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Revision 1.144 by root, Mon Apr 7 12:33:29 2008 UTC vs.
Revision 1.181 by root, Fri Sep 19 03:47:50 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_<type>
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
274	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
275	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
276		300
277	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
278	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
279	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
280	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
281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
282	C<ev_default_init>.	306	C<ev_default_init>.
283		307
284	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
…		…
293	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
294	thing, believe me).	318	thing, believe me).
295		319
296	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
297		321
298	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
299	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
300	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
301	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
302	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
303	around bugs.	327	around bugs.
…		…
310		334
311	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,
312	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
313	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
314	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
315	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
316	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
317		341
318	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
319	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
320	flag.	344	flag.
321		345
322	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>
323	environment variable.	347	environment variable.
324		348
325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
326		350
327	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
…		…
329	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
330	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
331	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.
332		356
333	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
334	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
335	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
336	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
337	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
338	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
339		367
340	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
341		369
342	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
343	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
344	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
345	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
346	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
347	performance tips.	375	performance tips.
348		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
349	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
350		381
351	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
352	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
353	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
354	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
355	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
356	cases and requiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
357	support for dup.	388	support for dup.
358		389
359	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
360	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
361	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
362	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
363	very well if you register events for both fds.	394	very well if you register events for both fds.
364		395
365	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
…		…
368		399
369	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
370	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible, i.e.
371	keep at least one watcher active per fd at all times.	402	keep at least one watcher active per fd at all times.
372		403
373	While nominally embeddeble in other event loops, this feature is broken in	404	While nominally embeddable in other event loops, this feature is broken in
374	all kernel versions tested so far.	405	all kernel versions tested so far.
		406
		407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		408	C<EVBACKEND_POLL>.
375		409
376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
377		411
378	Kqueue deserves special mention, as at the time of this writing, it	412	Kqueue deserves special mention, as at the time of this writing, it
379	was broken on all BSDs except NetBSD (usually it doesn't work reliably	413	was broken on all BSDs except NetBSD (usually it doesn't work reliably
380	with anything but sockets and pipes, except on Darwin, where of course	414	with anything but sockets and pipes, except on Darwin, where of course
381	it's completely useless). For this reason it's not being "autodetected"	415	it's completely useless). For this reason it's not being "auto-detected"
382	unless you explicitly specify it explicitly in the flags (i.e. using	416	unless you explicitly specify it explicitly in the flags (i.e. using
383	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
384	system like NetBSD.	418	system like NetBSD.
385		419
386	You still can embed kqueue into a normal poll or select backend and use it	420	You still can embed kqueue into a normal poll or select backend and use it
…		…
388	the target platform). See C<ev_embed> watchers for more info.	422	the target platform). See C<ev_embed> watchers for more info.
389		423
390	It scales in the same way as the epoll backend, but the interface to the	424	It scales in the same way as the epoll backend, but the interface to the
391	kernel is more efficient (which says nothing about its actual speed, of	425	kernel is more efficient (which says nothing about its actual speed, of
392	course). While stopping, setting and starting an I/O watcher does never	426	course). While stopping, setting and starting an I/O watcher does never
393	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
394	two event changes per incident, support for C<fork ()> is very bad and it	428	two event changes per incident, support for C<fork ()> is very bad and it
395	drops fds silently in similarly hard-to-detect cases.	429	drops fds silently in similarly hard-to-detect cases.
396		430
397	This backend usually performs well under most conditions.	431	This backend usually performs well under most conditions.
398		432
…		…
401	almost everywhere, you should only use it when you have a lot of sockets	435	almost everywhere, you should only use it when you have a lot of sockets
402	(for which it usually works), by embedding it into another event loop	436	(for which it usually works), by embedding it into another event loop
403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
404	sockets.	438	sockets.
405		439
		440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		442	C<NOTE_EOF>.
		443
406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	444	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
407		445
408	This is not implemented yet (and might never be, unless you send me an	446	This is not implemented yet (and might never be, unless you send me an
409	implementation). According to reports, C</dev/poll> only supports sockets	447	implementation). According to reports, C</dev/poll> only supports sockets
410	and is not embeddable, which would limit the usefulness of this backend	448	and is not embeddable, which would limit the usefulness of this backend
…		…
413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	451	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
414		452
415	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	453	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
416	it's really slow, but it still scales very well (O(active_fds)).	454	it's really slow, but it still scales very well (O(active_fds)).
417		455
418	Please note that solaris event ports can deliver a lot of spurious	456	Please note that Solaris event ports can deliver a lot of spurious
419	notifications, so you need to use non-blocking I/O or other means to avoid	457	notifications, so you need to use non-blocking I/O or other means to avoid
420	blocking when no data (or space) is available.	458	blocking when no data (or space) is available.
421		459
422	While this backend scales well, it requires one system call per active	460	While this backend scales well, it requires one system call per active
423	file descriptor per loop iteration. For small and medium numbers of file	461	file descriptor per loop iteration. For small and medium numbers of file
424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
425	might perform better.	463	might perform better.
426		464
427	On the positive side, ignoring the spurious readyness notifications, this	465	On the positive side, ignoring the spurious readiness notifications, this
428	backend actually performed to specification in all tests and is fully	466	backend actually performed to specification in all tests and is fully
429	embeddable, which is a rare feat among the OS-specific backends.	467	embeddable, which is a rare feat among the OS-specific backends.
		468
		469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		470	C<EVBACKEND_POLL>.
430		471
431	=item C<EVBACKEND_ALL>	472	=item C<EVBACKEND_ALL>
432		473
433	Try all backends (even potentially broken ones that wouldn't be tried	474	Try all backends (even potentially broken ones that wouldn't be tried
434	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	475	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
436		477
437	It is definitely not recommended to use this flag.	478	It is definitely not recommended to use this flag.
438		479
439	=back	480	=back
440		481
441	If one or more of these are ored into the flags value, then only these	482	If one or more of these are or'ed into the flags value, then only these
442	backends will be tried (in the reverse order as listed here). If none are	483	backends will be tried (in the reverse order as listed here). If none are
443	specified, all backends in C<ev_recommended_backends ()> will be tried.	484	specified, all backends in C<ev_recommended_backends ()> will be tried.
444		485
445	The most typical usage is like this:	486	The most typical usage is like this:
446		487
447	if (!ev_default_loop (0))	488	if (!ev_default_loop (0))
448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
449		490
450	Restrict libev to the select and poll backends, and do not allow	491	Restrict libev to the select and poll backends, and do not allow
451	environment settings to be taken into account:	492	environment settings to be taken into account:
452		493
453	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
454		495
455	Use whatever libev has to offer, but make sure that kqueue is used if	496	Use whatever libev has to offer, but make sure that kqueue is used if
456	available (warning, breaks stuff, best use only with your own private	497	available (warning, breaks stuff, best use only with your own private
457	event loop and only if you know the OS supports your types of fds):	498	event loop and only if you know the OS supports your types of fds):
458		499
459	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
460		501
461	=item struct ev_loop *ev_loop_new (unsigned int flags)	502	=item struct ev_loop *ev_loop_new (unsigned int flags)
462		503
463	Similar to C<ev_default_loop>, but always creates a new event loop that is	504	Similar to C<ev_default_loop>, but always creates a new event loop that is
464	always distinct from the default loop. Unlike the default loop, it cannot	505	always distinct from the default loop. Unlike the default loop, it cannot
…		…
469	libev with threads is indeed to create one loop per thread, and using the	510	libev with threads is indeed to create one loop per thread, and using the
470	default loop in the "main" or "initial" thread.	511	default loop in the "main" or "initial" thread.
471		512
472	Example: Try to create a event loop that uses epoll and nothing else.	513	Example: Try to create a event loop that uses epoll and nothing else.
473		514
474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
475	if (!epoller)	516	if (!epoller)
476	fatal ("no epoll found here, maybe it hides under your chair");	517	fatal ("no epoll found here, maybe it hides under your chair");
477		518
478	=item ev_default_destroy ()	519	=item ev_default_destroy ()
479		520
480	Destroys the default loop again (frees all memory and kernel state	521	Destroys the default loop again (frees all memory and kernel state
481	etc.). None of the active event watchers will be stopped in the normal	522	etc.). None of the active event watchers will be stopped in the normal
482	sense, so e.g. C<ev_is_active> might still return true. It is your	523	sense, so e.g. C<ev_is_active> might still return true. It is your
483	responsibility to either stop all watchers cleanly yoursef I<before>	524	responsibility to either stop all watchers cleanly yourself I<before>
484	calling this function, or cope with the fact afterwards (which is usually	525	calling this function, or cope with the fact afterwards (which is usually
485	the easiest thing, you can just ignore the watchers and/or C<free ()> them	526	the easiest thing, you can just ignore the watchers and/or C<free ()> them
486	for example).	527	for example).
487		528
488	Note that certain global state, such as signal state, will not be freed by	529	Note that certain global state, such as signal state, will not be freed by
…		…
549	received events and started processing them. This timestamp does not	590	received events and started processing them. This timestamp does not
550	change as long as callbacks are being processed, and this is also the base	591	change as long as callbacks are being processed, and this is also the base
551	time used for relative timers. You can treat it as the timestamp of the	592	time used for relative timers. You can treat it as the timestamp of the
552	event occurring (or more correctly, libev finding out about it).	593	event occurring (or more correctly, libev finding out about it).
553		594
		595	=item ev_now_update (loop)
		596
		597	Establishes the current time by querying the kernel, updating the time
		598	returned by C<ev_now ()> in the progress. This is a costly operation and
		599	is usually done automatically within C<ev_loop ()>.
		600
		601	This function is rarely useful, but when some event callback runs for a
		602	very long time without entering the event loop, updating libev's idea of
		603	the current time is a good idea.
		604
		605	See also "The special problem of time updates" in the C<ev_timer> section.
		606
554	=item ev_loop (loop, int flags)	607	=item ev_loop (loop, int flags)
555		608
556	Finally, this is it, the event handler. This function usually is called	609	Finally, this is it, the event handler. This function usually is called
557	after you initialised all your watchers and you want to start handling	610	after you initialised all your watchers and you want to start handling
558	events.	611	events.
…		…
569	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
570	those events and any outstanding ones, but will not block your process in	623	those events and any outstanding ones, but will not block your process in
571	case there are no events and will return after one iteration of the loop.	624	case there are no events and will return after one iteration of the loop.
572		625
573	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
574	neccessary) and will handle those and any outstanding ones. It will block	627	necessary) and will handle those and any outstanding ones. It will block
575	your process until at least one new event arrives, and will return after	628	your process until at least one new event arrives, and will return after
576	one iteration of the loop. This is useful if you are waiting for some	629	one iteration of the loop. This is useful if you are waiting for some
577	external event in conjunction with something not expressible using other	630	external event in conjunction with something not expressible using other
578	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
579	usually a better approach for this kind of thing.	632	usually a better approach for this kind of thing.
580		633
581	Here are the gory details of what C<ev_loop> does:	634	Here are the gory details of what C<ev_loop> does:
582		635
583	- Before the first iteration, call any pending watchers.	636	- Before the first iteration, call any pending watchers.
584	* If EVFLAG_FORKCHECK was used, check for a fork.	637	* If EVFLAG_FORKCHECK was used, check for a fork.
585	- If a fork was detected, queue and call all fork watchers.	638	- If a fork was detected (by any means), queue and call all fork watchers.
586	- Queue and call all prepare watchers.	639	- Queue and call all prepare watchers.
587	- If we have been forked, recreate the kernel state.	640	- If we have been forked, detach and recreate the kernel state
		641	as to not disturb the other process.
588	- Update the kernel state with all outstanding changes.	642	- Update the kernel state with all outstanding changes.
589	- Update the "event loop time".	643	- Update the "event loop time" (ev_now ()).
590	- Calculate for how long to sleep or block, if at all	644	- Calculate for how long to sleep or block, if at all
591	(active idle watchers, EVLOOP_NONBLOCK or not having	645	(active idle watchers, EVLOOP_NONBLOCK or not having
592	any active watchers at all will result in not sleeping).	646	any active watchers at all will result in not sleeping).
593	- Sleep if the I/O and timer collect interval say so.	647	- Sleep if the I/O and timer collect interval say so.
594	- Block the process, waiting for any events.	648	- Block the process, waiting for any events.
595	- Queue all outstanding I/O (fd) events.	649	- Queue all outstanding I/O (fd) events.
596	- Update the "event loop time" and do time jump handling.	650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
597	- Queue all outstanding timers.	651	- Queue all outstanding timers.
598	- Queue all outstanding periodics.	652	- Queue all outstanding periodics.
599	- If no events are pending now, queue all idle watchers.	653	- Unless any events are pending now, queue all idle watchers.
600	- Queue all check watchers.	654	- Queue all check watchers.
601	- Call all queued watchers in reverse order (i.e. check watchers first).	655	- Call all queued watchers in reverse order (i.e. check watchers first).
602	Signals and child watchers are implemented as I/O watchers, and will	656	Signals and child watchers are implemented as I/O watchers, and will
603	be handled here by queueing them when their watcher gets executed.	657	be handled here by queueing them when their watcher gets executed.
604	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
609	anymore.	663	anymore.
610		664
611	... queue jobs here, make sure they register event watchers as long	665	... queue jobs here, make sure they register event watchers as long
612	... as they still have work to do (even an idle watcher will do..)	666	... as they still have work to do (even an idle watcher will do..)
613	ev_loop (my_loop, 0);	667	ev_loop (my_loop, 0);
614	... jobs done. yeah!	668	... jobs done or somebody called unloop. yeah!
615		669
616	=item ev_unloop (loop, how)	670	=item ev_unloop (loop, how)
617		671
618	Can be used to make a call to C<ev_loop> return early (but only after it	672	Can be used to make a call to C<ev_loop> return early (but only after it
619	has processed all outstanding events). The C<how> argument must be either	673	has processed all outstanding events). The C<how> argument must be either
…		…
640	respectively).	694	respectively).
641		695
642	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
643	running when nothing else is active.	697	running when nothing else is active.
644		698
645	struct ev_signal exitsig;	699	struct ev_signal exitsig;
646	ev_signal_init (&exitsig, sig_cb, SIGINT);	700	ev_signal_init (&exitsig, sig_cb, SIGINT);
647	ev_signal_start (loop, &exitsig);	701	ev_signal_start (loop, &exitsig);
648	evf_unref (loop);	702	evf_unref (loop);
649		703
650	Example: For some weird reason, unregister the above signal handler again.	704	Example: For some weird reason, unregister the above signal handler again.
651		705
652	ev_ref (loop);	706	ev_ref (loop);
653	ev_signal_stop (loop, &exitsig);	707	ev_signal_stop (loop, &exitsig);
654		708
655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	709	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
656		710
657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	711	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
658		712
659	These advanced functions influence the time that libev will spend waiting	713	These advanced functions influence the time that libev will spend waiting
660	for events. Both are by default C<0>, meaning that libev will try to	714	for events. Both time intervals are by default C<0>, meaning that libev
661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	715	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		716	latency.
662		717
663	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
664	allows libev to delay invocation of I/O and timer/periodic callbacks to	719	allows libev to delay invocation of I/O and timer/periodic callbacks
665	increase efficiency of loop iterations.	720	to increase efficiency of loop iterations (or to increase power-saving
		721	opportunities).
666		722
667	The background is that sometimes your program runs just fast enough to	723	The background is that sometimes your program runs just fast enough to
668	handle one (or very few) event(s) per loop iteration. While this makes	724	handle one (or very few) event(s) per loop iteration. While this makes
669	the program responsive, it also wastes a lot of CPU time to poll for new	725	the program responsive, it also wastes a lot of CPU time to poll for new
670	events, especially with backends like C<select ()> which have a high	726	events, especially with backends like C<select ()> which have a high
…		…
680	to spend more time collecting timeouts, at the expense of increased	736	to spend more time collecting timeouts, at the expense of increased
681	latency (the watcher callback will be called later). C<ev_io> watchers	737	latency (the watcher callback will be called later). C<ev_io> watchers
682	will not be affected. Setting this to a non-null value will not introduce	738	will not be affected. Setting this to a non-null value will not introduce
683	any overhead in libev.	739	any overhead in libev.
