ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC vs.
Revision 1.216 by root, Thu Nov 13 15:55:38 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// 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	49	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	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	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	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
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	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
116	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
117	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
118	it, you should treat it as some floatingpoint value. Unlike the name	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	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	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
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	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
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	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_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	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
174	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
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	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
182	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
183	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
184	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
185	(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
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	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,
209	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.
210		234
211	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
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
226	}	250	}
227		251
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		256
233	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
234	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
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	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
237	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
238	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
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
252		276
253	=back	277	=back
254		278
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	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 C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	283	I<function>).
260		284
261	If you use threads, a common model is to run the default event loop	285	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	286	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	287	not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		288
268	=over 4	289	=over 4
269		290
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		292
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	296	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		297
277	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
278	function.	299	function.
279		300
		301	Note that this function is I<not> thread-safe, so if you want to use it
		302	from multiple threads, you have to lock (note also that this is unlikely,
		303	as loops cannot be shared easily between threads anyway).
		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	362	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	390
359	cases and rewiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
361		407
362	While stopping, setting and starting an I/O watcher in the same iteration	408	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	409	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	410	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
367		413	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		414
372	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	416	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
375		422
		423	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		424	faster than epoll for maybe up to a hundred file descriptors, depending on
		425	the usage. So sad.
		426
376	While nominally embeddeble in other event loops, this feature is broken in	427	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	428	all kernel versions tested so far.
		429
		430	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		431	C<EVBACKEND_POLL>.
378		432
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	433	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		434
381	Kqueue deserves special mention, as at the time of this writing, it	435	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	436	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	437	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	438	it's completely useless). Unlike epoll, however, whose brokenness
		439	is by design, these kqueue bugs can (and eventually will) be fixed
		440	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	441	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	442	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	443	system like NetBSD.
388		444
389	You still can embed kqueue into a normal poll or select backend and use it	445	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	446	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	447	the target platform). See C<ev_embed> watchers for more info.
392		448
393	It scales in the same way as the epoll backend, but the interface to the	449	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	450	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	451	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	452	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	453	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	454	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		455	cases
399		456
400	This backend usually performs well under most conditions.	457	This backend usually performs well under most conditions.
401		458
402	While nominally embeddable in other event loops, this doesn't work	459	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	460	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	461	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	462	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	464	using it only for sockets.
		465
		466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		468	C<NOTE_EOF>.
408		469
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	470	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		471
411	This is not implemented yet (and might never be, unless you send me an	472	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	473	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	477	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		478
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	479	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	480	it's really slow, but it still scales very well (O(active_fds)).
420		481
421	Please note that solaris event ports can deliver a lot of spurious	482	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	483	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	484	blocking when no data (or space) is available.
424		485
425	While this backend scales well, it requires one system call per active	486	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	487	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	488	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	489	might perform better.
429		490
430	On the positive side, ignoring the spurious readyness notifications, this	491	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	492	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	493	in all tests and is fully embeddable, which is a rare feat among the
		494	OS-specific backends (I vastly prefer correctness over speed hacks).
		495
		496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		497	C<EVBACKEND_POLL>.
433		498
434	=item C<EVBACKEND_ALL>	499	=item C<EVBACKEND_ALL>
435		500
436	Try all backends (even potentially broken ones that wouldn't be tried	501	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	502	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		504
440	It is definitely not recommended to use this flag.	505	It is definitely not recommended to use this flag.
441		506
442	=back	507	=back
443		508
444	If one or more of these are ored into the flags value, then only these	509	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	510	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	511	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		512
448	The most typical usage is like this:	513	Example: This is the most typical usage.
449		514
450	if (!ev_default_loop (0))	515	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		517
453	Restrict libev to the select and poll backends, and do not allow	518	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	519	environment settings to be taken into account:
455		520
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		522
458	Use whatever libev has to offer, but make sure that kqueue is used if	523	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	524	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	525	private event loop and only if you know the OS supports your types of
		526	fds):
461		527
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		529
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	530	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		531
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	532	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	533	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	534	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	535	undefined behaviour (or a failed assertion if assertions are enabled).
470		536
		537	Note that this function I<is> thread-safe, and the recommended way to use
		538	libev with threads is indeed to create one loop per thread, and using the
		539	default loop in the "main" or "initial" thread.
		540
471	Example: Try to create a event loop that uses epoll and nothing else.	541	Example: Try to create a event loop that uses epoll and nothing else.
472		542
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	544	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	545	fatal ("no epoll found here, maybe it hides under your chair");
476		546
477	=item ev_default_destroy ()	547	=item ev_default_destroy ()
478		548
479	Destroys the default loop again (frees all memory and kernel state	549	Destroys the default loop again (frees all memory and kernel state
480	etc.). None of the active event watchers will be stopped in the normal	550	etc.). None of the active event watchers will be stopped in the normal
481	sense, so e.g. C<ev_is_active> might still return true. It is your	551	sense, so e.g. C<ev_is_active> might still return true. It is your
482	responsibility to either stop all watchers cleanly yoursef I<before>	552	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	553	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	554	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	555	for example).
486		556
487	Note that certain global state, such as signal state, will not be freed by	557	Note that certain global state, such as signal state (and installed signal
488	this function, and related watchers (such as signal and child watchers)	558	handlers), will not be freed by this function, and related watchers (such
489	would need to be stopped manually.	559	as signal and child watchers) would need to be stopped manually.
490		560
491	In general it is not advisable to call this function except in the	561	In general it is not advisable to call this function except in the
492	rare occasion where you really need to free e.g. the signal handling	562	rare occasion where you really need to free e.g. the signal handling
493	pipe fds. If you need dynamically allocated loops it is better to use	563	pipe fds. If you need dynamically allocated loops it is better to use
494	C<ev_loop_new> and C<ev_loop_destroy>).	564	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
519		589
520	=item ev_loop_fork (loop)	590	=item ev_loop_fork (loop)
521		591
522	Like C<ev_default_fork>, but acts on an event loop created by	592	Like C<ev_default_fork>, but acts on an event loop created by
523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
524	after fork, and how you do this is entirely your own problem.	594	after fork that you want to re-use in the child, and how you do this is
		595	entirely your own problem.
525		596
526	=item int ev_is_default_loop (loop)	597	=item int ev_is_default_loop (loop)
527		598
528	Returns true when the given loop actually is the default loop, false otherwise.	599	Returns true when the given loop is, in fact, the default loop, and false
		600	otherwise.
529		601
530	=item unsigned int ev_loop_count (loop)	602	=item unsigned int ev_loop_count (loop)
531		603
532	Returns the count of loop iterations for the loop, which is identical to	604	Returns the count of loop iterations for the loop, which is identical to
533	the number of times libev did poll for new events. It starts at C<0> and	605	the number of times libev did poll for new events. It starts at C<0> and
…		…
548	received events and started processing them. This timestamp does not	620	received events and started processing them. This timestamp does not
549	change as long as callbacks are being processed, and this is also the base	621	change as long as callbacks are being processed, and this is also the base
550	time used for relative timers. You can treat it as the timestamp of the	622	time used for relative timers. You can treat it as the timestamp of the
551	event occurring (or more correctly, libev finding out about it).	623	event occurring (or more correctly, libev finding out about it).
552		624
		625	=item ev_now_update (loop)
		626
		627	Establishes the current time by querying the kernel, updating the time
		628	returned by C<ev_now ()> in the progress. This is a costly operation and
		629	is usually done automatically within C<ev_loop ()>.
		630
		631	This function is rarely useful, but when some event callback runs for a
		632	very long time without entering the event loop, updating libev's idea of
		633	the current time is a good idea.
		634
		635	See also "The special problem of time updates" in the C<ev_timer> section.
		636
553	=item ev_loop (loop, int flags)	637	=item ev_loop (loop, int flags)
554		638
555	Finally, this is it, the event handler. This function usually is called	639	Finally, this is it, the event handler. This function usually is called
556	after you initialised all your watchers and you want to start handling	640	after you initialised all your watchers and you want to start handling
557	events.	641	events.
…		…
559	If the flags argument is specified as C<0>, it will not return until	643	If the flags argument is specified as C<0>, it will not return until
560	either no event watchers are active anymore or C<ev_unloop> was called.	644	either no event watchers are active anymore or C<ev_unloop> was called.
561		645
562	Please note that an explicit C<ev_unloop> is usually better than	646	Please note that an explicit C<ev_unloop> is usually better than
563	relying on all watchers to be stopped when deciding when a program has	647	relying on all watchers to be stopped when deciding when a program has
564	finished (especially in interactive programs), but having a program that	648	finished (especially in interactive programs), but having a program
565	automatically loops as long as it has to and no longer by virtue of	649	that automatically loops as long as it has to and no longer by virtue
566	relying on its watchers stopping correctly is a thing of beauty.	650	of relying on its watchers stopping correctly, that is truly a thing of
		651	beauty.
567		652
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	654	those events and any already outstanding ones, but will not block your
570	case there are no events and will return after one iteration of the loop.	655	process in case there are no events and will return after one iteration of
		656	the loop.
571		657
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	659	necessary) and will handle those and any already outstanding ones. It
574	your process until at least one new event arrives, and will return after	660	will block your process until at least one new event arrives (which could
575	one iteration of the loop. This is useful if you are waiting for some	661	be an event internal to libev itself, so there is no guarantee that a
576	external event in conjunction with something not expressible using other	662	user-registered callback will be called), and will return after one
		663	iteration of the loop.
		664
		665	This is useful if you are waiting for some external event in conjunction
		666	with something not expressible using other libev watchers (i.e. "roll your
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	668	usually a better approach for this kind of thing.
579		669
580	Here are the gory details of what C<ev_loop> does:	670	Here are the gory details of what C<ev_loop> does:
581		671
582	- Before the first iteration, call any pending watchers.	672	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	673	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	674	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	675	- Queue and call all prepare watchers.
586	- If we have been forked, recreate the kernel state.	676	- If we have been forked, detach and recreate the kernel state
		677	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	678	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	679	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	680	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	681	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	682	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	683	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	684	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	685	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	687	- Queue all expired timers.
597	- Queue all outstanding periodics.	688	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	689	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	690	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	691	- Call all queued watchers in reverse order (i.e. check watchers first).
601	Signals and child watchers are implemented as I/O watchers, and will	692	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	693	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
608	anymore.	699	anymore.
609		700
610	... queue jobs here, make sure they register event watchers as long	701	... queue jobs here, make sure they register event watchers as long
611	... as they still have work to do (even an idle watcher will do..)	702	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	703	ev_loop (my_loop, 0);
613	... jobs done. yeah!	704	... jobs done or somebody called unloop. yeah!
614		705
615	=item ev_unloop (loop, how)	706	=item ev_unloop (loop, how)
616		707
617	Can be used to make a call to C<ev_loop> return early (but only after it	708	Can be used to make a call to C<ev_loop> return early (but only after it
618	has processed all outstanding events). The C<how> argument must be either	709	has processed all outstanding events). The C<how> argument must be either
619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
621		712
622	This "unloop state" will be cleared when entering C<ev_loop> again.	713	This "unloop state" will be cleared when entering C<ev_loop> again.
623		714
		715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		716
624	=item ev_ref (loop)	717	=item ev_ref (loop)
625		718
626	=item ev_unref (loop)	719	=item ev_unref (loop)
627		720
628	Ref/unref can be used to add or remove a reference count on the event	721	Ref/unref can be used to add or remove a reference count on the event
629	loop: Every watcher keeps one reference, and as long as the reference	722	loop: Every watcher keeps one reference, and as long as the reference
630	count is nonzero, C<ev_loop> will not return on its own. If you have	723	count is nonzero, C<ev_loop> will not return on its own.
		724
631	a watcher you never unregister that should not keep C<ev_loop> from	725	If you have a watcher you never unregister that should not keep C<ev_loop>
632	returning, ev_unref() after starting, and ev_ref() before stopping it. For	726	from returning, call ev_unref() after starting, and ev_ref() before
		727	stopping it.
		728
633	example, libev itself uses this for its internal signal pipe: It is not	729	As an example, libev itself uses this for its internal signal pipe: It is
634	visible to the libev user and should not keep C<ev_loop> from exiting if	730	not visible to the libev user and should not keep C<ev_loop> from exiting
635	no event watchers registered by it are active. It is also an excellent	731	if no event watchers registered by it are active. It is also an excellent
636	way to do this for generic recurring timers or from within third-party	732	way to do this for generic recurring timers or from within third-party
637	libraries. Just remember to I<unref after start> and I<ref before stop>	733	libraries. Just remember to I<unref after start> and I<ref before stop>
638	(but only if the watcher wasn't active before, or was active before,	734	(but only if the watcher wasn't active before, or was active before,
639	respectively).	735	respectively).
640		736
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
642	running when nothing else is active.	738	running when nothing else is active.
643		739
644	struct ev_signal exitsig;	740	ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	741	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	742	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	743	evf_unref (loop);
648		744
649	Example: For some weird reason, unregister the above signal handler again.	745	Example: For some weird reason, unregister the above signal handler again.
650		746
651	ev_ref (loop);	747	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	748	ev_signal_stop (loop, &exitsig);
653		749
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	750	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		751
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		753
658	These advanced functions influence the time that libev will spend waiting	754	These advanced functions influence the time that libev will spend waiting
659	for events. Both are by default C<0>, meaning that libev will try to	755	for events. Both time intervals are by default C<0>, meaning that libev
660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	756	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		757	latency.
661		758
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	759	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
663	allows libev to delay invocation of I/O and timer/periodic callbacks to	760	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	761	to increase efficiency of loop iterations (or to increase power-saving
		762	opportunities).
665		763
666	The background is that sometimes your program runs just fast enough to	764	The idea is that sometimes your program runs just fast enough to handle
667	handle one (or very few) event(s) per loop iteration. While this makes	765	one (or very few) event(s) per loop iteration. While this makes the
668	the program responsive, it also wastes a lot of CPU time to poll for new	766	program responsive, it also wastes a lot of CPU time to poll for new
669	events, especially with backends like C<select ()> which have a high	767	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	768	overhead for the actual polling but can deliver many events at once.
671		769
672	By setting a higher I<io collect interval> you allow libev to spend more	770	By setting a higher I<io collect interval> you allow libev to spend more
673	time collecting I/O events, so you can handle more events per iteration,	771	time collecting I/O events, so you can handle more events per iteration,
…		…
675	C<ev_timer>) will be not affected. Setting this to a non-null value will	773	C<ev_timer>) will be not affected. Setting this to a non-null value will
676	introduce an additional C<ev_sleep ()> call into most loop iterations.	774	introduce an additional C<ev_sleep ()> call into most loop iterations.
677		775
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	776	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	777	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	778	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	779	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	780	value will not introduce any overhead in libev.
683		781
684	Many (busy) programs can usually benefit by setting the io collect	782	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	783	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	784	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	785	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	786	as this approaches the timing granularity of most systems.
		787
		788	Setting the I<timeout collect interval> can improve the opportunity for
		789	saving power, as the program will "bundle" timer callback invocations that
		790	are "near" in time together, by delaying some, thus reducing the number of
		791	times the process sleeps and wakes up again. Another useful technique to
		792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		793	they fire on, say, one-second boundaries only.
		794
		795	=item ev_loop_verify (loop)
		796
		797	This function only does something when C<EV_VERIFY> support has been
		798	compiled in, which is the default for non-minimal builds. It tries to go
		799	through all internal structures and checks them for validity. If anything
		800	is found to be inconsistent, it will print an error message to standard
		801	error and call C<abort ()>.
		802
		803	This can be used to catch bugs inside libev itself: under normal
		804	circumstances, this function will never abort as of course libev keeps its
		805	data structures consistent.
689		806
690	=back	807	=back
691		808
692		809
693	=head1 ANATOMY OF A WATCHER	810	=head1 ANATOMY OF A WATCHER
		811
		812	In the following description, uppercase C<TYPE> in names stands for the
		813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		814	watchers and C<ev_io_start> for I/O watchers.
694		815
695	A watcher is a structure that you create and register to record your	816	A watcher is a structure that you create and register to record your
696	interest in some event. For instance, if you want to wait for STDIN to	817	interest in some event. For instance, if you want to wait for STDIN to
697	become readable, you would create an C<ev_io> watcher for that:	818	become readable, you would create an C<ev_io> watcher for that:
698		819
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
700	{	821	{
701	ev_io_stop (w);	822	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	823	ev_unloop (loop, EVUNLOOP_ALL);
703	}	824	}
704		825
705	struct ev_loop *loop = ev_default_loop (0);	826	struct ev_loop *loop = ev_default_loop (0);
		827
706	struct ev_io stdin_watcher;	828	ev_io stdin_watcher;
		829
707	ev_init (&stdin_watcher, my_cb);	830	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	832	ev_io_start (loop, &stdin_watcher);
		833
710	ev_loop (loop, 0);	834	ev_loop (loop, 0);
711		835
712	As you can see, you are responsible for allocating the memory for your	836	As you can see, you are responsible for allocating the memory for your
713	watcher structures (and it is usually a bad idea to do this on the stack,	837	watcher structures (and it is I<usually> a bad idea to do this on the
714	although this can sometimes be quite valid).	838	stack).
		839
		840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
715		842
716	Each watcher structure must be initialised by a call to C<ev_init	843	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	844	(watcher *, callback)>, which expects a callback to be provided. This
718	callback gets invoked each time the event occurs (or, in the case of io	845	callback gets invoked each time the event occurs (or, in the case of I/O
719	watchers, each time the event loop detects that the file descriptor given	846	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	847	is readable and/or writable).
721		848
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
723	with arguments specific to this watcher type. There is also a macro	850	macro to configure it, with arguments specific to the watcher type. There
724	to combine initialisation and setting in one call: C<< ev_<type>_init	851	is also a macro to combine initialisation and setting in one call: C<<
725	(watcher *, callback, ...) >>.	852	ev_TYPE_init (watcher *, callback, ...) >>.
726		853
727	To make the watcher actually watch out for events, you have to start it	854	To make the watcher actually watch out for events, you have to start it
728	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	855	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
729	*) >>), and you can stop watching for events at any time by calling the	856	*) >>), and you can stop watching for events at any time by calling the
730	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	857	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
731		858
732	As long as your watcher is active (has been started but not stopped) you	859	As long as your watcher is active (has been started but not stopped) you
733	must not touch the values stored in it. Most specifically you must never	860	must not touch the values stored in it. Most specifically you must never
734	reinitialise it or call its C<set> macro.	861	reinitialise it or call its C<ev_TYPE_set> macro.
735		862
736	Each and every callback receives the event loop pointer as first, the	863	Each and every callback receives the event loop pointer as first, the
737	registered watcher structure as second, and a bitset of received events as	864	registered watcher structure as second, and a bitset of received events as
738	third argument.	865	third argument.
739		866
…		…
799		926
800	The given async watcher has been asynchronously notified (see C<ev_async>).	927	The given async watcher has been asynchronously notified (see C<ev_async>).
801		928
802	=item C<EV_ERROR>	929	=item C<EV_ERROR>
803		930
804	An unspecified error has occured, the watcher has been stopped. This might	931	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	932	happen because the watcher could not be properly started because libev
806	ran out of memory, a file descriptor was found to be closed or any other	933	ran out of memory, a file descriptor was found to be closed or any other
		934	problem. Libev considers these application bugs.
