ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC vs.
Revision 1.174 by root, Mon Aug 18 23:23:45 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 occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
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	376	but it scales phenomenally better. While poll and select usually scale
319	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
320	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
321	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
322	cases and rewuiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
323	support for dup:	381	support for dup.
324		382
325	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
326	will 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
327	(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
328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
329	very well if you register events for both fds.	387	very well if you register events for both fds.
330		388
331	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
332	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
333	(or space) is available.	391	(or space) is available.
334		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
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		401
337	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
338	was broken on I<all> BSDs (usually it doesn't work with anything but	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
339	sockets and pipes, except on Darwin, where of course it's completely	404	with anything but sockets and pipes, except on Darwin, where of course
340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
341	is used by default there). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
342	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
343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	408	system like NetBSD.
345		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.
		413
346	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
347	kernel is more efficient (which says nothing about its actual speed,	415	kernel is more efficient (which says nothing about its actual speed, of
348	of course). While stopping, setting and starting an I/O watcher does	416	course). While stopping, setting and starting an I/O watcher does never
349	never cause an extra syscall as with epoll, it still adds up to two event	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
350	changes per incident, support for C<fork ()> is very bad and it drops fds	418	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	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.
352		429
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		431
355	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.
356		436
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		438
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
360	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)).
361		441
362	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
363	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
364	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.
365		454
366	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
367		456
368	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
369	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
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		460
		461	It is definitely not recommended to use this flag.
		462
372	=back	463	=back
373		464
374	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
375	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
376	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		468
379	The most typical usage is like this:	469	The most typical usage is like this:
380		470
381	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
383		473
384	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
385	environment settings to be taken into account:	475	environment settings to be taken into account:
386		476
387	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
388		478
389	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
390	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
391	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):
392		482
393	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
394		484
395	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
396		486
397	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
398	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
399	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
400	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
401		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
402	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.
403		497
404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
405	if (!epoller)	499	if (!epoller)
406	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
407		501
408	=item ev_default_destroy ()	502	=item ev_default_destroy ()
409		503
410	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
411	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
412	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
413	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
414	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
415	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
416	for example).	510	for example).
417		511
418	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
…		…
429	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
430	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
431		525
432	=item ev_default_fork ()	526	=item ev_default_fork ()
433		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
435	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
436	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
437	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.
438		534
439	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
440	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
441	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
442		538
443	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
444	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
445	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
446		542
447	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
448		544
449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
450	without calling this function, so if you force one of those backends you
451	do not need to care.
452
453	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
454		546
455	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
456	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
457	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.
458		554
459	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
460		556
461	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
462	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
…		…
497	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
498	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
499	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.
500		596
501	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
502	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
503	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
504	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
505	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
506	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
507	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
508		604
509	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
510		606
511	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	609	- If a fork was detected (by any means), queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
515	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
517	- Calculate for how long to block.	615	- Calculate for how long to sleep or block, if at all
		616	(active idle watchers, EVLOOP_NONBLOCK or not having
		617	any active watchers at all will result in not sleeping).
		618	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
521	- Queue all outstanding timers.	622	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
524	- Queue all check watchers.	625	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	626	- Call all queued watchers in reverse order (i.e. check watchers first).
526	Signals and child watchers are implemented as I/O watchers, and will	627	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
530		632
531	Example: Queue some jobs and then loop until no events are outsanding	633	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	634	anymore.
533		635
534	... queue jobs here, make sure they register event watchers as long	636	... queue jobs here, make sure they register event watchers as long
535	... as they still have work to do (even an idle watcher will do..)	637	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
537	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
538		640
539	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
540		642
541	Can be used to make a call to C<ev_loop> return early (but only after it	643	Can be used to make a call to C<ev_loop> return early (but only after it
542	has processed all outstanding events). The C<how> argument must be either	644	has processed all outstanding events). The C<how> argument must be either
543	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
544	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		647
		648	This "unloop state" will be cleared when entering C<ev_loop> again.
545		649
546	=item ev_ref (loop)	650	=item ev_ref (loop)
547		651
548	=item ev_unref (loop)	652	=item ev_unref (loop)
549		653
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	658	returning, ev_unref() after starting, and ev_ref() before stopping it. For
555	example, libev itself uses this for its internal signal pipe: It is not	659	example, libev itself uses this for its internal signal pipe: It is not
556	visible to the libev user and should not keep C<ev_loop> from exiting if	660	visible to the libev user and should not keep C<ev_loop> from exiting if
557	no event watchers registered by it are active. It is also an excellent	661	no event watchers registered by it are active. It is also an excellent
558	way to do this for generic recurring timers or from within third-party	662	way to do this for generic recurring timers or from within third-party
559	libraries. Just remember to I<unref after start> and I<ref before stop>.	663	libraries. Just remember to I<unref after start> and I<ref before stop>
		664	(but only if the watcher wasn't active before, or was active before,
		665	respectively).
560		666
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	668	running when nothing else is active.
563		669
564	struct ev_signal exitsig;	670	struct ev_signal exitsig;
565	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
566	ev_signal_start (loop, &exitsig);	672	ev_signal_start (loop, &exitsig);
567	evf_unref (loop);	673	evf_unref (loop);
568		674
569	Example: For some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
570		676
571	ev_ref (loop);	677	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	678	ev_signal_stop (loop, &exitsig);
		679
		680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		681
		682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		683
		684	These advanced functions influence the time that libev will spend waiting
		685	for events. Both time intervals are by default C<0>, meaning that libev
		686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
		688
		689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		690	allows libev to delay invocation of I/O and timer/periodic callbacks
		691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
		693
		694	The background is that sometimes your program runs just fast enough to
		695	handle one (or very few) event(s) per loop iteration. While this makes
		696	the program responsive, it also wastes a lot of CPU time to poll for new
		697	events, especially with backends like C<select ()> which have a high
		698	overhead for the actual polling but can deliver many events at once.
		699
		700	By setting a higher I<io collect interval> you allow libev to spend more
		701	time collecting I/O events, so you can handle more events per iteration,
		702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		703	C<ev_timer>) will be not affected. Setting this to a non-null value will
		704	introduce an additional C<ev_sleep ()> call into most loop iterations.
		705
		706	Likewise, by setting a higher I<timeout collect interval> you allow libev
		707	to spend more time collecting timeouts, at the expense of increased
		708	latency (the watcher callback will be called later). C<ev_io> watchers
		709	will not be affected. Setting this to a non-null value will not introduce
		710	any overhead in libev.
		711
		712	Many (busy) programs can usually benefit by setting the I/O collect
		713	interval to a value near C<0.1> or so, which is often enough for
		714	interactive servers (of course not for games), likewise for timeouts. It
		715	usually doesn't make much sense to set it to a lower value than C<0.01>,
		716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
573		735
574	=back	736	=back
575		737
576		738
577	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
578		740
579	A watcher is a structure that you create and register to record your	741	A watcher is a structure that you create and register to record your
580	interest in some event. For instance, if you want to wait for STDIN to	742	interest in some event. For instance, if you want to wait for STDIN to
581	become readable, you would create an C<ev_io> watcher for that:	743	become readable, you would create an C<ev_io> watcher for that:
582		744
583	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
584	{	746	{
585	ev_io_stop (w);	747	ev_io_stop (w);
586	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
587	}	749	}
588		750
589	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
590	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
591	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
592	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
593	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
594	ev_loop (loop, 0);	756	ev_loop (loop, 0);
595		757
596	As you can see, you are responsible for allocating the memory for your	758	As you can see, you are responsible for allocating the memory for your
597	watcher structures (and it is usually a bad idea to do this on the stack,	759	watcher structures (and it is usually a bad idea to do this on the stack,
598	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
599		761
600	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
601	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
602	callback gets invoked each time the event occurs (or, in the case of io	764	callback gets invoked each time the event occurs (or, in the case of I/O
603	watchers, each time the event loop detects that the file descriptor given	765	watchers, each time the event loop detects that the file descriptor given
604	is readable and/or writable).	766	is readable and/or writable).
605		767
606	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
607	with arguments specific to this watcher type. There is also a macro	769	with arguments specific to this watcher type. There is also a macro
…		…
677	=item C<EV_FORK>	839	=item C<EV_FORK>
678		840
679	The event loop has been resumed in the child process after fork (see	841	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	842	C<ev_fork>).
681		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
682	=item C<EV_ERROR>	848	=item C<EV_ERROR>
683		849
684	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
686	ran out of memory, a file descriptor was found to be closed or any other	852	ran out of memory, a file descriptor was found to be closed or any other
687	problem. You best act on it by reporting the problem and somehow coping	853	problem. You best act on it by reporting the problem and somehow coping
688	with the watcher being stopped.	854	with the watcher being stopped.
689		855
690	Libev will usually signal a few "dummy" events together with an error,	856	Libev will usually signal a few "dummy" events together with an error,
691	for example it might indicate that a fd is readable or writable, and if	857	for example it might indicate that a fd is readable or writable, and if
692	your callbacks is well-written it can just attempt the operation and cope	858	your callbacks is well-written it can just attempt the operation and cope
693	with the error from read() or write(). This will not work in multithreaded	859	with the error from read() or write(). This will not work in multi-threaded
694	programs, though, so beware.	860	programs, though, so beware.
695		861
696	=back	862	=back
697		863
698	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
728	Although some watcher types do not have type-specific arguments	894	Although some watcher types do not have type-specific arguments
729	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
730		896
731	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
732		898
733	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
734	calls into a single call. This is the most convinient method to initialise	900	calls into a single call. This is the most convenient method to initialise
735	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
736		902
737	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
738		904
739	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
822	to associate arbitrary data with your watcher. If you need more data and	988	to associate arbitrary data with your watcher. If you need more data and
823	don't want to allocate memory and store a pointer to it in that data	989	don't want to allocate memory and store a pointer to it in that data
824	member, you can also "subclass" the watcher type and provide your own	990	member, you can also "subclass" the watcher type and provide your own
825	data:	991	data:
826		992
827	struct my_io	993	struct my_io
828	{	994	{
829	struct ev_io io;	995	struct ev_io io;
830	int otherfd;	996	int otherfd;
831	void *somedata;	997	void *somedata;
832	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
833	}	999	}
834		1000
835	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
836	can cast it back to your own type:	1002	can cast it back to your own type:
837		1003
838	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
839	{	1005	{
840	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
841	...	1007	...
842	}	1008	}
843		1009
844	More interesting and less C-conformant ways of casting your callback type	1010	More interesting and less C-conformant ways of casting your callback type
845	instead have been omitted.	1011	instead have been omitted.
846		1012
847	Another common scenario is having some data structure with multiple	1013	Another common scenario is having some data structure with multiple
848	watchers:	1014	watchers:
849		1015
850	struct my_biggy	1016	struct my_biggy
851	{	1017	{
852	int some_data;	1018	int some_data;
853	ev_timer t1;	1019	ev_timer t1;
854	ev_timer t2;	1020	ev_timer t2;
855	}	1021	}
856		1022
857	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
858	you need to use C<offsetof>:	1024	you need to use C<offsetof>:
859		1025
860	#include <stddef.h>	1026	#include <stddef.h>
861		1027
862	static void	1028	static void
863	t1_cb (EV_P_ struct ev_timer *w, int revents)	1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
864	{	1030	{
865	struct my_biggy big = (struct my_biggy *	1031	struct my_biggy big = (struct my_biggy *
866	(((char *)w) - offsetof (struct my_biggy, t1));	1032	(((char *)w) - offsetof (struct my_biggy, t1));
867	}	1033	}
868		1034
869	static void	1035	static void
870	t2_cb (EV_P_ struct ev_timer *w, int revents)	1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
871	{	1037	{
872	struct my_biggy big = (struct my_biggy *	1038	struct my_biggy big = (struct my_biggy *
873	(((char *)w) - offsetof (struct my_biggy, t2));	1039	(((char *)w) - offsetof (struct my_biggy, t2));
874	}	1040	}
875		1041
876		1042
877	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
878		1044
879	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
…		…
903	In general you can register as many read and/or write event watchers per	1069	In general you can register as many read and/or write event watchers per
904	fd as you want (as long as you don't confuse yourself). Setting all file	1070	fd as you want (as long as you don't confuse yourself). Setting all file
905	descriptors to non-blocking mode is also usually a good idea (but not	1071	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1072	required if you know what you are doing).
907		1073
908	You have to be careful with dup'ed file descriptors, though. Some backends
909	(the linux epoll backend is a notable example) cannot handle dup'ed file
910	descriptors correctly if you register interest in two or more fds pointing
911	to the same underlying file/socket/etc. description (that is, they share
912	the same underlying "file open").
913
914	If you must do this, then force the use of a known-to-be-good backend	1074	If you must do this, then force the use of a known-to-be-good backend
915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
917		1077
918	Another thing you have to watch out for is that it is quite easy to	1078	Another thing you have to watch out for is that it is quite easy to
919	receive "spurious" readyness notifications, that is your callback might	1079	receive "spurious" readiness notifications, that is your callback might
920	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
921	because there is no data. Not only are some backends known to create a	1081	because there is no data. Not only are some backends known to create a
922	lot of those (for example solaris ports), it is very easy to get into	1082	lot of those (for example Solaris ports), it is very easy to get into
923	this situation even with a relatively standard program structure. Thus	1083	this situation even with a relatively standard program structure. Thus
924	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning
925	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
926		1086
927	If you cannot run the fd in non-blocking mode (for example you should not	1087	If you cannot run the fd in non-blocking mode (for example you should not
928	play around with an Xlib connection), then you have to seperately re-test	1088	play around with an Xlib connection), then you have to separately re-test
929	whether a file descriptor is really ready with a known-to-be good interface	1089	whether a file descriptor is really ready with a known-to-be good interface
930	such as poll (fortunately in our Xlib example, Xlib already does this on	1090	such as poll (fortunately in our Xlib example, Xlib already does this on
931	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
932		1092
933	=head3 The special problem of disappearing file descriptors	1093	=head3 The special problem of disappearing file descriptors
…		…
949		1109
950	This is how one would do it normally anyway, the important point is that	1110	This is how one would do it normally anyway, the important point is that
951	the libev application should not optimise around libev but should leave	1111	the libev application should not optimise around libev but should leave
952	optimisations to libev.	1112	optimisations to libev.
953		1113
954	=head3 Ths special problem of dup'ed file descriptors	1114	=head3 The special problem of dup'ed file descriptors
955		1115
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1116	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1117	but only events for the underlying file descriptions. That means when you
958	have C<dup ()>'ed file descriptors and register events for them, only one	1118	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1119	events for them, only one file descriptor might actually receive events.
