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Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC vs.
Revision 1.177 by root, Mon Sep 8 17:27:42 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
265	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
266	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
267	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	306	C<ev_default_init>.
271		307
272	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
281	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
282	thing, believe me).	318	thing, believe me).
283		319
284	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
285		321
286	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
287	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
290	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
291	around bugs.	327	around bugs.
…		…
297	enabling this flag.	333	enabling this flag.
298		334
299	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
300	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
301	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
302	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
303	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
304	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
305		341
306	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
307	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
308	flag.	344	flag.
309		345
310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
311	environment variable.	347	environment variable.
312		348
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		350
315	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
317	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
318	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
319	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
320		356
321	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
322	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
323	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
324	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
325	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
326	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
327		363
328	=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)
329		365
330	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
331	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
339	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,
340	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
341	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
342	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
343	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
344	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
345	support for dup.	381	support for dup.
346		382
347	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
348	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
349	(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
350	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
351	very well if you register events for both fds.	387	very well if you register events for both fds.
352		388
353	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
…		…
356		392
357	Best performance from this backend is achieved by not unregistering all	393	Best performance from this backend is achieved by not unregistering all
358	watchers for a file descriptor until it has been closed, if possible, i.e.	394	watchers for a file descriptor until it has been closed, if possible, i.e.
359	keep at least one watcher active per fd at all times.	395	keep at least one watcher active per fd at all times.
360		396
361	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
362	all kernel versions tested so far.	398	all kernel versions tested so far.
363		399
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		401
366	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
367	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
368	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
369	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"
370	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
371	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)
372	system like NetBSD.	408	system like NetBSD.
373		409
374	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
…		…
376	the target platform). See C<ev_embed> watchers for more info.	412	the target platform). See C<ev_embed> watchers for more info.
377		413
378	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
379	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
380	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
381	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
382	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
383	drops fds silently in similarly hard-to-detect cases.	419	drops fds silently in similarly hard-to-detect cases.
384		420
385	This backend usually performs well under most conditions.	421	This backend usually performs well under most conditions.
386		422
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		438
403	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,
404	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)).
405		441
406	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
407	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
408	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
409		445
410	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
411	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
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	449	might perform better.
414		450
415	On the positive side, ignoring the spurious readyness notifications, this	451	On the positive side, ignoring the spurious readiness notifications, this
416	backend actually performed to specification in all tests and is fully	452	backend actually performed to specification in all tests and is fully
417	embeddable, which is a rare feat among the OS-specific backends.	453	embeddable, which is a rare feat among the OS-specific backends.
418		454
419	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
420		456
…		…
424		460
425	It is definitely not recommended to use this flag.	461	It is definitely not recommended to use this flag.
426		462
427	=back	463	=back
428		464
429	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
430	backends will be tried (in the reverse order as listed here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
431	specified, all backends in C<ev_recommended_backends ()> will be tried.	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		468
433	The most typical usage is like this:	469	The most typical usage is like this:
434		470
435	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		473
438	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
439	environment settings to be taken into account:	475	environment settings to be taken into account:
440		476
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		478
443	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
444	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
445	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):
446		482
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		484
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		486
451	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
452	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
453	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
454	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
455		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
456	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.
457		497
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	499	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
461		501
462	=item ev_default_destroy ()	502	=item ev_default_destroy ()
463		503
464	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
465	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
466	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
467	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
468	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
469	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
470	for example).	510	for example).
471		511
472	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
…		…
506		546
507	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
508	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
509	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.
510		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
		554
511	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
512		556
513	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
514	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
515	happily wraps around with enough iterations.	559	happily wraps around with enough iterations.
…		…
529	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
530	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
531	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
532	event occurring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
533		577
		578	=item ev_now_update (loop)
		579
		580	Establishes the current time by querying the kernel, updating the time
		581	returned by C<ev_now ()> in the progress. This is a costly operation and
		582	is usually done automatically within C<ev_loop ()>.
		583
		584	This function is rarely useful, but when some event callback runs for a
		585	very long time without entering the event loop, updating libev's idea of
		586	the current time is a good idea.
		587
		588	See also "The special problem of time updates" in the C<ev_timer> section.
		589
534	=item ev_loop (loop, int flags)	590	=item ev_loop (loop, int flags)
535		591
536	Finally, this is it, the event handler. This function usually is called	592	Finally, this is it, the event handler. This function usually is called
537	after you initialised all your watchers and you want to start handling	593	after you initialised all your watchers and you want to start handling
538	events.	594	events.
…		…
549	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
550	those events and any outstanding ones, but will not block your process in	606	those events and any outstanding ones, but will not block your process in
551	case there are no events and will return after one iteration of the loop.	607	case there are no events and will return after one iteration of the loop.
552		608
553	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
554	neccessary) and will handle those and any outstanding ones. It will block	610	necessary) and will handle those and any outstanding ones. It will block
555	your process until at least one new event arrives, and will return after	611	your process until at least one new event arrives, and will return after
556	one iteration of the loop. This is useful if you are waiting for some	612	one iteration of the loop. This is useful if you are waiting for some
557	external event in conjunction with something not expressible using other	613	external event in conjunction with something not expressible using other
558	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
559	usually a better approach for this kind of thing.	615	usually a better approach for this kind of thing.
560		616
561	Here are the gory details of what C<ev_loop> does:	617	Here are the gory details of what C<ev_loop> does:
562		618
563	- Before the first iteration, call any pending watchers.	619	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	620	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- If a fork was detected, queue and call all fork watchers.	621	- If a fork was detected (by any means), queue and call all fork watchers.
566	- Queue and call all prepare watchers.	622	- Queue and call all prepare watchers.
567	- If we have been forked, recreate the kernel state.	623	- If we have been forked, detach and recreate the kernel state
		624	as to not disturb the other process.
568	- Update the kernel state with all outstanding changes.	625	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	626	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	627	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	628	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	629	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	630	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	631	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	632	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	634	- Queue all outstanding timers.
578	- Queue all outstanding periodics.	635	- Queue all outstanding periodics.
579	- If no events are pending now, queue all idle watchers.	636	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	637	- Queue all check watchers.
581	- Call all queued watchers in reverse order (i.e. check watchers first).	638	- Call all queued watchers in reverse order (i.e. check watchers first).
582	Signals and child watchers are implemented as I/O watchers, and will	639	Signals and child watchers are implemented as I/O watchers, and will
583	be handled here by queueing them when their watcher gets executed.	640	be handled here by queueing them when their watcher gets executed.
584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
589	anymore.	646	anymore.
590		647
591	... queue jobs here, make sure they register event watchers as long	648	... queue jobs here, make sure they register event watchers as long
592	... as they still have work to do (even an idle watcher will do..)	649	... as they still have work to do (even an idle watcher will do..)
593	ev_loop (my_loop, 0);	650	ev_loop (my_loop, 0);
594	... jobs done. yeah!	651	... jobs done or somebody called unloop. yeah!
595		652
596	=item ev_unloop (loop, how)	653	=item ev_unloop (loop, how)
597		654
598	Can be used to make a call to C<ev_loop> return early (but only after it	655	Can be used to make a call to C<ev_loop> return early (but only after it
599	has processed all outstanding events). The C<how> argument must be either	656	has processed all outstanding events). The C<how> argument must be either
…		…
620	respectively).	677	respectively).
621		678
622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
623	running when nothing else is active.	680	running when nothing else is active.
624		681
625	struct ev_signal exitsig;	682	struct ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	683	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	684	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	685	evf_unref (loop);
629		686
630	Example: For some weird reason, unregister the above signal handler again.	687	Example: For some weird reason, unregister the above signal handler again.
631		688
632	ev_ref (loop);	689	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	690	ev_signal_stop (loop, &exitsig);
634		691
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	692	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		693
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	694	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		695
639	These advanced functions influence the time that libev will spend waiting	696	These advanced functions influence the time that libev will spend waiting
640	for events. Both are by default C<0>, meaning that libev will try to	697	for events. Both time intervals are by default C<0>, meaning that libev
641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	698	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		699	latency.
642		700
643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
644	allows libev to delay invocation of I/O and timer/periodic callbacks to	702	allows libev to delay invocation of I/O and timer/periodic callbacks
645	increase efficiency of loop iterations.	703	to increase efficiency of loop iterations (or to increase power-saving
		704	opportunities).
646		705
647	The background is that sometimes your program runs just fast enough to	706	The background is that sometimes your program runs just fast enough to
648	handle one (or very few) event(s) per loop iteration. While this makes	707	handle one (or very few) event(s) per loop iteration. While this makes
649	the program responsive, it also wastes a lot of CPU time to poll for new	708	the program responsive, it also wastes a lot of CPU time to poll for new
650	events, especially with backends like C<select ()> which have a high	709	events, especially with backends like C<select ()> which have a high
…		…
660	to spend more time collecting timeouts, at the expense of increased	719	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	720	latency (the watcher callback will be called later). C<ev_io> watchers
662	will not be affected. Setting this to a non-null value will not introduce	721	will not be affected. Setting this to a non-null value will not introduce
663	any overhead in libev.	722	any overhead in libev.
664		723
665	Many (busy) programs can usually benefit by setting the io collect	724	Many (busy) programs can usually benefit by setting the I/O collect
666	interval to a value near C<0.1> or so, which is often enough for	725	interval to a value near C<0.1> or so, which is often enough for
667	interactive servers (of course not for games), likewise for timeouts. It	726	interactive servers (of course not for games), likewise for timeouts. It
668	usually doesn't make much sense to set it to a lower value than C<0.01>,	727	usually doesn't make much sense to set it to a lower value than C<0.01>,
669	as this approsaches the timing granularity of most systems.	728	as this approaches the timing granularity of most systems.
		729
		730	Setting the I<timeout collect interval> can improve the opportunity for
		731	saving power, as the program will "bundle" timer callback invocations that
		732	are "near" in time together, by delaying some, thus reducing the number of
		733	times the process sleeps and wakes up again. Another useful technique to
		734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		735	they fire on, say, one-second boundaries only.
		736
		737	=item ev_loop_verify (loop)
		738
		739	This function only does something when C<EV_VERIFY> support has been
		740	compiled in. It tries to go through all internal structures and checks
		741	them for validity. If anything is found to be inconsistent, it will print
		742	an error message to standard error and call C<abort ()>.
		743
		744	This can be used to catch bugs inside libev itself: under normal
		745	circumstances, this function will never abort as of course libev keeps its
		746	data structures consistent.
670		747
671	=back	748	=back
672		749
673		750
674	=head1 ANATOMY OF A WATCHER	751	=head1 ANATOMY OF A WATCHER
675		752
676	A watcher is a structure that you create and register to record your	753	A watcher is a structure that you create and register to record your
677	interest in some event. For instance, if you want to wait for STDIN to	754	interest in some event. For instance, if you want to wait for STDIN to
678	become readable, you would create an C<ev_io> watcher for that:	755	become readable, you would create an C<ev_io> watcher for that:
679		756
680	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
681	{	758	{
682	ev_io_stop (w);	759	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	760	ev_unloop (loop, EVUNLOOP_ALL);
684	}	761	}
685		762
686	struct ev_loop *loop = ev_default_loop (0);	763	struct ev_loop *loop = ev_default_loop (0);
687	struct ev_io stdin_watcher;	764	struct ev_io stdin_watcher;
688	ev_init (&stdin_watcher, my_cb);	765	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	767	ev_io_start (loop, &stdin_watcher);
691	ev_loop (loop, 0);	768	ev_loop (loop, 0);
692		769
693	As you can see, you are responsible for allocating the memory for your	770	As you can see, you are responsible for allocating the memory for your
694	watcher structures (and it is usually a bad idea to do this on the stack,	771	watcher structures (and it is usually a bad idea to do this on the stack,
695	although this can sometimes be quite valid).	772	although this can sometimes be quite valid).
696		773
697	Each watcher structure must be initialised by a call to C<ev_init	774	Each watcher structure must be initialised by a call to C<ev_init
698	(watcher *, callback)>, which expects a callback to be provided. This	775	(watcher *, callback)>, which expects a callback to be provided. This
699	callback gets invoked each time the event occurs (or, in the case of io	776	callback gets invoked each time the event occurs (or, in the case of I/O
700	watchers, each time the event loop detects that the file descriptor given	777	watchers, each time the event loop detects that the file descriptor given
701	is readable and/or writable).	778	is readable and/or writable).
702		779
703	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
704	with arguments specific to this watcher type. There is also a macro	781	with arguments specific to this watcher type. There is also a macro
…		…
780		857
781	The given async watcher has been asynchronously notified (see C<ev_async>).	858	The given async watcher has been asynchronously notified (see C<ev_async>).
782		859
783	=item C<EV_ERROR>	860	=item C<EV_ERROR>
784		861
785	An unspecified error has occured, the watcher has been stopped. This might	862	An unspecified error has occurred, the watcher has been stopped. This might
786	happen because the watcher could not be properly started because libev	863	happen because the watcher could not be properly started because libev
787	ran out of memory, a file descriptor was found to be closed or any other	864	ran out of memory, a file descriptor was found to be closed or any other
788	problem. You best act on it by reporting the problem and somehow coping	865	problem. You best act on it by reporting the problem and somehow coping
789	with the watcher being stopped.	866	with the watcher being stopped.
790		867
791	Libev will usually signal a few "dummy" events together with an error,	868	Libev will usually signal a few "dummy" events together with an error,
792	for example it might indicate that a fd is readable or writable, and if	869	for example it might indicate that a fd is readable or writable, and if
793	your callbacks is well-written it can just attempt the operation and cope	870	your callbacks is well-written it can just attempt the operation and cope
794	with the error from read() or write(). This will not work in multithreaded	871	with the error from read() or write(). This will not work in multi-threaded
795	programs, though, so beware.	872	programs, though, so beware.
796		873
797	=back	874	=back
798		875
799	=head2 GENERIC WATCHER FUNCTIONS	876	=head2 GENERIC WATCHER FUNCTIONS
…		…
829	Although some watcher types do not have type-specific arguments	906	Although some watcher types do not have type-specific arguments
830	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
831		908
832	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
833		910
834	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
835	calls into a single call. This is the most convinient method to initialise	912	calls into a single call. This is the most convenient method to initialise
836	a watcher. The same limitations apply, of course.	913	a watcher. The same limitations apply, of course.