		935
807	problem. You best act on it by reporting the problem and somehow coping	936	You best act on it by reporting the problem and somehow coping with the
808	with the watcher being stopped.	937	watcher being stopped. Note that well-written programs should not receive
		938	an error ever, so when your watcher receives it, this usually indicates a
		939	bug in your program.
809		940
810	Libev will usually signal a few "dummy" events together with an error,	941	Libev will usually signal a few "dummy" events together with an error, for
811	for example it might indicate that a fd is readable or writable, and if	942	example it might indicate that a fd is readable or writable, and if your
812	your callbacks is well-written it can just attempt the operation and cope	943	callbacks is well-written it can just attempt the operation and cope with
813	with the error from read() or write(). This will not work in multithreaded	944	the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	945	programs, though, as the fd could already be closed and reused for another
		946	thing, so beware.
815		947
816	=back	948	=back
817		949
818	=head2 GENERIC WATCHER FUNCTIONS	950	=head2 GENERIC WATCHER FUNCTIONS
819
820	In the following description, C<TYPE> stands for the watcher type,
821	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
822		951
823	=over 4	952	=over 4
824		953
825	=item C<ev_init> (ev_TYPE *watcher, callback)	954	=item C<ev_init> (ev_TYPE *watcher, callback)
826		955
…		…
832	which rolls both calls into one.	961	which rolls both calls into one.
833		962
834	You can reinitialise a watcher at any time as long as it has been stopped	963	You can reinitialise a watcher at any time as long as it has been stopped
835	(or never started) and there are no pending events outstanding.	964	(or never started) and there are no pending events outstanding.
836		965
837	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	966	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
838	int revents)>.	967	int revents)>.
		968
		969	Example: Initialise an C<ev_io> watcher in two steps.
		970
		971	ev_io w;
		972	ev_init (&w, my_cb);
		973	ev_io_set (&w, STDIN_FILENO, EV_READ);
839		974
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	975	=item C<ev_TYPE_set> (ev_TYPE *, [args])
841		976
842	This macro initialises the type-specific parts of a watcher. You need to	977	This macro initialises the type-specific parts of a watcher. You need to
843	call C<ev_init> at least once before you call this macro, but you can	978	call C<ev_init> at least once before you call this macro, but you can
…		…
846	difference to the C<ev_init> macro).	981	difference to the C<ev_init> macro).
847		982
848	Although some watcher types do not have type-specific arguments	983	Although some watcher types do not have type-specific arguments
849	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	984	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		985
		986	See C<ev_init>, above, for an example.
		987
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	988	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		989
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	990	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	991	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	992	a watcher. The same limitations apply, of course.
		993
		994	Example: Initialise and set an C<ev_io> watcher in one step.
		995
		996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
856		997
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		999
859	Starts (activates) the given watcher. Only active watchers will receive	1000	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	1001	events. If the watcher is already active nothing will happen.
861		1002
		1003	Example: Start the C<ev_io> watcher that is being abused as example in this
		1004	whole section.
		1005
		1006	ev_io_start (EV_DEFAULT_UC, &w);
		1007
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
863		1009
864	Stops the given watcher again (if active) and clears the pending	1010	Stops the given watcher if active, and clears the pending status (whether
		1011	the watcher was active or not).
		1012
865	status. It is possible that stopped watchers are pending (for example,	1013	It is possible that stopped watchers are pending - for example,
866	non-repeating timers are being stopped when they become pending), but	1014	non-repeating timers are being stopped when they become pending - but
867	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1015	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
868	you want to free or reuse the memory used by the watcher it is therefore a	1016	pending. If you want to free or reuse the memory used by the watcher it is
869	good idea to always call its C<ev_TYPE_stop> function.	1017	therefore a good idea to always call its C<ev_TYPE_stop> function.
870		1018
871	=item bool ev_is_active (ev_TYPE *watcher)	1019	=item bool ev_is_active (ev_TYPE *watcher)
872		1020
873	Returns a true value iff the watcher is active (i.e. it has been started	1021	Returns a true value iff the watcher is active (i.e. it has been started
874	and not yet been stopped). As long as a watcher is active you must not modify	1022	and not yet been stopped). As long as a watcher is active you must not modify
…		…
916	The default priority used by watchers when no priority has been set is	1064	The default priority used by watchers when no priority has been set is
917	always C<0>, which is supposed to not be too high and not be too low :).	1065	always C<0>, which is supposed to not be too high and not be too low :).
918		1066
919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
920	fine, as long as you do not mind that the priority value you query might	1068	fine, as long as you do not mind that the priority value you query might
921	or might not have been adjusted to be within valid range.	1069	or might not have been clamped to the valid range.
922		1070
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1072
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
926	C<loop> nor C<revents> need to be valid as long as the watcher callback	1074	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1075	can deal with that fact, as both are simply passed through to the
		1076	callback.
928		1077
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1078	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1079
931	If the watcher is pending, this function returns clears its pending status	1080	If the watcher is pending, this function clears its pending status and
932	and returns its C<revents> bitset (as if its callback was invoked). If the	1081	returns its C<revents> bitset (as if its callback was invoked). If the
933	watcher isn't pending it does nothing and returns C<0>.	1082	watcher isn't pending it does nothing and returns C<0>.
934		1083
		1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1085	callback to be invoked, which can be accomplished with this function.
		1086
935	=back	1087	=back
936		1088
937		1089
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1091
940	Each watcher has, by default, a member C<void *data> that you can change	1092	Each watcher has, by default, a member C<void *data> that you can change
941	and read at any time, libev will completely ignore it. This can be used	1093	and read at any time: libev will completely ignore it. This can be used
942	to associate arbitrary data with your watcher. If you need more data and	1094	to associate arbitrary data with your watcher. If you need more data and
943	don't want to allocate memory and store a pointer to it in that data	1095	don't want to allocate memory and store a pointer to it in that data
944	member, you can also "subclass" the watcher type and provide your own	1096	member, you can also "subclass" the watcher type and provide your own
945	data:	1097	data:
946		1098
947	struct my_io	1099	struct my_io
948	{	1100	{
949	struct ev_io io;	1101	ev_io io;
950	int otherfd;	1102	int otherfd;
951	void *somedata;	1103	void *somedata;
952	struct whatever *mostinteresting;	1104	struct whatever *mostinteresting;
953	}	1105	};
		1106
		1107	...
		1108	struct my_io w;
		1109	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1110
955	And since your callback will be called with a pointer to the watcher, you	1111	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1112	can cast it back to your own type:
957		1113
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1114	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
959	{	1115	{
960	struct my_io *w = (struct my_io *)w_;	1116	struct my_io *w = (struct my_io *)w_;
961	...	1117	...
962	}	1118	}
963		1119
964	More interesting and less C-conformant ways of casting your callback type	1120	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1121	instead have been omitted.
966		1122
967	Another common scenario is having some data structure with multiple	1123	Another common scenario is to use some data structure with multiple
968	watchers:	1124	embedded watchers:
969		1125
970	struct my_biggy	1126	struct my_biggy
971	{	1127	{
972	int some_data;	1128	int some_data;
973	ev_timer t1;	1129	ev_timer t1;
974	ev_timer t2;	1130	ev_timer t2;
975	}	1131	}
976		1132
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1133	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1134	complicated: Either you store the address of your C<my_biggy> struct
		1135	in the C<data> member of the watcher (for woozies), or you need to use
		1136	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1137	programmers):
979		1138
980	#include <stddef.h>	1139	#include <stddef.h>
981		1140
982	static void	1141	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1142	t1_cb (EV_P_ ev_timer *w, int revents)
984	{	1143	{
985	struct my_biggy big = (struct my_biggy *	1144	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1145	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1146	}
988		1147
989	static void	1148	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1149	t2_cb (EV_P_ ev_timer *w, int revents)
991	{	1150	{
992	struct my_biggy big = (struct my_biggy *	1151	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1152	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1153	}
995		1154
996		1155
997	=head1 WATCHER TYPES	1156	=head1 WATCHER TYPES
998		1157
999	This section describes each watcher in detail, but will not repeat	1158	This section describes each watcher in detail, but will not repeat
…		…
1023	In general you can register as many read and/or write event watchers per	1182	In general you can register as many read and/or write event watchers per
1024	fd as you want (as long as you don't confuse yourself). Setting all file	1183	fd as you want (as long as you don't confuse yourself). Setting all file
1025	descriptors to non-blocking mode is also usually a good idea (but not	1184	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1185	required if you know what you are doing).
1027		1186
1028	If you must do this, then force the use of a known-to-be-good backend	1187	If you cannot use non-blocking mode, then force the use of a
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1188	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1031		1190
1032	Another thing you have to watch out for is that it is quite easy to	1191	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1192	receive "spurious" readiness notifications, that is your callback might
1034	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1035	because there is no data. Not only are some backends known to create a	1194	because there is no data. Not only are some backends known to create a
1036	lot of those (for example solaris ports), it is very easy to get into	1195	lot of those (for example Solaris ports), it is very easy to get into
1037	this situation even with a relatively standard program structure. Thus	1196	this situation even with a relatively standard program structure. Thus
1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1197	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1198	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1199
1041	If you cannot run the fd in non-blocking mode (for example you should not	1200	If you cannot run the fd in non-blocking mode (for example you should
1042	play around with an Xlib connection), then you have to seperately re-test	1201	not play around with an Xlib connection), then you have to separately
1043	whether a file descriptor is really ready with a known-to-be good interface	1202	re-test whether a file descriptor is really ready with a known-to-be good
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1203	interface such as poll (fortunately in our Xlib example, Xlib already
1045	its own, so its quite safe to use).	1204	does this on its own, so its quite safe to use). Some people additionally
		1205	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1206	indefinitely.
		1207
		1208	But really, best use non-blocking mode.
1046		1209
1047	=head3 The special problem of disappearing file descriptors	1210	=head3 The special problem of disappearing file descriptors
1048		1211
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1212	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1050	descriptor (either by calling C<close> explicitly or by any other means,	1213	descriptor (either due to calling C<close> explicitly or any other means,
1051	such as C<dup>). The reason is that you register interest in some file	1214	such as C<dup2>). The reason is that you register interest in some file
1052	descriptor, but when it goes away, the operating system will silently drop	1215	descriptor, but when it goes away, the operating system will silently drop
1053	this interest. If another file descriptor with the same number then is	1216	this interest. If another file descriptor with the same number then is
1054	registered with libev, there is no efficient way to see that this is, in	1217	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1218	fact, a different file descriptor.
1056		1219
…		…
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1250	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1251	C<EVBACKEND_POLL>.
1089		1252
1090	=head3 The special problem of SIGPIPE	1253	=head3 The special problem of SIGPIPE
1091		1254
1092	While not really specific to libev, it is easy to forget about SIGPIPE:	1255	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1093	when reading from a pipe whose other end has been closed, your program	1256	when writing to a pipe whose other end has been closed, your program gets
1094	gets send a SIGPIPE, which, by default, aborts your program. For most	1257	sent a SIGPIPE, which, by default, aborts your program. For most programs
1095	programs this is sensible behaviour, for daemons, this is usually	1258	this is sensible behaviour, for daemons, this is usually undesirable.
1096	undesirable.
1097		1259
1098	So when you encounter spurious, unexplained daemon exits, make sure you	1260	So when you encounter spurious, unexplained daemon exits, make sure you
1099	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1100	somewhere, as that would have given you a big clue).	1262	somewhere, as that would have given you a big clue).
1101		1263
…		…
1107	=item ev_io_init (ev_io *, callback, int fd, int events)	1269	=item ev_io_init (ev_io *, callback, int fd, int events)
1108		1270
1109	=item ev_io_set (ev_io *, int fd, int events)	1271	=item ev_io_set (ev_io *, int fd, int events)
1110		1272
1111	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1273	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1112	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1274	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1113	C<EV_READ | EV_WRITE> to receive the given events.	1275	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1114		1276
1115	=item int fd [read-only]	1277	=item int fd [read-only]
1116		1278
1117	The file descriptor being watched.	1279	The file descriptor being watched.
1118		1280
…		…
1126		1288
1127	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1289	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1128	readable, but only once. Since it is likely line-buffered, you could	1290	readable, but only once. Since it is likely line-buffered, you could
1129	attempt to read a whole line in the callback.	1291	attempt to read a whole line in the callback.
1130		1292
1131	static void	1293	static void
1132	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1294	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1133	{	1295	{
1134	ev_io_stop (loop, w);	1296	ev_io_stop (loop, w);
1135	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1297	.. read from stdin here (or from w->fd) and handle any I/O errors
1136	}	1298	}
1137		1299
1138	...	1300	...
1139	struct ev_loop *loop = ev_default_init (0);	1301	struct ev_loop *loop = ev_default_init (0);
1140	struct ev_io stdin_readable;	1302	ev_io stdin_readable;
1141	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1142	ev_io_start (loop, &stdin_readable);	1304	ev_io_start (loop, &stdin_readable);
1143	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1144		1306
1145		1307
1146	=head2 C<ev_timer> - relative and optionally repeating timeouts	1308	=head2 C<ev_timer> - relative and optionally repeating timeouts
1147		1309
1148	Timer watchers are simple relative timers that generate an event after a	1310	Timer watchers are simple relative timers that generate an event after a
1149	given time, and optionally repeating in regular intervals after that.	1311	given time, and optionally repeating in regular intervals after that.
1150		1312
1151	The timers are based on real time, that is, if you register an event that	1313	The timers are based on real time, that is, if you register an event that
1152	times out after an hour and you reset your system clock to last years	1314	times out after an hour and you reset your system clock to January last
1153	time, it will still time out after (roughly) and hour. "Roughly" because	1315	year, it will still time out after (roughly) one hour. "Roughly" because
1154	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1155	monotonic clock option helps a lot here).	1317	monotonic clock option helps a lot here).
		1318
		1319	The callback is guaranteed to be invoked only I<after> its timeout has
		1320	passed, but if multiple timers become ready during the same loop iteration
		1321	then order of execution is undefined.
		1322
		1323	=head3 Be smart about timeouts
		1324
		1325	Many real-world problems involve some kind of timeout, usually for error
		1326	recovery. A typical example is an HTTP request - if the other side hangs,
		1327	you want to raise some error after a while.
		1328
		1329	What follows are some ways to handle this problem, from obvious and
		1330	inefficient to smart and efficient.
		1331
		1332	In the following, a 60 second activity timeout is assumed - a timeout that
		1333	gets reset to 60 seconds each time there is activity (e.g. each time some
		1334	data or other life sign was received).
		1335
		1336	=over 4
		1337
		1338	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1339
		1340	This is the most obvious, but not the most simple way: In the beginning,
		1341	start the watcher:
		1342
		1343	ev_timer_init (timer, callback, 60., 0.);
		1344	ev_timer_start (loop, timer);
		1345
		1346	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1347	and start it again:
		1348
		1349	ev_timer_stop (loop, timer);
		1350	ev_timer_set (timer, 60., 0.);
		1351	ev_timer_start (loop, timer);
		1352
		1353	This is relatively simple to implement, but means that each time there is
		1354	some activity, libev will first have to remove the timer from its internal
		1355	data structure and then add it again. Libev tries to be fast, but it's
		1356	still not a constant-time operation.
		1357
		1358	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1359
		1360	This is the easiest way, and involves using C<ev_timer_again> instead of
		1361	C<ev_timer_start>.
		1362
		1363	To implement this, configure an C<ev_timer> with a C<repeat> value
		1364	of C<60> and then call C<ev_timer_again> at start and each time you
		1365	successfully read or write some data. If you go into an idle state where
		1366	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1367	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1368
		1369	That means you can ignore both the C<ev_timer_start> function and the
		1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1371	member and C<ev_timer_again>.
		1372
		1373	At start:
		1374
		1375	ev_timer_init (timer, callback);
		1376	timer->repeat = 60.;
		1377	ev_timer_again (loop, timer);
		1378
		1379	Each time there is some activity:
		1380
		1381	ev_timer_again (loop, timer);
		1382
		1383	It is even possible to change the time-out on the fly, regardless of
		1384	whether the watcher is active or not:
		1385
		1386	timer->repeat = 30.;
		1387	ev_timer_again (loop, timer);
		1388
		1389	This is slightly more efficient then stopping/starting the timer each time
		1390	you want to modify its timeout value, as libev does not have to completely
		1391	remove and re-insert the timer from/into its internal data structure.
		1392
		1393	It is, however, even simpler than the "obvious" way to do it.
		1394
		1395	=item 3. Let the timer time out, but then re-arm it as required.
		1396
		1397	This method is more tricky, but usually most efficient: Most timeouts are
		1398	relatively long compared to the intervals between other activity - in
		1399	our example, within 60 seconds, there are usually many I/O events with
		1400	associated activity resets.
		1401
		1402	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1403	but remember the time of last activity, and check for a real timeout only
		1404	within the callback:
		1405
		1406	ev_tstamp last_activity; // time of last activity
		1407
		1408	static void
		1409	callback (EV_P_ ev_timer *w, int revents)
		1410	{
		1411	ev_tstamp now = ev_now (EV_A);
		1412	ev_tstamp timeout = last_activity + 60.;
		1413
		1414	// if last_activity + 60. is older than now, we did time out
		1415	if (timeout < now)
		1416	{
		1417	// timeout occured, take action
		1418	}
		1419	else
		1420	{
		1421	// callback was invoked, but there was some activity, re-arm
		1422	// the watcher to fire in last_activity + 60, which is
		1423	// guaranteed to be in the future, so "again" is positive:
		1424	w->repeat = timeout - now;
		1425	ev_timer_again (EV_A_ w);
		1426	}
		1427	}
		1428
		1429	To summarise the callback: first calculate the real timeout (defined
		1430	as "60 seconds after the last activity"), then check if that time has
		1431	been reached, which means something I<did>, in fact, time out. Otherwise
		1432	the callback was invoked too early (C<timeout> is in the future), so
		1433	re-schedule the timer to fire at that future time, to see if maybe we have
		1434	a timeout then.
		1435
		1436	Note how C<ev_timer_again> is used, taking advantage of the
		1437	C<ev_timer_again> optimisation when the timer is already running.
		1438
		1439	This scheme causes more callback invocations (about one every 60 seconds
		1440	minus half the average time between activity), but virtually no calls to
		1441	libev to change the timeout.
		1442
		1443	To start the timer, simply initialise the watcher and set C<last_activity>
		1444	to the current time (meaning we just have some activity :), then call the
		1445	callback, which will "do the right thing" and start the timer:
		1446
		1447	ev_timer_init (timer, callback);
		1448	last_activity = ev_now (loop);
		1449	callback (loop, timer, EV_TIMEOUT);
		1450
		1451	And when there is some activity, simply store the current time in
		1452	C<last_activity>, no libev calls at all:
		1453
		1454	last_actiivty = ev_now (loop);
		1455
		1456	This technique is slightly more complex, but in most cases where the
		1457	time-out is unlikely to be triggered, much more efficient.
		1458
		1459	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1460	callback :) - just change the timeout and invoke the callback, which will
		1461	fix things for you.
		1462
		1463	=item 4. Wee, just use a double-linked list for your timeouts.
		1464
		1465	If there is not one request, but many thousands (millions...), all
		1466	employing some kind of timeout with the same timeout value, then one can
		1467	do even better:
		1468
		1469	When starting the timeout, calculate the timeout value and put the timeout
		1470	at the I<end> of the list.
		1471
		1472	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1473	the list is expected to fire (for example, using the technique #3).
