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Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC vs.
Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_<type>
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260
261	If you use threads, a common model is to run the default event loop
262	in your main thread (or in a separate thread) and for each thread you
263	create, you also create another event loop. Libev itself does no locking
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		284
268	=over 4	285	=over 4
269		286
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		288
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		293
277	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
278	function.	295	function.
279		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
342		367
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		369
345	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	375	performance tips.
351		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		381
354	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	388	support for dup.
361		389
362	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	394	very well if you register events for both fds.
367		395
368	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
…		…
371		399
372	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible, i.e.
374	keep at least one watcher active per fd at all times.	402	keep at least one watcher active per fd at all times.
375		403
376	While nominally embeddeble in other event loops, this feature is broken in	404	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	405	all kernel versions tested so far.
		406
		407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		408	C<EVBACKEND_POLL>.
378		409
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		411
381	Kqueue deserves special mention, as at the time of this writing, it	412	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	413	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	414	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	415	it's completely useless). For this reason it's not being "auto-detected"
385	unless you explicitly specify it explicitly in the flags (i.e. using	416	unless you explicitly specify it explicitly in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	418	system like NetBSD.
388		419
389	You still can embed kqueue into a normal poll or select backend and use it	420	You still can embed kqueue into a normal poll or select backend and use it
…		…
391	the target platform). See C<ev_embed> watchers for more info.	422	the target platform). See C<ev_embed> watchers for more info.
392		423
393	It scales in the same way as the epoll backend, but the interface to the	424	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	425	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	426	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	428	two event changes per incident, support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	429	drops fds silently in similarly hard-to-detect cases.
399		430
400	This backend usually performs well under most conditions.	431	This backend usually performs well under most conditions.
401		432
…		…
404	almost everywhere, you should only use it when you have a lot of sockets	435	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	436	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
407	sockets.	438	sockets.
408		439
		440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		442	C<NOTE_EOF>.
		443
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	444	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		445
411	This is not implemented yet (and might never be, unless you send me an	446	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	447	implementation). According to reports, C</dev/poll> only supports sockets
413	and is not embeddable, which would limit the usefulness of this backend	448	and is not embeddable, which would limit the usefulness of this backend
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	451	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		452
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	453	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	454	it's really slow, but it still scales very well (O(active_fds)).
420		455
421	Please note that solaris event ports can deliver a lot of spurious	456	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	457	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	458	blocking when no data (or space) is available.
424		459
425	While this backend scales well, it requires one system call per active	460	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	461	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	463	might perform better.
429		464
430	On the positive side, ignoring the spurious readyness notifications, this	465	On the positive side, ignoring the spurious readiness notifications, this
431	backend actually performed to specification in all tests and is fully	466	backend actually performed to specification in all tests and is fully
432	embeddable, which is a rare feat among the OS-specific backends.	467	embeddable, which is a rare feat among the OS-specific backends.
		468
		469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		470	C<EVBACKEND_POLL>.
433		471
434	=item C<EVBACKEND_ALL>	472	=item C<EVBACKEND_ALL>
435		473
436	Try all backends (even potentially broken ones that wouldn't be tried	474	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	475	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		477
440	It is definitely not recommended to use this flag.	478	It is definitely not recommended to use this flag.
441		479
442	=back	480	=back
443		481
444	If one or more of these are ored into the flags value, then only these	482	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	483	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	484	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		485
448	The most typical usage is like this:	486	The most typical usage is like this:
449		487
450	if (!ev_default_loop (0))	488	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		490
453	Restrict libev to the select and poll backends, and do not allow	491	Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	492	environment settings to be taken into account:
455		493
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		495
458	Use whatever libev has to offer, but make sure that kqueue is used if	496	Use whatever libev has to offer, but make sure that kqueue is used if
459	available (warning, breaks stuff, best use only with your own private	497	available (warning, breaks stuff, best use only with your own private
460	event loop and only if you know the OS supports your types of fds):	498	event loop and only if you know the OS supports your types of fds):
461		499
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		501
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	502	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		503
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	504	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	505	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	506	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	507	undefined behaviour (or a failed assertion if assertions are enabled).
470		508
		509	Note that this function I<is> thread-safe, and the recommended way to use
		510	libev with threads is indeed to create one loop per thread, and using the
		511	default loop in the "main" or "initial" thread.
		512
471	Example: Try to create a event loop that uses epoll and nothing else.	513	Example: Try to create a event loop that uses epoll and nothing else.
472		514
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	516	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	517	fatal ("no epoll found here, maybe it hides under your chair");
476		518
477	=item ev_default_destroy ()	519	=item ev_default_destroy ()
478		520
479	Destroys the default loop again (frees all memory and kernel state	521	Destroys the default loop again (frees all memory and kernel state
480	etc.). None of the active event watchers will be stopped in the normal	522	etc.). None of the active event watchers will be stopped in the normal
481	sense, so e.g. C<ev_is_active> might still return true. It is your	523	sense, so e.g. C<ev_is_active> might still return true. It is your
482	responsibility to either stop all watchers cleanly yoursef I<before>	524	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	525	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	526	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	527	for example).
486		528
487	Note that certain global state, such as signal state, will not be freed by	529	Note that certain global state, such as signal state, will not be freed by
…		…
548	received events and started processing them. This timestamp does not	590	received events and started processing them. This timestamp does not
549	change as long as callbacks are being processed, and this is also the base	591	change as long as callbacks are being processed, and this is also the base
550	time used for relative timers. You can treat it as the timestamp of the	592	time used for relative timers. You can treat it as the timestamp of the
551	event occurring (or more correctly, libev finding out about it).	593	event occurring (or more correctly, libev finding out about it).
552		594
		595	=item ev_now_update (loop)
		596
		597	Establishes the current time by querying the kernel, updating the time
		598	returned by C<ev_now ()> in the progress. This is a costly operation and
		599	is usually done automatically within C<ev_loop ()>.
		600
		601	This function is rarely useful, but when some event callback runs for a
		602	very long time without entering the event loop, updating libev's idea of
		603	the current time is a good idea.
		604
		605	See also "The special problem of time updates" in the C<ev_timer> section.
		606
553	=item ev_loop (loop, int flags)	607	=item ev_loop (loop, int flags)
554		608
555	Finally, this is it, the event handler. This function usually is called	609	Finally, this is it, the event handler. This function usually is called
556	after you initialised all your watchers and you want to start handling	610	after you initialised all your watchers and you want to start handling
557	events.	611	events.
…		…
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	623	those events and any outstanding ones, but will not block your process in
570	case there are no events and will return after one iteration of the loop.	624	case there are no events and will return after one iteration of the loop.
571		625
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	627	necessary) and will handle those and any outstanding ones. It will block
574	your process until at least one new event arrives, and will return after	628	your process until at least one new event arrives, and will return after
575	one iteration of the loop. This is useful if you are waiting for some	629	one iteration of the loop. This is useful if you are waiting for some
576	external event in conjunction with something not expressible using other	630	external event in conjunction with something not expressible using other
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	632	usually a better approach for this kind of thing.
579		633
580	Here are the gory details of what C<ev_loop> does:	634	Here are the gory details of what C<ev_loop> does:
581		635
582	- Before the first iteration, call any pending watchers.	636	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	637	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	638	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	639	- Queue and call all prepare watchers.
586	- If we have been forked, recreate the kernel state.	640	- If we have been forked, detach and recreate the kernel state
		641	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	642	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	643	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	644	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	645	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	646	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	647	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	648	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	649	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	651	- Queue all outstanding timers.
597	- Queue all outstanding periodics.	652	- Queue all outstanding periodics.
598	- If no events are pending now, queue all idle watchers.	653	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	654	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	655	- Call all queued watchers in reverse order (i.e. check watchers first).
601	Signals and child watchers are implemented as I/O watchers, and will	656	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	657	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
608	anymore.	663	anymore.
609		664
610	... queue jobs here, make sure they register event watchers as long	665	... queue jobs here, make sure they register event watchers as long
611	... as they still have work to do (even an idle watcher will do..)	666	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	667	ev_loop (my_loop, 0);
613	... jobs done. yeah!	668	... jobs done or somebody called unloop. yeah!
614		669
615	=item ev_unloop (loop, how)	670	=item ev_unloop (loop, how)
616		671
617	Can be used to make a call to C<ev_loop> return early (but only after it	672	Can be used to make a call to C<ev_loop> return early (but only after it
618	has processed all outstanding events). The C<how> argument must be either	673	has processed all outstanding events). The C<how> argument must be either
…		…
639	respectively).	694	respectively).
640		695
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
642	running when nothing else is active.	697	running when nothing else is active.
643		698
644	struct ev_signal exitsig;	699	struct ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	700	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	701	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	702	evf_unref (loop);
648		703
649	Example: For some weird reason, unregister the above signal handler again.	704	Example: For some weird reason, unregister the above signal handler again.
650		705
651	ev_ref (loop);	706	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	707	ev_signal_stop (loop, &exitsig);
653		708
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	709	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		710
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	711	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		712
658	These advanced functions influence the time that libev will spend waiting	713	These advanced functions influence the time that libev will spend waiting
659	for events. Both are by default C<0>, meaning that libev will try to	714	for events. Both time intervals are by default C<0>, meaning that libev
660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	715	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		716	latency.
661		717
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
663	allows libev to delay invocation of I/O and timer/periodic callbacks to	719	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	720	to increase efficiency of loop iterations (or to increase power-saving
		721	opportunities).
665		722
666	The background is that sometimes your program runs just fast enough to	723	The background is that sometimes your program runs just fast enough to
667	handle one (or very few) event(s) per loop iteration. While this makes	724	handle one (or very few) event(s) per loop iteration. While this makes
668	the program responsive, it also wastes a lot of CPU time to poll for new	725	the program responsive, it also wastes a lot of CPU time to poll for new
669	events, especially with backends like C<select ()> which have a high	726	events, especially with backends like C<select ()> which have a high
…		…
679	to spend more time collecting timeouts, at the expense of increased	736	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	737	latency (the watcher callback will be called later). C<ev_io> watchers
681	will not be affected. Setting this to a non-null value will not introduce	738	will not be affected. Setting this to a non-null value will not introduce
682	any overhead in libev.	739	any overhead in libev.
683		740
684	Many (busy) programs can usually benefit by setting the io collect	741	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	742	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	743	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	744	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	745	as this approaches the timing granularity of most systems.
		746
		747	Setting the I<timeout collect interval> can improve the opportunity for
		748	saving power, as the program will "bundle" timer callback invocations that
		749	are "near" in time together, by delaying some, thus reducing the number of
		750	times the process sleeps and wakes up again. Another useful technique to
		751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		752	they fire on, say, one-second boundaries only.
		753
		754	=item ev_loop_verify (loop)
		755
		756	This function only does something when C<EV_VERIFY> support has been
		757	compiled in. It tries to go through all internal structures and checks
		758	them for validity. If anything is found to be inconsistent, it will print
		759	an error message to standard error and call C<abort ()>.
		760
		761	This can be used to catch bugs inside libev itself: under normal
		762	circumstances, this function will never abort as of course libev keeps its
		763	data structures consistent.
689		764
690	=back	765	=back
691		766
692		767
693	=head1 ANATOMY OF A WATCHER	768	=head1 ANATOMY OF A WATCHER
694		769
695	A watcher is a structure that you create and register to record your	770	A watcher is a structure that you create and register to record your
696	interest in some event. For instance, if you want to wait for STDIN to	771	interest in some event. For instance, if you want to wait for STDIN to
697	become readable, you would create an C<ev_io> watcher for that:	772	become readable, you would create an C<ev_io> watcher for that:
698		773
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
700	{	775	{
701	ev_io_stop (w);	776	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	777	ev_unloop (loop, EVUNLOOP_ALL);
703	}	778	}
704		779
705	struct ev_loop *loop = ev_default_loop (0);	780	struct ev_loop *loop = ev_default_loop (0);
706	struct ev_io stdin_watcher;	781	struct ev_io stdin_watcher;
707	ev_init (&stdin_watcher, my_cb);	782	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	784	ev_io_start (loop, &stdin_watcher);
710	ev_loop (loop, 0);	785	ev_loop (loop, 0);
711		786
712	As you can see, you are responsible for allocating the memory for your	787	As you can see, you are responsible for allocating the memory for your
713	watcher structures (and it is usually a bad idea to do this on the stack,	788	watcher structures (and it is usually a bad idea to do this on the stack,
714	although this can sometimes be quite valid).	789	although this can sometimes be quite valid).
715		790
716	Each watcher structure must be initialised by a call to C<ev_init	791	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	792	(watcher *, callback)>, which expects a callback to be provided. This
718	callback gets invoked each time the event occurs (or, in the case of io	793	callback gets invoked each time the event occurs (or, in the case of I/O
719	watchers, each time the event loop detects that the file descriptor given	794	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	795	is readable and/or writable).
721		796
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
723	with arguments specific to this watcher type. There is also a macro	798	with arguments specific to this watcher type. There is also a macro
…		…
799		874
800	The given async watcher has been asynchronously notified (see C<ev_async>).	875	The given async watcher has been asynchronously notified (see C<ev_async>).
801		876
802	=item C<EV_ERROR>	877	=item C<EV_ERROR>
803		878
804	An unspecified error has occured, the watcher has been stopped. This might	879	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	880	happen because the watcher could not be properly started because libev
806	ran out of memory, a file descriptor was found to be closed or any other	881	ran out of memory, a file descriptor was found to be closed or any other
807	problem. You best act on it by reporting the problem and somehow coping	882	problem. You best act on it by reporting the problem and somehow coping
808	with the watcher being stopped.	883	with the watcher being stopped.
809		884
810	Libev will usually signal a few "dummy" events together with an error,	885	Libev will usually signal a few "dummy" events together with an error,
811	for example it might indicate that a fd is readable or writable, and if	886	for example it might indicate that a fd is readable or writable, and if
812	your callbacks is well-written it can just attempt the operation and cope	887	your callbacks is well-written it can just attempt the operation and cope
813	with the error from read() or write(). This will not work in multithreaded	888	with the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	889	programs, though, so beware.
815		890
816	=back	891	=back
817		892
818	=head2 GENERIC WATCHER FUNCTIONS	893	=head2 GENERIC WATCHER FUNCTIONS
…		…
848	Although some watcher types do not have type-specific arguments	923	Although some watcher types do not have type-specific arguments
849	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		925
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		927
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	929	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	930	a watcher. The same limitations apply, of course.