837		914
838	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
839		916
840	Starts (activates) the given watcher. Only active watchers will receive	917	Starts (activates) the given watcher. Only active watchers will receive
…		…
923	to associate arbitrary data with your watcher. If you need more data and	1000	to associate arbitrary data with your watcher. If you need more data and
924	don't want to allocate memory and store a pointer to it in that data	1001	don't want to allocate memory and store a pointer to it in that data
925	member, you can also "subclass" the watcher type and provide your own	1002	member, you can also "subclass" the watcher type and provide your own
926	data:	1003	data:
927		1004
928	struct my_io	1005	struct my_io
929	{	1006	{
930	struct ev_io io;	1007	struct ev_io io;
931	int otherfd;	1008	int otherfd;
932	void *somedata;	1009	void *somedata;
933	struct whatever *mostinteresting;	1010	struct whatever *mostinteresting;
934	}	1011	}
935		1012
936	And since your callback will be called with a pointer to the watcher, you	1013	And since your callback will be called with a pointer to the watcher, you
937	can cast it back to your own type:	1014	can cast it back to your own type:
938		1015
939	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
940	{	1017	{
941	struct my_io *w = (struct my_io *)w_;	1018	struct my_io *w = (struct my_io *)w_;
942	...	1019	...
943	}	1020	}
944		1021
945	More interesting and less C-conformant ways of casting your callback type	1022	More interesting and less C-conformant ways of casting your callback type
946	instead have been omitted.	1023	instead have been omitted.
947		1024
948	Another common scenario is having some data structure with multiple	1025	Another common scenario is having some data structure with multiple
949	watchers:	1026	watchers:
950		1027
951	struct my_biggy	1028	struct my_biggy
952	{	1029	{
953	int some_data;	1030	int some_data;
954	ev_timer t1;	1031	ev_timer t1;
955	ev_timer t2;	1032	ev_timer t2;
956	}	1033	}
957		1034
958	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,
959	you need to use C<offsetof>:	1036	you need to use C<offsetof>:
960		1037
961	#include <stddef.h>	1038	#include <stddef.h>
962		1039
963	static void	1040	static void
964	t1_cb (EV_P_ struct ev_timer *w, int revents)	1041	t1_cb (EV_P_ struct ev_timer *w, int revents)
965	{	1042	{
966	struct my_biggy big = (struct my_biggy *	1043	struct my_biggy big = (struct my_biggy *
967	(((char *)w) - offsetof (struct my_biggy, t1));	1044	(((char *)w) - offsetof (struct my_biggy, t1));
968	}	1045	}
969		1046
970	static void	1047	static void
971	t2_cb (EV_P_ struct ev_timer *w, int revents)	1048	t2_cb (EV_P_ struct ev_timer *w, int revents)
972	{	1049	{
973	struct my_biggy big = (struct my_biggy *	1050	struct my_biggy big = (struct my_biggy *
974	(((char *)w) - offsetof (struct my_biggy, t2));	1051	(((char *)w) - offsetof (struct my_biggy, t2));
975	}	1052	}
976		1053
977		1054
978	=head1 WATCHER TYPES	1055	=head1 WATCHER TYPES
979		1056
980	This section describes each watcher in detail, but will not repeat	1057	This section describes each watcher in detail, but will not repeat
…		…
1009	If you must do this, then force the use of a known-to-be-good backend	1086	If you must do this, then force the use of a known-to-be-good backend
1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1011	C<EVBACKEND_POLL>).	1088	C<EVBACKEND_POLL>).
1012		1089
1013	Another thing you have to watch out for is that it is quite easy to	1090	Another thing you have to watch out for is that it is quite easy to
1014	receive "spurious" readyness notifications, that is your callback might	1091	receive "spurious" readiness notifications, that is your callback might
1015	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1016	because there is no data. Not only are some backends known to create a	1093	because there is no data. Not only are some backends known to create a
1017	lot of those (for example solaris ports), it is very easy to get into	1094	lot of those (for example Solaris ports), it is very easy to get into
1018	this situation even with a relatively standard program structure. Thus	1095	this situation even with a relatively standard program structure. Thus
1019	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1021		1098
1022	If you cannot run the fd in non-blocking mode (for example you should not	1099	If you cannot run the fd in non-blocking mode (for example you should not
1023	play around with an Xlib connection), then you have to seperately re-test	1100	play around with an Xlib connection), then you have to separately re-test
1024	whether a file descriptor is really ready with a known-to-be good interface	1101	whether a file descriptor is really ready with a known-to-be good interface
1025	such as poll (fortunately in our Xlib example, Xlib already does this on	1102	such as poll (fortunately in our Xlib example, Xlib already does this on
1026	its own, so its quite safe to use).	1103	its own, so its quite safe to use).
1027		1104
1028	=head3 The special problem of disappearing file descriptors	1105	=head3 The special problem of disappearing file descriptors
…		…
1066	To support fork in your programs, you either have to call	1143	To support fork in your programs, you either have to call
1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1144	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1146	C<EVBACKEND_POLL>.
1070		1147
		1148	=head3 The special problem of SIGPIPE
		1149
		1150	While not really specific to libev, it is easy to forget about SIGPIPE:
		1151	when writing to a pipe whose other end has been closed, your program gets
		1152	send a SIGPIPE, which, by default, aborts your program. For most programs
		1153	this is sensible behaviour, for daemons, this is usually undesirable.
		1154
		1155	So when you encounter spurious, unexplained daemon exits, make sure you
		1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1157	somewhere, as that would have given you a big clue).
		1158
1071		1159
1072	=head3 Watcher-Specific Functions	1160	=head3 Watcher-Specific Functions
1073		1161
1074	=over 4	1162	=over 4
1075		1163
1076	=item ev_io_init (ev_io *, callback, int fd, int events)	1164	=item ev_io_init (ev_io *, callback, int fd, int events)
1077		1165
1078	=item ev_io_set (ev_io *, int fd, int events)	1166	=item ev_io_set (ev_io *, int fd, int events)
1079		1167
1080	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1081	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1082	C<EV_READ | EV_WRITE> to receive the given events.	1170	C<EV_READ | EV_WRITE> to receive the given events.
1083		1171
1084	=item int fd [read-only]	1172	=item int fd [read-only]
1085		1173
1086	The file descriptor being watched.	1174	The file descriptor being watched.
…		…
1095		1183
1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1097	readable, but only once. Since it is likely line-buffered, you could	1185	readable, but only once. Since it is likely line-buffered, you could
1098	attempt to read a whole line in the callback.	1186	attempt to read a whole line in the callback.
1099		1187
1100	static void	1188	static void
1101	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1102	{	1190	{
1103	ev_io_stop (loop, w);	1191	ev_io_stop (loop, w);
1104	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1105	}	1193	}
1106		1194
1107	...	1195	...
1108	struct ev_loop *loop = ev_default_init (0);	1196	struct ev_loop *loop = ev_default_init (0);
1109	struct ev_io stdin_readable;	1197	struct ev_io stdin_readable;
1110	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1111	ev_io_start (loop, &stdin_readable);	1199	ev_io_start (loop, &stdin_readable);
1112	ev_loop (loop, 0);	1200	ev_loop (loop, 0);
1113		1201
1114		1202
1115	=head2 C<ev_timer> - relative and optionally repeating timeouts	1203	=head2 C<ev_timer> - relative and optionally repeating timeouts
1116		1204
1117	Timer watchers are simple relative timers that generate an event after a	1205	Timer watchers are simple relative timers that generate an event after a
1118	given time, and optionally repeating in regular intervals after that.	1206	given time, and optionally repeating in regular intervals after that.
1119		1207
1120	The timers are based on real time, that is, if you register an event that	1208	The timers are based on real time, that is, if you register an event that
1121	times out after an hour and you reset your system clock to last years	1209	times out after an hour and you reset your system clock to January last
1122	time, it will still time out after (roughly) and hour. "Roughly" because	1210	year, it will still time out after (roughly) and hour. "Roughly" because
1123	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1124	monotonic clock option helps a lot here).	1212	monotonic clock option helps a lot here).
		1213
		1214	The callback is guaranteed to be invoked only after its timeout has passed,
		1215	but if multiple timers become ready during the same loop iteration then
		1216	order of execution is undefined.
		1217
		1218	=head3 The special problem of time updates
		1219
		1220	Establishing the current time is a costly operation (it usually takes at
		1221	least two system calls): EV therefore updates its idea of the current
		1222	time only before and after C<ev_loop> polls for new events, which causes
		1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1224	lots of events.
1125		1225
1126	The relative timeouts are calculated relative to the C<ev_now ()>	1226	The relative timeouts are calculated relative to the C<ev_now ()>
1127	time. This is usually the right thing as this timestamp refers to the time	1227	time. This is usually the right thing as this timestamp refers to the time
1128	of the event triggering whatever timeout you are modifying/starting. If	1228	of the event triggering whatever timeout you are modifying/starting. If
1129	you suspect event processing to be delayed and you I<need> to base the timeout	1229	you suspect event processing to be delayed and you I<need> to base the
1130	on the current time, use something like this to adjust for this:	1230	timeout on the current time, use something like this to adjust for this:
1131		1231
1132	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1133		1233
1134	The callback is guarenteed to be invoked only when its timeout has passed,	1234	If the event loop is suspended for a long time, you can also force an
1135	but if multiple timers become ready during the same loop iteration then	1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1136	order of execution is undefined.	1236	()>.
1137		1237
1138	=head3 Watcher-Specific Functions and Data Members	1238	=head3 Watcher-Specific Functions and Data Members
1139		1239
1140	=over 4	1240	=over 4
1141		1241
1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1242	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1143		1243
1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1244	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1145		1245
1146	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1246	Configure the timer to trigger after C<after> seconds. If C<repeat>
1147	C<0.>, then it will automatically be stopped. If it is positive, then the	1247	is C<0.>, then it will automatically be stopped once the timeout is
1148	timer will automatically be configured to trigger again C<repeat> seconds	1248	reached. If it is positive, then the timer will automatically be
1149	later, again, and again, until stopped manually.	1249	configured to trigger again C<repeat> seconds later, again, and again,
		1250	until stopped manually.
1150		1251
1151	The timer itself will do a best-effort at avoiding drift, that is, if you	1252	The timer itself will do a best-effort at avoiding drift, that is, if
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1253	you configure a timer to trigger every 10 seconds, then it will normally
1153	exactly 10 second intervals. If, however, your program cannot keep up with	1254	trigger at exactly 10 second intervals. If, however, your program cannot
1154	the timer (because it takes longer than those 10 seconds to do stuff) the	1255	keep up with the timer (because it takes longer than those 10 seconds to
1155	timer will not fire more than once per event loop iteration.	1256	do stuff) the timer will not fire more than once per event loop iteration.
1156		1257
1157	=item ev_timer_again (loop)	1258	=item ev_timer_again (loop, ev_timer *)
1158		1259
1159	This will act as if the timer timed out and restart it again if it is	1260	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1261	repeating. The exact semantics are:
1161		1262
1162	If the timer is pending, its pending status is cleared.	1263	If the timer is pending, its pending status is cleared.
1163		1264
1164	If the timer is started but nonrepeating, stop it (as if it timed out).	1265	If the timer is started but non-repeating, stop it (as if it timed out).
1165		1266
1166	If the timer is repeating, either start it if necessary (with the	1267	If the timer is repeating, either start it if necessary (with the
1167	C<repeat> value), or reset the running timer to the C<repeat> value.	1268	C<repeat> value), or reset the running timer to the C<repeat> value.
1168		1269
1169	This sounds a bit complicated, but here is a useful and typical	1270	This sounds a bit complicated, but here is a useful and typical
1170	example: Imagine you have a tcp connection and you want a so-called idle	1271	example: Imagine you have a TCP connection and you want a so-called idle
1171	timeout, that is, you want to be called when there have been, say, 60	1272	timeout, that is, you want to be called when there have been, say, 60
1172	seconds of inactivity on the socket. The easiest way to do this is to	1273	seconds of inactivity on the socket. The easiest way to do this is to
1173	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1174	C<ev_timer_again> each time you successfully read or write some data. If	1275	C<ev_timer_again> each time you successfully read or write some data. If
1175	you go into an idle state where you do not expect data to travel on the	1276	you go into an idle state where you do not expect data to travel on the
…		…
1201		1302
1202	=head3 Examples	1303	=head3 Examples
1203		1304
1204	Example: Create a timer that fires after 60 seconds.	1305	Example: Create a timer that fires after 60 seconds.
1205		1306
1206	static void	1307	static void
1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1208	{	1309	{
1209	.. one minute over, w is actually stopped right here	1310	.. one minute over, w is actually stopped right here
1210	}	1311	}
1211		1312
1212	struct ev_timer mytimer;	1313	struct ev_timer mytimer;
1213	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1214	ev_timer_start (loop, &mytimer);	1315	ev_timer_start (loop, &mytimer);
1215		1316
1216	Example: Create a timeout timer that times out after 10 seconds of	1317	Example: Create a timeout timer that times out after 10 seconds of
1217	inactivity.	1318	inactivity.
1218		1319
1219	static void	1320	static void
1220	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1221	{	1322	{
1222	.. ten seconds without any activity	1323	.. ten seconds without any activity
1223	}	1324	}
1224		1325
1225	struct ev_timer mytimer;	1326	struct ev_timer mytimer;
1226	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1227	ev_timer_again (&mytimer); /* start timer */	1328	ev_timer_again (&mytimer); /* start timer */
1228	ev_loop (loop, 0);	1329	ev_loop (loop, 0);
1229		1330
1230	// and in some piece of code that gets executed on any "activity":	1331	// and in some piece of code that gets executed on any "activity":
1231	// reset the timeout to start ticking again at 10 seconds	1332	// reset the timeout to start ticking again at 10 seconds
1232	ev_timer_again (&mytimer);	1333	ev_timer_again (&mytimer);
1233		1334
1234		1335
1235	=head2 C<ev_periodic> - to cron or not to cron?	1336	=head2 C<ev_periodic> - to cron or not to cron?
1236		1337
1237	Periodic watchers are also timers of a kind, but they are very versatile	1338	Periodic watchers are also timers of a kind, but they are very versatile
1238	(and unfortunately a bit complex).	1339	(and unfortunately a bit complex).
1239		1340
1240	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1241	but on wallclock time (absolute time). You can tell a periodic watcher	1342	but on wall clock time (absolute time). You can tell a periodic watcher
1242	to trigger "at" some specific point in time. For example, if you tell a	1343	to trigger after some specific point in time. For example, if you tell a
1243	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1244	+ 10.>) and then reset your system clock to the last year, then it will	1345	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1346	clock to January of the previous year, then it will take more than year
1245	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1246	roughly 10 seconds later).	1348	roughly 10 seconds later as it uses a relative timeout).
1247		1349
1248	They can also be used to implement vastly more complex timers, such as	1350	C<ev_periodic>s can also be used to implement vastly more complex timers,
1249	triggering an event on each midnight, local time or other, complicated,	1351	such as triggering an event on each "midnight, local time", or other
1250	rules.	1352	complicated, rules.
1251		1353
1252	As with timers, the callback is guarenteed to be invoked only when the	1354	As with timers, the callback is guaranteed to be invoked only when the
1253	time (C<at>) has been passed, but if multiple periodic timers become ready	1355	time (C<at>) has passed, but if multiple periodic timers become ready
1254	during the same loop iteration then order of execution is undefined.	1356	during the same loop iteration then order of execution is undefined.