		1474
		1475	When there is some activity, remove the timer from the list, recalculate
		1476	the timeout, append it to the end of the list again, and make sure to
		1477	update the C<ev_timer> if it was taken from the beginning of the list.
		1478
		1479	This way, one can manage an unlimited number of timeouts in O(1) time for
		1480	starting, stopping and updating the timers, at the expense of a major
		1481	complication, and having to use a constant timeout. The constant timeout
		1482	ensures that the list stays sorted.
		1483
		1484	=back
		1485
		1486	So which method the best?
		1487
		1488	Method #2 is a simple no-brain-required solution that is adequate in most
		1489	situations. Method #3 requires a bit more thinking, but handles many cases
		1490	better, and isn't very complicated either. In most case, choosing either
		1491	one is fine, with #3 being better in typical situations.
		1492
		1493	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1494	rather complicated, but extremely efficient, something that really pays
		1495	off after the first million or so of active timers, i.e. it's usually
		1496	overkill :)
		1497
		1498	=head3 The special problem of time updates
		1499
		1500	Establishing the current time is a costly operation (it usually takes at
		1501	least two system calls): EV therefore updates its idea of the current
		1502	time only before and after C<ev_loop> collects new events, which causes a
		1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1504	lots of events in one iteration.
1156		1505
1157	The relative timeouts are calculated relative to the C<ev_now ()>	1506	The relative timeouts are calculated relative to the C<ev_now ()>
1158	time. This is usually the right thing as this timestamp refers to the time	1507	time. This is usually the right thing as this timestamp refers to the time
1159	of the event triggering whatever timeout you are modifying/starting. If	1508	of the event triggering whatever timeout you are modifying/starting. If
1160	you suspect event processing to be delayed and you I<need> to base the timeout	1509	you suspect event processing to be delayed and you I<need> to base the
1161	on the current time, use something like this to adjust for this:	1510	timeout on the current time, use something like this to adjust for this:
1162		1511
1163	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1512	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1164		1513
1165	The callback is guarenteed to be invoked only when its timeout has passed,	1514	If the event loop is suspended for a long time, you can also force an
1166	but if multiple timers become ready during the same loop iteration then	1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1167	order of execution is undefined.	1516	()>.
1168		1517
1169	=head3 Watcher-Specific Functions and Data Members	1518	=head3 Watcher-Specific Functions and Data Members
1170		1519
1171	=over 4	1520	=over 4
1172		1521
1173	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1174		1523
1175	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1176		1525
1177	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1526	Configure the timer to trigger after C<after> seconds. If C<repeat>
1178	C<0.>, then it will automatically be stopped. If it is positive, then the	1527	is C<0.>, then it will automatically be stopped once the timeout is
1179	timer will automatically be configured to trigger again C<repeat> seconds	1528	reached. If it is positive, then the timer will automatically be
1180	later, again, and again, until stopped manually.	1529	configured to trigger again C<repeat> seconds later, again, and again,
		1530	until stopped manually.
1181		1531
1182	The timer itself will do a best-effort at avoiding drift, that is, if you	1532	The timer itself will do a best-effort at avoiding drift, that is, if
1183	configure a timer to trigger every 10 seconds, then it will trigger at	1533	you configure a timer to trigger every 10 seconds, then it will normally
1184	exactly 10 second intervals. If, however, your program cannot keep up with	1534	trigger at exactly 10 second intervals. If, however, your program cannot
1185	the timer (because it takes longer than those 10 seconds to do stuff) the	1535	keep up with the timer (because it takes longer than those 10 seconds to
1186	timer will not fire more than once per event loop iteration.	1536	do stuff) the timer will not fire more than once per event loop iteration.
1187		1537
1188	=item ev_timer_again (loop, ev_timer *)	1538	=item ev_timer_again (loop, ev_timer *)
1189		1539
1190	This will act as if the timer timed out and restart it again if it is	1540	This will act as if the timer timed out and restart it again if it is
1191	repeating. The exact semantics are:	1541	repeating. The exact semantics are:
1192		1542
1193	If the timer is pending, its pending status is cleared.	1543	If the timer is pending, its pending status is cleared.
1194		1544
1195	If the timer is started but nonrepeating, stop it (as if it timed out).	1545	If the timer is started but non-repeating, stop it (as if it timed out).
1196		1546
1197	If the timer is repeating, either start it if necessary (with the	1547	If the timer is repeating, either start it if necessary (with the
1198	C<repeat> value), or reset the running timer to the C<repeat> value.	1548	C<repeat> value), or reset the running timer to the C<repeat> value.
1199		1549
1200	This sounds a bit complicated, but here is a useful and typical	1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1201	example: Imagine you have a tcp connection and you want a so-called idle	1551	usage example.
1202	timeout, that is, you want to be called when there have been, say, 60
1203	seconds of inactivity on the socket. The easiest way to do this is to
1204	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1205	C<ev_timer_again> each time you successfully read or write some data. If
1206	you go into an idle state where you do not expect data to travel on the
1207	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1208	automatically restart it if need be.
1209
1210	That means you can ignore the C<after> value and C<ev_timer_start>
1211	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1212
1213	ev_timer_init (timer, callback, 0., 5.);
1214	ev_timer_again (loop, timer);
1215	...
1216	timer->again = 17.;
1217	ev_timer_again (loop, timer);
1218	...
1219	timer->again = 10.;
1220	ev_timer_again (loop, timer);
1221
1222	This is more slightly efficient then stopping/starting the timer each time
1223	you want to modify its timeout value.
1224		1552
1225	=item ev_tstamp repeat [read-write]	1553	=item ev_tstamp repeat [read-write]
1226		1554
1227	The current C<repeat> value. Will be used each time the watcher times out	1555	The current C<repeat> value. Will be used each time the watcher times out
1228	or C<ev_timer_again> is called and determines the next timeout (if any),	1556	or C<ev_timer_again> is called, and determines the next timeout (if any),
1229	which is also when any modifications are taken into account.	1557	which is also when any modifications are taken into account.
1230		1558
1231	=back	1559	=back
1232		1560
1233	=head3 Examples	1561	=head3 Examples
1234		1562
1235	Example: Create a timer that fires after 60 seconds.	1563	Example: Create a timer that fires after 60 seconds.
1236		1564
1237	static void	1565	static void
1238	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1566	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1239	{	1567	{
1240	.. one minute over, w is actually stopped right here	1568	.. one minute over, w is actually stopped right here
1241	}	1569	}
1242		1570
1243	struct ev_timer mytimer;	1571	ev_timer mytimer;
1244	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1572	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1245	ev_timer_start (loop, &mytimer);	1573	ev_timer_start (loop, &mytimer);
1246		1574
1247	Example: Create a timeout timer that times out after 10 seconds of	1575	Example: Create a timeout timer that times out after 10 seconds of
1248	inactivity.	1576	inactivity.
1249		1577
1250	static void	1578	static void
1251	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1579	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1252	{	1580	{
1253	.. ten seconds without any activity	1581	.. ten seconds without any activity
1254	}	1582	}
1255		1583
1256	struct ev_timer mytimer;	1584	ev_timer mytimer;
1257	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1258	ev_timer_again (&mytimer); /* start timer */	1586	ev_timer_again (&mytimer); /* start timer */
1259	ev_loop (loop, 0);	1587	ev_loop (loop, 0);
1260		1588
1261	// and in some piece of code that gets executed on any "activity":	1589	// and in some piece of code that gets executed on any "activity":
1262	// reset the timeout to start ticking again at 10 seconds	1590	// reset the timeout to start ticking again at 10 seconds
1263	ev_timer_again (&mytimer);	1591	ev_timer_again (&mytimer);
1264		1592
1265		1593
1266	=head2 C<ev_periodic> - to cron or not to cron?	1594	=head2 C<ev_periodic> - to cron or not to cron?
1267		1595
1268	Periodic watchers are also timers of a kind, but they are very versatile	1596	Periodic watchers are also timers of a kind, but they are very versatile
1269	(and unfortunately a bit complex).	1597	(and unfortunately a bit complex).
1270		1598
1271	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1272	but on wallclock time (absolute time). You can tell a periodic watcher	1600	but on wall clock time (absolute time). You can tell a periodic watcher
1273	to trigger "at" some specific point in time. For example, if you tell a	1601	to trigger after some specific point in time. For example, if you tell a
1274	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1275	+ 10.>) and then reset your system clock to the last year, then it will	1603	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1604	clock to January of the previous year, then it will take more than year
1276	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1277	roughly 10 seconds later).	1606	roughly 10 seconds later as it uses a relative timeout).
1278		1607
1279	They can also be used to implement vastly more complex timers, such as	1608	C<ev_periodic>s can also be used to implement vastly more complex timers,
1280	triggering an event on each midnight, local time or other, complicated,	1609	such as triggering an event on each "midnight, local time", or other
1281	rules.	1610	complicated rules.
1282		1611
1283	As with timers, the callback is guarenteed to be invoked only when the	1612	As with timers, the callback is guaranteed to be invoked only when the
1284	time (C<at>) has been passed, but if multiple periodic timers become ready	1613	time (C<at>) has passed, but if multiple periodic timers become ready
1285	during the same loop iteration then order of execution is undefined.	1614	during the same loop iteration, then order of execution is undefined.
1286		1615
1287	=head3 Watcher-Specific Functions and Data Members	1616	=head3 Watcher-Specific Functions and Data Members
1288		1617
1289	=over 4	1618	=over 4
1290		1619
1291	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1292		1621
1293	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1294		1623
1295	Lots of arguments, lets sort it out... There are basically three modes of	1624	Lots of arguments, lets sort it out... There are basically three modes of
1296	operation, and we will explain them from simplest to complex:	1625	operation, and we will explain them from simplest to most complex:
1297		1626
1298	=over 4	1627	=over 4
1299		1628
1300	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1301		1630
1302	In this configuration the watcher triggers an event at the wallclock time	1631	In this configuration the watcher triggers an event after the wall clock
1303	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1632	time C<at> has passed. It will not repeat and will not adjust when a time
1304	that is, if it is to be run at January 1st 2011 then it will run when the	1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1305	system time reaches or surpasses this time.	1634	only run when the system clock reaches or surpasses this time.
1306		1635
1307	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1308		1637
1309	In this mode the watcher will always be scheduled to time out at the next	1638	In this mode the watcher will always be scheduled to time out at the next
1310	C<at + N * interval> time (for some integer N, which can also be negative)	1639	C<at + N * interval> time (for some integer N, which can also be negative)
1311	and then repeat, regardless of any time jumps.	1640	and then repeat, regardless of any time jumps.
1312		1641
1313	This can be used to create timers that do not drift with respect to system	1642	This can be used to create timers that do not drift with respect to the
1314	time:	1643	system clock, for example, here is a C<ev_periodic> that triggers each
		1644	hour, on the hour:
1315		1645
1316	ev_periodic_set (&periodic, 0., 3600., 0);	1646	ev_periodic_set (&periodic, 0., 3600., 0);
1317		1647
1318	This doesn't mean there will always be 3600 seconds in between triggers,	1648	This doesn't mean there will always be 3600 seconds in between triggers,
1319	but only that the the callback will be called when the system time shows a	1649	but only that the callback will be called when the system time shows a
1320	full hour (UTC), or more correctly, when the system time is evenly divisible	1650	full hour (UTC), or more correctly, when the system time is evenly divisible
1321	by 3600.	1651	by 3600.
1322		1652
1323	Another way to think about it (for the mathematically inclined) is that	1653	Another way to think about it (for the mathematically inclined) is that
1324	C<ev_periodic> will try to run the callback in this mode at the next possible	1654	C<ev_periodic> will try to run the callback in this mode at the next possible
1325	time where C<time = at (mod interval)>, regardless of any time jumps.	1655	time where C<time = at (mod interval)>, regardless of any time jumps.
1326		1656
1327	For numerical stability it is preferable that the C<at> value is near	1657	For numerical stability it is preferable that the C<at> value is near
1328	C<ev_now ()> (the current time), but there is no range requirement for	1658	C<ev_now ()> (the current time), but there is no range requirement for
1329	this value.	1659	this value, and in fact is often specified as zero.
		1660
		1661	Note also that there is an upper limit to how often a timer can fire (CPU
		1662	speed for example), so if C<interval> is very small then timing stability
		1663	will of course deteriorate. Libev itself tries to be exact to be about one
		1664	millisecond (if the OS supports it and the machine is fast enough).
1330		1665
1331	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1332		1667
1333	In this mode the values for C<interval> and C<at> are both being	1668	In this mode the values for C<interval> and C<at> are both being
1334	ignored. Instead, each time the periodic watcher gets scheduled, the	1669	ignored. Instead, each time the periodic watcher gets scheduled, the
1335	reschedule callback will be called with the watcher as first, and the	1670	reschedule callback will be called with the watcher as first, and the
1336	current time as second argument.	1671	current time as second argument.
1337		1672
1338	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1339	ever, or make any event loop modifications>. If you need to stop it,	1674	ever, or make ANY event loop modifications whatsoever>.
1340	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1341	starting an C<ev_prepare> watcher, which is legal).
1342		1675
		1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1678	only event loop modification you are allowed to do).
		1679
1343	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1680	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1344	ev_tstamp now)>, e.g.:	1681	*w, ev_tstamp now)>, e.g.:
1345		1682
		1683	static ev_tstamp
1346	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1684	my_rescheduler (ev_periodic *w, ev_tstamp now)
1347	{	1685	{
1348	return now + 60.;	1686	return now + 60.;
1349	}	1687	}
1350		1688
1351	It must return the next time to trigger, based on the passed time value	1689	It must return the next time to trigger, based on the passed time value
1352	(that is, the lowest time value larger than to the second argument). It	1690	(that is, the lowest time value larger than to the second argument). It
1353	will usually be called just before the callback will be triggered, but	1691	will usually be called just before the callback will be triggered, but
1354	might be called at other times, too.	1692	might be called at other times, too.
1355		1693
1356	NOTE: I<< This callback must always return a time that is later than the	1694	NOTE: I<< This callback must always return a time that is higher than or
1357	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1695	equal to the passed C<now> value >>.
1358		1696
1359	This can be used to create very complex timers, such as a timer that	1697	This can be used to create very complex timers, such as a timer that
1360	triggers on each midnight, local time. To do this, you would calculate the	1698	triggers on "next midnight, local time". To do this, you would calculate the
1361	next midnight after C<now> and return the timestamp value for this. How	1699	next midnight after C<now> and return the timestamp value for this. How
1362	you do this is, again, up to you (but it is not trivial, which is the main	1700	you do this is, again, up to you (but it is not trivial, which is the main
1363	reason I omitted it as an example).	1701	reason I omitted it as an example).
1364		1702
1365	=back	1703	=back
…		…
1369	Simply stops and restarts the periodic watcher again. This is only useful	1707	Simply stops and restarts the periodic watcher again. This is only useful
1370	when you changed some parameters or the reschedule callback would return	1708	when you changed some parameters or the reschedule callback would return
1371	a different time than the last time it was called (e.g. in a crond like	1709	a different time than the last time it was called (e.g. in a crond like
1372	program when the crontabs have changed).	1710	program when the crontabs have changed).
1373		1711
		1712	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1713
		1714	When active, returns the absolute time that the watcher is supposed to
		1715	trigger next.
		1716
1374	=item ev_tstamp offset [read-write]	1717	=item ev_tstamp offset [read-write]
1375		1718
1376	When repeating, this contains the offset value, otherwise this is the	1719	When repeating, this contains the offset value, otherwise this is the
1377	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1378		1721
…		…
1383		1726
1384	The current interval value. Can be modified any time, but changes only	1727	The current interval value. Can be modified any time, but changes only
1385	take effect when the periodic timer fires or C<ev_periodic_again> is being	1728	take effect when the periodic timer fires or C<ev_periodic_again> is being
1386	called.	1729	called.
1387		1730
1388	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1731	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1389		1732
1390	The current reschedule callback, or C<0>, if this functionality is	1733	The current reschedule callback, or C<0>, if this functionality is
1391	switched off. Can be changed any time, but changes only take effect when	1734	switched off. Can be changed any time, but changes only take effect when
1392	the periodic timer fires or C<ev_periodic_again> is being called.	1735	the periodic timer fires or C<ev_periodic_again> is being called.
1393		1736
1394	=item ev_tstamp at [read-only]
1395
1396	When active, contains the absolute time that the watcher is supposed to
1397	trigger next.
1398
1399	=back	1737	=back
1400		1738
1401	=head3 Examples	1739	=head3 Examples
1402		1740
1403	Example: Call a callback every hour, or, more precisely, whenever the	1741	Example: Call a callback every hour, or, more precisely, whenever the
1404	system clock is divisible by 3600. The callback invocation times have	1742	system time is divisible by 3600. The callback invocation times have
1405	potentially a lot of jittering, but good long-term stability.	1743	potentially a lot of jitter, but good long-term stability.
1406		1744
1407	static void	1745	static void
1408	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1409	{	1747	{
1410	... its now a full hour (UTC, or TAI or whatever your clock follows)	1748	... its now a full hour (UTC, or TAI or whatever your clock follows)
1411	}	1749	}
1412		1750
1413	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1414	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1752	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1415	ev_periodic_start (loop, &hourly_tick);	1753	ev_periodic_start (loop, &hourly_tick);
1416		1754
1417	Example: The same as above, but use a reschedule callback to do it:	1755	Example: The same as above, but use a reschedule callback to do it:
1418		1756
1419	#include <math.h>	1757	#include <math.h>
1420		1758
1421	static ev_tstamp	1759	static ev_tstamp
1422	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1760	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1423	{	1761	{
1424	return fmod (now, 3600.) + 3600.;	1762	return now + (3600. - fmod (now, 3600.));
1425	}	1763	}
1426		1764
1427	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1765	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1428		1766
1429	Example: Call a callback every hour, starting now:	1767	Example: Call a callback every hour, starting now:
1430		1768
1431	struct ev_periodic hourly_tick;	1769	ev_periodic hourly_tick;
1432	ev_periodic_init (&hourly_tick, clock_cb,	1770	ev_periodic_init (&hourly_tick, clock_cb,
1433	fmod (ev_now (loop), 3600.), 3600., 0);	1771	fmod (ev_now (loop), 3600.), 3600., 0);
1434	ev_periodic_start (loop, &hourly_tick);	1772	ev_periodic_start (loop, &hourly_tick);
1435		1773
1436		1774
1437	=head2 C<ev_signal> - signal me when a signal gets signalled!	1775	=head2 C<ev_signal> - signal me when a signal gets signalled!
1438		1776
1439	Signal watchers will trigger an event when the process receives a specific	1777	Signal watchers will trigger an event when the process receives a specific
1440	signal one or more times. Even though signals are very asynchronous, libev	1778	signal one or more times. Even though signals are very asynchronous, libev
1441	will try it's best to deliver signals synchronously, i.e. as part of the	1779	will try it's best to deliver signals synchronously, i.e. as part of the
1442	normal event processing, like any other event.	1780	normal event processing, like any other event.
1443		1781
		1782	If you want signals asynchronously, just use C<sigaction> as you would
		1783	do without libev and forget about sharing the signal. You can even use
		1784	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1785
1444	You can configure as many watchers as you like per signal. Only when the	1786	You can configure as many watchers as you like per signal. Only when the
1445	first watcher gets started will libev actually register a signal watcher	1787	first watcher gets started will libev actually register a signal handler
1446	with the kernel (thus it coexists with your own signal handlers as long	1788	with the kernel (thus it coexists with your own signal handlers as long as
1447	as you don't register any with libev). Similarly, when the last signal	1789	you don't register any with libev for the same signal). Similarly, when
1448	watcher for a signal is stopped libev will reset the signal handler to	1790	the last signal watcher for a signal is stopped, libev will reset the
1449	SIG_DFL (regardless of what it was set to before).	1791	signal handler to SIG_DFL (regardless of what it was set to before).
