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Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC vs.
Revision 1.171 by root, Tue Jul 8 09:49:15 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
217		256
218	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		284
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
263	function.	295	function.
264		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
265	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
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		310
268	The following flags are supported:	311	The following flags are supported:
269		312
…		…
274	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
275	thing, believe me).	318	thing, believe me).
276		319
277	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
278		321
279	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
280	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
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	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
283	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
284	around bugs.	327	around bugs.
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	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,
293	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
294	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
295	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
296	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	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
300	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
301	flag.	344	flag.
302		345
303	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>
304	environment variable.	347	environment variable.
305		348
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		350
308	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
…		…
310	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
311	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
312	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.
313		356
314	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
315	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
316	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
317	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
318	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
319	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
320		363
321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
322		365
323	And this is your standard poll(2) backend. It's more complicated	366	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
332	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
333	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
336	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
337	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
338	support for dup.	381	support for dup.
339		382
340	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
342	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
344	very well if you register events for both fds.	387	very well if you register events for both fds.
345		388
346	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
…		…
349		392
350	Best performance from this backend is achieved by not unregistering all	393	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	394	watchers for a file descriptor until it has been closed, if possible, i.e.
352	keep at least one watcher active per fd at all times.	395	keep at least one watcher active per fd at all times.
353		396
354	While nominally embeddeble in other event loops, this feature is broken in	397	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	398	all kernel versions tested so far.
356		399
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		401
359	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
361	with anything but sockets and pipes, except on Darwin, where of course	404	with anything but sockets and pipes, except on Darwin, where of course
362	it's completely useless). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
363	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365	system like NetBSD.	408	system like NetBSD.
366		409
367	You still can embed kqueue into a normal poll or select backend and use it	410	You still can embed kqueue into a normal poll or select backend and use it
…		…
369	the target platform). See C<ev_embed> watchers for more info.	412	the target platform). See C<ev_embed> watchers for more info.
370		413
371	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
372	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
373	course). While stopping, setting and starting an I/O watcher does never	416	course). While stopping, setting and starting an I/O watcher does never
374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
375	two event changes per incident, support for C<fork ()> is very bad and it	418	two event changes per incident, support for C<fork ()> is very bad and it
376	drops fds silently in similarly hard-to-detect cases.	419	drops fds silently in similarly hard-to-detect cases.
377		420
378	This backend usually performs well under most conditions.	421	This backend usually performs well under most conditions.
379		422
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		438
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
397	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
398		441
399	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
400	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
401	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
402		445
403	While this backend scales well, it requires one system call per active	446	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	447	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	449	might perform better.
407		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
		454
408	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
409		456
410	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		460
414	It is definitely not recommended to use this flag.	461	It is definitely not recommended to use this flag.
415		462
416	=back	463	=back
417		464
418	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		468
423	The most typical usage is like this:	469	The most typical usage is like this:
424		470
425	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		473
428	Restrict libev to the select and poll backends, and do not allow	474	Restrict libev to the select and poll backends, and do not allow
429	environment settings to be taken into account:	475	environment settings to be taken into account:
430		476
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		478
433	Use whatever libev has to offer, but make sure that kqueue is used if	479	Use whatever libev has to offer, but make sure that kqueue is used if
434	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
435	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
436		482
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		484
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		486
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
445		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
446	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
447		497
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	499	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
451		501
452	=item ev_default_destroy ()	502	=item ev_default_destroy ()
453		503
454	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
458	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
459	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	510	for example).
461		511
462	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
475		525
476	=item ev_default_fork ()	526	=item ev_default_fork ()
477		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
481	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
482		534
483	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
486		538
487	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
490		542
491	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
492		544
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
498		546
499	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
502		554
503	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
504		556
505	Returns the count of loop iterations for the loop, which is identical to	557	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
542	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
543	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
544		596
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
546	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
547	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
548	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
549	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
552		604
553	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
554		606
555	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
556	* If EVFLAG_FORKCHECK was used, check for a fork.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- If a fork was detected, queue and call all fork watchers.	609	- If a fork was detected (by any means), queue and call all fork watchers.
558	- Queue and call all prepare watchers.	610	- Queue and call all prepare watchers.
559	- If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
560	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
561	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
562	- Calculate for how long to sleep or block, if at all	615	- Calculate for how long to sleep or block, if at all
563	(active idle watchers, EVLOOP_NONBLOCK or not having	616	(active idle watchers, EVLOOP_NONBLOCK or not having
564	any active watchers at all will result in not sleeping).	617	any active watchers at all will result in not sleeping).
565	- Sleep if the I/O and timer collect interval say so.	618	- Sleep if the I/O and timer collect interval say so.
566	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
567	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
568	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
569	- Queue all outstanding timers.	622	- Queue all outstanding timers.
570	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
571	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
572	- Queue all check watchers.	625	- Queue all check watchers.
573	- Call all queued watchers in reverse order (i.e. check watchers first).	626	- Call all queued watchers in reverse order (i.e. check watchers first).
574	Signals and child watchers are implemented as I/O watchers, and will	627	Signals and child watchers are implemented as I/O watchers, and will
575	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
581	anymore.	634	anymore.
582		635
583	... queue jobs here, make sure they register event watchers as long	636	... queue jobs here, make sure they register event watchers as long
584	... as they still have work to do (even an idle watcher will do..)	637	... as they still have work to do (even an idle watcher will do..)
585	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
586	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
587		640
588	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
589		642
590	Can be used to make a call to C<ev_loop> return early (but only after it	643	Can be used to make a call to C<ev_loop> return early (but only after it
591	has processed all outstanding events). The C<how> argument must be either	644	has processed all outstanding events). The C<how> argument must be either
…		…
612	respectively).	665	respectively).
613		666
614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
615	running when nothing else is active.	668	running when nothing else is active.
616		669
617	struct ev_signal exitsig;	670	struct ev_signal exitsig;
618	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
619	ev_signal_start (loop, &exitsig);	672	ev_signal_start (loop, &exitsig);
620	evf_unref (loop);	673	evf_unref (loop);
621		674
622	Example: For some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
623		676
624	ev_ref (loop);	677	ev_ref (loop);
625	ev_signal_stop (loop, &exitsig);	678	ev_signal_stop (loop, &exitsig);
626		679
627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
628		681
629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
630		683
631	These advanced functions influence the time that libev will spend waiting	684	These advanced functions influence the time that libev will spend waiting
632	for events. Both are by default C<0>, meaning that libev will try to	685	for events. Both time intervals are by default C<0>, meaning that libev
633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
634		688
635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
636	allows libev to delay invocation of I/O and timer/periodic callbacks to	690	allows libev to delay invocation of I/O and timer/periodic callbacks
637	increase efficiency of loop iterations.	691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
638		693
639	The background is that sometimes your program runs just fast enough to	694	The background is that sometimes your program runs just fast enough to
640	handle one (or very few) event(s) per loop iteration. While this makes	695	handle one (or very few) event(s) per loop iteration. While this makes
641	the program responsive, it also wastes a lot of CPU time to poll for new	696	the program responsive, it also wastes a lot of CPU time to poll for new
642	events, especially with backends like C<select ()> which have a high	697	events, especially with backends like C<select ()> which have a high
…		…
652	to spend more time collecting timeouts, at the expense of increased	707	to spend more time collecting timeouts, at the expense of increased
653	latency (the watcher callback will be called later). C<ev_io> watchers	708	latency (the watcher callback will be called later). C<ev_io> watchers
654	will not be affected. Setting this to a non-null value will not introduce	709	will not be affected. Setting this to a non-null value will not introduce
655	any overhead in libev.	710	any overhead in libev.
656		711
657	Many (busy) programs can usually benefit by setting the io collect	712	Many (busy) programs can usually benefit by setting the I/O collect
658	interval to a value near C<0.1> or so, which is often enough for	713	interval to a value near C<0.1> or so, which is often enough for
659	interactive servers (of course not for games), likewise for timeouts. It	714	interactive servers (of course not for games), likewise for timeouts. It
660	usually doesn't make much sense to set it to a lower value than C<0.01>,	715	usually doesn't make much sense to set it to a lower value than C<0.01>,
661	as this approsaches the timing granularity of most systems.	716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
662		735
663	=back	736	=back
664		737
665		738
666	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
667		740
668	A watcher is a structure that you create and register to record your	741	A watcher is a structure that you create and register to record your
669	interest in some event. For instance, if you want to wait for STDIN to	742	interest in some event. For instance, if you want to wait for STDIN to
670	become readable, you would create an C<ev_io> watcher for that:	743	become readable, you would create an C<ev_io> watcher for that:
671		744
672	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
673	{	746	{
674	ev_io_stop (w);	747	ev_io_stop (w);
675	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
676	}	749	}
677		750
678	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
679	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
680	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
681	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
682	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
683	ev_loop (loop, 0);	756	ev_loop (loop, 0);
684		757
685	As you can see, you are responsible for allocating the memory for your	758	As you can see, you are responsible for allocating the memory for your
686	watcher structures (and it is usually a bad idea to do this on the stack,	759	watcher structures (and it is usually a bad idea to do this on the stack,
687	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
688		761
689	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
690	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
691	callback gets invoked each time the event occurs (or, in the case of io	764	callback gets invoked each time the event occurs (or, in the case of I/O
692	watchers, each time the event loop detects that the file descriptor given	765	watchers, each time the event loop detects that the file descriptor given
693	is readable and/or writable).	766	is readable and/or writable).
694		767
695	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
696	with arguments specific to this watcher type. There is also a macro	769	with arguments specific to this watcher type. There is also a macro
…		…
766	=item C<EV_FORK>	839	=item C<EV_FORK>
767		840
768	The event loop has been resumed in the child process after fork (see	841	The event loop has been resumed in the child process after fork (see
769	C<ev_fork>).	842	C<ev_fork>).
770		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
771	=item C<EV_ERROR>	848	=item C<EV_ERROR>
772		849
773	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
774	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
775	ran out of memory, a file descriptor was found to be closed or any other	852	ran out of memory, a file descriptor was found to be closed or any other
776	problem. You best act on it by reporting the problem and somehow coping	853	problem. You best act on it by reporting the problem and somehow coping
777	with the watcher being stopped.	854	with the watcher being stopped.
778		855
779	Libev will usually signal a few "dummy" events together with an error,	856	Libev will usually signal a few "dummy" events together with an error,
780	for example it might indicate that a fd is readable or writable, and if	857	for example it might indicate that a fd is readable or writable, and if
781	your callbacks is well-written it can just attempt the operation and cope	858	your callbacks is well-written it can just attempt the operation and cope
782	with the error from read() or write(). This will not work in multithreaded	859	with the error from read() or write(). This will not work in multi-threaded
783	programs, though, so beware.	860	programs, though, so beware.
784		861
785	=back	862	=back
786		863
787	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
817	Although some watcher types do not have type-specific arguments	894	Although some watcher types do not have type-specific arguments
818	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
819		896
820	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
821		898
822	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
823	calls into a single call. This is the most convinient method to initialise	900	calls into a single call. This is the most convenient method to initialise
824	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
825		902
826	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
827		904
828	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
911	to associate arbitrary data with your watcher. If you need more data and	988	to associate arbitrary data with your watcher. If you need more data and
912	don't want to allocate memory and store a pointer to it in that data	989	don't want to allocate memory and store a pointer to it in that data
913	member, you can also "subclass" the watcher type and provide your own	990	member, you can also "subclass" the watcher type and provide your own
914	data:	991	data:
915		992
916	struct my_io	993	struct my_io
917	{	994	{
918	struct ev_io io;	995	struct ev_io io;
919	int otherfd;	996	int otherfd;
920	void *somedata;	997	void *somedata;
921	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
922	}	999	}
923		1000
924	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
925	can cast it back to your own type:	1002	can cast it back to your own type:
926		1003
927	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
928	{	1005	{
929	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
930	...	1007	...
931	}	1008	}
932		1009
933	More interesting and less C-conformant ways of casting your callback type	1010	More interesting and less C-conformant ways of casting your callback type
934	instead have been omitted.	1011	instead have been omitted.
935		1012
936	Another common scenario is having some data structure with multiple	1013	Another common scenario is having some data structure with multiple
937	watchers:	1014	watchers:
938		1015
939	struct my_biggy	1016	struct my_biggy
940	{	1017	{
941	int some_data;	1018	int some_data;
942	ev_timer t1;	1019	ev_timer t1;
943	ev_timer t2;	1020	ev_timer t2;
944	}	1021	}
945		1022
946	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
947	you need to use C<offsetof>:	1024	you need to use C<offsetof>:
948		1025
949	#include <stddef.h>	1026	#include <stddef.h>
950		1027
951	static void	1028	static void
952	t1_cb (EV_P_ struct ev_timer *w, int revents)	1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
953	{	1030	{
954	struct my_biggy big = (struct my_biggy *	1031	struct my_biggy big = (struct my_biggy *
955	(((char *)w) - offsetof (struct my_biggy, t1));	1032	(((char *)w) - offsetof (struct my_biggy, t1));
956	}	1033	}
957		1034
958	static void	1035	static void
959	t2_cb (EV_P_ struct ev_timer *w, int revents)	1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
960	{	1037	{
961	struct my_biggy big = (struct my_biggy *	1038	struct my_biggy big = (struct my_biggy *
962	(((char *)w) - offsetof (struct my_biggy, t2));	1039	(((char *)w) - offsetof (struct my_biggy, t2));
963	}	1040	}
964		1041
965		1042
966	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
967		1044
968	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
…		…
997	If you must do this, then force the use of a known-to-be-good backend	1074	If you must do this, then force the use of a known-to-be-good backend
998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
999	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
1000		1077
1001	Another thing you have to watch out for is that it is quite easy to	1078	Another thing you have to watch out for is that it is quite easy to
1002	receive "spurious" readyness notifications, that is your callback might	1079	receive "spurious" readiness notifications, that is your callback might
1003	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1004	because there is no data. Not only are some backends known to create a	1081	because there is no data. Not only are some backends known to create a
1005	lot of those (for example solaris ports), it is very easy to get into	1082	lot of those (for example Solaris ports), it is very easy to get into
1006	this situation even with a relatively standard program structure. Thus	1083	this situation even with a relatively standard program structure. Thus
1007	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1008	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1009		1086
1010	If you cannot run the fd in non-blocking mode (for example you should not	1087	If you cannot run the fd in non-blocking mode (for example you should not
1011	play around with an Xlib connection), then you have to seperately re-test	1088	play around with an Xlib connection), then you have to separately re-test
1012	whether a file descriptor is really ready with a known-to-be good interface	1089	whether a file descriptor is really ready with a known-to-be good interface
1013	such as poll (fortunately in our Xlib example, Xlib already does this on	1090	such as poll (fortunately in our Xlib example, Xlib already does this on
1014	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
1015		1092
1016	=head3 The special problem of disappearing file descriptors	1093	=head3 The special problem of disappearing file descriptors
…		…
1054	To support fork in your programs, you either have to call	1131	To support fork in your programs, you either have to call
1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1057	C<EVBACKEND_POLL>.	1134	C<EVBACKEND_POLL>.
