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Revision 1.51 by root, Tue Nov 27 19:23:31 2007 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		9	=head2 EXAMPLE PROGRAM
		10
		11	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		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);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
8		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		66
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		70
11	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
12	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
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	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
16	(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
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	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
20	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
21	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
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	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
49	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
50	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
51	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
52		142
53	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
54		144
55	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
56	library in any way.	146	library in any way.
…		…
61		151
62	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
63	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
64	you actually want to know.	154	you actually want to know.
65		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
66	=item int ev_version_major ()	162	=item int ev_version_major ()
67		163
68	=item int ev_version_minor ()	164	=item int ev_version_minor ()
69		165
70	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
71	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
72	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
73	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
74	version of the library your program was compiled against.	170	version of the library your program was compiled against.
75		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
76	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,
77	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
78	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
79	not a problem.	178	not a problem.
80		179
81	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
82	version:	181	version.
83		182
84	assert (("libev version mismatch",	183	assert (("libev version mismatch",
85	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
86	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
87		186
88	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
89		188
90	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
91	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
93	a description of the set values.	192	a description of the set values.
94		193
95	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
96	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
97		196
98	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
99	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
100		199
101	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
102		201
103	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
104	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
105	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
106	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
107	(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
108	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
109		208
110	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
111		210
…		…
115	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
116	recommended ones.	215	recommended ones.
117		216
118	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
119		218
120	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
121		220
122	Sets the allocation function to use (the prototype is similar to the	221	Sets the allocation function to use (the prototype is similar - the
123	realloc C function, the semantics are identical). It is used to allocate	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
124	and free memory (no surprises here). If it returns zero when memory	223	used to allocate and free memory (no surprises here). If it returns zero
125	needs to be allocated, the library might abort or take some potentially	224	when memory needs to be allocated (C<size != 0>), the library might abort
126	destructive action. The default is your system realloc function.	225	or take some potentially destructive action.
		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.
127		230
128	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
129	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,
130	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.
131		234
132	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
133	retries: better than mine).	236	retries (example requires a standards-compliant C<realloc>).
134		237
135	static void *	238	static void *
136	persistent_realloc (void *ptr, long size)	239	persistent_realloc (void *ptr, size_t size)
137	{	240	{
138	for (;;)	241	for (;;)
139	{	242	{
140	void *newptr = realloc (ptr, size);	243	void *newptr = realloc (ptr, size);
141		244
…		…
147	}	250	}
148		251
149	...	252	...
150	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
151		254
152	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
153		256
154	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
155	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
156	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
157	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
158	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
159	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
160	(such as abort).	263	(such as abort).
161		264
162	Example: do the same thing as libev does internally:	265	Example: This is basically the same thing that libev does internally, too.
163		266
164	static void	267	static void
165	fatal_error (const char *msg)	268	fatal_error (const char *msg)
166	{	269	{
167	perror (msg);	270	perror (msg);
…		…
177		280
178	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
179	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
180	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
181		284
182	If you use threads, a common model is to run the default event loop
183	in your main thread (or in a separate thread) and for each thread you
184	create, you also create another event loop. Libev itself does no locking
185	whatsoever, so if you mix calls to the same event loop in different
186	threads, make sure you lock (this is usually a bad idea, though, even if
187	done correctly, because it's hideous and inefficient).
188
189	=over 4	285	=over 4
190		286
191	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
192		288
193	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
…		…
196	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
197		293
198	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
199	function.	295	function.
200		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
201	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
202	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>).
203		310
204	The following flags are supported:	311	The following flags are supported:
205		312
…		…
210	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
211	thing, believe me).	318	thing, believe me).
212		319
213	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
214		321
215	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
216	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
217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
218	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
219	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
220	around bugs.	327	around bugs.
221		328
		329	=item C<EVFLAG_FORKCHECK>
		330
		331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		332	a fork, you can also make libev check for a fork in each iteration by
		333	enabling this flag.
		334
		335	This works by calling C<getpid ()> on every iteration of the loop,
		336	and thus this might slow down your event loop if you do a lot of loop
		337	iterations and little real work, but is usually not noticeable (on my
		338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		339	without a system call and thus I<very> fast, but my GNU/Linux system also has
		340	C<pthread_atfork> which is even faster).
		341
		342	The big advantage of this flag is that you can forget about fork (and
		343	forget about forgetting to tell libev about forking) when you use this
		344	flag.
		345
		346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
		347	environment variable.
		348
222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
223		350
224	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
225	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,
226	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
227	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
228	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.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
229		367
230	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
231		369
232	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
233	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
234	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
235	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
236		379
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		381
239	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
240	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
241	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	384	like O(total_fds) where n is the total number of fds (or the highest fd),
242	either O(1) or O(active_fds).	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
		386	of shortcomings, such as silently dropping events in some hard-to-detect
		387	cases and requiring a system call per fd change, no fork support and bad
		388	support for dup.
243		389
244	While stopping and starting an I/O watcher in the same iteration will	390	While stopping, setting and starting an I/O watcher in the same iteration
245	result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
246	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
247	best to avoid that. Also, dup()ed file descriptors might not work very	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
248	well if you register events for both fds.	394	very well if you register events for both fds.
249		395
250	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
251	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
252	(or space) is available.	398	(or space) is available.
253		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		413
256	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
257	was broken on all BSDs except NetBSD (usually it doesn't work with	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
258	anything but sockets and pipes, except on Darwin, where of course its	416	anything but sockets and pipes, except on Darwin, where of course it's
259	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
260	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
261	C<EVBACKEND_KQUEUE>).	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		420
		421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
262		424
263	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
264	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
265	course). While starting and stopping an I/O watcher does not cause an	427	course). While stopping, setting and starting an I/O watcher does never
266	extra syscall as with epoll, it still adds up to four event changes per	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
267	incident, so its best to avoid that.	429	two event changes per incident. Support for C<fork ()> is very bad and it
		430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
268		444
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		446
271	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
272		451
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		453
275	This uses the Solaris 10 port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
276	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
277		456
278	Please note that solaris ports can result in a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
279	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
280	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
281		473
282	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
283		475
284	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
285	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
287		479
		480	It is definitely not recommended to use this flag.
		481
288	=back	482	=back
289		483
290	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
291	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
292	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
293	order of their flag values :)
294		487
295	The most typical usage is like this:	488	Example: This is the most typical usage.
296		489
297	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
299		492
300	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
301	environment settings to be taken into account:	494	environment settings to be taken into account:
302		495
303	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
304		497
305	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
306	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
307	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
308		502
309	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
310		504
311	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
312		506
313	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
314	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
315	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
316	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
317		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
318	Example: try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
319		517
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	519	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
323		521
324	=item ev_default_destroy ()	522	=item ev_default_destroy ()
325		523
326	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
327	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
328	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
329	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
330	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
331	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	530	for example).
		531
		532	Note that certain global state, such as signal state, will not be freed by
		533	this function, and related watchers (such as signal and child watchers)
		534	would need to be stopped manually.
		535
		536	In general it is not advisable to call this function except in the
		537	rare occasion where you really need to free e.g. the signal handling
		538	pipe fds. If you need dynamically allocated loops it is better to use
		539	C<ev_loop_new> and C<ev_loop_destroy>).
333		540
334	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
335		542
336	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
337	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
338		545
339	=item ev_default_fork ()	546	=item ev_default_fork ()
340		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
341	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
342	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
343	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
344	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
345		554
346	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
347	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
348	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
349		558
350	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
351	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
352	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
353		562
354	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
355		564
356	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
357	without calling this function, so if you force one of those backends you
358	do not need to care.
359
360	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
361		566
362	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
363	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
364	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
		576
		577	=item unsigned int ev_loop_count (loop)
		578
		579	Returns the count of loop iterations for the loop, which is identical to
		580	the number of times libev did poll for new events. It starts at C<0> and
		581	happily wraps around with enough iterations.
		582
		583	This value can sometimes be useful as a generation counter of sorts (it
		584	"ticks" the number of loop iterations), as it roughly corresponds with
		585	C<ev_prepare> and C<ev_check> calls.
365		586
366	=item unsigned int ev_backend (loop)	587	=item unsigned int ev_backend (loop)
367		588
368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
369	use.	590	use.
…		…
372		593
373	Returns the current "event loop time", which is the time the event loop	594	Returns the current "event loop time", which is the time the event loop
374	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
375	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
376	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
377	event occuring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
378		611
379	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
380		613
381	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
382	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
…		…
385	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
386	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
387		620
388	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
389	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
390	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
391	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
392	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
393		627
394	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
395	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
396	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
397		632
398	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
399	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
400	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
401	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
402	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
403	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
404	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
405		644
406	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
407		646
408	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
		649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
411	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
413	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
417	- Queue all outstanding timers.	662	- Queue all expired timers.
418	- Queue all outstanding periodics.	663	- Queue all expired periodics.
419	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
420	- Queue all check watchers.	665	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
422	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
426		672
427	Example: queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	674	anymore.
429		675
430	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
431	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
433	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
434		680
435	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
436		682
437	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
438	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
439	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
440	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
441		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
442	=item ev_ref (loop)	692	=item ev_ref (loop)
443		693
444	=item ev_unref (loop)	694	=item ev_unref (loop)
445		695
446	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
447	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
448	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
449	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
451	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
452	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
453	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
454	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
455	libraries. Just remember to I<unref after start> and I<ref before stop>.	708	libraries. Just remember to I<unref after start> and I<ref before stop>
		709	(but only if the watcher wasn't active before, or was active before,
		710	respectively).
456		711
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	713	running when nothing else is active.
459		714
460	struct dv_signal exitsig;	715	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	717	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	718	evf_unref (loop);
464		719
465	Example: for some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
466		721
467	ev_ref (myloop);	722	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
		724
		725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		726
		727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		728
		729	These advanced functions influence the time that libev will spend waiting
		730	for events. Both time intervals are by default C<0>, meaning that libev
		731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
		733
		734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		735	allows libev to delay invocation of I/O and timer/periodic callbacks
		736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
		738
		739	The idea is that sometimes your program runs just fast enough to handle
		740	one (or very few) event(s) per loop iteration. While this makes the
		741	program responsive, it also wastes a lot of CPU time to poll for new
		742	events, especially with backends like C<select ()> which have a high
		743	overhead for the actual polling but can deliver many events at once.
		744
		745	By setting a higher I<io collect interval> you allow libev to spend more
		746	time collecting I/O events, so you can handle more events per iteration,
		747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		748	C<ev_timer>) will be not affected. Setting this to a non-null value will
		749	introduce an additional C<ev_sleep ()> call into most loop iterations.
		750
		751	Likewise, by setting a higher I<timeout collect interval> you allow libev
		752	to spend more time collecting timeouts, at the expense of increased
		753	latency/jitter/inexactness (the watcher callback will be called
		754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		755	value will not introduce any overhead in libev.
		756
		757	Many (busy) programs can usually benefit by setting the I/O collect
		758	interval to a value near C<0.1> or so, which is often enough for
		759	interactive servers (of course not for games), likewise for timeouts. It
		760	usually doesn't make much sense to set it to a lower value than C<0.01>,
		761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
469		781
470	=back	782	=back
471		783
472		784
473	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
474		786
475	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
477	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
478		790
479	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
480	{	792	{
481	ev_io_stop (w);	793	ev_io_stop (w);
482	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
483	}	795	}
484		796
485	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
486	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
487	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
488	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
489	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
490	ev_loop (loop, 0);	802	ev_loop (loop, 0);
491		803
492	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
493	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
494	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
495		807
496	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
497	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
498	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
499	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
500	is readable and/or writable).	812	is readable and/or writable).
501		813
502	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
503	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
573	=item C<EV_FORK>	885	=item C<EV_FORK>
574		886
575	The event loop has been resumed in the child process after fork (see	887	The event loop has been resumed in the child process after fork (see
576	C<ev_fork>).	888	C<ev_fork>).
577		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
578	=item C<EV_ERROR>	894	=item C<EV_ERROR>
579		895
580	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
581	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
582	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
583	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
584	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
585		905
586	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
587	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
588	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
589	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
590	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
591		912
592	=back	913	=back
593		914
594	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
595		916
…		…
611	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
612		933
613	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
614	int revents)>.	935	int revents)>.
615		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
		942
616	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
617		944
618	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
619	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
620	call C<ev_TYPE_set> any number of times. You must not, however, call this	947	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
622	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
623		950
624	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
625	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
626		953
		954	See C<ev_init>, above, for an example.
		955
627	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
628		957
629	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
630	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
631	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
632		965
633	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
634		967
635	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
636	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
637		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
638	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
639		977
640	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
641	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
642	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
643	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
644	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
645	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
646		986
647	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
648		988
649	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
650	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	993	=item bool ev_is_pending (ev_TYPE *watcher)
654		994
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	995	Returns a true value iff the watcher is pending, (i.e. it has outstanding
656	events but its callback has not yet been invoked). As long as a watcher	996	events but its callback has not yet been invoked). As long as a watcher
657	is pending (but not active) you must not call an init function on it (but	997	is pending (but not active) you must not call an init function on it (but
658	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	998	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	999	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1000	it).
660		1001
661	=item callback = ev_cb (ev_TYPE *watcher)	1002	=item callback ev_cb (ev_TYPE *watcher)
662		1003
663	Returns the callback currently set on the watcher.	1004	Returns the callback currently set on the watcher.
664		1005
665	=item ev_cb_set (ev_TYPE *watcher, callback)	1006	=item ev_cb_set (ev_TYPE *watcher, callback)
666		1007
667	Change the callback. You can change the callback at virtually any time	1008	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	1009	(modulo threads).
669		1010
		1011	=item ev_set_priority (ev_TYPE *watcher, priority)
		1012
		1013	=item int ev_priority (ev_TYPE *watcher)
		1014
		1015	Set and query the priority of the watcher. The priority is a small
		1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1017	(default: C<-2>). Pending watchers with higher priority will be invoked
		1018	before watchers with lower priority, but priority will not keep watchers
		1019	from being executed (except for C<ev_idle> watchers).
		1020
		1021	This means that priorities are I<only> used for ordering callback
		1022	invocation after new events have been received. This is useful, for
		1023	example, to reduce latency after idling, or more often, to bind two
		1024	watchers on the same event and make sure one is called first.
		1025
		1026	If you need to suppress invocation when higher priority events are pending
		1027	you need to look at C<ev_idle> watchers, which provide this functionality.
		1028
		1029	You I<must not> change the priority of a watcher as long as it is active or
		1030	pending.
		1031
		1032	The default priority used by watchers when no priority has been set is
		1033	always C<0>, which is supposed to not be too high and not be too low :).
		1034
		1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1036	fine, as long as you do not mind that the priority value you query might
		1037	or might not have been adjusted to be within valid range.
		1038
		1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1040
		1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
		1045
		1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1047
		1048	If the watcher is pending, this function clears its pending status and
		1049	returns its C<revents> bitset (as if its callback was invoked). If the
		1050	watcher isn't pending it does nothing and returns C<0>.
