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Revision 1.95 by root, Fri Dec 21 05:10:01 2007 UTC vs.
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
115		130
116	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
117	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	133	you actually want to know.
119		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	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
		139	this is a subsecond-resolution C<sleep ()>.
		140
120	=item int ev_version_major ()	141	=item int ev_version_major ()
121		142
122	=item int ev_version_minor ()	143	=item int ev_version_minor ()
123		144
124	You can find out the major and minor ABI version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
…		…
175	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
176		197
177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
178		199
179	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
180	semantics is identical - to the realloc C function). It is used to	201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
181	allocate and free memory (no surprises here). If it returns zero when	202	used to allocate and free memory (no surprises here). If it returns zero
182	memory needs to be allocated, the library might abort or take some	203	when memory needs to be allocated (C<size != 0>), the library might abort
183	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
184	function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
185		209
186	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
187	free some memory if it cannot allocate memory, to use a special allocator,	211	free some memory if it cannot allocate memory, to use a special allocator,
188	or even to sleep a while and retry until some memory is available.	212	or even to sleep a while and retry until some memory is available.
189		213
190	Example: Replace the libev allocator with one that waits a bit and then	214	Example: Replace the libev allocator with one that waits a bit and then
191	retries).	215	retries (example requires a standards-compliant C<realloc>).
192		216
193	static void *	217	static void *
194	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
195	{	219	{
196	for (;;)	220	for (;;)
…		…
235		259
236	An event loop is described by a C<struct ev_loop *>. The library knows two	260	An event loop is described by a C<struct ev_loop *>. The library knows two
237	types of such loops, the I<default> loop, which supports signals and child	261	types of such loops, the I<default> loop, which supports signals and child
238	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
239		263
240	If you use threads, a common model is to run the default event loop
241	in your main thread (or in a separate thread) and for each thread you
242	create, you also create another event loop. Libev itself does no locking
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246
247	=over 4	264	=over 4
248		265
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		267
251	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
…		…
253	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		272
256	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
257	function.	274	function.
		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
258		286
259	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
261		289
262	The following flags are supported:	290	The following flags are supported:
…		…
284	enabling this flag.	312	enabling this flag.
285		313
286	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
287	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
288	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
289	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
290	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
291	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
292		320
293	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
294	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
295	flag.	323	flag.
…		…
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		329
302	This is your standard select(2) backend. Not I<completely> standard, as	330	This is your standard select(2) backend. Not I<completely> standard, as
303	libev tries to roll its own fd_set with no limits on the number of fds,	331	libev tries to roll its own fd_set with no limits on the number of fds,
304	but if that fails, expect a fairly low limit on the number of fds when	332	but if that fails, expect a fairly low limit on the number of fds when
305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
306	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
307		342
308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309		344
310	And this is your standard poll(2) backend. It's more complicated than	345	And this is your standard poll(2) backend. It's more complicated
311	select, but handles sparse fds better and has no artificial limit on the	346	than select, but handles sparse fds better and has no artificial
312	number of fds you can use (except it will slow down considerably with a	347	limit on the number of fds you can use (except it will slow down
313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
314		351
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		353
317	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
318	but it scales phenomenally better. While poll and select usually scale	355	but it scales phenomenally better. While poll and select usually scale
319	like O(total_fds) where n is the total number of fds (or the highest fd),	356	like O(total_fds) where n is the total number of fds (or the highest fd),
320	epoll scales either O(1) or O(active_fds). The epoll design has a number	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
321	of shortcomings, such as silently dropping events in some hard-to-detect	358	of shortcomings, such as silently dropping events in some hard-to-detect
322	cases and rewuiring a syscall per fd change, no fork support and bad	359	cases and requiring a syscall per fd change, no fork support and bad
323	support for dup:	360	support for dup.
324		361
325	While stopping, setting and starting an I/O watcher in the same iteration	362	While stopping, setting and starting an I/O watcher in the same iteration
326	will result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
327	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
330		367
331	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
332	need to use non-blocking I/O or other means to avoid blocking when no data	369	need to use non-blocking I/O or other means to avoid blocking when no data
333	(or space) is available.	370	(or space) is available.
334		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		380
337	Kqueue deserves special mention, as at the time of this writing, it	381	Kqueue deserves special mention, as at the time of this writing, it
338	was broken on I<all> BSDs (usually it doesn't work with anything but	382	was broken on all BSDs except NetBSD (usually it doesn't work reliably
339	sockets and pipes, except on Darwin, where of course it's completely	383	with anything but sockets and pipes, except on Darwin, where of course
340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
341	is used by default there). For this reason it's not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
342	unless you explicitly specify it explicitly in the flags (i.e. using	385	unless you explicitly specify it explicitly in the flags (i.e. using
343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	387	system like NetBSD.
345		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
		392
346	It scales in the same way as the epoll backend, but the interface to the	393	It scales in the same way as the epoll backend, but the interface to the
347	kernel is more efficient (which says nothing about its actual speed,	394	kernel is more efficient (which says nothing about its actual speed, of
348	of course). While stopping, setting and starting an I/O watcher does	395	course). While stopping, setting and starting an I/O watcher does never
349	never cause an extra syscall as with epoll, it still adds up to two event	396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
350	changes per incident, support for C<fork ()> is very bad and it drops fds	397	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
352		408
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		410
355	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
356		415
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		417
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
360	it's really slow, but it still scales very well (O(active_fds)).	419	it's really slow, but it still scales very well (O(active_fds)).
361		420
362	Please note that solaris event ports can deliver a lot of spurious	421	Please note that solaris event ports can deliver a lot of spurious
363	notifications, so you need to use non-blocking I/O or other means to avoid	422	notifications, so you need to use non-blocking I/O or other means to avoid
364	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
365		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
		433
366	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
367		435
368	Try all backends (even potentially broken ones that wouldn't be tried	436	Try all backends (even potentially broken ones that wouldn't be tried
369	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		439
		440	It is definitely not recommended to use this flag.
		441
372	=back	442	=back
373		443
374	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
375	backends will be tried (in the reverse order as given here). If none are	445	backends will be tried (in the reverse order as listed here). If none are
376	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		447
379	The most typical usage is like this:	448	The most typical usage is like this:
380		449
381	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
396		465
397	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	Similar to C<ev_default_loop>, but always creates a new event loop that is
398	always distinct from the default loop. Unlike the default loop, it cannot	467	always distinct from the default loop. Unlike the default loop, it cannot
399	handle signal and child watchers, and attempts to do so will be greeted by	468	handle signal and child watchers, and attempts to do so will be greeted by
400	undefined behaviour (or a failed assertion if assertions are enabled).	469	undefined behaviour (or a failed assertion if assertions are enabled).
		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
401		474
402	Example: Try to create a event loop that uses epoll and nothing else.	475	Example: Try to create a event loop that uses epoll and nothing else.
403		476
404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
405	if (!epoller)	478	if (!epoller)
…		…
429	Like C<ev_default_destroy>, but destroys an event loop created by an	502	Like C<ev_default_destroy>, but destroys an event loop created by an
430	earlier call to C<ev_loop_new>.	503	earlier call to C<ev_loop_new>.
431		504
432	=item ev_default_fork ()	505	=item ev_default_fork ()
433		506
		507	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	508	to reinitialise the kernel state for backends that have one. Despite the
435	one. Despite the name, you can call it anytime, but it makes most sense	509	name, you can call it anytime, but it makes most sense after forking, in
436	after forking, in either the parent or child process (or both, but that	510	the child process (or both child and parent, but that again makes little
437	again makes little sense).	511	sense). You I<must> call it in the child before using any of the libev
		512	functions, and it will only take effect at the next C<ev_loop> iteration.