1255		1357
1256	=head3 Watcher-Specific Functions and Data Members	1358	=head3 Watcher-Specific Functions and Data Members
1257		1359
1258	=over 4	1360	=over 4
…		…
1266		1368
1267	=over 4	1369	=over 4
1268		1370
1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1270		1372
1271	In this configuration the watcher triggers an event at the wallclock time	1373	In this configuration the watcher triggers an event after the wall clock
1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1374	time C<at> has passed and doesn't repeat. It will not adjust when a time
1273	that is, if it is to be run at January 1st 2011 then it will run when the	1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1274	system time reaches or surpasses this time.	1376	run when the system time reaches or surpasses this time.
1275		1377
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277		1379
1278	In this mode the watcher will always be scheduled to time out at the next	1380	In this mode the watcher will always be scheduled to time out at the next
1279	C<at + N * interval> time (for some integer N, which can also be negative)	1381	C<at + N * interval> time (for some integer N, which can also be negative)
1280	and then repeat, regardless of any time jumps.	1382	and then repeat, regardless of any time jumps.
1281		1383
1282	This can be used to create timers that do not drift with respect to system	1384	This can be used to create timers that do not drift with respect to system
1283	time:	1385	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1386	the hour:
1284		1387
1285	ev_periodic_set (&periodic, 0., 3600., 0);	1388	ev_periodic_set (&periodic, 0., 3600., 0);
1286		1389
1287	This doesn't mean there will always be 3600 seconds in between triggers,	1390	This doesn't mean there will always be 3600 seconds in between triggers,
1288	but only that the the callback will be called when the system time shows a	1391	but only that the callback will be called when the system time shows a
1289	full hour (UTC), or more correctly, when the system time is evenly divisible	1392	full hour (UTC), or more correctly, when the system time is evenly divisible
1290	by 3600.	1393	by 3600.
1291		1394
1292	Another way to think about it (for the mathematically inclined) is that	1395	Another way to think about it (for the mathematically inclined) is that
1293	C<ev_periodic> will try to run the callback in this mode at the next possible	1396	C<ev_periodic> will try to run the callback in this mode at the next possible
1294	time where C<time = at (mod interval)>, regardless of any time jumps.	1397	time where C<time = at (mod interval)>, regardless of any time jumps.
1295		1398
1296	For numerical stability it is preferable that the C<at> value is near	1399	For numerical stability it is preferable that the C<at> value is near
1297	C<ev_now ()> (the current time), but there is no range requirement for	1400	C<ev_now ()> (the current time), but there is no range requirement for
1298	this value.	1401	this value, and in fact is often specified as zero.
		1402
		1403	Note also that there is an upper limit to how often a timer can fire (CPU
		1404	speed for example), so if C<interval> is very small then timing stability
		1405	will of course deteriorate. Libev itself tries to be exact to be about one
		1406	millisecond (if the OS supports it and the machine is fast enough).
1299		1407
1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1301		1409
1302	In this mode the values for C<interval> and C<at> are both being	1410	In this mode the values for C<interval> and C<at> are both being
1303	ignored. Instead, each time the periodic watcher gets scheduled, the	1411	ignored. Instead, each time the periodic watcher gets scheduled, the
1304	reschedule callback will be called with the watcher as first, and the	1412	reschedule callback will be called with the watcher as first, and the
1305	current time as second argument.	1413	current time as second argument.
1306		1414
1307	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1308	ever, or make any event loop modifications>. If you need to stop it,	1416	ever, or make ANY event loop modifications whatsoever>.
1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1310	starting an C<ev_prepare> watcher, which is legal).
1311		1417
		1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1420	only event loop modification you are allowed to do).
		1421
1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1313	ev_tstamp now)>, e.g.:	1423	*w, ev_tstamp now)>, e.g.:
1314		1424
1315	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1316	{	1426	{
1317	return now + 60.;	1427	return now + 60.;
1318	}	1428	}
…		…
1320	It must return the next time to trigger, based on the passed time value	1430	It must return the next time to trigger, based on the passed time value
1321	(that is, the lowest time value larger than to the second argument). It	1431	(that is, the lowest time value larger than to the second argument). It
1322	will usually be called just before the callback will be triggered, but	1432	will usually be called just before the callback will be triggered, but
1323	might be called at other times, too.	1433	might be called at other times, too.
1324		1434
1325	NOTE: I<< This callback must always return a time that is later than the	1435	NOTE: I<< This callback must always return a time that is higher than or
1326	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1436	equal to the passed C<now> value >>.
1327		1437
1328	This can be used to create very complex timers, such as a timer that	1438	This can be used to create very complex timers, such as a timer that
1329	triggers on each midnight, local time. To do this, you would calculate the	1439	triggers on "next midnight, local time". To do this, you would calculate the
1330	next midnight after C<now> and return the timestamp value for this. How	1440	next midnight after C<now> and return the timestamp value for this. How
1331	you do this is, again, up to you (but it is not trivial, which is the main	1441	you do this is, again, up to you (but it is not trivial, which is the main
1332	reason I omitted it as an example).	1442	reason I omitted it as an example).
1333		1443
1334	=back	1444	=back
…		…
1338	Simply stops and restarts the periodic watcher again. This is only useful	1448	Simply stops and restarts the periodic watcher again. This is only useful
1339	when you changed some parameters or the reschedule callback would return	1449	when you changed some parameters or the reschedule callback would return
1340	a different time than the last time it was called (e.g. in a crond like	1450	a different time than the last time it was called (e.g. in a crond like
1341	program when the crontabs have changed).	1451	program when the crontabs have changed).
1342		1452
		1453	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1454
		1455	When active, returns the absolute time that the watcher is supposed to
		1456	trigger next.
		1457
1343	=item ev_tstamp offset [read-write]	1458	=item ev_tstamp offset [read-write]
1344		1459
1345	When repeating, this contains the offset value, otherwise this is the	1460	When repeating, this contains the offset value, otherwise this is the
1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1347		1462
…		…
1358		1473
1359	The current reschedule callback, or C<0>, if this functionality is	1474	The current reschedule callback, or C<0>, if this functionality is
1360	switched off. Can be changed any time, but changes only take effect when	1475	switched off. Can be changed any time, but changes only take effect when
1361	the periodic timer fires or C<ev_periodic_again> is being called.	1476	the periodic timer fires or C<ev_periodic_again> is being called.
1362		1477
1363	=item ev_tstamp at [read-only]
1364
1365	When active, contains the absolute time that the watcher is supposed to
1366	trigger next.
1367
1368	=back	1478	=back
1369		1479
1370	=head3 Examples	1480	=head3 Examples
1371		1481
1372	Example: Call a callback every hour, or, more precisely, whenever the	1482	Example: Call a callback every hour, or, more precisely, whenever the
1373	system clock is divisible by 3600. The callback invocation times have	1483	system clock is divisible by 3600. The callback invocation times have
1374	potentially a lot of jittering, but good long-term stability.	1484	potentially a lot of jitter, but good long-term stability.
1375		1485
1376	static void	1486	static void
1377	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1378	{	1488	{
1379	... its now a full hour (UTC, or TAI or whatever your clock follows)	1489	... its now a full hour (UTC, or TAI or whatever your clock follows)
1380	}	1490	}
1381		1491
1382	struct ev_periodic hourly_tick;	1492	struct ev_periodic hourly_tick;
1383	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1384	ev_periodic_start (loop, &hourly_tick);	1494	ev_periodic_start (loop, &hourly_tick);
1385		1495
1386	Example: The same as above, but use a reschedule callback to do it:	1496	Example: The same as above, but use a reschedule callback to do it:
1387		1497
1388	#include <math.h>	1498	#include <math.h>
1389		1499
1390	static ev_tstamp	1500	static ev_tstamp
1391	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1392	{	1502	{
1393	return fmod (now, 3600.) + 3600.;	1503	return fmod (now, 3600.) + 3600.;
1394	}	1504	}
1395		1505
1396	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1397		1507
1398	Example: Call a callback every hour, starting now:	1508	Example: Call a callback every hour, starting now:
1399		1509
1400	struct ev_periodic hourly_tick;	1510	struct ev_periodic hourly_tick;
1401	ev_periodic_init (&hourly_tick, clock_cb,	1511	ev_periodic_init (&hourly_tick, clock_cb,
1402	fmod (ev_now (loop), 3600.), 3600., 0);	1512	fmod (ev_now (loop), 3600.), 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1513	ev_periodic_start (loop, &hourly_tick);
1404		1514
1405		1515
1406	=head2 C<ev_signal> - signal me when a signal gets signalled!	1516	=head2 C<ev_signal> - signal me when a signal gets signalled!
1407		1517
1408	Signal watchers will trigger an event when the process receives a specific	1518	Signal watchers will trigger an event when the process receives a specific
…		…
1415	with the kernel (thus it coexists with your own signal handlers as long	1525	with the kernel (thus it coexists with your own signal handlers as long
1416	as you don't register any with libev). Similarly, when the last signal	1526	as you don't register any with libev). Similarly, when the last signal
1417	watcher for a signal is stopped libev will reset the signal handler to	1527	watcher for a signal is stopped libev will reset the signal handler to
1418	SIG_DFL (regardless of what it was set to before).	1528	SIG_DFL (regardless of what it was set to before).
1419		1529
		1530	If possible and supported, libev will install its handlers with
		1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1532	interrupted. If you have a problem with system calls getting interrupted by
		1533	signals you can block all signals in an C<ev_check> watcher and unblock
		1534	them in an C<ev_prepare> watcher.
		1535
1420	=head3 Watcher-Specific Functions and Data Members	1536	=head3 Watcher-Specific Functions and Data Members
1421		1537
1422	=over 4	1538	=over 4
1423		1539
1424	=item ev_signal_init (ev_signal *, callback, int signum)	1540	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1432		1548
1433	The signal the watcher watches out for.	1549	The signal the watcher watches out for.
1434		1550
1435	=back	1551	=back
1436		1552
		1553	=head3 Examples
		1554
		1555	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1556
		1557	static void
		1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1559	{
		1560	ev_unloop (loop, EVUNLOOP_ALL);
		1561	}
		1562
		1563	struct ev_signal signal_watcher;
		1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1565	ev_signal_start (loop, &sigint_cb);
		1566
1437		1567
1438	=head2 C<ev_child> - watch out for process status changes	1568	=head2 C<ev_child> - watch out for process status changes
1439		1569
1440	Child watchers trigger when your process receives a SIGCHLD in response to	1570	Child watchers trigger when your process receives a SIGCHLD in response to
1441	some child status changes (most typically when a child of yours dies).	1571	some child status changes (most typically when a child of yours dies). It
		1572	is permissible to install a child watcher I<after> the child has been
		1573	forked (which implies it might have already exited), as long as the event
		1574	loop isn't entered (or is continued from a watcher).
		1575
		1576	Only the default event loop is capable of handling signals, and therefore
		1577	you can only register child watchers in the default event loop.
		1578
		1579	=head3 Process Interaction
		1580
		1581	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1582	initialised. This is necessary to guarantee proper behaviour even if
		1583	the first child watcher is started after the child exits. The occurrence
		1584	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1585	synchronously as part of the event loop processing. Libev always reaps all
		1586	children, even ones not watched.
		1587
		1588	=head3 Overriding the Built-In Processing
		1589
		1590	Libev offers no special support for overriding the built-in child
		1591	processing, but if your application collides with libev's default child
		1592	handler, you can override it easily by installing your own handler for
		1593	C<SIGCHLD> after initialising the default loop, and making sure the
		1594	default loop never gets destroyed. You are encouraged, however, to use an
		1595	event-based approach to child reaping and thus use libev's support for
		1596	that, so other libev users can use C<ev_child> watchers freely.
		1597
		1598	=head3 Stopping the Child Watcher
		1599
		1600	Currently, the child watcher never gets stopped, even when the
		1601	child terminates, so normally one needs to stop the watcher in the
		1602	callback. Future versions of libev might stop the watcher automatically
		1603	when a child exit is detected.
1442		1604
1443	=head3 Watcher-Specific Functions and Data Members	1605	=head3 Watcher-Specific Functions and Data Members
1444		1606
1445	=over 4	1607	=over 4
1446		1608
…		…
1472		1634
1473	=back	1635	=back
1474		1636
1475	=head3 Examples	1637	=head3 Examples
1476		1638
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1639	Example: C<fork()> a new process and install a child handler to wait for
		1640	its completion.
1478		1641
		1642	ev_child cw;
		1643
1479	static void	1644	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1645	child_cb (EV_P_ struct ev_child *w, int revents)
1481	{	1646	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1647	ev_child_stop (EV_A_ w);
		1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	1649	}
1484		1650
1485	struct ev_signal signal_watcher;	1651	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1652
1487	ev_signal_start (loop, &sigint_cb);	1653	if (pid < 0)
		1654	// error
		1655	else if (pid == 0)
		1656	{
		1657	// the forked child executes here
		1658	exit (1);
		1659	}
		1660	else
		1661	{
		1662	ev_child_init (&cw, child_cb, pid, 0);
		1663	ev_child_start (EV_DEFAULT_ &cw);
		1664	}
1488		1665
1489		1666
1490	=head2 C<ev_stat> - did the file attributes just change?	1667	=head2 C<ev_stat> - did the file attributes just change?
1491		1668
1492	This watches a filesystem path for attribute changes. That is, it calls	1669	This watches a file system path for attribute changes. That is, it calls
1493	C<stat> regularly (or when the OS says it changed) and sees if it changed	1670	C<stat> regularly (or when the OS says it changed) and sees if it changed
1494	compared to the last time, invoking the callback if it did.	1671	compared to the last time, invoking the callback if it did.
1495		1672
1496	The path does not need to exist: changing from "path exists" to "path does	1673	The path does not need to exist: changing from "path exists" to "path does
1497	not exist" is a status change like any other. The condition "path does	1674	not exist" is a status change like any other. The condition "path does
…		…
1515	as even with OS-supported change notifications, this can be	1692	as even with OS-supported change notifications, this can be
1516	resource-intensive.	1693	resource-intensive.
1517		1694
1518	At the time of this writing, only the Linux inotify interface is	1695	At the time of this writing, only the Linux inotify interface is
1519	implemented (implementing kqueue support is left as an exercise for the	1696	implemented (implementing kqueue support is left as an exercise for the
		1697	reader, note, however, that the author sees no way of implementing ev_stat
1520	reader). Inotify will be used to give hints only and should not change the	1698	semantics with kqueue). Inotify will be used to give hints only and should
1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1699	not change the semantics of C<ev_stat> watchers, which means that libev
1522	to fall back to regular polling again even with inotify, but changes are	1700	sometimes needs to fall back to regular polling again even with inotify,
1523	usually detected immediately, and if the file exists there will be no	1701	but changes are usually detected immediately, and if the file exists there
1524	polling.	1702	will be no polling.
