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Revision 1.51 by root, Tue Nov 27 19:23:31 2007 UTC vs.
Revision 1.171 by root, Tue Jul 8 09:49:15 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
…		…
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))
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
…		…
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));
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);
…		…
176	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
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
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		284
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
…		…
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.
229		363
230	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
231		365
232	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
233	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
234	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
235	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
236		372
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		374
239	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
240	but it scales phenomenally better. While poll and select usually scale like	376	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	377	like O(total_fds) where n is the total number of fds (or the highest fd),
242	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
243		382
244	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
245	result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
246	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
247	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
248	well if you register events for both fds.	387	very well if you register events for both fds.
249		388
250	Please note that epoll sometimes generates spurious notifications, so you	389	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	390	need to use non-blocking I/O or other means to avoid blocking when no data
252	(or space) is available.	391	(or space) is available.
253		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		401
256	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
257	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
258	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
259	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
260	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
261	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
262		413
263	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
264	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
265	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
266	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
267	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
268		429
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		431
271	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
272		436
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		438
275	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
276	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
277		441
278	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
279	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
280	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
281		454
282	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
283		456
284	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
285	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
287		460
		461	It is definitely not recommended to use this flag.
		462
288	=back	463	=back
289		464
290	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
291	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
292	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
293	order of their flag values :)
294		468
295	The most typical usage is like this:	469	The most typical usage is like this:
296		470
297	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
299		473
300	Restrict libev to the select and poll backends, and do not allow	474	Restrict libev to the select and poll backends, and do not allow
301	environment settings to be taken into account:	475	environment settings to be taken into account:
302		476
303	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
304		478
305	Use whatever libev has to offer, but make sure that kqueue is used if	479	Use whatever libev has to offer, but make sure that kqueue is used if
306	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
307	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
308		482
309	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
310		484
311	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
312		486
313	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
314	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
315	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
316	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
317		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
318	Example: try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
319		497
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	499	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
323		501
324	=item ev_default_destroy ()	502	=item ev_default_destroy ()
325		503
326	Destroys the default loop again (frees all memory and kernel state	504	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	505	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	506	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>	507	responsibility to either stop all watchers cleanly yourself I<before>
330	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
331	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
333		520
334	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
335		522
336	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
337	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
338		525
339	=item ev_default_fork ()	526	=item ev_default_fork ()
340		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
341	This function reinitialises the kernel state for backends that have	529	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	530	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	531	the child process (or both child and parent, but that again makes little
344	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
345		534
346	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
347	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
348	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
349		538
350	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
351	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
352	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
353		542
354	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
355		544
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)	545	=item ev_loop_fork (loop)
361		546
362	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
363	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
364	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
		554
		555	=item unsigned int ev_loop_count (loop)
		556
		557	Returns the count of loop iterations for the loop, which is identical to
		558	the number of times libev did poll for new events. It starts at C<0> and
		559	happily wraps around with enough iterations.
		560
		561	This value can sometimes be useful as a generation counter of sorts (it
		562	"ticks" the number of loop iterations), as it roughly corresponds with
		563	C<ev_prepare> and C<ev_check> calls.
365		564
366	=item unsigned int ev_backend (loop)	565	=item unsigned int ev_backend (loop)
367		566
368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
369	use.	568	use.
…		…
372		571
373	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
374	received events and started processing them. This timestamp does not	573	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	574	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	575	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).	576	event occurring (or more correctly, libev finding out about it).
378		577
379	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
380		579
381	Finally, this is it, the event handler. This function usually is called	580	Finally, this is it, the event handler. This function usually is called
382	after you initialised all your watchers and you want to start handling	581	after you initialised all your watchers and you want to start handling
…		…
394	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
395	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
396	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
397		596
398	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
399	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
400	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
401	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
402	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
403	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
404	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
405		604
406	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
407		606
408	* If there are no active watchers (reference count is zero), return.	607	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
		609	- If a fork was detected (by any means), queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
411	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
413	- Calculate for how long to block.	615	- Calculate for how long to sleep or block, if at all
		616	(active idle watchers, EVLOOP_NONBLOCK or not having
		617	any active watchers at all will result in not sleeping).
		618	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
417	- Queue all outstanding timers.	622	- Queue all outstanding timers.
418	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
419	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
420	- Queue all check watchers.	625	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	626	- Call all queued watchers in reverse order (i.e. check watchers first).
422	Signals and child watchers are implemented as I/O watchers, and will	627	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
426		632
427	Example: queue some jobs and then loop until no events are outsanding	633	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	634	anymore.
429		635
430	... queue jobs here, make sure they register event watchers as long	636	... 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..)	637	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
433	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
434		640
435	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
436		642
437	Can be used to make a call to C<ev_loop> return early (but only after it	643	Can be used to make a call to C<ev_loop> return early (but only after it
438	has processed all outstanding events). The C<how> argument must be either	644	has processed all outstanding events). The C<how> argument must be either
439	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
440	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		647
		648	This "unloop state" will be cleared when entering C<ev_loop> again.
441		649
442	=item ev_ref (loop)	650	=item ev_ref (loop)
443		651
444	=item ev_unref (loop)	652	=item ev_unref (loop)
445		653
…		…
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	658	returning, ev_unref() after starting, and ev_ref() before stopping it. For
451	example, libev itself uses this for its internal signal pipe: It is not	659	example, libev itself uses this for its internal signal pipe: It is not
452	visible to the libev user and should not keep C<ev_loop> from exiting if	660	visible to the libev user and should not keep C<ev_loop> from exiting if
453	no event watchers registered by it are active. It is also an excellent	661	no event watchers registered by it are active. It is also an excellent
454	way to do this for generic recurring timers or from within third-party	662	way to do this for generic recurring timers or from within third-party
455	libraries. Just remember to I<unref after start> and I<ref before stop>.	663	libraries. Just remember to I<unref after start> and I<ref before stop>
		664	(but only if the watcher wasn't active before, or was active before,
		665	respectively).
456		666
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	668	running when nothing else is active.
459		669
460	struct dv_signal exitsig;	670	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	672	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	673	evf_unref (loop);
464		674
465	Example: for some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
466		676
467	ev_ref (myloop);	677	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	678	ev_signal_stop (loop, &exitsig);
		679
		680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		681
		682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		683
		684	These advanced functions influence the time that libev will spend waiting
		685	for events. Both time intervals are by default C<0>, meaning that libev
		686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
		688
		689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		690	allows libev to delay invocation of I/O and timer/periodic callbacks
		691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
		693
		694	The background is that sometimes your program runs just fast enough to
		695	handle one (or very few) event(s) per loop iteration. While this makes
		696	the program responsive, it also wastes a lot of CPU time to poll for new
		697	events, especially with backends like C<select ()> which have a high
		698	overhead for the actual polling but can deliver many events at once.
		699
		700	By setting a higher I<io collect interval> you allow libev to spend more
		701	time collecting I/O events, so you can handle more events per iteration,
		702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		703	C<ev_timer>) will be not affected. Setting this to a non-null value will
		704	introduce an additional C<ev_sleep ()> call into most loop iterations.
		705
		706	Likewise, by setting a higher I<timeout collect interval> you allow libev
		707	to spend more time collecting timeouts, at the expense of increased
		708	latency (the watcher callback will be called later). C<ev_io> watchers
		709	will not be affected. Setting this to a non-null value will not introduce
		710	any overhead in libev.
		711
		712	Many (busy) programs can usually benefit by setting the I/O collect
		713	interval to a value near C<0.1> or so, which is often enough for
		714	interactive servers (of course not for games), likewise for timeouts. It
		715	usually doesn't make much sense to set it to a lower value than C<0.01>,
		716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
469		735
470	=back	736	=back
471		737
472		738
473	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
474		740
475	A watcher is a structure that you create and register to record your	741	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	742	interest in some event. For instance, if you want to wait for STDIN to
477	become readable, you would create an C<ev_io> watcher for that:	743	become readable, you would create an C<ev_io> watcher for that:
478		744
479	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
480	{	746	{
481	ev_io_stop (w);	747	ev_io_stop (w);
482	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
483	}	749	}
484		750
485	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
486	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
487	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
488	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
489	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
490	ev_loop (loop, 0);	756	ev_loop (loop, 0);
491		757
492	As you can see, you are responsible for allocating the memory for your	758	As you can see, you are responsible for allocating the memory for your
493	watcher structures (and it is usually a bad idea to do this on the stack,	759	watcher structures (and it is usually a bad idea to do this on the stack,
494	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
495		761
496	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
497	(watcher *, callback)>, which expects a callback to be provided. This	763	(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	764	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	765	watchers, each time the event loop detects that the file descriptor given
500	is readable and/or writable).	766	is readable and/or writable).
501		767
502	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
503	with arguments specific to this watcher type. There is also a macro	769	with arguments specific to this watcher type. There is also a macro
…		…
573	=item C<EV_FORK>	839	=item C<EV_FORK>
574		840
575	The event loop has been resumed in the child process after fork (see	841	The event loop has been resumed in the child process after fork (see
576	C<ev_fork>).	842	C<ev_fork>).
577		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
578	=item C<EV_ERROR>	848	=item C<EV_ERROR>
579		849
580	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
581	happen because the watcher could not be properly started because libev	851	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	852	ran out of memory, a file descriptor was found to be closed or any other
583	problem. You best act on it by reporting the problem and somehow coping	853	problem. You best act on it by reporting the problem and somehow coping
584	with the watcher being stopped.	854	with the watcher being stopped.
585		855
586	Libev will usually signal a few "dummy" events together with an error,	856	Libev will usually signal a few "dummy" events together with an error,
587	for example it might indicate that a fd is readable or writable, and if	857	for example it might indicate that a fd is readable or writable, and if
588	your callbacks is well-written it can just attempt the operation and cope	858	your callbacks is well-written it can just attempt the operation and cope
589	with the error from read() or write(). This will not work in multithreaded	859	with the error from read() or write(). This will not work in multi-threaded
590	programs, though, so beware.	860	programs, though, so beware.
591		861
592	=back	862	=back
593		863
594	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
624	Although some watcher types do not have type-specific arguments	894	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.	895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
626		896
627	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
628		898
629	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
630	calls into a single call. This is the most convinient method to initialise	900	calls into a single call. This is the most convenient method to initialise
631	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
632		902
633	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
634		904
635	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	923	=item bool ev_is_pending (ev_TYPE *watcher)
654		924
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	925	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	926	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	927	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	928	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	929	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		930	it).
660		931
661	=item callback = ev_cb (ev_TYPE *watcher)	932	=item callback ev_cb (ev_TYPE *watcher)
662		933
663	Returns the callback currently set on the watcher.	934	Returns the callback currently set on the watcher.
664		935
665	=item ev_cb_set (ev_TYPE *watcher, callback)	936	=item ev_cb_set (ev_TYPE *watcher, callback)
666		937
667	Change the callback. You can change the callback at virtually any time	938	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	939	(modulo threads).
		940
		941	=item ev_set_priority (ev_TYPE *watcher, priority)
		942
		943	=item int ev_priority (ev_TYPE *watcher)
		944
		945	Set and query the priority of the watcher. The priority is a small
		946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		947	(default: C<-2>). Pending watchers with higher priority will be invoked
		948	before watchers with lower priority, but priority will not keep watchers
		949	from being executed (except for C<ev_idle> watchers).
		950
		951	This means that priorities are I<only> used for ordering callback
		952	invocation after new events have been received. This is useful, for
		953	example, to reduce latency after idling, or more often, to bind two
		954	watchers on the same event and make sure one is called first.
		955
		956	If you need to suppress invocation when higher priority events are pending
		957	you need to look at C<ev_idle> watchers, which provide this functionality.
		958
		959	You I<must not> change the priority of a watcher as long as it is active or
		960	pending.
		961
		962	The default priority used by watchers when no priority has been set is
		963	always C<0>, which is supposed to not be too high and not be too low :).
		964
		965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		966	fine, as long as you do not mind that the priority value you query might
		967	or might not have been adjusted to be within valid range.
		968
		969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		970
		971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		972	C<loop> nor C<revents> need to be valid as long as the watcher callback
		973	can deal with that fact.
		974
		975	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		976
		977	If the watcher is pending, this function returns clears its pending status
		978	and returns its C<revents> bitset (as if its callback was invoked). If the
		979	watcher isn't pending it does nothing and returns C<0>.
669		980
670	=back	981	=back
671		982
672		983
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
677	to associate arbitrary data with your watcher. If you need more data and	988	to associate arbitrary data with your watcher. If you need more data and
678	don't want to allocate memory and store a pointer to it in that data	989	don't want to allocate memory and store a pointer to it in that data
679	member, you can also "subclass" the watcher type and provide your own	990	member, you can also "subclass" the watcher type and provide your own
680	data:	991	data:
681		992
682	struct my_io	993	struct my_io
683	{	994	{
684	struct ev_io io;	995	struct ev_io io;
685	int otherfd;	996	int otherfd;
686	void *somedata;	997	void *somedata;
687	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
688	}	999	}
689		1000
690	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
691	can cast it back to your own type:	1002	can cast it back to your own type:
692		1003
693	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
694	{	1005	{
695	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
696	...	1007	...