856		931
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		933
859	Starts (activates) the given watcher. Only active watchers will receive	934	Starts (activates) the given watcher. Only active watchers will receive
…		…
942	to associate arbitrary data with your watcher. If you need more data and	1017	to associate arbitrary data with your watcher. If you need more data and
943	don't want to allocate memory and store a pointer to it in that data	1018	don't want to allocate memory and store a pointer to it in that data
944	member, you can also "subclass" the watcher type and provide your own	1019	member, you can also "subclass" the watcher type and provide your own
945	data:	1020	data:
946		1021
947	struct my_io	1022	struct my_io
948	{	1023	{
949	struct ev_io io;	1024	struct ev_io io;
950	int otherfd;	1025	int otherfd;
951	void *somedata;	1026	void *somedata;
952	struct whatever *mostinteresting;	1027	struct whatever *mostinteresting;
953	}	1028	};
		1029
		1030	...
		1031	struct my_io w;
		1032	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1033
955	And since your callback will be called with a pointer to the watcher, you	1034	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1035	can cast it back to your own type:
957		1036
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
959	{	1038	{
960	struct my_io *w = (struct my_io *)w_;	1039	struct my_io *w = (struct my_io *)w_;
961	...	1040	...
962	}	1041	}
963		1042
964	More interesting and less C-conformant ways of casting your callback type	1043	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1044	instead have been omitted.
966		1045
967	Another common scenario is having some data structure with multiple	1046	Another common scenario is to use some data structure with multiple
968	watchers:	1047	embedded watchers:
969		1048
970	struct my_biggy	1049	struct my_biggy
971	{	1050	{
972	int some_data;	1051	int some_data;
973	ev_timer t1;	1052	ev_timer t1;
974	ev_timer t2;	1053	ev_timer t2;
975	}	1054	}
976		1055
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1056	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1057	complicated: Either you store the address of your C<my_biggy> struct
		1058	in the C<data> member of the watcher, or you need to use some pointer
		1059	arithmetic using C<offsetof> inside your watchers:
979		1060
980	#include <stddef.h>	1061	#include <stddef.h>
981		1062
982	static void	1063	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1064	t1_cb (EV_P_ struct ev_timer *w, int revents)
984	{	1065	{
985	struct my_biggy big = (struct my_biggy *	1066	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1067	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1068	}
988		1069
989	static void	1070	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1071	t2_cb (EV_P_ struct ev_timer *w, int revents)
991	{	1072	{
992	struct my_biggy big = (struct my_biggy *	1073	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1074	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1075	}
995		1076
996		1077
997	=head1 WATCHER TYPES	1078	=head1 WATCHER TYPES
998		1079
999	This section describes each watcher in detail, but will not repeat	1080	This section describes each watcher in detail, but will not repeat
…		…
1028	If you must do this, then force the use of a known-to-be-good backend	1109	If you must do this, then force the use of a known-to-be-good backend
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1030	C<EVBACKEND_POLL>).	1111	C<EVBACKEND_POLL>).
1031		1112
1032	Another thing you have to watch out for is that it is quite easy to	1113	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1114	receive "spurious" readiness notifications, that is your callback might
1034	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1035	because there is no data. Not only are some backends known to create a	1116	because there is no data. Not only are some backends known to create a
1036	lot of those (for example solaris ports), it is very easy to get into	1117	lot of those (for example Solaris ports), it is very easy to get into
1037	this situation even with a relatively standard program structure. Thus	1118	this situation even with a relatively standard program structure. Thus
1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1121
1041	If you cannot run the fd in non-blocking mode (for example you should not	1122	If you cannot run the fd in non-blocking mode (for example you should not
1042	play around with an Xlib connection), then you have to seperately re-test	1123	play around with an Xlib connection), then you have to separately re-test
1043	whether a file descriptor is really ready with a known-to-be good interface	1124	whether a file descriptor is really ready with a known-to-be good interface
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1125	such as poll (fortunately in our Xlib example, Xlib already does this on
1045	its own, so its quite safe to use).	1126	its own, so its quite safe to use).
1046		1127
1047	=head3 The special problem of disappearing file descriptors	1128	=head3 The special problem of disappearing file descriptors
…		…
1085	To support fork in your programs, you either have to call	1166	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1167	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1169	C<EVBACKEND_POLL>.
1089		1170
		1171	=head3 The special problem of SIGPIPE
		1172
		1173	While not really specific to libev, it is easy to forget about SIGPIPE:
		1174	when writing to a pipe whose other end has been closed, your program gets
		1175	send a SIGPIPE, which, by default, aborts your program. For most programs
		1176	this is sensible behaviour, for daemons, this is usually undesirable.
		1177
		1178	So when you encounter spurious, unexplained daemon exits, make sure you
		1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1180	somewhere, as that would have given you a big clue).
		1181
1090		1182
1091	=head3 Watcher-Specific Functions	1183	=head3 Watcher-Specific Functions
1092		1184
1093	=over 4	1185	=over 4
1094		1186
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1187	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1188
1097	=item ev_io_set (ev_io *, int fd, int events)	1189	=item ev_io_set (ev_io *, int fd, int events)
1098		1190
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1101	C<EV_READ | EV_WRITE> to receive the given events.	1193	C<EV_READ | EV_WRITE> to receive the given events.
1102		1194
1103	=item int fd [read-only]	1195	=item int fd [read-only]
1104		1196
1105	The file descriptor being watched.	1197	The file descriptor being watched.
…		…
1114		1206
1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1116	readable, but only once. Since it is likely line-buffered, you could	1208	readable, but only once. Since it is likely line-buffered, you could
1117	attempt to read a whole line in the callback.	1209	attempt to read a whole line in the callback.
1118		1210
1119	static void	1211	static void
1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1121	{	1213	{
1122	ev_io_stop (loop, w);	1214	ev_io_stop (loop, w);
1123	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1124	}	1216	}
1125		1217
1126	...	1218	...
1127	struct ev_loop *loop = ev_default_init (0);	1219	struct ev_loop *loop = ev_default_init (0);
1128	struct ev_io stdin_readable;	1220	struct ev_io stdin_readable;
1129	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1130	ev_io_start (loop, &stdin_readable);	1222	ev_io_start (loop, &stdin_readable);
1131	ev_loop (loop, 0);	1223	ev_loop (loop, 0);
1132		1224
1133		1225
1134	=head2 C<ev_timer> - relative and optionally repeating timeouts	1226	=head2 C<ev_timer> - relative and optionally repeating timeouts
1135		1227
1136	Timer watchers are simple relative timers that generate an event after a	1228	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1229	given time, and optionally repeating in regular intervals after that.
1138		1230
1139	The timers are based on real time, that is, if you register an event that	1231	The timers are based on real time, that is, if you register an event that
1140	times out after an hour and you reset your system clock to last years	1232	times out after an hour and you reset your system clock to January last
1141	time, it will still time out after (roughly) and hour. "Roughly" because	1233	year, it will still time out after (roughly) and hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1235	monotonic clock option helps a lot here).
		1236
		1237	The callback is guaranteed to be invoked only after its timeout has passed,
		1238	but if multiple timers become ready during the same loop iteration then
		1239	order of execution is undefined.
		1240
		1241	=head3 The special problem of time updates
		1242
		1243	Establishing the current time is a costly operation (it usually takes at
		1244	least two system calls): EV therefore updates its idea of the current
		1245	time only before and after C<ev_loop> polls for new events, which causes
		1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1247	lots of events.
1144		1248
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1249	The relative timeouts are calculated relative to the C<ev_now ()>
1146	time. This is usually the right thing as this timestamp refers to the time	1250	time. This is usually the right thing as this timestamp refers to the time
1147	of the event triggering whatever timeout you are modifying/starting. If	1251	of the event triggering whatever timeout you are modifying/starting. If
1148	you suspect event processing to be delayed and you I<need> to base the timeout	1252	you suspect event processing to be delayed and you I<need> to base the
1149	on the current time, use something like this to adjust for this:	1253	timeout on the current time, use something like this to adjust for this:
1150		1254
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1255	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1256
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1257	If the event loop is suspended for a long time, you can also force an
1154	but if multiple timers become ready during the same loop iteration then	1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1155	order of execution is undefined.	1259	()>.
1156		1260
1157	=head3 Watcher-Specific Functions and Data Members	1261	=head3 Watcher-Specific Functions and Data Members
1158		1262
1159	=over 4	1263	=over 4
1160		1264
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1266
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1267	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1268
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1269	Configure the timer to trigger after C<after> seconds. If C<repeat>
1166	C<0.>, then it will automatically be stopped. If it is positive, then the	1270	is C<0.>, then it will automatically be stopped once the timeout is
1167	timer will automatically be configured to trigger again C<repeat> seconds	1271	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1272	configured to trigger again C<repeat> seconds later, again, and again,
		1273	until stopped manually.
1169		1274
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1275	The timer itself will do a best-effort at avoiding drift, that is, if
1171	configure a timer to trigger every 10 seconds, then it will trigger at	1276	you configure a timer to trigger every 10 seconds, then it will normally
1172	exactly 10 second intervals. If, however, your program cannot keep up with	1277	trigger at exactly 10 second intervals. If, however, your program cannot
1173	the timer (because it takes longer than those 10 seconds to do stuff) the	1278	keep up with the timer (because it takes longer than those 10 seconds to
1174	timer will not fire more than once per event loop iteration.	1279	do stuff) the timer will not fire more than once per event loop iteration.
1175		1280
1176	=item ev_timer_again (loop, ev_timer *)	1281	=item ev_timer_again (loop, ev_timer *)
1177		1282
1178	This will act as if the timer timed out and restart it again if it is	1283	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1284	repeating. The exact semantics are:
1180		1285
1181	If the timer is pending, its pending status is cleared.	1286	If the timer is pending, its pending status is cleared.
1182		1287
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	1288	If the timer is started but non-repeating, stop it (as if it timed out).
1184		1289
1185	If the timer is repeating, either start it if necessary (with the	1290	If the timer is repeating, either start it if necessary (with the
1186	C<repeat> value), or reset the running timer to the C<repeat> value.	1291	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		1292
1188	This sounds a bit complicated, but here is a useful and typical	1293	This sounds a bit complicated, but here is a useful and typical
1189	example: Imagine you have a tcp connection and you want a so-called idle	1294	example: Imagine you have a TCP connection and you want a so-called idle
1190	timeout, that is, you want to be called when there have been, say, 60	1295	timeout, that is, you want to be called when there have been, say, 60
1191	seconds of inactivity on the socket. The easiest way to do this is to	1296	seconds of inactivity on the socket. The easiest way to do this is to
1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1193	C<ev_timer_again> each time you successfully read or write some data. If	1298	C<ev_timer_again> each time you successfully read or write some data. If
1194	you go into an idle state where you do not expect data to travel on the	1299	you go into an idle state where you do not expect data to travel on the
…		…
1220		1325
1221	=head3 Examples	1326	=head3 Examples
1222		1327
1223	Example: Create a timer that fires after 60 seconds.	1328	Example: Create a timer that fires after 60 seconds.
1224		1329
1225	static void	1330	static void
1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1227	{	1332	{
1228	.. one minute over, w is actually stopped right here	1333	.. one minute over, w is actually stopped right here
1229	}	1334	}
1230		1335
1231	struct ev_timer mytimer;	1336	struct ev_timer mytimer;
1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233	ev_timer_start (loop, &mytimer);	1338	ev_timer_start (loop, &mytimer);
1234		1339
1235	Example: Create a timeout timer that times out after 10 seconds of	1340	Example: Create a timeout timer that times out after 10 seconds of
1236	inactivity.	1341	inactivity.
1237		1342
1238	static void	1343	static void
1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1240	{	1345	{
1241	.. ten seconds without any activity	1346	.. ten seconds without any activity
1242	}	1347	}
1243		1348
1244	struct ev_timer mytimer;	1349	struct ev_timer mytimer;
1245	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1246	ev_timer_again (&mytimer); /* start timer */	1351	ev_timer_again (&mytimer); /* start timer */
1247	ev_loop (loop, 0);	1352	ev_loop (loop, 0);
1248		1353
1249	// and in some piece of code that gets executed on any "activity":	1354	// and in some piece of code that gets executed on any "activity":
1250	// reset the timeout to start ticking again at 10 seconds	1355	// reset the timeout to start ticking again at 10 seconds
1251	ev_timer_again (&mytimer);	1356	ev_timer_again (&mytimer);
1252		1357
1253		1358
1254	=head2 C<ev_periodic> - to cron or not to cron?	1359	=head2 C<ev_periodic> - to cron or not to cron?
1255		1360
1256	Periodic watchers are also timers of a kind, but they are very versatile	1361	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	1362	(and unfortunately a bit complex).
1258		1363
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1260	but on wallclock time (absolute time). You can tell a periodic watcher	1365	but on wall clock time (absolute time). You can tell a periodic watcher
1261	to trigger "at" some specific point in time. For example, if you tell a	1366	to trigger after some specific point in time. For example, if you tell a
1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1263	+ 10.>) and then reset your system clock to the last year, then it will	1368	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1369	clock to January of the previous year, then it will take more than year
1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1265	roughly 10 seconds later).	1371	roughly 10 seconds later as it uses a relative timeout).
1266		1372
1267	They can also be used to implement vastly more complex timers, such as	1373	C<ev_periodic>s can also be used to implement vastly more complex timers,
1268	triggering an event on each midnight, local time or other, complicated,	1374	such as triggering an event on each "midnight, local time", or other
1269	rules.	1375	complicated, rules.
1270		1376
1271	As with timers, the callback is guarenteed to be invoked only when the	1377	As with timers, the callback is guaranteed to be invoked only when the
1272	time (C<at>) has been passed, but if multiple periodic timers become ready	1378	time (C<at>) has passed, but if multiple periodic timers become ready
1273	during the same loop iteration then order of execution is undefined.	1379	during the same loop iteration then order of execution is undefined.
1274		1380
1275	=head3 Watcher-Specific Functions and Data Members	1381	=head3 Watcher-Specific Functions and Data Members
1276		1382
1277	=over 4	1383	=over 4
…		…
1285		1391
1286	=over 4	1392	=over 4
1287		1393
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1289		1395
1290	In this configuration the watcher triggers an event at the wallclock time	1396	In this configuration the watcher triggers an event after the wall clock
1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1397	time C<at> has passed and doesn't repeat. It will not adjust when a time
1292	that is, if it is to be run at January 1st 2011 then it will run when the	1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1293	system time reaches or surpasses this time.	1399	run when the system time reaches or surpasses this time.
