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Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC vs.
Revision 1.184 by root, Tue Sep 23 09:11:14 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_ struct 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_ struct 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	struct 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
…		…
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
…		…
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))
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 (;;)
…		…
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));
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.
…		…
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 library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260		284
261	If you use threads, a common model is to run the default event loop
262	in your main thread (or in a separate thread) and for each thread you
263	create, you also create another event loop. Libev itself does no locking
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
268	=over 4	285	=over 4
269		286
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		288
272	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		293
277	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
278	function.	295	function.
279		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	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	302	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	303	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	304	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	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	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	336	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	337	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	338	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	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	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	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	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.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	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	358	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	359	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	360	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	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
342		367
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		369
345	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	371	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	372	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,	373	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	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	375	performance tips.
351		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		381
354	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	383	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),	384	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	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	388	support for dup.
361		389
362	While stopping, setting and starting an I/O watcher in the same iteration	390	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	391	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	394	very well if you register events for both fds.
367		395
368	Please note that epoll sometimes generates spurious notifications, so you	396	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	397	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.	398	(or space) is available.
371		399
372	Best performance from this backend is achieved by not unregistering all	400	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.	401	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
375		405
376	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	407	all kernel versions tested so far.
378		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		413
381	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		420
389	You still can embed kqueue into a normal poll or select backend and use it	421	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	422	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.	423	the target platform). See C<ev_embed> watchers for more info.
392		424
393	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	427	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	428	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	429	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
399		431
400	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
401		433
402	While nominally embeddable in other event loops, this doesn't work	434	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	435	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	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
408		444
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		446
411	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		453
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	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)).	455	it's really slow, but it still scales very well (O(active_fds)).
420		456
421	Please note that solaris event ports can deliver a lot of spurious	457	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	458	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
424		460
425	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	464	might perform better.
429		465
430	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
433		473
434	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
435		475
436	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		479
440	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
441		481
442	=back	482	=back
443		483
444	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	485	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.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		487
448	The most typical usage is like this:	488	Example: This is the most typical usage.
449		489
450	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		492
453	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	494	environment settings to be taken into account:
455		495
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		497
458	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	499	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):	500	private event loop and only if you know the OS supports your types of
		501	fds):
461		502
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		504
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		506
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
470		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
471	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
472		517
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	519	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
476		521
477	=item ev_default_destroy ()	522	=item ev_default_destroy ()
478		523
479	Destroys the default loop again (frees all memory and kernel state	524	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	525	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	526	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>	527	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	530	for example).
486		531
487	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
519		564
520	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
521		566
522	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
524	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
525		571
526	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
527		573
528	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
529		576
530	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
531		578
532	Returns the count of loop iterations for the loop, which is identical to	579	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	580	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	595	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	596	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	597	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).	598	event occurring (or more correctly, libev finding out about it).
552		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
553	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
554		613
555	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
556	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
557	events.	616	events.
…		…
559	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
560	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
561		620
562	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
563	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
564	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
565	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
566	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
567		627
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
570	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
571		632
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	634	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	635	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	636	be an event internal to libev itself, so there is no guarentee that a
576	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
579		644
580	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
581		646
582	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
586	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	662	- Queue all expired timers.
597	- Queue all outstanding periodics.	663	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	665	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
601	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
608	anymore.	674	anymore.
609		675
610	... queue jobs here, make sure they register event watchers as long	676	... 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..)	677	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
613	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
614		680
615	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
616		682
617	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
618	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
…		…
625		691
626	=item ev_unref (loop)	692	=item ev_unref (loop)
627		693
628	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
629	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
630	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
631	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
632	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
633	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
634	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
635	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
636	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
637	libraries. Just remember to I<unref after start> and I<ref before stop>	706	libraries. Just remember to I<unref after start> and I<ref before stop>
638	(but only if the watcher wasn't active before, or was active before,	707	(but only if the watcher wasn't active before, or was active before,
639	respectively).	708	respectively).
640		709
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
642	running when nothing else is active.	711	running when nothing else is active.
643		712
644	struct ev_signal exitsig;	713	struct ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	716	evf_unref (loop);
648		717
649	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
650		719
651	ev_ref (loop);	720	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
653		722
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		724
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		726
658	These advanced functions influence the time that libev will spend waiting	727	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	728	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.	729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
661		731
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	732	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	733	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
665		736
666	The background is that sometimes your program runs just fast enough to	737	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	738	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	739	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	740	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	741	overhead for the actual polling but can deliver many events at once.
671		742
672	By setting a higher I<io collect interval> you allow libev to spend more	743	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,	744	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	746	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.	747	introduce an additional C<ev_sleep ()> call into most loop iterations.
677		748
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	749	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	750	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	751	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	753	value will not introduce any overhead in libev.
683		754
684	Many (busy) programs can usually benefit by setting the io collect	755	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	756	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	757	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>,	758	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.	759	as this approaches the timing granularity of most systems.
		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
		768	=item ev_loop_verify (loop)
		769
		770	This function only does something when C<EV_VERIFY> support has been
		771	compiled in. which is the default for non-minimal builds. It tries to go
		772	through all internal structures and checks them for validity. If anything
		773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
		775
		776	This can be used to catch bugs inside libev itself: under normal
		777	circumstances, this function will never abort as of course libev keeps its
		778	data structures consistent.
689		779
690	=back	780	=back
691		781
692		782
693	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
694		784
695	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
696	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
697	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
698		788
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
700	{	790	{
701	ev_io_stop (w);	791	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
703	}	793	}
704		794
705	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
706	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
707	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
710	ev_loop (loop, 0);	800	ev_loop (loop, 0);
711		801
712	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
713	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
714	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
715		805
716	Each watcher structure must be initialised by a call to C<ev_init	806	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	807	(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	808	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	809	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	810	is readable and/or writable).
721		811
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
723	with arguments specific to this watcher type. There is also a macro	813	with arguments specific to this watcher type. There is also a macro
…		…
799		889
800	The given async watcher has been asynchronously notified (see C<ev_async>).	890	The given async watcher has been asynchronously notified (see C<ev_async>).
801		891
802	=item C<EV_ERROR>	892	=item C<EV_ERROR>
803		893
804	An unspecified error has occured, the watcher has been stopped. This might	894	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	895	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	896	ran out of memory, a file descriptor was found to be closed or any other
807	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
808	with the watcher being stopped.	898	with the watcher being stopped.
809		899
810	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
811	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
812	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
813	with the error from read() or write(). This will not work in multithreaded	903	the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
815		906
816	=back	907	=back
817		908
818	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
819		910
…		…
835	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
836		927
837	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
838	int revents)>.	929	int revents)>.
839		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
841		938
842	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
843	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
844	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
846	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
847		944
848	Although some watcher types do not have type-specific arguments	945	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.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		947
		948	See C<ev_init>, above, for an example.
		949
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		951
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	953	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
856		959
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		961
859	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
861		969
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
863		971
864	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
865	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
922		1030
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1032
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1033	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	1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
928		1037
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1039
931	If the watcher is pending, this function returns clears its pending status	1040	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	1041	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>.	1042	watcher isn't pending it does nothing and returns C<0>.
934		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
935	=back	1047	=back
936		1048
937		1049
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1051
940	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
941	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
942	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
943	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
944	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
945	data:	1057	data:
946		1058
947	struct my_io	1059	struct my_io
948	{	1060	{
949	struct ev_io io;	1061	struct ev_io io;
950	int otherfd;	1062	int otherfd;
951	void *somedata;	1063	void *somedata;
952	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
953	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1070
955	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1072	can cast it back to your own type:
957		1073
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
959	{	1075	{
960	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
961	...	1077	...
962	}	1078	}
963		1079
964	More interesting and less C-conformant ways of casting your callback type	1080	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1081	instead have been omitted.
966		1082
967	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
968	watchers:	1084	embedded watchers:
969		1085
970	struct my_biggy	1086	struct my_biggy
971	{	1087	{
972	int some_data;	1088	int some_data;
973	ev_timer t1;	1089	ev_timer t1;
974	ev_timer t2;	1090	ev_timer t2;
975	}	1091	}
976		1092
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1093	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
979		1098
980	#include <stddef.h>	1099	#include <stddef.h>
981		1100
982	static void	1101	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
984	{	1103	{
985	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1106	}
988		1107
989	static void	1108	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
991	{	1110	{
992	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1113	}
995		1114
996		1115
997	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
998		1117
999	This section describes each watcher in detail, but will not repeat	1118	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	1142	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	1143	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	1144	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1145	required if you know what you are doing).
1027		1146
1028	If you must do this, then force the use of a known-to-be-good backend	1147	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	1148	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1031		1150
1032	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1152	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	1153	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	1154	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	1155	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	1156	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	1157	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.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1159
1041	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
1042	play around with an Xlib connection), then you have to seperately re-test	1161	not play around with an Xlib connection), then you have to separately
1043	whether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
1045	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
1046		1169
1047	=head3 The special problem of disappearing file descriptors	1170	=head3 The special problem of disappearing file descriptors
1048		1171
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1172	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,	1173	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	1174	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	1175	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	1176	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	1177	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1178	fact, a different file descriptor.
1056		1179
…		…
1085	To support fork in your programs, you either have to call	1208	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1211	C<EVBACKEND_POLL>.
1089		1212
		1213	=head3 The special problem of SIGPIPE
		1214
		1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1216	when writing to a pipe whose other end has been closed, your program gets
		1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1218	this is sensible behaviour, for daemons, this is usually undesirable.
		1219
		1220	So when you encounter spurious, unexplained daemon exits, make sure you
		1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1222	somewhere, as that would have given you a big clue).
		1223
1090		1224
1091	=head3 Watcher-Specific Functions	1225	=head3 Watcher-Specific Functions
1092		1226
1093	=over 4	1227	=over 4
1094		1228
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1230
1097	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
1098		1232
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1101	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1102		1236
1103	=item int fd [read-only]	1237	=item int fd [read-only]
1104		1238
1105	The file descriptor being watched.	1239	The file descriptor being watched.
1106		1240
…		…
1114		1248
1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1116	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
1117	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
1118		1252
1119	static void	1253	static void
1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1121	{	1255	{
1122	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
1123	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
1124	}	1258	}
1125		1259
1126	...	1260	...
1127	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
1128	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
1129	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1130	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
1131	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
1132		1266
1133		1267
1134	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
1135		1269
1136	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
1138		1272
1139	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
1140	times out after an hour and you reset your system clock to last years	1274	times out after an hour and you reset your system clock to January last
1141	time, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
1144		1290
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
1146	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
1147	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
1148	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
1149	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
1150		1296
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1298
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
1154	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1155	order of execution is undefined.	1301	()>.
1156		1302
1157	=head3 Watcher-Specific Functions and Data Members	1303	=head3 Watcher-Specific Functions and Data Members
1158		1304
1159	=over 4	1305	=over 4
1160		1306
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1308
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1310
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1311	Configure the timer to trigger after C<after> seconds. If C<repeat>
1166	C<0.>, then it will automatically be stopped. If it is positive, then the	1312	is C<0.>, then it will automatically be stopped once the timeout is
1167	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
1169		1316
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1317	The timer itself will do a best-effort at avoiding drift, that is, if
1171	configure a timer to trigger every 10 seconds, then it will trigger at	1318	you configure a timer to trigger every 10 seconds, then it will normally
1172	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
1173	the timer (because it takes longer than those 10 seconds to do stuff) the	1320	keep up with the timer (because it takes longer than those 10 seconds to
1174	timer will not fire more than once per event loop iteration.	1321	do stuff) the timer will not fire more than once per event loop iteration.
1175		1322
1176	=item ev_timer_again (loop, ev_timer *)	1323	=item ev_timer_again (loop, ev_timer *)
1177		1324
1178	This will act as if the timer timed out and restart it again if it is	1325	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
1180		1327
1181	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
1182		1329
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	1330	If the timer is started but non-repeating, stop it (as if it timed out).