697	}	1008	}
698		1009
699	More interesting and less C-conformant ways of catsing your callback type	1010	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	1011	instead have been omitted.
		1012
		1013	Another common scenario is having some data structure with multiple
		1014	watchers:
		1015
		1016	struct my_biggy
		1017	{
		1018	int some_data;
		1019	ev_timer t1;
		1020	ev_timer t2;
		1021	}
		1022
		1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		1024	you need to use C<offsetof>:
		1025
		1026	#include <stddef.h>
		1027
		1028	static void
		1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
		1030	{
		1031	struct my_biggy big = (struct my_biggy *
		1032	(((char *)w) - offsetof (struct my_biggy, t1));
		1033	}
		1034
		1035	static void
		1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
		1037	{
		1038	struct my_biggy big = (struct my_biggy *
		1039	(((char *)w) - offsetof (struct my_biggy, t2));
		1040	}
701		1041
702		1042
703	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
704		1044
705	This section describes each watcher in detail, but will not repeat	1045	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	1069	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	1070	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	1071	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	1072	required if you know what you are doing).
733		1073
734	You have to be careful with dup'ed file descriptors, though. Some backends
735	(the linux epoll backend is a notable example) cannot handle dup'ed file
736	descriptors correctly if you register interest in two or more fds pointing
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	1074	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	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
743		1077
744	Another thing you have to watch out for is that it is quite easy to	1078	Another thing you have to watch out for is that it is quite easy to
745	receive "spurious" readyness notifications, that is your callback might	1079	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	1080	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	1081	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	1082	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	1083	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	1084	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.	1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1086
753	If you cannot run the fd in non-blocking mode (for example you should not	1087	If you cannot run the fd in non-blocking mode (for example you should not
754	play around with an Xlib connection), then you have to seperately re-test	1088	play around with an Xlib connection), then you have to separately re-test
755	wether a file descriptor is really ready with a known-to-be good interface	1089	whether a file descriptor is really ready with a known-to-be good interface
756	such as poll (fortunately in our Xlib example, Xlib already does this on	1090	such as poll (fortunately in our Xlib example, Xlib already does this on
757	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
758		1092
		1093	=head3 The special problem of disappearing file descriptors
		1094
		1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1096	descriptor (either by calling C<close> explicitly or by any other means,
		1097	such as C<dup>). The reason is that you register interest in some file
		1098	descriptor, but when it goes away, the operating system will silently drop
		1099	this interest. If another file descriptor with the same number then is
		1100	registered with libev, there is no efficient way to see that this is, in
		1101	fact, a different file descriptor.
		1102
		1103	To avoid having to explicitly tell libev about such cases, libev follows
		1104	the following policy: Each time C<ev_io_set> is being called, libev
		1105	will assume that this is potentially a new file descriptor, otherwise
		1106	it is assumed that the file descriptor stays the same. That means that
		1107	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1108	descriptor even if the file descriptor number itself did not change.
		1109
		1110	This is how one would do it normally anyway, the important point is that
		1111	the libev application should not optimise around libev but should leave
		1112	optimisations to libev.
		1113
		1114	=head3 The special problem of dup'ed file descriptors
		1115
		1116	Some backends (e.g. epoll), cannot register events for file descriptors,
		1117	but only events for the underlying file descriptions. That means when you
		1118	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1119	events for them, only one file descriptor might actually receive events.
		1120
		1121	There is no workaround possible except not registering events
		1122	for potentially C<dup ()>'ed file descriptors, or to resort to
		1123	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1124
		1125	=head3 The special problem of fork
		1126
		1127	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1128	useless behaviour. Libev fully supports fork, but needs to be told about
		1129	it in the child.
		1130
		1131	To support fork in your programs, you either have to call
		1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1134	C<EVBACKEND_POLL>.
		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when reading from a pipe whose other end has been closed, your program
		1140	gets send a SIGPIPE, which, by default, aborts your program. For most
		1141	programs this is sensible behaviour, for daemons, this is usually
		1142	undesirable.
		1143
		1144	So when you encounter spurious, unexplained daemon exits, make sure you
		1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1146	somewhere, as that would have given you a big clue).
		1147
		1148
		1149	=head3 Watcher-Specific Functions
		1150
759	=over 4	1151	=over 4
760		1152
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1153	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1154
763	=item ev_io_set (ev_io *, int fd, int events)	1155	=item ev_io_set (ev_io *, int fd, int events)
764		1156
765	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
766	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
767	C<EV_READ | EV_WRITE> to receive the given events.	1159	C<EV_READ | EV_WRITE> to receive the given events.
768		1160
769	=item int fd [read-only]	1161	=item int fd [read-only]
770		1162
771	The file descriptor being watched.	1163	The file descriptor being watched.
…		…
774		1166
775	The events being watched.	1167	The events being watched.
776		1168
777	=back	1169	=back
778		1170
		1171	=head3 Examples
		1172
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
780	readable, but only once. Since it is likely line-buffered, you could	1174	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1175	attempt to read a whole line in the callback.
782		1176
783	static void	1177	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1179	{
786	ev_io_stop (loop, w);	1180	ev_io_stop (loop, w);
787	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors
788	}	1182	}
789		1183
790	...	1184	...
791	struct ev_loop *loop = ev_default_init (0);	1185	struct ev_loop *loop = ev_default_init (0);
792	struct ev_io stdin_readable;	1186	struct ev_io stdin_readable;
793	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
794	ev_io_start (loop, &stdin_readable);	1188	ev_io_start (loop, &stdin_readable);
795	ev_loop (loop, 0);	1189	ev_loop (loop, 0);
796		1190
797		1191
798	=head2 C<ev_timer> - relative and optionally repeating timeouts	1192	=head2 C<ev_timer> - relative and optionally repeating timeouts
799		1193
800	Timer watchers are simple relative timers that generate an event after a	1194	Timer watchers are simple relative timers that generate an event after a
801	given time, and optionally repeating in regular intervals after that.	1195	given time, and optionally repeating in regular intervals after that.
802		1196
803	The timers are based on real time, that is, if you register an event that	1197	The timers are based on real time, that is, if you register an event that
804	times out after an hour and you reset your system clock to last years	1198	times out after an hour and you reset your system clock to January last
805	time, it will still time out after (roughly) and hour. "Roughly" because	1199	year, it will still time out after (roughly) and hour. "Roughly" because
806	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the
807	monotonic clock option helps a lot here).	1201	monotonic clock option helps a lot here).
808		1202
809	The relative timeouts are calculated relative to the C<ev_now ()>	1203	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	1204	time. This is usually the right thing as this timestamp refers to the time
…		…
812	you suspect event processing to be delayed and you I<need> to base the timeout	1206	you suspect event processing to be delayed and you I<need> to base the timeout
813	on the current time, use something like this to adjust for this:	1207	on the current time, use something like this to adjust for this:
814		1208
815	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
816		1210
817	The callback is guarenteed to be invoked only when its timeout has passed,	1211	The callback is guaranteed to be invoked only after its timeout has passed,
818	but if multiple timers become ready during the same loop iteration then	1212	but if multiple timers become ready during the same loop iteration then
819	order of execution is undefined.	1213	order of execution is undefined.
820		1214
		1215	=head3 Watcher-Specific Functions and Data Members
		1216
821	=over 4	1217	=over 4
822		1218
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1219	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1220
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1221	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
826		1222
827	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1223	Configure the timer to trigger after C<after> seconds. If C<repeat>
828	C<0.>, then it will automatically be stopped. If it is positive, then the	1224	is C<0.>, then it will automatically be stopped once the timeout is
829	timer will automatically be configured to trigger again C<repeat> seconds	1225	reached. If it is positive, then the timer will automatically be
830	later, again, and again, until stopped manually.	1226	configured to trigger again C<repeat> seconds later, again, and again,
		1227	until stopped manually.
831		1228
832	The timer itself will do a best-effort at avoiding drift, that is, if you	1229	The timer itself will do a best-effort at avoiding drift, that is, if
833	configure a timer to trigger every 10 seconds, then it will trigger at	1230	you configure a timer to trigger every 10 seconds, then it will normally
834	exactly 10 second intervals. If, however, your program cannot keep up with	1231	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	1232	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.	1233	do stuff) the timer will not fire more than once per event loop iteration.
837		1234
838	=item ev_timer_again (loop)	1235	=item ev_timer_again (loop, ev_timer *)
839		1236
840	This will act as if the timer timed out and restart it again if it is	1237	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1238	repeating. The exact semantics are:
842		1239
		1240	If the timer is pending, its pending status is cleared.
		1241
843	If the timer is started but nonrepeating, stop it.	1242	If the timer is started but non-repeating, stop it (as if it timed out).
844		1243
845	If the timer is repeating, either start it if necessary (with the repeat	1244	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1245	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1246
848	This sounds a bit complicated, but here is a useful and typical	1247	This sounds a bit complicated, but here is a useful and typical
849	example: Imagine you have a tcp connection and you want a so-called	1248	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,	1249	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	1250	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	1251	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	1252	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	1253	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	1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1255	automatically restart it if need be.
857		1256
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1257	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1259
861	ev_timer_init (timer, callback, 0., 5.);	1260	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1261	ev_timer_again (loop, timer);
863	...	1262	...
864	timer->again = 17.;	1263	timer->again = 17.;
865	ev_timer_again (loop, timer);	1264	ev_timer_again (loop, timer);
866	...	1265	...
867	timer->again = 10.;	1266	timer->again = 10.;
868	ev_timer_again (loop, timer);	1267	ev_timer_again (loop, timer);
869		1268
870	This is more efficient then stopping/starting the timer eahc time you want	1269	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1270	you want to modify its timeout value.
872		1271
873	=item ev_tstamp repeat [read-write]	1272	=item ev_tstamp repeat [read-write]
874		1273
875	The current C<repeat> value. Will be used each time the watcher times out	1274	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),	1275	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.	1276	which is also when any modifications are taken into account.
878		1277
879	=back	1278	=back
880		1279
		1280	=head3 Examples
		1281
881	Example: create a timer that fires after 60 seconds.	1282	Example: Create a timer that fires after 60 seconds.
882		1283
883	static void	1284	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1286	{
886	.. one minute over, w is actually stopped right here	1287	.. one minute over, w is actually stopped right here
887	}	1288	}
888		1289
889	struct ev_timer mytimer;	1290	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1292	ev_timer_start (loop, &mytimer);
892		1293
893	Example: create a timeout timer that times out after 10 seconds of	1294	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1295	inactivity.
895		1296
896	static void	1297	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1299	{
899	.. ten seconds without any activity	1300	.. ten seconds without any activity
900	}	1301	}
901		1302
902	struct ev_timer mytimer;	1303	struct ev_timer mytimer;
903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
904	ev_timer_again (&mytimer); /* start timer */	1305	ev_timer_again (&mytimer); /* start timer */
905	ev_loop (loop, 0);	1306	ev_loop (loop, 0);
906		1307
907	// and in some piece of code that gets executed on any "activity":	1308	// and in some piece of code that gets executed on any "activity":
908	// reset the timeout to start ticking again at 10 seconds	1309	// reset the timeout to start ticking again at 10 seconds
909	ev_timer_again (&mytimer);	1310	ev_timer_again (&mytimer);
910		1311
911		1312
912	=head2 C<ev_periodic> - to cron or not to cron?	1313	=head2 C<ev_periodic> - to cron or not to cron?
913		1314
914	Periodic watchers are also timers of a kind, but they are very versatile	1315	Periodic watchers are also timers of a kind, but they are very versatile
915	(and unfortunately a bit complex).	1316	(and unfortunately a bit complex).
916		1317
917	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
918	but on wallclock time (absolute time). You can tell a periodic watcher	1319	but on wall clock time (absolute time). You can tell a periodic watcher
919	to trigger "at" some specific point in time. For example, if you tell a	1320	to trigger after some specific point in time. For example, if you tell a
920	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
921	+ 10.>) and then reset your system clock to the last year, then it will	1322	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1323	clock to January of the previous year, then it will take more than year
922	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
923	roughly 10 seconds later and of course not if you reset your system time	1325	roughly 10 seconds later as it uses a relative timeout).
924	again).
925		1326
926	They can also be used to implement vastly more complex timers, such as	1327	C<ev_periodic>s can also be used to implement vastly more complex timers,
927	triggering an event on eahc midnight, local time.	1328	such as triggering an event on each "midnight, local time", or other
		1329	complicated, rules.
928		1330
929	As with timers, the callback is guarenteed to be invoked only when the	1331	As with timers, the callback is guaranteed to be invoked only when the
930	time (C<at>) has been passed, but if multiple periodic timers become ready	1332	time (C<at>) has passed, but if multiple periodic timers become ready
931	during the same loop iteration then order of execution is undefined.	1333	during the same loop iteration then order of execution is undefined.
		1334
		1335	=head3 Watcher-Specific Functions and Data Members
932		1336
933	=over 4	1337	=over 4
934		1338
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1340
…		…
939	Lots of arguments, lets sort it out... There are basically three modes of	1343	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1344	operation, and we will explain them from simplest to complex:
941		1345
942	=over 4	1346	=over 4
943		1347
944	=item * absolute timer (interval = reschedule_cb = 0)	1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1349
946	In this configuration the watcher triggers an event at the wallclock time	1350	In this configuration the watcher triggers an event after the wall clock
947	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1351	time C<at> has passed and doesn't repeat. It will not adjust when a time
948	that is, if it is to be run at January 1st 2011 then it will run when the	1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will
949	system time reaches or surpasses this time.	1353	run when the system time reaches or surpasses this time.