		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
670	=back	1055	=back
671		1056
672		1057
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
674		1059
675	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
676	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
677	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
678	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
679	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
680	data:	1065	data:
681		1066
682	struct my_io	1067	struct my_io
683	{	1068	{
684	struct ev_io io;	1069	struct ev_io io;
685	int otherfd;	1070	int otherfd;
686	void *somedata;	1071	void *somedata;
687	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
688	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
689		1078
690	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
691	can cast it back to your own type:	1080	can cast it back to your own type:
692		1081
693	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
694	{	1083	{
695	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
696	...	1085	...
697	}	1086	}
698		1087
699	More interesting and less C-conformant ways of catsing your callback type	1088	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	1089	instead have been omitted.
		1090
		1091	Another common scenario is to use some data structure with multiple
		1092	embedded watchers:
		1093
		1094	struct my_biggy
		1095	{
		1096	int some_data;
		1097	ev_timer t1;
		1098	ev_timer t2;
		1099	}
		1100
		1101	In this case getting the pointer to C<my_biggy> is a bit more
		1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
		1106
		1107	#include <stddef.h>
		1108
		1109	static void
		1110	t1_cb (EV_P_ struct ev_timer *w, int revents)
		1111	{
		1112	struct my_biggy big = (struct my_biggy *
		1113	(((char *)w) - offsetof (struct my_biggy, t1));
		1114	}
		1115
		1116	static void
		1117	t2_cb (EV_P_ struct ev_timer *w, int revents)
		1118	{
		1119	struct my_biggy big = (struct my_biggy *
		1120	(((char *)w) - offsetof (struct my_biggy, t2));
		1121	}
701		1122
702		1123
703	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
704		1125
705	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
729	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
730	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
731	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	1153	required if you know what you are doing).
733		1154
734	You have to be careful with dup'ed file descriptors, though. Some backends	1155	If you cannot use non-blocking mode, then force the use of a
735	(the linux epoll backend is a notable example) cannot handle dup'ed file	1156	known-to-be-good backend (at the time of this writing, this includes only
736	descriptors correctly if you register interest in two or more fds pointing	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
737	to the same underlying file/socket/etc. description (that is, they share
738	the same underlying "file open").
739
740	If you must do this, then force the use of a known-to-be-good backend
741	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).
743		1158
744	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
745	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
746	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
747	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
748	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
749	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
750	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
751	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1167
753	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
754	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
755	wether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
756	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
757	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
		1177
		1178	=head3 The special problem of disappearing file descriptors
		1179
		1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1181	descriptor (either due to calling C<close> explicitly or any other means,
		1182	such as C<dup2>). The reason is that you register interest in some file
		1183	descriptor, but when it goes away, the operating system will silently drop
		1184	this interest. If another file descriptor with the same number then is
		1185	registered with libev, there is no efficient way to see that this is, in
		1186	fact, a different file descriptor.
		1187
		1188	To avoid having to explicitly tell libev about such cases, libev follows
		1189	the following policy: Each time C<ev_io_set> is being called, libev
		1190	will assume that this is potentially a new file descriptor, otherwise
		1191	it is assumed that the file descriptor stays the same. That means that
		1192	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1193	descriptor even if the file descriptor number itself did not change.
		1194
		1195	This is how one would do it normally anyway, the important point is that
		1196	the libev application should not optimise around libev but should leave
		1197	optimisations to libev.
		1198
		1199	=head3 The special problem of dup'ed file descriptors
		1200
		1201	Some backends (e.g. epoll), cannot register events for file descriptors,
		1202	but only events for the underlying file descriptions. That means when you
		1203	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1204	events for them, only one file descriptor might actually receive events.
		1205
		1206	There is no workaround possible except not registering events
		1207	for potentially C<dup ()>'ed file descriptors, or to resort to
		1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1209
		1210	=head3 The special problem of fork
		1211
		1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1213	useless behaviour. Libev fully supports fork, but needs to be told about
		1214	it in the child.
		1215
		1216	To support fork in your programs, you either have to call
		1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1219	C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of SIGPIPE
		1222
		1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1224	when writing to a pipe whose other end has been closed, your program gets
		1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1226	this is sensible behaviour, for daemons, this is usually undesirable.
		1227
		1228	So when you encounter spurious, unexplained daemon exits, make sure you
		1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1230	somewhere, as that would have given you a big clue).
		1231
		1232
		1233	=head3 Watcher-Specific Functions
758		1234
759	=over 4	1235	=over 4
760		1236
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1238
763	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
764		1240
765	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
766	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
767	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
768		1244
769	=item int fd [read-only]	1245	=item int fd [read-only]
770		1246
771	The file descriptor being watched.	1247	The file descriptor being watched.
772		1248
…		…
774		1250
775	The events being watched.	1251	The events being watched.
776		1252
777	=back	1253	=back
778		1254
		1255	=head3 Examples
		1256
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
780	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1259	attempt to read a whole line in the callback.
782		1260
783	static void	1261	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1263	{
786	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
787	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
788	}	1266	}
789		1267
790	...	1268	...
791	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
792	struct ev_io stdin_readable;	1270	struct ev_io stdin_readable;
793	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
794	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
795	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
796		1274
797		1275
798	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
799		1277
800	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
801	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
802		1280
803	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
804	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
805	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
806	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
807	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 The special problem of time updates
		1292
		1293	Establishing the current time is a costly operation (it usually takes at
		1294	least two system calls): EV therefore updates its idea of the current
		1295	time only before and after C<ev_loop> collects new events, which causes a
		1296	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1297	lots of events in one iteration.
808		1298
809	The relative timeouts are calculated relative to the C<ev_now ()>	1299	The relative timeouts are calculated relative to the C<ev_now ()>
810	time. This is usually the right thing as this timestamp refers to the time	1300	time. This is usually the right thing as this timestamp refers to the time
811	of the event triggering whatever timeout you are modifying/starting. If	1301	of the event triggering whatever timeout you are modifying/starting. If
812	you suspect event processing to be delayed and you I<need> to base the timeout	1302	you suspect event processing to be delayed and you I<need> to base the
813	on the current time, use something like this to adjust for this:	1303	timeout on the current time, use something like this to adjust for this:
814		1304
815	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1305	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
816		1306
817	The callback is guarenteed to be invoked only when its timeout has passed,	1307	If the event loop is suspended for a long time, you can also force an
818	but if multiple timers become ready during the same loop iteration then	1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update
819	order of execution is undefined.	1309	()>.
		1310
		1311	=head3 Watcher-Specific Functions and Data Members
820		1312
821	=over 4	1313	=over 4
822		1314
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1315	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1316
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1317	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
826		1318
827	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1319	Configure the timer to trigger after C<after> seconds. If C<repeat>
828	C<0.>, then it will automatically be stopped. If it is positive, then the	1320	is C<0.>, then it will automatically be stopped once the timeout is
829	timer will automatically be configured to trigger again C<repeat> seconds	1321	reached. If it is positive, then the timer will automatically be
830	later, again, and again, until stopped manually.	1322	configured to trigger again C<repeat> seconds later, again, and again,
		1323	until stopped manually.
831		1324
832	The timer itself will do a best-effort at avoiding drift, that is, if you	1325	The timer itself will do a best-effort at avoiding drift, that is, if
833	configure a timer to trigger every 10 seconds, then it will trigger at	1326	you configure a timer to trigger every 10 seconds, then it will normally
834	exactly 10 second intervals. If, however, your program cannot keep up with	1327	trigger at exactly 10 second intervals. If, however, your program cannot
835	the timer (because it takes longer than those 10 seconds to do stuff) the	1328	keep up with the timer (because it takes longer than those 10 seconds to
836	timer will not fire more than once per event loop iteration.	1329	do stuff) the timer will not fire more than once per event loop iteration.
837		1330
838	=item ev_timer_again (loop)	1331	=item ev_timer_again (loop, ev_timer *)
839		1332
840	This will act as if the timer timed out and restart it again if it is	1333	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1334	repeating. The exact semantics are:
842		1335
		1336	If the timer is pending, its pending status is cleared.
		1337
843	If the timer is started but nonrepeating, stop it.	1338	If the timer is started but non-repeating, stop it (as if it timed out).
844		1339
845	If the timer is repeating, either start it if necessary (with the repeat	1340	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1341	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1342
848	This sounds a bit complicated, but here is a useful and typical	1343	This sounds a bit complicated, but here is a useful and typical
849	example: Imagine you have a tcp connection and you want a so-called	1344	example: Imagine you have a TCP connection and you want a so-called idle
850	idle timeout, that is, you want to be called when there have been,	1345	timeout, that is, you want to be called when there have been, say, 60
851	say, 60 seconds of inactivity on the socket. The easiest way to do	1346	seconds of inactivity on the socket. The easiest way to do this is to
852	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
853	C<ev_timer_again> each time you successfully read or write some data. If	1348	C<ev_timer_again> each time you successfully read or write some data. If
854	you go into an idle state where you do not expect data to travel on the	1349	you go into an idle state where you do not expect data to travel on the
855	socket, you can stop the timer, and again will automatically restart it if	1350	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1351	automatically restart it if need be.
857		1352
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1353	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1354	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1355
861	ev_timer_init (timer, callback, 0., 5.);	1356	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
863	...	1358	...
864	timer->again = 17.;	1359	timer->again = 17.;
865	ev_timer_again (loop, timer);	1360	ev_timer_again (loop, timer);
866	...	1361	...
867	timer->again = 10.;	1362	timer->again = 10.;
868	ev_timer_again (loop, timer);	1363	ev_timer_again (loop, timer);
869		1364
870	This is more efficient then stopping/starting the timer eahc time you want	1365	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1366	you want to modify its timeout value.
		1367
		1368	Note, however, that it is often even more efficient to remember the
		1369	time of the last activity and let the timer time-out naturally. In the
		1370	callback, you then check whether the time-out is real, or, if there was
		1371	some activity, you reschedule the watcher to time-out in "last_activity +
		1372	timeout - ev_now ()" seconds.
872		1373
873	=item ev_tstamp repeat [read-write]	1374	=item ev_tstamp repeat [read-write]
874		1375
875	The current C<repeat> value. Will be used each time the watcher times out	1376	The current C<repeat> value. Will be used each time the watcher times out
876	or C<ev_timer_again> is called and determines the next timeout (if any),	1377	or C<ev_timer_again> is called, and determines the next timeout (if any),
877	which is also when any modifications are taken into account.	1378	which is also when any modifications are taken into account.
878		1379
879	=back	1380	=back
880		1381
		1382	=head3 Examples
		1383
881	Example: create a timer that fires after 60 seconds.	1384	Example: Create a timer that fires after 60 seconds.
882		1385
883	static void	1386	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1388	{
886	.. one minute over, w is actually stopped right here	1389	.. one minute over, w is actually stopped right here
887	}	1390	}
888		1391
889	struct ev_timer mytimer;	1392	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1394	ev_timer_start (loop, &mytimer);
892		1395
893	Example: create a timeout timer that times out after 10 seconds of	1396	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1397	inactivity.
895		1398
896	static void	1399	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1401	{
899	.. ten seconds without any activity	1402	.. ten seconds without any activity
900	}	1403	}
901		1404
902	struct ev_timer mytimer;	1405	struct ev_timer mytimer;
903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
904	ev_timer_again (&mytimer); /* start timer */	1407	ev_timer_again (&mytimer); /* start timer */
905	ev_loop (loop, 0);	1408	ev_loop (loop, 0);
906		1409
907	// and in some piece of code that gets executed on any "activity":	1410	// and in some piece of code that gets executed on any "activity":
908	// reset the timeout to start ticking again at 10 seconds	1411	// reset the timeout to start ticking again at 10 seconds
909	ev_timer_again (&mytimer);	1412	ev_timer_again (&mytimer);
910		1413
911		1414
912	=head2 C<ev_periodic> - to cron or not to cron?	1415	=head2 C<ev_periodic> - to cron or not to cron?
913		1416
914	Periodic watchers are also timers of a kind, but they are very versatile	1417	Periodic watchers are also timers of a kind, but they are very versatile
915	(and unfortunately a bit complex).	1418	(and unfortunately a bit complex).
916		1419
917	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
918	but on wallclock time (absolute time). You can tell a periodic watcher	1421	but on wall clock time (absolute time). You can tell a periodic watcher
919	to trigger "at" some specific point in time. For example, if you tell a	1422	to trigger after some specific point in time. For example, if you tell a
920	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
921	+ 10.>) and then reset your system clock to the last year, then it will	1424	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1425	clock to January of the previous year, then it will take more than year
922	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
923	roughly 10 seconds later and of course not if you reset your system time	1427	roughly 10 seconds later as it uses a relative timeout).
924	again).
925		1428
926	They can also be used to implement vastly more complex timers, such as	1429	C<ev_periodic>s can also be used to implement vastly more complex timers,
927	triggering an event on eahc midnight, local time.	1430	such as triggering an event on each "midnight, local time", or other
		1431	complicated rules.
928		1432
929	As with timers, the callback is guarenteed to be invoked only when the	1433	As with timers, the callback is guaranteed to be invoked only when the
930	time (C<at>) has been passed, but if multiple periodic timers become ready	1434	time (C<at>) has passed, but if multiple periodic timers become ready
931	during the same loop iteration then order of execution is undefined.	1435	during the same loop iteration, then order of execution is undefined.
		1436
		1437	=head3 Watcher-Specific Functions and Data Members
932		1438
933	=over 4	1439	=over 4
934		1440
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1442
937	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
938		1444
939	Lots of arguments, lets sort it out... There are basically three modes of	1445	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1446	operation, and we will explain them from simplest to most complex:
941		1447
942	=over 4	1448	=over 4
943		1449
944	=item * absolute timer (interval = reschedule_cb = 0)	1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1451
946	In this configuration the watcher triggers an event at the wallclock time	1452	In this configuration the watcher triggers an event after the wall clock
947	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1453	time C<at> has passed. It will not repeat and will not adjust when a time
948	that is, if it is to be run at January 1st 2011 then it will run when the	1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will
949	system time reaches or surpasses this time.	1455	only run when the system clock reaches or surpasses this time.
950		1456
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1458
953	In this mode the watcher will always be scheduled to time out at the next	1459	In this mode the watcher will always be scheduled to time out at the next
954	C<at + N * interval> time (for some integer N) and then repeat, regardless	1460	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1461	and then repeat, regardless of any time jumps.
956		1462
957	This can be used to create timers that do not drift with respect to system	1463	This can be used to create timers that do not drift with respect to the
958	time:	1464	system clock, for example, here is a C<ev_periodic> that triggers each
		1465	hour, on the hour:
959		1466
960	ev_periodic_set (&periodic, 0., 3600., 0);	1467	ev_periodic_set (&periodic, 0., 3600., 0);
961		1468
962	This doesn't mean there will always be 3600 seconds in between triggers,	1469	This doesn't mean there will always be 3600 seconds in between triggers,
963	but only that the the callback will be called when the system time shows a	1470	but only that the callback will be called when the system time shows a
964	full hour (UTC), or more correctly, when the system time is evenly divisible	1471	full hour (UTC), or more correctly, when the system time is evenly divisible
965	by 3600.	1472	by 3600.
966		1473
967	Another way to think about it (for the mathematically inclined) is that	1474	Another way to think about it (for the mathematically inclined) is that
968	C<ev_periodic> will try to run the callback in this mode at the next possible	1475	C<ev_periodic> will try to run the callback in this mode at the next possible
969	time where C<time = at (mod interval)>, regardless of any time jumps.	1476	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1477
		1478	For numerical stability it is preferable that the C<at> value is near
		1479	C<ev_now ()> (the current time), but there is no range requirement for
		1480	this value, and in fact is often specified as zero.