438		513
439	You I<must> call this function in the child process after forking if and	514	On the other hand, you only need to call this function in the child
440	only if you want to use the event library in both processes. If you just	515	process if and only if you want to use the event library in the child. If
441	fork+exec, you don't have to call it.	516	you just fork+exec, you don't have to call it at all.
442		517
443	The function itself is quite fast and it's usually not a problem to call	518	The function itself is quite fast and it's usually not a problem to call
444	it just in case after a fork. To make this easy, the function will fit in	519	it just in case after a fork. To make this easy, the function will fit in
445	quite nicely into a call to C<pthread_atfork>:	520	quite nicely into a call to C<pthread_atfork>:
446		521
447	pthread_atfork (0, 0, ev_default_fork);	522	pthread_atfork (0, 0, ev_default_fork);
448		523
449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
450	without calling this function, so if you force one of those backends you
451	do not need to care.
452
453	=item ev_loop_fork (loop)	524	=item ev_loop_fork (loop)
454		525
455	Like C<ev_default_fork>, but acts on an event loop created by	526	Like C<ev_default_fork>, but acts on an event loop created by
456	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
457	after fork, and how you do this is entirely your own problem.	528	after fork, and how you do this is entirely your own problem.
		529
		530	=item int ev_is_default_loop (loop)
		531
		532	Returns true when the given loop actually is the default loop, false otherwise.
458		533
459	=item unsigned int ev_loop_count (loop)	534	=item unsigned int ev_loop_count (loop)
460		535
461	Returns the count of loop iterations for the loop, which is identical to	536	Returns the count of loop iterations for the loop, which is identical to
462	the number of times libev did poll for new events. It starts at C<0> and	537	the number of times libev did poll for new events. It starts at C<0> and
…		…
507	usually a better approach for this kind of thing.	582	usually a better approach for this kind of thing.
508		583
509	Here are the gory details of what C<ev_loop> does:	584	Here are the gory details of what C<ev_loop> does:
510		585
511	- Before the first iteration, call any pending watchers.	586	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	587	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	588	- If a fork was detected, queue and call all fork watchers.
		589	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	590	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	591	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	592	- Update the "event loop time".
517	- Calculate for how long to block.	593	- Calculate for how long to sleep or block, if at all
		594	(active idle watchers, EVLOOP_NONBLOCK or not having
		595	any active watchers at all will result in not sleeping).
		596	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	597	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	598	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	599	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	600	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	601	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	602	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	603	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	604	- Call all queued watchers in reverse order (i.e. check watchers first).
526	Signals and child watchers are implemented as I/O watchers, and will	605	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	606	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	608	were used, or there are no active watchers, return, otherwise
		609	continue with step *.
530		610
531	Example: Queue some jobs and then loop until no events are outsanding	611	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	612	anymore.
533		613
534	... queue jobs here, make sure they register event watchers as long	614	... queue jobs here, make sure they register event watchers as long
535	... as they still have work to do (even an idle watcher will do..)	615	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	616	ev_loop (my_loop, 0);
…		…
540		620
541	Can be used to make a call to C<ev_loop> return early (but only after it	621	Can be used to make a call to C<ev_loop> return early (but only after it
542	has processed all outstanding events). The C<how> argument must be either	622	has processed all outstanding events). The C<how> argument must be either
543	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
544	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		625
		626	This "unloop state" will be cleared when entering C<ev_loop> again.
545		627
546	=item ev_ref (loop)	628	=item ev_ref (loop)
547		629
548	=item ev_unref (loop)	630	=item ev_unref (loop)
549		631
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	636	returning, ev_unref() after starting, and ev_ref() before stopping it. For
555	example, libev itself uses this for its internal signal pipe: It is not	637	example, libev itself uses this for its internal signal pipe: It is not
556	visible to the libev user and should not keep C<ev_loop> from exiting if	638	visible to the libev user and should not keep C<ev_loop> from exiting if
557	no event watchers registered by it are active. It is also an excellent	639	no event watchers registered by it are active. It is also an excellent
558	way to do this for generic recurring timers or from within third-party	640	way to do this for generic recurring timers or from within third-party
559	libraries. Just remember to I<unref after start> and I<ref before stop>.	641	libraries. Just remember to I<unref after start> and I<ref before stop>
		642	(but only if the watcher wasn't active before, or was active before,
		643	respectively).
560		644
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	646	running when nothing else is active.
563		647
564	struct ev_signal exitsig;	648	struct ev_signal exitsig;
…		…
568		652
569	Example: For some weird reason, unregister the above signal handler again.	653	Example: For some weird reason, unregister the above signal handler again.
570		654
571	ev_ref (loop);	655	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	656	ev_signal_stop (loop, &exitsig);
		657
		658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		659
		660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		661
		662	These advanced functions influence the time that libev will spend waiting
		663	for events. Both are by default C<0>, meaning that libev will try to
		664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		665
		666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		667	allows libev to delay invocation of I/O and timer/periodic callbacks to
		668	increase efficiency of loop iterations.
		669
		670	The background is that sometimes your program runs just fast enough to
		671	handle one (or very few) event(s) per loop iteration. While this makes
		672	the program responsive, it also wastes a lot of CPU time to poll for new
		673	events, especially with backends like C<select ()> which have a high
		674	overhead for the actual polling but can deliver many events at once.
		675
		676	By setting a higher I<io collect interval> you allow libev to spend more
		677	time collecting I/O events, so you can handle more events per iteration,
		678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		679	C<ev_timer>) will be not affected. Setting this to a non-null value will
		680	introduce an additional C<ev_sleep ()> call into most loop iterations.
		681
		682	Likewise, by setting a higher I<timeout collect interval> you allow libev
		683	to spend more time collecting timeouts, at the expense of increased
		684	latency (the watcher callback will be called later). C<ev_io> watchers
		685	will not be affected. Setting this to a non-null value will not introduce
		686	any overhead in libev.
		687
		688	Many (busy) programs can usually benefit by setting the io collect
		689	interval to a value near C<0.1> or so, which is often enough for
		690	interactive servers (of course not for games), likewise for timeouts. It
		691	usually doesn't make much sense to set it to a lower value than C<0.01>,
		692	as this approsaches the timing granularity of most systems.
573		693
574	=back	694	=back
575		695
576		696
577	=head1 ANATOMY OF A WATCHER	697	=head1 ANATOMY OF A WATCHER
…		…
676		796
677	=item C<EV_FORK>	797	=item C<EV_FORK>
678		798
679	The event loop has been resumed in the child process after fork (see	799	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	800	C<ev_fork>).
		801
		802	=item C<EV_ASYNC>
		803
		804	The given async watcher has been asynchronously notified (see C<ev_async>).
681		805
682	=item C<EV_ERROR>	806	=item C<EV_ERROR>
683		807
684	An unspecified error has occured, the watcher has been stopped. This might	808	An unspecified error has occured, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	809	happen because the watcher could not be properly started because libev
…		…
903	In general you can register as many read and/or write event watchers per	1027	In general you can register as many read and/or write event watchers per
904	fd as you want (as long as you don't confuse yourself). Setting all file	1028	fd as you want (as long as you don't confuse yourself). Setting all file
905	descriptors to non-blocking mode is also usually a good idea (but not	1029	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1030	required if you know what you are doing).
907		1031
908	You have to be careful with dup'ed file descriptors, though. Some backends
909	(the linux epoll backend is a notable example) cannot handle dup'ed file
910	descriptors correctly if you register interest in two or more fds pointing
911	to the same underlying file/socket/etc. description (that is, they share
912	the same underlying "file open").