950		1354
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1356
953	In this mode the watcher will always be scheduled to time out at the next	1357	In this mode the watcher will always be scheduled to time out at the next
954	C<at + N * interval> time (for some integer N) and then repeat, regardless	1358	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1359	and then repeat, regardless of any time jumps.
956		1360
957	This can be used to create timers that do not drift with respect to system	1361	This can be used to create timers that do not drift with respect to system
958	time:	1362	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1363	the hour:
959		1364
960	ev_periodic_set (&periodic, 0., 3600., 0);	1365	ev_periodic_set (&periodic, 0., 3600., 0);
961		1366
962	This doesn't mean there will always be 3600 seconds in between triggers,	1367	This doesn't mean there will always be 3600 seconds in between triggers,
963	but only that the the callback will be called when the system time shows a	1368	but only that the callback will be called when the system time shows a
964	full hour (UTC), or more correctly, when the system time is evenly divisible	1369	full hour (UTC), or more correctly, when the system time is evenly divisible
965	by 3600.	1370	by 3600.
966		1371
967	Another way to think about it (for the mathematically inclined) is that	1372	Another way to think about it (for the mathematically inclined) is that
968	C<ev_periodic> will try to run the callback in this mode at the next possible	1373	C<ev_periodic> will try to run the callback in this mode at the next possible
969	time where C<time = at (mod interval)>, regardless of any time jumps.	1374	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1375
		1376	For numerical stability it is preferable that the C<at> value is near
		1377	C<ev_now ()> (the current time), but there is no range requirement for
		1378	this value, and in fact is often specified as zero.
		1379
		1380	Note also that there is an upper limit to how often a timer can fire (CPU
		1381	speed for example), so if C<interval> is very small then timing stability
		1382	will of course deteriorate. Libev itself tries to be exact to be about one
		1383	millisecond (if the OS supports it and the machine is fast enough).
		1384
971	=item * manual reschedule mode (reschedule_cb = callback)	1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1386
973	In this mode the values for C<interval> and C<at> are both being	1387	In this mode the values for C<interval> and C<at> are both being
974	ignored. Instead, each time the periodic watcher gets scheduled, the	1388	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1389	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1390	current time as second argument.
977		1391
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
979	ever, or make any event loop modifications>. If you need to stop it,	1393	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		1394
		1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1397	only event loop modification you are allowed to do).
		1398
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
984	ev_tstamp now)>, e.g.:	1400	*w, ev_tstamp now)>, e.g.:
985		1401
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
987	{	1403	{
988	return now + 60.;	1404	return now + 60.;
989	}	1405	}
…		…
991	It must return the next time to trigger, based on the passed time value	1407	It must return the next time to trigger, based on the passed time value
992	(that is, the lowest time value larger than to the second argument). It	1408	(that is, the lowest time value larger than to the second argument). It
993	will usually be called just before the callback will be triggered, but	1409	will usually be called just before the callback will be triggered, but
994	might be called at other times, too.	1410	might be called at other times, too.
995		1411
996	NOTE: I<< This callback must always return a time that is later than the	1412	NOTE: I<< This callback must always return a time that is higher than or
997	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1413	equal to the passed C<now> value >>.
998		1414
999	This can be used to create very complex timers, such as a timer that	1415	This can be used to create very complex timers, such as a timer that
1000	triggers on each midnight, local time. To do this, you would calculate the	1416	triggers on "next midnight, local time". To do this, you would calculate the
1001	next midnight after C<now> and return the timestamp value for this. How	1417	next midnight after C<now> and return the timestamp value for this. How
1002	you do this is, again, up to you (but it is not trivial, which is the main	1418	you do this is, again, up to you (but it is not trivial, which is the main
1003	reason I omitted it as an example).	1419	reason I omitted it as an example).
1004		1420
1005	=back	1421	=back
…		…
1009	Simply stops and restarts the periodic watcher again. This is only useful	1425	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1426	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	1427	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1428	program when the crontabs have changed).
1013		1429
		1430	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1431
		1432	When active, returns the absolute time that the watcher is supposed to
		1433	trigger next.
		1434
		1435	=item ev_tstamp offset [read-write]
		1436
		1437	When repeating, this contains the offset value, otherwise this is the
		1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1439
		1440	Can be modified any time, but changes only take effect when the periodic
		1441	timer fires or C<ev_periodic_again> is being called.
		1442
1014	=item ev_tstamp interval [read-write]	1443	=item ev_tstamp interval [read-write]
1015		1444
1016	The current interval value. Can be modified any time, but changes only	1445	The current interval value. Can be modified any time, but changes only
1017	take effect when the periodic timer fires or C<ev_periodic_again> is being	1446	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1447	called.
…		…
1023	switched off. Can be changed any time, but changes only take effect when	1452	switched off. Can be changed any time, but changes only take effect when
1024	the periodic timer fires or C<ev_periodic_again> is being called.	1453	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1454
1026	=back	1455	=back
1027		1456
		1457	=head3 Examples
		1458
1028	Example: call a callback every hour, or, more precisely, whenever the	1459	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1460	system clock is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1461	potentially a lot of jitter, but good long-term stability.
1031		1462
1032	static void	1463	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1034	{	1465	{
1035	... its now a full hour (UTC, or TAI or whatever your clock follows)	1466	... its now a full hour (UTC, or TAI or whatever your clock follows)
1036	}	1467	}
1037		1468
1038	struct ev_periodic hourly_tick;	1469	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1471	ev_periodic_start (loop, &hourly_tick);
1041		1472
1042	Example: the same as above, but use a reschedule callback to do it:	1473	Example: The same as above, but use a reschedule callback to do it:
1043		1474
1044	#include <math.h>	1475	#include <math.h>
1045		1476
1046	static ev_tstamp	1477	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1048	{	1479	{
1049	return fmod (now, 3600.) + 3600.;	1480	return fmod (now, 3600.) + 3600.;
1050	}	1481	}
1051		1482
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1484
1054	Example: call a callback every hour, starting now:	1485	Example: Call a callback every hour, starting now:
1055		1486
1056	struct ev_periodic hourly_tick;	1487	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1488	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1489	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1490	ev_periodic_start (loop, &hourly_tick);
1060		1491
1061		1492
1062	=head2 C<ev_signal> - signal me when a signal gets signalled!	1493	=head2 C<ev_signal> - signal me when a signal gets signalled!
1063		1494
1064	Signal watchers will trigger an event when the process receives a specific	1495	Signal watchers will trigger an event when the process receives a specific
…		…
1071	with the kernel (thus it coexists with your own signal handlers as long	1502	with the kernel (thus it coexists with your own signal handlers as long
1072	as you don't register any with libev). Similarly, when the last signal	1503	as you don't register any with libev). Similarly, when the last signal
1073	watcher for a signal is stopped libev will reset the signal handler to	1504	watcher for a signal is stopped libev will reset the signal handler to
1074	SIG_DFL (regardless of what it was set to before).	1505	SIG_DFL (regardless of what it was set to before).
1075		1506
		1507	If possible and supported, libev will install its handlers with
		1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1509	interrupted. If you have a problem with system calls getting interrupted by
		1510	signals you can block all signals in an C<ev_check> watcher and unblock
		1511	them in an C<ev_prepare> watcher.
		1512
		1513	=head3 Watcher-Specific Functions and Data Members
		1514
1076	=over 4	1515	=over 4
1077		1516
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1517	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1518
1080	=item ev_signal_set (ev_signal *, int signum)	1519	=item ev_signal_set (ev_signal *, int signum)
…		…
1086		1525
1087	The signal the watcher watches out for.	1526	The signal the watcher watches out for.
1088		1527
1089	=back	1528	=back
1090		1529
		1530	=head3 Examples
		1531
		1532	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1533
		1534	static void
		1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1536	{
		1537	ev_unloop (loop, EVUNLOOP_ALL);
		1538	}
		1539
		1540	struct ev_signal signal_watcher;
		1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1542	ev_signal_start (loop, &sigint_cb);
		1543
1091		1544
1092	=head2 C<ev_child> - watch out for process status changes	1545	=head2 C<ev_child> - watch out for process status changes
1093		1546
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1547	Child watchers trigger when your process receives a SIGCHLD in response to
1095	some child status changes (most typically when a child of yours dies).	1548	some child status changes (most typically when a child of yours dies). It
		1549	is permissible to install a child watcher I<after> the child has been
		1550	forked (which implies it might have already exited), as long as the event
		1551	loop isn't entered (or is continued from a watcher).
		1552
		1553	Only the default event loop is capable of handling signals, and therefore
		1554	you can only register child watchers in the default event loop.
		1555
		1556	=head3 Process Interaction
		1557
		1558	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1559	initialised. This is necessary to guarantee proper behaviour even if
		1560	the first child watcher is started after the child exits. The occurrence
		1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1562	synchronously as part of the event loop processing. Libev always reaps all
		1563	children, even ones not watched.
		1564
		1565	=head3 Overriding the Built-In Processing
		1566
		1567	Libev offers no special support for overriding the built-in child
		1568	processing, but if your application collides with libev's default child
		1569	handler, you can override it easily by installing your own handler for
		1570	C<SIGCHLD> after initialising the default loop, and making sure the
		1571	default loop never gets destroyed. You are encouraged, however, to use an
		1572	event-based approach to child reaping and thus use libev's support for
		1573	that, so other libev users can use C<ev_child> watchers freely.
		1574
		1575	=head3 Watcher-Specific Functions and Data Members
1096		1576
1097	=over 4	1577	=over 4
1098		1578
1099	=item ev_child_init (ev_child *, callback, int pid)	1579	=item ev_child_init (ev_child *, callback, int pid, int trace)
1100		1580
1101	=item ev_child_set (ev_child *, int pid)	1581	=item ev_child_set (ev_child *, int pid, int trace)
1102		1582
1103	Configures the watcher to wait for status changes of process C<pid> (or	1583	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	1584	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	1585	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	1586	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	1587	C<waitpid> documentation). The C<rpid> member contains the pid of the
1108	process causing the status change.	1588	process causing the status change. C<trace> must be either C<0> (only
		1589	activate the watcher when the process terminates) or C<1> (additionally
		1590	activate the watcher when the process is stopped or continued).
1109		1591
1110	=item int pid [read-only]	1592	=item int pid [read-only]
1111		1593
1112	The process id this watcher watches out for, or C<0>, meaning any process id.	1594	The process id this watcher watches out for, or C<0>, meaning any process id.
1113		1595
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1602	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1603	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1604
1123	=back	1605	=back
1124		1606
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1607	=head3 Examples
1126		1608
		1609	Example: C<fork()> a new process and install a child handler to wait for
		1610	its completion.
		1611
		1612	ev_child cw;
		1613
1127	static void	1614	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1615	child_cb (EV_P_ struct ev_child *w, int revents)
1129	{	1616	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1617	ev_child_stop (EV_A_ w);
		1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1131	}	1619	}
1132		1620
1133	struct ev_signal signal_watcher;	1621	pid_t pid = fork ();
1134	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1622
1135	ev_signal_start (loop, &sigint_cb);	1623	if (pid < 0)
		1624	// error
		1625	else if (pid == 0)
		1626	{
		1627	// the forked child executes here
		1628	exit (1);
		1629	}
		1630	else
		1631	{
		1632	ev_child_init (&cw, child_cb, pid, 0);
		1633	ev_child_start (EV_DEFAULT_ &cw);
		1634	}
1136		1635
1137		1636
1138	=head2 C<ev_stat> - did the file attributes just change?	1637	=head2 C<ev_stat> - did the file attributes just change?
1139		1638
1140	This watches a filesystem path for attribute changes. That is, it calls	1639	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	1640	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.	1641	compared to the last time, invoking the callback if it did.
1143		1642
1144	The path does not need to exist: changing from "path exists" to "path does	1643	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	1644	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	1645	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	1646	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1647	the stat buffer having unspecified contents.
1149		1648
		1649	The path I<should> be absolute and I<must not> end in a slash. If it is
		1650	relative and your working directory changes, the behaviour is undefined.
		1651
1150	Since there is no standard to do this, the portable implementation simply	1652	Since there is no standard to do this, the portable implementation simply
1151	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1152	can specify a recommended polling interval for this case. If you specify	1654	can specify a recommended polling interval for this case. If you specify
1153	a polling interval of C<0> (highly recommended!) then a I<suitable,	1655	a polling interval of C<0> (highly recommended!) then a I<suitable,
1154	unspecified default> value will be used (which you can expect to be around	1656	unspecified default> value will be used (which you can expect to be around
1155	five seconds, although this might change dynamically). Libev will also	1657	five seconds, although this might change dynamically). Libev will also
1156	impose a minimum interval which is currently around C<0.1>, but thats	1658	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1158		1660
1159	This watcher type is not meant for massive numbers of stat watchers,	1661	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1662	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1663	resource-intensive.