1058		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when reading from a pipe whose other end has been closed, your program
		1140	gets send a SIGPIPE, which, by default, aborts your program. For most
		1141	programs this is sensible behaviour, for daemons, this is usually
		1142	undesirable.
		1143
		1144	So when you encounter spurious, unexplained daemon exits, make sure you
		1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1146	somewhere, as that would have given you a big clue).
		1147
1059		1148
1060	=head3 Watcher-Specific Functions	1149	=head3 Watcher-Specific Functions
1061		1150
1062	=over 4	1151	=over 4
1063		1152
1064	=item ev_io_init (ev_io *, callback, int fd, int events)	1153	=item ev_io_init (ev_io *, callback, int fd, int events)
1065		1154
1066	=item ev_io_set (ev_io *, int fd, int events)	1155	=item ev_io_set (ev_io *, int fd, int events)
1067		1156
1068	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1069	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1070	C<EV_READ | EV_WRITE> to receive the given events.	1159	C<EV_READ | EV_WRITE> to receive the given events.
1071		1160
1072	=item int fd [read-only]	1161	=item int fd [read-only]
1073		1162
1074	The file descriptor being watched.	1163	The file descriptor being watched.
…		…
1083		1172
1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1085	readable, but only once. Since it is likely line-buffered, you could	1174	readable, but only once. Since it is likely line-buffered, you could
1086	attempt to read a whole line in the callback.	1175	attempt to read a whole line in the callback.
1087		1176
1088	static void	1177	static void
1089	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1090	{	1179	{
1091	ev_io_stop (loop, w);	1180	ev_io_stop (loop, w);
1092	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1093	}	1182	}
1094		1183
1095	...	1184	...
1096	struct ev_loop *loop = ev_default_init (0);	1185	struct ev_loop *loop = ev_default_init (0);
1097	struct ev_io stdin_readable;	1186	struct ev_io stdin_readable;
1098	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1099	ev_io_start (loop, &stdin_readable);	1188	ev_io_start (loop, &stdin_readable);
1100	ev_loop (loop, 0);	1189	ev_loop (loop, 0);
1101		1190
1102		1191
1103	=head2 C<ev_timer> - relative and optionally repeating timeouts	1192	=head2 C<ev_timer> - relative and optionally repeating timeouts
1104		1193
1105	Timer watchers are simple relative timers that generate an event after a	1194	Timer watchers are simple relative timers that generate an event after a
1106	given time, and optionally repeating in regular intervals after that.	1195	given time, and optionally repeating in regular intervals after that.
1107		1196
1108	The timers are based on real time, that is, if you register an event that	1197	The timers are based on real time, that is, if you register an event that
1109	times out after an hour and you reset your system clock to last years	1198	times out after an hour and you reset your system clock to January last
1110	time, it will still time out after (roughly) and hour. "Roughly" because	1199	year, it will still time out after (roughly) and hour. "Roughly" because
1111	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1112	monotonic clock option helps a lot here).	1201	monotonic clock option helps a lot here).
1113		1202
1114	The relative timeouts are calculated relative to the C<ev_now ()>	1203	The relative timeouts are calculated relative to the C<ev_now ()>
1115	time. This is usually the right thing as this timestamp refers to the time	1204	time. This is usually the right thing as this timestamp refers to the time
…		…
1117	you suspect event processing to be delayed and you I<need> to base the timeout	1206	you suspect event processing to be delayed and you I<need> to base the timeout
1118	on the current time, use something like this to adjust for this:	1207	on the current time, use something like this to adjust for this:
1119		1208
1120	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1121		1210
1122	The callback is guarenteed to be invoked only when its timeout has passed,	1211	The callback is guaranteed to be invoked only after its timeout has passed,
1123	but if multiple timers become ready during the same loop iteration then	1212	but if multiple timers become ready during the same loop iteration then
1124	order of execution is undefined.	1213	order of execution is undefined.
1125		1214
1126	=head3 Watcher-Specific Functions and Data Members	1215	=head3 Watcher-Specific Functions and Data Members
1127		1216
…		…
1129		1218
1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1219	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1131		1220
1132	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1221	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1133		1222
1134	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1223	Configure the timer to trigger after C<after> seconds. If C<repeat>
1135	C<0.>, then it will automatically be stopped. If it is positive, then the	1224	is C<0.>, then it will automatically be stopped once the timeout is
1136	timer will automatically be configured to trigger again C<repeat> seconds	1225	reached. If it is positive, then the timer will automatically be
1137	later, again, and again, until stopped manually.	1226	configured to trigger again C<repeat> seconds later, again, and again,
		1227	until stopped manually.
1138		1228
1139	The timer itself will do a best-effort at avoiding drift, that is, if you	1229	The timer itself will do a best-effort at avoiding drift, that is, if
1140	configure a timer to trigger every 10 seconds, then it will trigger at	1230	you configure a timer to trigger every 10 seconds, then it will normally
1141	exactly 10 second intervals. If, however, your program cannot keep up with	1231	trigger at exactly 10 second intervals. If, however, your program cannot
1142	the timer (because it takes longer than those 10 seconds to do stuff) the	1232	keep up with the timer (because it takes longer than those 10 seconds to
1143	timer will not fire more than once per event loop iteration.	1233	do stuff) the timer will not fire more than once per event loop iteration.
1144		1234
1145	=item ev_timer_again (loop)	1235	=item ev_timer_again (loop, ev_timer *)
1146		1236
1147	This will act as if the timer timed out and restart it again if it is	1237	This will act as if the timer timed out and restart it again if it is
1148	repeating. The exact semantics are:	1238	repeating. The exact semantics are:
1149		1239
1150	If the timer is pending, its pending status is cleared.	1240	If the timer is pending, its pending status is cleared.
1151		1241
1152	If the timer is started but nonrepeating, stop it (as if it timed out).	1242	If the timer is started but non-repeating, stop it (as if it timed out).
1153		1243
1154	If the timer is repeating, either start it if necessary (with the	1244	If the timer is repeating, either start it if necessary (with the
1155	C<repeat> value), or reset the running timer to the C<repeat> value.	1245	C<repeat> value), or reset the running timer to the C<repeat> value.
1156		1246
1157	This sounds a bit complicated, but here is a useful and typical	1247	This sounds a bit complicated, but here is a useful and typical
1158	example: Imagine you have a tcp connection and you want a so-called idle	1248	example: Imagine you have a TCP connection and you want a so-called idle
1159	timeout, that is, you want to be called when there have been, say, 60	1249	timeout, that is, you want to be called when there have been, say, 60
1160	seconds of inactivity on the socket. The easiest way to do this is to	1250	seconds of inactivity on the socket. The easiest way to do this is to
1161	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1162	C<ev_timer_again> each time you successfully read or write some data. If	1252	C<ev_timer_again> each time you successfully read or write some data. If
1163	you go into an idle state where you do not expect data to travel on the	1253	you go into an idle state where you do not expect data to travel on the
…		…
1189		1279
1190	=head3 Examples	1280	=head3 Examples
1191		1281
1192	Example: Create a timer that fires after 60 seconds.	1282	Example: Create a timer that fires after 60 seconds.
1193		1283
1194	static void	1284	static void
1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1196	{	1286	{
1197	.. one minute over, w is actually stopped right here	1287	.. one minute over, w is actually stopped right here
1198	}	1288	}
1199		1289
1200	struct ev_timer mytimer;	1290	struct ev_timer mytimer;
1201	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1202	ev_timer_start (loop, &mytimer);	1292	ev_timer_start (loop, &mytimer);
1203		1293
1204	Example: Create a timeout timer that times out after 10 seconds of	1294	Example: Create a timeout timer that times out after 10 seconds of
1205	inactivity.	1295	inactivity.
1206		1296
1207	static void	1297	static void
1208	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1209	{	1299	{
1210	.. ten seconds without any activity	1300	.. ten seconds without any activity
1211	}	1301	}
1212		1302
1213	struct ev_timer mytimer;	1303	struct ev_timer mytimer;
1214	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1215	ev_timer_again (&mytimer); /* start timer */	1305	ev_timer_again (&mytimer); /* start timer */
1216	ev_loop (loop, 0);	1306	ev_loop (loop, 0);
1217		1307
1218	// and in some piece of code that gets executed on any "activity":	1308	// and in some piece of code that gets executed on any "activity":
1219	// reset the timeout to start ticking again at 10 seconds	1309	// reset the timeout to start ticking again at 10 seconds
1220	ev_timer_again (&mytimer);	1310	ev_timer_again (&mytimer);
1221		1311
1222		1312
1223	=head2 C<ev_periodic> - to cron or not to cron?	1313	=head2 C<ev_periodic> - to cron or not to cron?
1224		1314
1225	Periodic watchers are also timers of a kind, but they are very versatile	1315	Periodic watchers are also timers of a kind, but they are very versatile
1226	(and unfortunately a bit complex).	1316	(and unfortunately a bit complex).
1227		1317
1228	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1229	but on wallclock time (absolute time). You can tell a periodic watcher	1319	but on wall clock time (absolute time). You can tell a periodic watcher
1230	to trigger "at" some specific point in time. For example, if you tell a	1320	to trigger after some specific point in time. For example, if you tell a
1231	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1232	+ 10.>) and then reset your system clock to the last year, then it will	1322	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1323	clock to January of the previous year, then it will take more than year
1233	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1234	roughly 10 seconds later).	1325	roughly 10 seconds later as it uses a relative timeout).
1235		1326
1236	They can also be used to implement vastly more complex timers, such as	1327	C<ev_periodic>s can also be used to implement vastly more complex timers,
1237	triggering an event on each midnight, local time or other, complicated,	1328	such as triggering an event on each "midnight, local time", or other
1238	rules.	1329	complicated, rules.
1239		1330
1240	As with timers, the callback is guarenteed to be invoked only when the	1331	As with timers, the callback is guaranteed to be invoked only when the
1241	time (C<at>) has been passed, but if multiple periodic timers become ready	1332	time (C<at>) has passed, but if multiple periodic timers become ready
1242	during the same loop iteration then order of execution is undefined.	1333	during the same loop iteration then order of execution is undefined.
1243		1334
1244	=head3 Watcher-Specific Functions and Data Members	1335	=head3 Watcher-Specific Functions and Data Members
1245		1336
1246	=over 4	1337	=over 4
…		…
1254		1345
1255	=over 4	1346	=over 4
1256		1347
1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1258		1349
1259	In this configuration the watcher triggers an event at the wallclock time	1350	In this configuration the watcher triggers an event after the wall clock
1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1351	time C<at> has passed and doesn't repeat. It will not adjust when a time
1261	that is, if it is to be run at January 1st 2011 then it will run when the	1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1262	system time reaches or surpasses this time.	1353	run when the system time reaches or surpasses this time.
1263		1354
1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1265		1356
1266	In this mode the watcher will always be scheduled to time out at the next	1357	In this mode the watcher will always be scheduled to time out at the next
1267	C<at + N * interval> time (for some integer N, which can also be negative)	1358	C<at + N * interval> time (for some integer N, which can also be negative)
1268	and then repeat, regardless of any time jumps.	1359	and then repeat, regardless of any time jumps.
1269		1360
1270	This can be used to create timers that do not drift with respect to system	1361	This can be used to create timers that do not drift with respect to system
1271	time:	1362	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1363	the hour:
1272		1364
1273	ev_periodic_set (&periodic, 0., 3600., 0);	1365	ev_periodic_set (&periodic, 0., 3600., 0);
1274		1366
1275	This doesn't mean there will always be 3600 seconds in between triggers,	1367	This doesn't mean there will always be 3600 seconds in between triggers,
1276	but only that the the callback will be called when the system time shows a	1368	but only that the callback will be called when the system time shows a
1277	full hour (UTC), or more correctly, when the system time is evenly divisible	1369	full hour (UTC), or more correctly, when the system time is evenly divisible
1278	by 3600.	1370	by 3600.
1279		1371
1280	Another way to think about it (for the mathematically inclined) is that	1372	Another way to think about it (for the mathematically inclined) is that
1281	C<ev_periodic> will try to run the callback in this mode at the next possible	1373	C<ev_periodic> will try to run the callback in this mode at the next possible
1282	time where C<time = at (mod interval)>, regardless of any time jumps.	1374	time where C<time = at (mod interval)>, regardless of any time jumps.
1283		1375
1284	For numerical stability it is preferable that the C<at> value is near	1376	For numerical stability it is preferable that the C<at> value is near
1285	C<ev_now ()> (the current time), but there is no range requirement for	1377	C<ev_now ()> (the current time), but there is no range requirement for
1286	this value.	1378	this value, and in fact is often specified as zero.
		1379
		1380	Note also that there is an upper limit to how often a timer can fire (CPU
		1381	speed for example), so if C<interval> is very small then timing stability
		1382	will of course deteriorate. Libev itself tries to be exact to be about one
		1383	millisecond (if the OS supports it and the machine is fast enough).
1287		1384
1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1289		1386
1290	In this mode the values for C<interval> and C<at> are both being	1387	In this mode the values for C<interval> and C<at> are both being
1291	ignored. Instead, each time the periodic watcher gets scheduled, the	1388	ignored. Instead, each time the periodic watcher gets scheduled, the
1292	reschedule callback will be called with the watcher as first, and the	1389	reschedule callback will be called with the watcher as first, and the
1293	current time as second argument.	1390	current time as second argument.
1294		1391
1295	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1296	ever, or make any event loop modifications>. If you need to stop it,	1393	ever, or make ANY event loop modifications whatsoever>.
1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1298	starting an C<ev_prepare> watcher, which is legal).
1299		1394
		1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1397	only event loop modification you are allowed to do).
		1398
1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1301	ev_tstamp now)>, e.g.:	1400	*w, ev_tstamp now)>, e.g.:
1302		1401
1303	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1304	{	1403	{
1305	return now + 60.;	1404	return now + 60.;
1306	}	1405	}
…		…
1308	It must return the next time to trigger, based on the passed time value	1407	It must return the next time to trigger, based on the passed time value
1309	(that is, the lowest time value larger than to the second argument). It	1408	(that is, the lowest time value larger than to the second argument). It
1310	will usually be called just before the callback will be triggered, but	1409	will usually be called just before the callback will be triggered, but
1311	might be called at other times, too.	1410	might be called at other times, too.
1312		1411
1313	NOTE: I<< This callback must always return a time that is later than the	1412	NOTE: I<< This callback must always return a time that is higher than or
1314	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1413	equal to the passed C<now> value >>.