960		1120
961	There is no workaorund possible except not registering events	1121	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1122	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1123	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1124
965	=head3 The special problem of fork	1125	=head3 The special problem of fork
966		1126
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1127	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
971	To support fork in your programs, you either have to call	1131	To support fork in your programs, you either have to call
972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
974	C<EVBACKEND_POLL>.	1134	C<EVBACKEND_POLL>.
975		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when writing to a pipe whose other end has been closed, your program gets
		1140	send a SIGPIPE, which, by default, aborts your program. For most programs
		1141	this is sensible behaviour, for daemons, this is usually undesirable.
		1142
		1143	So when you encounter spurious, unexplained daemon exits, make sure you
		1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1145	somewhere, as that would have given you a big clue).
		1146
976		1147
977	=head3 Watcher-Specific Functions	1148	=head3 Watcher-Specific Functions
978		1149
979	=over 4	1150	=over 4
980		1151
981	=item ev_io_init (ev_io *, callback, int fd, int events)	1152	=item ev_io_init (ev_io *, callback, int fd, int events)
982		1153
983	=item ev_io_set (ev_io *, int fd, int events)	1154	=item ev_io_set (ev_io *, int fd, int events)
984		1155
985	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
986	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
987	C<EV_READ | EV_WRITE> to receive the given events.	1158	C<EV_READ | EV_WRITE> to receive the given events.
988		1159
989	=item int fd [read-only]	1160	=item int fd [read-only]
990		1161
991	The file descriptor being watched.	1162	The file descriptor being watched.
…		…
993	=item int events [read-only]	1164	=item int events [read-only]
994		1165
995	The events being watched.	1166	The events being watched.
996		1167
997	=back	1168	=back
		1169
		1170	=head3 Examples
998		1171
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1000	readable, but only once. Since it is likely line-buffered, you could	1173	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1174	attempt to read a whole line in the callback.
1002		1175
1003	static void	1176	static void
1004	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1005	{	1178	{
1006	ev_io_stop (loop, w);	1179	ev_io_stop (loop, w);
1007	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1008	}	1181	}
1009		1182
1010	...	1183	...
1011	struct ev_loop *loop = ev_default_init (0);	1184	struct ev_loop *loop = ev_default_init (0);
1012	struct ev_io stdin_readable;	1185	struct ev_io stdin_readable;
1013	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1014	ev_io_start (loop, &stdin_readable);	1187	ev_io_start (loop, &stdin_readable);
1015	ev_loop (loop, 0);	1188	ev_loop (loop, 0);
1016		1189
1017		1190
1018	=head2 C<ev_timer> - relative and optionally repeating timeouts	1191	=head2 C<ev_timer> - relative and optionally repeating timeouts
1019		1192
1020	Timer watchers are simple relative timers that generate an event after a	1193	Timer watchers are simple relative timers that generate an event after a
1021	given time, and optionally repeating in regular intervals after that.	1194	given time, and optionally repeating in regular intervals after that.
1022		1195
1023	The timers are based on real time, that is, if you register an event that	1196	The timers are based on real time, that is, if you register an event that
1024	times out after an hour and you reset your system clock to last years	1197	times out after an hour and you reset your system clock to January last
1025	time, it will still time out after (roughly) and hour. "Roughly" because	1198	year, it will still time out after (roughly) and hour. "Roughly" because
1026	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1027	monotonic clock option helps a lot here).	1200	monotonic clock option helps a lot here).
1028		1201
1029	The relative timeouts are calculated relative to the C<ev_now ()>	1202	The relative timeouts are calculated relative to the C<ev_now ()>
1030	time. This is usually the right thing as this timestamp refers to the time	1203	time. This is usually the right thing as this timestamp refers to the time
…		…
1032	you suspect event processing to be delayed and you I<need> to base the timeout	1205	you suspect event processing to be delayed and you I<need> to base the timeout
1033	on the current time, use something like this to adjust for this:	1206	on the current time, use something like this to adjust for this:
1034		1207
1035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1208	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1036		1209
1037	The callback is guarenteed to be invoked only when its timeout has passed,	1210	The callback is guaranteed to be invoked only after its timeout has passed,
1038	but if multiple timers become ready during the same loop iteration then	1211	but if multiple timers become ready during the same loop iteration then
1039	order of execution is undefined.	1212	order of execution is undefined.
1040		1213
1041	=head3 Watcher-Specific Functions and Data Members	1214	=head3 Watcher-Specific Functions and Data Members
1042		1215
…		…
1044		1217
1045	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1218	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1046		1219
1047	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1220	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1048		1221
1049	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1222	Configure the timer to trigger after C<after> seconds. If C<repeat>
1050	C<0.>, then it will automatically be stopped. If it is positive, then the	1223	is C<0.>, then it will automatically be stopped once the timeout is
1051	timer will automatically be configured to trigger again C<repeat> seconds	1224	reached. If it is positive, then the timer will automatically be
1052	later, again, and again, until stopped manually.	1225	configured to trigger again C<repeat> seconds later, again, and again,
		1226	until stopped manually.
1053		1227
1054	The timer itself will do a best-effort at avoiding drift, that is, if you	1228	The timer itself will do a best-effort at avoiding drift, that is, if
1055	configure a timer to trigger every 10 seconds, then it will trigger at	1229	you configure a timer to trigger every 10 seconds, then it will normally
1056	exactly 10 second intervals. If, however, your program cannot keep up with	1230	trigger at exactly 10 second intervals. If, however, your program cannot
1057	the timer (because it takes longer than those 10 seconds to do stuff) the	1231	keep up with the timer (because it takes longer than those 10 seconds to
1058	timer will not fire more than once per event loop iteration.	1232	do stuff) the timer will not fire more than once per event loop iteration.
1059		1233
1060	=item ev_timer_again (loop)	1234	=item ev_timer_again (loop, ev_timer *)
1061		1235
1062	This will act as if the timer timed out and restart it again if it is	1236	This will act as if the timer timed out and restart it again if it is
1063	repeating. The exact semantics are:	1237	repeating. The exact semantics are:
1064		1238
1065	If the timer is pending, its pending status is cleared.	1239	If the timer is pending, its pending status is cleared.
1066		1240
1067	If the timer is started but nonrepeating, stop it (as if it timed out).	1241	If the timer is started but non-repeating, stop it (as if it timed out).
1068		1242
1069	If the timer is repeating, either start it if necessary (with the	1243	If the timer is repeating, either start it if necessary (with the
1070	C<repeat> value), or reset the running timer to the C<repeat> value.	1244	C<repeat> value), or reset the running timer to the C<repeat> value.
1071		1245
1072	This sounds a bit complicated, but here is a useful and typical	1246	This sounds a bit complicated, but here is a useful and typical
1073	example: Imagine you have a tcp connection and you want a so-called idle	1247	example: Imagine you have a TCP connection and you want a so-called idle
1074	timeout, that is, you want to be called when there have been, say, 60	1248	timeout, that is, you want to be called when there have been, say, 60
1075	seconds of inactivity on the socket. The easiest way to do this is to	1249	seconds of inactivity on the socket. The easiest way to do this is to
1076	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1250	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1077	C<ev_timer_again> each time you successfully read or write some data. If	1251	C<ev_timer_again> each time you successfully read or write some data. If
1078	you go into an idle state where you do not expect data to travel on the	1252	you go into an idle state where you do not expect data to travel on the
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1274	or C<ev_timer_again> is called and determines the next timeout (if any),
1101	which is also when any modifications are taken into account.	1275	which is also when any modifications are taken into account.
1102		1276
1103	=back	1277	=back
1104		1278
		1279	=head3 Examples
		1280
1105	Example: Create a timer that fires after 60 seconds.	1281	Example: Create a timer that fires after 60 seconds.
1106		1282
1107	static void	1283	static void
1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1284	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1109	{	1285	{
1110	.. one minute over, w is actually stopped right here	1286	.. one minute over, w is actually stopped right here
1111	}	1287	}
1112		1288
1113	struct ev_timer mytimer;	1289	struct ev_timer mytimer;
1114	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1290	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1115	ev_timer_start (loop, &mytimer);	1291	ev_timer_start (loop, &mytimer);
1116		1292
1117	Example: Create a timeout timer that times out after 10 seconds of	1293	Example: Create a timeout timer that times out after 10 seconds of
1118	inactivity.	1294	inactivity.
1119		1295
1120	static void	1296	static void
1121	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1297	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1122	{	1298	{
1123	.. ten seconds without any activity	1299	.. ten seconds without any activity
1124	}	1300	}
1125		1301
1126	struct ev_timer mytimer;	1302	struct ev_timer mytimer;
1127	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1303	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1128	ev_timer_again (&mytimer); /* start timer */	1304	ev_timer_again (&mytimer); /* start timer */
1129	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1130		1306
1131	// and in some piece of code that gets executed on any "activity":	1307	// and in some piece of code that gets executed on any "activity":
1132	// reset the timeout to start ticking again at 10 seconds	1308	// reset the timeout to start ticking again at 10 seconds
1133	ev_timer_again (&mytimer);	1309	ev_timer_again (&mytimer);
1134		1310
1135		1311
1136	=head2 C<ev_periodic> - to cron or not to cron?	1312	=head2 C<ev_periodic> - to cron or not to cron?
1137		1313
1138	Periodic watchers are also timers of a kind, but they are very versatile	1314	Periodic watchers are also timers of a kind, but they are very versatile
1139	(and unfortunately a bit complex).	1315	(and unfortunately a bit complex).
1140		1316
1141	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1317	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1142	but on wallclock time (absolute time). You can tell a periodic watcher	1318	but on wall clock time (absolute time). You can tell a periodic watcher
1143	to trigger "at" some specific point in time. For example, if you tell a	1319	to trigger after some specific point in time. For example, if you tell a
1144	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1320	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1145	+ 10.>) and then reset your system clock to the last year, then it will	1321	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1322	clock to January of the previous year, then it will take more than year
1146	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1323	to trigger the event (unlike an C<ev_timer>, which would still trigger
1147	roughly 10 seconds later).	1324	roughly 10 seconds later as it uses a relative timeout).
1148		1325
1149	They can also be used to implement vastly more complex timers, such as	1326	C<ev_periodic>s can also be used to implement vastly more complex timers,
1150	triggering an event on each midnight, local time or other, complicated,	1327	such as triggering an event on each "midnight, local time", or other
1151	rules.	1328	complicated, rules.
1152		1329
1153	As with timers, the callback is guarenteed to be invoked only when the	1330	As with timers, the callback is guaranteed to be invoked only when the
1154	time (C<at>) has been passed, but if multiple periodic timers become ready	1331	time (C<at>) has passed, but if multiple periodic timers become ready
1155	during the same loop iteration then order of execution is undefined.	1332	during the same loop iteration then order of execution is undefined.
1156		1333
1157	=head3 Watcher-Specific Functions and Data Members	1334	=head3 Watcher-Specific Functions and Data Members
1158		1335
1159	=over 4	1336	=over 4
…		…
1167		1344
1168	=over 4	1345	=over 4
1169		1346
1170	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1347	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1171		1348
1172	In this configuration the watcher triggers an event at the wallclock time	1349	In this configuration the watcher triggers an event after the wall clock
1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1350	time C<at> has passed and doesn't repeat. It will not adjust when a time
1174	that is, if it is to be run at January 1st 2011 then it will run when the	1351	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1175	system time reaches or surpasses this time.	1352	run when the system time reaches or surpasses this time.
1176		1353
1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1354	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1178		1355
1179	In this mode the watcher will always be scheduled to time out at the next	1356	In this mode the watcher will always be scheduled to time out at the next
1180	C<at + N * interval> time (for some integer N, which can also be negative)	1357	C<at + N * interval> time (for some integer N, which can also be negative)
1181	and then repeat, regardless of any time jumps.	1358	and then repeat, regardless of any time jumps.
1182		1359
1183	This can be used to create timers that do not drift with respect to system	1360	This can be used to create timers that do not drift with respect to system
1184	time:	1361	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1362	the hour:
1185		1363
1186	ev_periodic_set (&periodic, 0., 3600., 0);	1364	ev_periodic_set (&periodic, 0., 3600., 0);
1187		1365
1188	This doesn't mean there will always be 3600 seconds in between triggers,	1366	This doesn't mean there will always be 3600 seconds in between triggers,
1189	but only that the the callback will be called when the system time shows a	1367	but only that the callback will be called when the system time shows a
1190	full hour (UTC), or more correctly, when the system time is evenly divisible	1368	full hour (UTC), or more correctly, when the system time is evenly divisible
1191	by 3600.	1369	by 3600.
1192		1370
1193	Another way to think about it (for the mathematically inclined) is that	1371	Another way to think about it (for the mathematically inclined) is that
1194	C<ev_periodic> will try to run the callback in this mode at the next possible	1372	C<ev_periodic> will try to run the callback in this mode at the next possible
1195	time where C<time = at (mod interval)>, regardless of any time jumps.	1373	time where C<time = at (mod interval)>, regardless of any time jumps.
1196		1374
1197	For numerical stability it is preferable that the C<at> value is near	1375	For numerical stability it is preferable that the C<at> value is near
1198	C<ev_now ()> (the current time), but there is no range requirement for	1376	C<ev_now ()> (the current time), but there is no range requirement for
1199	this value.	1377	this value, and in fact is often specified as zero.
		1378
		1379	Note also that there is an upper limit to how often a timer can fire (CPU
		1380	speed for example), so if C<interval> is very small then timing stability
		1381	will of course deteriorate. Libev itself tries to be exact to be about one
		1382	millisecond (if the OS supports it and the machine is fast enough).
1200		1383
1201	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1384	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1202		1385
1203	In this mode the values for C<interval> and C<at> are both being	1386	In this mode the values for C<interval> and C<at> are both being
1204	ignored. Instead, each time the periodic watcher gets scheduled, the	1387	ignored. Instead, each time the periodic watcher gets scheduled, the
1205	reschedule callback will be called with the watcher as first, and the	1388	reschedule callback will be called with the watcher as first, and the
1206	current time as second argument.	1389	current time as second argument.
1207		1390
1208	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1391	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1209	ever, or make any event loop modifications>. If you need to stop it,	1392	ever, or make ANY event loop modifications whatsoever>.
1210	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1211	starting an C<ev_prepare> watcher, which is legal).