1162		1664
1163	At the time of this writing, no specific OS backends are implemented, but	1665	At the time of this writing, only the Linux inotify interface is
1164	if demand increases, at least a kqueue and inotify backend will be added.	1666	implemented (implementing kqueue support is left as an exercise for the
		1667	reader, note, however, that the author sees no way of implementing ev_stat
		1668	semantics with kqueue). Inotify will be used to give hints only and should
		1669	not change the semantics of C<ev_stat> watchers, which means that libev
		1670	sometimes needs to fall back to regular polling again even with inotify,
		1671	but changes are usually detected immediately, and if the file exists there
		1672	will be no polling.
		1673
		1674	=head3 ABI Issues (Largefile Support)
		1675
		1676	Libev by default (unless the user overrides this) uses the default
		1677	compilation environment, which means that on systems with large file
		1678	support disabled by default, you get the 32 bit version of the stat
		1679	structure. When using the library from programs that change the ABI to
		1680	use 64 bit file offsets the programs will fail. In that case you have to
		1681	compile libev with the same flags to get binary compatibility. This is
		1682	obviously the case with any flags that change the ABI, but the problem is
		1683	most noticeably disabled with ev_stat and large file support.
		1684
		1685	The solution for this is to lobby your distribution maker to make large
		1686	file interfaces available by default (as e.g. FreeBSD does) and not
		1687	optional. Libev cannot simply switch on large file support because it has
		1688	to exchange stat structures with application programs compiled using the
		1689	default compilation environment.
		1690
		1691	=head3 Inotify
		1692
		1693	When C<inotify (7)> support has been compiled into libev (generally only
		1694	available on Linux) and present at runtime, it will be used to speed up
		1695	change detection where possible. The inotify descriptor will be created lazily
		1696	when the first C<ev_stat> watcher is being started.
		1697
		1698	Inotify presence does not change the semantics of C<ev_stat> watchers
		1699	except that changes might be detected earlier, and in some cases, to avoid
		1700	making regular C<stat> calls. Even in the presence of inotify support
		1701	there are many cases where libev has to resort to regular C<stat> polling.
		1702
		1703	(There is no support for kqueue, as apparently it cannot be used to
		1704	implement this functionality, due to the requirement of having a file
		1705	descriptor open on the object at all times).
		1706
		1707	=head3 The special problem of stat time resolution
		1708
		1709	The C<stat ()> system call only supports full-second resolution portably, and
		1710	even on systems where the resolution is higher, many file systems still
		1711	only support whole seconds.
		1712
		1713	That means that, if the time is the only thing that changes, you can
		1714	easily miss updates: on the first update, C<ev_stat> detects a change and
		1715	calls your callback, which does something. When there is another update
		1716	within the same second, C<ev_stat> will be unable to detect it as the stat
		1717	data does not change.
		1718
		1719	The solution to this is to delay acting on a change for slightly more
		1720	than a second (or till slightly after the next full second boundary), using
		1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1722	ev_timer_again (loop, w)>).
		1723
		1724	The C<.02> offset is added to work around small timing inconsistencies
		1725	of some operating systems (where the second counter of the current time
		1726	might be be delayed. One such system is the Linux kernel, where a call to
		1727	C<gettimeofday> might return a timestamp with a full second later than
		1728	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1729	update file times then there will be a small window where the kernel uses
		1730	the previous second to update file times but libev might already execute
		1731	the timer callback).
		1732
		1733	=head3 Watcher-Specific Functions and Data Members
1165		1734
1166	=over 4	1735	=over 4
1167		1736
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1737	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1738
…		…
1173	C<path>. The C<interval> is a hint on how quickly a change is expected to	1742	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	1743	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	1744	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.	1745	path for as long as the watcher is active.
1177		1746
1178	The callback will be receive C<EV_STAT> when a change was detected,	1747	The callback will receive C<EV_STAT> when a change was detected, relative
1179	relative to the attributes at the time the watcher was started (or the	1748	to the attributes at the time the watcher was started (or the last change
1180	last change was detected).	1749	was detected).
1181		1750
1182	=item ev_stat_stat (ev_stat *)	1751	=item ev_stat_stat (loop, ev_stat *)
1183		1752
1184	Updates the stat buffer immediately with new values. If you change the	1753	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	1754	watched path in your callback, you could call this function to avoid
1186	detecting this change (while introducing a race condition). Can also be	1755	detecting this change (while introducing a race condition if you are not
1187	useful simply to find out the new values.	1756	the only one changing the path). Can also be useful simply to find out the
		1757	new values.
1188		1758
1189	=item ev_statdata attr [read-only]	1759	=item ev_statdata attr [read-only]
1190		1760
1191	The most-recently detected attributes of the file. Although the type is of	1761	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	1762	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	1763	suitable for your system, but you can only rely on the POSIX-standardised
		1764	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.	1765	some error while C<stat>ing the file.
1195		1766
1196	=item ev_statdata prev [read-only]	1767	=item ev_statdata prev [read-only]
1197		1768
1198	The previous attributes of the file. The callback gets invoked whenever	1769	The previous attributes of the file. The callback gets invoked whenever
1199	C<prev> != C<attr>.	1770	C<prev> != C<attr>, or, more precisely, one or more of these members
		1771	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1772	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1200		1773
1201	=item ev_tstamp interval [read-only]	1774	=item ev_tstamp interval [read-only]
1202		1775
1203	The specified interval.	1776	The specified interval.
1204		1777
1205	=item const char *path [read-only]	1778	=item const char *path [read-only]
1206		1779
1207	The filesystem path that is being watched.	1780	The file system path that is being watched.
1208		1781
1209	=back	1782	=back
1210		1783
		1784	=head3 Examples
		1785
1211	Example: Watch C</etc/passwd> for attribute changes.	1786	Example: Watch C</etc/passwd> for attribute changes.
1212		1787
1213	static void	1788	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1789	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1215	{	1790	{
1216	/* /etc/passwd changed in some way */	1791	/* /etc/passwd changed in some way */
1217	if (w->attr.st_nlink)	1792	if (w->attr.st_nlink)
1218	{	1793	{
1219	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1794	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1220	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1795	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1221	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1796	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1222	}	1797	}
1223	else	1798	else
1224	/* you shalt not abuse printf for puts */	1799	/* you shalt not abuse printf for puts */
1225	puts ("wow, /etc/passwd is not there, expect problems. "	1800	puts ("wow, /etc/passwd is not there, expect problems. "
1226	"if this is windows, they already arrived\n");	1801	"if this is windows, they already arrived\n");
1227	}	1802	}
1228		1803
1229	...	1804	...
1230	ev_stat passwd;	1805	ev_stat passwd;
1231		1806
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1807	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1808	ev_stat_start (loop, &passwd);
		1809
		1810	Example: Like above, but additionally use a one-second delay so we do not
		1811	miss updates (however, frequent updates will delay processing, too, so
		1812	one might do the work both on C<ev_stat> callback invocation I<and> on
		1813	C<ev_timer> callback invocation).
		1814
		1815	static ev_stat passwd;
		1816	static ev_timer timer;
		1817
		1818	static void
		1819	timer_cb (EV_P_ ev_timer *w, int revents)
		1820	{
		1821	ev_timer_stop (EV_A_ w);
		1822
		1823	/* now it's one second after the most recent passwd change */
		1824	}
		1825
		1826	static void
		1827	stat_cb (EV_P_ ev_stat *w, int revents)
		1828	{
		1829	/* reset the one-second timer */
		1830	ev_timer_again (EV_A_ &timer);
		1831	}
		1832
		1833	...
		1834	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1835	ev_stat_start (loop, &passwd);
		1836	ev_timer_init (&timer, timer_cb, 0., 1.02);
1234		1837
1235		1838
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1839	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1840
1238	Idle watchers trigger events when there are no other events are pending	1841	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	1842	priority are pending (prepare, check and other idle watchers do not
1240	as your process is busy handling sockets or timeouts (or even signals,	1843	count).
1241	imagine) it will not be triggered. But when your process is idle all idle	1844
1242	watchers are being called again and again, once per event loop iteration -	1845	That is, as long as your process is busy handling sockets or timeouts
		1846	(or even signals, imagine) of the same or higher priority it will not be
		1847	triggered. But when your process is idle (or only lower-priority watchers
		1848	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	1849	iteration - until stopped, that is, or your process receives more events
1244	busy.	1850	and becomes busy again with higher priority stuff.
1245		1851
1246	The most noteworthy effect is that as long as any idle watchers are	1852	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.	1853	active, the process will not block when waiting for new events.
1248		1854
1249	Apart from keeping your process non-blocking (which is a useful	1855	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	1856	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1857	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1858	event loop has handled all outstanding events.
1253		1859
		1860	=head3 Watcher-Specific Functions and Data Members
		1861
1254	=over 4	1862	=over 4
1255		1863
1256	=item ev_idle_init (ev_signal *, callback)	1864	=item ev_idle_init (ev_signal *, callback)
1257		1865
1258	Initialises and configures the idle watcher - it has no parameters of any	1866	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,	1867	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1868	believe me.
1261		1869
1262	=back	1870	=back
1263		1871
		1872	=head3 Examples
		1873
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1875	callback, free it. Also, use no error checking, as usual.
1266		1876
1267	static void	1877	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1879	{
1270	free (w);	1880	free (w);
1271	// now do something you wanted to do when the program has	1881	// now do something you wanted to do when the program has
1272	// no longer asnything immediate to do.	1882	// no longer anything immediate to do.
1273	}	1883	}
1274		1884
1275	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1276	ev_idle_init (idle_watcher, idle_cb);	1886	ev_idle_init (idle_watcher, idle_cb);
1277	ev_idle_start (loop, idle_cb);	1887	ev_idle_start (loop, idle_cb);
1278		1888
1279		1889
1280	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1281		1891
1282	Prepare and check watchers are usually (but not always) used in tandem:	1892	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1301		1911
1302	This is done by examining in each prepare call which file descriptors need	1912	This is done by examining in each prepare call which file descriptors need
1303	to be watched by the other library, registering C<ev_io> watchers for	1913	to be watched by the other library, registering C<ev_io> watchers for
1304	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1305	provide just this functionality). Then, in the check watcher you check for	1915	provide just this functionality). Then, in the check watcher you check for
1306	any events that occured (by checking the pending status of all watchers	1916	any events that occurred (by checking the pending status of all watchers
1307	and stopping them) and call back into the library. The I/O and timer	1917	and stopping them) and call back into the library. The I/O and timer
1308	callbacks will never actually be called (but must be valid nevertheless,	1918	callbacks will never actually be called (but must be valid nevertheless,
1309	because you never know, you know?).	1919	because you never know, you know?).
1310		1920
1311	As another example, the Perl Coro module uses these hooks to integrate	1921	As another example, the Perl Coro module uses these hooks to integrate
…		…
1315	with priority higher than or equal to the event loop and one coroutine	1925	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	1926	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	1927	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	1928	low-priority coroutines to idle/background tasks).
1319		1929
		1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1931	priority, to ensure that they are being run before any other watchers
		1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1933	too) should not activate ("feed") events into libev. While libev fully
		1934	supports this, they might get executed before other C<ev_check> watchers
		1935	did their job. As C<ev_check> watchers are often used to embed other
		1936	(non-libev) event loops those other event loops might be in an unusable
		1937	state until their C<ev_check> watcher ran (always remind yourself to
		1938	coexist peacefully with others).
		1939
		1940	=head3 Watcher-Specific Functions and Data Members
		1941
1320	=over 4	1942	=over 4
1321		1943
1322	=item ev_prepare_init (ev_prepare *, callback)	1944	=item ev_prepare_init (ev_prepare *, callback)
1323		1945
1324	=item ev_check_init (ev_check *, callback)	1946	=item ev_check_init (ev_check *, callback)
…		…
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1949	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.	1950	macros, but using them is utterly, utterly and completely pointless.
1329		1951
1330	=back	1952	=back
1331		1953
1332	Example: To include a library such as adns, you would add IO watchers	1954	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	1955
		1956	There are a number of principal ways to embed other event loops or modules
		1957	into libev. Here are some ideas on how to include libadns into libev
		1958	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1959	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1960	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1961	Glib event loop).
		1962
		1963	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	1964	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	1965	is pseudo-code only of course. This requires you to either use a low
		1966	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1967	the callbacks for the IO/timeout watchers might not have been called yet.
1336		1968
1337	static ev_io iow [nfd];	1969	static ev_io iow [nfd];
1338	static ev_timer tw;	1970	static ev_timer tw;
1339		1971
1340	static void	1972	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	1973	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	1974	{
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	}	1975	}
1349		1976
1350	// create io watchers for each fd and a timer before blocking	1977	// create io watchers for each fd and a timer before blocking
1351	static void	1978	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	1980	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	1981	int timeout = 3600000;
		1982	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	1983	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		1985
1358	/* the callback is illegal, but won't be called as we stop during check */	1986	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	1987	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	1988	ev_timer_start (loop, &tw);
1361		1989
1362	// create on ev_io per pollfd	1990	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	1991	for (int i = 0; i < nfd; ++i)
1364	{	1992	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	1993	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	1994	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1995	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		1996
1369	fds [i].revents = 0;	1997	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	1998	ev_io_start (loop, iow + i);
1372	}	1999	}
1373	}	2000	}
1374		2001
1375	// stop all watchers after blocking	2002	// stop all watchers after blocking
1376	static void	2003	static void
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	2005	{
1379	ev_timer_stop (loop, &tw);	2006	ev_timer_stop (loop, &tw);
1380		2007
1381	for (int i = 0; i < nfd; ++i)	2008	for (int i = 0; i < nfd; ++i)
		2009	{
		2010	// set the relevant poll flags
		2011	// could also call adns_processreadable etc. here
		2012	struct pollfd *fd = fds + i;
		2013	int revents = ev_clear_pending (iow + i);
		2014	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2015	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2016
		2017	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	2018	ev_io_stop (loop, iow + i);
		2019	}
1383		2020
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2021	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1385	}	2022	}
		2023
		2024	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2025	in the prepare watcher and would dispose of the check watcher.
