ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs.
Revision 1.193 by root, Wed Oct 1 04:25:25 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	/* this is the only header you need */
8	#include <ev.h>	7	#include <ev.h>
9		8
10	/* what follows is a fully working example program */	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>
11	ev_io stdin_watcher;	16	ev_io stdin_watcher;
12	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
13		18
14	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
15	static void	21	static void
16	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
17	{	23	{
18	/* puts ("stdin ready"); */	24	puts ("stdin ready");
19	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
20	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
21	}	31	}
22		32
		33	// another callback, this time for a time-out
23	static void	34	static void
24	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
25	{	36	{
26	/* puts ("timeout"); */	37	puts ("timeout");
27	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
28	}	40	}
29		41
30	int	42	int
31	main (void)	43	main (void)
32	{	44	{
		45	// use the default event loop unless you have special needs
33	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
34		47
35	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
36	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
37	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
38		52
		53	// initialise a timer watcher, then start it
39	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
40	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
41	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
42		57
43	/* loop till timeout or data ready */	58	// now wait for events to arrive
44	ev_loop (loop, 0);	59	ev_loop (loop, 0);
45		60
		61	// unloop was called, so exit
46	return 0;	62	return 0;
47	}	63	}
48		64
49	=head1 DESCRIPTION	65	=head1 DESCRIPTION
50		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
51	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
52	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
53	these event sources and provide your program with events.	73	these event sources and provide your program with events.
54		74
55	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
56	(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
57	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
59	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
60	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
61	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
62	watcher.	82	watcher.
63		83
64	=head1 FEATURES	84	=head2 FEATURES
65		85
66	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
67	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
68	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
69	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
70	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
71	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
72	it to libevent for example).	99	for example).
73		100
74	=head1 CONVENTIONS	101	=head2 CONVENTIONS
75		102
76	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
77	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
78	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
79	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
80	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
81	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
82	will not have this argument.	109	this argument.
83		110
84	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
85		112
86	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
87	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
88	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
89	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
90	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
91	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
92		142
93	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
94		144
95	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
96	library in any way.	146	library in any way.
…		…
101		151
102	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
103	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
104	you actually want to know.	154	you actually want to know.
105		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
106	=item int ev_version_major ()	162	=item int ev_version_major ()
107		163
108	=item int ev_version_minor ()	164	=item int ev_version_minor ()
109		165
110	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
111	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
112	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
113	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
114	version of the library your program was compiled against.	170	version of the library your program was compiled against.
115		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
116	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,
117	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
118	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
119	not a problem.	178	not a problem.
120		179
121	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
122	version:	181	version.
123		182
124	assert (("libev version mismatch",	183	assert (("libev version mismatch",
125	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
126	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
127		186
128	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
129		188
130	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_*>
131	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
133	a description of the set values.	192	a description of the set values.
134		193
135	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
136	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
137		196
138	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
139	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
140		199
141	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
142		201
143	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
144	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
145	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
146	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
147	(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
148	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
149		208
150	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
151		210
…		…
155	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
156	recommended ones.	215	recommended ones.
157		216
158	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
159		218
160	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
161		220
162	Sets the allocation function to use (the prototype and semantics are	221	Sets the allocation function to use (the prototype is similar - the
163	identical to the realloc C function). It is used to allocate and free	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
164	memory (no surprises here). If it returns zero when memory needs to be	223	used to allocate and free memory (no surprises here). If it returns zero
165	allocated, the library might abort or take some potentially destructive	224	when memory needs to be allocated (C<size != 0>), the library might abort
166	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.
167		230
168	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
169	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,
170	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.
171		234
172	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
173	retries: better than mine).	236	retries (example requires a standards-compliant C<realloc>).
174		237
175	static void *	238	static void *
176	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
177	{	240	{
178	for (;;)	241	for (;;)
…		…
187	}	250	}
188		251
189	...	252	...
190	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
191		254
192	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
193		256
194	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
195	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
196	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
197	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
198	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
199	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
200	(such as abort).	263	(such as abort).
201		264
202	Example: do the same thing as libev does internally:	265	Example: This is basically the same thing that libev does internally, too.
203		266
204	static void	267	static void
205	fatal_error (const char *msg)	268	fatal_error (const char *msg)
206	{	269	{
207	perror (msg);	270	perror (msg);
…		…
217		280
218	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
219	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
220	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
221		284
222	If you use threads, a common model is to run the default event loop
223	in your main thread (or in a separate thread) and for each thread you
224	create, you also create another event loop. Libev itself does no locking
225	whatsoever, so if you mix calls to the same event loop in different
226	threads, make sure you lock (this is usually a bad idea, though, even if
227	done correctly, because it's hideous and inefficient).
228
229	=over 4	285	=over 4
230		286
231	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
232		288
233	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
236	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
237		293
238	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
239	function.	295	function.
240		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
241	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
242	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>).
243		310
244	The following flags are supported:	311	The following flags are supported:
245		312
…		…
250	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
251	thing, believe me).	318	thing, believe me).
252		319
253	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
254		321
255	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
256	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
257	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
258	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
259	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
260	around bugs.	327	around bugs.
261		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
262	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
263		350
264	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
265	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,
266	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
267	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
268	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
269		367
270	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
271		369
272	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
273	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
274	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
275	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
276		379
277	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
278		381
279	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
280	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
281	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	384	like O(total_fds) where n is the total number of fds (or the highest fd),
282	either O(1) or O(active_fds).	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
		386	of shortcomings, such as silently dropping events in some hard-to-detect
		387	cases and requiring a system call per fd change, no fork support and bad
		388	support for dup.
283		389
284	While stopping and starting an I/O watcher in the same iteration will	390	While stopping, setting and starting an I/O watcher in the same iteration
285	result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
286	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
287	best to avoid that. Also, dup()ed file descriptors might not work very	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
288	well if you register events for both fds.	394	very well if you register events for both fds.
289		395
290	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
291	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
292	(or space) is available.	398	(or space) is available.
293		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
294	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
295		413
296	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
297	was broken on all BSDs except NetBSD (usually it doesn't work with	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
298	anything but sockets and pipes, except on Darwin, where of course its	416	anything but sockets and pipes, except on Darwin, where of course it's
299	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
300	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
301	C<EVBACKEND_KQUEUE>).	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		420
		421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
302		424
303	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
304	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
305	course). While starting and stopping an I/O watcher does not cause an	427	course). While stopping, setting and starting an I/O watcher does never
306	extra syscall as with epoll, it still adds up to four event changes per	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
307	incident, so its best to avoid that.	429	two event changes per incident. Support for C<fork ()> is very bad and it
		430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
308		444
309	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
310		446
311	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
312		451
313	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
314		453
315	This uses the Solaris 10 port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
316	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
317		456
318	Please note that solaris ports can result in a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
319	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
320	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
321		473
322	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
323		475
324	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
325	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
326	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
327		479
		480	It is definitely not recommended to use this flag.
		481
328	=back	482	=back
329		483
330	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
331	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
332	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
333	order of their flag values :)
334		487
335	The most typical usage is like this:	488	Example: This is the most typical usage.
336		489
337	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
338	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
339		492
340	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
341	environment settings to be taken into account:	494	environment settings to be taken into account:
342		495
343	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
344		497
345	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
346	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
347	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
348		502
349	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
350		504
351	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
352		506
353	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
354	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
355	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
356	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
357		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
358	Example: try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
359		517
360	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361	if (!epoller)	519	if (!epoller)
362	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
363		521
364	=item ev_default_destroy ()	522	=item ev_default_destroy ()
365		523
366	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
367	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
368	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
369	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
370	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
371	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
372	for example).	530	for example).
		531
		532	Note that certain global state, such as signal state, will not be freed by
		533	this function, and related watchers (such as signal and child watchers)
		534	would need to be stopped manually.
		535
		536	In general it is not advisable to call this function except in the
		537	rare occasion where you really need to free e.g. the signal handling
		538	pipe fds. If you need dynamically allocated loops it is better to use
		539	C<ev_loop_new> and C<ev_loop_destroy>).
373		540
374	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
375		542
376	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
377	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
378		545
379	=item ev_default_fork ()	546	=item ev_default_fork ()
380		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
381	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
382	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
383	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
384	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
385		554
386	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
387	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
388	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
389		558
390	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
391	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
392	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
393		562
394	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
395		564
396	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
397	without calling this function, so if you force one of those backends you
398	do not need to care.
399
400	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
401		566
402	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
403	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
404	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
		576
		577	=item unsigned int ev_loop_count (loop)
		578
		579	Returns the count of loop iterations for the loop, which is identical to
		580	the number of times libev did poll for new events. It starts at C<0> and
		581	happily wraps around with enough iterations.
		582
		583	This value can sometimes be useful as a generation counter of sorts (it
		584	"ticks" the number of loop iterations), as it roughly corresponds with
		585	C<ev_prepare> and C<ev_check> calls.
405		586
406	=item unsigned int ev_backend (loop)	587	=item unsigned int ev_backend (loop)
407		588
408	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
409	use.	590	use.
…		…
412		593
413	Returns the current "event loop time", which is the time the event loop	594	Returns the current "event loop time", which is the time the event loop
414	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
415	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
416	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
417	event occuring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
418		611
419	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
420		613
421	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
422	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
…		…
425	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
426	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
427		620
428	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
429	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
430	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
431	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
432	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
433		627
434	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
435	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
436	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
437		632
438	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
439	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
440	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
441	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
442	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
443	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
444	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
445		644
446	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
447		646
448	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
449	- Queue prepare watchers and then call all outstanding watchers.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
		649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
450	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
451	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
452	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
453	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
454	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
455	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
456	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
457	- Queue all outstanding timers.	662	- Queue all expired timers.
458	- Queue all outstanding periodics.	663	- Queue all expired periodics.
459	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
460	- Queue all check watchers.	665	- Queue all check watchers.
461	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
462	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
463	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
464	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
465	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
466		672
467	Example: queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
468	anymore.	674	anymore.
469		675
470	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
471	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
472	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
473	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
474		680
475	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
476		682
477	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
478	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
479	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
480	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
481		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
482	=item ev_ref (loop)	690	=item ev_ref (loop)
483		691
484	=item ev_unref (loop)	692	=item ev_unref (loop)
485		693
486	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
487	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
488	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
489	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
490	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
491	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
492	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
493	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
494	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
495	libraries. Just remember to I<unref after start> and I<ref before stop>.	706	libraries. Just remember to I<unref after start> and I<ref before stop>
		707	(but only if the watcher wasn't active before, or was active before,
		708	respectively).
496		709
497	Example: create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
498	running when nothing else is active.	711	running when nothing else is active.
499		712
500	struct dv_signal exitsig;	713	struct ev_signal exitsig;
501	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
502	ev_signal_start (myloop, &exitsig);	715	ev_signal_start (loop, &exitsig);
503	evf_unref (myloop);	716	evf_unref (loop);
504		717
505	Example: for some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
506		719
507	ev_ref (myloop);	720	ev_ref (loop);
508	ev_signal_stop (myloop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
		722
		723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		724
		725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		726
		727	These advanced functions influence the time that libev will spend waiting
		728	for events. Both time intervals are by default C<0>, meaning that libev
		729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
		731
		732	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		733	allows libev to delay invocation of I/O and timer/periodic callbacks
		734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
		736
		737	The idea is that sometimes your program runs just fast enough to handle
		738	one (or very few) event(s) per loop iteration. While this makes the
		739	program responsive, it also wastes a lot of CPU time to poll for new
		740	events, especially with backends like C<select ()> which have a high
		741	overhead for the actual polling but can deliver many events at once.
		742
		743	By setting a higher I<io collect interval> you allow libev to spend more
		744	time collecting I/O events, so you can handle more events per iteration,
		745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		746	C<ev_timer>) will be not affected. Setting this to a non-null value will
		747	introduce an additional C<ev_sleep ()> call into most loop iterations.
		748
		749	Likewise, by setting a higher I<timeout collect interval> you allow libev
		750	to spend more time collecting timeouts, at the expense of increased
		751	latency/jitter/inexactness (the watcher callback will be called
		752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		753	value will not introduce any overhead in libev.
		754
		755	Many (busy) programs can usually benefit by setting the I/O collect
		756	interval to a value near C<0.1> or so, which is often enough for
		757	interactive servers (of course not for games), likewise for timeouts. It
		758	usually doesn't make much sense to set it to a lower value than C<0.01>,
		759	as this approaches the timing granularity of most systems.
		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
		768	=item ev_loop_verify (loop)
		769
		770	This function only does something when C<EV_VERIFY> support has been
		771	compiled in. which is the default for non-minimal builds. It tries to go
		772	through all internal structures and checks them for validity. If anything
		773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
		775
		776	This can be used to catch bugs inside libev itself: under normal
		777	circumstances, this function will never abort as of course libev keeps its
		778	data structures consistent.
509		779
510	=back	780	=back
511		781
512		782
513	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
514		784
515	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
516	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
517	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
518		788
519	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
520	{	790	{
521	ev_io_stop (w);	791	ev_io_stop (w);
522	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
523	}	793	}
524		794
525	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
526	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
527	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
528	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
529	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
530	ev_loop (loop, 0);	800	ev_loop (loop, 0);
531		801
532	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
533	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
534	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
535		805
536	Each watcher structure must be initialised by a call to C<ev_init	806	Each watcher structure must be initialised by a call to C<ev_init
537	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
538	callback gets invoked each time the event occurs (or, in the case of io	808	callback gets invoked each time the event occurs (or, in the case of I/O
539	watchers, each time the event loop detects that the file descriptor given	809	watchers, each time the event loop detects that the file descriptor given
540	is readable and/or writable).	810	is readable and/or writable).
541		811
542	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
543	with arguments specific to this watcher type. There is also a macro	813	with arguments specific to this watcher type. There is also a macro
…		…
613	=item C<EV_FORK>	883	=item C<EV_FORK>
614		884
615	The event loop has been resumed in the child process after fork (see	885	The event loop has been resumed in the child process after fork (see
616	C<ev_fork>).	886	C<ev_fork>).
617		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
618	=item C<EV_ERROR>	892	=item C<EV_ERROR>
619		893
620	An unspecified error has occured, the watcher has been stopped. This might	894	An unspecified error has occurred, the watcher has been stopped. This might
621	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
622	ran out of memory, a file descriptor was found to be closed or any other	896	ran out of memory, a file descriptor was found to be closed or any other
623	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
624	with the watcher being stopped.	898	with the watcher being stopped.
625		899
626	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
627	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
628	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
629	with the error from read() or write(). This will not work in multithreaded	903	the error from read() or write(). This will not work in multi-threaded
630	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
631		906
632	=back	907	=back
633		908
634	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
635		910
…		…
651	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
652		927
653	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
654	int revents)>.	929	int revents)>.
