ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs.
Revision 1.174 by root, Mon Aug 18 23:23:45 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		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.
52		141
53		142
54	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
55		144
56	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
…		…
62		151
63	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
64	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
65	you actually want to know.	154	you actually want to know.
66		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
67	=item int ev_version_major ()	162	=item int ev_version_major ()
68		163
69	=item int ev_version_minor ()	164	=item int ev_version_minor ()
70		165
71	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
72	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
73	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
74	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
75	version of the library your program was compiled against.	170	version of the library your program was compiled against.
76		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
77	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,
78	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
79	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
80	not a problem.	178	not a problem.
81		179
82	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
83	version:	181	version.
84		182
85	assert (("libev version mismatch",	183	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
88		186
89	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
90		188
91	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_*>
92	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
94	a description of the set values.	192	a description of the set values.
95		193
96	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
97	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
98		196
99	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
100	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
101		199
102	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
103		201
104	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
105	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
106	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
107	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
108	(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
109	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
110		208
111	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
112		210
…		…
118		216
119	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
120		218
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		220
123	Sets the allocation function to use (the prototype is similar to the	221	Sets the allocation function to use (the prototype is similar - the
124	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
125	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
126	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
127	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.
128		230
129	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
130	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,
131	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.
132		234
133	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
134	retries: better than mine).	236	retries (example requires a standards-compliant C<realloc>).
135		237
136	static void *	238	static void *
137	persistent_realloc (void *ptr, long size)	239	persistent_realloc (void *ptr, size_t size)
138	{	240	{
139	for (;;)	241	for (;;)
140	{	242	{
141	void *newptr = realloc (ptr, size);	243	void *newptr = realloc (ptr, size);
142		244
…		…
150	...	252	...
151	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
152		254
153	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
154		256
155	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
156	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
157	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
158	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
159	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
160	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
161	(such as abort).	263	(such as abort).
162		264
163	Example: do the same thing as libev does internally:	265	Example: This is basically the same thing that libev does internally, too.
164		266
165	static void	267	static void
166	fatal_error (const char *msg)	268	fatal_error (const char *msg)
167	{	269	{
168	perror (msg);	270	perror (msg);
…		…
177	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
178		280
179	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
180	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
181	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
182
183	If you use threads, a common model is to run the default event loop
184	in your main thread (or in a separate thread) and for each thread you
185	create, you also create another event loop. Libev itself does no locking
186	whatsoever, so if you mix calls to the same event loop in different
187	threads, make sure you lock (this is usually a bad idea, though, even if
188	done correctly, because it's hideous and inefficient).
189		284
190	=over 4	285	=over 4
191		286
192	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
193		288
…		…
197	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
198		293
199	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
200	function.	295	function.
201		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
202	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
203	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>).
204		310
205	The following flags are supported:	311	The following flags are supported:
206		312
…		…
211	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
212	thing, believe me).	318	thing, believe me).
213		319
214	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
215		321
216	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
217	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
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	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
220	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
221	around bugs.	327	around bugs.
222		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
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		350
225	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
226	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,
227	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
228	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
229	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.
230		363
231	=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)
232		365
233	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
234	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
235	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
236	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.
237		372
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		374
240	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,
241	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
242	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),
243	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.
244		382
245	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
246	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
247	(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
248	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
249	well if you register events for both fds.	387	very well if you register events for both fds.
250		388
251	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
252	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
253	(or space) is available.	391	(or space) is available.
254		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
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		401
257	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
258	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
259	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
260	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
261	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
262	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.
263		413
264	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
265	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
266	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
267	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
268	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.
269		429
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		431
272	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.
273		436
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		438
276	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,
277	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)).
278		441
279	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
280	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
281	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.
282		454
283	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
284		456
285	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
286	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
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288		460
		461	It is definitely not recommended to use this flag.
		462
289	=back	463	=back
290		464
291	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
292	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
293	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
294	order of their flag values :)
295		468
296	The most typical usage is like this:	469	The most typical usage is like this:
297		470
298	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
300		473
301	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
302	environment settings to be taken into account:	475	environment settings to be taken into account:
303		476
304	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
305		478
306	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
307	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
308	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):
309		482
310	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
311		484
312	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
313		486
314	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
315	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
316	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
317	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
318		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
319	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.
320		497
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	499	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
324		501
325	=item ev_default_destroy ()	502	=item ev_default_destroy ()
326		503
327	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
328	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
329	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
330	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
331	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
332	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
333	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>).
334		520
335	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
336		522
337	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
338	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
339		525
340	=item ev_default_fork ()	526	=item ev_default_fork ()
341		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
342	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
343	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
344	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
345	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.
346		534
347	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
348	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
349	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
350		538
351	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
352	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
353	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
354		542
355	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
356		544
357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
358	without calling this function, so if you force one of those backends you
359	do not need to care.
360
361	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
362		546
363	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
364	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
365	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.
366		564
367	=item unsigned int ev_backend (loop)	565	=item unsigned int ev_backend (loop)
368		566
369	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
370	use.	568	use.
…		…
373		571
374	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
375	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
376	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
377	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
378	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
379		577
380	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
381		579
382	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
383	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
…		…
395	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
396	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
397	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.
398		596
399	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
400	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
401	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
402	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
403	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
404	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
405	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
406		604
407	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
408		606
409	* If there are no active watchers (reference count is zero), return.	607	- Before the first iteration, call any pending watchers.
410	- 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.
411	- 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.
412	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
414	- 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.
415	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
418	- Queue all outstanding timers.	622	- Queue all outstanding timers.
419	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
420	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
421	- Queue all check watchers.	625	- Queue all check watchers.
422	- 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).
423	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
424	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
425	- 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
426	were used, return, otherwise continue with step *.	630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
427		632
428	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
429	anymore.	634	anymore.
430		635
431	... queue jobs here, make sure they register event watchers as long	636	... queue jobs here, make sure they register event watchers as long
432	... 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..)
433	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
434	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
435		640
436	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
437		642
438	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
439	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
440	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
441	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.
442		649
443	=item ev_ref (loop)	650	=item ev_ref (loop)
444		651
445	=item ev_unref (loop)	652	=item ev_unref (loop)
446		653
…		…
451	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
452	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
453	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
454	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
455	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
456	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).
457		666
458	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>
459	running when nothing else is active.	668	running when nothing else is active.
460		669
461	struct dv_signal exitsig;	670	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	672	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	673	evf_unref (loop);
465		674
466	Example: for some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
467		676
468	ev_ref (myloop);	677	ev_ref (loop);
469	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.
470		735
471	=back	736	=back
472		737
473		738
474	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
475		740
476	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
477	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
478	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:
479		744
480	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)
481	{	746	{
482	ev_io_stop (w);	747	ev_io_stop (w);
483	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
484	}	749	}
485		750
486	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
487	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
488	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
489	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
490	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
491	ev_loop (loop, 0);	756	ev_loop (loop, 0);
492		757
493	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
494	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,
495	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
496		761
497	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
498	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
499	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
500	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
501	is readable and/or writable).	766	is readable and/or writable).
502		767
503	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
504	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
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	809	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		810
546	=item C<EV_CHILD>	811	=item C<EV_CHILD>
547		812
548	The pid specified in the C<ev_child> watcher has received a status change.	813	The pid specified in the C<ev_child> watcher has received a status change.
		814
		815	=item C<EV_STAT>
		816
		817	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		818
550	=item C<EV_IDLE>	819	=item C<EV_IDLE>
551		820
552	The C<ev_idle> watcher has determined that you have nothing better to do.	821	The C<ev_idle> watcher has determined that you have nothing better to do.
553		822
…		…
561	received events. Callbacks of both watcher types can start and stop as	830	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	831	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	832	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	833	C<ev_loop> from blocking).
565		834
		835	=item C<EV_EMBED>
		836
		837	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		838
		839	=item C<EV_FORK>
		840
		841	The event loop has been resumed in the child process after fork (see
		842	C<ev_fork>).
		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
566	=item C<EV_ERROR>	848	=item C<EV_ERROR>
567		849
568	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
569	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
570	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
571	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
572	with the watcher being stopped.	854	with the watcher being stopped.
573		855
574	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,
575	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
576	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
577	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
578	programs, though, so beware.	860	programs, though, so beware.
579		861
580	=back	862	=back
581		863
582	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
612	Although some watcher types do not have type-specific arguments	894	Although some watcher types do not have type-specific arguments
613	(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.
614		896
615	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
616		898
617	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
618	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
619	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
620		902
621	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
622		904
623	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	923	=item bool ev_is_pending (ev_TYPE *watcher)
642		924
643	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
644	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
645	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
646	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
647	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).
648		931
649	=item callback = ev_cb (ev_TYPE *watcher)	932	=item callback ev_cb (ev_TYPE *watcher)
650		933
651	Returns the callback currently set on the watcher.	934	Returns the callback currently set on the watcher.
652		935
653	=item ev_cb_set (ev_TYPE *watcher, callback)	936	=item ev_cb_set (ev_TYPE *watcher, callback)
654		937
655	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
656	(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>.
657		980
658	=back	981	=back
659		982
660		983
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
665	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
666	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
667	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
668	data:	991	data:
669		992
670	struct my_io	993	struct my_io
671	{	994	{
672	struct ev_io io;	995	struct ev_io io;
673	int otherfd;	996	int otherfd;
674	void *somedata;	997	void *somedata;
675	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
676	}	999	}
677		1000
678	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
679	can cast it back to your own type:	1002	can cast it back to your own type:
680		1003
681	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)
682	{	1005	{
683	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
684	...	1007	...
685	}	1008	}
686		1009
687	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
688	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	}
689		1041
690		1042
691	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
692		1044
693	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	1046	information given in the last section. Any initialisation/set macros,
		1047	functions and members specific to the watcher type are explained.
		1048
		1049	Members are additionally marked with either I<[read-only]>, meaning that,
		1050	while the watcher is active, you can look at the member and expect some
		1051	sensible content, but you must not modify it (you can modify it while the
		1052	watcher is stopped to your hearts content), or I<[read-write]>, which
		1053	means you can expect it to have some sensible content while the watcher
		1054	is active, but you can also modify it. Modifying it may not do something
		1055	sensible or take immediate effect (or do anything at all), but libev will
		1056	not crash or malfunction in any way.
695		1057
696		1058
697	=head2 C<ev_io> - is this file descriptor readable or writable?	1059	=head2 C<ev_io> - is this file descriptor readable or writable?
698		1060
699	I/O watchers check whether a file descriptor is readable or writable	1061	I/O watchers check whether a file descriptor is readable or writable
…		…
707	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
708	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
709	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
710	required if you know what you are doing).	1072	required if you know what you are doing).
711		1073
712	You have to be careful with dup'ed file descriptors, though. Some backends
713	(the linux epoll backend is a notable example) cannot handle dup'ed file
714	descriptors correctly if you register interest in two or more fds pointing
715	to the same underlying file/socket/etc. description (that is, they share
716	the same underlying "file open").
717
718	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
719	(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
720	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
721		1077
722	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
723	receive "spurious" readyness notifications, that is your callback might	1079	receive "spurious" readiness notifications, that is your callback might
724	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
725	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
726	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
727	this situation even with a relatively standard program structure. Thus	1083	this situation even with a relatively standard program structure. Thus
728	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
729	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.
730		1086
731	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
732	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
733	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
734	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
735	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
736		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 writing to a pipe whose other end has been closed, your program gets
		1140	send a SIGPIPE, which, by default, aborts your program. For most programs
		1141	this is sensible behaviour, for daemons, this is usually undesirable.
		1142
		1143	So when you encounter spurious, unexplained daemon exits, make sure you
		1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1145	somewhere, as that would have given you a big clue).
		1146
		1147
		1148	=head3 Watcher-Specific Functions
		1149
737	=over 4	1150	=over 4
738		1151
739	=item ev_io_init (ev_io *, callback, int fd, int events)	1152	=item ev_io_init (ev_io *, callback, int fd, int events)
740		1153
741	=item ev_io_set (ev_io *, int fd, int events)	1154	=item ev_io_set (ev_io *, int fd, int events)
742		1155
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ | EV_WRITE> to receive the given events.	1158	C<EV_READ | EV_WRITE> to receive the given events.
746		1159
		1160	=item int fd [read-only]
		1161
		1162	The file descriptor being watched.
		1163
		1164	=item int events [read-only]
		1165
		1166	The events being watched.
		1167
747	=back	1168	=back
748		1169
		1170	=head3 Examples
		1171
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	1173	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	1174	attempt to read a whole line in the callback.
752		1175
753	static void	1176	static void
754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
755	{	1178	{
756	ev_io_stop (loop, w);	1179	ev_io_stop (loop, w);
757	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors
758	}	1181	}
759		1182
760	...	1183	...
761	struct ev_loop *loop = ev_default_init (0);	1184	struct ev_loop *loop = ev_default_init (0);
762	struct ev_io stdin_readable;	1185	struct ev_io stdin_readable;
763	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
764	ev_io_start (loop, &stdin_readable);	1187	ev_io_start (loop, &stdin_readable);
765	ev_loop (loop, 0);	1188	ev_loop (loop, 0);
766		1189
767		1190
768	=head2 C<ev_timer> - relative and optionally repeating timeouts	1191	=head2 C<ev_timer> - relative and optionally repeating timeouts
769		1192
770	Timer watchers are simple relative timers that generate an event after a	1193	Timer watchers are simple relative timers that generate an event after a
771	given time, and optionally repeating in regular intervals after that.	1194	given time, and optionally repeating in regular intervals after that.