1315		1414
1316	This can be used to create very complex timers, such as a timer that	1415	This can be used to create very complex timers, such as a timer that
1317	triggers on each midnight, local time. To do this, you would calculate the	1416	triggers on "next midnight, local time". To do this, you would calculate the
1318	next midnight after C<now> and return the timestamp value for this. How	1417	next midnight after C<now> and return the timestamp value for this. How
1319	you do this is, again, up to you (but it is not trivial, which is the main	1418	you do this is, again, up to you (but it is not trivial, which is the main
1320	reason I omitted it as an example).	1419	reason I omitted it as an example).
1321		1420
1322	=back	1421	=back
…		…
1326	Simply stops and restarts the periodic watcher again. This is only useful	1425	Simply stops and restarts the periodic watcher again. This is only useful
1327	when you changed some parameters or the reschedule callback would return	1426	when you changed some parameters or the reschedule callback would return
1328	a different time than the last time it was called (e.g. in a crond like	1427	a different time than the last time it was called (e.g. in a crond like
1329	program when the crontabs have changed).	1428	program when the crontabs have changed).
1330		1429
		1430	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1431
		1432	When active, returns the absolute time that the watcher is supposed to
		1433	trigger next.
		1434
1331	=item ev_tstamp offset [read-write]	1435	=item ev_tstamp offset [read-write]
1332		1436
1333	When repeating, this contains the offset value, otherwise this is the	1437	When repeating, this contains the offset value, otherwise this is the
1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1335		1439
…		…
1346		1450
1347	The current reschedule callback, or C<0>, if this functionality is	1451	The current reschedule callback, or C<0>, if this functionality is
1348	switched off. Can be changed any time, but changes only take effect when	1452	switched off. Can be changed any time, but changes only take effect when
1349	the periodic timer fires or C<ev_periodic_again> is being called.	1453	the periodic timer fires or C<ev_periodic_again> is being called.
1350		1454
1351	=item ev_tstamp at [read-only]
1352
1353	When active, contains the absolute time that the watcher is supposed to
1354	trigger next.
1355
1356	=back	1455	=back
1357		1456
1358	=head3 Examples	1457	=head3 Examples
1359		1458
1360	Example: Call a callback every hour, or, more precisely, whenever the	1459	Example: Call a callback every hour, or, more precisely, whenever the
1361	system clock is divisible by 3600. The callback invocation times have	1460	system clock is divisible by 3600. The callback invocation times have
1362	potentially a lot of jittering, but good long-term stability.	1461	potentially a lot of jitter, but good long-term stability.
1363		1462
1364	static void	1463	static void
1365	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1366	{	1465	{
1367	... its now a full hour (UTC, or TAI or whatever your clock follows)	1466	... its now a full hour (UTC, or TAI or whatever your clock follows)
1368	}	1467	}
1369		1468
1370	struct ev_periodic hourly_tick;	1469	struct ev_periodic hourly_tick;
1371	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1372	ev_periodic_start (loop, &hourly_tick);	1471	ev_periodic_start (loop, &hourly_tick);
1373		1472
1374	Example: The same as above, but use a reschedule callback to do it:	1473	Example: The same as above, but use a reschedule callback to do it:
1375		1474
1376	#include <math.h>	1475	#include <math.h>
1377		1476
1378	static ev_tstamp	1477	static ev_tstamp
1379	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1380	{	1479	{
1381	return fmod (now, 3600.) + 3600.;	1480	return fmod (now, 3600.) + 3600.;
1382	}	1481	}
1383		1482
1384	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1385		1484
1386	Example: Call a callback every hour, starting now:	1485	Example: Call a callback every hour, starting now:
1387		1486
1388	struct ev_periodic hourly_tick;	1487	struct ev_periodic hourly_tick;
1389	ev_periodic_init (&hourly_tick, clock_cb,	1488	ev_periodic_init (&hourly_tick, clock_cb,
1390	fmod (ev_now (loop), 3600.), 3600., 0);	1489	fmod (ev_now (loop), 3600.), 3600., 0);
1391	ev_periodic_start (loop, &hourly_tick);	1490	ev_periodic_start (loop, &hourly_tick);
1392		1491
1393		1492
1394	=head2 C<ev_signal> - signal me when a signal gets signalled!	1493	=head2 C<ev_signal> - signal me when a signal gets signalled!
1395		1494
1396	Signal watchers will trigger an event when the process receives a specific	1495	Signal watchers will trigger an event when the process receives a specific
…		…
1403	with the kernel (thus it coexists with your own signal handlers as long	1502	with the kernel (thus it coexists with your own signal handlers as long
1404	as you don't register any with libev). Similarly, when the last signal	1503	as you don't register any with libev). Similarly, when the last signal
1405	watcher for a signal is stopped libev will reset the signal handler to	1504	watcher for a signal is stopped libev will reset the signal handler to
1406	SIG_DFL (regardless of what it was set to before).	1505	SIG_DFL (regardless of what it was set to before).
1407		1506
		1507	If possible and supported, libev will install its handlers with
		1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1509	interrupted. If you have a problem with system calls getting interrupted by
		1510	signals you can block all signals in an C<ev_check> watcher and unblock
		1511	them in an C<ev_prepare> watcher.
		1512
1408	=head3 Watcher-Specific Functions and Data Members	1513	=head3 Watcher-Specific Functions and Data Members
1409		1514
1410	=over 4	1515	=over 4
1411		1516
1412	=item ev_signal_init (ev_signal *, callback, int signum)	1517	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1420		1525
1421	The signal the watcher watches out for.	1526	The signal the watcher watches out for.
1422		1527
1423	=back	1528	=back
1424		1529
		1530	=head3 Examples
		1531
		1532	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1533
		1534	static void
		1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1536	{
		1537	ev_unloop (loop, EVUNLOOP_ALL);
		1538	}
		1539
		1540	struct ev_signal signal_watcher;
		1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1542	ev_signal_start (loop, &sigint_cb);
		1543
1425		1544
1426	=head2 C<ev_child> - watch out for process status changes	1545	=head2 C<ev_child> - watch out for process status changes
1427		1546
1428	Child watchers trigger when your process receives a SIGCHLD in response to	1547	Child watchers trigger when your process receives a SIGCHLD in response to
1429	some child status changes (most typically when a child of yours dies).	1548	some child status changes (most typically when a child of yours dies). It
		1549	is permissible to install a child watcher I<after> the child has been
		1550	forked (which implies it might have already exited), as long as the event
		1551	loop isn't entered (or is continued from a watcher).
		1552
		1553	Only the default event loop is capable of handling signals, and therefore
		1554	you can only register child watchers in the default event loop.
		1555
		1556	=head3 Process Interaction
		1557
		1558	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1559	initialised. This is necessary to guarantee proper behaviour even if
		1560	the first child watcher is started after the child exits. The occurrence
		1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1562	synchronously as part of the event loop processing. Libev always reaps all
		1563	children, even ones not watched.
		1564
		1565	=head3 Overriding the Built-In Processing
		1566
		1567	Libev offers no special support for overriding the built-in child
		1568	processing, but if your application collides with libev's default child
		1569	handler, you can override it easily by installing your own handler for
		1570	C<SIGCHLD> after initialising the default loop, and making sure the
		1571	default loop never gets destroyed. You are encouraged, however, to use an
		1572	event-based approach to child reaping and thus use libev's support for
		1573	that, so other libev users can use C<ev_child> watchers freely.
1430		1574
1431	=head3 Watcher-Specific Functions and Data Members	1575	=head3 Watcher-Specific Functions and Data Members
1432		1576
1433	=over 4	1577	=over 4
1434		1578
1435	=item ev_child_init (ev_child *, callback, int pid)	1579	=item ev_child_init (ev_child *, callback, int pid, int trace)
1436		1580
1437	=item ev_child_set (ev_child *, int pid)	1581	=item ev_child_set (ev_child *, int pid, int trace)
1438		1582
1439	Configures the watcher to wait for status changes of process C<pid> (or	1583	Configures the watcher to wait for status changes of process C<pid> (or
1440	I<any> process if C<pid> is specified as C<0>). The callback can look	1584	I<any> process if C<pid> is specified as C<0>). The callback can look
1441	at the C<rstatus> member of the C<ev_child> watcher structure to see	1585	at the C<rstatus> member of the C<ev_child> watcher structure to see
1442	the status word (use the macros from C<sys/wait.h> and see your systems	1586	the status word (use the macros from C<sys/wait.h> and see your systems
1443	C<waitpid> documentation). The C<rpid> member contains the pid of the	1587	C<waitpid> documentation). The C<rpid> member contains the pid of the
1444	process causing the status change.	1588	process causing the status change. C<trace> must be either C<0> (only
		1589	activate the watcher when the process terminates) or C<1> (additionally
		1590	activate the watcher when the process is stopped or continued).
1445		1591
1446	=item int pid [read-only]	1592	=item int pid [read-only]
1447		1593
1448	The process id this watcher watches out for, or C<0>, meaning any process id.	1594	The process id this watcher watches out for, or C<0>, meaning any process id.
1449		1595
…		…
1458		1604
1459	=back	1605	=back
1460		1606
1461	=head3 Examples	1607	=head3 Examples
1462		1608
1463	Example: Try to exit cleanly on SIGINT and SIGTERM.	1609	Example: C<fork()> a new process and install a child handler to wait for
		1610	its completion.
1464		1611
		1612	ev_child cw;
		1613
1465	static void	1614	static void
1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1615	child_cb (EV_P_ struct ev_child *w, int revents)
1467	{	1616	{
1468	ev_unloop (loop, EVUNLOOP_ALL);	1617	ev_child_stop (EV_A_ w);
		1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1469	}	1619	}
1470		1620
1471	struct ev_signal signal_watcher;	1621	pid_t pid = fork ();
1472	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1622
1473	ev_signal_start (loop, &sigint_cb);	1623	if (pid < 0)
		1624	// error
		1625	else if (pid == 0)
		1626	{
		1627	// the forked child executes here
		1628	exit (1);
		1629	}
		1630	else
		1631	{
		1632	ev_child_init (&cw, child_cb, pid, 0);
		1633	ev_child_start (EV_DEFAULT_ &cw);
		1634	}
1474		1635
1475		1636
1476	=head2 C<ev_stat> - did the file attributes just change?	1637	=head2 C<ev_stat> - did the file attributes just change?
1477		1638
1478	This watches a filesystem path for attribute changes. That is, it calls	1639	This watches a file system path for attribute changes. That is, it calls
1479	C<stat> regularly (or when the OS says it changed) and sees if it changed	1640	C<stat> regularly (or when the OS says it changed) and sees if it changed
1480	compared to the last time, invoking the callback if it did.	1641	compared to the last time, invoking the callback if it did.
1481		1642
1482	The path does not need to exist: changing from "path exists" to "path does	1643	The path does not need to exist: changing from "path exists" to "path does
1483	not exist" is a status change like any other. The condition "path does	1644	not exist" is a status change like any other. The condition "path does
…		…
1501	as even with OS-supported change notifications, this can be	1662	as even with OS-supported change notifications, this can be
1502	resource-intensive.	1663	resource-intensive.
1503		1664
1504	At the time of this writing, only the Linux inotify interface is	1665	At the time of this writing, only the Linux inotify interface is
1505	implemented (implementing kqueue support is left as an exercise for the	1666	implemented (implementing kqueue support is left as an exercise for the
		1667	reader, note, however, that the author sees no way of implementing ev_stat
1506	reader). Inotify will be used to give hints only and should not change the	1668	semantics with kqueue). Inotify will be used to give hints only and should
1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1669	not change the semantics of C<ev_stat> watchers, which means that libev
1508	to fall back to regular polling again even with inotify, but changes are	1670	sometimes needs to fall back to regular polling again even with inotify,
1509	usually detected immediately, and if the file exists there will be no	1671	but changes are usually detected immediately, and if the file exists there
1510	polling.	1672	will be no polling.
		1673
		1674	=head3 ABI Issues (Largefile Support)
		1675
		1676	Libev by default (unless the user overrides this) uses the default
		1677	compilation environment, which means that on systems with large file
		1678	support disabled by default, you get the 32 bit version of the stat
		1679	structure. When using the library from programs that change the ABI to
		1680	use 64 bit file offsets the programs will fail. In that case you have to
		1681	compile libev with the same flags to get binary compatibility. This is
		1682	obviously the case with any flags that change the ABI, but the problem is
		1683	most noticeably disabled with ev_stat and large file support.
		1684
		1685	The solution for this is to lobby your distribution maker to make large
		1686	file interfaces available by default (as e.g. FreeBSD does) and not
		1687	optional. Libev cannot simply switch on large file support because it has
		1688	to exchange stat structures with application programs compiled using the
		1689	default compilation environment.
1511		1690
1512	=head3 Inotify	1691	=head3 Inotify
1513		1692
1514	When C<inotify (7)> support has been compiled into libev (generally only	1693	When C<inotify (7)> support has been compiled into libev (generally only
1515	available on Linux) and present at runtime, it will be used to speed up	1694	available on Linux) and present at runtime, it will be used to speed up
1516	change detection where possible. The inotify descriptor will be created lazily	1695	change detection where possible. The inotify descriptor will be created lazily
1517	when the first C<ev_stat> watcher is being started.	1696	when the first C<ev_stat> watcher is being started.
1518		1697
1519	Inotify presense does not change the semantics of C<ev_stat> watchers	1698	Inotify presence does not change the semantics of C<ev_stat> watchers
1520	except that changes might be detected earlier, and in some cases, to avoid	1699	except that changes might be detected earlier, and in some cases, to avoid
1521	making regular C<stat> calls. Even in the presense of inotify support	1700	making regular C<stat> calls. Even in the presence of inotify support
1522	there are many cases where libev has to resort to regular C<stat> polling.	1701	there are many cases where libev has to resort to regular C<stat> polling.
1523		1702
1524	(There is no support for kqueue, as apparently it cannot be used to	1703	(There is no support for kqueue, as apparently it cannot be used to
1525	implement this functionality, due to the requirement of having a file	1704	implement this functionality, due to the requirement of having a file
1526	descriptor open on the object at all times).	1705	descriptor open on the object at all times).
1527		1706
1528	=head3 The special problem of stat time resolution	1707	=head3 The special problem of stat time resolution
1529		1708
1530	The C<stat ()> syscall only supports full-second resolution portably, and	1709	The C<stat ()> system call only supports full-second resolution portably, and
1531	even on systems where the resolution is higher, many filesystems still	1710	even on systems where the resolution is higher, many file systems still
1532	only support whole seconds.	1711	only support whole seconds.
1533		1712
1534	That means that, if the time is the only thing that changes, you might	1713	That means that, if the time is the only thing that changes, you can
1535	miss updates: on the first update, C<ev_stat> detects a change and calls	1714	easily miss updates: on the first update, C<ev_stat> detects a change and
1536	your callback, which does something. When there is another update within	1715	calls your callback, which does something. When there is another update
1537	the same second, C<ev_stat> will be unable to detect it.	1716	within the same second, C<ev_stat> will be unable to detect it as the stat
		1717	data does not change.