1184		1331
1185	If the timer is repeating, either start it if necessary (with the	1332	If the timer is repeating, either start it if necessary (with the
1186	C<repeat> value), or reset the running timer to the C<repeat> value.	1333	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		1334
1188	This sounds a bit complicated, but here is a useful and typical	1335	This sounds a bit complicated, but here is a useful and typical
1189	example: Imagine you have a tcp connection and you want a so-called idle	1336	example: Imagine you have a TCP connection and you want a so-called idle
1190	timeout, that is, you want to be called when there have been, say, 60	1337	timeout, that is, you want to be called when there have been, say, 60
1191	seconds of inactivity on the socket. The easiest way to do this is to	1338	seconds of inactivity on the socket. The easiest way to do this is to
1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1193	C<ev_timer_again> each time you successfully read or write some data. If	1340	C<ev_timer_again> each time you successfully read or write some data. If
1194	you go into an idle state where you do not expect data to travel on the	1341	you go into an idle state where you do not expect data to travel on the
…		…
1208	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1209		1356
1210	This is more slightly efficient then stopping/starting the timer each time	1357	This is more slightly efficient then stopping/starting the timer each time
1211	you want to modify its timeout value.	1358	you want to modify its timeout value.
1212		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
		1365
1213	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1214		1367
1215	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
1216	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
1217	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1218		1371
1219	=back	1372	=back
1220		1373
1221	=head3 Examples	1374	=head3 Examples
1222		1375
1223	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1224		1377
1225	static void	1378	static void
1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1227	{	1380	{
1228	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1229	}	1382	}
1230		1383
1231	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1234		1387
1235	Example: Create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
1236	inactivity.	1389	inactivity.
1237		1390
1238	static void	1391	static void
1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1240	{	1393	{
1241	.. ten seconds without any activity	1394	.. ten seconds without any activity
1242	}	1395	}
1243		1396
1244	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1245	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1246	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1247	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1248		1401
1249	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
1250	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1251	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1252		1405
1253		1406
1254	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1255		1408
1256	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1258		1411
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1260	but on wallclock time (absolute time). You can tell a periodic watcher	1413	but on wall clock time (absolute time). You can tell a periodic watcher
1261	to trigger "at" some specific point in time. For example, if you tell a	1414	to trigger after some specific point in time. For example, if you tell a
1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1263	+ 10.>) and then reset your system clock to the last year, then it will	1416	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1417	clock to January of the previous year, then it will take more than year
1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1265	roughly 10 seconds later).	1419	roughly 10 seconds later as it uses a relative timeout).
1266		1420
1267	They can also be used to implement vastly more complex timers, such as	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
1268	triggering an event on each midnight, local time or other, complicated,	1422	such as triggering an event on each "midnight, local time", or other
1269	rules.	1423	complicated rules.
1270		1424
1271	As with timers, the callback is guarenteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
1272	time (C<at>) has been passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
1273	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
1274		1428
1275	=head3 Watcher-Specific Functions and Data Members	1429	=head3 Watcher-Specific Functions and Data Members
1276		1430
1277	=over 4	1431	=over 4
1278		1432
1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1280		1434
1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1282		1436
1283	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
1284	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1285		1439
1286	=over 4	1440	=over 4
1287		1441
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1289		1443
1290	In this configuration the watcher triggers an event at the wallclock time	1444	In this configuration the watcher triggers an event after the wall clock
1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1445	time C<at> has passed. It will not repeat and will not adjust when a time
1292	that is, if it is to be run at January 1st 2011 then it will run when the	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1293	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1294		1448
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1296		1450
1297	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
1298	C<at + N * interval> time (for some integer N, which can also be negative)	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1299	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1300		1454
1301	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
1302	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1303		1458
1304	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1305		1460
1306	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1307	but only that the the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
1308	full hour (UTC), or more correctly, when the system time is evenly divisible	1463	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	1464	by 3600.
1310		1465
1311	Another way to think about it (for the mathematically inclined) is that	1466	Another way to think about it (for the mathematically inclined) is that
1312	C<ev_periodic> will try to run the callback in this mode at the next possible	1467	C<ev_periodic> will try to run the callback in this mode at the next possible
1313	time where C<time = at (mod interval)>, regardless of any time jumps.	1468	time where C<time = at (mod interval)>, regardless of any time jumps.
1314		1469
1315	For numerical stability it is preferable that the C<at> value is near	1470	For numerical stability it is preferable that the C<at> value is near
1316	C<ev_now ()> (the current time), but there is no range requirement for	1471	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	1472	this value, and in fact is often specified as zero.
		1473
		1474	Note also that there is an upper limit to how often a timer can fire (CPU
		1475	speed for example), so if C<interval> is very small then timing stability
		1476	will of course deteriorate. Libev itself tries to be exact to be about one
		1477	millisecond (if the OS supports it and the machine is fast enough).
1318		1478
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1320		1480
1321	In this mode the values for C<interval> and C<at> are both being	1481	In this mode the values for C<interval> and C<at> are both being
1322	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	1483	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	1484	current time as second argument.
1325		1485
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1327	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1329	starting an C<ev_prepare> watcher, which is legal).
1330		1488
		1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1491	only event loop modification you are allowed to do).
		1492
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1332	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1333		1495
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1335	{	1497	{
1336	return now + 60.;	1498	return now + 60.;
1337	}	1499	}
…		…
1339	It must return the next time to trigger, based on the passed time value	1501	It must return the next time to trigger, based on the passed time value
1340	(that is, the lowest time value larger than to the second argument). It	1502	(that is, the lowest time value larger than to the second argument). It
1341	will usually be called just before the callback will be triggered, but	1503	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	1504	might be called at other times, too.
1343		1505
1344	NOTE: I<< This callback must always return a time that is later than the	1506	NOTE: I<< This callback must always return a time that is higher than or
1345	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1346		1508
1347	This can be used to create very complex timers, such as a timer that	1509	This can be used to create very complex timers, such as a timer that
1348	triggers on each midnight, local time. To do this, you would calculate the	1510	triggers on "next midnight, local time". To do this, you would calculate the
1349	next midnight after C<now> and return the timestamp value for this. How	1511	next midnight after C<now> and return the timestamp value for this. How
1350	you do this is, again, up to you (but it is not trivial, which is the main	1512	you do this is, again, up to you (but it is not trivial, which is the main
1351	reason I omitted it as an example).	1513	reason I omitted it as an example).
1352		1514
1353	=back	1515	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1519	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	1521	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1522	program when the crontabs have changed).
1361		1523
		1524	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1525
		1526	When active, returns the absolute time that the watcher is supposed to
		1527	trigger next.
		1528
1362	=item ev_tstamp offset [read-write]	1529	=item ev_tstamp offset [read-write]
1363		1530
1364	When repeating, this contains the offset value, otherwise this is the	1531	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1533
…		…
1377		1544
1378	The current reschedule callback, or C<0>, if this functionality is	1545	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	1546	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	1547	the periodic timer fires or C<ev_periodic_again> is being called.
1381		1548
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386
1387	=back	1549	=back
1388		1550
1389	=head3 Examples	1551	=head3 Examples
1390		1552
1391	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1394		1556
1395	static void	1557	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1397	{	1559	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1399	}	1561	}
1400		1562
1401	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1404		1566
1405	Example: The same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1406		1568
1407	#include <math.h>	1569	#include <math.h>
1408		1570
1409	static ev_tstamp	1571	static ev_tstamp
1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1411	{	1573	{
1412	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1413	}	1575	}
1414		1576
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1416		1578
1417	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1418		1580
1419	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1420	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1421	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1422	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1423		1585
1424		1586
1425	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1426		1588
1427	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1428	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1429	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1430	normal event processing, like any other event.	1592	normal event processing, like any other event.
1431		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1432	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1433	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1434	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1435	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1436	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1437	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
1438		1604
1439	If possible and supported, libev will install its handlers with	1605	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1441	interrupted. If you have a problem with syscalls getting interrupted by	1607	interrupted. If you have a problem with system calls getting interrupted by
1442	signals you can block all signals in an C<ev_check> watcher and unblock	1608	signals you can block all signals in an C<ev_check> watcher and unblock
1443	them in an C<ev_prepare> watcher.	1609	them in an C<ev_prepare> watcher.
1444		1610
1445	=head3 Watcher-Specific Functions and Data Members	1611	=head3 Watcher-Specific Functions and Data Members
1446		1612
…		…
1461		1627
1462	=head3 Examples	1628	=head3 Examples
1463		1629
1464	Example: Try to exit cleanly on SIGINT and SIGTERM.	1630	Example: Try to exit cleanly on SIGINT and SIGTERM.
1465		1631
1466	static void	1632	static void
1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1468	{	1634	{
1469	ev_unloop (loop, EVUNLOOP_ALL);	1635	ev_unloop (loop, EVUNLOOP_ALL);
1470	}	1636	}
1471		1637
1472	struct ev_signal signal_watcher;	1638	struct ev_signal signal_watcher;
1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474	ev_signal_start (loop, &sigint_cb);	1640	ev_signal_start (loop, &sigint_cb);
1475		1641
1476		1642
1477	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1478		1644
1479	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1480	some child status changes (most typically when a child of yours dies). It	1646	some child status changes (most typically when a child of yours dies or
1481	is permissible to install a child watcher I<after> the child has been	1647	exits). It is permissible to install a child watcher I<after> the child
1482	forked (which implies it might have already exited), as long as the event	1648	has been forked (which implies it might have already exited), as long
1483	loop isn't entered (or is continued from a watcher).	1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
1484		1653
1485	Only the default event loop is capable of handling signals, and therefore	1654	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	1655	you can only register child watchers in the default event loop.
1487		1656
1488	=head3 Process Interaction	1657	=head3 Process Interaction
1489		1658
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	1660	initialised. This is necessary to guarantee proper behaviour even if
1492	the first child watcher is started after the child exits. The occurance	1661	the first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	1663	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	1664	children, even ones not watched.
1496		1665
1497	=head3 Overriding the Built-In Processing	1666	=head3 Overriding the Built-In Processing
…		…
1501	handler, you can override it easily by installing your own handler for	1670	handler, you can override it easily by installing your own handler for
1502	C<SIGCHLD> after initialising the default loop, and making sure the	1671	C<SIGCHLD> after initialising the default loop, and making sure the
1503	default loop never gets destroyed. You are encouraged, however, to use an	1672	default loop never gets destroyed. You are encouraged, however, to use an
1504	event-based approach to child reaping and thus use libev's support for	1673	event-based approach to child reaping and thus use libev's support for
1505	that, so other libev users can use C<ev_child> watchers freely.	1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
1506		1682
1507	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1508		1684
1509	=over 4	1685	=over 4
1510		1686
…		…
1539	=head3 Examples	1715	=head3 Examples
1540		1716
1541	Example: C<fork()> a new process and install a child handler to wait for	1717	Example: C<fork()> a new process and install a child handler to wait for
1542	its completion.	1718	its completion.
1543		1719
1544	ev_child cw;	1720	ev_child cw;
1545		1721
1546	static void	1722	static void
1547	child_cb (EV_P_ struct ev_child *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1548	{	1724	{
1549	ev_child_stop (EV_A_ w);	1725	ev_child_stop (EV_A_ w);
1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1551	}	1727	}
1552		1728
1553	pid_t pid = fork ();	1729	pid_t pid = fork ();
1554		1730
1555	if (pid < 0)	1731	if (pid < 0)
1556	// error	1732	// error
1557	else if (pid == 0)	1733	else if (pid == 0)
1558	{	1734	{
1559	// the forked child executes here	1735	// the forked child executes here
1560	exit (1);	1736	exit (1);
1561	}	1737	}
1562	else	1738	else
1563	{	1739	{
1564	ev_child_init (&cw, child_cb, pid, 0);	1740	ev_child_init (&cw, child_cb, pid, 0);
1565	ev_child_start (EV_DEFAULT_ &cw);	1741	ev_child_start (EV_DEFAULT_ &cw);
1566	}	1742	}
1567		1743
1568		1744
1569	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1570		1746
1571	This watches a filesystem path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
1572	C<stat> regularly (or when the OS says it changed) and sees if it changed	1748	C<stat> regularly (or when the OS says it changed) and sees if it changed
1573	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1574		1750
1575	The path does not need to exist: changing from "path exists" to "path does	1751	The path does not need to exist: changing from "path exists" to "path does
1576	not exist" is a status change like any other. The condition "path does	1752	not exist" is a status change like any other. The condition "path does
…		…
1579	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1580		1756
1581	The path I<should> be absolute and I<must not> end in a slash. If it is	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1582	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1583		1759
1584	Since there is no standard to do this, the portable implementation simply	1760	Since there is no standard kernel interface to do this, the portable
1585	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1586	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1587	a polling interval of C<0> (highly recommended!) then a I<suitable,	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1588	unspecified default> value will be used (which you can expect to be around	1764	then a I<suitable, unspecified default> value will be used (which
1589	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1590	impose a minimum interval which is currently around C<0.1>, but thats	1766	dynamically). Libev will also impose a minimum interval which is currently
1591	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1592		1768
1593	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1594	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1771	resource-intensive.