684		740
685	Many (busy) programs can usually benefit by setting the io collect	741	Many (busy) programs can usually benefit by setting the I/O collect
686	interval to a value near C<0.1> or so, which is often enough for	742	interval to a value near C<0.1> or so, which is often enough for
687	interactive servers (of course not for games), likewise for timeouts. It	743	interactive servers (of course not for games), likewise for timeouts. It
688	usually doesn't make much sense to set it to a lower value than C<0.01>,	744	usually doesn't make much sense to set it to a lower value than C<0.01>,
689	as this approsaches the timing granularity of most systems.	745	as this approaches the timing granularity of most systems.
		746
		747	Setting the I<timeout collect interval> can improve the opportunity for
		748	saving power, as the program will "bundle" timer callback invocations that
		749	are "near" in time together, by delaying some, thus reducing the number of
		750	times the process sleeps and wakes up again. Another useful technique to
		751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		752	they fire on, say, one-second boundaries only.
		753
		754	=item ev_loop_verify (loop)
		755
		756	This function only does something when C<EV_VERIFY> support has been
		757	compiled in. It tries to go through all internal structures and checks
		758	them for validity. If anything is found to be inconsistent, it will print
		759	an error message to standard error and call C<abort ()>.
		760
		761	This can be used to catch bugs inside libev itself: under normal
		762	circumstances, this function will never abort as of course libev keeps its
		763	data structures consistent.
690		764
691	=back	765	=back
692		766
693		767
694	=head1 ANATOMY OF A WATCHER	768	=head1 ANATOMY OF A WATCHER
695		769
696	A watcher is a structure that you create and register to record your	770	A watcher is a structure that you create and register to record your
697	interest in some event. For instance, if you want to wait for STDIN to	771	interest in some event. For instance, if you want to wait for STDIN to
698	become readable, you would create an C<ev_io> watcher for that:	772	become readable, you would create an C<ev_io> watcher for that:
699		773
700	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
701	{	775	{
702	ev_io_stop (w);	776	ev_io_stop (w);
703	ev_unloop (loop, EVUNLOOP_ALL);	777	ev_unloop (loop, EVUNLOOP_ALL);
704	}	778	}
705		779
706	struct ev_loop *loop = ev_default_loop (0);	780	struct ev_loop *loop = ev_default_loop (0);
707	struct ev_io stdin_watcher;	781	struct ev_io stdin_watcher;
708	ev_init (&stdin_watcher, my_cb);	782	ev_init (&stdin_watcher, my_cb);
709	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
710	ev_io_start (loop, &stdin_watcher);	784	ev_io_start (loop, &stdin_watcher);
711	ev_loop (loop, 0);	785	ev_loop (loop, 0);
712		786
713	As you can see, you are responsible for allocating the memory for your	787	As you can see, you are responsible for allocating the memory for your
714	watcher structures (and it is usually a bad idea to do this on the stack,	788	watcher structures (and it is usually a bad idea to do this on the stack,
715	although this can sometimes be quite valid).	789	although this can sometimes be quite valid).
716		790
717	Each watcher structure must be initialised by a call to C<ev_init	791	Each watcher structure must be initialised by a call to C<ev_init
718	(watcher *, callback)>, which expects a callback to be provided. This	792	(watcher *, callback)>, which expects a callback to be provided. This
719	callback gets invoked each time the event occurs (or, in the case of io	793	callback gets invoked each time the event occurs (or, in the case of I/O
720	watchers, each time the event loop detects that the file descriptor given	794	watchers, each time the event loop detects that the file descriptor given
721	is readable and/or writable).	795	is readable and/or writable).
722		796
723	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
724	with arguments specific to this watcher type. There is also a macro	798	with arguments specific to this watcher type. There is also a macro
…		…
800		874
801	The given async watcher has been asynchronously notified (see C<ev_async>).	875	The given async watcher has been asynchronously notified (see C<ev_async>).
802		876
803	=item C<EV_ERROR>	877	=item C<EV_ERROR>
804		878
805	An unspecified error has occured, the watcher has been stopped. This might	879	An unspecified error has occurred, the watcher has been stopped. This might
806	happen because the watcher could not be properly started because libev	880	happen because the watcher could not be properly started because libev
807	ran out of memory, a file descriptor was found to be closed or any other	881	ran out of memory, a file descriptor was found to be closed or any other
808	problem. You best act on it by reporting the problem and somehow coping	882	problem. You best act on it by reporting the problem and somehow coping
809	with the watcher being stopped.	883	with the watcher being stopped.
810		884
811	Libev will usually signal a few "dummy" events together with an error,	885	Libev will usually signal a few "dummy" events together with an error,
812	for example it might indicate that a fd is readable or writable, and if	886	for example it might indicate that a fd is readable or writable, and if
813	your callbacks is well-written it can just attempt the operation and cope	887	your callbacks is well-written it can just attempt the operation and cope
814	with the error from read() or write(). This will not work in multithreaded	888	with the error from read() or write(). This will not work in multi-threaded
815	programs, though, so beware.	889	programs, though, so beware.
816		890
817	=back	891	=back
818		892
819	=head2 GENERIC WATCHER FUNCTIONS	893	=head2 GENERIC WATCHER FUNCTIONS
…		…
849	Although some watcher types do not have type-specific arguments	923	Although some watcher types do not have type-specific arguments
850	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
851		925
852	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
853		927
854	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
855	calls into a single call. This is the most convinient method to initialise	929	calls into a single call. This is the most convenient method to initialise
856	a watcher. The same limitations apply, of course.	930	a watcher. The same limitations apply, of course.
857		931
858	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
859		933
860	Starts (activates) the given watcher. Only active watchers will receive	934	Starts (activates) the given watcher. Only active watchers will receive
…		…
943	to associate arbitrary data with your watcher. If you need more data and	1017	to associate arbitrary data with your watcher. If you need more data and
944	don't want to allocate memory and store a pointer to it in that data	1018	don't want to allocate memory and store a pointer to it in that data
945	member, you can also "subclass" the watcher type and provide your own	1019	member, you can also "subclass" the watcher type and provide your own
946	data:	1020	data:
947		1021
948	struct my_io	1022	struct my_io
949	{	1023	{
950	struct ev_io io;	1024	struct ev_io io;
951	int otherfd;	1025	int otherfd;
952	void *somedata;	1026	void *somedata;
953	struct whatever *mostinteresting;	1027	struct whatever *mostinteresting;
954	}	1028	};
		1029
		1030	...
		1031	struct my_io w;
		1032	ev_io_init (&w.io, my_cb, fd, EV_READ);
955		1033
956	And since your callback will be called with a pointer to the watcher, you	1034	And since your callback will be called with a pointer to the watcher, you
957	can cast it back to your own type:	1035	can cast it back to your own type:
958		1036
959	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
960	{	1038	{
961	struct my_io *w = (struct my_io *)w_;	1039	struct my_io *w = (struct my_io *)w_;
962	...	1040	...
963	}	1041	}
964		1042
965	More interesting and less C-conformant ways of casting your callback type	1043	More interesting and less C-conformant ways of casting your callback type
966	instead have been omitted.	1044	instead have been omitted.
967		1045
968	Another common scenario is having some data structure with multiple	1046	Another common scenario is to use some data structure with multiple
969	watchers:	1047	embedded watchers:
970		1048
971	struct my_biggy	1049	struct my_biggy
972	{	1050	{
973	int some_data;	1051	int some_data;
974	ev_timer t1;	1052	ev_timer t1;
975	ev_timer t2;	1053	ev_timer t2;
976	}	1054	}
977		1055
978	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1056	In this case getting the pointer to C<my_biggy> is a bit more
979	you need to use C<offsetof>:	1057	complicated: Either you store the address of your C<my_biggy> struct
		1058	in the C<data> member of the watcher, or you need to use some pointer
		1059	arithmetic using C<offsetof> inside your watchers:
980		1060
981	#include <stddef.h>	1061	#include <stddef.h>
982		1062
983	static void	1063	static void
984	t1_cb (EV_P_ struct ev_timer *w, int revents)	1064	t1_cb (EV_P_ struct ev_timer *w, int revents)
985	{	1065	{
986	struct my_biggy big = (struct my_biggy *	1066	struct my_biggy big = (struct my_biggy *
987	(((char *)w) - offsetof (struct my_biggy, t1));	1067	(((char *)w) - offsetof (struct my_biggy, t1));
988	}	1068	}
989		1069
990	static void	1070	static void
991	t2_cb (EV_P_ struct ev_timer *w, int revents)	1071	t2_cb (EV_P_ struct ev_timer *w, int revents)
992	{	1072	{
993	struct my_biggy big = (struct my_biggy *	1073	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t2));	1074	(((char *)w) - offsetof (struct my_biggy, t2));
995	}	1075	}
996		1076
997		1077
998	=head1 WATCHER TYPES	1078	=head1 WATCHER TYPES
999		1079
1000	This section describes each watcher in detail, but will not repeat	1080	This section describes each watcher in detail, but will not repeat
…		…
1029	If you must do this, then force the use of a known-to-be-good backend	1109	If you must do this, then force the use of a known-to-be-good backend
1030	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1031	C<EVBACKEND_POLL>).	1111	C<EVBACKEND_POLL>).
1032		1112
1033	Another thing you have to watch out for is that it is quite easy to	1113	Another thing you have to watch out for is that it is quite easy to
1034	receive "spurious" readyness notifications, that is your callback might	1114	receive "spurious" readiness notifications, that is your callback might
1035	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1036	because there is no data. Not only are some backends known to create a	1116	because there is no data. Not only are some backends known to create a
1037	lot of those (for example solaris ports), it is very easy to get into	1117	lot of those (for example Solaris ports), it is very easy to get into
1038	this situation even with a relatively standard program structure. Thus	1118	this situation even with a relatively standard program structure. Thus
1039	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1040	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1041		1121
1042	If you cannot run the fd in non-blocking mode (for example you should not	1122	If you cannot run the fd in non-blocking mode (for example you should not
1043	play around with an Xlib connection), then you have to seperately re-test	1123	play around with an Xlib connection), then you have to separately re-test
1044	whether a file descriptor is really ready with a known-to-be good interface	1124	whether a file descriptor is really ready with a known-to-be good interface
1045	such as poll (fortunately in our Xlib example, Xlib already does this on	1125	such as poll (fortunately in our Xlib example, Xlib already does this on
1046	its own, so its quite safe to use).	1126	its own, so its quite safe to use).
1047		1127
1048	=head3 The special problem of disappearing file descriptors	1128	=head3 The special problem of disappearing file descriptors
…		…
1089	C<EVBACKEND_POLL>.	1169	C<EVBACKEND_POLL>.
1090		1170
1091	=head3 The special problem of SIGPIPE	1171	=head3 The special problem of SIGPIPE
1092		1172
1093	While not really specific to libev, it is easy to forget about SIGPIPE:	1173	While not really specific to libev, it is easy to forget about SIGPIPE:
1094	when reading from a pipe whose other end has been closed, your program	1174	when writing to a pipe whose other end has been closed, your program gets
1095	gets send a SIGPIPE, which, by default, aborts your program. For most	1175	send a SIGPIPE, which, by default, aborts your program. For most programs
1096	programs this is sensible behaviour, for daemons, this is usually	1176	this is sensible behaviour, for daemons, this is usually undesirable.
1097	undesirable.
1098		1177
1099	So when you encounter spurious, unexplained daemon exits, make sure you	1178	So when you encounter spurious, unexplained daemon exits, make sure you
1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1101	somewhere, as that would have given you a big clue).	1180	somewhere, as that would have given you a big clue).
1102		1181
…		…
1108	=item ev_io_init (ev_io *, callback, int fd, int events)	1187	=item ev_io_init (ev_io *, callback, int fd, int events)
1109		1188
1110	=item ev_io_set (ev_io *, int fd, int events)	1189	=item ev_io_set (ev_io *, int fd, int events)
1111		1190
1112	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1113	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1114	C<EV_READ | EV_WRITE> to receive the given events.	1193	C<EV_READ | EV_WRITE> to receive the given events.
1115		1194
1116	=item int fd [read-only]	1195	=item int fd [read-only]
1117		1196
1118	The file descriptor being watched.	1197	The file descriptor being watched.
…		…
1127		1206
1128	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1129	readable, but only once. Since it is likely line-buffered, you could	1208	readable, but only once. Since it is likely line-buffered, you could
1130	attempt to read a whole line in the callback.	1209	attempt to read a whole line in the callback.
1131		1210
1132	static void	1211	static void
1133	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1134	{	1213	{
1135	ev_io_stop (loop, w);	1214	ev_io_stop (loop, w);
1136	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1137	}	1216	}
1138		1217
1139	...	1218	...
1140	struct ev_loop *loop = ev_default_init (0);	1219	struct ev_loop *loop = ev_default_init (0);
1141	struct ev_io stdin_readable;	1220	struct ev_io stdin_readable;
1142	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1143	ev_io_start (loop, &stdin_readable);	1222	ev_io_start (loop, &stdin_readable);
1144	ev_loop (loop, 0);	1223	ev_loop (loop, 0);
1145		1224
1146		1225
1147	=head2 C<ev_timer> - relative and optionally repeating timeouts	1226	=head2 C<ev_timer> - relative and optionally repeating timeouts
1148		1227
1149	Timer watchers are simple relative timers that generate an event after a	1228	Timer watchers are simple relative timers that generate an event after a
1150	given time, and optionally repeating in regular intervals after that.	1229	given time, and optionally repeating in regular intervals after that.
1151		1230
1152	The timers are based on real time, that is, if you register an event that	1231	The timers are based on real time, that is, if you register an event that
1153	times out after an hour and you reset your system clock to last years	1232	times out after an hour and you reset your system clock to January last
1154	time, it will still time out after (roughly) and hour. "Roughly" because	1233	year, it will still time out after (roughly) and hour. "Roughly" because
1155	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1156	monotonic clock option helps a lot here).	1235	monotonic clock option helps a lot here).
		1236
		1237	The callback is guaranteed to be invoked only after its timeout has passed,
		1238	but if multiple timers become ready during the same loop iteration then
		1239	order of execution is undefined.
		1240
		1241	=head3 The special problem of time updates
		1242
		1243	Establishing the current time is a costly operation (it usually takes at
		1244	least two system calls): EV therefore updates its idea of the current
		1245	time only before and after C<ev_loop> polls for new events, which causes
		1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1247	lots of events.
1157		1248
1158	The relative timeouts are calculated relative to the C<ev_now ()>	1249	The relative timeouts are calculated relative to the C<ev_now ()>
1159	time. This is usually the right thing as this timestamp refers to the time	1250	time. This is usually the right thing as this timestamp refers to the time
1160	of the event triggering whatever timeout you are modifying/starting. If	1251	of the event triggering whatever timeout you are modifying/starting. If
1161	you suspect event processing to be delayed and you I<need> to base the timeout	1252	you suspect event processing to be delayed and you I<need> to base the
1162	on the current time, use something like this to adjust for this:	1253	timeout on the current time, use something like this to adjust for this:
1163		1254
1164	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1255	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1165		1256
1166	The callback is guarenteed to be invoked only when its timeout has passed,	1257	If the event loop is suspended for a long time, you can also force an
1167	but if multiple timers become ready during the same loop iteration then	1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1168	order of execution is undefined.	1259	()>.
1169		1260
1170	=head3 Watcher-Specific Functions and Data Members	1261	=head3 Watcher-Specific Functions and Data Members
1171		1262
1172	=over 4	1263	=over 4
1173		1264
1174	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1175		1266
1176	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1267	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1177		1268
1178	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1269	Configure the timer to trigger after C<after> seconds. If C<repeat>
1179	C<0.>, then it will automatically be stopped. If it is positive, then the	1270	is C<0.>, then it will automatically be stopped once the timeout is
1180	timer will automatically be configured to trigger again C<repeat> seconds	1271	reached. If it is positive, then the timer will automatically be
1181	later, again, and again, until stopped manually.	1272	configured to trigger again C<repeat> seconds later, again, and again,
		1273	until stopped manually.