772		1195
773	The timers are based on real time, that is, if you register an event that	1196	The timers are based on real time, that is, if you register an event that
774	times out after an hour and you reset your system clock to last years	1197	times out after an hour and you reset your system clock to January last
775	time, it will still time out after (roughly) and hour. "Roughly" because	1198	year, it will still time out after (roughly) and hour. "Roughly" because
776	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the
777	monotonic clock option helps a lot here).	1200	monotonic clock option helps a lot here).
778		1201
779	The relative timeouts are calculated relative to the C<ev_now ()>	1202	The relative timeouts are calculated relative to the C<ev_now ()>
780	time. This is usually the right thing as this timestamp refers to the time	1203	time. This is usually the right thing as this timestamp refers to the time
…		…
782	you suspect event processing to be delayed and you I<need> to base the timeout	1205	you suspect event processing to be delayed and you I<need> to base the timeout
783	on the current time, use something like this to adjust for this:	1206	on the current time, use something like this to adjust for this:
784		1207
785	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1208	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
786		1209
787	The callback is guarenteed to be invoked only when its timeout has passed,	1210	The callback is guaranteed to be invoked only after its timeout has passed,
788	but if multiple timers become ready during the same loop iteration then	1211	but if multiple timers become ready during the same loop iteration then
789	order of execution is undefined.	1212	order of execution is undefined.
790		1213
		1214	=head3 Watcher-Specific Functions and Data Members
		1215
791	=over 4	1216	=over 4
792		1217
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1218	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1219
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1220	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
796		1221
797	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1222	Configure the timer to trigger after C<after> seconds. If C<repeat>
798	C<0.>, then it will automatically be stopped. If it is positive, then the	1223	is C<0.>, then it will automatically be stopped once the timeout is
799	timer will automatically be configured to trigger again C<repeat> seconds	1224	reached. If it is positive, then the timer will automatically be
800	later, again, and again, until stopped manually.	1225	configured to trigger again C<repeat> seconds later, again, and again,
		1226	until stopped manually.
801		1227
802	The timer itself will do a best-effort at avoiding drift, that is, if you	1228	The timer itself will do a best-effort at avoiding drift, that is, if
803	configure a timer to trigger every 10 seconds, then it will trigger at	1229	you configure a timer to trigger every 10 seconds, then it will normally
804	exactly 10 second intervals. If, however, your program cannot keep up with	1230	trigger at exactly 10 second intervals. If, however, your program cannot
805	the timer (because it takes longer than those 10 seconds to do stuff) the	1231	keep up with the timer (because it takes longer than those 10 seconds to
806	timer will not fire more than once per event loop iteration.	1232	do stuff) the timer will not fire more than once per event loop iteration.
807		1233
808	=item ev_timer_again (loop)	1234	=item ev_timer_again (loop, ev_timer *)
809		1235
810	This will act as if the timer timed out and restart it again if it is	1236	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1237	repeating. The exact semantics are:
812		1238
		1239	If the timer is pending, its pending status is cleared.
		1240
813	If the timer is started but nonrepeating, stop it.	1241	If the timer is started but non-repeating, stop it (as if it timed out).
814		1242
815	If the timer is repeating, either start it if necessary (with the repeat	1243	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1244	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1245
818	This sounds a bit complicated, but here is a useful and typical	1246	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1247	example: Imagine you have a TCP connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1248	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1249	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1250	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1251	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1252	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1253	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1254	automatically restart it if need be.
		1255
		1256	That means you can ignore the C<after> value and C<ev_timer_start>
		1257	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1258
		1259	ev_timer_init (timer, callback, 0., 5.);
		1260	ev_timer_again (loop, timer);
		1261	...
		1262	timer->again = 17.;
		1263	ev_timer_again (loop, timer);
		1264	...
		1265	timer->again = 10.;
		1266	ev_timer_again (loop, timer);
		1267
		1268	This is more slightly efficient then stopping/starting the timer each time
		1269	you want to modify its timeout value.
		1270
		1271	=item ev_tstamp repeat [read-write]
		1272
		1273	The current C<repeat> value. Will be used each time the watcher times out
		1274	or C<ev_timer_again> is called and determines the next timeout (if any),
		1275	which is also when any modifications are taken into account.
826		1276
827	=back	1277	=back
828		1278
		1279	=head3 Examples
		1280
829	Example: create a timer that fires after 60 seconds.	1281	Example: Create a timer that fires after 60 seconds.
830		1282
831	static void	1283	static void
832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1284	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
833	{	1285	{
834	.. one minute over, w is actually stopped right here	1286	.. one minute over, w is actually stopped right here
835	}	1287	}
836		1288
837	struct ev_timer mytimer;	1289	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1290	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1291	ev_timer_start (loop, &mytimer);
840		1292
841	Example: create a timeout timer that times out after 10 seconds of	1293	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1294	inactivity.
843		1295
844	static void	1296	static void
845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1297	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
846	{	1298	{
847	.. ten seconds without any activity	1299	.. ten seconds without any activity
848	}	1300	}
849		1301
850	struct ev_timer mytimer;	1302	struct ev_timer mytimer;
851	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1303	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
852	ev_timer_again (&mytimer); /* start timer */	1304	ev_timer_again (&mytimer); /* start timer */
853	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
854		1306
855	// and in some piece of code that gets executed on any "activity":	1307	// and in some piece of code that gets executed on any "activity":
856	// reset the timeout to start ticking again at 10 seconds	1308	// reset the timeout to start ticking again at 10 seconds
857	ev_timer_again (&mytimer);	1309	ev_timer_again (&mytimer);
858		1310
859		1311
860	=head2 C<ev_periodic> - to cron or not to cron?	1312	=head2 C<ev_periodic> - to cron or not to cron?
861		1313
862	Periodic watchers are also timers of a kind, but they are very versatile	1314	Periodic watchers are also timers of a kind, but they are very versatile
863	(and unfortunately a bit complex).	1315	(and unfortunately a bit complex).
864		1316
865	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1317	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
866	but on wallclock time (absolute time). You can tell a periodic watcher	1318	but on wall clock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1319	to trigger after some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1320	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1321	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1322	clock to January of the previous year, then it will take more than year
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1323	to trigger the event (unlike an C<ev_timer>, which would still trigger
871	roughly 10 seconds later and of course not if you reset your system time	1324	roughly 10 seconds later as it uses a relative timeout).
872	again).
873		1325
874	They can also be used to implement vastly more complex timers, such as	1326	C<ev_periodic>s can also be used to implement vastly more complex timers,
875	triggering an event on eahc midnight, local time.	1327	such as triggering an event on each "midnight, local time", or other
		1328	complicated, rules.
876		1329
877	As with timers, the callback is guarenteed to be invoked only when the	1330	As with timers, the callback is guaranteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1331	time (C<at>) has passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1332	during the same loop iteration then order of execution is undefined.
		1333
		1334	=head3 Watcher-Specific Functions and Data Members
880		1335
881	=over 4	1336	=over 4
882		1337
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1338	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1339
…		…
887	Lots of arguments, lets sort it out... There are basically three modes of	1342	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1343	operation, and we will explain them from simplest to complex:
889		1344
890	=over 4	1345	=over 4
891		1346
892	=item * absolute timer (interval = reschedule_cb = 0)	1347	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1348
894	In this configuration the watcher triggers an event at the wallclock time	1349	In this configuration the watcher triggers an event after the wall clock
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1350	time C<at> has passed and doesn't repeat. It will not adjust when a time
896	that is, if it is to be run at January 1st 2011 then it will run when the	1351	jump occurs, that is, if it is to be run at January 1st 2011 then it will
897	system time reaches or surpasses this time.	1352	run when the system time reaches or surpasses this time.
898		1353
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1354	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1355
901	In this mode the watcher will always be scheduled to time out at the next	1356	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1357	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1358	and then repeat, regardless of any time jumps.
904		1359
905	This can be used to create timers that do not drift with respect to system	1360	This can be used to create timers that do not drift with respect to system
906	time:	1361	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1362	the hour:
907		1363
908	ev_periodic_set (&periodic, 0., 3600., 0);	1364	ev_periodic_set (&periodic, 0., 3600., 0);
909		1365
910	This doesn't mean there will always be 3600 seconds in between triggers,	1366	This doesn't mean there will always be 3600 seconds in between triggers,
911	but only that the the callback will be called when the system time shows a	1367	but only that the callback will be called when the system time shows a
912	full hour (UTC), or more correctly, when the system time is evenly divisible	1368	full hour (UTC), or more correctly, when the system time is evenly divisible
913	by 3600.	1369	by 3600.
914		1370
915	Another way to think about it (for the mathematically inclined) is that	1371	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1372	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1373	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1374
		1375	For numerical stability it is preferable that the C<at> value is near
		1376	C<ev_now ()> (the current time), but there is no range requirement for
		1377	this value, and in fact is often specified as zero.
		1378
		1379	Note also that there is an upper limit to how often a timer can fire (CPU
		1380	speed for example), so if C<interval> is very small then timing stability
		1381	will of course deteriorate. Libev itself tries to be exact to be about one
		1382	millisecond (if the OS supports it and the machine is fast enough).
		1383
919	=item * manual reschedule mode (reschedule_cb = callback)	1384	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1385
921	In this mode the values for C<interval> and C<at> are both being	1386	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1387	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1388	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1389	current time as second argument.
925		1390
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1391	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1392	ever, or make ANY event loop modifications whatsoever>.
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).
930		1393
		1394	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1395	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1396	only event loop modification you are allowed to do).
		1397
931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1398	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
932	ev_tstamp now)>, e.g.:	1399	*w, ev_tstamp now)>, e.g.:
933		1400
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1401	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
935	{	1402	{
936	return now + 60.;	1403	return now + 60.;
937	}	1404	}
…		…
939	It must return the next time to trigger, based on the passed time value	1406	It must return the next time to trigger, based on the passed time value
940	(that is, the lowest time value larger than to the second argument). It	1407	(that is, the lowest time value larger than to the second argument). It
941	will usually be called just before the callback will be triggered, but	1408	will usually be called just before the callback will be triggered, but
942	might be called at other times, too.	1409	might be called at other times, too.
943		1410
944	NOTE: I<< This callback must always return a time that is later than the	1411	NOTE: I<< This callback must always return a time that is higher than or
945	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1412	equal to the passed C<now> value >>.
946		1413
947	This can be used to create very complex timers, such as a timer that	1414	This can be used to create very complex timers, such as a timer that
948	triggers on each midnight, local time. To do this, you would calculate the	1415	triggers on "next midnight, local time". To do this, you would calculate the
949	next midnight after C<now> and return the timestamp value for this. How	1416	next midnight after C<now> and return the timestamp value for this. How
950	you do this is, again, up to you (but it is not trivial, which is the main	1417	you do this is, again, up to you (but it is not trivial, which is the main
951	reason I omitted it as an example).	1418	reason I omitted it as an example).
952		1419
953	=back	1420	=back
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1424	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1425	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1426	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1427	program when the crontabs have changed).
961		1428
		1429	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1430
		1431	When active, returns the absolute time that the watcher is supposed to
		1432	trigger next.
		1433
		1434	=item ev_tstamp offset [read-write]
		1435
		1436	When repeating, this contains the offset value, otherwise this is the
		1437	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1438
		1439	Can be modified any time, but changes only take effect when the periodic
		1440	timer fires or C<ev_periodic_again> is being called.
		1441
		1442	=item ev_tstamp interval [read-write]
		1443
		1444	The current interval value. Can be modified any time, but changes only
		1445	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1446	called.
		1447
		1448	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1449
		1450	The current reschedule callback, or C<0>, if this functionality is
		1451	switched off. Can be changed any time, but changes only take effect when
		1452	the periodic timer fires or C<ev_periodic_again> is being called.
		1453
962	=back	1454	=back
963		1455
		1456	=head3 Examples
		1457
964	Example: call a callback every hour, or, more precisely, whenever the	1458	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1459	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1460	potentially a lot of jitter, but good long-term stability.
967		1461
968	static void	1462	static void
969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1463	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
970	{	1464	{
971	... its now a full hour (UTC, or TAI or whatever your clock follows)	1465	... its now a full hour (UTC, or TAI or whatever your clock follows)
972	}	1466	}
973		1467
974	struct ev_periodic hourly_tick;	1468	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1469	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1470	ev_periodic_start (loop, &hourly_tick);
977		1471
978	Example: the same as above, but use a reschedule callback to do it:	1472	Example: The same as above, but use a reschedule callback to do it:
979		1473
980	#include <math.h>	1474	#include <math.h>
981		1475
982	static ev_tstamp	1476	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1477	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
984	{	1478	{
985	return fmod (now, 3600.) + 3600.;	1479	return fmod (now, 3600.) + 3600.;
986	}	1480	}
987		1481
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1482	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1483
990	Example: call a callback every hour, starting now:	1484	Example: Call a callback every hour, starting now:
991		1485
992	struct ev_periodic hourly_tick;	1486	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1487	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1488	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1489	ev_periodic_start (loop, &hourly_tick);
996		1490
997		1491
998	=head2 C<ev_signal> - signal me when a signal gets signalled!	1492	=head2 C<ev_signal> - signal me when a signal gets signalled!
999		1493
1000	Signal watchers will trigger an event when the process receives a specific	1494	Signal watchers will trigger an event when the process receives a specific
…		…
1007	with the kernel (thus it coexists with your own signal handlers as long	1501	with the kernel (thus it coexists with your own signal handlers as long
1008	as you don't register any with libev). Similarly, when the last signal	1502	as you don't register any with libev). Similarly, when the last signal
1009	watcher for a signal is stopped libev will reset the signal handler to	1503	watcher for a signal is stopped libev will reset the signal handler to
1010	SIG_DFL (regardless of what it was set to before).	1504	SIG_DFL (regardless of what it was set to before).
1011		1505
		1506	If possible and supported, libev will install its handlers with
		1507	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1508	interrupted. If you have a problem with system calls getting interrupted by
		1509	signals you can block all signals in an C<ev_check> watcher and unblock
		1510	them in an C<ev_prepare> watcher.