		1703
		1704	=head3 ABI Issues (Largefile Support)
		1705
		1706	Libev by default (unless the user overrides this) uses the default
		1707	compilation environment, which means that on systems with large file
		1708	support disabled by default, you get the 32 bit version of the stat
		1709	structure. When using the library from programs that change the ABI to
		1710	use 64 bit file offsets the programs will fail. In that case you have to
		1711	compile libev with the same flags to get binary compatibility. This is
		1712	obviously the case with any flags that change the ABI, but the problem is
		1713	most noticeably disabled with ev_stat and large file support.
		1714
		1715	The solution for this is to lobby your distribution maker to make large
		1716	file interfaces available by default (as e.g. FreeBSD does) and not
		1717	optional. Libev cannot simply switch on large file support because it has
		1718	to exchange stat structures with application programs compiled using the
		1719	default compilation environment.
1525		1720
1526	=head3 Inotify	1721	=head3 Inotify
1527		1722
1528	When C<inotify (7)> support has been compiled into libev (generally only	1723	When C<inotify (7)> support has been compiled into libev (generally only
1529	available on Linux) and present at runtime, it will be used to speed up	1724	available on Linux) and present at runtime, it will be used to speed up
1530	change detection where possible. The inotify descriptor will be created lazily	1725	change detection where possible. The inotify descriptor will be created lazily
1531	when the first C<ev_stat> watcher is being started.	1726	when the first C<ev_stat> watcher is being started.
1532		1727
1533	Inotify presense does not change the semantics of C<ev_stat> watchers	1728	Inotify presence does not change the semantics of C<ev_stat> watchers
1534	except that changes might be detected earlier, and in some cases, to avoid	1729	except that changes might be detected earlier, and in some cases, to avoid
1535	making regular C<stat> calls. Even in the presense of inotify support	1730	making regular C<stat> calls. Even in the presence of inotify support
1536	there are many cases where libev has to resort to regular C<stat> polling.	1731	there are many cases where libev has to resort to regular C<stat> polling.
1537		1732
1538	(There is no support for kqueue, as apparently it cannot be used to	1733	(There is no support for kqueue, as apparently it cannot be used to
1539	implement this functionality, due to the requirement of having a file	1734	implement this functionality, due to the requirement of having a file
1540	descriptor open on the object at all times).	1735	descriptor open on the object at all times).
1541		1736
1542	=head3 The special problem of stat time resolution	1737	=head3 The special problem of stat time resolution
1543		1738
1544	The C<stat ()> syscall only supports full-second resolution portably, and	1739	The C<stat ()> system call only supports full-second resolution portably, and
1545	even on systems where the resolution is higher, many filesystems still	1740	even on systems where the resolution is higher, many file systems still
1546	only support whole seconds.	1741	only support whole seconds.
1547		1742
1548	That means that, if the time is the only thing that changes, you might	1743	That means that, if the time is the only thing that changes, you can
1549	miss updates: on the first update, C<ev_stat> detects a change and calls	1744	easily miss updates: on the first update, C<ev_stat> detects a change and
1550	your callback, which does something. When there is another update within	1745	calls your callback, which does something. When there is another update
1551	the same second, C<ev_stat> will be unable to detect it.	1746	within the same second, C<ev_stat> will be unable to detect it as the stat
		1747	data does not change.
1552		1748
1553	The solution to this is to delay acting on a change for a second (or till	1749	The solution to this is to delay acting on a change for slightly more
1554	the next second boundary), using a roughly one-second delay C<ev_timer>	1750	than a second (or till slightly after the next full second boundary), using
1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1556	is added to work around small timing inconsistencies of some operating	1752	ev_timer_again (loop, w)>).
1557	systems.	1753
		1754	The C<.02> offset is added to work around small timing inconsistencies
		1755	of some operating systems (where the second counter of the current time
		1756	might be be delayed. One such system is the Linux kernel, where a call to
		1757	C<gettimeofday> might return a timestamp with a full second later than
		1758	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1759	update file times then there will be a small window where the kernel uses
		1760	the previous second to update file times but libev might already execute
		1761	the timer callback).
1558		1762
1559	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1560		1764
1561	=over 4	1765	=over 4
1562		1766
…		…
1568	C<path>. The C<interval> is a hint on how quickly a change is expected to	1772	C<path>. The C<interval> is a hint on how quickly a change is expected to
1569	be detected and should normally be specified as C<0> to let libev choose	1773	be detected and should normally be specified as C<0> to let libev choose
1570	a suitable value. The memory pointed to by C<path> must point to the same	1774	a suitable value. The memory pointed to by C<path> must point to the same
1571	path for as long as the watcher is active.	1775	path for as long as the watcher is active.
1572		1776
1573	The callback will be receive C<EV_STAT> when a change was detected,	1777	The callback will receive C<EV_STAT> when a change was detected, relative
1574	relative to the attributes at the time the watcher was started (or the	1778	to the attributes at the time the watcher was started (or the last change
1575	last change was detected).	1779	was detected).
1576		1780
1577	=item ev_stat_stat (ev_stat *)	1781	=item ev_stat_stat (loop, ev_stat *)
1578		1782
1579	Updates the stat buffer immediately with new values. If you change the	1783	Updates the stat buffer immediately with new values. If you change the
1580	watched path in your callback, you could call this fucntion to avoid	1784	watched path in your callback, you could call this function to avoid
1581	detecting this change (while introducing a race condition). Can also be	1785	detecting this change (while introducing a race condition if you are not
1582	useful simply to find out the new values.	1786	the only one changing the path). Can also be useful simply to find out the
		1787	new values.
1583		1788
1584	=item ev_statdata attr [read-only]	1789	=item ev_statdata attr [read-only]
1585		1790
1586	The most-recently detected attributes of the file. Although the type is of	1791	The most-recently detected attributes of the file. Although the type is
1587	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1792	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1588	suitable for your system. If the C<st_nlink> member is C<0>, then there	1793	suitable for your system, but you can only rely on the POSIX-standardised
		1794	members to be present. If the C<st_nlink> member is C<0>, then there was
1589	was some error while C<stat>ing the file.	1795	some error while C<stat>ing the file.
1590		1796
1591	=item ev_statdata prev [read-only]	1797	=item ev_statdata prev [read-only]
1592		1798
1593	The previous attributes of the file. The callback gets invoked whenever	1799	The previous attributes of the file. The callback gets invoked whenever
1594	C<prev> != C<attr>.	1800	C<prev> != C<attr>, or, more precisely, one or more of these members
		1801	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1802	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1595		1803
1596	=item ev_tstamp interval [read-only]	1804	=item ev_tstamp interval [read-only]
1597		1805
1598	The specified interval.	1806	The specified interval.
1599		1807
1600	=item const char *path [read-only]	1808	=item const char *path [read-only]
1601		1809
1602	The filesystem path that is being watched.	1810	The file system path that is being watched.
1603		1811
1604	=back	1812	=back
1605		1813
1606	=head3 Examples	1814	=head3 Examples
1607		1815
1608	Example: Watch C</etc/passwd> for attribute changes.	1816	Example: Watch C</etc/passwd> for attribute changes.
1609		1817
1610	static void	1818	static void
1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1819	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1612	{	1820	{
1613	/* /etc/passwd changed in some way */	1821	/* /etc/passwd changed in some way */
1614	if (w->attr.st_nlink)	1822	if (w->attr.st_nlink)
1615	{	1823	{
1616	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1824	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1617	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1825	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1618	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1826	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1619	}	1827	}
1620	else	1828	else
1621	/* you shalt not abuse printf for puts */	1829	/* you shalt not abuse printf for puts */
1622	puts ("wow, /etc/passwd is not there, expect problems. "	1830	puts ("wow, /etc/passwd is not there, expect problems. "
1623	"if this is windows, they already arrived\n");	1831	"if this is windows, they already arrived\n");
1624	}	1832	}
1625		1833
1626	...	1834	...
1627	ev_stat passwd;	1835	ev_stat passwd;
1628		1836
1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1837	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1630	ev_stat_start (loop, &passwd);	1838	ev_stat_start (loop, &passwd);
1631		1839
1632	Example: Like above, but additionally use a one-second delay so we do not	1840	Example: Like above, but additionally use a one-second delay so we do not
1633	miss updates (however, frequent updates will delay processing, too, so	1841	miss updates (however, frequent updates will delay processing, too, so
1634	one might do the work both on C<ev_stat> callback invocation I<and> on	1842	one might do the work both on C<ev_stat> callback invocation I<and> on
1635	C<ev_timer> callback invocation).	1843	C<ev_timer> callback invocation).
1636		1844
1637	static ev_stat passwd;	1845	static ev_stat passwd;
1638	static ev_timer timer;	1846	static ev_timer timer;
1639		1847
1640	static void	1848	static void
1641	timer_cb (EV_P_ ev_timer *w, int revents)	1849	timer_cb (EV_P_ ev_timer *w, int revents)
1642	{	1850	{
1643	ev_timer_stop (EV_A_ w);	1851	ev_timer_stop (EV_A_ w);
1644		1852
1645	/* now it's one second after the most recent passwd change */	1853	/* now it's one second after the most recent passwd change */
1646	}	1854	}
1647		1855
1648	static void	1856	static void
1649	stat_cb (EV_P_ ev_stat *w, int revents)	1857	stat_cb (EV_P_ ev_stat *w, int revents)
1650	{	1858	{
1651	/* reset the one-second timer */	1859	/* reset the one-second timer */
1652	ev_timer_again (EV_A_ &timer);	1860	ev_timer_again (EV_A_ &timer);
1653	}	1861	}
1654		1862
1655	...	1863	...
1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1864	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657	ev_stat_start (loop, &passwd);	1865	ev_stat_start (loop, &passwd);
1658	ev_timer_init (&timer, timer_cb, 0., 1.01);	1866	ev_timer_init (&timer, timer_cb, 0., 1.02);
1659		1867
1660		1868
1661	=head2 C<ev_idle> - when you've got nothing better to do...	1869	=head2 C<ev_idle> - when you've got nothing better to do...
1662		1870
1663	Idle watchers trigger events when no other events of the same or higher	1871	Idle watchers trigger events when no other events of the same or higher
…		…
1694	=head3 Examples	1902	=head3 Examples
1695		1903
1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1697	callback, free it. Also, use no error checking, as usual.	1905	callback, free it. Also, use no error checking, as usual.
1698		1906
1699	static void	1907	static void
1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1701	{	1909	{
1702	free (w);	1910	free (w);
1703	// now do something you wanted to do when the program has	1911	// now do something you wanted to do when the program has
1704	// no longer anything immediate to do.	1912	// no longer anything immediate to do.
1705	}	1913	}
1706		1914
1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1708	ev_idle_init (idle_watcher, idle_cb);	1916	ev_idle_init (idle_watcher, idle_cb);
1709	ev_idle_start (loop, idle_cb);	1917	ev_idle_start (loop, idle_cb);
1710		1918
1711		1919
1712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1713		1921
1714	Prepare and check watchers are usually (but not always) used in tandem:	1922	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1733		1941
1734	This is done by examining in each prepare call which file descriptors need	1942	This is done by examining in each prepare call which file descriptors need
1735	to be watched by the other library, registering C<ev_io> watchers for	1943	to be watched by the other library, registering C<ev_io> watchers for
1736	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1737	provide just this functionality). Then, in the check watcher you check for	1945	provide just this functionality). Then, in the check watcher you check for
1738	any events that occured (by checking the pending status of all watchers	1946	any events that occurred (by checking the pending status of all watchers
1739	and stopping them) and call back into the library. The I/O and timer	1947	and stopping them) and call back into the library. The I/O and timer
1740	callbacks will never actually be called (but must be valid nevertheless,	1948	callbacks will never actually be called (but must be valid nevertheless,
1741	because you never know, you know?).	1949	because you never know, you know?).
1742		1950
1743	As another example, the Perl Coro module uses these hooks to integrate	1951	As another example, the Perl Coro module uses these hooks to integrate
…		…
1751		1959
1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1753	priority, to ensure that they are being run before any other watchers	1961	priority, to ensure that they are being run before any other watchers
1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1755	too) should not activate ("feed") events into libev. While libev fully	1963	too) should not activate ("feed") events into libev. While libev fully
1756	supports this, they will be called before other C<ev_check> watchers	1964	supports this, they might get executed before other C<ev_check> watchers
1757	did their job. As C<ev_check> watchers are often used to embed other	1965	did their job. As C<ev_check> watchers are often used to embed other
1758	(non-libev) event loops those other event loops might be in an unusable	1966	(non-libev) event loops those other event loops might be in an unusable
1759	state until their C<ev_check> watcher ran (always remind yourself to	1967	state until their C<ev_check> watcher ran (always remind yourself to
1760	coexist peacefully with others).	1968	coexist peacefully with others).
1761		1969
…		…
1776	=head3 Examples	1984	=head3 Examples
1777		1985
1778	There are a number of principal ways to embed other event loops or modules	1986	There are a number of principal ways to embed other event loops or modules
1779	into libev. Here are some ideas on how to include libadns into libev	1987	into libev. Here are some ideas on how to include libadns into libev
1780	(there is a Perl module named C<EV::ADNS> that does this, which you could	1988	(there is a Perl module named C<EV::ADNS> that does this, which you could
1781	use for an actually working example. Another Perl module named C<EV::Glib>	1989	use as a working example. Another Perl module named C<EV::Glib> embeds a
1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1990	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1783	into the Glib event loop).	1991	Glib event loop).
1784		1992
1785	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1993	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1786	and in a check watcher, destroy them and call into libadns. What follows	1994	and in a check watcher, destroy them and call into libadns. What follows
1787	is pseudo-code only of course. This requires you to either use a low	1995	is pseudo-code only of course. This requires you to either use a low
1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1996	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1789	the callbacks for the IO/timeout watchers might not have been called yet.	1997	the callbacks for the IO/timeout watchers might not have been called yet.
1790		1998
1791	static ev_io iow [nfd];	1999	static ev_io iow [nfd];
1792	static ev_timer tw;	2000	static ev_timer tw;
1793		2001
1794	static void	2002	static void
1795	io_cb (ev_loop *loop, ev_io *w, int revents)	2003	io_cb (ev_loop *loop, ev_io *w, int revents)
1796	{	2004	{
1797	}	2005	}
1798		2006
1799	// create io watchers for each fd and a timer before blocking	2007	// create io watchers for each fd and a timer before blocking
1800	static void	2008	static void
1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1802	{	2010	{
1803	int timeout = 3600000;	2011	int timeout = 3600000;
1804	struct pollfd fds [nfd];	2012	struct pollfd fds [nfd];
1805	// actual code will need to loop here and realloc etc.	2013	// actual code will need to loop here and realloc etc.