655		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
656	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
657		938
658	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
659	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
660	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
662	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
663		944
664	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
665	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
666		947
		948	See C<ev_init>, above, for an example.
		949
667	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
668		951
669	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
670	calls into a single call. This is the most convinient method to initialise	953	calls into a single call. This is the most convenient method to initialise
671	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
672		959
673	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
674		961
675	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
676	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
677		969
678	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
679		971
680	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
681	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
693	=item bool ev_is_pending (ev_TYPE *watcher)	985	=item bool ev_is_pending (ev_TYPE *watcher)
694		986
695	Returns a true value iff the watcher is pending, (i.e. it has outstanding	987	Returns a true value iff the watcher is pending, (i.e. it has outstanding
696	events but its callback has not yet been invoked). As long as a watcher	988	events but its callback has not yet been invoked). As long as a watcher
697	is pending (but not active) you must not call an init function on it (but	989	is pending (but not active) you must not call an init function on it (but
698	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	990	C<ev_TYPE_set> is safe), you must not change its priority, and you must
699	libev (e.g. you cnanot C<free ()> it).	991	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		992	it).
700		993
701	=item callback = ev_cb (ev_TYPE *watcher)	994	=item callback ev_cb (ev_TYPE *watcher)
702		995
703	Returns the callback currently set on the watcher.	996	Returns the callback currently set on the watcher.
704		997
705	=item ev_cb_set (ev_TYPE *watcher, callback)	998	=item ev_cb_set (ev_TYPE *watcher, callback)
706		999
707	Change the callback. You can change the callback at virtually any time	1000	Change the callback. You can change the callback at virtually any time
708	(modulo threads).	1001	(modulo threads).
709		1002
		1003	=item ev_set_priority (ev_TYPE *watcher, priority)
		1004
		1005	=item int ev_priority (ev_TYPE *watcher)
		1006
		1007	Set and query the priority of the watcher. The priority is a small
		1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1009	(default: C<-2>). Pending watchers with higher priority will be invoked
		1010	before watchers with lower priority, but priority will not keep watchers
		1011	from being executed (except for C<ev_idle> watchers).
		1012
		1013	This means that priorities are I<only> used for ordering callback
		1014	invocation after new events have been received. This is useful, for
		1015	example, to reduce latency after idling, or more often, to bind two
		1016	watchers on the same event and make sure one is called first.
		1017
		1018	If you need to suppress invocation when higher priority events are pending
		1019	you need to look at C<ev_idle> watchers, which provide this functionality.
		1020
		1021	You I<must not> change the priority of a watcher as long as it is active or
		1022	pending.
		1023
		1024	The default priority used by watchers when no priority has been set is
		1025	always C<0>, which is supposed to not be too high and not be too low :).
		1026
		1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1028	fine, as long as you do not mind that the priority value you query might
		1029	or might not have been adjusted to be within valid range.
		1030
		1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1032
		1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
		1037
		1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1039
		1040	If the watcher is pending, this function clears its pending status and
		1041	returns its C<revents> bitset (as if its callback was invoked). If the
		1042	watcher isn't pending it does nothing and returns C<0>.
		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
710	=back	1047	=back
711		1048
712		1049
713	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
714		1051
715	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
716	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
717	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
718	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
719	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
720	data:	1057	data:
721		1058
722	struct my_io	1059	struct my_io
723	{	1060	{
724	struct ev_io io;	1061	struct ev_io io;
725	int otherfd;	1062	int otherfd;
726	void *somedata;	1063	void *somedata;
727	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
728	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
729		1070
730	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
731	can cast it back to your own type:	1072	can cast it back to your own type:
732		1073
733	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
734	{	1075	{
735	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
736	...	1077	...
737	}	1078	}
738		1079
739	More interesting and less C-conformant ways of catsing your callback type	1080	More interesting and less C-conformant ways of casting your callback type
740	have been omitted....	1081	instead have been omitted.
		1082
		1083	Another common scenario is to use some data structure with multiple
		1084	embedded watchers:
		1085
		1086	struct my_biggy
		1087	{
		1088	int some_data;
		1089	ev_timer t1;
		1090	ev_timer t2;
		1091	}
		1092
		1093	In this case getting the pointer to C<my_biggy> is a bit more
		1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
		1098
		1099	#include <stddef.h>
		1100
		1101	static void
		1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
		1103	{
		1104	struct my_biggy big = (struct my_biggy *
		1105	(((char *)w) - offsetof (struct my_biggy, t1));
		1106	}
		1107
		1108	static void
		1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
		1110	{
		1111	struct my_biggy big = (struct my_biggy *
		1112	(((char *)w) - offsetof (struct my_biggy, t2));
		1113	}
741		1114
742		1115
743	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
744		1117
745	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
769	In general you can register as many read and/or write event watchers per	1142	In general you can register as many read and/or write event watchers per
770	fd as you want (as long as you don't confuse yourself). Setting all file	1143	fd as you want (as long as you don't confuse yourself). Setting all file
771	descriptors to non-blocking mode is also usually a good idea (but not	1144	descriptors to non-blocking mode is also usually a good idea (but not
772	required if you know what you are doing).	1145	required if you know what you are doing).
773		1146
774	You have to be careful with dup'ed file descriptors, though. Some backends	1147	If you cannot use non-blocking mode, then force the use of a
775	(the linux epoll backend is a notable example) cannot handle dup'ed file	1148	known-to-be-good backend (at the time of this writing, this includes only
776	descriptors correctly if you register interest in two or more fds pointing	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
777	to the same underlying file/socket/etc. description (that is, they share
778	the same underlying "file open").
779
780	If you must do this, then force the use of a known-to-be-good backend
781	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
782	C<EVBACKEND_POLL>).
783		1150
784	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
785	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
786	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
787	because there is no data. Not only are some backends known to create a	1154	because there is no data. Not only are some backends known to create a
788	lot of those (for example solaris ports), it is very easy to get into	1155	lot of those (for example Solaris ports), it is very easy to get into
789	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
790	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
791	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
792		1159
793	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
794	play around with an Xlib connection), then you have to seperately re-test	1161	not play around with an Xlib connection), then you have to separately
795	wether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
796	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
797	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
		1169
		1170	=head3 The special problem of disappearing file descriptors
		1171
		1172	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1173	descriptor (either due to calling C<close> explicitly or any other means,
		1174	such as C<dup2>). The reason is that you register interest in some file
		1175	descriptor, but when it goes away, the operating system will silently drop
		1176	this interest. If another file descriptor with the same number then is
		1177	registered with libev, there is no efficient way to see that this is, in
		1178	fact, a different file descriptor.
		1179
		1180	To avoid having to explicitly tell libev about such cases, libev follows
		1181	the following policy: Each time C<ev_io_set> is being called, libev
		1182	will assume that this is potentially a new file descriptor, otherwise
		1183	it is assumed that the file descriptor stays the same. That means that
		1184	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1185	descriptor even if the file descriptor number itself did not change.
		1186
		1187	This is how one would do it normally anyway, the important point is that
		1188	the libev application should not optimise around libev but should leave
		1189	optimisations to libev.
		1190
		1191	=head3 The special problem of dup'ed file descriptors
		1192
		1193	Some backends (e.g. epoll), cannot register events for file descriptors,
		1194	but only events for the underlying file descriptions. That means when you
		1195	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1196	events for them, only one file descriptor might actually receive events.
		1197
		1198	There is no workaround possible except not registering events
		1199	for potentially C<dup ()>'ed file descriptors, or to resort to
		1200	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1201
		1202	=head3 The special problem of fork
		1203
		1204	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1205	useless behaviour. Libev fully supports fork, but needs to be told about
		1206	it in the child.
		1207
		1208	To support fork in your programs, you either have to call
		1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1211	C<EVBACKEND_POLL>.
		1212
		1213	=head3 The special problem of SIGPIPE
		1214
		1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1216	when writing to a pipe whose other end has been closed, your program gets
		1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1218	this is sensible behaviour, for daemons, this is usually undesirable.
		1219
		1220	So when you encounter spurious, unexplained daemon exits, make sure you
		1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1222	somewhere, as that would have given you a big clue).
		1223
		1224
		1225	=head3 Watcher-Specific Functions
798		1226
799	=over 4	1227	=over 4
800		1228
801	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
802		1230
803	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
804		1232
805	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
806	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
807	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
808		1236
809	=item int fd [read-only]	1237	=item int fd [read-only]
810		1238
811	The file descriptor being watched.	1239	The file descriptor being watched.
812		1240
…		…
814		1242
815	The events being watched.	1243	The events being watched.
816		1244
817	=back	1245	=back
818		1246
		1247	=head3 Examples
		1248
819	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
820	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
821	attempt to read a whole line in the callback:	1251	attempt to read a whole line in the callback.
822		1252
823	static void	1253	static void
824	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
825	{	1255	{
826	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
827	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
828	}	1258	}
829		1259
830	...	1260	...
831	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
832	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
833	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
835	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
836		1266
837		1267
838	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
839		1269
840	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
841	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
842		1272
843	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
844	times out after an hour and you reset your system clock to last years	1274	times out after an hour and you reset your system clock to January last
845	time, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
846	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
847	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
848		1290
849	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
850	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
851	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
852	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
853	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
854		1296
855	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
856		1298
857	The callback is guarenteed to be invoked only when its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
858	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
859	order of execution is undefined.	1301	()>.
		1302
		1303	=head3 Watcher-Specific Functions and Data Members
860		1304
861	=over 4	1305	=over 4
862		1306
863	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
864		1308
865	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
866		1310
867	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1311	Configure the timer to trigger after C<after> seconds. If C<repeat>
868	C<0.>, then it will automatically be stopped. If it is positive, then the	1312	is C<0.>, then it will automatically be stopped once the timeout is
869	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
870	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
871		1316
872	The timer itself will do a best-effort at avoiding drift, that is, if you	1317	The timer itself will do a best-effort at avoiding drift, that is, if
873	configure a timer to trigger every 10 seconds, then it will trigger at	1318	you configure a timer to trigger every 10 seconds, then it will normally
874	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
875	the timer (because it takes longer than those 10 seconds to do stuff) the	1320	keep up with the timer (because it takes longer than those 10 seconds to
876	timer will not fire more than once per event loop iteration.	1321	do stuff) the timer will not fire more than once per event loop iteration.
877		1322
878	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
879		1324
880	This will act as if the timer timed out and restart it again if it is	1325	This will act as if the timer timed out and restart it again if it is
881	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
882		1327
		1328	If the timer is pending, its pending status is cleared.
		1329
883	If the timer is started but nonrepeating, stop it.	1330	If the timer is started but non-repeating, stop it (as if it timed out).
884		1331
885	If the timer is repeating, either start it if necessary (with the repeat	1332	If the timer is repeating, either start it if necessary (with the
886	value), or reset the running timer to the repeat value.	1333	C<repeat> value), or reset the running timer to the C<repeat> value.
887		1334
888	This sounds a bit complicated, but here is a useful and typical	1335	This sounds a bit complicated, but here is a useful and typical
889	example: Imagine you have a tcp connection and you want a so-called	1336	example: Imagine you have a TCP connection and you want a so-called idle
890	idle timeout, that is, you want to be called when there have been,	1337	timeout, that is, you want to be called when there have been, say, 60
891	say, 60 seconds of inactivity on the socket. The easiest way to do	1338	seconds of inactivity on the socket. The easiest way to do this is to
892	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
893	C<ev_timer_again> each time you successfully read or write some data. If	1340	C<ev_timer_again> each time you successfully read or write some data. If
894	you go into an idle state where you do not expect data to travel on the	1341	you go into an idle state where you do not expect data to travel on the
895	socket, you can stop the timer, and again will automatically restart it if	1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
896	need be.	1343	automatically restart it if need be.
897		1344
898	You can also ignore the C<after> value and C<ev_timer_start> altogether	1345	That means you can ignore the C<after> value and C<ev_timer_start>
899	and only ever use the C<repeat> value:	1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
900		1347
901	ev_timer_init (timer, callback, 0., 5.);	1348	ev_timer_init (timer, callback, 0., 5.);
902	ev_timer_again (loop, timer);	1349	ev_timer_again (loop, timer);
903	...	1350	...
904	timer->again = 17.;	1351	timer->again = 17.;
905	ev_timer_again (loop, timer);	1352	ev_timer_again (loop, timer);
906	...	1353	...
907	timer->again = 10.;	1354	timer->again = 10.;
908	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
909		1356
910	This is more efficient then stopping/starting the timer eahc time you want	1357	This is more slightly efficient then stopping/starting the timer each time
911	to modify its timeout value.	1358	you want to modify its timeout value.
		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
912		1365
913	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
914		1367
915	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
916	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
917	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
918		1371
919	=back	1372	=back
920		1373
		1374	=head3 Examples
		1375
921	Example: create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
922		1377
923	static void	1378	static void
924	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
925	{	1380	{
926	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
927	}	1382	}
928		1383
929	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
930	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
931	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
932		1387
933	Example: create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
934	inactivity.	1389	inactivity.
935		1390
936	static void	1391	static void
937	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
938	{	1393	{
939	.. ten seconds without any activity	1394	.. ten seconds without any activity
940	}	1395	}
941		1396
942	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
943	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
944	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
945	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
946		1401
947	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
948	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
949	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
950		1405
951		1406
952	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
953		1408
954	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
955	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
956		1411
957	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
958	but on wallclock time (absolute time). You can tell a periodic watcher	1413	but on wall clock time (absolute time). You can tell a periodic watcher
959	to trigger "at" some specific point in time. For example, if you tell a	1414	to trigger after some specific point in time. For example, if you tell a
960	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
961	+ 10.>) and then reset your system clock to the last year, then it will	1416	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1417	clock to January of the previous year, then it will take more than year
962	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
963	roughly 10 seconds later and of course not if you reset your system time	1419	roughly 10 seconds later as it uses a relative timeout).
964	again).
965		1420
966	They can also be used to implement vastly more complex timers, such as	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
967	triggering an event on eahc midnight, local time.	1422	such as triggering an event on each "midnight, local time", or other
		1423	complicated rules.
968		1424
969	As with timers, the callback is guarenteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
970	time (C<at>) has been passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
971	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
		1428
		1429	=head3 Watcher-Specific Functions and Data Members
972		1430
973	=over 4	1431	=over 4
974		1432
975	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
976		1434
977	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
978		1436
979	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
980	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
981		1439
982	=over 4	1440	=over 4
983		1441
984	=item * absolute timer (interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
985		1443
986	In this configuration the watcher triggers an event at the wallclock time	1444	In this configuration the watcher triggers an event after the wall clock
987	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1445	time C<at> has passed. It will not repeat and will not adjust when a time
988	that is, if it is to be run at January 1st 2011 then it will run when the	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
989	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
990		1448
991	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
992		1450
993	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
994	C<at + N * interval> time (for some integer N) and then repeat, regardless	1452	C<at + N * interval> time (for some integer N, which can also be negative)
995	of any time jumps.	1453	and then repeat, regardless of any time jumps.