		1511
		1512	=head3 Watcher-Specific Functions and Data Members
		1513
1012	=over 4	1514	=over 4
1013		1515
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1516	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1517
1016	=item ev_signal_set (ev_signal *, int signum)	1518	=item ev_signal_set (ev_signal *, int signum)
1017		1519
1018	Configures the watcher to trigger on the given signal number (usually one	1520	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1521	of the C<SIGxxx> constants).
1020		1522
		1523	=item int signum [read-only]
		1524
		1525	The signal the watcher watches out for.
		1526
1021	=back	1527	=back
1022		1528
		1529	=head3 Examples
		1530
		1531	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1532
		1533	static void
		1534	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1535	{
		1536	ev_unloop (loop, EVUNLOOP_ALL);
		1537	}
		1538
		1539	struct ev_signal signal_watcher;
		1540	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1541	ev_signal_start (loop, &sigint_cb);
		1542
1023		1543
1024	=head2 C<ev_child> - watch out for process status changes	1544	=head2 C<ev_child> - watch out for process status changes
1025		1545
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1546	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1547	some child status changes (most typically when a child of yours dies). It
		1548	is permissible to install a child watcher I<after> the child has been
		1549	forked (which implies it might have already exited), as long as the event
		1550	loop isn't entered (or is continued from a watcher).
		1551
		1552	Only the default event loop is capable of handling signals, and therefore
		1553	you can only register child watchers in the default event loop.
		1554
		1555	=head3 Process Interaction
		1556
		1557	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1558	initialised. This is necessary to guarantee proper behaviour even if
		1559	the first child watcher is started after the child exits. The occurrence
		1560	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1561	synchronously as part of the event loop processing. Libev always reaps all
		1562	children, even ones not watched.
		1563
		1564	=head3 Overriding the Built-In Processing
		1565
		1566	Libev offers no special support for overriding the built-in child
		1567	processing, but if your application collides with libev's default child
		1568	handler, you can override it easily by installing your own handler for
		1569	C<SIGCHLD> after initialising the default loop, and making sure the
		1570	default loop never gets destroyed. You are encouraged, however, to use an
		1571	event-based approach to child reaping and thus use libev's support for
		1572	that, so other libev users can use C<ev_child> watchers freely.
		1573
		1574	=head3 Stopping the Child Watcher
		1575
		1576	Currently, the child watcher never gets stopped, even when the
		1577	child terminates, so normally one needs to stop the watcher in the
		1578	callback. Future versions of libev might stop the watcher automatically
		1579	when a child exit is detected.
		1580
		1581	=head3 Watcher-Specific Functions and Data Members
1028		1582
1029	=over 4	1583	=over 4
1030		1584
1031	=item ev_child_init (ev_child *, callback, int pid)	1585	=item ev_child_init (ev_child *, callback, int pid, int trace)
1032		1586
1033	=item ev_child_set (ev_child *, int pid)	1587	=item ev_child_set (ev_child *, int pid, int trace)
1034		1588
1035	Configures the watcher to wait for status changes of process C<pid> (or	1589	Configures the watcher to wait for status changes of process C<pid> (or
1036	I<any> process if C<pid> is specified as C<0>). The callback can look	1590	I<any> process if C<pid> is specified as C<0>). The callback can look
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1591	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1592	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1593	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1594	process causing the status change. C<trace> must be either C<0> (only
		1595	activate the watcher when the process terminates) or C<1> (additionally
		1596	activate the watcher when the process is stopped or continued).
		1597
		1598	=item int pid [read-only]
		1599
		1600	The process id this watcher watches out for, or C<0>, meaning any process id.
		1601
		1602	=item int rpid [read-write]
		1603
		1604	The process id that detected a status change.
		1605
		1606	=item int rstatus [read-write]
		1607
		1608	The process exit/trace status caused by C<rpid> (see your systems
		1609	C<waitpid> and C<sys/wait.h> documentation for details).
1041		1610
1042	=back	1611	=back
1043		1612
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1613	=head3 Examples
1045		1614
		1615	Example: C<fork()> a new process and install a child handler to wait for
		1616	its completion.
		1617
		1618	ev_child cw;
		1619
1046	static void	1620	static void
1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1621	child_cb (EV_P_ struct ev_child *w, int revents)
1048	{	1622	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1623	ev_child_stop (EV_A_ w);
		1624	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1050	}	1625	}
1051		1626
1052	struct ev_signal signal_watcher;	1627	pid_t pid = fork ();
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1628
1054	ev_signal_start (loop, &sigint_cb);	1629	if (pid < 0)
		1630	// error
		1631	else if (pid == 0)
		1632	{
		1633	// the forked child executes here
		1634	exit (1);
		1635	}
		1636	else
		1637	{
		1638	ev_child_init (&cw, child_cb, pid, 0);
		1639	ev_child_start (EV_DEFAULT_ &cw);
		1640	}
		1641
		1642
		1643	=head2 C<ev_stat> - did the file attributes just change?
		1644
		1645	This watches a file system path for attribute changes. That is, it calls
		1646	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1647	compared to the last time, invoking the callback if it did.
		1648
		1649	The path does not need to exist: changing from "path exists" to "path does
		1650	not exist" is a status change like any other. The condition "path does
		1651	not exist" is signified by the C<st_nlink> field being zero (which is
		1652	otherwise always forced to be at least one) and all the other fields of
		1653	the stat buffer having unspecified contents.
		1654
		1655	The path I<should> be absolute and I<must not> end in a slash. If it is
		1656	relative and your working directory changes, the behaviour is undefined.
		1657
		1658	Since there is no standard to do this, the portable implementation simply
		1659	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1660	can specify a recommended polling interval for this case. If you specify
		1661	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1662	unspecified default> value will be used (which you can expect to be around
		1663	five seconds, although this might change dynamically). Libev will also
		1664	impose a minimum interval which is currently around C<0.1>, but thats
		1665	usually overkill.
		1666
		1667	This watcher type is not meant for massive numbers of stat watchers,
		1668	as even with OS-supported change notifications, this can be
		1669	resource-intensive.
		1670
		1671	At the time of this writing, only the Linux inotify interface is
		1672	implemented (implementing kqueue support is left as an exercise for the
		1673	reader, note, however, that the author sees no way of implementing ev_stat
		1674	semantics with kqueue). Inotify will be used to give hints only and should
		1675	not change the semantics of C<ev_stat> watchers, which means that libev
		1676	sometimes needs to fall back to regular polling again even with inotify,
		1677	but changes are usually detected immediately, and if the file exists there
		1678	will be no polling.
		1679
		1680	=head3 ABI Issues (Largefile Support)
		1681
		1682	Libev by default (unless the user overrides this) uses the default
		1683	compilation environment, which means that on systems with large file
		1684	support disabled by default, you get the 32 bit version of the stat
		1685	structure. When using the library from programs that change the ABI to
		1686	use 64 bit file offsets the programs will fail. In that case you have to
		1687	compile libev with the same flags to get binary compatibility. This is
		1688	obviously the case with any flags that change the ABI, but the problem is
		1689	most noticeably disabled with ev_stat and large file support.
		1690
		1691	The solution for this is to lobby your distribution maker to make large
		1692	file interfaces available by default (as e.g. FreeBSD does) and not
		1693	optional. Libev cannot simply switch on large file support because it has
		1694	to exchange stat structures with application programs compiled using the
		1695	default compilation environment.
		1696
		1697	=head3 Inotify
		1698
		1699	When C<inotify (7)> support has been compiled into libev (generally only
		1700	available on Linux) and present at runtime, it will be used to speed up
		1701	change detection where possible. The inotify descriptor will be created lazily
		1702	when the first C<ev_stat> watcher is being started.
		1703
		1704	Inotify presence does not change the semantics of C<ev_stat> watchers
		1705	except that changes might be detected earlier, and in some cases, to avoid
		1706	making regular C<stat> calls. Even in the presence of inotify support
		1707	there are many cases where libev has to resort to regular C<stat> polling.
		1708
		1709	(There is no support for kqueue, as apparently it cannot be used to
		1710	implement this functionality, due to the requirement of having a file
		1711	descriptor open on the object at all times).
		1712
		1713	=head3 The special problem of stat time resolution
		1714
		1715	The C<stat ()> system call only supports full-second resolution portably, and
		1716	even on systems where the resolution is higher, many file systems still
		1717	only support whole seconds.
		1718
		1719	That means that, if the time is the only thing that changes, you can
		1720	easily miss updates: on the first update, C<ev_stat> detects a change and
		1721	calls your callback, which does something. When there is another update
		1722	within the same second, C<ev_stat> will be unable to detect it as the stat
		1723	data does not change.
		1724
		1725	The solution to this is to delay acting on a change for slightly more
		1726	than a second (or till slightly after the next full second boundary), using
		1727	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1728	ev_timer_again (loop, w)>).
		1729
		1730	The C<.02> offset is added to work around small timing inconsistencies
		1731	of some operating systems (where the second counter of the current time
		1732	might be be delayed. One such system is the Linux kernel, where a call to
		1733	C<gettimeofday> might return a timestamp with a full second later than
		1734	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1735	update file times then there will be a small window where the kernel uses
		1736	the previous second to update file times but libev might already execute
		1737	the timer callback).
		1738
		1739	=head3 Watcher-Specific Functions and Data Members
		1740
		1741	=over 4
		1742
		1743	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1744
		1745	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1746
		1747	Configures the watcher to wait for status changes of the given
		1748	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1749	be detected and should normally be specified as C<0> to let libev choose
		1750	a suitable value. The memory pointed to by C<path> must point to the same
		1751	path for as long as the watcher is active.
		1752
		1753	The callback will receive C<EV_STAT> when a change was detected, relative
		1754	to the attributes at the time the watcher was started (or the last change
		1755	was detected).
		1756
		1757	=item ev_stat_stat (loop, ev_stat *)
		1758
		1759	Updates the stat buffer immediately with new values. If you change the
		1760	watched path in your callback, you could call this function to avoid
		1761	detecting this change (while introducing a race condition if you are not
		1762	the only one changing the path). Can also be useful simply to find out the
		1763	new values.
		1764
		1765	=item ev_statdata attr [read-only]
		1766
		1767	The most-recently detected attributes of the file. Although the type is
		1768	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1769	suitable for your system, but you can only rely on the POSIX-standardised
		1770	members to be present. If the C<st_nlink> member is C<0>, then there was
		1771	some error while C<stat>ing the file.
		1772
		1773	=item ev_statdata prev [read-only]
		1774
		1775	The previous attributes of the file. The callback gets invoked whenever
		1776	C<prev> != C<attr>, or, more precisely, one or more of these members
		1777	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1778	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
		1779
		1780	=item ev_tstamp interval [read-only]
		1781
		1782	The specified interval.
		1783
		1784	=item const char *path [read-only]
		1785
		1786	The file system path that is being watched.
		1787
		1788	=back
		1789
		1790	=head3 Examples
		1791
		1792	Example: Watch C</etc/passwd> for attribute changes.
		1793
		1794	static void
		1795	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1796	{
		1797	/* /etc/passwd changed in some way */
		1798	if (w->attr.st_nlink)
		1799	{
		1800	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1801	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1802	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1803	}
		1804	else
		1805	/* you shalt not abuse printf for puts */
		1806	puts ("wow, /etc/passwd is not there, expect problems. "
		1807	"if this is windows, they already arrived\n");
		1808	}
		1809
		1810	...
		1811	ev_stat passwd;
		1812
		1813	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1814	ev_stat_start (loop, &passwd);
		1815
		1816	Example: Like above, but additionally use a one-second delay so we do not
		1817	miss updates (however, frequent updates will delay processing, too, so
		1818	one might do the work both on C<ev_stat> callback invocation I<and> on
		1819	C<ev_timer> callback invocation).
		1820
		1821	static ev_stat passwd;
		1822	static ev_timer timer;
		1823
		1824	static void
		1825	timer_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_timer_stop (EV_A_ w);
		1828
		1829	/* now it's one second after the most recent passwd change */
		1830	}
		1831
		1832	static void
		1833	stat_cb (EV_P_ ev_stat *w, int revents)
		1834	{
		1835	/* reset the one-second timer */
		1836	ev_timer_again (EV_A_ &timer);
		1837	}
		1838
		1839	...
		1840	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1841	ev_stat_start (loop, &passwd);
		1842	ev_timer_init (&timer, timer_cb, 0., 1.02);
1055		1843
1056		1844
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1845	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1846
1059	Idle watchers trigger events when there are no other events are pending	1847	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1848	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1849	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1850
1063	watchers are being called again and again, once per event loop iteration -	1851	That is, as long as your process is busy handling sockets or timeouts
		1852	(or even signals, imagine) of the same or higher priority it will not be
		1853	triggered. But when your process is idle (or only lower-priority watchers
		1854	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1855	iteration - until stopped, that is, or your process receives more events
1065	busy.	1856	and becomes busy again with higher priority stuff.
1066		1857
1067	The most noteworthy effect is that as long as any idle watchers are	1858	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1859	active, the process will not block when waiting for new events.
1069		1860
1070	Apart from keeping your process non-blocking (which is a useful	1861	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1862	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1863	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1864	event loop has handled all outstanding events.