1596		1772
1597	At the time of this writing, only the Linux inotify interface is	1773	At the time of this writing, the only OS-specific interface implemented
1598	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1599	reader). Inotify will be used to give hints only and should not change the	1775	an exercise for the reader. Note, however, that the author sees no way
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1601	to fall back to regular polling again even with inotify, but changes are
1602	usually detected immediately, and if the file exists there will be no
1603	polling.
1604		1777
1605	=head3 Inotify	1778	=head3 ABI Issues (Largefile Support)
		1779
		1780	Libev by default (unless the user overrides this) uses the default
		1781	compilation environment, which means that on systems with large file
		1782	support disabled by default, you get the 32 bit version of the stat
		1783	structure. When using the library from programs that change the ABI to
		1784	use 64 bit file offsets the programs will fail. In that case you have to
		1785	compile libev with the same flags to get binary compatibility. This is
		1786	obviously the case with any flags that change the ABI, but the problem is
		1787	most noticeably disabled with ev_stat and large file support.
		1788
		1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
1606		1796
1607	When C<inotify (7)> support has been compiled into libev (generally only	1797	When C<inotify (7)> support has been compiled into libev (generally only
1608	available on Linux) and present at runtime, it will be used to speed up	1798	available with Linux) and present at runtime, it will be used to speed up
1609	change detection where possible. The inotify descriptor will be created lazily	1799	change detection where possible. The inotify descriptor will be created lazily
1610	when the first C<ev_stat> watcher is being started.	1800	when the first C<ev_stat> watcher is being started.
1611		1801
1612	Inotify presense does not change the semantics of C<ev_stat> watchers	1802	Inotify presence does not change the semantics of C<ev_stat> watchers
1613	except that changes might be detected earlier, and in some cases, to avoid	1803	except that changes might be detected earlier, and in some cases, to avoid
1614	making regular C<stat> calls. Even in the presense of inotify support	1804	making regular C<stat> calls. Even in the presence of inotify support
1615	there are many cases where libev has to resort to regular C<stat> polling.	1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
1616		1807
1617	(There is no support for kqueue, as apparently it cannot be used to	1808	There is no support for kqueue, as apparently it cannot be used to
1618	implement this functionality, due to the requirement of having a file	1809	implement this functionality, due to the requirement of having a file
1619	descriptor open on the object at all times).	1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
1620		1812
1621	=head3 The special problem of stat time resolution	1813	=head3 The special problem of stat time resolution
1622		1814
1623	The C<stat ()> syscall only supports full-second resolution portably, and	1815	The C<stat ()> system call only supports full-second resolution portably, and
1624	even on systems where the resolution is higher, many filesystems still	1816	even on systems where the resolution is higher, most file systems still
1625	only support whole seconds.	1817	only support whole seconds.
1626		1818
1627	That means that, if the time is the only thing that changes, you might	1819	That means that, if the time is the only thing that changes, you can
1628	miss updates: on the first update, C<ev_stat> detects a change and calls	1820	easily miss updates: on the first update, C<ev_stat> detects a change and
1629	your callback, which does something. When there is another update within	1821	calls your callback, which does something. When there is another update
1630	the same second, C<ev_stat> will be unable to detect it.	1822	within the same second, C<ev_stat> will be unable to detect unless the
		1823	stat data does change in other ways (e.g. file size).
1631		1824
1632	The solution to this is to delay acting on a change for a second (or till	1825	The solution to this is to delay acting on a change for slightly more
1633	the next second boundary), using a roughly one-second delay C<ev_timer>	1826	than a second (or till slightly after the next full second boundary), using
1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1635	is added to work around small timing inconsistencies of some operating	1828	ev_timer_again (loop, w)>).
1636	systems.	1829
		1830	The C<.02> offset is added to work around small timing inconsistencies
		1831	of some operating systems (where the second counter of the current time
		1832	might be be delayed. One such system is the Linux kernel, where a call to
		1833	C<gettimeofday> might return a timestamp with a full second later than
		1834	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1835	update file times then there will be a small window where the kernel uses
		1836	the previous second to update file times but libev might already execute
		1837	the timer callback).
1637		1838
1638	=head3 Watcher-Specific Functions and Data Members	1839	=head3 Watcher-Specific Functions and Data Members
1639		1840
1640	=over 4	1841	=over 4
1641		1842
…		…
1647	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1648	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1649	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1650	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1651		1852
1652	The callback will be receive C<EV_STAT> when a change was detected,	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1653	relative to the attributes at the time the watcher was started (or the	1854	relative to the attributes at the time the watcher was started (or the
1654	last change was detected).	1855	last change was detected).
1655		1856
1656	=item ev_stat_stat (loop, ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1657		1858
1658	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1659	watched path in your callback, you could call this fucntion to avoid	1860	watched path in your callback, you could call this function to avoid
1660	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1661	useful simply to find out the new values.	1862	the only one changing the path). Can also be useful simply to find out the
		1863	new values.
1662		1864
1663	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1664		1866
1665	The most-recently detected attributes of the file. Although the type is of	1867	The most-recently detected attributes of the file. Although the type is
1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1868	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1667	suitable for your system. If the C<st_nlink> member is C<0>, then there	1869	suitable for your system, but you can only rely on the POSIX-standardised
		1870	members to be present. If the C<st_nlink> member is C<0>, then there was
1668	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1669		1872
1670	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1671		1874
1672	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1673	C<prev> != C<attr>.	1876	C<prev> != C<attr>, or, more precisely, one or more of these members
		1877	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1878	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1674		1879
1675	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1676		1881
1677	The specified interval.	1882	The specified interval.
1678		1883
1679	=item const char *path [read-only]	1884	=item const char *path [read-only]
1680		1885
1681	The filesystem path that is being watched.	1886	The file system path that is being watched.
1682		1887
1683	=back	1888	=back
1684		1889
1685	=head3 Examples	1890	=head3 Examples
1686		1891
1687	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1688		1893
1689	static void	1894	static void
1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1691	{	1896	{
1692	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1693	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1694	{	1899	{
1695	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1696	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1697	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1698	}	1903	}
1699	else	1904	else
1700	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1701	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1702	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1703	}	1908	}
1704		1909
1705	...	1910	...
1706	ev_stat passwd;	1911	ev_stat passwd;
1707		1912
1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1709	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
1710		1915
1711	Example: Like above, but additionally use a one-second delay so we do not	1916	Example: Like above, but additionally use a one-second delay so we do not
1712	miss updates (however, frequent updates will delay processing, too, so	1917	miss updates (however, frequent updates will delay processing, too, so
1713	one might do the work both on C<ev_stat> callback invocation I<and> on	1918	one might do the work both on C<ev_stat> callback invocation I<and> on
1714	C<ev_timer> callback invocation).	1919	C<ev_timer> callback invocation).
1715		1920
1716	static ev_stat passwd;	1921	static ev_stat passwd;
1717	static ev_timer timer;	1922	static ev_timer timer;
1718		1923
1719	static void	1924	static void
1720	timer_cb (EV_P_ ev_timer *w, int revents)	1925	timer_cb (EV_P_ ev_timer *w, int revents)
1721	{	1926	{
1722	ev_timer_stop (EV_A_ w);	1927	ev_timer_stop (EV_A_ w);
1723		1928
1724	/* now it's one second after the most recent passwd change */	1929	/* now it's one second after the most recent passwd change */
1725	}	1930	}
1726		1931
1727	static void	1932	static void
1728	stat_cb (EV_P_ ev_stat *w, int revents)	1933	stat_cb (EV_P_ ev_stat *w, int revents)
1729	{	1934	{
1730	/* reset the one-second timer */	1935	/* reset the one-second timer */
1731	ev_timer_again (EV_A_ &timer);	1936	ev_timer_again (EV_A_ &timer);
1732	}	1937	}
1733		1938
1734	...	1939	...
1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	1941	ev_stat_start (loop, &passwd);
1737	ev_timer_init (&timer, timer_cb, 0., 1.01);	1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1738		1943
1739		1944
1740	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1741		1946
1742	Idle watchers trigger events when no other events of the same or higher	1947	Idle watchers trigger events when no other events of the same or higher
1743	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1744	count).	1949	as receiving "events").
1745		1950
1746	That is, as long as your process is busy handling sockets or timeouts	1951	That is, as long as your process is busy handling sockets or timeouts
1747	(or even signals, imagine) of the same or higher priority it will not be	1952	(or even signals, imagine) of the same or higher priority it will not be
1748	triggered. But when your process is idle (or only lower-priority watchers	1953	triggered. But when your process is idle (or only lower-priority watchers
1749	are pending), the idle watchers are being called once per event loop	1954	are pending), the idle watchers are being called once per event loop
…		…
1773	=head3 Examples	1978	=head3 Examples
1774		1979
1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1776	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1777		1982
1778	static void	1983	static void
1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1780	{	1985	{
1781	free (w);	1986	free (w);
1782	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1783	// no longer anything immediate to do.	1988	// no longer anything immediate to do.
1784	}	1989	}
1785		1990
1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1787	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1788	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1789		1994
1790		1995
1791	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1792		1997
1793	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1794	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1795	afterwards.	2000	afterwards.
1796		2001
1797	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1798	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1801	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1802	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1803	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1804		2009
1805	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1806	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1807	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1808	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1809	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1810	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1811	watcher).	2016	watcher).
1812		2017
1813	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1814	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1816	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1817	any events that occured (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1818	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1819	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1820	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1821		2026
1822	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1823	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1824	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1825	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1828	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1829	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1830		2035
1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1832	priority, to ensure that they are being run before any other watchers	2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1834	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1835	supports this, they will be called before other C<ev_check> watchers	2042	might get executed before other C<ev_check> watchers did their job. As
1836	did their job. As C<ev_check> watchers are often used to embed other	2043	C<ev_check> watchers are often used to embed other (non-libev) event
1837	(non-libev) event loops those other event loops might be in an unusable	2044	loops those other event loops might be in an unusable state until their
1838	state until their C<ev_check> watcher ran (always remind yourself to	2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1839	coexist peacefully with others).	2046	others).
1840		2047
1841	=head3 Watcher-Specific Functions and Data Members	2048	=head3 Watcher-Specific Functions and Data Members
1842		2049
1843	=over 4	2050	=over 4
1844		2051
…		…
1846		2053
1847	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1848		2055
1849	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1850	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1851	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1852		2060
1853	=back	2061	=back
1854		2062
1855	=head3 Examples	2063	=head3 Examples
1856		2064
1857	There are a number of principal ways to embed other event loops or modules	2065	There are a number of principal ways to embed other event loops or modules
1858	into libev. Here are some ideas on how to include libadns into libev	2066	into libev. Here are some ideas on how to include libadns into libev
1859	(there is a Perl module named C<EV::ADNS> that does this, which you could	2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
1860	use for an actually working example. Another Perl module named C<EV::Glib>	2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1862	into the Glib event loop).	2070	Glib event loop).