1294		1400
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1296		1402
1297	In this mode the watcher will always be scheduled to time out at the next	1403	In this mode the watcher will always be scheduled to time out at the next
1298	C<at + N * interval> time (for some integer N, which can also be negative)	1404	C<at + N * interval> time (for some integer N, which can also be negative)
1299	and then repeat, regardless of any time jumps.	1405	and then repeat, regardless of any time jumps.
1300		1406
1301	This can be used to create timers that do not drift with respect to system	1407	This can be used to create timers that do not drift with respect to system
1302	time:	1408	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1409	the hour:
1303		1410
1304	ev_periodic_set (&periodic, 0., 3600., 0);	1411	ev_periodic_set (&periodic, 0., 3600., 0);
1305		1412
1306	This doesn't mean there will always be 3600 seconds in between triggers,	1413	This doesn't mean there will always be 3600 seconds in between triggers,
1307	but only that the the callback will be called when the system time shows a	1414	but only that the callback will be called when the system time shows a
1308	full hour (UTC), or more correctly, when the system time is evenly divisible	1415	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	1416	by 3600.
1310		1417
1311	Another way to think about it (for the mathematically inclined) is that	1418	Another way to think about it (for the mathematically inclined) is that
1312	C<ev_periodic> will try to run the callback in this mode at the next possible	1419	C<ev_periodic> will try to run the callback in this mode at the next possible
1313	time where C<time = at (mod interval)>, regardless of any time jumps.	1420	time where C<time = at (mod interval)>, regardless of any time jumps.
1314		1421
1315	For numerical stability it is preferable that the C<at> value is near	1422	For numerical stability it is preferable that the C<at> value is near
1316	C<ev_now ()> (the current time), but there is no range requirement for	1423	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	1424	this value, and in fact is often specified as zero.
		1425
		1426	Note also that there is an upper limit to how often a timer can fire (CPU
		1427	speed for example), so if C<interval> is very small then timing stability
		1428	will of course deteriorate. Libev itself tries to be exact to be about one
		1429	millisecond (if the OS supports it and the machine is fast enough).
1318		1430
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1320		1432
1321	In this mode the values for C<interval> and C<at> are both being	1433	In this mode the values for C<interval> and C<at> are both being
1322	ignored. Instead, each time the periodic watcher gets scheduled, the	1434	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	1435	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	1436	current time as second argument.
1325		1437
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1327	ever, or make any event loop modifications>. If you need to stop it,	1439	ever, or make ANY event loop modifications whatsoever>.
1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1329	starting an C<ev_prepare> watcher, which is legal).
1330		1440
		1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1443	only event loop modification you are allowed to do).
		1444
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1332	ev_tstamp now)>, e.g.:	1446	*w, ev_tstamp now)>, e.g.:
1333		1447
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1335	{	1449	{
1336	return now + 60.;	1450	return now + 60.;
1337	}	1451	}
…		…
1339	It must return the next time to trigger, based on the passed time value	1453	It must return the next time to trigger, based on the passed time value
1340	(that is, the lowest time value larger than to the second argument). It	1454	(that is, the lowest time value larger than to the second argument). It
1341	will usually be called just before the callback will be triggered, but	1455	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	1456	might be called at other times, too.
1343		1457
1344	NOTE: I<< This callback must always return a time that is later than the	1458	NOTE: I<< This callback must always return a time that is higher than or
1345	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1459	equal to the passed C<now> value >>.
1346		1460
1347	This can be used to create very complex timers, such as a timer that	1461	This can be used to create very complex timers, such as a timer that
1348	triggers on each midnight, local time. To do this, you would calculate the	1462	triggers on "next midnight, local time". To do this, you would calculate the
1349	next midnight after C<now> and return the timestamp value for this. How	1463	next midnight after C<now> and return the timestamp value for this. How
1350	you do this is, again, up to you (but it is not trivial, which is the main	1464	you do this is, again, up to you (but it is not trivial, which is the main
1351	reason I omitted it as an example).	1465	reason I omitted it as an example).
1352		1466
1353	=back	1467	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1471	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1472	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	1473	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1474	program when the crontabs have changed).
1361		1475
		1476	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1477
		1478	When active, returns the absolute time that the watcher is supposed to
		1479	trigger next.
		1480
1362	=item ev_tstamp offset [read-write]	1481	=item ev_tstamp offset [read-write]
1363		1482
1364	When repeating, this contains the offset value, otherwise this is the	1483	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1485
…		…
1377		1496
1378	The current reschedule callback, or C<0>, if this functionality is	1497	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	1498	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	1499	the periodic timer fires or C<ev_periodic_again> is being called.
1381		1500
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386
1387	=back	1501	=back
1388		1502
1389	=head3 Examples	1503	=head3 Examples
1390		1504
1391	Example: Call a callback every hour, or, more precisely, whenever the	1505	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	1506	system clock is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	1507	potentially a lot of jitter, but good long-term stability.
1394		1508
1395	static void	1509	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1397	{	1511	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	1512	... its now a full hour (UTC, or TAI or whatever your clock follows)
1399	}	1513	}
1400		1514
1401	struct ev_periodic hourly_tick;	1515	struct ev_periodic hourly_tick;
1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1517	ev_periodic_start (loop, &hourly_tick);
1404		1518
1405	Example: The same as above, but use a reschedule callback to do it:	1519	Example: The same as above, but use a reschedule callback to do it:
1406		1520
1407	#include <math.h>	1521	#include <math.h>
1408		1522
1409	static ev_tstamp	1523	static ev_tstamp
1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1411	{	1525	{
1412	return fmod (now, 3600.) + 3600.;	1526	return fmod (now, 3600.) + 3600.;
1413	}	1527	}
1414		1528
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1416		1530
1417	Example: Call a callback every hour, starting now:	1531	Example: Call a callback every hour, starting now:
1418		1532
1419	struct ev_periodic hourly_tick;	1533	struct ev_periodic hourly_tick;
1420	ev_periodic_init (&hourly_tick, clock_cb,	1534	ev_periodic_init (&hourly_tick, clock_cb,
1421	fmod (ev_now (loop), 3600.), 3600., 0);	1535	fmod (ev_now (loop), 3600.), 3600., 0);
1422	ev_periodic_start (loop, &hourly_tick);	1536	ev_periodic_start (loop, &hourly_tick);
1423		1537
1424		1538
1425	=head2 C<ev_signal> - signal me when a signal gets signalled!	1539	=head2 C<ev_signal> - signal me when a signal gets signalled!
1426		1540
1427	Signal watchers will trigger an event when the process receives a specific	1541	Signal watchers will trigger an event when the process receives a specific
…		…
1435	as you don't register any with libev). Similarly, when the last signal	1549	as you don't register any with libev). Similarly, when the last signal
1436	watcher for a signal is stopped libev will reset the signal handler to	1550	watcher for a signal is stopped libev will reset the signal handler to
1437	SIG_DFL (regardless of what it was set to before).	1551	SIG_DFL (regardless of what it was set to before).
1438		1552
1439	If possible and supported, libev will install its handlers with	1553	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1441	interrupted. If you have a problem with syscalls getting interrupted by	1555	interrupted. If you have a problem with system calls getting interrupted by
1442	signals you can block all signals in an C<ev_check> watcher and unblock	1556	signals you can block all signals in an C<ev_check> watcher and unblock
1443	them in an C<ev_prepare> watcher.	1557	them in an C<ev_prepare> watcher.
1444		1558
1445	=head3 Watcher-Specific Functions and Data Members	1559	=head3 Watcher-Specific Functions and Data Members
1446		1560
…		…
1461		1575
1462	=head3 Examples	1576	=head3 Examples
1463		1577
1464	Example: Try to exit cleanly on SIGINT and SIGTERM.	1578	Example: Try to exit cleanly on SIGINT and SIGTERM.
1465		1579
1466	static void	1580	static void
1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1468	{	1582	{
1469	ev_unloop (loop, EVUNLOOP_ALL);	1583	ev_unloop (loop, EVUNLOOP_ALL);
1470	}	1584	}
1471		1585
1472	struct ev_signal signal_watcher;	1586	struct ev_signal signal_watcher;
1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474	ev_signal_start (loop, &sigint_cb);	1588	ev_signal_start (loop, &sigint_cb);
1475		1589
1476		1590
1477	=head2 C<ev_child> - watch out for process status changes	1591	=head2 C<ev_child> - watch out for process status changes
1478		1592
1479	Child watchers trigger when your process receives a SIGCHLD in response to	1593	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1481	is permissible to install a child watcher I<after> the child has been	1595	is permissible to install a child watcher I<after> the child has been
1482	forked (which implies it might have already exited), as long as the event	1596	forked (which implies it might have already exited), as long as the event
1483	loop isn't entered (or is continued from a watcher).	1597	loop isn't entered (or is continued from a watcher).
1484		1598
1485	Only the default event loop is capable of handling signals, and therefore	1599	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	1600	you can only register child watchers in the default event loop.
1487		1601
1488	=head3 Process Interaction	1602	=head3 Process Interaction
1489		1603
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	1604	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	1605	initialised. This is necessary to guarantee proper behaviour even if
1492	the first child watcher is started after the child exits. The occurance	1606	the first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	1608	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	1609	children, even ones not watched.
1496		1610
1497	=head3 Overriding the Built-In Processing	1611	=head3 Overriding the Built-In Processing
…		…
1501	handler, you can override it easily by installing your own handler for	1615	handler, you can override it easily by installing your own handler for
1502	C<SIGCHLD> after initialising the default loop, and making sure the	1616	C<SIGCHLD> after initialising the default loop, and making sure the
1503	default loop never gets destroyed. You are encouraged, however, to use an	1617	default loop never gets destroyed. You are encouraged, however, to use an
1504	event-based approach to child reaping and thus use libev's support for	1618	event-based approach to child reaping and thus use libev's support for
1505	that, so other libev users can use C<ev_child> watchers freely.	1619	that, so other libev users can use C<ev_child> watchers freely.
		1620
		1621	=head3 Stopping the Child Watcher
		1622
		1623	Currently, the child watcher never gets stopped, even when the
		1624	child terminates, so normally one needs to stop the watcher in the
		1625	callback. Future versions of libev might stop the watcher automatically
		1626	when a child exit is detected.
1506		1627
1507	=head3 Watcher-Specific Functions and Data Members	1628	=head3 Watcher-Specific Functions and Data Members
1508		1629
1509	=over 4	1630	=over 4
1510		1631
…		…
1539	=head3 Examples	1660	=head3 Examples
1540		1661
1541	Example: C<fork()> a new process and install a child handler to wait for	1662	Example: C<fork()> a new process and install a child handler to wait for
1542	its completion.	1663	its completion.
1543		1664
1544	ev_child cw;	1665	ev_child cw;
1545		1666
1546	static void	1667	static void
1547	child_cb (EV_P_ struct ev_child *w, int revents)	1668	child_cb (EV_P_ struct ev_child *w, int revents)
1548	{	1669	{
1549	ev_child_stop (EV_A_ w);	1670	ev_child_stop (EV_A_ w);
1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1551	}	1672	}
1552		1673
1553	pid_t pid = fork ();	1674	pid_t pid = fork ();
1554		1675
1555	if (pid < 0)	1676	if (pid < 0)
1556	// error	1677	// error
1557	else if (pid == 0)	1678	else if (pid == 0)
1558	{	1679	{
1559	// the forked child executes here	1680	// the forked child executes here
1560	exit (1);	1681	exit (1);
1561	}	1682	}
1562	else	1683	else
1563	{	1684	{
1564	ev_child_init (&cw, child_cb, pid, 0);	1685	ev_child_init (&cw, child_cb, pid, 0);
1565	ev_child_start (EV_DEFAULT_ &cw);	1686	ev_child_start (EV_DEFAULT_ &cw);
1566	}	1687	}
1567		1688
1568		1689
1569	=head2 C<ev_stat> - did the file attributes just change?	1690	=head2 C<ev_stat> - did the file attributes just change?
1570		1691
1571	This watches a filesystem path for attribute changes. That is, it calls	1692	This watches a file system path for attribute changes. That is, it calls
1572	C<stat> regularly (or when the OS says it changed) and sees if it changed	1693	C<stat> regularly (or when the OS says it changed) and sees if it changed
1573	compared to the last time, invoking the callback if it did.	1694	compared to the last time, invoking the callback if it did.
1574		1695
1575	The path does not need to exist: changing from "path exists" to "path does	1696	The path does not need to exist: changing from "path exists" to "path does
1576	not exist" is a status change like any other. The condition "path does	1697	not exist" is a status change like any other. The condition "path does
…		…
1594	as even with OS-supported change notifications, this can be	1715	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1716	resource-intensive.
1596		1717
1597	At the time of this writing, only the Linux inotify interface is	1718	At the time of this writing, only the Linux inotify interface is
1598	implemented (implementing kqueue support is left as an exercise for the	1719	implemented (implementing kqueue support is left as an exercise for the
		1720	reader, note, however, that the author sees no way of implementing ev_stat
1599	reader). Inotify will be used to give hints only and should not change the	1721	semantics with kqueue). Inotify will be used to give hints only and should
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1722	not change the semantics of C<ev_stat> watchers, which means that libev
1601	to fall back to regular polling again even with inotify, but changes are	1723	sometimes needs to fall back to regular polling again even with inotify,
1602	usually detected immediately, and if the file exists there will be no	1724	but changes are usually detected immediately, and if the file exists there
1603	polling.	1725	will be no polling.
		1726
		1727	=head3 ABI Issues (Largefile Support)
		1728
		1729	Libev by default (unless the user overrides this) uses the default
		1730	compilation environment, which means that on systems with large file
		1731	support disabled by default, you get the 32 bit version of the stat
		1732	structure. When using the library from programs that change the ABI to
		1733	use 64 bit file offsets the programs will fail. In that case you have to
		1734	compile libev with the same flags to get binary compatibility. This is
		1735	obviously the case with any flags that change the ABI, but the problem is
		1736	most noticeably disabled with ev_stat and large file support.
		1737
		1738	The solution for this is to lobby your distribution maker to make large
		1739	file interfaces available by default (as e.g. FreeBSD does) and not
		1740	optional. Libev cannot simply switch on large file support because it has
		1741	to exchange stat structures with application programs compiled using the
		1742	default compilation environment.