1538		1718
1539	The solution to this is to delay acting on a change for a second (or till	1719	The solution to this is to delay acting on a change for slightly more
1540	the next second boundary), using a roughly one-second delay C<ev_timer>	1720	than a second (or till slightly after the next full second boundary), using
1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1542	is added to work around small timing inconsistencies of some operating	1722	ev_timer_again (loop, w)>).
1543	systems.	1723
		1724	The C<.02> offset is added to work around small timing inconsistencies
		1725	of some operating systems (where the second counter of the current time
		1726	might be be delayed. One such system is the Linux kernel, where a call to
		1727	C<gettimeofday> might return a timestamp with a full second later than
		1728	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1729	update file times then there will be a small window where the kernel uses
		1730	the previous second to update file times but libev might already execute
		1731	the timer callback).
1544		1732
1545	=head3 Watcher-Specific Functions and Data Members	1733	=head3 Watcher-Specific Functions and Data Members
1546		1734
1547	=over 4	1735	=over 4
1548		1736
…		…
1554	C<path>. The C<interval> is a hint on how quickly a change is expected to	1742	C<path>. The C<interval> is a hint on how quickly a change is expected to
1555	be detected and should normally be specified as C<0> to let libev choose	1743	be detected and should normally be specified as C<0> to let libev choose
1556	a suitable value. The memory pointed to by C<path> must point to the same	1744	a suitable value. The memory pointed to by C<path> must point to the same
1557	path for as long as the watcher is active.	1745	path for as long as the watcher is active.
1558		1746
1559	The callback will be receive C<EV_STAT> when a change was detected,	1747	The callback will receive C<EV_STAT> when a change was detected, relative
1560	relative to the attributes at the time the watcher was started (or the	1748	to the attributes at the time the watcher was started (or the last change
1561	last change was detected).	1749	was detected).
1562		1750
1563	=item ev_stat_stat (ev_stat *)	1751	=item ev_stat_stat (loop, ev_stat *)
1564		1752
1565	Updates the stat buffer immediately with new values. If you change the	1753	Updates the stat buffer immediately with new values. If you change the
1566	watched path in your callback, you could call this fucntion to avoid	1754	watched path in your callback, you could call this function to avoid
1567	detecting this change (while introducing a race condition). Can also be	1755	detecting this change (while introducing a race condition if you are not
1568	useful simply to find out the new values.	1756	the only one changing the path). Can also be useful simply to find out the
		1757	new values.
1569		1758
1570	=item ev_statdata attr [read-only]	1759	=item ev_statdata attr [read-only]
1571		1760
1572	The most-recently detected attributes of the file. Although the type is of	1761	The most-recently detected attributes of the file. Although the type is
1573	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1762	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1574	suitable for your system. If the C<st_nlink> member is C<0>, then there	1763	suitable for your system, but you can only rely on the POSIX-standardised
		1764	members to be present. If the C<st_nlink> member is C<0>, then there was
1575	was some error while C<stat>ing the file.	1765	some error while C<stat>ing the file.
1576		1766
1577	=item ev_statdata prev [read-only]	1767	=item ev_statdata prev [read-only]
1578		1768
1579	The previous attributes of the file. The callback gets invoked whenever	1769	The previous attributes of the file. The callback gets invoked whenever
1580	C<prev> != C<attr>.	1770	C<prev> != C<attr>, or, more precisely, one or more of these members
		1771	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1772	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1581		1773
1582	=item ev_tstamp interval [read-only]	1774	=item ev_tstamp interval [read-only]
1583		1775
1584	The specified interval.	1776	The specified interval.
1585		1777
1586	=item const char *path [read-only]	1778	=item const char *path [read-only]
1587		1779
1588	The filesystem path that is being watched.	1780	The file system path that is being watched.
1589		1781
1590	=back	1782	=back
1591		1783
1592	=head3 Examples	1784	=head3 Examples
1593		1785
1594	Example: Watch C</etc/passwd> for attribute changes.	1786	Example: Watch C</etc/passwd> for attribute changes.
1595		1787
1596	static void	1788	static void
1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1789	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1598	{	1790	{
1599	/* /etc/passwd changed in some way */	1791	/* /etc/passwd changed in some way */
1600	if (w->attr.st_nlink)	1792	if (w->attr.st_nlink)
1601	{	1793	{
1602	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1794	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1603	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1795	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1604	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1796	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1605	}	1797	}
1606	else	1798	else
1607	/* you shalt not abuse printf for puts */	1799	/* you shalt not abuse printf for puts */
1608	puts ("wow, /etc/passwd is not there, expect problems. "	1800	puts ("wow, /etc/passwd is not there, expect problems. "
1609	"if this is windows, they already arrived\n");	1801	"if this is windows, they already arrived\n");
1610	}	1802	}
1611		1803
1612	...	1804	...
1613	ev_stat passwd;	1805	ev_stat passwd;
1614		1806
1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1807	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1616	ev_stat_start (loop, &passwd);	1808	ev_stat_start (loop, &passwd);
1617		1809
1618	Example: Like above, but additionally use a one-second delay so we do not	1810	Example: Like above, but additionally use a one-second delay so we do not
1619	miss updates (however, frequent updates will delay processing, too, so	1811	miss updates (however, frequent updates will delay processing, too, so
1620	one might do the work both on C<ev_stat> callback invocation I<and> on	1812	one might do the work both on C<ev_stat> callback invocation I<and> on
1621	C<ev_timer> callback invocation).	1813	C<ev_timer> callback invocation).
1622		1814
1623	static ev_stat passwd;	1815	static ev_stat passwd;
1624	static ev_timer timer;	1816	static ev_timer timer;
1625		1817
1626	static void	1818	static void
1627	timer_cb (EV_P_ ev_timer *w, int revents)	1819	timer_cb (EV_P_ ev_timer *w, int revents)
1628	{	1820	{
1629	ev_timer_stop (EV_A_ w);	1821	ev_timer_stop (EV_A_ w);
1630		1822
1631	/* now it's one second after the most recent passwd change */	1823	/* now it's one second after the most recent passwd change */
1632	}	1824	}
1633		1825
1634	static void	1826	static void
1635	stat_cb (EV_P_ ev_stat *w, int revents)	1827	stat_cb (EV_P_ ev_stat *w, int revents)
1636	{	1828	{
1637	/* reset the one-second timer */	1829	/* reset the one-second timer */
1638	ev_timer_again (EV_A_ &timer);	1830	ev_timer_again (EV_A_ &timer);
1639	}	1831	}
1640		1832
1641	...	1833	...
1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1834	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1643	ev_stat_start (loop, &passwd);	1835	ev_stat_start (loop, &passwd);
1644	ev_timer_init (&timer, timer_cb, 0., 1.01);	1836	ev_timer_init (&timer, timer_cb, 0., 1.02);
1645		1837
1646		1838
1647	=head2 C<ev_idle> - when you've got nothing better to do...	1839	=head2 C<ev_idle> - when you've got nothing better to do...
1648		1840
1649	Idle watchers trigger events when no other events of the same or higher	1841	Idle watchers trigger events when no other events of the same or higher
…		…
1680	=head3 Examples	1872	=head3 Examples
1681		1873
1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1683	callback, free it. Also, use no error checking, as usual.	1875	callback, free it. Also, use no error checking, as usual.
1684		1876
1685	static void	1877	static void
1686	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1687	{	1879	{
1688	free (w);	1880	free (w);
1689	// now do something you wanted to do when the program has	1881	// now do something you wanted to do when the program has
1690	// no longer asnything immediate to do.	1882	// no longer anything immediate to do.
1691	}	1883	}
1692		1884
1693	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1694	ev_idle_init (idle_watcher, idle_cb);	1886	ev_idle_init (idle_watcher, idle_cb);
1695	ev_idle_start (loop, idle_cb);	1887	ev_idle_start (loop, idle_cb);
1696		1888
1697		1889
1698	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1699		1891
1700	Prepare and check watchers are usually (but not always) used in tandem:	1892	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1719		1911
1720	This is done by examining in each prepare call which file descriptors need	1912	This is done by examining in each prepare call which file descriptors need
1721	to be watched by the other library, registering C<ev_io> watchers for	1913	to be watched by the other library, registering C<ev_io> watchers for
1722	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1723	provide just this functionality). Then, in the check watcher you check for	1915	provide just this functionality). Then, in the check watcher you check for
1724	any events that occured (by checking the pending status of all watchers	1916	any events that occurred (by checking the pending status of all watchers
1725	and stopping them) and call back into the library. The I/O and timer	1917	and stopping them) and call back into the library. The I/O and timer
1726	callbacks will never actually be called (but must be valid nevertheless,	1918	callbacks will never actually be called (but must be valid nevertheless,
1727	because you never know, you know?).	1919	because you never know, you know?).
1728		1920
1729	As another example, the Perl Coro module uses these hooks to integrate	1921	As another example, the Perl Coro module uses these hooks to integrate
…		…
1737		1929
1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1739	priority, to ensure that they are being run before any other watchers	1931	priority, to ensure that they are being run before any other watchers
1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1741	too) should not activate ("feed") events into libev. While libev fully	1933	too) should not activate ("feed") events into libev. While libev fully
1742	supports this, they will be called before other C<ev_check> watchers	1934	supports this, they might get executed before other C<ev_check> watchers
1743	did their job. As C<ev_check> watchers are often used to embed other	1935	did their job. As C<ev_check> watchers are often used to embed other
1744	(non-libev) event loops those other event loops might be in an unusable	1936	(non-libev) event loops those other event loops might be in an unusable
1745	state until their C<ev_check> watcher ran (always remind yourself to	1937	state until their C<ev_check> watcher ran (always remind yourself to
1746	coexist peacefully with others).	1938	coexist peacefully with others).
1747		1939
…		…
1762	=head3 Examples	1954	=head3 Examples
1763		1955
1764	There are a number of principal ways to embed other event loops or modules	1956	There are a number of principal ways to embed other event loops or modules
1765	into libev. Here are some ideas on how to include libadns into libev	1957	into libev. Here are some ideas on how to include libadns into libev
1766	(there is a Perl module named C<EV::ADNS> that does this, which you could	1958	(there is a Perl module named C<EV::ADNS> that does this, which you could
1767	use for an actually working example. Another Perl module named C<EV::Glib>	1959	use as a working example. Another Perl module named C<EV::Glib> embeds a
1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1960	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1769	into the Glib event loop).	1961	Glib event loop).
1770		1962
1771	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1963	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1772	and in a check watcher, destroy them and call into libadns. What follows	1964	and in a check watcher, destroy them and call into libadns. What follows
1773	is pseudo-code only of course. This requires you to either use a low	1965	is pseudo-code only of course. This requires you to either use a low
1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1966	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1775	the callbacks for the IO/timeout watchers might not have been called yet.	1967	the callbacks for the IO/timeout watchers might not have been called yet.
1776		1968
1777	static ev_io iow [nfd];	1969	static ev_io iow [nfd];
1778	static ev_timer tw;	1970	static ev_timer tw;
1779		1971
1780	static void	1972	static void
1781	io_cb (ev_loop *loop, ev_io *w, int revents)	1973	io_cb (ev_loop *loop, ev_io *w, int revents)
1782	{	1974	{
1783	}	1975	}
1784		1976
1785	// create io watchers for each fd and a timer before blocking	1977	// create io watchers for each fd and a timer before blocking
1786	static void	1978	static void
1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1788	{	1980	{
1789	int timeout = 3600000;	1981	int timeout = 3600000;
1790	struct pollfd fds [nfd];	1982	struct pollfd fds [nfd];
1791	// actual code will need to loop here and realloc etc.	1983	// actual code will need to loop here and realloc etc.
1792	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1793		1985
1794	/* the callback is illegal, but won't be called as we stop during check */	1986	/* the callback is illegal, but won't be called as we stop during check */
1795	ev_timer_init (&tw, 0, timeout * 1e-3);	1987	ev_timer_init (&tw, 0, timeout * 1e-3);
1796	ev_timer_start (loop, &tw);	1988	ev_timer_start (loop, &tw);
1797		1989
1798	// create one ev_io per pollfd	1990	// create one ev_io per pollfd
1799	for (int i = 0; i < nfd; ++i)	1991	for (int i = 0; i < nfd; ++i)
1800	{	1992	{
1801	ev_io_init (iow + i, io_cb, fds [i].fd,	1993	ev_io_init (iow + i, io_cb, fds [i].fd,
1802	((fds [i].events & POLLIN ? EV_READ : 0)	1994	((fds [i].events & POLLIN ? EV_READ : 0)
1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1995	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1804		1996
1805	fds [i].revents = 0;	1997	fds [i].revents = 0;
1806	ev_io_start (loop, iow + i);	1998	ev_io_start (loop, iow + i);
1807	}	1999	}
1808	}	2000	}
1809		2001
1810	// stop all watchers after blocking	2002	// stop all watchers after blocking
1811	static void	2003	static void
1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1813	{	2005	{
1814	ev_timer_stop (loop, &tw);	2006	ev_timer_stop (loop, &tw);
1815		2007
1816	for (int i = 0; i < nfd; ++i)	2008	for (int i = 0; i < nfd; ++i)
1817	{	2009	{
1818	// set the relevant poll flags	2010	// set the relevant poll flags
1819	// could also call adns_processreadable etc. here	2011	// could also call adns_processreadable etc. here
1820	struct pollfd *fd = fds + i;	2012	struct pollfd *fd = fds + i;
1821	int revents = ev_clear_pending (iow + i);	2013	int revents = ev_clear_pending (iow + i);
1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2014	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2015	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1824		2016
1825	// now stop the watcher	2017	// now stop the watcher
1826	ev_io_stop (loop, iow + i);	2018	ev_io_stop (loop, iow + i);
1827	}	2019	}
1828		2020
1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2021	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1830	}	2022	}
1831		2023
1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2024	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1833	in the prepare watcher and would dispose of the check watcher.	2025	in the prepare watcher and would dispose of the check watcher.
1834		2026
1835	Method 3: If the module to be embedded supports explicit event	2027	Method 3: If the module to be embedded supports explicit event
1836	notification (adns does), you can also make use of the actual watcher	2028	notification (libadns does), you can also make use of the actual watcher
1837	callbacks, and only destroy/create the watchers in the prepare watcher.	2029	callbacks, and only destroy/create the watchers in the prepare watcher.