		1481
		1482	Note also that there is an upper limit to how often a timer can fire (CPU
		1483	speed for example), so if C<interval> is very small then timing stability
		1484	will of course deteriorate. Libev itself tries to be exact to be about one
		1485	millisecond (if the OS supports it and the machine is fast enough).
		1486
971	=item * manual reschedule mode (reschedule_cb = callback)	1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1488
973	In this mode the values for C<interval> and C<at> are both being	1489	In this mode the values for C<interval> and C<at> are both being
974	ignored. Instead, each time the periodic watcher gets scheduled, the	1490	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1491	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1492	current time as second argument.
977		1493
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
979	ever, or make any event loop modifications>. If you need to stop it,	1495	ever, or make ANY event loop modifications whatsoever>.
980	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
981	starting a prepare watcher).
982		1496
		1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1499	only event loop modification you are allowed to do).
		1500
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
984	ev_tstamp now)>, e.g.:	1502	*w, ev_tstamp now)>, e.g.:
985		1503
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
987	{	1505	{
988	return now + 60.;	1506	return now + 60.;
989	}	1507	}
…		…
991	It must return the next time to trigger, based on the passed time value	1509	It must return the next time to trigger, based on the passed time value
992	(that is, the lowest time value larger than to the second argument). It	1510	(that is, the lowest time value larger than to the second argument). It
993	will usually be called just before the callback will be triggered, but	1511	will usually be called just before the callback will be triggered, but
994	might be called at other times, too.	1512	might be called at other times, too.
995		1513
996	NOTE: I<< This callback must always return a time that is later than the	1514	NOTE: I<< This callback must always return a time that is higher than or
997	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1515	equal to the passed C<now> value >>.
998		1516
999	This can be used to create very complex timers, such as a timer that	1517	This can be used to create very complex timers, such as a timer that
1000	triggers on each midnight, local time. To do this, you would calculate the	1518	triggers on "next midnight, local time". To do this, you would calculate the
1001	next midnight after C<now> and return the timestamp value for this. How	1519	next midnight after C<now> and return the timestamp value for this. How
1002	you do this is, again, up to you (but it is not trivial, which is the main	1520	you do this is, again, up to you (but it is not trivial, which is the main
1003	reason I omitted it as an example).	1521	reason I omitted it as an example).
1004		1522
1005	=back	1523	=back
…		…
1009	Simply stops and restarts the periodic watcher again. This is only useful	1527	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1528	when you changed some parameters or the reschedule callback would return
1011	a different time than the last time it was called (e.g. in a crond like	1529	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1530	program when the crontabs have changed).
1013		1531
		1532	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1533
		1534	When active, returns the absolute time that the watcher is supposed to
		1535	trigger next.
		1536
		1537	=item ev_tstamp offset [read-write]
		1538
		1539	When repeating, this contains the offset value, otherwise this is the
		1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1541
		1542	Can be modified any time, but changes only take effect when the periodic
		1543	timer fires or C<ev_periodic_again> is being called.
		1544
1014	=item ev_tstamp interval [read-write]	1545	=item ev_tstamp interval [read-write]
1015		1546
1016	The current interval value. Can be modified any time, but changes only	1547	The current interval value. Can be modified any time, but changes only
1017	take effect when the periodic timer fires or C<ev_periodic_again> is being	1548	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1549	called.
…		…
1023	switched off. Can be changed any time, but changes only take effect when	1554	switched off. Can be changed any time, but changes only take effect when
1024	the periodic timer fires or C<ev_periodic_again> is being called.	1555	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1556
1026	=back	1557	=back
1027		1558
		1559	=head3 Examples
		1560
1028	Example: call a callback every hour, or, more precisely, whenever the	1561	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1562	system time is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1563	potentially a lot of jitter, but good long-term stability.
1031		1564
1032	static void	1565	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1034	{	1567	{
1035	... its now a full hour (UTC, or TAI or whatever your clock follows)	1568	... its now a full hour (UTC, or TAI or whatever your clock follows)
1036	}	1569	}
1037		1570
1038	struct ev_periodic hourly_tick;	1571	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1573	ev_periodic_start (loop, &hourly_tick);
1041		1574
1042	Example: the same as above, but use a reschedule callback to do it:	1575	Example: The same as above, but use a reschedule callback to do it:
1043		1576
1044	#include <math.h>	1577	#include <math.h>
1045		1578
1046	static ev_tstamp	1579	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1048	{	1581	{
1049	return fmod (now, 3600.) + 3600.;	1582	return now + (3600. - fmod (now, 3600.));
1050	}	1583	}
1051		1584
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1586
1054	Example: call a callback every hour, starting now:	1587	Example: Call a callback every hour, starting now:
1055		1588
1056	struct ev_periodic hourly_tick;	1589	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1590	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1591	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1592	ev_periodic_start (loop, &hourly_tick);
1060		1593
1061		1594
1062	=head2 C<ev_signal> - signal me when a signal gets signalled!	1595	=head2 C<ev_signal> - signal me when a signal gets signalled!
1063		1596
1064	Signal watchers will trigger an event when the process receives a specific	1597	Signal watchers will trigger an event when the process receives a specific
1065	signal one or more times. Even though signals are very asynchronous, libev	1598	signal one or more times. Even though signals are very asynchronous, libev
1066	will try it's best to deliver signals synchronously, i.e. as part of the	1599	will try it's best to deliver signals synchronously, i.e. as part of the
1067	normal event processing, like any other event.	1600	normal event processing, like any other event.
1068		1601
		1602	If you want signals asynchronously, just use C<sigaction> as you would
		1603	do without libev and forget about sharing the signal. You can even use
		1604	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1605
1069	You can configure as many watchers as you like per signal. Only when the	1606	You can configure as many watchers as you like per signal. Only when the
1070	first watcher gets started will libev actually register a signal watcher	1607	first watcher gets started will libev actually register a signal handler
1071	with the kernel (thus it coexists with your own signal handlers as long	1608	with the kernel (thus it coexists with your own signal handlers as long as
1072	as you don't register any with libev). Similarly, when the last signal	1609	you don't register any with libev for the same signal). Similarly, when
1073	watcher for a signal is stopped libev will reset the signal handler to	1610	the last signal watcher for a signal is stopped, libev will reset the
1074	SIG_DFL (regardless of what it was set to before).	1611	signal handler to SIG_DFL (regardless of what it was set to before).
		1612
		1613	If possible and supported, libev will install its handlers with
		1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1615	interrupted. If you have a problem with system calls getting interrupted by
		1616	signals you can block all signals in an C<ev_check> watcher and unblock
		1617	them in an C<ev_prepare> watcher.
		1618
		1619	=head3 Watcher-Specific Functions and Data Members
1075		1620
1076	=over 4	1621	=over 4
1077		1622
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1623	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1624
…		…
1086		1631
1087	The signal the watcher watches out for.	1632	The signal the watcher watches out for.
1088		1633
1089	=back	1634	=back
1090		1635
		1636	=head3 Examples
		1637
		1638	Example: Try to exit cleanly on SIGINT.
		1639
		1640	static void
		1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1642	{
		1643	ev_unloop (loop, EVUNLOOP_ALL);
		1644	}
		1645
		1646	struct ev_signal signal_watcher;
		1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1648	ev_signal_start (loop, &signal_watcher);
		1649
1091		1650
1092	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1093		1652
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
1095	some child status changes (most typically when a child of yours dies).	1654	some child status changes (most typically when a child of yours dies or
		1655	exits). It is permissible to install a child watcher I<after> the child
		1656	has been forked (which implies it might have already exited), as long
		1657	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1658	forking and then immediately registering a watcher for the child is fine,
		1659	but forking and registering a watcher a few event loop iterations later is
		1660	not.
		1661
		1662	Only the default event loop is capable of handling signals, and therefore
		1663	you can only register child watchers in the default event loop.
		1664
		1665	=head3 Process Interaction
		1666
		1667	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1668	initialised. This is necessary to guarantee proper behaviour even if
		1669	the first child watcher is started after the child exits. The occurrence
		1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1671	synchronously as part of the event loop processing. Libev always reaps all
		1672	children, even ones not watched.
		1673
		1674	=head3 Overriding the Built-In Processing
		1675
		1676	Libev offers no special support for overriding the built-in child
		1677	processing, but if your application collides with libev's default child
		1678	handler, you can override it easily by installing your own handler for
		1679	C<SIGCHLD> after initialising the default loop, and making sure the
		1680	default loop never gets destroyed. You are encouraged, however, to use an
		1681	event-based approach to child reaping and thus use libev's support for
		1682	that, so other libev users can use C<ev_child> watchers freely.
		1683
		1684	=head3 Stopping the Child Watcher
		1685
		1686	Currently, the child watcher never gets stopped, even when the
		1687	child terminates, so normally one needs to stop the watcher in the
		1688	callback. Future versions of libev might stop the watcher automatically
		1689	when a child exit is detected.
		1690
		1691	=head3 Watcher-Specific Functions and Data Members
1096		1692
1097	=over 4	1693	=over 4
1098		1694
1099	=item ev_child_init (ev_child *, callback, int pid)	1695	=item ev_child_init (ev_child *, callback, int pid, int trace)
1100		1696
1101	=item ev_child_set (ev_child *, int pid)	1697	=item ev_child_set (ev_child *, int pid, int trace)
1102		1698
1103	Configures the watcher to wait for status changes of process C<pid> (or	1699	Configures the watcher to wait for status changes of process C<pid> (or
1104	I<any> process if C<pid> is specified as C<0>). The callback can look	1700	I<any> process if C<pid> is specified as C<0>). The callback can look
1105	at the C<rstatus> member of the C<ev_child> watcher structure to see	1701	at the C<rstatus> member of the C<ev_child> watcher structure to see
1106	the status word (use the macros from C<sys/wait.h> and see your systems	1702	the status word (use the macros from C<sys/wait.h> and see your systems
1107	C<waitpid> documentation). The C<rpid> member contains the pid of the	1703	C<waitpid> documentation). The C<rpid> member contains the pid of the
1108	process causing the status change.	1704	process causing the status change. C<trace> must be either C<0> (only
		1705	activate the watcher when the process terminates) or C<1> (additionally
		1706	activate the watcher when the process is stopped or continued).
1109		1707
1110	=item int pid [read-only]	1708	=item int pid [read-only]
1111		1709
1112	The process id this watcher watches out for, or C<0>, meaning any process id.	1710	The process id this watcher watches out for, or C<0>, meaning any process id.
1113		1711
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1718	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1719	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1720
1123	=back	1721	=back
1124		1722
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1723	=head3 Examples
1126		1724
		1725	Example: C<fork()> a new process and install a child handler to wait for
		1726	its completion.
		1727
		1728	ev_child cw;
		1729
1127	static void	1730	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1731	child_cb (EV_P_ struct ev_child *w, int revents)
1129	{	1732	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1733	ev_child_stop (EV_A_ w);
		1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1131	}	1735	}
1132		1736
1133	struct ev_signal signal_watcher;	1737	pid_t pid = fork ();
1134	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1738
1135	ev_signal_start (loop, &sigint_cb);	1739	if (pid < 0)
		1740	// error
		1741	else if (pid == 0)
		1742	{
		1743	// the forked child executes here
		1744	exit (1);
		1745	}
		1746	else
		1747	{
		1748	ev_child_init (&cw, child_cb, pid, 0);
		1749	ev_child_start (EV_DEFAULT_ &cw);
		1750	}
1136		1751
1137		1752
1138	=head2 C<ev_stat> - did the file attributes just change?	1753	=head2 C<ev_stat> - did the file attributes just change?
1139		1754
1140	This watches a filesystem path for attribute changes. That is, it calls	1755	This watches a file system path for attribute changes. That is, it calls
1141	C<stat> regularly (or when the OS says it changed) and sees if it changed	1756	C<stat> regularly (or when the OS says it changed) and sees if it changed
1142	compared to the last time, invoking the callback if it did.	1757	compared to the last time, invoking the callback if it did.
1143		1758
1144	The path does not need to exist: changing from "path exists" to "path does	1759	The path does not need to exist: changing from "path exists" to "path does
1145	not exist" is a status change like any other. The condition "path does	1760	not exist" is a status change like any other. The condition "path does
1146	not exist" is signified by the C<st_nlink> field being zero (which is	1761	not exist" is signified by the C<st_nlink> field being zero (which is
1147	otherwise always forced to be at least one) and all the other fields of	1762	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1763	the stat buffer having unspecified contents.
1149		1764
1150	Since there is no standard to do this, the portable implementation simply	1765	The path I<should> be absolute and I<must not> end in a slash. If it is
1151	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1766	relative and your working directory changes, the behaviour is undefined.
1152	can specify a recommended polling interval for this case. If you specify	1767
1153	a polling interval of C<0> (highly recommended!) then a I<suitable,	1768	Since there is no standard kernel interface to do this, the portable
1154	unspecified default> value will be used (which you can expect to be around	1769	implementation simply calls C<stat (2)> regularly on the path to see if
1155	five seconds, although this might change dynamically). Libev will also	1770	it changed somehow. You can specify a recommended polling interval for
1156	impose a minimum interval which is currently around C<0.1>, but thats	1771	this case. If you specify a polling interval of C<0> (highly recommended!)
1157	usually overkill.	1772	then a I<suitable, unspecified default> value will be used (which
		1773	you can expect to be around five seconds, although this might change
		1774	dynamically). Libev will also impose a minimum interval which is currently
		1775	around C<0.1>, but thats usually overkill.
1158		1776
1159	This watcher type is not meant for massive numbers of stat watchers,	1777	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1778	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1779	resource-intensive.
1162		1780
1163	At the time of this writing, no specific OS backends are implemented, but	1781	At the time of this writing, the only OS-specific interface implemented
1164	if demand increases, at least a kqueue and inotify backend will be added.	1782	is the Linux inotify interface (implementing kqueue support is left as
		1783	an exercise for the reader. Note, however, that the author sees no way
		1784	of implementing C<ev_stat> semantics with kqueue).
		1785
		1786	=head3 ABI Issues (Largefile Support)
		1787
		1788	Libev by default (unless the user overrides this) uses the default
		1789	compilation environment, which means that on systems with large file
		1790	support disabled by default, you get the 32 bit version of the stat
		1791	structure. When using the library from programs that change the ABI to
		1792	use 64 bit file offsets the programs will fail. In that case you have to
		1793	compile libev with the same flags to get binary compatibility. This is
		1794	obviously the case with any flags that change the ABI, but the problem is
		1795	most noticeably disabled with ev_stat and large file support.
		1796
		1797	The solution for this is to lobby your distribution maker to make large
		1798	file interfaces available by default (as e.g. FreeBSD does) and not
		1799	optional. Libev cannot simply switch on large file support because it has
		1800	to exchange stat structures with application programs compiled using the
		1801	default compilation environment.
		1802
		1803	=head3 Inotify and Kqueue
		1804
		1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
		1807	implementations) and present at runtime, it will be used to speed up
		1808	change detection where possible. The inotify descriptor will be created
		1809	lazily when the first C<ev_stat> watcher is being started.