1182		1274
1183	The timer itself will do a best-effort at avoiding drift, that is, if you	1275	The timer itself will do a best-effort at avoiding drift, that is, if
1184	configure a timer to trigger every 10 seconds, then it will trigger at	1276	you configure a timer to trigger every 10 seconds, then it will normally
1185	exactly 10 second intervals. If, however, your program cannot keep up with	1277	trigger at exactly 10 second intervals. If, however, your program cannot
1186	the timer (because it takes longer than those 10 seconds to do stuff) the	1278	keep up with the timer (because it takes longer than those 10 seconds to
1187	timer will not fire more than once per event loop iteration.	1279	do stuff) the timer will not fire more than once per event loop iteration.
1188		1280
1189	=item ev_timer_again (loop, ev_timer *)	1281	=item ev_timer_again (loop, ev_timer *)
1190		1282
1191	This will act as if the timer timed out and restart it again if it is	1283	This will act as if the timer timed out and restart it again if it is
1192	repeating. The exact semantics are:	1284	repeating. The exact semantics are:
1193		1285
1194	If the timer is pending, its pending status is cleared.	1286	If the timer is pending, its pending status is cleared.
1195		1287
1196	If the timer is started but nonrepeating, stop it (as if it timed out).	1288	If the timer is started but non-repeating, stop it (as if it timed out).
1197		1289
1198	If the timer is repeating, either start it if necessary (with the	1290	If the timer is repeating, either start it if necessary (with the
1199	C<repeat> value), or reset the running timer to the C<repeat> value.	1291	C<repeat> value), or reset the running timer to the C<repeat> value.
1200		1292
1201	This sounds a bit complicated, but here is a useful and typical	1293	This sounds a bit complicated, but here is a useful and typical
1202	example: Imagine you have a tcp connection and you want a so-called idle	1294	example: Imagine you have a TCP connection and you want a so-called idle
1203	timeout, that is, you want to be called when there have been, say, 60	1295	timeout, that is, you want to be called when there have been, say, 60
1204	seconds of inactivity on the socket. The easiest way to do this is to	1296	seconds of inactivity on the socket. The easiest way to do this is to
1205	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1206	C<ev_timer_again> each time you successfully read or write some data. If	1298	C<ev_timer_again> each time you successfully read or write some data. If
1207	you go into an idle state where you do not expect data to travel on the	1299	you go into an idle state where you do not expect data to travel on the
…		…
1233		1325
1234	=head3 Examples	1326	=head3 Examples
1235		1327
1236	Example: Create a timer that fires after 60 seconds.	1328	Example: Create a timer that fires after 60 seconds.
1237		1329
1238	static void	1330	static void
1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1240	{	1332	{
1241	.. one minute over, w is actually stopped right here	1333	.. one minute over, w is actually stopped right here
1242	}	1334	}
1243		1335
1244	struct ev_timer mytimer;	1336	struct ev_timer mytimer;
1245	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1246	ev_timer_start (loop, &mytimer);	1338	ev_timer_start (loop, &mytimer);
1247		1339
1248	Example: Create a timeout timer that times out after 10 seconds of	1340	Example: Create a timeout timer that times out after 10 seconds of
1249	inactivity.	1341	inactivity.
1250		1342
1251	static void	1343	static void
1252	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1253	{	1345	{
1254	.. ten seconds without any activity	1346	.. ten seconds without any activity
1255	}	1347	}
1256		1348
1257	struct ev_timer mytimer;	1349	struct ev_timer mytimer;
1258	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1259	ev_timer_again (&mytimer); /* start timer */	1351	ev_timer_again (&mytimer); /* start timer */
1260	ev_loop (loop, 0);	1352	ev_loop (loop, 0);
1261		1353
1262	// and in some piece of code that gets executed on any "activity":	1354	// and in some piece of code that gets executed on any "activity":
1263	// reset the timeout to start ticking again at 10 seconds	1355	// reset the timeout to start ticking again at 10 seconds
1264	ev_timer_again (&mytimer);	1356	ev_timer_again (&mytimer);
1265		1357
1266		1358
1267	=head2 C<ev_periodic> - to cron or not to cron?	1359	=head2 C<ev_periodic> - to cron or not to cron?
1268		1360
1269	Periodic watchers are also timers of a kind, but they are very versatile	1361	Periodic watchers are also timers of a kind, but they are very versatile
1270	(and unfortunately a bit complex).	1362	(and unfortunately a bit complex).
1271		1363
1272	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1273	but on wallclock time (absolute time). You can tell a periodic watcher	1365	but on wall clock time (absolute time). You can tell a periodic watcher
1274	to trigger "at" some specific point in time. For example, if you tell a	1366	to trigger after some specific point in time. For example, if you tell a
1275	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1276	+ 10.>) and then reset your system clock to the last year, then it will	1368	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1369	clock to January of the previous year, then it will take more than year
1277	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1278	roughly 10 seconds later).	1371	roughly 10 seconds later as it uses a relative timeout).
1279		1372
1280	They can also be used to implement vastly more complex timers, such as	1373	C<ev_periodic>s can also be used to implement vastly more complex timers,
1281	triggering an event on each midnight, local time or other, complicated,	1374	such as triggering an event on each "midnight, local time", or other
1282	rules.	1375	complicated, rules.
1283		1376
1284	As with timers, the callback is guarenteed to be invoked only when the	1377	As with timers, the callback is guaranteed to be invoked only when the
1285	time (C<at>) has been passed, but if multiple periodic timers become ready	1378	time (C<at>) has passed, but if multiple periodic timers become ready
1286	during the same loop iteration then order of execution is undefined.	1379	during the same loop iteration then order of execution is undefined.
1287		1380
1288	=head3 Watcher-Specific Functions and Data Members	1381	=head3 Watcher-Specific Functions and Data Members
1289		1382
1290	=over 4	1383	=over 4
…		…
1298		1391
1299	=over 4	1392	=over 4
1300		1393
1301	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1302		1395
1303	In this configuration the watcher triggers an event at the wallclock time	1396	In this configuration the watcher triggers an event after the wall clock
1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1397	time C<at> has passed and doesn't repeat. It will not adjust when a time
1305	that is, if it is to be run at January 1st 2011 then it will run when the	1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1306	system time reaches or surpasses this time.	1399	run when the system time reaches or surpasses this time.
1307		1400
1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1309		1402
1310	In this mode the watcher will always be scheduled to time out at the next	1403	In this mode the watcher will always be scheduled to time out at the next
1311	C<at + N * interval> time (for some integer N, which can also be negative)	1404	C<at + N * interval> time (for some integer N, which can also be negative)
1312	and then repeat, regardless of any time jumps.	1405	and then repeat, regardless of any time jumps.
1313		1406
1314	This can be used to create timers that do not drift with respect to system	1407	This can be used to create timers that do not drift with respect to system
1315	time:	1408	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1409	the hour:
1316		1410
1317	ev_periodic_set (&periodic, 0., 3600., 0);	1411	ev_periodic_set (&periodic, 0., 3600., 0);
1318		1412
1319	This doesn't mean there will always be 3600 seconds in between triggers,	1413	This doesn't mean there will always be 3600 seconds in between triggers,
1320	but only that the the callback will be called when the system time shows a	1414	but only that the callback will be called when the system time shows a
1321	full hour (UTC), or more correctly, when the system time is evenly divisible	1415	full hour (UTC), or more correctly, when the system time is evenly divisible
1322	by 3600.	1416	by 3600.
1323		1417
1324	Another way to think about it (for the mathematically inclined) is that	1418	Another way to think about it (for the mathematically inclined) is that
1325	C<ev_periodic> will try to run the callback in this mode at the next possible	1419	C<ev_periodic> will try to run the callback in this mode at the next possible
1326	time where C<time = at (mod interval)>, regardless of any time jumps.	1420	time where C<time = at (mod interval)>, regardless of any time jumps.
1327		1421
1328	For numerical stability it is preferable that the C<at> value is near	1422	For numerical stability it is preferable that the C<at> value is near
1329	C<ev_now ()> (the current time), but there is no range requirement for	1423	C<ev_now ()> (the current time), but there is no range requirement for
1330	this value.	1424	this value, and in fact is often specified as zero.
		1425
		1426	Note also that there is an upper limit to how often a timer can fire (CPU
		1427	speed for example), so if C<interval> is very small then timing stability
		1428	will of course deteriorate. Libev itself tries to be exact to be about one
		1429	millisecond (if the OS supports it and the machine is fast enough).
1331		1430
1332	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1333		1432
1334	In this mode the values for C<interval> and C<at> are both being	1433	In this mode the values for C<interval> and C<at> are both being
1335	ignored. Instead, each time the periodic watcher gets scheduled, the	1434	ignored. Instead, each time the periodic watcher gets scheduled, the
1336	reschedule callback will be called with the watcher as first, and the	1435	reschedule callback will be called with the watcher as first, and the
1337	current time as second argument.	1436	current time as second argument.
1338		1437
1339	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1340	ever, or make any event loop modifications>. If you need to stop it,	1439	ever, or make ANY event loop modifications whatsoever>.
1341	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1342	starting an C<ev_prepare> watcher, which is legal).
1343		1440
		1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1443	only event loop modification you are allowed to do).
		1444
1344	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1345	ev_tstamp now)>, e.g.:	1446	*w, ev_tstamp now)>, e.g.:
1346		1447
1347	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1348	{	1449	{
1349	return now + 60.;	1450	return now + 60.;
1350	}	1451	}
…		…
1352	It must return the next time to trigger, based on the passed time value	1453	It must return the next time to trigger, based on the passed time value
1353	(that is, the lowest time value larger than to the second argument). It	1454	(that is, the lowest time value larger than to the second argument). It
1354	will usually be called just before the callback will be triggered, but	1455	will usually be called just before the callback will be triggered, but
1355	might be called at other times, too.	1456	might be called at other times, too.
1356		1457
1357	NOTE: I<< This callback must always return a time that is later than the	1458	NOTE: I<< This callback must always return a time that is higher than or
1358	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1459	equal to the passed C<now> value >>.
1359		1460
1360	This can be used to create very complex timers, such as a timer that	1461	This can be used to create very complex timers, such as a timer that
1361	triggers on each midnight, local time. To do this, you would calculate the	1462	triggers on "next midnight, local time". To do this, you would calculate the
1362	next midnight after C<now> and return the timestamp value for this. How	1463	next midnight after C<now> and return the timestamp value for this. How
1363	you do this is, again, up to you (but it is not trivial, which is the main	1464	you do this is, again, up to you (but it is not trivial, which is the main
1364	reason I omitted it as an example).	1465	reason I omitted it as an example).
1365		1466
1366	=back	1467	=back
…		…
1370	Simply stops and restarts the periodic watcher again. This is only useful	1471	Simply stops and restarts the periodic watcher again. This is only useful
1371	when you changed some parameters or the reschedule callback would return	1472	when you changed some parameters or the reschedule callback would return
1372	a different time than the last time it was called (e.g. in a crond like	1473	a different time than the last time it was called (e.g. in a crond like
1373	program when the crontabs have changed).	1474	program when the crontabs have changed).
1374		1475
		1476	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1477
		1478	When active, returns the absolute time that the watcher is supposed to
		1479	trigger next.
		1480
1375	=item ev_tstamp offset [read-write]	1481	=item ev_tstamp offset [read-write]
1376		1482
1377	When repeating, this contains the offset value, otherwise this is the	1483	When repeating, this contains the offset value, otherwise this is the
1378	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1379		1485
…		…
1390		1496
1391	The current reschedule callback, or C<0>, if this functionality is	1497	The current reschedule callback, or C<0>, if this functionality is
1392	switched off. Can be changed any time, but changes only take effect when	1498	switched off. Can be changed any time, but changes only take effect when
1393	the periodic timer fires or C<ev_periodic_again> is being called.	1499	the periodic timer fires or C<ev_periodic_again> is being called.
1394		1500
1395	=item ev_tstamp at [read-only]
1396
1397	When active, contains the absolute time that the watcher is supposed to
1398	trigger next.
1399
1400	=back	1501	=back
1401		1502
1402	=head3 Examples	1503	=head3 Examples
1403		1504
1404	Example: Call a callback every hour, or, more precisely, whenever the	1505	Example: Call a callback every hour, or, more precisely, whenever the
1405	system clock is divisible by 3600. The callback invocation times have	1506	system clock is divisible by 3600. The callback invocation times have
1406	potentially a lot of jittering, but good long-term stability.	1507	potentially a lot of jitter, but good long-term stability.
1407		1508
1408	static void	1509	static void
1409	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1410	{	1511	{
1411	... its now a full hour (UTC, or TAI or whatever your clock follows)	1512	... its now a full hour (UTC, or TAI or whatever your clock follows)
1412	}	1513	}
1413		1514
1414	struct ev_periodic hourly_tick;	1515	struct ev_periodic hourly_tick;
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1416	ev_periodic_start (loop, &hourly_tick);	1517	ev_periodic_start (loop, &hourly_tick);
1417		1518
1418	Example: The same as above, but use a reschedule callback to do it:	1519	Example: The same as above, but use a reschedule callback to do it:
1419		1520
1420	#include <math.h>	1521	#include <math.h>
1421		1522
1422	static ev_tstamp	1523	static ev_tstamp
1423	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1424	{	1525	{
1425	return fmod (now, 3600.) + 3600.;	1526	return fmod (now, 3600.) + 3600.;
1426	}	1527	}
1427		1528
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1429		1530
1430	Example: Call a callback every hour, starting now:	1531	Example: Call a callback every hour, starting now:
1431		1532
1432	struct ev_periodic hourly_tick;	1533	struct ev_periodic hourly_tick;
1433	ev_periodic_init (&hourly_tick, clock_cb,	1534	ev_periodic_init (&hourly_tick, clock_cb,
1434	fmod (ev_now (loop), 3600.), 3600., 0);	1535	fmod (ev_now (loop), 3600.), 3600., 0);
1435	ev_periodic_start (loop, &hourly_tick);	1536	ev_periodic_start (loop, &hourly_tick);
1436		1537
1437		1538
1438	=head2 C<ev_signal> - signal me when a signal gets signalled!	1539	=head2 C<ev_signal> - signal me when a signal gets signalled!
1439		1540
1440	Signal watchers will trigger an event when the process receives a specific	1541	Signal watchers will trigger an event when the process receives a specific
…		…
1448	as you don't register any with libev). Similarly, when the last signal	1549	as you don't register any with libev). Similarly, when the last signal
1449	watcher for a signal is stopped libev will reset the signal handler to	1550	watcher for a signal is stopped libev will reset the signal handler to
1450	SIG_DFL (regardless of what it was set to before).	1551	SIG_DFL (regardless of what it was set to before).
1451		1552
1452	If possible and supported, libev will install its handlers with	1553	If possible and supported, libev will install its handlers with
1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1454	interrupted. If you have a problem with syscalls getting interrupted by	1555	interrupted. If you have a problem with system calls getting interrupted by
1455	signals you can block all signals in an C<ev_check> watcher and unblock	1556	signals you can block all signals in an C<ev_check> watcher and unblock
1456	them in an C<ev_prepare> watcher.	1557	them in an C<ev_prepare> watcher.
1457		1558
1458	=head3 Watcher-Specific Functions and Data Members	1559	=head3 Watcher-Specific Functions and Data Members
1459		1560
…		…
1474		1575
1475	=head3 Examples	1576	=head3 Examples
1476		1577
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1578	Example: Try to exit cleanly on SIGINT and SIGTERM.
1478		1579
1479	static void	1580	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1481	{	1582	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1583	ev_unloop (loop, EVUNLOOP_ALL);
1483	}	1584	}
1484		1585
1485	struct ev_signal signal_watcher;	1586	struct ev_signal signal_watcher;
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1487	ev_signal_start (loop, &sigint_cb);	1588	ev_signal_start (loop, &sigint_cb);
1488		1589
1489		1590
1490	=head2 C<ev_child> - watch out for process status changes	1591	=head2 C<ev_child> - watch out for process status changes
1491		1592
1492	Child watchers trigger when your process receives a SIGCHLD in response to	1593	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1494	is permissible to install a child watcher I<after> the child has been	1595	is permissible to install a child watcher I<after> the child has been
1495	forked (which implies it might have already exited), as long as the event	1596	forked (which implies it might have already exited), as long as the event
1496	loop isn't entered (or is continued from a watcher).	1597	loop isn't entered (or is continued from a watcher).