1838		2030
1839	static void	2031	static void
1840	timer_cb (EV_P_ ev_timer *w, int revents)	2032	timer_cb (EV_P_ ev_timer *w, int revents)
1841	{	2033	{
1842	adns_state ads = (adns_state)w->data;	2034	adns_state ads = (adns_state)w->data;
1843	update_now (EV_A);	2035	update_now (EV_A);
1844		2036
1845	adns_processtimeouts (ads, &tv_now);	2037	adns_processtimeouts (ads, &tv_now);
1846	}	2038	}
1847		2039
1848	static void	2040	static void
1849	io_cb (EV_P_ ev_io *w, int revents)	2041	io_cb (EV_P_ ev_io *w, int revents)
1850	{	2042	{
1851	adns_state ads = (adns_state)w->data;	2043	adns_state ads = (adns_state)w->data;
1852	update_now (EV_A);	2044	update_now (EV_A);
1853		2045
1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2046	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2047	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1856	}	2048	}
1857		2049
1858	// do not ever call adns_afterpoll	2050	// do not ever call adns_afterpoll
1859		2051
1860	Method 4: Do not use a prepare or check watcher because the module you	2052	Method 4: Do not use a prepare or check watcher because the module you
1861	want to embed is too inflexible to support it. Instead, youc na override	2053	want to embed is too inflexible to support it. Instead, you can override
1862	their poll function. The drawback with this solution is that the main	2054	their poll function. The drawback with this solution is that the main
1863	loop is now no longer controllable by EV. The C<Glib::EV> module does	2055	loop is now no longer controllable by EV. The C<Glib::EV> module does
1864	this.	2056	this.
1865		2057
1866	static gint	2058	static gint
1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1868	{	2060	{
1869	int got_events = 0;	2061	int got_events = 0;
1870		2062
1871	for (n = 0; n < nfds; ++n)	2063	for (n = 0; n < nfds; ++n)
1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2064	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1873		2065
1874	if (timeout >= 0)	2066	if (timeout >= 0)
1875	// create/start timer	2067	// create/start timer
1876		2068
1877	// poll	2069	// poll
1878	ev_loop (EV_A_ 0);	2070	ev_loop (EV_A_ 0);
1879		2071
1880	// stop timer again	2072	// stop timer again
1881	if (timeout >= 0)	2073	if (timeout >= 0)
1882	ev_timer_stop (EV_A_ &to);	2074	ev_timer_stop (EV_A_ &to);
1883		2075
1884	// stop io watchers again - their callbacks should have set	2076	// stop io watchers again - their callbacks should have set
1885	for (n = 0; n < nfds; ++n)	2077	for (n = 0; n < nfds; ++n)
1886	ev_io_stop (EV_A_ iow [n]);	2078	ev_io_stop (EV_A_ iow [n]);
1887		2079
1888	return got_events;	2080	return got_events;
1889	}	2081	}
1890		2082
1891		2083
1892	=head2 C<ev_embed> - when one backend isn't enough...	2084	=head2 C<ev_embed> - when one backend isn't enough...
1893		2085
1894	This is a rather advanced watcher type that lets you embed one event loop	2086	This is a rather advanced watcher type that lets you embed one event loop
…		…
1950		2142
1951	Configures the watcher to embed the given loop, which must be	2143	Configures the watcher to embed the given loop, which must be
1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2144	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1953	invoked automatically, otherwise it is the responsibility of the callback	2145	invoked automatically, otherwise it is the responsibility of the callback
1954	to invoke it (it will continue to be called until the sweep has been done,	2146	to invoke it (it will continue to be called until the sweep has been done,
1955	if you do not want thta, you need to temporarily stop the embed watcher).	2147	if you do not want that, you need to temporarily stop the embed watcher).
1956		2148
1957	=item ev_embed_sweep (loop, ev_embed *)	2149	=item ev_embed_sweep (loop, ev_embed *)
1958		2150
1959	Make a single, non-blocking sweep over the embedded loop. This works	2151	Make a single, non-blocking sweep over the embedded loop. This works
1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2152	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1961	apropriate way for embedded loops.	2153	appropriate way for embedded loops.
1962		2154
1963	=item struct ev_loop *other [read-only]	2155	=item struct ev_loop *other [read-only]
1964		2156
1965	The embedded event loop.	2157	The embedded event loop.
1966		2158
…		…
1968		2160
1969	=head3 Examples	2161	=head3 Examples
1970		2162
1971	Example: Try to get an embeddable event loop and embed it into the default	2163	Example: Try to get an embeddable event loop and embed it into the default
1972	event loop. If that is not possible, use the default loop. The default	2164	event loop. If that is not possible, use the default loop. The default
1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2165	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1975	used).	2167	used).
1976		2168
1977	struct ev_loop *loop_hi = ev_default_init (0);	2169	struct ev_loop *loop_hi = ev_default_init (0);
1978	struct ev_loop *loop_lo = 0;	2170	struct ev_loop *loop_lo = 0;
1979	struct ev_embed embed;	2171	struct ev_embed embed;
1980		2172
1981	// see if there is a chance of getting one that works	2173	// see if there is a chance of getting one that works
1982	// (remember that a flags value of 0 means autodetection)	2174	// (remember that a flags value of 0 means autodetection)
1983	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1984	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1985	: 0;	2177	: 0;
1986		2178
1987	// if we got one, then embed it, otherwise default to loop_hi	2179	// if we got one, then embed it, otherwise default to loop_hi
1988	if (loop_lo)	2180	if (loop_lo)
1989	{	2181	{
1990	ev_embed_init (&embed, 0, loop_lo);	2182	ev_embed_init (&embed, 0, loop_lo);
1991	ev_embed_start (loop_hi, &embed);	2183	ev_embed_start (loop_hi, &embed);
1992	}	2184	}
1993	else	2185	else
1994	loop_lo = loop_hi;	2186	loop_lo = loop_hi;
1995		2187
1996	Example: Check if kqueue is available but not recommended and create	2188	Example: Check if kqueue is available but not recommended and create
1997	a kqueue backend for use with sockets (which usually work with any	2189	a kqueue backend for use with sockets (which usually work with any
1998	kqueue implementation). Store the kqueue/socket-only event loop in	2190	kqueue implementation). Store the kqueue/socket-only event loop in
1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2000		2192
2001	struct ev_loop *loop = ev_default_init (0);	2193	struct ev_loop *loop = ev_default_init (0);
2002	struct ev_loop *loop_socket = 0;	2194	struct ev_loop *loop_socket = 0;
2003	struct ev_embed embed;	2195	struct ev_embed embed;
2004		2196
2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2007	{	2199	{
2008	ev_embed_init (&embed, 0, loop_socket);	2200	ev_embed_init (&embed, 0, loop_socket);
2009	ev_embed_start (loop, &embed);	2201	ev_embed_start (loop, &embed);
2010	}	2202	}
2011		2203
2012	if (!loop_socket)	2204	if (!loop_socket)
2013	loop_socket = loop;	2205	loop_socket = loop;
2014		2206
2015	// now use loop_socket for all sockets, and loop for everything else	2207	// now use loop_socket for all sockets, and loop for everything else
2016		2208
2017		2209
2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2210	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2019		2211
2020	Fork watchers are called when a C<fork ()> was detected (usually because	2212	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2036	believe me.	2228	believe me.
2037		2229
2038	=back	2230	=back
2039		2231
2040		2232
		2233	=head2 C<ev_async> - how to wake up another event loop
		2234
		2235	In general, you cannot use an C<ev_loop> from multiple threads or other
		2236	asynchronous sources such as signal handlers (as opposed to multiple event
		2237	loops - those are of course safe to use in different threads).
		2238
		2239	Sometimes, however, you need to wake up another event loop you do not
		2240	control, for example because it belongs to another thread. This is what
		2241	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2242	can signal it by calling C<ev_async_send>, which is thread- and signal
		2243	safe.
		2244
		2245	This functionality is very similar to C<ev_signal> watchers, as signals,
		2246	too, are asynchronous in nature, and signals, too, will be compressed
		2247	(i.e. the number of callback invocations may be less than the number of
		2248	C<ev_async_sent> calls).
		2249
		2250	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2251	just the default loop.
		2252
		2253	=head3 Queueing
		2254
		2255	C<ev_async> does not support queueing of data in any way. The reason
		2256	is that the author does not know of a simple (or any) algorithm for a
		2257	multiple-writer-single-reader queue that works in all cases and doesn't
		2258	need elaborate support such as pthreads.
		2259
		2260	That means that if you want to queue data, you have to provide your own
		2261	queue. But at least I can tell you would implement locking around your
		2262	queue:
		2263
		2264	=over 4
		2265
		2266	=item queueing from a signal handler context
		2267
		2268	To implement race-free queueing, you simply add to the queue in the signal
		2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2270	some fictitious SIGUSR1 handler:
		2271
		2272	static ev_async mysig;
		2273
		2274	static void
		2275	sigusr1_handler (void)
		2276	{
		2277	sometype data;
		2278
		2279	// no locking etc.
		2280	queue_put (data);
		2281	ev_async_send (EV_DEFAULT_ &mysig);
		2282	}
		2283
		2284	static void
		2285	mysig_cb (EV_P_ ev_async *w, int revents)
		2286	{
		2287	sometype data;
		2288	sigset_t block, prev;
		2289
		2290	sigemptyset (&block);
		2291	sigaddset (&block, SIGUSR1);
		2292	sigprocmask (SIG_BLOCK, &block, &prev);
		2293
		2294	while (queue_get (&data))
		2295	process (data);
		2296
		2297	if (sigismember (&prev, SIGUSR1)
		2298	sigprocmask (SIG_UNBLOCK, &block, 0);
		2299	}
		2300
		2301	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2302	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2303	either...).
		2304
		2305	=item queueing from a thread context
		2306
		2307	The strategy for threads is different, as you cannot (easily) block
		2308	threads but you can easily preempt them, so to queue safely you need to
		2309	employ a traditional mutex lock, such as in this pthread example:
		2310
		2311	static ev_async mysig;
		2312	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2313
		2314	static void
		2315	otherthread (void)
		2316	{
		2317	// only need to lock the actual queueing operation
		2318	pthread_mutex_lock (&mymutex);
		2319	queue_put (data);
		2320	pthread_mutex_unlock (&mymutex);
		2321
		2322	ev_async_send (EV_DEFAULT_ &mysig);
		2323	}
		2324
		2325	static void
		2326	mysig_cb (EV_P_ ev_async *w, int revents)
		2327	{
		2328	pthread_mutex_lock (&mymutex);
		2329
		2330	while (queue_get (&data))
		2331	process (data);
		2332
		2333	pthread_mutex_unlock (&mymutex);
		2334	}
		2335
		2336	=back
		2337
		2338
		2339	=head3 Watcher-Specific Functions and Data Members
		2340
		2341	=over 4
		2342
		2343	=item ev_async_init (ev_async *, callback)
		2344
		2345	Initialises and configures the async watcher - it has no parameters of any
		2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2347	believe me.
		2348
		2349	=item ev_async_send (loop, ev_async *)
		2350
		2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2353	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2355	section below on what exactly this means).
		2356
		2357	This call incurs the overhead of a system call only once per loop iteration,
		2358	so while the overhead might be noticeable, it doesn't apply to repeated
		2359	calls to C<ev_async_send>.
		2360
		2361	=item bool = ev_async_pending (ev_async *)
		2362
		2363	Returns a non-zero value when C<ev_async_send> has been called on the
		2364	watcher but the event has not yet been processed (or even noted) by the
		2365	event loop.
		2366
		2367	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2368	the loop iterates next and checks for the watcher to have become active,
		2369	it will reset the flag again. C<ev_async_pending> can be used to very
		2370	quickly check whether invoking the loop might be a good idea.
		2371
		2372	Not that this does I<not> check whether the watcher itself is pending, only
		2373	whether it has been requested to make this watcher pending.
		2374
		2375	=back
		2376
		2377
2041	=head1 OTHER FUNCTIONS	2378	=head1 OTHER FUNCTIONS
2042		2379
2043	There are some other functions of possible interest. Described. Here. Now.	2380	There are some other functions of possible interest. Described. Here. Now.
2044		2381
2045	=over 4	2382	=over 4
…		…
2052	or timeout without having to allocate/configure/start/stop/free one or	2389	or timeout without having to allocate/configure/start/stop/free one or
2053	more watchers yourself.	2390	more watchers yourself.
2054		2391
2055	If C<fd> is less than 0, then no I/O watcher will be started and events	2392	If C<fd> is less than 0, then no I/O watcher will be started and events
2056	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2057	C<events> set will be craeted and started.	2394	C<events> set will be created and started.
2058		2395
2059	If C<timeout> is less than 0, then no timeout watcher will be	2396	If C<timeout> is less than 0, then no timeout watcher will be
2060	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2061	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2062	dubious value.	2399	dubious value.
…		…
2064	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2065	passed an C<revents> set like normal event callbacks (a combination of	2402	passed an C<revents> set like normal event callbacks (a combination of
2066	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2067	value passed to C<ev_once>:	2404	value passed to C<ev_once>:
2068		2405
2069	static void stdin_ready (int revents, void *arg)	2406	static void stdin_ready (int revents, void *arg)
2070	{	2407	{
2071	if (revents & EV_TIMEOUT)	2408	if (revents & EV_TIMEOUT)
2072	/* doh, nothing entered */;	2409	/* doh, nothing entered */;
2073	else if (revents & EV_READ)	2410	else if (revents & EV_READ)
2074	/* stdin might have data for us, joy! */;	2411	/* stdin might have data for us, joy! */;
2075	}	2412	}
2076		2413
2077	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2078		2415
2079	=item ev_feed_event (ev_loop *, watcher *, int revents)	2416	=item ev_feed_event (ev_loop *, watcher *, int revents)
2080		2417
2081	Feeds the given event set into the event loop, as if the specified event	2418	Feeds the given event set into the event loop, as if the specified event
2082	had happened for the specified watcher (which must be a pointer to an	2419	had happened for the specified watcher (which must be a pointer to an
…		…
2087	Feed an event on the given fd, as if a file descriptor backend detected	2424	Feed an event on the given fd, as if a file descriptor backend detected
2088	the given events it.	2425	the given events it.
2089		2426
2090	=item ev_feed_signal_event (ev_loop *loop, int signum)	2427	=item ev_feed_signal_event (ev_loop *loop, int signum)
2091		2428
2092	Feed an event as if the given signal occured (C<loop> must be the default	2429	Feed an event as if the given signal occurred (C<loop> must be the default
2093	loop!).	2430	loop!).
2094		2431
2095	=back	2432	=back
2096		2433
2097		2434
…		…
2113		2450
2114	=item * Priorities are not currently supported. Initialising priorities	2451	=item * Priorities are not currently supported. Initialising priorities
2115	will fail and all watchers will have the same priority, even though there	2452	will fail and all watchers will have the same priority, even though there
2116	is an ev_pri field.	2453	is an ev_pri field.
2117		2454
		2455	=item * In libevent, the last base created gets the signals, in libev, the
		2456	first base created (== the default loop) gets the signals.
		2457
2118	=item * Other members are not supported.	2458	=item * Other members are not supported.
2119		2459
2120	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2460	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2121	to use the libev header file and library.	2461	to use the libev header file and library.
2122		2462
2123	=back	2463	=back
2124		2464
2125	=head1 C++ SUPPORT	2465	=head1 C++ SUPPORT
2126		2466
2127	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2467	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2128	you to use some convinience methods to start/stop watchers and also change	2468	you to use some convenience methods to start/stop watchers and also change
2129	the callback model to a model using method callbacks on objects.	2469	the callback model to a model using method callbacks on objects.
