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Revision 1.163 by root, Sat May 31 23:19:23 2008 UTC

…		…
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
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
117		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
122	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	170	version of the library your program was compiled against.
127		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
128	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	178	not a problem.
132		179
133	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	181	version.
…		…
153	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
154		201
155	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
156	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
157	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
158	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
159	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
160	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
161		208
162	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
163		210
…		…
170	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
171		218
172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
173		220
174	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
175	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
176	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
177	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
178	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
179	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
180		230
181	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
182	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
183	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
184		234
185	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
186	retries).	236	retries (example requires a standards-compliant C<realloc>).
187		237
188	static void *	238	static void *
189	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
190	{	240	{
191	for (;;)	241	for (;;)
…		…
202	...	252	...
203	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
204		254
205	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
206		256
207	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
208	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
209	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
210	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
211	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
212	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
213	(such as abort).	263	(such as abort).
214		264
215	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
230		280
231	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
232	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
233	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
234		284
235	If you use threads, a common model is to run the default event loop
236	in your main thread (or in a separate thread) and for each thread you
237	create, you also create another event loop. Libev itself does no locking
238	whatsoever, so if you mix calls to the same event loop in different
239	threads, make sure you lock (this is usually a bad idea, though, even if
240	done correctly, because it's hideous and inefficient).
241
242	=over 4	285	=over 4
243		286
244	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
245		288
246	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		293
251	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
252	function.	295	function.
253		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
254	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		310
257	The following flags are supported:	311	The following flags are supported:
258		312
…		…
263	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
264	thing, believe me).	318	thing, believe me).
265		319
266	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
267		321
268	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
269	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
271	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
272	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
273	around bugs.	327	around bugs.
…		…
279	enabling this flag.	333	enabling this flag.
280		334
281	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
287		341
288	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
290	flag.	344	flag.
291		345
292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
293	environment variable.	347	environment variable.
294		348
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		350
297	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
302		363
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		365
305	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
309		372
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		374
312	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	377	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
316		382
317	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
319	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	387	very well if you register events for both fds.
322		388
323	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	390	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	391	(or space) is available.
326		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		401
329	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
335		413
336	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
341		429
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		431
344	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
345		436
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		438
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
350		441
351	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
354		454
355	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
356		456
357	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		460
		461	It is definitely not recommended to use this flag.
		462
361	=back	463	=back
362		464
363	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		468
368	The most typical usage is like this:	469	The most typical usage is like this:
369		470
370	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
387	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
388	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
389	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
390		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
391	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
392		497
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	499	if (!epoller)
395	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
…		…
397	=item ev_default_destroy ()	502	=item ev_default_destroy ()
398		503
399	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
403	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
406		520
407	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
408		522
409	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
411		525
412	=item ev_default_fork ()	526	=item ev_default_fork ()
413		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
417	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
418		534
419	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
422		538
423	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
426		542
427	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
428		544
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
434		546
435	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
438		554
439	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
440		556
441	Returns the count of loop iterations for the loop, which is identical to	557	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		571
456	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
461		577
462	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
463		579
464	Finally, this is it, the event handler. This function usually is called	580	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	581	after you initialised all your watchers and you want to start handling
…		…
477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
478	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
479	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
480		596
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
482	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
483	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
484	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
485	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
488		604
489	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
490		606
491	* If there are no active watchers (reference count is zero), return.	607	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
		609	- If a fork was detected, queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	611	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	612	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	613	- Update the "event loop time".
496	- Calculate for how long to block.	614	- Calculate for how long to sleep or block, if at all
		615	(active idle watchers, EVLOOP_NONBLOCK or not having
		616	any active watchers at all will result in not sleeping).
		617	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	618	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	619	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	620	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	621	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	622	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	623	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	624	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	625	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	626	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	627	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	629	were used, or there are no active watchers, return, otherwise
		630	continue with step *.
509		631
510	Example: Queue some jobs and then loop until no events are outsanding	632	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	633	anymore.
512		634
513	... queue jobs here, make sure they register event watchers as long	635	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	636	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	637	ev_loop (my_loop, 0);
…		…
519		641
520	Can be used to make a call to C<ev_loop> return early (but only after it	642	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	643	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		646
		647	This "unloop state" will be cleared when entering C<ev_loop> again.
524		648
525	=item ev_ref (loop)	649	=item ev_ref (loop)
526		650
527	=item ev_unref (loop)	651	=item ev_unref (loop)
528		652
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	657	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	658	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	659	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	660	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	661	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	662	libraries. Just remember to I<unref after start> and I<ref before stop>
		663	(but only if the watcher wasn't active before, or was active before,
		664	respectively).
539		665
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	667	running when nothing else is active.
542		668
543	struct ev_signal exitsig;	669	struct ev_signal exitsig;
…		…
547		673
548	Example: For some weird reason, unregister the above signal handler again.	674	Example: For some weird reason, unregister the above signal handler again.
549		675
550	ev_ref (loop);	676	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	677	ev_signal_stop (loop, &exitsig);
		678
		679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		680
		681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		682
		683	These advanced functions influence the time that libev will spend waiting
		684	for events. Both are by default C<0>, meaning that libev will try to
		685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		686
		687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		688	allows libev to delay invocation of I/O and timer/periodic callbacks to
		689	increase efficiency of loop iterations.
		690
		691	The background is that sometimes your program runs just fast enough to
		692	handle one (or very few) event(s) per loop iteration. While this makes
		693	the program responsive, it also wastes a lot of CPU time to poll for new
		694	events, especially with backends like C<select ()> which have a high
		695	overhead for the actual polling but can deliver many events at once.
		696
		697	By setting a higher I<io collect interval> you allow libev to spend more
		698	time collecting I/O events, so you can handle more events per iteration,
		699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		700	C<ev_timer>) will be not affected. Setting this to a non-null value will
		701	introduce an additional C<ev_sleep ()> call into most loop iterations.
		702
		703	Likewise, by setting a higher I<timeout collect interval> you allow libev
		704	to spend more time collecting timeouts, at the expense of increased
		705	latency (the watcher callback will be called later). C<ev_io> watchers
		706	will not be affected. Setting this to a non-null value will not introduce
		707	any overhead in libev.
		708
		709	Many (busy) programs can usually benefit by setting the I/O collect
		710	interval to a value near C<0.1> or so, which is often enough for
		711	interactive servers (of course not for games), likewise for timeouts. It
		712	usually doesn't make much sense to set it to a lower value than C<0.01>,
		713	as this approaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
552		725
553	=back	726	=back
554		727
555		728
556	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
…		…
576	watcher structures (and it is usually a bad idea to do this on the stack,	749	watcher structures (and it is usually a bad idea to do this on the stack,
577	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
578		751
579	Each watcher structure must be initialised by a call to C<ev_init	752	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
581	callback gets invoked each time the event occurs (or, in the case of io	754	callback gets invoked each time the event occurs (or, in the case of I/O
582	watchers, each time the event loop detects that the file descriptor given	755	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	756	is readable and/or writable).
584		757
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
586	with arguments specific to this watcher type. There is also a macro	759	with arguments specific to this watcher type. There is also a macro
…		…
656	=item C<EV_FORK>	829	=item C<EV_FORK>
657		830
658	The event loop has been resumed in the child process after fork (see	831	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	832	C<ev_fork>).
660		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
		837
661	=item C<EV_ERROR>	838	=item C<EV_ERROR>
662		839
663	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
665	ran out of memory, a file descriptor was found to be closed or any other	842	ran out of memory, a file descriptor was found to be closed or any other
666	problem. You best act on it by reporting the problem and somehow coping	843	problem. You best act on it by reporting the problem and somehow coping
667	with the watcher being stopped.	844	with the watcher being stopped.
668		845
669	Libev will usually signal a few "dummy" events together with an error,	846	Libev will usually signal a few "dummy" events together with an error,
670	for example it might indicate that a fd is readable or writable, and if	847	for example it might indicate that a fd is readable or writable, and if
671	your callbacks is well-written it can just attempt the operation and cope	848	your callbacks is well-written it can just attempt the operation and cope
672	with the error from read() or write(). This will not work in multithreaded	849	with the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	850	programs, though, so beware.
674		851
675	=back	852	=back
676		853
677	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
707	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
708	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		886
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		888
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
713	calls into a single call. This is the most convinient method to initialise	890	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
715		892
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		894
718	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
882	In general you can register as many read and/or write event watchers per	1059	In general you can register as many read and/or write event watchers per
883	fd as you want (as long as you don't confuse yourself). Setting all file	1060	fd as you want (as long as you don't confuse yourself). Setting all file
884	descriptors to non-blocking mode is also usually a good idea (but not	1061	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	1062	required if you know what you are doing).
886		1063
887	You have to be careful with dup'ed file descriptors, though. Some backends
888	(the linux epoll backend is a notable example) cannot handle dup'ed file
889	descriptors correctly if you register interest in two or more fds pointing
890	to the same underlying file/socket/etc. description (that is, they share
891	the same underlying "file open").
892
893	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
896		1067
897	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
898	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
899	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
900	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
901	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example Solaris ports), it is very easy to get into
902	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
903	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
904	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.