1497		1598
1498	Only the default event loop is capable of handling signals, and therefore	1599	Only the default event loop is capable of handling signals, and therefore
1499	you can only rgeister child watchers in the default event loop.	1600	you can only register child watchers in the default event loop.
1500		1601
1501	=head3 Process Interaction	1602	=head3 Process Interaction
1502		1603
1503	Libev grabs C<SIGCHLD> as soon as the default event loop is	1604	Libev grabs C<SIGCHLD> as soon as the default event loop is
1504	initialised. This is necessary to guarantee proper behaviour even if	1605	initialised. This is necessary to guarantee proper behaviour even if
1505	the first child watcher is started after the child exits. The occurance	1606	the first child watcher is started after the child exits. The occurrence
1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1507	synchronously as part of the event loop processing. Libev always reaps all	1608	synchronously as part of the event loop processing. Libev always reaps all
1508	children, even ones not watched.	1609	children, even ones not watched.
1509		1610
1510	=head3 Overriding the Built-In Processing	1611	=head3 Overriding the Built-In Processing
…		…
1514	handler, you can override it easily by installing your own handler for	1615	handler, you can override it easily by installing your own handler for
1515	C<SIGCHLD> after initialising the default loop, and making sure the	1616	C<SIGCHLD> after initialising the default loop, and making sure the
1516	default loop never gets destroyed. You are encouraged, however, to use an	1617	default loop never gets destroyed. You are encouraged, however, to use an
1517	event-based approach to child reaping and thus use libev's support for	1618	event-based approach to child reaping and thus use libev's support for
1518	that, so other libev users can use C<ev_child> watchers freely.	1619	that, so other libev users can use C<ev_child> watchers freely.
		1620
		1621	=head3 Stopping the Child Watcher
		1622
		1623	Currently, the child watcher never gets stopped, even when the
		1624	child terminates, so normally one needs to stop the watcher in the
		1625	callback. Future versions of libev might stop the watcher automatically
		1626	when a child exit is detected.
1519		1627
1520	=head3 Watcher-Specific Functions and Data Members	1628	=head3 Watcher-Specific Functions and Data Members
1521		1629
1522	=over 4	1630	=over 4
1523		1631
…		…
1552	=head3 Examples	1660	=head3 Examples
1553		1661
1554	Example: C<fork()> a new process and install a child handler to wait for	1662	Example: C<fork()> a new process and install a child handler to wait for
1555	its completion.	1663	its completion.
1556		1664
1557	ev_child cw;	1665	ev_child cw;
1558		1666
1559	static void	1667	static void
1560	child_cb (EV_P_ struct ev_child *w, int revents)	1668	child_cb (EV_P_ struct ev_child *w, int revents)
1561	{	1669	{
1562	ev_child_stop (EV_A_ w);	1670	ev_child_stop (EV_A_ w);
1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1564	}	1672	}
1565		1673
1566	pid_t pid = fork ();	1674	pid_t pid = fork ();
1567		1675
1568	if (pid < 0)	1676	if (pid < 0)
1569	// error	1677	// error
1570	else if (pid == 0)	1678	else if (pid == 0)
1571	{	1679	{
1572	// the forked child executes here	1680	// the forked child executes here
1573	exit (1);	1681	exit (1);
1574	}	1682	}
1575	else	1683	else
1576	{	1684	{
1577	ev_child_init (&cw, child_cb, pid, 0);	1685	ev_child_init (&cw, child_cb, pid, 0);
1578	ev_child_start (EV_DEFAULT_ &cw);	1686	ev_child_start (EV_DEFAULT_ &cw);
1579	}	1687	}
1580		1688
1581		1689
1582	=head2 C<ev_stat> - did the file attributes just change?	1690	=head2 C<ev_stat> - did the file attributes just change?
1583		1691
1584	This watches a filesystem path for attribute changes. That is, it calls	1692	This watches a file system path for attribute changes. That is, it calls
1585	C<stat> regularly (or when the OS says it changed) and sees if it changed	1693	C<stat> regularly (or when the OS says it changed) and sees if it changed
1586	compared to the last time, invoking the callback if it did.	1694	compared to the last time, invoking the callback if it did.
1587		1695
1588	The path does not need to exist: changing from "path exists" to "path does	1696	The path does not need to exist: changing from "path exists" to "path does
1589	not exist" is a status change like any other. The condition "path does	1697	not exist" is a status change like any other. The condition "path does
…		…
1607	as even with OS-supported change notifications, this can be	1715	as even with OS-supported change notifications, this can be
1608	resource-intensive.	1716	resource-intensive.
1609		1717
1610	At the time of this writing, only the Linux inotify interface is	1718	At the time of this writing, only the Linux inotify interface is
1611	implemented (implementing kqueue support is left as an exercise for the	1719	implemented (implementing kqueue support is left as an exercise for the
		1720	reader, note, however, that the author sees no way of implementing ev_stat
1612	reader). Inotify will be used to give hints only and should not change the	1721	semantics with kqueue). Inotify will be used to give hints only and should
1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1722	not change the semantics of C<ev_stat> watchers, which means that libev
1614	to fall back to regular polling again even with inotify, but changes are	1723	sometimes needs to fall back to regular polling again even with inotify,
1615	usually detected immediately, and if the file exists there will be no	1724	but changes are usually detected immediately, and if the file exists there
1616	polling.	1725	will be no polling.
1617		1726
1618	=head3 ABI Issues (Largefile Support)	1727	=head3 ABI Issues (Largefile Support)
1619		1728
1620	Libev by default (unless the user overrides this) uses the default	1729	Libev by default (unless the user overrides this) uses the default
1621	compilation environment, which means that on systems with optionally	1730	compilation environment, which means that on systems with large file
1622	disabled large file support, you get the 32 bit version of the stat	1731	support disabled by default, you get the 32 bit version of the stat
1623	structure. When using the library from programs that change the ABI to	1732	structure. When using the library from programs that change the ABI to
1624	use 64 bit file offsets the programs will fail. In that case you have to	1733	use 64 bit file offsets the programs will fail. In that case you have to
1625	compile libev with the same flags to get binary compatibility. This is	1734	compile libev with the same flags to get binary compatibility. This is
1626	obviously the case with any flags that change the ABI, but the problem is	1735	obviously the case with any flags that change the ABI, but the problem is
1627	most noticably with ev_stat and largefile support.	1736	most noticeably disabled with ev_stat and large file support.
		1737
		1738	The solution for this is to lobby your distribution maker to make large
		1739	file interfaces available by default (as e.g. FreeBSD does) and not
		1740	optional. Libev cannot simply switch on large file support because it has
		1741	to exchange stat structures with application programs compiled using the
		1742	default compilation environment.
1628		1743
1629	=head3 Inotify	1744	=head3 Inotify
1630		1745
1631	When C<inotify (7)> support has been compiled into libev (generally only	1746	When C<inotify (7)> support has been compiled into libev (generally only
1632	available on Linux) and present at runtime, it will be used to speed up	1747	available on Linux) and present at runtime, it will be used to speed up
1633	change detection where possible. The inotify descriptor will be created lazily	1748	change detection where possible. The inotify descriptor will be created lazily
1634	when the first C<ev_stat> watcher is being started.	1749	when the first C<ev_stat> watcher is being started.
1635		1750
1636	Inotify presense does not change the semantics of C<ev_stat> watchers	1751	Inotify presence does not change the semantics of C<ev_stat> watchers
1637	except that changes might be detected earlier, and in some cases, to avoid	1752	except that changes might be detected earlier, and in some cases, to avoid
1638	making regular C<stat> calls. Even in the presense of inotify support	1753	making regular C<stat> calls. Even in the presence of inotify support
1639	there are many cases where libev has to resort to regular C<stat> polling.	1754	there are many cases where libev has to resort to regular C<stat> polling.
1640		1755
1641	(There is no support for kqueue, as apparently it cannot be used to	1756	(There is no support for kqueue, as apparently it cannot be used to
1642	implement this functionality, due to the requirement of having a file	1757	implement this functionality, due to the requirement of having a file
1643	descriptor open on the object at all times).	1758	descriptor open on the object at all times).
1644		1759
1645	=head3 The special problem of stat time resolution	1760	=head3 The special problem of stat time resolution
1646		1761
1647	The C<stat ()> syscall only supports full-second resolution portably, and	1762	The C<stat ()> system call only supports full-second resolution portably, and
1648	even on systems where the resolution is higher, many filesystems still	1763	even on systems where the resolution is higher, many file systems still
1649	only support whole seconds.	1764	only support whole seconds.
1650		1765
1651	That means that, if the time is the only thing that changes, you might	1766	That means that, if the time is the only thing that changes, you can
1652	miss updates: on the first update, C<ev_stat> detects a change and calls	1767	easily miss updates: on the first update, C<ev_stat> detects a change and
1653	your callback, which does something. When there is another update within	1768	calls your callback, which does something. When there is another update
1654	the same second, C<ev_stat> will be unable to detect it.	1769	within the same second, C<ev_stat> will be unable to detect it as the stat
		1770	data does not change.
1655		1771
1656	The solution to this is to delay acting on a change for a second (or till	1772	The solution to this is to delay acting on a change for slightly more
1657	the next second boundary), using a roughly one-second delay C<ev_timer>	1773	than a second (or till slightly after the next full second boundary), using
1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1659	is added to work around small timing inconsistencies of some operating	1775	ev_timer_again (loop, w)>).
1660	systems.	1776
		1777	The C<.02> offset is added to work around small timing inconsistencies
		1778	of some operating systems (where the second counter of the current time
		1779	might be be delayed. One such system is the Linux kernel, where a call to
		1780	C<gettimeofday> might return a timestamp with a full second later than
		1781	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1782	update file times then there will be a small window where the kernel uses
		1783	the previous second to update file times but libev might already execute
		1784	the timer callback).
1661		1785
1662	=head3 Watcher-Specific Functions and Data Members	1786	=head3 Watcher-Specific Functions and Data Members
1663		1787
1664	=over 4	1788	=over 4
1665		1789
…		…
1671	C<path>. The C<interval> is a hint on how quickly a change is expected to	1795	C<path>. The C<interval> is a hint on how quickly a change is expected to
1672	be detected and should normally be specified as C<0> to let libev choose	1796	be detected and should normally be specified as C<0> to let libev choose
1673	a suitable value. The memory pointed to by C<path> must point to the same	1797	a suitable value. The memory pointed to by C<path> must point to the same
1674	path for as long as the watcher is active.	1798	path for as long as the watcher is active.
1675		1799
1676	The callback will be receive C<EV_STAT> when a change was detected,	1800	The callback will receive C<EV_STAT> when a change was detected, relative
1677	relative to the attributes at the time the watcher was started (or the	1801	to the attributes at the time the watcher was started (or the last change
1678	last change was detected).	1802	was detected).
1679		1803
1680	=item ev_stat_stat (loop, ev_stat *)	1804	=item ev_stat_stat (loop, ev_stat *)
1681		1805
1682	Updates the stat buffer immediately with new values. If you change the	1806	Updates the stat buffer immediately with new values. If you change the
1683	watched path in your callback, you could call this fucntion to avoid	1807	watched path in your callback, you could call this function to avoid
1684	detecting this change (while introducing a race condition). Can also be	1808	detecting this change (while introducing a race condition if you are not
1685	useful simply to find out the new values.	1809	the only one changing the path). Can also be useful simply to find out the
		1810	new values.
1686		1811
1687	=item ev_statdata attr [read-only]	1812	=item ev_statdata attr [read-only]
1688		1813
1689	The most-recently detected attributes of the file. Although the type is of	1814	The most-recently detected attributes of the file. Although the type is
1690	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1815	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1691	suitable for your system. If the C<st_nlink> member is C<0>, then there	1816	suitable for your system, but you can only rely on the POSIX-standardised
		1817	members to be present. If the C<st_nlink> member is C<0>, then there was
1692	was some error while C<stat>ing the file.	1818	some error while C<stat>ing the file.
1693		1819
1694	=item ev_statdata prev [read-only]	1820	=item ev_statdata prev [read-only]
1695		1821
1696	The previous attributes of the file. The callback gets invoked whenever	1822	The previous attributes of the file. The callback gets invoked whenever
1697	C<prev> != C<attr>.	1823	C<prev> != C<attr>, or, more precisely, one or more of these members
		1824	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1825	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1698		1826
1699	=item ev_tstamp interval [read-only]	1827	=item ev_tstamp interval [read-only]
1700		1828
1701	The specified interval.	1829	The specified interval.
1702		1830
1703	=item const char *path [read-only]	1831	=item const char *path [read-only]
1704		1832
1705	The filesystem path that is being watched.	1833	The file system path that is being watched.
1706		1834
1707	=back	1835	=back
1708		1836
1709	=head3 Examples	1837	=head3 Examples
1710		1838
1711	Example: Watch C</etc/passwd> for attribute changes.	1839	Example: Watch C</etc/passwd> for attribute changes.
1712		1840
1713	static void	1841	static void
1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1842	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1715	{	1843	{
1716	/* /etc/passwd changed in some way */	1844	/* /etc/passwd changed in some way */
1717	if (w->attr.st_nlink)	1845	if (w->attr.st_nlink)
1718	{	1846	{
1719	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1847	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1720	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1848	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1721	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1849	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1722	}	1850	}
1723	else	1851	else
1724	/* you shalt not abuse printf for puts */	1852	/* you shalt not abuse printf for puts */
1725	puts ("wow, /etc/passwd is not there, expect problems. "	1853	puts ("wow, /etc/passwd is not there, expect problems. "
1726	"if this is windows, they already arrived\n");	1854	"if this is windows, they already arrived\n");
1727	}	1855	}
1728		1856
1729	...	1857	...
1730	ev_stat passwd;	1858	ev_stat passwd;
1731		1859
1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1860	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1733	ev_stat_start (loop, &passwd);	1861	ev_stat_start (loop, &passwd);
1734		1862
1735	Example: Like above, but additionally use a one-second delay so we do not	1863	Example: Like above, but additionally use a one-second delay so we do not
1736	miss updates (however, frequent updates will delay processing, too, so	1864	miss updates (however, frequent updates will delay processing, too, so
1737	one might do the work both on C<ev_stat> callback invocation I<and> on	1865	one might do the work both on C<ev_stat> callback invocation I<and> on
1738	C<ev_timer> callback invocation).	1866	C<ev_timer> callback invocation).
1739		1867
1740	static ev_stat passwd;	1868	static ev_stat passwd;
1741	static ev_timer timer;	1869	static ev_timer timer;
1742		1870
1743	static void	1871	static void
1744	timer_cb (EV_P_ ev_timer *w, int revents)	1872	timer_cb (EV_P_ ev_timer *w, int revents)
1745	{	1873	{
1746	ev_timer_stop (EV_A_ w);	1874	ev_timer_stop (EV_A_ w);
1747		1875
1748	/* now it's one second after the most recent passwd change */	1876	/* now it's one second after the most recent passwd change */
1749	}	1877	}
1750		1878
1751	static void	1879	static void
1752	stat_cb (EV_P_ ev_stat *w, int revents)	1880	stat_cb (EV_P_ ev_stat *w, int revents)
1753	{	1881	{
1754	/* reset the one-second timer */	1882	/* reset the one-second timer */
1755	ev_timer_again (EV_A_ &timer);	1883	ev_timer_again (EV_A_ &timer);
1756	}	1884	}
1757		1885
1758	...	1886	...
1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1887	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	1888	ev_stat_start (loop, &passwd);
1761	ev_timer_init (&timer, timer_cb, 0., 1.01);	1889	ev_timer_init (&timer, timer_cb, 0., 1.02);
1762		1890
1763		1891
1764	=head2 C<ev_idle> - when you've got nothing better to do...	1892	=head2 C<ev_idle> - when you've got nothing better to do...