2130		2470
2131	To use it,	2471	To use it,
2132		2472
2133	#include <ev++.h>	2473	#include <ev++.h>
2134		2474
2135	This automatically includes F<ev.h> and puts all of its definitions (many	2475	This automatically includes F<ev.h> and puts all of its definitions (many
2136	of them macros) into the global namespace. All C++ specific things are	2476	of them macros) into the global namespace. All C++ specific things are
2137	put into the C<ev> namespace. It should support all the same embedding	2477	put into the C<ev> namespace. It should support all the same embedding
2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2478	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2205	your compiler is good :), then the method will be fully inlined into the	2545	your compiler is good :), then the method will be fully inlined into the
2206	thunking function, making it as fast as a direct C callback.	2546	thunking function, making it as fast as a direct C callback.
2207		2547
2208	Example: simple class declaration and watcher initialisation	2548	Example: simple class declaration and watcher initialisation
2209		2549
2210	struct myclass	2550	struct myclass
2211	{	2551	{
2212	void io_cb (ev::io &w, int revents) { }	2552	void io_cb (ev::io &w, int revents) { }
2213	}	2553	}
2214		2554
2215	myclass obj;	2555	myclass obj;
2216	ev::io iow;	2556	ev::io iow;
2217	iow.set <myclass, &myclass::io_cb> (&obj);	2557	iow.set <myclass, &myclass::io_cb> (&obj);
2218		2558
2219	=item w->set<function> (void *data = 0)	2559	=item w->set<function> (void *data = 0)
2220		2560
2221	Also sets a callback, but uses a static method or plain function as	2561	Also sets a callback, but uses a static method or plain function as
2222	callback. The optional C<data> argument will be stored in the watcher's	2562	callback. The optional C<data> argument will be stored in the watcher's
…		…
2226		2566
2227	See the method-C<set> above for more details.	2567	See the method-C<set> above for more details.
2228		2568
2229	Example:	2569	Example:
2230		2570
2231	static void io_cb (ev::io &w, int revents) { }	2571	static void io_cb (ev::io &w, int revents) { }
2232	iow.set <io_cb> ();	2572	iow.set <io_cb> ();
2233		2573
2234	=item w->set (struct ev_loop *)	2574	=item w->set (struct ev_loop *)
2235		2575
2236	Associates a different C<struct ev_loop> with this watcher. You can only	2576	Associates a different C<struct ev_loop> with this watcher. You can only
2237	do this when the watcher is inactive (and not pending either).	2577	do this when the watcher is inactive (and not pending either).
2238		2578
2239	=item w->set ([args])	2579	=item w->set ([arguments])
2240		2580
2241	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2581	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2242	called at least once. Unlike the C counterpart, an active watcher gets	2582	called at least once. Unlike the C counterpart, an active watcher gets
2243	automatically stopped and restarted when reconfiguring it with this	2583	automatically stopped and restarted when reconfiguring it with this
2244	method.	2584	method.
2245		2585
2246	=item w->start ()	2586	=item w->start ()
…		…
2270	=back	2610	=back
2271		2611
2272	Example: Define a class with an IO and idle watcher, start one of them in	2612	Example: Define a class with an IO and idle watcher, start one of them in
2273	the constructor.	2613	the constructor.
2274		2614
2275	class myclass	2615	class myclass
2276	{	2616	{
2277	ev_io io; void io_cb (ev::io &w, int revents);	2617	ev::io io; void io_cb (ev::io &w, int revents);
2278	ev_idle idle void idle_cb (ev::idle &w, int revents);	2618	ev:idle idle void idle_cb (ev::idle &w, int revents);
2279		2619
2280	myclass ();	2620	myclass (int fd)
2281	}	2621	{
2282
2283	myclass::myclass (int fd)
2284	{
2285	io .set <myclass, &myclass::io_cb > (this);	2622	io .set <myclass, &myclass::io_cb > (this);
2286	idle.set <myclass, &myclass::idle_cb> (this);	2623	idle.set <myclass, &myclass::idle_cb> (this);
2287		2624
2288	io.start (fd, ev::READ);	2625	io.start (fd, ev::READ);
		2626	}
2289	}	2627	};
		2628
		2629
		2630	=head1 OTHER LANGUAGE BINDINGS
		2631
		2632	Libev does not offer other language bindings itself, but bindings for a
		2633	number of languages exist in the form of third-party packages. If you know
		2634	any interesting language binding in addition to the ones listed here, drop
		2635	me a note.
		2636
		2637	=over 4
		2638
		2639	=item Perl
		2640
		2641	The EV module implements the full libev API and is actually used to test
		2642	libev. EV is developed together with libev. Apart from the EV core module,
		2643	there are additional modules that implement libev-compatible interfaces
		2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2646
		2647	It can be found and installed via CPAN, its homepage is at
		2648	L<http://software.schmorp.de/pkg/EV>.
		2649
		2650	=item Python
		2651
		2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2653	seems to be quite complete and well-documented. Note, however, that the
		2654	patch they require for libev is outright dangerous as it breaks the ABI
		2655	for everybody else, and therefore, should never be applied in an installed
		2656	libev (if python requires an incompatible ABI then it needs to embed
		2657	libev).
		2658
		2659	=item Ruby
		2660
		2661	Tony Arcieri has written a ruby extension that offers access to a subset
		2662	of the libev API and adds file handle abstractions, asynchronous DNS and
		2663	more on top of it. It can be found via gem servers. Its homepage is at
		2664	L<http://rev.rubyforge.org/>.
		2665
		2666	=item D
		2667
		2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2670
		2671	=back
2290		2672
2291		2673
2292	=head1 MACRO MAGIC	2674	=head1 MACRO MAGIC
2293		2675
2294	Libev can be compiled with a variety of options, the most fundamantal	2676	Libev can be compiled with a variety of options, the most fundamental
2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2677	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2296	functions and callbacks have an initial C<struct ev_loop *> argument.	2678	functions and callbacks have an initial C<struct ev_loop *> argument.
2297		2679
2298	To make it easier to write programs that cope with either variant, the	2680	To make it easier to write programs that cope with either variant, the
2299	following macros are defined:	2681	following macros are defined:
…		…
2304		2686
2305	This provides the loop I<argument> for functions, if one is required ("ev	2687	This provides the loop I<argument> for functions, if one is required ("ev
2306	loop argument"). The C<EV_A> form is used when this is the sole argument,	2688	loop argument"). The C<EV_A> form is used when this is the sole argument,
2307	C<EV_A_> is used when other arguments are following. Example:	2689	C<EV_A_> is used when other arguments are following. Example:
2308		2690
2309	ev_unref (EV_A);	2691	ev_unref (EV_A);
2310	ev_timer_add (EV_A_ watcher);	2692	ev_timer_add (EV_A_ watcher);
2311	ev_loop (EV_A_ 0);	2693	ev_loop (EV_A_ 0);
2312		2694
2313	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2695	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2314	which is often provided by the following macro.	2696	which is often provided by the following macro.
2315		2697
2316	=item C<EV_P>, C<EV_P_>	2698	=item C<EV_P>, C<EV_P_>
2317		2699
2318	This provides the loop I<parameter> for functions, if one is required ("ev	2700	This provides the loop I<parameter> for functions, if one is required ("ev
2319	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2701	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2320	C<EV_P_> is used when other parameters are following. Example:	2702	C<EV_P_> is used when other parameters are following. Example:
2321		2703
2322	// this is how ev_unref is being declared	2704	// this is how ev_unref is being declared
2323	static void ev_unref (EV_P);	2705	static void ev_unref (EV_P);
2324		2706
2325	// this is how you can declare your typical callback	2707	// this is how you can declare your typical callback
2326	static void cb (EV_P_ ev_timer *w, int revents)	2708	static void cb (EV_P_ ev_timer *w, int revents)
2327		2709
2328	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2710	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2329	suitable for use with C<EV_A>.	2711	suitable for use with C<EV_A>.
2330		2712
2331	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2713	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2332		2714
2333	Similar to the other two macros, this gives you the value of the default	2715	Similar to the other two macros, this gives you the value of the default
2334	loop, if multiple loops are supported ("ev loop default").	2716	loop, if multiple loops are supported ("ev loop default").
		2717
		2718	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2719
		2720	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2721	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2722	is undefined when the default loop has not been initialised by a previous
		2723	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2724
		2725	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2726	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2335		2727
2336	=back	2728	=back
2337		2729
2338	Example: Declare and initialise a check watcher, utilising the above	2730	Example: Declare and initialise a check watcher, utilising the above
2339	macros so it will work regardless of whether multiple loops are supported	2731	macros so it will work regardless of whether multiple loops are supported
2340	or not.	2732	or not.
2341		2733
2342	static void	2734	static void
2343	check_cb (EV_P_ ev_timer *w, int revents)	2735	check_cb (EV_P_ ev_timer *w, int revents)
2344	{	2736	{
2345	ev_check_stop (EV_A_ w);	2737	ev_check_stop (EV_A_ w);
2346	}	2738	}
2347		2739
2348	ev_check check;	2740	ev_check check;
2349	ev_check_init (&check, check_cb);	2741	ev_check_init (&check, check_cb);
2350	ev_check_start (EV_DEFAULT_ &check);	2742	ev_check_start (EV_DEFAULT_ &check);
2351	ev_loop (EV_DEFAULT_ 0);	2743	ev_loop (EV_DEFAULT_ 0);
2352		2744
2353	=head1 EMBEDDING	2745	=head1 EMBEDDING
2354		2746
2355	Libev can (and often is) directly embedded into host	2747	Libev can (and often is) directly embedded into host
2356	applications. Examples of applications that embed it include the Deliantra	2748	applications. Examples of applications that embed it include the Deliantra
…		…
2363	libev somewhere in your source tree).	2755	libev somewhere in your source tree).
2364		2756
2365	=head2 FILESETS	2757	=head2 FILESETS
2366		2758
2367	Depending on what features you need you need to include one or more sets of files	2759	Depending on what features you need you need to include one or more sets of files
2368	in your app.	2760	in your application.
2369		2761
2370	=head3 CORE EVENT LOOP	2762	=head3 CORE EVENT LOOP
2371		2763
2372	To include only the libev core (all the C<ev_*> functions), with manual	2764	To include only the libev core (all the C<ev_*> functions), with manual
2373	configuration (no autoconf):	2765	configuration (no autoconf):
2374		2766
2375	#define EV_STANDALONE 1	2767	#define EV_STANDALONE 1
2376	#include "ev.c"	2768	#include "ev.c"
2377		2769
2378	This will automatically include F<ev.h>, too, and should be done in a	2770	This will automatically include F<ev.h>, too, and should be done in a
2379	single C source file only to provide the function implementations. To use	2771	single C source file only to provide the function implementations. To use
2380	it, do the same for F<ev.h> in all files wishing to use this API (best	2772	it, do the same for F<ev.h> in all files wishing to use this API (best
2381	done by writing a wrapper around F<ev.h> that you can include instead and	2773	done by writing a wrapper around F<ev.h> that you can include instead and
2382	where you can put other configuration options):	2774	where you can put other configuration options):
2383		2775
2384	#define EV_STANDALONE 1	2776	#define EV_STANDALONE 1
2385	#include "ev.h"	2777	#include "ev.h"
2386		2778
2387	Both header files and implementation files can be compiled with a C++	2779	Both header files and implementation files can be compiled with a C++
2388	compiler (at least, thats a stated goal, and breakage will be treated	2780	compiler (at least, thats a stated goal, and breakage will be treated
2389	as a bug).	2781	as a bug).
2390		2782
2391	You need the following files in your source tree, or in a directory	2783	You need the following files in your source tree, or in a directory
2392	in your include path (e.g. in libev/ when using -Ilibev):	2784	in your include path (e.g. in libev/ when using -Ilibev):
2393		2785
2394	ev.h	2786	ev.h
2395	ev.c	2787	ev.c
2396	ev_vars.h	2788	ev_vars.h
2397	ev_wrap.h	2789	ev_wrap.h
2398		2790
2399	ev_win32.c required on win32 platforms only	2791	ev_win32.c required on win32 platforms only
2400		2792
2401	ev_select.c only when select backend is enabled (which is enabled by default)	2793	ev_select.c only when select backend is enabled (which is enabled by default)
2402	ev_poll.c only when poll backend is enabled (disabled by default)	2794	ev_poll.c only when poll backend is enabled (disabled by default)
2403	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2795	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2404	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2796	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2405	ev_port.c only when the solaris port backend is enabled (disabled by default)	2797	ev_port.c only when the solaris port backend is enabled (disabled by default)
2406		2798
2407	F<ev.c> includes the backend files directly when enabled, so you only need	2799	F<ev.c> includes the backend files directly when enabled, so you only need
2408	to compile this single file.	2800	to compile this single file.
2409		2801
2410	=head3 LIBEVENT COMPATIBILITY API	2802	=head3 LIBEVENT COMPATIBILITY API
2411		2803
2412	To include the libevent compatibility API, also include:	2804	To include the libevent compatibility API, also include:
2413		2805
2414	#include "event.c"	2806	#include "event.c"
2415		2807
2416	in the file including F<ev.c>, and:	2808	in the file including F<ev.c>, and:
2417		2809
2418	#include "event.h"	2810	#include "event.h"
2419		2811
2420	in the files that want to use the libevent API. This also includes F<ev.h>.	2812	in the files that want to use the libevent API. This also includes F<ev.h>.
2421		2813
2422	You need the following additional files for this:	2814	You need the following additional files for this:
2423		2815
2424	event.h	2816	event.h
2425	event.c	2817	event.c
2426		2818
2427	=head3 AUTOCONF SUPPORT	2819	=head3 AUTOCONF SUPPORT
2428		2820
2429	Instead of using C<EV_STANDALONE=1> and providing your config in	2821	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2430	whatever way you want, you can also C<m4_include([libev.m4])> in your	2822	whatever way you want, you can also C<m4_include([libev.m4])> in your
2431	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2823	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2432	include F<config.h> and configure itself accordingly.	2824	include F<config.h> and configure itself accordingly.
2433		2825
2434	For this of course you need the m4 file:	2826	For this of course you need the m4 file:
2435		2827
2436	libev.m4	2828	libev.m4
2437		2829
2438	=head2 PREPROCESSOR SYMBOLS/MACROS	2830	=head2 PREPROCESSOR SYMBOLS/MACROS
2439		2831
2440	Libev can be configured via a variety of preprocessor symbols you have to define	2832	Libev can be configured via a variety of preprocessor symbols you have to
2441	before including any of its files. The default is not to build for multiplicity	2833	define before including any of its files. The default in the absence of
2442	and only include the select backend.	2834	autoconf is noted for every option.