1212		1393
		1394	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1395	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1396	only event loop modification you are allowed to do).
		1397
1213	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1398	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1214	ev_tstamp now)>, e.g.:	1399	*w, ev_tstamp now)>, e.g.:
1215		1400
1216	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1401	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1217	{	1402	{
1218	return now + 60.;	1403	return now + 60.;
1219	}	1404	}
…		…
1221	It must return the next time to trigger, based on the passed time value	1406	It must return the next time to trigger, based on the passed time value
1222	(that is, the lowest time value larger than to the second argument). It	1407	(that is, the lowest time value larger than to the second argument). It
1223	will usually be called just before the callback will be triggered, but	1408	will usually be called just before the callback will be triggered, but
1224	might be called at other times, too.	1409	might be called at other times, too.
1225		1410
1226	NOTE: I<< This callback must always return a time that is later than the	1411	NOTE: I<< This callback must always return a time that is higher than or
1227	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1412	equal to the passed C<now> value >>.
1228		1413
1229	This can be used to create very complex timers, such as a timer that	1414	This can be used to create very complex timers, such as a timer that
1230	triggers on each midnight, local time. To do this, you would calculate the	1415	triggers on "next midnight, local time". To do this, you would calculate the
1231	next midnight after C<now> and return the timestamp value for this. How	1416	next midnight after C<now> and return the timestamp value for this. How
1232	you do this is, again, up to you (but it is not trivial, which is the main	1417	you do this is, again, up to you (but it is not trivial, which is the main
1233	reason I omitted it as an example).	1418	reason I omitted it as an example).
1234		1419
1235	=back	1420	=back
…		…
1239	Simply stops and restarts the periodic watcher again. This is only useful	1424	Simply stops and restarts the periodic watcher again. This is only useful
1240	when you changed some parameters or the reschedule callback would return	1425	when you changed some parameters or the reschedule callback would return
1241	a different time than the last time it was called (e.g. in a crond like	1426	a different time than the last time it was called (e.g. in a crond like
1242	program when the crontabs have changed).	1427	program when the crontabs have changed).
1243		1428
		1429	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1430
		1431	When active, returns the absolute time that the watcher is supposed to
		1432	trigger next.
		1433
1244	=item ev_tstamp offset [read-write]	1434	=item ev_tstamp offset [read-write]
1245		1435
1246	When repeating, this contains the offset value, otherwise this is the	1436	When repeating, this contains the offset value, otherwise this is the
1247	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1437	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1248		1438
…		…
1259		1449
1260	The current reschedule callback, or C<0>, if this functionality is	1450	The current reschedule callback, or C<0>, if this functionality is
1261	switched off. Can be changed any time, but changes only take effect when	1451	switched off. Can be changed any time, but changes only take effect when
1262	the periodic timer fires or C<ev_periodic_again> is being called.	1452	the periodic timer fires or C<ev_periodic_again> is being called.
1263		1453
1264	=item ev_tstamp at [read-only]
1265
1266	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.
1268
1269	=back	1454	=back
		1455
		1456	=head3 Examples
1270		1457
1271	Example: Call a callback every hour, or, more precisely, whenever the	1458	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1459	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1460	potentially a lot of jitter, but good long-term stability.
1274		1461
1275	static void	1462	static void
1276	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1463	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1277	{	1464	{
1278	... its now a full hour (UTC, or TAI or whatever your clock follows)	1465	... its now a full hour (UTC, or TAI or whatever your clock follows)
1279	}	1466	}
1280		1467
1281	struct ev_periodic hourly_tick;	1468	struct ev_periodic hourly_tick;
1282	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1469	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1283	ev_periodic_start (loop, &hourly_tick);	1470	ev_periodic_start (loop, &hourly_tick);
1284		1471
1285	Example: The same as above, but use a reschedule callback to do it:	1472	Example: The same as above, but use a reschedule callback to do it:
1286		1473
1287	#include <math.h>	1474	#include <math.h>
1288		1475
1289	static ev_tstamp	1476	static ev_tstamp
1290	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1477	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1291	{	1478	{
1292	return fmod (now, 3600.) + 3600.;	1479	return fmod (now, 3600.) + 3600.;
1293	}	1480	}
1294		1481
1295	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1482	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1296		1483
1297	Example: Call a callback every hour, starting now:	1484	Example: Call a callback every hour, starting now:
1298		1485
1299	struct ev_periodic hourly_tick;	1486	struct ev_periodic hourly_tick;
1300	ev_periodic_init (&hourly_tick, clock_cb,	1487	ev_periodic_init (&hourly_tick, clock_cb,
1301	fmod (ev_now (loop), 3600.), 3600., 0);	1488	fmod (ev_now (loop), 3600.), 3600., 0);
1302	ev_periodic_start (loop, &hourly_tick);	1489	ev_periodic_start (loop, &hourly_tick);
1303		1490
1304		1491
1305	=head2 C<ev_signal> - signal me when a signal gets signalled!	1492	=head2 C<ev_signal> - signal me when a signal gets signalled!
1306		1493
1307	Signal watchers will trigger an event when the process receives a specific	1494	Signal watchers will trigger an event when the process receives a specific
…		…
1314	with the kernel (thus it coexists with your own signal handlers as long	1501	with the kernel (thus it coexists with your own signal handlers as long
1315	as you don't register any with libev). Similarly, when the last signal	1502	as you don't register any with libev). Similarly, when the last signal
1316	watcher for a signal is stopped libev will reset the signal handler to	1503	watcher for a signal is stopped libev will reset the signal handler to
1317	SIG_DFL (regardless of what it was set to before).	1504	SIG_DFL (regardless of what it was set to before).
1318		1505
		1506	If possible and supported, libev will install its handlers with
		1507	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1508	interrupted. If you have a problem with system calls getting interrupted by
		1509	signals you can block all signals in an C<ev_check> watcher and unblock
		1510	them in an C<ev_prepare> watcher.
		1511
1319	=head3 Watcher-Specific Functions and Data Members	1512	=head3 Watcher-Specific Functions and Data Members
1320		1513
1321	=over 4	1514	=over 4
1322		1515
1323	=item ev_signal_init (ev_signal *, callback, int signum)	1516	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1331		1524
1332	The signal the watcher watches out for.	1525	The signal the watcher watches out for.
1333		1526
1334	=back	1527	=back
1335		1528
		1529	=head3 Examples
		1530
		1531	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1532
		1533	static void
		1534	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1535	{
		1536	ev_unloop (loop, EVUNLOOP_ALL);
		1537	}
		1538
		1539	struct ev_signal signal_watcher;
		1540	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1541	ev_signal_start (loop, &sigint_cb);
		1542
1336		1543
1337	=head2 C<ev_child> - watch out for process status changes	1544	=head2 C<ev_child> - watch out for process status changes
1338		1545
1339	Child watchers trigger when your process receives a SIGCHLD in response to	1546	Child watchers trigger when your process receives a SIGCHLD in response to
1340	some child status changes (most typically when a child of yours dies).	1547	some child status changes (most typically when a child of yours dies). It
		1548	is permissible to install a child watcher I<after> the child has been
		1549	forked (which implies it might have already exited), as long as the event
		1550	loop isn't entered (or is continued from a watcher).
		1551
		1552	Only the default event loop is capable of handling signals, and therefore
		1553	you can only register child watchers in the default event loop.
		1554
		1555	=head3 Process Interaction
		1556
		1557	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1558	initialised. This is necessary to guarantee proper behaviour even if
		1559	the first child watcher is started after the child exits. The occurrence
		1560	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1561	synchronously as part of the event loop processing. Libev always reaps all
		1562	children, even ones not watched.
		1563
		1564	=head3 Overriding the Built-In Processing
		1565
		1566	Libev offers no special support for overriding the built-in child
		1567	processing, but if your application collides with libev's default child
		1568	handler, you can override it easily by installing your own handler for
		1569	C<SIGCHLD> after initialising the default loop, and making sure the
		1570	default loop never gets destroyed. You are encouraged, however, to use an
		1571	event-based approach to child reaping and thus use libev's support for
		1572	that, so other libev users can use C<ev_child> watchers freely.
		1573
		1574	=head3 Stopping the Child Watcher
		1575
		1576	Currently, the child watcher never gets stopped, even when the
		1577	child terminates, so normally one needs to stop the watcher in the
		1578	callback. Future versions of libev might stop the watcher automatically
		1579	when a child exit is detected.
1341		1580
1342	=head3 Watcher-Specific Functions and Data Members	1581	=head3 Watcher-Specific Functions and Data Members
1343		1582
1344	=over 4	1583	=over 4
1345		1584
1346	=item ev_child_init (ev_child *, callback, int pid)	1585	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1586
1348	=item ev_child_set (ev_child *, int pid)	1587	=item ev_child_set (ev_child *, int pid, int trace)
1349		1588
1350	Configures the watcher to wait for status changes of process C<pid> (or	1589	Configures the watcher to wait for status changes of process C<pid> (or
1351	I<any> process if C<pid> is specified as C<0>). The callback can look	1590	I<any> process if C<pid> is specified as C<0>). The callback can look
1352	at the C<rstatus> member of the C<ev_child> watcher structure to see	1591	at the C<rstatus> member of the C<ev_child> watcher structure to see
1353	the status word (use the macros from C<sys/wait.h> and see your systems	1592	the status word (use the macros from C<sys/wait.h> and see your systems
1354	C<waitpid> documentation). The C<rpid> member contains the pid of the	1593	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1594	process causing the status change. C<trace> must be either C<0> (only
		1595	activate the watcher when the process terminates) or C<1> (additionally
		1596	activate the watcher when the process is stopped or continued).
1356		1597
1357	=item int pid [read-only]	1598	=item int pid [read-only]
1358		1599
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1600	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1601
…		…
1367	The process exit/trace status caused by C<rpid> (see your systems	1608	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1609	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1610
1370	=back	1611	=back
1371		1612
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1613	=head3 Examples
1373		1614
		1615	Example: C<fork()> a new process and install a child handler to wait for
		1616	its completion.
		1617
		1618	ev_child cw;
		1619
1374	static void	1620	static void
1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1621	child_cb (EV_P_ struct ev_child *w, int revents)
1376	{	1622	{
1377	ev_unloop (loop, EVUNLOOP_ALL);	1623	ev_child_stop (EV_A_ w);
		1624	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1378	}	1625	}
1379		1626
1380	struct ev_signal signal_watcher;	1627	pid_t pid = fork ();
1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1628
1382	ev_signal_start (loop, &sigint_cb);	1629	if (pid < 0)
		1630	// error
		1631	else if (pid == 0)
		1632	{
		1633	// the forked child executes here
		1634	exit (1);
		1635	}
		1636	else
		1637	{
		1638	ev_child_init (&cw, child_cb, pid, 0);
		1639	ev_child_start (EV_DEFAULT_ &cw);
		1640	}
1383		1641
1384		1642
1385	=head2 C<ev_stat> - did the file attributes just change?	1643	=head2 C<ev_stat> - did the file attributes just change?
1386		1644
1387	This watches a filesystem path for attribute changes. That is, it calls	1645	This watches a file system path for attribute changes. That is, it calls
1388	C<stat> regularly (or when the OS says it changed) and sees if it changed	1646	C<stat> regularly (or when the OS says it changed) and sees if it changed
1389	compared to the last time, invoking the callback if it did.	1647	compared to the last time, invoking the callback if it did.
1390		1648
1391	The path does not need to exist: changing from "path exists" to "path does	1649	The path does not need to exist: changing from "path exists" to "path does
1392	not exist" is a status change like any other. The condition "path does	1650	not exist" is a status change like any other. The condition "path does
…		…
1410	as even with OS-supported change notifications, this can be	1668	as even with OS-supported change notifications, this can be
1411	resource-intensive.	1669	resource-intensive.
1412		1670
1413	At the time of this writing, only the Linux inotify interface is	1671	At the time of this writing, only the Linux inotify interface is
1414	implemented (implementing kqueue support is left as an exercise for the	1672	implemented (implementing kqueue support is left as an exercise for the
		1673	reader, note, however, that the author sees no way of implementing ev_stat
1415	reader). Inotify will be used to give hints only and should not change the	1674	semantics with kqueue). Inotify will be used to give hints only and should
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1675	not change the semantics of C<ev_stat> watchers, which means that libev
1417	to fall back to regular polling again even with inotify, but changes are	1676	sometimes needs to fall back to regular polling again even with inotify,
1418	usually detected immediately, and if the file exists there will be no	1677	but changes are usually detected immediately, and if the file exists there
1419	polling.	1678	will be no polling.
		1679
		1680	=head3 ABI Issues (Largefile Support)
		1681
		1682	Libev by default (unless the user overrides this) uses the default
		1683	compilation environment, which means that on systems with large file
		1684	support disabled by default, you get the 32 bit version of the stat
		1685	structure. When using the library from programs that change the ABI to
		1686	use 64 bit file offsets the programs will fail. In that case you have to
		1687	compile libev with the same flags to get binary compatibility. This is
		1688	obviously the case with any flags that change the ABI, but the problem is
		1689	most noticeably disabled with ev_stat and large file support.
		1690
		1691	The solution for this is to lobby your distribution maker to make large
		1692	file interfaces available by default (as e.g. FreeBSD does) and not
		1693	optional. Libev cannot simply switch on large file support because it has
		1694	to exchange stat structures with application programs compiled using the
		1695	default compilation environment.
		1696
		1697	=head3 Inotify
		1698
		1699	When C<inotify (7)> support has been compiled into libev (generally only
		1700	available on Linux) and present at runtime, it will be used to speed up
		1701	change detection where possible. The inotify descriptor will be created lazily
		1702	when the first C<ev_stat> watcher is being started.
		1703
		1704	Inotify presence does not change the semantics of C<ev_stat> watchers
		1705	except that changes might be detected earlier, and in some cases, to avoid
		1706	making regular C<stat> calls. Even in the presence of inotify support
		1707	there are many cases where libev has to resort to regular C<stat> polling.
		1708
		1709	(There is no support for kqueue, as apparently it cannot be used to
		1710	implement this functionality, due to the requirement of having a file
		1711	descriptor open on the object at all times).
		1712
		1713	=head3 The special problem of stat time resolution
		1714
		1715	The C<stat ()> system call only supports full-second resolution portably, and
		1716	even on systems where the resolution is higher, many file systems still
		1717	only support whole seconds.