1765		1893
1766	Idle watchers trigger events when no other events of the same or higher	1894	Idle watchers trigger events when no other events of the same or higher
…		…
1797	=head3 Examples	1925	=head3 Examples
1798		1926
1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1800	callback, free it. Also, use no error checking, as usual.	1928	callback, free it. Also, use no error checking, as usual.
1801		1929
1802	static void	1930	static void
1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1804	{	1932	{
1805	free (w);	1933	free (w);
1806	// now do something you wanted to do when the program has	1934	// now do something you wanted to do when the program has
1807	// no longer anything immediate to do.	1935	// no longer anything immediate to do.
1808	}	1936	}
1809		1937
1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1811	ev_idle_init (idle_watcher, idle_cb);	1939	ev_idle_init (idle_watcher, idle_cb);
1812	ev_idle_start (loop, idle_cb);	1940	ev_idle_start (loop, idle_cb);
1813		1941
1814		1942
1815	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1816		1944
1817	Prepare and check watchers are usually (but not always) used in tandem:	1945	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1836		1964
1837	This is done by examining in each prepare call which file descriptors need	1965	This is done by examining in each prepare call which file descriptors need
1838	to be watched by the other library, registering C<ev_io> watchers for	1966	to be watched by the other library, registering C<ev_io> watchers for
1839	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1840	provide just this functionality). Then, in the check watcher you check for	1968	provide just this functionality). Then, in the check watcher you check for
1841	any events that occured (by checking the pending status of all watchers	1969	any events that occurred (by checking the pending status of all watchers
1842	and stopping them) and call back into the library. The I/O and timer	1970	and stopping them) and call back into the library. The I/O and timer
1843	callbacks will never actually be called (but must be valid nevertheless,	1971	callbacks will never actually be called (but must be valid nevertheless,
1844	because you never know, you know?).	1972	because you never know, you know?).
1845		1973
1846	As another example, the Perl Coro module uses these hooks to integrate	1974	As another example, the Perl Coro module uses these hooks to integrate
…		…
1854		1982
1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1856	priority, to ensure that they are being run before any other watchers	1984	priority, to ensure that they are being run before any other watchers
1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1858	too) should not activate ("feed") events into libev. While libev fully	1986	too) should not activate ("feed") events into libev. While libev fully
1859	supports this, they will be called before other C<ev_check> watchers	1987	supports this, they might get executed before other C<ev_check> watchers
1860	did their job. As C<ev_check> watchers are often used to embed other	1988	did their job. As C<ev_check> watchers are often used to embed other
1861	(non-libev) event loops those other event loops might be in an unusable	1989	(non-libev) event loops those other event loops might be in an unusable
1862	state until their C<ev_check> watcher ran (always remind yourself to	1990	state until their C<ev_check> watcher ran (always remind yourself to
1863	coexist peacefully with others).	1991	coexist peacefully with others).
1864		1992
…		…
1879	=head3 Examples	2007	=head3 Examples
1880		2008
1881	There are a number of principal ways to embed other event loops or modules	2009	There are a number of principal ways to embed other event loops or modules
1882	into libev. Here are some ideas on how to include libadns into libev	2010	into libev. Here are some ideas on how to include libadns into libev
1883	(there is a Perl module named C<EV::ADNS> that does this, which you could	2011	(there is a Perl module named C<EV::ADNS> that does this, which you could
1884	use for an actually working example. Another Perl module named C<EV::Glib>	2012	use as a working example. Another Perl module named C<EV::Glib> embeds a
1885	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2013	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1886	into the Glib event loop).	2014	Glib event loop).
1887		2015
1888	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2016	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1889	and in a check watcher, destroy them and call into libadns. What follows	2017	and in a check watcher, destroy them and call into libadns. What follows
1890	is pseudo-code only of course. This requires you to either use a low	2018	is pseudo-code only of course. This requires you to either use a low
1891	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2019	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1892	the callbacks for the IO/timeout watchers might not have been called yet.	2020	the callbacks for the IO/timeout watchers might not have been called yet.
1893		2021
1894	static ev_io iow [nfd];	2022	static ev_io iow [nfd];
1895	static ev_timer tw;	2023	static ev_timer tw;
1896		2024
1897	static void	2025	static void
1898	io_cb (ev_loop *loop, ev_io *w, int revents)	2026	io_cb (ev_loop *loop, ev_io *w, int revents)
1899	{	2027	{
1900	}	2028	}
1901		2029
1902	// create io watchers for each fd and a timer before blocking	2030	// create io watchers for each fd and a timer before blocking
1903	static void	2031	static void
1904	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1905	{	2033	{
1906	int timeout = 3600000;	2034	int timeout = 3600000;
1907	struct pollfd fds [nfd];	2035	struct pollfd fds [nfd];
1908	// actual code will need to loop here and realloc etc.	2036	// actual code will need to loop here and realloc etc.
1909	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1910		2038
1911	/* the callback is illegal, but won't be called as we stop during check */	2039	/* the callback is illegal, but won't be called as we stop during check */
1912	ev_timer_init (&tw, 0, timeout * 1e-3);	2040	ev_timer_init (&tw, 0, timeout * 1e-3);
1913	ev_timer_start (loop, &tw);	2041	ev_timer_start (loop, &tw);
1914		2042
1915	// create one ev_io per pollfd	2043	// create one ev_io per pollfd
1916	for (int i = 0; i < nfd; ++i)	2044	for (int i = 0; i < nfd; ++i)
1917	{	2045	{
1918	ev_io_init (iow + i, io_cb, fds [i].fd,	2046	ev_io_init (iow + i, io_cb, fds [i].fd,
1919	((fds [i].events & POLLIN ? EV_READ : 0)	2047	((fds [i].events & POLLIN ? EV_READ : 0)
1920	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2048	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1921		2049
1922	fds [i].revents = 0;	2050	fds [i].revents = 0;
1923	ev_io_start (loop, iow + i);	2051	ev_io_start (loop, iow + i);
1924	}	2052	}
1925	}	2053	}
1926		2054
1927	// stop all watchers after blocking	2055	// stop all watchers after blocking
1928	static void	2056	static void
1929	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1930	{	2058	{
1931	ev_timer_stop (loop, &tw);	2059	ev_timer_stop (loop, &tw);
1932		2060
1933	for (int i = 0; i < nfd; ++i)	2061	for (int i = 0; i < nfd; ++i)
1934	{	2062	{
1935	// set the relevant poll flags	2063	// set the relevant poll flags
1936	// could also call adns_processreadable etc. here	2064	// could also call adns_processreadable etc. here
1937	struct pollfd *fd = fds + i;	2065	struct pollfd *fd = fds + i;
1938	int revents = ev_clear_pending (iow + i);	2066	int revents = ev_clear_pending (iow + i);
1939	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2067	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1940	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2068	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1941		2069
1942	// now stop the watcher	2070	// now stop the watcher
1943	ev_io_stop (loop, iow + i);	2071	ev_io_stop (loop, iow + i);
1944	}	2072	}
1945		2073
1946	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2074	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1947	}	2075	}
1948		2076
1949	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2077	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1950	in the prepare watcher and would dispose of the check watcher.	2078	in the prepare watcher and would dispose of the check watcher.
1951		2079
1952	Method 3: If the module to be embedded supports explicit event	2080	Method 3: If the module to be embedded supports explicit event
1953	notification (adns does), you can also make use of the actual watcher	2081	notification (libadns does), you can also make use of the actual watcher
1954	callbacks, and only destroy/create the watchers in the prepare watcher.	2082	callbacks, and only destroy/create the watchers in the prepare watcher.
1955		2083
1956	static void	2084	static void
1957	timer_cb (EV_P_ ev_timer *w, int revents)	2085	timer_cb (EV_P_ ev_timer *w, int revents)
1958	{	2086	{
1959	adns_state ads = (adns_state)w->data;	2087	adns_state ads = (adns_state)w->data;
1960	update_now (EV_A);	2088	update_now (EV_A);
1961		2089
1962	adns_processtimeouts (ads, &tv_now);	2090	adns_processtimeouts (ads, &tv_now);
1963	}	2091	}
1964		2092
1965	static void	2093	static void
1966	io_cb (EV_P_ ev_io *w, int revents)	2094	io_cb (EV_P_ ev_io *w, int revents)
1967	{	2095	{
1968	adns_state ads = (adns_state)w->data;	2096	adns_state ads = (adns_state)w->data;
1969	update_now (EV_A);	2097	update_now (EV_A);
1970		2098
1971	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2099	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1972	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2100	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1973	}	2101	}
1974		2102
1975	// do not ever call adns_afterpoll	2103	// do not ever call adns_afterpoll
1976		2104
1977	Method 4: Do not use a prepare or check watcher because the module you	2105	Method 4: Do not use a prepare or check watcher because the module you
1978	want to embed is too inflexible to support it. Instead, youc na override	2106	want to embed is too inflexible to support it. Instead, you can override
1979	their poll function. The drawback with this solution is that the main	2107	their poll function. The drawback with this solution is that the main
1980	loop is now no longer controllable by EV. The C<Glib::EV> module does	2108	loop is now no longer controllable by EV. The C<Glib::EV> module does
1981	this.	2109	this.
1982		2110
1983	static gint	2111	static gint
1984	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1985	{	2113	{
1986	int got_events = 0;	2114	int got_events = 0;
1987		2115
1988	for (n = 0; n < nfds; ++n)	2116	for (n = 0; n < nfds; ++n)
1989	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2117	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1990		2118
1991	if (timeout >= 0)	2119	if (timeout >= 0)
1992	// create/start timer	2120	// create/start timer
1993		2121
1994	// poll	2122	// poll
1995	ev_loop (EV_A_ 0);	2123	ev_loop (EV_A_ 0);
1996		2124
1997	// stop timer again	2125	// stop timer again
1998	if (timeout >= 0)	2126	if (timeout >= 0)
1999	ev_timer_stop (EV_A_ &to);	2127	ev_timer_stop (EV_A_ &to);
2000		2128
2001	// stop io watchers again - their callbacks should have set	2129	// stop io watchers again - their callbacks should have set
2002	for (n = 0; n < nfds; ++n)	2130	for (n = 0; n < nfds; ++n)
2003	ev_io_stop (EV_A_ iow [n]);	2131	ev_io_stop (EV_A_ iow [n]);
2004		2132
2005	return got_events;	2133	return got_events;
2006	}	2134	}
2007		2135
2008		2136
2009	=head2 C<ev_embed> - when one backend isn't enough...	2137	=head2 C<ev_embed> - when one backend isn't enough...
2010		2138
2011	This is a rather advanced watcher type that lets you embed one event loop	2139	This is a rather advanced watcher type that lets you embed one event loop
…		…
2067		2195
2068	Configures the watcher to embed the given loop, which must be	2196	Configures the watcher to embed the given loop, which must be
2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2070	invoked automatically, otherwise it is the responsibility of the callback	2198	invoked automatically, otherwise it is the responsibility of the callback
2071	to invoke it (it will continue to be called until the sweep has been done,	2199	to invoke it (it will continue to be called until the sweep has been done,
2072	if you do not want thta, you need to temporarily stop the embed watcher).	2200	if you do not want that, you need to temporarily stop the embed watcher).
2073		2201
2074	=item ev_embed_sweep (loop, ev_embed *)	2202	=item ev_embed_sweep (loop, ev_embed *)
2075		2203
2076	Make a single, non-blocking sweep over the embedded loop. This works	2204	Make a single, non-blocking sweep over the embedded loop. This works
2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2078	apropriate way for embedded loops.	2206	appropriate way for embedded loops.
2079		2207
2080	=item struct ev_loop *other [read-only]	2208	=item struct ev_loop *other [read-only]
2081		2209
2082	The embedded event loop.	2210	The embedded event loop.
2083		2211
…		…
2085		2213
2086	=head3 Examples	2214	=head3 Examples
2087		2215
2088	Example: Try to get an embeddable event loop and embed it into the default	2216	Example: Try to get an embeddable event loop and embed it into the default
2089	event loop. If that is not possible, use the default loop. The default	2217	event loop. If that is not possible, use the default loop. The default
2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2218	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2092	used).	2220	used).
2093		2221
2094	struct ev_loop *loop_hi = ev_default_init (0);	2222	struct ev_loop *loop_hi = ev_default_init (0);
2095	struct ev_loop *loop_lo = 0;	2223	struct ev_loop *loop_lo = 0;
2096	struct ev_embed embed;	2224	struct ev_embed embed;
2097		2225
2098	// see if there is a chance of getting one that works	2226	// see if there is a chance of getting one that works
2099	// (remember that a flags value of 0 means autodetection)	2227	// (remember that a flags value of 0 means autodetection)
2100	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2101	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2102	: 0;	2230	: 0;
2103		2231
2104	// if we got one, then embed it, otherwise default to loop_hi	2232	// if we got one, then embed it, otherwise default to loop_hi
2105	if (loop_lo)	2233	if (loop_lo)
2106	{	2234	{
2107	ev_embed_init (&embed, 0, loop_lo);	2235	ev_embed_init (&embed, 0, loop_lo);
2108	ev_embed_start (loop_hi, &embed);	2236	ev_embed_start (loop_hi, &embed);
2109	}	2237	}
2110	else	2238	else
2111	loop_lo = loop_hi;	2239	loop_lo = loop_hi;
2112		2240
2113	Example: Check if kqueue is available but not recommended and create	2241	Example: Check if kqueue is available but not recommended and create
2114	a kqueue backend for use with sockets (which usually work with any	2242	a kqueue backend for use with sockets (which usually work with any
2115	kqueue implementation). Store the kqueue/socket-only event loop in	2243	kqueue implementation). Store the kqueue/socket-only event loop in
2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2117		2245
2118	struct ev_loop *loop = ev_default_init (0);	2246	struct ev_loop *loop = ev_default_init (0);
2119	struct ev_loop *loop_socket = 0;	2247	struct ev_loop *loop_socket = 0;
2120	struct ev_embed embed;	2248	struct ev_embed embed;
2121		2249
2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2124	{	2252	{
2125	ev_embed_init (&embed, 0, loop_socket);	2253	ev_embed_init (&embed, 0, loop_socket);
2126	ev_embed_start (loop, &embed);	2254	ev_embed_start (loop, &embed);
2127	}	2255	}
2128		2256
2129	if (!loop_socket)	2257	if (!loop_socket)
2130	loop_socket = loop;	2258	loop_socket = loop;
2131		2259
2132	// now use loop_socket for all sockets, and loop for everything else	2260	// now use loop_socket for all sockets, and loop for everything else
2133		2261
2134		2262
2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2136		2264
2137	Fork watchers are called when a C<fork ()> was detected (usually because	2265	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2190		2318
2191	=item queueing from a signal handler context	2319	=item queueing from a signal handler context
2192		2320
2193	To implement race-free queueing, you simply add to the queue in the signal	2321	To implement race-free queueing, you simply add to the queue in the signal
2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for
2195	some fictitiuous SIGUSR1 handler:	2323	some fictitious SIGUSR1 handler:
2196		2324
2197	static ev_async mysig;	2325	static ev_async mysig;
2198		2326
2199	static void	2327	static void
2200	sigusr1_handler (void)	2328	sigusr1_handler (void)
…		…
2274	=item ev_async_send (loop, ev_async *)	2402	=item ev_async_send (loop, ev_async *)
2275		2403
2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2278	C<ev_feed_event>, this call is safe to do in other threads, signal or	2406	C<ev_feed_event>, this call is safe to do in other threads, signal or
2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2280	section below on what exactly this means).	2408	section below on what exactly this means).
2281		2409
2282	This call incurs the overhead of a syscall only once per loop iteration,	2410	This call incurs the overhead of a system call only once per loop iteration,
2283	so while the overhead might be noticable, it doesn't apply to repeated	2411	so while the overhead might be noticeable, it doesn't apply to repeated
2284	calls to C<ev_async_send>.	2412	calls to C<ev_async_send>.
2285		2413
2286	=item bool = ev_async_pending (ev_async *)	2414	=item bool = ev_async_pending (ev_async *)
2287		2415
2288	Returns a non-zero value when C<ev_async_send> has been called on the	2416	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2290	event loop.	2418	event loop.