913
914	If you must do this, then force the use of a known-to-be-good backend	1032	If you must do this, then force the use of a known-to-be-good backend
915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1034	C<EVBACKEND_POLL>).
917		1035
918	Another thing you have to watch out for is that it is quite easy to	1036	Another thing you have to watch out for is that it is quite easy to
…		…
952	optimisations to libev.	1070	optimisations to libev.
953		1071
954	=head3 The special problem of dup'ed file descriptors	1072	=head3 The special problem of dup'ed file descriptors
955		1073
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1074	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1075	but only events for the underlying file descriptions. That means when you
958	have C<dup ()>'ed file descriptors and register events for them, only one	1076	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1077	events for them, only one file descriptor might actually receive events.
960		1078
961	There is no workaorund possible except not registering events	1079	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1080	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1081	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1082
965	=head3 The special problem of fork	1083	=head3 The special problem of fork
966		1084
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1085	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
971	To support fork in your programs, you either have to call	1089	To support fork in your programs, you either have to call
972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1090	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
974	C<EVBACKEND_POLL>.	1092	C<EVBACKEND_POLL>.
975		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
976		1106
977	=head3 Watcher-Specific Functions	1107	=head3 Watcher-Specific Functions
978		1108
979	=over 4	1109	=over 4
980		1110
…		…
993	=item int events [read-only]	1123	=item int events [read-only]
994		1124
995	The events being watched.	1125	The events being watched.
996		1126
997	=back	1127	=back
		1128
		1129	=head3 Examples
998		1130
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1000	readable, but only once. Since it is likely line-buffered, you could	1132	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1133	attempt to read a whole line in the callback.
1002		1134
…		…
1055	configure a timer to trigger every 10 seconds, then it will trigger at	1187	configure a timer to trigger every 10 seconds, then it will trigger at
1056	exactly 10 second intervals. If, however, your program cannot keep up with	1188	exactly 10 second intervals. If, however, your program cannot keep up with
1057	the timer (because it takes longer than those 10 seconds to do stuff) the	1189	the timer (because it takes longer than those 10 seconds to do stuff) the
1058	timer will not fire more than once per event loop iteration.	1190	timer will not fire more than once per event loop iteration.
1059		1191
1060	=item ev_timer_again (loop)	1192	=item ev_timer_again (loop, ev_timer *)
1061		1193
1062	This will act as if the timer timed out and restart it again if it is	1194	This will act as if the timer timed out and restart it again if it is
1063	repeating. The exact semantics are:	1195	repeating. The exact semantics are:
1064		1196
1065	If the timer is pending, its pending status is cleared.	1197	If the timer is pending, its pending status is cleared.
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1232	or C<ev_timer_again> is called and determines the next timeout (if any),
1101	which is also when any modifications are taken into account.	1233	which is also when any modifications are taken into account.
1102		1234
1103	=back	1235	=back
1104		1236
		1237	=head3 Examples
		1238
1105	Example: Create a timer that fires after 60 seconds.	1239	Example: Create a timer that fires after 60 seconds.
1106		1240
1107	static void	1241	static void
1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1109	{	1243	{
…		…
1172	In this configuration the watcher triggers an event at the wallclock time	1306	In this configuration the watcher triggers an event at the wallclock time
1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1174	that is, if it is to be run at January 1st 2011 then it will run when the	1308	that is, if it is to be run at January 1st 2011 then it will run when the
1175	system time reaches or surpasses this time.	1309	system time reaches or surpasses this time.
1176		1310
1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1178		1312
1179	In this mode the watcher will always be scheduled to time out at the next	1313	In this mode the watcher will always be scheduled to time out at the next
1180	C<at + N * interval> time (for some integer N, which can also be negative)	1314	C<at + N * interval> time (for some integer N, which can also be negative)
1181	and then repeat, regardless of any time jumps.	1315	and then repeat, regardless of any time jumps.
1182		1316
…		…
1265		1399
1266	When active, contains the absolute time that the watcher is supposed to	1400	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1401	trigger next.
1268		1402
1269	=back	1403	=back
		1404
		1405	=head3 Examples
1270		1406
1271	Example: Call a callback every hour, or, more precisely, whenever the	1407	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1408	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1409	potentially a lot of jittering, but good long-term stability.
1274		1410
…		…
1314	with the kernel (thus it coexists with your own signal handlers as long	1450	with the kernel (thus it coexists with your own signal handlers as long
1315	as you don't register any with libev). Similarly, when the last signal	1451	as you don't register any with libev). Similarly, when the last signal
1316	watcher for a signal is stopped libev will reset the signal handler to	1452	watcher for a signal is stopped libev will reset the signal handler to
1317	SIG_DFL (regardless of what it was set to before).	1453	SIG_DFL (regardless of what it was set to before).
1318		1454
		1455	If possible and supported, libev will install its handlers with
		1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1457	interrupted. If you have a problem with syscalls getting interrupted by
		1458	signals you can block all signals in an C<ev_check> watcher and unblock
		1459	them in an C<ev_prepare> watcher.
		1460
1319	=head3 Watcher-Specific Functions and Data Members	1461	=head3 Watcher-Specific Functions and Data Members
1320		1462
1321	=over 4	1463	=over 4
1322		1464
1323	=item ev_signal_init (ev_signal *, callback, int signum)	1465	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1331		1473
1332	The signal the watcher watches out for.	1474	The signal the watcher watches out for.
1333		1475
1334	=back	1476	=back
1335		1477
		1478	=head3 Examples
		1479
		1480	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1481
		1482	static void
		1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1484	{
		1485	ev_unloop (loop, EVUNLOOP_ALL);
		1486	}
		1487
		1488	struct ev_signal signal_watcher;
		1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1490	ev_signal_start (loop, &sigint_cb);
		1491
1336		1492
1337	=head2 C<ev_child> - watch out for process status changes	1493	=head2 C<ev_child> - watch out for process status changes
1338		1494
1339	Child watchers trigger when your process receives a SIGCHLD in response to	1495	Child watchers trigger when your process receives a SIGCHLD in response to
1340	some child status changes (most typically when a child of yours dies).	1496	some child status changes (most typically when a child of yours dies). It
		1497	is permissible to install a child watcher I<after> the child has been
		1498	forked (which implies it might have already exited), as long as the event
		1499	loop isn't entered (or is continued from a watcher).
		1500
		1501	Only the default event loop is capable of handling signals, and therefore
		1502	you can only rgeister child watchers in the default event loop.
		1503
		1504	=head3 Process Interaction
		1505
		1506	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1507	initialised. This is necessary to guarantee proper behaviour even if
		1508	the first child watcher is started after the child exits. The occurance
		1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1510	synchronously as part of the event loop processing. Libev always reaps all
		1511	children, even ones not watched.
		1512
		1513	=head3 Overriding the Built-In Processing
		1514
		1515	Libev offers no special support for overriding the built-in child
		1516	processing, but if your application collides with libev's default child
		1517	handler, you can override it easily by installing your own handler for
		1518	C<SIGCHLD> after initialising the default loop, and making sure the
		1519	default loop never gets destroyed. You are encouraged, however, to use an
		1520	event-based approach to child reaping and thus use libev's support for
		1521	that, so other libev users can use C<ev_child> watchers freely.