905		1076
906	If you cannot run the fd in non-blocking mode (for example you should not	1077	If you cannot run the fd in non-blocking mode (for example you should not
907	play around with an Xlib connection), then you have to seperately re-test	1078	play around with an Xlib connection), then you have to separately re-test
908	whether a file descriptor is really ready with a known-to-be good interface	1079	whether a file descriptor is really ready with a known-to-be good interface
909	such as poll (fortunately in our Xlib example, Xlib already does this on	1080	such as poll (fortunately in our Xlib example, Xlib already does this on
910	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
911		1082
		1083	=head3 The special problem of disappearing file descriptors
		1084
		1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1086	descriptor (either by calling C<close> explicitly or by any other means,
		1087	such as C<dup>). The reason is that you register interest in some file
		1088	descriptor, but when it goes away, the operating system will silently drop
		1089	this interest. If another file descriptor with the same number then is
		1090	registered with libev, there is no efficient way to see that this is, in
		1091	fact, a different file descriptor.
		1092
		1093	To avoid having to explicitly tell libev about such cases, libev follows
		1094	the following policy: Each time C<ev_io_set> is being called, libev
		1095	will assume that this is potentially a new file descriptor, otherwise
		1096	it is assumed that the file descriptor stays the same. That means that
		1097	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1098	descriptor even if the file descriptor number itself did not change.
		1099
		1100	This is how one would do it normally anyway, the important point is that
		1101	the libev application should not optimise around libev but should leave
		1102	optimisations to libev.
		1103
		1104	=head3 The special problem of dup'ed file descriptors
		1105
		1106	Some backends (e.g. epoll), cannot register events for file descriptors,
		1107	but only events for the underlying file descriptions. That means when you
		1108	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1109	events for them, only one file descriptor might actually receive events.
		1110
		1111	There is no workaround possible except not registering events
		1112	for potentially C<dup ()>'ed file descriptors, or to resort to
		1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1114
		1115	=head3 The special problem of fork
		1116
		1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1118	useless behaviour. Libev fully supports fork, but needs to be told about
		1119	it in the child.
		1120
		1121	To support fork in your programs, you either have to call
		1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1124	C<EVBACKEND_POLL>.
		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
		1138
		1139	=head3 Watcher-Specific Functions
		1140
912	=over 4	1141	=over 4
913		1142
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1144
916	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
917		1146
918	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
919	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
920	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
921		1150
922	=item int fd [read-only]	1151	=item int fd [read-only]
923		1152
924	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
926	=item int events [read-only]	1155	=item int events [read-only]
927		1156
928	The events being watched.	1157	The events being watched.
929		1158
930	=back	1159	=back
		1160
		1161	=head3 Examples
931		1162
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
933	readable, but only once. Since it is likely line-buffered, you could	1164	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1165	attempt to read a whole line in the callback.
935		1166
…		…
952		1183
953	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
954	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
955		1186
956	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
957	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to January last
958	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
959	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
960	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
961		1192
962	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
963	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
965	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
966	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
967		1198
968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
969		1200
970	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guaranteed to be invoked only after its timeout has passed,
971	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
972	order of execution is undefined.	1203	order of execution is undefined.
973		1204
		1205	=head3 Watcher-Specific Functions and Data Members
		1206
974	=over 4	1207	=over 4
975		1208
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1210
978	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
979		1212
980	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
981	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
982	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
983	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
984		1218
985	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
986	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
987	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
988	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
989	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
990		1224
991	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
992		1226
993	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
994	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
995		1229
996	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
997		1231
998	If the timer is started but nonrepeating, stop it (as if it timed out).	1232	If the timer is started but non-repeating, stop it (as if it timed out).
999		1233
1000	If the timer is repeating, either start it if necessary (with the	1234	If the timer is repeating, either start it if necessary (with the
1001	C<repeat> value), or reset the running timer to the C<repeat> value.	1235	C<repeat> value), or reset the running timer to the C<repeat> value.
1002		1236
1003	This sounds a bit complicated, but here is a useful and typical	1237	This sounds a bit complicated, but here is a useful and typical
1004	example: Imagine you have a tcp connection and you want a so-called idle	1238	example: Imagine you have a TCP connection and you want a so-called idle
1005	timeout, that is, you want to be called when there have been, say, 60	1239	timeout, that is, you want to be called when there have been, say, 60
1006	seconds of inactivity on the socket. The easiest way to do this is to	1240	seconds of inactivity on the socket. The easiest way to do this is to
1007	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1008	C<ev_timer_again> each time you successfully read or write some data. If	1242	C<ev_timer_again> each time you successfully read or write some data. If
1009	you go into an idle state where you do not expect data to travel on the	1243	you go into an idle state where you do not expect data to travel on the
…		…
1031	or C<ev_timer_again> is called and determines the next timeout (if any),	1265	or C<ev_timer_again> is called and determines the next timeout (if any),
1032	which is also when any modifications are taken into account.	1266	which is also when any modifications are taken into account.
1033		1267
1034	=back	1268	=back
1035		1269
		1270	=head3 Examples
		1271
1036	Example: Create a timer that fires after 60 seconds.	1272	Example: Create a timer that fires after 60 seconds.
1037		1273
1038	static void	1274	static void
1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1040	{	1276	{
…		…
1068		1304
1069	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1070	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1071		1307
1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1073	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wall clock time (absolute time). You can tell a periodic watcher
1074	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1076	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to January of the previous year, then it will take more than year
1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1078	roughly 10 seconds later and of course not if you reset your system time	1315	roughly 10 seconds later as it uses a relative timeout).
1079	again).
1080		1316
1081	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on eahc midnight, local time.	1318	such as triggering an event on each "midnight, local time", or other
		1319	complicated, rules.
1083		1320
1084	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guaranteed to be invoked only when the
1085	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
		1324
		1325	=head3 Watcher-Specific Functions and Data Members
1087		1326
1088	=over 4	1327	=over 4
1089		1328
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1330
…		…
1094	Lots of arguments, lets sort it out... There are basically three modes of	1333	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1334	operation, and we will explain them from simplest to complex:
1096		1335
1097	=over 4	1336	=over 4
1098		1337
1099	=item * absolute timer (interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1339
1101	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wall clock
1102	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1103	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1104	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1105		1344
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1346
1108	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1109	C<at + N * interval> time (for some integer N) and then repeat, regardless	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1349	and then repeat, regardless of any time jumps.
1111		1350
1112	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1113	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1114		1354
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1116		1356
1117	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1118	but only that the the callback will be called when the system time shows a	1358	but only that the callback will be called when the system time shows a
1119	full hour (UTC), or more correctly, when the system time is evenly divisible	1359	full hour (UTC), or more correctly, when the system time is evenly divisible
1120	by 3600.	1360	by 3600.
1121		1361
1122	Another way to think about it (for the mathematically inclined) is that	1362	Another way to think about it (for the mathematically inclined) is that
1123	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1124	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1365
		1366	For numerical stability it is preferable that the C<at> value is near
		1367	C<ev_now ()> (the current time), but there is no range requirement for
		1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (CPU
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course deteriorate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
		1374
1126	=item * manual reschedule mode (reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1376
1128	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1129	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1380	current time as second argument.
1132		1381
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1134	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1135	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1136	starting a prepare watcher).
1137		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1138	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1139	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1140		1391
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1142	{	1393	{
1143	return now + 60.;	1394	return now + 60.;
1144	}	1395	}
…		…
1146	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1147	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1148	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1149	might be called at other times, too.	1400	might be called at other times, too.
1150		1401
1151	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1152	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1153		1404
1154	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1155	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1156	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1157	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1158	reason I omitted it as an example).	1409	reason I omitted it as an example).
1159		1410
1160	=back	1411	=back
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1166	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1418	program when the crontabs have changed).
1168		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
		1425	=item ev_tstamp offset [read-write]
		1426
		1427	When repeating, this contains the offset value, otherwise this is the
		1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1429
		1430	Can be modified any time, but changes only take effect when the periodic
		1431	timer fires or C<ev_periodic_again> is being called.
		1432
1169	=item ev_tstamp interval [read-write]	1433	=item ev_tstamp interval [read-write]
1170		1434
1171	The current interval value. Can be modified any time, but changes only	1435	The current interval value. Can be modified any time, but changes only
1172	take effect when the periodic timer fires or C<ev_periodic_again> is being	1436	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1437	called.
…		…
1178	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1179	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1444
1181	=back	1445	=back
1182		1446
		1447	=head3 Examples
		1448
1183	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1186		1452
1187	static void	1453	static void
1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1189	{	1455	{
1190	... its now a full hour (UTC, or TAI or whatever your clock follows)	1456	... its now a full hour (UTC, or TAI or whatever your clock follows)
…		…
1226	with the kernel (thus it coexists with your own signal handlers as long	1492	with the kernel (thus it coexists with your own signal handlers as long
1227	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1228	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1229	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1230		1496
		1497	If possible and supported, libev will install its handlers with
		1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1499	interrupted. If you have a problem with system calls getting interrupted by
		1500	signals you can block all signals in an C<ev_check> watcher and unblock
		1501	them in an C<ev_prepare> watcher.