2291		2419
2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2293	the loop iterates next and checks for the watcher to have become active,	2421	the loop iterates next and checks for the watcher to have become active,
2294	it will reset the flag again. C<ev_async_pending> can be used to very	2422	it will reset the flag again. C<ev_async_pending> can be used to very
2295	quickly check wether invoking the loop might be a good idea.	2423	quickly check whether invoking the loop might be a good idea.
2296		2424
2297	Not that this does I<not> check wether the watcher itself is pending, only	2425	Not that this does I<not> check whether the watcher itself is pending, only
2298	wether it has been requested to make this watcher pending.	2426	whether it has been requested to make this watcher pending.
2299		2427
2300	=back	2428	=back
2301		2429
2302		2430
2303	=head1 OTHER FUNCTIONS	2431	=head1 OTHER FUNCTIONS
…		…
2314	or timeout without having to allocate/configure/start/stop/free one or	2442	or timeout without having to allocate/configure/start/stop/free one or
2315	more watchers yourself.	2443	more watchers yourself.
2316		2444
2317	If C<fd> is less than 0, then no I/O watcher will be started and events	2445	If C<fd> is less than 0, then no I/O watcher will be started and events
2318	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2319	C<events> set will be craeted and started.	2447	C<events> set will be created and started.
2320		2448
2321	If C<timeout> is less than 0, then no timeout watcher will be	2449	If C<timeout> is less than 0, then no timeout watcher will be
2322	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2323	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2324	dubious value.	2452	dubious value.
…		…
2326	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2327	passed an C<revents> set like normal event callbacks (a combination of	2455	passed an C<revents> set like normal event callbacks (a combination of
2328	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2329	value passed to C<ev_once>:	2457	value passed to C<ev_once>:
2330		2458
2331	static void stdin_ready (int revents, void *arg)	2459	static void stdin_ready (int revents, void *arg)
2332	{	2460	{
2333	if (revents & EV_TIMEOUT)	2461	if (revents & EV_TIMEOUT)
2334	/* doh, nothing entered */;	2462	/* doh, nothing entered */;
2335	else if (revents & EV_READ)	2463	else if (revents & EV_READ)
2336	/* stdin might have data for us, joy! */;	2464	/* stdin might have data for us, joy! */;
2337	}	2465	}
2338		2466
2339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2340		2468
2341	=item ev_feed_event (ev_loop *, watcher *, int revents)	2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2342		2470
2343	Feeds the given event set into the event loop, as if the specified event	2471	Feeds the given event set into the event loop, as if the specified event
2344	had happened for the specified watcher (which must be a pointer to an	2472	had happened for the specified watcher (which must be a pointer to an
…		…
2349	Feed an event on the given fd, as if a file descriptor backend detected	2477	Feed an event on the given fd, as if a file descriptor backend detected
2350	the given events it.	2478	the given events it.
2351		2479
2352	=item ev_feed_signal_event (ev_loop *loop, int signum)	2480	=item ev_feed_signal_event (ev_loop *loop, int signum)
2353		2481
2354	Feed an event as if the given signal occured (C<loop> must be the default	2482	Feed an event as if the given signal occurred (C<loop> must be the default
2355	loop!).	2483	loop!).
2356		2484
2357	=back	2485	=back
2358		2486
2359		2487
…		…
2375		2503
2376	=item * Priorities are not currently supported. Initialising priorities	2504	=item * Priorities are not currently supported. Initialising priorities
2377	will fail and all watchers will have the same priority, even though there	2505	will fail and all watchers will have the same priority, even though there
2378	is an ev_pri field.	2506	is an ev_pri field.
2379		2507
		2508	=item * In libevent, the last base created gets the signals, in libev, the
		2509	first base created (== the default loop) gets the signals.
		2510
2380	=item * Other members are not supported.	2511	=item * Other members are not supported.
2381		2512
2382	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2513	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2383	to use the libev header file and library.	2514	to use the libev header file and library.
2384		2515
2385	=back	2516	=back
2386		2517
2387	=head1 C++ SUPPORT	2518	=head1 C++ SUPPORT
2388		2519
2389	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2520	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2390	you to use some convinience methods to start/stop watchers and also change	2521	you to use some convenience methods to start/stop watchers and also change
2391	the callback model to a model using method callbacks on objects.	2522	the callback model to a model using method callbacks on objects.
2392		2523
2393	To use it,	2524	To use it,
2394		2525
2395	#include <ev++.h>	2526	#include <ev++.h>
2396		2527
2397	This automatically includes F<ev.h> and puts all of its definitions (many	2528	This automatically includes F<ev.h> and puts all of its definitions (many
2398	of them macros) into the global namespace. All C++ specific things are	2529	of them macros) into the global namespace. All C++ specific things are
2399	put into the C<ev> namespace. It should support all the same embedding	2530	put into the C<ev> namespace. It should support all the same embedding
2400	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2531	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2467	your compiler is good :), then the method will be fully inlined into the	2598	your compiler is good :), then the method will be fully inlined into the
2468	thunking function, making it as fast as a direct C callback.	2599	thunking function, making it as fast as a direct C callback.
2469		2600
2470	Example: simple class declaration and watcher initialisation	2601	Example: simple class declaration and watcher initialisation
2471		2602
2472	struct myclass	2603	struct myclass
2473	{	2604	{
2474	void io_cb (ev::io &w, int revents) { }	2605	void io_cb (ev::io &w, int revents) { }
2475	}	2606	}
2476		2607
2477	myclass obj;	2608	myclass obj;
2478	ev::io iow;	2609	ev::io iow;
2479	iow.set <myclass, &myclass::io_cb> (&obj);	2610	iow.set <myclass, &myclass::io_cb> (&obj);
2480		2611
2481	=item w->set<function> (void *data = 0)	2612	=item w->set<function> (void *data = 0)
2482		2613
2483	Also sets a callback, but uses a static method or plain function as	2614	Also sets a callback, but uses a static method or plain function as
2484	callback. The optional C<data> argument will be stored in the watcher's	2615	callback. The optional C<data> argument will be stored in the watcher's
…		…
2488		2619
2489	See the method-C<set> above for more details.	2620	See the method-C<set> above for more details.
2490		2621
2491	Example:	2622	Example:
2492		2623
2493	static void io_cb (ev::io &w, int revents) { }	2624	static void io_cb (ev::io &w, int revents) { }
2494	iow.set <io_cb> ();	2625	iow.set <io_cb> ();
2495		2626
2496	=item w->set (struct ev_loop *)	2627	=item w->set (struct ev_loop *)
2497		2628
2498	Associates a different C<struct ev_loop> with this watcher. You can only	2629	Associates a different C<struct ev_loop> with this watcher. You can only
2499	do this when the watcher is inactive (and not pending either).	2630	do this when the watcher is inactive (and not pending either).
2500		2631
2501	=item w->set ([args])	2632	=item w->set ([arguments])
2502		2633
2503	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2504	called at least once. Unlike the C counterpart, an active watcher gets	2635	called at least once. Unlike the C counterpart, an active watcher gets
2505	automatically stopped and restarted when reconfiguring it with this	2636	automatically stopped and restarted when reconfiguring it with this
2506	method.	2637	method.
2507		2638
2508	=item w->start ()	2639	=item w->start ()
…		…
2532	=back	2663	=back
2533		2664
2534	Example: Define a class with an IO and idle watcher, start one of them in	2665	Example: Define a class with an IO and idle watcher, start one of them in
2535	the constructor.	2666	the constructor.
2536		2667
2537	class myclass	2668	class myclass
2538	{	2669	{
2539	ev::io io; void io_cb (ev::io &w, int revents);	2670	ev::io io; void io_cb (ev::io &w, int revents);
2540	ev:idle idle void idle_cb (ev::idle &w, int revents);	2671	ev:idle idle void idle_cb (ev::idle &w, int revents);
2541		2672
2542	myclass (int fd)	2673	myclass (int fd)
2543	{	2674	{
2544	io .set <myclass, &myclass::io_cb > (this);	2675	io .set <myclass, &myclass::io_cb > (this);
2545	idle.set <myclass, &myclass::idle_cb> (this);	2676	idle.set <myclass, &myclass::idle_cb> (this);
2546		2677
2547	io.start (fd, ev::READ);	2678	io.start (fd, ev::READ);
2548	}	2679	}
2549	};	2680	};
2550		2681
2551		2682
2552	=head1 OTHER LANGUAGE BINDINGS	2683	=head1 OTHER LANGUAGE BINDINGS
2553		2684
2554	Libev does not offer other language bindings itself, but bindings for a	2685	Libev does not offer other language bindings itself, but bindings for a
2555	numbe rof languages exist in the form of third-party packages. If you know	2686	number of languages exist in the form of third-party packages. If you know
2556	any interesting language binding in addition to the ones listed here, drop	2687	any interesting language binding in addition to the ones listed here, drop
2557	me a note.	2688	me a note.
2558		2689
2559	=over 4	2690	=over 4
2560		2691
…		…
2564	libev. EV is developed together with libev. Apart from the EV core module,	2695	libev. EV is developed together with libev. Apart from the EV core module,
2565	there are additional modules that implement libev-compatible interfaces	2696	there are additional modules that implement libev-compatible interfaces
2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2568		2699
2569	It can be found and installed via CPAN, its homepage is found at	2700	It can be found and installed via CPAN, its homepage is at
2570	L<http://software.schmorp.de/pkg/EV>.	2701	L<http://software.schmorp.de/pkg/EV>.
2571		2702
		2703	=item Python
		2704
		2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2706	seems to be quite complete and well-documented. Note, however, that the
		2707	patch they require for libev is outright dangerous as it breaks the ABI
		2708	for everybody else, and therefore, should never be applied in an installed
		2709	libev (if python requires an incompatible ABI then it needs to embed
		2710	libev).
		2711
2572	=item Ruby	2712	=item Ruby
2573		2713
2574	Tony Arcieri has written a ruby extension that offers access to a subset	2714	Tony Arcieri has written a ruby extension that offers access to a subset
2575	of the libev API and adds filehandle abstractions, asynchronous DNS and	2715	of the libev API and adds file handle abstractions, asynchronous DNS and
2576	more on top of it. It can be found via gem servers. Its homepage is at	2716	more on top of it. It can be found via gem servers. Its homepage is at
2577	L<http://rev.rubyforge.org/>.	2717	L<http://rev.rubyforge.org/>.
2578		2718
2579	=item D	2719	=item D
2580		2720
2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2583		2723
2584	=back	2724	=back
2585		2725
2586		2726
2587	=head1 MACRO MAGIC	2727	=head1 MACRO MAGIC
2588		2728
2589	Libev can be compiled with a variety of options, the most fundamantal	2729	Libev can be compiled with a variety of options, the most fundamental
2590	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2730	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2591	functions and callbacks have an initial C<struct ev_loop *> argument.	2731	functions and callbacks have an initial C<struct ev_loop *> argument.
2592		2732
2593	To make it easier to write programs that cope with either variant, the	2733	To make it easier to write programs that cope with either variant, the
2594	following macros are defined:	2734	following macros are defined:
…		…
2599		2739
2600	This provides the loop I<argument> for functions, if one is required ("ev	2740	This provides the loop I<argument> for functions, if one is required ("ev
2601	loop argument"). The C<EV_A> form is used when this is the sole argument,	2741	loop argument"). The C<EV_A> form is used when this is the sole argument,
2602	C<EV_A_> is used when other arguments are following. Example:	2742	C<EV_A_> is used when other arguments are following. Example:
2603		2743
2604	ev_unref (EV_A);	2744	ev_unref (EV_A);
2605	ev_timer_add (EV_A_ watcher);	2745	ev_timer_add (EV_A_ watcher);
2606	ev_loop (EV_A_ 0);	2746	ev_loop (EV_A_ 0);
2607		2747
2608	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2609	which is often provided by the following macro.	2749	which is often provided by the following macro.
2610		2750
2611	=item C<EV_P>, C<EV_P_>	2751	=item C<EV_P>, C<EV_P_>
2612		2752
2613	This provides the loop I<parameter> for functions, if one is required ("ev	2753	This provides the loop I<parameter> for functions, if one is required ("ev
2614	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2754	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2615	C<EV_P_> is used when other parameters are following. Example:	2755	C<EV_P_> is used when other parameters are following. Example:
2616		2756
2617	// this is how ev_unref is being declared	2757	// this is how ev_unref is being declared
2618	static void ev_unref (EV_P);	2758	static void ev_unref (EV_P);
2619		2759
2620	// this is how you can declare your typical callback	2760	// this is how you can declare your typical callback
2621	static void cb (EV_P_ ev_timer *w, int revents)	2761	static void cb (EV_P_ ev_timer *w, int revents)
2622		2762
2623	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2763	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2624	suitable for use with C<EV_A>.	2764	suitable for use with C<EV_A>.
2625		2765
2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2766	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2642		2782
2643	Example: Declare and initialise a check watcher, utilising the above	2783	Example: Declare and initialise a check watcher, utilising the above
2644	macros so it will work regardless of whether multiple loops are supported	2784	macros so it will work regardless of whether multiple loops are supported
2645	or not.	2785	or not.
2646		2786
2647	static void	2787	static void
2648	check_cb (EV_P_ ev_timer *w, int revents)	2788	check_cb (EV_P_ ev_timer *w, int revents)
2649	{	2789	{
2650	ev_check_stop (EV_A_ w);	2790	ev_check_stop (EV_A_ w);
2651	}	2791	}
2652		2792
2653	ev_check check;	2793	ev_check check;
2654	ev_check_init (&check, check_cb);	2794	ev_check_init (&check, check_cb);
2655	ev_check_start (EV_DEFAULT_ &check);	2795	ev_check_start (EV_DEFAULT_ &check);
2656	ev_loop (EV_DEFAULT_ 0);	2796	ev_loop (EV_DEFAULT_ 0);
2657		2797
2658	=head1 EMBEDDING	2798	=head1 EMBEDDING
2659		2799
2660	Libev can (and often is) directly embedded into host	2800	Libev can (and often is) directly embedded into host
2661	applications. Examples of applications that embed it include the Deliantra	2801	applications. Examples of applications that embed it include the Deliantra
…		…
2668	libev somewhere in your source tree).	2808	libev somewhere in your source tree).
2669		2809
2670	=head2 FILESETS	2810	=head2 FILESETS
2671		2811
2672	Depending on what features you need you need to include one or more sets of files	2812	Depending on what features you need you need to include one or more sets of files
2673	in your app.	2813	in your application.
2674		2814
2675	=head3 CORE EVENT LOOP	2815	=head3 CORE EVENT LOOP
2676		2816
2677	To include only the libev core (all the C<ev_*> functions), with manual	2817	To include only the libev core (all the C<ev_*> functions), with manual
2678	configuration (no autoconf):	2818	configuration (no autoconf):
2679		2819
2680	#define EV_STANDALONE 1	2820	#define EV_STANDALONE 1
2681	#include "ev.c"	2821	#include "ev.c"
2682		2822
2683	This will automatically include F<ev.h>, too, and should be done in a	2823	This will automatically include F<ev.h>, too, and should be done in a
2684	single C source file only to provide the function implementations. To use	2824	single C source file only to provide the function implementations. To use
2685	it, do the same for F<ev.h> in all files wishing to use this API (best	2825	it, do the same for F<ev.h> in all files wishing to use this API (best
2686	done by writing a wrapper around F<ev.h> that you can include instead and	2826	done by writing a wrapper around F<ev.h> that you can include instead and
2687	where you can put other configuration options):	2827	where you can put other configuration options):
2688		2828
2689	#define EV_STANDALONE 1	2829	#define EV_STANDALONE 1
2690	#include "ev.h"	2830	#include "ev.h"
2691		2831
2692	Both header files and implementation files can be compiled with a C++	2832	Both header files and implementation files can be compiled with a C++
2693	compiler (at least, thats a stated goal, and breakage will be treated	2833	compiler (at least, thats a stated goal, and breakage will be treated
2694	as a bug).	2834	as a bug).