1074		1865
		1866	=head3 Watcher-Specific Functions and Data Members
		1867
1075	=over 4	1868	=over 4
1076		1869
1077	=item ev_idle_init (ev_signal *, callback)	1870	=item ev_idle_init (ev_signal *, callback)
1078		1871
1079	Initialises and configures the idle watcher - it has no parameters of any	1872	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1874	believe me.
1082		1875
1083	=back	1876	=back
1084		1877
		1878	=head3 Examples
		1879
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1880	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1881	callback, free it. Also, use no error checking, as usual.
1087		1882
1088	static void	1883	static void
1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1884	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090	{	1885	{
1091	free (w);	1886	free (w);
1092	// now do something you wanted to do when the program has	1887	// now do something you wanted to do when the program has
1093	// no longer asnything immediate to do.	1888	// no longer anything immediate to do.
1094	}	1889	}
1095		1890
1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1891	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1097	ev_idle_init (idle_watcher, idle_cb);	1892	ev_idle_init (idle_watcher, idle_cb);
1098	ev_idle_start (loop, idle_cb);	1893	ev_idle_start (loop, idle_cb);
1099		1894
1100		1895
1101	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1896	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1102		1897
1103	Prepare and check watchers are usually (but not always) used in tandem:	1898	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1122		1917
1123	This is done by examining in each prepare call which file descriptors need	1918	This is done by examining in each prepare call which file descriptors need
1124	to be watched by the other library, registering C<ev_io> watchers for	1919	to be watched by the other library, registering C<ev_io> watchers for
1125	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1920	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1126	provide just this functionality). Then, in the check watcher you check for	1921	provide just this functionality). Then, in the check watcher you check for
1127	any events that occured (by checking the pending status of all watchers	1922	any events that occurred (by checking the pending status of all watchers
1128	and stopping them) and call back into the library. The I/O and timer	1923	and stopping them) and call back into the library. The I/O and timer
1129	callbacks will never actually be called (but must be valid nevertheless,	1924	callbacks will never actually be called (but must be valid nevertheless,
1130	because you never know, you know?).	1925	because you never know, you know?).
1131		1926
1132	As another example, the Perl Coro module uses these hooks to integrate	1927	As another example, the Perl Coro module uses these hooks to integrate
…		…
1136	with priority higher than or equal to the event loop and one coroutine	1931	with priority higher than or equal to the event loop and one coroutine
1137	of lower priority, but only once, using idle watchers to keep the event	1932	of lower priority, but only once, using idle watchers to keep the event
1138	loop from blocking if lower-priority coroutines are active, thus mapping	1933	loop from blocking if lower-priority coroutines are active, thus mapping
1139	low-priority coroutines to idle/background tasks).	1934	low-priority coroutines to idle/background tasks).
1140		1935
		1936	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1937	priority, to ensure that they are being run before any other watchers
		1938	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1939	too) should not activate ("feed") events into libev. While libev fully
		1940	supports this, they might get executed before other C<ev_check> watchers
		1941	did their job. As C<ev_check> watchers are often used to embed other
		1942	(non-libev) event loops those other event loops might be in an unusable
		1943	state until their C<ev_check> watcher ran (always remind yourself to
		1944	coexist peacefully with others).
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
		1947
1141	=over 4	1948	=over 4
1142		1949
1143	=item ev_prepare_init (ev_prepare *, callback)	1950	=item ev_prepare_init (ev_prepare *, callback)
1144		1951
1145	=item ev_check_init (ev_check *, callback)	1952	=item ev_check_init (ev_check *, callback)
…		…
1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1955	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1149	macros, but using them is utterly, utterly and completely pointless.	1956	macros, but using them is utterly, utterly and completely pointless.
1150		1957
1151	=back	1958	=back
1152		1959
1153	Example: To include a library such as adns, you would add IO watchers	1960	=head3 Examples
1154	and a timeout watcher in a prepare handler, as required by libadns, and	1961
		1962	There are a number of principal ways to embed other event loops or modules
		1963	into libev. Here are some ideas on how to include libadns into libev
		1964	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1965	use as a working example. Another Perl module named C<EV::Glib> embeds a
		1966	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		1967	Glib event loop).
		1968
		1969	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1155	in a check watcher, destroy them and call into libadns. What follows is	1970	and in a check watcher, destroy them and call into libadns. What follows
1156	pseudo-code only of course:	1971	is pseudo-code only of course. This requires you to either use a low
		1972	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1973	the callbacks for the IO/timeout watchers might not have been called yet.
1157		1974
1158	static ev_io iow [nfd];	1975	static ev_io iow [nfd];
1159	static ev_timer tw;	1976	static ev_timer tw;
1160		1977
1161	static void	1978	static void
1162	io_cb (ev_loop *loop, ev_io *w, int revents)	1979	io_cb (ev_loop *loop, ev_io *w, int revents)
1163	{	1980	{
1164	// set the relevant poll flags
1165	// could also call adns_processreadable etc. here
1166	struct pollfd *fd = (struct pollfd *)w->data;
1167	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1168	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1169	}	1981	}
1170		1982
1171	// create io watchers for each fd and a timer before blocking	1983	// create io watchers for each fd and a timer before blocking
1172	static void	1984	static void
1173	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1985	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1174	{	1986	{
1175	int timeout = 3600000;truct pollfd fds [nfd];	1987	int timeout = 3600000;
		1988	struct pollfd fds [nfd];
1176	// actual code will need to loop here and realloc etc.	1989	// actual code will need to loop here and realloc etc.
1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1990	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1178		1991
1179	/* the callback is illegal, but won't be called as we stop during check */	1992	/* the callback is illegal, but won't be called as we stop during check */
1180	ev_timer_init (&tw, 0, timeout * 1e-3);	1993	ev_timer_init (&tw, 0, timeout * 1e-3);
1181	ev_timer_start (loop, &tw);	1994	ev_timer_start (loop, &tw);
1182		1995
1183	// create on ev_io per pollfd	1996	// create one ev_io per pollfd
1184	for (int i = 0; i < nfd; ++i)	1997	for (int i = 0; i < nfd; ++i)
1185	{	1998	{
1186	ev_io_init (iow + i, io_cb, fds [i].fd,	1999	ev_io_init (iow + i, io_cb, fds [i].fd,
1187	((fds [i].events & POLLIN ? EV_READ : 0)	2000	((fds [i].events & POLLIN ? EV_READ : 0)
1188	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2001	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1189		2002
1190	fds [i].revents = 0;	2003	fds [i].revents = 0;
1191	iow [i].data = fds + i;
1192	ev_io_start (loop, iow + i);	2004	ev_io_start (loop, iow + i);
1193	}	2005	}
1194	}	2006	}
1195		2007
1196	// stop all watchers after blocking	2008	// stop all watchers after blocking
1197	static void	2009	static void
1198	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2010	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1199	{	2011	{
1200	ev_timer_stop (loop, &tw);	2012	ev_timer_stop (loop, &tw);
1201		2013
1202	for (int i = 0; i < nfd; ++i)	2014	for (int i = 0; i < nfd; ++i)
		2015	{
		2016	// set the relevant poll flags
		2017	// could also call adns_processreadable etc. here
		2018	struct pollfd *fd = fds + i;
		2019	int revents = ev_clear_pending (iow + i);
		2020	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2021	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2022
		2023	// now stop the watcher
1203	ev_io_stop (loop, iow + i);	2024	ev_io_stop (loop, iow + i);
		2025	}
1204		2026
1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2027	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1206	}	2028	}
		2029
		2030	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2031	in the prepare watcher and would dispose of the check watcher.
		2032
		2033	Method 3: If the module to be embedded supports explicit event
		2034	notification (libadns does), you can also make use of the actual watcher
		2035	callbacks, and only destroy/create the watchers in the prepare watcher.
		2036
		2037	static void
		2038	timer_cb (EV_P_ ev_timer *w, int revents)
		2039	{
		2040	adns_state ads = (adns_state)w->data;
		2041	update_now (EV_A);
		2042
		2043	adns_processtimeouts (ads, &tv_now);
		2044	}
		2045
		2046	static void
		2047	io_cb (EV_P_ ev_io *w, int revents)
		2048	{
		2049	adns_state ads = (adns_state)w->data;
		2050	update_now (EV_A);
		2051
		2052	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2053	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2054	}
		2055
		2056	// do not ever call adns_afterpoll
		2057
		2058	Method 4: Do not use a prepare or check watcher because the module you
		2059	want to embed is too inflexible to support it. Instead, you can override
		2060	their poll function. The drawback with this solution is that the main
		2061	loop is now no longer controllable by EV. The C<Glib::EV> module does
		2062	this.
		2063
		2064	static gint
		2065	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2066	{
		2067	int got_events = 0;
		2068
		2069	for (n = 0; n < nfds; ++n)
		2070	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2071
		2072	if (timeout >= 0)
		2073	// create/start timer
		2074
		2075	// poll
		2076	ev_loop (EV_A_ 0);
		2077
		2078	// stop timer again
		2079	if (timeout >= 0)
		2080	ev_timer_stop (EV_A_ &to);
		2081
		2082	// stop io watchers again - their callbacks should have set
		2083	for (n = 0; n < nfds; ++n)
		2084	ev_io_stop (EV_A_ iow [n]);
		2085
		2086	return got_events;
		2087	}
1207		2088
1208		2089
1209	=head2 C<ev_embed> - when one backend isn't enough...	2090	=head2 C<ev_embed> - when one backend isn't enough...
1210		2091
1211	This is a rather advanced watcher type that lets you embed one event loop	2092	This is a rather advanced watcher type that lets you embed one event loop
…		…
1253	portable one.	2134	portable one.
1254		2135
1255	So when you want to use this feature you will always have to be prepared	2136	So when you want to use this feature you will always have to be prepared
1256	that you cannot get an embeddable loop. The recommended way to get around	2137	that you cannot get an embeddable loop. The recommended way to get around
1257	this is to have a separate variables for your embeddable loop, try to	2138	this is to have a separate variables for your embeddable loop, try to
1258	create it, and if that fails, use the normal loop for everything:	2139	create it, and if that fails, use the normal loop for everything.
1259		2140
1260	struct ev_loop *loop_hi = ev_default_init (0);	2141	=head3 Watcher-Specific Functions and Data Members
1261	struct ev_loop *loop_lo = 0;
1262	struct ev_embed embed;
1263
1264	// see if there is a chance of getting one that works
1265	// (remember that a flags value of 0 means autodetection)
1266	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1267	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1268	: 0;
1269
1270	// if we got one, then embed it, otherwise default to loop_hi
1271	if (loop_lo)
1272	{
1273	ev_embed_init (&embed, 0, loop_lo);
1274	ev_embed_start (loop_hi, &embed);
1275	}
1276	else
1277	loop_lo = loop_hi;
1278		2142
1279	=over 4	2143	=over 4
1280		2144
1281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2145	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1282		2146
…		…
1284		2148
1285	Configures the watcher to embed the given loop, which must be	2149	Configures the watcher to embed the given loop, which must be
1286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2150	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1287	invoked automatically, otherwise it is the responsibility of the callback	2151	invoked automatically, otherwise it is the responsibility of the callback
1288	to invoke it (it will continue to be called until the sweep has been done,	2152	to invoke it (it will continue to be called until the sweep has been done,
1289	if you do not want thta, you need to temporarily stop the embed watcher).	2153	if you do not want that, you need to temporarily stop the embed watcher).
1290		2154
1291	=item ev_embed_sweep (loop, ev_embed *)	2155	=item ev_embed_sweep (loop, ev_embed *)
1292		2156
1293	Make a single, non-blocking sweep over the embedded loop. This works	2157	Make a single, non-blocking sweep over the embedded loop. This works
1294	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2158	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1295	apropriate way for embedded loops.	2159	appropriate way for embedded loops.
		2160
		2161	=item struct ev_loop *other [read-only]
		2162
		2163	The embedded event loop.
		2164
		2165	=back
		2166
		2167	=head3 Examples
		2168
		2169	Example: Try to get an embeddable event loop and embed it into the default
		2170	event loop. If that is not possible, use the default loop. The default
		2171	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2172	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2173	used).
		2174
		2175	struct ev_loop *loop_hi = ev_default_init (0);
		2176	struct ev_loop *loop_lo = 0;
		2177	struct ev_embed embed;
		2178
		2179	// see if there is a chance of getting one that works
		2180	// (remember that a flags value of 0 means autodetection)
		2181	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2182	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2183	: 0;
		2184
		2185	// if we got one, then embed it, otherwise default to loop_hi
		2186	if (loop_lo)
		2187	{
		2188	ev_embed_init (&embed, 0, loop_lo);
		2189	ev_embed_start (loop_hi, &embed);
		2190	}
		2191	else
		2192	loop_lo = loop_hi;
		2193
		2194	Example: Check if kqueue is available but not recommended and create
		2195	a kqueue backend for use with sockets (which usually work with any
		2196	kqueue implementation). Store the kqueue/socket-only event loop in
		2197	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2198
		2199	struct ev_loop *loop = ev_default_init (0);
		2200	struct ev_loop *loop_socket = 0;
		2201	struct ev_embed embed;
		2202
		2203	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2204	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2205	{
		2206	ev_embed_init (&embed, 0, loop_socket);
		2207	ev_embed_start (loop, &embed);
		2208	}
		2209
		2210	if (!loop_socket)
		2211	loop_socket = loop;
		2212
		2213	// now use loop_socket for all sockets, and loop for everything else
		2214
		2215
		2216	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2217
		2218	Fork watchers are called when a C<fork ()> was detected (usually because
		2219	whoever is a good citizen cared to tell libev about it by calling
		2220	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2221	event loop blocks next and before C<ev_check> watchers are being called,
		2222	and only in the child after the fork. If whoever good citizen calling
		2223	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2224	handlers will be invoked, too, of course.
