a pointer to an	2403	had happened for the specified watcher (which must be a pointer to an
…		…
1872	Feed an event on the given fd, as if a file descriptor backend detected	2408	Feed an event on the given fd, as if a file descriptor backend detected
1873	the given events it.	2409	the given events it.
1874		2410
1875	=item ev_feed_signal_event (ev_loop *loop, int signum)	2411	=item ev_feed_signal_event (ev_loop *loop, int signum)
1876		2412
1877	Feed an event as if the given signal occured (C<loop> must be the default	2413	Feed an event as if the given signal occurred (C<loop> must be the default
1878	loop!).	2414	loop!).
1879		2415
1880	=back	2416	=back
1881		2417
1882		2418
…		…
1898		2434
1899	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
1900	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
1901	is an ev_pri field.	2437	is an ev_pri field.
1902		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
1903	=item * Other members are not supported.	2442	=item * Other members are not supported.
1904		2443
1905	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1906	to use the libev header file and library.	2445	to use the libev header file and library.
1907		2446
1908	=back	2447	=back
1909		2448
1910	=head1 C++ SUPPORT	2449	=head1 C++ SUPPORT
1911		2450
1912	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2451	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1913	you to use some convinience methods to start/stop watchers and also change	2452	you to use some convenience methods to start/stop watchers and also change
1914	the callback model to a model using method callbacks on objects.	2453	the callback model to a model using method callbacks on objects.
1915		2454
1916	To use it,	2455	To use it,
1917		2456
1918	#include <ev++.h>	2457	#include <ev++.h>
1919		2458
1920	This automatically includes F<ev.h> and puts all of its definitions (many	2459	This automatically includes F<ev.h> and puts all of its definitions (many
1921	of them macros) into the global namespace. All C++ specific things are	2460	of them macros) into the global namespace. All C++ specific things are
1922	put into the C<ev> namespace. It should support all the same embedding	2461	put into the C<ev> namespace. It should support all the same embedding
1923	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1990	your compiler is good :), then the method will be fully inlined into the	2529	your compiler is good :), then the method will be fully inlined into the
1991	thunking function, making it as fast as a direct C callback.	2530	thunking function, making it as fast as a direct C callback.
1992		2531
1993	Example: simple class declaration and watcher initialisation	2532	Example: simple class declaration and watcher initialisation
1994		2533
1995	struct myclass	2534	struct myclass
1996	{	2535	{
1997	void io_cb (ev::io &w, int revents) { }	2536	void io_cb (ev::io &w, int revents) { }
1998	}	2537	}
1999		2538
2000	myclass obj;	2539	myclass obj;
2001	ev::io iow;	2540	ev::io iow;
2002	iow.set <myclass, &myclass::io_cb> (&obj);	2541	iow.set <myclass, &myclass::io_cb> (&obj);
2003		2542
2004	=item w->set<function> (void *data = 0)	2543	=item w->set<function> (void *data = 0)
2005		2544
2006	Also sets a callback, but uses a static method or plain function as	2545	Also sets a callback, but uses a static method or plain function as
2007	callback. The optional C<data> argument will be stored in the watcher's	2546	callback. The optional C<data> argument will be stored in the watcher's
…		…
2011		2550
2012	See the method-C<set> above for more details.	2551	See the method-C<set> above for more details.
2013		2552
2014	Example:	2553	Example:
2015		2554
2016	static void io_cb (ev::io &w, int revents) { }	2555	static void io_cb (ev::io &w, int revents) { }
2017	iow.set <io_cb> ();	2556	iow.set <io_cb> ();
2018		2557
2019	=item w->set (struct ev_loop *)	2558	=item w->set (struct ev_loop *)
2020		2559
2021	Associates a different C<struct ev_loop> with this watcher. You can only	2560	Associates a different C<struct ev_loop> with this watcher. You can only
2022	do this when the watcher is inactive (and not pending either).	2561	do this when the watcher is inactive (and not pending either).
2023		2562
2024	=item w->set ([args])	2563	=item w->set ([arguments])
2025		2564
2026	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2027	called at least once. Unlike the C counterpart, an active watcher gets	2566	called at least once. Unlike the C counterpart, an active watcher gets
2028	automatically stopped and restarted when reconfiguring it with this	2567	automatically stopped and restarted when reconfiguring it with this
2029	method.	2568	method.
2030		2569
2031	=item w->start ()	2570	=item w->start ()
…		…
2055	=back	2594	=back
2056		2595
2057	Example: Define a class with an IO and idle watcher, start one of them in	2596	Example: Define a class with an IO and idle watcher, start one of them in
2058	the constructor.	2597	the constructor.