2695		2835
2696	You need the following files in your source tree, or in a directory	2836	You need the following files in your source tree, or in a directory
2697	in your include path (e.g. in libev/ when using -Ilibev):	2837	in your include path (e.g. in libev/ when using -Ilibev):
2698		2838
2699	ev.h	2839	ev.h
2700	ev.c	2840	ev.c
2701	ev_vars.h	2841	ev_vars.h
2702	ev_wrap.h	2842	ev_wrap.h
2703		2843
2704	ev_win32.c required on win32 platforms only	2844	ev_win32.c required on win32 platforms only
2705		2845
2706	ev_select.c only when select backend is enabled (which is enabled by default)	2846	ev_select.c only when select backend is enabled (which is enabled by default)
2707	ev_poll.c only when poll backend is enabled (disabled by default)	2847	ev_poll.c only when poll backend is enabled (disabled by default)
2708	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2848	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2709	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2849	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2710	ev_port.c only when the solaris port backend is enabled (disabled by default)	2850	ev_port.c only when the solaris port backend is enabled (disabled by default)
2711		2851
2712	F<ev.c> includes the backend files directly when enabled, so you only need	2852	F<ev.c> includes the backend files directly when enabled, so you only need
2713	to compile this single file.	2853	to compile this single file.
2714		2854
2715	=head3 LIBEVENT COMPATIBILITY API	2855	=head3 LIBEVENT COMPATIBILITY API
2716		2856
2717	To include the libevent compatibility API, also include:	2857	To include the libevent compatibility API, also include:
2718		2858
2719	#include "event.c"	2859	#include "event.c"
2720		2860
2721	in the file including F<ev.c>, and:	2861	in the file including F<ev.c>, and:
2722		2862
2723	#include "event.h"	2863	#include "event.h"
2724		2864
2725	in the files that want to use the libevent API. This also includes F<ev.h>.	2865	in the files that want to use the libevent API. This also includes F<ev.h>.
2726		2866
2727	You need the following additional files for this:	2867	You need the following additional files for this:
2728		2868
2729	event.h	2869	event.h
2730	event.c	2870	event.c
2731		2871
2732	=head3 AUTOCONF SUPPORT	2872	=head3 AUTOCONF SUPPORT
2733		2873
2734	Instead of using C<EV_STANDALONE=1> and providing your config in	2874	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2735	whatever way you want, you can also C<m4_include([libev.m4])> in your	2875	whatever way you want, you can also C<m4_include([libev.m4])> in your
2736	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2876	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2737	include F<config.h> and configure itself accordingly.	2877	include F<config.h> and configure itself accordingly.
2738		2878
2739	For this of course you need the m4 file:	2879	For this of course you need the m4 file:
2740		2880
2741	libev.m4	2881	libev.m4
2742		2882
2743	=head2 PREPROCESSOR SYMBOLS/MACROS	2883	=head2 PREPROCESSOR SYMBOLS/MACROS
2744		2884
2745	Libev can be configured via a variety of preprocessor symbols you have to	2885	Libev can be configured via a variety of preprocessor symbols you have to
2746	define before including any of its files. The default in the absense of	2886	define before including any of its files. The default in the absence of
2747	autoconf is noted for every option.	2887	autoconf is noted for every option.
2748		2888
2749	=over 4	2889	=over 4
2750		2890
2751	=item EV_STANDALONE	2891	=item EV_STANDALONE
…		…
2757	F<event.h> that are not directly supported by the libev core alone.	2897	F<event.h> that are not directly supported by the libev core alone.
2758		2898
2759	=item EV_USE_MONOTONIC	2899	=item EV_USE_MONOTONIC
2760		2900
2761	If defined to be C<1>, libev will try to detect the availability of the	2901	If defined to be C<1>, libev will try to detect the availability of the
2762	monotonic clock option at both compiletime and runtime. Otherwise no use	2902	monotonic clock option at both compile time and runtime. Otherwise no use
2763	of the monotonic clock option will be attempted. If you enable this, you	2903	of the monotonic clock option will be attempted. If you enable this, you
2764	usually have to link against librt or something similar. Enabling it when	2904	usually have to link against librt or something similar. Enabling it when
2765	the functionality isn't available is safe, though, although you have	2905	the functionality isn't available is safe, though, although you have
2766	to make sure you link against any libraries where the C<clock_gettime>	2906	to make sure you link against any libraries where the C<clock_gettime>
2767	function is hiding in (often F<-lrt>).	2907	function is hiding in (often F<-lrt>).
2768		2908
2769	=item EV_USE_REALTIME	2909	=item EV_USE_REALTIME
2770		2910
2771	If defined to be C<1>, libev will try to detect the availability of the	2911	If defined to be C<1>, libev will try to detect the availability of the
2772	realtime clock option at compiletime (and assume its availability at	2912	real-time clock option at compile time (and assume its availability at
2773	runtime if successful). Otherwise no use of the realtime clock option will	2913	runtime if successful). Otherwise no use of the real-time clock option will
2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2777		2917
2778	=item EV_USE_NANOSLEEP	2918	=item EV_USE_NANOSLEEP
…		…
2789	2.7 or newer, otherwise disabled.	2929	2.7 or newer, otherwise disabled.
2790		2930
2791	=item EV_USE_SELECT	2931	=item EV_USE_SELECT
2792		2932
2793	If undefined or defined to be C<1>, libev will compile in support for the	2933	If undefined or defined to be C<1>, libev will compile in support for the
2794	C<select>(2) backend. No attempt at autodetection will be done: if no	2934	C<select>(2) backend. No attempt at auto-detection will be done: if no
2795	other method takes over, select will be it. Otherwise the select backend	2935	other method takes over, select will be it. Otherwise the select backend
2796	will not be compiled in.	2936	will not be compiled in.
2797		2937
2798	=item EV_SELECT_USE_FD_SET	2938	=item EV_SELECT_USE_FD_SET
2799		2939
2800	If defined to C<1>, then the select backend will use the system C<fd_set>	2940	If defined to C<1>, then the select backend will use the system C<fd_set>
2801	structure. This is useful if libev doesn't compile due to a missing	2941	structure. This is useful if libev doesn't compile due to a missing
2802	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2803	exotic systems. This usually limits the range of file descriptors to some	2943	exotic systems. This usually limits the range of file descriptors to some
2804	low limit such as 1024 or might have other limitations (winsocket only	2944	low limit such as 1024 or might have other limitations (winsocket only
2805	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2806	influence the size of the C<fd_set> used.	2946	influence the size of the C<fd_set> used.
2807		2947
…		…
2856	otherwise another method will be used as fallback. This is the preferred	2996	otherwise another method will be used as fallback. This is the preferred
2857	backend for Solaris 10 systems.	2997	backend for Solaris 10 systems.
2858		2998
2859	=item EV_USE_DEVPOLL	2999	=item EV_USE_DEVPOLL
2860		3000
2861	reserved for future expansion, works like the USE symbols above.	3001	Reserved for future expansion, works like the USE symbols above.
2862		3002
2863	=item EV_USE_INOTIFY	3003	=item EV_USE_INOTIFY
2864		3004
2865	If defined to be C<1>, libev will compile in support for the Linux inotify	3005	If defined to be C<1>, libev will compile in support for the Linux inotify
2866	interface to speed up C<ev_stat> watchers. Its actual availability will	3006	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2873	access is atomic with respect to other threads or signal contexts. No such	3013	access is atomic with respect to other threads or signal contexts. No such
2874	type is easily found in the C language, so you can provide your own type	3014	type is easily found in the C language, so you can provide your own type
2875	that you know is safe for your purposes. It is used both for signal handler "locking"	3015	that you know is safe for your purposes. It is used both for signal handler "locking"
2876	as well as for signal and thread safety in C<ev_async> watchers.	3016	as well as for signal and thread safety in C<ev_async> watchers.
2877		3017
2878	In the absense of this define, libev will use C<sig_atomic_t volatile>	3018	In the absence of this define, libev will use C<sig_atomic_t volatile>
2879	(from F<signal.h>), which is usually good enough on most platforms.	3019	(from F<signal.h>), which is usually good enough on most platforms.
2880		3020
2881	=item EV_H	3021	=item EV_H
2882		3022
2883	The name of the F<ev.h> header file used to include it. The default if	3023	The name of the F<ev.h> header file used to include it. The default if
…		…
2922	When doing priority-based operations, libev usually has to linearly search	3062	When doing priority-based operations, libev usually has to linearly search
2923	all the priorities, so having many of them (hundreds) uses a lot of space	3063	all the priorities, so having many of them (hundreds) uses a lot of space
2924	and time, so using the defaults of five priorities (-2 .. +2) is usually	3064	and time, so using the defaults of five priorities (-2 .. +2) is usually
2925	fine.	3065	fine.
2926		3066
2927	If your embedding app does not need any priorities, defining these both to	3067	If your embedding application does not need any priorities, defining these both to
2928	C<0> will save some memory and cpu.	3068	C<0> will save some memory and CPU.
2929		3069
2930	=item EV_PERIODIC_ENABLE	3070	=item EV_PERIODIC_ENABLE
2931		3071
2932	If undefined or defined to be C<1>, then periodic timers are supported. If	3072	If undefined or defined to be C<1>, then periodic timers are supported. If
2933	defined to be C<0>, then they are not. Disabling them saves a few kB of	3073	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	defined to be C<0>, then they are not.	3100	defined to be C<0>, then they are not.
2961		3101
2962	=item EV_MINIMAL	3102	=item EV_MINIMAL
2963		3103
2964	If you need to shave off some kilobytes of code at the expense of some	3104	If you need to shave off some kilobytes of code at the expense of some
2965	speed, define this symbol to C<1>. Currently only used for gcc to override	3105	speed, define this symbol to C<1>. Currently this is used to override some
2966	some inlining decisions, saves roughly 30% codesize of amd64.	3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3107	much smaller 2-heap for timer management over the default 4-heap.
2967		3108
2968	=item EV_PID_HASHSIZE	3109	=item EV_PID_HASHSIZE
2969		3110
2970	C<ev_child> watchers use a small hash table to distribute workload by	3111	C<ev_child> watchers use a small hash table to distribute workload by
2971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2979	usually more than enough. If you need to manage thousands of C<ev_stat>	3120	usually more than enough. If you need to manage thousands of C<ev_stat>
2980	watchers you might want to increase this value (I<must> be a power of	3121	watchers you might want to increase this value (I<must> be a power of
2981	two).	3122	two).
2982		3123
		3124	=item EV_USE_4HEAP
		3125
		3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3128	to C<1>. The 4-heap uses more complicated (longer) code but has
		3129	noticeably faster performance with many (thousands) of watchers.
		3130
		3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3132	(disabled).
		3133
		3134	=item EV_HEAP_CACHE_AT
		3135
		3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3137	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3140	but avoids random read accesses on heap changes. This improves performance
		3141	noticeably with with many (hundreds) of watchers.
		3142
		3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3144	(disabled).
		3145
		3146	=item EV_VERIFY
		3147
		3148	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3149	be done: If set to C<0>, no internal verification code will be compiled
		3150	in. If set to C<1>, then verification code will be compiled in, but not
		3151	called. If set to C<2>, then the internal verification code will be
		3152	called once per loop, which can slow down libev. If set to C<3>, then the
		3153	verification code will be called very frequently, which will slow down
		3154	libev considerably.
		3155
		3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3157	C<0.>
		3158
2983	=item EV_COMMON	3159	=item EV_COMMON
2984		3160
2985	By default, all watchers have a C<void *data> member. By redefining	3161	By default, all watchers have a C<void *data> member. By redefining
2986	this macro to a something else you can include more and other types of	3162	this macro to a something else you can include more and other types of
2987	members. You have to define it each time you include one of the files,	3163	members. You have to define it each time you include one of the files,
2988	though, and it must be identical each time.	3164	though, and it must be identical each time.
2989		3165
2990	For example, the perl EV module uses something like this:	3166	For example, the perl EV module uses something like this:
2991		3167
2992	#define EV_COMMON \	3168	#define EV_COMMON \
2993	SV *self; /* contains this struct */ \	3169	SV *self; /* contains this struct */ \
2994	SV *cb_sv, *fh /* note no trailing ";" */	3170	SV *cb_sv, *fh /* note no trailing ";" */
2995		3171
2996	=item EV_CB_DECLARE (type)	3172	=item EV_CB_DECLARE (type)
2997		3173
2998	=item EV_CB_INVOKE (watcher, revents)	3174	=item EV_CB_INVOKE (watcher, revents)
2999		3175
…		…
3006	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3007	method calls instead of plain function calls in C++.	3183	method calls instead of plain function calls in C++.
3008		3184
3009	=head2 EXPORTED API SYMBOLS	3185	=head2 EXPORTED API SYMBOLS
3010		3186
3011	If you need to re-export the API (e.g. via a dll) and you need a list of	3187	If you need to re-export the API (e.g. via a DLL) and you need a list of
3012	exported symbols, you can use the provided F<Symbol.*> files which list	3188	exported symbols, you can use the provided F<Symbol.*> files which list
3013	all public symbols, one per line:	3189	all public symbols, one per line:
3014		3190
3015	Symbols.ev for libev proper	3191	Symbols.ev for libev proper
3016	Symbols.event for the libevent emulation	3192	Symbols.event for the libevent emulation
3017		3193
3018	This can also be used to rename all public symbols to avoid clashes with	3194	This can also be used to rename all public symbols to avoid clashes with
3019	multiple versions of libev linked together (which is obviously bad in	3195	multiple versions of libev linked together (which is obviously bad in
3020	itself, but sometimes it is inconvinient to avoid this).	3196	itself, but sometimes it is inconvenient to avoid this).
3021		3197
3022	A sed command like this will create wrapper C<#define>'s that you need to	3198	A sed command like this will create wrapper C<#define>'s that you need to
3023	include before including F<ev.h>:	3199	include before including F<ev.h>:
3024		3200
3025	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3201	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3042	file.	3218	file.
3043		3219
3044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3045	that everybody includes and which overrides some configure choices:	3221	that everybody includes and which overrides some configure choices:
3046		3222
3047	#define EV_MINIMAL 1	3223	#define EV_MINIMAL 1
3048	#define EV_USE_POLL 0	3224	#define EV_USE_POLL 0
3049	#define EV_MULTIPLICITY 0	3225	#define EV_MULTIPLICITY 0
3050	#define EV_PERIODIC_ENABLE 0	3226	#define EV_PERIODIC_ENABLE 0
3051	#define EV_STAT_ENABLE 0	3227	#define EV_STAT_ENABLE 0
3052	#define EV_FORK_ENABLE 0	3228	#define EV_FORK_ENABLE 0
3053	#define EV_CONFIG_H <config.h>	3229	#define EV_CONFIG_H <config.h>
3054	#define EV_MINPRI 0	3230	#define EV_MINPRI 0
3055	#define EV_MAXPRI 0	3231	#define EV_MAXPRI 0
3056		3232
3057	#include "ev++.h"	3233	#include "ev++.h"
3058		3234
3059	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3060		3236
3061	#include "ev_cpp.h"	3237	#include "ev_cpp.h"
3062	#include "ev.c"	3238	#include "ev.c"
3063		3239
3064		3240
3065	=head1 THREADS AND COROUTINES	3241	=head1 THREADS AND COROUTINES
3066		3242
3067	=head2 THREADS	3243	=head2 THREADS
3068		3244
3069	Libev itself is completely threadsafe, but it uses no locking. This	3245	Libev itself is thread-safe (unless the opposite is specifically
		3246	documented for a function), but it uses no locking itself. This means that
3070	means that you can use as many loops as you want in parallel, as long as	3247	you can use as many loops as you want in parallel, as long as only one
3071	only one thread ever calls into one libev function with the same loop	3248	thread ever calls into one libev function with the same loop parameter:
3072	parameter.	3249	libev guarentees that different event loops share no data structures that
		3250	need locking.
3073		3251
3074	Or put differently: calls with different loop parameters can be done in	3252	Or to put it differently: calls with different loop parameters can be done
3075	parallel from multiple threads, calls with the same loop parameter must be	3253	concurrently from multiple threads, calls with the same loop parameter
3076	done serially (but can be done from different threads, as long as only one	3254	must be done serially (but can be done from different threads, as long as
3077	thread ever is inside a call at any point in time, e.g. by using a mutex	3255	only one thread ever is inside a call at any point in time, e.g. by using
3078	per loop).	3256	a mutex per loop).