		1718
		1719	That means that, if the time is the only thing that changes, you can
		1720	easily miss updates: on the first update, C<ev_stat> detects a change and
		1721	calls your callback, which does something. When there is another update
		1722	within the same second, C<ev_stat> will be unable to detect it as the stat
		1723	data does not change.
		1724
		1725	The solution to this is to delay acting on a change for slightly more
		1726	than a second (or till slightly after the next full second boundary), using
		1727	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1728	ev_timer_again (loop, w)>).
		1729
		1730	The C<.02> offset is added to work around small timing inconsistencies
		1731	of some operating systems (where the second counter of the current time
		1732	might be be delayed. One such system is the Linux kernel, where a call to
		1733	C<gettimeofday> might return a timestamp with a full second later than
		1734	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1735	update file times then there will be a small window where the kernel uses
		1736	the previous second to update file times but libev might already execute
		1737	the timer callback).
1420		1738
1421	=head3 Watcher-Specific Functions and Data Members	1739	=head3 Watcher-Specific Functions and Data Members
1422		1740
1423	=over 4	1741	=over 4
1424		1742
…		…
1430	C<path>. The C<interval> is a hint on how quickly a change is expected to	1748	C<path>. The C<interval> is a hint on how quickly a change is expected to
1431	be detected and should normally be specified as C<0> to let libev choose	1749	be detected and should normally be specified as C<0> to let libev choose
1432	a suitable value. The memory pointed to by C<path> must point to the same	1750	a suitable value. The memory pointed to by C<path> must point to the same
1433	path for as long as the watcher is active.	1751	path for as long as the watcher is active.
1434		1752
1435	The callback will be receive C<EV_STAT> when a change was detected,	1753	The callback will receive C<EV_STAT> when a change was detected, relative
1436	relative to the attributes at the time the watcher was started (or the	1754	to the attributes at the time the watcher was started (or the last change
1437	last change was detected).	1755	was detected).
1438		1756
1439	=item ev_stat_stat (ev_stat *)	1757	=item ev_stat_stat (loop, ev_stat *)
1440		1758
1441	Updates the stat buffer immediately with new values. If you change the	1759	Updates the stat buffer immediately with new values. If you change the
1442	watched path in your callback, you could call this fucntion to avoid	1760	watched path in your callback, you could call this function to avoid
1443	detecting this change (while introducing a race condition). Can also be	1761	detecting this change (while introducing a race condition if you are not
1444	useful simply to find out the new values.	1762	the only one changing the path). Can also be useful simply to find out the
		1763	new values.
1445		1764
1446	=item ev_statdata attr [read-only]	1765	=item ev_statdata attr [read-only]
1447		1766
1448	The most-recently detected attributes of the file. Although the type is of	1767	The most-recently detected attributes of the file. Although the type is
1449	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1768	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1450	suitable for your system. If the C<st_nlink> member is C<0>, then there	1769	suitable for your system, but you can only rely on the POSIX-standardised
		1770	members to be present. If the C<st_nlink> member is C<0>, then there was
1451	was some error while C<stat>ing the file.	1771	some error while C<stat>ing the file.
1452		1772
1453	=item ev_statdata prev [read-only]	1773	=item ev_statdata prev [read-only]
1454		1774
1455	The previous attributes of the file. The callback gets invoked whenever	1775	The previous attributes of the file. The callback gets invoked whenever
1456	C<prev> != C<attr>.	1776	C<prev> != C<attr>, or, more precisely, one or more of these members
		1777	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1778	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1457		1779
1458	=item ev_tstamp interval [read-only]	1780	=item ev_tstamp interval [read-only]
1459		1781
1460	The specified interval.	1782	The specified interval.
1461		1783
1462	=item const char *path [read-only]	1784	=item const char *path [read-only]
1463		1785
1464	The filesystem path that is being watched.	1786	The file system path that is being watched.
1465		1787
1466	=back	1788	=back
1467		1789
		1790	=head3 Examples
		1791
1468	Example: Watch C</etc/passwd> for attribute changes.	1792	Example: Watch C</etc/passwd> for attribute changes.
1469		1793
1470	static void	1794	static void
1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1795	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1472	{	1796	{
1473	/* /etc/passwd changed in some way */	1797	/* /etc/passwd changed in some way */
1474	if (w->attr.st_nlink)	1798	if (w->attr.st_nlink)
1475	{	1799	{
1476	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1800	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1477	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1801	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1478	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1802	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1479	}	1803	}
1480	else	1804	else
1481	/* you shalt not abuse printf for puts */	1805	/* you shalt not abuse printf for puts */
1482	puts ("wow, /etc/passwd is not there, expect problems. "	1806	puts ("wow, /etc/passwd is not there, expect problems. "
1483	"if this is windows, they already arrived\n");	1807	"if this is windows, they already arrived\n");
1484	}	1808	}
1485		1809
1486	...	1810	...
1487	ev_stat passwd;	1811	ev_stat passwd;
1488		1812
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1813	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1814	ev_stat_start (loop, &passwd);
		1815
		1816	Example: Like above, but additionally use a one-second delay so we do not
		1817	miss updates (however, frequent updates will delay processing, too, so
		1818	one might do the work both on C<ev_stat> callback invocation I<and> on
		1819	C<ev_timer> callback invocation).
		1820
		1821	static ev_stat passwd;
		1822	static ev_timer timer;
		1823
		1824	static void
		1825	timer_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_timer_stop (EV_A_ w);
		1828
		1829	/* now it's one second after the most recent passwd change */
		1830	}
		1831
		1832	static void
		1833	stat_cb (EV_P_ ev_stat *w, int revents)
		1834	{
		1835	/* reset the one-second timer */
		1836	ev_timer_again (EV_A_ &timer);
		1837	}
		1838
		1839	...
		1840	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1841	ev_stat_start (loop, &passwd);
		1842	ev_timer_init (&timer, timer_cb, 0., 1.02);
1491		1843
1492		1844
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1845	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1846
1495	Idle watchers trigger events when no other events of the same or higher	1847	Idle watchers trigger events when no other events of the same or higher
…		…
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1874	believe me.
1523		1875
1524	=back	1876	=back
1525		1877
		1878	=head3 Examples
		1879
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1880	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1881	callback, free it. Also, use no error checking, as usual.
1528		1882
1529	static void	1883	static void
1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1884	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1531	{	1885	{
1532	free (w);	1886	free (w);
1533	// now do something you wanted to do when the program has	1887	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1888	// no longer anything immediate to do.
1535	}	1889	}
1536		1890
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1891	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1892	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1893	ev_idle_start (loop, idle_cb);
1540		1894
1541		1895
1542	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1896	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1543		1897
1544	Prepare and check watchers are usually (but not always) used in tandem:	1898	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1563		1917
1564	This is done by examining in each prepare call which file descriptors need	1918	This is done by examining in each prepare call which file descriptors need
1565	to be watched by the other library, registering C<ev_io> watchers for	1919	to be watched by the other library, registering C<ev_io> watchers for
1566	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1920	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1567	provide just this functionality). Then, in the check watcher you check for	1921	provide just this functionality). Then, in the check watcher you check for
1568	any events that occured (by checking the pending status of all watchers	1922	any events that occurred (by checking the pending status of all watchers
1569	and stopping them) and call back into the library. The I/O and timer	1923	and stopping them) and call back into the library. The I/O and timer
1570	callbacks will never actually be called (but must be valid nevertheless,	1924	callbacks will never actually be called (but must be valid nevertheless,
1571	because you never know, you know?).	1925	because you never know, you know?).
1572		1926
1573	As another example, the Perl Coro module uses these hooks to integrate	1927	As another example, the Perl Coro module uses these hooks to integrate
…		…
1581		1935
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1936	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1583	priority, to ensure that they are being run before any other watchers	1937	priority, to ensure that they are being run before any other watchers
1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1938	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1585	too) should not activate ("feed") events into libev. While libev fully	1939	too) should not activate ("feed") events into libev. While libev fully
1586	supports this, they will be called before other C<ev_check> watchers did	1940	supports this, they might get executed before other C<ev_check> watchers
1587	their job. As C<ev_check> watchers are often used to embed other event	1941	did their job. As C<ev_check> watchers are often used to embed other
1588	loops those other event loops might be in an unusable state until their	1942	(non-libev) event loops those other event loops might be in an unusable
1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1943	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1944	coexist peacefully with others).
1591		1945
1592	=head3 Watcher-Specific Functions and Data Members	1946	=head3 Watcher-Specific Functions and Data Members
1593		1947
1594	=over 4	1948	=over 4
1595		1949
…		…
1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1955	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1602	macros, but using them is utterly, utterly and completely pointless.	1956	macros, but using them is utterly, utterly and completely pointless.
1603		1957
1604	=back	1958	=back
1605		1959
		1960	=head3 Examples
		1961
1606	There are a number of principal ways to embed other event loops or modules	1962	There are a number of principal ways to embed other event loops or modules
1607	into libev. Here are some ideas on how to include libadns into libev	1963	into libev. Here are some ideas on how to include libadns into libev
1608	(there is a Perl module named C<EV::ADNS> that does this, which you could	1964	(there is a Perl module named C<EV::ADNS> that does this, which you could
1609	use for an actually working example. Another Perl module named C<EV::Glib>	1965	use as a working example. Another Perl module named C<EV::Glib> embeds a
1610	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1966	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1611	into the Glib event loop).	1967	Glib event loop).
1612		1968
1613	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1969	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1614	and in a check watcher, destroy them and call into libadns. What follows	1970	and in a check watcher, destroy them and call into libadns. What follows
1615	is pseudo-code only of course. This requires you to either use a low	1971	is pseudo-code only of course. This requires you to either use a low
1616	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1972	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1617	the callbacks for the IO/timeout watchers might not have been called yet.	1973	the callbacks for the IO/timeout watchers might not have been called yet.
1618		1974
1619	static ev_io iow [nfd];	1975	static ev_io iow [nfd];
1620	static ev_timer tw;	1976	static ev_timer tw;
1621		1977
1622	static void	1978	static void
1623	io_cb (ev_loop *loop, ev_io *w, int revents)	1979	io_cb (ev_loop *loop, ev_io *w, int revents)
1624	{	1980	{
1625	}	1981	}
1626		1982
1627	// create io watchers for each fd and a timer before blocking	1983	// create io watchers for each fd and a timer before blocking
1628	static void	1984	static void
1629	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1985	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1630	{	1986	{
1631	int timeout = 3600000;	1987	int timeout = 3600000;
1632	struct pollfd fds [nfd];	1988	struct pollfd fds [nfd];
1633	// actual code will need to loop here and realloc etc.	1989	// actual code will need to loop here and realloc etc.
1634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1990	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1635		1991
1636	/* the callback is illegal, but won't be called as we stop during check */	1992	/* the callback is illegal, but won't be called as we stop during check */
1637	ev_timer_init (&tw, 0, timeout * 1e-3);	1993	ev_timer_init (&tw, 0, timeout * 1e-3);
1638	ev_timer_start (loop, &tw);	1994	ev_timer_start (loop, &tw);
1639		1995
1640	// create one ev_io per pollfd	1996	// create one ev_io per pollfd
1641	for (int i = 0; i < nfd; ++i)	1997	for (int i = 0; i < nfd; ++i)
1642	{	1998	{
1643	ev_io_init (iow + i, io_cb, fds [i].fd,	1999	ev_io_init (iow + i, io_cb, fds [i].fd,
1644	((fds [i].events & POLLIN ? EV_READ : 0)	2000	((fds [i].events & POLLIN ? EV_READ : 0)
1645	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2001	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1646		2002
1647	fds [i].revents = 0;	2003	fds [i].revents = 0;
1648	ev_io_start (loop, iow + i);	2004	ev_io_start (loop, iow + i);
1649	}	2005	}
1650	}	2006	}
1651		2007
1652	// stop all watchers after blocking	2008	// stop all watchers after blocking
1653	static void	2009	static void
1654	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2010	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1655	{	2011	{
1656	ev_timer_stop (loop, &tw);	2012	ev_timer_stop (loop, &tw);
1657		2013
1658	for (int i = 0; i < nfd; ++i)	2014	for (int i = 0; i < nfd; ++i)
1659	{	2015	{
1660	// set the relevant poll flags	2016	// set the relevant poll flags
1661	// could also call adns_processreadable etc. here	2017	// could also call adns_processreadable etc. here
1662	struct pollfd *fd = fds + i;	2018	struct pollfd *fd = fds + i;
1663	int revents = ev_clear_pending (iow + i);	2019	int revents = ev_clear_pending (iow + i);
1664	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2020	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1665	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2021	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1666		2022
1667	// now stop the watcher	2023	// now stop the watcher
1668	ev_io_stop (loop, iow + i);	2024	ev_io_stop (loop, iow + i);
1669	}	2025	}
1670		2026
1671	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2027	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1672	}	2028	}
1673		2029
1674	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2030	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1675	in the prepare watcher and would dispose of the check watcher.	2031	in the prepare watcher and would dispose of the check watcher.
1676		2032
1677	Method 3: If the module to be embedded supports explicit event	2033	Method 3: If the module to be embedded supports explicit event
1678	notification (adns does), you can also make use of the actual watcher	2034	notification (libadns does), you can also make use of the actual watcher
1679	callbacks, and only destroy/create the watchers in the prepare watcher.	2035	callbacks, and only destroy/create the watchers in the prepare watcher.
1680		2036
1681	static void	2037	static void
1682	timer_cb (EV_P_ ev_timer *w, int revents)	2038	timer_cb (EV_P_ ev_timer *w, int revents)
1683	{	2039	{
1684	adns_state ads = (adns_state)w->data;	2040	adns_state ads = (adns_state)w->data;
1685	update_now (EV_A);	2041	update_now (EV_A);
1686		2042
1687	adns_processtimeouts (ads, &tv_now);	2043	adns_processtimeouts (ads, &tv_now);
1688	}	2044	}
1689		2045
1690	static void	2046	static void
1691	io_cb (EV_P_ ev_io *w, int revents)	2047	io_cb (EV_P_ ev_io *w, int revents)
1692	{	2048	{
1693	adns_state ads = (adns_state)w->data;	2049	adns_state ads = (adns_state)w->data;
1694	update_now (EV_A);	2050	update_now (EV_A);
1695		2051
1696	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2052	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1697	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2053	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1698	}	2054	}
1699		2055
1700	// do not ever call adns_afterpoll	2056	// do not ever call adns_afterpoll
1701		2057
1702	Method 4: Do not use a prepare or check watcher because the module you	2058	Method 4: Do not use a prepare or check watcher because the module you
1703	want to embed is too inflexible to support it. Instead, youc na override	2059	want to embed is too inflexible to support it. Instead, you can override
1704	their poll function. The drawback with this solution is that the main	2060	their poll function. The drawback with this solution is that the main
1705	loop is now no longer controllable by EV. The C<Glib::EV> module does	2061	loop is now no longer controllable by EV. The C<Glib::EV> module does
1706	this.	2062	this.