1604		1743
1605	=head3 Inotify	1744	=head3 Inotify
1606		1745
1607	When C<inotify (7)> support has been compiled into libev (generally only	1746	When C<inotify (7)> support has been compiled into libev (generally only
1608	available on Linux) and present at runtime, it will be used to speed up	1747	available on Linux) and present at runtime, it will be used to speed up
1609	change detection where possible. The inotify descriptor will be created lazily	1748	change detection where possible. The inotify descriptor will be created lazily
1610	when the first C<ev_stat> watcher is being started.	1749	when the first C<ev_stat> watcher is being started.
1611		1750
1612	Inotify presense does not change the semantics of C<ev_stat> watchers	1751	Inotify presence does not change the semantics of C<ev_stat> watchers
1613	except that changes might be detected earlier, and in some cases, to avoid	1752	except that changes might be detected earlier, and in some cases, to avoid
1614	making regular C<stat> calls. Even in the presense of inotify support	1753	making regular C<stat> calls. Even in the presence of inotify support
1615	there are many cases where libev has to resort to regular C<stat> polling.	1754	there are many cases where libev has to resort to regular C<stat> polling.
1616		1755
1617	(There is no support for kqueue, as apparently it cannot be used to	1756	(There is no support for kqueue, as apparently it cannot be used to
1618	implement this functionality, due to the requirement of having a file	1757	implement this functionality, due to the requirement of having a file
1619	descriptor open on the object at all times).	1758	descriptor open on the object at all times).
1620		1759
1621	=head3 The special problem of stat time resolution	1760	=head3 The special problem of stat time resolution
1622		1761
1623	The C<stat ()> syscall only supports full-second resolution portably, and	1762	The C<stat ()> system call only supports full-second resolution portably, and
1624	even on systems where the resolution is higher, many filesystems still	1763	even on systems where the resolution is higher, many file systems still
1625	only support whole seconds.	1764	only support whole seconds.
1626		1765
1627	That means that, if the time is the only thing that changes, you might	1766	That means that, if the time is the only thing that changes, you can
1628	miss updates: on the first update, C<ev_stat> detects a change and calls	1767	easily miss updates: on the first update, C<ev_stat> detects a change and
1629	your callback, which does something. When there is another update within	1768	calls your callback, which does something. When there is another update
1630	the same second, C<ev_stat> will be unable to detect it.	1769	within the same second, C<ev_stat> will be unable to detect it as the stat
		1770	data does not change.
1631		1771
1632	The solution to this is to delay acting on a change for a second (or till	1772	The solution to this is to delay acting on a change for slightly more
1633	the next second boundary), using a roughly one-second delay C<ev_timer>	1773	than a second (or till slightly after the next full second boundary), using
1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1635	is added to work around small timing inconsistencies of some operating	1775	ev_timer_again (loop, w)>).
1636	systems.	1776
		1777	The C<.02> offset is added to work around small timing inconsistencies
		1778	of some operating systems (where the second counter of the current time
		1779	might be be delayed. One such system is the Linux kernel, where a call to
		1780	C<gettimeofday> might return a timestamp with a full second later than
		1781	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1782	update file times then there will be a small window where the kernel uses
		1783	the previous second to update file times but libev might already execute
		1784	the timer callback).
1637		1785
1638	=head3 Watcher-Specific Functions and Data Members	1786	=head3 Watcher-Specific Functions and Data Members
1639		1787
1640	=over 4	1788	=over 4
1641		1789
…		…
1647	C<path>. The C<interval> is a hint on how quickly a change is expected to	1795	C<path>. The C<interval> is a hint on how quickly a change is expected to
1648	be detected and should normally be specified as C<0> to let libev choose	1796	be detected and should normally be specified as C<0> to let libev choose
1649	a suitable value. The memory pointed to by C<path> must point to the same	1797	a suitable value. The memory pointed to by C<path> must point to the same
1650	path for as long as the watcher is active.	1798	path for as long as the watcher is active.
1651		1799
1652	The callback will be receive C<EV_STAT> when a change was detected,	1800	The callback will receive C<EV_STAT> when a change was detected, relative
1653	relative to the attributes at the time the watcher was started (or the	1801	to the attributes at the time the watcher was started (or the last change
1654	last change was detected).	1802	was detected).
1655		1803
1656	=item ev_stat_stat (loop, ev_stat *)	1804	=item ev_stat_stat (loop, ev_stat *)
1657		1805
1658	Updates the stat buffer immediately with new values. If you change the	1806	Updates the stat buffer immediately with new values. If you change the
1659	watched path in your callback, you could call this fucntion to avoid	1807	watched path in your callback, you could call this function to avoid
1660	detecting this change (while introducing a race condition). Can also be	1808	detecting this change (while introducing a race condition if you are not
1661	useful simply to find out the new values.	1809	the only one changing the path). Can also be useful simply to find out the
		1810	new values.
1662		1811
1663	=item ev_statdata attr [read-only]	1812	=item ev_statdata attr [read-only]
1664		1813
1665	The most-recently detected attributes of the file. Although the type is of	1814	The most-recently detected attributes of the file. Although the type is
1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1815	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1667	suitable for your system. If the C<st_nlink> member is C<0>, then there	1816	suitable for your system, but you can only rely on the POSIX-standardised
		1817	members to be present. If the C<st_nlink> member is C<0>, then there was
1668	was some error while C<stat>ing the file.	1818	some error while C<stat>ing the file.
1669		1819
1670	=item ev_statdata prev [read-only]	1820	=item ev_statdata prev [read-only]
1671		1821
1672	The previous attributes of the file. The callback gets invoked whenever	1822	The previous attributes of the file. The callback gets invoked whenever
1673	C<prev> != C<attr>.	1823	C<prev> != C<attr>, or, more precisely, one or more of these members
		1824	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1825	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1674		1826
1675	=item ev_tstamp interval [read-only]	1827	=item ev_tstamp interval [read-only]
1676		1828
1677	The specified interval.	1829	The specified interval.
1678		1830
1679	=item const char *path [read-only]	1831	=item const char *path [read-only]
1680		1832
1681	The filesystem path that is being watched.	1833	The file system path that is being watched.
1682		1834
1683	=back	1835	=back
1684		1836
1685	=head3 Examples	1837	=head3 Examples
1686		1838
1687	Example: Watch C</etc/passwd> for attribute changes.	1839	Example: Watch C</etc/passwd> for attribute changes.
1688		1840
1689	static void	1841	static void
1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1842	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1691	{	1843	{
1692	/* /etc/passwd changed in some way */	1844	/* /etc/passwd changed in some way */
1693	if (w->attr.st_nlink)	1845	if (w->attr.st_nlink)
1694	{	1846	{
1695	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1847	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1696	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1848	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1697	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1849	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1698	}	1850	}
1699	else	1851	else
1700	/* you shalt not abuse printf for puts */	1852	/* you shalt not abuse printf for puts */
1701	puts ("wow, /etc/passwd is not there, expect problems. "	1853	puts ("wow, /etc/passwd is not there, expect problems. "
1702	"if this is windows, they already arrived\n");	1854	"if this is windows, they already arrived\n");
1703	}	1855	}
1704		1856
1705	...	1857	...
1706	ev_stat passwd;	1858	ev_stat passwd;
1707		1859
1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1860	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1709	ev_stat_start (loop, &passwd);	1861	ev_stat_start (loop, &passwd);
1710		1862
1711	Example: Like above, but additionally use a one-second delay so we do not	1863	Example: Like above, but additionally use a one-second delay so we do not
1712	miss updates (however, frequent updates will delay processing, too, so	1864	miss updates (however, frequent updates will delay processing, too, so
1713	one might do the work both on C<ev_stat> callback invocation I<and> on	1865	one might do the work both on C<ev_stat> callback invocation I<and> on
1714	C<ev_timer> callback invocation).	1866	C<ev_timer> callback invocation).
1715		1867
1716	static ev_stat passwd;	1868	static ev_stat passwd;
1717	static ev_timer timer;	1869	static ev_timer timer;
1718		1870
1719	static void	1871	static void
1720	timer_cb (EV_P_ ev_timer *w, int revents)	1872	timer_cb (EV_P_ ev_timer *w, int revents)
1721	{	1873	{
1722	ev_timer_stop (EV_A_ w);	1874	ev_timer_stop (EV_A_ w);
1723		1875
1724	/* now it's one second after the most recent passwd change */	1876	/* now it's one second after the most recent passwd change */
1725	}	1877	}
1726		1878
1727	static void	1879	static void
1728	stat_cb (EV_P_ ev_stat *w, int revents)	1880	stat_cb (EV_P_ ev_stat *w, int revents)
1729	{	1881	{
1730	/* reset the one-second timer */	1882	/* reset the one-second timer */
1731	ev_timer_again (EV_A_ &timer);	1883	ev_timer_again (EV_A_ &timer);
1732	}	1884	}
1733		1885
1734	...	1886	...
1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1887	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	1888	ev_stat_start (loop, &passwd);
1737	ev_timer_init (&timer, timer_cb, 0., 1.01);	1889	ev_timer_init (&timer, timer_cb, 0., 1.02);
1738		1890
1739		1891
1740	=head2 C<ev_idle> - when you've got nothing better to do...	1892	=head2 C<ev_idle> - when you've got nothing better to do...
1741		1893
1742	Idle watchers trigger events when no other events of the same or higher	1894	Idle watchers trigger events when no other events of the same or higher
…		…
1773	=head3 Examples	1925	=head3 Examples
1774		1926
1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1776	callback, free it. Also, use no error checking, as usual.	1928	callback, free it. Also, use no error checking, as usual.
1777		1929
1778	static void	1930	static void
1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1780	{	1932	{
1781	free (w);	1933	free (w);
1782	// now do something you wanted to do when the program has	1934	// now do something you wanted to do when the program has
1783	// no longer anything immediate to do.	1935	// no longer anything immediate to do.
1784	}	1936	}
1785		1937
1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1787	ev_idle_init (idle_watcher, idle_cb);	1939	ev_idle_init (idle_watcher, idle_cb);
1788	ev_idle_start (loop, idle_cb);	1940	ev_idle_start (loop, idle_cb);
1789		1941
1790		1942
1791	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1792		1944
1793	Prepare and check watchers are usually (but not always) used in tandem:	1945	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1812		1964
1813	This is done by examining in each prepare call which file descriptors need	1965	This is done by examining in each prepare call which file descriptors need
1814	to be watched by the other library, registering C<ev_io> watchers for	1966	to be watched by the other library, registering C<ev_io> watchers for
1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1816	provide just this functionality). Then, in the check watcher you check for	1968	provide just this functionality). Then, in the check watcher you check for
1817	any events that occured (by checking the pending status of all watchers	1969	any events that occurred (by checking the pending status of all watchers
1818	and stopping them) and call back into the library. The I/O and timer	1970	and stopping them) and call back into the library. The I/O and timer
1819	callbacks will never actually be called (but must be valid nevertheless,	1971	callbacks will never actually be called (but must be valid nevertheless,
1820	because you never know, you know?).	1972	because you never know, you know?).
1821		1973
1822	As another example, the Perl Coro module uses these hooks to integrate	1974	As another example, the Perl Coro module uses these hooks to integrate
…		…
1830		1982
1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1832	priority, to ensure that they are being run before any other watchers	1984	priority, to ensure that they are being run before any other watchers
1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1834	too) should not activate ("feed") events into libev. While libev fully	1986	too) should not activate ("feed") events into libev. While libev fully
1835	supports this, they will be called before other C<ev_check> watchers	1987	supports this, they might get executed before other C<ev_check> watchers
1836	did their job. As C<ev_check> watchers are often used to embed other	1988	did their job. As C<ev_check> watchers are often used to embed other
1837	(non-libev) event loops those other event loops might be in an unusable	1989	(non-libev) event loops those other event loops might be in an unusable
1838	state until their C<ev_check> watcher ran (always remind yourself to	1990	state until their C<ev_check> watcher ran (always remind yourself to
1839	coexist peacefully with others).	1991	coexist peacefully with others).
1840		1992
…		…
1855	=head3 Examples	2007	=head3 Examples
1856		2008
1857	There are a number of principal ways to embed other event loops or modules	2009	There are a number of principal ways to embed other event loops or modules
1858	into libev. Here are some ideas on how to include libadns into libev	2010	into libev. Here are some ideas on how to include libadns into libev
1859	(there is a Perl module named C<EV::ADNS> that does this, which you could	2011	(there is a Perl module named C<EV::ADNS> that does this, which you could
1860	use for an actually working example. Another Perl module named C<EV::Glib>	2012	use as a working example. Another Perl module named C<EV::Glib> embeds a
1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2013	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1862	into the Glib event loop).	2014	Glib event loop).
1863		2015
1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2016	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1865	and in a check watcher, destroy them and call into libadns. What follows	2017	and in a check watcher, destroy them and call into libadns. What follows
1866	is pseudo-code only of course. This requires you to either use a low	2018	is pseudo-code only of course. This requires you to either use a low
1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2019	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1868	the callbacks for the IO/timeout watchers might not have been called yet.	2020	the callbacks for the IO/timeout watchers might not have been called yet.
1869		2021
1870	static ev_io iow [nfd];	2022	static ev_io iow [nfd];
1871	static ev_timer tw;	2023	static ev_timer tw;
1872		2024
1873	static void	2025	static void
1874	io_cb (ev_loop *loop, ev_io *w, int revents)	2026	io_cb (ev_loop *loop, ev_io *w, int revents)
1875	{	2027	{
1876	}	2028	}
1877		2029
1878	// create io watchers for each fd and a timer before blocking	2030	// create io watchers for each fd and a timer before blocking
1879	static void	2031	static void
1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1881	{	2033	{
1882	int timeout = 3600000;	2034	int timeout = 3600000;
1883	struct pollfd fds [nfd];	2035	struct pollfd fds [nfd];
1884	// actual code will need to loop here and realloc etc.	2036	// actual code will need to loop here and realloc etc.