996		1454
997	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
998	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
999		1458
1000	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1001		1460
1002	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1003	but only that the the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
1004	full hour (UTC), or more correctly, when the system time is evenly divisible	1463	full hour (UTC), or more correctly, when the system time is evenly divisible
1005	by 3600.	1464	by 3600.
1006		1465
1007	Another way to think about it (for the mathematically inclined) is that	1466	Another way to think about it (for the mathematically inclined) is that
1008	C<ev_periodic> will try to run the callback in this mode at the next possible	1467	C<ev_periodic> will try to run the callback in this mode at the next possible
1009	time where C<time = at (mod interval)>, regardless of any time jumps.	1468	time where C<time = at (mod interval)>, regardless of any time jumps.
1010		1469
		1470	For numerical stability it is preferable that the C<at> value is near
		1471	C<ev_now ()> (the current time), but there is no range requirement for
		1472	this value, and in fact is often specified as zero.
		1473
		1474	Note also that there is an upper limit to how often a timer can fire (CPU
		1475	speed for example), so if C<interval> is very small then timing stability
		1476	will of course deteriorate. Libev itself tries to be exact to be about one
		1477	millisecond (if the OS supports it and the machine is fast enough).
		1478
1011	=item * manual reschedule mode (reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1012		1480
1013	In this mode the values for C<interval> and C<at> are both being	1481	In this mode the values for C<interval> and C<at> are both being
1014	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1015	reschedule callback will be called with the watcher as first, and the	1483	reschedule callback will be called with the watcher as first, and the
1016	current time as second argument.	1484	current time as second argument.
1017		1485
1018	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1019	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1020	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1021	starting a prepare watcher).
1022		1488
		1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1491	only event loop modification you are allowed to do).
		1492
1023	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1024	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1025		1495
1026	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1027	{	1497	{
1028	return now + 60.;	1498	return now + 60.;
1029	}	1499	}
…		…
1031	It must return the next time to trigger, based on the passed time value	1501	It must return the next time to trigger, based on the passed time value
1032	(that is, the lowest time value larger than to the second argument). It	1502	(that is, the lowest time value larger than to the second argument). It
1033	will usually be called just before the callback will be triggered, but	1503	will usually be called just before the callback will be triggered, but
1034	might be called at other times, too.	1504	might be called at other times, too.
1035		1505
1036	NOTE: I<< This callback must always return a time that is later than the	1506	NOTE: I<< This callback must always return a time that is higher than or
1037	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1038		1508
1039	This can be used to create very complex timers, such as a timer that	1509	This can be used to create very complex timers, such as a timer that
1040	triggers on each midnight, local time. To do this, you would calculate the	1510	triggers on "next midnight, local time". To do this, you would calculate the
1041	next midnight after C<now> and return the timestamp value for this. How	1511	next midnight after C<now> and return the timestamp value for this. How
1042	you do this is, again, up to you (but it is not trivial, which is the main	1512	you do this is, again, up to you (but it is not trivial, which is the main
1043	reason I omitted it as an example).	1513	reason I omitted it as an example).
1044		1514
1045	=back	1515	=back
…		…
1049	Simply stops and restarts the periodic watcher again. This is only useful	1519	Simply stops and restarts the periodic watcher again. This is only useful
1050	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1051	a different time than the last time it was called (e.g. in a crond like	1521	a different time than the last time it was called (e.g. in a crond like
1052	program when the crontabs have changed).	1522	program when the crontabs have changed).
1053		1523
		1524	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1525
		1526	When active, returns the absolute time that the watcher is supposed to
		1527	trigger next.
		1528
		1529	=item ev_tstamp offset [read-write]
		1530
		1531	When repeating, this contains the offset value, otherwise this is the
		1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1533
		1534	Can be modified any time, but changes only take effect when the periodic
		1535	timer fires or C<ev_periodic_again> is being called.
		1536
1054	=item ev_tstamp interval [read-write]	1537	=item ev_tstamp interval [read-write]
1055		1538
1056	The current interval value. Can be modified any time, but changes only	1539	The current interval value. Can be modified any time, but changes only
1057	take effect when the periodic timer fires or C<ev_periodic_again> is being	1540	take effect when the periodic timer fires or C<ev_periodic_again> is being
1058	called.	1541	called.
…		…
1063	switched off. Can be changed any time, but changes only take effect when	1546	switched off. Can be changed any time, but changes only take effect when
1064	the periodic timer fires or C<ev_periodic_again> is being called.	1547	the periodic timer fires or C<ev_periodic_again> is being called.
1065		1548
1066	=back	1549	=back
1067		1550
		1551	=head3 Examples
		1552
1068	Example: call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1069	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1070	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1071		1556
1072	static void	1557	static void
1073	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1074	{	1559	{
1075	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1076	}	1561	}
1077		1562
1078	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1079	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1080	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1081		1566
1082	Example: the same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1083		1568
1084	#include <math.h>	1569	#include <math.h>
1085		1570
1086	static ev_tstamp	1571	static ev_tstamp
1087	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1088	{	1573	{
1089	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1090	}	1575	}
1091		1576
1092	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1093		1578
1094	Example: call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1095		1580
1096	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1097	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1098	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1099	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1100		1585
1101		1586
1102	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1103		1588
1104	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1105	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1106	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1107	normal event processing, like any other event.	1592	normal event processing, like any other event.
1108		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1109	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1110	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1111	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1112	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1113	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1114	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
		1604
		1605	If possible and supported, libev will install its handlers with
		1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1607	interrupted. If you have a problem with system calls getting interrupted by
		1608	signals you can block all signals in an C<ev_check> watcher and unblock
		1609	them in an C<ev_prepare> watcher.
		1610
		1611	=head3 Watcher-Specific Functions and Data Members
1115		1612
1116	=over 4	1613	=over 4
1117		1614
1118	=item ev_signal_init (ev_signal *, callback, int signum)	1615	=item ev_signal_init (ev_signal *, callback, int signum)
1119		1616
…		…
1126		1623
1127	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1128		1625
1129	=back	1626	=back
1130		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT.
		1631
		1632	static void
		1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1634	{
		1635	ev_unloop (loop, EVUNLOOP_ALL);
		1636	}
		1637
		1638	struct ev_signal signal_watcher;
		1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1640	ev_signal_start (loop, &signal_watcher);
		1641
1131		1642
1132	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1133		1644
1134	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1135	some child status changes (most typically when a child of yours dies).	1646	some child status changes (most typically when a child of yours dies or
		1647	exits). It is permissible to install a child watcher I<after> the child
		1648	has been forked (which implies it might have already exited), as long
		1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
		1653
		1654	Only the default event loop is capable of handling signals, and therefore
		1655	you can only register child watchers in the default event loop.
		1656
		1657	=head3 Process Interaction
		1658
		1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1660	initialised. This is necessary to guarantee proper behaviour even if
		1661	the first child watcher is started after the child exits. The occurrence
		1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1663	synchronously as part of the event loop processing. Libev always reaps all
		1664	children, even ones not watched.
		1665
		1666	=head3 Overriding the Built-In Processing
		1667
		1668	Libev offers no special support for overriding the built-in child
		1669	processing, but if your application collides with libev's default child
		1670	handler, you can override it easily by installing your own handler for
		1671	C<SIGCHLD> after initialising the default loop, and making sure the
		1672	default loop never gets destroyed. You are encouraged, however, to use an
		1673	event-based approach to child reaping and thus use libev's support for
		1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
		1682
		1683	=head3 Watcher-Specific Functions and Data Members
1136		1684
1137	=over 4	1685	=over 4
1138		1686
1139	=item ev_child_init (ev_child *, callback, int pid)	1687	=item ev_child_init (ev_child *, callback, int pid, int trace)
1140		1688
1141	=item ev_child_set (ev_child *, int pid)	1689	=item ev_child_set (ev_child *, int pid, int trace)
1142		1690
1143	Configures the watcher to wait for status changes of process C<pid> (or	1691	Configures the watcher to wait for status changes of process C<pid> (or
1144	I<any> process if C<pid> is specified as C<0>). The callback can look	1692	I<any> process if C<pid> is specified as C<0>). The callback can look
1145	at the C<rstatus> member of the C<ev_child> watcher structure to see	1693	at the C<rstatus> member of the C<ev_child> watcher structure to see
1146	the status word (use the macros from C<sys/wait.h> and see your systems	1694	the status word (use the macros from C<sys/wait.h> and see your systems
1147	C<waitpid> documentation). The C<rpid> member contains the pid of the	1695	C<waitpid> documentation). The C<rpid> member contains the pid of the
1148	process causing the status change.	1696	process causing the status change. C<trace> must be either C<0> (only
		1697	activate the watcher when the process terminates) or C<1> (additionally
		1698	activate the watcher when the process is stopped or continued).
1149		1699
1150	=item int pid [read-only]	1700	=item int pid [read-only]
1151		1701
1152	The process id this watcher watches out for, or C<0>, meaning any process id.	1702	The process id this watcher watches out for, or C<0>, meaning any process id.
1153		1703
…		…
1160	The process exit/trace status caused by C<rpid> (see your systems	1710	The process exit/trace status caused by C<rpid> (see your systems
1161	C<waitpid> and C<sys/wait.h> documentation for details).	1711	C<waitpid> and C<sys/wait.h> documentation for details).
1162		1712
1163	=back	1713	=back
1164		1714
1165	Example: try to exit cleanly on SIGINT and SIGTERM.	1715	=head3 Examples
1166		1716
		1717	Example: C<fork()> a new process and install a child handler to wait for
		1718	its completion.
		1719
		1720	ev_child cw;
		1721
1167	static void	1722	static void
1168	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1169	{	1724	{
1170	ev_unloop (loop, EVUNLOOP_ALL);	1725	ev_child_stop (EV_A_ w);
		1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1171	}	1727	}
1172		1728
1173	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1174	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1175	ev_signal_start (loop, &sigint_cb);	1731	if (pid < 0)
		1732	// error
		1733	else if (pid == 0)
		1734	{
		1735	// the forked child executes here
		1736	exit (1);
		1737	}
		1738	else
		1739	{
		1740	ev_child_init (&cw, child_cb, pid, 0);
		1741	ev_child_start (EV_DEFAULT_ &cw);
		1742	}
1176		1743
1177		1744
1178	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1179		1746
1180	This watches a filesystem path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
1181	C<stat> regularly (or when the OS says it changed) and sees if it changed	1748	C<stat> regularly (or when the OS says it changed) and sees if it changed
1182	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1183		1750
1184	The path does not need to exist: changing from "path exists" to "path does	1751	The path does not need to exist: changing from "path exists" to "path does
1185	not exist" is a status change like any other. The condition "path does	1752	not exist" is a status change like any other. The condition "path does
1186	not exist" is signified by the C<st_nlink> field being zero (which is	1753	not exist" is signified by the C<st_nlink> field being zero (which is
1187	otherwise always forced to be at least one) and all the other fields of	1754	otherwise always forced to be at least one) and all the other fields of
1188	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1189		1756
1190	Since there is no standard to do this, the portable implementation simply	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1191	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1758	relative and your working directory changes, the behaviour is undefined.
1192	can specify a recommended polling interval for this case. If you specify	1759
1193	a polling interval of C<0> (highly recommended!) then a I<suitable,	1760	Since there is no standard kernel interface to do this, the portable
1194	unspecified default> value will be used (which you can expect to be around	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1195	five seconds, although this might change dynamically). Libev will also	1762	it changed somehow. You can specify a recommended polling interval for
1196	impose a minimum interval which is currently around C<0.1>, but thats	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1197	usually overkill.	1764	then a I<suitable, unspecified default> value will be used (which
		1765	you can expect to be around five seconds, although this might change
		1766	dynamically). Libev will also impose a minimum interval which is currently
		1767	around C<0.1>, but thats usually overkill.
1198		1768
1199	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1200	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1201	resource-intensive.	1771	resource-intensive.
1202		1772
1203	At the time of this writing, no specific OS backends are implemented, but	1773	At the time of this writing, the only OS-specific interface implemented
1204	if demand increases, at least a kqueue and inotify backend will be added.	1774	is the Linux inotify interface (implementing kqueue support is left as
		1775	an exercise for the reader. Note, however, that the author sees no way
		1776	of implementing C<ev_stat> semantics with kqueue).
		1777
		1778	=head3 ABI Issues (Largefile Support)
		1779
		1780	Libev by default (unless the user overrides this) uses the default
		1781	compilation environment, which means that on systems with large file
		1782	support disabled by default, you get the 32 bit version of the stat
		1783	structure. When using the library from programs that change the ABI to
		1784	use 64 bit file offsets the programs will fail. In that case you have to
		1785	compile libev with the same flags to get binary compatibility. This is
		1786	obviously the case with any flags that change the ABI, but the problem is
		1787	most noticeably disabled with ev_stat and large file support.
		1788
		1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
		1796
		1797	When C<inotify (7)> support has been compiled into libev (generally only
		1798	available with Linux) and present at runtime, it will be used to speed up
		1799	change detection where possible. The inotify descriptor will be created lazily
		1800	when the first C<ev_stat> watcher is being started.
		1801
		1802	Inotify presence does not change the semantics of C<ev_stat> watchers
		1803	except that changes might be detected earlier, and in some cases, to avoid
		1804	making regular C<stat> calls. Even in the presence of inotify support
		1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
		1807
		1808	There is no support for kqueue, as apparently it cannot be used to
		1809	implement this functionality, due to the requirement of having a file
		1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
		1812
		1813	=head3 The special problem of stat time resolution
		1814
		1815	The C<stat ()> system call only supports full-second resolution portably, and
		1816	even on systems where the resolution is higher, most file systems still
		1817	only support whole seconds.
		1818
		1819	That means that, if the time is the only thing that changes, you can
		1820	easily miss updates: on the first update, C<ev_stat> detects a change and
		1821	calls your callback, which does something. When there is another update
		1822	within the same second, C<ev_stat> will be unable to detect unless the
		1823	stat data does change in other ways (e.g. file size).
		1824
		1825	The solution to this is to delay acting on a change for slightly more
		1826	than a second (or till slightly after the next full second boundary), using
		1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1828	ev_timer_again (loop, w)>).
		1829
		1830	The C<.02> offset is added to work around small timing inconsistencies
		1831	of some operating systems (where the second counter of the current time
		1832	might be be delayed. One such system is the Linux kernel, where a call to
		1833	C<gettimeofday> might return a timestamp with a full second later than
		1834	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1835	update file times then there will be a small window where the kernel uses
		1836	the previous second to update file times but libev might already execute
		1837	the timer callback).
		1838
		1839	=head3 Watcher-Specific Functions and Data Members
1205		1840
1206	=over 4	1841	=over 4
1207		1842
1208	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1843	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1209		1844
…		…
1213	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1214	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1215	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1216	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1217		1852
1218	The callback will be receive C<EV_STAT> when a change was detected,	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1219	relative to the attributes at the time the watcher was started (or the	1854	relative to the attributes at the time the watcher was started (or the
1220	last change was detected).	1855	last change was detected).
