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Revision 1.121 by root, Mon Jan 28 12:13:54 2008 UTC vs.
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* 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
38	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);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	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
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	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
58	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
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	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
101	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
102	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
103	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
104	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
105	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
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	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
123	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
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	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
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	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_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	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
159	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
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	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
167	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
168	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
169	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
170	(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
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	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
187	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
188	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
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	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.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	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,
194	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.
195		234
196	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
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
217		256
218	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
219	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
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	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
222	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
223	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
224	(such as abort).	263	(such as abort).
225		264
226	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.
…		…
241		280
242	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
243	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
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245		284
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
257	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
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	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
263	function.	295	function.
264		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
265	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
266	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
267	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
268	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
269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	306	C<ev_default_init>.
271		307
272	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
…		…
281	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
282	thing, believe me).	318	thing, believe me).
283		319
284	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
285		321
286	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
287	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
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	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
290	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
291	around bugs.	327	around bugs.
…		…
297	enabling this flag.	333	enabling this flag.
298		334
299	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,
300	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
301	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
302	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
303	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
304	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
305		341
306	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
307	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
308	flag.	344	flag.
309		345
310	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>
311	environment variable.	347	environment variable.
312		348
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		350
315	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
…		…
317	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
318	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
319	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.
320		356
321	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
322	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
323	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
324	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
325	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
326	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).
327		367
328	=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)
329		369
330	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
331	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
332	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
333	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,
334	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
335	performance tips.	375	performance tips.
336		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
337	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
338		381
339	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,
340	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
341	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),
342	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
343	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
344	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
345	support for dup.	388	support for dup.
346		389
347	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
348	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
349	(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
350	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
351	very well if you register events for both fds.	394	very well if you register events for both fds.
352		395
353	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
354	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
355	(or space) is available.	398	(or space) is available.
356		399
357	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
358	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,
359	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.
360		405
361	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
362	all kernel versions tested so far.	407	all kernel versions tested so far.
363		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		413
366	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
367	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
368	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
369	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
370	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
371	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.
372	system like NetBSD.
373		420
374	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
375	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
376	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
377		424
378	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
379	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
380	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
381	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
382	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
383	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
384		431
385	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
386		433
387	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
388	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
389	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
390	(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
391	(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,
392	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>.
393		444
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		446
396	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
397	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		453
403	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,
404	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)).
405		456
406	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
407	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
408	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
409		460
410	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
411	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
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	464	might perform better.
414		465
415	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
417	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>.
418		473
419	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
420		475
421	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
422	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
…		…
424		479
425	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
426		481
427	=back	482	=back
428		483
429	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
430	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
431	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		487
433	The most typical usage is like this:	488	Example: This is the most typical usage.
434		489
435	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		492
438	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
439	environment settings to be taken into account:	494	environment settings to be taken into account:
440		495
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		497
443	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
444	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
445	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):
446		502
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		504
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		506
451	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
452	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
453	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
454	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
455		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
456	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.
457		517
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	519	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
461		521
462	=item ev_default_destroy ()	522	=item ev_default_destroy ()
463		523
464	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
465	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
466	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
467	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
468	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
469	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
470	for example).	530	for example).
471		531
472	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
…		…
504		564
505	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
506		566
507	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
508	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
509	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
510		576
511	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
512		578
513	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
514	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
…		…
529	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
530	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
531	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
532	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
533		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
534	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
535		613
536	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
537	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
538	events.	616	events.
…		…
540	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
541	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.
542		620
543	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
544	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
545	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
546	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
547	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.
548		627
549	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
550	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
551	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.
552		632
553	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
554	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
555	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
556	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
557	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
558	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
559	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
560		644
561	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
562		646
563	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- 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.
566	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
567	- 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.
568	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	662	- Queue all expired timers.
578	- Queue all outstanding periodics.	663	- Queue all expired periodics.
579	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	665	- Queue all check watchers.
581	- 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).
582	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
583	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
584	- 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
…		…
589	anymore.	674	anymore.
590		675
591	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
592	... 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..)
593	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
594	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
595		680
596	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
597		682
598	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
599	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
…		…
606		691
607	=item ev_unref (loop)	692	=item ev_unref (loop)
608		693
609	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
610	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
611	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
612	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>
613	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
614	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
615	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
616	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
617	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
618	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>
619	(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,
620	respectively).	708	respectively).
621		709
622	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>
623	running when nothing else is active.	711	running when nothing else is active.
624		712
625	struct ev_signal exitsig;	713	struct ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	716	evf_unref (loop);
629		717
630	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
631		719
632	ev_ref (loop);	720	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
634		722
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		724
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		726
639	These advanced functions influence the time that libev will spend waiting	727	These advanced functions influence the time that libev will spend waiting
640	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
641	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.
642		731
643	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>)
644	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
645	increase efficiency of loop iterations.	734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
646		736
647	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
648	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
649	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
650	events, especially with backends like C<select ()> which have a high	740	events, especially with backends like C<select ()> which have a high
651	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.
652		742
653	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
654	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,
…		…
656	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
657	introduce an additional C<ev_sleep ()> call into most loop iterations.	747	introduce an additional C<ev_sleep ()> call into most loop iterations.
658		748
659	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
660	to spend more time collecting timeouts, at the expense of increased	750	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	751	latency/jitter/inexactness (the watcher callback will be called
662	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
663	any overhead in libev.	753	value will not introduce any overhead in libev.
664		754
665	Many (busy) programs can usually benefit by setting the io collect	755	Many (busy) programs can usually benefit by setting the I/O collect
666	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
667	interactive servers (of course not for games), likewise for timeouts. It	757	interactive servers (of course not for games), likewise for timeouts. It
668	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>,
669	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.
670		779
671	=back	780	=back
672		781
673		782
674	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
675		784
676	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
677	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
678	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:
679		788
680	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)
681	{	790	{
682	ev_io_stop (w);	791	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
684	}	793	}
685		794
686	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
687	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
688	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
691	ev_loop (loop, 0);	800	ev_loop (loop, 0);
692		801
693	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
694	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,
695	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
696		805
697	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
698	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
699	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
700	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
701	is readable and/or writable).	810	is readable and/or writable).
702		811
703	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
704	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
…		…
774	=item C<EV_FORK>	883	=item C<EV_FORK>
775		884
776	The event loop has been resumed in the child process after fork (see	885	The event loop has been resumed in the child process after fork (see
777	C<ev_fork>).	886	C<ev_fork>).
778		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
779	=item C<EV_ERROR>	892	=item C<EV_ERROR>
780		893
781	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
782	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
783	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
784	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
785	with the watcher being stopped.	898	with the watcher being stopped.
786		899
787	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
788	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
789	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
790	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
791	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
792		906
793	=back	907	=back
794		908
795	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
796		910
…		…
812	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
813		927
814	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,
815	int revents)>.	929	int revents)>.
816		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
817	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
818		938
819	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
820	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
821	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
…		…
823	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
824		944
825	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
826	(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.
827		947
		948	See C<ev_init>, above, for an example.
		949
828	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
829		951
830	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
831	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
832	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);
833		959
834	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
835		961
836	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
837	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);
838		969
839	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
840		971
841	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
842	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
899		1030
900	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
901		1032
902	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
903	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
904	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
905		1037
906	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
907		1039
908	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
909	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
910	watcher isn't pending it does nothing and returns C<0>.	1042	watcher isn't pending it does nothing and returns C<0>.
911		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
912	=back	1047	=back
913		1048
914		1049
915	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
916		1051
917	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
918	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
919	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
920	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
921	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
922	data:	1057	data:
923		1058
924	struct my_io	1059	struct my_io
925	{	1060	{
926	struct ev_io io;	1061	struct ev_io io;
927	int otherfd;	1062	int otherfd;
928	void *somedata;	1063	void *somedata;
929	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
930	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
931		1070
932	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
933	can cast it back to your own type:	1072	can cast it back to your own type:
934		1073
935	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)
936	{	1075	{
937	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
938	...	1077	...
939	}	1078	}
940		1079
941	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
942	instead have been omitted.	1081	instead have been omitted.
943		1082
944	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
945	watchers:	1084	embedded watchers:
946		1085
947	struct my_biggy	1086	struct my_biggy
948	{	1087	{
949	int some_data;	1088	int some_data;
950	ev_timer t1;	1089	ev_timer t1;
951	ev_timer t2;	1090	ev_timer t2;
952	}	1091	}
953		1092
954	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
955	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):
956		1098
957	#include <stddef.h>	1099	#include <stddef.h>
958		1100
959	static void	1101	static void
960	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
961	{	1103	{
962	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
963	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
964	}	1106	}
965		1107
966	static void	1108	static void
967	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
968	{	1110	{
969	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
970	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
971	}	1113	}
972		1114
973		1115
974	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
975		1117
976	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
1000	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
1001	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
1002	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
1003	required if you know what you are doing).	1145	required if you know what you are doing).
1004		1146
1005	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
1006	(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
1007	C<EVBACKEND_POLL>).	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1008		1150
1009	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
1010	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
1011	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
1012	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
1013	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
1014	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
1015	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
1016	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.
1017		1159
1018	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
1019	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
1020	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
1021	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
1022	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.
1023		1169
1024	=head3 The special problem of disappearing file descriptors	1170	=head3 The special problem of disappearing file descriptors
1025		1171
1026	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
1027	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,
1028	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
1029	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
1030	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
1031	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
1032	fact, a different file descriptor.	1178	fact, a different file descriptor.
1033		1179
…		…
1062	To support fork in your programs, you either have to call	1208	To support fork in your programs, you either have to call
1063	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,
1064	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1065	C<EVBACKEND_POLL>.	1211	C<EVBACKEND_POLL>.
1066		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
1067		1224
1068	=head3 Watcher-Specific Functions	1225	=head3 Watcher-Specific Functions
1069		1226
1070	=over 4	1227	=over 4
1071		1228
1072	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
1073		1230
1074	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
1075		1232
1076	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
1077	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
1078	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.
1079		1236
1080	=item int fd [read-only]	1237	=item int fd [read-only]
1081		1238
1082	The file descriptor being watched.	1239	The file descriptor being watched.
1083		1240
…		…
1091		1248
1092	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
1093	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
1094	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
1095		1252
1096	static void	1253	static void
1097	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)
1098	{	1255	{
1099	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
1100	.. 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
1101	}	1258	}
1102		1259
1103	...	1260	...