		1810
		1811	Inotify presence does not change the semantics of C<ev_stat> watchers
		1812	except that changes might be detected earlier, and in some cases, to avoid
		1813	making regular C<stat> calls. Even in the presence of inotify support
		1814	there are many cases where libev has to resort to regular C<stat> polling,
		1815	but as long as the path exists, libev usually gets away without polling.
		1816
		1817	There is no support for kqueue, as apparently it cannot be used to
		1818	implement this functionality, due to the requirement of having a file
		1819	descriptor open on the object at all times, and detecting renames, unlinks
		1820	etc. is difficult.
		1821
		1822	=head3 The special problem of stat time resolution
		1823
		1824	The C<stat ()> system call only supports full-second resolution portably, and
		1825	even on systems where the resolution is higher, most file systems still
		1826	only support whole seconds.
		1827
		1828	That means that, if the time is the only thing that changes, you can
		1829	easily miss updates: on the first update, C<ev_stat> detects a change and
		1830	calls your callback, which does something. When there is another update
		1831	within the same second, C<ev_stat> will be unable to detect unless the
		1832	stat data does change in other ways (e.g. file size).
		1833
		1834	The solution to this is to delay acting on a change for slightly more
		1835	than a second (or till slightly after the next full second boundary), using
		1836	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1837	ev_timer_again (loop, w)>).
		1838
		1839	The C<.02> offset is added to work around small timing inconsistencies
		1840	of some operating systems (where the second counter of the current time
		1841	might be be delayed. One such system is the Linux kernel, where a call to
		1842	C<gettimeofday> might return a timestamp with a full second later than
		1843	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1844	update file times then there will be a small window where the kernel uses
		1845	the previous second to update file times but libev might already execute
		1846	the timer callback).
		1847
		1848	=head3 Watcher-Specific Functions and Data Members
1165		1849
1166	=over 4	1850	=over 4
1167		1851
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1852	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1853
…		…
1173	C<path>. The C<interval> is a hint on how quickly a change is expected to	1857	C<path>. The C<interval> is a hint on how quickly a change is expected to
1174	be detected and should normally be specified as C<0> to let libev choose	1858	be detected and should normally be specified as C<0> to let libev choose
1175	a suitable value. The memory pointed to by C<path> must point to the same	1859	a suitable value. The memory pointed to by C<path> must point to the same
1176	path for as long as the watcher is active.	1860	path for as long as the watcher is active.
1177		1861
1178	The callback will be receive C<EV_STAT> when a change was detected,	1862	The callback will receive an C<EV_STAT> event when a change was detected,
1179	relative to the attributes at the time the watcher was started (or the	1863	relative to the attributes at the time the watcher was started (or the
1180	last change was detected).	1864	last change was detected).
1181		1865
1182	=item ev_stat_stat (ev_stat *)	1866	=item ev_stat_stat (loop, ev_stat *)
1183		1867
1184	Updates the stat buffer immediately with new values. If you change the	1868	Updates the stat buffer immediately with new values. If you change the
1185	watched path in your callback, you could call this fucntion to avoid	1869	watched path in your callback, you could call this function to avoid
1186	detecting this change (while introducing a race condition). Can also be	1870	detecting this change (while introducing a race condition if you are not
1187	useful simply to find out the new values.	1871	the only one changing the path). Can also be useful simply to find out the
		1872	new values.
1188		1873
1189	=item ev_statdata attr [read-only]	1874	=item ev_statdata attr [read-only]
1190		1875
1191	The most-recently detected attributes of the file. Although the type is of	1876	The most-recently detected attributes of the file. Although the type is
1192	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1877	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1193	suitable for your system. If the C<st_nlink> member is C<0>, then there	1878	suitable for your system, but you can only rely on the POSIX-standardised
		1879	members to be present. If the C<st_nlink> member is C<0>, then there was
1194	was some error while C<stat>ing the file.	1880	some error while C<stat>ing the file.
1195		1881
1196	=item ev_statdata prev [read-only]	1882	=item ev_statdata prev [read-only]
1197		1883
1198	The previous attributes of the file. The callback gets invoked whenever	1884	The previous attributes of the file. The callback gets invoked whenever
1199	C<prev> != C<attr>.	1885	C<prev> != C<attr>, or, more precisely, one or more of these members
		1886	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1887	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1200		1888
1201	=item ev_tstamp interval [read-only]	1889	=item ev_tstamp interval [read-only]
1202		1890
1203	The specified interval.	1891	The specified interval.
1204		1892
1205	=item const char *path [read-only]	1893	=item const char *path [read-only]
1206		1894
1207	The filesystem path that is being watched.	1895	The file system path that is being watched.
1208		1896
1209	=back	1897	=back
1210		1898
		1899	=head3 Examples
		1900
1211	Example: Watch C</etc/passwd> for attribute changes.	1901	Example: Watch C</etc/passwd> for attribute changes.
1212		1902
1213	static void	1903	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1904	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1215	{	1905	{
1216	/* /etc/passwd changed in some way */	1906	/* /etc/passwd changed in some way */
1217	if (w->attr.st_nlink)	1907	if (w->attr.st_nlink)
1218	{	1908	{
1219	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1909	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1220	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1910	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1221	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1911	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1222	}	1912	}
1223	else	1913	else
1224	/* you shalt not abuse printf for puts */	1914	/* you shalt not abuse printf for puts */
1225	puts ("wow, /etc/passwd is not there, expect problems. "	1915	puts ("wow, /etc/passwd is not there, expect problems. "
1226	"if this is windows, they already arrived\n");	1916	"if this is windows, they already arrived\n");
1227	}	1917	}
1228		1918
1229	...	1919	...
1230	ev_stat passwd;	1920	ev_stat passwd;
1231		1921
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1922	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1923	ev_stat_start (loop, &passwd);
		1924
		1925	Example: Like above, but additionally use a one-second delay so we do not
		1926	miss updates (however, frequent updates will delay processing, too, so
		1927	one might do the work both on C<ev_stat> callback invocation I<and> on
		1928	C<ev_timer> callback invocation).
		1929
		1930	static ev_stat passwd;
		1931	static ev_timer timer;
		1932
		1933	static void
		1934	timer_cb (EV_P_ ev_timer *w, int revents)
		1935	{
		1936	ev_timer_stop (EV_A_ w);
		1937
		1938	/* now it's one second after the most recent passwd change */
		1939	}
		1940
		1941	static void
		1942	stat_cb (EV_P_ ev_stat *w, int revents)
		1943	{
		1944	/* reset the one-second timer */
		1945	ev_timer_again (EV_A_ &timer);
		1946	}
		1947
		1948	...
		1949	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1950	ev_stat_start (loop, &passwd);
		1951	ev_timer_init (&timer, timer_cb, 0., 1.02);
1234		1952
1235		1953
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1954	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1955
1238	Idle watchers trigger events when there are no other events are pending	1956	Idle watchers trigger events when no other events of the same or higher
1239	(prepare, check and other idle watchers do not count). That is, as long	1957	priority are pending (prepare, check and other idle watchers do not count
1240	as your process is busy handling sockets or timeouts (or even signals,	1958	as receiving "events").
1241	imagine) it will not be triggered. But when your process is idle all idle	1959
1242	watchers are being called again and again, once per event loop iteration -	1960	That is, as long as your process is busy handling sockets or timeouts
		1961	(or even signals, imagine) of the same or higher priority it will not be
		1962	triggered. But when your process is idle (or only lower-priority watchers
		1963	are pending), the idle watchers are being called once per event loop
1243	until stopped, that is, or your process receives more events and becomes	1964	iteration - until stopped, that is, or your process receives more events
1244	busy.	1965	and becomes busy again with higher priority stuff.
1245		1966
1246	The most noteworthy effect is that as long as any idle watchers are	1967	The most noteworthy effect is that as long as any idle watchers are
1247	active, the process will not block when waiting for new events.	1968	active, the process will not block when waiting for new events.
1248		1969
1249	Apart from keeping your process non-blocking (which is a useful	1970	Apart from keeping your process non-blocking (which is a useful
1250	effect on its own sometimes), idle watchers are a good place to do	1971	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1972	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1973	event loop has handled all outstanding events.
1253		1974
		1975	=head3 Watcher-Specific Functions and Data Members
		1976
1254	=over 4	1977	=over 4
1255		1978
1256	=item ev_idle_init (ev_signal *, callback)	1979	=item ev_idle_init (ev_signal *, callback)
1257		1980
1258	Initialises and configures the idle watcher - it has no parameters of any	1981	Initialises and configures the idle watcher - it has no parameters of any
1259	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1983	believe me.
1261		1984
1262	=back	1985	=back
1263		1986
		1987	=head3 Examples
		1988
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1990	callback, free it. Also, use no error checking, as usual.
1266		1991
1267	static void	1992	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1994	{
1270	free (w);	1995	free (w);
1271	// now do something you wanted to do when the program has	1996	// now do something you wanted to do when the program has
1272	// no longer asnything immediate to do.	1997	// no longer anything immediate to do.
1273	}	1998	}
1274		1999
1275	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1276	ev_idle_init (idle_watcher, idle_cb);	2001	ev_idle_init (idle_watcher, idle_cb);
1277	ev_idle_start (loop, idle_cb);	2002	ev_idle_start (loop, idle_cb);
1278		2003
1279		2004
1280	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1281		2006
1282	Prepare and check watchers are usually (but not always) used in tandem:	2007	Prepare and check watchers are usually (but not always) used in pairs:
1283	prepare watchers get invoked before the process blocks and check watchers	2008	prepare watchers get invoked before the process blocks and check watchers
1284	afterwards.	2009	afterwards.
1285		2010
1286	You I<must not> call C<ev_loop> or similar functions that enter	2011	You I<must not> call C<ev_loop> or similar functions that enter
1287	the current event loop from either C<ev_prepare> or C<ev_check>	2012	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1290	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2015	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1291	C<ev_check> so if you have one watcher of each kind they will always be	2016	C<ev_check> so if you have one watcher of each kind they will always be
1292	called in pairs bracketing the blocking call.	2017	called in pairs bracketing the blocking call.
1293		2018
1294	Their main purpose is to integrate other event mechanisms into libev and	2019	Their main purpose is to integrate other event mechanisms into libev and
1295	their use is somewhat advanced. This could be used, for example, to track	2020	their use is somewhat advanced. They could be used, for example, to track
1296	variable changes, implement your own watchers, integrate net-snmp or a	2021	variable changes, implement your own watchers, integrate net-snmp or a
1297	coroutine library and lots more. They are also occasionally useful if	2022	coroutine library and lots more. They are also occasionally useful if
1298	you cache some data and want to flush it before blocking (for example,	2023	you cache some data and want to flush it before blocking (for example,
1299	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2024	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1300	watcher).	2025	watcher).
1301		2026
1302	This is done by examining in each prepare call which file descriptors need	2027	This is done by examining in each prepare call which file descriptors
1303	to be watched by the other library, registering C<ev_io> watchers for	2028	need to be watched by the other library, registering C<ev_io> watchers
1304	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2029	for them and starting an C<ev_timer> watcher for any timeouts (many
1305	provide just this functionality). Then, in the check watcher you check for	2030	libraries provide exactly this functionality). Then, in the check watcher,
1306	any events that occured (by checking the pending status of all watchers	2031	you check for any events that occurred (by checking the pending status
1307	and stopping them) and call back into the library. The I/O and timer	2032	of all watchers and stopping them) and call back into the library. The
1308	callbacks will never actually be called (but must be valid nevertheless,	2033	I/O and timer callbacks will never actually be called (but must be valid
1309	because you never know, you know?).	2034	nevertheless, because you never know, you know?).
1310		2035
1311	As another example, the Perl Coro module uses these hooks to integrate	2036	As another example, the Perl Coro module uses these hooks to integrate
1312	coroutines into libev programs, by yielding to other active coroutines	2037	coroutines into libev programs, by yielding to other active coroutines
1313	during each prepare and only letting the process block if no coroutines	2038	during each prepare and only letting the process block if no coroutines
1314	are ready to run (it's actually more complicated: it only runs coroutines	2039	are ready to run (it's actually more complicated: it only runs coroutines
1315	with priority higher than or equal to the event loop and one coroutine	2040	with priority higher than or equal to the event loop and one coroutine
1316	of lower priority, but only once, using idle watchers to keep the event	2041	of lower priority, but only once, using idle watchers to keep the event
1317	loop from blocking if lower-priority coroutines are active, thus mapping	2042	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	2043	low-priority coroutines to idle/background tasks).
1319		2044
		2045	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2046	priority, to ensure that they are being run before any other watchers
		2047	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2048
		2049	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2050	activate ("feed") events into libev. While libev fully supports this, they
		2051	might get executed before other C<ev_check> watchers did their job. As
		2052	C<ev_check> watchers are often used to embed other (non-libev) event
		2053	loops those other event loops might be in an unusable state until their
		2054	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2055	others).
		2056
		2057	=head3 Watcher-Specific Functions and Data Members
		2058
1320	=over 4	2059	=over 4
1321		2060
1322	=item ev_prepare_init (ev_prepare *, callback)	2061	=item ev_prepare_init (ev_prepare *, callback)
1323		2062
1324	=item ev_check_init (ev_check *, callback)	2063	=item ev_check_init (ev_check *, callback)
1325		2064
1326	Initialises and configures the prepare or check watcher - they have no	2065	Initialises and configures the prepare or check watcher - they have no
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2066	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1328	macros, but using them is utterly, utterly and completely pointless.	2067	macros, but using them is utterly, utterly, utterly and completely
		2068	pointless.
1329		2069
1330	=back	2070	=back
1331		2071
1332	Example: To include a library such as adns, you would add IO watchers	2072	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	2073
		2074	There are a number of principal ways to embed other event loops or modules
		2075	into libev. Here are some ideas on how to include libadns into libev
		2076	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2077	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2078	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2079	Glib event loop).
		2080
		2081	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1334	in a check watcher, destroy them and call into libadns. What follows is	2082	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	2083	is pseudo-code only of course. This requires you to either use a low
		2084	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2085	the callbacks for the IO/timeout watchers might not have been called yet.
1336		2086
1337	static ev_io iow [nfd];	2087	static ev_io iow [nfd];
1338	static ev_timer tw;	2088	static ev_timer tw;
1339		2089
1340	static void	2090	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	2091	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	2092	{
1343	// set the relevant poll flags
1344	// could also call adns_processreadable etc. here
1345	struct pollfd *fd = (struct pollfd *)w->data;
1346	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1347	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1348	}	2093	}
1349		2094
1350	// create io watchers for each fd and a timer before blocking	2095	// create io watchers for each fd and a timer before blocking
1351	static void	2096	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	2098	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	2099	int timeout = 3600000;
		2100	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	2101	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		2103
1358	/* the callback is illegal, but won't be called as we stop during check */	2104	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	2105	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	2106	ev_timer_start (loop, &tw);
1361		2107
1362	// create on ev_io per pollfd	2108	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	2109	for (int i = 0; i < nfd; ++i)
1364	{	2110	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	2111	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	2112	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2113	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		2114
1369	fds [i].revents = 0;	2115	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	2116	ev_io_start (loop, iow + i);
1372	}	2117	}
1373	}	2118	}
1374		2119
1375	// stop all watchers after blocking	2120	// stop all watchers after blocking
1376	static void	2121	static void
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	2123	{
1379	ev_timer_stop (loop, &tw);	2124	ev_timer_stop (loop, &tw);
1380		2125
1381	for (int i = 0; i < nfd; ++i)	2126	for (int i = 0; i < nfd; ++i)
		2127	{
		2128	// set the relevant poll flags
		2129	// could also call adns_processreadable etc. here
		2130	struct pollfd *fd = fds + i;
		2131	int revents = ev_clear_pending (iow + i);
		2132	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2133	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2134
		2135	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	2136	ev_io_stop (loop, iow + i);
		2137	}
1383		2138
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2139	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1385	}	2140	}
		2141
		2142	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2143	in the prepare watcher and would dispose of the check watcher.