1221		1856
1222	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1223		1858
1224	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1225	watched path in your callback, you could call this fucntion to avoid	1860	watched path in your callback, you could call this function to avoid
1226	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1227	useful simply to find out the new values.	1862	the only one changing the path). Can also be useful simply to find out the
		1863	new values.
1228		1864
1229	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1230		1866
1231	The most-recently detected attributes of the file. Although the type is of	1867	The most-recently detected attributes of the file. Although the type is
1232	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1868	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1233	suitable for your system. If the C<st_nlink> member is C<0>, then there	1869	suitable for your system, but you can only rely on the POSIX-standardised
		1870	members to be present. If the C<st_nlink> member is C<0>, then there was
1234	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1235		1872
1236	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1237		1874
1238	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1239	C<prev> != C<attr>.	1876	C<prev> != C<attr>, or, more precisely, one or more of these members
		1877	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1878	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1240		1879
1241	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1242		1881
1243	The specified interval.	1882	The specified interval.
1244		1883
1245	=item const char *path [read-only]	1884	=item const char *path [read-only]
1246		1885
1247	The filesystem path that is being watched.	1886	The file system path that is being watched.
1248		1887
1249	=back	1888	=back
1250		1889
		1890	=head3 Examples
		1891
1251	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1252		1893
1253	static void	1894	static void
1254	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1255	{	1896	{
1256	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1257	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1258	{	1899	{
1259	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1260	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1261	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1262	}	1903	}
1263	else	1904	else
1264	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1265	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1266	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1267	}	1908	}
1268		1909
1269	...	1910	...
1270	ev_stat passwd;	1911	ev_stat passwd;
1271		1912
1272	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1273	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
		1915
		1916	Example: Like above, but additionally use a one-second delay so we do not
		1917	miss updates (however, frequent updates will delay processing, too, so
		1918	one might do the work both on C<ev_stat> callback invocation I<and> on
		1919	C<ev_timer> callback invocation).
		1920
		1921	static ev_stat passwd;
		1922	static ev_timer timer;
		1923
		1924	static void
		1925	timer_cb (EV_P_ ev_timer *w, int revents)
		1926	{
		1927	ev_timer_stop (EV_A_ w);
		1928
		1929	/* now it's one second after the most recent passwd change */
		1930	}
		1931
		1932	static void
		1933	stat_cb (EV_P_ ev_stat *w, int revents)
		1934	{
		1935	/* reset the one-second timer */
		1936	ev_timer_again (EV_A_ &timer);
		1937	}
		1938
		1939	...
		1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1941	ev_stat_start (loop, &passwd);
		1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1274		1943
1275		1944
1276	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1277		1946
1278	Idle watchers trigger events when there are no other events are pending	1947	Idle watchers trigger events when no other events of the same or higher
1279	(prepare, check and other idle watchers do not count). That is, as long	1948	priority are pending (prepare, check and other idle watchers do not count
1280	as your process is busy handling sockets or timeouts (or even signals,	1949	as receiving "events").
1281	imagine) it will not be triggered. But when your process is idle all idle	1950
1282	watchers are being called again and again, once per event loop iteration -	1951	That is, as long as your process is busy handling sockets or timeouts
		1952	(or even signals, imagine) of the same or higher priority it will not be
		1953	triggered. But when your process is idle (or only lower-priority watchers
		1954	are pending), the idle watchers are being called once per event loop
1283	until stopped, that is, or your process receives more events and becomes	1955	iteration - until stopped, that is, or your process receives more events
1284	busy.	1956	and becomes busy again with higher priority stuff.
1285		1957
1286	The most noteworthy effect is that as long as any idle watchers are	1958	The most noteworthy effect is that as long as any idle watchers are
1287	active, the process will not block when waiting for new events.	1959	active, the process will not block when waiting for new events.
1288		1960
1289	Apart from keeping your process non-blocking (which is a useful	1961	Apart from keeping your process non-blocking (which is a useful
1290	effect on its own sometimes), idle watchers are a good place to do	1962	effect on its own sometimes), idle watchers are a good place to do
1291	"pseudo-background processing", or delay processing stuff to after the	1963	"pseudo-background processing", or delay processing stuff to after the
1292	event loop has handled all outstanding events.	1964	event loop has handled all outstanding events.
1293		1965
		1966	=head3 Watcher-Specific Functions and Data Members
		1967
1294	=over 4	1968	=over 4
1295		1969
1296	=item ev_idle_init (ev_signal *, callback)	1970	=item ev_idle_init (ev_signal *, callback)
1297		1971
1298	Initialises and configures the idle watcher - it has no parameters of any	1972	Initialises and configures the idle watcher - it has no parameters of any
1299	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1300	believe me.	1974	believe me.
1301		1975
1302	=back	1976	=back
1303		1977
		1978	=head3 Examples
		1979
1304	Example: dynamically allocate an C<ev_idle>, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1305	callback, free it. Alos, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1306		1982
1307	static void	1983	static void
1308	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1309	{	1985	{
1310	free (w);	1986	free (w);
1311	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1312	// no longer asnything immediate to do.	1988	// no longer anything immediate to do.
1313	}	1989	}
1314		1990
1315	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1316	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1317	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1318		1994
1319		1995
1320	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1321		1997
1322	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1323	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1324	afterwards.	2000	afterwards.
1325		2001
1326	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1327	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1330	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1331	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1332	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1333		2009
1334	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1335	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1336	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1337	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1338	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1339	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1340	watcher).	2016	watcher).
1341		2017
1342	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1343	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1344	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1345	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1346	any events that occured (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1347	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1348	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1349	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1350		2026
1351	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1352	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1353	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1354	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
1355	with priority higher than or equal to the event loop and one coroutine	2031	with priority higher than or equal to the event loop and one coroutine
1356	of lower priority, but only once, using idle watchers to keep the event	2032	of lower priority, but only once, using idle watchers to keep the event
1357	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1358	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1359		2035
		2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
		2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2041	activate ("feed") events into libev. While libev fully supports this, they
		2042	might get executed before other C<ev_check> watchers did their job. As
		2043	C<ev_check> watchers are often used to embed other (non-libev) event
		2044	loops those other event loops might be in an unusable state until their
		2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2046	others).
		2047
		2048	=head3 Watcher-Specific Functions and Data Members
		2049
1360	=over 4	2050	=over 4
1361		2051
1362	=item ev_prepare_init (ev_prepare *, callback)	2052	=item ev_prepare_init (ev_prepare *, callback)
1363		2053
1364	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1365		2055
1366	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1367	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1368	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1369		2060
1370	=back	2061	=back
1371		2062
1372	Example: To include a library such as adns, you would add IO watchers	2063	=head3 Examples
1373	and a timeout watcher in a prepare handler, as required by libadns, and	2064
		2065	There are a number of principal ways to embed other event loops or modules
		2066	into libev. Here are some ideas on how to include libadns into libev
		2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2070	Glib event loop).
		2071
		2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1374	in a check watcher, destroy them and call into libadns. What follows is	2073	and in a check watcher, destroy them and call into libadns. What follows
1375	pseudo-code only of course:	2074	is pseudo-code only of course. This requires you to either use a low
		2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2076	the callbacks for the IO/timeout watchers might not have been called yet.
1376		2077
1377	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1378	static ev_timer tw;	2079	static ev_timer tw;
1379		2080
1380	static void	2081	static void
1381	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1382	{	2083	{
1383	// set the relevant poll flags
1384	// could also call adns_processreadable etc. here
1385	struct pollfd *fd = (struct pollfd *)w->data;
1386	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1387	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1388	}	2084	}
1389		2085
1390	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1391	static void	2087	static void
1392	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1393	{	2089	{
1394	int timeout = 3600000;truct pollfd fds [nfd];	2090	int timeout = 3600000;
		2091	struct pollfd fds [nfd];
1395	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1396	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1397		2094
1398	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1399	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1400	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1401		2098
1402	// create on ev_io per pollfd	2099	// create one ev_io per pollfd
1403	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1404	{	2101	{
1405	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1406	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1407	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1408		2105
1409	fds [i].revents = 0;	2106	fds [i].revents = 0;
1410	iow [i].data = fds + i;
1411	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1412	}	2108	}
1413	}	2109	}
1414		2110
1415	// stop all watchers after blocking	2111	// stop all watchers after blocking
1416	static void	2112	static void
1417	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1418	{	2114	{
1419	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1420		2116
1421	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
		2118	{
		2119	// set the relevant poll flags
		2120	// could also call adns_processreadable etc. here
		2121	struct pollfd *fd = fds + i;
		2122	int revents = ev_clear_pending (iow + i);
		2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2125
		2126	// now stop the watcher
1422	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
		2128	}
1423		2129
1424	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1425	}	2131	}
		2132
		2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2134	in the prepare watcher and would dispose of the check watcher.
		2135
		2136	Method 3: If the module to be embedded supports explicit event
		2137	notification (libadns does), you can also make use of the actual watcher
		2138	callbacks, and only destroy/create the watchers in the prepare watcher.
		2139
		2140	static void
		2141	timer_cb (EV_P_ ev_timer *w, int revents)
		2142	{
		2143	adns_state ads = (adns_state)w->data;
		2144	update_now (EV_A);
		2145
		2146	adns_processtimeouts (ads, &tv_now);
		2147	}
		2148
		2149	static void
		2150	io_cb (EV_P_ ev_io *w, int revents)
		2151	{
		2152	adns_state ads = (adns_state)w->data;
		2153	update_now (EV_A);
		2154
		2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2157	}
		2158
		2159	// do not ever call adns_afterpoll
		2160
		2161	Method 4: Do not use a prepare or check watcher because the module you
		2162	want to embed is not flexible enough to support it. Instead, you can
		2163	override their poll function. The drawback with this solution is that the
		2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
		2167
		2168	static gint
		2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2170	{
		2171	int got_events = 0;
		2172
		2173	for (n = 0; n < nfds; ++n)
		2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2175
		2176	if (timeout >= 0)
		2177	// create/start timer
		2178
		2179	// poll
		2180	ev_loop (EV_A_ 0);
		2181
		2182	// stop timer again
		2183	if (timeout >= 0)
		2184	ev_timer_stop (EV_A_ &to);
		2185
		2186	// stop io watchers again - their callbacks should have set
		2187	for (n = 0; n < nfds; ++n)
		2188	ev_io_stop (EV_A_ iow [n]);
		2189
		2190	return got_events;
		2191	}
1426		2192
1427		2193
1428	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1429		2195
1430	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
…		…
1436	prioritise I/O.	2202	prioritise I/O.
1437		2203
1438	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
1439	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
1440	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
1441	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
1442	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
1443	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
1444	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1445		2212
1446	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
1447	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
1448	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
1449	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
1450	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
1451		2218
1452	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
1453	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
1454	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1455	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
1463	interested in that.	2230	interested in that.
1464		2231
1465	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1466	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1467	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
1468	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1469		2237
1470	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
1471	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1472	portable one.	2240	portable one.
1473		2241
1474	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
1475	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
1476	this is to have a separate variables for your embeddable loop, try to	2244	this is to have a separate variables for your embeddable loop, try to
1477	create it, and if that fails, use the normal loop for everything:	2245	create it, and if that fails, use the normal loop for everything.
1478		2246
1479	struct ev_loop *loop_hi = ev_default_init (0);	2247	=head3 C<ev_embed> and fork
1480	struct ev_loop *loop_lo = 0;
1481	struct ev_embed embed;
1482
1483	// see if there is a chance of getting one that works
1484	// (remember that a flags value of 0 means autodetection)
1485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1487	: 0;
1488		2248
1489	// if we got one, then embed it, otherwise default to loop_hi	2249	While the C<ev_embed> watcher is running, forks in the embedding loop will
1490	if (loop_lo)	2250	automatically be applied to the embedded loop as well, so no special
1491	{	2251	fork handling is required in that case. When the watcher is not running,
1492	ev_embed_init (&embed, 0, loop_lo);	2252	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1493	ev_embed_start (loop_hi, &embed);	2253	as applicable.
1494	}	2254
1495	else	2255	=head3 Watcher-Specific Functions and Data Members
1496	loop_lo = loop_hi;
1497		2256
1498	=over 4	2257	=over 4
1499		2258
1500	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2259	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1501		2260
…		…
1503		2262
1504	Configures the watcher to embed the given loop, which must be	2263	Configures the watcher to embed the given loop, which must be
1505	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2264	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1506	invoked automatically, otherwise it is the responsibility of the callback	2265	invoked automatically, otherwise it is the responsibility of the callback
1507	to invoke it (it will continue to be called until the sweep has been done,	2266	to invoke it (it will continue to be called until the sweep has been done,
1508	if you do not want thta, you need to temporarily stop the embed watcher).	2267	if you do not want that, you need to temporarily stop the embed watcher).
1509		2268
1510	=item ev_embed_sweep (loop, ev_embed *)	2269	=item ev_embed_sweep (loop, ev_embed *)
1511		2270
1512	Make a single, non-blocking sweep over the embedded loop. This works	2271	Make a single, non-blocking sweep over the embedded loop. This works
1513	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2272	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1514	apropriate way for embedded loops.	2273	appropriate way for embedded loops.
1515		2274
1516	=item struct ev_loop *loop [read-only]	2275	=item struct ev_loop *other [read-only]
1517		2276
1518	The embedded event loop.	2277	The embedded event loop.
1519		2278
1520	=back	2279	=back
		2280
		2281	=head3 Examples
		2282
		2283	Example: Try to get an embeddable event loop and embed it into the default
		2284	event loop. If that is not possible, use the default loop. The default
		2285	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2287	used).
		2288
		2289	struct ev_loop *loop_hi = ev_default_init (0);
		2290	struct ev_loop *loop_lo = 0;
		2291	struct ev_embed embed;
		2292
		2293	// see if there is a chance of getting one that works
		2294	// (remember that a flags value of 0 means autodetection)
		2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2297	: 0;
		2298
		2299	// if we got one, then embed it, otherwise default to loop_hi
		2300	if (loop_lo)
		2301	{
		2302	ev_embed_init (&embed, 0, loop_lo);
		2303	ev_embed_start (loop_hi, &embed);
		2304	}
		2305	else
		2306	loop_lo = loop_hi;
		2307
		2308	Example: Check if kqueue is available but not recommended and create
		2309	a kqueue backend for use with sockets (which usually work with any
		2310	kqueue implementation). Store the kqueue/socket-only event loop in
		2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2312
		2313	struct ev_loop *loop = ev_default_init (0);
		2314	struct ev_loop *loop_socket = 0;
		2315	struct ev_embed embed;
		2316
		2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2319	{
		2320	ev_embed_init (&embed, 0, loop_socket);
		2321	ev_embed_start (loop, &embed);
		2322	}
		2323
		2324	if (!loop_socket)
		2325	loop_socket = loop;
		2326
		2327	// now use loop_socket for all sockets, and loop for everything else
1521		2328
1522		2329
1523	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2330	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1524		2331
1525	Fork watchers are called when a C<fork ()> was detected (usually because	2332	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1528	event loop blocks next and before C<ev_check> watchers are being called,	2335	event loop blocks next and before C<ev_check> watchers are being called,
1529	and only in the child after the fork. If whoever good citizen calling	2336	and only in the child after the fork. If whoever good citizen calling
1530	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1531	handlers will be invoked, too, of course.	2338	handlers will be invoked, too, of course.