1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1807		2015
1808	/* the callback is illegal, but won't be called as we stop during check */	2016	/* the callback is illegal, but won't be called as we stop during check */
1809	ev_timer_init (&tw, 0, timeout * 1e-3);	2017	ev_timer_init (&tw, 0, timeout * 1e-3);
1810	ev_timer_start (loop, &tw);	2018	ev_timer_start (loop, &tw);
1811		2019
1812	// create one ev_io per pollfd	2020	// create one ev_io per pollfd
1813	for (int i = 0; i < nfd; ++i)	2021	for (int i = 0; i < nfd; ++i)
1814	{	2022	{
1815	ev_io_init (iow + i, io_cb, fds [i].fd,	2023	ev_io_init (iow + i, io_cb, fds [i].fd,
1816	((fds [i].events & POLLIN ? EV_READ : 0)	2024	((fds [i].events & POLLIN ? EV_READ : 0)
1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2025	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1818		2026
1819	fds [i].revents = 0;	2027	fds [i].revents = 0;
1820	ev_io_start (loop, iow + i);	2028	ev_io_start (loop, iow + i);
1821	}	2029	}
1822	}	2030	}
1823		2031
1824	// stop all watchers after blocking	2032	// stop all watchers after blocking
1825	static void	2033	static void
1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1827	{	2035	{
1828	ev_timer_stop (loop, &tw);	2036	ev_timer_stop (loop, &tw);
1829		2037
1830	for (int i = 0; i < nfd; ++i)	2038	for (int i = 0; i < nfd; ++i)
1831	{	2039	{
1832	// set the relevant poll flags	2040	// set the relevant poll flags
1833	// could also call adns_processreadable etc. here	2041	// could also call adns_processreadable etc. here
1834	struct pollfd *fd = fds + i;	2042	struct pollfd *fd = fds + i;
1835	int revents = ev_clear_pending (iow + i);	2043	int revents = ev_clear_pending (iow + i);
1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2044	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2045	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1838		2046
1839	// now stop the watcher	2047	// now stop the watcher
1840	ev_io_stop (loop, iow + i);	2048	ev_io_stop (loop, iow + i);
1841	}	2049	}
1842		2050
1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2051	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1844	}	2052	}
1845		2053
1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2054	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1847	in the prepare watcher and would dispose of the check watcher.	2055	in the prepare watcher and would dispose of the check watcher.
1848		2056
1849	Method 3: If the module to be embedded supports explicit event	2057	Method 3: If the module to be embedded supports explicit event
1850	notification (adns does), you can also make use of the actual watcher	2058	notification (libadns does), you can also make use of the actual watcher
1851	callbacks, and only destroy/create the watchers in the prepare watcher.	2059	callbacks, and only destroy/create the watchers in the prepare watcher.
1852		2060
1853	static void	2061	static void
1854	timer_cb (EV_P_ ev_timer *w, int revents)	2062	timer_cb (EV_P_ ev_timer *w, int revents)
1855	{	2063	{
1856	adns_state ads = (adns_state)w->data;	2064	adns_state ads = (adns_state)w->data;
1857	update_now (EV_A);	2065	update_now (EV_A);
1858		2066
1859	adns_processtimeouts (ads, &tv_now);	2067	adns_processtimeouts (ads, &tv_now);
1860	}	2068	}
1861		2069
1862	static void	2070	static void
1863	io_cb (EV_P_ ev_io *w, int revents)	2071	io_cb (EV_P_ ev_io *w, int revents)
1864	{	2072	{
1865	adns_state ads = (adns_state)w->data;	2073	adns_state ads = (adns_state)w->data;
1866	update_now (EV_A);	2074	update_now (EV_A);
1867		2075
1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2076	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2077	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1870	}	2078	}
1871		2079
1872	// do not ever call adns_afterpoll	2080	// do not ever call adns_afterpoll
1873		2081
1874	Method 4: Do not use a prepare or check watcher because the module you	2082	Method 4: Do not use a prepare or check watcher because the module you
1875	want to embed is too inflexible to support it. Instead, youc na override	2083	want to embed is too inflexible to support it. Instead, you can override
1876	their poll function. The drawback with this solution is that the main	2084	their poll function. The drawback with this solution is that the main
1877	loop is now no longer controllable by EV. The C<Glib::EV> module does	2085	loop is now no longer controllable by EV. The C<Glib::EV> module does
1878	this.	2086	this.
1879		2087
1880	static gint	2088	static gint
1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1882	{	2090	{
1883	int got_events = 0;	2091	int got_events = 0;
1884		2092
1885	for (n = 0; n < nfds; ++n)	2093	for (n = 0; n < nfds; ++n)
1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2094	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1887		2095
1888	if (timeout >= 0)	2096	if (timeout >= 0)
1889	// create/start timer	2097	// create/start timer
1890		2098
1891	// poll	2099	// poll
1892	ev_loop (EV_A_ 0);	2100	ev_loop (EV_A_ 0);
1893		2101
1894	// stop timer again	2102	// stop timer again
1895	if (timeout >= 0)	2103	if (timeout >= 0)
1896	ev_timer_stop (EV_A_ &to);	2104	ev_timer_stop (EV_A_ &to);
1897		2105
1898	// stop io watchers again - their callbacks should have set	2106	// stop io watchers again - their callbacks should have set
1899	for (n = 0; n < nfds; ++n)	2107	for (n = 0; n < nfds; ++n)
1900	ev_io_stop (EV_A_ iow [n]);	2108	ev_io_stop (EV_A_ iow [n]);
1901		2109
1902	return got_events;	2110	return got_events;
1903	}	2111	}
1904		2112
1905		2113
1906	=head2 C<ev_embed> - when one backend isn't enough...	2114	=head2 C<ev_embed> - when one backend isn't enough...
1907		2115
1908	This is a rather advanced watcher type that lets you embed one event loop	2116	This is a rather advanced watcher type that lets you embed one event loop
…		…
1964		2172
1965	Configures the watcher to embed the given loop, which must be	2173	Configures the watcher to embed the given loop, which must be
1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2174	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967	invoked automatically, otherwise it is the responsibility of the callback	2175	invoked automatically, otherwise it is the responsibility of the callback
1968	to invoke it (it will continue to be called until the sweep has been done,	2176	to invoke it (it will continue to be called until the sweep has been done,
1969	if you do not want thta, you need to temporarily stop the embed watcher).	2177	if you do not want that, you need to temporarily stop the embed watcher).
1970		2178
1971	=item ev_embed_sweep (loop, ev_embed *)	2179	=item ev_embed_sweep (loop, ev_embed *)
1972		2180
1973	Make a single, non-blocking sweep over the embedded loop. This works	2181	Make a single, non-blocking sweep over the embedded loop. This works
1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2182	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975	apropriate way for embedded loops.	2183	appropriate way for embedded loops.
1976		2184
1977	=item struct ev_loop *other [read-only]	2185	=item struct ev_loop *other [read-only]
1978		2186
1979	The embedded event loop.	2187	The embedded event loop.
1980		2188
…		…
1982		2190
1983	=head3 Examples	2191	=head3 Examples
1984		2192
1985	Example: Try to get an embeddable event loop and embed it into the default	2193	Example: Try to get an embeddable event loop and embed it into the default
1986	event loop. If that is not possible, use the default loop. The default	2194	event loop. If that is not possible, use the default loop. The default
1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2195	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1989	used).	2197	used).
1990		2198
1991	struct ev_loop *loop_hi = ev_default_init (0);	2199	struct ev_loop *loop_hi = ev_default_init (0);
1992	struct ev_loop *loop_lo = 0;	2200	struct ev_loop *loop_lo = 0;
1993	struct ev_embed embed;	2201	struct ev_embed embed;
1994		2202
1995	// see if there is a chance of getting one that works	2203	// see if there is a chance of getting one that works
1996	// (remember that a flags value of 0 means autodetection)	2204	// (remember that a flags value of 0 means autodetection)
1997	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1998	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1999	: 0;	2207	: 0;
2000		2208
2001	// if we got one, then embed it, otherwise default to loop_hi	2209	// if we got one, then embed it, otherwise default to loop_hi
2002	if (loop_lo)	2210	if (loop_lo)
2003	{	2211	{
2004	ev_embed_init (&embed, 0, loop_lo);	2212	ev_embed_init (&embed, 0, loop_lo);
2005	ev_embed_start (loop_hi, &embed);	2213	ev_embed_start (loop_hi, &embed);
2006	}	2214	}
2007	else	2215	else
2008	loop_lo = loop_hi;	2216	loop_lo = loop_hi;
2009		2217
2010	Example: Check if kqueue is available but not recommended and create	2218	Example: Check if kqueue is available but not recommended and create
2011	a kqueue backend for use with sockets (which usually work with any	2219	a kqueue backend for use with sockets (which usually work with any
2012	kqueue implementation). Store the kqueue/socket-only event loop in	2220	kqueue implementation). Store the kqueue/socket-only event loop in
2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2014		2222
2015	struct ev_loop *loop = ev_default_init (0);	2223	struct ev_loop *loop = ev_default_init (0);
2016	struct ev_loop *loop_socket = 0;	2224	struct ev_loop *loop_socket = 0;
2017	struct ev_embed embed;	2225	struct ev_embed embed;
2018		2226
2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021	{	2229	{
2022	ev_embed_init (&embed, 0, loop_socket);	2230	ev_embed_init (&embed, 0, loop_socket);
2023	ev_embed_start (loop, &embed);	2231	ev_embed_start (loop, &embed);
2024	}	2232	}
2025		2233
2026	if (!loop_socket)	2234	if (!loop_socket)
2027	loop_socket = loop;	2235	loop_socket = loop;
2028		2236
2029	// now use loop_socket for all sockets, and loop for everything else	2237	// now use loop_socket for all sockets, and loop for everything else
2030		2238
2031		2239
2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2240	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2033		2241
2034	Fork watchers are called when a C<fork ()> was detected (usually because	2242	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2087		2295
2088	=item queueing from a signal handler context	2296	=item queueing from a signal handler context
2089		2297
2090	To implement race-free queueing, you simply add to the queue in the signal	2298	To implement race-free queueing, you simply add to the queue in the signal
2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for
2092	some fictitiuous SIGUSR1 handler:	2300	some fictitious SIGUSR1 handler:
2093		2301
2094	static ev_async mysig;	2302	static ev_async mysig;
2095		2303
2096	static void	2304	static void
2097	sigusr1_handler (void)	2305	sigusr1_handler (void)
2098	{	2306	{
2099	sometype data;	2307	sometype data;
2100		2308
2101	// no locking etc.	2309	// no locking etc.
2102	queue_put (data);	2310	queue_put (data);
2103	ev_async_send (DEFAULT_ &mysig);	2311	ev_async_send (EV_DEFAULT_ &mysig);
2104	}	2312	}
2105		2313
2106	static void	2314	static void
2107	mysig_cb (EV_P_ ev_async *w, int revents)	2315	mysig_cb (EV_P_ ev_async *w, int revents)
2108	{	2316	{
…		…
2139	// only need to lock the actual queueing operation	2347	// only need to lock the actual queueing operation
2140	pthread_mutex_lock (&mymutex);	2348	pthread_mutex_lock (&mymutex);
2141	queue_put (data);	2349	queue_put (data);
2142	pthread_mutex_unlock (&mymutex);	2350	pthread_mutex_unlock (&mymutex);
2143		2351
2144	ev_async_send (DEFAULT_ &mysig);	2352	ev_async_send (EV_DEFAULT_ &mysig);
2145	}	2353	}
2146		2354
2147	static void	2355	static void
2148	mysig_cb (EV_P_ ev_async *w, int revents)	2356	mysig_cb (EV_P_ ev_async *w, int revents)
2149	{	2357	{
…		…
2171	=item ev_async_send (loop, ev_async *)	2379	=item ev_async_send (loop, ev_async *)
2172		2380
2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2175	C<ev_feed_event>, this call is safe to do in other threads, signal or	2383	C<ev_feed_event>, this call is safe to do in other threads, signal or
2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2177	section below on what exactly this means).	2385	section below on what exactly this means).
2178		2386
2179	This call incurs the overhead of a syscall only once per loop iteration,	2387	This call incurs the overhead of a system call only once per loop iteration,
2180	so while the overhead might be noticable, it doesn't apply to repeated	2388	so while the overhead might be noticeable, it doesn't apply to repeated
2181	calls to C<ev_async_send>.	2389	calls to C<ev_async_send>.
		2390
		2391	=item bool = ev_async_pending (ev_async *)
		2392
		2393	Returns a non-zero value when C<ev_async_send> has been called on the
		2394	watcher but the event has not yet been processed (or even noted) by the
		2395	event loop.
		2396
		2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2398	the loop iterates next and checks for the watcher to have become active,
		2399	it will reset the flag again. C<ev_async_pending> can be used to very
		2400	quickly check whether invoking the loop might be a good idea.
		2401
		2402	Not that this does I<not> check whether the watcher itself is pending, only
		2403	whether it has been requested to make this watcher pending.
2182		2404
2183	=back	2405	=back
2184		2406
2185		2407
2186	=head1 OTHER FUNCTIONS	2408	=head1 OTHER FUNCTIONS
…		…
2197	or timeout without having to allocate/configure/start/stop/free one or	2419	or timeout without having to allocate/configure/start/stop/free one or
2198	more watchers yourself.	2420	more watchers yourself.
2199		2421
2200	If C<fd> is less than 0, then no I/O watcher will be started and events	2422	If C<fd> is less than 0, then no I/O watcher will be started and events
2201	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2202	C<events> set will be craeted and started.	2424	C<events> set will be created and started.
2203		2425
2204	If C<timeout> is less than 0, then no timeout watcher will be	2426	If C<timeout> is less than 0, then no timeout watcher will be
2205	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2206	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2207	dubious value.	2429	dubious value.
…		…
2209	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2210	passed an C<revents> set like normal event callbacks (a combination of	2432	passed an C<revents> set like normal event callbacks (a combination of
2211	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2212	value passed to C<ev_once>:	2434	value passed to C<ev_once>:
2213		2435
2214	static void stdin_ready (int revents, void *arg)	2436	static void stdin_ready (int revents, void *arg)
2215	{	2437	{
2216	if (revents & EV_TIMEOUT)	2438	if (revents & EV_TIMEOUT)
2217	/* doh, nothing entered */;	2439	/* doh, nothing entered */;
2218	else if (revents & EV_READ)	2440	else if (revents & EV_READ)
2219	/* stdin might have data for us, joy! */;	2441	/* stdin might have data for us, joy! */;
2220	}	2442	}
2221		2443
2222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2223		2445
2224	=item ev_feed_event (ev_loop *, watcher *, int revents)	2446	=item ev_feed_event (ev_loop *, watcher *, int revents)
2225		2447
2226	Feeds the given event set into the event loop, as if the specified event	2448	Feeds the given event set into the event loop, as if the specified event
2227	had happened for the specified watcher (which must be a pointer to an	2449	had happened for the specified watcher (which must be a pointer to an
…		…
2232	Feed an event on the given fd, as if a file descriptor backend detected	2454	Feed an event on the given fd, as if a file descriptor backend detected
2233	the given events it.	2455	the given events it.