		2026
		2027	Method 3: If the module to be embedded supports explicit event
		2028	notification (libadns does), you can also make use of the actual watcher
		2029	callbacks, and only destroy/create the watchers in the prepare watcher.
		2030
		2031	static void
		2032	timer_cb (EV_P_ ev_timer *w, int revents)
		2033	{
		2034	adns_state ads = (adns_state)w->data;
		2035	update_now (EV_A);
		2036
		2037	adns_processtimeouts (ads, &tv_now);
		2038	}
		2039
		2040	static void
		2041	io_cb (EV_P_ ev_io *w, int revents)
		2042	{
		2043	adns_state ads = (adns_state)w->data;
		2044	update_now (EV_A);
		2045
		2046	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2047	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2048	}
		2049
		2050	// do not ever call adns_afterpoll
		2051
		2052	Method 4: Do not use a prepare or check watcher because the module you
		2053	want to embed is too inflexible to support it. Instead, you can override
		2054	their poll function. The drawback with this solution is that the main
		2055	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2056	this.
		2057
		2058	static gint
		2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2060	{
		2061	int got_events = 0;
		2062
		2063	for (n = 0; n < nfds; ++n)
		2064	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2065
		2066	if (timeout >= 0)
		2067	// create/start timer
		2068
		2069	// poll
		2070	ev_loop (EV_A_ 0);
		2071
		2072	// stop timer again
		2073	if (timeout >= 0)
		2074	ev_timer_stop (EV_A_ &to);
		2075
		2076	// stop io watchers again - their callbacks should have set
		2077	for (n = 0; n < nfds; ++n)
		2078	ev_io_stop (EV_A_ iow [n]);
		2079
		2080	return got_events;
		2081	}
1386		2082
1387		2083
1388	=head2 C<ev_embed> - when one backend isn't enough...	2084	=head2 C<ev_embed> - when one backend isn't enough...
1389		2085
1390	This is a rather advanced watcher type that lets you embed one event loop	2086	This is a rather advanced watcher type that lets you embed one event loop
…		…
1432	portable one.	2128	portable one.
1433		2129
1434	So when you want to use this feature you will always have to be prepared	2130	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	2131	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	2132	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:	2133	create it, and if that fails, use the normal loop for everything.
1438		2134
1439	struct ev_loop *loop_hi = ev_default_init (0);	2135	=head3 Watcher-Specific Functions and Data Members
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
1449	// if we got one, then embed it, otherwise default to loop_hi
1450	if (loop_lo)
1451	{
1452	ev_embed_init (&embed, 0, loop_lo);
1453	ev_embed_start (loop_hi, &embed);
1454	}
1455	else
1456	loop_lo = loop_hi;
1457		2136
1458	=over 4	2137	=over 4
1459		2138
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2139	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1461		2140
…		…
1463		2142
1464	Configures the watcher to embed the given loop, which must be	2143	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	2144	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	2145	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,	2146	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).	2147	if you do not want that, you need to temporarily stop the embed watcher).
1469		2148
1470	=item ev_embed_sweep (loop, ev_embed *)	2149	=item ev_embed_sweep (loop, ev_embed *)
1471		2150
1472	Make a single, non-blocking sweep over the embedded loop. This works	2151	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	2152	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1474	apropriate way for embedded loops.	2153	appropriate way for embedded loops.
1475		2154
1476	=item struct ev_loop *loop [read-only]	2155	=item struct ev_loop *other [read-only]
1477		2156
1478	The embedded event loop.	2157	The embedded event loop.
1479		2158
1480	=back	2159	=back
		2160
		2161	=head3 Examples
		2162
		2163	Example: Try to get an embeddable event loop and embed it into the default
		2164	event loop. If that is not possible, use the default loop. The default
		2165	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2167	used).
		2168
		2169	struct ev_loop *loop_hi = ev_default_init (0);
		2170	struct ev_loop *loop_lo = 0;
		2171	struct ev_embed embed;
		2172
		2173	// see if there is a chance of getting one that works
		2174	// (remember that a flags value of 0 means autodetection)
		2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2177	: 0;
		2178
		2179	// if we got one, then embed it, otherwise default to loop_hi
		2180	if (loop_lo)
		2181	{
		2182	ev_embed_init (&embed, 0, loop_lo);
		2183	ev_embed_start (loop_hi, &embed);
		2184	}
		2185	else
		2186	loop_lo = loop_hi;
		2187
		2188	Example: Check if kqueue is available but not recommended and create
		2189	a kqueue backend for use with sockets (which usually work with any
		2190	kqueue implementation). Store the kqueue/socket-only event loop in
		2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2192
		2193	struct ev_loop *loop = ev_default_init (0);
		2194	struct ev_loop *loop_socket = 0;
		2195	struct ev_embed embed;
		2196
		2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2199	{
		2200	ev_embed_init (&embed, 0, loop_socket);
		2201	ev_embed_start (loop, &embed);
		2202	}
		2203
		2204	if (!loop_socket)
		2205	loop_socket = loop;
		2206
		2207	// now use loop_socket for all sockets, and loop for everything else
1481		2208
1482		2209
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2210	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2211
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2212	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,	2215	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	2216	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	2217	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2218	handlers will be invoked, too, of course.
1492		2219
		2220	=head3 Watcher-Specific Functions and Data Members
		2221
1493	=over 4	2222	=over 4
1494		2223
1495	=item ev_fork_init (ev_signal *, callback)	2224	=item ev_fork_init (ev_signal *, callback)
1496		2225
1497	Initialises and configures the fork watcher - it has no parameters of any	2226	Initialises and configures the fork watcher - it has no parameters of any
1498	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2227	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1499	believe me.	2228	believe me.
		2229
		2230	=back
		2231
		2232
		2233	=head2 C<ev_async> - how to wake up another event loop
		2234
		2235	In general, you cannot use an C<ev_loop> from multiple threads or other
		2236	asynchronous sources such as signal handlers (as opposed to multiple event
		2237	loops - those are of course safe to use in different threads).
		2238
		2239	Sometimes, however, you need to wake up another event loop you do not
		2240	control, for example because it belongs to another thread. This is what
		2241	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2242	can signal it by calling C<ev_async_send>, which is thread- and signal
		2243	safe.
		2244
		2245	This functionality is very similar to C<ev_signal> watchers, as signals,
		2246	too, are asynchronous in nature, and signals, too, will be compressed
		2247	(i.e. the number of callback invocations may be less than the number of
		2248	C<ev_async_sent> calls).
		2249
		2250	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2251	just the default loop.
		2252
		2253	=head3 Queueing
		2254
		2255	C<ev_async> does not support queueing of data in any way. The reason
		2256	is that the author does not know of a simple (or any) algorithm for a
		2257	multiple-writer-single-reader queue that works in all cases and doesn't
		2258	need elaborate support such as pthreads.
		2259
		2260	That means that if you want to queue data, you have to provide your own
		2261	queue. But at least I can tell you would implement locking around your
		2262	queue:
		2263
		2264	=over 4
		2265
		2266	=item queueing from a signal handler context
		2267
		2268	To implement race-free queueing, you simply add to the queue in the signal
		2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2270	some fictitious SIGUSR1 handler:
		2271
		2272	static ev_async mysig;
		2273
		2274	static void
		2275	sigusr1_handler (void)
		2276	{
		2277	sometype data;
		2278
		2279	// no locking etc.
		2280	queue_put (data);
		2281	ev_async_send (EV_DEFAULT_ &mysig);
		2282	}
		2283
		2284	static void
		2285	mysig_cb (EV_P_ ev_async *w, int revents)
		2286	{
		2287	sometype data;
		2288	sigset_t block, prev;
		2289
		2290	sigemptyset (&block);
		2291	sigaddset (&block, SIGUSR1);
		2292	sigprocmask (SIG_BLOCK, &block, &prev);
		2293
		2294	while (queue_get (&data))
		2295	process (data);
		2296
		2297	if (sigismember (&prev, SIGUSR1)
		2298	sigprocmask (SIG_UNBLOCK, &block, 0);
		2299	}
		2300
		2301	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2302	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2303	either...).
		2304
		2305	=item queueing from a thread context
		2306
		2307	The strategy for threads is different, as you cannot (easily) block
		2308	threads but you can easily preempt them, so to queue safely you need to
		2309	employ a traditional mutex lock, such as in this pthread example:
		2310
		2311	static ev_async mysig;
		2312	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2313
		2314	static void
		2315	otherthread (void)
		2316	{
		2317	// only need to lock the actual queueing operation
		2318	pthread_mutex_lock (&mymutex);
		2319	queue_put (data);
		2320	pthread_mutex_unlock (&mymutex);
		2321
		2322	ev_async_send (EV_DEFAULT_ &mysig);
		2323	}
		2324
		2325	static void
		2326	mysig_cb (EV_P_ ev_async *w, int revents)
		2327	{
		2328	pthread_mutex_lock (&mymutex);
		2329
		2330	while (queue_get (&data))
		2331	process (data);
		2332
		2333	pthread_mutex_unlock (&mymutex);
		2334	}
		2335
		2336	=back
		2337
		2338
		2339	=head3 Watcher-Specific Functions and Data Members
		2340
		2341	=over 4
		2342
		2343	=item ev_async_init (ev_async *, callback)
		2344
		2345	Initialises and configures the async watcher - it has no parameters of any
		2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2347	believe me.
		2348
		2349	=item ev_async_send (loop, ev_async *)
		2350
		2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2353	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2355	section below on what exactly this means).
		2356
		2357	This call incurs the overhead of a system call only once per loop iteration,
		2358	so while the overhead might be noticeable, it doesn't apply to repeated
		2359	calls to C<ev_async_send>.
		2360
		2361	=item bool = ev_async_pending (ev_async *)
		2362
		2363	Returns a non-zero value when C<ev_async_send> has been called on the
		2364	watcher but the event has not yet been processed (or even noted) by the
		2365	event loop.
		2366
		2367	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2368	the loop iterates next and checks for the watcher to have become active,
		2369	it will reset the flag again. C<ev_async_pending> can be used to very
		2370	quickly check whether invoking the loop might be a good idea.
		2371
		2372	Not that this does I<not> check whether the watcher itself is pending, only
		2373	whether it has been requested to make this watcher pending.
1500		2374
1501	=back	2375	=back
1502		2376
1503		2377
1504	=head1 OTHER FUNCTIONS	2378	=head1 OTHER FUNCTIONS
…		…
1515	or timeout without having to allocate/configure/start/stop/free one or	2389	or timeout without having to allocate/configure/start/stop/free one or
1516	more watchers yourself.	2390	more watchers yourself.
1517		2391
1518	If C<fd> is less than 0, then no I/O watcher will be started and events	2392	If C<fd> is less than 0, then no I/O watcher will be started and events
1519	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1520	C<events> set will be craeted and started.	2394	C<events> set will be created and started.
1521		2395
1522	If C<timeout> is less than 0, then no timeout watcher will be	2396	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	2397	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	2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1525	dubious value.	2399	dubious value.
…		…
1527	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2401	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	2402	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>	2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1530	value passed to C<ev_once>:	2404	value passed to C<ev_once>:
1531		2405
1532	static void stdin_ready (int revents, void *arg)	2406	static void stdin_ready (int revents, void *arg)
1533	{	2407	{
1534	if (revents & EV_TIMEOUT)	2408	if (revents & EV_TIMEOUT)
1535	/* doh, nothing entered */;	2409	/* doh, nothing entered */;
1536	else if (revents & EV_READ)	2410	else if (revents & EV_READ)
1537	/* stdin might have data for us, joy! */;	2411	/* stdin might have data for us, joy! */;
1538	}	2412	}
1539		2413
1540	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1541		2415
1542	=item ev_feed_event (ev_loop *, watcher *, int revents)	2416	=item ev_feed_event (ev_loop *, watcher *, int revents)
1543		2417
1544	Feeds the given event set into the event loop, as if the specified event	2418	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	2419	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	2424	Feed an event on the given fd, as if a file descriptor backend detected
1551	the given events it.	2425	the given events it.
1552		2426
1553	=item ev_feed_signal_event (ev_loop *loop, int signum)	2427	=item ev_feed_signal_event (ev_loop *loop, int signum)
1554		2428
1555	Feed an event as if the given signal occured (C<loop> must be the default	2429	Feed an event as if the given signal occurred (C<loop> must be the default
1556	loop!).	2430	loop!).