1885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1886		2038
1887	/* the callback is illegal, but won't be called as we stop during check */	2039	/* the callback is illegal, but won't be called as we stop during check */
1888	ev_timer_init (&tw, 0, timeout * 1e-3);	2040	ev_timer_init (&tw, 0, timeout * 1e-3);
1889	ev_timer_start (loop, &tw);	2041	ev_timer_start (loop, &tw);
1890		2042
1891	// create one ev_io per pollfd	2043	// create one ev_io per pollfd
1892	for (int i = 0; i < nfd; ++i)	2044	for (int i = 0; i < nfd; ++i)
1893	{	2045	{
1894	ev_io_init (iow + i, io_cb, fds [i].fd,	2046	ev_io_init (iow + i, io_cb, fds [i].fd,
1895	((fds [i].events & POLLIN ? EV_READ : 0)	2047	((fds [i].events & POLLIN ? EV_READ : 0)
1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2048	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1897		2049
1898	fds [i].revents = 0;	2050	fds [i].revents = 0;
1899	ev_io_start (loop, iow + i);	2051	ev_io_start (loop, iow + i);
1900	}	2052	}
1901	}	2053	}
1902		2054
1903	// stop all watchers after blocking	2055	// stop all watchers after blocking
1904	static void	2056	static void
1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1906	{	2058	{
1907	ev_timer_stop (loop, &tw);	2059	ev_timer_stop (loop, &tw);
1908		2060
1909	for (int i = 0; i < nfd; ++i)	2061	for (int i = 0; i < nfd; ++i)
1910	{	2062	{
1911	// set the relevant poll flags	2063	// set the relevant poll flags
1912	// could also call adns_processreadable etc. here	2064	// could also call adns_processreadable etc. here
1913	struct pollfd *fd = fds + i;	2065	struct pollfd *fd = fds + i;
1914	int revents = ev_clear_pending (iow + i);	2066	int revents = ev_clear_pending (iow + i);
1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2067	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2068	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1917		2069
1918	// now stop the watcher	2070	// now stop the watcher
1919	ev_io_stop (loop, iow + i);	2071	ev_io_stop (loop, iow + i);
1920	}	2072	}
1921		2073
1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2074	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1923	}	2075	}
1924		2076
1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2077	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1926	in the prepare watcher and would dispose of the check watcher.	2078	in the prepare watcher and would dispose of the check watcher.
1927		2079
1928	Method 3: If the module to be embedded supports explicit event	2080	Method 3: If the module to be embedded supports explicit event
1929	notification (adns does), you can also make use of the actual watcher	2081	notification (libadns does), you can also make use of the actual watcher
1930	callbacks, and only destroy/create the watchers in the prepare watcher.	2082	callbacks, and only destroy/create the watchers in the prepare watcher.
1931		2083
1932	static void	2084	static void
1933	timer_cb (EV_P_ ev_timer *w, int revents)	2085	timer_cb (EV_P_ ev_timer *w, int revents)
1934	{	2086	{
1935	adns_state ads = (adns_state)w->data;	2087	adns_state ads = (adns_state)w->data;
1936	update_now (EV_A);	2088	update_now (EV_A);
1937		2089
1938	adns_processtimeouts (ads, &tv_now);	2090	adns_processtimeouts (ads, &tv_now);
1939	}	2091	}
1940		2092
1941	static void	2093	static void
1942	io_cb (EV_P_ ev_io *w, int revents)	2094	io_cb (EV_P_ ev_io *w, int revents)
1943	{	2095	{
1944	adns_state ads = (adns_state)w->data;	2096	adns_state ads = (adns_state)w->data;
1945	update_now (EV_A);	2097	update_now (EV_A);
1946		2098
1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2099	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2100	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1949	}	2101	}
1950		2102
1951	// do not ever call adns_afterpoll	2103	// do not ever call adns_afterpoll
1952		2104
1953	Method 4: Do not use a prepare or check watcher because the module you	2105	Method 4: Do not use a prepare or check watcher because the module you
1954	want to embed is too inflexible to support it. Instead, youc na override	2106	want to embed is too inflexible to support it. Instead, you can override
1955	their poll function. The drawback with this solution is that the main	2107	their poll function. The drawback with this solution is that the main
1956	loop is now no longer controllable by EV. The C<Glib::EV> module does	2108	loop is now no longer controllable by EV. The C<Glib::EV> module does
1957	this.	2109	this.
1958		2110
1959	static gint	2111	static gint
1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1961	{	2113	{
1962	int got_events = 0;	2114	int got_events = 0;
1963		2115
1964	for (n = 0; n < nfds; ++n)	2116	for (n = 0; n < nfds; ++n)
1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2117	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1966		2118
1967	if (timeout >= 0)	2119	if (timeout >= 0)
1968	// create/start timer	2120	// create/start timer
1969		2121
1970	// poll	2122	// poll
1971	ev_loop (EV_A_ 0);	2123	ev_loop (EV_A_ 0);
1972		2124
1973	// stop timer again	2125	// stop timer again
1974	if (timeout >= 0)	2126	if (timeout >= 0)
1975	ev_timer_stop (EV_A_ &to);	2127	ev_timer_stop (EV_A_ &to);
1976		2128
1977	// stop io watchers again - their callbacks should have set	2129	// stop io watchers again - their callbacks should have set
1978	for (n = 0; n < nfds; ++n)	2130	for (n = 0; n < nfds; ++n)
1979	ev_io_stop (EV_A_ iow [n]);	2131	ev_io_stop (EV_A_ iow [n]);
1980		2132
1981	return got_events;	2133	return got_events;
1982	}	2134	}
1983		2135
1984		2136
1985	=head2 C<ev_embed> - when one backend isn't enough...	2137	=head2 C<ev_embed> - when one backend isn't enough...
1986		2138
1987	This is a rather advanced watcher type that lets you embed one event loop	2139	This is a rather advanced watcher type that lets you embed one event loop
…		…
2043		2195
2044	Configures the watcher to embed the given loop, which must be	2196	Configures the watcher to embed the given loop, which must be
2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2046	invoked automatically, otherwise it is the responsibility of the callback	2198	invoked automatically, otherwise it is the responsibility of the callback
2047	to invoke it (it will continue to be called until the sweep has been done,	2199	to invoke it (it will continue to be called until the sweep has been done,
2048	if you do not want thta, you need to temporarily stop the embed watcher).	2200	if you do not want that, you need to temporarily stop the embed watcher).
2049		2201
2050	=item ev_embed_sweep (loop, ev_embed *)	2202	=item ev_embed_sweep (loop, ev_embed *)
2051		2203
2052	Make a single, non-blocking sweep over the embedded loop. This works	2204	Make a single, non-blocking sweep over the embedded loop. This works
2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2054	apropriate way for embedded loops.	2206	appropriate way for embedded loops.
2055		2207
2056	=item struct ev_loop *other [read-only]	2208	=item struct ev_loop *other [read-only]
2057		2209
2058	The embedded event loop.	2210	The embedded event loop.
2059		2211
…		…
2061		2213
2062	=head3 Examples	2214	=head3 Examples
2063		2215
2064	Example: Try to get an embeddable event loop and embed it into the default	2216	Example: Try to get an embeddable event loop and embed it into the default
2065	event loop. If that is not possible, use the default loop. The default	2217	event loop. If that is not possible, use the default loop. The default
2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2218	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2068	used).	2220	used).
2069		2221
2070	struct ev_loop *loop_hi = ev_default_init (0);	2222	struct ev_loop *loop_hi = ev_default_init (0);
2071	struct ev_loop *loop_lo = 0;	2223	struct ev_loop *loop_lo = 0;
2072	struct ev_embed embed;	2224	struct ev_embed embed;
2073		2225
2074	// see if there is a chance of getting one that works	2226	// see if there is a chance of getting one that works
2075	// (remember that a flags value of 0 means autodetection)	2227	// (remember that a flags value of 0 means autodetection)
2076	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2077	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2078	: 0;	2230	: 0;
2079		2231
2080	// if we got one, then embed it, otherwise default to loop_hi	2232	// if we got one, then embed it, otherwise default to loop_hi
2081	if (loop_lo)	2233	if (loop_lo)
2082	{	2234	{
2083	ev_embed_init (&embed, 0, loop_lo);	2235	ev_embed_init (&embed, 0, loop_lo);
2084	ev_embed_start (loop_hi, &embed);	2236	ev_embed_start (loop_hi, &embed);
2085	}	2237	}
2086	else	2238	else
2087	loop_lo = loop_hi;	2239	loop_lo = loop_hi;
2088		2240
2089	Example: Check if kqueue is available but not recommended and create	2241	Example: Check if kqueue is available but not recommended and create
2090	a kqueue backend for use with sockets (which usually work with any	2242	a kqueue backend for use with sockets (which usually work with any
2091	kqueue implementation). Store the kqueue/socket-only event loop in	2243	kqueue implementation). Store the kqueue/socket-only event loop in
2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2093		2245
2094	struct ev_loop *loop = ev_default_init (0);	2246	struct ev_loop *loop = ev_default_init (0);
2095	struct ev_loop *loop_socket = 0;	2247	struct ev_loop *loop_socket = 0;
2096	struct ev_embed embed;	2248	struct ev_embed embed;
2097		2249
2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2100	{	2252	{
2101	ev_embed_init (&embed, 0, loop_socket);	2253	ev_embed_init (&embed, 0, loop_socket);
2102	ev_embed_start (loop, &embed);	2254	ev_embed_start (loop, &embed);
2103	}	2255	}
2104		2256
2105	if (!loop_socket)	2257	if (!loop_socket)
2106	loop_socket = loop;	2258	loop_socket = loop;
2107		2259
2108	// now use loop_socket for all sockets, and loop for everything else	2260	// now use loop_socket for all sockets, and loop for everything else
2109		2261
2110		2262
2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2112		2264
2113	Fork watchers are called when a C<fork ()> was detected (usually because	2265	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2166		2318
2167	=item queueing from a signal handler context	2319	=item queueing from a signal handler context
2168		2320
2169	To implement race-free queueing, you simply add to the queue in the signal	2321	To implement race-free queueing, you simply add to the queue in the signal
2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for
2171	some fictitiuous SIGUSR1 handler:	2323	some fictitious SIGUSR1 handler:
2172		2324
2173	static ev_async mysig;	2325	static ev_async mysig;
2174		2326
2175	static void	2327	static void
2176	sigusr1_handler (void)	2328	sigusr1_handler (void)
…		…
2250	=item ev_async_send (loop, ev_async *)	2402	=item ev_async_send (loop, ev_async *)
2251		2403
2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2254	C<ev_feed_event>, this call is safe to do in other threads, signal or	2406	C<ev_feed_event>, this call is safe to do in other threads, signal or
2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2256	section below on what exactly this means).	2408	section below on what exactly this means).
2257		2409
2258	This call incurs the overhead of a syscall only once per loop iteration,	2410	This call incurs the overhead of a system call only once per loop iteration,
2259	so while the overhead might be noticable, it doesn't apply to repeated	2411	so while the overhead might be noticeable, it doesn't apply to repeated
2260	calls to C<ev_async_send>.	2412	calls to C<ev_async_send>.
		2413
		2414	=item bool = ev_async_pending (ev_async *)
		2415
		2416	Returns a non-zero value when C<ev_async_send> has been called on the
		2417	watcher but the event has not yet been processed (or even noted) by the
		2418	event loop.
		2419
		2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2421	the loop iterates next and checks for the watcher to have become active,
		2422	it will reset the flag again. C<ev_async_pending> can be used to very
		2423	quickly check whether invoking the loop might be a good idea.
		2424
		2425	Not that this does I<not> check whether the watcher itself is pending, only
		2426	whether it has been requested to make this watcher pending.
2261		2427
2262	=back	2428	=back
2263		2429
2264		2430
2265	=head1 OTHER FUNCTIONS	2431	=head1 OTHER FUNCTIONS
…		…
2276	or timeout without having to allocate/configure/start/stop/free one or	2442	or timeout without having to allocate/configure/start/stop/free one or
2277	more watchers yourself.	2443	more watchers yourself.
2278		2444
2279	If C<fd> is less than 0, then no I/O watcher will be started and events	2445	If C<fd> is less than 0, then no I/O watcher will be started and events
2280	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2281	C<events> set will be craeted and started.	2447	C<events> set will be created and started.
2282		2448
2283	If C<timeout> is less than 0, then no timeout watcher will be	2449	If C<timeout> is less than 0, then no timeout watcher will be
2284	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2285	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2286	dubious value.	2452	dubious value.
…		…
2288	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2289	passed an C<revents> set like normal event callbacks (a combination of	2455	passed an C<revents> set like normal event callbacks (a combination of
2290	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2291	value passed to C<ev_once>:	2457	value passed to C<ev_once>:
2292		2458
2293	static void stdin_ready (int revents, void *arg)	2459	static void stdin_ready (int revents, void *arg)
2294	{	2460	{
2295	if (revents & EV_TIMEOUT)	2461	if (revents & EV_TIMEOUT)
2296	/* doh, nothing entered */;	2462	/* doh, nothing entered */;
2297	else if (revents & EV_READ)	2463	else if (revents & EV_READ)
2298	/* stdin might have data for us, joy! */;	2464	/* stdin might have data for us, joy! */;
2299	}	2465	}
2300		2466
2301	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2302		2468
2303	=item ev_feed_event (ev_loop *, watcher *, int revents)	2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2304		2470
2305	Feeds the given event set into the event loop, as if the specified event	2471	Feeds the given event set into the event loop, as if the specified event
2306	had happened for the specified watcher (which must be a pointer to an	2472	had happened for the specified watcher (which must be a pointer to an
…		…
2311	Feed an event on the given fd, as if a file descriptor backend detected	2477	Feed an event on the given fd, as if a file descriptor backend detected
2312	the given events it.	2478	the given events it.
2313		2479
2314	=item ev_feed_signal_event (ev_loop *loop, int signum)	2480	=item ev_feed_signal_event (ev_loop *loop, int signum)
2315		2481
2316	Feed an event as if the given signal occured (C<loop> must be the default	2482	Feed an event as if the given signal occurred (C<loop> must be the default
2317	loop!).	2483	loop!).
2318		2484
2319	=back	2485	=back
2320		2486
2321		2487
…		…
2337		2503
2338	=item * Priorities are not currently supported. Initialising priorities	2504	=item * Priorities are not currently supported. Initialising priorities
2339	will fail and all watchers will have the same priority, even though there	2505	will fail and all watchers will have the same priority, even though there
2340	is an ev_pri field.	2506	is an ev_pri field.
2341		2507
		2508	=item * In libevent, the last base created gets the signals, in libev, the
		2509	first base created (== the default loop) gets the signals.
		2510
2342	=item * Other members are not supported.	2511	=item * Other members are not supported.
2343		2512
2344	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2513	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2345	to use the libev header file and library.	2514	to use the libev header file and library.
2346		2515
2347	=back	2516	=back
2348		2517
2349	=head1 C++ SUPPORT	2518	=head1 C++ SUPPORT
2350		2519
2351	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2520	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2352	you to use some convinience methods to start/stop watchers and also change	2521	you to use some convenience methods to start/stop watchers and also change
2353	the callback model to a model using method callbacks on objects.	2522	the callback model to a model using method callbacks on objects.