1450		1792
1451	If possible and supported, libev will install its handlers with	1793	If possible and supported, libev will install its handlers with
1452	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1453	interrupted. If you have a problem with syscalls getting interrupted by	1795	interrupted. If you have a problem with system calls getting interrupted by
1454	signals you can block all signals in an C<ev_check> watcher and unblock	1796	signals you can block all signals in an C<ev_check> watcher and unblock
1455	them in an C<ev_prepare> watcher.	1797	them in an C<ev_prepare> watcher.
1456		1798
1457	=head3 Watcher-Specific Functions and Data Members	1799	=head3 Watcher-Specific Functions and Data Members
1458		1800
…		…
1471		1813
1472	=back	1814	=back
1473		1815
1474	=head3 Examples	1816	=head3 Examples
1475		1817
1476	Example: Try to exit cleanly on SIGINT and SIGTERM.	1818	Example: Try to exit cleanly on SIGINT.
1477		1819
1478	static void	1820	static void
1479	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1480	{	1822	{
1481	ev_unloop (loop, EVUNLOOP_ALL);	1823	ev_unloop (loop, EVUNLOOP_ALL);
1482	}	1824	}
1483		1825
1484	struct ev_signal signal_watcher;	1826	ev_signal signal_watcher;
1485	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1486	ev_signal_start (loop, &sigint_cb);	1828	ev_signal_start (loop, &signal_watcher);
1487		1829
1488		1830
1489	=head2 C<ev_child> - watch out for process status changes	1831	=head2 C<ev_child> - watch out for process status changes
1490		1832
1491	Child watchers trigger when your process receives a SIGCHLD in response to	1833	Child watchers trigger when your process receives a SIGCHLD in response to
1492	some child status changes (most typically when a child of yours dies). It	1834	some child status changes (most typically when a child of yours dies or
1493	is permissible to install a child watcher I<after> the child has been	1835	exits). It is permissible to install a child watcher I<after> the child
1494	forked (which implies it might have already exited), as long as the event	1836	has been forked (which implies it might have already exited), as long
1495	loop isn't entered (or is continued from a watcher).	1837	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1838	forking and then immediately registering a watcher for the child is fine,
		1839	but forking and registering a watcher a few event loop iterations later is
		1840	not.
1496		1841
1497	Only the default event loop is capable of handling signals, and therefore	1842	Only the default event loop is capable of handling signals, and therefore
1498	you can only rgeister child watchers in the default event loop.	1843	you can only register child watchers in the default event loop.
1499		1844
1500	=head3 Process Interaction	1845	=head3 Process Interaction
1501		1846
1502	Libev grabs C<SIGCHLD> as soon as the default event loop is	1847	Libev grabs C<SIGCHLD> as soon as the default event loop is
1503	initialised. This is necessary to guarantee proper behaviour even if	1848	initialised. This is necessary to guarantee proper behaviour even if
1504	the first child watcher is started after the child exits. The occurance	1849	the first child watcher is started after the child exits. The occurrence
1505	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1506	synchronously as part of the event loop processing. Libev always reaps all	1851	synchronously as part of the event loop processing. Libev always reaps all
1507	children, even ones not watched.	1852	children, even ones not watched.
1508		1853
1509	=head3 Overriding the Built-In Processing	1854	=head3 Overriding the Built-In Processing
…		…
1513	handler, you can override it easily by installing your own handler for	1858	handler, you can override it easily by installing your own handler for
1514	C<SIGCHLD> after initialising the default loop, and making sure the	1859	C<SIGCHLD> after initialising the default loop, and making sure the
1515	default loop never gets destroyed. You are encouraged, however, to use an	1860	default loop never gets destroyed. You are encouraged, however, to use an
1516	event-based approach to child reaping and thus use libev's support for	1861	event-based approach to child reaping and thus use libev's support for
1517	that, so other libev users can use C<ev_child> watchers freely.	1862	that, so other libev users can use C<ev_child> watchers freely.
		1863
		1864	=head3 Stopping the Child Watcher
		1865
		1866	Currently, the child watcher never gets stopped, even when the
		1867	child terminates, so normally one needs to stop the watcher in the
		1868	callback. Future versions of libev might stop the watcher automatically
		1869	when a child exit is detected.
1518		1870
1519	=head3 Watcher-Specific Functions and Data Members	1871	=head3 Watcher-Specific Functions and Data Members
1520		1872
1521	=over 4	1873	=over 4
1522		1874
…		…
1551	=head3 Examples	1903	=head3 Examples
1552		1904
1553	Example: C<fork()> a new process and install a child handler to wait for	1905	Example: C<fork()> a new process and install a child handler to wait for
1554	its completion.	1906	its completion.
1555		1907
1556	ev_child cw;	1908	ev_child cw;
1557		1909
1558	static void	1910	static void
1559	child_cb (EV_P_ struct ev_child *w, int revents)	1911	child_cb (EV_P_ ev_child *w, int revents)
1560	{	1912	{
1561	ev_child_stop (EV_A_ w);	1913	ev_child_stop (EV_A_ w);
1562	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1914	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1563	}	1915	}
1564		1916
1565	pid_t pid = fork ();	1917	pid_t pid = fork ();
1566		1918
1567	if (pid < 0)	1919	if (pid < 0)
1568	// error	1920	// error
1569	else if (pid == 0)	1921	else if (pid == 0)
1570	{	1922	{
1571	// the forked child executes here	1923	// the forked child executes here
1572	exit (1);	1924	exit (1);
1573	}	1925	}
1574	else	1926	else
1575	{	1927	{
1576	ev_child_init (&cw, child_cb, pid, 0);	1928	ev_child_init (&cw, child_cb, pid, 0);
1577	ev_child_start (EV_DEFAULT_ &cw);	1929	ev_child_start (EV_DEFAULT_ &cw);
1578	}	1930	}
1579		1931
1580		1932
1581	=head2 C<ev_stat> - did the file attributes just change?	1933	=head2 C<ev_stat> - did the file attributes just change?
1582		1934
1583	This watches a filesystem path for attribute changes. That is, it calls	1935	This watches a file system path for attribute changes. That is, it calls
1584	C<stat> regularly (or when the OS says it changed) and sees if it changed	1936	C<stat> on that path in regular intervals (or when the OS says it changed)
1585	compared to the last time, invoking the callback if it did.	1937	and sees if it changed compared to the last time, invoking the callback if
		1938	it did.
1586		1939
1587	The path does not need to exist: changing from "path exists" to "path does	1940	The path does not need to exist: changing from "path exists" to "path does
1588	not exist" is a status change like any other. The condition "path does	1941	not exist" is a status change like any other. The condition "path does not
1589	not exist" is signified by the C<st_nlink> field being zero (which is	1942	exist" (or more correctly "path cannot be stat'ed") is signified by the
1590	otherwise always forced to be at least one) and all the other fields of	1943	C<st_nlink> field being zero (which is otherwise always forced to be at
1591	the stat buffer having unspecified contents.	1944	least one) and all the other fields of the stat buffer having unspecified
		1945	contents.
1592		1946
1593	The path I<should> be absolute and I<must not> end in a slash. If it is	1947	The path I<must not> end in a slash or contain special components such as
		1948	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1594	relative and your working directory changes, the behaviour is undefined.	1949	your working directory changes, then the behaviour is undefined.
1595		1950
1596	Since there is no standard to do this, the portable implementation simply	1951	Since there is no portable change notification interface available, the
1597	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1952	portable implementation simply calls C<stat(2)> regularly on the path
1598	can specify a recommended polling interval for this case. If you specify	1953	to see if it changed somehow. You can specify a recommended polling
1599	a polling interval of C<0> (highly recommended!) then a I<suitable,	1954	interval for this case. If you specify a polling interval of C<0> (highly
1600	unspecified default> value will be used (which you can expect to be around	1955	recommended!) then a I<suitable, unspecified default> value will be used
1601	five seconds, although this might change dynamically). Libev will also	1956	(which you can expect to be around five seconds, although this might
1602	impose a minimum interval which is currently around C<0.1>, but thats	1957	change dynamically). Libev will also impose a minimum interval which is
1603	usually overkill.	1958	currently around C<0.1>, but that's usually overkill.
1604		1959
1605	This watcher type is not meant for massive numbers of stat watchers,	1960	This watcher type is not meant for massive numbers of stat watchers,
1606	as even with OS-supported change notifications, this can be	1961	as even with OS-supported change notifications, this can be
1607	resource-intensive.	1962	resource-intensive.
1608		1963
1609	At the time of this writing, only the Linux inotify interface is	1964	At the time of this writing, the only OS-specific interface implemented
1610	implemented (implementing kqueue support is left as an exercise for the	1965	is the Linux inotify interface (implementing kqueue support is left as an
1611	reader). Inotify will be used to give hints only and should not change the	1966	exercise for the reader. Note, however, that the author sees no way of
1612	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1967	implementing C<ev_stat> semantics with kqueue, except as a hint).
1613	to fall back to regular polling again even with inotify, but changes are
1614	usually detected immediately, and if the file exists there will be no
1615	polling.
1616		1968
1617	=head3 ABI Issues (Largefile Support)	1969	=head3 ABI Issues (Largefile Support)
1618		1970
1619	Libev by default (unless the user overrides this) uses the default	1971	Libev by default (unless the user overrides this) uses the default
1620	compilation environment, which means that on systems with optionally	1972	compilation environment, which means that on systems with large file
1621	disabled large file support, you get the 32 bit version of the stat	1973	support disabled by default, you get the 32 bit version of the stat
1622	structure. When using the library from programs that change the ABI to	1974	structure. When using the library from programs that change the ABI to
1623	use 64 bit file offsets the programs will fail. In that case you have to	1975	use 64 bit file offsets the programs will fail. In that case you have to
1624	compile libev with the same flags to get binary compatibility. This is	1976	compile libev with the same flags to get binary compatibility. This is
1625	obviously the case with any flags that change the ABI, but the problem is	1977	obviously the case with any flags that change the ABI, but the problem is
1626	most noticably with ev_stat and largefile support.	1978	most noticeably displayed with ev_stat and large file support.
1627		1979
1628	=head3 Inotify	1980	The solution for this is to lobby your distribution maker to make large
		1981	file interfaces available by default (as e.g. FreeBSD does) and not
		1982	optional. Libev cannot simply switch on large file support because it has
		1983	to exchange stat structures with application programs compiled using the
		1984	default compilation environment.
1629		1985
		1986	=head3 Inotify and Kqueue
		1987
1630	When C<inotify (7)> support has been compiled into libev (generally only	1988	When C<inotify (7)> support has been compiled into libev and present at
1631	available on Linux) and present at runtime, it will be used to speed up	1989	runtime, it will be used to speed up change detection where possible. The
1632	change detection where possible. The inotify descriptor will be created lazily	1990	inotify descriptor will be created lazily when the first C<ev_stat>
1633	when the first C<ev_stat> watcher is being started.	1991	watcher is being started.
1634		1992
1635	Inotify presense does not change the semantics of C<ev_stat> watchers	1993	Inotify presence does not change the semantics of C<ev_stat> watchers
1636	except that changes might be detected earlier, and in some cases, to avoid	1994	except that changes might be detected earlier, and in some cases, to avoid
1637	making regular C<stat> calls. Even in the presense of inotify support	1995	making regular C<stat> calls. Even in the presence of inotify support
1638	there are many cases where libev has to resort to regular C<stat> polling.	1996	there are many cases where libev has to resort to regular C<stat> polling,
		1997	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1998	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1999	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2000	xfs are fully working) libev usually gets away without polling.
1639		2001
1640	(There is no support for kqueue, as apparently it cannot be used to	2002	There is no support for kqueue, as apparently it cannot be used to
1641	implement this functionality, due to the requirement of having a file	2003	implement this functionality, due to the requirement of having a file
1642	descriptor open on the object at all times).	2004	descriptor open on the object at all times, and detecting renames, unlinks
		2005	etc. is difficult.
		2006
		2007	=head3 C<stat ()> is a synchronous operation
		2008
		2009	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2010	the process. The exception are C<ev_stat> watchers - those call C<stat
		2011	()>, which is a synchronous operation.
		2012
		2013	For local paths, this usually doesn't matter: unless the system is very
		2014	busy or the intervals between stat's are large, a stat call will be fast,
		2015	as the path data is suually in memory already (except when starting the
		2016	watcher).
		2017
		2018	For networked file systems, calling C<stat ()> can block an indefinite
		2019	time due to network issues, and even under good conditions, a stat call
		2020	often takes multiple milliseconds.
		2021
		2022	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2023	paths, although this is fully supported by libev.
1643		2024
1644	=head3 The special problem of stat time resolution	2025	=head3 The special problem of stat time resolution
1645		2026
1646	The C<stat ()> syscall only supports full-second resolution portably, and	2027	The C<stat ()> system call only supports full-second resolution portably,
1647	even on systems where the resolution is higher, many filesystems still	2028	and even on systems where the resolution is higher, most file systems
1648	only support whole seconds.	2029	still only support whole seconds.
1649		2030
1650	That means that, if the time is the only thing that changes, you might	2031	That means that, if the time is the only thing that changes, you can
1651	miss updates: on the first update, C<ev_stat> detects a change and calls	2032	easily miss updates: on the first update, C<ev_stat> detects a change and
1652	your callback, which does something. When there is another update within	2033	calls your callback, which does something. When there is another update
1653	the same second, C<ev_stat> will be unable to detect it.	2034	within the same second, C<ev_stat> will be unable to detect unless the
		2035	stat data does change in other ways (e.g. file size).
1654		2036
1655	The solution to this is to delay acting on a change for a second (or till	2037	The solution to this is to delay acting on a change for slightly more
1656	the next second boundary), using a roughly one-second delay C<ev_timer>	2038	than a second (or till slightly after the next full second boundary), using
1657	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2039	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1658	is added to work around small timing inconsistencies of some operating	2040	ev_timer_again (loop, w)>).
1659	systems.	2041
		2042	The C<.02> offset is added to work around small timing inconsistencies
		2043	of some operating systems (where the second counter of the current time
		2044	might be be delayed. One such system is the Linux kernel, where a call to
		2045	C<gettimeofday> might return a timestamp with a full second later than
		2046	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2047	update file times then there will be a small window where the kernel uses
		2048	the previous second to update file times but libev might already execute
		2049	the timer callback).
1660		2050
1661	=head3 Watcher-Specific Functions and Data Members	2051	=head3 Watcher-Specific Functions and Data Members
1662		2052
1663	=over 4	2053	=over 4
1664		2054
…		…
1670	C<path>. The C<interval> is a hint on how quickly a change is expected to	2060	C<path>. The C<interval> is a hint on how quickly a change is expected to
1671	be detected and should normally be specified as C<0> to let libev choose	2061	be detected and should normally be specified as C<0> to let libev choose
1672	a suitable value. The memory pointed to by C<path> must point to the same	2062	a suitable value. The memory pointed to by C<path> must point to the same
1673	path for as long as the watcher is active.	2063	path for as long as the watcher is active.
1674		2064
1675	The callback will be receive C<EV_STAT> when a change was detected,	2065	The callback will receive an C<EV_STAT> event when a change was detected,
1676	relative to the attributes at the time the watcher was started (or the	2066	relative to the attributes at the time the watcher was started (or the
1677	last change was detected).	2067	last change was detected).
1678		2068
1679	=item ev_stat_stat (loop, ev_stat *)	2069	=item ev_stat_stat (loop, ev_stat *)
1680		2070
1681	Updates the stat buffer immediately with new values. If you change the	2071	Updates the stat buffer immediately with new values. If you change the
1682	watched path in your callback, you could call this fucntion to avoid	2072	watched path in your callback, you could call this function to avoid
1683	detecting this change (while introducing a race condition). Can also be	2073	detecting this change (while introducing a race condition if you are not
1684	useful simply to find out the new values.	2074	the only one changing the path). Can also be useful simply to find out the
		2075	new values.
1685		2076
1686	=item ev_statdata attr [read-only]	2077	=item ev_statdata attr [read-only]
1687		2078
1688	The most-recently detected attributes of the file. Although the type is of	2079	The most-recently detected attributes of the file. Although the type is
1689	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2080	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1690	suitable for your system. If the C<st_nlink> member is C<0>, then there	2081	suitable for your system, but you can only rely on the POSIX-standardised
		2082	members to be present. If the C<st_nlink> member is C<0>, then there was
1691	was some error while C<stat>ing the file.	2083	some error while C<stat>ing the file.
1692		2084
1693	=item ev_statdata prev [read-only]	2085	=item ev_statdata prev [read-only]
1694		2086
1695	The previous attributes of the file. The callback gets invoked whenever	2087	The previous attributes of the file. The callback gets invoked whenever
1696	C<prev> != C<attr>.	2088	C<prev> != C<attr>, or, more precisely, one or more of these members
		2089	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2090	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1697		2091
1698	=item ev_tstamp interval [read-only]	2092	=item ev_tstamp interval [read-only]
1699		2093
1700	The specified interval.	2094	The specified interval.
1701		2095
1702	=item const char *path [read-only]	2096	=item const char *path [read-only]
1703		2097
1704	The filesystem path that is being watched.	2098	The file system path that is being watched.
1705		2099
1706	=back	2100	=back
1707		2101
1708	=head3 Examples	2102	=head3 Examples
1709		2103
1710	Example: Watch C</etc/passwd> for attribute changes.	2104	Example: Watch C</etc/passwd> for attribute changes.
1711		2105
1712	static void	2106	static void
1713	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2107	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1714	{	2108	{
1715	/* /etc/passwd changed in some way */	2109	/* /etc/passwd changed in some way */
1716	if (w->attr.st_nlink)	2110	if (w->attr.st_nlink)
1717	{	2111	{
1718	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2112	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1719	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2113	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1720	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2114	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1721	}	2115	}
1722	else	2116	else
1723	/* you shalt not abuse printf for puts */	2117	/* you shalt not abuse printf for puts */
1724	puts ("wow, /etc/passwd is not there, expect problems. "	2118	puts ("wow, /etc/passwd is not there, expect problems. "
1725	"if this is windows, they already arrived\n");	2119	"if this is windows, they already arrived\n");
1726	}	2120	}
1727		2121
1728	...	2122	...