2059		2598
2060	class myclass	2599	class myclass
2061	{	2600	{
2062	ev_io io; void io_cb (ev::io &w, int revents);	2601	ev::io io; void io_cb (ev::io &w, int revents);
2063	ev_idle idle void idle_cb (ev::idle &w, int revents);	2602	ev:idle idle void idle_cb (ev::idle &w, int revents);
2064		2603
2065	myclass ();	2604	myclass (int fd)
2066	}	2605	{
2067
2068	myclass::myclass (int fd)
2069	{
2070	io .set <myclass, &myclass::io_cb > (this);	2606	io .set <myclass, &myclass::io_cb > (this);
2071	idle.set <myclass, &myclass::idle_cb> (this);	2607	idle.set <myclass, &myclass::idle_cb> (this);
2072		2608
2073	io.start (fd, ev::READ);	2609	io.start (fd, ev::READ);
		2610	}
2074	}	2611	};
		2612
		2613
		2614	=head1 OTHER LANGUAGE BINDINGS
		2615
		2616	Libev does not offer other language bindings itself, but bindings for a
		2617	number of languages exist in the form of third-party packages. If you know
		2618	any interesting language binding in addition to the ones listed here, drop
		2619	me a note.
		2620
		2621	=over 4
		2622
		2623	=item Perl
		2624
		2625	The EV module implements the full libev API and is actually used to test
		2626	libev. EV is developed together with libev. Apart from the EV core module,
		2627	there are additional modules that implement libev-compatible interfaces
		2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2630
		2631	It can be found and installed via CPAN, its homepage is found at
		2632	L<http://software.schmorp.de/pkg/EV>.
		2633
		2634	=item Ruby
		2635
		2636	Tony Arcieri has written a ruby extension that offers access to a subset
		2637	of the libev API and adds file handle abstractions, asynchronous DNS and
		2638	more on top of it. It can be found via gem servers. Its homepage is at
		2639	L<http://rev.rubyforge.org/>.
		2640
		2641	=item D
		2642
		2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2645
		2646	=back
2075		2647
2076		2648
2077	=head1 MACRO MAGIC	2649	=head1 MACRO MAGIC
2078		2650
2079	Libev can be compiled with a variety of options, the most fundamantal	2651	Libev can be compiled with a variety of options, the most fundamental
2080	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2652	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2081	functions and callbacks have an initial C<struct ev_loop *> argument.	2653	functions and callbacks have an initial C<struct ev_loop *> argument.
2082		2654
2083	To make it easier to write programs that cope with either variant, the	2655	To make it easier to write programs that cope with either variant, the
2084	following macros are defined:	2656	following macros are defined:
…		…
2089		2661
2090	This provides the loop I<argument> for functions, if one is required ("ev	2662	This provides the loop I<argument> for functions, if one is required ("ev
2091	loop argument"). The C<EV_A> form is used when this is the sole argument,	2663	loop argument"). The C<EV_A> form is used when this is the sole argument,
2092	C<EV_A_> is used when other arguments are following. Example:	2664	C<EV_A_> is used when other arguments are following. Example:
2093		2665
2094	ev_unref (EV_A);	2666	ev_unref (EV_A);
2095	ev_timer_add (EV_A_ watcher);	2667	ev_timer_add (EV_A_ watcher);
2096	ev_loop (EV_A_ 0);	2668	ev_loop (EV_A_ 0);
2097		2669
2098	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2099	which is often provided by the following macro.	2671	which is often provided by the following macro.
2100		2672
2101	=item C<EV_P>, C<EV_P_>	2673	=item C<EV_P>, C<EV_P_>
2102		2674
2103	This provides the loop I<parameter> for functions, if one is required ("ev	2675	This provides the loop I<parameter> for functions, if one is required ("ev
2104	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2105	C<EV_P_> is used when other parameters are following. Example:	2677	C<EV_P_> is used when other parameters are following. Example:
2106		2678
2107	// this is how ev_unref is being declared	2679	// this is how ev_unref is being declared
2108	static void ev_unref (EV_P);	2680	static void ev_unref (EV_P);
2109		2681
2110	// this is how you can declare your typical callback	2682	// this is how you can declare your typical callback
2111	static void cb (EV_P_ ev_timer *w, int revents)	2683	static void cb (EV_P_ ev_timer *w, int revents)
2112		2684
2113	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2114	suitable for use with C<EV_A>.	2686	suitable for use with C<EV_A>.
2115		2687
2116	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2117		2689
2118	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
2119	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2120		2702
2121	=back	2703	=back
2122		2704
2123	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
2124	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
2125	or not.	2707	or not.
2126		2708
2127	static void	2709	static void
2128	check_cb (EV_P_ ev_timer *w, int revents)	2710	check_cb (EV_P_ ev_timer *w, int revents)
2129	{	2711	{
2130	ev_check_stop (EV_A_ w);	2712	ev_check_stop (EV_A_ w);
2131	}	2713	}
2132		2714
2133	ev_check check;	2715	ev_check check;
2134	ev_check_init (&check, check_cb);	2716	ev_check_init (&check, check_cb);
2135	ev_check_start (EV_DEFAULT_ &check);	2717	ev_check_start (EV_DEFAULT_ &check);
2136	ev_loop (EV_DEFAULT_ 0);	2718	ev_loop (EV_DEFAULT_ 0);
2137		2719
2138	=head1 EMBEDDING	2720	=head1 EMBEDDING
2139		2721
2140	Libev can (and often is) directly embedded into host	2722	Libev can (and often is) directly embedded into host
2141	applications. Examples of applications that embed it include the Deliantra	2723	applications. Examples of applications that embed it include the Deliantra
2142	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2724	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2143	and rxvt-unicode.	2725	and rxvt-unicode.