1532		2339
		2340	=head3 Watcher-Specific Functions and Data Members
		2341
1533	=over 4	2342	=over 4
1534		2343
1535	=item ev_fork_init (ev_signal *, callback)	2344	=item ev_fork_init (ev_signal *, callback)
1536		2345
1537	Initialises and configures the fork watcher - it has no parameters of any	2346	Initialises and configures the fork watcher - it has no parameters of any
…		…
1539	believe me.	2348	believe me.
1540		2349
1541	=back	2350	=back
1542		2351
1543		2352
		2353	=head2 C<ev_async> - how to wake up another event loop
		2354
		2355	In general, you cannot use an C<ev_loop> from multiple threads or other
		2356	asynchronous sources such as signal handlers (as opposed to multiple event
		2357	loops - those are of course safe to use in different threads).
		2358
		2359	Sometimes, however, you need to wake up another event loop you do not
		2360	control, for example because it belongs to another thread. This is what
		2361	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2362	can signal it by calling C<ev_async_send>, which is thread- and signal
		2363	safe.
		2364
		2365	This functionality is very similar to C<ev_signal> watchers, as signals,
		2366	too, are asynchronous in nature, and signals, too, will be compressed
		2367	(i.e. the number of callback invocations may be less than the number of
		2368	C<ev_async_sent> calls).
		2369
		2370	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2371	just the default loop.
		2372
		2373	=head3 Queueing
		2374
		2375	C<ev_async> does not support queueing of data in any way. The reason
		2376	is that the author does not know of a simple (or any) algorithm for a
		2377	multiple-writer-single-reader queue that works in all cases and doesn't
		2378	need elaborate support such as pthreads.
		2379
		2380	That means that if you want to queue data, you have to provide your own
		2381	queue. But at least I can tell you how to implement locking around your
		2382	queue:
		2383
		2384	=over 4
		2385
		2386	=item queueing from a signal handler context
		2387
		2388	To implement race-free queueing, you simply add to the queue in the signal
		2389	handler but you block the signal handler in the watcher callback. Here is
		2390	an example that does that for some fictitious SIGUSR1 handler:
		2391
		2392	static ev_async mysig;
		2393
		2394	static void
		2395	sigusr1_handler (void)
		2396	{
		2397	sometype data;
		2398
		2399	// no locking etc.
		2400	queue_put (data);
		2401	ev_async_send (EV_DEFAULT_ &mysig);
		2402	}
		2403
		2404	static void
		2405	mysig_cb (EV_P_ ev_async *w, int revents)
		2406	{
		2407	sometype data;
		2408	sigset_t block, prev;
		2409
		2410	sigemptyset (&block);
		2411	sigaddset (&block, SIGUSR1);
		2412	sigprocmask (SIG_BLOCK, &block, &prev);
		2413
		2414	while (queue_get (&data))
		2415	process (data);
		2416
		2417	if (sigismember (&prev, SIGUSR1)
		2418	sigprocmask (SIG_UNBLOCK, &block, 0);
		2419	}
		2420
		2421	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2422	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2423	either...).
		2424
		2425	=item queueing from a thread context
		2426
		2427	The strategy for threads is different, as you cannot (easily) block
		2428	threads but you can easily preempt them, so to queue safely you need to
		2429	employ a traditional mutex lock, such as in this pthread example:
		2430
		2431	static ev_async mysig;
		2432	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2433
		2434	static void
		2435	otherthread (void)
		2436	{
		2437	// only need to lock the actual queueing operation
		2438	pthread_mutex_lock (&mymutex);
		2439	queue_put (data);
		2440	pthread_mutex_unlock (&mymutex);
		2441
		2442	ev_async_send (EV_DEFAULT_ &mysig);
		2443	}
		2444
		2445	static void
		2446	mysig_cb (EV_P_ ev_async *w, int revents)
		2447	{
		2448	pthread_mutex_lock (&mymutex);
		2449
		2450	while (queue_get (&data))
		2451	process (data);
		2452
		2453	pthread_mutex_unlock (&mymutex);
		2454	}
		2455
		2456	=back
		2457
		2458
		2459	=head3 Watcher-Specific Functions and Data Members
		2460
		2461	=over 4
		2462
		2463	=item ev_async_init (ev_async *, callback)
		2464
		2465	Initialises and configures the async watcher - it has no parameters of any
		2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2467	trust me.
		2468
		2469	=item ev_async_send (loop, ev_async *)
		2470
		2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2473	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2475	section below on what exactly this means).
		2476
		2477	This call incurs the overhead of a system call only once per loop iteration,
		2478	so while the overhead might be noticeable, it doesn't apply to repeated
		2479	calls to C<ev_async_send>.
		2480
		2481	=item bool = ev_async_pending (ev_async *)
		2482
		2483	Returns a non-zero value when C<ev_async_send> has been called on the
		2484	watcher but the event has not yet been processed (or even noted) by the
		2485	event loop.
		2486
		2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2488	the loop iterates next and checks for the watcher to have become active,
		2489	it will reset the flag again. C<ev_async_pending> can be used to very
		2490	quickly check whether invoking the loop might be a good idea.
		2491
		2492	Not that this does I<not> check whether the watcher itself is pending, only
		2493	whether it has been requested to make this watcher pending.
		2494
		2495	=back
		2496
		2497
1544	=head1 OTHER FUNCTIONS	2498	=head1 OTHER FUNCTIONS
1545		2499
1546	There are some other functions of possible interest. Described. Here. Now.	2500	There are some other functions of possible interest. Described. Here. Now.
1547		2501
1548	=over 4	2502	=over 4
1549		2503
1550	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1551		2505
1552	This function combines a simple timer and an I/O watcher, calls your	2506	This function combines a simple timer and an I/O watcher, calls your
1553	callback on whichever event happens first and automatically stop both	2507	callback on whichever event happens first and automatically stops both
1554	watchers. This is useful if you want to wait for a single event on an fd	2508	watchers. This is useful if you want to wait for a single event on an fd
1555	or timeout without having to allocate/configure/start/stop/free one or	2509	or timeout without having to allocate/configure/start/stop/free one or
1556	more watchers yourself.	2510	more watchers yourself.
1557		2511
1558	If C<fd> is less than 0, then no I/O watcher will be started and events	2512	If C<fd> is less than 0, then no I/O watcher will be started and the
1559	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2513	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1560	C<events> set will be craeted and started.	2514	the given C<fd> and C<events> set will be created and started.
1561		2515
1562	If C<timeout> is less than 0, then no timeout watcher will be	2516	If C<timeout> is less than 0, then no timeout watcher will be
1563	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1564	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2518	repeat = 0) will be started. C<0> is a valid timeout.
1565	dubious value.
1566		2519
1567	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2520	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1568	passed an C<revents> set like normal event callbacks (a combination of	2521	passed an C<revents> set like normal event callbacks (a combination of
1569	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2522	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1570	value passed to C<ev_once>:	2523	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2524	a timeout and an io event at the same time - you probably should give io
		2525	events precedence.
1571		2526
		2527	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2528
1572	static void stdin_ready (int revents, void *arg)	2529	static void stdin_ready (int revents, void *arg)
1573	{	2530	{
1574	if (revents & EV_TIMEOUT)
1575	/* doh, nothing entered */;
1576	else if (revents & EV_READ)	2531	if (revents & EV_READ)
1577	/* stdin might have data for us, joy! */;	2532	/* stdin might have data for us, joy! */;
		2533	else if (revents & EV_TIMEOUT)
		2534	/* doh, nothing entered */;
1578	}	2535	}
1579		2536
1580	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2537	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1581		2538
1582	=item ev_feed_event (ev_loop *, watcher *, int revents)	2539	=item ev_feed_event (ev_loop *, watcher *, int revents)
1583		2540
1584	Feeds the given event set into the event loop, as if the specified event	2541	Feeds the given event set into the event loop, as if the specified event
1585	had happened for the specified watcher (which must be a pointer to an	2542	had happened for the specified watcher (which must be a pointer to an
…		…
1590	Feed an event on the given fd, as if a file descriptor backend detected	2547	Feed an event on the given fd, as if a file descriptor backend detected
1591	the given events it.	2548	the given events it.
1592		2549
1593	=item ev_feed_signal_event (ev_loop *loop, int signum)	2550	=item ev_feed_signal_event (ev_loop *loop, int signum)
1594		2551
1595	Feed an event as if the given signal occured (C<loop> must be the default	2552	Feed an event as if the given signal occurred (C<loop> must be the default
1596	loop!).	2553	loop!).
1597		2554
1598	=back	2555	=back
1599		2556
1600		2557
…		…
1616		2573
1617	=item * Priorities are not currently supported. Initialising priorities	2574	=item * Priorities are not currently supported. Initialising priorities
1618	will fail and all watchers will have the same priority, even though there	2575	will fail and all watchers will have the same priority, even though there
1619	is an ev_pri field.	2576	is an ev_pri field.
1620		2577
		2578	=item * In libevent, the last base created gets the signals, in libev, the
		2579	first base created (== the default loop) gets the signals.
		2580
1621	=item * Other members are not supported.	2581	=item * Other members are not supported.
1622		2582
1623	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2583	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1624	to use the libev header file and library.	2584	to use the libev header file and library.
1625		2585
1626	=back	2586	=back
1627		2587
1628	=head1 C++ SUPPORT	2588	=head1 C++ SUPPORT
1629		2589
1630	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2590	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1631	you to use some convinience methods to start/stop watchers and also change	2591	you to use some convenience methods to start/stop watchers and also change
1632	the callback model to a model using method callbacks on objects.	2592	the callback model to a model using method callbacks on objects.
1633		2593
1634	To use it,	2594	To use it,
1635		2595
1636	#include <ev++.h>	2596	#include <ev++.h>
1637		2597
1638	(it is not installed by default). This automatically includes F<ev.h>	2598	This automatically includes F<ev.h> and puts all of its definitions (many
1639	and puts all of its definitions (many of them macros) into the global	2599	of them macros) into the global namespace. All C++ specific things are
1640	namespace. All C++ specific things are put into the C<ev> namespace.	2600	put into the C<ev> namespace. It should support all the same embedding
		2601	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1641		2602
1642	It should support all the same embedding options as F<ev.h>, most notably	2603	Care has been taken to keep the overhead low. The only data member the C++
1643	C<EV_MULTIPLICITY>.	2604	classes add (compared to plain C-style watchers) is the event loop pointer
		2605	that the watcher is associated with (or no additional members at all if
		2606	you disable C<EV_MULTIPLICITY> when embedding libev).
		2607
		2608	Currently, functions, and static and non-static member functions can be
		2609	used as callbacks. Other types should be easy to add as long as they only
		2610	need one additional pointer for context. If you need support for other
		2611	types of functors please contact the author (preferably after implementing
		2612	it).
1644		2613
1645	Here is a list of things available in the C<ev> namespace:	2614	Here is a list of things available in the C<ev> namespace:
1646		2615
1647	=over 4	2616	=over 4
1648		2617
…		…
1664		2633
1665	All of those classes have these methods:	2634	All of those classes have these methods:
1666		2635
1667	=over 4	2636	=over 4
1668		2637
1669	=item ev::TYPE::TYPE (object *, object::method *)	2638	=item ev::TYPE::TYPE ()
1670		2639
1671	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2640	=item ev::TYPE::TYPE (struct ev_loop *)
1672		2641
1673	=item ev::TYPE::~TYPE	2642	=item ev::TYPE::~TYPE
1674		2643
1675	The constructor takes a pointer to an object and a method pointer to	2644	The constructor (optionally) takes an event loop to associate the watcher
1676	the event handler callback to call in this class. The constructor calls	2645	with. If it is omitted, it will use C<EV_DEFAULT>.
1677	C<ev_init> for you, which means you have to call the C<set> method	2646
1678	before starting it. If you do not specify a loop then the constructor	2647	The constructor calls C<ev_init> for you, which means you have to call the
1679	automatically associates the default loop with this watcher.	2648	C<set> method before starting it.
		2649
		2650	It will not set a callback, however: You have to call the templated C<set>
		2651	method to set a callback before you can start the watcher.
		2652
		2653	(The reason why you have to use a method is a limitation in C++ which does
		2654	not allow explicit template arguments for constructors).
1680		2655
1681	The destructor automatically stops the watcher if it is active.	2656	The destructor automatically stops the watcher if it is active.
		2657
		2658	=item w->set<class, &class::method> (object *)
		2659
		2660	This method sets the callback method to call. The method has to have a
		2661	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2662	first argument and the C<revents> as second. The object must be given as
		2663	parameter and is stored in the C<data> member of the watcher.
		2664
		2665	This method synthesizes efficient thunking code to call your method from
		2666	the C callback that libev requires. If your compiler can inline your
		2667	callback (i.e. it is visible to it at the place of the C<set> call and
		2668	your compiler is good :), then the method will be fully inlined into the
		2669	thunking function, making it as fast as a direct C callback.
		2670
		2671	Example: simple class declaration and watcher initialisation
		2672
		2673	struct myclass
		2674	{
		2675	void io_cb (ev::io &w, int revents) { }
		2676	}
		2677
		2678	myclass obj;
		2679	ev::io iow;
		2680	iow.set <myclass, &myclass::io_cb> (&obj);
		2681
		2682	=item w->set<function> (void *data = 0)
		2683
		2684	Also sets a callback, but uses a static method or plain function as
		2685	callback. The optional C<data> argument will be stored in the watcher's
		2686	C<data> member and is free for you to use.
		2687
		2688	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2689
		2690	See the method-C<set> above for more details.
		2691
		2692	Example: Use a plain function as callback.
		2693
		2694	static void io_cb (ev::io &w, int revents) { }
		2695	iow.set <io_cb> ();
1682		2696
1683	=item w->set (struct ev_loop *)	2697	=item w->set (struct ev_loop *)
1684		2698
1685	Associates a different C<struct ev_loop> with this watcher. You can only	2699	Associates a different C<struct ev_loop> with this watcher. You can only
1686	do this when the watcher is inactive (and not pending either).	2700	do this when the watcher is inactive (and not pending either).
1687		2701
1688	=item w->set ([args])	2702	=item w->set ([arguments])
1689		2703
1690	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2704	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1691	called at least once. Unlike the C counterpart, an active watcher gets	2705	called at least once. Unlike the C counterpart, an active watcher gets
1692	automatically stopped and restarted.	2706	automatically stopped and restarted when reconfiguring it with this
		2707	method.