2354		2523
2355	To use it,	2524	To use it,
2356		2525
2357	#include <ev++.h>	2526	#include <ev++.h>
2358		2527
2359	This automatically includes F<ev.h> and puts all of its definitions (many	2528	This automatically includes F<ev.h> and puts all of its definitions (many
2360	of them macros) into the global namespace. All C++ specific things are	2529	of them macros) into the global namespace. All C++ specific things are
2361	put into the C<ev> namespace. It should support all the same embedding	2530	put into the C<ev> namespace. It should support all the same embedding
2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2531	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2429	your compiler is good :), then the method will be fully inlined into the	2598	your compiler is good :), then the method will be fully inlined into the
2430	thunking function, making it as fast as a direct C callback.	2599	thunking function, making it as fast as a direct C callback.
2431		2600
2432	Example: simple class declaration and watcher initialisation	2601	Example: simple class declaration and watcher initialisation
2433		2602
2434	struct myclass	2603	struct myclass
2435	{	2604	{
2436	void io_cb (ev::io &w, int revents) { }	2605	void io_cb (ev::io &w, int revents) { }
2437	}	2606	}
2438		2607
2439	myclass obj;	2608	myclass obj;
2440	ev::io iow;	2609	ev::io iow;
2441	iow.set <myclass, &myclass::io_cb> (&obj);	2610	iow.set <myclass, &myclass::io_cb> (&obj);
2442		2611
2443	=item w->set<function> (void *data = 0)	2612	=item w->set<function> (void *data = 0)
2444		2613
2445	Also sets a callback, but uses a static method or plain function as	2614	Also sets a callback, but uses a static method or plain function as
2446	callback. The optional C<data> argument will be stored in the watcher's	2615	callback. The optional C<data> argument will be stored in the watcher's
…		…
2450		2619
2451	See the method-C<set> above for more details.	2620	See the method-C<set> above for more details.
2452		2621
2453	Example:	2622	Example:
2454		2623
2455	static void io_cb (ev::io &w, int revents) { }	2624	static void io_cb (ev::io &w, int revents) { }
2456	iow.set <io_cb> ();	2625	iow.set <io_cb> ();
2457		2626
2458	=item w->set (struct ev_loop *)	2627	=item w->set (struct ev_loop *)
2459		2628
2460	Associates a different C<struct ev_loop> with this watcher. You can only	2629	Associates a different C<struct ev_loop> with this watcher. You can only
2461	do this when the watcher is inactive (and not pending either).	2630	do this when the watcher is inactive (and not pending either).
2462		2631
2463	=item w->set ([args])	2632	=item w->set ([arguments])
2464		2633
2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2466	called at least once. Unlike the C counterpart, an active watcher gets	2635	called at least once. Unlike the C counterpart, an active watcher gets
2467	automatically stopped and restarted when reconfiguring it with this	2636	automatically stopped and restarted when reconfiguring it with this
2468	method.	2637	method.
2469		2638
2470	=item w->start ()	2639	=item w->start ()
…		…
2494	=back	2663	=back
2495		2664
2496	Example: Define a class with an IO and idle watcher, start one of them in	2665	Example: Define a class with an IO and idle watcher, start one of them in
2497	the constructor.	2666	the constructor.
2498		2667
2499	class myclass	2668	class myclass
2500	{	2669	{
2501	ev::io io; void io_cb (ev::io &w, int revents);	2670	ev::io io; void io_cb (ev::io &w, int revents);
2502	ev:idle idle void idle_cb (ev::idle &w, int revents);	2671	ev:idle idle void idle_cb (ev::idle &w, int revents);
2503		2672
2504	myclass (int fd)	2673	myclass (int fd)
2505	{	2674	{
2506	io .set <myclass, &myclass::io_cb > (this);	2675	io .set <myclass, &myclass::io_cb > (this);
2507	idle.set <myclass, &myclass::idle_cb> (this);	2676	idle.set <myclass, &myclass::idle_cb> (this);
2508		2677
2509	io.start (fd, ev::READ);	2678	io.start (fd, ev::READ);
2510	}	2679	}
2511	};	2680	};
2512		2681
2513		2682
2514	=head1 OTHER LANGUAGE BINDINGS	2683	=head1 OTHER LANGUAGE BINDINGS
2515		2684
2516	Libev does not offer other language bindings itself, but bindings for a	2685	Libev does not offer other language bindings itself, but bindings for a
2517	numbe rof languages exist in the form of third-party packages. If you know	2686	number of languages exist in the form of third-party packages. If you know
2518	any interesting language binding in addition to the ones listed here, drop	2687	any interesting language binding in addition to the ones listed here, drop
2519	me a note.	2688	me a note.
2520		2689
2521	=over 4	2690	=over 4
2522		2691
…		…
2526	libev. EV is developed together with libev. Apart from the EV core module,	2695	libev. EV is developed together with libev. Apart from the EV core module,
2527	there are additional modules that implement libev-compatible interfaces	2696	there are additional modules that implement libev-compatible interfaces
2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2530		2699
2531	It can be found and installed via CPAN, its homepage is found at	2700	It can be found and installed via CPAN, its homepage is at
2532	L<http://software.schmorp.de/pkg/EV>.	2701	L<http://software.schmorp.de/pkg/EV>.
2533		2702
		2703	=item Python
		2704
		2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2706	seems to be quite complete and well-documented. Note, however, that the
		2707	patch they require for libev is outright dangerous as it breaks the ABI
		2708	for everybody else, and therefore, should never be applied in an installed
		2709	libev (if python requires an incompatible ABI then it needs to embed
		2710	libev).
		2711
2534	=item Ruby	2712	=item Ruby
2535		2713
2536	Tony Arcieri has written a ruby extension that offers access to a subset	2714	Tony Arcieri has written a ruby extension that offers access to a subset
2537	of the libev API and adds filehandle abstractions, asynchronous DNS and	2715	of the libev API and adds file handle abstractions, asynchronous DNS and
2538	more on top of it. It can be found via gem servers. Its homepage is at	2716	more on top of it. It can be found via gem servers. Its homepage is at
2539	L<http://rev.rubyforge.org/>.	2717	L<http://rev.rubyforge.org/>.
2540		2718
2541	=item D	2719	=item D
2542		2720
2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2545		2723
2546	=back	2724	=back
2547		2725
2548		2726
2549	=head1 MACRO MAGIC	2727	=head1 MACRO MAGIC
2550		2728
2551	Libev can be compiled with a variety of options, the most fundamantal	2729	Libev can be compiled with a variety of options, the most fundamental
2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2730	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2553	functions and callbacks have an initial C<struct ev_loop *> argument.	2731	functions and callbacks have an initial C<struct ev_loop *> argument.
2554		2732
2555	To make it easier to write programs that cope with either variant, the	2733	To make it easier to write programs that cope with either variant, the
2556	following macros are defined:	2734	following macros are defined:
…		…
2561		2739
2562	This provides the loop I<argument> for functions, if one is required ("ev	2740	This provides the loop I<argument> for functions, if one is required ("ev
2563	loop argument"). The C<EV_A> form is used when this is the sole argument,	2741	loop argument"). The C<EV_A> form is used when this is the sole argument,
2564	C<EV_A_> is used when other arguments are following. Example:	2742	C<EV_A_> is used when other arguments are following. Example:
2565		2743
2566	ev_unref (EV_A);	2744	ev_unref (EV_A);
2567	ev_timer_add (EV_A_ watcher);	2745	ev_timer_add (EV_A_ watcher);
2568	ev_loop (EV_A_ 0);	2746	ev_loop (EV_A_ 0);
2569		2747
2570	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2571	which is often provided by the following macro.	2749	which is often provided by the following macro.
2572		2750
2573	=item C<EV_P>, C<EV_P_>	2751	=item C<EV_P>, C<EV_P_>
2574		2752
2575	This provides the loop I<parameter> for functions, if one is required ("ev	2753	This provides the loop I<parameter> for functions, if one is required ("ev
2576	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2754	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2577	C<EV_P_> is used when other parameters are following. Example:	2755	C<EV_P_> is used when other parameters are following. Example:
2578		2756
2579	// this is how ev_unref is being declared	2757	// this is how ev_unref is being declared
2580	static void ev_unref (EV_P);	2758	static void ev_unref (EV_P);
2581		2759
2582	// this is how you can declare your typical callback	2760	// this is how you can declare your typical callback
2583	static void cb (EV_P_ ev_timer *w, int revents)	2761	static void cb (EV_P_ ev_timer *w, int revents)
2584		2762
2585	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2763	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2586	suitable for use with C<EV_A>.	2764	suitable for use with C<EV_A>.
2587		2765
2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2766	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2589		2767
2590	Similar to the other two macros, this gives you the value of the default	2768	Similar to the other two macros, this gives you the value of the default
2591	loop, if multiple loops are supported ("ev loop default").	2769	loop, if multiple loops are supported ("ev loop default").
		2770
		2771	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2772
		2773	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2774	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2775	is undefined when the default loop has not been initialised by a previous
		2776	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2777
		2778	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2779	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2592		2780
2593	=back	2781	=back
2594		2782
2595	Example: Declare and initialise a check watcher, utilising the above	2783	Example: Declare and initialise a check watcher, utilising the above
2596	macros so it will work regardless of whether multiple loops are supported	2784	macros so it will work regardless of whether multiple loops are supported
2597	or not.	2785	or not.
2598		2786
2599	static void	2787	static void
2600	check_cb (EV_P_ ev_timer *w, int revents)	2788	check_cb (EV_P_ ev_timer *w, int revents)
2601	{	2789	{
2602	ev_check_stop (EV_A_ w);	2790	ev_check_stop (EV_A_ w);
2603	}	2791	}
2604		2792
2605	ev_check check;	2793	ev_check check;
2606	ev_check_init (&check, check_cb);	2794	ev_check_init (&check, check_cb);
2607	ev_check_start (EV_DEFAULT_ &check);	2795	ev_check_start (EV_DEFAULT_ &check);
2608	ev_loop (EV_DEFAULT_ 0);	2796	ev_loop (EV_DEFAULT_ 0);
2609		2797
2610	=head1 EMBEDDING	2798	=head1 EMBEDDING
2611		2799
2612	Libev can (and often is) directly embedded into host	2800	Libev can (and often is) directly embedded into host
2613	applications. Examples of applications that embed it include the Deliantra	2801	applications. Examples of applications that embed it include the Deliantra
…		…
2620	libev somewhere in your source tree).	2808	libev somewhere in your source tree).
2621		2809
2622	=head2 FILESETS	2810	=head2 FILESETS
2623		2811
2624	Depending on what features you need you need to include one or more sets of files	2812	Depending on what features you need you need to include one or more sets of files
2625	in your app.	2813	in your application.
2626		2814
2627	=head3 CORE EVENT LOOP	2815	=head3 CORE EVENT LOOP
2628		2816
2629	To include only the libev core (all the C<ev_*> functions), with manual	2817	To include only the libev core (all the C<ev_*> functions), with manual
2630	configuration (no autoconf):	2818	configuration (no autoconf):
2631		2819
2632	#define EV_STANDALONE 1	2820	#define EV_STANDALONE 1
2633	#include "ev.c"	2821	#include "ev.c"
2634		2822
2635	This will automatically include F<ev.h>, too, and should be done in a	2823	This will automatically include F<ev.h>, too, and should be done in a
2636	single C source file only to provide the function implementations. To use	2824	single C source file only to provide the function implementations. To use
2637	it, do the same for F<ev.h> in all files wishing to use this API (best	2825	it, do the same for F<ev.h> in all files wishing to use this API (best
2638	done by writing a wrapper around F<ev.h> that you can include instead and	2826	done by writing a wrapper around F<ev.h> that you can include instead and
2639	where you can put other configuration options):	2827	where you can put other configuration options):
2640		2828
2641	#define EV_STANDALONE 1	2829	#define EV_STANDALONE 1
2642	#include "ev.h"	2830	#include "ev.h"
2643		2831
2644	Both header files and implementation files can be compiled with a C++	2832	Both header files and implementation files can be compiled with a C++
2645	compiler (at least, thats a stated goal, and breakage will be treated	2833	compiler (at least, thats a stated goal, and breakage will be treated
2646	as a bug).	2834	as a bug).
2647		2835
2648	You need the following files in your source tree, or in a directory	2836	You need the following files in your source tree, or in a directory
2649	in your include path (e.g. in libev/ when using -Ilibev):	2837	in your include path (e.g. in libev/ when using -Ilibev):
2650		2838
2651	ev.h	2839	ev.h
2652	ev.c	2840	ev.c
2653	ev_vars.h	2841	ev_vars.h
2654	ev_wrap.h	2842	ev_wrap.h
2655		2843
2656	ev_win32.c required on win32 platforms only	2844	ev_win32.c required on win32 platforms only
2657		2845
2658	ev_select.c only when select backend is enabled (which is enabled by default)	2846	ev_select.c only when select backend is enabled (which is enabled by default)
2659	ev_poll.c only when poll backend is enabled (disabled by default)	2847	ev_poll.c only when poll backend is enabled (disabled by default)
2660	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2848	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2661	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2849	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2662	ev_port.c only when the solaris port backend is enabled (disabled by default)	2850	ev_port.c only when the solaris port backend is enabled (disabled by default)
2663		2851
2664	F<ev.c> includes the backend files directly when enabled, so you only need	2852	F<ev.c> includes the backend files directly when enabled, so you only need
2665	to compile this single file.	2853	to compile this single file.
2666		2854
2667	=head3 LIBEVENT COMPATIBILITY API	2855	=head3 LIBEVENT COMPATIBILITY API
2668		2856
2669	To include the libevent compatibility API, also include:	2857	To include the libevent compatibility API, also include:
2670		2858
2671	#include "event.c"	2859	#include "event.c"
2672		2860
2673	in the file including F<ev.c>, and:	2861	in the file including F<ev.c>, and:
2674		2862
2675	#include "event.h"	2863	#include "event.h"
2676		2864
2677	in the files that want to use the libevent API. This also includes F<ev.h>.	2865	in the files that want to use the libevent API. This also includes F<ev.h>.
2678		2866
2679	You need the following additional files for this:	2867	You need the following additional files for this:
2680		2868
2681	event.h	2869	event.h
2682	event.c	2870	event.c
2683		2871
2684	=head3 AUTOCONF SUPPORT	2872	=head3 AUTOCONF SUPPORT
2685		2873
2686	Instead of using C<EV_STANDALONE=1> and providing your config in	2874	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2687	whatever way you want, you can also C<m4_include([libev.m4])> in your	2875	whatever way you want, you can also C<m4_include([libev.m4])> in your
2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2876	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2689	include F<config.h> and configure itself accordingly.	2877	include F<config.h> and configure itself accordingly.