1341		1522
1342	=head3 Watcher-Specific Functions and Data Members	1523	=head3 Watcher-Specific Functions and Data Members
1343		1524
1344	=over 4	1525	=over 4
1345		1526
1346	=item ev_child_init (ev_child *, callback, int pid)	1527	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1528
1348	=item ev_child_set (ev_child *, int pid)	1529	=item ev_child_set (ev_child *, int pid, int trace)
1349		1530
1350	Configures the watcher to wait for status changes of process C<pid> (or	1531	Configures the watcher to wait for status changes of process C<pid> (or
1351	I<any> process if C<pid> is specified as C<0>). The callback can look	1532	I<any> process if C<pid> is specified as C<0>). The callback can look
1352	at the C<rstatus> member of the C<ev_child> watcher structure to see	1533	at the C<rstatus> member of the C<ev_child> watcher structure to see
1353	the status word (use the macros from C<sys/wait.h> and see your systems	1534	the status word (use the macros from C<sys/wait.h> and see your systems
1354	C<waitpid> documentation). The C<rpid> member contains the pid of the	1535	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1536	process causing the status change. C<trace> must be either C<0> (only
		1537	activate the watcher when the process terminates) or C<1> (additionally
		1538	activate the watcher when the process is stopped or continued).
1356		1539
1357	=item int pid [read-only]	1540	=item int pid [read-only]
1358		1541
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1542	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1543
…		…
1367	The process exit/trace status caused by C<rpid> (see your systems	1550	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1551	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1552
1370	=back	1553	=back
1371		1554
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1555	=head3 Examples
		1556
		1557	Example: C<fork()> a new process and install a child handler to wait for
		1558	its completion.
		1559
		1560	ev_child cw;
1373		1561
1374	static void	1562	static void
1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1563	child_cb (EV_P_ struct ev_child *w, int revents)
1376	{	1564	{
1377	ev_unloop (loop, EVUNLOOP_ALL);	1565	ev_child_stop (EV_A_ w);
		1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1378	}	1567	}
1379		1568
1380	struct ev_signal signal_watcher;	1569	pid_t pid = fork ();
1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1570
1382	ev_signal_start (loop, &sigint_cb);	1571	if (pid < 0)
		1572	// error
		1573	else if (pid == 0)
		1574	{
		1575	// the forked child executes here
		1576	exit (1);
		1577	}
		1578	else
		1579	{
		1580	ev_child_init (&cw, child_cb, pid, 0);
		1581	ev_child_start (EV_DEFAULT_ &cw);
		1582	}
1383		1583
1384		1584
1385	=head2 C<ev_stat> - did the file attributes just change?	1585	=head2 C<ev_stat> - did the file attributes just change?
1386		1586
1387	This watches a filesystem path for attribute changes. That is, it calls	1587	This watches a filesystem path for attribute changes. That is, it calls
…		…
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1417	to fall back to regular polling again even with inotify, but changes are	1617	to fall back to regular polling again even with inotify, but changes are
1418	usually detected immediately, and if the file exists there will be no	1618	usually detected immediately, and if the file exists there will be no
1419	polling.	1619	polling.
1420		1620
		1621	=head3 ABI Issues (Largefile Support)
		1622
		1623	Libev by default (unless the user overrides this) uses the default
		1624	compilation environment, which means that on systems with optionally
		1625	disabled large file support, you get the 32 bit version of the stat
		1626	structure. When using the library from programs that change the ABI to
		1627	use 64 bit file offsets the programs will fail. In that case you have to
		1628	compile libev with the same flags to get binary compatibility. This is
		1629	obviously the case with any flags that change the ABI, but the problem is
		1630	most noticably with ev_stat and largefile support.
		1631
		1632	=head3 Inotify
		1633
		1634	When C<inotify (7)> support has been compiled into libev (generally only
		1635	available on Linux) and present at runtime, it will be used to speed up
		1636	change detection where possible. The inotify descriptor will be created lazily
		1637	when the first C<ev_stat> watcher is being started.
		1638
		1639	Inotify presence does not change the semantics of C<ev_stat> watchers
		1640	except that changes might be detected earlier, and in some cases, to avoid
		1641	making regular C<stat> calls. Even in the presence of inotify support
		1642	there are many cases where libev has to resort to regular C<stat> polling.
		1643
		1644	(There is no support for kqueue, as apparently it cannot be used to
		1645	implement this functionality, due to the requirement of having a file
		1646	descriptor open on the object at all times).
		1647
		1648	=head3 The special problem of stat time resolution
		1649
		1650	The C<stat ()> syscall only supports full-second resolution portably, and
		1651	even on systems where the resolution is higher, many filesystems still
		1652	only support whole seconds.
		1653
		1654	That means that, if the time is the only thing that changes, you might
		1655	miss updates: on the first update, C<ev_stat> detects a change and calls
		1656	your callback, which does something. When there is another update within
		1657	the same second, C<ev_stat> will be unable to detect it.
		1658
		1659	The solution to this is to delay acting on a change for a second (or till
		1660	the next second boundary), using a roughly one-second delay C<ev_timer>
		1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1662	is added to work around small timing inconsistencies of some operating
		1663	systems.
		1664
1421	=head3 Watcher-Specific Functions and Data Members	1665	=head3 Watcher-Specific Functions and Data Members
1422		1666
1423	=over 4	1667	=over 4
1424		1668
1425	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1669	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
…		…
1434		1678
1435	The callback will be receive C<EV_STAT> when a change was detected,	1679	The callback will be receive C<EV_STAT> when a change was detected,
1436	relative to the attributes at the time the watcher was started (or the	1680	relative to the attributes at the time the watcher was started (or the
1437	last change was detected).	1681	last change was detected).
1438		1682
1439	=item ev_stat_stat (ev_stat *)	1683	=item ev_stat_stat (loop, ev_stat *)
1440		1684
1441	Updates the stat buffer immediately with new values. If you change the	1685	Updates the stat buffer immediately with new values. If you change the
1442	watched path in your callback, you could call this fucntion to avoid	1686	watched path in your callback, you could call this fucntion to avoid
1443	detecting this change (while introducing a race condition). Can also be	1687	detecting this change (while introducing a race condition). Can also be
1444	useful simply to find out the new values.	1688	useful simply to find out the new values.
…		…
1462	=item const char *path [read-only]	1706	=item const char *path [read-only]
1463		1707
1464	The filesystem path that is being watched.	1708	The filesystem path that is being watched.
1465		1709
1466	=back	1710	=back
		1711
		1712	=head3 Examples
1467		1713
1468	Example: Watch C</etc/passwd> for attribute changes.	1714	Example: Watch C</etc/passwd> for attribute changes.
1469		1715
1470	static void	1716	static void
1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1484	}	1730	}
1485		1731
1486	...	1732	...
1487	ev_stat passwd;	1733	ev_stat passwd;
1488		1734
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1736	ev_stat_start (loop, &passwd);
		1737
		1738	Example: Like above, but additionally use a one-second delay so we do not
		1739	miss updates (however, frequent updates will delay processing, too, so
		1740	one might do the work both on C<ev_stat> callback invocation I<and> on
		1741	C<ev_timer> callback invocation).
		1742
		1743	static ev_stat passwd;
		1744	static ev_timer timer;
		1745
		1746	static void
		1747	timer_cb (EV_P_ ev_timer *w, int revents)
		1748	{
		1749	ev_timer_stop (EV_A_ w);
		1750
		1751	/* now it's one second after the most recent passwd change */
		1752	}
		1753
		1754	static void
		1755	stat_cb (EV_P_ ev_stat *w, int revents)
		1756	{
		1757	/* reset the one-second timer */
		1758	ev_timer_again (EV_A_ &timer);
		1759	}
		1760
		1761	...