1693		2708
1694	=item w->start ()	2709	=item w->start ()
1695		2710
1696	Starts the watcher. Note that there is no C<loop> argument as the	2711	Starts the watcher. Note that there is no C<loop> argument, as the
1697	constructor already takes the loop.	2712	constructor already stores the event loop.
1698		2713
1699	=item w->stop ()	2714	=item w->stop ()
1700		2715
1701	Stops the watcher if it is active. Again, no C<loop> argument.	2716	Stops the watcher if it is active. Again, no C<loop> argument.
1702		2717
1703	=item w->again () C<ev::timer>, C<ev::periodic> only	2718	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1704		2719
1705	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2720	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1706	C<ev_TYPE_again> function.	2721	C<ev_TYPE_again> function.
1707		2722
1708	=item w->sweep () C<ev::embed> only	2723	=item w->sweep () (C<ev::embed> only)
1709		2724
1710	Invokes C<ev_embed_sweep>.	2725	Invokes C<ev_embed_sweep>.
1711		2726
1712	=item w->update () C<ev::stat> only	2727	=item w->update () (C<ev::stat> only)
1713		2728
1714	Invokes C<ev_stat_stat>.	2729	Invokes C<ev_stat_stat>.
1715		2730
1716	=back	2731	=back
1717		2732
1718	=back	2733	=back
1719		2734
1720	Example: Define a class with an IO and idle watcher, start one of them in	2735	Example: Define a class with an IO and idle watcher, start one of them in
1721	the constructor.	2736	the constructor.
1722		2737
1723	class myclass	2738	class myclass
1724	{	2739	{
1725	ev_io io; void io_cb (ev::io &w, int revents);	2740	ev::io io ; void io_cb (ev::io &w, int revents);
1726	ev_idle idle void idle_cb (ev::idle &w, int revents);	2741	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1727		2742
1728	myclass ();	2743	myclass (int fd)
1729	}	2744	{
		2745	io .set <myclass, &myclass::io_cb > (this);
		2746	idle.set <myclass, &myclass::idle_cb> (this);
1730		2747
1731	myclass::myclass (int fd)
1732	: io (this, &myclass::io_cb),
1733	idle (this, &myclass::idle_cb)
1734	{
1735	io.start (fd, ev::READ);	2748	io.start (fd, ev::READ);
		2749	}
1736	}	2750	};
		2751
		2752
		2753	=head1 OTHER LANGUAGE BINDINGS
		2754
		2755	Libev does not offer other language bindings itself, but bindings for a
		2756	number of languages exist in the form of third-party packages. If you know
		2757	any interesting language binding in addition to the ones listed here, drop
		2758	me a note.
		2759
		2760	=over 4
		2761
		2762	=item Perl
		2763
		2764	The EV module implements the full libev API and is actually used to test
		2765	libev. EV is developed together with libev. Apart from the EV core module,
		2766	there are additional modules that implement libev-compatible interfaces
		2767	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2768	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2769	and C<EV::Glib>).
		2770
		2771	It can be found and installed via CPAN, its homepage is at
		2772	L<http://software.schmorp.de/pkg/EV>.
		2773
		2774	=item Python
		2775
		2776	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2777	seems to be quite complete and well-documented. Note, however, that the
		2778	patch they require for libev is outright dangerous as it breaks the ABI
		2779	for everybody else, and therefore, should never be applied in an installed
		2780	libev (if python requires an incompatible ABI then it needs to embed
		2781	libev).
		2782
		2783	=item Ruby
		2784
		2785	Tony Arcieri has written a ruby extension that offers access to a subset
		2786	of the libev API and adds file handle abstractions, asynchronous DNS and
		2787	more on top of it. It can be found via gem servers. Its homepage is at
		2788	L<http://rev.rubyforge.org/>.
		2789
		2790	=item D
		2791
		2792	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2793	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2794
		2795	=back
1737		2796
1738		2797
1739	=head1 MACRO MAGIC	2798	=head1 MACRO MAGIC
1740		2799
1741	Libev can be compiled with a variety of options, the most fundemantal is	2800	Libev can be compiled with a variety of options, the most fundamental
1742	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2801	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1743	callbacks have an initial C<struct ev_loop *> argument.	2802	functions and callbacks have an initial C<struct ev_loop *> argument.
1744		2803
1745	To make it easier to write programs that cope with either variant, the	2804	To make it easier to write programs that cope with either variant, the
1746	following macros are defined:	2805	following macros are defined:
1747		2806
1748	=over 4	2807	=over 4
…		…
1751		2810
1752	This provides the loop I<argument> for functions, if one is required ("ev	2811	This provides the loop I<argument> for functions, if one is required ("ev
1753	loop argument"). The C<EV_A> form is used when this is the sole argument,	2812	loop argument"). The C<EV_A> form is used when this is the sole argument,
1754	C<EV_A_> is used when other arguments are following. Example:	2813	C<EV_A_> is used when other arguments are following. Example:
1755		2814
1756	ev_unref (EV_A);	2815	ev_unref (EV_A);
1757	ev_timer_add (EV_A_ watcher);	2816	ev_timer_add (EV_A_ watcher);
1758	ev_loop (EV_A_ 0);	2817	ev_loop (EV_A_ 0);
1759		2818
1760	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2819	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1761	which is often provided by the following macro.	2820	which is often provided by the following macro.
1762		2821
1763	=item C<EV_P>, C<EV_P_>	2822	=item C<EV_P>, C<EV_P_>
1764		2823
1765	This provides the loop I<parameter> for functions, if one is required ("ev	2824	This provides the loop I<parameter> for functions, if one is required ("ev
1766	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2825	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1767	C<EV_P_> is used when other parameters are following. Example:	2826	C<EV_P_> is used when other parameters are following. Example:
1768		2827
1769	// this is how ev_unref is being declared	2828	// this is how ev_unref is being declared
1770	static void ev_unref (EV_P);	2829	static void ev_unref (EV_P);
1771		2830
1772	// this is how you can declare your typical callback	2831	// this is how you can declare your typical callback
1773	static void cb (EV_P_ ev_timer *w, int revents)	2832	static void cb (EV_P_ ev_timer *w, int revents)
1774		2833
1775	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2834	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1776	suitable for use with C<EV_A>.	2835	suitable for use with C<EV_A>.
1777		2836
1778	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2837	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1779		2838
1780	Similar to the other two macros, this gives you the value of the default	2839	Similar to the other two macros, this gives you the value of the default
1781	loop, if multiple loops are supported ("ev loop default").	2840	loop, if multiple loops are supported ("ev loop default").
1782		2841
		2842	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2843
		2844	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2845	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2846	is undefined when the default loop has not been initialised by a previous
		2847	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2848
		2849	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2850	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2851
1783	=back	2852	=back
1784		2853
1785	Example: Declare and initialise a check watcher, working regardless of	2854	Example: Declare and initialise a check watcher, utilising the above
1786	wether multiple loops are supported or not.	2855	macros so it will work regardless of whether multiple loops are supported
		2856	or not.
1787		2857
1788	static void	2858	static void
1789	check_cb (EV_P_ ev_timer *w, int revents)	2859	check_cb (EV_P_ ev_timer *w, int revents)
1790	{	2860	{
1791	ev_check_stop (EV_A_ w);	2861	ev_check_stop (EV_A_ w);
1792	}	2862	}
1793		2863
1794	ev_check check;	2864	ev_check check;
1795	ev_check_init (&check, check_cb);	2865	ev_check_init (&check, check_cb);
1796	ev_check_start (EV_DEFAULT_ &check);	2866	ev_check_start (EV_DEFAULT_ &check);
1797	ev_loop (EV_DEFAULT_ 0);	2867	ev_loop (EV_DEFAULT_ 0);
1798
1799		2868
1800	=head1 EMBEDDING	2869	=head1 EMBEDDING
1801		2870
1802	Libev can (and often is) directly embedded into host	2871	Libev can (and often is) directly embedded into host
1803	applications. Examples of applications that embed it include the Deliantra	2872	applications. Examples of applications that embed it include the Deliantra
1804	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2873	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1805	and rxvt-unicode.	2874	and rxvt-unicode.
1806		2875
1807	The goal is to enable you to just copy the neecssary files into your	2876	The goal is to enable you to just copy the necessary files into your
1808	source directory without having to change even a single line in them, so	2877	source directory without having to change even a single line in them, so
1809	you can easily upgrade by simply copying (or having a checked-out copy of	2878	you can easily upgrade by simply copying (or having a checked-out copy of
1810	libev somewhere in your source tree).	2879	libev somewhere in your source tree).
1811		2880
1812	=head2 FILESETS	2881	=head2 FILESETS
1813		2882
1814	Depending on what features you need you need to include one or more sets of files	2883	Depending on what features you need you need to include one or more sets of files
1815	in your app.	2884	in your application.
1816		2885
1817	=head3 CORE EVENT LOOP	2886	=head3 CORE EVENT LOOP
1818		2887
1819	To include only the libev core (all the C<ev_*> functions), with manual	2888	To include only the libev core (all the C<ev_*> functions), with manual
1820	configuration (no autoconf):	2889	configuration (no autoconf):
1821		2890
1822	#define EV_STANDALONE 1	2891	#define EV_STANDALONE 1
1823	#include "ev.c"	2892	#include "ev.c"
1824		2893
1825	This will automatically include F<ev.h>, too, and should be done in a	2894	This will automatically include F<ev.h>, too, and should be done in a
1826	single C source file only to provide the function implementations. To use	2895	single C source file only to provide the function implementations. To use
1827	it, do the same for F<ev.h> in all files wishing to use this API (best	2896	it, do the same for F<ev.h> in all files wishing to use this API (best
1828	done by writing a wrapper around F<ev.h> that you can include instead and	2897	done by writing a wrapper around F<ev.h> that you can include instead and
1829	where you can put other configuration options):	2898	where you can put other configuration options):
1830		2899
1831	#define EV_STANDALONE 1	2900	#define EV_STANDALONE 1
1832	#include "ev.h"	2901	#include "ev.h"
1833		2902
1834	Both header files and implementation files can be compiled with a C++	2903	Both header files and implementation files can be compiled with a C++
1835	compiler (at least, thats a stated goal, and breakage will be treated	2904	compiler (at least, thats a stated goal, and breakage will be treated
1836	as a bug).	2905	as a bug).
1837		2906
1838	You need the following files in your source tree, or in a directory	2907	You need the following files in your source tree, or in a directory
1839	in your include path (e.g. in libev/ when using -Ilibev):	2908	in your include path (e.g. in libev/ when using -Ilibev):
1840		2909
1841	ev.h	2910	ev.h
1842	ev.c	2911	ev.c
1843	ev_vars.h	2912	ev_vars.h
1844	ev_wrap.h	2913	ev_wrap.h
1845		2914
1846	ev_win32.c required on win32 platforms only	2915	ev_win32.c required on win32 platforms only
1847		2916
1848	ev_select.c only when select backend is enabled (which is by default)	2917	ev_select.c only when select backend is enabled (which is enabled by default)
1849	ev_poll.c only when poll backend is enabled (disabled by default)	2918	ev_poll.c only when poll backend is enabled (disabled by default)
1850	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2919	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1851	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2920	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1852	ev_port.c only when the solaris port backend is enabled (disabled by default)	2921	ev_port.c only when the solaris port backend is enabled (disabled by default)
1853		2922
1854	F<ev.c> includes the backend files directly when enabled, so you only need	2923	F<ev.c> includes the backend files directly when enabled, so you only need
1855	to compile this single file.	2924	to compile this single file.
1856		2925
1857	=head3 LIBEVENT COMPATIBILITY API	2926	=head3 LIBEVENT COMPATIBILITY API
1858		2927
1859	To include the libevent compatibility API, also include:	2928	To include the libevent compatibility API, also include:
1860		2929
1861	#include "event.c"	2930	#include "event.c"
1862		2931
1863	in the file including F<ev.c>, and:	2932	in the file including F<ev.c>, and:
1864		2933
1865	#include "event.h"	2934	#include "event.h"
1866		2935
1867	in the files that want to use the libevent API. This also includes F<ev.h>.	2936	in the files that want to use the libevent API. This also includes F<ev.h>.
1868		2937
1869	You need the following additional files for this:	2938	You need the following additional files for this:
1870		2939
1871	event.h	2940	event.h
1872	event.c	2941	event.c
1873		2942
1874	=head3 AUTOCONF SUPPORT	2943	=head3 AUTOCONF SUPPORT
1875		2944
1876	Instead of using C<EV_STANDALONE=1> and providing your config in	2945	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1877	whatever way you want, you can also C<m4_include([libev.m4])> in your	2946	whatever way you want, you can also C<m4_include([libev.m4])> in your
1878	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2947	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1879	include F<config.h> and configure itself accordingly.	2948	include F<config.h> and configure itself accordingly.
1880		2949
1881	For this of course you need the m4 file:	2950	For this of course you need the m4 file:
1882		2951
1883	libev.m4	2952	libev.m4
1884		2953
1885	=head2 PREPROCESSOR SYMBOLS/MACROS	2954	=head2 PREPROCESSOR SYMBOLS/MACROS
1886		2955
1887	Libev can be configured via a variety of preprocessor symbols you have to define	2956	Libev can be configured via a variety of preprocessor symbols you have to
1888	before including any of its files. The default is not to build for multiplicity	2957	define before including any of its files. The default in the absence of
1889	and only include the select backend.	2958	autoconf is documented for every option.
1890		2959
1891	=over 4	2960	=over 4
1892		2961
1893	=item EV_STANDALONE	2962	=item EV_STANDALONE
1894		2963
…		…
1899	F<event.h> that are not directly supported by the libev core alone.	2968	F<event.h> that are not directly supported by the libev core alone.
1900		2969
1901	=item EV_USE_MONOTONIC	2970	=item EV_USE_MONOTONIC
1902		2971
1903	If defined to be C<1>, libev will try to detect the availability of the	2972	If defined to be C<1>, libev will try to detect the availability of the
1904	monotonic clock option at both compiletime and runtime. Otherwise no use	2973	monotonic clock option at both compile time and runtime. Otherwise no use
1905	of the monotonic clock option will be attempted. If you enable this, you	2974	of the monotonic clock option will be attempted. If you enable this, you
1906	usually have to link against librt or something similar. Enabling it when	2975	usually have to link against librt or something similar. Enabling it when
1907	the functionality isn't available is safe, though, althoguh you have	2976	the functionality isn't available is safe, though, although you have
1908	to make sure you link against any libraries where the C<clock_gettime>	2977	to make sure you link against any libraries where the C<clock_gettime>
1909	function is hiding in (often F<-lrt>).	2978	function is hiding in (often F<-lrt>).