		2144
		2145	Method 3: If the module to be embedded supports explicit event
		2146	notification (libadns does), you can also make use of the actual watcher
		2147	callbacks, and only destroy/create the watchers in the prepare watcher.
		2148
		2149	static void
		2150	timer_cb (EV_P_ ev_timer *w, int revents)
		2151	{
		2152	adns_state ads = (adns_state)w->data;
		2153	update_now (EV_A);
		2154
		2155	adns_processtimeouts (ads, &tv_now);
		2156	}
		2157
		2158	static void
		2159	io_cb (EV_P_ ev_io *w, int revents)
		2160	{
		2161	adns_state ads = (adns_state)w->data;
		2162	update_now (EV_A);
		2163
		2164	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2165	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2166	}
		2167
		2168	// do not ever call adns_afterpoll
		2169
		2170	Method 4: Do not use a prepare or check watcher because the module you
		2171	want to embed is not flexible enough to support it. Instead, you can
		2172	override their poll function. The drawback with this solution is that the
		2173	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2174	this approach, effectively embedding EV as a client into the horrible
		2175	libglib event loop.
		2176
		2177	static gint
		2178	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2179	{
		2180	int got_events = 0;
		2181
		2182	for (n = 0; n < nfds; ++n)
		2183	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2184
		2185	if (timeout >= 0)
		2186	// create/start timer
		2187
		2188	// poll
		2189	ev_loop (EV_A_ 0);
		2190
		2191	// stop timer again
		2192	if (timeout >= 0)
		2193	ev_timer_stop (EV_A_ &to);
		2194
		2195	// stop io watchers again - their callbacks should have set
		2196	for (n = 0; n < nfds; ++n)
		2197	ev_io_stop (EV_A_ iow [n]);
		2198
		2199	return got_events;
		2200	}
1386		2201
1387		2202
1388	=head2 C<ev_embed> - when one backend isn't enough...	2203	=head2 C<ev_embed> - when one backend isn't enough...
1389		2204
1390	This is a rather advanced watcher type that lets you embed one event loop	2205	This is a rather advanced watcher type that lets you embed one event loop
…		…
1396	prioritise I/O.	2211	prioritise I/O.
1397		2212
1398	As an example for a bug workaround, the kqueue backend might only support	2213	As an example for a bug workaround, the kqueue backend might only support
1399	sockets on some platform, so it is unusable as generic backend, but you	2214	sockets on some platform, so it is unusable as generic backend, but you
1400	still want to make use of it because you have many sockets and it scales	2215	still want to make use of it because you have many sockets and it scales
1401	so nicely. In this case, you would create a kqueue-based loop and embed it	2216	so nicely. In this case, you would create a kqueue-based loop and embed
1402	into your default loop (which might use e.g. poll). Overall operation will	2217	it into your default loop (which might use e.g. poll). Overall operation
1403	be a bit slower because first libev has to poll and then call kevent, but	2218	will be a bit slower because first libev has to call C<poll> and then
1404	at least you can use both at what they are best.	2219	C<kevent>, but at least you can use both mechanisms for what they are
		2220	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1405		2221
1406	As for prioritising I/O: rarely you have the case where some fds have	2222	As for prioritising I/O: under rare circumstances you have the case where
1407	to be watched and handled very quickly (with low latency), and even	2223	some fds have to be watched and handled very quickly (with low latency),
1408	priorities and idle watchers might have too much overhead. In this case	2224	and even priorities and idle watchers might have too much overhead. In
1409	you would put all the high priority stuff in one loop and all the rest in	2225	this case you would put all the high priority stuff in one loop and all
1410	a second one, and embed the second one in the first.	2226	the rest in a second one, and embed the second one in the first.
1411		2227
1412	As long as the watcher is active, the callback will be invoked every time	2228	As long as the watcher is active, the callback will be invoked every time
1413	there might be events pending in the embedded loop. The callback must then	2229	there might be events pending in the embedded loop. The callback must then
1414	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1415	their callbacks (you could also start an idle watcher to give the embedded	2231	their callbacks (you could also start an idle watcher to give the embedded
…		…
1423	interested in that.	2239	interested in that.
1424		2240
1425	Also, there have not currently been made special provisions for forking:	2241	Also, there have not currently been made special provisions for forking:
1426	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1427	but you will also have to stop and restart any C<ev_embed> watchers	2243	but you will also have to stop and restart any C<ev_embed> watchers
1428	yourself.	2244	yourself - but you can use a fork watcher to handle this automatically,
		2245	and future versions of libev might do just that.
1429		2246
1430	Unfortunately, not all backends are embeddable, only the ones returned by	2247	Unfortunately, not all backends are embeddable: only the ones returned by
1431	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1432	portable one.	2249	portable one.
1433		2250
1434	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
1435	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
1436	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
1437	create it, and if that fails, use the normal loop for everything:	2254	create it, and if that fails, use the normal loop for everything.
1438		2255
1439	struct ev_loop *loop_hi = ev_default_init (0);	2256	=head3 C<ev_embed> and fork
1440	struct ev_loop *loop_lo = 0;
1441	struct ev_embed embed;
1442
1443	// see if there is a chance of getting one that works
1444	// (remember that a flags value of 0 means autodetection)
1445	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1446	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1447	: 0;
1448		2257
1449	// if we got one, then embed it, otherwise default to loop_hi	2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
1450	if (loop_lo)	2259	automatically be applied to the embedded loop as well, so no special
1451	{	2260	fork handling is required in that case. When the watcher is not running,
1452	ev_embed_init (&embed, 0, loop_lo);	2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1453	ev_embed_start (loop_hi, &embed);	2262	as applicable.
1454	}	2263
1455	else	2264	=head3 Watcher-Specific Functions and Data Members
1456	loop_lo = loop_hi;
1457		2265
1458	=over 4	2266	=over 4
1459		2267
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2268	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1461		2269
…		…
1463		2271
1464	Configures the watcher to embed the given loop, which must be	2272	Configures the watcher to embed the given loop, which must be
1465	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2273	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1466	invoked automatically, otherwise it is the responsibility of the callback	2274	invoked automatically, otherwise it is the responsibility of the callback
1467	to invoke it (it will continue to be called until the sweep has been done,	2275	to invoke it (it will continue to be called until the sweep has been done,
1468	if you do not want thta, you need to temporarily stop the embed watcher).	2276	if you do not want that, you need to temporarily stop the embed watcher).
1469		2277
1470	=item ev_embed_sweep (loop, ev_embed *)	2278	=item ev_embed_sweep (loop, ev_embed *)
1471		2279
1472	Make a single, non-blocking sweep over the embedded loop. This works	2280	Make a single, non-blocking sweep over the embedded loop. This works
1473	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2281	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1474	apropriate way for embedded loops.	2282	appropriate way for embedded loops.
1475		2283
1476	=item struct ev_loop *loop [read-only]	2284	=item struct ev_loop *other [read-only]
1477		2285
1478	The embedded event loop.	2286	The embedded event loop.
1479		2287
1480	=back	2288	=back
		2289
		2290	=head3 Examples
		2291
		2292	Example: Try to get an embeddable event loop and embed it into the default
		2293	event loop. If that is not possible, use the default loop. The default
		2294	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2296	used).
		2297
		2298	struct ev_loop *loop_hi = ev_default_init (0);
		2299	struct ev_loop *loop_lo = 0;
		2300	struct ev_embed embed;
		2301
		2302	// see if there is a chance of getting one that works
		2303	// (remember that a flags value of 0 means autodetection)
		2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2306	: 0;
		2307
		2308	// if we got one, then embed it, otherwise default to loop_hi
		2309	if (loop_lo)
		2310	{
		2311	ev_embed_init (&embed, 0, loop_lo);
		2312	ev_embed_start (loop_hi, &embed);
		2313	}
		2314	else
		2315	loop_lo = loop_hi;
		2316
		2317	Example: Check if kqueue is available but not recommended and create
		2318	a kqueue backend for use with sockets (which usually work with any
		2319	kqueue implementation). Store the kqueue/socket-only event loop in
		2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2321
		2322	struct ev_loop *loop = ev_default_init (0);
		2323	struct ev_loop *loop_socket = 0;
		2324	struct ev_embed embed;
		2325
		2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2328	{
		2329	ev_embed_init (&embed, 0, loop_socket);
		2330	ev_embed_start (loop, &embed);
		2331	}
		2332
		2333	if (!loop_socket)
		2334	loop_socket = loop;
		2335
		2336	// now use loop_socket for all sockets, and loop for everything else
1481		2337
1482		2338
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2339	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2340
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2341	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1488	event loop blocks next and before C<ev_check> watchers are being called,	2344	event loop blocks next and before C<ev_check> watchers are being called,
1489	and only in the child after the fork. If whoever good citizen calling	2345	and only in the child after the fork. If whoever good citizen calling
1490	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2346	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2347	handlers will be invoked, too, of course.
1492		2348
		2349	=head3 Watcher-Specific Functions and Data Members
		2350
1493	=over 4	2351	=over 4
1494		2352
1495	=item ev_fork_init (ev_signal *, callback)	2353	=item ev_fork_init (ev_signal *, callback)
1496		2354
1497	Initialises and configures the fork watcher - it has no parameters of any	2355	Initialises and configures the fork watcher - it has no parameters of any
…		…
1499	believe me.	2357	believe me.
1500		2358
1501	=back	2359	=back
1502		2360
1503		2361
		2362	=head2 C<ev_async> - how to wake up another event loop
		2363
		2364	In general, you cannot use an C<ev_loop> from multiple threads or other
		2365	asynchronous sources such as signal handlers (as opposed to multiple event
		2366	loops - those are of course safe to use in different threads).
		2367
		2368	Sometimes, however, you need to wake up another event loop you do not
		2369	control, for example because it belongs to another thread. This is what
		2370	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2371	can signal it by calling C<ev_async_send>, which is thread- and signal
		2372	safe.
		2373
		2374	This functionality is very similar to C<ev_signal> watchers, as signals,
		2375	too, are asynchronous in nature, and signals, too, will be compressed
		2376	(i.e. the number of callback invocations may be less than the number of
		2377	C<ev_async_sent> calls).
		2378
		2379	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2380	just the default loop.
		2381
		2382	=head3 Queueing
		2383
		2384	C<ev_async> does not support queueing of data in any way. The reason
		2385	is that the author does not know of a simple (or any) algorithm for a
		2386	multiple-writer-single-reader queue that works in all cases and doesn't
		2387	need elaborate support such as pthreads.
		2388
		2389	That means that if you want to queue data, you have to provide your own
		2390	queue. But at least I can tell you how to implement locking around your
		2391	queue:
		2392
		2393	=over 4
		2394
		2395	=item queueing from a signal handler context
		2396
		2397	To implement race-free queueing, you simply add to the queue in the signal
		2398	handler but you block the signal handler in the watcher callback. Here is
		2399	an example that does that for some fictitious SIGUSR1 handler:
		2400
		2401	static ev_async mysig;
		2402
		2403	static void
		2404	sigusr1_handler (void)
		2405	{
		2406	sometype data;
		2407
		2408	// no locking etc.
		2409	queue_put (data);
		2410	ev_async_send (EV_DEFAULT_ &mysig);
		2411	}
		2412
		2413	static void
		2414	mysig_cb (EV_P_ ev_async *w, int revents)
		2415	{
		2416	sometype data;
		2417	sigset_t block, prev;
		2418
		2419	sigemptyset (&block);
		2420	sigaddset (&block, SIGUSR1);
		2421	sigprocmask (SIG_BLOCK, &block, &prev);
		2422
		2423	while (queue_get (&data))
		2424	process (data);
		2425
		2426	if (sigismember (&prev, SIGUSR1)
		2427	sigprocmask (SIG_UNBLOCK, &block, 0);
		2428	}
		2429
		2430	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2431	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2432	either...).
		2433
		2434	=item queueing from a thread context
		2435
		2436	The strategy for threads is different, as you cannot (easily) block
		2437	threads but you can easily preempt them, so to queue safely you need to
		2438	employ a traditional mutex lock, such as in this pthread example:
		2439
		2440	static ev_async mysig;
		2441	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2442
		2443	static void
		2444	otherthread (void)
		2445	{
		2446	// only need to lock the actual queueing operation
		2447	pthread_mutex_lock (&mymutex);
		2448	queue_put (data);
		2449	pthread_mutex_unlock (&mymutex);
		2450
		2451	ev_async_send (EV_DEFAULT_ &mysig);
		2452	}
		2453
		2454	static void
		2455	mysig_cb (EV_P_ ev_async *w, int revents)
		2456	{
		2457	pthread_mutex_lock (&mymutex);
		2458
		2459	while (queue_get (&data))
		2460	process (data);
		2461
		2462	pthread_mutex_unlock (&mymutex);
		2463	}
		2464
		2465	=back
		2466
		2467
		2468	=head3 Watcher-Specific Functions and Data Members
		2469
		2470	=over 4
		2471
		2472	=item ev_async_init (ev_async *, callback)
		2473
		2474	Initialises and configures the async watcher - it has no parameters of any
		2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2476	trust me.
		2477
		2478	=item ev_async_send (loop, ev_async *)
		2479
		2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2482	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2484	section below on what exactly this means).
		2485
		2486	This call incurs the overhead of a system call only once per loop iteration,
		2487	so while the overhead might be noticeable, it doesn't apply to repeated
		2488	calls to C<ev_async_send>.
		2489
		2490	=item bool = ev_async_pending (ev_async *)
		2491
		2492	Returns a non-zero value when C<ev_async_send> has been called on the
		2493	watcher but the event has not yet been processed (or even noted) by the
		2494	event loop.
		2495
		2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2497	the loop iterates next and checks for the watcher to have become active,
		2498	it will reset the flag again. C<ev_async_pending> can be used to very
		2499	quickly check whether invoking the loop might be a good idea.
		2500
		2501	Not that this does I<not> check whether the watcher itself is pending, only
		2502	whether it has been requested to make this watcher pending.
		2503
		2504	=back
		2505
		2506
1504	=head1 OTHER FUNCTIONS	2507	=head1 OTHER FUNCTIONS
1505		2508
1506	There are some other functions of possible interest. Described. Here. Now.	2509	There are some other functions of possible interest. Described. Here. Now.
1507		2510
1508	=over 4	2511	=over 4
1509		2512
1510	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1511		2514
1512	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
1513	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
1514	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
1515	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
1516	more watchers yourself.	2519	more watchers yourself.