		1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1763	ev_stat_start (loop, &passwd);
		1764	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1765
1492		1766
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1767	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1768
1495	Idle watchers trigger events when no other events of the same or higher	1769	Idle watchers trigger events when no other events of the same or higher
…		…
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1796	believe me.
1523		1797
1524	=back	1798	=back
1525		1799
		1800	=head3 Examples
		1801
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1803	callback, free it. Also, use no error checking, as usual.
1528		1804
1529	static void	1805	static void
1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1531	{	1807	{
1532	free (w);	1808	free (w);
1533	// now do something you wanted to do when the program has	1809	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1810	// no longer anything immediate to do.
1535	}	1811	}
1536		1812
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1814	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1815	ev_idle_start (loop, idle_cb);
…		…
1581		1857
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1583	priority, to ensure that they are being run before any other watchers	1859	priority, to ensure that they are being run before any other watchers
1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1585	too) should not activate ("feed") events into libev. While libev fully	1861	too) should not activate ("feed") events into libev. While libev fully
1586	supports this, they will be called before other C<ev_check> watchers did	1862	supports this, they will be called before other C<ev_check> watchers
1587	their job. As C<ev_check> watchers are often used to embed other event	1863	did their job. As C<ev_check> watchers are often used to embed other
1588	loops those other event loops might be in an unusable state until their	1864	(non-libev) event loops those other event loops might be in an unusable
1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1865	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1866	coexist peacefully with others).
1591		1867
1592	=head3 Watcher-Specific Functions and Data Members	1868	=head3 Watcher-Specific Functions and Data Members
1593		1869
1594	=over 4	1870	=over 4
1595		1871
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1876	Initialises and configures the prepare or check watcher - they have no
1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1602	macros, but using them is utterly, utterly and completely pointless.	1878	macros, but using them is utterly, utterly and completely pointless.
1603		1879
1604	=back	1880	=back
		1881
		1882	=head3 Examples
1605		1883
1606	There are a number of principal ways to embed other event loops or modules	1884	There are a number of principal ways to embed other event loops or modules
1607	into libev. Here are some ideas on how to include libadns into libev	1885	into libev. Here are some ideas on how to include libadns into libev
1608	(there is a Perl module named C<EV::ADNS> that does this, which you could	1886	(there is a Perl module named C<EV::ADNS> that does this, which you could
1609	use for an actually working example. Another Perl module named C<EV::Glib>	1887	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	2012	=head2 C<ev_embed> - when one backend isn't enough...
1735		2013
1736	This is a rather advanced watcher type that lets you embed one event loop	2014	This is a rather advanced watcher type that lets you embed one event loop
1737	into another (currently only C<ev_io> events are supported in the embedded	2015	into another (currently only C<ev_io> events are supported in the embedded
1738	loop, other types of watchers might be handled in a delayed or incorrect	2016	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	2017	fashion and must not be used).
1740		2018
1741	There are primarily two reasons you would want that: work around bugs and	2019	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	2020	prioritise I/O.
1743		2021
1744	As an example for a bug workaround, the kqueue backend might only support	2022	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	2056	portable one.
1779		2057
1780	So when you want to use this feature you will always have to be prepared	2058	So when you want to use this feature you will always have to be prepared
1781	that you cannot get an embeddable loop. The recommended way to get around	2059	that you cannot get an embeddable loop. The recommended way to get around
1782	this is to have a separate variables for your embeddable loop, try to	2060	this is to have a separate variables for your embeddable loop, try to
1783	create it, and if that fails, use the normal loop for everything:	2061	create it, and if that fails, use the normal loop for everything.
		2062
		2063	=head3 Watcher-Specific Functions and Data Members
		2064
		2065	=over 4
		2066
		2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2068
		2069	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2070
		2071	Configures the watcher to embed the given loop, which must be
		2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2073	invoked automatically, otherwise it is the responsibility of the callback
		2074	to invoke it (it will continue to be called until the sweep has been done,
		2075	if you do not want thta, you need to temporarily stop the embed watcher).
		2076
		2077	=item ev_embed_sweep (loop, ev_embed *)
		2078
		2079	Make a single, non-blocking sweep over the embedded loop. This works
		2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2081	apropriate way for embedded loops.
		2082
		2083	=item struct ev_loop *other [read-only]
		2084
		2085	The embedded event loop.
		2086
		2087	=back
		2088
		2089	=head3 Examples
		2090
		2091	Example: Try to get an embeddable event loop and embed it into the default
		2092	event loop. If that is not possible, use the default loop. The default
		2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2095	used).
1784		2096
1785	struct ev_loop *loop_hi = ev_default_init (0);	2097	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	2098	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	2099	struct ev_embed embed;
1788		2100
…		…
1799	ev_embed_start (loop_hi, &embed);	2111	ev_embed_start (loop_hi, &embed);
1800	}	2112	}
1801	else	2113	else
1802	loop_lo = loop_hi;	2114	loop_lo = loop_hi;
1803		2115
1804	=head2 Portability notes	2116	Example: Check if kqueue is available but not recommended and create
		2117	a kqueue backend for use with sockets (which usually work with any
		2118	kqueue implementation). Store the kqueue/socket-only event loop in
		2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2120
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2121	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2122	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2123	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2124
1810	will always eport the epoll fd as ready, even when no events are pending.	2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2127	{
		2128	ev_embed_init (&embed, 0, loop_socket);
		2129	ev_embed_start (loop, &embed);
		2130	}
1811		2131
1812	While libev allows embedding these backends (they are contained in	2132	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2133	loop_socket = loop;
1814	work.
1815		2134
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2135	// now use loop_socket for all sockets, and loop for everything else
1817	usually works) and possibly another thread and a pipe or so to report to
1818	your main event loop.
1819
1820	=head3 Watcher-Specific Functions and Data Members
1821
1822	=over 4
1823
1824	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1825
1826	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1827
1828	Configures the watcher to embed the given loop, which must be
1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1830	invoked automatically, otherwise it is the responsibility of the callback
1831	to invoke it (it will continue to be called until the sweep has been done,
1832	if you do not want thta, you need to temporarily stop the embed watcher).
1833
1834	=item ev_embed_sweep (loop, ev_embed *)
1835
1836	Make a single, non-blocking sweep over the embedded loop. This works
1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1838	apropriate way for embedded loops.
1839
1840	=item struct ev_loop *other [read-only]
1841
1842	The embedded event loop.
1843
1844	=back
1845		2136
1846		2137
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2139
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2140	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2156	believe me.
1866		2157
1867	=back	2158	=back
1868		2159
1869		2160
		2161	=head2 C<ev_async> - how to wake up another event loop
		2162
		2163	In general, you cannot use an C<ev_loop> from multiple threads or other
		2164	asynchronous sources such as signal handlers (as opposed to multiple event
		2165	loops - those are of course safe to use in different threads).
		2166
		2167	Sometimes, however, you need to wake up another event loop you do not
		2168	control, for example because it belongs to another thread. This is what
		2169	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2170	can signal it by calling C<ev_async_send>, which is thread- and signal
		2171	safe.
		2172
		2173	This functionality is very similar to C<ev_signal> watchers, as signals,
		2174	too, are asynchronous in nature, and signals, too, will be compressed
		2175	(i.e. the number of callback invocations may be less than the number of
		2176	C<ev_async_sent> calls).
		2177
		2178	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2179	just the default loop.
		2180
		2181	=head3 Queueing
		2182
		2183	C<ev_async> does not support queueing of data in any way. The reason
		2184	is that the author does not know of a simple (or any) algorithm for a
		2185	multiple-writer-single-reader queue that works in all cases and doesn't
		2186	need elaborate support such as pthreads.