2443		2835
2444	=over 4	2836	=over 4
2445		2837
2446	=item EV_STANDALONE	2838	=item EV_STANDALONE
2447		2839
…		…
2452	F<event.h> that are not directly supported by the libev core alone.	2844	F<event.h> that are not directly supported by the libev core alone.
2453		2845
2454	=item EV_USE_MONOTONIC	2846	=item EV_USE_MONOTONIC
2455		2847
2456	If defined to be C<1>, libev will try to detect the availability of the	2848	If defined to be C<1>, libev will try to detect the availability of the
2457	monotonic clock option at both compiletime and runtime. Otherwise no use	2849	monotonic clock option at both compile time and runtime. Otherwise no use
2458	of the monotonic clock option will be attempted. If you enable this, you	2850	of the monotonic clock option will be attempted. If you enable this, you
2459	usually have to link against librt or something similar. Enabling it when	2851	usually have to link against librt or something similar. Enabling it when
2460	the functionality isn't available is safe, though, although you have	2852	the functionality isn't available is safe, though, although you have
2461	to make sure you link against any libraries where the C<clock_gettime>	2853	to make sure you link against any libraries where the C<clock_gettime>
2462	function is hiding in (often F<-lrt>).	2854	function is hiding in (often F<-lrt>).
2463		2855
2464	=item EV_USE_REALTIME	2856	=item EV_USE_REALTIME
2465		2857
2466	If defined to be C<1>, libev will try to detect the availability of the	2858	If defined to be C<1>, libev will try to detect the availability of the
2467	realtime clock option at compiletime (and assume its availability at	2859	real-time clock option at compile time (and assume its availability at
2468	runtime if successful). Otherwise no use of the realtime clock option will	2860	runtime if successful). Otherwise no use of the real-time clock option will
2469	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2472		2864
2473	=item EV_USE_NANOSLEEP	2865	=item EV_USE_NANOSLEEP
2474		2866
2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2476	and will use it for delays. Otherwise it will use C<select ()>.	2868	and will use it for delays. Otherwise it will use C<select ()>.
2477		2869
		2870	=item EV_USE_EVENTFD
		2871
		2872	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2873	available and will probe for kernel support at runtime. This will improve
		2874	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2875	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2876	2.7 or newer, otherwise disabled.
		2877
2478	=item EV_USE_SELECT	2878	=item EV_USE_SELECT
2479		2879
2480	If undefined or defined to be C<1>, libev will compile in support for the	2880	If undefined or defined to be C<1>, libev will compile in support for the
2481	C<select>(2) backend. No attempt at autodetection will be done: if no	2881	C<select>(2) backend. No attempt at auto-detection will be done: if no
2482	other method takes over, select will be it. Otherwise the select backend	2882	other method takes over, select will be it. Otherwise the select backend
2483	will not be compiled in.	2883	will not be compiled in.
2484		2884
2485	=item EV_SELECT_USE_FD_SET	2885	=item EV_SELECT_USE_FD_SET
2486		2886
2487	If defined to C<1>, then the select backend will use the system C<fd_set>	2887	If defined to C<1>, then the select backend will use the system C<fd_set>
2488	structure. This is useful if libev doesn't compile due to a missing	2888	structure. This is useful if libev doesn't compile due to a missing
2489	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2889	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2490	exotic systems. This usually limits the range of file descriptors to some	2890	exotic systems. This usually limits the range of file descriptors to some
2491	low limit such as 1024 or might have other limitations (winsocket only	2891	low limit such as 1024 or might have other limitations (winsocket only
2492	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2493	influence the size of the C<fd_set> used.	2893	influence the size of the C<fd_set> used.
2494		2894
…		…
2518		2918
2519	=item EV_USE_EPOLL	2919	=item EV_USE_EPOLL
2520		2920
2521	If defined to be C<1>, libev will compile in support for the Linux	2921	If defined to be C<1>, libev will compile in support for the Linux
2522	C<epoll>(7) backend. Its availability will be detected at runtime,	2922	C<epoll>(7) backend. Its availability will be detected at runtime,
2523	otherwise another method will be used as fallback. This is the	2923	otherwise another method will be used as fallback. This is the preferred
2524	preferred backend for GNU/Linux systems.	2924	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2925	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2525		2926
2526	=item EV_USE_KQUEUE	2927	=item EV_USE_KQUEUE
2527		2928
2528	If defined to be C<1>, libev will compile in support for the BSD style	2929	If defined to be C<1>, libev will compile in support for the BSD style
2529	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2930	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2542	otherwise another method will be used as fallback. This is the preferred	2943	otherwise another method will be used as fallback. This is the preferred
2543	backend for Solaris 10 systems.	2944	backend for Solaris 10 systems.
2544		2945
2545	=item EV_USE_DEVPOLL	2946	=item EV_USE_DEVPOLL
2546		2947
2547	reserved for future expansion, works like the USE symbols above.	2948	Reserved for future expansion, works like the USE symbols above.
2548		2949
2549	=item EV_USE_INOTIFY	2950	=item EV_USE_INOTIFY
2550		2951
2551	If defined to be C<1>, libev will compile in support for the Linux inotify	2952	If defined to be C<1>, libev will compile in support for the Linux inotify
2552	interface to speed up C<ev_stat> watchers. Its actual availability will	2953	interface to speed up C<ev_stat> watchers. Its actual availability will
2553	be detected at runtime.	2954	be detected at runtime. If undefined, it will be enabled if the headers
		2955	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2956
		2957	=item EV_ATOMIC_T
		2958
		2959	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2960	access is atomic with respect to other threads or signal contexts. No such
		2961	type is easily found in the C language, so you can provide your own type
		2962	that you know is safe for your purposes. It is used both for signal handler "locking"
		2963	as well as for signal and thread safety in C<ev_async> watchers.
		2964
		2965	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2966	(from F<signal.h>), which is usually good enough on most platforms.
2554		2967
2555	=item EV_H	2968	=item EV_H
2556		2969
2557	The name of the F<ev.h> header file used to include it. The default if	2970	The name of the F<ev.h> header file used to include it. The default if
2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2971	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2559	virtually rename the F<ev.h> header file in case of conflicts.	2972	used to virtually rename the F<ev.h> header file in case of conflicts.
2560		2973
2561	=item EV_CONFIG_H	2974	=item EV_CONFIG_H
2562		2975
2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2976	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2977	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2565	C<EV_H>, above.	2978	C<EV_H>, above.
2566		2979
2567	=item EV_EVENT_H	2980	=item EV_EVENT_H
2568		2981
2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2982	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2983	of how the F<event.h> header can be found, the default is C<"event.h">.
2571		2984
2572	=item EV_PROTOTYPES	2985	=item EV_PROTOTYPES
2573		2986
2574	If defined to be C<0>, then F<ev.h> will not define any function	2987	If defined to be C<0>, then F<ev.h> will not define any function
2575	prototypes, but still define all the structs and other symbols. This is	2988	prototypes, but still define all the structs and other symbols. This is
…		…
2596	When doing priority-based operations, libev usually has to linearly search	3009	When doing priority-based operations, libev usually has to linearly search
2597	all the priorities, so having many of them (hundreds) uses a lot of space	3010	all the priorities, so having many of them (hundreds) uses a lot of space
2598	and time, so using the defaults of five priorities (-2 .. +2) is usually	3011	and time, so using the defaults of five priorities (-2 .. +2) is usually
2599	fine.	3012	fine.
2600		3013
2601	If your embedding app does not need any priorities, defining these both to	3014	If your embedding application does not need any priorities, defining these both to
2602	C<0> will save some memory and cpu.	3015	C<0> will save some memory and CPU.
2603		3016
2604	=item EV_PERIODIC_ENABLE	3017	=item EV_PERIODIC_ENABLE
2605		3018
2606	If undefined or defined to be C<1>, then periodic timers are supported. If	3019	If undefined or defined to be C<1>, then periodic timers are supported. If
2607	defined to be C<0>, then they are not. Disabling them saves a few kB of	3020	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2626	=item EV_FORK_ENABLE	3039	=item EV_FORK_ENABLE
2627		3040
2628	If undefined or defined to be C<1>, then fork watchers are supported. If	3041	If undefined or defined to be C<1>, then fork watchers are supported. If
2629	defined to be C<0>, then they are not.	3042	defined to be C<0>, then they are not.
2630		3043
		3044	=item EV_ASYNC_ENABLE
		3045
		3046	If undefined or defined to be C<1>, then async watchers are supported. If
		3047	defined to be C<0>, then they are not.
		3048
2631	=item EV_MINIMAL	3049	=item EV_MINIMAL
2632		3050
2633	If you need to shave off some kilobytes of code at the expense of some	3051	If you need to shave off some kilobytes of code at the expense of some
2634	speed, define this symbol to C<1>. Currently only used for gcc to override	3052	speed, define this symbol to C<1>. Currently this is used to override some
2635	some inlining decisions, saves roughly 30% codesize of amd64.	3053	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3054	much smaller 2-heap for timer management over the default 4-heap.
2636		3055
2637	=item EV_PID_HASHSIZE	3056	=item EV_PID_HASHSIZE
2638		3057
2639	C<ev_child> watchers use a small hash table to distribute workload by	3058	C<ev_child> watchers use a small hash table to distribute workload by
2640	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3059	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2647	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3066	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2648	usually more than enough. If you need to manage thousands of C<ev_stat>	3067	usually more than enough. If you need to manage thousands of C<ev_stat>
2649	watchers you might want to increase this value (I<must> be a power of	3068	watchers you might want to increase this value (I<must> be a power of
2650	two).	3069	two).
2651		3070
		3071	=item EV_USE_4HEAP
		3072
		3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3075	to C<1>. The 4-heap uses more complicated (longer) code but has
		3076	noticeably faster performance with many (thousands) of watchers.
		3077
		3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3079	(disabled).
		3080
		3081	=item EV_HEAP_CACHE_AT
		3082
		3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3084	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3087	but avoids random read accesses on heap changes. This improves performance
		3088	noticeably with with many (hundreds) of watchers.
		3089
		3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3091	(disabled).
		3092
		3093	=item EV_VERIFY
		3094
		3095	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3096	be done: If set to C<0>, no internal verification code will be compiled
		3097	in. If set to C<1>, then verification code will be compiled in, but not
		3098	called. If set to C<2>, then the internal verification code will be
		3099	called once per loop, which can slow down libev. If set to C<3>, then the
		3100	verification code will be called very frequently, which will slow down
		3101	libev considerably.
		3102
		3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3104	C<0.>
		3105
2652	=item EV_COMMON	3106	=item EV_COMMON
2653		3107
2654	By default, all watchers have a C<void *data> member. By redefining	3108	By default, all watchers have a C<void *data> member. By redefining
2655	this macro to a something else you can include more and other types of	3109	this macro to a something else you can include more and other types of
2656	members. You have to define it each time you include one of the files,	3110	members. You have to define it each time you include one of the files,
2657	though, and it must be identical each time.	3111	though, and it must be identical each time.
2658		3112
2659	For example, the perl EV module uses something like this:	3113	For example, the perl EV module uses something like this:
2660		3114
2661	#define EV_COMMON \	3115	#define EV_COMMON \
2662	SV *self; /* contains this struct */ \	3116	SV *self; /* contains this struct */ \
2663	SV *cb_sv, *fh /* note no trailing ";" */	3117	SV *cb_sv, *fh /* note no trailing ";" */
2664		3118
2665	=item EV_CB_DECLARE (type)	3119	=item EV_CB_DECLARE (type)
2666		3120
2667	=item EV_CB_INVOKE (watcher, revents)	3121	=item EV_CB_INVOKE (watcher, revents)
2668		3122
…		…
2675	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2676	method calls instead of plain function calls in C++.	3130	method calls instead of plain function calls in C++.
2677		3131
2678	=head2 EXPORTED API SYMBOLS	3132	=head2 EXPORTED API SYMBOLS
2679		3133
2680	If you need to re-export the API (e.g. via a dll) and you need a list of	3134	If you need to re-export the API (e.g. via a DLL) and you need a list of
2681	exported symbols, you can use the provided F<Symbol.*> files which list	3135	exported symbols, you can use the provided F<Symbol.*> files which list
2682	all public symbols, one per line:	3136	all public symbols, one per line:
2683		3137
2684	Symbols.ev for libev proper	3138	Symbols.ev for libev proper
2685	Symbols.event for the libevent emulation	3139	Symbols.event for the libevent emulation
2686		3140
2687	This can also be used to rename all public symbols to avoid clashes with	3141	This can also be used to rename all public symbols to avoid clashes with
2688	multiple versions of libev linked together (which is obviously bad in	3142	multiple versions of libev linked together (which is obviously bad in
2689	itself, but sometimes it is inconvinient to avoid this).	3143	itself, but sometimes it is inconvenient to avoid this).
2690		3144
2691	A sed command like this will create wrapper C<#define>'s that you need to	3145	A sed command like this will create wrapper C<#define>'s that you need to
2692	include before including F<ev.h>:	3146	include before including F<ev.h>:
2693		3147
2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3148	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2711	file.	3165	file.
2712		3166
2713	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3167	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2714	that everybody includes and which overrides some configure choices:	3168	that everybody includes and which overrides some configure choices:
2715		3169
2716	#define EV_MINIMAL 1	3170	#define EV_MINIMAL 1
2717	#define EV_USE_POLL 0	3171	#define EV_USE_POLL 0
2718	#define EV_MULTIPLICITY 0	3172	#define EV_MULTIPLICITY 0
2719	#define EV_PERIODIC_ENABLE 0	3173	#define EV_PERIODIC_ENABLE 0
2720	#define EV_STAT_ENABLE 0	3174	#define EV_STAT_ENABLE 0
2721	#define EV_FORK_ENABLE 0	3175	#define EV_FORK_ENABLE 0
2722	#define EV_CONFIG_H <config.h>	3176	#define EV_CONFIG_H <config.h>
2723	#define EV_MINPRI 0	3177	#define EV_MINPRI 0
2724	#define EV_MAXPRI 0	3178	#define EV_MAXPRI 0
2725		3179
2726	#include "ev++.h"	3180	#include "ev++.h"
2727		3181
2728	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2729		3183
2730	#include "ev_cpp.h"	3184	#include "ev_cpp.h"
2731	#include "ev.c"	3185	#include "ev.c"
		3186
		3187
		3188	=head1 THREADS AND COROUTINES
		3189
		3190	=head2 THREADS
		3191
		3192	Libev itself is completely thread-safe, but it uses no locking. This
		3193	means that you can use as many loops as you want in parallel, as long as
		3194	only one thread ever calls into one libev function with the same loop
		3195	parameter.
		3196
		3197	Or put differently: calls with different loop parameters can be done in
		3198	parallel from multiple threads, calls with the same loop parameter must be
		3199	done serially (but can be done from different threads, as long as only one
		3200	thread ever is inside a call at any point in time, e.g. by using a mutex
		3201	per loop).