1910		2979
1911	=item EV_USE_REALTIME	2980	=item EV_USE_REALTIME
1912		2981
1913	If defined to be C<1>, libev will try to detect the availability of the	2982	If defined to be C<1>, libev will try to detect the availability of the
1914	realtime clock option at compiletime (and assume its availability at	2983	real-time clock option at compile time (and assume its availability at
1915	runtime if successful). Otherwise no use of the realtime clock option will	2984	runtime if successful). Otherwise no use of the real-time clock option will
1916	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2985	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1917	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2986	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1918	in the description of C<EV_USE_MONOTONIC>, though.	2987	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2988
		2989	=item EV_USE_NANOSLEEP
		2990
		2991	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2992	and will use it for delays. Otherwise it will use C<select ()>.
		2993
		2994	=item EV_USE_EVENTFD
		2995
		2996	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2997	available and will probe for kernel support at runtime. This will improve
		2998	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2999	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3000	2.7 or newer, otherwise disabled.
1919		3001
1920	=item EV_USE_SELECT	3002	=item EV_USE_SELECT
1921		3003
1922	If undefined or defined to be C<1>, libev will compile in support for the	3004	If undefined or defined to be C<1>, libev will compile in support for the
1923	C<select>(2) backend. No attempt at autodetection will be done: if no	3005	C<select>(2) backend. No attempt at auto-detection will be done: if no
1924	other method takes over, select will be it. Otherwise the select backend	3006	other method takes over, select will be it. Otherwise the select backend
1925	will not be compiled in.	3007	will not be compiled in.
1926		3008
1927	=item EV_SELECT_USE_FD_SET	3009	=item EV_SELECT_USE_FD_SET
1928		3010
1929	If defined to C<1>, then the select backend will use the system C<fd_set>	3011	If defined to C<1>, then the select backend will use the system C<fd_set>
1930	structure. This is useful if libev doesn't compile due to a missing	3012	structure. This is useful if libev doesn't compile due to a missing
1931	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3013	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
1932	exotic systems. This usually limits the range of file descriptors to some	3014	exotic systems. This usually limits the range of file descriptors to some
1933	low limit such as 1024 or might have other limitations (winsocket only	3015	low limit such as 1024 or might have other limitations (winsocket only
1934	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3016	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1935	influence the size of the C<fd_set> used.	3017	influence the size of the C<fd_set> used.
1936		3018
…		…
1942	be used is the winsock select). This means that it will call	3024	be used is the winsock select). This means that it will call
1943	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3025	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1944	it is assumed that all these functions actually work on fds, even	3026	it is assumed that all these functions actually work on fds, even
1945	on win32. Should not be defined on non-win32 platforms.	3027	on win32. Should not be defined on non-win32 platforms.
1946		3028
		3029	=item EV_FD_TO_WIN32_HANDLE
		3030
		3031	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3032	file descriptors to socket handles. When not defining this symbol (the
		3033	default), then libev will call C<_get_osfhandle>, which is usually
		3034	correct. In some cases, programs use their own file descriptor management,
		3035	in which case they can provide this function to map fds to socket handles.
		3036
1947	=item EV_USE_POLL	3037	=item EV_USE_POLL
1948		3038
1949	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3039	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1950	backend. Otherwise it will be enabled on non-win32 platforms. It	3040	backend. Otherwise it will be enabled on non-win32 platforms. It
1951	takes precedence over select.	3041	takes precedence over select.
1952		3042
1953	=item EV_USE_EPOLL	3043	=item EV_USE_EPOLL
1954		3044
1955	If defined to be C<1>, libev will compile in support for the Linux	3045	If defined to be C<1>, libev will compile in support for the Linux
1956	C<epoll>(7) backend. Its availability will be detected at runtime,	3046	C<epoll>(7) backend. Its availability will be detected at runtime,
1957	otherwise another method will be used as fallback. This is the	3047	otherwise another method will be used as fallback. This is the preferred
1958	preferred backend for GNU/Linux systems.	3048	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3049	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
1959		3050
1960	=item EV_USE_KQUEUE	3051	=item EV_USE_KQUEUE
1961		3052
1962	If defined to be C<1>, libev will compile in support for the BSD style	3053	If defined to be C<1>, libev will compile in support for the BSD style
1963	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3054	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
1976	otherwise another method will be used as fallback. This is the preferred	3067	otherwise another method will be used as fallback. This is the preferred
1977	backend for Solaris 10 systems.	3068	backend for Solaris 10 systems.
1978		3069
1979	=item EV_USE_DEVPOLL	3070	=item EV_USE_DEVPOLL
1980		3071
1981	reserved for future expansion, works like the USE symbols above.	3072	Reserved for future expansion, works like the USE symbols above.
		3073
		3074	=item EV_USE_INOTIFY
		3075
		3076	If defined to be C<1>, libev will compile in support for the Linux inotify
		3077	interface to speed up C<ev_stat> watchers. Its actual availability will
		3078	be detected at runtime. If undefined, it will be enabled if the headers
		3079	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3080
		3081	=item EV_ATOMIC_T
		3082
		3083	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3084	access is atomic with respect to other threads or signal contexts. No such
		3085	type is easily found in the C language, so you can provide your own type
		3086	that you know is safe for your purposes. It is used both for signal handler "locking"
		3087	as well as for signal and thread safety in C<ev_async> watchers.
		3088
		3089	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3090	(from F<signal.h>), which is usually good enough on most platforms.
1982		3091
1983	=item EV_H	3092	=item EV_H
1984		3093
1985	The name of the F<ev.h> header file used to include it. The default if	3094	The name of the F<ev.h> header file used to include it. The default if
1986	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3095	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1987	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3096	used to virtually rename the F<ev.h> header file in case of conflicts.
1988		3097
1989	=item EV_CONFIG_H	3098	=item EV_CONFIG_H
1990		3099
1991	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3100	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1992	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3101	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1993	C<EV_H>, above.	3102	C<EV_H>, above.
1994		3103
1995	=item EV_EVENT_H	3104	=item EV_EVENT_H
1996		3105
1997	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3106	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1998	of how the F<event.h> header can be found.	3107	of how the F<event.h> header can be found, the default is C<"event.h">.
1999		3108
2000	=item EV_PROTOTYPES	3109	=item EV_PROTOTYPES
2001		3110
2002	If defined to be C<0>, then F<ev.h> will not define any function	3111	If defined to be C<0>, then F<ev.h> will not define any function
2003	prototypes, but still define all the structs and other symbols. This is	3112	prototypes, but still define all the structs and other symbols. This is
…		…
2010	will have the C<struct ev_loop *> as first argument, and you can create	3119	will have the C<struct ev_loop *> as first argument, and you can create
2011	additional independent event loops. Otherwise there will be no support	3120	additional independent event loops. Otherwise there will be no support
2012	for multiple event loops and there is no first event loop pointer	3121	for multiple event loops and there is no first event loop pointer
2013	argument. Instead, all functions act on the single default loop.	3122	argument. Instead, all functions act on the single default loop.
2014		3123
		3124	=item EV_MINPRI
		3125
		3126	=item EV_MAXPRI
		3127
		3128	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3129	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3130	provide for more priorities by overriding those symbols (usually defined
		3131	to be C<-2> and C<2>, respectively).
		3132
		3133	When doing priority-based operations, libev usually has to linearly search
		3134	all the priorities, so having many of them (hundreds) uses a lot of space
		3135	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3136	fine.
		3137
		3138	If your embedding application does not need any priorities, defining these
		3139	both to C<0> will save some memory and CPU.
		3140
2015	=item EV_PERIODIC_ENABLE	3141	=item EV_PERIODIC_ENABLE
2016		3142
2017	If undefined or defined to be C<1>, then periodic timers are supported. If	3143	If undefined or defined to be C<1>, then periodic timers are supported. If
2018	defined to be C<0>, then they are not. Disabling them saves a few kB of	3144	defined to be C<0>, then they are not. Disabling them saves a few kB of
2019	code.	3145	code.
2020		3146
		3147	=item EV_IDLE_ENABLE
		3148
		3149	If undefined or defined to be C<1>, then idle watchers are supported. If
		3150	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3151	code.
		3152
2021	=item EV_EMBED_ENABLE	3153	=item EV_EMBED_ENABLE
2022		3154
2023	If undefined or defined to be C<1>, then embed watchers are supported. If	3155	If undefined or defined to be C<1>, then embed watchers are supported. If
2024	defined to be C<0>, then they are not.	3156	defined to be C<0>, then they are not. Embed watchers rely on most other
		3157	watcher types, which therefore must not be disabled.
2025		3158
2026	=item EV_STAT_ENABLE	3159	=item EV_STAT_ENABLE
2027		3160
2028	If undefined or defined to be C<1>, then stat watchers are supported. If	3161	If undefined or defined to be C<1>, then stat watchers are supported. If
2029	defined to be C<0>, then they are not.	3162	defined to be C<0>, then they are not.
…		…
2031	=item EV_FORK_ENABLE	3164	=item EV_FORK_ENABLE
2032		3165
2033	If undefined or defined to be C<1>, then fork watchers are supported. If	3166	If undefined or defined to be C<1>, then fork watchers are supported. If
2034	defined to be C<0>, then they are not.	3167	defined to be C<0>, then they are not.
2035		3168
		3169	=item EV_ASYNC_ENABLE
		3170
		3171	If undefined or defined to be C<1>, then async watchers are supported. If
		3172	defined to be C<0>, then they are not.
		3173
2036	=item EV_MINIMAL	3174	=item EV_MINIMAL
2037		3175
2038	If you need to shave off some kilobytes of code at the expense of some	3176	If you need to shave off some kilobytes of code at the expense of some
2039	speed, define this symbol to C<1>. Currently only used for gcc to override	3177	speed, define this symbol to C<1>. Currently this is used to override some
2040	some inlining decisions, saves roughly 30% codesize of amd64.	3178	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3179	much smaller 2-heap for timer management over the default 4-heap.
2041		3180
2042	=item EV_PID_HASHSIZE	3181	=item EV_PID_HASHSIZE
2043		3182
2044	C<ev_child> watchers use a small hash table to distribute workload by	3183	C<ev_child> watchers use a small hash table to distribute workload by
2045	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3184	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2046	than enough. If you need to manage thousands of children you might want to	3185	than enough. If you need to manage thousands of children you might want to
2047	increase this value.	3186	increase this value (I<must> be a power of two).
		3187
		3188	=item EV_INOTIFY_HASHSIZE
		3189
		3190	C<ev_stat> watchers use a small hash table to distribute workload by
		3191	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		3192	usually more than enough. If you need to manage thousands of C<ev_stat>
		3193	watchers you might want to increase this value (I<must> be a power of
		3194	two).
		3195
		3196	=item EV_USE_4HEAP
		3197
		3198	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3199	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3200	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3201	faster performance with many (thousands) of watchers.
		3202
		3203	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3204	(disabled).
		3205
		3206	=item EV_HEAP_CACHE_AT
		3207
		3208	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3209	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3210	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3211	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3212	but avoids random read accesses on heap changes. This improves performance
		3213	noticeably with many (hundreds) of watchers.
		3214
		3215	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3216	(disabled).
		3217
		3218	=item EV_VERIFY
		3219
		3220	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3221	be done: If set to C<0>, no internal verification code will be compiled
		3222	in. If set to C<1>, then verification code will be compiled in, but not
		3223	called. If set to C<2>, then the internal verification code will be
		3224	called once per loop, which can slow down libev. If set to C<3>, then the
		3225	verification code will be called very frequently, which will slow down
		3226	libev considerably.
		3227
		3228	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3229	C<0>.
2048		3230
2049	=item EV_COMMON	3231	=item EV_COMMON
2050		3232
2051	By default, all watchers have a C<void *data> member. By redefining	3233	By default, all watchers have a C<void *data> member. By redefining
2052	this macro to a something else you can include more and other types of	3234	this macro to a something else you can include more and other types of
2053	members. You have to define it each time you include one of the files,	3235	members. You have to define it each time you include one of the files,
2054	though, and it must be identical each time.	3236	though, and it must be identical each time.
2055		3237
2056	For example, the perl EV module uses something like this:	3238	For example, the perl EV module uses something like this:
2057		3239
2058	#define EV_COMMON \	3240	#define EV_COMMON \
2059	SV *self; /* contains this struct */ \	3241	SV *self; /* contains this struct */ \
2060	SV *cb_sv, *fh /* note no trailing ";" */	3242	SV *cb_sv, *fh /* note no trailing ";" */
2061		3243
2062	=item EV_CB_DECLARE (type)	3244	=item EV_CB_DECLARE (type)
2063		3245
2064	=item EV_CB_INVOKE (watcher, revents)	3246	=item EV_CB_INVOKE (watcher, revents)
2065		3247
2066	=item ev_set_cb (ev, cb)	3248	=item ev_set_cb (ev, cb)
2067		3249
2068	Can be used to change the callback member declaration in each watcher,	3250	Can be used to change the callback member declaration in each watcher,
2069	and the way callbacks are invoked and set. Must expand to a struct member	3251	and the way callbacks are invoked and set. Must expand to a struct member
2070	definition and a statement, respectively. See the F<ev.v> header file for	3252	definition and a statement, respectively. See the F<ev.h> header file for
2071	their default definitions. One possible use for overriding these is to	3253	their default definitions. One possible use for overriding these is to
2072	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3254	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2073	method calls instead of plain function calls in C++.	3255	method calls instead of plain function calls in C++.
		3256
		3257	=back
		3258
		3259	=head2 EXPORTED API SYMBOLS
		3260
		3261	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3262	exported symbols, you can use the provided F<Symbol.*> files which list
		3263	all public symbols, one per line:
		3264
		3265	Symbols.ev for libev proper
		3266	Symbols.event for the libevent emulation
		3267
		3268	This can also be used to rename all public symbols to avoid clashes with
		3269	multiple versions of libev linked together (which is obviously bad in
		3270	itself, but sometimes it is inconvenient to avoid this).
		3271
		3272	A sed command like this will create wrapper C<#define>'s that you need to
		3273	include before including F<ev.h>:
		3274
		3275	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3276
		3277	This would create a file F<wrap.h> which essentially looks like this:
		3278
		3279	#define ev_backend myprefix_ev_backend
		3280	#define ev_check_start myprefix_ev_check_start
		3281	#define ev_check_stop myprefix_ev_check_stop
		3282	...
2074		3283
2075	=head2 EXAMPLES	3284	=head2 EXAMPLES
2076		3285
2077	For a real-world example of a program the includes libev	3286	For a real-world example of a program the includes libev
2078	verbatim, you can have a look at the EV perl module	3287	verbatim, you can have a look at the EV perl module
…		…
2081	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3290	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2082	will be compiled. It is pretty complex because it provides its own header	3291	will be compiled. It is pretty complex because it provides its own header
2083	file.	3292	file.