1517		2520
1518	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
1519	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1520	C<events> set will be craeted and started.	2523	the given C<fd> and C<events> set will be created and started.
1521		2524
1522	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
1523	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1524	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
1525	dubious value.
1526		2528
1527	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2529	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1528	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
1529	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1530	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
1531		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2537
1532	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
1533	{	2539	{
1534	if (revents & EV_TIMEOUT)
1535	/* doh, nothing entered */;
1536	else if (revents & EV_READ)	2540	if (revents & EV_READ)
1537	/* stdin might have data for us, joy! */;	2541	/* stdin might have data for us, joy! */;
		2542	else if (revents & EV_TIMEOUT)
		2543	/* doh, nothing entered */;
1538	}	2544	}
1539		2545
1540	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1541		2547
1542	=item ev_feed_event (ev_loop *, watcher *, int revents)	2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
1543		2549
1544	Feeds the given event set into the event loop, as if the specified event	2550	Feeds the given event set into the event loop, as if the specified event
1545	had happened for the specified watcher (which must be a pointer to an	2551	had happened for the specified watcher (which must be a pointer to an
…		…
1550	Feed an event on the given fd, as if a file descriptor backend detected	2556	Feed an event on the given fd, as if a file descriptor backend detected
1551	the given events it.	2557	the given events it.
1552		2558
1553	=item ev_feed_signal_event (ev_loop *loop, int signum)	2559	=item ev_feed_signal_event (ev_loop *loop, int signum)
1554		2560
1555	Feed an event as if the given signal occured (C<loop> must be the default	2561	Feed an event as if the given signal occurred (C<loop> must be the default
1556	loop!).	2562	loop!).
1557		2563
1558	=back	2564	=back
1559		2565
1560		2566
…		…
1576		2582
1577	=item * Priorities are not currently supported. Initialising priorities	2583	=item * Priorities are not currently supported. Initialising priorities
1578	will fail and all watchers will have the same priority, even though there	2584	will fail and all watchers will have the same priority, even though there
1579	is an ev_pri field.	2585	is an ev_pri field.
1580		2586
		2587	=item * In libevent, the last base created gets the signals, in libev, the
		2588	first base created (== the default loop) gets the signals.
		2589
1581	=item * Other members are not supported.	2590	=item * Other members are not supported.
1582		2591
1583	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2592	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1584	to use the libev header file and library.	2593	to use the libev header file and library.
1585		2594
1586	=back	2595	=back
1587		2596
1588	=head1 C++ SUPPORT	2597	=head1 C++ SUPPORT
1589		2598
1590	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2599	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1591	you to use some convinience methods to start/stop watchers and also change	2600	you to use some convenience methods to start/stop watchers and also change
1592	the callback model to a model using method callbacks on objects.	2601	the callback model to a model using method callbacks on objects.
1593		2602
1594	To use it,	2603	To use it,
1595		2604
1596	#include <ev++.h>	2605	#include <ev++.h>
1597		2606
1598	(it is not installed by default). This automatically includes F<ev.h>	2607	This automatically includes F<ev.h> and puts all of its definitions (many
1599	and puts all of its definitions (many of them macros) into the global	2608	of them macros) into the global namespace. All C++ specific things are
1600	namespace. All C++ specific things are put into the C<ev> namespace.	2609	put into the C<ev> namespace. It should support all the same embedding
		2610	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2611
1602	It should support all the same embedding options as F<ev.h>, most notably	2612	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2613	classes add (compared to plain C-style watchers) is the event loop pointer
		2614	that the watcher is associated with (or no additional members at all if
		2615	you disable C<EV_MULTIPLICITY> when embedding libev).
		2616
		2617	Currently, functions, and static and non-static member functions can be
		2618	used as callbacks. Other types should be easy to add as long as they only
		2619	need one additional pointer for context. If you need support for other
		2620	types of functors please contact the author (preferably after implementing
		2621	it).
1604		2622
1605	Here is a list of things available in the C<ev> namespace:	2623	Here is a list of things available in the C<ev> namespace:
1606		2624
1607	=over 4	2625	=over 4
1608		2626
…		…
1624		2642
1625	All of those classes have these methods:	2643	All of those classes have these methods:
1626		2644
1627	=over 4	2645	=over 4
1628		2646
1629	=item ev::TYPE::TYPE (object *, object::method *)	2647	=item ev::TYPE::TYPE ()
1630		2648
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2649	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2650
1633	=item ev::TYPE::~TYPE	2651	=item ev::TYPE::~TYPE
1634		2652
1635	The constructor takes a pointer to an object and a method pointer to	2653	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2654	with. If it is omitted, it will use C<EV_DEFAULT>.
1637	C<ev_init> for you, which means you have to call the C<set> method	2655
1638	before starting it. If you do not specify a loop then the constructor	2656	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2657	C<set> method before starting it.
		2658
		2659	It will not set a callback, however: You have to call the templated C<set>
		2660	method to set a callback before you can start the watcher.
		2661
		2662	(The reason why you have to use a method is a limitation in C++ which does
		2663	not allow explicit template arguments for constructors).
1640		2664
1641	The destructor automatically stops the watcher if it is active.	2665	The destructor automatically stops the watcher if it is active.
		2666
		2667	=item w->set<class, &class::method> (object *)
		2668
		2669	This method sets the callback method to call. The method has to have a
		2670	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2671	first argument and the C<revents> as second. The object must be given as
		2672	parameter and is stored in the C<data> member of the watcher.
		2673
		2674	This method synthesizes efficient thunking code to call your method from
		2675	the C callback that libev requires. If your compiler can inline your
		2676	callback (i.e. it is visible to it at the place of the C<set> call and
		2677	your compiler is good :), then the method will be fully inlined into the
		2678	thunking function, making it as fast as a direct C callback.
		2679
		2680	Example: simple class declaration and watcher initialisation
		2681
		2682	struct myclass
		2683	{
		2684	void io_cb (ev::io &w, int revents) { }
		2685	}
		2686
		2687	myclass obj;
		2688	ev::io iow;
		2689	iow.set <myclass, &myclass::io_cb> (&obj);
		2690
		2691	=item w->set<function> (void *data = 0)
		2692
		2693	Also sets a callback, but uses a static method or plain function as
		2694	callback. The optional C<data> argument will be stored in the watcher's
		2695	C<data> member and is free for you to use.
		2696
		2697	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2698
		2699	See the method-C<set> above for more details.
		2700
		2701	Example: Use a plain function as callback.
		2702
		2703	static void io_cb (ev::io &w, int revents) { }
		2704	iow.set <io_cb> ();
1642		2705
1643	=item w->set (struct ev_loop *)	2706	=item w->set (struct ev_loop *)
1644		2707
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2708	Associates a different C<struct ev_loop> with this watcher. You can only
1646	do this when the watcher is inactive (and not pending either).	2709	do this when the watcher is inactive (and not pending either).
1647		2710
1648	=item w->set ([args])	2711	=item w->set ([arguments])
1649		2712
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2713	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1651	called at least once. Unlike the C counterpart, an active watcher gets	2714	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2715	automatically stopped and restarted when reconfiguring it with this
		2716	method.
1653		2717
1654	=item w->start ()	2718	=item w->start ()
1655		2719
1656	Starts the watcher. Note that there is no C<loop> argument as the	2720	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2721	constructor already stores the event loop.
1658		2722
1659	=item w->stop ()	2723	=item w->stop ()
1660		2724
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2725	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2726
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2727	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2728
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2729	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2730	C<ev_TYPE_again> function.
1667		2731
1668	=item w->sweep () C<ev::embed> only	2732	=item w->sweep () (C<ev::embed> only)
1669		2733
1670	Invokes C<ev_embed_sweep>.	2734	Invokes C<ev_embed_sweep>.
1671		2735
1672	=item w->update () C<ev::stat> only	2736	=item w->update () (C<ev::stat> only)
1673		2737
1674	Invokes C<ev_stat_stat>.	2738	Invokes C<ev_stat_stat>.
1675		2739
1676	=back	2740	=back
1677		2741
1678	=back	2742	=back
1679		2743
1680	Example: Define a class with an IO and idle watcher, start one of them in	2744	Example: Define a class with an IO and idle watcher, start one of them in
1681	the constructor.	2745	the constructor.
1682		2746
1683	class myclass	2747	class myclass
1684	{	2748	{
1685	ev_io io; void io_cb (ev::io &w, int revents);	2749	ev::io io ; void io_cb (ev::io &w, int revents);
1686	ev_idle idle void idle_cb (ev::idle &w, int revents);	2750	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1687		2751
1688	myclass ();	2752	myclass (int fd)
1689	}	2753	{
		2754	io .set <myclass, &myclass::io_cb > (this);
		2755	idle.set <myclass, &myclass::idle_cb> (this);
1690		2756
1691	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{
1695	io.start (fd, ev::READ);	2757	io.start (fd, ev::READ);
		2758	}
1696	}	2759	};
		2760
		2761
		2762	=head1 OTHER LANGUAGE BINDINGS
		2763
		2764	Libev does not offer other language bindings itself, but bindings for a
		2765	number of languages exist in the form of third-party packages. If you know
		2766	any interesting language binding in addition to the ones listed here, drop
		2767	me a note.
		2768
		2769	=over 4
		2770
		2771	=item Perl
		2772
		2773	The EV module implements the full libev API and is actually used to test
		2774	libev. EV is developed together with libev. Apart from the EV core module,
		2775	there are additional modules that implement libev-compatible interfaces
		2776	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2777	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2778	and C<EV::Glib>).
		2779
		2780	It can be found and installed via CPAN, its homepage is at
		2781	L<http://software.schmorp.de/pkg/EV>.
		2782
		2783	=item Python
		2784
		2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2786	seems to be quite complete and well-documented. Note, however, that the
		2787	patch they require for libev is outright dangerous as it breaks the ABI
		2788	for everybody else, and therefore, should never be applied in an installed
		2789	libev (if python requires an incompatible ABI then it needs to embed
		2790	libev).
		2791
		2792	=item Ruby
		2793
		2794	Tony Arcieri has written a ruby extension that offers access to a subset
		2795	of the libev API and adds file handle abstractions, asynchronous DNS and
		2796	more on top of it. It can be found via gem servers. Its homepage is at
		2797	L<http://rev.rubyforge.org/>.
		2798
		2799	=item D
		2800
		2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2803
		2804	=back
1697		2805
1698		2806
1699	=head1 MACRO MAGIC	2807	=head1 MACRO MAGIC
1700		2808
1701	Libev can be compiled with a variety of options, the most fundemantal is	2809	Libev can be compiled with a variety of options, the most fundamental
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2810	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2811	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2812
1705	To make it easier to write programs that cope with either variant, the	2813	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2814	following macros are defined:
1707		2815
1708	=over 4	2816	=over 4
…		…
1711		2819
1712	This provides the loop I<argument> for functions, if one is required ("ev	2820	This provides the loop I<argument> for functions, if one is required ("ev
1713	loop argument"). The C<EV_A> form is used when this is the sole argument,	2821	loop argument"). The C<EV_A> form is used when this is the sole argument,
1714	C<EV_A_> is used when other arguments are following. Example:	2822	C<EV_A_> is used when other arguments are following. Example:
1715		2823
1716	ev_unref (EV_A);	2824	ev_unref (EV_A);
1717	ev_timer_add (EV_A_ watcher);	2825	ev_timer_add (EV_A_ watcher);
1718	ev_loop (EV_A_ 0);	2826	ev_loop (EV_A_ 0);
1719		2827
1720	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2828	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1721	which is often provided by the following macro.	2829	which is often provided by the following macro.
1722		2830
1723	=item C<EV_P>, C<EV_P_>	2831	=item C<EV_P>, C<EV_P_>
1724		2832
1725	This provides the loop I<parameter> for functions, if one is required ("ev	2833	This provides the loop I<parameter> for functions, if one is required ("ev
1726	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2834	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1727	C<EV_P_> is used when other parameters are following. Example:	2835	C<EV_P_> is used when other parameters are following. Example:
1728		2836
1729	// this is how ev_unref is being declared	2837	// this is how ev_unref is being declared
1730	static void ev_unref (EV_P);	2838	static void ev_unref (EV_P);
1731		2839
1732	// this is how you can declare your typical callback	2840	// this is how you can declare your typical callback
1733	static void cb (EV_P_ ev_timer *w, int revents)	2841	static void cb (EV_P_ ev_timer *w, int revents)
1734		2842
1735	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2843	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1736	suitable for use with C<EV_A>.	2844	suitable for use with C<EV_A>.
1737		2845
1738	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1739		2847
1740	Similar to the other two macros, this gives you the value of the default	2848	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2849	loop, if multiple loops are supported ("ev loop default").
1742		2850
		2851	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2852
		2853	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2854	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2855	is undefined when the default loop has not been initialised by a previous
		2856	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2857
		2858	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2859	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2860
1743	=back	2861	=back
1744		2862
1745	Example: Declare and initialise a check watcher, working regardless of	2863	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2864	macros so it will work regardless of whether multiple loops are supported
		2865	or not.
1747		2866
1748	static void	2867	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2868	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2869	{
1751	ev_check_stop (EV_A_ w);	2870	ev_check_stop (EV_A_ w);
1752	}	2871	}
1753		2872
1754	ev_check check;	2873	ev_check check;
1755	ev_check_init (&check, check_cb);	2874	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2875	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2876	ev_loop (EV_DEFAULT_ 0);
1758
1759		2877
1760	=head1 EMBEDDING	2878	=head1 EMBEDDING
1761		2879
1762	Libev can (and often is) directly embedded into host	2880	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2881	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2882	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2883	and rxvt-unicode.
1766		2884
1767	The goal is to enable you to just copy the neecssary files into your	2885	The goal is to enable you to just copy the necessary files into your
1768	source directory without having to change even a single line in them, so	2886	source directory without having to change even a single line in them, so
1769	you can easily upgrade by simply copying (or having a checked-out copy of	2887	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2888	libev somewhere in your source tree).
1771		2889
1772	=head2 FILESETS	2890	=head2 FILESETS
1773		2891
1774	Depending on what features you need you need to include one or more sets of files	2892	Depending on what features you need you need to include one or more sets of files
1775	in your app.	2893	in your application.
1776		2894
1777	=head3 CORE EVENT LOOP	2895	=head3 CORE EVENT LOOP
1778		2896
1779	To include only the libev core (all the C<ev_*> functions), with manual	2897	To include only the libev core (all the C<ev_*> functions), with manual
1780	configuration (no autoconf):	2898	configuration (no autoconf):
1781		2899
1782	#define EV_STANDALONE 1	2900	#define EV_STANDALONE 1
1783	#include "ev.c"	2901	#include "ev.c"
1784		2902
1785	This will automatically include F<ev.h>, too, and should be done in a	2903	This will automatically include F<ev.h>, too, and should be done in a
1786	single C source file only to provide the function implementations. To use	2904	single C source file only to provide the function implementations. To use
1787	it, do the same for F<ev.h> in all files wishing to use this API (best	2905	it, do the same for F<ev.h> in all files wishing to use this API (best
1788	done by writing a wrapper around F<ev.h> that you can include instead and	2906	done by writing a wrapper around F<ev.h> that you can include instead and
1789	where you can put other configuration options):	2907	where you can put other configuration options):
1790		2908
1791	#define EV_STANDALONE 1	2909	#define EV_STANDALONE 1
1792	#include "ev.h"	2910	#include "ev.h"
1793		2911
1794	Both header files and implementation files can be compiled with a C++	2912	Both header files and implementation files can be compiled with a C++
1795	compiler (at least, thats a stated goal, and breakage will be treated	2913	compiler (at least, thats a stated goal, and breakage will be treated
1796	as a bug).	2914	as a bug).