1729	ev_stat passwd;	2123	ev_stat passwd;
1730		2124
1731	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2125	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1732	ev_stat_start (loop, &passwd);	2126	ev_stat_start (loop, &passwd);
1733		2127
1734	Example: Like above, but additionally use a one-second delay so we do not	2128	Example: Like above, but additionally use a one-second delay so we do not
1735	miss updates (however, frequent updates will delay processing, too, so	2129	miss updates (however, frequent updates will delay processing, too, so
1736	one might do the work both on C<ev_stat> callback invocation I<and> on	2130	one might do the work both on C<ev_stat> callback invocation I<and> on
1737	C<ev_timer> callback invocation).	2131	C<ev_timer> callback invocation).
1738		2132
1739	static ev_stat passwd;	2133	static ev_stat passwd;
1740	static ev_timer timer;	2134	static ev_timer timer;
1741		2135
1742	static void	2136	static void
1743	timer_cb (EV_P_ ev_timer *w, int revents)	2137	timer_cb (EV_P_ ev_timer *w, int revents)
1744	{	2138	{
1745	ev_timer_stop (EV_A_ w);	2139	ev_timer_stop (EV_A_ w);
1746		2140
1747	/* now it's one second after the most recent passwd change */	2141	/* now it's one second after the most recent passwd change */
1748	}	2142	}
1749		2143
1750	static void	2144	static void
1751	stat_cb (EV_P_ ev_stat *w, int revents)	2145	stat_cb (EV_P_ ev_stat *w, int revents)
1752	{	2146	{
1753	/* reset the one-second timer */	2147	/* reset the one-second timer */
1754	ev_timer_again (EV_A_ &timer);	2148	ev_timer_again (EV_A_ &timer);
1755	}	2149	}
1756		2150
1757	...	2151	...
1758	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2152	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1759	ev_stat_start (loop, &passwd);	2153	ev_stat_start (loop, &passwd);
1760	ev_timer_init (&timer, timer_cb, 0., 1.01);	2154	ev_timer_init (&timer, timer_cb, 0., 1.02);
1761		2155
1762		2156
1763	=head2 C<ev_idle> - when you've got nothing better to do...	2157	=head2 C<ev_idle> - when you've got nothing better to do...
1764		2158
1765	Idle watchers trigger events when no other events of the same or higher	2159	Idle watchers trigger events when no other events of the same or higher
1766	priority are pending (prepare, check and other idle watchers do not	2160	priority are pending (prepare, check and other idle watchers do not count
1767	count).	2161	as receiving "events").
1768		2162
1769	That is, as long as your process is busy handling sockets or timeouts	2163	That is, as long as your process is busy handling sockets or timeouts
1770	(or even signals, imagine) of the same or higher priority it will not be	2164	(or even signals, imagine) of the same or higher priority it will not be
1771	triggered. But when your process is idle (or only lower-priority watchers	2165	triggered. But when your process is idle (or only lower-priority watchers
1772	are pending), the idle watchers are being called once per event loop	2166	are pending), the idle watchers are being called once per event loop
…		…
1796	=head3 Examples	2190	=head3 Examples
1797		2191
1798	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2192	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1799	callback, free it. Also, use no error checking, as usual.	2193	callback, free it. Also, use no error checking, as usual.
1800		2194
1801	static void	2195	static void
1802	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2196	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1803	{	2197	{
1804	free (w);	2198	free (w);
1805	// now do something you wanted to do when the program has	2199	// now do something you wanted to do when the program has
1806	// no longer anything immediate to do.	2200	// no longer anything immediate to do.
1807	}	2201	}
1808		2202
1809	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1810	ev_idle_init (idle_watcher, idle_cb);	2204	ev_idle_init (idle_watcher, idle_cb);
1811	ev_idle_start (loop, idle_cb);	2205	ev_idle_start (loop, idle_cb);
1812		2206
1813		2207
1814	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1815		2209
1816	Prepare and check watchers are usually (but not always) used in tandem:	2210	Prepare and check watchers are usually (but not always) used in pairs:
1817	prepare watchers get invoked before the process blocks and check watchers	2211	prepare watchers get invoked before the process blocks and check watchers
1818	afterwards.	2212	afterwards.
1819		2213
1820	You I<must not> call C<ev_loop> or similar functions that enter	2214	You I<must not> call C<ev_loop> or similar functions that enter
1821	the current event loop from either C<ev_prepare> or C<ev_check>	2215	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1824	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1825	C<ev_check> so if you have one watcher of each kind they will always be	2219	C<ev_check> so if you have one watcher of each kind they will always be
1826	called in pairs bracketing the blocking call.	2220	called in pairs bracketing the blocking call.
1827		2221
1828	Their main purpose is to integrate other event mechanisms into libev and	2222	Their main purpose is to integrate other event mechanisms into libev and
1829	their use is somewhat advanced. This could be used, for example, to track	2223	their use is somewhat advanced. They could be used, for example, to track
1830	variable changes, implement your own watchers, integrate net-snmp or a	2224	variable changes, implement your own watchers, integrate net-snmp or a
1831	coroutine library and lots more. They are also occasionally useful if	2225	coroutine library and lots more. They are also occasionally useful if
1832	you cache some data and want to flush it before blocking (for example,	2226	you cache some data and want to flush it before blocking (for example,
1833	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2227	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1834	watcher).	2228	watcher).
1835		2229
1836	This is done by examining in each prepare call which file descriptors need	2230	This is done by examining in each prepare call which file descriptors
1837	to be watched by the other library, registering C<ev_io> watchers for	2231	need to be watched by the other library, registering C<ev_io> watchers
1838	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2232	for them and starting an C<ev_timer> watcher for any timeouts (many
1839	provide just this functionality). Then, in the check watcher you check for	2233	libraries provide exactly this functionality). Then, in the check watcher,
1840	any events that occured (by checking the pending status of all watchers	2234	you check for any events that occurred (by checking the pending status
1841	and stopping them) and call back into the library. The I/O and timer	2235	of all watchers and stopping them) and call back into the library. The
1842	callbacks will never actually be called (but must be valid nevertheless,	2236	I/O and timer callbacks will never actually be called (but must be valid
1843	because you never know, you know?).	2237	nevertheless, because you never know, you know?).
1844		2238
1845	As another example, the Perl Coro module uses these hooks to integrate	2239	As another example, the Perl Coro module uses these hooks to integrate
1846	coroutines into libev programs, by yielding to other active coroutines	2240	coroutines into libev programs, by yielding to other active coroutines
1847	during each prepare and only letting the process block if no coroutines	2241	during each prepare and only letting the process block if no coroutines
1848	are ready to run (it's actually more complicated: it only runs coroutines	2242	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1851	loop from blocking if lower-priority coroutines are active, thus mapping	2245	loop from blocking if lower-priority coroutines are active, thus mapping
1852	low-priority coroutines to idle/background tasks).	2246	low-priority coroutines to idle/background tasks).
1853		2247
1854	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2248	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1855	priority, to ensure that they are being run before any other watchers	2249	priority, to ensure that they are being run before any other watchers
		2250	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2251
1856	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2252	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1857	too) should not activate ("feed") events into libev. While libev fully	2253	activate ("feed") events into libev. While libev fully supports this, they
1858	supports this, they will be called before other C<ev_check> watchers	2254	might get executed before other C<ev_check> watchers did their job. As
1859	did their job. As C<ev_check> watchers are often used to embed other	2255	C<ev_check> watchers are often used to embed other (non-libev) event
1860	(non-libev) event loops those other event loops might be in an unusable	2256	loops those other event loops might be in an unusable state until their
1861	state until their C<ev_check> watcher ran (always remind yourself to	2257	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1862	coexist peacefully with others).	2258	others).
1863		2259
1864	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
1865		2261
1866	=over 4	2262	=over 4
1867		2263
…		…
1869		2265
1870	=item ev_check_init (ev_check *, callback)	2266	=item ev_check_init (ev_check *, callback)
1871		2267
1872	Initialises and configures the prepare or check watcher - they have no	2268	Initialises and configures the prepare or check watcher - they have no
1873	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2269	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1874	macros, but using them is utterly, utterly and completely pointless.	2270	macros, but using them is utterly, utterly, utterly and completely
		2271	pointless.
1875		2272
1876	=back	2273	=back
1877		2274
1878	=head3 Examples	2275	=head3 Examples
1879		2276
1880	There are a number of principal ways to embed other event loops or modules	2277	There are a number of principal ways to embed other event loops or modules
1881	into libev. Here are some ideas on how to include libadns into libev	2278	into libev. Here are some ideas on how to include libadns into libev
1882	(there is a Perl module named C<EV::ADNS> that does this, which you could	2279	(there is a Perl module named C<EV::ADNS> that does this, which you could
1883	use for an actually working example. Another Perl module named C<EV::Glib>	2280	use as a working example. Another Perl module named C<EV::Glib> embeds a
1884	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2281	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1885	into the Glib event loop).	2282	Glib event loop).
1886		2283
1887	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2284	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1888	and in a check watcher, destroy them and call into libadns. What follows	2285	and in a check watcher, destroy them and call into libadns. What follows
1889	is pseudo-code only of course. This requires you to either use a low	2286	is pseudo-code only of course. This requires you to either use a low
1890	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2287	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1891	the callbacks for the IO/timeout watchers might not have been called yet.	2288	the callbacks for the IO/timeout watchers might not have been called yet.
1892		2289
1893	static ev_io iow [nfd];	2290	static ev_io iow [nfd];
1894	static ev_timer tw;	2291	static ev_timer tw;
1895		2292
1896	static void	2293	static void
1897	io_cb (ev_loop *loop, ev_io *w, int revents)	2294	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1898	{	2295	{
1899	}	2296	}
1900		2297
1901	// create io watchers for each fd and a timer before blocking	2298	// create io watchers for each fd and a timer before blocking
1902	static void	2299	static void
1903	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2300	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1904	{	2301	{
1905	int timeout = 3600000;	2302	int timeout = 3600000;
1906	struct pollfd fds [nfd];	2303	struct pollfd fds [nfd];
1907	// actual code will need to loop here and realloc etc.	2304	// actual code will need to loop here and realloc etc.
1908	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1909		2306
1910	/* the callback is illegal, but won't be called as we stop during check */	2307	/* the callback is illegal, but won't be called as we stop during check */
1911	ev_timer_init (&tw, 0, timeout * 1e-3);	2308	ev_timer_init (&tw, 0, timeout * 1e-3);
1912	ev_timer_start (loop, &tw);	2309	ev_timer_start (loop, &tw);
1913		2310
1914	// create one ev_io per pollfd	2311	// create one ev_io per pollfd
1915	for (int i = 0; i < nfd; ++i)	2312	for (int i = 0; i < nfd; ++i)
1916	{	2313	{
1917	ev_io_init (iow + i, io_cb, fds [i].fd,	2314	ev_io_init (iow + i, io_cb, fds [i].fd,
1918	((fds [i].events & POLLIN ? EV_READ : 0)	2315	((fds [i].events & POLLIN ? EV_READ : 0)
1919	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2316	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1920		2317
1921	fds [i].revents = 0;	2318	fds [i].revents = 0;
1922	ev_io_start (loop, iow + i);	2319	ev_io_start (loop, iow + i);
1923	}	2320	}
1924	}	2321	}
1925		2322
1926	// stop all watchers after blocking	2323	// stop all watchers after blocking
1927	static void	2324	static void
1928	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2325	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1929	{	2326	{
1930	ev_timer_stop (loop, &tw);	2327	ev_timer_stop (loop, &tw);
1931		2328
1932	for (int i = 0; i < nfd; ++i)	2329	for (int i = 0; i < nfd; ++i)
1933	{	2330	{
1934	// set the relevant poll flags	2331	// set the relevant poll flags
1935	// could also call adns_processreadable etc. here	2332	// could also call adns_processreadable etc. here
1936	struct pollfd *fd = fds + i;	2333	struct pollfd *fd = fds + i;
1937	int revents = ev_clear_pending (iow + i);	2334	int revents = ev_clear_pending (iow + i);
1938	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2335	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1939	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2336	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1940		2337
1941	// now stop the watcher	2338	// now stop the watcher
1942	ev_io_stop (loop, iow + i);	2339	ev_io_stop (loop, iow + i);
1943	}	2340	}
1944		2341
1945	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2342	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1946	}	2343	}
1947		2344
1948	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2345	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1949	in the prepare watcher and would dispose of the check watcher.	2346	in the prepare watcher and would dispose of the check watcher.
1950		2347
1951	Method 3: If the module to be embedded supports explicit event	2348	Method 3: If the module to be embedded supports explicit event
1952	notification (adns does), you can also make use of the actual watcher	2349	notification (libadns does), you can also make use of the actual watcher
1953	callbacks, and only destroy/create the watchers in the prepare watcher.	2350	callbacks, and only destroy/create the watchers in the prepare watcher.
1954		2351
1955	static void	2352	static void
1956	timer_cb (EV_P_ ev_timer *w, int revents)	2353	timer_cb (EV_P_ ev_timer *w, int revents)
1957	{	2354	{
1958	adns_state ads = (adns_state)w->data;	2355	adns_state ads = (adns_state)w->data;
1959	update_now (EV_A);	2356	update_now (EV_A);
1960		2357
1961	adns_processtimeouts (ads, &tv_now);	2358	adns_processtimeouts (ads, &tv_now);
1962	}	2359	}
1963		2360
1964	static void	2361	static void
1965	io_cb (EV_P_ ev_io *w, int revents)	2362	io_cb (EV_P_ ev_io *w, int revents)
1966	{	2363	{
1967	adns_state ads = (adns_state)w->data;	2364	adns_state ads = (adns_state)w->data;
1968	update_now (EV_A);	2365	update_now (EV_A);
1969		2366
1970	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2367	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1971	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2368	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1972	}	2369	}
1973		2370
1974	// do not ever call adns_afterpoll	2371	// do not ever call adns_afterpoll
1975		2372
1976	Method 4: Do not use a prepare or check watcher because the module you	2373	Method 4: Do not use a prepare or check watcher because the module you
1977	want to embed is too inflexible to support it. Instead, youc na override	2374	want to embed is not flexible enough to support it. Instead, you can
1978	their poll function. The drawback with this solution is that the main	2375	override their poll function. The drawback with this solution is that the
1979	loop is now no longer controllable by EV. The C<Glib::EV> module does	2376	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1980	this.	2377	this approach, effectively embedding EV as a client into the horrible
		2378	libglib event loop.
1981		2379
1982	static gint	2380	static gint
1983	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2381	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1984	{	2382	{
1985	int got_events = 0;	2383	int got_events = 0;
1986		2384
1987	for (n = 0; n < nfds; ++n)	2385	for (n = 0; n < nfds; ++n)
1988	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2386	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1989		2387
1990	if (timeout >= 0)	2388	if (timeout >= 0)
1991	// create/start timer	2389	// create/start timer
1992		2390
1993	// poll	2391	// poll
1994	ev_loop (EV_A_ 0);	2392	ev_loop (EV_A_ 0);
1995		2393
1996	// stop timer again	2394	// stop timer again
1997	if (timeout >= 0)	2395	if (timeout >= 0)
1998	ev_timer_stop (EV_A_ &to);	2396	ev_timer_stop (EV_A_ &to);
1999		2397
2000	// stop io watchers again - their callbacks should have set	2398	// stop io watchers again - their callbacks should have set
2001	for (n = 0; n < nfds; ++n)	2399	for (n = 0; n < nfds; ++n)
2002	ev_io_stop (EV_A_ iow [n]);	2400	ev_io_stop (EV_A_ iow [n]);
2003		2401
2004	return got_events;	2402	return got_events;
2005	}	2403	}
2006		2404
2007		2405
2008	=head2 C<ev_embed> - when one backend isn't enough...	2406	=head2 C<ev_embed> - when one backend isn't enough...
2009		2407
2010	This is a rather advanced watcher type that lets you embed one event loop	2408	This is a rather advanced watcher type that lets you embed one event loop
…		…
2016	prioritise I/O.	2414	prioritise I/O.
2017		2415
2018	As an example for a bug workaround, the kqueue backend might only support	2416	As an example for a bug workaround, the kqueue backend might only support
2019	sockets on some platform, so it is unusable as generic backend, but you	2417	sockets on some platform, so it is unusable as generic backend, but you
2020	still want to make use of it because you have many sockets and it scales	2418	still want to make use of it because you have many sockets and it scales
2021	so nicely. In this case, you would create a kqueue-based loop and embed it	2419	so nicely. In this case, you would create a kqueue-based loop and embed
2022	into your default loop (which might use e.g. poll). Overall operation will	2420	it into your default loop (which might use e.g. poll). Overall operation
2023	be a bit slower because first libev has to poll and then call kevent, but	2421	will be a bit slower because first libev has to call C<poll> and then
2024	at least you can use both at what they are best.	2422	C<kevent>, but at least you can use both mechanisms for what they are
		2423	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2025		2424
2026	As for prioritising I/O: rarely you have the case where some fds have	2425	As for prioritising I/O: under rare circumstances you have the case where
2027	to be watched and handled very quickly (with low latency), and even	2426	some fds have to be watched and handled very quickly (with low latency),
2028	priorities and idle watchers might have too much overhead. In this case	2427	and even priorities and idle watchers might have too much overhead. In
2029	you would put all the high priority stuff in one loop and all the rest in	2428	this case you would put all the high priority stuff in one loop and all
2030	a second one, and embed the second one in the first.	2429	the rest in a second one, and embed the second one in the first.
2031		2430
2032	As long as the watcher is active, the callback will be invoked every time	2431	As long as the watcher is active, the callback will be invoked every time
2033	there might be events pending in the embedded loop. The callback must then	2432	there might be events pending in the embedded loop. The callback must then
2034	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2035	their callbacks (you could also start an idle watcher to give the embedded	2434	their callbacks (you could also start an idle watcher to give the embedded
…		…
2043	interested in that.	2442	interested in that.
2044		2443
2045	Also, there have not currently been made special provisions for forking:	2444	Also, there have not currently been made special provisions for forking:
2046	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2047	but you will also have to stop and restart any C<ev_embed> watchers	2446	but you will also have to stop and restart any C<ev_embed> watchers
2048	yourself.	2447	yourself - but you can use a fork watcher to handle this automatically,
		2448	and future versions of libev might do just that.
2049		2449
2050	Unfortunately, not all backends are embeddable, only the ones returned by	2450	Unfortunately, not all backends are embeddable: only the ones returned by
2051	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2052	portable one.	2452	portable one.
2053		2453
2054	So when you want to use this feature you will always have to be prepared	2454	So when you want to use this feature you will always have to be prepared
2055	that you cannot get an embeddable loop. The recommended way to get around	2455	that you cannot get an embeddable loop. The recommended way to get around
2056	this is to have a separate variables for your embeddable loop, try to	2456	this is to have a separate variables for your embeddable loop, try to
2057	create it, and if that fails, use the normal loop for everything.	2457	create it, and if that fails, use the normal loop for everything.
2058		2458
		2459	=head3 C<ev_embed> and fork
		2460
		2461	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2462	automatically be applied to the embedded loop as well, so no special
		2463	fork handling is required in that case. When the watcher is not running,
		2464	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2465	as applicable.
		2466
2059	=head3 Watcher-Specific Functions and Data Members	2467	=head3 Watcher-Specific Functions and Data Members
2060		2468
2061	=over 4	2469	=over 4
2062		2470
2063	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2471	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2066		2474
2067	Configures the watcher to embed the given loop, which must be	2475	Configures the watcher to embed the given loop, which must be
2068	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2476	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2069	invoked automatically, otherwise it is the responsibility of the callback	2477	invoked automatically, otherwise it is the responsibility of the callback
2070	to invoke it (it will continue to be called until the sweep has been done,	2478	to invoke it (it will continue to be called until the sweep has been done,
2071	if you do not want thta, you need to temporarily stop the embed watcher).	2479	if you do not want that, you need to temporarily stop the embed watcher).
2072		2480
2073	=item ev_embed_sweep (loop, ev_embed *)	2481	=item ev_embed_sweep (loop, ev_embed *)
2074		2482
2075	Make a single, non-blocking sweep over the embedded loop. This works	2483	Make a single, non-blocking sweep over the embedded loop. This works
2076	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2077	apropriate way for embedded loops.	2485	appropriate way for embedded loops.