2084		3293
2085	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3294	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2086	that everybody includes and which overrides some autoconf choices:	3295	that everybody includes and which overrides some configure choices:
2087		3296
		3297	#define EV_MINIMAL 1
2088	#define EV_USE_POLL 0	3298	#define EV_USE_POLL 0
2089	#define EV_MULTIPLICITY 0	3299	#define EV_MULTIPLICITY 0
2090	#define EV_PERIODICS 0	3300	#define EV_PERIODIC_ENABLE 0
		3301	#define EV_STAT_ENABLE 0
		3302	#define EV_FORK_ENABLE 0
2091	#define EV_CONFIG_H <config.h>	3303	#define EV_CONFIG_H <config.h>
		3304	#define EV_MINPRI 0
		3305	#define EV_MAXPRI 0
2092		3306
2093	#include "ev++.h"	3307	#include "ev++.h"
2094		3308
2095	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3309	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2096		3310
2097	#include "ev_cpp.h"	3311	#include "ev_cpp.h"
2098	#include "ev.c"	3312	#include "ev.c"
2099		3313
		3314	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2100		3315
		3316	=head2 THREADS AND COROUTINES
		3317
		3318	=head3 THREADS
		3319
		3320	All libev functions are reentrant and thread-safe unless explicitly
		3321	documented otherwise, but libev implements no locking itself. This means
		3322	that you can use as many loops as you want in parallel, as long as there
		3323	are no concurrent calls into any libev function with the same loop
		3324	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3325	of course): libev guarantees that different event loops share no data
		3326	structures that need any locking.
		3327
		3328	Or to put it differently: calls with different loop parameters can be done
		3329	concurrently from multiple threads, calls with the same loop parameter
		3330	must be done serially (but can be done from different threads, as long as
		3331	only one thread ever is inside a call at any point in time, e.g. by using
		3332	a mutex per loop).
		3333
		3334	Specifically to support threads (and signal handlers), libev implements
		3335	so-called C<ev_async> watchers, which allow some limited form of
		3336	concurrency on the same event loop, namely waking it up "from the
		3337	outside".
		3338
		3339	If you want to know which design (one loop, locking, or multiple loops
		3340	without or something else still) is best for your problem, then I cannot
		3341	help you, but here is some generic advice:
		3342
		3343	=over 4
		3344
		3345	=item * most applications have a main thread: use the default libev loop
		3346	in that thread, or create a separate thread running only the default loop.
		3347
		3348	This helps integrating other libraries or software modules that use libev
		3349	themselves and don't care/know about threading.
		3350
		3351	=item * one loop per thread is usually a good model.
		3352
		3353	Doing this is almost never wrong, sometimes a better-performance model
		3354	exists, but it is always a good start.
		3355
		3356	=item * other models exist, such as the leader/follower pattern, where one
		3357	loop is handed through multiple threads in a kind of round-robin fashion.
		3358
		3359	Choosing a model is hard - look around, learn, know that usually you can do
		3360	better than you currently do :-)
		3361
		3362	=item * often you need to talk to some other thread which blocks in the
		3363	event loop.
		3364
		3365	C<ev_async> watchers can be used to wake them up from other threads safely
		3366	(or from signal contexts...).
		3367
		3368	An example use would be to communicate signals or other events that only
		3369	work in the default loop by registering the signal watcher with the
		3370	default loop and triggering an C<ev_async> watcher from the default loop
		3371	watcher callback into the event loop interested in the signal.
		3372
		3373	=back
		3374
		3375	=head3 COROUTINES
		3376
		3377	Libev is very accommodating to coroutines ("cooperative threads"):
		3378	libev fully supports nesting calls to its functions from different
		3379	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3380	different coroutines, and switch freely between both coroutines running the
		3381	loop, as long as you don't confuse yourself). The only exception is that
		3382	you must not do this from C<ev_periodic> reschedule callbacks.
		3383
		3384	Care has been taken to ensure that libev does not keep local state inside
		3385	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3386	they do not clal any callbacks.
		3387
		3388	=head2 COMPILER WARNINGS
		3389
		3390	Depending on your compiler and compiler settings, you might get no or a
		3391	lot of warnings when compiling libev code. Some people are apparently
		3392	scared by this.
		3393
		3394	However, these are unavoidable for many reasons. For one, each compiler
		3395	has different warnings, and each user has different tastes regarding
		3396	warning options. "Warn-free" code therefore cannot be a goal except when
		3397	targeting a specific compiler and compiler-version.
		3398
		3399	Another reason is that some compiler warnings require elaborate
		3400	workarounds, or other changes to the code that make it less clear and less
		3401	maintainable.
		3402
		3403	And of course, some compiler warnings are just plain stupid, or simply
		3404	wrong (because they don't actually warn about the condition their message
		3405	seems to warn about). For example, certain older gcc versions had some
		3406	warnings that resulted an extreme number of false positives. These have
		3407	been fixed, but some people still insist on making code warn-free with
		3408	such buggy versions.
		3409
		3410	While libev is written to generate as few warnings as possible,
		3411	"warn-free" code is not a goal, and it is recommended not to build libev
		3412	with any compiler warnings enabled unless you are prepared to cope with
		3413	them (e.g. by ignoring them). Remember that warnings are just that:
		3414	warnings, not errors, or proof of bugs.
		3415
		3416
		3417	=head2 VALGRIND
		3418
		3419	Valgrind has a special section here because it is a popular tool that is
		3420	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3421
		3422	If you think you found a bug (memory leak, uninitialised data access etc.)
		3423	in libev, then check twice: If valgrind reports something like:
		3424
		3425	==2274== definitely lost: 0 bytes in 0 blocks.
		3426	==2274== possibly lost: 0 bytes in 0 blocks.
		3427	==2274== still reachable: 256 bytes in 1 blocks.
		3428
		3429	Then there is no memory leak, just as memory accounted to global variables
		3430	is not a memleak - the memory is still being refernced, and didn't leak.
		3431
		3432	Similarly, under some circumstances, valgrind might report kernel bugs
		3433	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3434	although an acceptable workaround has been found here), or it might be
		3435	confused.
		3436
		3437	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3438	make it into some kind of religion.
		3439
		3440	If you are unsure about something, feel free to contact the mailing list
		3441	with the full valgrind report and an explanation on why you think this
		3442	is a bug in libev (best check the archives, too :). However, don't be
		3443	annoyed when you get a brisk "this is no bug" answer and take the chance
		3444	of learning how to interpret valgrind properly.
		3445
		3446	If you need, for some reason, empty reports from valgrind for your project
		3447	I suggest using suppression lists.
		3448
		3449
		3450	=head1 PORTABILITY NOTES
		3451
		3452	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3453
		3454	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3455	requires, and its I/O model is fundamentally incompatible with the POSIX
		3456	model. Libev still offers limited functionality on this platform in
		3457	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3458	descriptors. This only applies when using Win32 natively, not when using
		3459	e.g. cygwin.
		3460
		3461	Lifting these limitations would basically require the full
		3462	re-implementation of the I/O system. If you are into these kinds of
		3463	things, then note that glib does exactly that for you in a very portable
		3464	way (note also that glib is the slowest event library known to man).
		3465
		3466	There is no supported compilation method available on windows except
		3467	embedding it into other applications.
		3468
		3469	Not a libev limitation but worth mentioning: windows apparently doesn't
		3470	accept large writes: instead of resulting in a partial write, windows will
		3471	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3472	so make sure you only write small amounts into your sockets (less than a
		3473	megabyte seems safe, but this apparently depends on the amount of memory
		3474	available).
		3475
		3476	Due to the many, low, and arbitrary limits on the win32 platform and
		3477	the abysmal performance of winsockets, using a large number of sockets
		3478	is not recommended (and not reasonable). If your program needs to use
		3479	more than a hundred or so sockets, then likely it needs to use a totally
		3480	different implementation for windows, as libev offers the POSIX readiness
		3481	notification model, which cannot be implemented efficiently on windows
		3482	(Microsoft monopoly games).
		3483
		3484	A typical way to use libev under windows is to embed it (see the embedding
		3485	section for details) and use the following F<evwrap.h> header file instead
		3486	of F<ev.h>:
		3487
		3488	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3489	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3490
		3491	#include "ev.h"
		3492
		3493	And compile the following F<evwrap.c> file into your project (make sure
		3494	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3495
		3496	#include "evwrap.h"
		3497	#include "ev.c"
		3498
		3499	=over 4
		3500
		3501	=item The winsocket select function
		3502
		3503	The winsocket C<select> function doesn't follow POSIX in that it
		3504	requires socket I<handles> and not socket I<file descriptors> (it is
		3505	also extremely buggy). This makes select very inefficient, and also
		3506	requires a mapping from file descriptors to socket handles (the Microsoft
		3507	C runtime provides the function C<_open_osfhandle> for this). See the
		3508	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3509	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3510
		3511	The configuration for a "naked" win32 using the Microsoft runtime
		3512	libraries and raw winsocket select is:
		3513
		3514	#define EV_USE_SELECT 1
		3515	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3516
		3517	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3518	complexity in the O(n²) range when using win32.
		3519
		3520	=item Limited number of file descriptors
		3521
		3522	Windows has numerous arbitrary (and low) limits on things.
		3523
		3524	Early versions of winsocket's select only supported waiting for a maximum
		3525	of C<64> handles (probably owning to the fact that all windows kernels
		3526	can only wait for C<64> things at the same time internally; Microsoft
		3527	recommends spawning a chain of threads and wait for 63 handles and the
		3528	previous thread in each. Great).
		3529
		3530	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3531	to some high number (e.g. C<2048>) before compiling the winsocket select
		3532	call (which might be in libev or elsewhere, for example, perl does its own
		3533	select emulation on windows).
		3534
		3535	Another limit is the number of file descriptors in the Microsoft runtime
		3536	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3537	or something like this inside Microsoft). You can increase this by calling
		3538	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3539	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3540	libraries.
		3541
		3542	This might get you to about C<512> or C<2048> sockets (depending on
		3543	windows version and/or the phase of the moon). To get more, you need to
		3544	wrap all I/O functions and provide your own fd management, but the cost of
		3545	calling select (O(n²)) will likely make this unworkable.
		3546
		3547	=back
		3548
		3549	=head2 PORTABILITY REQUIREMENTS
		3550
		3551	In addition to a working ISO-C implementation and of course the
		3552	backend-specific APIs, libev relies on a few additional extensions:
		3553
		3554	=over 4
		3555
		3556	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3557	calling conventions regardless of C<ev_watcher_type *>.
		3558
		3559	Libev assumes not only that all watcher pointers have the same internal
		3560	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3561	assumes that the same (machine) code can be used to call any watcher
		3562	callback: The watcher callbacks have different type signatures, but libev
		3563	calls them using an C<ev_watcher *> internally.
		3564
		3565	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3566
		3567	The type C<sig_atomic_t volatile> (or whatever is defined as
		3568	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3569	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3570	believed to be sufficiently portable.
		3571
		3572	=item C<sigprocmask> must work in a threaded environment
		3573
		3574	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3575	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3576	pthread implementations will either allow C<sigprocmask> in the "main
		3577	thread" or will block signals process-wide, both behaviours would
		3578	be compatible with libev. Interaction between C<sigprocmask> and
		3579	C<pthread_sigmask> could complicate things, however.
		3580
		3581	The most portable way to handle signals is to block signals in all threads
		3582	except the initial one, and run the default loop in the initial thread as
		3583	well.
		3584
		3585	=item C<long> must be large enough for common memory allocation sizes
		3586
		3587	To improve portability and simplify its API, libev uses C<long> internally
		3588	instead of C<size_t> when allocating its data structures. On non-POSIX
		3589	systems (Microsoft...) this might be unexpectedly low, but is still at
		3590	least 31 bits everywhere, which is enough for hundreds of millions of
		3591	watchers.
		3592
		3593	=item C<double> must hold a time value in seconds with enough accuracy
		3594
		3595	The type C<double> is used to represent timestamps. It is required to
		3596	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3597	enough for at least into the year 4000. This requirement is fulfilled by
		3598	implementations implementing IEEE 754 (basically all existing ones).
		3599
		3600	=back
		3601
		3602	If you know of other additional requirements drop me a note.
		3603
		3604
2101	=head1 COMPLEXITIES	3605	=head1 ALGORITHMIC COMPLEXITIES
2102		3606
2103	In this section the complexities of (many of) the algorithms used inside	3607	In this section the complexities of (many of) the algorithms used inside
2104	libev will be explained. For complexity discussions about backends see the	3608	libev will be documented. For complexity discussions about backends see
2105	documentation for C<ev_default_init>.	3609	the documentation for C<ev_default_init>.
		3610
		3611	All of the following are about amortised time: If an array needs to be
		3612	extended, libev needs to realloc and move the whole array, but this
		3613	happens asymptotically rarer with higher number of elements, so O(1) might
		3614	mean that libev does a lengthy realloc operation in rare cases, but on
		3615	average it is much faster and asymptotically approaches constant time.
2106		3616
2107	=over 4	3617	=over 4
2108		3618
2109	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3619	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2110		3620
		3621	This means that, when you have a watcher that triggers in one hour and
		3622	there are 100 watchers that would trigger before that, then inserting will
		3623	have to skip roughly seven (C<ld 100>) of these watchers.
		3624
2111	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3625	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2112		3626
		3627	That means that changing a timer costs less than removing/adding them,
		3628	as only the relative motion in the event queue has to be paid for.
		3629
2113	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3630	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2114		3631
		3632	These just add the watcher into an array or at the head of a list.
		3633
2115	=item Stopping check/prepare/idle watchers: O(1)	3634	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2116		3635
2117	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	3636	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2118		3637
		3638	These watchers are stored in lists, so they need to be walked to find the
		3639	correct watcher to remove. The lists are usually short (you don't usually
		3640	have many watchers waiting for the same fd or signal: one is typical, two
		3641	is rare).
		3642
2119	=item Finding the next timer per loop iteration: O(1)	3643	=item Finding the next timer in each loop iteration: O(1)
		3644
		3645	By virtue of using a binary or 4-heap, the next timer is always found at a
		3646	fixed position in the storage array.
2120		3647
2121	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3648	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2122		3649
2123	=item Activating one watcher: O(1)	3650	A change means an I/O watcher gets started or stopped, which requires
		3651	libev to recalculate its status (and possibly tell the kernel, depending
		3652	on backend and whether C<ev_io_set> was used).
		3653
		3654	=item Activating one watcher (putting it into the pending state): O(1)
		3655
		3656	=item Priority handling: O(number_of_priorities)
		3657
		3658	Priorities are implemented by allocating some space for each
		3659	priority. When doing priority-based operations, libev usually has to
		3660	linearly search all the priorities, but starting/stopping and activating
		3661	watchers becomes O(1) with respect to priority handling.
		3662
		3663	=item Sending an ev_async: O(1)
		3664
		3665	=item Processing ev_async_send: O(number_of_async_watchers)
		3666
		3667	=item Processing signals: O(max_signal_number)
		3668
		3669	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3670	calls in the current loop iteration. Checking for async and signal events
		3671	involves iterating over all running async watchers or all signal numbers.
2124		3672
2125	=back	3673	=back
2126		3674
2127		3675
2128	=head1 AUTHOR	3676	=head1 AUTHOR

Diff Legend

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