2234		2456
2235	=item ev_feed_signal_event (ev_loop *loop, int signum)	2457	=item ev_feed_signal_event (ev_loop *loop, int signum)
2236		2458
2237	Feed an event as if the given signal occured (C<loop> must be the default	2459	Feed an event as if the given signal occurred (C<loop> must be the default
2238	loop!).	2460	loop!).
2239		2461
2240	=back	2462	=back
2241		2463
2242		2464
…		…
2258		2480
2259	=item * Priorities are not currently supported. Initialising priorities	2481	=item * Priorities are not currently supported. Initialising priorities
2260	will fail and all watchers will have the same priority, even though there	2482	will fail and all watchers will have the same priority, even though there
2261	is an ev_pri field.	2483	is an ev_pri field.
2262		2484
		2485	=item * In libevent, the last base created gets the signals, in libev, the
		2486	first base created (== the default loop) gets the signals.
		2487
2263	=item * Other members are not supported.	2488	=item * Other members are not supported.
2264		2489
2265	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2490	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2266	to use the libev header file and library.	2491	to use the libev header file and library.
2267		2492
2268	=back	2493	=back
2269		2494
2270	=head1 C++ SUPPORT	2495	=head1 C++ SUPPORT
2271		2496
2272	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2497	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2273	you to use some convinience methods to start/stop watchers and also change	2498	you to use some convenience methods to start/stop watchers and also change
2274	the callback model to a model using method callbacks on objects.	2499	the callback model to a model using method callbacks on objects.
2275		2500
2276	To use it,	2501	To use it,
2277		2502
2278	#include <ev++.h>	2503	#include <ev++.h>
2279		2504
2280	This automatically includes F<ev.h> and puts all of its definitions (many	2505	This automatically includes F<ev.h> and puts all of its definitions (many
2281	of them macros) into the global namespace. All C++ specific things are	2506	of them macros) into the global namespace. All C++ specific things are
2282	put into the C<ev> namespace. It should support all the same embedding	2507	put into the C<ev> namespace. It should support all the same embedding
2283	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2508	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2350	your compiler is good :), then the method will be fully inlined into the	2575	your compiler is good :), then the method will be fully inlined into the
2351	thunking function, making it as fast as a direct C callback.	2576	thunking function, making it as fast as a direct C callback.
2352		2577
2353	Example: simple class declaration and watcher initialisation	2578	Example: simple class declaration and watcher initialisation
2354		2579
2355	struct myclass	2580	struct myclass
2356	{	2581	{
2357	void io_cb (ev::io &w, int revents) { }	2582	void io_cb (ev::io &w, int revents) { }
2358	}	2583	}
2359		2584
2360	myclass obj;	2585	myclass obj;
2361	ev::io iow;	2586	ev::io iow;
2362	iow.set <myclass, &myclass::io_cb> (&obj);	2587	iow.set <myclass, &myclass::io_cb> (&obj);
2363		2588
2364	=item w->set<function> (void *data = 0)	2589	=item w->set<function> (void *data = 0)
2365		2590
2366	Also sets a callback, but uses a static method or plain function as	2591	Also sets a callback, but uses a static method or plain function as
2367	callback. The optional C<data> argument will be stored in the watcher's	2592	callback. The optional C<data> argument will be stored in the watcher's
…		…
2371		2596
2372	See the method-C<set> above for more details.	2597	See the method-C<set> above for more details.
2373		2598
2374	Example:	2599	Example:
2375		2600
2376	static void io_cb (ev::io &w, int revents) { }	2601	static void io_cb (ev::io &w, int revents) { }
2377	iow.set <io_cb> ();	2602	iow.set <io_cb> ();
2378		2603
2379	=item w->set (struct ev_loop *)	2604	=item w->set (struct ev_loop *)
2380		2605
2381	Associates a different C<struct ev_loop> with this watcher. You can only	2606	Associates a different C<struct ev_loop> with this watcher. You can only
2382	do this when the watcher is inactive (and not pending either).	2607	do this when the watcher is inactive (and not pending either).
2383		2608
2384	=item w->set ([args])	2609	=item w->set ([arguments])
2385		2610
2386	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2611	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2387	called at least once. Unlike the C counterpart, an active watcher gets	2612	called at least once. Unlike the C counterpart, an active watcher gets
2388	automatically stopped and restarted when reconfiguring it with this	2613	automatically stopped and restarted when reconfiguring it with this
2389	method.	2614	method.
2390		2615
2391	=item w->start ()	2616	=item w->start ()
…		…
2415	=back	2640	=back
2416		2641
2417	Example: Define a class with an IO and idle watcher, start one of them in	2642	Example: Define a class with an IO and idle watcher, start one of them in
2418	the constructor.	2643	the constructor.
2419		2644
2420	class myclass	2645	class myclass
2421	{	2646	{
2422	ev::io io; void io_cb (ev::io &w, int revents);	2647	ev::io io; void io_cb (ev::io &w, int revents);
2423	ev:idle idle void idle_cb (ev::idle &w, int revents);	2648	ev:idle idle void idle_cb (ev::idle &w, int revents);
2424		2649
2425	myclass (int fd)	2650	myclass (int fd)
2426	{	2651	{
2427	io .set <myclass, &myclass::io_cb > (this);	2652	io .set <myclass, &myclass::io_cb > (this);
2428	idle.set <myclass, &myclass::idle_cb> (this);	2653	idle.set <myclass, &myclass::idle_cb> (this);
2429		2654
2430	io.start (fd, ev::READ);	2655	io.start (fd, ev::READ);
2431	}	2656	}
2432	};	2657	};
		2658
		2659
		2660	=head1 OTHER LANGUAGE BINDINGS
		2661
		2662	Libev does not offer other language bindings itself, but bindings for a
		2663	number of languages exist in the form of third-party packages. If you know
		2664	any interesting language binding in addition to the ones listed here, drop
		2665	me a note.
		2666
		2667	=over 4
		2668
		2669	=item Perl
		2670
		2671	The EV module implements the full libev API and is actually used to test
		2672	libev. EV is developed together with libev. Apart from the EV core module,
		2673	there are additional modules that implement libev-compatible interfaces
		2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2676
		2677	It can be found and installed via CPAN, its homepage is at
		2678	L<http://software.schmorp.de/pkg/EV>.
		2679
		2680	=item Python
		2681
		2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2683	seems to be quite complete and well-documented. Note, however, that the
		2684	patch they require for libev is outright dangerous as it breaks the ABI
		2685	for everybody else, and therefore, should never be applied in an installed
		2686	libev (if python requires an incompatible ABI then it needs to embed
		2687	libev).
		2688
		2689	=item Ruby
		2690
		2691	Tony Arcieri has written a ruby extension that offers access to a subset
		2692	of the libev API and adds file handle abstractions, asynchronous DNS and
		2693	more on top of it. It can be found via gem servers. Its homepage is at
		2694	L<http://rev.rubyforge.org/>.
		2695
		2696	=item D
		2697
		2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2700
		2701	=back
2433		2702
2434		2703
2435	=head1 MACRO MAGIC	2704	=head1 MACRO MAGIC
2436		2705
2437	Libev can be compiled with a variety of options, the most fundamantal	2706	Libev can be compiled with a variety of options, the most fundamental
2438	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2707	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2439	functions and callbacks have an initial C<struct ev_loop *> argument.	2708	functions and callbacks have an initial C<struct ev_loop *> argument.
2440		2709
2441	To make it easier to write programs that cope with either variant, the	2710	To make it easier to write programs that cope with either variant, the
2442	following macros are defined:	2711	following macros are defined:
…		…
2447		2716
2448	This provides the loop I<argument> for functions, if one is required ("ev	2717	This provides the loop I<argument> for functions, if one is required ("ev
2449	loop argument"). The C<EV_A> form is used when this is the sole argument,	2718	loop argument"). The C<EV_A> form is used when this is the sole argument,
2450	C<EV_A_> is used when other arguments are following. Example:	2719	C<EV_A_> is used when other arguments are following. Example:
2451		2720
2452	ev_unref (EV_A);	2721	ev_unref (EV_A);
2453	ev_timer_add (EV_A_ watcher);	2722	ev_timer_add (EV_A_ watcher);
2454	ev_loop (EV_A_ 0);	2723	ev_loop (EV_A_ 0);
2455		2724
2456	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2725	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2457	which is often provided by the following macro.	2726	which is often provided by the following macro.
2458		2727
2459	=item C<EV_P>, C<EV_P_>	2728	=item C<EV_P>, C<EV_P_>
2460		2729
2461	This provides the loop I<parameter> for functions, if one is required ("ev	2730	This provides the loop I<parameter> for functions, if one is required ("ev
2462	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2731	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2463	C<EV_P_> is used when other parameters are following. Example:	2732	C<EV_P_> is used when other parameters are following. Example:
2464		2733
2465	// this is how ev_unref is being declared	2734	// this is how ev_unref is being declared
2466	static void ev_unref (EV_P);	2735	static void ev_unref (EV_P);
2467		2736
2468	// this is how you can declare your typical callback	2737	// this is how you can declare your typical callback
2469	static void cb (EV_P_ ev_timer *w, int revents)	2738	static void cb (EV_P_ ev_timer *w, int revents)
2470		2739
2471	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2740	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2472	suitable for use with C<EV_A>.	2741	suitable for use with C<EV_A>.
2473		2742
2474	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2743	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2475		2744
2476	Similar to the other two macros, this gives you the value of the default	2745	Similar to the other two macros, this gives you the value of the default
2477	loop, if multiple loops are supported ("ev loop default").	2746	loop, if multiple loops are supported ("ev loop default").
		2747
		2748	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2749
		2750	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2751	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2752	is undefined when the default loop has not been initialised by a previous
		2753	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2754
		2755	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2756	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2478		2757
2479	=back	2758	=back
2480		2759
2481	Example: Declare and initialise a check watcher, utilising the above	2760	Example: Declare and initialise a check watcher, utilising the above
2482	macros so it will work regardless of whether multiple loops are supported	2761	macros so it will work regardless of whether multiple loops are supported
2483	or not.	2762	or not.
2484		2763
2485	static void	2764	static void
2486	check_cb (EV_P_ ev_timer *w, int revents)	2765	check_cb (EV_P_ ev_timer *w, int revents)
2487	{	2766	{
2488	ev_check_stop (EV_A_ w);	2767	ev_check_stop (EV_A_ w);
2489	}	2768	}
2490		2769
2491	ev_check check;	2770	ev_check check;
2492	ev_check_init (&check, check_cb);	2771	ev_check_init (&check, check_cb);
2493	ev_check_start (EV_DEFAULT_ &check);	2772	ev_check_start (EV_DEFAULT_ &check);
2494	ev_loop (EV_DEFAULT_ 0);	2773	ev_loop (EV_DEFAULT_ 0);
2495		2774
2496	=head1 EMBEDDING	2775	=head1 EMBEDDING
2497		2776
2498	Libev can (and often is) directly embedded into host	2777	Libev can (and often is) directly embedded into host
2499	applications. Examples of applications that embed it include the Deliantra	2778	applications. Examples of applications that embed it include the Deliantra
…		…
2506	libev somewhere in your source tree).	2785	libev somewhere in your source tree).
2507		2786
2508	=head2 FILESETS	2787	=head2 FILESETS
2509		2788
2510	Depending on what features you need you need to include one or more sets of files	2789	Depending on what features you need you need to include one or more sets of files
2511	in your app.	2790	in your application.
2512		2791
2513	=head3 CORE EVENT LOOP	2792	=head3 CORE EVENT LOOP
2514		2793
2515	To include only the libev core (all the C<ev_*> functions), with manual	2794	To include only the libev core (all the C<ev_*> functions), with manual
2516	configuration (no autoconf):	2795	configuration (no autoconf):
2517		2796
2518	#define EV_STANDALONE 1	2797	#define EV_STANDALONE 1
2519	#include "ev.c"	2798	#include "ev.c"
2520		2799
2521	This will automatically include F<ev.h>, too, and should be done in a	2800	This will automatically include F<ev.h>, too, and should be done in a
2522	single C source file only to provide the function implementations. To use	2801	single C source file only to provide the function implementations. To use
2523	it, do the same for F<ev.h> in all files wishing to use this API (best	2802	it, do the same for F<ev.h> in all files wishing to use this API (best
2524	done by writing a wrapper around F<ev.h> that you can include instead and	2803	done by writing a wrapper around F<ev.h> that you can include instead and
2525	where you can put other configuration options):	2804	where you can put other configuration options):
2526		2805
2527	#define EV_STANDALONE 1	2806	#define EV_STANDALONE 1
2528	#include "ev.h"	2807	#include "ev.h"
2529		2808
2530	Both header files and implementation files can be compiled with a C++	2809	Both header files and implementation files can be compiled with a C++
2531	compiler (at least, thats a stated goal, and breakage will be treated	2810	compiler (at least, thats a stated goal, and breakage will be treated
2532	as a bug).	2811	as a bug).
2533		2812
2534	You need the following files in your source tree, or in a directory	2813	You need the following files in your source tree, or in a directory
2535	in your include path (e.g. in libev/ when using -Ilibev):	2814	in your include path (e.g. in libev/ when using -Ilibev):
2536		2815
2537	ev.h	2816	ev.h
2538	ev.c	2817	ev.c
2539	ev_vars.h	2818	ev_vars.h
2540	ev_wrap.h	2819	ev_wrap.h
2541		2820
2542	ev_win32.c required on win32 platforms only	2821	ev_win32.c required on win32 platforms only
2543		2822
2544	ev_select.c only when select backend is enabled (which is enabled by default)	2823	ev_select.c only when select backend is enabled (which is enabled by default)
2545	ev_poll.c only when poll backend is enabled (disabled by default)	2824	ev_poll.c only when poll backend is enabled (disabled by default)
2546	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2825	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2547	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2826	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2548	ev_port.c only when the solaris port backend is enabled (disabled by default)	2827	ev_port.c only when the solaris port backend is enabled (disabled by default)
2549		2828
2550	F<ev.c> includes the backend files directly when enabled, so you only need	2829	F<ev.c> includes the backend files directly when enabled, so you only need
2551	to compile this single file.	2830	to compile this single file.
2552		2831
2553	=head3 LIBEVENT COMPATIBILITY API	2832	=head3 LIBEVENT COMPATIBILITY API
2554		2833
2555	To include the libevent compatibility API, also include:	2834	To include the libevent compatibility API, also include:
2556		2835
2557	#include "event.c"	2836	#include "event.c"
2558		2837
2559	in the file including F<ev.c>, and:	2838	in the file including F<ev.c>, and:
2560		2839
2561	#include "event.h"	2840	#include "event.h"
2562		2841
2563	in the files that want to use the libevent API. This also includes F<ev.h>.	2842	in the files that want to use the libevent API. This also includes F<ev.h>.