1104	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
1105	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
1106	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);
1107	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
1108	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
1109		1266
1110		1267
1111	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
1112		1269
1113	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
1114	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
1115		1272
1116	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
1117	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
1118	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
1119	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1120	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.
1121		1290
1122	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
1123	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
1124	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
1125	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
1126	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:
1127		1296
1128	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1129		1298
1130	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
1131	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
1132	order of execution is undefined.	1301	()>.
1133		1302
1134	=head3 Watcher-Specific Functions and Data Members	1303	=head3 Watcher-Specific Functions and Data Members
1135		1304
1136	=over 4	1305	=over 4
1137		1306
1138	=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)
1139		1308
1140	=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)
1141		1310
1142	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>
1143	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
1144	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
1145	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
1146		1316
1147	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
1148	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
1149	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
1150	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
1151	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.
1152		1322
1153	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
1154		1324
1155	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
1156	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
1157		1327
1158	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
1159		1329
1160	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).
1161		1331
1162	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
1163	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.
1164		1334
1165	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
1166	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
1167	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
1168	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
1169	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
1170	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
1171	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
…		…
1185	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1186		1356
1187	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
1188	you want to modify its timeout value.	1358	you want to modify its timeout value.
1189		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
1190	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1191		1367
1192	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
1193	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),
1194	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1195		1371
1196	=back	1372	=back
1197		1373
1198	=head3 Examples	1374	=head3 Examples
1199		1375
1200	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1201		1377
1202	static void	1378	static void
1203	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)
1204	{	1380	{
1205	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1206	}	1382	}
1207		1383
1208	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1209	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1210	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1211		1387
1212	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
1213	inactivity.	1389	inactivity.
1214		1390
1215	static void	1391	static void
1216	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)
1217	{	1393	{
1218	.. ten seconds without any activity	1394	.. ten seconds without any activity
1219	}	1395	}
1220		1396
1221	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1222	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 */
1223	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1224	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1225		1401
1226	// 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":
1227	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1228	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1229		1405
1230		1406
1231	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1232		1408
1233	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
1234	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1235		1411
1236	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)
1237	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
1238	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
1239	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 ()
1240	+ 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
1241	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
1242	roughly 10 seconds later).	1419	roughly 10 seconds later as it uses a relative timeout).
1243		1420
1244	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,
1245	triggering an event on each midnight, local time or other, complicated,	1422	such as triggering an event on each "midnight, local time", or other
1246	rules.	1423	complicated rules.
1247		1424
1248	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
1249	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
1250	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
1251		1428
1252	=head3 Watcher-Specific Functions and Data Members	1429	=head3 Watcher-Specific Functions and Data Members
1253		1430
1254	=over 4	1431	=over 4
1255		1432
1256	=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)
1257		1434
1258	=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)
1259		1436
1260	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
1261	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1262		1439
1263	=over 4	1440	=over 4
1264		1441
1265	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1266		1443
1267	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
1268	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
1269	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
1270	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1271		1448
1272	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1273		1450
1274	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
1275	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)
1276	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1277		1454
1278	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
1279	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1280		1458
1281	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1282		1460
1283	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,
1284	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
1285	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
1286	by 3600.	1464	by 3600.
1287		1465
1288	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
1289	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
1290	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.
1291		1469
1292	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
1293	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
1294	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).
1295		1478
1296	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1297		1480
1298	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
1299	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1300	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
1301	current time as second argument.	1484	current time as second argument.
1302		1485
1303	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,
1304	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1305	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1306	starting an C<ev_prepare> watcher, which is legal).
1307		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
1308	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
1309	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1310		1495
1311	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)
1312	{	1497	{
1313	return now + 60.;	1498	return now + 60.;
1314	}	1499	}
…		…
1316	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
1317	(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
1318	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
1319	might be called at other times, too.	1504	might be called at other times, too.
1320		1505
1321	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
1322	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1323		1508
1324	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
1325	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
1326	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
1327	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
1328	reason I omitted it as an example).	1513	reason I omitted it as an example).
1329		1514
1330	=back	1515	=back
…		…
1334	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
1335	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1336	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
1337	program when the crontabs have changed).	1522	program when the crontabs have changed).
1338		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
1339	=item ev_tstamp offset [read-write]	1529	=item ev_tstamp offset [read-write]
1340		1530
1341	When repeating, this contains the offset value, otherwise this is the	1531	When repeating, this contains the offset value, otherwise this is the
1342	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>).
1343		1533
…		…
1354		1544
1355	The current reschedule callback, or C<0>, if this functionality is	1545	The current reschedule callback, or C<0>, if this functionality is
1356	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
1357	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.
1358		1548
1359	=item ev_tstamp at [read-only]
1360
1361	When active, contains the absolute time that the watcher is supposed to
1362	trigger next.
1363
1364	=back	1549	=back
1365		1550
1366	=head3 Examples	1551	=head3 Examples
1367		1552
1368	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1369	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1370	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1371		1556
1372	static void	1557	static void
1373	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)
1374	{	1559	{
1375	... 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)
1376	}	1561	}
1377		1562
1378	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1379	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1380	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1381		1566
1382	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:
1383		1568
1384	#include <math.h>	1569	#include <math.h>
1385		1570
1386	static ev_tstamp	1571	static ev_tstamp
1387	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1388	{	1573	{
1389	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1390	}	1575	}
1391		1576
1392	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);
1393		1578
1394	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1395		1580
1396	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1397	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1398	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1399	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1400		1585
1401		1586
1402	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1403		1588
1404	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
1405	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
1406	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
1407	normal event processing, like any other event.	1592	normal event processing, like any other event.
1408		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
1409	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
1410	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1411	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
1412	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
1413	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
1414	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
		1604
		1605	If possible and supported, libev will install its handlers with
		1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1607	interrupted. If you have a problem with system calls getting interrupted by
		1608	signals you can block all signals in an C<ev_check> watcher and unblock
		1609	them in an C<ev_prepare> watcher.
1415		1610
1416	=head3 Watcher-Specific Functions and Data Members	1611	=head3 Watcher-Specific Functions and Data Members
1417		1612
1418	=over 4	1613	=over 4
1419		1614
…		…
1428		1623
1429	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1430		1625
1431	=back	1626	=back
1432		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1631
		1632	static void
		1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1634	{
		1635	ev_unloop (loop, EVUNLOOP_ALL);
		1636	}
		1637
		1638	struct ev_signal signal_watcher;
		1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1640	ev_signal_start (loop, &sigint_cb);
		1641
1433		1642
1434	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1435		1644
1436	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
1437	some child status changes (most typically when a child of yours dies).	1646	some child status changes (most typically when a child of yours dies or
		1647	exits). It is permissible to install a child watcher I<after> the child
		1648	has been forked (which implies it might have already exited), as long
		1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
		1653
		1654	Only the default event loop is capable of handling signals, and therefore
		1655	you can only register child watchers in the default event loop.
		1656
		1657	=head3 Process Interaction
		1658
		1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1660	initialised. This is necessary to guarantee proper behaviour even if
		1661	the first child watcher is started after the child exits. The occurrence
		1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1663	synchronously as part of the event loop processing. Libev always reaps all
		1664	children, even ones not watched.
		1665
		1666	=head3 Overriding the Built-In Processing
		1667
		1668	Libev offers no special support for overriding the built-in child
		1669	processing, but if your application collides with libev's default child
		1670	handler, you can override it easily by installing your own handler for
		1671	C<SIGCHLD> after initialising the default loop, and making sure the
		1672	default loop never gets destroyed. You are encouraged, however, to use an
		1673	event-based approach to child reaping and thus use libev's support for
		1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
1438		1682
1439	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1440		1684
1441	=over 4	1685	=over 4
1442		1686
…		…
1468		1712
1469	=back	1713	=back
1470		1714
1471	=head3 Examples	1715	=head3 Examples
1472		1716
1473	Example: Try to exit cleanly on SIGINT and SIGTERM.	1717	Example: C<fork()> a new process and install a child handler to wait for
		1718	its completion.
1474		1719
		1720	ev_child cw;
		1721
1475	static void	1722	static void
1476	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1477	{	1724	{
1478	ev_unloop (loop, EVUNLOOP_ALL);	1725	ev_child_stop (EV_A_ w);
		1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1479	}	1727	}
1480		1728
1481	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1482	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1483	ev_signal_start (loop, &sigint_cb);	1731	if (pid < 0)
		1732	// error
		1733	else if (pid == 0)
		1734	{
		1735	// the forked child executes here
		1736	exit (1);
		1737	}
		1738	else
		1739	{
		1740	ev_child_init (&cw, child_cb, pid, 0);
		1741	ev_child_start (EV_DEFAULT_ &cw);
		1742	}
1484		1743
1485		1744
1486	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1487		1746
1488	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
1489	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
1490	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1491		1750
1492	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
1493	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
…		…
1496	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1497		1756
1498	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
1499	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1500		1759
1501	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
1502	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
1503	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1504	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!)
1505	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
1506	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1507	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
1508	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1509		1768
1510	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,
1511	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1512	resource-intensive.	1771	resource-intensive.
1513		1772
1514	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
1515	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1516	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
1517	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1518	to fall back to regular polling again even with inotify, but changes are
1519	usually detected immediately, and if the file exists there will be no
1520	polling.
1521		1777
1522	=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
1523		1796
1524	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
1525	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
1526	change detection where possible. The inotify descriptor will be created lazily	1799	change detection where possible. The inotify descriptor will be created lazily
1527	when the first C<ev_stat> watcher is being started.	1800	when the first C<ev_stat> watcher is being started.
1528		1801
1529	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
1530	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
1531	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
1532	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.
1533		1807
1534	(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
1535	implement this functionality, due to the requirement of having a file	1809	implement this functionality, due to the requirement of having a file
1536	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.
1537		1812
1538	=head3 The special problem of stat time resolution	1813	=head3 The special problem of stat time resolution
1539		1814
1540	The C<stat ()> syscall only supports full-second resolution portably, and	1815	The C<stat ()> system call only supports full-second resolution portably, and
1541	even on systems where the resolution is higher, many filesystems still	1816	even on systems where the resolution is higher, most file systems still
1542	only support whole seconds.	1817	only support whole seconds.