2690		2878
2691	For this of course you need the m4 file:	2879	For this of course you need the m4 file:
2692		2880
2693	libev.m4	2881	libev.m4
2694		2882
2695	=head2 PREPROCESSOR SYMBOLS/MACROS	2883	=head2 PREPROCESSOR SYMBOLS/MACROS
2696		2884
2697	Libev can be configured via a variety of preprocessor symbols you have to define	2885	Libev can be configured via a variety of preprocessor symbols you have to
2698	before including any of its files. The default is not to build for multiplicity	2886	define before including any of its files. The default in the absence of
2699	and only include the select backend.	2887	autoconf is noted for every option.
2700		2888
2701	=over 4	2889	=over 4
2702		2890
2703	=item EV_STANDALONE	2891	=item EV_STANDALONE
2704		2892
…		…
2709	F<event.h> that are not directly supported by the libev core alone.	2897	F<event.h> that are not directly supported by the libev core alone.
2710		2898
2711	=item EV_USE_MONOTONIC	2899	=item EV_USE_MONOTONIC
2712		2900
2713	If defined to be C<1>, libev will try to detect the availability of the	2901	If defined to be C<1>, libev will try to detect the availability of the
2714	monotonic clock option at both compiletime and runtime. Otherwise no use	2902	monotonic clock option at both compile time and runtime. Otherwise no use
2715	of the monotonic clock option will be attempted. If you enable this, you	2903	of the monotonic clock option will be attempted. If you enable this, you
2716	usually have to link against librt or something similar. Enabling it when	2904	usually have to link against librt or something similar. Enabling it when
2717	the functionality isn't available is safe, though, although you have	2905	the functionality isn't available is safe, though, although you have
2718	to make sure you link against any libraries where the C<clock_gettime>	2906	to make sure you link against any libraries where the C<clock_gettime>
2719	function is hiding in (often F<-lrt>).	2907	function is hiding in (often F<-lrt>).
2720		2908
2721	=item EV_USE_REALTIME	2909	=item EV_USE_REALTIME
2722		2910
2723	If defined to be C<1>, libev will try to detect the availability of the	2911	If defined to be C<1>, libev will try to detect the availability of the
2724	realtime clock option at compiletime (and assume its availability at	2912	real-time clock option at compile time (and assume its availability at
2725	runtime if successful). Otherwise no use of the realtime clock option will	2913	runtime if successful). Otherwise no use of the real-time clock option will
2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2729		2917
2730	=item EV_USE_NANOSLEEP	2918	=item EV_USE_NANOSLEEP
2731		2919
2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2733	and will use it for delays. Otherwise it will use C<select ()>.	2921	and will use it for delays. Otherwise it will use C<select ()>.
2734		2922
		2923	=item EV_USE_EVENTFD
		2924
		2925	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2926	available and will probe for kernel support at runtime. This will improve
		2927	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2928	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2929	2.7 or newer, otherwise disabled.
		2930
2735	=item EV_USE_SELECT	2931	=item EV_USE_SELECT
2736		2932
2737	If undefined or defined to be C<1>, libev will compile in support for the	2933	If undefined or defined to be C<1>, libev will compile in support for the
2738	C<select>(2) backend. No attempt at autodetection will be done: if no	2934	C<select>(2) backend. No attempt at auto-detection will be done: if no
2739	other method takes over, select will be it. Otherwise the select backend	2935	other method takes over, select will be it. Otherwise the select backend
2740	will not be compiled in.	2936	will not be compiled in.
2741		2937
2742	=item EV_SELECT_USE_FD_SET	2938	=item EV_SELECT_USE_FD_SET
2743		2939
2744	If defined to C<1>, then the select backend will use the system C<fd_set>	2940	If defined to C<1>, then the select backend will use the system C<fd_set>
2745	structure. This is useful if libev doesn't compile due to a missing	2941	structure. This is useful if libev doesn't compile due to a missing
2746	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2747	exotic systems. This usually limits the range of file descriptors to some	2943	exotic systems. This usually limits the range of file descriptors to some
2748	low limit such as 1024 or might have other limitations (winsocket only	2944	low limit such as 1024 or might have other limitations (winsocket only
2749	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2750	influence the size of the C<fd_set> used.	2946	influence the size of the C<fd_set> used.
2751		2947
…		…
2775		2971
2776	=item EV_USE_EPOLL	2972	=item EV_USE_EPOLL
2777		2973
2778	If defined to be C<1>, libev will compile in support for the Linux	2974	If defined to be C<1>, libev will compile in support for the Linux
2779	C<epoll>(7) backend. Its availability will be detected at runtime,	2975	C<epoll>(7) backend. Its availability will be detected at runtime,
2780	otherwise another method will be used as fallback. This is the	2976	otherwise another method will be used as fallback. This is the preferred
2781	preferred backend for GNU/Linux systems.	2977	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2978	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2782		2979
2783	=item EV_USE_KQUEUE	2980	=item EV_USE_KQUEUE
2784		2981
2785	If defined to be C<1>, libev will compile in support for the BSD style	2982	If defined to be C<1>, libev will compile in support for the BSD style
2786	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2983	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2799	otherwise another method will be used as fallback. This is the preferred	2996	otherwise another method will be used as fallback. This is the preferred
2800	backend for Solaris 10 systems.	2997	backend for Solaris 10 systems.
2801		2998
2802	=item EV_USE_DEVPOLL	2999	=item EV_USE_DEVPOLL
2803		3000
2804	reserved for future expansion, works like the USE symbols above.	3001	Reserved for future expansion, works like the USE symbols above.
2805		3002
2806	=item EV_USE_INOTIFY	3003	=item EV_USE_INOTIFY
2807		3004
2808	If defined to be C<1>, libev will compile in support for the Linux inotify	3005	If defined to be C<1>, libev will compile in support for the Linux inotify
2809	interface to speed up C<ev_stat> watchers. Its actual availability will	3006	interface to speed up C<ev_stat> watchers. Its actual availability will
2810	be detected at runtime.	3007	be detected at runtime. If undefined, it will be enabled if the headers
		3008	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2811		3009
2812	=item EV_ATOMIC_T	3010	=item EV_ATOMIC_T
2813		3011
2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3012	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815	access is atomic with respect to other threads or signal contexts. No such	3013	access is atomic with respect to other threads or signal contexts. No such
2816	type is easily found in the C language, so you can provide your own type	3014	type is easily found in the C language, so you can provide your own type
2817	that you know is safe for your purposes. It is used both for signal handler "locking"	3015	that you know is safe for your purposes. It is used both for signal handler "locking"
2818	as well as for signal and thread safety in C<ev_async> watchers.	3016	as well as for signal and thread safety in C<ev_async> watchers.
2819		3017
2820	In the absense of this define, libev will use C<sig_atomic_t volatile>	3018	In the absence of this define, libev will use C<sig_atomic_t volatile>
2821	(from F<signal.h>), which is usually good enough on most platforms.	3019	(from F<signal.h>), which is usually good enough on most platforms.
2822		3020
2823	=item EV_H	3021	=item EV_H
2824		3022
2825	The name of the F<ev.h> header file used to include it. The default if	3023	The name of the F<ev.h> header file used to include it. The default if
…		…
2864	When doing priority-based operations, libev usually has to linearly search	3062	When doing priority-based operations, libev usually has to linearly search
2865	all the priorities, so having many of them (hundreds) uses a lot of space	3063	all the priorities, so having many of them (hundreds) uses a lot of space
2866	and time, so using the defaults of five priorities (-2 .. +2) is usually	3064	and time, so using the defaults of five priorities (-2 .. +2) is usually
2867	fine.	3065	fine.
2868		3066
2869	If your embedding app does not need any priorities, defining these both to	3067	If your embedding application does not need any priorities, defining these both to
2870	C<0> will save some memory and cpu.	3068	C<0> will save some memory and CPU.
2871		3069
2872	=item EV_PERIODIC_ENABLE	3070	=item EV_PERIODIC_ENABLE
2873		3071
2874	If undefined or defined to be C<1>, then periodic timers are supported. If	3072	If undefined or defined to be C<1>, then periodic timers are supported. If
2875	defined to be C<0>, then they are not. Disabling them saves a few kB of	3073	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2902	defined to be C<0>, then they are not.	3100	defined to be C<0>, then they are not.
2903		3101
2904	=item EV_MINIMAL	3102	=item EV_MINIMAL
2905		3103
2906	If you need to shave off some kilobytes of code at the expense of some	3104	If you need to shave off some kilobytes of code at the expense of some
2907	speed, define this symbol to C<1>. Currently only used for gcc to override	3105	speed, define this symbol to C<1>. Currently this is used to override some
2908	some inlining decisions, saves roughly 30% codesize of amd64.	3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3107	much smaller 2-heap for timer management over the default 4-heap.
2909		3108
2910	=item EV_PID_HASHSIZE	3109	=item EV_PID_HASHSIZE
2911		3110
2912	C<ev_child> watchers use a small hash table to distribute workload by	3111	C<ev_child> watchers use a small hash table to distribute workload by
2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2921	usually more than enough. If you need to manage thousands of C<ev_stat>	3120	usually more than enough. If you need to manage thousands of C<ev_stat>
2922	watchers you might want to increase this value (I<must> be a power of	3121	watchers you might want to increase this value (I<must> be a power of
2923	two).	3122	two).
2924		3123
		3124	=item EV_USE_4HEAP
		3125
		3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3128	to C<1>. The 4-heap uses more complicated (longer) code but has
		3129	noticeably faster performance with many (thousands) of watchers.
		3130
		3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3132	(disabled).
		3133
		3134	=item EV_HEAP_CACHE_AT
		3135
		3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3137	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3140	but avoids random read accesses on heap changes. This improves performance
		3141	noticeably with with many (hundreds) of watchers.
		3142
		3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3144	(disabled).
		3145
		3146	=item EV_VERIFY
		3147
		3148	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3149	be done: If set to C<0>, no internal verification code will be compiled
		3150	in. If set to C<1>, then verification code will be compiled in, but not
		3151	called. If set to C<2>, then the internal verification code will be
		3152	called once per loop, which can slow down libev. If set to C<3>, then the
		3153	verification code will be called very frequently, which will slow down
		3154	libev considerably.
		3155
		3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3157	C<0.>
		3158
2925	=item EV_COMMON	3159	=item EV_COMMON
2926		3160
2927	By default, all watchers have a C<void *data> member. By redefining	3161	By default, all watchers have a C<void *data> member. By redefining
2928	this macro to a something else you can include more and other types of	3162	this macro to a something else you can include more and other types of
2929	members. You have to define it each time you include one of the files,	3163	members. You have to define it each time you include one of the files,
2930	though, and it must be identical each time.	3164	though, and it must be identical each time.
2931		3165
2932	For example, the perl EV module uses something like this:	3166	For example, the perl EV module uses something like this:
2933		3167
2934	#define EV_COMMON \	3168	#define EV_COMMON \
2935	SV *self; /* contains this struct */ \	3169	SV *self; /* contains this struct */ \
2936	SV *cb_sv, *fh /* note no trailing ";" */	3170	SV *cb_sv, *fh /* note no trailing ";" */
2937		3171
2938	=item EV_CB_DECLARE (type)	3172	=item EV_CB_DECLARE (type)
2939		3173
2940	=item EV_CB_INVOKE (watcher, revents)	3174	=item EV_CB_INVOKE (watcher, revents)
2941		3175
…		…
2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2949	method calls instead of plain function calls in C++.	3183	method calls instead of plain function calls in C++.
2950		3184
2951	=head2 EXPORTED API SYMBOLS	3185	=head2 EXPORTED API SYMBOLS
2952		3186
2953	If you need to re-export the API (e.g. via a dll) and you need a list of	3187	If you need to re-export the API (e.g. via a DLL) and you need a list of
2954	exported symbols, you can use the provided F<Symbol.*> files which list	3188	exported symbols, you can use the provided F<Symbol.*> files which list
2955	all public symbols, one per line:	3189	all public symbols, one per line:
2956		3190
2957	Symbols.ev for libev proper	3191	Symbols.ev for libev proper
2958	Symbols.event for the libevent emulation	3192	Symbols.event for the libevent emulation
2959		3193
2960	This can also be used to rename all public symbols to avoid clashes with	3194	This can also be used to rename all public symbols to avoid clashes with
2961	multiple versions of libev linked together (which is obviously bad in	3195	multiple versions of libev linked together (which is obviously bad in
2962	itself, but sometimes it is inconvinient to avoid this).	3196	itself, but sometimes it is inconvenient to avoid this).
2963		3197
2964	A sed command like this will create wrapper C<#define>'s that you need to	3198	A sed command like this will create wrapper C<#define>'s that you need to
2965	include before including F<ev.h>:	3199	include before including F<ev.h>:
2966		3200
2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3201	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2984	file.	3218	file.
2985		3219
2986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2987	that everybody includes and which overrides some configure choices:	3221	that everybody includes and which overrides some configure choices:
2988		3222
2989	#define EV_MINIMAL 1	3223	#define EV_MINIMAL 1
2990	#define EV_USE_POLL 0	3224	#define EV_USE_POLL 0
2991	#define EV_MULTIPLICITY 0	3225	#define EV_MULTIPLICITY 0
2992	#define EV_PERIODIC_ENABLE 0	3226	#define EV_PERIODIC_ENABLE 0
2993	#define EV_STAT_ENABLE 0	3227	#define EV_STAT_ENABLE 0
2994	#define EV_FORK_ENABLE 0	3228	#define EV_FORK_ENABLE 0
2995	#define EV_CONFIG_H <config.h>	3229	#define EV_CONFIG_H <config.h>
2996	#define EV_MINPRI 0	3230	#define EV_MINPRI 0
2997	#define EV_MAXPRI 0	3231	#define EV_MAXPRI 0
2998		3232
2999	#include "ev++.h"	3233	#include "ev++.h"
3000		3234
3001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3002		3236
3003	#include "ev_cpp.h"	3237	#include "ev_cpp.h"
3004	#include "ev.c"	3238	#include "ev.c"
		3239
		3240
		3241	=head1 THREADS AND COROUTINES
		3242
		3243	=head2 THREADS
		3244
		3245	Libev itself is completely thread-safe, but it uses no locking. This
		3246	means that you can use as many loops as you want in parallel, as long as
		3247	only one thread ever calls into one libev function with the same loop
		3248	parameter.