		2187
		2188	That means that if you want to queue data, you have to provide your own
		2189	queue. But at least I can tell you would implement locking around your
		2190	queue:
		2191
		2192	=over 4
		2193
		2194	=item queueing from a signal handler context
		2195
		2196	To implement race-free queueing, you simply add to the queue in the signal
		2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2198	some fictitiuous SIGUSR1 handler:
		2199
		2200	static ev_async mysig;
		2201
		2202	static void
		2203	sigusr1_handler (void)
		2204	{
		2205	sometype data;
		2206
		2207	// no locking etc.
		2208	queue_put (data);
		2209	ev_async_send (EV_DEFAULT_ &mysig);
		2210	}
		2211
		2212	static void
		2213	mysig_cb (EV_P_ ev_async *w, int revents)
		2214	{
		2215	sometype data;
		2216	sigset_t block, prev;
		2217
		2218	sigemptyset (&block);
		2219	sigaddset (&block, SIGUSR1);
		2220	sigprocmask (SIG_BLOCK, &block, &prev);
		2221
		2222	while (queue_get (&data))
		2223	process (data);
		2224
		2225	if (sigismember (&prev, SIGUSR1)
		2226	sigprocmask (SIG_UNBLOCK, &block, 0);
		2227	}
		2228
		2229	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2230	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2231	either...).
		2232
		2233	=item queueing from a thread context
		2234
		2235	The strategy for threads is different, as you cannot (easily) block
		2236	threads but you can easily preempt them, so to queue safely you need to
		2237	employ a traditional mutex lock, such as in this pthread example:
		2238
		2239	static ev_async mysig;
		2240	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2241
		2242	static void
		2243	otherthread (void)
		2244	{
		2245	// only need to lock the actual queueing operation
		2246	pthread_mutex_lock (&mymutex);
		2247	queue_put (data);
		2248	pthread_mutex_unlock (&mymutex);
		2249
		2250	ev_async_send (EV_DEFAULT_ &mysig);
		2251	}
		2252
		2253	static void
		2254	mysig_cb (EV_P_ ev_async *w, int revents)
		2255	{
		2256	pthread_mutex_lock (&mymutex);
		2257
		2258	while (queue_get (&data))
		2259	process (data);
		2260
		2261	pthread_mutex_unlock (&mymutex);
		2262	}
		2263
		2264	=back
		2265
		2266
		2267	=head3 Watcher-Specific Functions and Data Members
		2268
		2269	=over 4
		2270
		2271	=item ev_async_init (ev_async *, callback)
		2272
		2273	Initialises and configures the async watcher - it has no parameters of any
		2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2275	believe me.
		2276
		2277	=item ev_async_send (loop, ev_async *)
		2278
		2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2281	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2283	section below on what exactly this means).
		2284
		2285	This call incurs the overhead of a syscall only once per loop iteration,
		2286	so while the overhead might be noticable, it doesn't apply to repeated
		2287	calls to C<ev_async_send>.
		2288
		2289	=item bool = ev_async_pending (ev_async *)
		2290
		2291	Returns a non-zero value when C<ev_async_send> has been called on the
		2292	watcher but the event has not yet been processed (or even noted) by the
		2293	event loop.
		2294
		2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2296	the loop iterates next and checks for the watcher to have become active,
		2297	it will reset the flag again. C<ev_async_pending> can be used to very
		2298	quickly check wether invoking the loop might be a good idea.
		2299
		2300	Not that this does I<not> check wether the watcher itself is pending, only
		2301	wether it has been requested to make this watcher pending.
		2302
		2303	=back
		2304
		2305
1870	=head1 OTHER FUNCTIONS	2306	=head1 OTHER FUNCTIONS
1871		2307
1872	There are some other functions of possible interest. Described. Here. Now.	2308	There are some other functions of possible interest. Described. Here. Now.
1873		2309
1874	=over 4	2310	=over 4
…		…
1942		2378
1943	=item * Priorities are not currently supported. Initialising priorities	2379	=item * Priorities are not currently supported. Initialising priorities
1944	will fail and all watchers will have the same priority, even though there	2380	will fail and all watchers will have the same priority, even though there
1945	is an ev_pri field.	2381	is an ev_pri field.
1946		2382
		2383	=item * In libevent, the last base created gets the signals, in libev, the
		2384	first base created (== the default loop) gets the signals.
		2385
1947	=item * Other members are not supported.	2386	=item * Other members are not supported.
1948		2387
1949	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2388	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1950	to use the libev header file and library.	2389	to use the libev header file and library.
1951		2390
…		…
2101	Example: Define a class with an IO and idle watcher, start one of them in	2540	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2541	the constructor.
2103		2542
2104	class myclass	2543	class myclass
2105	{	2544	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2545	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2546	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2547
2109	myclass ();	2548	myclass (int fd)
2110	}
2111
2112	myclass::myclass (int fd)
2113	{	2549	{
2114	io .set <myclass, &myclass::io_cb > (this);	2550	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2551	idle.set <myclass, &myclass::idle_cb> (this);
2116		2552
2117	io.start (fd, ev::READ);	2553	io.start (fd, ev::READ);
		2554	}
2118	}	2555	};
		2556
		2557
		2558	=head1 OTHER LANGUAGE BINDINGS
		2559
		2560	Libev does not offer other language bindings itself, but bindings for a
		2561	numbe rof languages exist in the form of third-party packages. If you know
		2562	any interesting language binding in addition to the ones listed here, drop
		2563	me a note.
		2564
		2565	=over 4
		2566
		2567	=item Perl
		2568
		2569	The EV module implements the full libev API and is actually used to test
		2570	libev. EV is developed together with libev. Apart from the EV core module,
		2571	there are additional modules that implement libev-compatible interfaces
		2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2574
		2575	It can be found and installed via CPAN, its homepage is found at
		2576	L<http://software.schmorp.de/pkg/EV>.
		2577
		2578	=item Ruby
		2579
		2580	Tony Arcieri has written a ruby extension that offers access to a subset
		2581	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2582	more on top of it. It can be found via gem servers. Its homepage is at
		2583	L<http://rev.rubyforge.org/>.
		2584
		2585	=item D
		2586
		2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2589
		2590	=back
2119		2591
2120		2592
2121	=head1 MACRO MAGIC	2593	=head1 MACRO MAGIC
2122		2594
2123	Libev can be compiled with a variety of options, the most fundamantal	2595	Libev can be compiled with a variety of options, the most fundamantal
…		…
2159		2631
2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2161		2633
2162	Similar to the other two macros, this gives you the value of the default	2634	Similar to the other two macros, this gives you the value of the default
2163	loop, if multiple loops are supported ("ev loop default").	2635	loop, if multiple loops are supported ("ev loop default").
		2636
		2637	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2638
		2639	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2640	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2641	is undefined when the default loop has not been initialised by a previous
		2642	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2643
		2644	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2645	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2164		2646
2165	=back	2647	=back
2166		2648
2167	Example: Declare and initialise a check watcher, utilising the above	2649	Example: Declare and initialise a check watcher, utilising the above
2168	macros so it will work regardless of whether multiple loops are supported	2650	macros so it will work regardless of whether multiple loops are supported
…		…
2264		2746
2265	libev.m4	2747	libev.m4
2266		2748
2267	=head2 PREPROCESSOR SYMBOLS/MACROS	2749	=head2 PREPROCESSOR SYMBOLS/MACROS
2268		2750
2269	Libev can be configured via a variety of preprocessor symbols you have to define	2751	Libev can be configured via a variety of preprocessor symbols you have to
2270	before including any of its files. The default is not to build for multiplicity	2752	define before including any of its files. The default in the absense of
2271	and only include the select backend.	2753	autoconf is noted for every option.