		1502
		1503	=head3 Watcher-Specific Functions and Data Members
		1504
1231	=over 4	1505	=over 4
1232		1506
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1508
1235	=item ev_signal_set (ev_signal *, int signum)	1509	=item ev_signal_set (ev_signal *, int signum)
…		…
1241		1515
1242	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1243		1517
1244	=back	1518	=back
1245		1519
		1520	=head3 Examples
		1521
		1522	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1523
		1524	static void
		1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1526	{
		1527	ev_unloop (loop, EVUNLOOP_ALL);
		1528	}
		1529
		1530	struct ev_signal signal_watcher;
		1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1532	ev_signal_start (loop, &sigint_cb);
		1533
1246		1534
1247	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1248		1536
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1537	Child watchers trigger when your process receives a SIGCHLD in response to
1250	some child status changes (most typically when a child of yours dies).	1538	some child status changes (most typically when a child of yours dies). It
		1539	is permissible to install a child watcher I<after> the child has been
		1540	forked (which implies it might have already exited), as long as the event
		1541	loop isn't entered (or is continued from a watcher).
		1542
		1543	Only the default event loop is capable of handling signals, and therefore
		1544	you can only register child watchers in the default event loop.
		1545
		1546	=head3 Process Interaction
		1547
		1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1549	initialised. This is necessary to guarantee proper behaviour even if
		1550	the first child watcher is started after the child exits. The occurrence
		1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1552	synchronously as part of the event loop processing. Libev always reaps all
		1553	children, even ones not watched.
		1554
		1555	=head3 Overriding the Built-In Processing
		1556
		1557	Libev offers no special support for overriding the built-in child
		1558	processing, but if your application collides with libev's default child
		1559	handler, you can override it easily by installing your own handler for
		1560	C<SIGCHLD> after initialising the default loop, and making sure the
		1561	default loop never gets destroyed. You are encouraged, however, to use an
		1562	event-based approach to child reaping and thus use libev's support for
		1563	that, so other libev users can use C<ev_child> watchers freely.
		1564
		1565	=head3 Watcher-Specific Functions and Data Members
1251		1566
1252	=over 4	1567	=over 4
1253		1568
1254	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1255		1570
1256	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1257		1572
1258	Configures the watcher to wait for status changes of process C<pid> (or	1573	Configures the watcher to wait for status changes of process C<pid> (or
1259	I<any> process if C<pid> is specified as C<0>). The callback can look	1574	I<any> process if C<pid> is specified as C<0>). The callback can look
1260	at the C<rstatus> member of the C<ev_child> watcher structure to see	1575	at the C<rstatus> member of the C<ev_child> watcher structure to see
1261	the status word (use the macros from C<sys/wait.h> and see your systems	1576	the status word (use the macros from C<sys/wait.h> and see your systems
1262	C<waitpid> documentation). The C<rpid> member contains the pid of the	1577	C<waitpid> documentation). The C<rpid> member contains the pid of the
1263	process causing the status change.	1578	process causing the status change. C<trace> must be either C<0> (only
		1579	activate the watcher when the process terminates) or C<1> (additionally
		1580	activate the watcher when the process is stopped or continued).
1264		1581
1265	=item int pid [read-only]	1582	=item int pid [read-only]
1266		1583
1267	The process id this watcher watches out for, or C<0>, meaning any process id.	1584	The process id this watcher watches out for, or C<0>, meaning any process id.
1268		1585
…		…
1275	The process exit/trace status caused by C<rpid> (see your systems	1592	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1593	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1594
1278	=back	1595	=back
1279		1596
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1597	=head3 Examples
		1598
		1599	Example: C<fork()> a new process and install a child handler to wait for
		1600	its completion.
		1601
		1602	ev_child cw;
1281		1603
1282	static void	1604	static void
1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1284	{	1606	{
1285	ev_unloop (loop, EVUNLOOP_ALL);	1607	ev_child_stop (EV_A_ w);
		1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1286	}	1609	}
1287		1610
1288	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1290	ev_signal_start (loop, &sigint_cb);	1613	if (pid < 0)
		1614	// error
		1615	else if (pid == 0)
		1616	{
		1617	// the forked child executes here
		1618	exit (1);
		1619	}
		1620	else
		1621	{
		1622	ev_child_init (&cw, child_cb, pid, 0);
		1623	ev_child_start (EV_DEFAULT_ &cw);
		1624	}
1291		1625
1292		1626
1293	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1294		1628
1295	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a file system path for attribute changes. That is, it calls
1296	C<stat> regularly (or when the OS says it changed) and sees if it changed	1630	C<stat> regularly (or when the OS says it changed) and sees if it changed
1297	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1298		1632
1299	The path does not need to exist: changing from "path exists" to "path does	1633	The path does not need to exist: changing from "path exists" to "path does
1300	not exist" is a status change like any other. The condition "path does	1634	not exist" is a status change like any other. The condition "path does
…		…
1318	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1319	resource-intensive.	1653	resource-intensive.
1320		1654
1321	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1322	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1323	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1325	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1326	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1327	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with optionally
		1668	disabled large file support, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticeably with ev_stat and large file support.
		1674
		1675	=head3 Inotify
		1676
		1677	When C<inotify (7)> support has been compiled into libev (generally only
		1678	available on Linux) and present at runtime, it will be used to speed up
		1679	change detection where possible. The inotify descriptor will be created lazily
		1680	when the first C<ev_stat> watcher is being started.
		1681
		1682	Inotify presence does not change the semantics of C<ev_stat> watchers
		1683	except that changes might be detected earlier, and in some cases, to avoid
		1684	making regular C<stat> calls. Even in the presence of inotify support
		1685	there are many cases where libev has to resort to regular C<stat> polling.
		1686
		1687	(There is no support for kqueue, as apparently it cannot be used to
		1688	implement this functionality, due to the requirement of having a file
		1689	descriptor open on the object at all times).
		1690
		1691	=head3 The special problem of stat time resolution
		1692
		1693	The C<stat ()> system call only supports full-second resolution portably, and
		1694	even on systems where the resolution is higher, many file systems still
		1695	only support whole seconds.
		1696
		1697	That means that, if the time is the only thing that changes, you can
		1698	easily miss updates: on the first update, C<ev_stat> detects a change and
		1699	calls your callback, which does something. When there is another update
		1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
		1702
		1703	The solution to this is to delay acting on a change for slightly more
		1704	than a second (or till slightly after the next full second boundary), using
		1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1706	ev_timer_again (loop, w)>).
		1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
		1716
		1717	=head3 Watcher-Specific Functions and Data Members
1328		1718
1329	=over 4	1719	=over 4
1330		1720
1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1721	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1332		1722
…		…
1336	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1337	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1338	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1339	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1340		1730
1341	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1342	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1343	last change was detected).	1733	was detected).
1344		1734
1345	=item ev_stat_stat (ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1346		1736
1347	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1348	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1349	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1350	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1351		1742
1352	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1353		1744
1354	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1355	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1356	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1357	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1358		1750
1359	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1360		1752
1361	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1362	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1363		1757
1364	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1365		1759
1366	The specified interval.	1760	The specified interval.
1367		1761
1368	=item const char *path [read-only]	1762	=item const char *path [read-only]
1369		1763
1370	The filesystem path that is being watched.	1764	The file system path that is being watched.
1371		1765
1372	=back	1766	=back
		1767
		1768	=head3 Examples
1373		1769
1374	Example: Watch C</etc/passwd> for attribute changes.	1770	Example: Watch C</etc/passwd> for attribute changes.
1375		1771
1376	static void	1772	static void
1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1390	}	1786	}
1391		1787
1392	...	1788	...
1393	ev_stat passwd;	1789	ev_stat passwd;
1394		1790
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	1792	ev_stat_start (loop, &passwd);
		1793
		1794	Example: Like above, but additionally use a one-second delay so we do not
		1795	miss updates (however, frequent updates will delay processing, too, so
		1796	one might do the work both on C<ev_stat> callback invocation I<and> on
		1797	C<ev_timer> callback invocation).
		1798
		1799	static ev_stat passwd;
		1800	static ev_timer timer;
		1801
		1802	static void
		1803	timer_cb (EV_P_ ev_timer *w, int revents)
		1804	{
		1805	ev_timer_stop (EV_A_ w);
		1806
		1807	/* now it's one second after the most recent passwd change */
		1808	}
		1809
		1810	static void
		1811	stat_cb (EV_P_ ev_stat *w, int revents)
		1812	{
		1813	/* reset the one-second timer */
		1814	ev_timer_again (EV_A_ &timer);
		1815	}
		1816
		1817	...
		1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1819	ev_stat_start (loop, &passwd);
		1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1397		1821
1398		1822
1399	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1400		1824
1401	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1415	Apart from keeping your process non-blocking (which is a useful	1839	Apart from keeping your process non-blocking (which is a useful
1416	effect on its own sometimes), idle watchers are a good place to do	1840	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	1841	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	1842	event loop has handled all outstanding events.
1419		1843
		1844	=head3 Watcher-Specific Functions and Data Members
		1845
1420	=over 4	1846	=over 4
1421		1847
1422	=item ev_idle_init (ev_signal *, callback)	1848	=item ev_idle_init (ev_signal *, callback)
1423		1849
1424	Initialises and configures the idle watcher - it has no parameters of any	1850	Initialises and configures the idle watcher - it has no parameters of any
1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	1852	believe me.
1427		1853
1428	=back	1854	=back
		1855
		1856	=head3 Examples
1429		1857
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	1859	callback, free it. Also, use no error checking, as usual.
1432		1860
1433	static void	1861	static void
1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1435	{	1863	{
1436	free (w);	1864	free (w);
1437	// now do something you wanted to do when the program has	1865	// now do something you wanted to do when the program has
1438	// no longer asnything immediate to do.	1866	// no longer anything immediate to do.