2078		2486
2079	=item struct ev_loop *other [read-only]	2487	=item struct ev_loop *other [read-only]
2080		2488
2081	The embedded event loop.	2489	The embedded event loop.
2082		2490
…		…
2084		2492
2085	=head3 Examples	2493	=head3 Examples
2086		2494
2087	Example: Try to get an embeddable event loop and embed it into the default	2495	Example: Try to get an embeddable event loop and embed it into the default
2088	event loop. If that is not possible, use the default loop. The default	2496	event loop. If that is not possible, use the default loop. The default
2089	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2497	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2090	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2498	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2091	used).	2499	used).
2092		2500
2093	struct ev_loop *loop_hi = ev_default_init (0);	2501	struct ev_loop *loop_hi = ev_default_init (0);
2094	struct ev_loop *loop_lo = 0;	2502	struct ev_loop *loop_lo = 0;
2095	struct ev_embed embed;	2503	ev_embed embed;
2096		2504
2097	// see if there is a chance of getting one that works	2505	// see if there is a chance of getting one that works
2098	// (remember that a flags value of 0 means autodetection)	2506	// (remember that a flags value of 0 means autodetection)
2099	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2507	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2100	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2508	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2101	: 0;	2509	: 0;
2102		2510
2103	// if we got one, then embed it, otherwise default to loop_hi	2511	// if we got one, then embed it, otherwise default to loop_hi
2104	if (loop_lo)	2512	if (loop_lo)
2105	{	2513	{
2106	ev_embed_init (&embed, 0, loop_lo);	2514	ev_embed_init (&embed, 0, loop_lo);
2107	ev_embed_start (loop_hi, &embed);	2515	ev_embed_start (loop_hi, &embed);
2108	}	2516	}
2109	else	2517	else
2110	loop_lo = loop_hi;	2518	loop_lo = loop_hi;
2111		2519
2112	Example: Check if kqueue is available but not recommended and create	2520	Example: Check if kqueue is available but not recommended and create
2113	a kqueue backend for use with sockets (which usually work with any	2521	a kqueue backend for use with sockets (which usually work with any
2114	kqueue implementation). Store the kqueue/socket-only event loop in	2522	kqueue implementation). Store the kqueue/socket-only event loop in
2115	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2523	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2116		2524
2117	struct ev_loop *loop = ev_default_init (0);	2525	struct ev_loop *loop = ev_default_init (0);
2118	struct ev_loop *loop_socket = 0;	2526	struct ev_loop *loop_socket = 0;
2119	struct ev_embed embed;	2527	ev_embed embed;
2120		2528
2121	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2529	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2122	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2530	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2123	{	2531	{
2124	ev_embed_init (&embed, 0, loop_socket);	2532	ev_embed_init (&embed, 0, loop_socket);
2125	ev_embed_start (loop, &embed);	2533	ev_embed_start (loop, &embed);
2126	}	2534	}
2127		2535
2128	if (!loop_socket)	2536	if (!loop_socket)
2129	loop_socket = loop;	2537	loop_socket = loop;
2130		2538
2131	// now use loop_socket for all sockets, and loop for everything else	2539	// now use loop_socket for all sockets, and loop for everything else
2132		2540
2133		2541
2134	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2542	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2135		2543
2136	Fork watchers are called when a C<fork ()> was detected (usually because	2544	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2180	is that the author does not know of a simple (or any) algorithm for a	2588	is that the author does not know of a simple (or any) algorithm for a
2181	multiple-writer-single-reader queue that works in all cases and doesn't	2589	multiple-writer-single-reader queue that works in all cases and doesn't
2182	need elaborate support such as pthreads.	2590	need elaborate support such as pthreads.
2183		2591
2184	That means that if you want to queue data, you have to provide your own	2592	That means that if you want to queue data, you have to provide your own
2185	queue. But at least I can tell you would implement locking around your	2593	queue. But at least I can tell you how to implement locking around your
2186	queue:	2594	queue:
2187		2595
2188	=over 4	2596	=over 4
2189		2597
2190	=item queueing from a signal handler context	2598	=item queueing from a signal handler context
2191		2599
2192	To implement race-free queueing, you simply add to the queue in the signal	2600	To implement race-free queueing, you simply add to the queue in the signal
2193	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2601	handler but you block the signal handler in the watcher callback. Here is
2194	some fictitiuous SIGUSR1 handler:	2602	an example that does that for some fictitious SIGUSR1 handler:
2195		2603
2196	static ev_async mysig;	2604	static ev_async mysig;
2197		2605
2198	static void	2606	static void
2199	sigusr1_handler (void)	2607	sigusr1_handler (void)
…		…
2265	=over 4	2673	=over 4
2266		2674
2267	=item ev_async_init (ev_async *, callback)	2675	=item ev_async_init (ev_async *, callback)
2268		2676
2269	Initialises and configures the async watcher - it has no parameters of any	2677	Initialises and configures the async watcher - it has no parameters of any
2270	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2678	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2271	believe me.	2679	trust me.
2272		2680
2273	=item ev_async_send (loop, ev_async *)	2681	=item ev_async_send (loop, ev_async *)
2274		2682
2275	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2683	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2276	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2277	C<ev_feed_event>, this call is safe to do in other threads, signal or	2685	C<ev_feed_event>, this call is safe to do from other threads, signal or
2278	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2279	section below on what exactly this means).	2687	section below on what exactly this means).
2280		2688
2281	This call incurs the overhead of a syscall only once per loop iteration,	2689	This call incurs the overhead of a system call only once per loop iteration,
2282	so while the overhead might be noticable, it doesn't apply to repeated	2690	so while the overhead might be noticeable, it doesn't apply to repeated
2283	calls to C<ev_async_send>.	2691	calls to C<ev_async_send>.
2284		2692
		2693	=item bool = ev_async_pending (ev_async *)
		2694
		2695	Returns a non-zero value when C<ev_async_send> has been called on the
		2696	watcher but the event has not yet been processed (or even noted) by the
		2697	event loop.
		2698
		2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2700	the loop iterates next and checks for the watcher to have become active,
		2701	it will reset the flag again. C<ev_async_pending> can be used to very
		2702	quickly check whether invoking the loop might be a good idea.
		2703
		2704	Not that this does I<not> check whether the watcher itself is pending, only
		2705	whether it has been requested to make this watcher pending.
		2706
2285	=back	2707	=back
2286		2708
2287		2709
2288	=head1 OTHER FUNCTIONS	2710	=head1 OTHER FUNCTIONS
2289		2711
…		…
2292	=over 4	2714	=over 4
2293		2715
2294	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2716	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2295		2717
2296	This function combines a simple timer and an I/O watcher, calls your	2718	This function combines a simple timer and an I/O watcher, calls your
2297	callback on whichever event happens first and automatically stop both	2719	callback on whichever event happens first and automatically stops both
2298	watchers. This is useful if you want to wait for a single event on an fd	2720	watchers. This is useful if you want to wait for a single event on an fd
2299	or timeout without having to allocate/configure/start/stop/free one or	2721	or timeout without having to allocate/configure/start/stop/free one or
2300	more watchers yourself.	2722	more watchers yourself.
2301		2723
2302	If C<fd> is less than 0, then no I/O watcher will be started and events	2724	If C<fd> is less than 0, then no I/O watcher will be started and the
2303	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2725	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2304	C<events> set will be craeted and started.	2726	the given C<fd> and C<events> set will be created and started.
2305		2727
2306	If C<timeout> is less than 0, then no timeout watcher will be	2728	If C<timeout> is less than 0, then no timeout watcher will be
2307	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2308	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2730	repeat = 0) will be started. C<0> is a valid timeout.
2309	dubious value.
2310		2731
2311	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2312	passed an C<revents> set like normal event callbacks (a combination of	2733	passed an C<revents> set like normal event callbacks (a combination of
2313	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2314	value passed to C<ev_once>:	2735	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2736	a timeout and an io event at the same time - you probably should give io
		2737	events precedence.
2315		2738
		2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2740
2316	static void stdin_ready (int revents, void *arg)	2741	static void stdin_ready (int revents, void *arg)
2317	{	2742	{
2318	if (revents & EV_TIMEOUT)
2319	/* doh, nothing entered */;
2320	else if (revents & EV_READ)	2743	if (revents & EV_READ)
2321	/* stdin might have data for us, joy! */;	2744	/* stdin might have data for us, joy! */;
		2745	else if (revents & EV_TIMEOUT)
		2746	/* doh, nothing entered */;
2322	}	2747	}
2323		2748
2324	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2325		2750
2326	=item ev_feed_event (ev_loop *, watcher *, int revents)	2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2327		2752
2328	Feeds the given event set into the event loop, as if the specified event	2753	Feeds the given event set into the event loop, as if the specified event
2329	had happened for the specified watcher (which must be a pointer to an	2754	had happened for the specified watcher (which must be a pointer to an
2330	initialised but not necessarily started event watcher).	2755	initialised but not necessarily started event watcher).
2331		2756
2332	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2333		2758
2334	Feed an event on the given fd, as if a file descriptor backend detected	2759	Feed an event on the given fd, as if a file descriptor backend detected
2335	the given events it.	2760	the given events it.
2336		2761
2337	=item ev_feed_signal_event (ev_loop *loop, int signum)	2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2338		2763
2339	Feed an event as if the given signal occured (C<loop> must be the default	2764	Feed an event as if the given signal occurred (C<loop> must be the default
2340	loop!).	2765	loop!).
2341		2766
2342	=back	2767	=back
2343		2768
2344		2769
…		…
2360		2785
2361	=item * Priorities are not currently supported. Initialising priorities	2786	=item * Priorities are not currently supported. Initialising priorities
2362	will fail and all watchers will have the same priority, even though there	2787	will fail and all watchers will have the same priority, even though there
2363	is an ev_pri field.	2788	is an ev_pri field.
2364		2789
		2790	=item * In libevent, the last base created gets the signals, in libev, the
		2791	first base created (== the default loop) gets the signals.
		2792
2365	=item * Other members are not supported.	2793	=item * Other members are not supported.
2366		2794
2367	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2795	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2368	to use the libev header file and library.	2796	to use the libev header file and library.
2369		2797
2370	=back	2798	=back
2371		2799
2372	=head1 C++ SUPPORT	2800	=head1 C++ SUPPORT
2373		2801
2374	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2802	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2375	you to use some convinience methods to start/stop watchers and also change	2803	you to use some convenience methods to start/stop watchers and also change
2376	the callback model to a model using method callbacks on objects.	2804	the callback model to a model using method callbacks on objects.
2377		2805
2378	To use it,	2806	To use it,
2379		2807
2380	#include <ev++.h>	2808	#include <ev++.h>
2381		2809
2382	This automatically includes F<ev.h> and puts all of its definitions (many	2810	This automatically includes F<ev.h> and puts all of its definitions (many
2383	of them macros) into the global namespace. All C++ specific things are	2811	of them macros) into the global namespace. All C++ specific things are
2384	put into the C<ev> namespace. It should support all the same embedding	2812	put into the C<ev> namespace. It should support all the same embedding
2385	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2813	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2452	your compiler is good :), then the method will be fully inlined into the	2880	your compiler is good :), then the method will be fully inlined into the
2453	thunking function, making it as fast as a direct C callback.	2881	thunking function, making it as fast as a direct C callback.
2454		2882
2455	Example: simple class declaration and watcher initialisation	2883	Example: simple class declaration and watcher initialisation
2456		2884
2457	struct myclass	2885	struct myclass
2458	{	2886	{
2459	void io_cb (ev::io &w, int revents) { }	2887	void io_cb (ev::io &w, int revents) { }
2460	}	2888	}
2461		2889
2462	myclass obj;	2890	myclass obj;
2463	ev::io iow;	2891	ev::io iow;
2464	iow.set <myclass, &myclass::io_cb> (&obj);	2892	iow.set <myclass, &myclass::io_cb> (&obj);
2465		2893
2466	=item w->set<function> (void *data = 0)	2894	=item w->set<function> (void *data = 0)
2467		2895
2468	Also sets a callback, but uses a static method or plain function as	2896	Also sets a callback, but uses a static method or plain function as
2469	callback. The optional C<data> argument will be stored in the watcher's	2897	callback. The optional C<data> argument will be stored in the watcher's
…		…
2471		2899
2472	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2900	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2473		2901
2474	See the method-C<set> above for more details.	2902	See the method-C<set> above for more details.
2475		2903
2476	Example:	2904	Example: Use a plain function as callback.
2477		2905
2478	static void io_cb (ev::io &w, int revents) { }	2906	static void io_cb (ev::io &w, int revents) { }
2479	iow.set <io_cb> ();	2907	iow.set <io_cb> ();
2480		2908
2481	=item w->set (struct ev_loop *)	2909	=item w->set (struct ev_loop *)
2482		2910
2483	Associates a different C<struct ev_loop> with this watcher. You can only	2911	Associates a different C<struct ev_loop> with this watcher. You can only
2484	do this when the watcher is inactive (and not pending either).	2912	do this when the watcher is inactive (and not pending either).
2485		2913
2486	=item w->set ([args])	2914	=item w->set ([arguments])
2487		2915
2488	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2489	called at least once. Unlike the C counterpart, an active watcher gets	2917	called at least once. Unlike the C counterpart, an active watcher gets
2490	automatically stopped and restarted when reconfiguring it with this	2918	automatically stopped and restarted when reconfiguring it with this
2491	method.	2919	method.
2492		2920
2493	=item w->start ()	2921	=item w->start ()
…		…
2517	=back	2945	=back
2518		2946
2519	Example: Define a class with an IO and idle watcher, start one of them in	2947	Example: Define a class with an IO and idle watcher, start one of them in
2520	the constructor.	2948	the constructor.
2521		2949
2522	class myclass	2950	class myclass
2523	{	2951	{
2524	ev::io io; void io_cb (ev::io &w, int revents);	2952	ev::io io ; void io_cb (ev::io &w, int revents);
2525	ev:idle idle void idle_cb (ev::idle &w, int revents);	2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2526		2954
2527	myclass (int fd)	2955	myclass (int fd)
2528	{	2956	{
2529	io .set <myclass, &myclass::io_cb > (this);	2957	io .set <myclass, &myclass::io_cb > (this);
2530	idle.set <myclass, &myclass::idle_cb> (this);	2958	idle.set <myclass, &myclass::idle_cb> (this);
2531		2959
2532	io.start (fd, ev::READ);	2960	io.start (fd, ev::READ);
2533	}	2961	}
2534	};	2962	};
2535		2963
2536		2964
2537	=head1 OTHER LANGUAGE BINDINGS	2965	=head1 OTHER LANGUAGE BINDINGS
2538		2966
2539	Libev does not offer other language bindings itself, but bindings for a	2967	Libev does not offer other language bindings itself, but bindings for a
2540	numbe rof languages exist in the form of third-party packages. If you know	2968	number of languages exist in the form of third-party packages. If you know
2541	any interesting language binding in addition to the ones listed here, drop	2969	any interesting language binding in addition to the ones listed here, drop
2542	me a note.	2970	me a note.
2543		2971
2544	=over 4	2972	=over 4
2545		2973
2546	=item Perl	2974	=item Perl
2547		2975
2548	The EV module implements the full libev API and is actually used to test	2976	The EV module implements the full libev API and is actually used to test
2549	libev. EV is developed together with libev. Apart from the EV core module,	2977	libev. EV is developed together with libev. Apart from the EV core module,
2550	there are additional modules that implement libev-compatible interfaces	2978	there are additional modules that implement libev-compatible interfaces
2551	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2979	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2552	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2980	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2981	and C<EV::Glib>).
2553		2982
2554	It can be found and installed via CPAN, its homepage is found at	2983	It can be found and installed via CPAN, its homepage is at
2555	L<http://software.schmorp.de/pkg/EV>.	2984	L<http://software.schmorp.de/pkg/EV>.
2556		2985
		2986	=item Python
		2987
		2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2989	seems to be quite complete and well-documented. Note, however, that the
		2990	patch they require for libev is outright dangerous as it breaks the ABI
		2991	for everybody else, and therefore, should never be applied in an installed
		2992	libev (if python requires an incompatible ABI then it needs to embed
		2993	libev).
		2994
2557	=item Ruby	2995	=item Ruby
2558		2996
2559	Tony Arcieri has written a ruby extension that offers access to a subset	2997	Tony Arcieri has written a ruby extension that offers access to a subset
2560	of the libev API and adds filehandle abstractions, asynchronous DNS and	2998	of the libev API and adds file handle abstractions, asynchronous DNS and
2561	more on top of it. It can be found via gem servers. Its homepage is at	2999	more on top of it. It can be found via gem servers. Its homepage is at
2562	L<http://rev.rubyforge.org/>.	3000	L<http://rev.rubyforge.org/>.
2563		3001
2564	=item D	3002	=item D
2565		3003
2566	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2567	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3006
		3007	=item Ocaml
		3008
		3009	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2568		3011
2569	=back	3012	=back
2570		3013
2571		3014
2572	=head1 MACRO MAGIC	3015	=head1 MACRO MAGIC
2573		3016
2574	Libev can be compiled with a variety of options, the most fundamantal	3017	Libev can be compiled with a variety of options, the most fundamental
2575	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3018	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2576	functions and callbacks have an initial C<struct ev_loop *> argument.	3019	functions and callbacks have an initial C<struct ev_loop *> argument.
2577		3020
2578	To make it easier to write programs that cope with either variant, the	3021	To make it easier to write programs that cope with either variant, the
2579	following macros are defined:	3022	following macros are defined:
…		…
2584		3027
2585	This provides the loop I<argument> for functions, if one is required ("ev	3028	This provides the loop I<argument> for functions, if one is required ("ev
2586	loop argument"). The C<EV_A> form is used when this is the sole argument,	3029	loop argument"). The C<EV_A> form is used when this is the sole argument,
2587	C<EV_A_> is used when other arguments are following. Example:	3030	C<EV_A_> is used when other arguments are following. Example:
2588		3031
2589	ev_unref (EV_A);	3032	ev_unref (EV_A);
2590	ev_timer_add (EV_A_ watcher);	3033	ev_timer_add (EV_A_ watcher);
2591	ev_loop (EV_A_ 0);	3034	ev_loop (EV_A_ 0);
2592		3035
2593	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2594	which is often provided by the following macro.	3037	which is often provided by the following macro.
2595		3038
2596	=item C<EV_P>, C<EV_P_>	3039	=item C<EV_P>, C<EV_P_>
2597		3040
2598	This provides the loop I<parameter> for functions, if one is required ("ev	3041	This provides the loop I<parameter> for functions, if one is required ("ev
2599	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3042	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2600	C<EV_P_> is used when other parameters are following. Example:	3043	C<EV_P_> is used when other parameters are following. Example:
2601		3044
2602	// this is how ev_unref is being declared	3045	// this is how ev_unref is being declared
2603	static void ev_unref (EV_P);	3046	static void ev_unref (EV_P);
2604		3047
2605	// this is how you can declare your typical callback	3048	// this is how you can declare your typical callback
2606	static void cb (EV_P_ ev_timer *w, int revents)	3049	static void cb (EV_P_ ev_timer *w, int revents)
2607		3050
2608	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3051	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2609	suitable for use with C<EV_A>.	3052	suitable for use with C<EV_A>.