1557		2431
1558	=back	2432	=back
1559		2433
1560		2434
…		…
1576		2450
1577	=item * Priorities are not currently supported. Initialising priorities	2451	=item * Priorities are not currently supported. Initialising priorities
1578	will fail and all watchers will have the same priority, even though there	2452	will fail and all watchers will have the same priority, even though there
1579	is an ev_pri field.	2453	is an ev_pri field.
1580		2454
		2455	=item * In libevent, the last base created gets the signals, in libev, the
		2456	first base created (== the default loop) gets the signals.
		2457
1581	=item * Other members are not supported.	2458	=item * Other members are not supported.
1582		2459
1583	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2460	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1584	to use the libev header file and library.	2461	to use the libev header file and library.
1585		2462
1586	=back	2463	=back
1587		2464
1588	=head1 C++ SUPPORT	2465	=head1 C++ SUPPORT
1589		2466
1590	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2467	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	2468	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.	2469	the callback model to a model using method callbacks on objects.
1593		2470
1594	To use it,	2471	To use it,
1595		2472
1596	#include <ev++.h>	2473	#include <ev++.h>
1597		2474
1598	(it is not installed by default). This automatically includes F<ev.h>	2475	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	2476	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.	2477	put into the C<ev> namespace. It should support all the same embedding
		2478	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2479
1602	It should support all the same embedding options as F<ev.h>, most notably	2480	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2481	classes add (compared to plain C-style watchers) is the event loop pointer
		2482	that the watcher is associated with (or no additional members at all if
		2483	you disable C<EV_MULTIPLICITY> when embedding libev).
		2484
		2485	Currently, functions, and static and non-static member functions can be
		2486	used as callbacks. Other types should be easy to add as long as they only
		2487	need one additional pointer for context. If you need support for other
		2488	types of functors please contact the author (preferably after implementing
		2489	it).
1604		2490
1605	Here is a list of things available in the C<ev> namespace:	2491	Here is a list of things available in the C<ev> namespace:
1606		2492
1607	=over 4	2493	=over 4
1608		2494
…		…
1624		2510
1625	All of those classes have these methods:	2511	All of those classes have these methods:
1626		2512
1627	=over 4	2513	=over 4
1628		2514
1629	=item ev::TYPE::TYPE (object *, object::method *)	2515	=item ev::TYPE::TYPE ()
1630		2516
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2517	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2518
1633	=item ev::TYPE::~TYPE	2519	=item ev::TYPE::~TYPE
1634		2520
1635	The constructor takes a pointer to an object and a method pointer to	2521	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2522	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	2523
1638	before starting it. If you do not specify a loop then the constructor	2524	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2525	C<set> method before starting it.
		2526
		2527	It will not set a callback, however: You have to call the templated C<set>
		2528	method to set a callback before you can start the watcher.
		2529
		2530	(The reason why you have to use a method is a limitation in C++ which does
		2531	not allow explicit template arguments for constructors).
1640		2532
1641	The destructor automatically stops the watcher if it is active.	2533	The destructor automatically stops the watcher if it is active.
		2534
		2535	=item w->set<class, &class::method> (object *)
		2536
		2537	This method sets the callback method to call. The method has to have a
		2538	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2539	first argument and the C<revents> as second. The object must be given as
		2540	parameter and is stored in the C<data> member of the watcher.
		2541
		2542	This method synthesizes efficient thunking code to call your method from
		2543	the C callback that libev requires. If your compiler can inline your
		2544	callback (i.e. it is visible to it at the place of the C<set> call and
		2545	your compiler is good :), then the method will be fully inlined into the
		2546	thunking function, making it as fast as a direct C callback.
		2547
		2548	Example: simple class declaration and watcher initialisation
		2549
		2550	struct myclass
		2551	{
		2552	void io_cb (ev::io &w, int revents) { }
		2553	}
		2554
		2555	myclass obj;
		2556	ev::io iow;
		2557	iow.set <myclass, &myclass::io_cb> (&obj);
		2558
		2559	=item w->set<function> (void *data = 0)
		2560
		2561	Also sets a callback, but uses a static method or plain function as
		2562	callback. The optional C<data> argument will be stored in the watcher's
		2563	C<data> member and is free for you to use.
		2564
		2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2566
		2567	See the method-C<set> above for more details.
		2568
		2569	Example:
		2570
		2571	static void io_cb (ev::io &w, int revents) { }
		2572	iow.set <io_cb> ();
1642		2573
1643	=item w->set (struct ev_loop *)	2574	=item w->set (struct ev_loop *)
1644		2575
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2576	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).	2577	do this when the watcher is inactive (and not pending either).
1647		2578
1648	=item w->set ([args])	2579	=item w->set ([arguments])
1649		2580
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2581	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	2582	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2583	automatically stopped and restarted when reconfiguring it with this
		2584	method.
1653		2585
1654	=item w->start ()	2586	=item w->start ()
1655		2587
1656	Starts the watcher. Note that there is no C<loop> argument as the	2588	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2589	constructor already stores the event loop.
1658		2590
1659	=item w->stop ()	2591	=item w->stop ()
1660		2592
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2593	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2594
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2595	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2596
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2597	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2598	C<ev_TYPE_again> function.
1667		2599
1668	=item w->sweep () C<ev::embed> only	2600	=item w->sweep () (C<ev::embed> only)
1669		2601
1670	Invokes C<ev_embed_sweep>.	2602	Invokes C<ev_embed_sweep>.
1671		2603
1672	=item w->update () C<ev::stat> only	2604	=item w->update () (C<ev::stat> only)
1673		2605
1674	Invokes C<ev_stat_stat>.	2606	Invokes C<ev_stat_stat>.
1675		2607
1676	=back	2608	=back
1677		2609
1678	=back	2610	=back
1679		2611
1680	Example: Define a class with an IO and idle watcher, start one of them in	2612	Example: Define a class with an IO and idle watcher, start one of them in
1681	the constructor.	2613	the constructor.
1682		2614
1683	class myclass	2615	class myclass
1684	{	2616	{
1685	ev_io io; void io_cb (ev::io &w, int revents);	2617	ev::io io; void io_cb (ev::io &w, int revents);
1686	ev_idle idle void idle_cb (ev::idle &w, int revents);	2618	ev:idle idle void idle_cb (ev::idle &w, int revents);
1687		2619
1688	myclass ();	2620	myclass (int fd)
1689	}	2621	{
		2622	io .set <myclass, &myclass::io_cb > (this);
		2623	idle.set <myclass, &myclass::idle_cb> (this);
1690		2624
1691	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{
1695	io.start (fd, ev::READ);	2625	io.start (fd, ev::READ);
		2626	}
1696	}	2627	};
		2628
		2629
		2630	=head1 OTHER LANGUAGE BINDINGS
		2631
		2632	Libev does not offer other language bindings itself, but bindings for a
		2633	number of languages exist in the form of third-party packages. If you know
		2634	any interesting language binding in addition to the ones listed here, drop
		2635	me a note.
		2636
		2637	=over 4
		2638
		2639	=item Perl
		2640
		2641	The EV module implements the full libev API and is actually used to test
		2642	libev. EV is developed together with libev. Apart from the EV core module,
		2643	there are additional modules that implement libev-compatible interfaces
		2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2646
		2647	It can be found and installed via CPAN, its homepage is at
		2648	L<http://software.schmorp.de/pkg/EV>.
		2649
		2650	=item Python
		2651
		2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2653	seems to be quite complete and well-documented. Note, however, that the
		2654	patch they require for libev is outright dangerous as it breaks the ABI
		2655	for everybody else, and therefore, should never be applied in an installed
		2656	libev (if python requires an incompatible ABI then it needs to embed
		2657	libev).
		2658
		2659	=item Ruby
		2660
		2661	Tony Arcieri has written a ruby extension that offers access to a subset
		2662	of the libev API and adds file handle abstractions, asynchronous DNS and
		2663	more on top of it. It can be found via gem servers. Its homepage is at
		2664	L<http://rev.rubyforge.org/>.
		2665
		2666	=item D
		2667
		2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2670
		2671	=back
1697		2672
1698		2673
1699	=head1 MACRO MAGIC	2674	=head1 MACRO MAGIC
1700		2675
1701	Libev can be compiled with a variety of options, the most fundemantal is	2676	Libev can be compiled with a variety of options, the most fundamental
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2677	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2678	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2679
1705	To make it easier to write programs that cope with either variant, the	2680	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2681	following macros are defined:
1707		2682
1708	=over 4	2683	=over 4
…		…
1711		2686
1712	This provides the loop I<argument> for functions, if one is required ("ev	2687	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,	2688	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:	2689	C<EV_A_> is used when other arguments are following. Example:
1715		2690
1716	ev_unref (EV_A);	2691	ev_unref (EV_A);
1717	ev_timer_add (EV_A_ watcher);	2692	ev_timer_add (EV_A_ watcher);
1718	ev_loop (EV_A_ 0);	2693	ev_loop (EV_A_ 0);
1719		2694
1720	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2695	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1721	which is often provided by the following macro.	2696	which is often provided by the following macro.
1722		2697
1723	=item C<EV_P>, C<EV_P_>	2698	=item C<EV_P>, C<EV_P_>
1724		2699
1725	This provides the loop I<parameter> for functions, if one is required ("ev	2700	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,	2701	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:	2702	C<EV_P_> is used when other parameters are following. Example:
1728		2703
1729	// this is how ev_unref is being declared	2704	// this is how ev_unref is being declared
1730	static void ev_unref (EV_P);	2705	static void ev_unref (EV_P);
1731		2706
1732	// this is how you can declare your typical callback	2707	// this is how you can declare your typical callback
1733	static void cb (EV_P_ ev_timer *w, int revents)	2708	static void cb (EV_P_ ev_timer *w, int revents)
1734		2709
1735	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2710	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1736	suitable for use with C<EV_A>.	2711	suitable for use with C<EV_A>.
1737		2712
1738	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2713	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1739		2714
1740	Similar to the other two macros, this gives you the value of the default	2715	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2716	loop, if multiple loops are supported ("ev loop default").
1742		2717
		2718	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2719
		2720	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2721	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2722	is undefined when the default loop has not been initialised by a previous
		2723	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2724
		2725	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2726	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2727
1743	=back	2728	=back
1744		2729
1745	Example: Declare and initialise a check watcher, working regardless of	2730	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2731	macros so it will work regardless of whether multiple loops are supported
		2732	or not.
1747		2733
1748	static void	2734	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2735	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2736	{
1751	ev_check_stop (EV_A_ w);	2737	ev_check_stop (EV_A_ w);
1752	}	2738	}
1753		2739
1754	ev_check check;	2740	ev_check check;
1755	ev_check_init (&check, check_cb);	2741	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2742	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2743	ev_loop (EV_DEFAULT_ 0);
1758
1759		2744
1760	=head1 EMBEDDING	2745	=head1 EMBEDDING
1761		2746
1762	Libev can (and often is) directly embedded into host	2747	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2748	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2749	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2750	and rxvt-unicode.
1766		2751
1767	The goal is to enable you to just copy the neecssary files into your	2752	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	2753	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	2754	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2755	libev somewhere in your source tree).
1771		2756
1772	=head2 FILESETS	2757	=head2 FILESETS
1773		2758
1774	Depending on what features you need you need to include one or more sets of files	2759	Depending on what features you need you need to include one or more sets of files
1775	in your app.	2760	in your application.
1776		2761
1777	=head3 CORE EVENT LOOP	2762	=head3 CORE EVENT LOOP
1778		2763
1779	To include only the libev core (all the C<ev_*> functions), with manual	2764	To include only the libev core (all the C<ev_*> functions), with manual
1780	configuration (no autoconf):	2765	configuration (no autoconf):
1781		2766
1782	#define EV_STANDALONE 1	2767	#define EV_STANDALONE 1
1783	#include "ev.c"	2768	#include "ev.c"
1784		2769
1785	This will automatically include F<ev.h>, too, and should be done in a	2770	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	2771	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	2772	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	2773	done by writing a wrapper around F<ev.h> that you can include instead and
1789	where you can put other configuration options):	2774	where you can put other configuration options):
1790		2775
1791	#define EV_STANDALONE 1	2776	#define EV_STANDALONE 1
1792	#include "ev.h"	2777	#include "ev.h"
1793		2778
1794	Both header files and implementation files can be compiled with a C++	2779	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	2780	compiler (at least, thats a stated goal, and breakage will be treated
1796	as a bug).	2781	as a bug).
1797		2782
1798	You need the following files in your source tree, or in a directory	2783	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):	2784	in your include path (e.g. in libev/ when using -Ilibev):
1800		2785
1801	ev.h	2786	ev.h
1802	ev.c	2787	ev.c
1803	ev_vars.h	2788	ev_vars.h
1804	ev_wrap.h	2789	ev_wrap.h
1805		2790
1806	ev_win32.c required on win32 platforms only	2791	ev_win32.c required on win32 platforms only
1807		2792
1808	ev_select.c only when select backend is enabled (which is by default)	2793	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)	2794	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)	2795	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)	2796	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)	2797	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2798
1814	F<ev.c> includes the backend files directly when enabled, so you only need	2799	F<ev.c> includes the backend files directly when enabled, so you only need
1815	to compile this single file.	2800	to compile this single file.