2144		2726
2145	The goal is to enable you to just copy the neecssary files into your	2727	The goal is to enable you to just copy the necessary files into your
2146	source directory without having to change even a single line in them, so	2728	source directory without having to change even a single line in them, so
2147	you can easily upgrade by simply copying (or having a checked-out copy of	2729	you can easily upgrade by simply copying (or having a checked-out copy of
2148	libev somewhere in your source tree).	2730	libev somewhere in your source tree).
2149		2731
2150	=head2 FILESETS	2732	=head2 FILESETS
2151		2733
2152	Depending on what features you need you need to include one or more sets of files	2734	Depending on what features you need you need to include one or more sets of files
2153	in your app.	2735	in your application.
2154		2736
2155	=head3 CORE EVENT LOOP	2737	=head3 CORE EVENT LOOP
2156		2738
2157	To include only the libev core (all the C<ev_*> functions), with manual	2739	To include only the libev core (all the C<ev_*> functions), with manual
2158	configuration (no autoconf):	2740	configuration (no autoconf):
2159		2741
2160	#define EV_STANDALONE 1	2742	#define EV_STANDALONE 1
2161	#include "ev.c"	2743	#include "ev.c"
2162		2744
2163	This will automatically include F<ev.h>, too, and should be done in a	2745	This will automatically include F<ev.h>, too, and should be done in a
2164	single C source file only to provide the function implementations. To use	2746	single C source file only to provide the function implementations. To use
2165	it, do the same for F<ev.h> in all files wishing to use this API (best	2747	it, do the same for F<ev.h> in all files wishing to use this API (best
2166	done by writing a wrapper around F<ev.h> that you can include instead and	2748	done by writing a wrapper around F<ev.h> that you can include instead and
2167	where you can put other configuration options):	2749	where you can put other configuration options):
2168		2750
2169	#define EV_STANDALONE 1	2751	#define EV_STANDALONE 1
2170	#include "ev.h"	2752	#include "ev.h"
2171		2753
2172	Both header files and implementation files can be compiled with a C++	2754	Both header files and implementation files can be compiled with a C++
2173	compiler (at least, thats a stated goal, and breakage will be treated	2755	compiler (at least, thats a stated goal, and breakage will be treated
2174	as a bug).	2756	as a bug).
2175		2757
2176	You need the following files in your source tree, or in a directory	2758	You need the following files in your source tree, or in a directory
2177	in your include path (e.g. in libev/ when using -Ilibev):	2759	in your include path (e.g. in libev/ when using -Ilibev):
2178		2760
2179	ev.h	2761	ev.h
2180	ev.c	2762	ev.c
2181	ev_vars.h	2763	ev_vars.h
2182	ev_wrap.h	2764	ev_wrap.h
2183		2765
2184	ev_win32.c required on win32 platforms only	2766	ev_win32.c required on win32 platforms only
2185		2767
2186	ev_select.c only when select backend is enabled (which is enabled by default)	2768	ev_select.c only when select backend is enabled (which is enabled by default)
2187	ev_poll.c only when poll backend is enabled (disabled by default)	2769	ev_poll.c only when poll backend is enabled (disabled by default)
2188	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2189	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2190	ev_port.c only when the solaris port backend is enabled (disabled by default)	2772	ev_port.c only when the solaris port backend is enabled (disabled by default)
2191		2773
2192	F<ev.c> includes the backend files directly when enabled, so you only need	2774	F<ev.c> includes the backend files directly when enabled, so you only need
2193	to compile this single file.	2775	to compile this single file.
2194		2776
2195	=head3 LIBEVENT COMPATIBILITY API	2777	=head3 LIBEVENT COMPATIBILITY API
2196		2778
2197	To include the libevent compatibility API, also include:	2779	To include the libevent compatibility API, also include:
2198		2780
2199	#include "event.c"	2781	#include "event.c"
2200		2782
2201	in the file including F<ev.c>, and:	2783	in the file including F<ev.c>, and:
2202		2784
2203	#include "event.h"	2785	#include "event.h"
2204		2786
2205	in the files that want to use the libevent API. This also includes F<ev.h>.	2787	in the files that want to use the libevent API. This also includes F<ev.h>.
2206		2788
2207	You need the following additional files for this:	2789	You need the following additional files for this:
2208		2790
2209	event.h	2791	event.h
2210	event.c	2792	event.c
2211		2793
2212	=head3 AUTOCONF SUPPORT	2794	=head3 AUTOCONF SUPPORT
2213		2795
2214	Instead of using C<EV_STANDALONE=1> and providing your config in	2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2215	whatever way you want, you can also C<m4_include([libev.m4])> in your	2797	whatever way you want, you can also C<m4_include([libev.m4])> in your
2216	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2217	include F<config.h> and configure itself accordingly.	2799	include F<config.h> and configure itself accordingly.