1797		2915
1798	You need the following files in your source tree, or in a directory	2916	You need the following files in your source tree, or in a directory
1799	in your include path (e.g. in libev/ when using -Ilibev):	2917	in your include path (e.g. in libev/ when using -Ilibev):
1800		2918
1801	ev.h	2919	ev.h
1802	ev.c	2920	ev.c
1803	ev_vars.h	2921	ev_vars.h
1804	ev_wrap.h	2922	ev_wrap.h
1805		2923
1806	ev_win32.c required on win32 platforms only	2924	ev_win32.c required on win32 platforms only
1807		2925
1808	ev_select.c only when select backend is enabled (which is by default)	2926	ev_select.c only when select backend is enabled (which is enabled by default)
1809	ev_poll.c only when poll backend is enabled (disabled by default)	2927	ev_poll.c only when poll backend is enabled (disabled by default)
1810	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2928	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1811	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2929	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1812	ev_port.c only when the solaris port backend is enabled (disabled by default)	2930	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2931
1814	F<ev.c> includes the backend files directly when enabled, so you only need	2932	F<ev.c> includes the backend files directly when enabled, so you only need
1815	to compile this single file.	2933	to compile this single file.
1816		2934
1817	=head3 LIBEVENT COMPATIBILITY API	2935	=head3 LIBEVENT COMPATIBILITY API
1818		2936
1819	To include the libevent compatibility API, also include:	2937	To include the libevent compatibility API, also include:
1820		2938
1821	#include "event.c"	2939	#include "event.c"
1822		2940
1823	in the file including F<ev.c>, and:	2941	in the file including F<ev.c>, and:
1824		2942
1825	#include "event.h"	2943	#include "event.h"
1826		2944
1827	in the files that want to use the libevent API. This also includes F<ev.h>.	2945	in the files that want to use the libevent API. This also includes F<ev.h>.
1828		2946
1829	You need the following additional files for this:	2947	You need the following additional files for this:
1830		2948
1831	event.h	2949	event.h
1832	event.c	2950	event.c
1833		2951
1834	=head3 AUTOCONF SUPPORT	2952	=head3 AUTOCONF SUPPORT
1835		2953
1836	Instead of using C<EV_STANDALONE=1> and providing your config in	2954	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1837	whatever way you want, you can also C<m4_include([libev.m4])> in your	2955	whatever way you want, you can also C<m4_include([libev.m4])> in your
1838	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2956	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1839	include F<config.h> and configure itself accordingly.	2957	include F<config.h> and configure itself accordingly.
1840		2958
1841	For this of course you need the m4 file:	2959	For this of course you need the m4 file:
1842		2960
1843	libev.m4	2961	libev.m4
1844		2962
1845	=head2 PREPROCESSOR SYMBOLS/MACROS	2963	=head2 PREPROCESSOR SYMBOLS/MACROS
1846		2964
1847	Libev can be configured via a variety of preprocessor symbols you have to define	2965	Libev can be configured via a variety of preprocessor symbols you have to
1848	before including any of its files. The default is not to build for multiplicity	2966	define before including any of its files. The default in the absence of
1849	and only include the select backend.	2967	autoconf is documented for every option.
1850		2968
1851	=over 4	2969	=over 4
1852		2970
1853	=item EV_STANDALONE	2971	=item EV_STANDALONE
1854		2972
…		…
1859	F<event.h> that are not directly supported by the libev core alone.	2977	F<event.h> that are not directly supported by the libev core alone.
1860		2978
1861	=item EV_USE_MONOTONIC	2979	=item EV_USE_MONOTONIC
1862		2980
1863	If defined to be C<1>, libev will try to detect the availability of the	2981	If defined to be C<1>, libev will try to detect the availability of the
1864	monotonic clock option at both compiletime and runtime. Otherwise no use	2982	monotonic clock option at both compile time and runtime. Otherwise no use
1865	of the monotonic clock option will be attempted. If you enable this, you	2983	of the monotonic clock option will be attempted. If you enable this, you
1866	usually have to link against librt or something similar. Enabling it when	2984	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2985	the functionality isn't available is safe, though, although you have
1868	to make sure you link against any libraries where the C<clock_gettime>	2986	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2987	function is hiding in (often F<-lrt>).
1870		2988
1871	=item EV_USE_REALTIME	2989	=item EV_USE_REALTIME
1872		2990
1873	If defined to be C<1>, libev will try to detect the availability of the	2991	If defined to be C<1>, libev will try to detect the availability of the
1874	realtime clock option at compiletime (and assume its availability at	2992	real-time clock option at compile time (and assume its availability at
1875	runtime if successful). Otherwise no use of the realtime clock option will	2993	runtime if successful). Otherwise no use of the real-time clock option will
1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1877	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2997
		2998	=item EV_USE_NANOSLEEP
		2999
		3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3001	and will use it for delays. Otherwise it will use C<select ()>.
		3002
		3003	=item EV_USE_EVENTFD
		3004
		3005	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3006	available and will probe for kernel support at runtime. This will improve
		3007	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3008	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3009	2.7 or newer, otherwise disabled.
1879		3010
1880	=item EV_USE_SELECT	3011	=item EV_USE_SELECT
1881		3012
1882	If undefined or defined to be C<1>, libev will compile in support for the	3013	If undefined or defined to be C<1>, libev will compile in support for the
1883	C<select>(2) backend. No attempt at autodetection will be done: if no	3014	C<select>(2) backend. No attempt at auto-detection will be done: if no
1884	other method takes over, select will be it. Otherwise the select backend	3015	other method takes over, select will be it. Otherwise the select backend
1885	will not be compiled in.	3016	will not be compiled in.
1886		3017
1887	=item EV_SELECT_USE_FD_SET	3018	=item EV_SELECT_USE_FD_SET
1888		3019
1889	If defined to C<1>, then the select backend will use the system C<fd_set>	3020	If defined to C<1>, then the select backend will use the system C<fd_set>
1890	structure. This is useful if libev doesn't compile due to a missing	3021	structure. This is useful if libev doesn't compile due to a missing
1891	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
1892	exotic systems. This usually limits the range of file descriptors to some	3023	exotic systems. This usually limits the range of file descriptors to some
1893	low limit such as 1024 or might have other limitations (winsocket only	3024	low limit such as 1024 or might have other limitations (winsocket only
1894	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1895	influence the size of the C<fd_set> used.	3026	influence the size of the C<fd_set> used.
1896		3027
…		…
1902	be used is the winsock select). This means that it will call	3033	be used is the winsock select). This means that it will call
1903	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3034	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1904	it is assumed that all these functions actually work on fds, even	3035	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	3036	on win32. Should not be defined on non-win32 platforms.
1906		3037
		3038	=item EV_FD_TO_WIN32_HANDLE
		3039
		3040	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3041	file descriptors to socket handles. When not defining this symbol (the
		3042	default), then libev will call C<_get_osfhandle>, which is usually
		3043	correct. In some cases, programs use their own file descriptor management,
		3044	in which case they can provide this function to map fds to socket handles.
		3045
1907	=item EV_USE_POLL	3046	=item EV_USE_POLL
1908		3047
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3048	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1910	backend. Otherwise it will be enabled on non-win32 platforms. It	3049	backend. Otherwise it will be enabled on non-win32 platforms. It
1911	takes precedence over select.	3050	takes precedence over select.
1912		3051
1913	=item EV_USE_EPOLL	3052	=item EV_USE_EPOLL
1914		3053
1915	If defined to be C<1>, libev will compile in support for the Linux	3054	If defined to be C<1>, libev will compile in support for the Linux
1916	C<epoll>(7) backend. Its availability will be detected at runtime,	3055	C<epoll>(7) backend. Its availability will be detected at runtime,
1917	otherwise another method will be used as fallback. This is the	3056	otherwise another method will be used as fallback. This is the preferred
1918	preferred backend for GNU/Linux systems.	3057	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3058	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
1919		3059
1920	=item EV_USE_KQUEUE	3060	=item EV_USE_KQUEUE
1921		3061
1922	If defined to be C<1>, libev will compile in support for the BSD style	3062	If defined to be C<1>, libev will compile in support for the BSD style
1923	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3063	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
1936	otherwise another method will be used as fallback. This is the preferred	3076	otherwise another method will be used as fallback. This is the preferred
1937	backend for Solaris 10 systems.	3077	backend for Solaris 10 systems.
1938		3078
1939	=item EV_USE_DEVPOLL	3079	=item EV_USE_DEVPOLL
1940		3080
1941	reserved for future expansion, works like the USE symbols above.	3081	Reserved for future expansion, works like the USE symbols above.
		3082
		3083	=item EV_USE_INOTIFY
		3084
		3085	If defined to be C<1>, libev will compile in support for the Linux inotify
		3086	interface to speed up C<ev_stat> watchers. Its actual availability will
		3087	be detected at runtime. If undefined, it will be enabled if the headers
		3088	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3089
		3090	=item EV_ATOMIC_T
		3091
		3092	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3093	access is atomic with respect to other threads or signal contexts. No such
		3094	type is easily found in the C language, so you can provide your own type
		3095	that you know is safe for your purposes. It is used both for signal handler "locking"
		3096	as well as for signal and thread safety in C<ev_async> watchers.
		3097
		3098	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3099	(from F<signal.h>), which is usually good enough on most platforms.
1942		3100
1943	=item EV_H	3101	=item EV_H
1944		3102
1945	The name of the F<ev.h> header file used to include it. The default if	3103	The name of the F<ev.h> header file used to include it. The default if
1946	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3104	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3105	used to virtually rename the F<ev.h> header file in case of conflicts.
1948		3106
1949	=item EV_CONFIG_H	3107	=item EV_CONFIG_H
1950		3108
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3109	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3110	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	3111	C<EV_H>, above.
1954		3112
1955	=item EV_EVENT_H	3113	=item EV_EVENT_H
1956		3114
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3115	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1958	of how the F<event.h> header can be found.	3116	of how the F<event.h> header can be found, the default is C<"event.h">.
1959		3117
1960	=item EV_PROTOTYPES	3118	=item EV_PROTOTYPES
1961		3119
1962	If defined to be C<0>, then F<ev.h> will not define any function	3120	If defined to be C<0>, then F<ev.h> will not define any function
1963	prototypes, but still define all the structs and other symbols. This is	3121	prototypes, but still define all the structs and other symbols. This is
…		…
1970	will have the C<struct ev_loop *> as first argument, and you can create	3128	will have the C<struct ev_loop *> as first argument, and you can create
1971	additional independent event loops. Otherwise there will be no support	3129	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	3130	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	3131	argument. Instead, all functions act on the single default loop.
1974		3132
		3133	=item EV_MINPRI
		3134
		3135	=item EV_MAXPRI
		3136
		3137	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3138	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3139	provide for more priorities by overriding those symbols (usually defined
		3140	to be C<-2> and C<2>, respectively).
		3141
		3142	When doing priority-based operations, libev usually has to linearly search
		3143	all the priorities, so having many of them (hundreds) uses a lot of space
		3144	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3145	fine.
		3146
		3147	If your embedding application does not need any priorities, defining these
		3148	both to C<0> will save some memory and CPU.
		3149
1975	=item EV_PERIODIC_ENABLE	3150	=item EV_PERIODIC_ENABLE
1976		3151
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	3152	If undefined or defined to be C<1>, then periodic timers are supported. If
1978	defined to be C<0>, then they are not. Disabling them saves a few kB of	3153	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	3154	code.
1980		3155
		3156	=item EV_IDLE_ENABLE
		3157
		3158	If undefined or defined to be C<1>, then idle watchers are supported. If
		3159	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3160	code.
		3161
1981	=item EV_EMBED_ENABLE	3162	=item EV_EMBED_ENABLE
1982		3163
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	3164	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	3165	defined to be C<0>, then they are not. Embed watchers rely on most other
		3166	watcher types, which therefore must not be disabled.
1985		3167
1986	=item EV_STAT_ENABLE	3168	=item EV_STAT_ENABLE
1987		3169
1988	If undefined or defined to be C<1>, then stat watchers are supported. If	3170	If undefined or defined to be C<1>, then stat watchers are supported. If
1989	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
…		…
1991	=item EV_FORK_ENABLE	3173	=item EV_FORK_ENABLE
1992		3174
1993	If undefined or defined to be C<1>, then fork watchers are supported. If	3175	If undefined or defined to be C<1>, then fork watchers are supported. If
1994	defined to be C<0>, then they are not.	3176	defined to be C<0>, then they are not.
1995		3177
		3178	=item EV_ASYNC_ENABLE
		3179
		3180	If undefined or defined to be C<1>, then async watchers are supported. If
		3181	defined to be C<0>, then they are not.
		3182
1996	=item EV_MINIMAL	3183	=item EV_MINIMAL
1997		3184
1998	If you need to shave off some kilobytes of code at the expense of some	3185	If you need to shave off some kilobytes of code at the expense of some
1999	speed, define this symbol to C<1>. Currently only used for gcc to override	3186	speed, define this symbol to C<1>. Currently this is used to override some
2000	some inlining decisions, saves roughly 30% codesize of amd64.	3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3188	much smaller 2-heap for timer management over the default 4-heap.
2001		3189
2002	=item EV_PID_HASHSIZE	3190	=item EV_PID_HASHSIZE
2003		3191
2004	C<ev_child> watchers use a small hash table to distribute workload by	3192	C<ev_child> watchers use a small hash table to distribute workload by
2005	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3193	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2006	than enough. If you need to manage thousands of children you might want to	3194	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	3195	increase this value (I<must> be a power of two).
		3196
		3197	=item EV_INOTIFY_HASHSIZE
		3198
		3199	C<ev_stat> watchers use a small hash table to distribute workload by
		3200	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3201	usually more than enough. If you need to manage thousands of C<ev_stat>
		3202	watchers you might want to increase this value (I<must> be a power of
		3203	two).
		3204
		3205	=item EV_USE_4HEAP
		3206
		3207	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3208	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3209	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3210	faster performance with many (thousands) of watchers.
		3211
		3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3213	(disabled).
		3214
		3215	=item EV_HEAP_CACHE_AT
		3216
		3217	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3218	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3219	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3220	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3221	but avoids random read accesses on heap changes. This improves performance
		3222	noticeably with many (hundreds) of watchers.
		3223
		3224	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3225	(disabled).
		3226
		3227	=item EV_VERIFY
		3228
		3229	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3230	be done: If set to C<0>, no internal verification code will be compiled
		3231	in. If set to C<1>, then verification code will be compiled in, but not
		3232	called. If set to C<2>, then the internal verification code will be
		3233	called once per loop, which can slow down libev. If set to C<3>, then the
		3234	verification code will be called very frequently, which will slow down
		3235	libev considerably.
		3236
		3237	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3238	C<0>.