1863		2071
1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1865	and in a check watcher, destroy them and call into libadns. What follows	2073	and in a check watcher, destroy them and call into libadns. What follows
1866	is pseudo-code only of course. This requires you to either use a low	2074	is pseudo-code only of course. This requires you to either use a low
1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1868	the callbacks for the IO/timeout watchers might not have been called yet.	2076	the callbacks for the IO/timeout watchers might not have been called yet.
1869		2077
1870	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1871	static ev_timer tw;	2079	static ev_timer tw;
1872		2080
1873	static void	2081	static void
1874	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1875	{	2083	{
1876	}	2084	}
1877		2085
1878	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1879	static void	2087	static void
1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1881	{	2089	{
1882	int timeout = 3600000;	2090	int timeout = 3600000;
1883	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1884	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1886		2094
1887	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1888	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1889	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1890		2098
1891	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1892	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1893	{	2101	{
1894	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1895	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1897		2105
1898	fds [i].revents = 0;	2106	fds [i].revents = 0;
1899	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1900	}	2108	}
1901	}	2109	}
1902		2110
1903	// stop all watchers after blocking	2111	// stop all watchers after blocking
1904	static void	2112	static void
1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1906	{	2114	{
1907	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1908		2116
1909	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1910	{	2118	{
1911	// set the relevant poll flags	2119	// set the relevant poll flags
1912	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1913	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1914	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1917		2125
1918	// now stop the watcher	2126	// now stop the watcher
1919	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
1920	}	2128	}
1921		2129
1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1923	}	2131	}
1924		2132
1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1926	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
1927		2135
1928	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
1929	notification (adns does), you can also make use of the actual watcher	2137	notification (libadns does), you can also make use of the actual watcher
1930	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
1931		2139
1932	static void	2140	static void
1933	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
1934	{	2142	{
1935	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
1936	update_now (EV_A);	2144	update_now (EV_A);
1937		2145
1938	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
1939	}	2147	}
1940		2148
1941	static void	2149	static void
1942	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
1943	{	2151	{
1944	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1945	update_now (EV_A);	2153	update_now (EV_A);
1946		2154
1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1949	}	2157	}
1950		2158
1951	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
1952		2160
1953	Method 4: Do not use a prepare or check watcher because the module you	2161	Method 4: Do not use a prepare or check watcher because the module you
1954	want to embed is too inflexible to support it. Instead, youc na override	2162	want to embed is not flexible enough to support it. Instead, you can
1955	their poll function. The drawback with this solution is that the main	2163	override their poll function. The drawback with this solution is that the
1956	loop is now no longer controllable by EV. The C<Glib::EV> module does	2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1957	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
1958		2167
1959	static gint	2168	static gint
1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1961	{	2170	{
1962	int got_events = 0;	2171	int got_events = 0;
1963		2172
1964	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1966		2175
1967	if (timeout >= 0)	2176	if (timeout >= 0)
1968	// create/start timer	2177	// create/start timer
1969		2178
1970	// poll	2179	// poll
1971	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
1972		2181
1973	// stop timer again	2182	// stop timer again
1974	if (timeout >= 0)	2183	if (timeout >= 0)
1975	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
1976		2185
1977	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
1978	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
1979	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
1980		2189
1981	return got_events;	2190	return got_events;
1982	}	2191	}
1983		2192
1984		2193
1985	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1986		2195
1987	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
…		…
1993	prioritise I/O.	2202	prioritise I/O.
1994		2203
1995	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
1996	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
1997	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
1998	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
1999	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
2000	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
2001	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2002		2212
2003	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
2004	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
2005	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
2006	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
2007	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
2008		2218
2009	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
2010	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
2011	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2012	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
2020	interested in that.	2230	interested in that.
2021		2231
2022	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
2023	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2024	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
2025	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
2026		2237
2027	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
2028	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2029	portable one.	2240	portable one.
2030		2241
2031	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
2032	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
…		…
2043		2254
2044	Configures the watcher to embed the given loop, which must be	2255	Configures the watcher to embed the given loop, which must be
2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2256	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2046	invoked automatically, otherwise it is the responsibility of the callback	2257	invoked automatically, otherwise it is the responsibility of the callback
2047	to invoke it (it will continue to be called until the sweep has been done,	2258	to invoke it (it will continue to be called until the sweep has been done,
2048	if you do not want thta, you need to temporarily stop the embed watcher).	2259	if you do not want that, you need to temporarily stop the embed watcher).
2049		2260
2050	=item ev_embed_sweep (loop, ev_embed *)	2261	=item ev_embed_sweep (loop, ev_embed *)
2051		2262
2052	Make a single, non-blocking sweep over the embedded loop. This works	2263	Make a single, non-blocking sweep over the embedded loop. This works
2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2264	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2054	apropriate way for embedded loops.	2265	appropriate way for embedded loops.
2055		2266
2056	=item struct ev_loop *other [read-only]	2267	=item struct ev_loop *other [read-only]
2057		2268
2058	The embedded event loop.	2269	The embedded event loop.
2059		2270
…		…
2061		2272
2062	=head3 Examples	2273	=head3 Examples
2063		2274
2064	Example: Try to get an embeddable event loop and embed it into the default	2275	Example: Try to get an embeddable event loop and embed it into the default
2065	event loop. If that is not possible, use the default loop. The default	2276	event loop. If that is not possible, use the default loop. The default
2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2277	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2068	used).	2279	used).
2069		2280
2070	struct ev_loop *loop_hi = ev_default_init (0);	2281	struct ev_loop *loop_hi = ev_default_init (0);
2071	struct ev_loop *loop_lo = 0;	2282	struct ev_loop *loop_lo = 0;
2072	struct ev_embed embed;	2283	struct ev_embed embed;
2073		2284
2074	// see if there is a chance of getting one that works	2285	// see if there is a chance of getting one that works
2075	// (remember that a flags value of 0 means autodetection)	2286	// (remember that a flags value of 0 means autodetection)
2076	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2077	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2078	: 0;	2289	: 0;
2079		2290
2080	// if we got one, then embed it, otherwise default to loop_hi	2291	// if we got one, then embed it, otherwise default to loop_hi
2081	if (loop_lo)	2292	if (loop_lo)
2082	{	2293	{
2083	ev_embed_init (&embed, 0, loop_lo);	2294	ev_embed_init (&embed, 0, loop_lo);
2084	ev_embed_start (loop_hi, &embed);	2295	ev_embed_start (loop_hi, &embed);
2085	}	2296	}
2086	else	2297	else
2087	loop_lo = loop_hi;	2298	loop_lo = loop_hi;
2088		2299
2089	Example: Check if kqueue is available but not recommended and create	2300	Example: Check if kqueue is available but not recommended and create
2090	a kqueue backend for use with sockets (which usually work with any	2301	a kqueue backend for use with sockets (which usually work with any
2091	kqueue implementation). Store the kqueue/socket-only event loop in	2302	kqueue implementation). Store the kqueue/socket-only event loop in
2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2093		2304
2094	struct ev_loop *loop = ev_default_init (0);	2305	struct ev_loop *loop = ev_default_init (0);
2095	struct ev_loop *loop_socket = 0;	2306	struct ev_loop *loop_socket = 0;
2096	struct ev_embed embed;	2307	struct ev_embed embed;
2097		2308
2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2100	{	2311	{
2101	ev_embed_init (&embed, 0, loop_socket);	2312	ev_embed_init (&embed, 0, loop_socket);
2102	ev_embed_start (loop, &embed);	2313	ev_embed_start (loop, &embed);
2103	}	2314	}
2104		2315
2105	if (!loop_socket)	2316	if (!loop_socket)
2106	loop_socket = loop;	2317	loop_socket = loop;
2107		2318
2108	// now use loop_socket for all sockets, and loop for everything else	2319	// now use loop_socket for all sockets, and loop for everything else
2109		2320
2110		2321
2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2322	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2112		2323
2113	Fork watchers are called when a C<fork ()> was detected (usually because	2324	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2157	is that the author does not know of a simple (or any) algorithm for a	2368	is that the author does not know of a simple (or any) algorithm for a
2158	multiple-writer-single-reader queue that works in all cases and doesn't	2369	multiple-writer-single-reader queue that works in all cases and doesn't
2159	need elaborate support such as pthreads.	2370	need elaborate support such as pthreads.
2160		2371
2161	That means that if you want to queue data, you have to provide your own	2372	That means that if you want to queue data, you have to provide your own
2162	queue. But at least I can tell you would implement locking around your	2373	queue. But at least I can tell you how to implement locking around your
2163	queue:	2374	queue:
2164		2375
2165	=over 4	2376	=over 4
2166		2377
2167	=item queueing from a signal handler context	2378	=item queueing from a signal handler context
2168		2379
2169	To implement race-free queueing, you simply add to the queue in the signal	2380	To implement race-free queueing, you simply add to the queue in the signal
2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for
2171	some fictitiuous SIGUSR1 handler:	2382	some fictitious SIGUSR1 handler:
2172		2383
2173	static ev_async mysig;	2384	static ev_async mysig;
2174		2385
2175	static void	2386	static void
2176	sigusr1_handler (void)	2387	sigusr1_handler (void)
…		…
2243		2454
2244	=item ev_async_init (ev_async *, callback)	2455	=item ev_async_init (ev_async *, callback)
2245		2456
2246	Initialises and configures the async watcher - it has no parameters of any	2457	Initialises and configures the async watcher - it has no parameters of any
2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2248	believe me.	2459	trust me.
2249		2460
2250	=item ev_async_send (loop, ev_async *)	2461	=item ev_async_send (loop, ev_async *)
2251		2462
2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2254	C<ev_feed_event>, this call is safe to do in other threads, signal or	2465	C<ev_feed_event>, this call is safe to do from other threads, signal or
2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2256	section below on what exactly this means).	2467	section below on what exactly this means).
2257		2468
2258	This call incurs the overhead of a syscall only once per loop iteration,	2469	This call incurs the overhead of a system call only once per loop iteration,
2259	so while the overhead might be noticable, it doesn't apply to repeated	2470	so while the overhead might be noticeable, it doesn't apply to repeated
2260	calls to C<ev_async_send>.	2471	calls to C<ev_async_send>.
		2472
		2473	=item bool = ev_async_pending (ev_async *)
		2474
		2475	Returns a non-zero value when C<ev_async_send> has been called on the
		2476	watcher but the event has not yet been processed (or even noted) by the
		2477	event loop.
		2478
		2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2480	the loop iterates next and checks for the watcher to have become active,
		2481	it will reset the flag again. C<ev_async_pending> can be used to very
		2482	quickly check whether invoking the loop might be a good idea.
		2483
		2484	Not that this does I<not> check whether the watcher itself is pending, only
		2485	whether it has been requested to make this watcher pending.
2261		2486
2262	=back	2487	=back
2263		2488
2264		2489
2265	=head1 OTHER FUNCTIONS	2490	=head1 OTHER FUNCTIONS
…		…
2276	or timeout without having to allocate/configure/start/stop/free one or	2501	or timeout without having to allocate/configure/start/stop/free one or
2277	more watchers yourself.	2502	more watchers yourself.
2278		2503
2279	If C<fd> is less than 0, then no I/O watcher will be started and events	2504	If C<fd> is less than 0, then no I/O watcher will be started and events
2280	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2281	C<events> set will be craeted and started.	2506	C<events> set will be created and started.
2282		2507
2283	If C<timeout> is less than 0, then no timeout watcher will be	2508	If C<timeout> is less than 0, then no timeout watcher will be
2284	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2285	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2286	dubious value.	2511	dubious value.