2218		2800
2219	For this of course you need the m4 file:	2801	For this of course you need the m4 file:
2220		2802
2221	libev.m4	2803	libev.m4
2222		2804
2223	=head2 PREPROCESSOR SYMBOLS/MACROS	2805	=head2 PREPROCESSOR SYMBOLS/MACROS
2224		2806
2225	Libev can be configured via a variety of preprocessor symbols you have to define	2807	Libev can be configured via a variety of preprocessor symbols you have to
2226	before including any of its files. The default is not to build for multiplicity	2808	define before including any of its files. The default in the absence of
2227	and only include the select backend.	2809	autoconf is noted for every option.
2228		2810
2229	=over 4	2811	=over 4
2230		2812
2231	=item EV_STANDALONE	2813	=item EV_STANDALONE
2232		2814
…		…
2237	F<event.h> that are not directly supported by the libev core alone.	2819	F<event.h> that are not directly supported by the libev core alone.
2238		2820
2239	=item EV_USE_MONOTONIC	2821	=item EV_USE_MONOTONIC
2240		2822
2241	If defined to be C<1>, libev will try to detect the availability of the	2823	If defined to be C<1>, libev will try to detect the availability of the
2242	monotonic clock option at both compiletime and runtime. Otherwise no use	2824	monotonic clock option at both compile time and runtime. Otherwise no use
2243	of the monotonic clock option will be attempted. If you enable this, you	2825	of the monotonic clock option will be attempted. If you enable this, you
2244	usually have to link against librt or something similar. Enabling it when	2826	usually have to link against librt or something similar. Enabling it when
2245	the functionality isn't available is safe, though, althoguh you have	2827	the functionality isn't available is safe, though, although you have
2246	to make sure you link against any libraries where the C<clock_gettime>	2828	to make sure you link against any libraries where the C<clock_gettime>
2247	function is hiding in (often F<-lrt>).	2829	function is hiding in (often F<-lrt>).
2248		2830
2249	=item EV_USE_REALTIME	2831	=item EV_USE_REALTIME
2250		2832
2251	If defined to be C<1>, libev will try to detect the availability of the	2833	If defined to be C<1>, libev will try to detect the availability of the
2252	realtime clock option at compiletime (and assume its availability at	2834	real-time clock option at compile time (and assume its availability at
2253	runtime if successful). Otherwise no use of the realtime clock option will	2835	runtime if successful). Otherwise no use of the real-time clock option will
2254	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2255	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2256	in the description of C<EV_USE_MONOTONIC>, though.	2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2839
		2840	=item EV_USE_NANOSLEEP
		2841
		2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2843	and will use it for delays. Otherwise it will use C<select ()>.
		2844
		2845	=item EV_USE_EVENTFD
		2846
		2847	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2848	available and will probe for kernel support at runtime. This will improve
		2849	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2850	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2851	2.7 or newer, otherwise disabled.
2257		2852
2258	=item EV_USE_SELECT	2853	=item EV_USE_SELECT
2259		2854
2260	If undefined or defined to be C<1>, libev will compile in support for the	2855	If undefined or defined to be C<1>, libev will compile in support for the
2261	C<select>(2) backend. No attempt at autodetection will be done: if no	2856	C<select>(2) backend. No attempt at auto-detection will be done: if no
2262	other method takes over, select will be it. Otherwise the select backend	2857	other method takes over, select will be it. Otherwise the select backend
2263	will not be compiled in.	2858	will not be compiled in.
2264		2859
2265	=item EV_SELECT_USE_FD_SET	2860	=item EV_SELECT_USE_FD_SET
2266		2861
2267	If defined to C<1>, then the select backend will use the system C<fd_set>	2862	If defined to C<1>, then the select backend will use the system C<fd_set>
2268	structure. This is useful if libev doesn't compile due to a missing	2863	structure. This is useful if libev doesn't compile due to a missing
2269	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2270	exotic systems. This usually limits the range of file descriptors to some	2865	exotic systems. This usually limits the range of file descriptors to some
2271	low limit such as 1024 or might have other limitations (winsocket only	2866	low limit such as 1024 or might have other limitations (winsocket only
2272	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2273	influence the size of the C<fd_set> used.	2868	influence the size of the C<fd_set> used.
2274		2869
…		…
2280	be used is the winsock select). This means that it will call	2875	be used is the winsock select). This means that it will call
2281	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2282	it is assumed that all these functions actually work on fds, even	2877	it is assumed that all these functions actually work on fds, even
2283	on win32. Should not be defined on non-win32 platforms.	2878	on win32. Should not be defined on non-win32 platforms.
2284		2879
		2880	=item EV_FD_TO_WIN32_HANDLE
		2881
		2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2883	file descriptors to socket handles. When not defining this symbol (the
		2884	default), then libev will call C<_get_osfhandle>, which is usually
		2885	correct. In some cases, programs use their own file descriptor management,
		2886	in which case they can provide this function to map fds to socket handles.