1439	}	1867	}
1440		1868
1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1442	ev_idle_init (idle_watcher, idle_cb);	1870	ev_idle_init (idle_watcher, idle_cb);
1443	ev_idle_start (loop, idle_cb);	1871	ev_idle_start (loop, idle_cb);
…		…
1467		1895
1468	This is done by examining in each prepare call which file descriptors need	1896	This is done by examining in each prepare call which file descriptors need
1469	to be watched by the other library, registering C<ev_io> watchers for	1897	to be watched by the other library, registering C<ev_io> watchers for
1470	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1471	provide just this functionality). Then, in the check watcher you check for	1899	provide just this functionality). Then, in the check watcher you check for
1472	any events that occured (by checking the pending status of all watchers	1900	any events that occurred (by checking the pending status of all watchers
1473	and stopping them) and call back into the library. The I/O and timer	1901	and stopping them) and call back into the library. The I/O and timer
1474	callbacks will never actually be called (but must be valid nevertheless,	1902	callbacks will never actually be called (but must be valid nevertheless,
1475	because you never know, you know?).	1903	because you never know, you know?).
1476		1904
1477	As another example, the Perl Coro module uses these hooks to integrate	1905	As another example, the Perl Coro module uses these hooks to integrate
…		…
1481	with priority higher than or equal to the event loop and one coroutine	1909	with priority higher than or equal to the event loop and one coroutine
1482	of lower priority, but only once, using idle watchers to keep the event	1910	of lower priority, but only once, using idle watchers to keep the event
1483	loop from blocking if lower-priority coroutines are active, thus mapping	1911	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	1912	low-priority coroutines to idle/background tasks).
1485		1913
		1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1915	priority, to ensure that they are being run before any other watchers
		1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1917	too) should not activate ("feed") events into libev. While libev fully
		1918	supports this, they might get executed before other C<ev_check> watchers
		1919	did their job. As C<ev_check> watchers are often used to embed other
		1920	(non-libev) event loops those other event loops might be in an unusable
		1921	state until their C<ev_check> watcher ran (always remind yourself to
		1922	coexist peacefully with others).
		1923
		1924	=head3 Watcher-Specific Functions and Data Members
		1925
1486	=over 4	1926	=over 4
1487		1927
1488	=item ev_prepare_init (ev_prepare *, callback)	1928	=item ev_prepare_init (ev_prepare *, callback)
1489		1929
1490	=item ev_check_init (ev_check *, callback)	1930	=item ev_check_init (ev_check *, callback)
…		…
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1494	macros, but using them is utterly, utterly and completely pointless.	1934	macros, but using them is utterly, utterly and completely pointless.
1495		1935
1496	=back	1936	=back
1497		1937
1498	Example: To include a library such as adns, you would add IO watchers	1938	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	1939
		1940	There are a number of principal ways to embed other event loops or modules
		1941	into libev. Here are some ideas on how to include libadns into libev
		1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1945	Glib event loop).
		1946
		1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1500	in a check watcher, destroy them and call into libadns. What follows is	1948	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	1949	is pseudo-code only of course. This requires you to either use a low
		1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1951	the callbacks for the IO/timeout watchers might not have been called yet.
1502		1952
1503	static ev_io iow [nfd];	1953	static ev_io iow [nfd];
1504	static ev_timer tw;	1954	static ev_timer tw;
1505		1955
1506	static void	1956	static void
1507	io_cb (ev_loop *loop, ev_io *w, int revents)	1957	io_cb (ev_loop *loop, ev_io *w, int revents)
1508	{	1958	{
1509	// set the relevant poll flags
1510	// could also call adns_processreadable etc. here
1511	struct pollfd *fd = (struct pollfd *)w->data;
1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1514	}	1959	}
1515		1960
1516	// create io watchers for each fd and a timer before blocking	1961	// create io watchers for each fd and a timer before blocking
1517	static void	1962	static void
1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1524		1969
1525	/* the callback is illegal, but won't be called as we stop during check */	1970	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	1971	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	1972	ev_timer_start (loop, &tw);
1528		1973
1529	// create on ev_io per pollfd	1974	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	1975	for (int i = 0; i < nfd; ++i)
1531	{	1976	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	1977	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	1978	((fds [i].events & POLLIN ? EV_READ : 0)
1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		1980
1536	fds [i].revents = 0;	1981	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	1982	ev_io_start (loop, iow + i);
1539	}	1983	}
1540	}	1984	}
1541		1985
1542	// stop all watchers after blocking	1986	// stop all watchers after blocking
…		…
1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1545	{	1989	{
1546	ev_timer_stop (loop, &tw);	1990	ev_timer_stop (loop, &tw);
1547		1991
1548	for (int i = 0; i < nfd; ++i)	1992	for (int i = 0; i < nfd; ++i)
		1993	{
		1994	// set the relevant poll flags
		1995	// could also call adns_processreadable etc. here
		1996	struct pollfd *fd = fds + i;
		1997	int revents = ev_clear_pending (iow + i);
		1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2000
		2001	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	2002	ev_io_stop (loop, iow + i);
		2003	}
1550		2004
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		2006	}
		2007
		2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2009	in the prepare watcher and would dispose of the check watcher.
		2010
		2011	Method 3: If the module to be embedded supports explicit event
		2012	notification (libadns does), you can also make use of the actual watcher
		2013	callbacks, and only destroy/create the watchers in the prepare watcher.
		2014
		2015	static void
		2016	timer_cb (EV_P_ ev_timer *w, int revents)
		2017	{
		2018	adns_state ads = (adns_state)w->data;
		2019	update_now (EV_A);
		2020
		2021	adns_processtimeouts (ads, &tv_now);
		2022	}
		2023
		2024	static void
		2025	io_cb (EV_P_ ev_io *w, int revents)
		2026	{
		2027	adns_state ads = (adns_state)w->data;
		2028	update_now (EV_A);
		2029
		2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2032	}
		2033
		2034	// do not ever call adns_afterpoll
		2035
		2036	Method 4: Do not use a prepare or check watcher because the module you
		2037	want to embed is too inflexible to support it. Instead, you can override
		2038	their poll function. The drawback with this solution is that the main
		2039	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2040	this.
		2041
		2042	static gint
		2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2044	{
		2045	int got_events = 0;
		2046
		2047	for (n = 0; n < nfds; ++n)
		2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2049
		2050	if (timeout >= 0)
		2051	// create/start timer
		2052
		2053	// poll
		2054	ev_loop (EV_A_ 0);
		2055
		2056	// stop timer again
		2057	if (timeout >= 0)
		2058	ev_timer_stop (EV_A_ &to);
		2059
		2060	// stop io watchers again - their callbacks should have set
		2061	for (n = 0; n < nfds; ++n)
		2062	ev_io_stop (EV_A_ iow [n]);
		2063
		2064	return got_events;
1552	}	2065	}
1553		2066
1554		2067
1555	=head2 C<ev_embed> - when one backend isn't enough...	2068	=head2 C<ev_embed> - when one backend isn't enough...
1556		2069
…		…
1599	portable one.	2112	portable one.
1600		2113
1601	So when you want to use this feature you will always have to be prepared	2114	So when you want to use this feature you will always have to be prepared
1602	that you cannot get an embeddable loop. The recommended way to get around	2115	that you cannot get an embeddable loop. The recommended way to get around
1603	this is to have a separate variables for your embeddable loop, try to	2116	this is to have a separate variables for your embeddable loop, try to
1604	create it, and if that fails, use the normal loop for everything:	2117	create it, and if that fails, use the normal loop for everything.
		2118
		2119	=head3 Watcher-Specific Functions and Data Members
		2120
		2121	=over 4
		2122
		2123	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2124
		2125	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2126
		2127	Configures the watcher to embed the given loop, which must be
		2128	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2129	invoked automatically, otherwise it is the responsibility of the callback
		2130	to invoke it (it will continue to be called until the sweep has been done,
		2131	if you do not want that, you need to temporarily stop the embed watcher).
		2132
		2133	=item ev_embed_sweep (loop, ev_embed *)
		2134
		2135	Make a single, non-blocking sweep over the embedded loop. This works
		2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2137	appropriate way for embedded loops.
		2138
		2139	=item struct ev_loop *other [read-only]
		2140
		2141	The embedded event loop.
		2142
		2143	=back
		2144
		2145	=head3 Examples
		2146
		2147	Example: Try to get an embeddable event loop and embed it into the default
		2148	event loop. If that is not possible, use the default loop. The default
		2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2151	used).