2272		2754
2273	=over 4	2755	=over 4
2274		2756
2275	=item EV_STANDALONE	2757	=item EV_STANDALONE
2276		2758
…		…
2297	runtime if successful). Otherwise no use of the realtime clock option will	2779	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2783
		2784	=item EV_USE_NANOSLEEP
		2785
		2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2787	and will use it for delays. Otherwise it will use C<select ()>.
		2788
		2789	=item EV_USE_EVENTFD
		2790
		2791	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2792	available and will probe for kernel support at runtime. This will improve
		2793	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2794	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2795	2.7 or newer, otherwise disabled.
		2796
2302	=item EV_USE_SELECT	2797	=item EV_USE_SELECT
2303		2798
2304	If undefined or defined to be C<1>, libev will compile in support for the	2799	If undefined or defined to be C<1>, libev will compile in support for the
2305	C<select>(2) backend. No attempt at autodetection will be done: if no	2800	C<select>(2) backend. No attempt at autodetection will be done: if no
2306	other method takes over, select will be it. Otherwise the select backend	2801	other method takes over, select will be it. Otherwise the select backend
…		…
2324	be used is the winsock select). This means that it will call	2819	be used is the winsock select). This means that it will call
2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2820	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2326	it is assumed that all these functions actually work on fds, even	2821	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2822	on win32. Should not be defined on non-win32 platforms.
2328		2823
		2824	=item EV_FD_TO_WIN32_HANDLE
		2825
		2826	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2827	file descriptors to socket handles. When not defining this symbol (the
		2828	default), then libev will call C<_get_osfhandle>, which is usually
		2829	correct. In some cases, programs use their own file descriptor management,
		2830	in which case they can provide this function to map fds to socket handles.
		2831
2329	=item EV_USE_POLL	2832	=item EV_USE_POLL
2330		2833
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2834	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2332	backend. Otherwise it will be enabled on non-win32 platforms. It	2835	backend. Otherwise it will be enabled on non-win32 platforms. It
2333	takes precedence over select.	2836	takes precedence over select.
2334		2837
2335	=item EV_USE_EPOLL	2838	=item EV_USE_EPOLL
2336		2839
2337	If defined to be C<1>, libev will compile in support for the Linux	2840	If defined to be C<1>, libev will compile in support for the Linux
2338	C<epoll>(7) backend. Its availability will be detected at runtime,	2841	C<epoll>(7) backend. Its availability will be detected at runtime,
2339	otherwise another method will be used as fallback. This is the	2842	otherwise another method will be used as fallback. This is the preferred
2340	preferred backend for GNU/Linux systems.	2843	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2844	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2341		2845
2342	=item EV_USE_KQUEUE	2846	=item EV_USE_KQUEUE
2343		2847
2344	If defined to be C<1>, libev will compile in support for the BSD style	2848	If defined to be C<1>, libev will compile in support for the BSD style
2345	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2849	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2364		2868
2365	=item EV_USE_INOTIFY	2869	=item EV_USE_INOTIFY
2366		2870
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2871	If defined to be C<1>, libev will compile in support for the Linux inotify
2368	interface to speed up C<ev_stat> watchers. Its actual availability will	2872	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2873	be detected at runtime. If undefined, it will be enabled if the headers
		2874	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2875
		2876	=item EV_ATOMIC_T
		2877
		2878	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2879	access is atomic with respect to other threads or signal contexts. No such
		2880	type is easily found in the C language, so you can provide your own type
		2881	that you know is safe for your purposes. It is used both for signal handler "locking"
		2882	as well as for signal and thread safety in C<ev_async> watchers.
		2883
		2884	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2885	(from F<signal.h>), which is usually good enough on most platforms.
2370		2886
2371	=item EV_H	2887	=item EV_H
2372		2888
2373	The name of the F<ev.h> header file used to include it. The default if	2889	The name of the F<ev.h> header file used to include it. The default if
2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2890	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2891	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2892
2377	=item EV_CONFIG_H	2893	=item EV_CONFIG_H
2378		2894
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2895	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2896	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2897	C<EV_H>, above.
2382		2898
2383	=item EV_EVENT_H	2899	=item EV_EVENT_H
2384		2900
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2901	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2386	of how the F<event.h> header can be found.	2902	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2903
2388	=item EV_PROTOTYPES	2904	=item EV_PROTOTYPES
2389		2905
2390	If defined to be C<0>, then F<ev.h> will not define any function	2906	If defined to be C<0>, then F<ev.h> will not define any function
2391	prototypes, but still define all the structs and other symbols. This is	2907	prototypes, but still define all the structs and other symbols. This is
…		…
2442	=item EV_FORK_ENABLE	2958	=item EV_FORK_ENABLE
2443		2959
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	2960	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	2961	defined to be C<0>, then they are not.
2446		2962
		2963	=item EV_ASYNC_ENABLE
		2964
		2965	If undefined or defined to be C<1>, then async watchers are supported. If
		2966	defined to be C<0>, then they are not.
		2967
2447	=item EV_MINIMAL	2968	=item EV_MINIMAL
2448		2969
2449	If you need to shave off some kilobytes of code at the expense of some	2970	If you need to shave off some kilobytes of code at the expense of some
2450	speed, define this symbol to C<1>. Currently only used for gcc to override	2971	speed, define this symbol to C<1>. Currently only used for gcc to override
2451	some inlining decisions, saves roughly 30% codesize of amd64.	2972	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2457	than enough. If you need to manage thousands of children you might want to	2978	than enough. If you need to manage thousands of children you might want to
2458	increase this value (I<must> be a power of two).	2979	increase this value (I<must> be a power of two).
2459		2980
2460	=item EV_INOTIFY_HASHSIZE	2981	=item EV_INOTIFY_HASHSIZE
2461		2982
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2983	C<ev_stat> watchers use a small hash table to distribute workload by
2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2464	usually more than enough. If you need to manage thousands of C<ev_stat>	2985	usually more than enough. If you need to manage thousands of C<ev_stat>
2465	watchers you might want to increase this value (I<must> be a power of	2986	watchers you might want to increase this value (I<must> be a power of
2466	two).	2987	two).
2467		2988
…		…
2545		3066
2546	#include "ev_cpp.h"	3067	#include "ev_cpp.h"
2547	#include "ev.c"	3068	#include "ev.c"
2548		3069
2549		3070
		3071	=head1 THREADS AND COROUTINES
		3072
		3073	=head2 THREADS
		3074
		3075	Libev itself is completely threadsafe, but it uses no locking. This
		3076	means that you can use as many loops as you want in parallel, as long as
		3077	only one thread ever calls into one libev function with the same loop
		3078	parameter.
		3079
		3080	Or put differently: calls with different loop parameters can be done in
		3081	parallel from multiple threads, calls with the same loop parameter must be
		3082	done serially (but can be done from different threads, as long as only one
		3083	thread ever is inside a call at any point in time, e.g. by using a mutex
		3084	per loop).
		3085
		3086	If you want to know which design is best for your problem, then I cannot
		3087	help you but by giving some generic advice:
		3088
		3089	=over 4
		3090
		3091	=item * most applications have a main thread: use the default libev loop
		3092	in that thread, or create a seperate thread running only the default loop.
		3093
		3094	This helps integrating other libraries or software modules that use libev
		3095	themselves and don't care/know about threading.
		3096
		3097	=item * one loop per thread is usually a good model.
		3098
		3099	Doing this is almost never wrong, sometimes a better-performance model
		3100	exists, but it is always a good start.