		2887
2285	=item EV_USE_POLL	2888	=item EV_USE_POLL
2286		2889
2287	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2288	backend. Otherwise it will be enabled on non-win32 platforms. It	2891	backend. Otherwise it will be enabled on non-win32 platforms. It
2289	takes precedence over select.	2892	takes precedence over select.
2290		2893
2291	=item EV_USE_EPOLL	2894	=item EV_USE_EPOLL
2292		2895
2293	If defined to be C<1>, libev will compile in support for the Linux	2896	If defined to be C<1>, libev will compile in support for the Linux
2294	C<epoll>(7) backend. Its availability will be detected at runtime,	2897	C<epoll>(7) backend. Its availability will be detected at runtime,
2295	otherwise another method will be used as fallback. This is the	2898	otherwise another method will be used as fallback. This is the preferred
2296	preferred backend for GNU/Linux systems.	2899	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2900	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2297		2901
2298	=item EV_USE_KQUEUE	2902	=item EV_USE_KQUEUE
2299		2903
2300	If defined to be C<1>, libev will compile in support for the BSD style	2904	If defined to be C<1>, libev will compile in support for the BSD style
2301	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2905	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2314	otherwise another method will be used as fallback. This is the preferred	2918	otherwise another method will be used as fallback. This is the preferred
2315	backend for Solaris 10 systems.	2919	backend for Solaris 10 systems.
2316		2920
2317	=item EV_USE_DEVPOLL	2921	=item EV_USE_DEVPOLL
2318		2922
2319	reserved for future expansion, works like the USE symbols above.	2923	Reserved for future expansion, works like the USE symbols above.
2320		2924
2321	=item EV_USE_INOTIFY	2925	=item EV_USE_INOTIFY
2322		2926
2323	If defined to be C<1>, libev will compile in support for the Linux inotify	2927	If defined to be C<1>, libev will compile in support for the Linux inotify
2324	interface to speed up C<ev_stat> watchers. Its actual availability will	2928	interface to speed up C<ev_stat> watchers. Its actual availability will
2325	be detected at runtime.	2929	be detected at runtime. If undefined, it will be enabled if the headers
		2930	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2931
		2932	=item EV_ATOMIC_T
		2933
		2934	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2935	access is atomic with respect to other threads or signal contexts. No such
		2936	type is easily found in the C language, so you can provide your own type
		2937	that you know is safe for your purposes. It is used both for signal handler "locking"
		2938	as well as for signal and thread safety in C<ev_async> watchers.
		2939
		2940	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2941	(from F<signal.h>), which is usually good enough on most platforms.
2326		2942
2327	=item EV_H	2943	=item EV_H
2328		2944
2329	The name of the F<ev.h> header file used to include it. The default if	2945	The name of the F<ev.h> header file used to include it. The default if
2330	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2331	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2947	used to virtually rename the F<ev.h> header file in case of conflicts.
2332		2948
2333	=item EV_CONFIG_H	2949	=item EV_CONFIG_H
2334		2950
2335	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2336	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2337	C<EV_H>, above.	2953	C<EV_H>, above.
2338		2954
2339	=item EV_EVENT_H	2955	=item EV_EVENT_H
2340		2956
2341	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2342	of how the F<event.h> header can be found.	2958	of how the F<event.h> header can be found, the default is C<"event.h">.
2343		2959
2344	=item EV_PROTOTYPES	2960	=item EV_PROTOTYPES
2345		2961
2346	If defined to be C<0>, then F<ev.h> will not define any function	2962	If defined to be C<0>, then F<ev.h> will not define any function
2347	prototypes, but still define all the structs and other symbols. This is	2963	prototypes, but still define all the structs and other symbols. This is
…		…
2368	When doing priority-based operations, libev usually has to linearly search	2984	When doing priority-based operations, libev usually has to linearly search
2369	all the priorities, so having many of them (hundreds) uses a lot of space	2985	all the priorities, so having many of them (hundreds) uses a lot of space
2370	and time, so using the defaults of five priorities (-2 .. +2) is usually	2986	and time, so using the defaults of five priorities (-2 .. +2) is usually
2371	fine.	2987	fine.
2372		2988
2373	If your embedding app does not need any priorities, defining these both to	2989	If your embedding application does not need any priorities, defining these both to
2374	C<0> will save some memory and cpu.	2990	C<0> will save some memory and CPU.
2375		2991
2376	=item EV_PERIODIC_ENABLE	2992	=item EV_PERIODIC_ENABLE
2377		2993
2378	If undefined or defined to be C<1>, then periodic timers are supported. If	2994	If undefined or defined to be C<1>, then periodic timers are supported. If
2379	defined to be C<0>, then they are not. Disabling them saves a few kB of	2995	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2398	=item EV_FORK_ENABLE	3014	=item EV_FORK_ENABLE
2399		3015
2400	If undefined or defined to be C<1>, then fork watchers are supported. If	3016	If undefined or defined to be C<1>, then fork watchers are supported. If
2401	defined to be C<0>, then they are not.	3017	defined to be C<0>, then they are not.