1605		2152
1606	struct ev_loop *loop_hi = ev_default_init (0);	2153	struct ev_loop *loop_hi = ev_default_init (0);
1607	struct ev_loop *loop_lo = 0;	2154	struct ev_loop *loop_lo = 0;
1608	struct ev_embed embed;	2155	struct ev_embed embed;
1609		2156
…		…
1620	ev_embed_start (loop_hi, &embed);	2167	ev_embed_start (loop_hi, &embed);
1621	}	2168	}
1622	else	2169	else
1623	loop_lo = loop_hi;	2170	loop_lo = loop_hi;
1624		2171
1625	=over 4	2172	Example: Check if kqueue is available but not recommended and create
		2173	a kqueue backend for use with sockets (which usually work with any
		2174	kqueue implementation). Store the kqueue/socket-only event loop in
		2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1626		2176
1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2177	struct ev_loop *loop = ev_default_init (0);
		2178	struct ev_loop *loop_socket = 0;
		2179	struct ev_embed embed;
		2180
		2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2183	{
		2184	ev_embed_init (&embed, 0, loop_socket);
		2185	ev_embed_start (loop, &embed);
		2186	}
1628		2187
1629	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2188	if (!loop_socket)
		2189	loop_socket = loop;
1630		2190
1631	Configures the watcher to embed the given loop, which must be	2191	// now use loop_socket for all sockets, and loop for everything else
1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1633	invoked automatically, otherwise it is the responsibility of the callback
1634	to invoke it (it will continue to be called until the sweep has been done,
1635	if you do not want thta, you need to temporarily stop the embed watcher).
1636
1637	=item ev_embed_sweep (loop, ev_embed *)
1638
1639	Make a single, non-blocking sweep over the embedded loop. This works
1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.
1642
1643	=item struct ev_loop *loop [read-only]
1644
1645	The embedded event loop.
1646
1647	=back
1648		2192
1649		2193
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2195
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2196	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1655	event loop blocks next and before C<ev_check> watchers are being called,	2199	event loop blocks next and before C<ev_check> watchers are being called,
1656	and only in the child after the fork. If whoever good citizen calling	2200	and only in the child after the fork. If whoever good citizen calling
1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2202	handlers will be invoked, too, of course.
1659		2203
		2204	=head3 Watcher-Specific Functions and Data Members
		2205
1660	=over 4	2206	=over 4
1661		2207
1662	=item ev_fork_init (ev_signal *, callback)	2208	=item ev_fork_init (ev_signal *, callback)
1663		2209
1664	Initialises and configures the fork watcher - it has no parameters of any	2210	Initialises and configures the fork watcher - it has no parameters of any
1665	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2211	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1666	believe me.	2212	believe me.
		2213
		2214	=back
		2215
		2216
		2217	=head2 C<ev_async> - how to wake up another event loop
		2218
		2219	In general, you cannot use an C<ev_loop> from multiple threads or other
		2220	asynchronous sources such as signal handlers (as opposed to multiple event
		2221	loops - those are of course safe to use in different threads).
		2222
		2223	Sometimes, however, you need to wake up another event loop you do not
		2224	control, for example because it belongs to another thread. This is what
		2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2226	can signal it by calling C<ev_async_send>, which is thread- and signal
		2227	safe.
		2228
		2229	This functionality is very similar to C<ev_signal> watchers, as signals,
		2230	too, are asynchronous in nature, and signals, too, will be compressed
		2231	(i.e. the number of callback invocations may be less than the number of
		2232	C<ev_async_sent> calls).
		2233
		2234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2235	just the default loop.
		2236
		2237	=head3 Queueing
		2238
		2239	C<ev_async> does not support queueing of data in any way. The reason
		2240	is that the author does not know of a simple (or any) algorithm for a
		2241	multiple-writer-single-reader queue that works in all cases and doesn't
		2242	need elaborate support such as pthreads.
		2243
		2244	That means that if you want to queue data, you have to provide your own
		2245	queue. But at least I can tell you would implement locking around your
		2246	queue:
		2247
		2248	=over 4
		2249
		2250	=item queueing from a signal handler context
		2251
		2252	To implement race-free queueing, you simply add to the queue in the signal
		2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2254	some fictitious SIGUSR1 handler:
		2255
		2256	static ev_async mysig;
		2257
		2258	static void
		2259	sigusr1_handler (void)
		2260	{
		2261	sometype data;
		2262
		2263	// no locking etc.
		2264	queue_put (data);
		2265	ev_async_send (EV_DEFAULT_ &mysig);
		2266	}
		2267
		2268	static void
		2269	mysig_cb (EV_P_ ev_async *w, int revents)
		2270	{
		2271	sometype data;
		2272	sigset_t block, prev;
		2273
		2274	sigemptyset (&block);
		2275	sigaddset (&block, SIGUSR1);
		2276	sigprocmask (SIG_BLOCK, &block, &prev);
		2277
		2278	while (queue_get (&data))
		2279	process (data);
		2280
		2281	if (sigismember (&prev, SIGUSR1)
		2282	sigprocmask (SIG_UNBLOCK, &block, 0);
		2283	}
		2284
		2285	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2286	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2287	either...).
		2288
		2289	=item queueing from a thread context
		2290
		2291	The strategy for threads is different, as you cannot (easily) block
		2292	threads but you can easily preempt them, so to queue safely you need to
		2293	employ a traditional mutex lock, such as in this pthread example:
		2294
		2295	static ev_async mysig;
		2296	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2297
		2298	static void
		2299	otherthread (void)
		2300	{
		2301	// only need to lock the actual queueing operation
		2302	pthread_mutex_lock (&mymutex);
		2303	queue_put (data);
		2304	pthread_mutex_unlock (&mymutex);
		2305
		2306	ev_async_send (EV_DEFAULT_ &mysig);
		2307	}
		2308
		2309	static void
		2310	mysig_cb (EV_P_ ev_async *w, int revents)
		2311	{
		2312	pthread_mutex_lock (&mymutex);
		2313
		2314	while (queue_get (&data))
		2315	process (data);
		2316
		2317	pthread_mutex_unlock (&mymutex);
		2318	}
		2319
		2320	=back
		2321
		2322
		2323	=head3 Watcher-Specific Functions and Data Members
		2324
		2325	=over 4
		2326
		2327	=item ev_async_init (ev_async *, callback)
		2328
		2329	Initialises and configures the async watcher - it has no parameters of any
		2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2331	believe me.
		2332
		2333	=item ev_async_send (loop, ev_async *)
		2334
		2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2337	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2339	section below on what exactly this means).
		2340
		2341	This call incurs the overhead of a system call only once per loop iteration,
		2342	so while the overhead might be noticeable, it doesn't apply to repeated
		2343	calls to C<ev_async_send>.
		2344
		2345	=item bool = ev_async_pending (ev_async *)
		2346
		2347	Returns a non-zero value when C<ev_async_send> has been called on the
		2348	watcher but the event has not yet been processed (or even noted) by the
		2349	event loop.
		2350
		2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2352	the loop iterates next and checks for the watcher to have become active,
		2353	it will reset the flag again. C<ev_async_pending> can be used to very
		2354	quickly check whether invoking the loop might be a good idea.
		2355
		2356	Not that this does I<not> check whether the watcher itself is pending, only
		2357	whether it has been requested to make this watcher pending.
1667		2358
1668	=back	2359	=back
1669		2360
1670		2361
1671	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
…		…
1682	or timeout without having to allocate/configure/start/stop/free one or	2373	or timeout without having to allocate/configure/start/stop/free one or
1683	more watchers yourself.	2374	more watchers yourself.
1684		2375
1685	If C<fd> is less than 0, then no I/O watcher will be started and events	2376	If C<fd> is less than 0, then no I/O watcher will be started and events
1686	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1687	C<events> set will be craeted and started.	2378	C<events> set will be created and started.
1688		2379
1689	If C<timeout> is less than 0, then no timeout watcher will be	2380	If C<timeout> is less than 0, then no timeout watcher will be
1690	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1691	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1692	dubious value.	2383	dubious value.
…		…
1717	Feed an event on the given fd, as if a file descriptor backend detected	2408	Feed an event on the given fd, as if a file descriptor backend detected
1718	the given events it.	2409	the given events it.
1719		2410
1720	=item ev_feed_signal_event (ev_loop *loop, int signum)	2411	=item ev_feed_signal_event (ev_loop *loop, int signum)
1721		2412
1722	Feed an event as if the given signal occured (C<loop> must be the default	2413	Feed an event as if the given signal occurred (C<loop> must be the default
1723	loop!).	2414	loop!).
1724		2415
1725	=back	2416	=back
1726		2417
1727		2418
…		…
1743		2434
1744	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
1745	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
1746	is an ev_pri field.	2437	is an ev_pri field.
1747		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
1748	=item * Other members are not supported.	2442	=item * Other members are not supported.
1749		2443
1750	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1751	to use the libev header file and library.	2445	to use the libev header file and library.
1752		2446
1753	=back	2447	=back
1754		2448
1755	=head1 C++ SUPPORT	2449	=head1 C++ SUPPORT
1756		2450
1757	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2451	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1758	you to use some convinience methods to start/stop watchers and also change	2452	you to use some convenience methods to start/stop watchers and also change
1759	the callback model to a model using method callbacks on objects.	2453	the callback model to a model using method callbacks on objects.
1760		2454
1761	To use it,	2455	To use it,
1762		2456
1763	#include <ev++.h>	2457	#include <ev++.h>
…		…
1844		2538
1845	myclass obj;	2539	myclass obj;
1846	ev::io iow;	2540	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2541	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2542
1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2543	=item w->set<function> (void *data = 0)
1850		2544
1851	Also sets a callback, but uses a static method or plain function as	2545	Also sets a callback, but uses a static method or plain function as
1852	callback. The optional C<data> argument will be stored in the watcher's	2546	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2547	C<data> member and is free for you to use.