…		…
2288	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2289	passed an C<revents> set like normal event callbacks (a combination of	2514	passed an C<revents> set like normal event callbacks (a combination of
2290	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2291	value passed to C<ev_once>:	2516	value passed to C<ev_once>:
2292		2517
2293	static void stdin_ready (int revents, void *arg)	2518	static void stdin_ready (int revents, void *arg)
2294	{	2519	{
2295	if (revents & EV_TIMEOUT)	2520	if (revents & EV_TIMEOUT)
2296	/* doh, nothing entered */;	2521	/* doh, nothing entered */;
2297	else if (revents & EV_READ)	2522	else if (revents & EV_READ)
2298	/* stdin might have data for us, joy! */;	2523	/* stdin might have data for us, joy! */;
2299	}	2524	}
2300		2525
2301	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2302		2527
2303	=item ev_feed_event (ev_loop *, watcher *, int revents)	2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2304		2529
2305	Feeds the given event set into the event loop, as if the specified event	2530	Feeds the given event set into the event loop, as if the specified event
2306	had happened for the specified watcher (which must be a pointer to an	2531	had happened for the specified watcher (which must be a pointer to an
…		…
2311	Feed an event on the given fd, as if a file descriptor backend detected	2536	Feed an event on the given fd, as if a file descriptor backend detected
2312	the given events it.	2537	the given events it.
2313		2538
2314	=item ev_feed_signal_event (ev_loop *loop, int signum)	2539	=item ev_feed_signal_event (ev_loop *loop, int signum)
2315		2540
2316	Feed an event as if the given signal occured (C<loop> must be the default	2541	Feed an event as if the given signal occurred (C<loop> must be the default
2317	loop!).	2542	loop!).
2318		2543
2319	=back	2544	=back
2320		2545
2321		2546
…		…
2337		2562
2338	=item * Priorities are not currently supported. Initialising priorities	2563	=item * Priorities are not currently supported. Initialising priorities
2339	will fail and all watchers will have the same priority, even though there	2564	will fail and all watchers will have the same priority, even though there
2340	is an ev_pri field.	2565	is an ev_pri field.
2341		2566
		2567	=item * In libevent, the last base created gets the signals, in libev, the
		2568	first base created (== the default loop) gets the signals.
		2569
2342	=item * Other members are not supported.	2570	=item * Other members are not supported.
2343		2571
2344	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2572	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2345	to use the libev header file and library.	2573	to use the libev header file and library.
2346		2574
2347	=back	2575	=back
2348		2576
2349	=head1 C++ SUPPORT	2577	=head1 C++ SUPPORT
2350		2578
2351	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2579	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2352	you to use some convinience methods to start/stop watchers and also change	2580	you to use some convenience methods to start/stop watchers and also change
2353	the callback model to a model using method callbacks on objects.	2581	the callback model to a model using method callbacks on objects.
2354		2582
2355	To use it,	2583	To use it,
2356		2584
2357	#include <ev++.h>	2585	#include <ev++.h>
2358		2586
2359	This automatically includes F<ev.h> and puts all of its definitions (many	2587	This automatically includes F<ev.h> and puts all of its definitions (many
2360	of them macros) into the global namespace. All C++ specific things are	2588	of them macros) into the global namespace. All C++ specific things are
2361	put into the C<ev> namespace. It should support all the same embedding	2589	put into the C<ev> namespace. It should support all the same embedding
2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2590	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2429	your compiler is good :), then the method will be fully inlined into the	2657	your compiler is good :), then the method will be fully inlined into the
2430	thunking function, making it as fast as a direct C callback.	2658	thunking function, making it as fast as a direct C callback.
2431		2659
2432	Example: simple class declaration and watcher initialisation	2660	Example: simple class declaration and watcher initialisation
2433		2661
2434	struct myclass	2662	struct myclass
2435	{	2663	{
2436	void io_cb (ev::io &w, int revents) { }	2664	void io_cb (ev::io &w, int revents) { }
2437	}	2665	}
2438		2666
2439	myclass obj;	2667	myclass obj;
2440	ev::io iow;	2668	ev::io iow;
2441	iow.set <myclass, &myclass::io_cb> (&obj);	2669	iow.set <myclass, &myclass::io_cb> (&obj);
2442		2670
2443	=item w->set<function> (void *data = 0)	2671	=item w->set<function> (void *data = 0)
2444		2672
2445	Also sets a callback, but uses a static method or plain function as	2673	Also sets a callback, but uses a static method or plain function as
2446	callback. The optional C<data> argument will be stored in the watcher's	2674	callback. The optional C<data> argument will be stored in the watcher's
…		…
2448		2676
2449	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2450		2678
2451	See the method-C<set> above for more details.	2679	See the method-C<set> above for more details.
2452		2680
2453	Example:	2681	Example: Use a plain function as callback.
2454		2682
2455	static void io_cb (ev::io &w, int revents) { }	2683	static void io_cb (ev::io &w, int revents) { }
2456	iow.set <io_cb> ();	2684	iow.set <io_cb> ();
2457		2685
2458	=item w->set (struct ev_loop *)	2686	=item w->set (struct ev_loop *)
2459		2687
2460	Associates a different C<struct ev_loop> with this watcher. You can only	2688	Associates a different C<struct ev_loop> with this watcher. You can only
2461	do this when the watcher is inactive (and not pending either).	2689	do this when the watcher is inactive (and not pending either).
2462		2690
2463	=item w->set ([args])	2691	=item w->set ([arguments])
2464		2692
2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2693	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2466	called at least once. Unlike the C counterpart, an active watcher gets	2694	called at least once. Unlike the C counterpart, an active watcher gets
2467	automatically stopped and restarted when reconfiguring it with this	2695	automatically stopped and restarted when reconfiguring it with this
2468	method.	2696	method.
2469		2697
2470	=item w->start ()	2698	=item w->start ()
…		…
2494	=back	2722	=back
2495		2723
2496	Example: Define a class with an IO and idle watcher, start one of them in	2724	Example: Define a class with an IO and idle watcher, start one of them in
2497	the constructor.	2725	the constructor.
2498		2726
2499	class myclass	2727	class myclass
2500	{	2728	{
2501	ev::io io; void io_cb (ev::io &w, int revents);	2729	ev::io io ; void io_cb (ev::io &w, int revents);
2502	ev:idle idle void idle_cb (ev::idle &w, int revents);	2730	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2503		2731
2504	myclass (int fd)	2732	myclass (int fd)
2505	{	2733	{
2506	io .set <myclass, &myclass::io_cb > (this);	2734	io .set <myclass, &myclass::io_cb > (this);
2507	idle.set <myclass, &myclass::idle_cb> (this);	2735	idle.set <myclass, &myclass::idle_cb> (this);
2508		2736
2509	io.start (fd, ev::READ);	2737	io.start (fd, ev::READ);
2510	}	2738	}
2511	};	2739	};
2512		2740
2513		2741
2514	=head1 OTHER LANGUAGE BINDINGS	2742	=head1 OTHER LANGUAGE BINDINGS
2515		2743
2516	Libev does not offer other language bindings itself, but bindings for a	2744	Libev does not offer other language bindings itself, but bindings for a
2517	numbe rof languages exist in the form of third-party packages. If you know	2745	number of languages exist in the form of third-party packages. If you know
2518	any interesting language binding in addition to the ones listed here, drop	2746	any interesting language binding in addition to the ones listed here, drop
2519	me a note.	2747	me a note.
2520		2748
2521	=over 4	2749	=over 4
2522		2750
2523	=item Perl	2751	=item Perl
2524		2752
2525	The EV module implements the full libev API and is actually used to test	2753	The EV module implements the full libev API and is actually used to test
2526	libev. EV is developed together with libev. Apart from the EV core module,	2754	libev. EV is developed together with libev. Apart from the EV core module,
2527	there are additional modules that implement libev-compatible interfaces	2755	there are additional modules that implement libev-compatible interfaces
2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2756	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2757	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2758	and C<EV::Glib>).
2530		2759
2531	It can be found and installed via CPAN, its homepage is found at	2760	It can be found and installed via CPAN, its homepage is at
2532	L<http://software.schmorp.de/pkg/EV>.	2761	L<http://software.schmorp.de/pkg/EV>.
2533		2762
		2763	=item Python
		2764
		2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2766	seems to be quite complete and well-documented. Note, however, that the
		2767	patch they require for libev is outright dangerous as it breaks the ABI
		2768	for everybody else, and therefore, should never be applied in an installed
		2769	libev (if python requires an incompatible ABI then it needs to embed
		2770	libev).
		2771
2534	=item Ruby	2772	=item Ruby
2535		2773
2536	Tony Arcieri has written a ruby extension that offers access to a subset	2774	Tony Arcieri has written a ruby extension that offers access to a subset
2537	of the libev API and adds filehandle abstractions, asynchronous DNS and	2775	of the libev API and adds file handle abstractions, asynchronous DNS and
2538	more on top of it. It can be found via gem servers. Its homepage is at	2776	more on top of it. It can be found via gem servers. Its homepage is at
2539	L<http://rev.rubyforge.org/>.	2777	L<http://rev.rubyforge.org/>.
2540		2778
2541	=item D	2779	=item D
2542		2780
2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2545		2783
2546	=back	2784	=back
2547		2785
2548		2786
2549	=head1 MACRO MAGIC	2787	=head1 MACRO MAGIC
2550		2788
2551	Libev can be compiled with a variety of options, the most fundamantal	2789	Libev can be compiled with a variety of options, the most fundamental
2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2790	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2553	functions and callbacks have an initial C<struct ev_loop *> argument.	2791	functions and callbacks have an initial C<struct ev_loop *> argument.
2554		2792
2555	To make it easier to write programs that cope with either variant, the	2793	To make it easier to write programs that cope with either variant, the
2556	following macros are defined:	2794	following macros are defined:
…		…
2561		2799
2562	This provides the loop I<argument> for functions, if one is required ("ev	2800	This provides the loop I<argument> for functions, if one is required ("ev
2563	loop argument"). The C<EV_A> form is used when this is the sole argument,	2801	loop argument"). The C<EV_A> form is used when this is the sole argument,
2564	C<EV_A_> is used when other arguments are following. Example:	2802	C<EV_A_> is used when other arguments are following. Example:
2565		2803
2566	ev_unref (EV_A);	2804	ev_unref (EV_A);
2567	ev_timer_add (EV_A_ watcher);	2805	ev_timer_add (EV_A_ watcher);
2568	ev_loop (EV_A_ 0);	2806	ev_loop (EV_A_ 0);
2569		2807
2570	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2808	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2571	which is often provided by the following macro.	2809	which is often provided by the following macro.
2572		2810
2573	=item C<EV_P>, C<EV_P_>	2811	=item C<EV_P>, C<EV_P_>
2574		2812
2575	This provides the loop I<parameter> for functions, if one is required ("ev	2813	This provides the loop I<parameter> for functions, if one is required ("ev
2576	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2814	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2577	C<EV_P_> is used when other parameters are following. Example:	2815	C<EV_P_> is used when other parameters are following. Example:
2578		2816
2579	// this is how ev_unref is being declared	2817	// this is how ev_unref is being declared
2580	static void ev_unref (EV_P);	2818	static void ev_unref (EV_P);
2581		2819
2582	// this is how you can declare your typical callback	2820	// this is how you can declare your typical callback
2583	static void cb (EV_P_ ev_timer *w, int revents)	2821	static void cb (EV_P_ ev_timer *w, int revents)
2584		2822
2585	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2823	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2586	suitable for use with C<EV_A>.	2824	suitable for use with C<EV_A>.
2587		2825
2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2826	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2589		2827
2590	Similar to the other two macros, this gives you the value of the default	2828	Similar to the other two macros, this gives you the value of the default
2591	loop, if multiple loops are supported ("ev loop default").	2829	loop, if multiple loops are supported ("ev loop default").
		2830
		2831	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2832
		2833	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2834	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2835	is undefined when the default loop has not been initialised by a previous
		2836	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2837
		2838	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2839	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2592		2840
2593	=back	2841	=back
2594		2842
2595	Example: Declare and initialise a check watcher, utilising the above	2843	Example: Declare and initialise a check watcher, utilising the above
2596	macros so it will work regardless of whether multiple loops are supported	2844	macros so it will work regardless of whether multiple loops are supported
2597	or not.	2845	or not.