2402		3018
		3019	=item EV_ASYNC_ENABLE
		3020
		3021	If undefined or defined to be C<1>, then async watchers are supported. If
		3022	defined to be C<0>, then they are not.
		3023
2403	=item EV_MINIMAL	3024	=item EV_MINIMAL
2404		3025
2405	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2406	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2407	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2408		3030
2409	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2410		3032
2411	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2412	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2413	than enough. If you need to manage thousands of children you might want to	3035	than enough. If you need to manage thousands of children you might want to
2414	increase this value (I<must> be a power of two).	3036	increase this value (I<must> be a power of two).
2415		3037
2416	=item EV_INOTIFY_HASHSIZE	3038	=item EV_INOTIFY_HASHSIZE
2417		3039
2418	C<ev_staz> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2419	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2420	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2421	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2422	two).	3044	two).
2423		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticeably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticeably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
		3080
2424	=item EV_COMMON	3081	=item EV_COMMON
2425		3082
2426	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2427	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
2428	members. You have to define it each time you include one of the files,	3085	members. You have to define it each time you include one of the files,
2429	though, and it must be identical each time.	3086	though, and it must be identical each time.
2430		3087
2431	For example, the perl EV module uses something like this:	3088	For example, the perl EV module uses something like this:
2432		3089
2433	#define EV_COMMON \	3090	#define EV_COMMON \
2434	SV *self; /* contains this struct */ \	3091	SV *self; /* contains this struct */ \
2435	SV *cb_sv, *fh /* note no trailing ";" */	3092	SV *cb_sv, *fh /* note no trailing ";" */
2436		3093
2437	=item EV_CB_DECLARE (type)	3094	=item EV_CB_DECLARE (type)
2438		3095
2439	=item EV_CB_INVOKE (watcher, revents)	3096	=item EV_CB_INVOKE (watcher, revents)
2440		3097
2441	=item ev_set_cb (ev, cb)	3098	=item ev_set_cb (ev, cb)
2442		3099
2443	Can be used to change the callback member declaration in each watcher,	3100	Can be used to change the callback member declaration in each watcher,
2444	and the way callbacks are invoked and set. Must expand to a struct member	3101	and the way callbacks are invoked and set. Must expand to a struct member
2445	definition and a statement, respectively. See the F<ev.v> header file for	3102	definition and a statement, respectively. See the F<ev.h> header file for
2446	their default definitions. One possible use for overriding these is to	3103	their default definitions. One possible use for overriding these is to
2447	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2448	method calls instead of plain function calls in C++.	3105	method calls instead of plain function calls in C++.
2449		3106
2450	=head2 EXPORTED API SYMBOLS	3107	=head2 EXPORTED API SYMBOLS
2451		3108
2452	If you need to re-export the API (e.g. via a dll) and you need a list of	3109	If you need to re-export the API (e.g. via a DLL) and you need a list of
2453	exported symbols, you can use the provided F<Symbol.*> files which list	3110	exported symbols, you can use the provided F<Symbol.*> files which list
2454	all public symbols, one per line:	3111	all public symbols, one per line:
2455		3112
2456	Symbols.ev for libev proper	3113	Symbols.ev for libev proper
2457	Symbols.event for the libevent emulation	3114	Symbols.event for the libevent emulation
2458		3115
2459	This can also be used to rename all public symbols to avoid clashes with	3116	This can also be used to rename all public symbols to avoid clashes with
2460	multiple versions of libev linked together (which is obviously bad in	3117	multiple versions of libev linked together (which is obviously bad in
2461	itself, but sometimes it is inconvinient to avoid this).	3118	itself, but sometimes it is inconvenient to avoid this).
2462		3119
2463	A sed comamnd like this will create wrapper C<#define>'s that you need to	3120	A sed command like this will create wrapper C<#define>'s that you need to
2464	include before including F<ev.h>:	3121	include before including F<ev.h>:
2465		3122
2466	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3123	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2467		3124
2468	This would create a file F<wrap.h> which essentially looks like this:	3125	This would create a file F<wrap.h> which essentially looks like this:
…		…
2483	file.	3140	file.
2484		3141
2485	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2486	that everybody includes and which overrides some configure choices:	3143	that everybody includes and which overrides some configure choices:
2487		3144
2488	#define EV_MINIMAL 1	3145	#define EV_MINIMAL 1
2489	#define EV_USE_POLL 0	3146	#define EV_USE_POLL 0
2490	#define EV_MULTIPLICITY 0	3147	#define EV_MULTIPLICITY 0
2491	#define EV_PERIODIC_ENABLE 0	3148	#define EV_PERIODIC_ENABLE 0
2492	#define EV_STAT_ENABLE 0	3149	#define EV_STAT_ENABLE 0
2493	#define EV_FORK_ENABLE 0	3150	#define EV_FORK_ENABLE 0
2494	#define EV_CONFIG_H <config.h>	3151	#define EV_CONFIG_H <config.h>
2495	#define EV_MINPRI 0	3152	#define EV_MINPRI 0
2496	#define EV_MAXPRI 0	3153	#define EV_MAXPRI 0
2497		3154
2498	#include "ev++.h"	3155	#include "ev++.h"
2499		3156
2500	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2501		3158
2502	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
2503	#include "ev.c"	3160	#include "ev.c"
		3161
		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely thread-safe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a separate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robin fashion.