		3249
		3250	Or put differently: calls with different loop parameters can be done in
		3251	parallel from multiple threads, calls with the same loop parameter must be
		3252	done serially (but can be done from different threads, as long as only one
		3253	thread ever is inside a call at any point in time, e.g. by using a mutex
		3254	per loop).
		3255
		3256	If you want to know which design (one loop, locking, or multiple loops
		3257	without or something else still) is best for your problem, then I cannot
		3258	help you. I can give some generic advice however:
		3259
		3260	=over 4
		3261
		3262	=item * most applications have a main thread: use the default libev loop
		3263	in that thread, or create a separate thread running only the default loop.
		3264
		3265	This helps integrating other libraries or software modules that use libev
		3266	themselves and don't care/know about threading.
		3267
		3268	=item * one loop per thread is usually a good model.
		3269
		3270	Doing this is almost never wrong, sometimes a better-performance model
		3271	exists, but it is always a good start.
		3272
		3273	=item * other models exist, such as the leader/follower pattern, where one
		3274	loop is handed through multiple threads in a kind of round-robin fashion.
		3275
		3276	Choosing a model is hard - look around, learn, know that usually you can do
		3277	better than you currently do :-)
		3278
		3279	=item * often you need to talk to some other thread which blocks in the
		3280	event loop - C<ev_async> watchers can be used to wake them up from other
		3281	threads safely (or from signal contexts...).
		3282
		3283	=back
		3284
		3285	=head2 COROUTINES
		3286
		3287	Libev is much more accommodating to coroutines ("cooperative threads"):
		3288	libev fully supports nesting calls to it's functions from different
		3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3290	different coroutines and switch freely between both coroutines running the
		3291	loop, as long as you don't confuse yourself). The only exception is that
		3292	you must not do this from C<ev_periodic> reschedule callbacks.
		3293
		3294	Care has been invested into making sure that libev does not keep local
		3295	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3296	switches.
3005		3297
3006		3298
3007	=head1 COMPLEXITIES	3299	=head1 COMPLEXITIES
3008		3300
3009	In this section the complexities of (many of) the algorithms used inside	3301	In this section the complexities of (many of) the algorithms used inside
…		…
3041	correct watcher to remove. The lists are usually short (you don't usually	3333	correct watcher to remove. The lists are usually short (you don't usually
3042	have many watchers waiting for the same fd or signal).	3334	have many watchers waiting for the same fd or signal).
3043		3335
3044	=item Finding the next timer in each loop iteration: O(1)	3336	=item Finding the next timer in each loop iteration: O(1)
3045		3337
3046	By virtue of using a binary heap, the next timer is always found at the	3338	By virtue of using a binary or 4-heap, the next timer is always found at a
3047	beginning of the storage array.	3339	fixed position in the storage array.
3048		3340
3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3050		3342
3051	A change means an I/O watcher gets started or stopped, which requires	3343	A change means an I/O watcher gets started or stopped, which requires
3052	libev to recalculate its status (and possibly tell the kernel, depending	3344	libev to recalculate its status (and possibly tell the kernel, depending
3053	on backend and wether C<ev_io_set> was used).	3345	on backend and whether C<ev_io_set> was used).
3054		3346
3055	=item Activating one watcher (putting it into the pending state): O(1)	3347	=item Activating one watcher (putting it into the pending state): O(1)
3056		3348
3057	=item Priority handling: O(number_of_priorities)	3349	=item Priority handling: O(number_of_priorities)
3058		3350
…		…
3065		3357
3066	=item Processing ev_async_send: O(number_of_async_watchers)	3358	=item Processing ev_async_send: O(number_of_async_watchers)
3067		3359
3068	=item Processing signals: O(max_signal_number)	3360	=item Processing signals: O(max_signal_number)
3069		3361
3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>	3362	Sending involves a system call I<iff> there were no other C<ev_async_send>
3071	calls in the current loop iteration. Checking for async and signal events	3363	calls in the current loop iteration. Checking for async and signal events
3072	involves iterating over all running async watchers or all signal numbers.	3364	involves iterating over all running async watchers or all signal numbers.
3073		3365
3074	=back	3366	=back
3075		3367
3076		3368
3077	=head1 Win32 platform limitations and workarounds	3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3078		3370
3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3080	requires, and its I/O model is fundamentally incompatible with the POSIX	3372	requires, and its I/O model is fundamentally incompatible with the POSIX
3081	model. Libev still offers limited functionality on this platform in	3373	model. Libev still offers limited functionality on this platform in
3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3083	descriptors. This only applies when using Win32 natively, not when using	3375	descriptors. This only applies when using Win32 natively, not when using
3084	e.g. cygwin.	3376	e.g. cygwin.
3085		3377
		3378	Lifting these limitations would basically require the full
		3379	re-implementation of the I/O system. If you are into these kinds of
		3380	things, then note that glib does exactly that for you in a very portable
		3381	way (note also that glib is the slowest event library known to man).
		3382
3086	There is no supported compilation method available on windows except	3383	There is no supported compilation method available on windows except
3087	embedding it into other applications.	3384	embedding it into other applications.
3088		3385
		3386	Not a libev limitation but worth mentioning: windows apparently doesn't
		3387	accept large writes: instead of resulting in a partial write, windows will
		3388	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3389	so make sure you only write small amounts into your sockets (less than a
		3390	megabyte seems safe, but thsi apparently depends on the amount of memory
		3391	available).
		3392
3089	Due to the many, low, and arbitrary limits on the win32 platform and the	3393	Due to the many, low, and arbitrary limits on the win32 platform and
3090	abysmal performance of winsockets, using a large number of sockets is not	3394	the abysmal performance of winsockets, using a large number of sockets
3091	recommended (and not reasonable). If your program needs to use more than	3395	is not recommended (and not reasonable). If your program needs to use
3092	a hundred or so sockets, then likely it needs to use a totally different	3396	more than a hundred or so sockets, then likely it needs to use a totally
3093	implementation for windows, as libev offers the POSIX model, which cannot	3397	different implementation for windows, as libev offers the POSIX readiness
3094	be implemented efficiently on windows (microsoft monopoly games).	3398	notification model, which cannot be implemented efficiently on windows
		3399	(Microsoft monopoly games).
		3400
		3401	A typical way to use libev under windows is to embed it (see the embedding
		3402	section for details) and use the following F<evwrap.h> header file instead
		3403	of F<ev.h>:
		3404
		3405	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3407
		3408	#include "ev.h"
		3409
		3410	And compile the following F<evwrap.c> file into your project (make sure
		3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3412
		3413	#include "evwrap.h"
		3414	#include "ev.c"
3095		3415
3096	=over 4	3416	=over 4
3097		3417
3098	=item The winsocket select function	3418	=item The winsocket select function
3099		3419
3100	The winsocket C<select> function doesn't follow POSIX in that it requires	3420	The winsocket C<select> function doesn't follow POSIX in that it
3101	socket I<handles> and not socket I<file descriptors>. This makes select	3421	requires socket I<handles> and not socket I<file descriptors> (it is
3102	very inefficient, and also requires a mapping from file descriptors	3422	also extremely buggy). This makes select very inefficient, and also
3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3423	requires a mapping from file descriptors to socket handles (the Microsoft
3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3424	C runtime provides the function C<_open_osfhandle> for this). See the
3105	symbols for more info.	3425	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3426	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3106		3427
3107	The configuration for a "naked" win32 using the microsoft runtime	3428	The configuration for a "naked" win32 using the Microsoft runtime
3108	libraries and raw winsocket select is:	3429	libraries and raw winsocket select is:
3109		3430
3110	#define EV_USE_SELECT 1	3431	#define EV_USE_SELECT 1
3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3432	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3112		3433
3113	Note that winsockets handling of fd sets is O(n), so you can easily get a	3434	Note that winsockets handling of fd sets is O(n), so you can easily get a
3114	complexity in the O(n²) range when using win32.	3435	complexity in the O(n²) range when using win32.
3115		3436
3116	=item Limited number of file descriptors	3437	=item Limited number of file descriptors
3117		3438
3118	Windows has numerous arbitrary (and low) limits on things. Early versions	3439	Windows has numerous arbitrary (and low) limits on things.
3119	of winsocket's select only supported waiting for a max. of C<64> handles	3440
		3441	Early versions of winsocket's select only supported waiting for a maximum
3120	(probably owning to the fact that all windows kernels can only wait for	3442	of C<64> handles (probably owning to the fact that all windows kernels
3121	C<64> things at the same time internally; microsoft recommends spawning a	3443	can only wait for C<64> things at the same time internally; Microsoft
3122	chain of threads and wait for 63 handles and the previous thread in each).	3444	recommends spawning a chain of threads and wait for 63 handles and the
		3445	previous thread in each. Great).
3123		3446
3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3447	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3125	to some high number (e.g. C<2048>) before compiling the winsocket select	3448	to some high number (e.g. C<2048>) before compiling the winsocket select
3126	call (which might be in libev or elsewhere, for example, perl does its own	3449	call (which might be in libev or elsewhere, for example, perl does its own
3127	select emulation on windows).	3450	select emulation on windows).
3128		3451
3129	Another limit is the number of file descriptors in the microsoft runtime	3452	Another limit is the number of file descriptors in the Microsoft runtime
3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3453	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3131	or something like this inside microsoft). You can increase this by calling	3454	or something like this inside Microsoft). You can increase this by calling
3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3455	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3133	arbitrary limit), but is broken in many versions of the microsoft runtime	3456	arbitrary limit), but is broken in many versions of the Microsoft runtime
3134	libraries.	3457	libraries.
3135		3458
3136	This might get you to about C<512> or C<2048> sockets (depending on	3459	This might get you to about C<512> or C<2048> sockets (depending on
3137	windows version and/or the phase of the moon). To get more, you need to	3460	windows version and/or the phase of the moon). To get more, you need to
3138	wrap all I/O functions and provide your own fd management, but the cost of	3461	wrap all I/O functions and provide your own fd management, but the cost of
3139	calling select (O(n²)) will likely make this unworkable.	3462	calling select (O(n²)) will likely make this unworkable.
3140		3463
3141	=back	3464	=back
3142		3465
3143		3466
		3467	=head1 PORTABILITY REQUIREMENTS
		3468
		3469	In addition to a working ISO-C implementation, libev relies on a few
		3470	additional extensions:
		3471
		3472	=over 4
		3473
		3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3475	calling conventions regardless of C<ev_watcher_type *>.
		3476
		3477	Libev assumes not only that all watcher pointers have the same internal
		3478	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3479	assumes that the same (machine) code can be used to call any watcher
		3480	callback: The watcher callbacks have different type signatures, but libev
		3481	calls them using an C<ev_watcher *> internally.
		3482
		3483	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3484
		3485	The type C<sig_atomic_t volatile> (or whatever is defined as
		3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3487	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3488	believed to be sufficiently portable.
		3489
		3490	=item C<sigprocmask> must work in a threaded environment
		3491
		3492	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3493	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3494	pthread implementations will either allow C<sigprocmask> in the "main
		3495	thread" or will block signals process-wide, both behaviours would
		3496	be compatible with libev. Interaction between C<sigprocmask> and
		3497	C<pthread_sigmask> could complicate things, however.
		3498
		3499	The most portable way to handle signals is to block signals in all threads
		3500	except the initial one, and run the default loop in the initial thread as
		3501	well.
		3502
		3503	=item C<long> must be large enough for common memory allocation sizes
		3504
		3505	To improve portability and simplify using libev, libev uses C<long>
		3506	internally instead of C<size_t> when allocating its data structures. On
		3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3508	is still at least 31 bits everywhere, which is enough for hundreds of
		3509	millions of watchers.
		3510
		3511	=item C<double> must hold a time value in seconds with enough accuracy
		3512
		3513	The type C<double> is used to represent timestamps. It is required to
		3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3515	enough for at least into the year 4000. This requirement is fulfilled by
		3516	implementations implementing IEEE 754 (basically all existing ones).
		3517
		3518	=back
		3519
		3520	If you know of other additional requirements drop me a note.
		3521
		3522
		3523	=head1 COMPILER WARNINGS
		3524
		3525	Depending on your compiler and compiler settings, you might get no or a
		3526	lot of warnings when compiling libev code. Some people are apparently
		3527	scared by this.
		3528
		3529	However, these are unavoidable for many reasons. For one, each compiler
		3530	has different warnings, and each user has different tastes regarding
		3531	warning options. "Warn-free" code therefore cannot be a goal except when
		3532	targeting a specific compiler and compiler-version.
		3533
		3534	Another reason is that some compiler warnings require elaborate
		3535	workarounds, or other changes to the code that make it less clear and less
		3536	maintainable.
		3537
		3538	And of course, some compiler warnings are just plain stupid, or simply
		3539	wrong (because they don't actually warn about the condition their message
		3540	seems to warn about).
		3541
		3542	While libev is written to generate as few warnings as possible,
		3543	"warn-free" code is not a goal, and it is recommended not to build libev
		3544	with any compiler warnings enabled unless you are prepared to cope with
		3545	them (e.g. by ignoring them). Remember that warnings are just that:
		3546	warnings, not errors, or proof of bugs.
		3547
		3548
		3549	=head1 VALGRIND
		3550
		3551	Valgrind has a special section here because it is a popular tool that is
		3552	highly useful, but valgrind reports are very hard to interpret.
		3553
		3554	If you think you found a bug (memory leak, uninitialised data access etc.)
		3555	in libev, then check twice: If valgrind reports something like:
		3556
		3557	==2274== definitely lost: 0 bytes in 0 blocks.
		3558	==2274== possibly lost: 0 bytes in 0 blocks.
		3559	==2274== still reachable: 256 bytes in 1 blocks.
		3560
		3561	Then there is no memory leak. Similarly, under some circumstances,
		3562	valgrind might report kernel bugs as if it were a bug in libev, or it
		3563	might be confused (it is a very good tool, but only a tool).
		3564
		3565	If you are unsure about something, feel free to contact the mailing list
		3566	with the full valgrind report and an explanation on why you think this is
		3567	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3568	no bug" answer and take the chance of learning how to interpret valgrind
		3569	properly.
		3570
		3571	If you need, for some reason, empty reports from valgrind for your project
		3572	I suggest using suppression lists.
		3573
		3574
3144	=head1 AUTHOR	3575	=head1 AUTHOR
3145		3576
3146	Marc Lehmann <libev@schmorp.de>.	3577	Marc Lehmann <libev@schmorp.de>.
3147		3578

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