2598		2846
2599	static void	2847	static void
2600	check_cb (EV_P_ ev_timer *w, int revents)	2848	check_cb (EV_P_ ev_timer *w, int revents)
2601	{	2849	{
2602	ev_check_stop (EV_A_ w);	2850	ev_check_stop (EV_A_ w);
2603	}	2851	}
2604		2852
2605	ev_check check;	2853	ev_check check;
2606	ev_check_init (&check, check_cb);	2854	ev_check_init (&check, check_cb);
2607	ev_check_start (EV_DEFAULT_ &check);	2855	ev_check_start (EV_DEFAULT_ &check);
2608	ev_loop (EV_DEFAULT_ 0);	2856	ev_loop (EV_DEFAULT_ 0);
2609		2857
2610	=head1 EMBEDDING	2858	=head1 EMBEDDING
2611		2859
2612	Libev can (and often is) directly embedded into host	2860	Libev can (and often is) directly embedded into host
2613	applications. Examples of applications that embed it include the Deliantra	2861	applications. Examples of applications that embed it include the Deliantra
…		…
2620	libev somewhere in your source tree).	2868	libev somewhere in your source tree).
2621		2869
2622	=head2 FILESETS	2870	=head2 FILESETS
2623		2871
2624	Depending on what features you need you need to include one or more sets of files	2872	Depending on what features you need you need to include one or more sets of files
2625	in your app.	2873	in your application.
2626		2874
2627	=head3 CORE EVENT LOOP	2875	=head3 CORE EVENT LOOP
2628		2876
2629	To include only the libev core (all the C<ev_*> functions), with manual	2877	To include only the libev core (all the C<ev_*> functions), with manual
2630	configuration (no autoconf):	2878	configuration (no autoconf):
2631		2879
2632	#define EV_STANDALONE 1	2880	#define EV_STANDALONE 1
2633	#include "ev.c"	2881	#include "ev.c"
2634		2882
2635	This will automatically include F<ev.h>, too, and should be done in a	2883	This will automatically include F<ev.h>, too, and should be done in a
2636	single C source file only to provide the function implementations. To use	2884	single C source file only to provide the function implementations. To use
2637	it, do the same for F<ev.h> in all files wishing to use this API (best	2885	it, do the same for F<ev.h> in all files wishing to use this API (best
2638	done by writing a wrapper around F<ev.h> that you can include instead and	2886	done by writing a wrapper around F<ev.h> that you can include instead and
2639	where you can put other configuration options):	2887	where you can put other configuration options):
2640		2888
2641	#define EV_STANDALONE 1	2889	#define EV_STANDALONE 1
2642	#include "ev.h"	2890	#include "ev.h"
2643		2891
2644	Both header files and implementation files can be compiled with a C++	2892	Both header files and implementation files can be compiled with a C++
2645	compiler (at least, thats a stated goal, and breakage will be treated	2893	compiler (at least, thats a stated goal, and breakage will be treated
2646	as a bug).	2894	as a bug).
2647		2895
2648	You need the following files in your source tree, or in a directory	2896	You need the following files in your source tree, or in a directory
2649	in your include path (e.g. in libev/ when using -Ilibev):	2897	in your include path (e.g. in libev/ when using -Ilibev):
2650		2898
2651	ev.h	2899	ev.h
2652	ev.c	2900	ev.c
2653	ev_vars.h	2901	ev_vars.h
2654	ev_wrap.h	2902	ev_wrap.h
2655		2903
2656	ev_win32.c required on win32 platforms only	2904	ev_win32.c required on win32 platforms only
2657		2905
2658	ev_select.c only when select backend is enabled (which is enabled by default)	2906	ev_select.c only when select backend is enabled (which is enabled by default)
2659	ev_poll.c only when poll backend is enabled (disabled by default)	2907	ev_poll.c only when poll backend is enabled (disabled by default)
2660	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2908	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2661	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2909	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2662	ev_port.c only when the solaris port backend is enabled (disabled by default)	2910	ev_port.c only when the solaris port backend is enabled (disabled by default)
2663		2911
2664	F<ev.c> includes the backend files directly when enabled, so you only need	2912	F<ev.c> includes the backend files directly when enabled, so you only need
2665	to compile this single file.	2913	to compile this single file.
2666		2914
2667	=head3 LIBEVENT COMPATIBILITY API	2915	=head3 LIBEVENT COMPATIBILITY API
2668		2916
2669	To include the libevent compatibility API, also include:	2917	To include the libevent compatibility API, also include:
2670		2918
2671	#include "event.c"	2919	#include "event.c"
2672		2920
2673	in the file including F<ev.c>, and:	2921	in the file including F<ev.c>, and:
2674		2922
2675	#include "event.h"	2923	#include "event.h"
2676		2924
2677	in the files that want to use the libevent API. This also includes F<ev.h>.	2925	in the files that want to use the libevent API. This also includes F<ev.h>.
2678		2926
2679	You need the following additional files for this:	2927	You need the following additional files for this:
2680		2928
2681	event.h	2929	event.h
2682	event.c	2930	event.c
2683		2931
2684	=head3 AUTOCONF SUPPORT	2932	=head3 AUTOCONF SUPPORT
2685		2933
2686	Instead of using C<EV_STANDALONE=1> and providing your config in	2934	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2687	whatever way you want, you can also C<m4_include([libev.m4])> in your	2935	whatever way you want, you can also C<m4_include([libev.m4])> in your
2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2936	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2689	include F<config.h> and configure itself accordingly.	2937	include F<config.h> and configure itself accordingly.
2690		2938
2691	For this of course you need the m4 file:	2939	For this of course you need the m4 file:
2692		2940
2693	libev.m4	2941	libev.m4
2694		2942
2695	=head2 PREPROCESSOR SYMBOLS/MACROS	2943	=head2 PREPROCESSOR SYMBOLS/MACROS
2696		2944
2697	Libev can be configured via a variety of preprocessor symbols you have to define	2945	Libev can be configured via a variety of preprocessor symbols you have to
2698	before including any of its files. The default is not to build for multiplicity	2946	define before including any of its files. The default in the absence of
2699	and only include the select backend.	2947	autoconf is documented for every option.
2700		2948
2701	=over 4	2949	=over 4
2702		2950
2703	=item EV_STANDALONE	2951	=item EV_STANDALONE
2704		2952
…		…
2709	F<event.h> that are not directly supported by the libev core alone.	2957	F<event.h> that are not directly supported by the libev core alone.
2710		2958
2711	=item EV_USE_MONOTONIC	2959	=item EV_USE_MONOTONIC
2712		2960
2713	If defined to be C<1>, libev will try to detect the availability of the	2961	If defined to be C<1>, libev will try to detect the availability of the
2714	monotonic clock option at both compiletime and runtime. Otherwise no use	2962	monotonic clock option at both compile time and runtime. Otherwise no use
2715	of the monotonic clock option will be attempted. If you enable this, you	2963	of the monotonic clock option will be attempted. If you enable this, you
2716	usually have to link against librt or something similar. Enabling it when	2964	usually have to link against librt or something similar. Enabling it when
2717	the functionality isn't available is safe, though, although you have	2965	the functionality isn't available is safe, though, although you have
2718	to make sure you link against any libraries where the C<clock_gettime>	2966	to make sure you link against any libraries where the C<clock_gettime>
2719	function is hiding in (often F<-lrt>).	2967	function is hiding in (often F<-lrt>).
2720		2968
2721	=item EV_USE_REALTIME	2969	=item EV_USE_REALTIME
2722		2970
2723	If defined to be C<1>, libev will try to detect the availability of the	2971	If defined to be C<1>, libev will try to detect the availability of the
2724	realtime clock option at compiletime (and assume its availability at	2972	real-time clock option at compile time (and assume its availability at
2725	runtime if successful). Otherwise no use of the realtime clock option will	2973	runtime if successful). Otherwise no use of the real-time clock option will
2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2729		2977
2730	=item EV_USE_NANOSLEEP	2978	=item EV_USE_NANOSLEEP
2731		2979
2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2733	and will use it for delays. Otherwise it will use C<select ()>.	2981	and will use it for delays. Otherwise it will use C<select ()>.
2734		2982
		2983	=item EV_USE_EVENTFD
		2984
		2985	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2986	available and will probe for kernel support at runtime. This will improve
		2987	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2988	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2989	2.7 or newer, otherwise disabled.
		2990
2735	=item EV_USE_SELECT	2991	=item EV_USE_SELECT
2736		2992
2737	If undefined or defined to be C<1>, libev will compile in support for the	2993	If undefined or defined to be C<1>, libev will compile in support for the
2738	C<select>(2) backend. No attempt at autodetection will be done: if no	2994	C<select>(2) backend. No attempt at auto-detection will be done: if no
2739	other method takes over, select will be it. Otherwise the select backend	2995	other method takes over, select will be it. Otherwise the select backend
2740	will not be compiled in.	2996	will not be compiled in.
2741		2997
2742	=item EV_SELECT_USE_FD_SET	2998	=item EV_SELECT_USE_FD_SET
2743		2999
2744	If defined to C<1>, then the select backend will use the system C<fd_set>	3000	If defined to C<1>, then the select backend will use the system C<fd_set>
2745	structure. This is useful if libev doesn't compile due to a missing	3001	structure. This is useful if libev doesn't compile due to a missing
2746	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2747	exotic systems. This usually limits the range of file descriptors to some	3003	exotic systems. This usually limits the range of file descriptors to some
2748	low limit such as 1024 or might have other limitations (winsocket only	3004	low limit such as 1024 or might have other limitations (winsocket only
2749	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2750	influence the size of the C<fd_set> used.	3006	influence the size of the C<fd_set> used.
2751		3007
…		…
2775		3031
2776	=item EV_USE_EPOLL	3032	=item EV_USE_EPOLL
2777		3033
2778	If defined to be C<1>, libev will compile in support for the Linux	3034	If defined to be C<1>, libev will compile in support for the Linux
2779	C<epoll>(7) backend. Its availability will be detected at runtime,	3035	C<epoll>(7) backend. Its availability will be detected at runtime,
2780	otherwise another method will be used as fallback. This is the	3036	otherwise another method will be used as fallback. This is the preferred
2781	preferred backend for GNU/Linux systems.	3037	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3038	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2782		3039
2783	=item EV_USE_KQUEUE	3040	=item EV_USE_KQUEUE
2784		3041
2785	If defined to be C<1>, libev will compile in support for the BSD style	3042	If defined to be C<1>, libev will compile in support for the BSD style
2786	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3043	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2799	otherwise another method will be used as fallback. This is the preferred	3056	otherwise another method will be used as fallback. This is the preferred
2800	backend for Solaris 10 systems.	3057	backend for Solaris 10 systems.
2801		3058
2802	=item EV_USE_DEVPOLL	3059	=item EV_USE_DEVPOLL
2803		3060
2804	reserved for future expansion, works like the USE symbols above.	3061	Reserved for future expansion, works like the USE symbols above.
2805		3062
2806	=item EV_USE_INOTIFY	3063	=item EV_USE_INOTIFY
2807		3064
2808	If defined to be C<1>, libev will compile in support for the Linux inotify	3065	If defined to be C<1>, libev will compile in support for the Linux inotify
2809	interface to speed up C<ev_stat> watchers. Its actual availability will	3066	interface to speed up C<ev_stat> watchers. Its actual availability will
2810	be detected at runtime.	3067	be detected at runtime. If undefined, it will be enabled if the headers
		3068	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2811		3069
2812	=item EV_ATOMIC_T	3070	=item EV_ATOMIC_T
2813		3071
2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3072	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815	access is atomic with respect to other threads or signal contexts. No such	3073	access is atomic with respect to other threads or signal contexts. No such
2816	type is easily found in the C language, so you can provide your own type	3074	type is easily found in the C language, so you can provide your own type
2817	that you know is safe for your purposes. It is used both for signal handler "locking"	3075	that you know is safe for your purposes. It is used both for signal handler "locking"
2818	as well as for signal and thread safety in C<ev_async> watchers.	3076	as well as for signal and thread safety in C<ev_async> watchers.
2819		3077
2820	In the absense of this define, libev will use C<sig_atomic_t volatile>	3078	In the absence of this define, libev will use C<sig_atomic_t volatile>
2821	(from F<signal.h>), which is usually good enough on most platforms.	3079	(from F<signal.h>), which is usually good enough on most platforms.