		3196
		3197	Choosing a model is hard - look around, learn, know that usually you can do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accommodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
2504		3218
2505		3219
2506	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
2507		3221
2508	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
…		…
2519		3233
2520	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2521		3235
2522	This means that, when you have a watcher that triggers in one hour and	3236	This means that, when you have a watcher that triggers in one hour and
2523	there are 100 watchers that would trigger before that then inserting will	3237	there are 100 watchers that would trigger before that then inserting will
2524	have to skip those 100 watchers.	3238	have to skip roughly seven (C<ld 100>) of these watchers.
2525		3239
2526	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2527		3241
2528	That means that for changing a timer costs less than removing/adding them	3242	That means that changing a timer costs less than removing/adding them
2529	as only the relative motion in the event queue has to be paid for.	3243	as only the relative motion in the event queue has to be paid for.
2530		3244
2531	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2532		3246
2533	These just add the watcher into an array or at the head of a list.	3247	These just add the watcher into an array or at the head of a list.
		3248
2534	=item Stopping check/prepare/idle watchers: O(1)	3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2535		3250
2536	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2537		3252
2538	These watchers are stored in lists then need to be walked to find the	3253	These watchers are stored in lists then need to be walked to find the
2539	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
2540	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
2541		3256
2542	=item Finding the next timer per loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
		3258
		3259	By virtue of using a binary or 4-heap, the next timer is always found at a
		3260	fixed position in the storage array.
2543		3261
2544	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2545		3263
2546	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
2547	libev to recalculate its status (and possibly tell the kernel).	3265	libev to recalculate its status (and possibly tell the kernel, depending
		3266	on backend and whether C<ev_io_set> was used).
2548		3267
2549	=item Activating one watcher: O(1)	3268	=item Activating one watcher (putting it into the pending state): O(1)
2550		3269
2551	=item Priority handling: O(number_of_priorities)	3270	=item Priority handling: O(number_of_priorities)
2552		3271
2553	Priorities are implemented by allocating some space for each	3272	Priorities are implemented by allocating some space for each
2554	priority. When doing priority-based operations, libev usually has to	3273	priority. When doing priority-based operations, libev usually has to
2555	linearly search all the priorities.	3274	linearly search all the priorities, but starting/stopping and activating
		3275	watchers becomes O(1) w.r.t. priority handling.
		3276
		3277	=item Sending an ev_async: O(1)
		3278
		3279	=item Processing ev_async_send: O(number_of_async_watchers)
		3280
		3281	=item Processing signals: O(max_signal_number)
		3282
		3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3284	calls in the current loop iteration. Checking for async and signal events
		3285	involves iterating over all running async watchers or all signal numbers.
2556		3286
2557	=back	3287	=back
2558		3288
2559		3289
		3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3291
		3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3293	requires, and its I/O model is fundamentally incompatible with the POSIX
		3294	model. Libev still offers limited functionality on this platform in
		3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3296	descriptors. This only applies when using Win32 natively, not when using
		3297	e.g. cygwin.
		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
		3304	There is no supported compilation method available on windows except
		3305	embedding it into other applications.
		3306
		3307	Not a libev limitation but worth mentioning: windows apparently doesn't
		3308	accept large writes: instead of resulting in a partial write, windows will
		3309	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3310	so make sure you only write small amounts into your sockets (less than a
		3311	megabyte seems safe, but thsi apparently depends on the amount of memory
		3312	available).
		3313
		3314	Due to the many, low, and arbitrary limits on the win32 platform and
		3315	the abysmal performance of winsockets, using a large number of sockets
		3316	is not recommended (and not reasonable). If your program needs to use
		3317	more than a hundred or so sockets, then likely it needs to use a totally
		3318	different implementation for windows, as libev offers the POSIX readiness
		3319	notification model, which cannot be implemented efficiently on windows
		3320	(Microsoft monopoly games).
		3321
		3322	=over 4
		3323
		3324	=item The winsocket select function
		3325
		3326	The winsocket C<select> function doesn't follow POSIX in that it
		3327	requires socket I<handles> and not socket I<file descriptors> (it is
		3328	also extremely buggy). This makes select very inefficient, and also
		3329	requires a mapping from file descriptors to socket handles. See the
		3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3332
		3333	The configuration for a "naked" win32 using the Microsoft runtime
		3334	libraries and raw winsocket select is:
		3335
		3336	#define EV_USE_SELECT 1
		3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3338
		3339	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3340	complexity in the O(n²) range when using win32.
		3341
		3342	=item Limited number of file descriptors
		3343
		3344	Windows has numerous arbitrary (and low) limits on things.
		3345
		3346	Early versions of winsocket's select only supported waiting for a maximum
		3347	of C<64> handles (probably owning to the fact that all windows kernels
		3348	can only wait for C<64> things at the same time internally; Microsoft
		3349	recommends spawning a chain of threads and wait for 63 handles and the
		3350	previous thread in each. Great).