		2225
		2226	=head3 Watcher-Specific Functions and Data Members
		2227
		2228	=over 4
		2229
		2230	=item ev_fork_init (ev_signal *, callback)
		2231
		2232	Initialises and configures the fork watcher - it has no parameters of any
		2233	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2234	believe me.
		2235
		2236	=back
		2237
		2238
		2239	=head2 C<ev_async> - how to wake up another event loop
		2240
		2241	In general, you cannot use an C<ev_loop> from multiple threads or other
		2242	asynchronous sources such as signal handlers (as opposed to multiple event
		2243	loops - those are of course safe to use in different threads).
		2244
		2245	Sometimes, however, you need to wake up another event loop you do not
		2246	control, for example because it belongs to another thread. This is what
		2247	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2248	can signal it by calling C<ev_async_send>, which is thread- and signal
		2249	safe.
		2250
		2251	This functionality is very similar to C<ev_signal> watchers, as signals,
		2252	too, are asynchronous in nature, and signals, too, will be compressed
		2253	(i.e. the number of callback invocations may be less than the number of
		2254	C<ev_async_sent> calls).
		2255
		2256	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2257	just the default loop.
		2258
		2259	=head3 Queueing
		2260
		2261	C<ev_async> does not support queueing of data in any way. The reason
		2262	is that the author does not know of a simple (or any) algorithm for a
		2263	multiple-writer-single-reader queue that works in all cases and doesn't
		2264	need elaborate support such as pthreads.
		2265
		2266	That means that if you want to queue data, you have to provide your own
		2267	queue. But at least I can tell you would implement locking around your
		2268	queue:
		2269
		2270	=over 4
		2271
		2272	=item queueing from a signal handler context
		2273
		2274	To implement race-free queueing, you simply add to the queue in the signal
		2275	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2276	some fictitious SIGUSR1 handler:
		2277
		2278	static ev_async mysig;
		2279
		2280	static void
		2281	sigusr1_handler (void)
		2282	{
		2283	sometype data;
		2284
		2285	// no locking etc.
		2286	queue_put (data);
		2287	ev_async_send (EV_DEFAULT_ &mysig);
		2288	}
		2289
		2290	static void
		2291	mysig_cb (EV_P_ ev_async *w, int revents)
		2292	{
		2293	sometype data;
		2294	sigset_t block, prev;
		2295
		2296	sigemptyset (&block);
		2297	sigaddset (&block, SIGUSR1);
		2298	sigprocmask (SIG_BLOCK, &block, &prev);
		2299
		2300	while (queue_get (&data))
		2301	process (data);
		2302
		2303	if (sigismember (&prev, SIGUSR1)
		2304	sigprocmask (SIG_UNBLOCK, &block, 0);
		2305	}
		2306
		2307	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2308	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2309	either...).
		2310
		2311	=item queueing from a thread context
		2312
		2313	The strategy for threads is different, as you cannot (easily) block
		2314	threads but you can easily preempt them, so to queue safely you need to
		2315	employ a traditional mutex lock, such as in this pthread example:
		2316
		2317	static ev_async mysig;
		2318	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2319
		2320	static void
		2321	otherthread (void)
		2322	{
		2323	// only need to lock the actual queueing operation
		2324	pthread_mutex_lock (&mymutex);
		2325	queue_put (data);
		2326	pthread_mutex_unlock (&mymutex);
		2327
		2328	ev_async_send (EV_DEFAULT_ &mysig);
		2329	}
		2330
		2331	static void
		2332	mysig_cb (EV_P_ ev_async *w, int revents)
		2333	{
		2334	pthread_mutex_lock (&mymutex);
		2335
		2336	while (queue_get (&data))
		2337	process (data);
		2338
		2339	pthread_mutex_unlock (&mymutex);
		2340	}
		2341
		2342	=back
		2343
		2344
		2345	=head3 Watcher-Specific Functions and Data Members
		2346
		2347	=over 4
		2348
		2349	=item ev_async_init (ev_async *, callback)
		2350
		2351	Initialises and configures the async watcher - it has no parameters of any
		2352	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2353	believe me.
		2354
		2355	=item ev_async_send (loop, ev_async *)
		2356
		2357	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2358	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2359	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2360	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2361	section below on what exactly this means).
		2362
		2363	This call incurs the overhead of a system call only once per loop iteration,
		2364	so while the overhead might be noticeable, it doesn't apply to repeated
		2365	calls to C<ev_async_send>.
		2366
		2367	=item bool = ev_async_pending (ev_async *)
		2368
		2369	Returns a non-zero value when C<ev_async_send> has been called on the
		2370	watcher but the event has not yet been processed (or even noted) by the
		2371	event loop.
		2372
		2373	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2374	the loop iterates next and checks for the watcher to have become active,
		2375	it will reset the flag again. C<ev_async_pending> can be used to very
		2376	quickly check whether invoking the loop might be a good idea.
		2377
		2378	Not that this does I<not> check whether the watcher itself is pending, only
		2379	whether it has been requested to make this watcher pending.
1296		2380
1297	=back	2381	=back
1298		2382
1299		2383
1300	=head1 OTHER FUNCTIONS	2384	=head1 OTHER FUNCTIONS
…		…
1311	or timeout without having to allocate/configure/start/stop/free one or	2395	or timeout without having to allocate/configure/start/stop/free one or
1312	more watchers yourself.	2396	more watchers yourself.
1313		2397
1314	If C<fd> is less than 0, then no I/O watcher will be started and events	2398	If C<fd> is less than 0, then no I/O watcher will be started and events
1315	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2399	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1316	C<events> set will be craeted and started.	2400	C<events> set will be created and started.
1317		2401
1318	If C<timeout> is less than 0, then no timeout watcher will be	2402	If C<timeout> is less than 0, then no timeout watcher will be
1319	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2403	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1320	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2404	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1321	dubious value.	2405	dubious value.
…		…
1323	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2407	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1324	passed an C<revents> set like normal event callbacks (a combination of	2408	passed an C<revents> set like normal event callbacks (a combination of
1325	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2409	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1326	value passed to C<ev_once>:	2410	value passed to C<ev_once>:
1327		2411
1328	static void stdin_ready (int revents, void *arg)	2412	static void stdin_ready (int revents, void *arg)
1329	{	2413	{
1330	if (revents & EV_TIMEOUT)	2414	if (revents & EV_TIMEOUT)
1331	/* doh, nothing entered */;	2415	/* doh, nothing entered */;
1332	else if (revents & EV_READ)	2416	else if (revents & EV_READ)
1333	/* stdin might have data for us, joy! */;	2417	/* stdin might have data for us, joy! */;
1334	}	2418	}
1335		2419
1336	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2420	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1337		2421
1338	=item ev_feed_event (ev_loop *, watcher *, int revents)	2422	=item ev_feed_event (ev_loop *, watcher *, int revents)
1339		2423
1340	Feeds the given event set into the event loop, as if the specified event	2424	Feeds the given event set into the event loop, as if the specified event
1341	had happened for the specified watcher (which must be a pointer to an	2425	had happened for the specified watcher (which must be a pointer to an
…		…
1346	Feed an event on the given fd, as if a file descriptor backend detected	2430	Feed an event on the given fd, as if a file descriptor backend detected
1347	the given events it.	2431	the given events it.
1348		2432
1349	=item ev_feed_signal_event (ev_loop *loop, int signum)	2433	=item ev_feed_signal_event (ev_loop *loop, int signum)
1350		2434
1351	Feed an event as if the given signal occured (C<loop> must be the default	2435	Feed an event as if the given signal occurred (C<loop> must be the default
1352	loop!).	2436	loop!).
1353		2437
1354	=back	2438	=back
1355		2439
1356		2440
…		…
1372		2456
1373	=item * Priorities are not currently supported. Initialising priorities	2457	=item * Priorities are not currently supported. Initialising priorities
1374	will fail and all watchers will have the same priority, even though there	2458	will fail and all watchers will have the same priority, even though there
1375	is an ev_pri field.	2459	is an ev_pri field.
1376		2460
		2461	=item * In libevent, the last base created gets the signals, in libev, the
		2462	first base created (== the default loop) gets the signals.
		2463
1377	=item * Other members are not supported.	2464	=item * Other members are not supported.
1378		2465
1379	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2466	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1380	to use the libev header file and library.	2467	to use the libev header file and library.
1381		2468
1382	=back	2469	=back
1383		2470
1384	=head1 C++ SUPPORT	2471	=head1 C++ SUPPORT
1385		2472
1386	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2473	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1387	you to use some convinience methods to start/stop watchers and also change	2474	you to use some convenience methods to start/stop watchers and also change
1388	the callback model to a model using method callbacks on objects.	2475	the callback model to a model using method callbacks on objects.
1389		2476
1390	To use it,	2477	To use it,
1391		2478
1392	#include <ev++.h>	2479	#include <ev++.h>
1393		2480
1394	(it is not installed by default). This automatically includes F<ev.h>	2481	This automatically includes F<ev.h> and puts all of its definitions (many
1395	and puts all of its definitions (many of them macros) into the global	2482	of them macros) into the global namespace. All C++ specific things are
1396	namespace. All C++ specific things are put into the C<ev> namespace.	2483	put into the C<ev> namespace. It should support all the same embedding
		2484	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1397		2485
1398	It should support all the same embedding options as F<ev.h>, most notably	2486	Care has been taken to keep the overhead low. The only data member the C++
1399	C<EV_MULTIPLICITY>.	2487	classes add (compared to plain C-style watchers) is the event loop pointer
		2488	that the watcher is associated with (or no additional members at all if
		2489	you disable C<EV_MULTIPLICITY> when embedding libev).
		2490
		2491	Currently, functions, and static and non-static member functions can be
		2492	used as callbacks. Other types should be easy to add as long as they only
		2493	need one additional pointer for context. If you need support for other
		2494	types of functors please contact the author (preferably after implementing
		2495	it).
1400		2496
1401	Here is a list of things available in the C<ev> namespace:	2497	Here is a list of things available in the C<ev> namespace:
1402		2498
1403	=over 4	2499	=over 4
1404		2500
…		…
1420		2516
1421	All of those classes have these methods:	2517	All of those classes have these methods:
1422		2518
1423	=over 4	2519	=over 4
1424		2520
1425	=item ev::TYPE::TYPE (object *, object::method *)	2521	=item ev::TYPE::TYPE ()
1426		2522
1427	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2523	=item ev::TYPE::TYPE (struct ev_loop *)
1428		2524
1429	=item ev::TYPE::~TYPE	2525	=item ev::TYPE::~TYPE
1430		2526
1431	The constructor takes a pointer to an object and a method pointer to	2527	The constructor (optionally) takes an event loop to associate the watcher
1432	the event handler callback to call in this class. The constructor calls	2528	with. If it is omitted, it will use C<EV_DEFAULT>.
1433	C<ev_init> for you, which means you have to call the C<set> method	2529
1434	before starting it. If you do not specify a loop then the constructor	2530	The constructor calls C<ev_init> for you, which means you have to call the
1435	automatically associates the default loop with this watcher.	2531	C<set> method before starting it.
		2532
		2533	It will not set a callback, however: You have to call the templated C<set>
		2534	method to set a callback before you can start the watcher.
		2535
		2536	(The reason why you have to use a method is a limitation in C++ which does
		2537	not allow explicit template arguments for constructors).
1436		2538
1437	The destructor automatically stops the watcher if it is active.	2539	The destructor automatically stops the watcher if it is active.
		2540
		2541	=item w->set<class, &class::method> (object *)
		2542
		2543	This method sets the callback method to call. The method has to have a
		2544	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2545	first argument and the C<revents> as second. The object must be given as
		2546	parameter and is stored in the C<data> member of the watcher.
		2547
		2548	This method synthesizes efficient thunking code to call your method from
		2549	the C callback that libev requires. If your compiler can inline your
		2550	callback (i.e. it is visible to it at the place of the C<set> call and
		2551	your compiler is good :), then the method will be fully inlined into the
		2552	thunking function, making it as fast as a direct C callback.
		2553
		2554	Example: simple class declaration and watcher initialisation
		2555
		2556	struct myclass
		2557	{
		2558	void io_cb (ev::io &w, int revents) { }
		2559	}
		2560
		2561	myclass obj;
		2562	ev::io iow;
		2563	iow.set <myclass, &myclass::io_cb> (&obj);
		2564
		2565	=item w->set<function> (void *data = 0)
		2566
		2567	Also sets a callback, but uses a static method or plain function as
		2568	callback. The optional C<data> argument will be stored in the watcher's
		2569	C<data> member and is free for you to use.
		2570
		2571	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2572
		2573	See the method-C<set> above for more details.
		2574
		2575	Example:
		2576
		2577	static void io_cb (ev::io &w, int revents) { }
		2578	iow.set <io_cb> ();
1438		2579
1439	=item w->set (struct ev_loop *)	2580	=item w->set (struct ev_loop *)
1440		2581
1441	Associates a different C<struct ev_loop> with this watcher. You can only	2582	Associates a different C<struct ev_loop> with this watcher. You can only
1442	do this when the watcher is inactive (and not pending either).	2583	do this when the watcher is inactive (and not pending either).
1443		2584
1444	=item w->set ([args])	2585	=item w->set ([arguments])
1445		2586
1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2587	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1447	called at least once. Unlike the C counterpart, an active watcher gets	2588	called at least once. Unlike the C counterpart, an active watcher gets
1448	automatically stopped and restarted.	2589	automatically stopped and restarted when reconfiguring it with this
		2590	method.