1543		1818
1544	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
1545	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
1546	your callback, which does something. When there is another update within	1821	calls your callback, which does something. When there is another update
1547	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).
1548		1824
1549	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
1550	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
1551	(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);
1552	is added to work around small timing inconsistencies of some operating	1828	ev_timer_again (loop, w)>).
1553	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).
1554		1838
1555	=head3 Watcher-Specific Functions and Data Members	1839	=head3 Watcher-Specific Functions and Data Members
1556		1840
1557	=over 4	1841	=over 4
1558		1842
…		…
1564	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
1565	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
1566	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
1567	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1568		1852
1569	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,
1570	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
1571	last change was detected).	1855	last change was detected).
1572		1856
1573	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1574		1858
1575	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
1576	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
1577	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1578	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.
1579		1864
1580	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1581		1866
1582	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
1583	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
1584	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
1585	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1586		1872
1587	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1588		1874
1589	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1590	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>.
1591		1879
1592	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1593		1881
1594	The specified interval.	1882	The specified interval.
1595		1883
1596	=item const char *path [read-only]	1884	=item const char *path [read-only]
1597		1885
1598	The filesystem path that is being watched.	1886	The file system path that is being watched.
1599		1887
1600	=back	1888	=back
1601		1889
1602	=head3 Examples	1890	=head3 Examples
1603		1891
1604	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1605		1893
1606	static void	1894	static void
1607	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1608	{	1896	{
1609	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1610	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1611	{	1899	{
1612	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1613	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1614	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1615	}	1903	}
1616	else	1904	else
1617	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1618	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1619	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1620	}	1908	}
1621		1909
1622	...	1910	...
1623	ev_stat passwd;	1911	ev_stat passwd;
1624		1912
1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1626	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
1627		1915
1628	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
1629	miss updates (however, frequent updates will delay processing, too, so	1917	miss updates (however, frequent updates will delay processing, too, so
1630	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
1631	C<ev_timer> callback invocation).	1919	C<ev_timer> callback invocation).
1632		1920
1633	static ev_stat passwd;	1921	static ev_stat passwd;
1634	static ev_timer timer;	1922	static ev_timer timer;
1635		1923
1636	static void	1924	static void
1637	timer_cb (EV_P_ ev_timer *w, int revents)	1925	timer_cb (EV_P_ ev_timer *w, int revents)
1638	{	1926	{
1639	ev_timer_stop (EV_A_ w);	1927	ev_timer_stop (EV_A_ w);
1640		1928
1641	/* now it's one second after the most recent passwd change */	1929	/* now it's one second after the most recent passwd change */
1642	}	1930	}
1643		1931
1644	static void	1932	static void
1645	stat_cb (EV_P_ ev_stat *w, int revents)	1933	stat_cb (EV_P_ ev_stat *w, int revents)
1646	{	1934	{
1647	/* reset the one-second timer */	1935	/* reset the one-second timer */
1648	ev_timer_again (EV_A_ &timer);	1936	ev_timer_again (EV_A_ &timer);
1649	}	1937	}
1650		1938
1651	...	1939	...
1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1653	ev_stat_start (loop, &passwd);	1941	ev_stat_start (loop, &passwd);
1654	ev_timer_init (&timer, timer_cb, 0., 1.01);	1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1655		1943
1656		1944
1657	=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...
1658		1946
1659	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
1660	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1661	count).	1949	as receiving "events").
1662		1950
1663	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
1664	(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
1665	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
1666	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
…		…
1690	=head3 Examples	1978	=head3 Examples
1691		1979
1692	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
1693	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1694		1982
1695	static void	1983	static void
1696	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)
1697	{	1985	{
1698	free (w);	1986	free (w);
1699	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1700	// no longer anything immediate to do.	1988	// no longer anything immediate to do.
1701	}	1989	}
1702		1990
1703	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1704	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1705	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1706		1994
1707		1995
1708	=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!
1709		1997
1710	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:
1711	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1712	afterwards.	2000	afterwards.
1713		2001
1714	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
1715	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>
…		…
1718	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,
1719	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
1720	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1721		2009
1722	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
1723	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
1724	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1725	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1726	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,
1727	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>
1728	watcher).	2016	watcher).
1729		2017
1730	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
1731	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
1732	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
1733	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1734	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
1735	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
1736	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
1737	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1738		2026
1739	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
1740	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1741	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
1742	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
…		…
1745	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1746	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1747		2035
1748	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>)
1749	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
1750	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
1751	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1752	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
1753	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
1754	(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
1755	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
1756	coexist peacefully with others).	2046	others).
1757		2047
1758	=head3 Watcher-Specific Functions and Data Members	2048	=head3 Watcher-Specific Functions and Data Members
1759		2049
1760	=over 4	2050	=over 4
1761		2051
…		…
1763		2053
1764	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1765		2055
1766	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1767	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>
1768	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1769		2060
1770	=back	2061	=back
1771		2062
1772	=head3 Examples	2063	=head3 Examples
1773		2064
1774	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
1775	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
1776	(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
1777	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
1778	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
1779	into the Glib event loop).	2070	Glib event loop).
1780		2071
1781	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,
1782	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
1783	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
1784	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
1785	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.
1786		2077
1787	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1788	static ev_timer tw;	2079	static ev_timer tw;
1789		2080
1790	static void	2081	static void
1791	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1792	{	2083	{
1793	}	2084	}
1794		2085
1795	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1796	static void	2087	static void
1797	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1798	{	2089	{
1799	int timeout = 3600000;	2090	int timeout = 3600000;
1800	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1801	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1803		2094
1804	/* 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 */
1805	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1806	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1807		2098
1808	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1809	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1810	{	2101	{
1811	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1812	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1813	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1814		2105
1815	fds [i].revents = 0;	2106	fds [i].revents = 0;
1816	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1817	}	2108	}
1818	}	2109	}
1819		2110
1820	// stop all watchers after blocking	2111	// stop all watchers after blocking
1821	static void	2112	static void
1822	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1823	{	2114	{
1824	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1825		2116
1826	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1827	{	2118	{
1828	// set the relevant poll flags	2119	// set the relevant poll flags
1829	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1830	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1831	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1832	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1833	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1834		2125
1835	// now stop the watcher	2126	// now stop the watcher
1836	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
1837	}	2128	}
1838		2129
1839	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1840	}	2131	}
1841		2132
1842	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>
1843	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
1844		2135
1845	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
1846	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
1847	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
1848		2139
1849	static void	2140	static void
1850	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
1851	{	2142	{
1852	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
1853	update_now (EV_A);	2144	update_now (EV_A);
1854		2145
1855	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
1856	}	2147	}
1857		2148
1858	static void	2149	static void
1859	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
1860	{	2151	{
1861	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1862	update_now (EV_A);	2153	update_now (EV_A);
1863		2154
1864	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1865	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1866	}	2157	}
1867		2158
1868	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
1869		2160
1870	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
1871	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
1872	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
1873	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
1874	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
1875		2167
1876	static gint	2168	static gint
1877	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1878	{	2170	{
1879	int got_events = 0;	2171	int got_events = 0;
1880		2172
1881	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
1882	// 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
1883		2175
1884	if (timeout >= 0)	2176	if (timeout >= 0)
1885	// create/start timer	2177	// create/start timer
1886		2178
1887	// poll	2179	// poll
1888	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
1889		2181
1890	// stop timer again	2182	// stop timer again
1891	if (timeout >= 0)	2183	if (timeout >= 0)
1892	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
1893		2185
1894	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
1895	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
1896	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
1897		2189
1898	return got_events;	2190	return got_events;
1899	}	2191	}
1900		2192
1901		2193
1902	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1903		2195
1904	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
…		…
1910	prioritise I/O.	2202	prioritise I/O.
1911		2203
1912	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
1913	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
1914	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
1915	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
1916	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
1917	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
1918	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 :)
1919		2212
1920	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
1921	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),
1922	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
1923	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
1924	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.
1925		2218
1926	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
1927	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
1928	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
1929	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
…		…
1937	interested in that.	2230	interested in that.
1938		2231
1939	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1940	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,
1941	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
1942	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1943		2237
1944	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable, only the ones returned by
1945	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1946	portable one.	2240	portable one.
1947		2241
…		…
1960		2254
1961	Configures the watcher to embed the given loop, which must be	2255	Configures the watcher to embed the given loop, which must be
1962	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
1963	invoked automatically, otherwise it is the responsibility of the callback	2257	invoked automatically, otherwise it is the responsibility of the callback
1964	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,
1965	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).
1966		2260
1967	=item ev_embed_sweep (loop, ev_embed *)	2261	=item ev_embed_sweep (loop, ev_embed *)
1968		2262
1969	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
1970	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
1971	apropriate way for embedded loops.	2265	appropriate way for embedded loops.
1972		2266
1973	=item struct ev_loop *other [read-only]	2267	=item struct ev_loop *other [read-only]
1974		2268
1975	The embedded event loop.	2269	The embedded event loop.
1976		2270
…		…
1978		2272
1979	=head3 Examples	2273	=head3 Examples
1980		2274
1981	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
1982	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
1983	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
1984	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
1985	used).	2279	used).
1986		2280
1987	struct ev_loop *loop_hi = ev_default_init (0);	2281	struct ev_loop *loop_hi = ev_default_init (0);
1988	struct ev_loop *loop_lo = 0;	2282	struct ev_loop *loop_lo = 0;
1989	struct ev_embed embed;	2283	struct ev_embed embed;
1990		2284
1991	// see if there is a chance of getting one that works	2285	// see if there is a chance of getting one that works
1992	// (remember that a flags value of 0 means autodetection)	2286	// (remember that a flags value of 0 means autodetection)
1993	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1994	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1995	: 0;	2289	: 0;
1996		2290
1997	// 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
1998	if (loop_lo)	2292	if (loop_lo)
1999	{	2293	{
2000	ev_embed_init (&embed, 0, loop_lo);	2294	ev_embed_init (&embed, 0, loop_lo);
2001	ev_embed_start (loop_hi, &embed);	2295	ev_embed_start (loop_hi, &embed);
2002	}	2296	}
2003	else	2297	else
2004	loop_lo = loop_hi;	2298	loop_lo = loop_hi;
2005		2299
2006	Example: Check if kqueue is available but not recommended and create	2300	Example: Check if kqueue is available but not recommended and create
2007	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
2008	kqueue implementation). Store the kqueue/socket-only event loop in	2302	kqueue implementation). Store the kqueue/socket-only event loop in
2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2010		2304
2011	struct ev_loop *loop = ev_default_init (0);	2305	struct ev_loop *loop = ev_default_init (0);
2012	struct ev_loop *loop_socket = 0;	2306	struct ev_loop *loop_socket = 0;
2013	struct ev_embed embed;	2307	struct ev_embed embed;
2014		2308
2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2017	{	2311	{
2018	ev_embed_init (&embed, 0, loop_socket);	2312	ev_embed_init (&embed, 0, loop_socket);
2019	ev_embed_start (loop, &embed);	2313	ev_embed_start (loop, &embed);
2020	}	2314	}
2021		2315
2022	if (!loop_socket)	2316	if (!loop_socket)
2023	loop_socket = loop;	2317	loop_socket = loop;
2024		2318
2025	// 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
2026		2320
2027		2321
2028	=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
2029		2323
2030	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
…		…
2046	believe me.	2340	believe me.