1854		2548
		2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2550
1855	See the method-C<set> above for more details.	2551	See the method-C<set> above for more details.
		2552
		2553	Example:
		2554
		2555	static void io_cb (ev::io &w, int revents) { }
		2556	iow.set <io_cb> ();
1856		2557
1857	=item w->set (struct ev_loop *)	2558	=item w->set (struct ev_loop *)
1858		2559
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2560	Associates a different C<struct ev_loop> with this watcher. You can only
1860	do this when the watcher is inactive (and not pending either).	2561	do this when the watcher is inactive (and not pending either).
1861		2562
1862	=item w->set ([args])	2563	=item w->set ([arguments])
1863		2564
1864	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1865	called at least once. Unlike the C counterpart, an active watcher gets	2566	called at least once. Unlike the C counterpart, an active watcher gets
1866	automatically stopped and restarted when reconfiguring it with this	2567	automatically stopped and restarted when reconfiguring it with this
1867	method.	2568	method.
1868		2569
1869	=item w->start ()	2570	=item w->start ()
…		…
1873		2574
1874	=item w->stop ()	2575	=item w->stop ()
1875		2576
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2577	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2578
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2579	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2580
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2581	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2582	C<ev_TYPE_again> function.
1882		2583
1883	=item w->sweep () C<ev::embed> only	2584	=item w->sweep () (C<ev::embed> only)
1884		2585
1885	Invokes C<ev_embed_sweep>.	2586	Invokes C<ev_embed_sweep>.
1886		2587
1887	=item w->update () C<ev::stat> only	2588	=item w->update () (C<ev::stat> only)
1888		2589
1889	Invokes C<ev_stat_stat>.	2590	Invokes C<ev_stat_stat>.
1890		2591
1891	=back	2592	=back
1892		2593
…		…
1895	Example: Define a class with an IO and idle watcher, start one of them in	2596	Example: Define a class with an IO and idle watcher, start one of them in
1896	the constructor.	2597	the constructor.
1897		2598
1898	class myclass	2599	class myclass
1899	{	2600	{
1900	ev_io io; void io_cb (ev::io &w, int revents);	2601	ev::io io; void io_cb (ev::io &w, int revents);
1901	ev_idle idle void idle_cb (ev::idle &w, int revents);	2602	ev:idle idle void idle_cb (ev::idle &w, int revents);
1902		2603
1903	myclass ();	2604	myclass (int fd)
1904	}
1905
1906	myclass::myclass (int fd)
1907	{	2605	{
1908	io .set <myclass, &myclass::io_cb > (this);	2606	io .set <myclass, &myclass::io_cb > (this);
1909	idle.set <myclass, &myclass::idle_cb> (this);	2607	idle.set <myclass, &myclass::idle_cb> (this);
1910		2608
1911	io.start (fd, ev::READ);	2609	io.start (fd, ev::READ);
		2610	}
1912	}	2611	};
		2612
		2613
		2614	=head1 OTHER LANGUAGE BINDINGS
		2615
		2616	Libev does not offer other language bindings itself, but bindings for a
		2617	number of languages exist in the form of third-party packages. If you know
		2618	any interesting language binding in addition to the ones listed here, drop
		2619	me a note.
		2620
		2621	=over 4
		2622
		2623	=item Perl
		2624
		2625	The EV module implements the full libev API and is actually used to test
		2626	libev. EV is developed together with libev. Apart from the EV core module,
		2627	there are additional modules that implement libev-compatible interfaces
		2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2630
		2631	It can be found and installed via CPAN, its homepage is found at
		2632	L<http://software.schmorp.de/pkg/EV>.
		2633
		2634	=item Ruby
		2635
		2636	Tony Arcieri has written a ruby extension that offers access to a subset
		2637	of the libev API and adds file handle abstractions, asynchronous DNS and
		2638	more on top of it. It can be found via gem servers. Its homepage is at
		2639	L<http://rev.rubyforge.org/>.
		2640
		2641	=item D
		2642
		2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2645
		2646	=back
1913		2647
1914		2648
1915	=head1 MACRO MAGIC	2649	=head1 MACRO MAGIC
1916		2650
1917	Libev can be compiled with a variety of options, the most fundemantal is	2651	Libev can be compiled with a variety of options, the most fundamental
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2652	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2653	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2654
1921	To make it easier to write programs that cope with either variant, the	2655	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2656	following macros are defined:
1923		2657
1924	=over 4	2658	=over 4
…		…
1953		2687
1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1955		2689
1956	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
1957	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1958		2702
1959	=back	2703	=back
1960		2704
1961	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
1962	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
…		…
1978	Libev can (and often is) directly embedded into host	2722	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	2723	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2724	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	2725	and rxvt-unicode.
1982		2726
1983	The goal is to enable you to just copy the neecssary files into your	2727	The goal is to enable you to just copy the necessary files into your
1984	source directory without having to change even a single line in them, so	2728	source directory without having to change even a single line in them, so
1985	you can easily upgrade by simply copying (or having a checked-out copy of	2729	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	2730	libev somewhere in your source tree).
1987		2731
1988	=head2 FILESETS	2732	=head2 FILESETS
1989		2733
1990	Depending on what features you need you need to include one or more sets of files	2734	Depending on what features you need you need to include one or more sets of files
1991	in your app.	2735	in your application.
1992		2736
1993	=head3 CORE EVENT LOOP	2737	=head3 CORE EVENT LOOP
1994		2738
1995	To include only the libev core (all the C<ev_*> functions), with manual	2739	To include only the libev core (all the C<ev_*> functions), with manual
1996	configuration (no autoconf):	2740	configuration (no autoconf):
…		…
2047	event.h	2791	event.h
2048	event.c	2792	event.c
2049		2793
2050	=head3 AUTOCONF SUPPORT	2794	=head3 AUTOCONF SUPPORT
2051		2795
2052	Instead of using C<EV_STANDALONE=1> and providing your config in	2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2053	whatever way you want, you can also C<m4_include([libev.m4])> in your	2797	whatever way you want, you can also C<m4_include([libev.m4])> in your
2054	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2055	include F<config.h> and configure itself accordingly.	2799	include F<config.h> and configure itself accordingly.
2056		2800
2057	For this of course you need the m4 file:	2801	For this of course you need the m4 file:
2058		2802
2059	libev.m4	2803	libev.m4
2060		2804
2061	=head2 PREPROCESSOR SYMBOLS/MACROS	2805	=head2 PREPROCESSOR SYMBOLS/MACROS
2062		2806
2063	Libev can be configured via a variety of preprocessor symbols you have to define	2807	Libev can be configured via a variety of preprocessor symbols you have to
2064	before including any of its files. The default is not to build for multiplicity	2808	define before including any of its files. The default in the absence of
2065	and only include the select backend.	2809	autoconf is noted for every option.
2066		2810
2067	=over 4	2811	=over 4
2068		2812
2069	=item EV_STANDALONE	2813	=item EV_STANDALONE
2070		2814
…		…
2075	F<event.h> that are not directly supported by the libev core alone.	2819	F<event.h> that are not directly supported by the libev core alone.
2076		2820
2077	=item EV_USE_MONOTONIC	2821	=item EV_USE_MONOTONIC
2078		2822
2079	If defined to be C<1>, libev will try to detect the availability of the	2823	If defined to be C<1>, libev will try to detect the availability of the
2080	monotonic clock option at both compiletime and runtime. Otherwise no use	2824	monotonic clock option at both compile time and runtime. Otherwise no use
2081	of the monotonic clock option will be attempted. If you enable this, you	2825	of the monotonic clock option will be attempted. If you enable this, you
2082	usually have to link against librt or something similar. Enabling it when	2826	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	2827	the functionality isn't available is safe, though, although you have
2084	to make sure you link against any libraries where the C<clock_gettime>	2828	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	2829	function is hiding in (often F<-lrt>).
2086		2830
2087	=item EV_USE_REALTIME	2831	=item EV_USE_REALTIME
2088		2832
2089	If defined to be C<1>, libev will try to detect the availability of the	2833	If defined to be C<1>, libev will try to detect the availability of the
2090	realtime clock option at compiletime (and assume its availability at	2834	real-time clock option at compile time (and assume its availability at
2091	runtime if successful). Otherwise no use of the realtime clock option will	2835	runtime if successful). Otherwise no use of the real-time clock option will
2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2839
		2840	=item EV_USE_NANOSLEEP
		2841
		2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2843	and will use it for delays. Otherwise it will use C<select ()>.
		2844
		2845	=item EV_USE_EVENTFD
		2846
		2847	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2848	available and will probe for kernel support at runtime. This will improve
		2849	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2850	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2851	2.7 or newer, otherwise disabled.
2095		2852
2096	=item EV_USE_SELECT	2853	=item EV_USE_SELECT
2097		2854
2098	If undefined or defined to be C<1>, libev will compile in support for the	2855	If undefined or defined to be C<1>, libev will compile in support for the
2099	C<select>(2) backend. No attempt at autodetection will be done: if no	2856	C<select>(2) backend. No attempt at auto-detection will be done: if no
2100	other method takes over, select will be it. Otherwise the select backend	2857	other method takes over, select will be it. Otherwise the select backend
2101	will not be compiled in.	2858	will not be compiled in.