1449		2591
1450	=item w->start ()	2592	=item w->start ()
1451		2593
1452	Starts the watcher. Note that there is no C<loop> argument as the	2594	Starts the watcher. Note that there is no C<loop> argument, as the
1453	constructor already takes the loop.	2595	constructor already stores the event loop.
1454		2596
1455	=item w->stop ()	2597	=item w->stop ()
1456		2598
1457	Stops the watcher if it is active. Again, no C<loop> argument.	2599	Stops the watcher if it is active. Again, no C<loop> argument.
1458		2600
1459	=item w->again () C<ev::timer>, C<ev::periodic> only	2601	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1460		2602
1461	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2603	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1462	C<ev_TYPE_again> function.	2604	C<ev_TYPE_again> function.
1463		2605
1464	=item w->sweep () C<ev::embed> only	2606	=item w->sweep () (C<ev::embed> only)
1465		2607
1466	Invokes C<ev_embed_sweep>.	2608	Invokes C<ev_embed_sweep>.
		2609
		2610	=item w->update () (C<ev::stat> only)
		2611
		2612	Invokes C<ev_stat_stat>.
1467		2613
1468	=back	2614	=back
1469		2615
1470	=back	2616	=back
1471		2617
1472	Example: Define a class with an IO and idle watcher, start one of them in	2618	Example: Define a class with an IO and idle watcher, start one of them in
1473	the constructor.	2619	the constructor.
1474		2620
1475	class myclass	2621	class myclass
1476	{	2622	{
1477	ev_io io; void io_cb (ev::io &w, int revents);	2623	ev::io io; void io_cb (ev::io &w, int revents);
1478	ev_idle idle void idle_cb (ev::idle &w, int revents);	2624	ev:idle idle void idle_cb (ev::idle &w, int revents);
1479		2625
1480	myclass ();	2626	myclass (int fd)
1481	}	2627	{
		2628	io .set <myclass, &myclass::io_cb > (this);
		2629	idle.set <myclass, &myclass::idle_cb> (this);
1482		2630
1483	myclass::myclass (int fd)
1484	: io (this, &myclass::io_cb),
1485	idle (this, &myclass::idle_cb)
1486	{
1487	io.start (fd, ev::READ);	2631	io.start (fd, ev::READ);
		2632	}
		2633	};
		2634
		2635
		2636	=head1 OTHER LANGUAGE BINDINGS
		2637
		2638	Libev does not offer other language bindings itself, but bindings for a
		2639	number of languages exist in the form of third-party packages. If you know
		2640	any interesting language binding in addition to the ones listed here, drop
		2641	me a note.
		2642
		2643	=over 4
		2644
		2645	=item Perl
		2646
		2647	The EV module implements the full libev API and is actually used to test
		2648	libev. EV is developed together with libev. Apart from the EV core module,
		2649	there are additional modules that implement libev-compatible interfaces
		2650	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2651	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2652
		2653	It can be found and installed via CPAN, its homepage is at
		2654	L<http://software.schmorp.de/pkg/EV>.
		2655
		2656	=item Python
		2657
		2658	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2659	seems to be quite complete and well-documented. Note, however, that the
		2660	patch they require for libev is outright dangerous as it breaks the ABI
		2661	for everybody else, and therefore, should never be applied in an installed
		2662	libev (if python requires an incompatible ABI then it needs to embed
		2663	libev).
		2664
		2665	=item Ruby
		2666
		2667	Tony Arcieri has written a ruby extension that offers access to a subset
		2668	of the libev API and adds file handle abstractions, asynchronous DNS and
		2669	more on top of it. It can be found via gem servers. Its homepage is at
		2670	L<http://rev.rubyforge.org/>.
		2671
		2672	=item D
		2673
		2674	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2675	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2676
		2677	=back
		2678
		2679
		2680	=head1 MACRO MAGIC
		2681
		2682	Libev can be compiled with a variety of options, the most fundamental
		2683	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2684	functions and callbacks have an initial C<struct ev_loop *> argument.
		2685
		2686	To make it easier to write programs that cope with either variant, the
		2687	following macros are defined:
		2688
		2689	=over 4
		2690
		2691	=item C<EV_A>, C<EV_A_>
		2692
		2693	This provides the loop I<argument> for functions, if one is required ("ev
		2694	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2695	C<EV_A_> is used when other arguments are following. Example:
		2696
		2697	ev_unref (EV_A);
		2698	ev_timer_add (EV_A_ watcher);
		2699	ev_loop (EV_A_ 0);
		2700
		2701	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2702	which is often provided by the following macro.
		2703
		2704	=item C<EV_P>, C<EV_P_>
		2705
		2706	This provides the loop I<parameter> for functions, if one is required ("ev
		2707	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2708	C<EV_P_> is used when other parameters are following. Example:
		2709
		2710	// this is how ev_unref is being declared
		2711	static void ev_unref (EV_P);
		2712
		2713	// this is how you can declare your typical callback
		2714	static void cb (EV_P_ ev_timer *w, int revents)
		2715
		2716	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2717	suitable for use with C<EV_A>.
		2718
		2719	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2720
		2721	Similar to the other two macros, this gives you the value of the default
		2722	loop, if multiple loops are supported ("ev loop default").
		2723
		2724	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2725
		2726	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2727	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2728	is undefined when the default loop has not been initialised by a previous
		2729	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2730
		2731	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2732	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2733
		2734	=back
		2735
		2736	Example: Declare and initialise a check watcher, utilising the above
		2737	macros so it will work regardless of whether multiple loops are supported
		2738	or not.
		2739
		2740	static void
		2741	check_cb (EV_P_ ev_timer *w, int revents)
		2742	{
		2743	ev_check_stop (EV_A_ w);
1488	}	2744	}
		2745
		2746	ev_check check;
		2747	ev_check_init (&check, check_cb);
		2748	ev_check_start (EV_DEFAULT_ &check);
		2749	ev_loop (EV_DEFAULT_ 0);
1489		2750
1490	=head1 EMBEDDING	2751	=head1 EMBEDDING
1491		2752
1492	Libev can (and often is) directly embedded into host	2753	Libev can (and often is) directly embedded into host
1493	applications. Examples of applications that embed it include the Deliantra	2754	applications. Examples of applications that embed it include the Deliantra
1494	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2755	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1495	and rxvt-unicode.	2756	and rxvt-unicode.
1496		2757
1497	The goal is to enable you to just copy the neecssary files into your	2758	The goal is to enable you to just copy the necessary files into your
1498	source directory without having to change even a single line in them, so	2759	source directory without having to change even a single line in them, so
1499	you can easily upgrade by simply copying (or having a checked-out copy of	2760	you can easily upgrade by simply copying (or having a checked-out copy of
1500	libev somewhere in your source tree).	2761	libev somewhere in your source tree).
1501		2762
1502	=head2 FILESETS	2763	=head2 FILESETS
1503		2764
1504	Depending on what features you need you need to include one or more sets of files	2765	Depending on what features you need you need to include one or more sets of files
1505	in your app.	2766	in your application.
1506		2767
1507	=head3 CORE EVENT LOOP	2768	=head3 CORE EVENT LOOP
1508		2769
1509	To include only the libev core (all the C<ev_*> functions), with manual	2770	To include only the libev core (all the C<ev_*> functions), with manual
1510	configuration (no autoconf):	2771	configuration (no autoconf):
1511		2772
1512	#define EV_STANDALONE 1	2773	#define EV_STANDALONE 1
1513	#include "ev.c"	2774	#include "ev.c"
1514		2775
1515	This will automatically include F<ev.h>, too, and should be done in a	2776	This will automatically include F<ev.h>, too, and should be done in a
1516	single C source file only to provide the function implementations. To use	2777	single C source file only to provide the function implementations. To use
1517	it, do the same for F<ev.h> in all files wishing to use this API (best	2778	it, do the same for F<ev.h> in all files wishing to use this API (best
1518	done by writing a wrapper around F<ev.h> that you can include instead and	2779	done by writing a wrapper around F<ev.h> that you can include instead and
1519	where you can put other configuration options):	2780	where you can put other configuration options):
1520		2781
1521	#define EV_STANDALONE 1	2782	#define EV_STANDALONE 1
1522	#include "ev.h"	2783	#include "ev.h"
1523		2784
1524	Both header files and implementation files can be compiled with a C++	2785	Both header files and implementation files can be compiled with a C++
1525	compiler (at least, thats a stated goal, and breakage will be treated	2786	compiler (at least, thats a stated goal, and breakage will be treated
1526	as a bug).	2787	as a bug).
1527		2788
1528	You need the following files in your source tree, or in a directory	2789	You need the following files in your source tree, or in a directory
1529	in your include path (e.g. in libev/ when using -Ilibev):	2790	in your include path (e.g. in libev/ when using -Ilibev):
1530		2791
1531	ev.h	2792	ev.h
1532	ev.c	2793	ev.c
1533	ev_vars.h	2794	ev_vars.h
1534	ev_wrap.h	2795	ev_wrap.h
1535		2796
1536	ev_win32.c required on win32 platforms only	2797	ev_win32.c required on win32 platforms only
1537		2798
1538	ev_select.c only when select backend is enabled (which is by default)	2799	ev_select.c only when select backend is enabled (which is enabled by default)
1539	ev_poll.c only when poll backend is enabled (disabled by default)	2800	ev_poll.c only when poll backend is enabled (disabled by default)
1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2801	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2802	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542	ev_port.c only when the solaris port backend is enabled (disabled by default)	2803	ev_port.c only when the solaris port backend is enabled (disabled by default)
1543		2804
1544	F<ev.c> includes the backend files directly when enabled, so you only need	2805	F<ev.c> includes the backend files directly when enabled, so you only need
1545	to compile this single file.	2806	to compile this single file.
1546		2807
1547	=head3 LIBEVENT COMPATIBILITY API	2808	=head3 LIBEVENT COMPATIBILITY API
1548		2809
1549	To include the libevent compatibility API, also include:	2810	To include the libevent compatibility API, also include:
1550		2811
1551	#include "event.c"	2812	#include "event.c"
1552		2813
1553	in the file including F<ev.c>, and:	2814	in the file including F<ev.c>, and:
1554		2815
1555	#include "event.h"	2816	#include "event.h"
1556		2817
1557	in the files that want to use the libevent API. This also includes F<ev.h>.	2818	in the files that want to use the libevent API. This also includes F<ev.h>.
1558		2819
1559	You need the following additional files for this:	2820	You need the following additional files for this:
1560		2821
1561	event.h	2822	event.h
1562	event.c	2823	event.c
1563		2824
1564	=head3 AUTOCONF SUPPORT	2825	=head3 AUTOCONF SUPPORT
1565		2826
1566	Instead of using C<EV_STANDALONE=1> and providing your config in	2827	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1567	whatever way you want, you can also C<m4_include([libev.m4])> in your	2828	whatever way you want, you can also C<m4_include([libev.m4])> in your
1568	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2829	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1569	include F<config.h> and configure itself accordingly.	2830	include F<config.h> and configure itself accordingly.
1570		2831
1571	For this of course you need the m4 file:	2832	For this of course you need the m4 file:
1572		2833
1573	libev.m4	2834	libev.m4
1574		2835
1575	=head2 PREPROCESSOR SYMBOLS/MACROS	2836	=head2 PREPROCESSOR SYMBOLS/MACROS
1576		2837
1577	Libev can be configured via a variety of preprocessor symbols you have to define	2838	Libev can be configured via a variety of preprocessor symbols you have to
1578	before including any of its files. The default is not to build for multiplicity	2839	define before including any of its files. The default in the absence of
1579	and only include the select backend.	2840	autoconf is noted for every option.
1580		2841
1581	=over 4	2842	=over 4
1582		2843
1583	=item EV_STANDALONE	2844	=item EV_STANDALONE
1584		2845
…		…
1589	F<event.h> that are not directly supported by the libev core alone.	2850	F<event.h> that are not directly supported by the libev core alone.
1590		2851
1591	=item EV_USE_MONOTONIC	2852	=item EV_USE_MONOTONIC
1592		2853
1593	If defined to be C<1>, libev will try to detect the availability of the	2854	If defined to be C<1>, libev will try to detect the availability of the
1594	monotonic clock option at both compiletime and runtime. Otherwise no use	2855	monotonic clock option at both compile time and runtime. Otherwise no use
1595	of the monotonic clock option will be attempted. If you enable this, you	2856	of the monotonic clock option will be attempted. If you enable this, you
1596	usually have to link against librt or something similar. Enabling it when	2857	usually have to link against librt or something similar. Enabling it when
1597	the functionality isn't available is safe, though, althoguh you have	2858	the functionality isn't available is safe, though, although you have
1598	to make sure you link against any libraries where the C<clock_gettime>	2859	to make sure you link against any libraries where the C<clock_gettime>
1599	function is hiding in (often F<-lrt>).	2860	function is hiding in (often F<-lrt>).
1600		2861
1601	=item EV_USE_REALTIME	2862	=item EV_USE_REALTIME
1602		2863
1603	If defined to be C<1>, libev will try to detect the availability of the	2864	If defined to be C<1>, libev will try to detect the availability of the
1604	realtime clock option at compiletime (and assume its availability at	2865	real-time clock option at compile time (and assume its availability at
1605	runtime if successful). Otherwise no use of the realtime clock option will	2866	runtime if successful). Otherwise no use of the real-time clock option will
1606	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2867	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1607	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2868	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1608	in the description of C<EV_USE_MONOTONIC>, though.	2869	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2870
		2871	=item EV_USE_NANOSLEEP
		2872
		2873	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2874	and will use it for delays. Otherwise it will use C<select ()>.