2047		2341
2048	=back	2342	=back
2049		2343
2050		2344
		2345	=head2 C<ev_async> - how to wake up another event loop
		2346
		2347	In general, you cannot use an C<ev_loop> from multiple threads or other
		2348	asynchronous sources such as signal handlers (as opposed to multiple event
		2349	loops - those are of course safe to use in different threads).
		2350
		2351	Sometimes, however, you need to wake up another event loop you do not
		2352	control, for example because it belongs to another thread. This is what
		2353	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2354	can signal it by calling C<ev_async_send>, which is thread- and signal
		2355	safe.
		2356
		2357	This functionality is very similar to C<ev_signal> watchers, as signals,
		2358	too, are asynchronous in nature, and signals, too, will be compressed
		2359	(i.e. the number of callback invocations may be less than the number of
		2360	C<ev_async_sent> calls).
		2361
		2362	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2363	just the default loop.
		2364
		2365	=head3 Queueing
		2366
		2367	C<ev_async> does not support queueing of data in any way. The reason
		2368	is that the author does not know of a simple (or any) algorithm for a
		2369	multiple-writer-single-reader queue that works in all cases and doesn't
		2370	need elaborate support such as pthreads.
		2371
		2372	That means that if you want to queue data, you have to provide your own
		2373	queue. But at least I can tell you would implement locking around your
		2374	queue:
		2375
		2376	=over 4
		2377
		2378	=item queueing from a signal handler context
		2379
		2380	To implement race-free queueing, you simply add to the queue in the signal
		2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2382	some fictitious SIGUSR1 handler:
		2383
		2384	static ev_async mysig;
		2385
		2386	static void
		2387	sigusr1_handler (void)
		2388	{
		2389	sometype data;
		2390
		2391	// no locking etc.
		2392	queue_put (data);
		2393	ev_async_send (EV_DEFAULT_ &mysig);
		2394	}
		2395
		2396	static void
		2397	mysig_cb (EV_P_ ev_async *w, int revents)
		2398	{
		2399	sometype data;
		2400	sigset_t block, prev;
		2401
		2402	sigemptyset (&block);
		2403	sigaddset (&block, SIGUSR1);
		2404	sigprocmask (SIG_BLOCK, &block, &prev);
		2405
		2406	while (queue_get (&data))
		2407	process (data);
		2408
		2409	if (sigismember (&prev, SIGUSR1)
		2410	sigprocmask (SIG_UNBLOCK, &block, 0);
		2411	}
		2412
		2413	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2414	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2415	either...).
		2416
		2417	=item queueing from a thread context
		2418
		2419	The strategy for threads is different, as you cannot (easily) block
		2420	threads but you can easily preempt them, so to queue safely you need to
		2421	employ a traditional mutex lock, such as in this pthread example:
		2422
		2423	static ev_async mysig;
		2424	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2425
		2426	static void
		2427	otherthread (void)
		2428	{
		2429	// only need to lock the actual queueing operation
		2430	pthread_mutex_lock (&mymutex);
		2431	queue_put (data);
		2432	pthread_mutex_unlock (&mymutex);
		2433
		2434	ev_async_send (EV_DEFAULT_ &mysig);
		2435	}
		2436
		2437	static void
		2438	mysig_cb (EV_P_ ev_async *w, int revents)
		2439	{
		2440	pthread_mutex_lock (&mymutex);
		2441
		2442	while (queue_get (&data))
		2443	process (data);
		2444
		2445	pthread_mutex_unlock (&mymutex);
		2446	}
		2447
		2448	=back
		2449
		2450
		2451	=head3 Watcher-Specific Functions and Data Members
		2452
		2453	=over 4
		2454
		2455	=item ev_async_init (ev_async *, callback)
		2456
		2457	Initialises and configures the async watcher - it has no parameters of any
		2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2459	believe me.
		2460
		2461	=item ev_async_send (loop, ev_async *)
		2462
		2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2465	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2467	section below on what exactly this means).
		2468
		2469	This call incurs the overhead of a system call only once per loop iteration,
		2470	so while the overhead might be noticeable, it doesn't apply to repeated
		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.
		2486
		2487	=back
		2488
		2489
2051	=head1 OTHER FUNCTIONS	2490	=head1 OTHER FUNCTIONS
2052		2491
2053	There are some other functions of possible interest. Described. Here. Now.	2492	There are some other functions of possible interest. Described. Here. Now.
2054		2493
2055	=over 4	2494	=over 4
…		…
2062	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
2063	more watchers yourself.	2502	more watchers yourself.
2064		2503
2065	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
2066	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
2067	C<events> set will be craeted and started.	2506	C<events> set will be created and started.
2068		2507
2069	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
2070	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
2071	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
2072	dubious value.	2511	dubious value.
…		…
2074	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
2075	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
2076	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>
2077	value passed to C<ev_once>:	2516	value passed to C<ev_once>:
2078		2517
2079	static void stdin_ready (int revents, void *arg)	2518	static void stdin_ready (int revents, void *arg)
2080	{	2519	{
2081	if (revents & EV_TIMEOUT)	2520	if (revents & EV_TIMEOUT)
2082	/* doh, nothing entered */;	2521	/* doh, nothing entered */;
2083	else if (revents & EV_READ)	2522	else if (revents & EV_READ)
2084	/* stdin might have data for us, joy! */;	2523	/* stdin might have data for us, joy! */;
2085	}	2524	}
2086		2525
2087	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2088		2527
2089	=item ev_feed_event (ev_loop *, watcher *, int revents)	2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2090		2529
2091	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
2092	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
…		…
2097	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
2098	the given events it.	2537	the given events it.
2099		2538
2100	=item ev_feed_signal_event (ev_loop *loop, int signum)	2539	=item ev_feed_signal_event (ev_loop *loop, int signum)
2101		2540
2102	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
2103	loop!).	2542	loop!).
2104		2543
2105	=back	2544	=back
2106		2545
2107		2546
…		…
2123		2562
2124	=item * Priorities are not currently supported. Initialising priorities	2563	=item * Priorities are not currently supported. Initialising priorities
2125	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
2126	is an ev_pri field.	2565	is an ev_pri field.
2127		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
2128	=item * Other members are not supported.	2570	=item * Other members are not supported.
2129		2571
2130	=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
2131	to use the libev header file and library.	2573	to use the libev header file and library.
2132		2574
2133	=back	2575	=back
2134		2576
2135	=head1 C++ SUPPORT	2577	=head1 C++ SUPPORT
2136		2578
2137	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
2138	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
2139	the callback model to a model using method callbacks on objects.	2581	the callback model to a model using method callbacks on objects.
2140		2582
2141	To use it,	2583	To use it,
2142		2584
2143	#include <ev++.h>	2585	#include <ev++.h>
2144		2586
2145	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
2146	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
2147	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
2148	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2590	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2215	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
2216	thunking function, making it as fast as a direct C callback.	2658	thunking function, making it as fast as a direct C callback.
2217		2659
2218	Example: simple class declaration and watcher initialisation	2660	Example: simple class declaration and watcher initialisation
2219		2661
2220	struct myclass	2662	struct myclass
2221	{	2663	{
2222	void io_cb (ev::io &w, int revents) { }	2664	void io_cb (ev::io &w, int revents) { }
2223	}	2665	}
2224		2666
2225	myclass obj;	2667	myclass obj;
2226	ev::io iow;	2668	ev::io iow;
2227	iow.set <myclass, &myclass::io_cb> (&obj);	2669	iow.set <myclass, &myclass::io_cb> (&obj);
2228		2670
2229	=item w->set<function> (void *data = 0)	2671	=item w->set<function> (void *data = 0)
2230		2672
2231	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
2232	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
…		…
2236		2678
2237	See the method-C<set> above for more details.	2679	See the method-C<set> above for more details.
2238		2680
2239	Example:	2681	Example:
2240		2682
2241	static void io_cb (ev::io &w, int revents) { }	2683	static void io_cb (ev::io &w, int revents) { }
2242	iow.set <io_cb> ();	2684	iow.set <io_cb> ();
2243		2685
2244	=item w->set (struct ev_loop *)	2686	=item w->set (struct ev_loop *)
2245		2687
2246	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
2247	do this when the watcher is inactive (and not pending either).	2689	do this when the watcher is inactive (and not pending either).
2248		2690
2249	=item w->set ([args])	2691	=item w->set ([arguments])
2250		2692
2251	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
2252	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
2253	automatically stopped and restarted when reconfiguring it with this	2695	automatically stopped and restarted when reconfiguring it with this
2254	method.	2696	method.
2255		2697
2256	=item w->start ()	2698	=item w->start ()
…		…
2280	=back	2722	=back
2281		2723
2282	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
2283	the constructor.	2725	the constructor.