		3202
		3203	If you want to know which design (one loop, locking, or multiple loops
		3204	without or something else still) is best for your problem, then I cannot
		3205	help you. I can give some generic advice however:
		3206
		3207	=over 4
		3208
		3209	=item * most applications have a main thread: use the default libev loop
		3210	in that thread, or create a separate thread running only the default loop.
		3211
		3212	This helps integrating other libraries or software modules that use libev
		3213	themselves and don't care/know about threading.
		3214
		3215	=item * one loop per thread is usually a good model.
		3216
		3217	Doing this is almost never wrong, sometimes a better-performance model
		3218	exists, but it is always a good start.
		3219
		3220	=item * other models exist, such as the leader/follower pattern, where one
		3221	loop is handed through multiple threads in a kind of round-robin fashion.
		3222
		3223	Choosing a model is hard - look around, learn, know that usually you can do
		3224	better than you currently do :-)
		3225
		3226	=item * often you need to talk to some other thread which blocks in the
		3227	event loop - C<ev_async> watchers can be used to wake them up from other
		3228	threads safely (or from signal contexts...).
		3229
		3230	=back
		3231
		3232	=head2 COROUTINES
		3233
		3234	Libev is much more accommodating to coroutines ("cooperative threads"):
		3235	libev fully supports nesting calls to it's functions from different
		3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3237	different coroutines and switch freely between both coroutines running the
		3238	loop, as long as you don't confuse yourself). The only exception is that
		3239	you must not do this from C<ev_periodic> reschedule callbacks.
		3240
		3241	Care has been invested into making sure that libev does not keep local
		3242	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3243	switches.
2732		3244
2733		3245
2734	=head1 COMPLEXITIES	3246	=head1 COMPLEXITIES
2735		3247
2736	In this section the complexities of (many of) the algorithms used inside	3248	In this section the complexities of (many of) the algorithms used inside
…		…
2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2755		3267
2756	That means that changing a timer costs less than removing/adding them	3268	That means that changing a timer costs less than removing/adding them
2757	as only the relative motion in the event queue has to be paid for.	3269	as only the relative motion in the event queue has to be paid for.
2758		3270
2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2760		3272
2761	These just add the watcher into an array or at the head of a list.	3273	These just add the watcher into an array or at the head of a list.
2762		3274
2763	=item Stopping check/prepare/idle watchers: O(1)	3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2764		3276
2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2766		3278
2767	These watchers are stored in lists then need to be walked to find the	3279	These watchers are stored in lists then need to be walked to find the
2768	correct watcher to remove. The lists are usually short (you don't usually	3280	correct watcher to remove. The lists are usually short (you don't usually
2769	have many watchers waiting for the same fd or signal).	3281	have many watchers waiting for the same fd or signal).
2770		3282
2771	=item Finding the next timer in each loop iteration: O(1)	3283	=item Finding the next timer in each loop iteration: O(1)
2772		3284
2773	By virtue of using a binary heap, the next timer is always found at the	3285	By virtue of using a binary or 4-heap, the next timer is always found at a
2774	beginning of the storage array.	3286	fixed position in the storage array.
2775		3287
2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2777		3289
2778	A change means an I/O watcher gets started or stopped, which requires	3290	A change means an I/O watcher gets started or stopped, which requires
2779	libev to recalculate its status (and possibly tell the kernel, depending	3291	libev to recalculate its status (and possibly tell the kernel, depending
2780	on backend and wether C<ev_io_set> was used).	3292	on backend and whether C<ev_io_set> was used).
2781		3293
2782	=item Activating one watcher (putting it into the pending state): O(1)	3294	=item Activating one watcher (putting it into the pending state): O(1)
2783		3295
2784	=item Priority handling: O(number_of_priorities)	3296	=item Priority handling: O(number_of_priorities)
2785		3297
2786	Priorities are implemented by allocating some space for each	3298	Priorities are implemented by allocating some space for each
2787	priority. When doing priority-based operations, libev usually has to	3299	priority. When doing priority-based operations, libev usually has to
2788	linearly search all the priorities, but starting/stopping and activating	3300	linearly search all the priorities, but starting/stopping and activating
2789	watchers becomes O(1) w.r.t. prioritiy handling.	3301	watchers becomes O(1) w.r.t. priority handling.
		3302
		3303	=item Sending an ev_async: O(1)
		3304
		3305	=item Processing ev_async_send: O(number_of_async_watchers)
		3306
		3307	=item Processing signals: O(max_signal_number)
		3308
		3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3310	calls in the current loop iteration. Checking for async and signal events
		3311	involves iterating over all running async watchers or all signal numbers.
2790		3312
2791	=back	3313	=back
2792		3314
2793		3315
2794	=head1 Win32 platform limitations and workarounds	3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2795		3317
2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2797	requires, and its I/O model is fundamentally incompatible with the POSIX	3319	requires, and its I/O model is fundamentally incompatible with the POSIX
2798	model. Libev still offers limited functionality on this platform in	3320	model. Libev still offers limited functionality on this platform in
2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2800	descriptors. This only applies when using Win32 natively, not when using	3322	descriptors. This only applies when using Win32 natively, not when using
2801	e.g. cygwin.	3323	e.g. cygwin.
2802		3324
		3325	Lifting these limitations would basically require the full
		3326	re-implementation of the I/O system. If you are into these kinds of
		3327	things, then note that glib does exactly that for you in a very portable
		3328	way (note also that glib is the slowest event library known to man).
		3329
2803	There is no supported compilation method available on windows except	3330	There is no supported compilation method available on windows except
2804	embedding it into other applications.	3331	embedding it into other applications.
2805		3332
		3333	Not a libev limitation but worth mentioning: windows apparently doesn't
		3334	accept large writes: instead of resulting in a partial write, windows will
		3335	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3336	so make sure you only write small amounts into your sockets (less than a
		3337	megabyte seems safe, but thsi apparently depends on the amount of memory
		3338	available).
		3339
2806	Due to the many, low, and arbitrary limits on the win32 platform and the	3340	Due to the many, low, and arbitrary limits on the win32 platform and
2807	abysmal performance of winsockets, using a large number of sockets is not	3341	the abysmal performance of winsockets, using a large number of sockets
2808	recommended (and not reasonable). If your program needs to use more than	3342	is not recommended (and not reasonable). If your program needs to use
2809	a hundred or so sockets, then likely it needs to use a totally different	3343	more than a hundred or so sockets, then likely it needs to use a totally
2810	implementation for windows, as libev offers the POSIX model, which cannot	3344	different implementation for windows, as libev offers the POSIX readiness
2811	be implemented efficiently on windows (microsoft monopoly games).	3345	notification model, which cannot be implemented efficiently on windows
		3346	(Microsoft monopoly games).
		3347
		3348	A typical way to use libev under windows is to embed it (see the embedding
		3349	section for details) and use the following F<evwrap.h> header file instead
		3350	of F<ev.h>:
		3351
		3352	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3354
		3355	#include "ev.h"
		3356
		3357	And compile the following F<evwrap.c> file into your project (make sure
		3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3359
		3360	#include "evwrap.h"
		3361	#include "ev.c"
2812		3362
2813	=over 4	3363	=over 4
2814		3364
2815	=item The winsocket select function	3365	=item The winsocket select function
2816		3366
2817	The winsocket C<select> function doesn't follow POSIX in that it requires	3367	The winsocket C<select> function doesn't follow POSIX in that it
2818	socket I<handles> and not socket I<file descriptors>. This makes select	3368	requires socket I<handles> and not socket I<file descriptors> (it is
2819	very inefficient, and also requires a mapping from file descriptors	3369	also extremely buggy). This makes select very inefficient, and also
2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3370	requires a mapping from file descriptors to socket handles (the Microsoft
2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3371	C runtime provides the function C<_open_osfhandle> for this). See the
2822	symbols for more info.	3372	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3373	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2823		3374
2824	The configuration for a "naked" win32 using the microsoft runtime	3375	The configuration for a "naked" win32 using the Microsoft runtime
2825	libraries and raw winsocket select is:	3376	libraries and raw winsocket select is:
2826		3377
2827	#define EV_USE_SELECT 1	3378	#define EV_USE_SELECT 1
2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3379	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2829		3380
2830	Note that winsockets handling of fd sets is O(n), so you can easily get a	3381	Note that winsockets handling of fd sets is O(n), so you can easily get a
2831	complexity in the O(n²) range when using win32.	3382	complexity in the O(n²) range when using win32.
2832		3383
2833	=item Limited number of file descriptors	3384	=item Limited number of file descriptors
2834		3385
2835	Windows has numerous arbitrary (and low) limits on things. Early versions	3386	Windows has numerous arbitrary (and low) limits on things.
2836	of winsocket's select only supported waiting for a max. of C<64> handles	3387
		3388	Early versions of winsocket's select only supported waiting for a maximum
2837	(probably owning to the fact that all windows kernels can only wait for	3389	of C<64> handles (probably owning to the fact that all windows kernels
2838	C<64> things at the same time internally; microsoft recommends spawning a	3390	can only wait for C<64> things at the same time internally; Microsoft
2839	chain of threads and wait for 63 handles and the previous thread in each).	3391	recommends spawning a chain of threads and wait for 63 handles and the
		3392	previous thread in each. Great).
2840		3393
2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2842	to some high number (e.g. C<2048>) before compiling the winsocket select	3395	to some high number (e.g. C<2048>) before compiling the winsocket select
2843	call (which might be in libev or elsewhere, for example, perl does its own	3396	call (which might be in libev or elsewhere, for example, perl does its own
2844	select emulation on windows).	3397	select emulation on windows).
2845		3398
2846	Another limit is the number of file descriptors in the microsoft runtime	3399	Another limit is the number of file descriptors in the Microsoft runtime
2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3400	libraries, which by default is C<64> (there must be a hidden I<64> fetish
2848	or something like this inside microsoft). You can increase this by calling	3401	or something like this inside Microsoft). You can increase this by calling
2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another
2850	arbitrary limit), but is broken in many versions of the microsoft runtime	3403	arbitrary limit), but is broken in many versions of the Microsoft runtime
2851	libraries.	3404	libraries.
2852		3405
2853	This might get you to about C<512> or C<2048> sockets (depending on	3406	This might get you to about C<512> or C<2048> sockets (depending on
2854	windows version and/or the phase of the moon). To get more, you need to	3407	windows version and/or the phase of the moon). To get more, you need to
2855	wrap all I/O functions and provide your own fd management, but the cost of	3408	wrap all I/O functions and provide your own fd management, but the cost of
2856	calling select (O(n²)) will likely make this unworkable.	3409	calling select (O(n²)) will likely make this unworkable.
2857		3410
2858	=back	3411	=back
2859		3412
2860		3413
		3414	=head1 PORTABILITY REQUIREMENTS
		3415
		3416	In addition to a working ISO-C implementation, libev relies on a few
		3417	additional extensions:
		3418
		3419	=over 4
		3420
		3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3422	calling conventions regardless of C<ev_watcher_type *>.
		3423
		3424	Libev assumes not only that all watcher pointers have the same internal
		3425	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3426	assumes that the same (machine) code can be used to call any watcher
		3427	callback: The watcher callbacks have different type signatures, but libev
		3428	calls them using an C<ev_watcher *> internally.
		3429
		3430	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3431
		3432	The type C<sig_atomic_t volatile> (or whatever is defined as
		3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3434	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3435	believed to be sufficiently portable.
		3436
		3437	=item C<sigprocmask> must work in a threaded environment
		3438
		3439	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3440	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3441	pthread implementations will either allow C<sigprocmask> in the "main
		3442	thread" or will block signals process-wide, both behaviours would
		3443	be compatible with libev. Interaction between C<sigprocmask> and
		3444	C<pthread_sigmask> could complicate things, however.
		3445
		3446	The most portable way to handle signals is to block signals in all threads
		3447	except the initial one, and run the default loop in the initial thread as
		3448	well.
		3449
		3450	=item C<long> must be large enough for common memory allocation sizes
		3451
		3452	To improve portability and simplify using libev, libev uses C<long>
		3453	internally instead of C<size_t> when allocating its data structures. On
		3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3455	is still at least 31 bits everywhere, which is enough for hundreds of
		3456	millions of watchers.
		3457
		3458	=item C<double> must hold a time value in seconds with enough accuracy
		3459
		3460	The type C<double> is used to represent timestamps. It is required to
		3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3462	enough for at least into the year 4000. This requirement is fulfilled by
		3463	implementations implementing IEEE 754 (basically all existing ones).
		3464
		3465	=back
		3466
		3467	If you know of other additional requirements drop me a note.
		3468
		3469
		3470	=head1 COMPILER WARNINGS
		3471
		3472	Depending on your compiler and compiler settings, you might get no or a
		3473	lot of warnings when compiling libev code. Some people are apparently
		3474	scared by this.
		3475
		3476	However, these are unavoidable for many reasons. For one, each compiler
		3477	has different warnings, and each user has different tastes regarding
		3478	warning options. "Warn-free" code therefore cannot be a goal except when
		3479	targeting a specific compiler and compiler-version.
		3480
		3481	Another reason is that some compiler warnings require elaborate
		3482	workarounds, or other changes to the code that make it less clear and less
		3483	maintainable.
		3484
		3485	And of course, some compiler warnings are just plain stupid, or simply
		3486	wrong (because they don't actually warn about the condition their message
		3487	seems to warn about).
		3488
		3489	While libev is written to generate as few warnings as possible,
		3490	"warn-free" code is not a goal, and it is recommended not to build libev
		3491	with any compiler warnings enabled unless you are prepared to cope with
		3492	them (e.g. by ignoring them). Remember that warnings are just that:
		3493	warnings, not errors, or proof of bugs.
		3494
		3495
		3496	=head1 VALGRIND
		3497
		3498	Valgrind has a special section here because it is a popular tool that is
		3499	highly useful, but valgrind reports are very hard to interpret.
		3500
		3501	If you think you found a bug (memory leak, uninitialised data access etc.)
		3502	in libev, then check twice: If valgrind reports something like:
		3503
		3504	==2274== definitely lost: 0 bytes in 0 blocks.
		3505	==2274== possibly lost: 0 bytes in 0 blocks.
		3506	==2274== still reachable: 256 bytes in 1 blocks.
		3507
		3508	Then there is no memory leak. Similarly, under some circumstances,
		3509	valgrind might report kernel bugs as if it were a bug in libev, or it
		3510	might be confused (it is a very good tool, but only a tool).
		3511
		3512	If you are unsure about something, feel free to contact the mailing list
		3513	with the full valgrind report and an explanation on why you think this is
		3514	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3515	no bug" answer and take the chance of learning how to interpret valgrind
		3516	properly.
		3517
		3518	If you need, for some reason, empty reports from valgrind for your project
		3519	I suggest using suppression lists.
		3520
		3521
2861	=head1 AUTHOR	3522	=head1 AUTHOR
2862		3523
2863	Marc Lehmann <libev@schmorp.de>.	3524	Marc Lehmann <libev@schmorp.de>.
2864		3525

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