1707		2063
1708	static gint	2064	static gint
1709	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2065	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1710	{	2066	{
1711	int got_events = 0;	2067	int got_events = 0;
1712		2068
1713	for (n = 0; n < nfds; ++n)	2069	for (n = 0; n < nfds; ++n)
1714	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2070	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1715		2071
1716	if (timeout >= 0)	2072	if (timeout >= 0)
1717	// create/start timer	2073	// create/start timer
1718		2074
1719	// poll	2075	// poll
1720	ev_loop (EV_A_ 0);	2076	ev_loop (EV_A_ 0);
1721		2077
1722	// stop timer again	2078	// stop timer again
1723	if (timeout >= 0)	2079	if (timeout >= 0)
1724	ev_timer_stop (EV_A_ &to);	2080	ev_timer_stop (EV_A_ &to);
1725		2081
1726	// stop io watchers again - their callbacks should have set	2082	// stop io watchers again - their callbacks should have set
1727	for (n = 0; n < nfds; ++n)	2083	for (n = 0; n < nfds; ++n)
1728	ev_io_stop (EV_A_ iow [n]);	2084	ev_io_stop (EV_A_ iow [n]);
1729		2085
1730	return got_events;	2086	return got_events;
1731	}	2087	}
1732		2088
1733		2089
1734	=head2 C<ev_embed> - when one backend isn't enough...	2090	=head2 C<ev_embed> - when one backend isn't enough...
1735		2091
1736	This is a rather advanced watcher type that lets you embed one event loop	2092	This is a rather advanced watcher type that lets you embed one event loop
1737	into another (currently only C<ev_io> events are supported in the embedded	2093	into another (currently only C<ev_io> events are supported in the embedded
1738	loop, other types of watchers might be handled in a delayed or incorrect	2094	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	2095	fashion and must not be used).
1740		2096
1741	There are primarily two reasons you would want that: work around bugs and	2097	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	2098	prioritise I/O.
1743		2099
1744	As an example for a bug workaround, the kqueue backend might only support	2100	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	2134	portable one.
1779		2135
1780	So when you want to use this feature you will always have to be prepared	2136	So when you want to use this feature you will always have to be prepared
1781	that you cannot get an embeddable loop. The recommended way to get around	2137	that you cannot get an embeddable loop. The recommended way to get around
1782	this is to have a separate variables for your embeddable loop, try to	2138	this is to have a separate variables for your embeddable loop, try to
1783	create it, and if that fails, use the normal loop for everything:	2139	create it, and if that fails, use the normal loop for everything.
1784
1785	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;
1788
1789	// see if there is a chance of getting one that works
1790	// (remember that a flags value of 0 means autodetection)
1791	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1792	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1793	: 0;
1794
1795	// if we got one, then embed it, otherwise default to loop_hi
1796	if (loop_lo)
1797	{
1798	ev_embed_init (&embed, 0, loop_lo);
1799	ev_embed_start (loop_hi, &embed);
1800	}
1801	else
1802	loop_lo = loop_hi;
1803
1804	=head2 Portability notes
1805
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1807	tried, in various ways. Usually the embedded event loop will simply never
1808	receive events, sometimes it will only trigger a few times, sometimes in a
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1810	will always eport the epoll fd as ready, even when no events are pending.
1811
1812	While libev allows embedding these backends (they are contained in
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually
1814	work.
1815
1816	When in doubt, create a dynamic event loop forced to use sockets (this
1817	usually works) and possibly another thread and a pipe or so to report to
1818	your main event loop.
1819		2140
1820	=head3 Watcher-Specific Functions and Data Members	2141	=head3 Watcher-Specific Functions and Data Members
1821		2142
1822	=over 4	2143	=over 4
1823		2144
…		…
1827		2148
1828	Configures the watcher to embed the given loop, which must be	2149	Configures the watcher to embed the given loop, which must be
1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2150	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1830	invoked automatically, otherwise it is the responsibility of the callback	2151	invoked automatically, otherwise it is the responsibility of the callback
1831	to invoke it (it will continue to be called until the sweep has been done,	2152	to invoke it (it will continue to be called until the sweep has been done,
1832	if you do not want thta, you need to temporarily stop the embed watcher).	2153	if you do not want that, you need to temporarily stop the embed watcher).
1833		2154
1834	=item ev_embed_sweep (loop, ev_embed *)	2155	=item ev_embed_sweep (loop, ev_embed *)
1835		2156
1836	Make a single, non-blocking sweep over the embedded loop. This works	2157	Make a single, non-blocking sweep over the embedded loop. This works
1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2158	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1838	apropriate way for embedded loops.	2159	appropriate way for embedded loops.
1839		2160
1840	=item struct ev_loop *other [read-only]	2161	=item struct ev_loop *other [read-only]
1841		2162
1842	The embedded event loop.	2163	The embedded event loop.
1843		2164
1844	=back	2165	=back
		2166
		2167	=head3 Examples
		2168
		2169	Example: Try to get an embeddable event loop and embed it into the default
		2170	event loop. If that is not possible, use the default loop. The default
		2171	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2172	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2173	used).
		2174
		2175	struct ev_loop *loop_hi = ev_default_init (0);
		2176	struct ev_loop *loop_lo = 0;
		2177	struct ev_embed embed;
		2178
		2179	// see if there is a chance of getting one that works
		2180	// (remember that a flags value of 0 means autodetection)
		2181	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2182	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2183	: 0;
		2184
		2185	// if we got one, then embed it, otherwise default to loop_hi
		2186	if (loop_lo)
		2187	{
		2188	ev_embed_init (&embed, 0, loop_lo);
		2189	ev_embed_start (loop_hi, &embed);
		2190	}
		2191	else
		2192	loop_lo = loop_hi;
		2193
		2194	Example: Check if kqueue is available but not recommended and create
		2195	a kqueue backend for use with sockets (which usually work with any
		2196	kqueue implementation). Store the kqueue/socket-only event loop in
		2197	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2198
		2199	struct ev_loop *loop = ev_default_init (0);
		2200	struct ev_loop *loop_socket = 0;
		2201	struct ev_embed embed;
		2202
		2203	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2204	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2205	{
		2206	ev_embed_init (&embed, 0, loop_socket);
		2207	ev_embed_start (loop, &embed);
		2208	}
		2209
		2210	if (!loop_socket)
		2211	loop_socket = loop;
		2212
		2213	// now use loop_socket for all sockets, and loop for everything else
1845		2214
1846		2215
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2216	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2217
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2218	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2234	believe me.
1866		2235
1867	=back	2236	=back
1868		2237
1869		2238
		2239	=head2 C<ev_async> - how to wake up another event loop
		2240
		2241	In general, you cannot use an C<ev_loop> from multiple threads or other
		2242	asynchronous sources such as signal handlers (as opposed to multiple event
		2243	loops - those are of course safe to use in different threads).
		2244
		2245	Sometimes, however, you need to wake up another event loop you do not
		2246	control, for example because it belongs to another thread. This is what
		2247	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2248	can signal it by calling C<ev_async_send>, which is thread- and signal
		2249	safe.
		2250
		2251	This functionality is very similar to C<ev_signal> watchers, as signals,
		2252	too, are asynchronous in nature, and signals, too, will be compressed
		2253	(i.e. the number of callback invocations may be less than the number of
		2254	C<ev_async_sent> calls).
		2255
		2256	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2257	just the default loop.
		2258
		2259	=head3 Queueing
		2260
		2261	C<ev_async> does not support queueing of data in any way. The reason
		2262	is that the author does not know of a simple (or any) algorithm for a
		2263	multiple-writer-single-reader queue that works in all cases and doesn't
		2264	need elaborate support such as pthreads.
		2265
		2266	That means that if you want to queue data, you have to provide your own
		2267	queue. But at least I can tell you would implement locking around your
		2268	queue:
		2269
		2270	=over 4
		2271
		2272	=item queueing from a signal handler context
		2273
		2274	To implement race-free queueing, you simply add to the queue in the signal
		2275	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2276	some fictitious SIGUSR1 handler:
		2277
		2278	static ev_async mysig;
		2279
		2280	static void
		2281	sigusr1_handler (void)
		2282	{
		2283	sometype data;
		2284
		2285	// no locking etc.
		2286	queue_put (data);
		2287	ev_async_send (EV_DEFAULT_ &mysig);
		2288	}
		2289
		2290	static void
		2291	mysig_cb (EV_P_ ev_async *w, int revents)
		2292	{
		2293	sometype data;
		2294	sigset_t block, prev;
		2295
		2296	sigemptyset (&block);
		2297	sigaddset (&block, SIGUSR1);
		2298	sigprocmask (SIG_BLOCK, &block, &prev);
		2299
		2300	while (queue_get (&data))
		2301	process (data);
		2302
		2303	if (sigismember (&prev, SIGUSR1)
		2304	sigprocmask (SIG_UNBLOCK, &block, 0);
		2305	}
		2306
		2307	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2308	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2309	either...).
		2310
		2311	=item queueing from a thread context
		2312
		2313	The strategy for threads is different, as you cannot (easily) block
		2314	threads but you can easily preempt them, so to queue safely you need to
		2315	employ a traditional mutex lock, such as in this pthread example:
		2316
		2317	static ev_async mysig;
		2318	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2319
		2320	static void
		2321	otherthread (void)
		2322	{
		2323	// only need to lock the actual queueing operation
		2324	pthread_mutex_lock (&mymutex);
		2325	queue_put (data);
		2326	pthread_mutex_unlock (&mymutex);
		2327
		2328	ev_async_send (EV_DEFAULT_ &mysig);
		2329	}
		2330
		2331	static void
		2332	mysig_cb (EV_P_ ev_async *w, int revents)
		2333	{
		2334	pthread_mutex_lock (&mymutex);
		2335
		2336	while (queue_get (&data))
		2337	process (data);
		2338
		2339	pthread_mutex_unlock (&mymutex);
		2340	}
		2341
		2342	=back
		2343
		2344
		2345	=head3 Watcher-Specific Functions and Data Members
		2346
		2347	=over 4
		2348
		2349	=item ev_async_init (ev_async *, callback)
		2350
		2351	Initialises and configures the async watcher - it has no parameters of any
		2352	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2353	believe me.
		2354
		2355	=item ev_async_send (loop, ev_async *)
		2356
		2357	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2358	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2359	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2360	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2361	section below on what exactly this means).
		2362
		2363	This call incurs the overhead of a system call only once per loop iteration,
		2364	so while the overhead might be noticeable, it doesn't apply to repeated
		2365	calls to C<ev_async_send>.
		2366
		2367	=item bool = ev_async_pending (ev_async *)
		2368
		2369	Returns a non-zero value when C<ev_async_send> has been called on the
		2370	watcher but the event has not yet been processed (or even noted) by the
		2371	event loop.
		2372
		2373	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2374	the loop iterates next and checks for the watcher to have become active,
		2375	it will reset the flag again. C<ev_async_pending> can be used to very
		2376	quickly check whether invoking the loop might be a good idea.
		2377
		2378	Not that this does I<not> check whether the watcher itself is pending, only
		2379	whether it has been requested to make this watcher pending.
		2380
		2381	=back
		2382
		2383
1870	=head1 OTHER FUNCTIONS	2384	=head1 OTHER FUNCTIONS
1871		2385
1872	There are some other functions of possible interest. Described. Here. Now.	2386	There are some other functions of possible interest. Described. Here. Now.
1873		2387
1874	=over 4	2388	=over 4
…		…
1881	or timeout without having to allocate/configure/start/stop/free one or	2395	or timeout without having to allocate/configure/start/stop/free one or
1882	more watchers yourself.	2396	more watchers yourself.
1883		2397
1884	If C<fd> is less than 0, then no I/O watcher will be started and events	2398	If C<fd> is less than 0, then no I/O watcher will be started and events
1885	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2399	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1886	C<events> set will be craeted and started.	2400	C<events> set will be created and started.
1887		2401
1888	If C<timeout> is less than 0, then no timeout watcher will be	2402	If C<timeout> is less than 0, then no timeout watcher will be
1889	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2403	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1890	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2404	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1891	dubious value.	2405	dubious value.
…		…
1893	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2407	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1894	passed an C<revents> set like normal event callbacks (a combination of	2408	passed an C<revents> set like normal event callbacks (a combination of
1895	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2409	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1896	value passed to C<ev_once>:	2410	value passed to C<ev_once>:
1897		2411
1898	static void stdin_ready (int revents, void *arg)	2412	static void stdin_ready (int revents, void *arg)
1899	{	2413	{
1900	if (revents & EV_TIMEOUT)	2414	if (revents & EV_TIMEOUT)
1901	/* doh, nothing entered */;	2415	/* doh, nothing entered */;
1902	else if (revents & EV_READ)	2416	else if (revents & EV_READ)
1903	/* stdin might have data for us, joy! */;	2417	/* stdin might have data for us, joy! */;
1904	}	2418	}
1905		2419
1906	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2420	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1907		2421
1908	=item ev_feed_event (ev_loop *, watcher *, int revents)	2422	=item ev_feed_event (ev_loop *, watcher *, int revents)
1909		2423
1910	Feeds the given event set into the event loop, as if the specified event	2424	Feeds the given event set into the event loop, as if the specified event
1911	had happened for the specified watcher (which must be a pointer to an	2425	had happened for the specified watcher (which must be a pointer to an
…		…
1916	Feed an event on the given fd, as if a file descriptor backend detected	2430	Feed an event on the given fd, as if a file descriptor backend detected
1917	the given events it.	2431	the given events it.
1918		2432
1919	=item ev_feed_signal_event (ev_loop *loop, int signum)	2433	=item ev_feed_signal_event (ev_loop *loop, int signum)
1920		2434
1921	Feed an event as if the given signal occured (C<loop> must be the default	2435	Feed an event as if the given signal occurred (C<loop> must be the default
1922	loop!).	2436	loop!).