3079		3257
3080	If you want to know which design is best for your problem, then I cannot	3258	Specifically to support threads (and signal handlers), libev implements
3081	help you but by giving some generic advice:	3259	so-called C<ev_async> watchers, which allow some limited form of
		3260	concurrency on the same event loop.
		3261
		3262	If you want to know which design (one loop, locking, or multiple loops
		3263	without or something else still) is best for your problem, then I cannot
		3264	help you. I can give some generic advice however:
3082		3265
3083	=over 4	3266	=over 4
3084		3267
3085	=item * most applications have a main thread: use the default libev loop	3268	=item * most applications have a main thread: use the default libev loop
3086	in that thread, or create a seperate thread running only the default loop.	3269	in that thread, or create a separate thread running only the default loop.
3087		3270
3088	This helps integrating other libraries or software modules that use libev	3271	This helps integrating other libraries or software modules that use libev
3089	themselves and don't care/know about threading.	3272	themselves and don't care/know about threading.
3090		3273
3091	=item * one loop per thread is usually a good model.	3274	=item * one loop per thread is usually a good model.
3092		3275
3093	Doing this is almost never wrong, sometimes a better-performance model	3276	Doing this is almost never wrong, sometimes a better-performance model
3094	exists, but it is always a good start.	3277	exists, but it is always a good start.
3095		3278
3096	=item * other models exist, such as the leader/follower pattern, where one	3279	=item * other models exist, such as the leader/follower pattern, where one
3097	loop is handed through multiple threads in a kind of round-robbin fashion.	3280	loop is handed through multiple threads in a kind of round-robin fashion.
3098		3281
3099	Chosing a model is hard - look around, learn, know that usually you cna do	3282	Choosing a model is hard - look around, learn, know that usually you can do
3100	better than you currently do :-)	3283	better than you currently do :-)
3101		3284
3102	=item * often you need to talk to some other thread which blocks in the	3285	=item * often you need to talk to some other thread which blocks in the
3103	event loop - C<ev_async> watchers can be used to wake them up from other	3286	event loop - C<ev_async> watchers can be used to wake them up from other
3104	threads safely (or from signal contexts...).	3287	threads safely (or from signal contexts...).
3105		3288
		3289	=item * some watcher types are only supported in the default loop - use
		3290	C<ev_async> watchers to tell your other loops about any such events.
		3291
3106	=back	3292	=back
3107		3293
3108	=head2 COROUTINES	3294	=head2 COROUTINES
3109		3295
3110	Libev is much more accomodating to coroutines ("cooperative threads"):	3296	Libev is much more accommodating to coroutines ("cooperative threads"):
3111	libev fully supports nesting calls to it's functions from different	3297	libev fully supports nesting calls to it's functions from different
3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3113	different coroutines and switch freely between both coroutines running the	3299	different coroutines and switch freely between both coroutines running the
3114	loop, as long as you don't confuse yourself). The only exception is that	3300	loop, as long as you don't confuse yourself). The only exception is that
3115	you must not do this from C<ev_periodic> reschedule callbacks.	3301	you must not do this from C<ev_periodic> reschedule callbacks.
3116		3302
3117	Care has been invested into making sure that libev does not keep local	3303	Care has been taken to ensure that libev does not keep local state inside
3118	state inside C<ev_loop>, and other calls do not usually allow coroutine	3304	C<ev_loop>, and other calls do not usually allow coroutine switches.
3119	switches.
3120		3305
3121		3306
3122	=head1 COMPLEXITIES	3307	=head1 COMPLEXITIES
3123		3308
3124	In this section the complexities of (many of) the algorithms used inside	3309	In this section the complexities of (many of) the algorithms used inside
…		…
3156	correct watcher to remove. The lists are usually short (you don't usually	3341	correct watcher to remove. The lists are usually short (you don't usually
3157	have many watchers waiting for the same fd or signal).	3342	have many watchers waiting for the same fd or signal).
3158		3343
3159	=item Finding the next timer in each loop iteration: O(1)	3344	=item Finding the next timer in each loop iteration: O(1)
3160		3345
3161	By virtue of using a binary heap, the next timer is always found at the	3346	By virtue of using a binary or 4-heap, the next timer is always found at a
3162	beginning of the storage array.	3347	fixed position in the storage array.
3163		3348
3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3349	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3165		3350
3166	A change means an I/O watcher gets started or stopped, which requires	3351	A change means an I/O watcher gets started or stopped, which requires
3167	libev to recalculate its status (and possibly tell the kernel, depending	3352	libev to recalculate its status (and possibly tell the kernel, depending
3168	on backend and wether C<ev_io_set> was used).	3353	on backend and whether C<ev_io_set> was used).
3169		3354
3170	=item Activating one watcher (putting it into the pending state): O(1)	3355	=item Activating one watcher (putting it into the pending state): O(1)
3171		3356
3172	=item Priority handling: O(number_of_priorities)	3357	=item Priority handling: O(number_of_priorities)
3173		3358
…		…
3180		3365
3181	=item Processing ev_async_send: O(number_of_async_watchers)	3366	=item Processing ev_async_send: O(number_of_async_watchers)
3182		3367
3183	=item Processing signals: O(max_signal_number)	3368	=item Processing signals: O(max_signal_number)
3184		3369
3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>	3370	Sending involves a system call I<iff> there were no other C<ev_async_send>
3186	calls in the current loop iteration. Checking for async and signal events	3371	calls in the current loop iteration. Checking for async and signal events
3187	involves iterating over all running async watchers or all signal numbers.	3372	involves iterating over all running async watchers or all signal numbers.
3188		3373
3189	=back	3374	=back
3190		3375
3191		3376
3192	=head1 Win32 platform limitations and workarounds	3377	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3193		3378
3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3379	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3195	requires, and its I/O model is fundamentally incompatible with the POSIX	3380	requires, and its I/O model is fundamentally incompatible with the POSIX
3196	model. Libev still offers limited functionality on this platform in	3381	model. Libev still offers limited functionality on this platform in
3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3382	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3198	descriptors. This only applies when using Win32 natively, not when using	3383	descriptors. This only applies when using Win32 natively, not when using
3199	e.g. cygwin.	3384	e.g. cygwin.
3200		3385
		3386	Lifting these limitations would basically require the full
		3387	re-implementation of the I/O system. If you are into these kinds of
		3388	things, then note that glib does exactly that for you in a very portable
		3389	way (note also that glib is the slowest event library known to man).
		3390
3201	There is no supported compilation method available on windows except	3391	There is no supported compilation method available on windows except
3202	embedding it into other applications.	3392	embedding it into other applications.
3203		3393
		3394	Not a libev limitation but worth mentioning: windows apparently doesn't
		3395	accept large writes: instead of resulting in a partial write, windows will
		3396	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3397	so make sure you only write small amounts into your sockets (less than a
		3398	megabyte seems safe, but thsi apparently depends on the amount of memory
		3399	available).
		3400
3204	Due to the many, low, and arbitrary limits on the win32 platform and the	3401	Due to the many, low, and arbitrary limits on the win32 platform and
3205	abysmal performance of winsockets, using a large number of sockets is not	3402	the abysmal performance of winsockets, using a large number of sockets
3206	recommended (and not reasonable). If your program needs to use more than	3403	is not recommended (and not reasonable). If your program needs to use
3207	a hundred or so sockets, then likely it needs to use a totally different	3404	more than a hundred or so sockets, then likely it needs to use a totally
3208	implementation for windows, as libev offers the POSIX model, which cannot	3405	different implementation for windows, as libev offers the POSIX readiness
3209	be implemented efficiently on windows (microsoft monopoly games).	3406	notification model, which cannot be implemented efficiently on windows
		3407	(Microsoft monopoly games).
		3408
		3409	A typical way to use libev under windows is to embed it (see the embedding
		3410	section for details) and use the following F<evwrap.h> header file instead
		3411	of F<ev.h>:
		3412
		3413	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3414	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3415
		3416	#include "ev.h"
		3417
		3418	And compile the following F<evwrap.c> file into your project (make sure
		3419	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3420
		3421	#include "evwrap.h"
		3422	#include "ev.c"
3210		3423
3211	=over 4	3424	=over 4
3212		3425
3213	=item The winsocket select function	3426	=item The winsocket select function
3214		3427
3215	The winsocket C<select> function doesn't follow POSIX in that it requires	3428	The winsocket C<select> function doesn't follow POSIX in that it
3216	socket I<handles> and not socket I<file descriptors>. This makes select	3429	requires socket I<handles> and not socket I<file descriptors> (it is
3217	very inefficient, and also requires a mapping from file descriptors	3430	also extremely buggy). This makes select very inefficient, and also
3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3431	requires a mapping from file descriptors to socket handles (the Microsoft
3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3432	C runtime provides the function C<_open_osfhandle> for this). See the
3220	symbols for more info.	3433	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3434	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3221		3435
3222	The configuration for a "naked" win32 using the microsoft runtime	3436	The configuration for a "naked" win32 using the Microsoft runtime
3223	libraries and raw winsocket select is:	3437	libraries and raw winsocket select is:
3224		3438
3225	#define EV_USE_SELECT 1	3439	#define EV_USE_SELECT 1
3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3440	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3227		3441
3228	Note that winsockets handling of fd sets is O(n), so you can easily get a	3442	Note that winsockets handling of fd sets is O(n), so you can easily get a
3229	complexity in the O(n²) range when using win32.	3443	complexity in the O(n²) range when using win32.
3230		3444
3231	=item Limited number of file descriptors	3445	=item Limited number of file descriptors
3232		3446
3233	Windows has numerous arbitrary (and low) limits on things. Early versions	3447	Windows has numerous arbitrary (and low) limits on things.
3234	of winsocket's select only supported waiting for a max. of C<64> handles	3448
		3449	Early versions of winsocket's select only supported waiting for a maximum
3235	(probably owning to the fact that all windows kernels can only wait for	3450	of C<64> handles (probably owning to the fact that all windows kernels
3236	C<64> things at the same time internally; microsoft recommends spawning a	3451	can only wait for C<64> things at the same time internally; Microsoft
3237	chain of threads and wait for 63 handles and the previous thread in each).	3452	recommends spawning a chain of threads and wait for 63 handles and the
		3453	previous thread in each. Great).
3238		3454
3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3455	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3240	to some high number (e.g. C<2048>) before compiling the winsocket select	3456	to some high number (e.g. C<2048>) before compiling the winsocket select
3241	call (which might be in libev or elsewhere, for example, perl does its own	3457	call (which might be in libev or elsewhere, for example, perl does its own
3242	select emulation on windows).	3458	select emulation on windows).
3243		3459
3244	Another limit is the number of file descriptors in the microsoft runtime	3460	Another limit is the number of file descriptors in the Microsoft runtime
3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3461	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3246	or something like this inside microsoft). You can increase this by calling	3462	or something like this inside Microsoft). You can increase this by calling
3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3463	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3248	arbitrary limit), but is broken in many versions of the microsoft runtime	3464	arbitrary limit), but is broken in many versions of the Microsoft runtime
3249	libraries.	3465	libraries.
3250		3466
3251	This might get you to about C<512> or C<2048> sockets (depending on	3467	This might get you to about C<512> or C<2048> sockets (depending on
3252	windows version and/or the phase of the moon). To get more, you need to	3468	windows version and/or the phase of the moon). To get more, you need to
3253	wrap all I/O functions and provide your own fd management, but the cost of	3469	wrap all I/O functions and provide your own fd management, but the cost of
3254	calling select (O(n²)) will likely make this unworkable.	3470	calling select (O(n²)) will likely make this unworkable.
3255		3471
3256	=back	3472	=back
3257		3473
3258		3474
		3475	=head1 PORTABILITY REQUIREMENTS
		3476
		3477	In addition to a working ISO-C implementation, libev relies on a few
		3478	additional extensions:
		3479
		3480	=over 4
		3481
		3482	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3483	calling conventions regardless of C<ev_watcher_type *>.
		3484
		3485	Libev assumes not only that all watcher pointers have the same internal
		3486	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3487	assumes that the same (machine) code can be used to call any watcher
		3488	callback: The watcher callbacks have different type signatures, but libev
		3489	calls them using an C<ev_watcher *> internally.
		3490
		3491	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3492
		3493	The type C<sig_atomic_t volatile> (or whatever is defined as
		3494	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3495	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3496	believed to be sufficiently portable.
		3497
		3498	=item C<sigprocmask> must work in a threaded environment
		3499
		3500	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3501	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3502	pthread implementations will either allow C<sigprocmask> in the "main
		3503	thread" or will block signals process-wide, both behaviours would
		3504	be compatible with libev. Interaction between C<sigprocmask> and
		3505	C<pthread_sigmask> could complicate things, however.
		3506
		3507	The most portable way to handle signals is to block signals in all threads
		3508	except the initial one, and run the default loop in the initial thread as
		3509	well.
		3510
		3511	=item C<long> must be large enough for common memory allocation sizes
		3512
		3513	To improve portability and simplify using libev, libev uses C<long>
		3514	internally instead of C<size_t> when allocating its data structures. On
		3515	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3516	is still at least 31 bits everywhere, which is enough for hundreds of
		3517	millions of watchers.
		3518
		3519	=item C<double> must hold a time value in seconds with enough accuracy
		3520
		3521	The type C<double> is used to represent timestamps. It is required to
		3522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3523	enough for at least into the year 4000. This requirement is fulfilled by
		3524	implementations implementing IEEE 754 (basically all existing ones).
		3525
		3526	=back
		3527
		3528	If you know of other additional requirements drop me a note.
		3529
		3530
		3531	=head1 COMPILER WARNINGS
		3532
		3533	Depending on your compiler and compiler settings, you might get no or a
		3534	lot of warnings when compiling libev code. Some people are apparently
		3535	scared by this.
		3536
		3537	However, these are unavoidable for many reasons. For one, each compiler
		3538	has different warnings, and each user has different tastes regarding
		3539	warning options. "Warn-free" code therefore cannot be a goal except when
		3540	targeting a specific compiler and compiler-version.
		3541
		3542	Another reason is that some compiler warnings require elaborate
		3543	workarounds, or other changes to the code that make it less clear and less
		3544	maintainable.
		3545
		3546	And of course, some compiler warnings are just plain stupid, or simply
		3547	wrong (because they don't actually warn about the condition their message
		3548	seems to warn about).
		3549
		3550	While libev is written to generate as few warnings as possible,
		3551	"warn-free" code is not a goal, and it is recommended not to build libev
		3552	with any compiler warnings enabled unless you are prepared to cope with
		3553	them (e.g. by ignoring them). Remember that warnings are just that:
		3554	warnings, not errors, or proof of bugs.
		3555
		3556
		3557	=head1 VALGRIND
		3558
		3559	Valgrind has a special section here because it is a popular tool that is
		3560	highly useful, but valgrind reports are very hard to interpret.
		3561
		3562	If you think you found a bug (memory leak, uninitialised data access etc.)
		3563	in libev, then check twice: If valgrind reports something like:
		3564
		3565	==2274== definitely lost: 0 bytes in 0 blocks.
		3566	==2274== possibly lost: 0 bytes in 0 blocks.
		3567	==2274== still reachable: 256 bytes in 1 blocks.
		3568
		3569	Then there is no memory leak. Similarly, under some circumstances,
		3570	valgrind might report kernel bugs as if it were a bug in libev, or it
		3571	might be confused (it is a very good tool, but only a tool).
		3572
		3573	If you are unsure about something, feel free to contact the mailing list
		3574	with the full valgrind report and an explanation on why you think this is
		3575	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3576	no bug" answer and take the chance of learning how to interpret valgrind
		3577	properly.
		3578
		3579	If you need, for some reason, empty reports from valgrind for your project
		3580	I suggest using suppression lists.
		3581
		3582
3259	=head1 AUTHOR	3583	=head1 AUTHOR
3260		3584
3261	Marc Lehmann <libev@schmorp.de>.	3585	Marc Lehmann <libev@schmorp.de>.
3262		3586

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