2564		2843
2565	You need the following additional files for this:	2844	You need the following additional files for this:
2566		2845
2567	event.h	2846	event.h
2568	event.c	2847	event.c
2569		2848
2570	=head3 AUTOCONF SUPPORT	2849	=head3 AUTOCONF SUPPORT
2571		2850
2572	Instead of using C<EV_STANDALONE=1> and providing your config in	2851	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2573	whatever way you want, you can also C<m4_include([libev.m4])> in your	2852	whatever way you want, you can also C<m4_include([libev.m4])> in your
2574	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2853	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2575	include F<config.h> and configure itself accordingly.	2854	include F<config.h> and configure itself accordingly.
2576		2855
2577	For this of course you need the m4 file:	2856	For this of course you need the m4 file:
2578		2857
2579	libev.m4	2858	libev.m4
2580		2859
2581	=head2 PREPROCESSOR SYMBOLS/MACROS	2860	=head2 PREPROCESSOR SYMBOLS/MACROS
2582		2861
2583	Libev can be configured via a variety of preprocessor symbols you have to define	2862	Libev can be configured via a variety of preprocessor symbols you have to
2584	before including any of its files. The default is not to build for multiplicity	2863	define before including any of its files. The default in the absence of
2585	and only include the select backend.	2864	autoconf is noted for every option.
2586		2865
2587	=over 4	2866	=over 4
2588		2867
2589	=item EV_STANDALONE	2868	=item EV_STANDALONE
2590		2869
…		…
2595	F<event.h> that are not directly supported by the libev core alone.	2874	F<event.h> that are not directly supported by the libev core alone.
2596		2875
2597	=item EV_USE_MONOTONIC	2876	=item EV_USE_MONOTONIC
2598		2877
2599	If defined to be C<1>, libev will try to detect the availability of the	2878	If defined to be C<1>, libev will try to detect the availability of the
2600	monotonic clock option at both compiletime and runtime. Otherwise no use	2879	monotonic clock option at both compile time and runtime. Otherwise no use
2601	of the monotonic clock option will be attempted. If you enable this, you	2880	of the monotonic clock option will be attempted. If you enable this, you
2602	usually have to link against librt or something similar. Enabling it when	2881	usually have to link against librt or something similar. Enabling it when
2603	the functionality isn't available is safe, though, although you have	2882	the functionality isn't available is safe, though, although you have
2604	to make sure you link against any libraries where the C<clock_gettime>	2883	to make sure you link against any libraries where the C<clock_gettime>
2605	function is hiding in (often F<-lrt>).	2884	function is hiding in (often F<-lrt>).
2606		2885
2607	=item EV_USE_REALTIME	2886	=item EV_USE_REALTIME
2608		2887
2609	If defined to be C<1>, libev will try to detect the availability of the	2888	If defined to be C<1>, libev will try to detect the availability of the
2610	realtime clock option at compiletime (and assume its availability at	2889	real-time clock option at compile time (and assume its availability at
2611	runtime if successful). Otherwise no use of the realtime clock option will	2890	runtime if successful). Otherwise no use of the real-time clock option will
2612	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2613	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2614	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2615		2894
2616	=item EV_USE_NANOSLEEP	2895	=item EV_USE_NANOSLEEP
2617		2896
2618	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2619	and will use it for delays. Otherwise it will use C<select ()>.	2898	and will use it for delays. Otherwise it will use C<select ()>.
2620		2899
		2900	=item EV_USE_EVENTFD
		2901
		2902	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2903	available and will probe for kernel support at runtime. This will improve
		2904	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2905	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2906	2.7 or newer, otherwise disabled.
		2907
2621	=item EV_USE_SELECT	2908	=item EV_USE_SELECT
2622		2909
2623	If undefined or defined to be C<1>, libev will compile in support for the	2910	If undefined or defined to be C<1>, libev will compile in support for the
2624	C<select>(2) backend. No attempt at autodetection will be done: if no	2911	C<select>(2) backend. No attempt at auto-detection will be done: if no
2625	other method takes over, select will be it. Otherwise the select backend	2912	other method takes over, select will be it. Otherwise the select backend
2626	will not be compiled in.	2913	will not be compiled in.
2627		2914
2628	=item EV_SELECT_USE_FD_SET	2915	=item EV_SELECT_USE_FD_SET
2629		2916
2630	If defined to C<1>, then the select backend will use the system C<fd_set>	2917	If defined to C<1>, then the select backend will use the system C<fd_set>
2631	structure. This is useful if libev doesn't compile due to a missing	2918	structure. This is useful if libev doesn't compile due to a missing
2632	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2633	exotic systems. This usually limits the range of file descriptors to some	2920	exotic systems. This usually limits the range of file descriptors to some
2634	low limit such as 1024 or might have other limitations (winsocket only	2921	low limit such as 1024 or might have other limitations (winsocket only
2635	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2636	influence the size of the C<fd_set> used.	2923	influence the size of the C<fd_set> used.
2637		2924
…		…
2661		2948
2662	=item EV_USE_EPOLL	2949	=item EV_USE_EPOLL
2663		2950
2664	If defined to be C<1>, libev will compile in support for the Linux	2951	If defined to be C<1>, libev will compile in support for the Linux
2665	C<epoll>(7) backend. Its availability will be detected at runtime,	2952	C<epoll>(7) backend. Its availability will be detected at runtime,
2666	otherwise another method will be used as fallback. This is the	2953	otherwise another method will be used as fallback. This is the preferred
2667	preferred backend for GNU/Linux systems.	2954	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2955	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2668		2956
2669	=item EV_USE_KQUEUE	2957	=item EV_USE_KQUEUE
2670		2958
2671	If defined to be C<1>, libev will compile in support for the BSD style	2959	If defined to be C<1>, libev will compile in support for the BSD style
2672	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2960	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2685	otherwise another method will be used as fallback. This is the preferred	2973	otherwise another method will be used as fallback. This is the preferred
2686	backend for Solaris 10 systems.	2974	backend for Solaris 10 systems.
2687		2975
2688	=item EV_USE_DEVPOLL	2976	=item EV_USE_DEVPOLL
2689		2977
2690	reserved for future expansion, works like the USE symbols above.	2978	Reserved for future expansion, works like the USE symbols above.
2691		2979
2692	=item EV_USE_INOTIFY	2980	=item EV_USE_INOTIFY
2693		2981
2694	If defined to be C<1>, libev will compile in support for the Linux inotify	2982	If defined to be C<1>, libev will compile in support for the Linux inotify
2695	interface to speed up C<ev_stat> watchers. Its actual availability will	2983	interface to speed up C<ev_stat> watchers. Its actual availability will
2696	be detected at runtime.	2984	be detected at runtime. If undefined, it will be enabled if the headers
		2985	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2697		2986
2698	=item EV_ATOMIC_T	2987	=item EV_ATOMIC_T
2699		2988
2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	2989	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2701	access is atomic with respect to other threads or signal contexts. No such	2990	access is atomic with respect to other threads or signal contexts. No such
2702	type is easily found in the C language, so you can provide your own type	2991	type is easily found in the C language, so you can provide your own type
2703	that you know is safe for your purposes. It is used both for signal handler "locking"	2992	that you know is safe for your purposes. It is used both for signal handler "locking"
2704	as well as for signal and thread safety in C<ev_async> watchers.	2993	as well as for signal and thread safety in C<ev_async> watchers.
2705		2994
2706	In the absense of this define, libev will use C<sig_atomic_t volatile>	2995	In the absence of this define, libev will use C<sig_atomic_t volatile>
2707	(from F<signal.h>), which is usually good enough on most platforms.	2996	(from F<signal.h>), which is usually good enough on most platforms.
2708		2997
2709	=item EV_H	2998	=item EV_H
2710		2999
2711	The name of the F<ev.h> header file used to include it. The default if	3000	The name of the F<ev.h> header file used to include it. The default if
…		…
2750	When doing priority-based operations, libev usually has to linearly search	3039	When doing priority-based operations, libev usually has to linearly search
2751	all the priorities, so having many of them (hundreds) uses a lot of space	3040	all the priorities, so having many of them (hundreds) uses a lot of space
2752	and time, so using the defaults of five priorities (-2 .. +2) is usually	3041	and time, so using the defaults of five priorities (-2 .. +2) is usually
2753	fine.	3042	fine.
2754		3043
2755	If your embedding app does not need any priorities, defining these both to	3044	If your embedding application does not need any priorities, defining these both to
2756	C<0> will save some memory and cpu.	3045	C<0> will save some memory and CPU.
2757		3046
2758	=item EV_PERIODIC_ENABLE	3047	=item EV_PERIODIC_ENABLE
2759		3048
2760	If undefined or defined to be C<1>, then periodic timers are supported. If	3049	If undefined or defined to be C<1>, then periodic timers are supported. If
2761	defined to be C<0>, then they are not. Disabling them saves a few kB of	3050	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2788	defined to be C<0>, then they are not.	3077	defined to be C<0>, then they are not.
2789		3078
2790	=item EV_MINIMAL	3079	=item EV_MINIMAL
2791		3080
2792	If you need to shave off some kilobytes of code at the expense of some	3081	If you need to shave off some kilobytes of code at the expense of some
2793	speed, define this symbol to C<1>. Currently only used for gcc to override	3082	speed, define this symbol to C<1>. Currently this is used to override some
2794	some inlining decisions, saves roughly 30% codesize of amd64.	3083	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3084	much smaller 2-heap for timer management over the default 4-heap.
2795		3085
2796	=item EV_PID_HASHSIZE	3086	=item EV_PID_HASHSIZE
2797		3087
2798	C<ev_child> watchers use a small hash table to distribute workload by	3088	C<ev_child> watchers use a small hash table to distribute workload by
2799	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3089	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2806	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3096	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2807	usually more than enough. If you need to manage thousands of C<ev_stat>	3097	usually more than enough. If you need to manage thousands of C<ev_stat>
2808	watchers you might want to increase this value (I<must> be a power of	3098	watchers you might want to increase this value (I<must> be a power of
2809	two).	3099	two).
2810		3100
		3101	=item EV_USE_4HEAP
		3102
		3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3105	to C<1>. The 4-heap uses more complicated (longer) code but has
		3106	noticeably faster performance with many (thousands) of watchers.
		3107
		3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3109	(disabled).
		3110
		3111	=item EV_HEAP_CACHE_AT
		3112
		3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3114	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3117	but avoids random read accesses on heap changes. This improves performance
		3118	noticeably with with many (hundreds) of watchers.
		3119
		3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3121	(disabled).
		3122
		3123	=item EV_VERIFY
		3124
		3125	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3126	be done: If set to C<0>, no internal verification code will be compiled
		3127	in. If set to C<1>, then verification code will be compiled in, but not
		3128	called. If set to C<2>, then the internal verification code will be
		3129	called once per loop, which can slow down libev. If set to C<3>, then the
		3130	verification code will be called very frequently, which will slow down
		3131	libev considerably.
		3132
		3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3134	C<0.>
		3135
2811	=item EV_COMMON	3136	=item EV_COMMON
2812		3137
2813	By default, all watchers have a C<void *data> member. By redefining	3138	By default, all watchers have a C<void *data> member. By redefining
2814	this macro to a something else you can include more and other types of	3139	this macro to a something else you can include more and other types of
2815	members. You have to define it each time you include one of the files,	3140	members. You have to define it each time you include one of the files,
2816	though, and it must be identical each time.	3141	though, and it must be identical each time.
2817		3142
2818	For example, the perl EV module uses something like this:	3143	For example, the perl EV module uses something like this:
2819		3144
2820	#define EV_COMMON \	3145	#define EV_COMMON \
2821	SV *self; /* contains this struct */ \	3146	SV *self; /* contains this struct */ \
2822	SV *cb_sv, *fh /* note no trailing ";" */	3147	SV *cb_sv, *fh /* note no trailing ";" */
2823		3148
2824	=item EV_CB_DECLARE (type)	3149	=item EV_CB_DECLARE (type)
2825		3150
2826	=item EV_CB_INVOKE (watcher, revents)	3151	=item EV_CB_INVOKE (watcher, revents)
2827		3152
…		…
2834	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2835	method calls instead of plain function calls in C++.	3160	method calls instead of plain function calls in C++.
2836		3161
2837	=head2 EXPORTED API SYMBOLS	3162	=head2 EXPORTED API SYMBOLS
2838		3163
2839	If you need to re-export the API (e.g. via a dll) and you need a list of	3164	If you need to re-export the API (e.g. via a DLL) and you need a list of
2840	exported symbols, you can use the provided F<Symbol.*> files which list	3165	exported symbols, you can use the provided F<Symbol.*> files which list
2841	all public symbols, one per line:	3166	all public symbols, one per line:
2842		3167
2843	Symbols.ev for libev proper	3168	Symbols.ev for libev proper
2844	Symbols.event for the libevent emulation	3169	Symbols.event for the libevent emulation
2845		3170
2846	This can also be used to rename all public symbols to avoid clashes with	3171	This can also be used to rename all public symbols to avoid clashes with
2847	multiple versions of libev linked together (which is obviously bad in	3172	multiple versions of libev linked together (which is obviously bad in
2848	itself, but sometimes it is inconvinient to avoid this).	3173	itself, but sometimes it is inconvenient to avoid this).
2849		3174
2850	A sed command like this will create wrapper C<#define>'s that you need to	3175	A sed command like this will create wrapper C<#define>'s that you need to
2851	include before including F<ev.h>:	3176	include before including F<ev.h>:
2852		3177
2853	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3178	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2870	file.	3195	file.
2871		3196
2872	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3197	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2873	that everybody includes and which overrides some configure choices:	3198	that everybody includes and which overrides some configure choices:
2874		3199
2875	#define EV_MINIMAL 1	3200	#define EV_MINIMAL 1
2876	#define EV_USE_POLL 0	3201	#define EV_USE_POLL 0
2877	#define EV_MULTIPLICITY 0	3202	#define EV_MULTIPLICITY 0
2878	#define EV_PERIODIC_ENABLE 0	3203	#define EV_PERIODIC_ENABLE 0
2879	#define EV_STAT_ENABLE 0	3204	#define EV_STAT_ENABLE 0
2880	#define EV_FORK_ENABLE 0	3205	#define EV_FORK_ENABLE 0
2881	#define EV_CONFIG_H <config.h>	3206	#define EV_CONFIG_H <config.h>
2882	#define EV_MINPRI 0	3207	#define EV_MINPRI 0
2883	#define EV_MAXPRI 0	3208	#define EV_MAXPRI 0
2884		3209
2885	#include "ev++.h"	3210	#include "ev++.h"
2886		3211
2887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2888		3213
2889	#include "ev_cpp.h"	3214	#include "ev_cpp.h"
2890	#include "ev.c"	3215	#include "ev.c"
		3216
		3217
		3218	=head1 THREADS AND COROUTINES
		3219
		3220	=head2 THREADS
		3221
		3222	Libev itself is completely thread-safe, but it uses no locking. This
		3223	means that you can use as many loops as you want in parallel, as long as
		3224	only one thread ever calls into one libev function with the same loop
		3225	parameter.