2610		3053
2611	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3054	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2612		3055
2613	Similar to the other two macros, this gives you the value of the default	3056	Similar to the other two macros, this gives you the value of the default
2614	loop, if multiple loops are supported ("ev loop default").	3057	loop, if multiple loops are supported ("ev loop default").
		3058
		3059	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3060
		3061	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3062	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3063	is undefined when the default loop has not been initialised by a previous
		3064	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3065
		3066	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3067	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2615		3068
2616	=back	3069	=back
2617		3070
2618	Example: Declare and initialise a check watcher, utilising the above	3071	Example: Declare and initialise a check watcher, utilising the above
2619	macros so it will work regardless of whether multiple loops are supported	3072	macros so it will work regardless of whether multiple loops are supported
2620	or not.	3073	or not.
2621		3074
2622	static void	3075	static void
2623	check_cb (EV_P_ ev_timer *w, int revents)	3076	check_cb (EV_P_ ev_timer *w, int revents)
2624	{	3077	{
2625	ev_check_stop (EV_A_ w);	3078	ev_check_stop (EV_A_ w);
2626	}	3079	}
2627		3080
2628	ev_check check;	3081	ev_check check;
2629	ev_check_init (&check, check_cb);	3082	ev_check_init (&check, check_cb);
2630	ev_check_start (EV_DEFAULT_ &check);	3083	ev_check_start (EV_DEFAULT_ &check);
2631	ev_loop (EV_DEFAULT_ 0);	3084	ev_loop (EV_DEFAULT_ 0);
2632		3085
2633	=head1 EMBEDDING	3086	=head1 EMBEDDING
2634		3087
2635	Libev can (and often is) directly embedded into host	3088	Libev can (and often is) directly embedded into host
2636	applications. Examples of applications that embed it include the Deliantra	3089	applications. Examples of applications that embed it include the Deliantra
…		…
2643	libev somewhere in your source tree).	3096	libev somewhere in your source tree).
2644		3097
2645	=head2 FILESETS	3098	=head2 FILESETS
2646		3099
2647	Depending on what features you need you need to include one or more sets of files	3100	Depending on what features you need you need to include one or more sets of files
2648	in your app.	3101	in your application.
2649		3102
2650	=head3 CORE EVENT LOOP	3103	=head3 CORE EVENT LOOP
2651		3104
2652	To include only the libev core (all the C<ev_*> functions), with manual	3105	To include only the libev core (all the C<ev_*> functions), with manual
2653	configuration (no autoconf):	3106	configuration (no autoconf):
2654		3107
2655	#define EV_STANDALONE 1	3108	#define EV_STANDALONE 1
2656	#include "ev.c"	3109	#include "ev.c"
2657		3110
2658	This will automatically include F<ev.h>, too, and should be done in a	3111	This will automatically include F<ev.h>, too, and should be done in a
2659	single C source file only to provide the function implementations. To use	3112	single C source file only to provide the function implementations. To use
2660	it, do the same for F<ev.h> in all files wishing to use this API (best	3113	it, do the same for F<ev.h> in all files wishing to use this API (best
2661	done by writing a wrapper around F<ev.h> that you can include instead and	3114	done by writing a wrapper around F<ev.h> that you can include instead and
2662	where you can put other configuration options):	3115	where you can put other configuration options):
2663		3116
2664	#define EV_STANDALONE 1	3117	#define EV_STANDALONE 1
2665	#include "ev.h"	3118	#include "ev.h"
2666		3119
2667	Both header files and implementation files can be compiled with a C++	3120	Both header files and implementation files can be compiled with a C++
2668	compiler (at least, thats a stated goal, and breakage will be treated	3121	compiler (at least, that's a stated goal, and breakage will be treated
2669	as a bug).	3122	as a bug).
2670		3123
2671	You need the following files in your source tree, or in a directory	3124	You need the following files in your source tree, or in a directory
2672	in your include path (e.g. in libev/ when using -Ilibev):	3125	in your include path (e.g. in libev/ when using -Ilibev):
2673		3126
2674	ev.h	3127	ev.h
2675	ev.c	3128	ev.c
2676	ev_vars.h	3129	ev_vars.h
2677	ev_wrap.h	3130	ev_wrap.h
2678		3131
2679	ev_win32.c required on win32 platforms only	3132	ev_win32.c required on win32 platforms only
2680		3133
2681	ev_select.c only when select backend is enabled (which is enabled by default)	3134	ev_select.c only when select backend is enabled (which is enabled by default)
2682	ev_poll.c only when poll backend is enabled (disabled by default)	3135	ev_poll.c only when poll backend is enabled (disabled by default)
2683	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3136	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2684	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3137	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2685	ev_port.c only when the solaris port backend is enabled (disabled by default)	3138	ev_port.c only when the solaris port backend is enabled (disabled by default)
2686		3139
2687	F<ev.c> includes the backend files directly when enabled, so you only need	3140	F<ev.c> includes the backend files directly when enabled, so you only need
2688	to compile this single file.	3141	to compile this single file.
2689		3142
2690	=head3 LIBEVENT COMPATIBILITY API	3143	=head3 LIBEVENT COMPATIBILITY API
2691		3144
2692	To include the libevent compatibility API, also include:	3145	To include the libevent compatibility API, also include:
2693		3146
2694	#include "event.c"	3147	#include "event.c"
2695		3148
2696	in the file including F<ev.c>, and:	3149	in the file including F<ev.c>, and:
2697		3150
2698	#include "event.h"	3151	#include "event.h"
2699		3152
2700	in the files that want to use the libevent API. This also includes F<ev.h>.	3153	in the files that want to use the libevent API. This also includes F<ev.h>.
2701		3154
2702	You need the following additional files for this:	3155	You need the following additional files for this:
2703		3156
2704	event.h	3157	event.h
2705	event.c	3158	event.c
2706		3159
2707	=head3 AUTOCONF SUPPORT	3160	=head3 AUTOCONF SUPPORT
2708		3161
2709	Instead of using C<EV_STANDALONE=1> and providing your config in	3162	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2710	whatever way you want, you can also C<m4_include([libev.m4])> in your	3163	whatever way you want, you can also C<m4_include([libev.m4])> in your
2711	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3164	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2712	include F<config.h> and configure itself accordingly.	3165	include F<config.h> and configure itself accordingly.
2713		3166
2714	For this of course you need the m4 file:	3167	For this of course you need the m4 file:
2715		3168
2716	libev.m4	3169	libev.m4
2717		3170
2718	=head2 PREPROCESSOR SYMBOLS/MACROS	3171	=head2 PREPROCESSOR SYMBOLS/MACROS
2719		3172
2720	Libev can be configured via a variety of preprocessor symbols you have to define	3173	Libev can be configured via a variety of preprocessor symbols you have to
2721	before including any of its files. The default is not to build for multiplicity	3174	define before including any of its files. The default in the absence of
2722	and only include the select backend.	3175	autoconf is documented for every option.
2723		3176
2724	=over 4	3177	=over 4
2725		3178
2726	=item EV_STANDALONE	3179	=item EV_STANDALONE
2727		3180
…		…
2732	F<event.h> that are not directly supported by the libev core alone.	3185	F<event.h> that are not directly supported by the libev core alone.
2733		3186
2734	=item EV_USE_MONOTONIC	3187	=item EV_USE_MONOTONIC
2735		3188
2736	If defined to be C<1>, libev will try to detect the availability of the	3189	If defined to be C<1>, libev will try to detect the availability of the
2737	monotonic clock option at both compiletime and runtime. Otherwise no use	3190	monotonic clock option at both compile time and runtime. Otherwise no use
2738	of the monotonic clock option will be attempted. If you enable this, you	3191	of the monotonic clock option will be attempted. If you enable this, you
2739	usually have to link against librt or something similar. Enabling it when	3192	usually have to link against librt or something similar. Enabling it when
2740	the functionality isn't available is safe, though, although you have	3193	the functionality isn't available is safe, though, although you have
2741	to make sure you link against any libraries where the C<clock_gettime>	3194	to make sure you link against any libraries where the C<clock_gettime>
2742	function is hiding in (often F<-lrt>).	3195	function is hiding in (often F<-lrt>).
2743		3196
2744	=item EV_USE_REALTIME	3197	=item EV_USE_REALTIME
2745		3198
2746	If defined to be C<1>, libev will try to detect the availability of the	3199	If defined to be C<1>, libev will try to detect the availability of the
2747	realtime clock option at compiletime (and assume its availability at	3200	real-time clock option at compile time (and assume its availability at
2748	runtime if successful). Otherwise no use of the realtime clock option will	3201	runtime if successful). Otherwise no use of the real-time clock option will
2749	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2750	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2751	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2752		3205
2753	=item EV_USE_NANOSLEEP	3206	=item EV_USE_NANOSLEEP
2754		3207
2755	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2756	and will use it for delays. Otherwise it will use C<select ()>.	3209	and will use it for delays. Otherwise it will use C<select ()>.
2757		3210
		3211	=item EV_USE_EVENTFD
		3212
		3213	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3214	available and will probe for kernel support at runtime. This will improve
		3215	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3216	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3217	2.7 or newer, otherwise disabled.
		3218
2758	=item EV_USE_SELECT	3219	=item EV_USE_SELECT
2759		3220
2760	If undefined or defined to be C<1>, libev will compile in support for the	3221	If undefined or defined to be C<1>, libev will compile in support for the
2761	C<select>(2) backend. No attempt at autodetection will be done: if no	3222	C<select>(2) backend. No attempt at auto-detection will be done: if no
2762	other method takes over, select will be it. Otherwise the select backend	3223	other method takes over, select will be it. Otherwise the select backend
2763	will not be compiled in.	3224	will not be compiled in.
2764		3225
2765	=item EV_SELECT_USE_FD_SET	3226	=item EV_SELECT_USE_FD_SET
2766		3227
2767	If defined to C<1>, then the select backend will use the system C<fd_set>	3228	If defined to C<1>, then the select backend will use the system C<fd_set>
2768	structure. This is useful if libev doesn't compile due to a missing	3229	structure. This is useful if libev doesn't compile due to a missing
2769	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2770	exotic systems. This usually limits the range of file descriptors to some	3231	exotic systems. This usually limits the range of file descriptors to some
2771	low limit such as 1024 or might have other limitations (winsocket only	3232	low limit such as 1024 or might have other limitations (winsocket only
2772	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2773	influence the size of the C<fd_set> used.	3234	influence the size of the C<fd_set> used.
2774		3235
…		…
2798		3259
2799	=item EV_USE_EPOLL	3260	=item EV_USE_EPOLL
2800		3261
2801	If defined to be C<1>, libev will compile in support for the Linux	3262	If defined to be C<1>, libev will compile in support for the Linux
2802	C<epoll>(7) backend. Its availability will be detected at runtime,	3263	C<epoll>(7) backend. Its availability will be detected at runtime,
2803	otherwise another method will be used as fallback. This is the	3264	otherwise another method will be used as fallback. This is the preferred
2804	preferred backend for GNU/Linux systems.	3265	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3266	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2805		3267
2806	=item EV_USE_KQUEUE	3268	=item EV_USE_KQUEUE
2807		3269
2808	If defined to be C<1>, libev will compile in support for the BSD style	3270	If defined to be C<1>, libev will compile in support for the BSD style
2809	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3271	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2822	otherwise another method will be used as fallback. This is the preferred	3284	otherwise another method will be used as fallback. This is the preferred
2823	backend for Solaris 10 systems.	3285	backend for Solaris 10 systems.
2824		3286
2825	=item EV_USE_DEVPOLL	3287	=item EV_USE_DEVPOLL
2826		3288
2827	reserved for future expansion, works like the USE symbols above.	3289	Reserved for future expansion, works like the USE symbols above.
2828		3290
2829	=item EV_USE_INOTIFY	3291	=item EV_USE_INOTIFY
2830		3292
2831	If defined to be C<1>, libev will compile in support for the Linux inotify	3293	If defined to be C<1>, libev will compile in support for the Linux inotify
2832	interface to speed up C<ev_stat> watchers. Its actual availability will	3294	interface to speed up C<ev_stat> watchers. Its actual availability will
2833	be detected at runtime.	3295	be detected at runtime. If undefined, it will be enabled if the headers
		3296	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2834		3297
2835	=item EV_ATOMIC_T	3298	=item EV_ATOMIC_T
2836		3299
2837	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3300	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2838	access is atomic with respect to other threads or signal contexts. No such	3301	access is atomic with respect to other threads or signal contexts. No such
2839	type is easily found in the C language, so you can provide your own type	3302	type is easily found in the C language, so you can provide your own type
2840	that you know is safe for your purposes. It is used both for signal handler "locking"	3303	that you know is safe for your purposes. It is used both for signal handler "locking"
2841	as well as for signal and thread safety in C<ev_async> watchers.	3304	as well as for signal and thread safety in C<ev_async> watchers.
2842		3305
2843	In the absense of this define, libev will use C<sig_atomic_t volatile>	3306	In the absence of this define, libev will use C<sig_atomic_t volatile>
2844	(from F<signal.h>), which is usually good enough on most platforms.	3307	(from F<signal.h>), which is usually good enough on most platforms.
2845		3308
2846	=item EV_H	3309	=item EV_H
2847		3310
2848	The name of the F<ev.h> header file used to include it. The default if	3311	The name of the F<ev.h> header file used to include it. The default if
…		…
2887	When doing priority-based operations, libev usually has to linearly search	3350	When doing priority-based operations, libev usually has to linearly search
2888	all the priorities, so having many of them (hundreds) uses a lot of space	3351	all the priorities, so having many of them (hundreds) uses a lot of space
2889	and time, so using the defaults of five priorities (-2 .. +2) is usually	3352	and time, so using the defaults of five priorities (-2 .. +2) is usually
2890	fine.	3353	fine.
2891		3354
2892	If your embedding app does not need any priorities, defining these both to	3355	If your embedding application does not need any priorities, defining these
2893	C<0> will save some memory and cpu.	3356	both to C<0> will save some memory and CPU.
2894		3357
2895	=item EV_PERIODIC_ENABLE	3358	=item EV_PERIODIC_ENABLE
2896		3359
2897	If undefined or defined to be C<1>, then periodic timers are supported. If	3360	If undefined or defined to be C<1>, then periodic timers are supported. If
2898	defined to be C<0>, then they are not. Disabling them saves a few kB of	3361	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2905	code.	3368	code.
2906		3369
2907	=item EV_EMBED_ENABLE	3370	=item EV_EMBED_ENABLE
2908		3371
2909	If undefined or defined to be C<1>, then embed watchers are supported. If	3372	If undefined or defined to be C<1>, then embed watchers are supported. If
2910	defined to be C<0>, then they are not.	3373	defined to be C<0>, then they are not. Embed watchers rely on most other
		3374	watcher types, which therefore must not be disabled.
2911		3375
2912	=item EV_STAT_ENABLE	3376	=item EV_STAT_ENABLE
2913		3377
2914	If undefined or defined to be C<1>, then stat watchers are supported. If	3378	If undefined or defined to be C<1>, then stat watchers are supported. If
2915	defined to be C<0>, then they are not.	3379	defined to be C<0>, then they are not.
…		…
2925	defined to be C<0>, then they are not.	3389	defined to be C<0>, then they are not.
2926		3390
2927	=item EV_MINIMAL	3391	=item EV_MINIMAL
2928		3392
2929	If you need to shave off some kilobytes of code at the expense of some	3393	If you need to shave off some kilobytes of code at the expense of some
2930	speed, define this symbol to C<1>. Currently only used for gcc to override	3394	speed, define this symbol to C<1>. Currently this is used to override some
2931	some inlining decisions, saves roughly 30% codesize of amd64.	3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3396	much smaller 2-heap for timer management over the default 4-heap.
2932		3397
2933	=item EV_PID_HASHSIZE	3398	=item EV_PID_HASHSIZE
2934		3399
2935	C<ev_child> watchers use a small hash table to distribute workload by	3400	C<ev_child> watchers use a small hash table to distribute workload by
2936	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2943	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2944	usually more than enough. If you need to manage thousands of C<ev_stat>	3409	usually more than enough. If you need to manage thousands of C<ev_stat>
2945	watchers you might want to increase this value (I<must> be a power of	3410	watchers you might want to increase this value (I<must> be a power of
2946	two).	3411	two).
2947		3412
		3413	=item EV_USE_4HEAP
		3414
		3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3418	faster performance with many (thousands) of watchers.
		3419
		3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3421	(disabled).
		3422
		3423	=item EV_HEAP_CACHE_AT
		3424
		3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3429	but avoids random read accesses on heap changes. This improves performance
		3430	noticeably with many (hundreds) of watchers.
		3431
		3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3433	(disabled).
		3434
		3435	=item EV_VERIFY
		3436
		3437	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3438	be done: If set to C<0>, no internal verification code will be compiled
		3439	in. If set to C<1>, then verification code will be compiled in, but not
		3440	called. If set to C<2>, then the internal verification code will be
		3441	called once per loop, which can slow down libev. If set to C<3>, then the
		3442	verification code will be called very frequently, which will slow down
		3443	libev considerably.
		3444
		3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3446	C<0>.
		3447
2948	=item EV_COMMON	3448	=item EV_COMMON
2949		3449
2950	By default, all watchers have a C<void *data> member. By redefining	3450	By default, all watchers have a C<void *data> member. By redefining
2951	this macro to a something else you can include more and other types of	3451	this macro to a something else you can include more and other types of
2952	members. You have to define it each time you include one of the files,	3452	members. You have to define it each time you include one of the files,
2953	though, and it must be identical each time.	3453	though, and it must be identical each time.
2954		3454
2955	For example, the perl EV module uses something like this:	3455	For example, the perl EV module uses something like this:
2956		3456
2957	#define EV_COMMON \	3457	#define EV_COMMON \
2958	SV *self; /* contains this struct */ \	3458	SV *self; /* contains this struct */ \
2959	SV *cb_sv, *fh /* note no trailing ";" */	3459	SV *cb_sv, *fh /* note no trailing ";" */
2960		3460
2961	=item EV_CB_DECLARE (type)	3461	=item EV_CB_DECLARE (type)
2962		3462
2963	=item EV_CB_INVOKE (watcher, revents)	3463	=item EV_CB_INVOKE (watcher, revents)
2964		3464
…		…
2969	definition and a statement, respectively. See the F<ev.h> header file for	3469	definition and a statement, respectively. See the F<ev.h> header file for
2970	their default definitions. One possible use for overriding these is to	3470	their default definitions. One possible use for overriding these is to
2971	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3471	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2972	method calls instead of plain function calls in C++.	3472	method calls instead of plain function calls in C++.
2973		3473
		3474	=back
		3475
2974	=head2 EXPORTED API SYMBOLS	3476	=head2 EXPORTED API SYMBOLS
2975		3477
2976	If you need to re-export the API (e.g. via a dll) and you need a list of	3478	If you need to re-export the API (e.g. via a DLL) and you need a list of
2977	exported symbols, you can use the provided F<Symbol.*> files which list	3479	exported symbols, you can use the provided F<Symbol.*> files which list
2978	all public symbols, one per line:	3480	all public symbols, one per line:
2979		3481
2980	Symbols.ev for libev proper	3482	Symbols.ev for libev proper
2981	Symbols.event for the libevent emulation	3483	Symbols.event for the libevent emulation
2982		3484
2983	This can also be used to rename all public symbols to avoid clashes with	3485	This can also be used to rename all public symbols to avoid clashes with
2984	multiple versions of libev linked together (which is obviously bad in	3486	multiple versions of libev linked together (which is obviously bad in
2985	itself, but sometimes it is inconvinient to avoid this).	3487	itself, but sometimes it is inconvenient to avoid this).