		2875
		2876	=item EV_USE_EVENTFD
		2877
		2878	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2879	available and will probe for kernel support at runtime. This will improve
		2880	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2881	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2882	2.7 or newer, otherwise disabled.
1609		2883
1610	=item EV_USE_SELECT	2884	=item EV_USE_SELECT
1611		2885
1612	If undefined or defined to be C<1>, libev will compile in support for the	2886	If undefined or defined to be C<1>, libev will compile in support for the
1613	C<select>(2) backend. No attempt at autodetection will be done: if no	2887	C<select>(2) backend. No attempt at auto-detection will be done: if no
1614	other method takes over, select will be it. Otherwise the select backend	2888	other method takes over, select will be it. Otherwise the select backend
1615	will not be compiled in.	2889	will not be compiled in.
1616		2890
1617	=item EV_SELECT_USE_FD_SET	2891	=item EV_SELECT_USE_FD_SET
1618		2892
1619	If defined to C<1>, then the select backend will use the system C<fd_set>	2893	If defined to C<1>, then the select backend will use the system C<fd_set>
1620	structure. This is useful if libev doesn't compile due to a missing	2894	structure. This is useful if libev doesn't compile due to a missing
1621	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2895	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
1622	exotic systems. This usually limits the range of file descriptors to some	2896	exotic systems. This usually limits the range of file descriptors to some
1623	low limit such as 1024 or might have other limitations (winsocket only	2897	low limit such as 1024 or might have other limitations (winsocket only
1624	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2898	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1625	influence the size of the C<fd_set> used.	2899	influence the size of the C<fd_set> used.
1626		2900
…		…
1632	be used is the winsock select). This means that it will call	2906	be used is the winsock select). This means that it will call
1633	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2907	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1634	it is assumed that all these functions actually work on fds, even	2908	it is assumed that all these functions actually work on fds, even
1635	on win32. Should not be defined on non-win32 platforms.	2909	on win32. Should not be defined on non-win32 platforms.
1636		2910
		2911	=item EV_FD_TO_WIN32_HANDLE
		2912
		2913	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2914	file descriptors to socket handles. When not defining this symbol (the
		2915	default), then libev will call C<_get_osfhandle>, which is usually
		2916	correct. In some cases, programs use their own file descriptor management,
		2917	in which case they can provide this function to map fds to socket handles.
		2918
1637	=item EV_USE_POLL	2919	=item EV_USE_POLL
1638		2920
1639	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2921	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1640	backend. Otherwise it will be enabled on non-win32 platforms. It	2922	backend. Otherwise it will be enabled on non-win32 platforms. It
1641	takes precedence over select.	2923	takes precedence over select.
1642		2924
1643	=item EV_USE_EPOLL	2925	=item EV_USE_EPOLL
1644		2926
1645	If defined to be C<1>, libev will compile in support for the Linux	2927	If defined to be C<1>, libev will compile in support for the Linux
1646	C<epoll>(7) backend. Its availability will be detected at runtime,	2928	C<epoll>(7) backend. Its availability will be detected at runtime,
1647	otherwise another method will be used as fallback. This is the	2929	otherwise another method will be used as fallback. This is the preferred
1648	preferred backend for GNU/Linux systems.	2930	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2931	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
1649		2932
1650	=item EV_USE_KQUEUE	2933	=item EV_USE_KQUEUE
1651		2934
1652	If defined to be C<1>, libev will compile in support for the BSD style	2935	If defined to be C<1>, libev will compile in support for the BSD style
1653	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2936	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
1666	otherwise another method will be used as fallback. This is the preferred	2949	otherwise another method will be used as fallback. This is the preferred
1667	backend for Solaris 10 systems.	2950	backend for Solaris 10 systems.
1668		2951
1669	=item EV_USE_DEVPOLL	2952	=item EV_USE_DEVPOLL
1670		2953
1671	reserved for future expansion, works like the USE symbols above.	2954	Reserved for future expansion, works like the USE symbols above.
		2955
		2956	=item EV_USE_INOTIFY
		2957
		2958	If defined to be C<1>, libev will compile in support for the Linux inotify
		2959	interface to speed up C<ev_stat> watchers. Its actual availability will
		2960	be detected at runtime. If undefined, it will be enabled if the headers
		2961	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2962
		2963	=item EV_ATOMIC_T
		2964
		2965	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2966	access is atomic with respect to other threads or signal contexts. No such
		2967	type is easily found in the C language, so you can provide your own type
		2968	that you know is safe for your purposes. It is used both for signal handler "locking"
		2969	as well as for signal and thread safety in C<ev_async> watchers.
		2970
		2971	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2972	(from F<signal.h>), which is usually good enough on most platforms.
1672		2973
1673	=item EV_H	2974	=item EV_H
1674		2975
1675	The name of the F<ev.h> header file used to include it. The default if	2976	The name of the F<ev.h> header file used to include it. The default if
1676	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2977	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1677	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2978	used to virtually rename the F<ev.h> header file in case of conflicts.
1678		2979
1679	=item EV_CONFIG_H	2980	=item EV_CONFIG_H
1680		2981
1681	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2982	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1682	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2983	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1683	C<EV_H>, above.	2984	C<EV_H>, above.
1684		2985
1685	=item EV_EVENT_H	2986	=item EV_EVENT_H
1686		2987
1687	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2988	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1688	of how the F<event.h> header can be found.	2989	of how the F<event.h> header can be found, the default is C<"event.h">.
1689		2990
1690	=item EV_PROTOTYPES	2991	=item EV_PROTOTYPES
1691		2992
1692	If defined to be C<0>, then F<ev.h> will not define any function	2993	If defined to be C<0>, then F<ev.h> will not define any function
1693	prototypes, but still define all the structs and other symbols. This is	2994	prototypes, but still define all the structs and other symbols. This is
…		…
1700	will have the C<struct ev_loop *> as first argument, and you can create	3001	will have the C<struct ev_loop *> as first argument, and you can create
1701	additional independent event loops. Otherwise there will be no support	3002	additional independent event loops. Otherwise there will be no support
1702	for multiple event loops and there is no first event loop pointer	3003	for multiple event loops and there is no first event loop pointer
1703	argument. Instead, all functions act on the single default loop.	3004	argument. Instead, all functions act on the single default loop.
1704		3005
		3006	=item EV_MINPRI
		3007
		3008	=item EV_MAXPRI
		3009
		3010	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3011	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3012	provide for more priorities by overriding those symbols (usually defined
		3013	to be C<-2> and C<2>, respectively).
		3014
		3015	When doing priority-based operations, libev usually has to linearly search
		3016	all the priorities, so having many of them (hundreds) uses a lot of space
		3017	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3018	fine.
		3019
		3020	If your embedding application does not need any priorities, defining these both to
		3021	C<0> will save some memory and CPU.
		3022
1705	=item EV_PERIODICS	3023	=item EV_PERIODIC_ENABLE
1706		3024
1707	If undefined or defined to be C<1>, then periodic timers are supported,	3025	If undefined or defined to be C<1>, then periodic timers are supported. If
1708	otherwise not. This saves a few kb of code.	3026	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3027	code.
		3028
		3029	=item EV_IDLE_ENABLE
		3030
		3031	If undefined or defined to be C<1>, then idle watchers are supported. If
		3032	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3033	code.
		3034
		3035	=item EV_EMBED_ENABLE
		3036
		3037	If undefined or defined to be C<1>, then embed watchers are supported. If
		3038	defined to be C<0>, then they are not.
		3039
		3040	=item EV_STAT_ENABLE
		3041
		3042	If undefined or defined to be C<1>, then stat watchers are supported. If
		3043	defined to be C<0>, then they are not.
		3044
		3045	=item EV_FORK_ENABLE
		3046
		3047	If undefined or defined to be C<1>, then fork watchers are supported. If
		3048	defined to be C<0>, then they are not.
		3049
		3050	=item EV_ASYNC_ENABLE
		3051
		3052	If undefined or defined to be C<1>, then async watchers are supported. If
		3053	defined to be C<0>, then they are not.
		3054
		3055	=item EV_MINIMAL
		3056
		3057	If you need to shave off some kilobytes of code at the expense of some
		3058	speed, define this symbol to C<1>. Currently this is used to override some
		3059	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3060	much smaller 2-heap for timer management over the default 4-heap.
		3061
		3062	=item EV_PID_HASHSIZE
		3063
		3064	C<ev_child> watchers use a small hash table to distribute workload by
		3065	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		3066	than enough. If you need to manage thousands of children you might want to
		3067	increase this value (I<must> be a power of two).
		3068
		3069	=item EV_INOTIFY_HASHSIZE
		3070
		3071	C<ev_stat> watchers use a small hash table to distribute workload by
		3072	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3073	usually more than enough. If you need to manage thousands of C<ev_stat>
		3074	watchers you might want to increase this value (I<must> be a power of
		3075	two).
		3076
		3077	=item EV_USE_4HEAP
		3078
		3079	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3080	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3081	to C<1>. The 4-heap uses more complicated (longer) code but has
		3082	noticeably faster performance with many (thousands) of watchers.
		3083
		3084	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3085	(disabled).
		3086
		3087	=item EV_HEAP_CACHE_AT
		3088
		3089	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3090	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3091	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3092	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3093	but avoids random read accesses on heap changes. This improves performance
		3094	noticeably with with many (hundreds) of watchers.
		3095
		3096	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3097	(disabled).
		3098
		3099	=item EV_VERIFY
		3100
		3101	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3102	be done: If set to C<0>, no internal verification code will be compiled
		3103	in. If set to C<1>, then verification code will be compiled in, but not
		3104	called. If set to C<2>, then the internal verification code will be
		3105	called once per loop, which can slow down libev. If set to C<3>, then the
		3106	verification code will be called very frequently, which will slow down
		3107	libev considerably.
		3108
		3109	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3110	C<0.>
1709		3111
1710	=item EV_COMMON	3112	=item EV_COMMON
1711		3113
1712	By default, all watchers have a C<void *data> member. By redefining	3114	By default, all watchers have a C<void *data> member. By redefining
1713	this macro to a something else you can include more and other types of	3115	this macro to a something else you can include more and other types of
1714	members. You have to define it each time you include one of the files,	3116	members. You have to define it each time you include one of the files,
1715	though, and it must be identical each time.	3117	though, and it must be identical each time.
1716		3118
1717	For example, the perl EV module uses something like this:	3119	For example, the perl EV module uses something like this:
1718		3120
1719	#define EV_COMMON \	3121	#define EV_COMMON \
1720	SV *self; /* contains this struct */ \	3122	SV *self; /* contains this struct */ \
1721	SV *cb_sv, *fh /* note no trailing ";" */	3123	SV *cb_sv, *fh /* note no trailing ";" */
1722		3124
1723	=item EV_CB_DECLARE (type)	3125	=item EV_CB_DECLARE (type)
1724		3126
1725	=item EV_CB_INVOKE (watcher, revents)	3127	=item EV_CB_INVOKE (watcher, revents)
1726		3128
1727	=item ev_set_cb (ev, cb)	3129	=item ev_set_cb (ev, cb)
1728		3130
1729	Can be used to change the callback member declaration in each watcher,	3131	Can be used to change the callback member declaration in each watcher,
1730	and the way callbacks are invoked and set. Must expand to a struct member	3132	and the way callbacks are invoked and set. Must expand to a struct member
1731	definition and a statement, respectively. See the F<ev.v> header file for	3133	definition and a statement, respectively. See the F<ev.h> header file for
1732	their default definitions. One possible use for overriding these is to	3134	their default definitions. One possible use for overriding these is to
1733	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3135	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1734	method calls instead of plain function calls in C++.	3136	method calls instead of plain function calls in C++.
		3137
		3138	=head2 EXPORTED API SYMBOLS
		3139
		3140	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3141	exported symbols, you can use the provided F<Symbol.*> files which list
		3142	all public symbols, one per line:
		3143
		3144	Symbols.ev for libev proper
		3145	Symbols.event for the libevent emulation
		3146
		3147	This can also be used to rename all public symbols to avoid clashes with
		3148	multiple versions of libev linked together (which is obviously bad in
		3149	itself, but sometimes it is inconvenient to avoid this).
		3150
		3151	A sed command like this will create wrapper C<#define>'s that you need to
		3152	include before including F<ev.h>:
		3153
		3154	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3155
		3156	This would create a file F<wrap.h> which essentially looks like this:
		3157
		3158	#define ev_backend myprefix_ev_backend
		3159	#define ev_check_start myprefix_ev_check_start
		3160	#define ev_check_stop myprefix_ev_check_stop
		3161	...
1735		3162
1736	=head2 EXAMPLES	3163	=head2 EXAMPLES
1737		3164
1738	For a real-world example of a program the includes libev	3165	For a real-world example of a program the includes libev
1739	verbatim, you can have a look at the EV perl module	3166	verbatim, you can have a look at the EV perl module
…		…
1742	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3169	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1743	will be compiled. It is pretty complex because it provides its own header	3170	will be compiled. It is pretty complex because it provides its own header
1744	file.	3171	file.