		3226
		3227	Or put differently: calls with different loop parameters can be done in
		3228	parallel from multiple threads, calls with the same loop parameter must be
		3229	done serially (but can be done from different threads, as long as only one
		3230	thread ever is inside a call at any point in time, e.g. by using a mutex
		3231	per loop).
		3232
		3233	If you want to know which design (one loop, locking, or multiple loops
		3234	without or something else still) is best for your problem, then I cannot
		3235	help you. I can give some generic advice however:
		3236
		3237	=over 4
		3238
		3239	=item * most applications have a main thread: use the default libev loop
		3240	in that thread, or create a separate thread running only the default loop.
		3241
		3242	This helps integrating other libraries or software modules that use libev
		3243	themselves and don't care/know about threading.
		3244
		3245	=item * one loop per thread is usually a good model.
		3246
		3247	Doing this is almost never wrong, sometimes a better-performance model
		3248	exists, but it is always a good start.
		3249
		3250	=item * other models exist, such as the leader/follower pattern, where one
		3251	loop is handed through multiple threads in a kind of round-robin fashion.
		3252
		3253	Choosing a model is hard - look around, learn, know that usually you can do
		3254	better than you currently do :-)
		3255
		3256	=item * often you need to talk to some other thread which blocks in the
		3257	event loop - C<ev_async> watchers can be used to wake them up from other
		3258	threads safely (or from signal contexts...).
		3259
		3260	=back
		3261
		3262	=head2 COROUTINES
		3263
		3264	Libev is much more accommodating to coroutines ("cooperative threads"):
		3265	libev fully supports nesting calls to it's functions from different
		3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3267	different coroutines and switch freely between both coroutines running the
		3268	loop, as long as you don't confuse yourself). The only exception is that
		3269	you must not do this from C<ev_periodic> reschedule callbacks.
		3270
		3271	Care has been invested into making sure that libev does not keep local
		3272	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3273	switches.
2891		3274
2892		3275
2893	=head1 COMPLEXITIES	3276	=head1 COMPLEXITIES
2894		3277
2895	In this section the complexities of (many of) the algorithms used inside	3278	In this section the complexities of (many of) the algorithms used inside
…		…
2927	correct watcher to remove. The lists are usually short (you don't usually	3310	correct watcher to remove. The lists are usually short (you don't usually
2928	have many watchers waiting for the same fd or signal).	3311	have many watchers waiting for the same fd or signal).
2929		3312
2930	=item Finding the next timer in each loop iteration: O(1)	3313	=item Finding the next timer in each loop iteration: O(1)
2931		3314
2932	By virtue of using a binary heap, the next timer is always found at the	3315	By virtue of using a binary or 4-heap, the next timer is always found at a
2933	beginning of the storage array.	3316	fixed position in the storage array.
2934		3317
2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2936		3319
2937	A change means an I/O watcher gets started or stopped, which requires	3320	A change means an I/O watcher gets started or stopped, which requires
2938	libev to recalculate its status (and possibly tell the kernel, depending	3321	libev to recalculate its status (and possibly tell the kernel, depending
2939	on backend and wether C<ev_io_set> was used).	3322	on backend and whether C<ev_io_set> was used).
2940		3323
2941	=item Activating one watcher (putting it into the pending state): O(1)	3324	=item Activating one watcher (putting it into the pending state): O(1)
2942		3325
2943	=item Priority handling: O(number_of_priorities)	3326	=item Priority handling: O(number_of_priorities)
2944		3327
…		…
2951		3334
2952	=item Processing ev_async_send: O(number_of_async_watchers)	3335	=item Processing ev_async_send: O(number_of_async_watchers)
2953		3336
2954	=item Processing signals: O(max_signal_number)	3337	=item Processing signals: O(max_signal_number)
2955		3338
2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>	3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
2957	calls in the current loop iteration. Checking for async and signal events	3340	calls in the current loop iteration. Checking for async and signal events
2958	involves iterating over all running async watchers or all signal numbers.	3341	involves iterating over all running async watchers or all signal numbers.
2959		3342
2960	=back	3343	=back
2961		3344
2962		3345
2963	=head1 Win32 platform limitations and workarounds	3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2964		3347
2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2966	requires, and its I/O model is fundamentally incompatible with the POSIX	3349	requires, and its I/O model is fundamentally incompatible with the POSIX
2967	model. Libev still offers limited functionality on this platform in	3350	model. Libev still offers limited functionality on this platform in
2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2969	descriptors. This only applies when using Win32 natively, not when using	3352	descriptors. This only applies when using Win32 natively, not when using
2970	e.g. cygwin.	3353	e.g. cygwin.
2971		3354
		3355	Lifting these limitations would basically require the full
		3356	re-implementation of the I/O system. If you are into these kinds of
		3357	things, then note that glib does exactly that for you in a very portable
		3358	way (note also that glib is the slowest event library known to man).
		3359
2972	There is no supported compilation method available on windows except	3360	There is no supported compilation method available on windows except
2973	embedding it into other applications.	3361	embedding it into other applications.
2974		3362
		3363	Not a libev limitation but worth mentioning: windows apparently doesn't
		3364	accept large writes: instead of resulting in a partial write, windows will
		3365	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3366	so make sure you only write small amounts into your sockets (less than a
		3367	megabyte seems safe, but thsi apparently depends on the amount of memory
		3368	available).
		3369
2975	Due to the many, low, and arbitrary limits on the win32 platform and the	3370	Due to the many, low, and arbitrary limits on the win32 platform and
2976	abysmal performance of winsockets, using a large number of sockets is not	3371	the abysmal performance of winsockets, using a large number of sockets
2977	recommended (and not reasonable). If your program needs to use more than	3372	is not recommended (and not reasonable). If your program needs to use
2978	a hundred or so sockets, then likely it needs to use a totally different	3373	more than a hundred or so sockets, then likely it needs to use a totally
2979	implementation for windows, as libev offers the POSIX model, which cannot	3374	different implementation for windows, as libev offers the POSIX readiness
2980	be implemented efficiently on windows (microsoft monopoly games).	3375	notification model, which cannot be implemented efficiently on windows
		3376	(Microsoft monopoly games).
		3377
		3378	A typical way to use libev under windows is to embed it (see the embedding
		3379	section for details) and use the following F<evwrap.h> header file instead
		3380	of F<ev.h>:
		3381
		3382	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3384
		3385	#include "ev.h"
		3386
		3387	And compile the following F<evwrap.c> file into your project (make sure
		3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3389
		3390	#include "evwrap.h"
		3391	#include "ev.c"
2981		3392
2982	=over 4	3393	=over 4
2983		3394
2984	=item The winsocket select function	3395	=item The winsocket select function
2985		3396
2986	The winsocket C<select> function doesn't follow POSIX in that it requires	3397	The winsocket C<select> function doesn't follow POSIX in that it
2987	socket I<handles> and not socket I<file descriptors>. This makes select	3398	requires socket I<handles> and not socket I<file descriptors> (it is
2988	very inefficient, and also requires a mapping from file descriptors	3399	also extremely buggy). This makes select very inefficient, and also
2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3400	requires a mapping from file descriptors to socket handles (the Microsoft
2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3401	C runtime provides the function C<_open_osfhandle> for this). See the
2991	symbols for more info.	3402	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3403	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2992		3404
2993	The configuration for a "naked" win32 using the microsoft runtime	3405	The configuration for a "naked" win32 using the Microsoft runtime
2994	libraries and raw winsocket select is:	3406	libraries and raw winsocket select is:
2995		3407
2996	#define EV_USE_SELECT 1	3408	#define EV_USE_SELECT 1
2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3409	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2998		3410
2999	Note that winsockets handling of fd sets is O(n), so you can easily get a	3411	Note that winsockets handling of fd sets is O(n), so you can easily get a
3000	complexity in the O(n²) range when using win32.	3412	complexity in the O(n²) range when using win32.
3001		3413
3002	=item Limited number of file descriptors	3414	=item Limited number of file descriptors
3003		3415
3004	Windows has numerous arbitrary (and low) limits on things. Early versions	3416	Windows has numerous arbitrary (and low) limits on things.
3005	of winsocket's select only supported waiting for a max. of C<64> handles	3417
		3418	Early versions of winsocket's select only supported waiting for a maximum
3006	(probably owning to the fact that all windows kernels can only wait for	3419	of C<64> handles (probably owning to the fact that all windows kernels
3007	C<64> things at the same time internally; microsoft recommends spawning a	3420	can only wait for C<64> things at the same time internally; Microsoft
3008	chain of threads and wait for 63 handles and the previous thread in each).	3421	recommends spawning a chain of threads and wait for 63 handles and the
		3422	previous thread in each. Great).
3009		3423
3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3011	to some high number (e.g. C<2048>) before compiling the winsocket select	3425	to some high number (e.g. C<2048>) before compiling the winsocket select
3012	call (which might be in libev or elsewhere, for example, perl does its own	3426	call (which might be in libev or elsewhere, for example, perl does its own
3013	select emulation on windows).	3427	select emulation on windows).
3014		3428
3015	Another limit is the number of file descriptors in the microsoft runtime	3429	Another limit is the number of file descriptors in the Microsoft runtime
3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3017	or something like this inside microsoft). You can increase this by calling	3431	or something like this inside Microsoft). You can increase this by calling
3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3019	arbitrary limit), but is broken in many versions of the microsoft runtime	3433	arbitrary limit), but is broken in many versions of the Microsoft runtime
3020	libraries.	3434	libraries.
3021		3435
3022	This might get you to about C<512> or C<2048> sockets (depending on	3436	This might get you to about C<512> or C<2048> sockets (depending on
3023	windows version and/or the phase of the moon). To get more, you need to	3437	windows version and/or the phase of the moon). To get more, you need to
3024	wrap all I/O functions and provide your own fd management, but the cost of	3438	wrap all I/O functions and provide your own fd management, but the cost of
3025	calling select (O(n²)) will likely make this unworkable.	3439	calling select (O(n²)) will likely make this unworkable.
3026		3440
3027	=back	3441	=back
3028		3442
3029		3443
		3444	=head1 PORTABILITY REQUIREMENTS
		3445
		3446	In addition to a working ISO-C implementation, libev relies on a few
		3447	additional extensions:
		3448
		3449	=over 4
		3450
		3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3452	calling conventions regardless of C<ev_watcher_type *>.
		3453
		3454	Libev assumes not only that all watcher pointers have the same internal
		3455	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3456	assumes that the same (machine) code can be used to call any watcher
		3457	callback: The watcher callbacks have different type signatures, but libev
		3458	calls them using an C<ev_watcher *> internally.
		3459
		3460	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3461
		3462	The type C<sig_atomic_t volatile> (or whatever is defined as
		3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3464	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3465	believed to be sufficiently portable.
		3466
		3467	=item C<sigprocmask> must work in a threaded environment
		3468
		3469	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3470	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3471	pthread implementations will either allow C<sigprocmask> in the "main
		3472	thread" or will block signals process-wide, both behaviours would
		3473	be compatible with libev. Interaction between C<sigprocmask> and
		3474	C<pthread_sigmask> could complicate things, however.
		3475
		3476	The most portable way to handle signals is to block signals in all threads
		3477	except the initial one, and run the default loop in the initial thread as
		3478	well.
		3479
		3480	=item C<long> must be large enough for common memory allocation sizes
		3481
		3482	To improve portability and simplify using libev, libev uses C<long>
		3483	internally instead of C<size_t> when allocating its data structures. On
		3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3485	is still at least 31 bits everywhere, which is enough for hundreds of
		3486	millions of watchers.
		3487
		3488	=item C<double> must hold a time value in seconds with enough accuracy
		3489
		3490	The type C<double> is used to represent timestamps. It is required to
		3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3492	enough for at least into the year 4000. This requirement is fulfilled by
		3493	implementations implementing IEEE 754 (basically all existing ones).
		3494
		3495	=back
		3496
		3497	If you know of other additional requirements drop me a note.
		3498
		3499
		3500	=head1 COMPILER WARNINGS
		3501
		3502	Depending on your compiler and compiler settings, you might get no or a
		3503	lot of warnings when compiling libev code. Some people are apparently
		3504	scared by this.
		3505
		3506	However, these are unavoidable for many reasons. For one, each compiler
		3507	has different warnings, and each user has different tastes regarding
		3508	warning options. "Warn-free" code therefore cannot be a goal except when
		3509	targeting a specific compiler and compiler-version.
		3510
		3511	Another reason is that some compiler warnings require elaborate
		3512	workarounds, or other changes to the code that make it less clear and less
		3513	maintainable.
		3514
		3515	And of course, some compiler warnings are just plain stupid, or simply
		3516	wrong (because they don't actually warn about the condition their message
		3517	seems to warn about).
		3518
		3519	While libev is written to generate as few warnings as possible,
		3520	"warn-free" code is not a goal, and it is recommended not to build libev
		3521	with any compiler warnings enabled unless you are prepared to cope with
		3522	them (e.g. by ignoring them). Remember that warnings are just that:
		3523	warnings, not errors, or proof of bugs.
		3524
		3525
		3526	=head1 VALGRIND
		3527
		3528	Valgrind has a special section here because it is a popular tool that is
		3529	highly useful, but valgrind reports are very hard to interpret.
		3530
		3531	If you think you found a bug (memory leak, uninitialised data access etc.)
		3532	in libev, then check twice: If valgrind reports something like:
		3533
		3534	==2274== definitely lost: 0 bytes in 0 blocks.
		3535	==2274== possibly lost: 0 bytes in 0 blocks.
		3536	==2274== still reachable: 256 bytes in 1 blocks.
		3537
		3538	Then there is no memory leak. Similarly, under some circumstances,
		3539	valgrind might report kernel bugs as if it were a bug in libev, or it
		3540	might be confused (it is a very good tool, but only a tool).
		3541
		3542	If you are unsure about something, feel free to contact the mailing list
		3543	with the full valgrind report and an explanation on why you think this is
		3544	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3545	no bug" answer and take the chance of learning how to interpret valgrind
		3546	properly.
		3547
		3548	If you need, for some reason, empty reports from valgrind for your project
		3549	I suggest using suppression lists.
		3550
		3551
3030	=head1 AUTHOR	3552	=head1 AUTHOR
3031		3553
3032	Marc Lehmann <libev@schmorp.de>.	3554	Marc Lehmann <libev@schmorp.de>.
3033		3555

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