		3101
		3102	=item * other models exist, such as the leader/follower pattern, where one
		3103	loop is handed through multiple threads in a kind of round-robbin fashion.
		3104
		3105	Chosing a model is hard - look around, learn, know that usually you cna do
		3106	better than you currently do :-)
		3107
		3108	=item * often you need to talk to some other thread which blocks in the
		3109	event loop - C<ev_async> watchers can be used to wake them up from other
		3110	threads safely (or from signal contexts...).
		3111
		3112	=back
		3113
		3114	=head2 COROUTINES
		3115
		3116	Libev is much more accomodating to coroutines ("cooperative threads"):
		3117	libev fully supports nesting calls to it's functions from different
		3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3119	different coroutines and switch freely between both coroutines running the
		3120	loop, as long as you don't confuse yourself). The only exception is that
		3121	you must not do this from C<ev_periodic> reschedule callbacks.
		3122
		3123	Care has been invested into making sure that libev does not keep local
		3124	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3125	switches.
		3126
		3127
2550	=head1 COMPLEXITIES	3128	=head1 COMPLEXITIES
2551		3129
2552	In this section the complexities of (many of) the algorithms used inside	3130	In this section the complexities of (many of) the algorithms used inside
2553	libev will be explained. For complexity discussions about backends see the	3131	libev will be explained. For complexity discussions about backends see the
2554	documentation for C<ev_default_init>.	3132	documentation for C<ev_default_init>.
…		…
2563		3141
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		3143
2566	This means that, when you have a watcher that triggers in one hour and	3144	This means that, when you have a watcher that triggers in one hour and
2567	there are 100 watchers that would trigger before that then inserting will	3145	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	3146	have to skip roughly seven (C<ld 100>) of these watchers.
2569		3147
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		3149
2572	That means that for changing a timer costs less than removing/adding them	3150	That means that changing a timer costs less than removing/adding them
2573	as only the relative motion in the event queue has to be paid for.	3151	as only the relative motion in the event queue has to be paid for.
2574		3152
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		3154
2577	These just add the watcher into an array or at the head of a list.	3155	These just add the watcher into an array or at the head of a list.
		3156
2578	=item Stopping check/prepare/idle watchers: O(1)	3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		3158
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		3160
2582	These watchers are stored in lists then need to be walked to find the	3161	These watchers are stored in lists then need to be walked to find the
2583	correct watcher to remove. The lists are usually short (you don't usually	3162	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	3163	have many watchers waiting for the same fd or signal).
2585		3164
2586	=item Finding the next timer per loop iteration: O(1)	3165	=item Finding the next timer in each loop iteration: O(1)
		3166
		3167	By virtue of using a binary heap, the next timer is always found at the
		3168	beginning of the storage array.
2587		3169
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		3171
2590	A change means an I/O watcher gets started or stopped, which requires	3172	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	3173	libev to recalculate its status (and possibly tell the kernel, depending
		3174	on backend and wether C<ev_io_set> was used).
2592		3175
2593	=item Activating one watcher: O(1)	3176	=item Activating one watcher (putting it into the pending state): O(1)
2594		3177
2595	=item Priority handling: O(number_of_priorities)	3178	=item Priority handling: O(number_of_priorities)
2596		3179
2597	Priorities are implemented by allocating some space for each	3180	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	3181	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	3182	linearly search all the priorities, but starting/stopping and activating
		3183	watchers becomes O(1) w.r.t. priority handling.
		3184
		3185	=item Sending an ev_async: O(1)
		3186
		3187	=item Processing ev_async_send: O(number_of_async_watchers)
		3188
		3189	=item Processing signals: O(max_signal_number)
		3190
		3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3192	calls in the current loop iteration. Checking for async and signal events
		3193	involves iterating over all running async watchers or all signal numbers.
2600		3194
2601	=back	3195	=back
2602		3196
2603		3197
		3198	=head1 Win32 platform limitations and workarounds
		3199
		3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3201	requires, and its I/O model is fundamentally incompatible with the POSIX
		3202	model. Libev still offers limited functionality on this platform in
		3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3204	descriptors. This only applies when using Win32 natively, not when using
		3205	e.g. cygwin.
		3206
		3207	There is no supported compilation method available on windows except
		3208	embedding it into other applications.
		3209
		3210	Due to the many, low, and arbitrary limits on the win32 platform and the
		3211	abysmal performance of winsockets, using a large number of sockets is not
		3212	recommended (and not reasonable). If your program needs to use more than
		3213	a hundred or so sockets, then likely it needs to use a totally different
		3214	implementation for windows, as libev offers the POSIX model, which cannot
		3215	be implemented efficiently on windows (microsoft monopoly games).
		3216
		3217	=over 4
		3218
		3219	=item The winsocket select function
		3220
		3221	The winsocket C<select> function doesn't follow POSIX in that it requires
		3222	socket I<handles> and not socket I<file descriptors>. This makes select
		3223	very inefficient, and also requires a mapping from file descriptors
		3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3226	symbols for more info.
		3227
		3228	The configuration for a "naked" win32 using the microsoft runtime
		3229	libraries and raw winsocket select is:
		3230
		3231	#define EV_USE_SELECT 1
		3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3233
		3234	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3235	complexity in the O(n²) range when using win32.
		3236
		3237	=item Limited number of file descriptors
		3238
		3239	Windows has numerous arbitrary (and low) limits on things. Early versions
		3240	of winsocket's select only supported waiting for a max. of C<64> handles
		3241	(probably owning to the fact that all windows kernels can only wait for
		3242	C<64> things at the same time internally; microsoft recommends spawning a
		3243	chain of threads and wait for 63 handles and the previous thread in each).
		3244
		3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3246	to some high number (e.g. C<2048>) before compiling the winsocket select
		3247	call (which might be in libev or elsewhere, for example, perl does its own
		3248	select emulation on windows).
		3249
		3250	Another limit is the number of file descriptors in the microsoft runtime
		3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3252	or something like this inside microsoft). You can increase this by calling
		3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3254	arbitrary limit), but is broken in many versions of the microsoft runtime
		3255	libraries.
		3256
		3257	This might get you to about C<512> or C<2048> sockets (depending on
		3258	windows version and/or the phase of the moon). To get more, you need to
		3259	wrap all I/O functions and provide your own fd management, but the cost of
		3260	calling select (O(n²)) will likely make this unworkable.
		3261
		3262	=back
		3263
		3264
		3265	=head1 PORTABILITY REQUIREMENTS
		3266
		3267	In addition to a working ISO-C implementation, libev relies on a few
		3268	additional extensions:
		3269
		3270	=over 4
		3271
		3272	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3273
		3274	The type C<sig_atomic_t volatile> (or whatever is defined as
		3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3276	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3277	believed to be sufficiently portable.
		3278
		3279	=item C<sigprocmask> must work in a threaded environment
		3280
		3281	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3282	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3283	pthread implementations will either allow C<sigprocmask> in the "main
		3284	thread" or will block signals process-wide, both behaviours would
		3285	be compatible with libev. Interaction between C<sigprocmask> and
		3286	C<pthread_sigmask> could complicate things, however.
		3287
		3288	The most portable way to handle signals is to block signals in all threads
		3289	except the initial one, and run the default loop in the initial thread as
		3290	well.
		3291
		3292	=back
		3293
		3294	If you know of other additional requirements drop me a note.
		3295
		3296
2604	=head1 AUTHOR	3297	=head1 AUTHOR
2605		3298
2606	Marc Lehmann <libev@schmorp.de>.	3299	Marc Lehmann <libev@schmorp.de>.
2607		3300

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