		3351
		3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3353	to some high number (e.g. C<2048>) before compiling the winsocket select
		3354	call (which might be in libev or elsewhere, for example, perl does its own
		3355	select emulation on windows).
		3356
		3357	Another limit is the number of file descriptors in the Microsoft runtime
		3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3359	or something like this inside Microsoft). You can increase this by calling
		3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3361	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3362	libraries.
		3363
		3364	This might get you to about C<512> or C<2048> sockets (depending on
		3365	windows version and/or the phase of the moon). To get more, you need to
		3366	wrap all I/O functions and provide your own fd management, but the cost of
		3367	calling select (O(n²)) will likely make this unworkable.
		3368
		3369	=back
		3370
		3371
		3372	=head1 PORTABILITY REQUIREMENTS
		3373
		3374	In addition to a working ISO-C implementation, libev relies on a few
		3375	additional extensions:
		3376
		3377	=over 4
		3378
		3379	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3380
		3381	The type C<sig_atomic_t volatile> (or whatever is defined as
		3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3383	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3384	believed to be sufficiently portable.
		3385
		3386	=item C<sigprocmask> must work in a threaded environment
		3387
		3388	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3389	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3390	pthread implementations will either allow C<sigprocmask> in the "main
		3391	thread" or will block signals process-wide, both behaviours would
		3392	be compatible with libev. Interaction between C<sigprocmask> and
		3393	C<pthread_sigmask> could complicate things, however.
		3394
		3395	The most portable way to handle signals is to block signals in all threads
		3396	except the initial one, and run the default loop in the initial thread as
		3397	well.
		3398
		3399	=item C<long> must be large enough for common memory allocation sizes
		3400
		3401	To improve portability and simplify using libev, libev uses C<long>
		3402	internally instead of C<size_t> when allocating its data structures. On
		3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3404	is still at least 31 bits everywhere, which is enough for hundreds of
		3405	millions of watchers.
		3406
		3407	=item C<double> must hold a time value in seconds with enough accuracy
		3408
		3409	The type C<double> is used to represent timestamps. It is required to
		3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3411	enough for at least into the year 4000. This requirement is fulfilled by
		3412	implementations implementing IEEE 754 (basically all existing ones).
		3413
		3414	=back
		3415
		3416	If you know of other additional requirements drop me a note.
		3417
		3418
		3419	=head1 COMPILER WARNINGS
		3420
		3421	Depending on your compiler and compiler settings, you might get no or a
		3422	lot of warnings when compiling libev code. Some people are apparently
		3423	scared by this.
		3424
		3425	However, these are unavoidable for many reasons. For one, each compiler
		3426	has different warnings, and each user has different tastes regarding
		3427	warning options. "Warn-free" code therefore cannot be a goal except when
		3428	targeting a specific compiler and compiler-version.
		3429
		3430	Another reason is that some compiler warnings require elaborate
		3431	workarounds, or other changes to the code that make it less clear and less
		3432	maintainable.
		3433
		3434	And of course, some compiler warnings are just plain stupid, or simply
		3435	wrong (because they don't actually warn about the condition their message
		3436	seems to warn about).
		3437
		3438	While libev is written to generate as few warnings as possible,
		3439	"warn-free" code is not a goal, and it is recommended not to build libev
		3440	with any compiler warnings enabled unless you are prepared to cope with
		3441	them (e.g. by ignoring them). Remember that warnings are just that:
		3442	warnings, not errors, or proof of bugs.
		3443
		3444
		3445	=head1 VALGRIND
		3446
		3447	Valgrind has a special section here because it is a popular tool that is
		3448	highly useful, but valgrind reports are very hard to interpret.
		3449
		3450	If you think you found a bug (memory leak, uninitialised data access etc.)
		3451	in libev, then check twice: If valgrind reports something like:
		3452
		3453	==2274== definitely lost: 0 bytes in 0 blocks.
		3454	==2274== possibly lost: 0 bytes in 0 blocks.
		3455	==2274== still reachable: 256 bytes in 1 blocks.
		3456
		3457	Then there is no memory leak. Similarly, under some circumstances,
		3458	valgrind might report kernel bugs as if it were a bug in libev, or it
		3459	might be confused (it is a very good tool, but only a tool).
		3460
		3461	If you are unsure about something, feel free to contact the mailing list
		3462	with the full valgrind report and an explanation on why you think this is
		3463	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3464	no bug" answer and take the chance of learning how to interpret valgrind
		3465	properly.
		3466
		3467	If you need, for some reason, empty reports from valgrind for your project
		3468	I suggest using suppression lists.
		3469
		3470
2560	=head1 AUTHOR	3471	=head1 AUTHOR
2561		3472
2562	Marc Lehmann <libev@schmorp.de>.	3473	Marc Lehmann <libev@schmorp.de>.
2563		3474

Diff Legend

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