2986		3488
2987	A sed command like this will create wrapper C<#define>'s that you need to	3489	A sed command like this will create wrapper C<#define>'s that you need to
2988	include before including F<ev.h>:	3490	include before including F<ev.h>:
2989		3491
2990	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3492	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3007	file.	3509	file.
3008		3510
3009	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3010	that everybody includes and which overrides some configure choices:	3512	that everybody includes and which overrides some configure choices:
3011		3513
3012	#define EV_MINIMAL 1	3514	#define EV_MINIMAL 1
3013	#define EV_USE_POLL 0	3515	#define EV_USE_POLL 0
3014	#define EV_MULTIPLICITY 0	3516	#define EV_MULTIPLICITY 0
3015	#define EV_PERIODIC_ENABLE 0	3517	#define EV_PERIODIC_ENABLE 0
3016	#define EV_STAT_ENABLE 0	3518	#define EV_STAT_ENABLE 0
3017	#define EV_FORK_ENABLE 0	3519	#define EV_FORK_ENABLE 0
3018	#define EV_CONFIG_H <config.h>	3520	#define EV_CONFIG_H <config.h>
3019	#define EV_MINPRI 0	3521	#define EV_MINPRI 0
3020	#define EV_MAXPRI 0	3522	#define EV_MAXPRI 0
3021		3523
3022	#include "ev++.h"	3524	#include "ev++.h"
3023		3525
3024	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3025		3527
3026	#include "ev_cpp.h"	3528	#include "ev_cpp.h"
3027	#include "ev.c"	3529	#include "ev.c"
3028		3530
		3531	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3029		3532
3030	=head1 COMPLEXITIES	3533	=head2 THREADS AND COROUTINES
3031		3534
3032	In this section the complexities of (many of) the algorithms used inside	3535	=head3 THREADS
3033	libev will be explained. For complexity discussions about backends see the
3034	documentation for C<ev_default_init>.
3035		3536
3036	All of the following are about amortised time: If an array needs to be	3537	All libev functions are reentrant and thread-safe unless explicitly
3037	extended, libev needs to realloc and move the whole array, but this	3538	documented otherwise, but libev implements no locking itself. This means
3038	happens asymptotically never with higher number of elements, so O(1) might	3539	that you can use as many loops as you want in parallel, as long as there
3039	mean it might do a lengthy realloc operation in rare cases, but on average	3540	are no concurrent calls into any libev function with the same loop
3040	it is much faster and asymptotically approaches constant time.	3541	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3542	of course): libev guarantees that different event loops share no data
		3543	structures that need any locking.
		3544
		3545	Or to put it differently: calls with different loop parameters can be done
		3546	concurrently from multiple threads, calls with the same loop parameter
		3547	must be done serially (but can be done from different threads, as long as
		3548	only one thread ever is inside a call at any point in time, e.g. by using
		3549	a mutex per loop).
		3550
		3551	Specifically to support threads (and signal handlers), libev implements
		3552	so-called C<ev_async> watchers, which allow some limited form of
		3553	concurrency on the same event loop, namely waking it up "from the
		3554	outside".
		3555
		3556	If you want to know which design (one loop, locking, or multiple loops
		3557	without or something else still) is best for your problem, then I cannot
		3558	help you, but here is some generic advice:
3041		3559
3042	=over 4	3560	=over 4
3043		3561
3044	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3562	=item * most applications have a main thread: use the default libev loop
		3563	in that thread, or create a separate thread running only the default loop.
3045		3564
3046	This means that, when you have a watcher that triggers in one hour and	3565	This helps integrating other libraries or software modules that use libev
3047	there are 100 watchers that would trigger before that then inserting will	3566	themselves and don't care/know about threading.
3048	have to skip roughly seven (C<ld 100>) of these watchers.
3049		3567
3050	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3568	=item * one loop per thread is usually a good model.
3051		3569
3052	That means that changing a timer costs less than removing/adding them	3570	Doing this is almost never wrong, sometimes a better-performance model
3053	as only the relative motion in the event queue has to be paid for.	3571	exists, but it is always a good start.
3054		3572
3055	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3573	=item * other models exist, such as the leader/follower pattern, where one
		3574	loop is handed through multiple threads in a kind of round-robin fashion.
3056		3575
3057	These just add the watcher into an array or at the head of a list.	3576	Choosing a model is hard - look around, learn, know that usually you can do
		3577	better than you currently do :-)
3058		3578
3059	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3579	=item * often you need to talk to some other thread which blocks in the
		3580	event loop.
3060		3581
3061	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3582	C<ev_async> watchers can be used to wake them up from other threads safely
		3583	(or from signal contexts...).
3062		3584
3063	These watchers are stored in lists then need to be walked to find the	3585	An example use would be to communicate signals or other events that only
3064	correct watcher to remove. The lists are usually short (you don't usually	3586	work in the default loop by registering the signal watcher with the
3065	have many watchers waiting for the same fd or signal).	3587	default loop and triggering an C<ev_async> watcher from the default loop
3066		3588	watcher callback into the event loop interested in the signal.
3067	=item Finding the next timer in each loop iteration: O(1)
3068
3069	By virtue of using a binary heap, the next timer is always found at the
3070	beginning of the storage array.
3071
3072	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3073
3074	A change means an I/O watcher gets started or stopped, which requires
3075	libev to recalculate its status (and possibly tell the kernel, depending
3076	on backend and wether C<ev_io_set> was used).
3077
3078	=item Activating one watcher (putting it into the pending state): O(1)
3079
3080	=item Priority handling: O(number_of_priorities)
3081
3082	Priorities are implemented by allocating some space for each
3083	priority. When doing priority-based operations, libev usually has to
3084	linearly search all the priorities, but starting/stopping and activating
3085	watchers becomes O(1) w.r.t. priority handling.
3086
3087	=item Sending an ev_async: O(1)
3088
3089	=item Processing ev_async_send: O(number_of_async_watchers)
3090
3091	=item Processing signals: O(max_signal_number)
3092
3093	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3094	calls in the current loop iteration. Checking for async and signal events
3095	involves iterating over all running async watchers or all signal numbers.
3096		3589
3097	=back	3590	=back
3098		3591
		3592	=head3 COROUTINES
3099		3593
3100	=head1 Win32 platform limitations and workarounds	3594	Libev is very accommodating to coroutines ("cooperative threads"):
		3595	libev fully supports nesting calls to its functions from different
		3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3597	different coroutines, and switch freely between both coroutines running the
		3598	loop, as long as you don't confuse yourself). The only exception is that
		3599	you must not do this from C<ev_periodic> reschedule callbacks.
		3600
		3601	Care has been taken to ensure that libev does not keep local state inside
		3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3603	they do not call any callbacks.
		3604
		3605	=head2 COMPILER WARNINGS
		3606
		3607	Depending on your compiler and compiler settings, you might get no or a
		3608	lot of warnings when compiling libev code. Some people are apparently
		3609	scared by this.
		3610
		3611	However, these are unavoidable for many reasons. For one, each compiler
		3612	has different warnings, and each user has different tastes regarding
		3613	warning options. "Warn-free" code therefore cannot be a goal except when
		3614	targeting a specific compiler and compiler-version.
		3615
		3616	Another reason is that some compiler warnings require elaborate
		3617	workarounds, or other changes to the code that make it less clear and less
		3618	maintainable.
		3619
		3620	And of course, some compiler warnings are just plain stupid, or simply
		3621	wrong (because they don't actually warn about the condition their message
		3622	seems to warn about). For example, certain older gcc versions had some
		3623	warnings that resulted an extreme number of false positives. These have
		3624	been fixed, but some people still insist on making code warn-free with
		3625	such buggy versions.
		3626
		3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
		3632
		3633
		3634	=head2 VALGRIND
		3635
		3636	Valgrind has a special section here because it is a popular tool that is
		3637	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3638
		3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
		3641
		3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
		3645
		3646	Then there is no memory leak, just as memory accounted to global variables
		3647	is not a memleak - the memory is still being referenced, and didn't leak.
		3648
		3649	Similarly, under some circumstances, valgrind might report kernel bugs
		3650	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3651	although an acceptable workaround has been found here), or it might be
		3652	confused.
		3653
		3654	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3655	make it into some kind of religion.
		3656
		3657	If you are unsure about something, feel free to contact the mailing list
		3658	with the full valgrind report and an explanation on why you think this
		3659	is a bug in libev (best check the archives, too :). However, don't be
		3660	annoyed when you get a brisk "this is no bug" answer and take the chance
		3661	of learning how to interpret valgrind properly.
		3662
		3663	If you need, for some reason, empty reports from valgrind for your project
		3664	I suggest using suppression lists.
		3665
		3666
		3667	=head1 PORTABILITY NOTES
		3668
		3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3101		3670
3102	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3103	requires, and its I/O model is fundamentally incompatible with the POSIX	3672	requires, and its I/O model is fundamentally incompatible with the POSIX
3104	model. Libev still offers limited functionality on this platform in	3673	model. Libev still offers limited functionality on this platform in
3105	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3106	descriptors. This only applies when using Win32 natively, not when using	3675	descriptors. This only applies when using Win32 natively, not when using
3107	e.g. cygwin.	3676	e.g. cygwin.
3108		3677
		3678	Lifting these limitations would basically require the full
		3679	re-implementation of the I/O system. If you are into these kinds of
		3680	things, then note that glib does exactly that for you in a very portable
		3681	way (note also that glib is the slowest event library known to man).
		3682
3109	There is no supported compilation method available on windows except	3683	There is no supported compilation method available on windows except
3110	embedding it into other applications.	3684	embedding it into other applications.
3111		3685
		3686	Not a libev limitation but worth mentioning: windows apparently doesn't
		3687	accept large writes: instead of resulting in a partial write, windows will
		3688	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3689	so make sure you only write small amounts into your sockets (less than a
		3690	megabyte seems safe, but this apparently depends on the amount of memory
		3691	available).
		3692
3112	Due to the many, low, and arbitrary limits on the win32 platform and the	3693	Due to the many, low, and arbitrary limits on the win32 platform and
3113	abysmal performance of winsockets, using a large number of sockets is not	3694	the abysmal performance of winsockets, using a large number of sockets
3114	recommended (and not reasonable). If your program needs to use more than	3695	is not recommended (and not reasonable). If your program needs to use
3115	a hundred or so sockets, then likely it needs to use a totally different	3696	more than a hundred or so sockets, then likely it needs to use a totally
3116	implementation for windows, as libev offers the POSIX model, which cannot	3697	different implementation for windows, as libev offers the POSIX readiness
3117	be implemented efficiently on windows (microsoft monopoly games).	3698	notification model, which cannot be implemented efficiently on windows
		3699	(Microsoft monopoly games).
		3700
		3701	A typical way to use libev under windows is to embed it (see the embedding
		3702	section for details) and use the following F<evwrap.h> header file instead
		3703	of F<ev.h>:
		3704
		3705	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3706	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3707
		3708	#include "ev.h"
		3709
		3710	And compile the following F<evwrap.c> file into your project (make sure
		3711	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3712
		3713	#include "evwrap.h"
		3714	#include "ev.c"
3118		3715
3119	=over 4	3716	=over 4
3120		3717
3121	=item The winsocket select function	3718	=item The winsocket select function
3122		3719
3123	The winsocket C<select> function doesn't follow POSIX in that it requires	3720	The winsocket C<select> function doesn't follow POSIX in that it
3124	socket I<handles> and not socket I<file descriptors>. This makes select	3721	requires socket I<handles> and not socket I<file descriptors> (it is
3125	very inefficient, and also requires a mapping from file descriptors	3722	also extremely buggy). This makes select very inefficient, and also
3126	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3723	requires a mapping from file descriptors to socket handles (the Microsoft
3127	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3724	C runtime provides the function C<_open_osfhandle> for this). See the
3128	symbols for more info.	3725	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3726	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3129		3727
3130	The configuration for a "naked" win32 using the microsoft runtime	3728	The configuration for a "naked" win32 using the Microsoft runtime
3131	libraries and raw winsocket select is:	3729	libraries and raw winsocket select is:
3132		3730
3133	#define EV_USE_SELECT 1	3731	#define EV_USE_SELECT 1
3134	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3135		3733
3136	Note that winsockets handling of fd sets is O(n), so you can easily get a	3734	Note that winsockets handling of fd sets is O(n), so you can easily get a
3137	complexity in the O(n²) range when using win32.	3735	complexity in the O(n²) range when using win32.
3138		3736
3139	=item Limited number of file descriptors	3737	=item Limited number of file descriptors
3140		3738
3141	Windows has numerous arbitrary (and low) limits on things. Early versions	3739	Windows has numerous arbitrary (and low) limits on things.
3142	of winsocket's select only supported waiting for a max. of C<64> handles	3740
		3741	Early versions of winsocket's select only supported waiting for a maximum
3143	(probably owning to the fact that all windows kernels can only wait for	3742	of C<64> handles (probably owning to the fact that all windows kernels
3144	C<64> things at the same time internally; microsoft recommends spawning a	3743	can only wait for C<64> things at the same time internally; Microsoft
3145	chain of threads and wait for 63 handles and the previous thread in each).	3744	recommends spawning a chain of threads and wait for 63 handles and the
		3745	previous thread in each. Great).
3146		3746
3147	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3148	to some high number (e.g. C<2048>) before compiling the winsocket select	3748	to some high number (e.g. C<2048>) before compiling the winsocket select
3149	call (which might be in libev or elsewhere, for example, perl does its own	3749	call (which might be in libev or elsewhere, for example, perl does its own
3150	select emulation on windows).	3750	select emulation on windows).
3151		3751
3152	Another limit is the number of file descriptors in the microsoft runtime	3752	Another limit is the number of file descriptors in the Microsoft runtime
3153	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3154	or something like this inside microsoft). You can increase this by calling	3754	or something like this inside Microsoft). You can increase this by calling
3155	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3156	arbitrary limit), but is broken in many versions of the microsoft runtime	3756	arbitrary limit), but is broken in many versions of the Microsoft runtime
3157	libraries.	3757	libraries.
3158		3758
3159	This might get you to about C<512> or C<2048> sockets (depending on	3759	This might get you to about C<512> or C<2048> sockets (depending on
3160	windows version and/or the phase of the moon). To get more, you need to	3760	windows version and/or the phase of the moon). To get more, you need to
3161	wrap all I/O functions and provide your own fd management, but the cost of	3761	wrap all I/O functions and provide your own fd management, but the cost of
3162	calling select (O(n²)) will likely make this unworkable.	3762	calling select (O(n²)) will likely make this unworkable.
3163		3763
3164	=back	3764	=back
3165		3765
		3766	=head2 PORTABILITY REQUIREMENTS
		3767
		3768	In addition to a working ISO-C implementation and of course the
		3769	backend-specific APIs, libev relies on a few additional extensions:
		3770
		3771	=over 4
		3772
		3773	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3774	calling conventions regardless of C<ev_watcher_type *>.
		3775
		3776	Libev assumes not only that all watcher pointers have the same internal
		3777	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3778	assumes that the same (machine) code can be used to call any watcher
		3779	callback: The watcher callbacks have different type signatures, but libev
		3780	calls them using an C<ev_watcher *> internally.
		3781
		3782	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3783
		3784	The type C<sig_atomic_t volatile> (or whatever is defined as
		3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3786	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3787	believed to be sufficiently portable.
		3788
		3789	=item C<sigprocmask> must work in a threaded environment
		3790
		3791	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3792	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3793	pthread implementations will either allow C<sigprocmask> in the "main
		3794	thread" or will block signals process-wide, both behaviours would
		3795	be compatible with libev. Interaction between C<sigprocmask> and
		3796	C<pthread_sigmask> could complicate things, however.
		3797
		3798	The most portable way to handle signals is to block signals in all threads
		3799	except the initial one, and run the default loop in the initial thread as
		3800	well.
		3801
		3802	=item C<long> must be large enough for common memory allocation sizes
		3803
		3804	To improve portability and simplify its API, libev uses C<long> internally
		3805	instead of C<size_t> when allocating its data structures. On non-POSIX
		3806	systems (Microsoft...) this might be unexpectedly low, but is still at
		3807	least 31 bits everywhere, which is enough for hundreds of millions of
		3808	watchers.
		3809
		3810	=item C<double> must hold a time value in seconds with enough accuracy
		3811
		3812	The type C<double> is used to represent timestamps. It is required to
		3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3814	enough for at least into the year 4000. This requirement is fulfilled by
		3815	implementations implementing IEEE 754 (basically all existing ones).
		3816
		3817	=back
		3818
		3819	If you know of other additional requirements drop me a note.
		3820
		3821
		3822	=head1 ALGORITHMIC COMPLEXITIES
		3823
		3824	In this section the complexities of (many of) the algorithms used inside
		3825	libev will be documented. For complexity discussions about backends see
		3826	the documentation for C<ev_default_init>.
		3827
		3828	All of the following are about amortised time: If an array needs to be
		3829	extended, libev needs to realloc and move the whole array, but this
		3830	happens asymptotically rarer with higher number of elements, so O(1) might
		3831	mean that libev does a lengthy realloc operation in rare cases, but on
		3832	average it is much faster and asymptotically approaches constant time.
		3833
		3834	=over 4
		3835
		3836	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3837
		3838	This means that, when you have a watcher that triggers in one hour and
		3839	there are 100 watchers that would trigger before that, then inserting will
		3840	have to skip roughly seven (C<ld 100>) of these watchers.
		3841
		3842	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3843
		3844	That means that changing a timer costs less than removing/adding them,
		3845	as only the relative motion in the event queue has to be paid for.
		3846
		3847	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3848
		3849	These just add the watcher into an array or at the head of a list.
		3850
		3851	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3852
		3853	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3854
		3855	These watchers are stored in lists, so they need to be walked to find the
		3856	correct watcher to remove. The lists are usually short (you don't usually
		3857	have many watchers waiting for the same fd or signal: one is typical, two
		3858	is rare).
		3859
		3860	=item Finding the next timer in each loop iteration: O(1)
		3861
		3862	By virtue of using a binary or 4-heap, the next timer is always found at a
		3863	fixed position in the storage array.
		3864
		3865	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3866
		3867	A change means an I/O watcher gets started or stopped, which requires
		3868	libev to recalculate its status (and possibly tell the kernel, depending
		3869	on backend and whether C<ev_io_set> was used).
		3870
		3871	=item Activating one watcher (putting it into the pending state): O(1)
		3872
		3873	=item Priority handling: O(number_of_priorities)
		3874
		3875	Priorities are implemented by allocating some space for each
		3876	priority. When doing priority-based operations, libev usually has to
		3877	linearly search all the priorities, but starting/stopping and activating
		3878	watchers becomes O(1) with respect to priority handling.
		3879
		3880	=item Sending an ev_async: O(1)
		3881
		3882	=item Processing ev_async_send: O(number_of_async_watchers)
		3883
		3884	=item Processing signals: O(max_signal_number)
		3885
		3886	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3887	calls in the current loop iteration. Checking for async and signal events
		3888	involves iterating over all running async watchers or all signal numbers.
		3889
		3890	=back
		3891
3166		3892
3167	=head1 AUTHOR	3893	=head1 AUTHOR
3168		3894
3169	Marc Lehmann <libev@schmorp.de>.	3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3170		3896

Diff Legend

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