2102		2859
2103	=item EV_SELECT_USE_FD_SET	2860	=item EV_SELECT_USE_FD_SET
2104		2861
2105	If defined to C<1>, then the select backend will use the system C<fd_set>	2862	If defined to C<1>, then the select backend will use the system C<fd_set>
2106	structure. This is useful if libev doesn't compile due to a missing	2863	structure. This is useful if libev doesn't compile due to a missing
2107	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2108	exotic systems. This usually limits the range of file descriptors to some	2865	exotic systems. This usually limits the range of file descriptors to some
2109	low limit such as 1024 or might have other limitations (winsocket only	2866	low limit such as 1024 or might have other limitations (winsocket only
2110	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2111	influence the size of the C<fd_set> used.	2868	influence the size of the C<fd_set> used.
2112		2869
…		…
2118	be used is the winsock select). This means that it will call	2875	be used is the winsock select). This means that it will call
2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2120	it is assumed that all these functions actually work on fds, even	2877	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	2878	on win32. Should not be defined on non-win32 platforms.
2122		2879
		2880	=item EV_FD_TO_WIN32_HANDLE
		2881
		2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2883	file descriptors to socket handles. When not defining this symbol (the
		2884	default), then libev will call C<_get_osfhandle>, which is usually
		2885	correct. In some cases, programs use their own file descriptor management,
		2886	in which case they can provide this function to map fds to socket handles.
		2887
2123	=item EV_USE_POLL	2888	=item EV_USE_POLL
2124		2889
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2126	backend. Otherwise it will be enabled on non-win32 platforms. It	2891	backend. Otherwise it will be enabled on non-win32 platforms. It
2127	takes precedence over select.	2892	takes precedence over select.
2128		2893
2129	=item EV_USE_EPOLL	2894	=item EV_USE_EPOLL
2130		2895
2131	If defined to be C<1>, libev will compile in support for the Linux	2896	If defined to be C<1>, libev will compile in support for the Linux
2132	C<epoll>(7) backend. Its availability will be detected at runtime,	2897	C<epoll>(7) backend. Its availability will be detected at runtime,
2133	otherwise another method will be used as fallback. This is the	2898	otherwise another method will be used as fallback. This is the preferred
2134	preferred backend for GNU/Linux systems.	2899	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2900	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2135		2901
2136	=item EV_USE_KQUEUE	2902	=item EV_USE_KQUEUE
2137		2903
2138	If defined to be C<1>, libev will compile in support for the BSD style	2904	If defined to be C<1>, libev will compile in support for the BSD style
2139	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2905	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2152	otherwise another method will be used as fallback. This is the preferred	2918	otherwise another method will be used as fallback. This is the preferred
2153	backend for Solaris 10 systems.	2919	backend for Solaris 10 systems.
2154		2920
2155	=item EV_USE_DEVPOLL	2921	=item EV_USE_DEVPOLL
2156		2922
2157	reserved for future expansion, works like the USE symbols above.	2923	Reserved for future expansion, works like the USE symbols above.
2158		2924
2159	=item EV_USE_INOTIFY	2925	=item EV_USE_INOTIFY
2160		2926
2161	If defined to be C<1>, libev will compile in support for the Linux inotify	2927	If defined to be C<1>, libev will compile in support for the Linux inotify
2162	interface to speed up C<ev_stat> watchers. Its actual availability will	2928	interface to speed up C<ev_stat> watchers. Its actual availability will
2163	be detected at runtime.	2929	be detected at runtime. If undefined, it will be enabled if the headers
		2930	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2931
		2932	=item EV_ATOMIC_T
		2933
		2934	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2935	access is atomic with respect to other threads or signal contexts. No such
		2936	type is easily found in the C language, so you can provide your own type
		2937	that you know is safe for your purposes. It is used both for signal handler "locking"
		2938	as well as for signal and thread safety in C<ev_async> watchers.
		2939
		2940	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2941	(from F<signal.h>), which is usually good enough on most platforms.
2164		2942
2165	=item EV_H	2943	=item EV_H
2166		2944
2167	The name of the F<ev.h> header file used to include it. The default if	2945	The name of the F<ev.h> header file used to include it. The default if
2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2947	used to virtually rename the F<ev.h> header file in case of conflicts.
2170		2948
2171	=item EV_CONFIG_H	2949	=item EV_CONFIG_H
2172		2950
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	2953	C<EV_H>, above.
2176		2954
2177	=item EV_EVENT_H	2955	=item EV_EVENT_H
2178		2956
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2180	of how the F<event.h> header can be found.	2958	of how the F<event.h> header can be found, the default is C<"event.h">.
2181		2959
2182	=item EV_PROTOTYPES	2960	=item EV_PROTOTYPES
2183		2961
2184	If defined to be C<0>, then F<ev.h> will not define any function	2962	If defined to be C<0>, then F<ev.h> will not define any function
2185	prototypes, but still define all the structs and other symbols. This is	2963	prototypes, but still define all the structs and other symbols. This is
…		…
2206	When doing priority-based operations, libev usually has to linearly search	2984	When doing priority-based operations, libev usually has to linearly search
2207	all the priorities, so having many of them (hundreds) uses a lot of space	2985	all the priorities, so having many of them (hundreds) uses a lot of space
2208	and time, so using the defaults of five priorities (-2 .. +2) is usually	2986	and time, so using the defaults of five priorities (-2 .. +2) is usually
2209	fine.	2987	fine.
2210		2988
2211	If your embedding app does not need any priorities, defining these both to	2989	If your embedding application does not need any priorities, defining these both to
2212	C<0> will save some memory and cpu.	2990	C<0> will save some memory and CPU.
2213		2991
2214	=item EV_PERIODIC_ENABLE	2992	=item EV_PERIODIC_ENABLE
2215		2993
2216	If undefined or defined to be C<1>, then periodic timers are supported. If	2994	If undefined or defined to be C<1>, then periodic timers are supported. If
2217	defined to be C<0>, then they are not. Disabling them saves a few kB of	2995	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2236	=item EV_FORK_ENABLE	3014	=item EV_FORK_ENABLE
2237		3015
2238	If undefined or defined to be C<1>, then fork watchers are supported. If	3016	If undefined or defined to be C<1>, then fork watchers are supported. If
2239	defined to be C<0>, then they are not.	3017	defined to be C<0>, then they are not.
2240		3018
		3019	=item EV_ASYNC_ENABLE
		3020
		3021	If undefined or defined to be C<1>, then async watchers are supported. If
		3022	defined to be C<0>, then they are not.
		3023
2241	=item EV_MINIMAL	3024	=item EV_MINIMAL
2242		3025
2243	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2244	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2245	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2246		3030
2247	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2248		3032
2249	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2250	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2251	than enough. If you need to manage thousands of children you might want to	3035	than enough. If you need to manage thousands of children you might want to
2252	increase this value (I<must> be a power of two).	3036	increase this value (I<must> be a power of two).
2253		3037
2254	=item EV_INOTIFY_HASHSIZE	3038	=item EV_INOTIFY_HASHSIZE
2255		3039
2256	C<ev_staz> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2258	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2259	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2260	two).	3044	two).
2261		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticeably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticeably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
		3080
2262	=item EV_COMMON	3081	=item EV_COMMON
2263		3082
2264	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2265	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
2266	members. You have to define it each time you include one of the files,	3085	members. You have to define it each time you include one of the files,
…		…
2278		3097
2279	=item ev_set_cb (ev, cb)	3098	=item ev_set_cb (ev, cb)
2280		3099
2281	Can be used to change the callback member declaration in each watcher,	3100	Can be used to change the callback member declaration in each watcher,
2282	and the way callbacks are invoked and set. Must expand to a struct member	3101	and the way callbacks are invoked and set. Must expand to a struct member
2283	definition and a statement, respectively. See the F<ev.v> header file for	3102	definition and a statement, respectively. See the F<ev.h> header file for
2284	their default definitions. One possible use for overriding these is to	3103	their default definitions. One possible use for overriding these is to
2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2286	method calls instead of plain function calls in C++.	3105	method calls instead of plain function calls in C++.
		3106
		3107	=head2 EXPORTED API SYMBOLS
		3108
		3109	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3110	exported symbols, you can use the provided F<Symbol.*> files which list
		3111	all public symbols, one per line:
		3112
		3113	Symbols.ev for libev proper
		3114	Symbols.event for the libevent emulation
		3115
		3116	This can also be used to rename all public symbols to avoid clashes with
		3117	multiple versions of libev linked together (which is obviously bad in
		3118	itself, but sometimes it is inconvenient to avoid this).
		3119
		3120	A sed command like this will create wrapper C<#define>'s that you need to
		3121	include before including F<ev.h>:
		3122
		3123	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3124
		3125	This would create a file F<wrap.h> which essentially looks like this:
		3126
		3127	#define ev_backend myprefix_ev_backend
		3128	#define ev_check_start myprefix_ev_check_start
		3129	#define ev_check_stop myprefix_ev_check_stop
		3130	...
2287		3131
2288	=head2 EXAMPLES	3132	=head2 EXAMPLES
2289		3133
2290	For a real-world example of a program the includes libev	3134	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	3135	verbatim, you can have a look at the EV perl module
…		…
2314		3158
2315	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
2316	#include "ev.c"	3160	#include "ev.c"
2317		3161
2318		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely thread-safe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a separate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robin fashion.