2284		2726
2285	class myclass	2727	class myclass
2286	{	2728	{
2287	ev::io io; void io_cb (ev::io &w, int revents);	2729	ev::io io; void io_cb (ev::io &w, int revents);
2288	ev:idle idle void idle_cb (ev::idle &w, int revents);	2730	ev:idle idle void idle_cb (ev::idle &w, int revents);
2289		2731
2290	myclass (int fd)	2732	myclass (int fd)
2291	{	2733	{
2292	io .set <myclass, &myclass::io_cb > (this);	2734	io .set <myclass, &myclass::io_cb > (this);
2293	idle.set <myclass, &myclass::idle_cb> (this);	2735	idle.set <myclass, &myclass::idle_cb> (this);
2294		2736
2295	io.start (fd, ev::READ);	2737	io.start (fd, ev::READ);
2296	}	2738	}
2297	};	2739	};
		2740
		2741
		2742	=head1 OTHER LANGUAGE BINDINGS
		2743
		2744	Libev does not offer other language bindings itself, but bindings for a
		2745	number of languages exist in the form of third-party packages. If you know
		2746	any interesting language binding in addition to the ones listed here, drop
		2747	me a note.
		2748
		2749	=over 4
		2750
		2751	=item Perl
		2752
		2753	The EV module implements the full libev API and is actually used to test
		2754	libev. EV is developed together with libev. Apart from the EV core module,
		2755	there are additional modules that implement libev-compatible interfaces
		2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2758
		2759	It can be found and installed via CPAN, its homepage is at
		2760	L<http://software.schmorp.de/pkg/EV>.
		2761
		2762	=item Python
		2763
		2764	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2765	seems to be quite complete and well-documented. Note, however, that the
		2766	patch they require for libev is outright dangerous as it breaks the ABI
		2767	for everybody else, and therefore, should never be applied in an installed
		2768	libev (if python requires an incompatible ABI then it needs to embed
		2769	libev).
		2770
		2771	=item Ruby
		2772
		2773	Tony Arcieri has written a ruby extension that offers access to a subset
		2774	of the libev API and adds file handle abstractions, asynchronous DNS and
		2775	more on top of it. It can be found via gem servers. Its homepage is at
		2776	L<http://rev.rubyforge.org/>.
		2777
		2778	=item D
		2779
		2780	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2782
		2783	=back
2298		2784
2299		2785
2300	=head1 MACRO MAGIC	2786	=head1 MACRO MAGIC
2301		2787
2302	Libev can be compiled with a variety of options, the most fundamantal	2788	Libev can be compiled with a variety of options, the most fundamental
2303	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2789	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2304	functions and callbacks have an initial C<struct ev_loop *> argument.	2790	functions and callbacks have an initial C<struct ev_loop *> argument.
2305		2791
2306	To make it easier to write programs that cope with either variant, the	2792	To make it easier to write programs that cope with either variant, the
2307	following macros are defined:	2793	following macros are defined:
…		…
2312		2798
2313	This provides the loop I<argument> for functions, if one is required ("ev	2799	This provides the loop I<argument> for functions, if one is required ("ev
2314	loop argument"). The C<EV_A> form is used when this is the sole argument,	2800	loop argument"). The C<EV_A> form is used when this is the sole argument,
2315	C<EV_A_> is used when other arguments are following. Example:	2801	C<EV_A_> is used when other arguments are following. Example:
2316		2802
2317	ev_unref (EV_A);	2803	ev_unref (EV_A);
2318	ev_timer_add (EV_A_ watcher);	2804	ev_timer_add (EV_A_ watcher);
2319	ev_loop (EV_A_ 0);	2805	ev_loop (EV_A_ 0);
2320		2806
2321	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2807	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2322	which is often provided by the following macro.	2808	which is often provided by the following macro.
2323		2809
2324	=item C<EV_P>, C<EV_P_>	2810	=item C<EV_P>, C<EV_P_>
2325		2811
2326	This provides the loop I<parameter> for functions, if one is required ("ev	2812	This provides the loop I<parameter> for functions, if one is required ("ev
2327	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2813	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2328	C<EV_P_> is used when other parameters are following. Example:	2814	C<EV_P_> is used when other parameters are following. Example:
2329		2815
2330	// this is how ev_unref is being declared	2816	// this is how ev_unref is being declared
2331	static void ev_unref (EV_P);	2817	static void ev_unref (EV_P);
2332		2818
2333	// this is how you can declare your typical callback	2819	// this is how you can declare your typical callback
2334	static void cb (EV_P_ ev_timer *w, int revents)	2820	static void cb (EV_P_ ev_timer *w, int revents)
2335		2821
2336	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2822	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2337	suitable for use with C<EV_A>.	2823	suitable for use with C<EV_A>.
2338		2824
2339	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2825	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2340		2826
2341	Similar to the other two macros, this gives you the value of the default	2827	Similar to the other two macros, this gives you the value of the default
2342	loop, if multiple loops are supported ("ev loop default").	2828	loop, if multiple loops are supported ("ev loop default").
		2829
		2830	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2831
		2832	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2833	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2834	is undefined when the default loop has not been initialised by a previous
		2835	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2836
		2837	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2838	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2343		2839
2344	=back	2840	=back
2345		2841
2346	Example: Declare and initialise a check watcher, utilising the above	2842	Example: Declare and initialise a check watcher, utilising the above
2347	macros so it will work regardless of whether multiple loops are supported	2843	macros so it will work regardless of whether multiple loops are supported
2348	or not.	2844	or not.
2349		2845
2350	static void	2846	static void
2351	check_cb (EV_P_ ev_timer *w, int revents)	2847	check_cb (EV_P_ ev_timer *w, int revents)
2352	{	2848	{
2353	ev_check_stop (EV_A_ w);	2849	ev_check_stop (EV_A_ w);
2354	}	2850	}
2355		2851
2356	ev_check check;	2852	ev_check check;
2357	ev_check_init (&check, check_cb);	2853	ev_check_init (&check, check_cb);
2358	ev_check_start (EV_DEFAULT_ &check);	2854	ev_check_start (EV_DEFAULT_ &check);
2359	ev_loop (EV_DEFAULT_ 0);	2855	ev_loop (EV_DEFAULT_ 0);
2360		2856
2361	=head1 EMBEDDING	2857	=head1 EMBEDDING
2362		2858
2363	Libev can (and often is) directly embedded into host	2859	Libev can (and often is) directly embedded into host
2364	applications. Examples of applications that embed it include the Deliantra	2860	applications. Examples of applications that embed it include the Deliantra
…		…
2371	libev somewhere in your source tree).	2867	libev somewhere in your source tree).
2372		2868
2373	=head2 FILESETS	2869	=head2 FILESETS
2374		2870
2375	Depending on what features you need you need to include one or more sets of files	2871	Depending on what features you need you need to include one or more sets of files
2376	in your app.	2872	in your application.
2377		2873
2378	=head3 CORE EVENT LOOP	2874	=head3 CORE EVENT LOOP
2379		2875
2380	To include only the libev core (all the C<ev_*> functions), with manual	2876	To include only the libev core (all the C<ev_*> functions), with manual
2381	configuration (no autoconf):	2877	configuration (no autoconf):
2382		2878
2383	#define EV_STANDALONE 1	2879	#define EV_STANDALONE 1
2384	#include "ev.c"	2880	#include "ev.c"
2385		2881
2386	This will automatically include F<ev.h>, too, and should be done in a	2882	This will automatically include F<ev.h>, too, and should be done in a
2387	single C source file only to provide the function implementations. To use	2883	single C source file only to provide the function implementations. To use
2388	it, do the same for F<ev.h> in all files wishing to use this API (best	2884	it, do the same for F<ev.h> in all files wishing to use this API (best
2389	done by writing a wrapper around F<ev.h> that you can include instead and	2885	done by writing a wrapper around F<ev.h> that you can include instead and
2390	where you can put other configuration options):	2886	where you can put other configuration options):
2391		2887
2392	#define EV_STANDALONE 1	2888	#define EV_STANDALONE 1
2393	#include "ev.h"	2889	#include "ev.h"
2394		2890
2395	Both header files and implementation files can be compiled with a C++	2891	Both header files and implementation files can be compiled with a C++
2396	compiler (at least, thats a stated goal, and breakage will be treated	2892	compiler (at least, thats a stated goal, and breakage will be treated
2397	as a bug).	2893	as a bug).
2398		2894
2399	You need the following files in your source tree, or in a directory	2895	You need the following files in your source tree, or in a directory
2400	in your include path (e.g. in libev/ when using -Ilibev):	2896	in your include path (e.g. in libev/ when using -Ilibev):
2401		2897
2402	ev.h	2898	ev.h
2403	ev.c	2899	ev.c
2404	ev_vars.h	2900	ev_vars.h
2405	ev_wrap.h	2901	ev_wrap.h
2406		2902
2407	ev_win32.c required on win32 platforms only	2903	ev_win32.c required on win32 platforms only
2408		2904
2409	ev_select.c only when select backend is enabled (which is enabled by default)	2905	ev_select.c only when select backend is enabled (which is enabled by default)
2410	ev_poll.c only when poll backend is enabled (disabled by default)	2906	ev_poll.c only when poll backend is enabled (disabled by default)
2411	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2907	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2412	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2908	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2413	ev_port.c only when the solaris port backend is enabled (disabled by default)	2909	ev_port.c only when the solaris port backend is enabled (disabled by default)
2414		2910
2415	F<ev.c> includes the backend files directly when enabled, so you only need	2911	F<ev.c> includes the backend files directly when enabled, so you only need
2416	to compile this single file.	2912	to compile this single file.
2417		2913
2418	=head3 LIBEVENT COMPATIBILITY API	2914	=head3 LIBEVENT COMPATIBILITY API
2419		2915
2420	To include the libevent compatibility API, also include:	2916	To include the libevent compatibility API, also include:
2421		2917
2422	#include "event.c"	2918	#include "event.c"
2423		2919
2424	in the file including F<ev.c>, and:	2920	in the file including F<ev.c>, and:
2425		2921
2426	#include "event.h"	2922	#include "event.h"
2427		2923
2428	in the files that want to use the libevent API. This also includes F<ev.h>.	2924	in the files that want to use the libevent API. This also includes F<ev.h>.
2429		2925
2430	You need the following additional files for this:	2926	You need the following additional files for this:
2431		2927
2432	event.h	2928	event.h
2433	event.c	2929	event.c
2434		2930
2435	=head3 AUTOCONF SUPPORT	2931	=head3 AUTOCONF SUPPORT
2436		2932
2437	Instead of using C<EV_STANDALONE=1> and providing your config in	2933	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2438	whatever way you want, you can also C<m4_include([libev.m4])> in your	2934	whatever way you want, you can also C<m4_include([libev.m4])> in your
2439	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2935	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2440	include F<config.h> and configure itself accordingly.	2936	include F<config.h> and configure itself accordingly.