1816		2801
1817	=head3 LIBEVENT COMPATIBILITY API	2802	=head3 LIBEVENT COMPATIBILITY API
1818		2803
1819	To include the libevent compatibility API, also include:	2804	To include the libevent compatibility API, also include:
1820		2805
1821	#include "event.c"	2806	#include "event.c"
1822		2807
1823	in the file including F<ev.c>, and:	2808	in the file including F<ev.c>, and:
1824		2809
1825	#include "event.h"	2810	#include "event.h"
1826		2811
1827	in the files that want to use the libevent API. This also includes F<ev.h>.	2812	in the files that want to use the libevent API. This also includes F<ev.h>.
1828		2813
1829	You need the following additional files for this:	2814	You need the following additional files for this:
1830		2815
1831	event.h	2816	event.h
1832	event.c	2817	event.c
1833		2818
1834	=head3 AUTOCONF SUPPORT	2819	=head3 AUTOCONF SUPPORT
1835		2820
1836	Instead of using C<EV_STANDALONE=1> and providing your config in	2821	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	2822	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	2823	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1839	include F<config.h> and configure itself accordingly.	2824	include F<config.h> and configure itself accordingly.
1840		2825
1841	For this of course you need the m4 file:	2826	For this of course you need the m4 file:
1842		2827
1843	libev.m4	2828	libev.m4
1844		2829
1845	=head2 PREPROCESSOR SYMBOLS/MACROS	2830	=head2 PREPROCESSOR SYMBOLS/MACROS
1846		2831
1847	Libev can be configured via a variety of preprocessor symbols you have to define	2832	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	2833	define before including any of its files. The default in the absence of
1849	and only include the select backend.	2834	autoconf is noted for every option.
1850		2835
1851	=over 4	2836	=over 4
1852		2837
1853	=item EV_STANDALONE	2838	=item EV_STANDALONE
1854		2839
…		…
1859	F<event.h> that are not directly supported by the libev core alone.	2844	F<event.h> that are not directly supported by the libev core alone.
1860		2845
1861	=item EV_USE_MONOTONIC	2846	=item EV_USE_MONOTONIC
1862		2847
1863	If defined to be C<1>, libev will try to detect the availability of the	2848	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	2849	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	2850	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	2851	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2852	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>	2853	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2854	function is hiding in (often F<-lrt>).
1870		2855
1871	=item EV_USE_REALTIME	2856	=item EV_USE_REALTIME
1872		2857
1873	If defined to be C<1>, libev will try to detect the availability of the	2858	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	2859	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	2860	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	2861	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	2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2864
		2865	=item EV_USE_NANOSLEEP
		2866
		2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2868	and will use it for delays. Otherwise it will use C<select ()>.
		2869
		2870	=item EV_USE_EVENTFD
		2871
		2872	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2873	available and will probe for kernel support at runtime. This will improve
		2874	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2875	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2876	2.7 or newer, otherwise disabled.
1879		2877
1880	=item EV_USE_SELECT	2878	=item EV_USE_SELECT
1881		2879
1882	If undefined or defined to be C<1>, libev will compile in support for the	2880	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	2881	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	2882	other method takes over, select will be it. Otherwise the select backend
1885	will not be compiled in.	2883	will not be compiled in.
1886		2884
1887	=item EV_SELECT_USE_FD_SET	2885	=item EV_SELECT_USE_FD_SET
1888		2886
1889	If defined to C<1>, then the select backend will use the system C<fd_set>	2887	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	2888	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	2889	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	2890	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	2891	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	2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1895	influence the size of the C<fd_set> used.	2893	influence the size of the C<fd_set> used.
1896		2894
…		…
1902	be used is the winsock select). This means that it will call	2900	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,	2901	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	2902	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	2903	on win32. Should not be defined on non-win32 platforms.
1906		2904
		2905	=item EV_FD_TO_WIN32_HANDLE
		2906
		2907	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2908	file descriptors to socket handles. When not defining this symbol (the
		2909	default), then libev will call C<_get_osfhandle>, which is usually
		2910	correct. In some cases, programs use their own file descriptor management,
		2911	in which case they can provide this function to map fds to socket handles.
		2912
1907	=item EV_USE_POLL	2913	=item EV_USE_POLL
1908		2914
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2915	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	2916	backend. Otherwise it will be enabled on non-win32 platforms. It
1911	takes precedence over select.	2917	takes precedence over select.
1912		2918
1913	=item EV_USE_EPOLL	2919	=item EV_USE_EPOLL
1914		2920
1915	If defined to be C<1>, libev will compile in support for the Linux	2921	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,	2922	C<epoll>(7) backend. Its availability will be detected at runtime,
1917	otherwise another method will be used as fallback. This is the	2923	otherwise another method will be used as fallback. This is the preferred
1918	preferred backend for GNU/Linux systems.	2924	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2925	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
1919		2926
1920	=item EV_USE_KQUEUE	2927	=item EV_USE_KQUEUE
1921		2928
1922	If defined to be C<1>, libev will compile in support for the BSD style	2929	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,	2930	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	2943	otherwise another method will be used as fallback. This is the preferred
1937	backend for Solaris 10 systems.	2944	backend for Solaris 10 systems.
1938		2945
1939	=item EV_USE_DEVPOLL	2946	=item EV_USE_DEVPOLL
1940		2947
1941	reserved for future expansion, works like the USE symbols above.	2948	Reserved for future expansion, works like the USE symbols above.
		2949
		2950	=item EV_USE_INOTIFY
		2951
		2952	If defined to be C<1>, libev will compile in support for the Linux inotify
		2953	interface to speed up C<ev_stat> watchers. Its actual availability will
		2954	be detected at runtime. If undefined, it will be enabled if the headers
		2955	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2956
		2957	=item EV_ATOMIC_T
		2958
		2959	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2960	access is atomic with respect to other threads or signal contexts. No such
		2961	type is easily found in the C language, so you can provide your own type
		2962	that you know is safe for your purposes. It is used both for signal handler "locking"
		2963	as well as for signal and thread safety in C<ev_async> watchers.
		2964
		2965	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2966	(from F<signal.h>), which is usually good enough on most platforms.
1942		2967
1943	=item EV_H	2968	=item EV_H
1944		2969
1945	The name of the F<ev.h> header file used to include it. The default if	2970	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	2971	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.	2972	used to virtually rename the F<ev.h> header file in case of conflicts.
1948		2973
1949	=item EV_CONFIG_H	2974	=item EV_CONFIG_H
1950		2975
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2976	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	2977	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	2978	C<EV_H>, above.
1954		2979
1955	=item EV_EVENT_H	2980	=item EV_EVENT_H
1956		2981
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2982	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.	2983	of how the F<event.h> header can be found, the default is C<"event.h">.
1959		2984
1960	=item EV_PROTOTYPES	2985	=item EV_PROTOTYPES
1961		2986
1962	If defined to be C<0>, then F<ev.h> will not define any function	2987	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	2988	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	2995	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	2996	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	2997	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	2998	argument. Instead, all functions act on the single default loop.
1974		2999
		3000	=item EV_MINPRI
		3001
		3002	=item EV_MAXPRI
		3003
		3004	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3005	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3006	provide for more priorities by overriding those symbols (usually defined
		3007	to be C<-2> and C<2>, respectively).
		3008
		3009	When doing priority-based operations, libev usually has to linearly search
		3010	all the priorities, so having many of them (hundreds) uses a lot of space
		3011	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3012	fine.
		3013
		3014	If your embedding application does not need any priorities, defining these both to
		3015	C<0> will save some memory and CPU.
		3016
1975	=item EV_PERIODIC_ENABLE	3017	=item EV_PERIODIC_ENABLE
1976		3018
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	3019	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	3020	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	3021	code.
1980		3022
		3023	=item EV_IDLE_ENABLE
		3024
		3025	If undefined or defined to be C<1>, then idle watchers are supported. If
		3026	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3027	code.
		3028
1981	=item EV_EMBED_ENABLE	3029	=item EV_EMBED_ENABLE
1982		3030
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	3031	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	3032	defined to be C<0>, then they are not.
1985		3033
…		…
1991	=item EV_FORK_ENABLE	3039	=item EV_FORK_ENABLE
1992		3040
1993	If undefined or defined to be C<1>, then fork watchers are supported. If	3041	If undefined or defined to be C<1>, then fork watchers are supported. If
1994	defined to be C<0>, then they are not.	3042	defined to be C<0>, then they are not.
1995		3043
		3044	=item EV_ASYNC_ENABLE
		3045
		3046	If undefined or defined to be C<1>, then async watchers are supported. If
		3047	defined to be C<0>, then they are not.
		3048
1996	=item EV_MINIMAL	3049	=item EV_MINIMAL
1997		3050
1998	If you need to shave off some kilobytes of code at the expense of some	3051	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	3052	speed, define this symbol to C<1>. Currently this is used to override some
2000	some inlining decisions, saves roughly 30% codesize of amd64.	3053	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3054	much smaller 2-heap for timer management over the default 4-heap.
2001		3055
2002	=item EV_PID_HASHSIZE	3056	=item EV_PID_HASHSIZE
2003		3057
2004	C<ev_child> watchers use a small hash table to distribute workload by	3058	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	3059	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	3060	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	3061	increase this value (I<must> be a power of two).
		3062
		3063	=item EV_INOTIFY_HASHSIZE
		3064
		3065	C<ev_stat> watchers use a small hash table to distribute workload by
		3066	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3067	usually more than enough. If you need to manage thousands of C<ev_stat>
		3068	watchers you might want to increase this value (I<must> be a power of
		3069	two).
		3070
		3071	=item EV_USE_4HEAP
		3072
		3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3075	to C<1>. The 4-heap uses more complicated (longer) code but has
		3076	noticeably faster performance with many (thousands) of watchers.
		3077
		3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3079	(disabled).
		3080
		3081	=item EV_HEAP_CACHE_AT
		3082
		3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3084	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3087	but avoids random read accesses on heap changes. This improves performance
		3088	noticeably with with many (hundreds) of watchers.
		3089
		3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3091	(disabled).
		3092
		3093	=item EV_VERIFY
		3094
		3095	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3096	be done: If set to C<0>, no internal verification code will be compiled
		3097	in. If set to C<1>, then verification code will be compiled in, but not
		3098	called. If set to C<2>, then the internal verification code will be
		3099	called once per loop, which can slow down libev. If set to C<3>, then the
		3100	verification code will be called very frequently, which will slow down
		3101	libev considerably.
		3102
		3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3104	C<0.>
2008		3105
2009	=item EV_COMMON	3106	=item EV_COMMON
2010		3107
2011	By default, all watchers have a C<void *data> member. By redefining	3108	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	3109	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,	3110	members. You have to define it each time you include one of the files,
2014	though, and it must be identical each time.	3111	though, and it must be identical each time.
2015		3112
2016	For example, the perl EV module uses something like this:	3113	For example, the perl EV module uses something like this:
2017		3114
2018	#define EV_COMMON \	3115	#define EV_COMMON \
2019	SV *self; /* contains this struct */ \	3116	SV *self; /* contains this struct */ \
2020	SV *cb_sv, *fh /* note no trailing ";" */	3117	SV *cb_sv, *fh /* note no trailing ";" */
2021		3118
2022	=item EV_CB_DECLARE (type)	3119	=item EV_CB_DECLARE (type)
2023		3120
2024	=item EV_CB_INVOKE (watcher, revents)	3121	=item EV_CB_INVOKE (watcher, revents)
2025		3122
2026	=item ev_set_cb (ev, cb)	3123	=item ev_set_cb (ev, cb)
2027		3124
2028	Can be used to change the callback member declaration in each watcher,	3125	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	3126	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	3127	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	3128	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	3129	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++.	3130	method calls instead of plain function calls in C++.
		3131
		3132	=head2 EXPORTED API SYMBOLS
		3133
		3134	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3135	exported symbols, you can use the provided F<Symbol.*> files which list
		3136	all public symbols, one per line:
		3137
		3138	Symbols.ev for libev proper
		3139	Symbols.event for the libevent emulation
		3140
		3141	This can also be used to rename all public symbols to avoid clashes with
		3142	multiple versions of libev linked together (which is obviously bad in
		3143	itself, but sometimes it is inconvenient to avoid this).
		3144
		3145	A sed command like this will create wrapper C<#define>'s that you need to
		3146	include before including F<ev.h>:
		3147
		3148	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3149
		3150	This would create a file F<wrap.h> which essentially looks like this:
		3151
		3152	#define ev_backend myprefix_ev_backend
		3153	#define ev_check_start myprefix_ev_check_start
		3154	#define ev_check_stop myprefix_ev_check_stop
		3155	...
2034		3156
2035	=head2 EXAMPLES	3157	=head2 EXAMPLES
2036		3158
2037	For a real-world example of a program the includes libev	3159	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	3160	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	3163	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	3164	will be compiled. It is pretty complex because it provides its own header
2043	file.	3165	file.