2822		3080
2823	=item EV_H	3081	=item EV_H
2824		3082
2825	The name of the F<ev.h> header file used to include it. The default if	3083	The name of the F<ev.h> header file used to include it. The default if
…		…
2864	When doing priority-based operations, libev usually has to linearly search	3122	When doing priority-based operations, libev usually has to linearly search
2865	all the priorities, so having many of them (hundreds) uses a lot of space	3123	all the priorities, so having many of them (hundreds) uses a lot of space
2866	and time, so using the defaults of five priorities (-2 .. +2) is usually	3124	and time, so using the defaults of five priorities (-2 .. +2) is usually
2867	fine.	3125	fine.
2868		3126
2869	If your embedding app does not need any priorities, defining these both to	3127	If your embedding application does not need any priorities, defining these
2870	C<0> will save some memory and cpu.	3128	both to C<0> will save some memory and CPU.
2871		3129
2872	=item EV_PERIODIC_ENABLE	3130	=item EV_PERIODIC_ENABLE
2873		3131
2874	If undefined or defined to be C<1>, then periodic timers are supported. If	3132	If undefined or defined to be C<1>, then periodic timers are supported. If
2875	defined to be C<0>, then they are not. Disabling them saves a few kB of	3133	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2882	code.	3140	code.
2883		3141
2884	=item EV_EMBED_ENABLE	3142	=item EV_EMBED_ENABLE
2885		3143
2886	If undefined or defined to be C<1>, then embed watchers are supported. If	3144	If undefined or defined to be C<1>, then embed watchers are supported. If
2887	defined to be C<0>, then they are not.	3145	defined to be C<0>, then they are not. Embed watchers rely on most other
		3146	watcher types, which therefore must not be disabled.
2888		3147
2889	=item EV_STAT_ENABLE	3148	=item EV_STAT_ENABLE
2890		3149
2891	If undefined or defined to be C<1>, then stat watchers are supported. If	3150	If undefined or defined to be C<1>, then stat watchers are supported. If
2892	defined to be C<0>, then they are not.	3151	defined to be C<0>, then they are not.
…		…
2902	defined to be C<0>, then they are not.	3161	defined to be C<0>, then they are not.
2903		3162
2904	=item EV_MINIMAL	3163	=item EV_MINIMAL
2905		3164
2906	If you need to shave off some kilobytes of code at the expense of some	3165	If you need to shave off some kilobytes of code at the expense of some
2907	speed, define this symbol to C<1>. Currently only used for gcc to override	3166	speed, define this symbol to C<1>. Currently this is used to override some
2908	some inlining decisions, saves roughly 30% codesize of amd64.	3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3168	much smaller 2-heap for timer management over the default 4-heap.
2909		3169
2910	=item EV_PID_HASHSIZE	3170	=item EV_PID_HASHSIZE
2911		3171
2912	C<ev_child> watchers use a small hash table to distribute workload by	3172	C<ev_child> watchers use a small hash table to distribute workload by
2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2921	usually more than enough. If you need to manage thousands of C<ev_stat>	3181	usually more than enough. If you need to manage thousands of C<ev_stat>
2922	watchers you might want to increase this value (I<must> be a power of	3182	watchers you might want to increase this value (I<must> be a power of
2923	two).	3183	two).
2924		3184
		3185	=item EV_USE_4HEAP
		3186
		3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3190	faster performance with many (thousands) of watchers.
		3191
		3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3193	(disabled).
		3194
		3195	=item EV_HEAP_CACHE_AT
		3196
		3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3201	but avoids random read accesses on heap changes. This improves performance
		3202	noticeably with many (hundreds) of watchers.
		3203
		3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3205	(disabled).
		3206
		3207	=item EV_VERIFY
		3208
		3209	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3210	be done: If set to C<0>, no internal verification code will be compiled
		3211	in. If set to C<1>, then verification code will be compiled in, but not
		3212	called. If set to C<2>, then the internal verification code will be
		3213	called once per loop, which can slow down libev. If set to C<3>, then the
		3214	verification code will be called very frequently, which will slow down
		3215	libev considerably.
		3216
		3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3218	C<0>.
		3219
2925	=item EV_COMMON	3220	=item EV_COMMON
2926		3221
2927	By default, all watchers have a C<void *data> member. By redefining	3222	By default, all watchers have a C<void *data> member. By redefining
2928	this macro to a something else you can include more and other types of	3223	this macro to a something else you can include more and other types of
2929	members. You have to define it each time you include one of the files,	3224	members. You have to define it each time you include one of the files,
2930	though, and it must be identical each time.	3225	though, and it must be identical each time.
2931		3226
2932	For example, the perl EV module uses something like this:	3227	For example, the perl EV module uses something like this:
2933		3228
2934	#define EV_COMMON \	3229	#define EV_COMMON \
2935	SV *self; /* contains this struct */ \	3230	SV *self; /* contains this struct */ \
2936	SV *cb_sv, *fh /* note no trailing ";" */	3231	SV *cb_sv, *fh /* note no trailing ";" */
2937		3232
2938	=item EV_CB_DECLARE (type)	3233	=item EV_CB_DECLARE (type)
2939		3234
2940	=item EV_CB_INVOKE (watcher, revents)	3235	=item EV_CB_INVOKE (watcher, revents)
2941		3236
…		…
2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2949	method calls instead of plain function calls in C++.	3244	method calls instead of plain function calls in C++.
2950		3245
2951	=head2 EXPORTED API SYMBOLS	3246	=head2 EXPORTED API SYMBOLS
2952		3247
2953	If you need to re-export the API (e.g. via a dll) and you need a list of	3248	If you need to re-export the API (e.g. via a DLL) and you need a list of
2954	exported symbols, you can use the provided F<Symbol.*> files which list	3249	exported symbols, you can use the provided F<Symbol.*> files which list
2955	all public symbols, one per line:	3250	all public symbols, one per line:
2956		3251
2957	Symbols.ev for libev proper	3252	Symbols.ev for libev proper
2958	Symbols.event for the libevent emulation	3253	Symbols.event for the libevent emulation
2959		3254
2960	This can also be used to rename all public symbols to avoid clashes with	3255	This can also be used to rename all public symbols to avoid clashes with
2961	multiple versions of libev linked together (which is obviously bad in	3256	multiple versions of libev linked together (which is obviously bad in
2962	itself, but sometimes it is inconvinient to avoid this).	3257	itself, but sometimes it is inconvenient to avoid this).
2963		3258
2964	A sed command like this will create wrapper C<#define>'s that you need to	3259	A sed command like this will create wrapper C<#define>'s that you need to
2965	include before including F<ev.h>:	3260	include before including F<ev.h>:
2966		3261
2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3262	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2984	file.	3279	file.
2985		3280
2986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3281	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2987	that everybody includes and which overrides some configure choices:	3282	that everybody includes and which overrides some configure choices:
2988		3283
2989	#define EV_MINIMAL 1	3284	#define EV_MINIMAL 1
2990	#define EV_USE_POLL 0	3285	#define EV_USE_POLL 0
2991	#define EV_MULTIPLICITY 0	3286	#define EV_MULTIPLICITY 0
2992	#define EV_PERIODIC_ENABLE 0	3287	#define EV_PERIODIC_ENABLE 0
2993	#define EV_STAT_ENABLE 0	3288	#define EV_STAT_ENABLE 0
2994	#define EV_FORK_ENABLE 0	3289	#define EV_FORK_ENABLE 0
2995	#define EV_CONFIG_H <config.h>	3290	#define EV_CONFIG_H <config.h>
2996	#define EV_MINPRI 0	3291	#define EV_MINPRI 0
2997	#define EV_MAXPRI 0	3292	#define EV_MAXPRI 0
2998		3293
2999	#include "ev++.h"	3294	#include "ev++.h"
3000		3295
3001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3002		3297
3003	#include "ev_cpp.h"	3298	#include "ev_cpp.h"
3004	#include "ev.c"	3299	#include "ev.c"
		3300
		3301
		3302	=head1 THREADS AND COROUTINES
		3303
		3304	=head2 THREADS
		3305
		3306	Libev itself is thread-safe (unless the opposite is specifically
		3307	documented for a function), but it uses no locking itself. This means that
		3308	you can use as many loops as you want in parallel, as long as only one
		3309	thread ever calls into one libev function with the same loop parameter:
		3310	libev guarantees that different event loops share no data structures that
		3311	need locking.
		3312
		3313	Or to put it differently: calls with different loop parameters can be done
		3314	concurrently from multiple threads, calls with the same loop parameter
		3315	must be done serially (but can be done from different threads, as long as
		3316	only one thread ever is inside a call at any point in time, e.g. by using
		3317	a mutex per loop).
		3318
		3319	Specifically to support threads (and signal handlers), libev implements
		3320	so-called C<ev_async> watchers, which allow some limited form of
		3321	concurrency on the same event loop.
		3322
		3323	If you want to know which design (one loop, locking, or multiple loops
		3324	without or something else still) is best for your problem, then I cannot
		3325	help you. I can give some generic advice however:
		3326
		3327	=over 4
		3328
		3329	=item * most applications have a main thread: use the default libev loop
		3330	in that thread, or create a separate thread running only the default loop.
		3331
		3332	This helps integrating other libraries or software modules that use libev
		3333	themselves and don't care/know about threading.
		3334
		3335	=item * one loop per thread is usually a good model.
		3336
		3337	Doing this is almost never wrong, sometimes a better-performance model
		3338	exists, but it is always a good start.
		3339
		3340	=item * other models exist, such as the leader/follower pattern, where one
		3341	loop is handed through multiple threads in a kind of round-robin fashion.
		3342
		3343	Choosing a model is hard - look around, learn, know that usually you can do
		3344	better than you currently do :-)
		3345
		3346	=item * often you need to talk to some other thread which blocks in the
		3347	event loop.
		3348
		3349	C<ev_async> watchers can be used to wake them up from other threads safely
		3350	(or from signal contexts...).
		3351
		3352	An example use would be to communicate signals or other events that only
		3353	work in the default loop by registering the signal watcher with the
		3354	default loop and triggering an C<ev_async> watcher from the default loop
		3355	watcher callback into the event loop interested in the signal.
		3356
		3357	=back
		3358
		3359	=head2 COROUTINES
		3360
		3361	Libev is much more accommodating to coroutines ("cooperative threads"):
		3362	libev fully supports nesting calls to it's functions from different
		3363	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3364	different coroutines and switch freely between both coroutines running the
		3365	loop, as long as you don't confuse yourself). The only exception is that
		3366	you must not do this from C<ev_periodic> reschedule callbacks.
		3367
		3368	Care has been taken to ensure that libev does not keep local state inside
		3369	C<ev_loop>, and other calls do not usually allow coroutine switches.
3005		3370
3006		3371
3007	=head1 COMPLEXITIES	3372	=head1 COMPLEXITIES
3008		3373
3009	In this section the complexities of (many of) the algorithms used inside	3374	In this section the complexities of (many of) the algorithms used inside
…		…
3041	correct watcher to remove. The lists are usually short (you don't usually	3406	correct watcher to remove. The lists are usually short (you don't usually
3042	have many watchers waiting for the same fd or signal).	3407	have many watchers waiting for the same fd or signal).
3043		3408
3044	=item Finding the next timer in each loop iteration: O(1)	3409	=item Finding the next timer in each loop iteration: O(1)
3045		3410
3046	By virtue of using a binary heap, the next timer is always found at the	3411	By virtue of using a binary or 4-heap, the next timer is always found at a
3047	beginning of the storage array.	3412	fixed position in the storage array.
3048		3413
3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3050		3415
3051	A change means an I/O watcher gets started or stopped, which requires	3416	A change means an I/O watcher gets started or stopped, which requires
3052	libev to recalculate its status (and possibly tell the kernel, depending	3417	libev to recalculate its status (and possibly tell the kernel, depending
3053	on backend and wether C<ev_io_set> was used).	3418	on backend and whether C<ev_io_set> was used).