2441		2937
2442	For this of course you need the m4 file:	2938	For this of course you need the m4 file:
2443		2939
2444	libev.m4	2940	libev.m4
2445		2941
2446	=head2 PREPROCESSOR SYMBOLS/MACROS	2942	=head2 PREPROCESSOR SYMBOLS/MACROS
2447		2943
2448	Libev can be configured via a variety of preprocessor symbols you have to define	2944	Libev can be configured via a variety of preprocessor symbols you have to
2449	before including any of its files. The default is not to build for multiplicity	2945	define before including any of its files. The default in the absence of
2450	and only include the select backend.	2946	autoconf is noted for every option.
2451		2947
2452	=over 4	2948	=over 4
2453		2949
2454	=item EV_STANDALONE	2950	=item EV_STANDALONE
2455		2951
…		…
2460	F<event.h> that are not directly supported by the libev core alone.	2956	F<event.h> that are not directly supported by the libev core alone.
2461		2957
2462	=item EV_USE_MONOTONIC	2958	=item EV_USE_MONOTONIC
2463		2959
2464	If defined to be C<1>, libev will try to detect the availability of the	2960	If defined to be C<1>, libev will try to detect the availability of the
2465	monotonic clock option at both compiletime and runtime. Otherwise no use	2961	monotonic clock option at both compile time and runtime. Otherwise no use
2466	of the monotonic clock option will be attempted. If you enable this, you	2962	of the monotonic clock option will be attempted. If you enable this, you
2467	usually have to link against librt or something similar. Enabling it when	2963	usually have to link against librt or something similar. Enabling it when
2468	the functionality isn't available is safe, though, although you have	2964	the functionality isn't available is safe, though, although you have
2469	to make sure you link against any libraries where the C<clock_gettime>	2965	to make sure you link against any libraries where the C<clock_gettime>
2470	function is hiding in (often F<-lrt>).	2966	function is hiding in (often F<-lrt>).
2471		2967
2472	=item EV_USE_REALTIME	2968	=item EV_USE_REALTIME
2473		2969
2474	If defined to be C<1>, libev will try to detect the availability of the	2970	If defined to be C<1>, libev will try to detect the availability of the
2475	realtime clock option at compiletime (and assume its availability at	2971	real-time clock option at compile time (and assume its availability at
2476	runtime if successful). Otherwise no use of the realtime clock option will	2972	runtime if successful). Otherwise no use of the real-time clock option will
2477	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2973	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2478	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2974	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2479	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2975	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2480		2976
2481	=item EV_USE_NANOSLEEP	2977	=item EV_USE_NANOSLEEP
2482		2978
2483	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2979	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2484	and will use it for delays. Otherwise it will use C<select ()>.	2980	and will use it for delays. Otherwise it will use C<select ()>.
2485		2981
		2982	=item EV_USE_EVENTFD
		2983
		2984	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2985	available and will probe for kernel support at runtime. This will improve
		2986	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2987	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2988	2.7 or newer, otherwise disabled.
		2989
2486	=item EV_USE_SELECT	2990	=item EV_USE_SELECT
2487		2991
2488	If undefined or defined to be C<1>, libev will compile in support for the	2992	If undefined or defined to be C<1>, libev will compile in support for the
2489	C<select>(2) backend. No attempt at autodetection will be done: if no	2993	C<select>(2) backend. No attempt at auto-detection will be done: if no
2490	other method takes over, select will be it. Otherwise the select backend	2994	other method takes over, select will be it. Otherwise the select backend
2491	will not be compiled in.	2995	will not be compiled in.
2492		2996
2493	=item EV_SELECT_USE_FD_SET	2997	=item EV_SELECT_USE_FD_SET
2494		2998
2495	If defined to C<1>, then the select backend will use the system C<fd_set>	2999	If defined to C<1>, then the select backend will use the system C<fd_set>
2496	structure. This is useful if libev doesn't compile due to a missing	3000	structure. This is useful if libev doesn't compile due to a missing
2497	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3001	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2498	exotic systems. This usually limits the range of file descriptors to some	3002	exotic systems. This usually limits the range of file descriptors to some
2499	low limit such as 1024 or might have other limitations (winsocket only	3003	low limit such as 1024 or might have other limitations (winsocket only
2500	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3004	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2501	influence the size of the C<fd_set> used.	3005	influence the size of the C<fd_set> used.
2502		3006
…		…
2526		3030
2527	=item EV_USE_EPOLL	3031	=item EV_USE_EPOLL
2528		3032
2529	If defined to be C<1>, libev will compile in support for the Linux	3033	If defined to be C<1>, libev will compile in support for the Linux
2530	C<epoll>(7) backend. Its availability will be detected at runtime,	3034	C<epoll>(7) backend. Its availability will be detected at runtime,
2531	otherwise another method will be used as fallback. This is the	3035	otherwise another method will be used as fallback. This is the preferred
2532	preferred backend for GNU/Linux systems.	3036	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3037	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2533		3038
2534	=item EV_USE_KQUEUE	3039	=item EV_USE_KQUEUE
2535		3040
2536	If defined to be C<1>, libev will compile in support for the BSD style	3041	If defined to be C<1>, libev will compile in support for the BSD style
2537	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3042	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2550	otherwise another method will be used as fallback. This is the preferred	3055	otherwise another method will be used as fallback. This is the preferred
2551	backend for Solaris 10 systems.	3056	backend for Solaris 10 systems.
2552		3057
2553	=item EV_USE_DEVPOLL	3058	=item EV_USE_DEVPOLL
2554		3059
2555	reserved for future expansion, works like the USE symbols above.	3060	Reserved for future expansion, works like the USE symbols above.
2556		3061
2557	=item EV_USE_INOTIFY	3062	=item EV_USE_INOTIFY
2558		3063
2559	If defined to be C<1>, libev will compile in support for the Linux inotify	3064	If defined to be C<1>, libev will compile in support for the Linux inotify
2560	interface to speed up C<ev_stat> watchers. Its actual availability will	3065	interface to speed up C<ev_stat> watchers. Its actual availability will
2561	be detected at runtime.	3066	be detected at runtime. If undefined, it will be enabled if the headers
		3067	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3068
		3069	=item EV_ATOMIC_T
		3070
		3071	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3072	access is atomic with respect to other threads or signal contexts. No such
		3073	type is easily found in the C language, so you can provide your own type
		3074	that you know is safe for your purposes. It is used both for signal handler "locking"
		3075	as well as for signal and thread safety in C<ev_async> watchers.
		3076
		3077	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3078	(from F<signal.h>), which is usually good enough on most platforms.
2562		3079
2563	=item EV_H	3080	=item EV_H
2564		3081
2565	The name of the F<ev.h> header file used to include it. The default if	3082	The name of the F<ev.h> header file used to include it. The default if
2566	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3083	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
2604	When doing priority-based operations, libev usually has to linearly search	3121	When doing priority-based operations, libev usually has to linearly search
2605	all the priorities, so having many of them (hundreds) uses a lot of space	3122	all the priorities, so having many of them (hundreds) uses a lot of space
2606	and time, so using the defaults of five priorities (-2 .. +2) is usually	3123	and time, so using the defaults of five priorities (-2 .. +2) is usually
2607	fine.	3124	fine.
2608		3125
2609	If your embedding app does not need any priorities, defining these both to	3126	If your embedding application does not need any priorities, defining these both to
2610	C<0> will save some memory and cpu.	3127	C<0> will save some memory and CPU.
2611		3128
2612	=item EV_PERIODIC_ENABLE	3129	=item EV_PERIODIC_ENABLE
2613		3130
2614	If undefined or defined to be C<1>, then periodic timers are supported. If	3131	If undefined or defined to be C<1>, then periodic timers are supported. If
2615	defined to be C<0>, then they are not. Disabling them saves a few kB of	3132	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2634	=item EV_FORK_ENABLE	3151	=item EV_FORK_ENABLE
2635		3152
2636	If undefined or defined to be C<1>, then fork watchers are supported. If	3153	If undefined or defined to be C<1>, then fork watchers are supported. If
2637	defined to be C<0>, then they are not.	3154	defined to be C<0>, then they are not.
2638		3155
		3156	=item EV_ASYNC_ENABLE
		3157
		3158	If undefined or defined to be C<1>, then async watchers are supported. If
		3159	defined to be C<0>, then they are not.
		3160
2639	=item EV_MINIMAL	3161	=item EV_MINIMAL
2640		3162
2641	If you need to shave off some kilobytes of code at the expense of some	3163	If you need to shave off some kilobytes of code at the expense of some
2642	speed, define this symbol to C<1>. Currently only used for gcc to override	3164	speed, define this symbol to C<1>. Currently this is used to override some
2643	some inlining decisions, saves roughly 30% codesize of amd64.	3165	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3166	much smaller 2-heap for timer management over the default 4-heap.
2644		3167
2645	=item EV_PID_HASHSIZE	3168	=item EV_PID_HASHSIZE
2646		3169
2647	C<ev_child> watchers use a small hash table to distribute workload by	3170	C<ev_child> watchers use a small hash table to distribute workload by
2648	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3171	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2655	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3178	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2656	usually more than enough. If you need to manage thousands of C<ev_stat>	3179	usually more than enough. If you need to manage thousands of C<ev_stat>
2657	watchers you might want to increase this value (I<must> be a power of	3180	watchers you might want to increase this value (I<must> be a power of
2658	two).	3181	two).
2659		3182
		3183	=item EV_USE_4HEAP
		3184
		3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3187	to C<1>. The 4-heap uses more complicated (longer) code but has
		3188	noticeably faster performance with many (thousands) of watchers.
		3189
		3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3191	(disabled).
		3192
		3193	=item EV_HEAP_CACHE_AT
		3194
		3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3196	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3199	but avoids random read accesses on heap changes. This improves performance
		3200	noticeably with with many (hundreds) of watchers.
		3201
		3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3203	(disabled).
		3204
		3205	=item EV_VERIFY
		3206
		3207	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3208	be done: If set to C<0>, no internal verification code will be compiled
		3209	in. If set to C<1>, then verification code will be compiled in, but not
		3210	called. If set to C<2>, then the internal verification code will be
		3211	called once per loop, which can slow down libev. If set to C<3>, then the
		3212	verification code will be called very frequently, which will slow down
		3213	libev considerably.