2044		3166
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3167	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:	3168	that everybody includes and which overrides some configure choices:
2047		3169
		3170	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	3171	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	3172	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	3173	#define EV_PERIODIC_ENABLE 0
		3174	#define EV_STAT_ENABLE 0
		3175	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	3176	#define EV_CONFIG_H <config.h>
		3177	#define EV_MINPRI 0
		3178	#define EV_MAXPRI 0
2052		3179
2053	#include "ev++.h"	3180	#include "ev++.h"
2054		3181
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		3183
2057	#include "ev_cpp.h"	3184	#include "ev_cpp.h"
2058	#include "ev.c"	3185	#include "ev.c"
		3186
		3187
		3188	=head1 THREADS AND COROUTINES
		3189
		3190	=head2 THREADS
		3191
		3192	Libev itself is completely thread-safe, but it uses no locking. This
		3193	means that you can use as many loops as you want in parallel, as long as
		3194	only one thread ever calls into one libev function with the same loop
		3195	parameter.
		3196
		3197	Or put differently: calls with different loop parameters can be done in
		3198	parallel from multiple threads, calls with the same loop parameter must be
		3199	done serially (but can be done from different threads, as long as only one
		3200	thread ever is inside a call at any point in time, e.g. by using a mutex
		3201	per loop).
		3202
		3203	If you want to know which design (one loop, locking, or multiple loops
		3204	without or something else still) is best for your problem, then I cannot
		3205	help you. I can give some generic advice however:
		3206
		3207	=over 4
		3208
		3209	=item * most applications have a main thread: use the default libev loop
		3210	in that thread, or create a separate thread running only the default loop.
		3211
		3212	This helps integrating other libraries or software modules that use libev
		3213	themselves and don't care/know about threading.
		3214
		3215	=item * one loop per thread is usually a good model.
		3216
		3217	Doing this is almost never wrong, sometimes a better-performance model
		3218	exists, but it is always a good start.
		3219
		3220	=item * other models exist, such as the leader/follower pattern, where one
		3221	loop is handed through multiple threads in a kind of round-robin fashion.
		3222
		3223	Choosing a model is hard - look around, learn, know that usually you can do
		3224	better than you currently do :-)
		3225
		3226	=item * often you need to talk to some other thread which blocks in the
		3227	event loop - C<ev_async> watchers can be used to wake them up from other
		3228	threads safely (or from signal contexts...).
		3229
		3230	=back
		3231
		3232	=head2 COROUTINES
		3233
		3234	Libev is much more accommodating to coroutines ("cooperative threads"):
		3235	libev fully supports nesting calls to it's functions from different
		3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3237	different coroutines and switch freely between both coroutines running the
		3238	loop, as long as you don't confuse yourself). The only exception is that
		3239	you must not do this from C<ev_periodic> reschedule callbacks.
		3240
		3241	Care has been invested into making sure that libev does not keep local
		3242	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3243	switches.
2059		3244
2060		3245
2061	=head1 COMPLEXITIES	3246	=head1 COMPLEXITIES
2062		3247
2063	In this section the complexities of (many of) the algorithms used inside	3248	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	3249	libev will be explained. For complexity discussions about backends see the
2065	documentation for C<ev_default_init>.	3250	documentation for C<ev_default_init>.
2066		3251
		3252	All of the following are about amortised time: If an array needs to be
		3253	extended, libev needs to realloc and move the whole array, but this
		3254	happens asymptotically never with higher number of elements, so O(1) might
		3255	mean it might do a lengthy realloc operation in rare cases, but on average
		3256	it is much faster and asymptotically approaches constant time.
		3257
2067	=over 4	3258	=over 4
2068		3259
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		3261
		3262	This means that, when you have a watcher that triggers in one hour and
		3263	there are 100 watchers that would trigger before that then inserting will
		3264	have to skip roughly seven (C<ld 100>) of these watchers.
		3265
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2072		3267
		3268	That means that changing a timer costs less than removing/adding them
		3269	as only the relative motion in the event queue has to be paid for.
		3270
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2074		3272
		3273	These just add the watcher into an array or at the head of a list.
		3274
2075	=item Stopping check/prepare/idle watchers: O(1)	3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2076		3276
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		3278
		3279	These watchers are stored in lists then need to be walked to find the
		3280	correct watcher to remove. The lists are usually short (you don't usually
		3281	have many watchers waiting for the same fd or signal).
		3282
2079	=item Finding the next timer per loop iteration: O(1)	3283	=item Finding the next timer in each loop iteration: O(1)
		3284
		3285	By virtue of using a binary or 4-heap, the next timer is always found at a
		3286	fixed position in the storage array.
2080		3287
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		3289
2083	=item Activating one watcher: O(1)	3290	A change means an I/O watcher gets started or stopped, which requires
		3291	libev to recalculate its status (and possibly tell the kernel, depending
		3292	on backend and whether C<ev_io_set> was used).
		3293
		3294	=item Activating one watcher (putting it into the pending state): O(1)
		3295
		3296	=item Priority handling: O(number_of_priorities)
		3297
		3298	Priorities are implemented by allocating some space for each
		3299	priority. When doing priority-based operations, libev usually has to
		3300	linearly search all the priorities, but starting/stopping and activating
		3301	watchers becomes O(1) w.r.t. priority handling.
		3302
		3303	=item Sending an ev_async: O(1)
		3304
		3305	=item Processing ev_async_send: O(number_of_async_watchers)
		3306
		3307	=item Processing signals: O(max_signal_number)
		3308
		3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3310	calls in the current loop iteration. Checking for async and signal events
		3311	involves iterating over all running async watchers or all signal numbers.
2084		3312
2085	=back	3313	=back
2086		3314
2087		3315
		3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3317
		3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3319	requires, and its I/O model is fundamentally incompatible with the POSIX
		3320	model. Libev still offers limited functionality on this platform in
		3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3322	descriptors. This only applies when using Win32 natively, not when using
		3323	e.g. cygwin.
		3324
		3325	Lifting these limitations would basically require the full
		3326	re-implementation of the I/O system. If you are into these kinds of
		3327	things, then note that glib does exactly that for you in a very portable
		3328	way (note also that glib is the slowest event library known to man).
		3329
		3330	There is no supported compilation method available on windows except
		3331	embedding it into other applications.
		3332
		3333	Not a libev limitation but worth mentioning: windows apparently doesn't
		3334	accept large writes: instead of resulting in a partial write, windows will
		3335	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3336	so make sure you only write small amounts into your sockets (less than a
		3337	megabyte seems safe, but thsi apparently depends on the amount of memory
		3338	available).
		3339
		3340	Due to the many, low, and arbitrary limits on the win32 platform and
		3341	the abysmal performance of winsockets, using a large number of sockets
		3342	is not recommended (and not reasonable). If your program needs to use
		3343	more than a hundred or so sockets, then likely it needs to use a totally
		3344	different implementation for windows, as libev offers the POSIX readiness
		3345	notification model, which cannot be implemented efficiently on windows
		3346	(Microsoft monopoly games).
		3347
		3348	A typical way to use libev under windows is to embed it (see the embedding
		3349	section for details) and use the following F<evwrap.h> header file instead
		3350	of F<ev.h>:
		3351
		3352	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3354
		3355	#include "ev.h"
		3356
		3357	And compile the following F<evwrap.c> file into your project (make sure
		3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3359
		3360	#include "evwrap.h"
		3361	#include "ev.c"
		3362
		3363	=over 4
		3364
		3365	=item The winsocket select function
		3366
		3367	The winsocket C<select> function doesn't follow POSIX in that it
		3368	requires socket I<handles> and not socket I<file descriptors> (it is
		3369	also extremely buggy). This makes select very inefficient, and also
		3370	requires a mapping from file descriptors to socket handles (the Microsoft
		3371	C runtime provides the function C<_open_osfhandle> for this). See the
		3372	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3373	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3374
		3375	The configuration for a "naked" win32 using the Microsoft runtime
		3376	libraries and raw winsocket select is:
		3377
		3378	#define EV_USE_SELECT 1
		3379	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3380
		3381	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3382	complexity in the O(n²) range when using win32.
		3383
		3384	=item Limited number of file descriptors
		3385
		3386	Windows has numerous arbitrary (and low) limits on things.
		3387
		3388	Early versions of winsocket's select only supported waiting for a maximum
		3389	of C<64> handles (probably owning to the fact that all windows kernels
		3390	can only wait for C<64> things at the same time internally; Microsoft
		3391	recommends spawning a chain of threads and wait for 63 handles and the
		3392	previous thread in each. Great).
		3393
		3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3395	to some high number (e.g. C<2048>) before compiling the winsocket select
		3396	call (which might be in libev or elsewhere, for example, perl does its own
		3397	select emulation on windows).
		3398
		3399	Another limit is the number of file descriptors in the Microsoft runtime
		3400	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3401	or something like this inside Microsoft). You can increase this by calling
		3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3403	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3404	libraries.
		3405
		3406	This might get you to about C<512> or C<2048> sockets (depending on
		3407	windows version and/or the phase of the moon). To get more, you need to
		3408	wrap all I/O functions and provide your own fd management, but the cost of
		3409	calling select (O(n²)) will likely make this unworkable.
		3410
		3411	=back
		3412
		3413
		3414	=head1 PORTABILITY REQUIREMENTS
		3415
		3416	In addition to a working ISO-C implementation, libev relies on a few
		3417	additional extensions:
		3418
		3419	=over 4
		3420
		3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3422	calling conventions regardless of C<ev_watcher_type *>.
		3423
		3424	Libev assumes not only that all watcher pointers have the same internal
		3425	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3426	assumes that the same (machine) code can be used to call any watcher
		3427	callback: The watcher callbacks have different type signatures, but libev
		3428	calls them using an C<ev_watcher *> internally.
		3429
		3430	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3431
		3432	The type C<sig_atomic_t volatile> (or whatever is defined as
		3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3434	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3435	believed to be sufficiently portable.
		3436
		3437	=item C<sigprocmask> must work in a threaded environment
		3438
		3439	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3440	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3441	pthread implementations will either allow C<sigprocmask> in the "main
		3442	thread" or will block signals process-wide, both behaviours would
		3443	be compatible with libev. Interaction between C<sigprocmask> and
		3444	C<pthread_sigmask> could complicate things, however.
		3445
		3446	The most portable way to handle signals is to block signals in all threads
		3447	except the initial one, and run the default loop in the initial thread as
		3448	well.
		3449
		3450	=item C<long> must be large enough for common memory allocation sizes
		3451
		3452	To improve portability and simplify using libev, libev uses C<long>
		3453	internally instead of C<size_t> when allocating its data structures. On
		3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3455	is still at least 31 bits everywhere, which is enough for hundreds of
		3456	millions of watchers.
		3457
		3458	=item C<double> must hold a time value in seconds with enough accuracy
		3459
		3460	The type C<double> is used to represent timestamps. It is required to
		3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3462	enough for at least into the year 4000. This requirement is fulfilled by
		3463	implementations implementing IEEE 754 (basically all existing ones).
		3464
		3465	=back
		3466
		3467	If you know of other additional requirements drop me a note.
		3468
		3469
		3470	=head1 COMPILER WARNINGS
		3471
		3472	Depending on your compiler and compiler settings, you might get no or a
		3473	lot of warnings when compiling libev code. Some people are apparently
		3474	scared by this.
		3475
		3476	However, these are unavoidable for many reasons. For one, each compiler
		3477	has different warnings, and each user has different tastes regarding
		3478	warning options. "Warn-free" code therefore cannot be a goal except when
		3479	targeting a specific compiler and compiler-version.
		3480
		3481	Another reason is that some compiler warnings require elaborate
		3482	workarounds, or other changes to the code that make it less clear and less
		3483	maintainable.
		3484
		3485	And of course, some compiler warnings are just plain stupid, or simply
		3486	wrong (because they don't actually warn about the condition their message
		3487	seems to warn about).
		3488
		3489	While libev is written to generate as few warnings as possible,
		3490	"warn-free" code is not a goal, and it is recommended not to build libev
		3491	with any compiler warnings enabled unless you are prepared to cope with
		3492	them (e.g. by ignoring them). Remember that warnings are just that:
		3493	warnings, not errors, or proof of bugs.
		3494
		3495
		3496	=head1 VALGRIND
		3497
		3498	Valgrind has a special section here because it is a popular tool that is
		3499	highly useful, but valgrind reports are very hard to interpret.
		3500
		3501	If you think you found a bug (memory leak, uninitialised data access etc.)
		3502	in libev, then check twice: If valgrind reports something like:
		3503
		3504	==2274== definitely lost: 0 bytes in 0 blocks.
		3505	==2274== possibly lost: 0 bytes in 0 blocks.
		3506	==2274== still reachable: 256 bytes in 1 blocks.
		3507
		3508	Then there is no memory leak. Similarly, under some circumstances,
		3509	valgrind might report kernel bugs as if it were a bug in libev, or it
		3510	might be confused (it is a very good tool, but only a tool).
		3511
		3512	If you are unsure about something, feel free to contact the mailing list
		3513	with the full valgrind report and an explanation on why you think this is
		3514	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3515	no bug" answer and take the chance of learning how to interpret valgrind
		3516	properly.
		3517
		3518	If you need, for some reason, empty reports from valgrind for your project
		3519	I suggest using suppression lists.
		3520
		3521
2088	=head1 AUTHOR	3522	=head1 AUTHOR
2089		3523
2090	Marc Lehmann <libev@schmorp.de>.	3524	Marc Lehmann <libev@schmorp.de>.
2091		3525

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