2008		3239
2009	=item EV_COMMON	3240	=item EV_COMMON
2010		3241
2011	By default, all watchers have a C<void *data> member. By redefining	3242	By default, all watchers have a C<void *data> member. By redefining
2012	this macro to a something else you can include more and other types of	3243	this macro to a something else you can include more and other types of
2013	members. You have to define it each time you include one of the files,	3244	members. You have to define it each time you include one of the files,
2014	though, and it must be identical each time.	3245	though, and it must be identical each time.
2015		3246
2016	For example, the perl EV module uses something like this:	3247	For example, the perl EV module uses something like this:
2017		3248
2018	#define EV_COMMON \	3249	#define EV_COMMON \
2019	SV *self; /* contains this struct */ \	3250	SV *self; /* contains this struct */ \
2020	SV *cb_sv, *fh /* note no trailing ";" */	3251	SV *cb_sv, *fh /* note no trailing ";" */
2021		3252
2022	=item EV_CB_DECLARE (type)	3253	=item EV_CB_DECLARE (type)
2023		3254
2024	=item EV_CB_INVOKE (watcher, revents)	3255	=item EV_CB_INVOKE (watcher, revents)
2025		3256
2026	=item ev_set_cb (ev, cb)	3257	=item ev_set_cb (ev, cb)
2027		3258
2028	Can be used to change the callback member declaration in each watcher,	3259	Can be used to change the callback member declaration in each watcher,
2029	and the way callbacks are invoked and set. Must expand to a struct member	3260	and the way callbacks are invoked and set. Must expand to a struct member
2030	definition and a statement, respectively. See the F<ev.v> header file for	3261	definition and a statement, respectively. See the F<ev.h> header file for
2031	their default definitions. One possible use for overriding these is to	3262	their default definitions. One possible use for overriding these is to
2032	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3263	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2033	method calls instead of plain function calls in C++.	3264	method calls instead of plain function calls in C++.
		3265
		3266	=back
		3267
		3268	=head2 EXPORTED API SYMBOLS
		3269
		3270	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3271	exported symbols, you can use the provided F<Symbol.*> files which list
		3272	all public symbols, one per line:
		3273
		3274	Symbols.ev for libev proper
		3275	Symbols.event for the libevent emulation
		3276
		3277	This can also be used to rename all public symbols to avoid clashes with
		3278	multiple versions of libev linked together (which is obviously bad in
		3279	itself, but sometimes it is inconvenient to avoid this).
		3280
		3281	A sed command like this will create wrapper C<#define>'s that you need to
		3282	include before including F<ev.h>:
		3283
		3284	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3285
		3286	This would create a file F<wrap.h> which essentially looks like this:
		3287
		3288	#define ev_backend myprefix_ev_backend
		3289	#define ev_check_start myprefix_ev_check_start
		3290	#define ev_check_stop myprefix_ev_check_stop
		3291	...
2034		3292
2035	=head2 EXAMPLES	3293	=head2 EXAMPLES
2036		3294
2037	For a real-world example of a program the includes libev	3295	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	3296	verbatim, you can have a look at the EV perl module
…		…
2041	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3299	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2042	will be compiled. It is pretty complex because it provides its own header	3300	will be compiled. It is pretty complex because it provides its own header
2043	file.	3301	file.
2044		3302
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3303	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2046	that everybody includes and which overrides some autoconf choices:	3304	that everybody includes and which overrides some configure choices:
2047		3305
		3306	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	3307	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	3308	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	3309	#define EV_PERIODIC_ENABLE 0
		3310	#define EV_STAT_ENABLE 0
		3311	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	3312	#define EV_CONFIG_H <config.h>
		3313	#define EV_MINPRI 0
		3314	#define EV_MAXPRI 0
2052		3315
2053	#include "ev++.h"	3316	#include "ev++.h"
2054		3317
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		3319
2057	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
2058	#include "ev.c"	3321	#include "ev.c"
2059		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2060		3324
		3325	=head2 THREADS AND COROUTINES
		3326
		3327	=head3 THREADS
		3328
		3329	All libev functions are reentrant and thread-safe unless explicitly
		3330	documented otherwise, but libev implements no locking itself. This means
		3331	that you can use as many loops as you want in parallel, as long as there
		3332	are no concurrent calls into any libev function with the same loop
		3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3334	of course): libev guarantees that different event loops share no data
		3335	structures that need any locking.
		3336
		3337	Or to put it differently: calls with different loop parameters can be done
		3338	concurrently from multiple threads, calls with the same loop parameter
		3339	must be done serially (but can be done from different threads, as long as
		3340	only one thread ever is inside a call at any point in time, e.g. by using
		3341	a mutex per loop).
		3342
		3343	Specifically to support threads (and signal handlers), libev implements
		3344	so-called C<ev_async> watchers, which allow some limited form of
		3345	concurrency on the same event loop, namely waking it up "from the
		3346	outside".
		3347
		3348	If you want to know which design (one loop, locking, or multiple loops
		3349	without or something else still) is best for your problem, then I cannot
		3350	help you, but here is some generic advice:
		3351
		3352	=over 4
		3353
		3354	=item * most applications have a main thread: use the default libev loop
		3355	in that thread, or create a separate thread running only the default loop.
		3356
		3357	This helps integrating other libraries or software modules that use libev
		3358	themselves and don't care/know about threading.
		3359
		3360	=item * one loop per thread is usually a good model.
		3361
		3362	Doing this is almost never wrong, sometimes a better-performance model
		3363	exists, but it is always a good start.
		3364
		3365	=item * other models exist, such as the leader/follower pattern, where one
		3366	loop is handed through multiple threads in a kind of round-robin fashion.
		3367
		3368	Choosing a model is hard - look around, learn, know that usually you can do
		3369	better than you currently do :-)
		3370
		3371	=item * often you need to talk to some other thread which blocks in the
		3372	event loop.
		3373
		3374	C<ev_async> watchers can be used to wake them up from other threads safely
		3375	(or from signal contexts...).
		3376
		3377	An example use would be to communicate signals or other events that only
		3378	work in the default loop by registering the signal watcher with the
		3379	default loop and triggering an C<ev_async> watcher from the default loop
		3380	watcher callback into the event loop interested in the signal.
		3381
		3382	=back
		3383
		3384	=head3 COROUTINES
		3385
		3386	Libev is very accommodating to coroutines ("cooperative threads"):
		3387	libev fully supports nesting calls to its functions from different
		3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3389	different coroutines, and switch freely between both coroutines running the
		3390	loop, as long as you don't confuse yourself). The only exception is that
		3391	you must not do this from C<ev_periodic> reschedule callbacks.
		3392
		3393	Care has been taken to ensure that libev does not keep local state inside
		3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3395	they do not clal any callbacks.
		3396
		3397	=head2 COMPILER WARNINGS
		3398
		3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
		3402
		3403	However, these are unavoidable for many reasons. For one, each compiler
		3404	has different warnings, and each user has different tastes regarding
		3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
		3407
		3408	Another reason is that some compiler warnings require elaborate
		3409	workarounds, or other changes to the code that make it less clear and less
		3410	maintainable.
		3411
		3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
		3418
		3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
		3424
		3425
		3426	=head2 VALGRIND
		3427
		3428	Valgrind has a special section here because it is a popular tool that is
		3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3430
		3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
		3433
		3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
		3437
		3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
		3440
		3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
		3445
		3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3447	make it into some kind of religion.
		3448
		3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
		3454
		3455	If you need, for some reason, empty reports from valgrind for your project
		3456	I suggest using suppression lists.
		3457
		3458
		3459	=head1 PORTABILITY NOTES
		3460
		3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3462
		3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3464	requires, and its I/O model is fundamentally incompatible with the POSIX
		3465	model. Libev still offers limited functionality on this platform in
		3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3467	descriptors. This only applies when using Win32 natively, not when using
		3468	e.g. cygwin.
		3469
		3470	Lifting these limitations would basically require the full
		3471	re-implementation of the I/O system. If you are into these kinds of
		3472	things, then note that glib does exactly that for you in a very portable
		3473	way (note also that glib is the slowest event library known to man).
		3474
		3475	There is no supported compilation method available on windows except
		3476	embedding it into other applications.
		3477
		3478	Not a libev limitation but worth mentioning: windows apparently doesn't
		3479	accept large writes: instead of resulting in a partial write, windows will
		3480	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3481	so make sure you only write small amounts into your sockets (less than a
		3482	megabyte seems safe, but this apparently depends on the amount of memory
		3483	available).
		3484
		3485	Due to the many, low, and arbitrary limits on the win32 platform and
		3486	the abysmal performance of winsockets, using a large number of sockets
		3487	is not recommended (and not reasonable). If your program needs to use
		3488	more than a hundred or so sockets, then likely it needs to use a totally
		3489	different implementation for windows, as libev offers the POSIX readiness
		3490	notification model, which cannot be implemented efficiently on windows
		3491	(Microsoft monopoly games).
		3492
		3493	A typical way to use libev under windows is to embed it (see the embedding
		3494	section for details) and use the following F<evwrap.h> header file instead
		3495	of F<ev.h>:
		3496
		3497	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3498	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3499
		3500	#include "ev.h"
		3501
		3502	And compile the following F<evwrap.c> file into your project (make sure
		3503	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3504
		3505	#include "evwrap.h"
		3506	#include "ev.c"
		3507
		3508	=over 4
		3509
		3510	=item The winsocket select function
		3511
		3512	The winsocket C<select> function doesn't follow POSIX in that it
		3513	requires socket I<handles> and not socket I<file descriptors> (it is
		3514	also extremely buggy). This makes select very inefficient, and also
		3515	requires a mapping from file descriptors to socket handles (the Microsoft
		3516	C runtime provides the function C<_open_osfhandle> for this). See the
		3517	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3518	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3519
		3520	The configuration for a "naked" win32 using the Microsoft runtime
		3521	libraries and raw winsocket select is:
		3522
		3523	#define EV_USE_SELECT 1
		3524	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3525
		3526	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3527	complexity in the O(n²) range when using win32.
		3528
		3529	=item Limited number of file descriptors
		3530
		3531	Windows has numerous arbitrary (and low) limits on things.
		3532
		3533	Early versions of winsocket's select only supported waiting for a maximum
		3534	of C<64> handles (probably owning to the fact that all windows kernels
		3535	can only wait for C<64> things at the same time internally; Microsoft
		3536	recommends spawning a chain of threads and wait for 63 handles and the
		3537	previous thread in each. Great).
		3538
		3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3540	to some high number (e.g. C<2048>) before compiling the winsocket select
		3541	call (which might be in libev or elsewhere, for example, perl does its own
		3542	select emulation on windows).
		3543
		3544	Another limit is the number of file descriptors in the Microsoft runtime
		3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3546	or something like this inside Microsoft). You can increase this by calling
		3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3548	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3549	libraries.
		3550
		3551	This might get you to about C<512> or C<2048> sockets (depending on
		3552	windows version and/or the phase of the moon). To get more, you need to
		3553	wrap all I/O functions and provide your own fd management, but the cost of
		3554	calling select (O(n²)) will likely make this unworkable.
		3555
		3556	=back
		3557
		3558	=head2 PORTABILITY REQUIREMENTS
		3559
		3560	In addition to a working ISO-C implementation and of course the
		3561	backend-specific APIs, libev relies on a few additional extensions:
		3562
		3563	=over 4
		3564
		3565	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3566	calling conventions regardless of C<ev_watcher_type *>.
		3567
		3568	Libev assumes not only that all watcher pointers have the same internal
		3569	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3570	assumes that the same (machine) code can be used to call any watcher
		3571	callback: The watcher callbacks have different type signatures, but libev
		3572	calls them using an C<ev_watcher *> internally.
		3573
		3574	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3575
		3576	The type C<sig_atomic_t volatile> (or whatever is defined as
		3577	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3578	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3579	believed to be sufficiently portable.
		3580
		3581	=item C<sigprocmask> must work in a threaded environment
		3582
		3583	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3584	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3585	pthread implementations will either allow C<sigprocmask> in the "main
		3586	thread" or will block signals process-wide, both behaviours would
		3587	be compatible with libev. Interaction between C<sigprocmask> and
		3588	C<pthread_sigmask> could complicate things, however.
		3589
		3590	The most portable way to handle signals is to block signals in all threads
		3591	except the initial one, and run the default loop in the initial thread as
		3592	well.
		3593
		3594	=item C<long> must be large enough for common memory allocation sizes
		3595
		3596	To improve portability and simplify its API, libev uses C<long> internally
		3597	instead of C<size_t> when allocating its data structures. On non-POSIX
		3598	systems (Microsoft...) this might be unexpectedly low, but is still at
		3599	least 31 bits everywhere, which is enough for hundreds of millions of
		3600	watchers.
		3601
		3602	=item C<double> must hold a time value in seconds with enough accuracy
		3603
		3604	The type C<double> is used to represent timestamps. It is required to
		3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3606	enough for at least into the year 4000. This requirement is fulfilled by
		3607	implementations implementing IEEE 754 (basically all existing ones).
		3608
		3609	=back
		3610
		3611	If you know of other additional requirements drop me a note.
		3612
		3613
2061	=head1 COMPLEXITIES	3614	=head1 ALGORITHMIC COMPLEXITIES
2062		3615
2063	In this section the complexities of (many of) the algorithms used inside	3616	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	3617	libev will be documented. For complexity discussions about backends see
2065	documentation for C<ev_default_init>.	3618	the documentation for C<ev_default_init>.
		3619
		3620	All of the following are about amortised time: If an array needs to be
		3621	extended, libev needs to realloc and move the whole array, but this
		3622	happens asymptotically rarer with higher number of elements, so O(1) might
		3623	mean that libev does a lengthy realloc operation in rare cases, but on
		3624	average it is much faster and asymptotically approaches constant time.
2066		3625
2067	=over 4	3626	=over 4
2068		3627
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		3629
		3630	This means that, when you have a watcher that triggers in one hour and
		3631	there are 100 watchers that would trigger before that, then inserting will
		3632	have to skip roughly seven (C<ld 100>) of these watchers.
		3633
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2072		3635
		3636	That means that changing a timer costs less than removing/adding them,
		3637	as only the relative motion in the event queue has to be paid for.
		3638
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2074		3640
		3641	These just add the watcher into an array or at the head of a list.
		3642
2075	=item Stopping check/prepare/idle watchers: O(1)	3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2076		3644
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		3646
		3647	These watchers are stored in lists, so they need to be walked to find the
		3648	correct watcher to remove. The lists are usually short (you don't usually
		3649	have many watchers waiting for the same fd or signal: one is typical, two
		3650	is rare).
		3651
2079	=item Finding the next timer per loop iteration: O(1)	3652	=item Finding the next timer in each loop iteration: O(1)
		3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
2080		3656
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		3658
2083	=item Activating one watcher: O(1)	3659	A change means an I/O watcher gets started or stopped, which requires
		3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
		3662
		3663	=item Activating one watcher (putting it into the pending state): O(1)
		3664
		3665	=item Priority handling: O(number_of_priorities)
		3666
		3667	Priorities are implemented by allocating some space for each
		3668	priority. When doing priority-based operations, libev usually has to
		3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
2084		3681
2085	=back	3682	=back
2086		3683
2087		3684
2088	=head1 AUTHOR	3685	=head1 AUTHOR

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