		3214
		3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3216	C<0.>
		3217
2660	=item EV_COMMON	3218	=item EV_COMMON
2661		3219
2662	By default, all watchers have a C<void *data> member. By redefining	3220	By default, all watchers have a C<void *data> member. By redefining
2663	this macro to a something else you can include more and other types of	3221	this macro to a something else you can include more and other types of
2664	members. You have to define it each time you include one of the files,	3222	members. You have to define it each time you include one of the files,
2665	though, and it must be identical each time.	3223	though, and it must be identical each time.
2666		3224
2667	For example, the perl EV module uses something like this:	3225	For example, the perl EV module uses something like this:
2668		3226
2669	#define EV_COMMON \	3227	#define EV_COMMON \
2670	SV *self; /* contains this struct */ \	3228	SV *self; /* contains this struct */ \
2671	SV *cb_sv, *fh /* note no trailing ";" */	3229	SV *cb_sv, *fh /* note no trailing ";" */
2672		3230
2673	=item EV_CB_DECLARE (type)	3231	=item EV_CB_DECLARE (type)
2674		3232
2675	=item EV_CB_INVOKE (watcher, revents)	3233	=item EV_CB_INVOKE (watcher, revents)
2676		3234
…		…
2683	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2684	method calls instead of plain function calls in C++.	3242	method calls instead of plain function calls in C++.
2685		3243
2686	=head2 EXPORTED API SYMBOLS	3244	=head2 EXPORTED API SYMBOLS
2687		3245
2688	If you need to re-export the API (e.g. via a dll) and you need a list of	3246	If you need to re-export the API (e.g. via a DLL) and you need a list of
2689	exported symbols, you can use the provided F<Symbol.*> files which list	3247	exported symbols, you can use the provided F<Symbol.*> files which list
2690	all public symbols, one per line:	3248	all public symbols, one per line:
2691		3249
2692	Symbols.ev for libev proper	3250	Symbols.ev for libev proper
2693	Symbols.event for the libevent emulation	3251	Symbols.event for the libevent emulation
2694		3252
2695	This can also be used to rename all public symbols to avoid clashes with	3253	This can also be used to rename all public symbols to avoid clashes with
2696	multiple versions of libev linked together (which is obviously bad in	3254	multiple versions of libev linked together (which is obviously bad in
2697	itself, but sometimes it is inconvinient to avoid this).	3255	itself, but sometimes it is inconvenient to avoid this).
2698		3256
2699	A sed command like this will create wrapper C<#define>'s that you need to	3257	A sed command like this will create wrapper C<#define>'s that you need to
2700	include before including F<ev.h>:	3258	include before including F<ev.h>:
2701		3259
2702	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3260	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2719	file.	3277	file.
2720		3278
2721	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3279	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2722	that everybody includes and which overrides some configure choices:	3280	that everybody includes and which overrides some configure choices:
2723		3281
2724	#define EV_MINIMAL 1	3282	#define EV_MINIMAL 1
2725	#define EV_USE_POLL 0	3283	#define EV_USE_POLL 0
2726	#define EV_MULTIPLICITY 0	3284	#define EV_MULTIPLICITY 0
2727	#define EV_PERIODIC_ENABLE 0	3285	#define EV_PERIODIC_ENABLE 0
2728	#define EV_STAT_ENABLE 0	3286	#define EV_STAT_ENABLE 0
2729	#define EV_FORK_ENABLE 0	3287	#define EV_FORK_ENABLE 0
2730	#define EV_CONFIG_H <config.h>	3288	#define EV_CONFIG_H <config.h>
2731	#define EV_MINPRI 0	3289	#define EV_MINPRI 0
2732	#define EV_MAXPRI 0	3290	#define EV_MAXPRI 0
2733		3291
2734	#include "ev++.h"	3292	#include "ev++.h"
2735		3293
2736	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2737		3295
2738	#include "ev_cpp.h"	3296	#include "ev_cpp.h"
2739	#include "ev.c"	3297	#include "ev.c"
		3298
		3299
		3300	=head1 THREADS AND COROUTINES
		3301
		3302	=head2 THREADS
		3303
		3304	Libev itself is thread-safe (unless the opposite is specifically
		3305	documented for a function), but it uses no locking itself. This means that
		3306	you can use as many loops as you want in parallel, as long as only one
		3307	thread ever calls into one libev function with the same loop parameter:
		3308	libev guarentees that different event loops share no data structures that
		3309	need locking.
		3310
		3311	Or to put it differently: calls with different loop parameters can be done
		3312	concurrently from multiple threads, calls with the same loop parameter
		3313	must be done serially (but can be done from different threads, as long as
		3314	only one thread ever is inside a call at any point in time, e.g. by using
		3315	a mutex per loop).
		3316
		3317	Specifically to support threads (and signal handlers), libev implements
		3318	so-called C<ev_async> watchers, which allow some limited form of
		3319	concurrency on the same event loop.
		3320
		3321	If you want to know which design (one loop, locking, or multiple loops
		3322	without or something else still) is best for your problem, then I cannot
		3323	help you. I can give some generic advice however:
		3324
		3325	=over 4
		3326
		3327	=item * most applications have a main thread: use the default libev loop
		3328	in that thread, or create a separate thread running only the default loop.
		3329
		3330	This helps integrating other libraries or software modules that use libev
		3331	themselves and don't care/know about threading.
		3332
		3333	=item * one loop per thread is usually a good model.
		3334
		3335	Doing this is almost never wrong, sometimes a better-performance model
		3336	exists, but it is always a good start.
		3337
		3338	=item * other models exist, such as the leader/follower pattern, where one
		3339	loop is handed through multiple threads in a kind of round-robin fashion.
		3340
		3341	Choosing a model is hard - look around, learn, know that usually you can do
		3342	better than you currently do :-)
		3343
		3344	=item * often you need to talk to some other thread which blocks in the
		3345	event loop.
		3346
		3347	C<ev_async> watchers can be used to wake them up from other threads safely
		3348	(or from signal contexts...).
		3349
		3350	An example use would be to communicate signals or other events that only
		3351	work in the default loop by registering the signal watcher with the
		3352	default loop and triggering an C<ev_async> watcher from the default loop
		3353	watcher callback into the event loop interested in the signal.
		3354
		3355	=back
		3356
		3357	=head2 COROUTINES
		3358
		3359	Libev is much more accommodating to coroutines ("cooperative threads"):
		3360	libev fully supports nesting calls to it's functions from different
		3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3362	different coroutines and switch freely between both coroutines running the
		3363	loop, as long as you don't confuse yourself). The only exception is that
		3364	you must not do this from C<ev_periodic> reschedule callbacks.
		3365
		3366	Care has been taken to ensure that libev does not keep local state inside
		3367	C<ev_loop>, and other calls do not usually allow coroutine switches.
2740		3368
2741		3369
2742	=head1 COMPLEXITIES	3370	=head1 COMPLEXITIES
2743		3371
2744	In this section the complexities of (many of) the algorithms used inside	3372	In this section the complexities of (many of) the algorithms used inside
…		…
2762	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2763		3391
2764	That means that changing a timer costs less than removing/adding them	3392	That means that changing a timer costs less than removing/adding them
2765	as only the relative motion in the event queue has to be paid for.	3393	as only the relative motion in the event queue has to be paid for.
2766		3394
2767	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2768		3396
2769	These just add the watcher into an array or at the head of a list.	3397	These just add the watcher into an array or at the head of a list.
2770		3398
2771	=item Stopping check/prepare/idle watchers: O(1)	3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2772		3400
2773	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2774		3402
2775	These watchers are stored in lists then need to be walked to find the	3403	These watchers are stored in lists then need to be walked to find the
2776	correct watcher to remove. The lists are usually short (you don't usually	3404	correct watcher to remove. The lists are usually short (you don't usually
2777	have many watchers waiting for the same fd or signal).	3405	have many watchers waiting for the same fd or signal).
2778		3406
2779	=item Finding the next timer in each loop iteration: O(1)	3407	=item Finding the next timer in each loop iteration: O(1)
2780		3408
2781	By virtue of using a binary heap, the next timer is always found at the	3409	By virtue of using a binary or 4-heap, the next timer is always found at a
2782	beginning of the storage array.	3410	fixed position in the storage array.
2783		3411
2784	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2785		3413
2786	A change means an I/O watcher gets started or stopped, which requires	3414	A change means an I/O watcher gets started or stopped, which requires
2787	libev to recalculate its status (and possibly tell the kernel, depending	3415	libev to recalculate its status (and possibly tell the kernel, depending
2788	on backend and wether C<ev_io_set> was used).	3416	on backend and whether C<ev_io_set> was used).
2789		3417
2790	=item Activating one watcher (putting it into the pending state): O(1)	3418	=item Activating one watcher (putting it into the pending state): O(1)
2791		3419
2792	=item Priority handling: O(number_of_priorities)	3420	=item Priority handling: O(number_of_priorities)
2793		3421
2794	Priorities are implemented by allocating some space for each	3422	Priorities are implemented by allocating some space for each
2795	priority. When doing priority-based operations, libev usually has to	3423	priority. When doing priority-based operations, libev usually has to
2796	linearly search all the priorities, but starting/stopping and activating	3424	linearly search all the priorities, but starting/stopping and activating
2797	watchers becomes O(1) w.r.t. prioritiy handling.	3425	watchers becomes O(1) w.r.t. priority handling.
		3426
		3427	=item Sending an ev_async: O(1)
		3428
		3429	=item Processing ev_async_send: O(number_of_async_watchers)
		3430
		3431	=item Processing signals: O(max_signal_number)
		3432
		3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3434	calls in the current loop iteration. Checking for async and signal events
		3435	involves iterating over all running async watchers or all signal numbers.
2798		3436
2799	=back	3437	=back
2800		3438
2801		3439
2802	=head1 Win32 platform limitations and workarounds	3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2803		3441
2804	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2805	requires, and its I/O model is fundamentally incompatible with the POSIX	3443	requires, and its I/O model is fundamentally incompatible with the POSIX
2806	model. Libev still offers limited functionality on this platform in	3444	model. Libev still offers limited functionality on this platform in
2807	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2808	descriptors. This only applies when using Win32 natively, not when using	3446	descriptors. This only applies when using Win32 natively, not when using
2809	e.g. cygwin.	3447	e.g. cygwin.