1923		2437
1924	=back	2438	=back
1925		2439
1926		2440
…		…
1942		2456
1943	=item * Priorities are not currently supported. Initialising priorities	2457	=item * Priorities are not currently supported. Initialising priorities
1944	will fail and all watchers will have the same priority, even though there	2458	will fail and all watchers will have the same priority, even though there
1945	is an ev_pri field.	2459	is an ev_pri field.
1946		2460
		2461	=item * In libevent, the last base created gets the signals, in libev, the
		2462	first base created (== the default loop) gets the signals.
		2463
1947	=item * Other members are not supported.	2464	=item * Other members are not supported.
1948		2465
1949	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2466	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1950	to use the libev header file and library.	2467	to use the libev header file and library.
1951		2468
1952	=back	2469	=back
1953		2470
1954	=head1 C++ SUPPORT	2471	=head1 C++ SUPPORT
1955		2472
1956	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2473	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1957	you to use some convinience methods to start/stop watchers and also change	2474	you to use some convenience methods to start/stop watchers and also change
1958	the callback model to a model using method callbacks on objects.	2475	the callback model to a model using method callbacks on objects.
1959		2476
1960	To use it,	2477	To use it,
1961		2478
1962	#include <ev++.h>	2479	#include <ev++.h>
1963		2480
1964	This automatically includes F<ev.h> and puts all of its definitions (many	2481	This automatically includes F<ev.h> and puts all of its definitions (many
1965	of them macros) into the global namespace. All C++ specific things are	2482	of them macros) into the global namespace. All C++ specific things are
1966	put into the C<ev> namespace. It should support all the same embedding	2483	put into the C<ev> namespace. It should support all the same embedding
1967	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2484	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2034	your compiler is good :), then the method will be fully inlined into the	2551	your compiler is good :), then the method will be fully inlined into the
2035	thunking function, making it as fast as a direct C callback.	2552	thunking function, making it as fast as a direct C callback.
2036		2553
2037	Example: simple class declaration and watcher initialisation	2554	Example: simple class declaration and watcher initialisation
2038		2555
2039	struct myclass	2556	struct myclass
2040	{	2557	{
2041	void io_cb (ev::io &w, int revents) { }	2558	void io_cb (ev::io &w, int revents) { }
2042	}	2559	}
2043		2560
2044	myclass obj;	2561	myclass obj;
2045	ev::io iow;	2562	ev::io iow;
2046	iow.set <myclass, &myclass::io_cb> (&obj);	2563	iow.set <myclass, &myclass::io_cb> (&obj);
2047		2564
2048	=item w->set<function> (void *data = 0)	2565	=item w->set<function> (void *data = 0)
2049		2566
2050	Also sets a callback, but uses a static method or plain function as	2567	Also sets a callback, but uses a static method or plain function as
2051	callback. The optional C<data> argument will be stored in the watcher's	2568	callback. The optional C<data> argument will be stored in the watcher's
…		…
2055		2572
2056	See the method-C<set> above for more details.	2573	See the method-C<set> above for more details.
2057		2574
2058	Example:	2575	Example:
2059		2576
2060	static void io_cb (ev::io &w, int revents) { }	2577	static void io_cb (ev::io &w, int revents) { }
2061	iow.set <io_cb> ();	2578	iow.set <io_cb> ();
2062		2579
2063	=item w->set (struct ev_loop *)	2580	=item w->set (struct ev_loop *)
2064		2581
2065	Associates a different C<struct ev_loop> with this watcher. You can only	2582	Associates a different C<struct ev_loop> with this watcher. You can only
2066	do this when the watcher is inactive (and not pending either).	2583	do this when the watcher is inactive (and not pending either).
2067		2584
2068	=item w->set ([args])	2585	=item w->set ([arguments])
2069		2586
2070	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2587	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2071	called at least once. Unlike the C counterpart, an active watcher gets	2588	called at least once. Unlike the C counterpart, an active watcher gets
2072	automatically stopped and restarted when reconfiguring it with this	2589	automatically stopped and restarted when reconfiguring it with this
2073	method.	2590	method.
2074		2591
2075	=item w->start ()	2592	=item w->start ()
…		…
2099	=back	2616	=back
2100		2617
2101	Example: Define a class with an IO and idle watcher, start one of them in	2618	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2619	the constructor.
2103		2620
2104	class myclass	2621	class myclass
2105	{	2622	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2623	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2624	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2625
2109	myclass ();	2626	myclass (int fd)
2110	}	2627	{
2111
2112	myclass::myclass (int fd)
2113	{
2114	io .set <myclass, &myclass::io_cb > (this);	2628	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2629	idle.set <myclass, &myclass::idle_cb> (this);
2116		2630
2117	io.start (fd, ev::READ);	2631	io.start (fd, ev::READ);
		2632	}
2118	}	2633	};
		2634
		2635
		2636	=head1 OTHER LANGUAGE BINDINGS
		2637
		2638	Libev does not offer other language bindings itself, but bindings for a
		2639	number of languages exist in the form of third-party packages. If you know
		2640	any interesting language binding in addition to the ones listed here, drop
		2641	me a note.
		2642
		2643	=over 4
		2644
		2645	=item Perl
		2646
		2647	The EV module implements the full libev API and is actually used to test
		2648	libev. EV is developed together with libev. Apart from the EV core module,
		2649	there are additional modules that implement libev-compatible interfaces
		2650	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2651	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2652
		2653	It can be found and installed via CPAN, its homepage is at
		2654	L<http://software.schmorp.de/pkg/EV>.
		2655
		2656	=item Python
		2657
		2658	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2659	seems to be quite complete and well-documented. Note, however, that the
		2660	patch they require for libev is outright dangerous as it breaks the ABI
		2661	for everybody else, and therefore, should never be applied in an installed
		2662	libev (if python requires an incompatible ABI then it needs to embed
		2663	libev).
		2664
		2665	=item Ruby
		2666
		2667	Tony Arcieri has written a ruby extension that offers access to a subset
		2668	of the libev API and adds file handle abstractions, asynchronous DNS and
		2669	more on top of it. It can be found via gem servers. Its homepage is at
		2670	L<http://rev.rubyforge.org/>.
		2671
		2672	=item D
		2673
		2674	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2675	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2676
		2677	=back
2119		2678
2120		2679
2121	=head1 MACRO MAGIC	2680	=head1 MACRO MAGIC
2122		2681
2123	Libev can be compiled with a variety of options, the most fundamantal	2682	Libev can be compiled with a variety of options, the most fundamental
2124	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2683	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2125	functions and callbacks have an initial C<struct ev_loop *> argument.	2684	functions and callbacks have an initial C<struct ev_loop *> argument.
2126		2685
2127	To make it easier to write programs that cope with either variant, the	2686	To make it easier to write programs that cope with either variant, the
2128	following macros are defined:	2687	following macros are defined:
…		…
2133		2692
2134	This provides the loop I<argument> for functions, if one is required ("ev	2693	This provides the loop I<argument> for functions, if one is required ("ev
2135	loop argument"). The C<EV_A> form is used when this is the sole argument,	2694	loop argument"). The C<EV_A> form is used when this is the sole argument,
2136	C<EV_A_> is used when other arguments are following. Example:	2695	C<EV_A_> is used when other arguments are following. Example:
2137		2696
2138	ev_unref (EV_A);	2697	ev_unref (EV_A);
2139	ev_timer_add (EV_A_ watcher);	2698	ev_timer_add (EV_A_ watcher);
2140	ev_loop (EV_A_ 0);	2699	ev_loop (EV_A_ 0);
2141		2700
2142	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2701	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2143	which is often provided by the following macro.	2702	which is often provided by the following macro.
2144		2703
2145	=item C<EV_P>, C<EV_P_>	2704	=item C<EV_P>, C<EV_P_>
2146		2705
2147	This provides the loop I<parameter> for functions, if one is required ("ev	2706	This provides the loop I<parameter> for functions, if one is required ("ev
2148	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2707	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2149	C<EV_P_> is used when other parameters are following. Example:	2708	C<EV_P_> is used when other parameters are following. Example:
2150		2709
2151	// this is how ev_unref is being declared	2710	// this is how ev_unref is being declared
2152	static void ev_unref (EV_P);	2711	static void ev_unref (EV_P);
2153		2712
2154	// this is how you can declare your typical callback	2713	// this is how you can declare your typical callback
2155	static void cb (EV_P_ ev_timer *w, int revents)	2714	static void cb (EV_P_ ev_timer *w, int revents)
2156		2715
2157	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2716	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2158	suitable for use with C<EV_A>.	2717	suitable for use with C<EV_A>.
2159		2718
2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2719	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2161		2720
2162	Similar to the other two macros, this gives you the value of the default	2721	Similar to the other two macros, this gives you the value of the default
2163	loop, if multiple loops are supported ("ev loop default").	2722	loop, if multiple loops are supported ("ev loop default").
		2723
		2724	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2725
		2726	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2727	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2728	is undefined when the default loop has not been initialised by a previous
		2729	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2730
		2731	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2732	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2164		2733
2165	=back	2734	=back
2166		2735
2167	Example: Declare and initialise a check watcher, utilising the above	2736	Example: Declare and initialise a check watcher, utilising the above
2168	macros so it will work regardless of whether multiple loops are supported	2737	macros so it will work regardless of whether multiple loops are supported
2169	or not.	2738	or not.
2170		2739
2171	static void	2740	static void
2172	check_cb (EV_P_ ev_timer *w, int revents)	2741	check_cb (EV_P_ ev_timer *w, int revents)
2173	{	2742	{
2174	ev_check_stop (EV_A_ w);	2743	ev_check_stop (EV_A_ w);
2175	}	2744	}
2176		2745
2177	ev_check check;	2746	ev_check check;
2178	ev_check_init (&check, check_cb);	2747	ev_check_init (&check, check_cb);
2179	ev_check_start (EV_DEFAULT_ &check);	2748	ev_check_start (EV_DEFAULT_ &check);
2180	ev_loop (EV_DEFAULT_ 0);	2749	ev_loop (EV_DEFAULT_ 0);
2181		2750
2182	=head1 EMBEDDING	2751	=head1 EMBEDDING
2183		2752
2184	Libev can (and often is) directly embedded into host	2753	Libev can (and often is) directly embedded into host
2185	applications. Examples of applications that embed it include the Deliantra	2754	applications. Examples of applications that embed it include the Deliantra
…		…
2192	libev somewhere in your source tree).	2761	libev somewhere in your source tree).
2193		2762
2194	=head2 FILESETS	2763	=head2 FILESETS
2195		2764
2196	Depending on what features you need you need to include one or more sets of files	2765	Depending on what features you need you need to include one or more sets of files
2197	in your app.	2766	in your application.
2198		2767
2199	=head3 CORE EVENT LOOP	2768	=head3 CORE EVENT LOOP
2200		2769
2201	To include only the libev core (all the C<ev_*> functions), with manual	2770	To include only the libev core (all the C<ev_*> functions), with manual
2202	configuration (no autoconf):	2771	configuration (no autoconf):
2203		2772
2204	#define EV_STANDALONE 1	2773	#define EV_STANDALONE 1
2205	#include "ev.c"	2774	#include "ev.c"
2206		2775
2207	This will automatically include F<ev.h>, too, and should be done in a	2776	This will automatically include F<ev.h>, too, and should be done in a
2208	single C source file only to provide the function implementations. To use	2777	single C source file only to provide the function implementations. To use
2209	it, do the same for F<ev.h> in all files wishing to use this API (best	2778	it, do the same for F<ev.h> in all files wishing to use this API (best
2210	done by writing a wrapper around F<ev.h> that you can include instead and	2779	done by writing a wrapper around F<ev.h> that you can include instead and
2211	where you can put other configuration options):	2780	where you can put other configuration options):
2212		2781
2213	#define EV_STANDALONE 1	2782	#define EV_STANDALONE 1
2214	#include "ev.h"	2783	#include "ev.h"
2215		2784
2216	Both header files and implementation files can be compiled with a C++	2785	Both header files and implementation files can be compiled with a C++
2217	compiler (at least, thats a stated goal, and breakage will be treated	2786	compiler (at least, thats a stated goal, and breakage will be treated
2218	as a bug).	2787	as a bug).
2219		2788
2220	You need the following files in your source tree, or in a directory	2789	You need the following files in your source tree, or in a directory
2221	in your include path (e.g. in libev/ when using -Ilibev):	2790	in your include path (e.g. in libev/ when using -Ilibev):
2222		2791
2223	ev.h	2792	ev.h
2224	ev.c	2793	ev.c
2225	ev_vars.h	2794	ev_vars.h
2226	ev_wrap.h	2795	ev_wrap.h
2227		2796
2228	ev_win32.c required on win32 platforms only	2797	ev_win32.c required on win32 platforms only
2229		2798
2230	ev_select.c only when select backend is enabled (which is enabled by default)	2799	ev_select.c only when select backend is enabled (which is enabled by default)
2231	ev_poll.c only when poll backend is enabled (disabled by default)	2800	ev_poll.c only when poll backend is enabled (disabled by default)
2232	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2801	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2233	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2802	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2234	ev_port.c only when the solaris port backend is enabled (disabled by default)	2803	ev_port.c only when the solaris port backend is enabled (disabled by default)
2235		2804
2236	F<ev.c> includes the backend files directly when enabled, so you only need	2805	F<ev.c> includes the backend files directly when enabled, so you only need
2237	to compile this single file.	2806	to compile this single file.
2238		2807
2239	=head3 LIBEVENT COMPATIBILITY API	2808	=head3 LIBEVENT COMPATIBILITY API
2240		2809
2241	To include the libevent compatibility API, also include:	2810	To include the libevent compatibility API, also include:
2242		2811
2243	#include "event.c"	2812	#include "event.c"
2244		2813
2245	in the file including F<ev.c>, and:	2814	in the file including F<ev.c>, and:
2246		2815
2247	#include "event.h"	2816	#include "event.h"
2248		2817
2249	in the files that want to use the libevent API. This also includes F<ev.h>.	2818	in the files that want to use the libevent API. This also includes F<ev.h>.
2250		2819
2251	You need the following additional files for this:	2820	You need the following additional files for this:
2252		2821
2253	event.h	2822	event.h
2254	event.c	2823	event.c
2255		2824
2256	=head3 AUTOCONF SUPPORT	2825	=head3 AUTOCONF SUPPORT
2257		2826
2258	Instead of using C<EV_STANDALONE=1> and providing your config in	2827	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2259	whatever way you want, you can also C<m4_include([libev.m4])> in your	2828	whatever way you want, you can also C<m4_include([libev.m4])> in your
2260	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2829	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2261	include F<config.h> and configure itself accordingly.	2830	include F<config.h> and configure itself accordingly.