1745		3172
1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3173	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1747	that everybody includes and which overrides some autoconf choices:	3174	that everybody includes and which overrides some configure choices:
1748		3175
		3176	#define EV_MINIMAL 1
1749	#define EV_USE_POLL 0	3177	#define EV_USE_POLL 0
1750	#define EV_MULTIPLICITY 0	3178	#define EV_MULTIPLICITY 0
1751	#define EV_PERIODICS 0	3179	#define EV_PERIODIC_ENABLE 0
		3180	#define EV_STAT_ENABLE 0
		3181	#define EV_FORK_ENABLE 0
1752	#define EV_CONFIG_H <config.h>	3182	#define EV_CONFIG_H <config.h>
		3183	#define EV_MINPRI 0
		3184	#define EV_MAXPRI 0
1753		3185
1754	#include "ev++.h"	3186	#include "ev++.h"
1755		3187
1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3188	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1757		3189
1758	#include "ev_cpp.h"	3190	#include "ev_cpp.h"
1759	#include "ev.c"	3191	#include "ev.c"
		3192
		3193
		3194	=head1 THREADS AND COROUTINES
		3195
		3196	=head2 THREADS
		3197
		3198	Libev itself is completely thread-safe, but it uses no locking. This
		3199	means that you can use as many loops as you want in parallel, as long as
		3200	only one thread ever calls into one libev function with the same loop
		3201	parameter.
		3202
		3203	Or put differently: calls with different loop parameters can be done in
		3204	parallel from multiple threads, calls with the same loop parameter must be
		3205	done serially (but can be done from different threads, as long as only one
		3206	thread ever is inside a call at any point in time, e.g. by using a mutex
		3207	per loop).
		3208
		3209	If you want to know which design (one loop, locking, or multiple loops
		3210	without or something else still) is best for your problem, then I cannot
		3211	help you. I can give some generic advice however:
		3212
		3213	=over 4
		3214
		3215	=item * most applications have a main thread: use the default libev loop
		3216	in that thread, or create a separate thread running only the default loop.
		3217
		3218	This helps integrating other libraries or software modules that use libev
		3219	themselves and don't care/know about threading.
		3220
		3221	=item * one loop per thread is usually a good model.
		3222
		3223	Doing this is almost never wrong, sometimes a better-performance model
		3224	exists, but it is always a good start.
		3225
		3226	=item * other models exist, such as the leader/follower pattern, where one
		3227	loop is handed through multiple threads in a kind of round-robin fashion.
		3228
		3229	Choosing a model is hard - look around, learn, know that usually you can do
		3230	better than you currently do :-)
		3231
		3232	=item * often you need to talk to some other thread which blocks in the
		3233	event loop - C<ev_async> watchers can be used to wake them up from other
		3234	threads safely (or from signal contexts...).
		3235
		3236	=back
		3237
		3238	=head2 COROUTINES
		3239
		3240	Libev is much more accommodating to coroutines ("cooperative threads"):
		3241	libev fully supports nesting calls to it's functions from different
		3242	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3243	different coroutines and switch freely between both coroutines running the
		3244	loop, as long as you don't confuse yourself). The only exception is that
		3245	you must not do this from C<ev_periodic> reschedule callbacks.
		3246
		3247	Care has been invested into making sure that libev does not keep local
		3248	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3249	switches.
1760		3250
1761		3251
1762	=head1 COMPLEXITIES	3252	=head1 COMPLEXITIES
1763		3253
1764	In this section the complexities of (many of) the algorithms used inside	3254	In this section the complexities of (many of) the algorithms used inside
1765	libev will be explained. For complexity discussions about backends see the	3255	libev will be explained. For complexity discussions about backends see the
1766	documentation for C<ev_default_init>.	3256	documentation for C<ev_default_init>.
1767		3257
		3258	All of the following are about amortised time: If an array needs to be
		3259	extended, libev needs to realloc and move the whole array, but this
		3260	happens asymptotically never with higher number of elements, so O(1) might
		3261	mean it might do a lengthy realloc operation in rare cases, but on average
		3262	it is much faster and asymptotically approaches constant time.
		3263
1768	=over 4	3264	=over 4
1769		3265
1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3266	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1771		3267
		3268	This means that, when you have a watcher that triggers in one hour and
		3269	there are 100 watchers that would trigger before that then inserting will
		3270	have to skip roughly seven (C<ld 100>) of these watchers.
		3271
1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3272	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
1773		3273
		3274	That means that changing a timer costs less than removing/adding them
		3275	as only the relative motion in the event queue has to be paid for.
		3276
1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3277	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
1775		3278
		3279	These just add the watcher into an array or at the head of a list.
		3280
1776	=item Stopping check/prepare/idle watchers: O(1)	3281	=item Stopping check/prepare/idle/fork/async watchers: O(1)
1777		3282
1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	3283	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
1779		3284
		3285	These watchers are stored in lists then need to be walked to find the
		3286	correct watcher to remove. The lists are usually short (you don't usually
		3287	have many watchers waiting for the same fd or signal).
		3288
1780	=item Finding the next timer per loop iteration: O(1)	3289	=item Finding the next timer in each loop iteration: O(1)
		3290
		3291	By virtue of using a binary or 4-heap, the next timer is always found at a
		3292	fixed position in the storage array.
1781		3293
1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3294	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1783		3295
1784	=item Activating one watcher: O(1)	3296	A change means an I/O watcher gets started or stopped, which requires
		3297	libev to recalculate its status (and possibly tell the kernel, depending
		3298	on backend and whether C<ev_io_set> was used).
		3299
		3300	=item Activating one watcher (putting it into the pending state): O(1)
		3301
		3302	=item Priority handling: O(number_of_priorities)
		3303
		3304	Priorities are implemented by allocating some space for each
		3305	priority. When doing priority-based operations, libev usually has to
		3306	linearly search all the priorities, but starting/stopping and activating
		3307	watchers becomes O(1) w.r.t. priority handling.
		3308
		3309	=item Sending an ev_async: O(1)
		3310
		3311	=item Processing ev_async_send: O(number_of_async_watchers)
		3312
		3313	=item Processing signals: O(max_signal_number)
		3314
		3315	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3316	calls in the current loop iteration. Checking for async and signal events
		3317	involves iterating over all running async watchers or all signal numbers.
1785		3318
1786	=back	3319	=back
1787		3320
1788		3321
		3322	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3323
		3324	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3325	requires, and its I/O model is fundamentally incompatible with the POSIX
		3326	model. Libev still offers limited functionality on this platform in
		3327	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3328	descriptors. This only applies when using Win32 natively, not when using
		3329	e.g. cygwin.
		3330
		3331	Lifting these limitations would basically require the full
		3332	re-implementation of the I/O system. If you are into these kinds of
		3333	things, then note that glib does exactly that for you in a very portable
		3334	way (note also that glib is the slowest event library known to man).
		3335
		3336	There is no supported compilation method available on windows except
		3337	embedding it into other applications.
		3338
		3339	Not a libev limitation but worth mentioning: windows apparently doesn't
		3340	accept large writes: instead of resulting in a partial write, windows will
		3341	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3342	so make sure you only write small amounts into your sockets (less than a
		3343	megabyte seems safe, but thsi apparently depends on the amount of memory
		3344	available).
		3345
		3346	Due to the many, low, and arbitrary limits on the win32 platform and
		3347	the abysmal performance of winsockets, using a large number of sockets
		3348	is not recommended (and not reasonable). If your program needs to use
		3349	more than a hundred or so sockets, then likely it needs to use a totally
		3350	different implementation for windows, as libev offers the POSIX readiness
		3351	notification model, which cannot be implemented efficiently on windows
		3352	(Microsoft monopoly games).
		3353
		3354	A typical way to use libev under windows is to embed it (see the embedding
		3355	section for details) and use the following F<evwrap.h> header file instead
		3356	of F<ev.h>:
		3357
		3358	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3359	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3360
		3361	#include "ev.h"
		3362
		3363	And compile the following F<evwrap.c> file into your project (make sure
		3364	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3365
		3366	#include "evwrap.h"
		3367	#include "ev.c"
		3368
		3369	=over 4
		3370
		3371	=item The winsocket select function
		3372
		3373	The winsocket C<select> function doesn't follow POSIX in that it
		3374	requires socket I<handles> and not socket I<file descriptors> (it is
		3375	also extremely buggy). This makes select very inefficient, and also
		3376	requires a mapping from file descriptors to socket handles (the Microsoft
		3377	C runtime provides the function C<_open_osfhandle> for this). See the
		3378	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3379	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3380
		3381	The configuration for a "naked" win32 using the Microsoft runtime
		3382	libraries and raw winsocket select is:
		3383
		3384	#define EV_USE_SELECT 1
		3385	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3386
		3387	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3388	complexity in the O(n²) range when using win32.
		3389
		3390	=item Limited number of file descriptors
		3391
		3392	Windows has numerous arbitrary (and low) limits on things.
		3393
		3394	Early versions of winsocket's select only supported waiting for a maximum
		3395	of C<64> handles (probably owning to the fact that all windows kernels
		3396	can only wait for C<64> things at the same time internally; Microsoft
		3397	recommends spawning a chain of threads and wait for 63 handles and the
		3398	previous thread in each. Great).
		3399
		3400	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3401	to some high number (e.g. C<2048>) before compiling the winsocket select
		3402	call (which might be in libev or elsewhere, for example, perl does its own
		3403	select emulation on windows).
		3404
		3405	Another limit is the number of file descriptors in the Microsoft runtime
		3406	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3407	or something like this inside Microsoft). You can increase this by calling
		3408	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3409	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3410	libraries.
		3411
		3412	This might get you to about C<512> or C<2048> sockets (depending on
		3413	windows version and/or the phase of the moon). To get more, you need to
		3414	wrap all I/O functions and provide your own fd management, but the cost of
		3415	calling select (O(n²)) will likely make this unworkable.
		3416
		3417	=back
		3418
		3419
		3420	=head1 PORTABILITY REQUIREMENTS
		3421
		3422	In addition to a working ISO-C implementation, libev relies on a few
		3423	additional extensions:
		3424
		3425	=over 4
		3426
		3427	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3428	calling conventions regardless of C<ev_watcher_type *>.
		3429
		3430	Libev assumes not only that all watcher pointers have the same internal
		3431	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3432	assumes that the same (machine) code can be used to call any watcher
		3433	callback: The watcher callbacks have different type signatures, but libev
		3434	calls them using an C<ev_watcher *> internally.
		3435
		3436	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3437
		3438	The type C<sig_atomic_t volatile> (or whatever is defined as
		3439	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3440	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3441	believed to be sufficiently portable.
		3442
		3443	=item C<sigprocmask> must work in a threaded environment
		3444
		3445	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3446	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3447	pthread implementations will either allow C<sigprocmask> in the "main
		3448	thread" or will block signals process-wide, both behaviours would
		3449	be compatible with libev. Interaction between C<sigprocmask> and
		3450	C<pthread_sigmask> could complicate things, however.
		3451
		3452	The most portable way to handle signals is to block signals in all threads
		3453	except the initial one, and run the default loop in the initial thread as
		3454	well.
		3455
		3456	=item C<long> must be large enough for common memory allocation sizes
		3457
		3458	To improve portability and simplify using libev, libev uses C<long>
		3459	internally instead of C<size_t> when allocating its data structures. On
		3460	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3461	is still at least 31 bits everywhere, which is enough for hundreds of
		3462	millions of watchers.
		3463
		3464	=item C<double> must hold a time value in seconds with enough accuracy
		3465
		3466	The type C<double> is used to represent timestamps. It is required to
		3467	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3468	enough for at least into the year 4000. This requirement is fulfilled by
		3469	implementations implementing IEEE 754 (basically all existing ones).
		3470
		3471	=back
		3472
		3473	If you know of other additional requirements drop me a note.
		3474
		3475
		3476	=head1 COMPILER WARNINGS
		3477
		3478	Depending on your compiler and compiler settings, you might get no or a
		3479	lot of warnings when compiling libev code. Some people are apparently
		3480	scared by this.
		3481
		3482	However, these are unavoidable for many reasons. For one, each compiler
		3483	has different warnings, and each user has different tastes regarding
		3484	warning options. "Warn-free" code therefore cannot be a goal except when
		3485	targeting a specific compiler and compiler-version.
		3486
		3487	Another reason is that some compiler warnings require elaborate
		3488	workarounds, or other changes to the code that make it less clear and less
		3489	maintainable.
		3490
		3491	And of course, some compiler warnings are just plain stupid, or simply
		3492	wrong (because they don't actually warn about the condition their message
		3493	seems to warn about).
		3494
		3495	While libev is written to generate as few warnings as possible,
		3496	"warn-free" code is not a goal, and it is recommended not to build libev
		3497	with any compiler warnings enabled unless you are prepared to cope with
		3498	them (e.g. by ignoring them). Remember that warnings are just that:
		3499	warnings, not errors, or proof of bugs.
		3500
		3501
		3502	=head1 VALGRIND
		3503
		3504	Valgrind has a special section here because it is a popular tool that is
		3505	highly useful, but valgrind reports are very hard to interpret.
		3506
		3507	If you think you found a bug (memory leak, uninitialised data access etc.)
		3508	in libev, then check twice: If valgrind reports something like:
		3509
		3510	==2274== definitely lost: 0 bytes in 0 blocks.
		3511	==2274== possibly lost: 0 bytes in 0 blocks.
		3512	==2274== still reachable: 256 bytes in 1 blocks.
		3513
		3514	Then there is no memory leak. Similarly, under some circumstances,
		3515	valgrind might report kernel bugs as if it were a bug in libev, or it
		3516	might be confused (it is a very good tool, but only a tool).
		3517
		3518	If you are unsure about something, feel free to contact the mailing list
		3519	with the full valgrind report and an explanation on why you think this is
		3520	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3521	no bug" answer and take the chance of learning how to interpret valgrind
		3522	properly.
		3523
		3524	If you need, for some reason, empty reports from valgrind for your project
		3525	I suggest using suppression lists.
		3526
		3527
1789	=head1 AUTHOR	3528	=head1 AUTHOR
1790		3529
1791	Marc Lehmann <libev@schmorp.de>.	3530	Marc Lehmann <libev@schmorp.de>.
1792		3531

Diff Legend

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