2810		3448
		3449	Lifting these limitations would basically require the full
		3450	re-implementation of the I/O system. If you are into these kinds of
		3451	things, then note that glib does exactly that for you in a very portable
		3452	way (note also that glib is the slowest event library known to man).
		3453
2811	There is no supported compilation method available on windows except	3454	There is no supported compilation method available on windows except
2812	embedding it into other applications.	3455	embedding it into other applications.
2813		3456
		3457	Not a libev limitation but worth mentioning: windows apparently doesn't
		3458	accept large writes: instead of resulting in a partial write, windows will
		3459	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3460	so make sure you only write small amounts into your sockets (less than a
		3461	megabyte seems safe, but thsi apparently depends on the amount of memory
		3462	available).
		3463
2814	Due to the many, low, and arbitrary limits on the win32 platform and the	3464	Due to the many, low, and arbitrary limits on the win32 platform and
2815	abysmal performance of winsockets, using a large number of sockets is not	3465	the abysmal performance of winsockets, using a large number of sockets
2816	recommended (and not reasonable). If your program needs to use more than	3466	is not recommended (and not reasonable). If your program needs to use
2817	a hundred or so sockets, then likely it needs to use a totally different	3467	more than a hundred or so sockets, then likely it needs to use a totally
2818	implementation for windows, as libev offers the POSIX model, which cannot	3468	different implementation for windows, as libev offers the POSIX readiness
2819	be implemented efficiently on windows (microsoft monopoly games).	3469	notification model, which cannot be implemented efficiently on windows
		3470	(Microsoft monopoly games).
		3471
		3472	A typical way to use libev under windows is to embed it (see the embedding
		3473	section for details) and use the following F<evwrap.h> header file instead
		3474	of F<ev.h>:
		3475
		3476	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3478
		3479	#include "ev.h"
		3480
		3481	And compile the following F<evwrap.c> file into your project (make sure
		3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3483
		3484	#include "evwrap.h"
		3485	#include "ev.c"
2820		3486
2821	=over 4	3487	=over 4
2822		3488
2823	=item The winsocket select function	3489	=item The winsocket select function
2824		3490
2825	The winsocket C<select> function doesn't follow POSIX in that it requires	3491	The winsocket C<select> function doesn't follow POSIX in that it
2826	socket I<handles> and not socket I<file descriptors>. This makes select	3492	requires socket I<handles> and not socket I<file descriptors> (it is
2827	very inefficient, and also requires a mapping from file descriptors	3493	also extremely buggy). This makes select very inefficient, and also
2828	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3494	requires a mapping from file descriptors to socket handles (the Microsoft
2829	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3495	C runtime provides the function C<_open_osfhandle> for this). See the
2830	symbols for more info.	3496	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3497	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2831		3498
2832	The configuration for a "naked" win32 using the microsoft runtime	3499	The configuration for a "naked" win32 using the Microsoft runtime
2833	libraries and raw winsocket select is:	3500	libraries and raw winsocket select is:
2834		3501
2835	#define EV_USE_SELECT 1	3502	#define EV_USE_SELECT 1
2836	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3503	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2837		3504
2838	Note that winsockets handling of fd sets is O(n), so you can easily get a	3505	Note that winsockets handling of fd sets is O(n), so you can easily get a
2839	complexity in the O(n²) range when using win32.	3506	complexity in the O(n²) range when using win32.
2840		3507
2841	=item Limited number of file descriptors	3508	=item Limited number of file descriptors
2842		3509
2843	Windows has numerous arbitrary (and low) limits on things. Early versions	3510	Windows has numerous arbitrary (and low) limits on things.
2844	of winsocket's select only supported waiting for a max. of C<64> handles	3511
		3512	Early versions of winsocket's select only supported waiting for a maximum
2845	(probably owning to the fact that all windows kernels can only wait for	3513	of C<64> handles (probably owning to the fact that all windows kernels
2846	C<64> things at the same time internally; microsoft recommends spawning a	3514	can only wait for C<64> things at the same time internally; Microsoft
2847	chain of threads and wait for 63 handles and the previous thread in each).	3515	recommends spawning a chain of threads and wait for 63 handles and the
		3516	previous thread in each. Great).
2848		3517
2849	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3518	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2850	to some high number (e.g. C<2048>) before compiling the winsocket select	3519	to some high number (e.g. C<2048>) before compiling the winsocket select
2851	call (which might be in libev or elsewhere, for example, perl does its own	3520	call (which might be in libev or elsewhere, for example, perl does its own
2852	select emulation on windows).	3521	select emulation on windows).
2853		3522
2854	Another limit is the number of file descriptors in the microsoft runtime	3523	Another limit is the number of file descriptors in the Microsoft runtime
2855	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3524	libraries, which by default is C<64> (there must be a hidden I<64> fetish
2856	or something like this inside microsoft). You can increase this by calling	3525	or something like this inside Microsoft). You can increase this by calling
2857	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3526	C<_setmaxstdio>, which can increase this limit to C<2048> (another
2858	arbitrary limit), but is broken in many versions of the microsoft runtime	3527	arbitrary limit), but is broken in many versions of the Microsoft runtime
2859	libraries.	3528	libraries.
2860		3529
2861	This might get you to about C<512> or C<2048> sockets (depending on	3530	This might get you to about C<512> or C<2048> sockets (depending on
2862	windows version and/or the phase of the moon). To get more, you need to	3531	windows version and/or the phase of the moon). To get more, you need to
2863	wrap all I/O functions and provide your own fd management, but the cost of	3532	wrap all I/O functions and provide your own fd management, but the cost of
2864	calling select (O(n²)) will likely make this unworkable.	3533	calling select (O(n²)) will likely make this unworkable.
2865		3534
2866	=back	3535	=back
2867		3536
2868		3537
		3538	=head1 PORTABILITY REQUIREMENTS
		3539
		3540	In addition to a working ISO-C implementation, libev relies on a few
		3541	additional extensions:
		3542
		3543	=over 4
		3544
		3545	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3546	calling conventions regardless of C<ev_watcher_type *>.
		3547
		3548	Libev assumes not only that all watcher pointers have the same internal
		3549	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3550	assumes that the same (machine) code can be used to call any watcher
		3551	callback: The watcher callbacks have different type signatures, but libev
		3552	calls them using an C<ev_watcher *> internally.
		3553
		3554	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3555
		3556	The type C<sig_atomic_t volatile> (or whatever is defined as
		3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3558	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3559	believed to be sufficiently portable.
		3560
		3561	=item C<sigprocmask> must work in a threaded environment
		3562
		3563	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3564	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3565	pthread implementations will either allow C<sigprocmask> in the "main
		3566	thread" or will block signals process-wide, both behaviours would
		3567	be compatible with libev. Interaction between C<sigprocmask> and
		3568	C<pthread_sigmask> could complicate things, however.
		3569
		3570	The most portable way to handle signals is to block signals in all threads
		3571	except the initial one, and run the default loop in the initial thread as
		3572	well.
		3573
		3574	=item C<long> must be large enough for common memory allocation sizes
		3575
		3576	To improve portability and simplify using libev, libev uses C<long>
		3577	internally instead of C<size_t> when allocating its data structures. On
		3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3579	is still at least 31 bits everywhere, which is enough for hundreds of
		3580	millions of watchers.
		3581
		3582	=item C<double> must hold a time value in seconds with enough accuracy
		3583
		3584	The type C<double> is used to represent timestamps. It is required to
		3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3586	enough for at least into the year 4000. This requirement is fulfilled by
		3587	implementations implementing IEEE 754 (basically all existing ones).
		3588
		3589	=back
		3590
		3591	If you know of other additional requirements drop me a note.
		3592
		3593
		3594	=head1 COMPILER WARNINGS
		3595
		3596	Depending on your compiler and compiler settings, you might get no or a
		3597	lot of warnings when compiling libev code. Some people are apparently
		3598	scared by this.
		3599
		3600	However, these are unavoidable for many reasons. For one, each compiler
		3601	has different warnings, and each user has different tastes regarding
		3602	warning options. "Warn-free" code therefore cannot be a goal except when
		3603	targeting a specific compiler and compiler-version.
		3604
		3605	Another reason is that some compiler warnings require elaborate
		3606	workarounds, or other changes to the code that make it less clear and less
		3607	maintainable.
		3608
		3609	And of course, some compiler warnings are just plain stupid, or simply
		3610	wrong (because they don't actually warn about the condition their message
		3611	seems to warn about).
		3612
		3613	While libev is written to generate as few warnings as possible,
		3614	"warn-free" code is not a goal, and it is recommended not to build libev
		3615	with any compiler warnings enabled unless you are prepared to cope with
		3616	them (e.g. by ignoring them). Remember that warnings are just that:
		3617	warnings, not errors, or proof of bugs.
		3618
		3619
		3620	=head1 VALGRIND
		3621
		3622	Valgrind has a special section here because it is a popular tool that is
		3623	highly useful, but valgrind reports are very hard to interpret.
		3624
		3625	If you think you found a bug (memory leak, uninitialised data access etc.)
		3626	in libev, then check twice: If valgrind reports something like:
		3627
		3628	==2274== definitely lost: 0 bytes in 0 blocks.
		3629	==2274== possibly lost: 0 bytes in 0 blocks.
		3630	==2274== still reachable: 256 bytes in 1 blocks.
		3631
		3632	Then there is no memory leak. Similarly, under some circumstances,
		3633	valgrind might report kernel bugs as if it were a bug in libev, or it
		3634	might be confused (it is a very good tool, but only a tool).
		3635
		3636	If you are unsure about something, feel free to contact the mailing list
		3637	with the full valgrind report and an explanation on why you think this is
		3638	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3639	no bug" answer and take the chance of learning how to interpret valgrind
		3640	properly.
		3641
		3642	If you need, for some reason, empty reports from valgrind for your project
		3643	I suggest using suppression lists.
		3644
		3645
2869	=head1 AUTHOR	3646	=head1 AUTHOR
2870		3647
2871	Marc Lehmann <libev@schmorp.de>.	3648	Marc Lehmann <libev@schmorp.de>.
2872		3649

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