		3196
		3197	Choosing a model is hard - look around, learn, know that usually you can do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accommodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
		3218
		3219
2319	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
2320		3221
2321	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
2322	libev will be explained. For complexity discussions about backends see the	3223	libev will be explained. For complexity discussions about backends see the
2323	documentation for C<ev_default_init>.	3224	documentation for C<ev_default_init>.
…		…
2332		3233
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		3235
2335	This means that, when you have a watcher that triggers in one hour and	3236	This means that, when you have a watcher that triggers in one hour and
2336	there are 100 watchers that would trigger before that then inserting will	3237	there are 100 watchers that would trigger before that then inserting will
2337	have to skip those 100 watchers.	3238	have to skip roughly seven (C<ld 100>) of these watchers.
2338		3239
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		3241
2341	That means that for changing a timer costs less than removing/adding them	3242	That means that changing a timer costs less than removing/adding them
2342	as only the relative motion in the event queue has to be paid for.	3243	as only the relative motion in the event queue has to be paid for.
2343		3244
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2345		3246
2346	These just add the watcher into an array or at the head of a list.	3247	These just add the watcher into an array or at the head of a list.
		3248
2347	=item Stopping check/prepare/idle watchers: O(1)	3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2348		3250
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		3252
2351	These watchers are stored in lists then need to be walked to find the	3253	These watchers are stored in lists then need to be walked to find the
2352	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
2354		3256
2355	=item Finding the next timer per loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
		3258
		3259	By virtue of using a binary or 4-heap, the next timer is always found at a
		3260	fixed position in the storage array.
2356		3261
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		3263
2359	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	3265	libev to recalculate its status (and possibly tell the kernel, depending
		3266	on backend and whether C<ev_io_set> was used).
2361		3267
2362	=item Activating one watcher: O(1)	3268	=item Activating one watcher (putting it into the pending state): O(1)
2363		3269
2364	=item Priority handling: O(number_of_priorities)	3270	=item Priority handling: O(number_of_priorities)
2365		3271
2366	Priorities are implemented by allocating some space for each	3272	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	3273	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	3274	linearly search all the priorities, but starting/stopping and activating
		3275	watchers becomes O(1) w.r.t. priority handling.
		3276
		3277	=item Sending an ev_async: O(1)
		3278
		3279	=item Processing ev_async_send: O(number_of_async_watchers)
		3280
		3281	=item Processing signals: O(max_signal_number)
		3282
		3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3284	calls in the current loop iteration. Checking for async and signal events
		3285	involves iterating over all running async watchers or all signal numbers.
2369		3286
2370	=back	3287	=back
2371		3288
2372		3289
		3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3291
		3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3293	requires, and its I/O model is fundamentally incompatible with the POSIX
		3294	model. Libev still offers limited functionality on this platform in
		3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3296	descriptors. This only applies when using Win32 natively, not when using
		3297	e.g. cygwin.
		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
		3304	There is no supported compilation method available on windows except
		3305	embedding it into other applications.
		3306
		3307	Not a libev limitation but worth mentioning: windows apparently doesn't
		3308	accept large writes: instead of resulting in a partial write, windows will
		3309	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3310	so make sure you only write small amounts into your sockets (less than a
		3311	megabyte seems safe, but thsi apparently depends on the amount of memory
		3312	available).
		3313
		3314	Due to the many, low, and arbitrary limits on the win32 platform and
		3315	the abysmal performance of winsockets, using a large number of sockets
		3316	is not recommended (and not reasonable). If your program needs to use
		3317	more than a hundred or so sockets, then likely it needs to use a totally
		3318	different implementation for windows, as libev offers the POSIX readiness
		3319	notification model, which cannot be implemented efficiently on windows
		3320	(Microsoft monopoly games).
		3321
		3322	=over 4
		3323
		3324	=item The winsocket select function
		3325
		3326	The winsocket C<select> function doesn't follow POSIX in that it
		3327	requires socket I<handles> and not socket I<file descriptors> (it is
		3328	also extremely buggy). This makes select very inefficient, and also
		3329	requires a mapping from file descriptors to socket handles. See the
		3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3332
		3333	The configuration for a "naked" win32 using the Microsoft runtime
		3334	libraries and raw winsocket select is:
		3335
		3336	#define EV_USE_SELECT 1
		3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3338
		3339	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3340	complexity in the O(n²) range when using win32.
		3341
		3342	=item Limited number of file descriptors
		3343
		3344	Windows has numerous arbitrary (and low) limits on things.
		3345
		3346	Early versions of winsocket's select only supported waiting for a maximum
		3347	of C<64> handles (probably owning to the fact that all windows kernels
		3348	can only wait for C<64> things at the same time internally; Microsoft
		3349	recommends spawning a chain of threads and wait for 63 handles and the
		3350	previous thread in each. Great).
		3351
		3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3353	to some high number (e.g. C<2048>) before compiling the winsocket select
		3354	call (which might be in libev or elsewhere, for example, perl does its own
		3355	select emulation on windows).
		3356
		3357	Another limit is the number of file descriptors in the Microsoft runtime
		3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3359	or something like this inside Microsoft). You can increase this by calling
		3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3361	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3362	libraries.
		3363
		3364	This might get you to about C<512> or C<2048> sockets (depending on
		3365	windows version and/or the phase of the moon). To get more, you need to
		3366	wrap all I/O functions and provide your own fd management, but the cost of
		3367	calling select (O(n²)) will likely make this unworkable.
		3368
		3369	=back
		3370
		3371
		3372	=head1 PORTABILITY REQUIREMENTS
		3373
		3374	In addition to a working ISO-C implementation, libev relies on a few
		3375	additional extensions:
		3376
		3377	=over 4
		3378
		3379	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3380
		3381	The type C<sig_atomic_t volatile> (or whatever is defined as
		3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3383	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3384	believed to be sufficiently portable.
		3385
		3386	=item C<sigprocmask> must work in a threaded environment
		3387
		3388	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3389	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3390	pthread implementations will either allow C<sigprocmask> in the "main
		3391	thread" or will block signals process-wide, both behaviours would
		3392	be compatible with libev. Interaction between C<sigprocmask> and
		3393	C<pthread_sigmask> could complicate things, however.
		3394
		3395	The most portable way to handle signals is to block signals in all threads
		3396	except the initial one, and run the default loop in the initial thread as
		3397	well.
		3398
		3399	=item C<long> must be large enough for common memory allocation sizes
		3400
		3401	To improve portability and simplify using libev, libev uses C<long>
		3402	internally instead of C<size_t> when allocating its data structures. On
		3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3404	is still at least 31 bits everywhere, which is enough for hundreds of
		3405	millions of watchers.
		3406
		3407	=item C<double> must hold a time value in seconds with enough accuracy
		3408
		3409	The type C<double> is used to represent timestamps. It is required to
		3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3411	enough for at least into the year 4000. This requirement is fulfilled by
		3412	implementations implementing IEEE 754 (basically all existing ones).
		3413
		3414	=back
		3415
		3416	If you know of other additional requirements drop me a note.
		3417
		3418
		3419	=head1 COMPILER WARNINGS
		3420
		3421	Depending on your compiler and compiler settings, you might get no or a
		3422	lot of warnings when compiling libev code. Some people are apparently
		3423	scared by this.
		3424
		3425	However, these are unavoidable for many reasons. For one, each compiler
		3426	has different warnings, and each user has different tastes regarding
		3427	warning options. "Warn-free" code therefore cannot be a goal except when
		3428	targeting a specific compiler and compiler-version.
		3429
		3430	Another reason is that some compiler warnings require elaborate
		3431	workarounds, or other changes to the code that make it less clear and less
		3432	maintainable.
		3433
		3434	And of course, some compiler warnings are just plain stupid, or simply
		3435	wrong (because they don't actually warn about the condition their message
		3436	seems to warn about).
		3437
		3438	While libev is written to generate as few warnings as possible,
		3439	"warn-free" code is not a goal, and it is recommended not to build libev
		3440	with any compiler warnings enabled unless you are prepared to cope with
		3441	them (e.g. by ignoring them). Remember that warnings are just that:
		3442	warnings, not errors, or proof of bugs.
		3443
		3444
		3445	=head1 VALGRIND
		3446
		3447	Valgrind has a special section here because it is a popular tool that is
		3448	highly useful, but valgrind reports are very hard to interpret.
		3449
		3450	If you think you found a bug (memory leak, uninitialised data access etc.)
		3451	in libev, then check twice: If valgrind reports something like:
		3452
		3453	==2274== definitely lost: 0 bytes in 0 blocks.
		3454	==2274== possibly lost: 0 bytes in 0 blocks.
		3455	==2274== still reachable: 256 bytes in 1 blocks.
		3456
		3457	Then there is no memory leak. Similarly, under some circumstances,
		3458	valgrind might report kernel bugs as if it were a bug in libev, or it
		3459	might be confused (it is a very good tool, but only a tool).
		3460
		3461	If you are unsure about something, feel free to contact the mailing list
		3462	with the full valgrind report and an explanation on why you think this is
		3463	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3464	no bug" answer and take the chance of learning how to interpret valgrind
		3465	properly.
		3466
		3467	If you need, for some reason, empty reports from valgrind for your project
		3468	I suggest using suppression lists.
		3469
		3470
2373	=head1 AUTHOR	3471	=head1 AUTHOR
2374		3472
2375	Marc Lehmann <libev@schmorp.de>.	3473	Marc Lehmann <libev@schmorp.de>.
2376		3474

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