2262		2831
2263	For this of course you need the m4 file:	2832	For this of course you need the m4 file:
2264		2833
2265	libev.m4	2834	libev.m4
2266		2835
2267	=head2 PREPROCESSOR SYMBOLS/MACROS	2836	=head2 PREPROCESSOR SYMBOLS/MACROS
2268		2837
2269	Libev can be configured via a variety of preprocessor symbols you have to define	2838	Libev can be configured via a variety of preprocessor symbols you have to
2270	before including any of its files. The default is not to build for multiplicity	2839	define before including any of its files. The default in the absence of
2271	and only include the select backend.	2840	autoconf is noted for every option.
2272		2841
2273	=over 4	2842	=over 4
2274		2843
2275	=item EV_STANDALONE	2844	=item EV_STANDALONE
2276		2845
…		…
2281	F<event.h> that are not directly supported by the libev core alone.	2850	F<event.h> that are not directly supported by the libev core alone.
2282		2851
2283	=item EV_USE_MONOTONIC	2852	=item EV_USE_MONOTONIC
2284		2853
2285	If defined to be C<1>, libev will try to detect the availability of the	2854	If defined to be C<1>, libev will try to detect the availability of the
2286	monotonic clock option at both compiletime and runtime. Otherwise no use	2855	monotonic clock option at both compile time and runtime. Otherwise no use
2287	of the monotonic clock option will be attempted. If you enable this, you	2856	of the monotonic clock option will be attempted. If you enable this, you
2288	usually have to link against librt or something similar. Enabling it when	2857	usually have to link against librt or something similar. Enabling it when
2289	the functionality isn't available is safe, though, although you have	2858	the functionality isn't available is safe, though, although you have
2290	to make sure you link against any libraries where the C<clock_gettime>	2859	to make sure you link against any libraries where the C<clock_gettime>
2291	function is hiding in (often F<-lrt>).	2860	function is hiding in (often F<-lrt>).
2292		2861
2293	=item EV_USE_REALTIME	2862	=item EV_USE_REALTIME
2294		2863
2295	If defined to be C<1>, libev will try to detect the availability of the	2864	If defined to be C<1>, libev will try to detect the availability of the
2296	realtime clock option at compiletime (and assume its availability at	2865	real-time clock option at compile time (and assume its availability at
2297	runtime if successful). Otherwise no use of the realtime clock option will	2866	runtime if successful). Otherwise no use of the real-time clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2867	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2868	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2869	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2870
		2871	=item EV_USE_NANOSLEEP
		2872
		2873	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2874	and will use it for delays. Otherwise it will use C<select ()>.
		2875
		2876	=item EV_USE_EVENTFD
		2877
		2878	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2879	available and will probe for kernel support at runtime. This will improve
		2880	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2881	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2882	2.7 or newer, otherwise disabled.
		2883
2302	=item EV_USE_SELECT	2884	=item EV_USE_SELECT
2303		2885
2304	If undefined or defined to be C<1>, libev will compile in support for the	2886	If undefined or defined to be C<1>, libev will compile in support for the
2305	C<select>(2) backend. No attempt at autodetection will be done: if no	2887	C<select>(2) backend. No attempt at auto-detection will be done: if no
2306	other method takes over, select will be it. Otherwise the select backend	2888	other method takes over, select will be it. Otherwise the select backend
2307	will not be compiled in.	2889	will not be compiled in.
2308		2890
2309	=item EV_SELECT_USE_FD_SET	2891	=item EV_SELECT_USE_FD_SET
2310		2892
2311	If defined to C<1>, then the select backend will use the system C<fd_set>	2893	If defined to C<1>, then the select backend will use the system C<fd_set>
2312	structure. This is useful if libev doesn't compile due to a missing	2894	structure. This is useful if libev doesn't compile due to a missing
2313	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2895	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2314	exotic systems. This usually limits the range of file descriptors to some	2896	exotic systems. This usually limits the range of file descriptors to some
2315	low limit such as 1024 or might have other limitations (winsocket only	2897	low limit such as 1024 or might have other limitations (winsocket only
2316	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2898	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2317	influence the size of the C<fd_set> used.	2899	influence the size of the C<fd_set> used.
2318		2900
…		…
2324	be used is the winsock select). This means that it will call	2906	be used is the winsock select). This means that it will call
2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2907	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2326	it is assumed that all these functions actually work on fds, even	2908	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2909	on win32. Should not be defined on non-win32 platforms.
2328		2910
		2911	=item EV_FD_TO_WIN32_HANDLE
		2912
		2913	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2914	file descriptors to socket handles. When not defining this symbol (the
		2915	default), then libev will call C<_get_osfhandle>, which is usually
		2916	correct. In some cases, programs use their own file descriptor management,
		2917	in which case they can provide this function to map fds to socket handles.
		2918
2329	=item EV_USE_POLL	2919	=item EV_USE_POLL
2330		2920
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2921	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2332	backend. Otherwise it will be enabled on non-win32 platforms. It	2922	backend. Otherwise it will be enabled on non-win32 platforms. It
2333	takes precedence over select.	2923	takes precedence over select.
2334		2924
2335	=item EV_USE_EPOLL	2925	=item EV_USE_EPOLL
2336		2926
2337	If defined to be C<1>, libev will compile in support for the Linux	2927	If defined to be C<1>, libev will compile in support for the Linux
2338	C<epoll>(7) backend. Its availability will be detected at runtime,	2928	C<epoll>(7) backend. Its availability will be detected at runtime,
2339	otherwise another method will be used as fallback. This is the	2929	otherwise another method will be used as fallback. This is the preferred
2340	preferred backend for GNU/Linux systems.	2930	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2931	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2341		2932
2342	=item EV_USE_KQUEUE	2933	=item EV_USE_KQUEUE
2343		2934
2344	If defined to be C<1>, libev will compile in support for the BSD style	2935	If defined to be C<1>, libev will compile in support for the BSD style
2345	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2936	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2358	otherwise another method will be used as fallback. This is the preferred	2949	otherwise another method will be used as fallback. This is the preferred
2359	backend for Solaris 10 systems.	2950	backend for Solaris 10 systems.
2360		2951
2361	=item EV_USE_DEVPOLL	2952	=item EV_USE_DEVPOLL
2362		2953
2363	reserved for future expansion, works like the USE symbols above.	2954	Reserved for future expansion, works like the USE symbols above.
2364		2955
2365	=item EV_USE_INOTIFY	2956	=item EV_USE_INOTIFY
2366		2957
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2958	If defined to be C<1>, libev will compile in support for the Linux inotify
2368	interface to speed up C<ev_stat> watchers. Its actual availability will	2959	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2960	be detected at runtime. If undefined, it will be enabled if the headers
		2961	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2962
		2963	=item EV_ATOMIC_T
		2964
		2965	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2966	access is atomic with respect to other threads or signal contexts. No such
		2967	type is easily found in the C language, so you can provide your own type
		2968	that you know is safe for your purposes. It is used both for signal handler "locking"
		2969	as well as for signal and thread safety in C<ev_async> watchers.
		2970
		2971	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2972	(from F<signal.h>), which is usually good enough on most platforms.
2370		2973
2371	=item EV_H	2974	=item EV_H
2372		2975
2373	The name of the F<ev.h> header file used to include it. The default if	2976	The name of the F<ev.h> header file used to include it. The default if
2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2977	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2978	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2979
2377	=item EV_CONFIG_H	2980	=item EV_CONFIG_H
2378		2981
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2982	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2983	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2984	C<EV_H>, above.
2382		2985
2383	=item EV_EVENT_H	2986	=item EV_EVENT_H
2384		2987
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2988	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2386	of how the F<event.h> header can be found.	2989	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2990
2388	=item EV_PROTOTYPES	2991	=item EV_PROTOTYPES
2389		2992
2390	If defined to be C<0>, then F<ev.h> will not define any function	2993	If defined to be C<0>, then F<ev.h> will not define any function
2391	prototypes, but still define all the structs and other symbols. This is	2994	prototypes, but still define all the structs and other symbols. This is
…		…
2412	When doing priority-based operations, libev usually has to linearly search	3015	When doing priority-based operations, libev usually has to linearly search
2413	all the priorities, so having many of them (hundreds) uses a lot of space	3016	all the priorities, so having many of them (hundreds) uses a lot of space
2414	and time, so using the defaults of five priorities (-2 .. +2) is usually	3017	and time, so using the defaults of five priorities (-2 .. +2) is usually
2415	fine.	3018	fine.
2416		3019
2417	If your embedding app does not need any priorities, defining these both to	3020	If your embedding application does not need any priorities, defining these both to
2418	C<0> will save some memory and cpu.	3021	C<0> will save some memory and CPU.
2419		3022
2420	=item EV_PERIODIC_ENABLE	3023	=item EV_PERIODIC_ENABLE
2421		3024
2422	If undefined or defined to be C<1>, then periodic timers are supported. If	3025	If undefined or defined to be C<1>, then periodic timers are supported. If
2423	defined to be C<0>, then they are not. Disabling them saves a few kB of	3026	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2442	=item EV_FORK_ENABLE	3045	=item EV_FORK_ENABLE
2443		3046
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	3047	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	3048	defined to be C<0>, then they are not.
2446		3049
		3050	=item EV_ASYNC_ENABLE
		3051
		3052	If undefined or defined to be C<1>, then async watchers are supported. If
		3053	defined to be C<0>, then they are not.
		3054
2447	=item EV_MINIMAL	3055	=item EV_MINIMAL
2448		3056
2449	If you need to shave off some kilobytes of code at the expense of some	3057	If you need to shave off some kilobytes of code at the expense of some
2450	speed, define this symbol to C<1>. Currently only used for gcc to override	3058	speed, define this symbol to C<1>. Currently this is used to override some
2451	some inlining decisions, saves roughly 30% codesize of amd64.	3059	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3060	much smaller 2-heap for timer management over the default 4-heap.
2452		3061
2453	=item EV_PID_HASHSIZE	3062	=item EV_PID_HASHSIZE
2454		3063
2455	C<ev_child> watchers use a small hash table to distribute workload by	3064	C<ev_child> watchers use a small hash table to distribute workload by
2456	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3065	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2457	than enough. If you need to manage thousands of children you might want to	3066	than enough. If you need to manage thousands of children you might want to
2458	increase this value (I<must> be a power of two).	3067	increase this value (I<must> be a power of two).
2459		3068
2460	=item EV_INOTIFY_HASHSIZE	3069	=item EV_INOTIFY_HASHSIZE
2461		3070
2462	C<ev_staz> watchers use a small hash table to distribute workload by	3071	C<ev_stat> watchers use a small hash table to distribute workload by
2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3072	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2464	usually more than enough. If you need to manage thousands of C<ev_stat>	3073	usually more than enough. If you need to manage thousands of C<ev_stat>
2465	watchers you might want to increase this value (I<must> be a power of	3074	watchers you might want to increase this value (I<must> be a power of
2466	two).	3075	two).
2467		3076
		3077	=item EV_USE_4HEAP
		3078
		3079	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3080	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3081	to C<1>. The 4-heap uses more complicated (longer) code but has
		3082	noticeably faster performance with many (thousands) of watchers.
		3083
		3084	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3085	(disabled).
		3086
		3087	=item EV_HEAP_CACHE_AT
		3088
		3089	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3090	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3091	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3092	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3093	but avoids random read accesses on heap changes. This improves performance
		3094	noticeably with with many (hundreds) of watchers.
		3095
		3096	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3097	(disabled).
		3098
		3099	=item EV_VERIFY
		3100
		3101	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3102	be done: If set to C<0>, no internal verification code will be compiled
		3103	in. If set to C<1>, then verification code will be compiled in, but not
		3104	called. If set to C<2>, then the internal verification code will be
		3105	called once per loop, which can slow down libev. If set to C<3>, then the
		3106	verification code will be called very frequently, which will slow down
		3107	libev considerably.
		3108
		3109	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3110	C<0.>
		3111
2468	=item EV_COMMON	3112	=item EV_COMMON
2469		3113
2470	By default, all watchers have a C<void *data> member. By redefining	3114	By default, all watchers have a C<void *data> member. By redefining
2471	this macro to a something else you can include more and other types of	3115	this macro to a something else you can include more and other types of
2472	members. You have to define it each time you include one of the files,	3116	members. You have to define it each time you include one of the files,
2473	though, and it must be identical each time.	3117	though, and it must be identical each time.
2474		3118
2475	For example, the perl EV module uses something like this:	3119	For example, the perl EV module uses something like this:
2476		3120
2477	#define EV_COMMON \	3121	#define EV_COMMON \
2478	SV *self; /* contains this struct */ \	3122	SV *self; /* contains this struct */ \
2479	SV *cb_sv, *fh /* note no trailing ";" */	3123	SV *cb_sv, *fh /* note no trailing ";" */
2480		3124
2481	=item EV_CB_DECLARE (type)	3125	=item EV_CB_DECLARE (type)
2482		3126
2483	=item EV_CB_INVOKE (watcher, revents)	3127	=item EV_CB_INVOKE (watcher, revents)
2484		3128
…		…
2491	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3135	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2492	method calls instead of plain function calls in C++.	3136	method calls instead of plain function calls in C++.
2493		3137
2494	=head2 EXPORTED API SYMBOLS	3138	=head2 EXPORTED API SYMBOLS
2495		3139
2496	If you need to re-export the API (e.g. via a dll) and you need a list of	3140	If you need to re-export the API (e.g. via a DLL) and you need a list of
2497	exported symbols, you can use the provided F<Symbol.*> files which list	3141	exported symbols, you can use the provided F<Symbol.*> files which list
2498	all public symbols, one per line:	3142	all public symbols, one per line:
2499		3143
2500	Symbols.ev for libev proper	3144	Symbols.ev for libev proper
2501	Symbols.event for the libevent emulation	3145	Symbols.event for the libevent emulation
2502		3146
2503	This can also be used to rename all public symbols to avoid clashes with	3147	This can also be used to rename all public symbols to avoid clashes with
2504	multiple versions of libev linked together (which is obviously bad in	3148	multiple versions of libev linked together (which is obviously bad in
2505	itself, but sometimes it is inconvinient to avoid this).	3149	itself, but sometimes it is inconvenient to avoid this).