3054		3419
3055	=item Activating one watcher (putting it into the pending state): O(1)	3420	=item Activating one watcher (putting it into the pending state): O(1)
3056		3421
3057	=item Priority handling: O(number_of_priorities)	3422	=item Priority handling: O(number_of_priorities)
3058		3423
3059	Priorities are implemented by allocating some space for each	3424	Priorities are implemented by allocating some space for each
3060	priority. When doing priority-based operations, libev usually has to	3425	priority. When doing priority-based operations, libev usually has to
3061	linearly search all the priorities, but starting/stopping and activating	3426	linearly search all the priorities, but starting/stopping and activating
3062	watchers becomes O(1) w.r.t. priority handling.	3427	watchers becomes O(1) with respect to priority handling.
3063		3428
3064	=item Sending an ev_async: O(1)	3429	=item Sending an ev_async: O(1)
3065		3430
3066	=item Processing ev_async_send: O(number_of_async_watchers)	3431	=item Processing ev_async_send: O(number_of_async_watchers)
3067		3432
3068	=item Processing signals: O(max_signal_number)	3433	=item Processing signals: O(max_signal_number)
3069		3434
3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>	3435	Sending involves a system call I<iff> there were no other C<ev_async_send>
3071	calls in the current loop iteration. Checking for async and signal events	3436	calls in the current loop iteration. Checking for async and signal events
3072	involves iterating over all running async watchers or all signal numbers.	3437	involves iterating over all running async watchers or all signal numbers.
3073		3438
3074	=back	3439	=back
3075		3440
3076		3441
3077	=head1 Win32 platform limitations and workarounds	3442	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3078		3443
3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3080	requires, and its I/O model is fundamentally incompatible with the POSIX	3445	requires, and its I/O model is fundamentally incompatible with the POSIX
3081	model. Libev still offers limited functionality on this platform in	3446	model. Libev still offers limited functionality on this platform in
3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3083	descriptors. This only applies when using Win32 natively, not when using	3448	descriptors. This only applies when using Win32 natively, not when using
3084	e.g. cygwin.	3449	e.g. cygwin.
3085		3450
		3451	Lifting these limitations would basically require the full
		3452	re-implementation of the I/O system. If you are into these kinds of
		3453	things, then note that glib does exactly that for you in a very portable
		3454	way (note also that glib is the slowest event library known to man).
		3455
3086	There is no supported compilation method available on windows except	3456	There is no supported compilation method available on windows except
3087	embedding it into other applications.	3457	embedding it into other applications.
3088		3458
		3459	Not a libev limitation but worth mentioning: windows apparently doesn't
		3460	accept large writes: instead of resulting in a partial write, windows will
		3461	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3462	so make sure you only write small amounts into your sockets (less than a
		3463	megabyte seems safe, but this apparently depends on the amount of memory
		3464	available).
		3465
3089	Due to the many, low, and arbitrary limits on the win32 platform and the	3466	Due to the many, low, and arbitrary limits on the win32 platform and
3090	abysmal performance of winsockets, using a large number of sockets is not	3467	the abysmal performance of winsockets, using a large number of sockets
3091	recommended (and not reasonable). If your program needs to use more than	3468	is not recommended (and not reasonable). If your program needs to use
3092	a hundred or so sockets, then likely it needs to use a totally different	3469	more than a hundred or so sockets, then likely it needs to use a totally
3093	implementation for windows, as libev offers the POSIX model, which cannot	3470	different implementation for windows, as libev offers the POSIX readiness
3094	be implemented efficiently on windows (microsoft monopoly games).	3471	notification model, which cannot be implemented efficiently on windows
		3472	(Microsoft monopoly games).
		3473
		3474	A typical way to use libev under windows is to embed it (see the embedding
		3475	section for details) and use the following F<evwrap.h> header file instead
		3476	of F<ev.h>:
		3477
		3478	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3479	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3480
		3481	#include "ev.h"
		3482
		3483	And compile the following F<evwrap.c> file into your project (make sure
		3484	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3485
		3486	#include "evwrap.h"
		3487	#include "ev.c"
3095		3488
3096	=over 4	3489	=over 4
3097		3490
3098	=item The winsocket select function	3491	=item The winsocket select function
3099		3492
3100	The winsocket C<select> function doesn't follow POSIX in that it requires	3493	The winsocket C<select> function doesn't follow POSIX in that it
3101	socket I<handles> and not socket I<file descriptors>. This makes select	3494	requires socket I<handles> and not socket I<file descriptors> (it is
3102	very inefficient, and also requires a mapping from file descriptors	3495	also extremely buggy). This makes select very inefficient, and also
3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3496	requires a mapping from file descriptors to socket handles (the Microsoft
3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3497	C runtime provides the function C<_open_osfhandle> for this). See the
3105	symbols for more info.	3498	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3499	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3106		3500
3107	The configuration for a "naked" win32 using the microsoft runtime	3501	The configuration for a "naked" win32 using the Microsoft runtime
3108	libraries and raw winsocket select is:	3502	libraries and raw winsocket select is:
3109		3503
3110	#define EV_USE_SELECT 1	3504	#define EV_USE_SELECT 1
3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3505	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3112		3506
3113	Note that winsockets handling of fd sets is O(n), so you can easily get a	3507	Note that winsockets handling of fd sets is O(n), so you can easily get a
3114	complexity in the O(n²) range when using win32.	3508	complexity in the O(n²) range when using win32.
3115		3509
3116	=item Limited number of file descriptors	3510	=item Limited number of file descriptors
3117		3511
3118	Windows has numerous arbitrary (and low) limits on things. Early versions	3512	Windows has numerous arbitrary (and low) limits on things.
3119	of winsocket's select only supported waiting for a max. of C<64> handles	3513
		3514	Early versions of winsocket's select only supported waiting for a maximum
3120	(probably owning to the fact that all windows kernels can only wait for	3515	of C<64> handles (probably owning to the fact that all windows kernels
3121	C<64> things at the same time internally; microsoft recommends spawning a	3516	can only wait for C<64> things at the same time internally; Microsoft
3122	chain of threads and wait for 63 handles and the previous thread in each).	3517	recommends spawning a chain of threads and wait for 63 handles and the
		3518	previous thread in each. Great).
3123		3519
3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3520	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3125	to some high number (e.g. C<2048>) before compiling the winsocket select	3521	to some high number (e.g. C<2048>) before compiling the winsocket select
3126	call (which might be in libev or elsewhere, for example, perl does its own	3522	call (which might be in libev or elsewhere, for example, perl does its own
3127	select emulation on windows).	3523	select emulation on windows).
3128		3524
3129	Another limit is the number of file descriptors in the microsoft runtime	3525	Another limit is the number of file descriptors in the Microsoft runtime
3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3526	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3131	or something like this inside microsoft). You can increase this by calling	3527	or something like this inside Microsoft). You can increase this by calling
3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3528	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3133	arbitrary limit), but is broken in many versions of the microsoft runtime	3529	arbitrary limit), but is broken in many versions of the Microsoft runtime
3134	libraries.	3530	libraries.
3135		3531
3136	This might get you to about C<512> or C<2048> sockets (depending on	3532	This might get you to about C<512> or C<2048> sockets (depending on
3137	windows version and/or the phase of the moon). To get more, you need to	3533	windows version and/or the phase of the moon). To get more, you need to
3138	wrap all I/O functions and provide your own fd management, but the cost of	3534	wrap all I/O functions and provide your own fd management, but the cost of
3139	calling select (O(n²)) will likely make this unworkable.	3535	calling select (O(n²)) will likely make this unworkable.
3140		3536
3141	=back	3537	=back
3142		3538
3143		3539
		3540	=head1 PORTABILITY REQUIREMENTS
		3541
		3542	In addition to a working ISO-C implementation, libev relies on a few
		3543	additional extensions:
		3544
		3545	=over 4
		3546
		3547	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3548	calling conventions regardless of C<ev_watcher_type *>.
		3549
		3550	Libev assumes not only that all watcher pointers have the same internal
		3551	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3552	assumes that the same (machine) code can be used to call any watcher
		3553	callback: The watcher callbacks have different type signatures, but libev
		3554	calls them using an C<ev_watcher *> internally.
		3555
		3556	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3557
		3558	The type C<sig_atomic_t volatile> (or whatever is defined as
		3559	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3560	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3561	believed to be sufficiently portable.
		3562
		3563	=item C<sigprocmask> must work in a threaded environment
		3564
		3565	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3566	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3567	pthread implementations will either allow C<sigprocmask> in the "main
		3568	thread" or will block signals process-wide, both behaviours would
		3569	be compatible with libev. Interaction between C<sigprocmask> and
		3570	C<pthread_sigmask> could complicate things, however.
		3571
		3572	The most portable way to handle signals is to block signals in all threads
		3573	except the initial one, and run the default loop in the initial thread as
		3574	well.
		3575
		3576	=item C<long> must be large enough for common memory allocation sizes
		3577
		3578	To improve portability and simplify using libev, libev uses C<long>
		3579	internally instead of C<size_t> when allocating its data structures. On
		3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3581	is still at least 31 bits everywhere, which is enough for hundreds of
		3582	millions of watchers.
		3583
		3584	=item C<double> must hold a time value in seconds with enough accuracy
		3585
		3586	The type C<double> is used to represent timestamps. It is required to
		3587	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3588	enough for at least into the year 4000. This requirement is fulfilled by
		3589	implementations implementing IEEE 754 (basically all existing ones).
		3590
		3591	=back
		3592
		3593	If you know of other additional requirements drop me a note.
		3594
		3595
		3596	=head1 COMPILER WARNINGS
		3597
		3598	Depending on your compiler and compiler settings, you might get no or a
		3599	lot of warnings when compiling libev code. Some people are apparently
		3600	scared by this.
		3601
		3602	However, these are unavoidable for many reasons. For one, each compiler
		3603	has different warnings, and each user has different tastes regarding
		3604	warning options. "Warn-free" code therefore cannot be a goal except when
		3605	targeting a specific compiler and compiler-version.
		3606
		3607	Another reason is that some compiler warnings require elaborate
		3608	workarounds, or other changes to the code that make it less clear and less
		3609	maintainable.
		3610
		3611	And of course, some compiler warnings are just plain stupid, or simply
		3612	wrong (because they don't actually warn about the condition their message
		3613	seems to warn about).
		3614
		3615	While libev is written to generate as few warnings as possible,
		3616	"warn-free" code is not a goal, and it is recommended not to build libev
		3617	with any compiler warnings enabled unless you are prepared to cope with
		3618	them (e.g. by ignoring them). Remember that warnings are just that:
		3619	warnings, not errors, or proof of bugs.
		3620
		3621
		3622	=head1 VALGRIND
		3623
		3624	Valgrind has a special section here because it is a popular tool that is
		3625	highly useful, but valgrind reports are very hard to interpret.
		3626
		3627	If you think you found a bug (memory leak, uninitialised data access etc.)
		3628	in libev, then check twice: If valgrind reports something like:
		3629
		3630	==2274== definitely lost: 0 bytes in 0 blocks.
		3631	==2274== possibly lost: 0 bytes in 0 blocks.
		3632	==2274== still reachable: 256 bytes in 1 blocks.
		3633
		3634	Then there is no memory leak. Similarly, under some circumstances,
		3635	valgrind might report kernel bugs as if it were a bug in libev, or it
		3636	might be confused (it is a very good tool, but only a tool).
		3637
		3638	If you are unsure about something, feel free to contact the mailing list
		3639	with the full valgrind report and an explanation on why you think this is
		3640	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3641	no bug" answer and take the chance of learning how to interpret valgrind
		3642	properly.
		3643
		3644	If you need, for some reason, empty reports from valgrind for your project
		3645	I suggest using suppression lists.
		3646
		3647
3144	=head1 AUTHOR	3648	=head1 AUTHOR
3145		3649
3146	Marc Lehmann <libev@schmorp.de>.	3650	Marc Lehmann <libev@schmorp.de>.
3147		3651

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