2506		3150
2507	A sed command like this will create wrapper C<#define>'s that you need to	3151	A sed command like this will create wrapper C<#define>'s that you need to
2508	include before including F<ev.h>:	3152	include before including F<ev.h>:
2509		3153
2510	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3154	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2527	file.	3171	file.
2528		3172
2529	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3173	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2530	that everybody includes and which overrides some configure choices:	3174	that everybody includes and which overrides some configure choices:
2531		3175
2532	#define EV_MINIMAL 1	3176	#define EV_MINIMAL 1
2533	#define EV_USE_POLL 0	3177	#define EV_USE_POLL 0
2534	#define EV_MULTIPLICITY 0	3178	#define EV_MULTIPLICITY 0
2535	#define EV_PERIODIC_ENABLE 0	3179	#define EV_PERIODIC_ENABLE 0
2536	#define EV_STAT_ENABLE 0	3180	#define EV_STAT_ENABLE 0
2537	#define EV_FORK_ENABLE 0	3181	#define EV_FORK_ENABLE 0
2538	#define EV_CONFIG_H <config.h>	3182	#define EV_CONFIG_H <config.h>
2539	#define EV_MINPRI 0	3183	#define EV_MINPRI 0
2540	#define EV_MAXPRI 0	3184	#define EV_MAXPRI 0
2541		3185
2542	#include "ev++.h"	3186	#include "ev++.h"
2543		3187
2544	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3188	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2545		3189
2546	#include "ev_cpp.h"	3190	#include "ev_cpp.h"
2547	#include "ev.c"	3191	#include "ev.c"
		3192
		3193
		3194	=head1 THREADS AND COROUTINES
		3195
		3196	=head2 THREADS
		3197
		3198	Libev itself is completely thread-safe, but it uses no locking. This
		3199	means that you can use as many loops as you want in parallel, as long as
		3200	only one thread ever calls into one libev function with the same loop
		3201	parameter.
		3202
		3203	Or put differently: calls with different loop parameters can be done in
		3204	parallel from multiple threads, calls with the same loop parameter must be
		3205	done serially (but can be done from different threads, as long as only one
		3206	thread ever is inside a call at any point in time, e.g. by using a mutex
		3207	per loop).
		3208
		3209	If you want to know which design (one loop, locking, or multiple loops
		3210	without or something else still) is best for your problem, then I cannot
		3211	help you. I can give some generic advice however:
		3212
		3213	=over 4
		3214
		3215	=item * most applications have a main thread: use the default libev loop
		3216	in that thread, or create a separate thread running only the default loop.
		3217
		3218	This helps integrating other libraries or software modules that use libev
		3219	themselves and don't care/know about threading.
		3220
		3221	=item * one loop per thread is usually a good model.
		3222
		3223	Doing this is almost never wrong, sometimes a better-performance model
		3224	exists, but it is always a good start.
		3225
		3226	=item * other models exist, such as the leader/follower pattern, where one
		3227	loop is handed through multiple threads in a kind of round-robin fashion.
		3228
		3229	Choosing a model is hard - look around, learn, know that usually you can do
		3230	better than you currently do :-)
		3231
		3232	=item * often you need to talk to some other thread which blocks in the
		3233	event loop - C<ev_async> watchers can be used to wake them up from other
		3234	threads safely (or from signal contexts...).
		3235
		3236	=back
		3237
		3238	=head2 COROUTINES
		3239
		3240	Libev is much more accommodating to coroutines ("cooperative threads"):
		3241	libev fully supports nesting calls to it's functions from different
		3242	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3243	different coroutines and switch freely between both coroutines running the
		3244	loop, as long as you don't confuse yourself). The only exception is that
		3245	you must not do this from C<ev_periodic> reschedule callbacks.
		3246
		3247	Care has been invested into making sure that libev does not keep local
		3248	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3249	switches.
2548		3250
2549		3251
2550	=head1 COMPLEXITIES	3252	=head1 COMPLEXITIES
2551		3253
2552	In this section the complexities of (many of) the algorithms used inside	3254	In this section the complexities of (many of) the algorithms used inside
…		…
2563		3265
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3266	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		3267
2566	This means that, when you have a watcher that triggers in one hour and	3268	This means that, when you have a watcher that triggers in one hour and
2567	there are 100 watchers that would trigger before that then inserting will	3269	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	3270	have to skip roughly seven (C<ld 100>) of these watchers.
2569		3271
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3272	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		3273
2572	That means that for changing a timer costs less than removing/adding them	3274	That means that changing a timer costs less than removing/adding them
2573	as only the relative motion in the event queue has to be paid for.	3275	as only the relative motion in the event queue has to be paid for.
2574		3276
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3277	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		3278
2577	These just add the watcher into an array or at the head of a list.	3279	These just add the watcher into an array or at the head of a list.
		3280
2578	=item Stopping check/prepare/idle watchers: O(1)	3281	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		3282
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3283	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		3284
2582	These watchers are stored in lists then need to be walked to find the	3285	These watchers are stored in lists then need to be walked to find the
2583	correct watcher to remove. The lists are usually short (you don't usually	3286	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	3287	have many watchers waiting for the same fd or signal).
2585		3288
2586	=item Finding the next timer per loop iteration: O(1)	3289	=item Finding the next timer in each loop iteration: O(1)
		3290
		3291	By virtue of using a binary or 4-heap, the next timer is always found at a
		3292	fixed position in the storage array.
2587		3293
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3294	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		3295
2590	A change means an I/O watcher gets started or stopped, which requires	3296	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	3297	libev to recalculate its status (and possibly tell the kernel, depending
		3298	on backend and whether C<ev_io_set> was used).
2592		3299
2593	=item Activating one watcher: O(1)	3300	=item Activating one watcher (putting it into the pending state): O(1)
2594		3301
2595	=item Priority handling: O(number_of_priorities)	3302	=item Priority handling: O(number_of_priorities)
2596		3303
2597	Priorities are implemented by allocating some space for each	3304	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	3305	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	3306	linearly search all the priorities, but starting/stopping and activating
		3307	watchers becomes O(1) w.r.t. priority handling.
		3308
		3309	=item Sending an ev_async: O(1)
		3310
		3311	=item Processing ev_async_send: O(number_of_async_watchers)
		3312
		3313	=item Processing signals: O(max_signal_number)
		3314
		3315	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3316	calls in the current loop iteration. Checking for async and signal events
		3317	involves iterating over all running async watchers or all signal numbers.
2600		3318
2601	=back	3319	=back
2602		3320
2603		3321
		3322	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3323
		3324	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3325	requires, and its I/O model is fundamentally incompatible with the POSIX
		3326	model. Libev still offers limited functionality on this platform in
		3327	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3328	descriptors. This only applies when using Win32 natively, not when using
		3329	e.g. cygwin.
		3330
		3331	Lifting these limitations would basically require the full
		3332	re-implementation of the I/O system. If you are into these kinds of
		3333	things, then note that glib does exactly that for you in a very portable
		3334	way (note also that glib is the slowest event library known to man).
		3335
		3336	There is no supported compilation method available on windows except
		3337	embedding it into other applications.
		3338
		3339	Not a libev limitation but worth mentioning: windows apparently doesn't
		3340	accept large writes: instead of resulting in a partial write, windows will
		3341	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3342	so make sure you only write small amounts into your sockets (less than a
		3343	megabyte seems safe, but thsi apparently depends on the amount of memory
		3344	available).
		3345
		3346	Due to the many, low, and arbitrary limits on the win32 platform and
		3347	the abysmal performance of winsockets, using a large number of sockets
		3348	is not recommended (and not reasonable). If your program needs to use
		3349	more than a hundred or so sockets, then likely it needs to use a totally
		3350	different implementation for windows, as libev offers the POSIX readiness
		3351	notification model, which cannot be implemented efficiently on windows
		3352	(Microsoft monopoly games).
		3353
		3354	A typical way to use libev under windows is to embed it (see the embedding
		3355	section for details) and use the following F<evwrap.h> header file instead
		3356	of F<ev.h>:
		3357
		3358	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3359	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3360
		3361	#include "ev.h"
		3362
		3363	And compile the following F<evwrap.c> file into your project (make sure
		3364	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3365
		3366	#include "evwrap.h"
		3367	#include "ev.c"
		3368
		3369	=over 4
		3370
		3371	=item The winsocket select function
		3372
		3373	The winsocket C<select> function doesn't follow POSIX in that it
		3374	requires socket I<handles> and not socket I<file descriptors> (it is
		3375	also extremely buggy). This makes select very inefficient, and also
		3376	requires a mapping from file descriptors to socket handles (the Microsoft
		3377	C runtime provides the function C<_open_osfhandle> for this). See the
		3378	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3379	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3380
		3381	The configuration for a "naked" win32 using the Microsoft runtime
		3382	libraries and raw winsocket select is:
		3383
		3384	#define EV_USE_SELECT 1
		3385	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3386
		3387	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3388	complexity in the O(n²) range when using win32.
		3389
		3390	=item Limited number of file descriptors
		3391
		3392	Windows has numerous arbitrary (and low) limits on things.
		3393
		3394	Early versions of winsocket's select only supported waiting for a maximum
		3395	of C<64> handles (probably owning to the fact that all windows kernels
		3396	can only wait for C<64> things at the same time internally; Microsoft
		3397	recommends spawning a chain of threads and wait for 63 handles and the
		3398	previous thread in each. Great).
		3399
		3400	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3401	to some high number (e.g. C<2048>) before compiling the winsocket select
		3402	call (which might be in libev or elsewhere, for example, perl does its own
		3403	select emulation on windows).
		3404
		3405	Another limit is the number of file descriptors in the Microsoft runtime
		3406	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3407	or something like this inside Microsoft). You can increase this by calling
		3408	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3409	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3410	libraries.
		3411
		3412	This might get you to about C<512> or C<2048> sockets (depending on
		3413	windows version and/or the phase of the moon). To get more, you need to
		3414	wrap all I/O functions and provide your own fd management, but the cost of
		3415	calling select (O(n²)) will likely make this unworkable.
		3416
		3417	=back
		3418
		3419
		3420	=head1 PORTABILITY REQUIREMENTS
		3421
		3422	In addition to a working ISO-C implementation, libev relies on a few
		3423	additional extensions:
		3424
		3425	=over 4
		3426
		3427	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3428	calling conventions regardless of C<ev_watcher_type *>.
		3429
		3430	Libev assumes not only that all watcher pointers have the same internal
		3431	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3432	assumes that the same (machine) code can be used to call any watcher
		3433	callback: The watcher callbacks have different type signatures, but libev
		3434	calls them using an C<ev_watcher *> internally.
		3435
		3436	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3437
		3438	The type C<sig_atomic_t volatile> (or whatever is defined as
		3439	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3440	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3441	believed to be sufficiently portable.
		3442
		3443	=item C<sigprocmask> must work in a threaded environment
		3444
		3445	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3446	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3447	pthread implementations will either allow C<sigprocmask> in the "main
		3448	thread" or will block signals process-wide, both behaviours would
		3449	be compatible with libev. Interaction between C<sigprocmask> and
		3450	C<pthread_sigmask> could complicate things, however.
		3451
		3452	The most portable way to handle signals is to block signals in all threads
		3453	except the initial one, and run the default loop in the initial thread as
		3454	well.
		3455
		3456	=item C<long> must be large enough for common memory allocation sizes
		3457
		3458	To improve portability and simplify using libev, libev uses C<long>
		3459	internally instead of C<size_t> when allocating its data structures. On
		3460	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3461	is still at least 31 bits everywhere, which is enough for hundreds of
		3462	millions of watchers.
		3463
		3464	=item C<double> must hold a time value in seconds with enough accuracy
		3465
		3466	The type C<double> is used to represent timestamps. It is required to
		3467	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3468	enough for at least into the year 4000. This requirement is fulfilled by
		3469	implementations implementing IEEE 754 (basically all existing ones).
		3470
		3471	=back
		3472
		3473	If you know of other additional requirements drop me a note.
		3474
		3475
		3476	=head1 COMPILER WARNINGS
		3477
		3478	Depending on your compiler and compiler settings, you might get no or a
		3479	lot of warnings when compiling libev code. Some people are apparently
		3480	scared by this.
		3481
		3482	However, these are unavoidable for many reasons. For one, each compiler
		3483	has different warnings, and each user has different tastes regarding
		3484	warning options. "Warn-free" code therefore cannot be a goal except when
		3485	targeting a specific compiler and compiler-version.
		3486
		3487	Another reason is that some compiler warnings require elaborate
		3488	workarounds, or other changes to the code that make it less clear and less
		3489	maintainable.
		3490
		3491	And of course, some compiler warnings are just plain stupid, or simply
		3492	wrong (because they don't actually warn about the condition their message
		3493	seems to warn about).
		3494
		3495	While libev is written to generate as few warnings as possible,
		3496	"warn-free" code is not a goal, and it is recommended not to build libev
		3497	with any compiler warnings enabled unless you are prepared to cope with
		3498	them (e.g. by ignoring them). Remember that warnings are just that:
		3499	warnings, not errors, or proof of bugs.
		3500
		3501
		3502	=head1 VALGRIND
		3503
		3504	Valgrind has a special section here because it is a popular tool that is
		3505	highly useful, but valgrind reports are very hard to interpret.
		3506
		3507	If you think you found a bug (memory leak, uninitialised data access etc.)
		3508	in libev, then check twice: If valgrind reports something like:
		3509
		3510	==2274== definitely lost: 0 bytes in 0 blocks.
		3511	==2274== possibly lost: 0 bytes in 0 blocks.
		3512	==2274== still reachable: 256 bytes in 1 blocks.
		3513
		3514	Then there is no memory leak. Similarly, under some circumstances,
		3515	valgrind might report kernel bugs as if it were a bug in libev, or it
		3516	might be confused (it is a very good tool, but only a tool).
		3517
		3518	If you are unsure about something, feel free to contact the mailing list
		3519	with the full valgrind report and an explanation on why you think this is
		3520	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3521	no bug" answer and take the chance of learning how to interpret valgrind
		3522	properly.
		3523
		3524	If you need, for some reason, empty reports from valgrind for your project
		3525	I suggest using suppression lists.
		3526
		3527
2604	=head1 AUTHOR	3528	=head1 AUTHOR
2605		3529
2606	Marc Lehmann <libev@schmorp.de>.	3530	Marc Lehmann <libev@schmorp.de>.
2607		3531

Diff Legend

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