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Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC vs.
Revision 1.196 by root, Tue Oct 21 20:04:14 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_<type>
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	250	}
230		251
231	...	252	...
232	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
233		254
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		256
236	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	263	(such as abort).
243		264
244	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
277	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
279		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
342		367
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		369
345	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	375	performance tips.
351		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		381
354	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and requiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	388	support for dup.
361		389
362	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	394	very well if you register events for both fds.
367		395
368	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.	398	(or space) is available.
371		399
372	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
375		405
376	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	407	all kernel versions tested so far.
378		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		413
381	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		420
389	You still can embed kqueue into a normal poll or select backend and use it	421	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	422	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.	423	the target platform). See C<ev_embed> watchers for more info.
392		424
393	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
399		431
400	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
401		433
402	While nominally embeddable in other event loops, this doesn't work	434	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	435	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	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
408		444
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		446
411	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		453
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
420		456
421	Please note that solaris event ports can deliver a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
424		460
425	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	464	might perform better.
429		465
430	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
433		473
434	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
435		475
436	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		479
440	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
441		481
442	=back	482	=back
443		483
444	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		487
448	The most typical usage is like this:	488	Example: This is the most typical usage.
449		489
450	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		492
453	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	494	environment settings to be taken into account:
455		495
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		497
458	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
461		502
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		504
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		506
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	513	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
474		515
475	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
476		517
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	519	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
480		521
481	=item ev_default_destroy ()	522	=item ev_default_destroy ()
482		523
483	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	530	for example).
490		531
491	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
523		564
524	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
525		566
526	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
529		571
530	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
531		573
532	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
533		576
534	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
535		578
536	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
556		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
557	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
558		613
559	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
561	events.	616	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
565		620
566	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
571		627
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
575		632
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
580	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
583		644
584	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
585		646
586	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	662	- Queue all expired timers.
601	- Queue all outstanding periodics.	663	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	665	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	674	anymore.
613		675
614	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
617	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
618		680
619	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
620		682
621	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		687
626	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
627		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
628	=item ev_ref (loop)	692	=item ev_ref (loop)
629		693
630	=item ev_unref (loop)	694	=item ev_unref (loop)
631		695
632	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
635	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
637	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	708	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,	709	(but only if the watcher wasn't active before, or was active before,
643	respectively).	710	respectively).
644		711
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	713	running when nothing else is active.
647		714
648	struct ev_signal exitsig;	715	struct ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	718	evf_unref (loop);
652		719
653	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
654		721
655	ev_ref (loop);	722	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
657		724
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		726
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		728
662	These advanced functions influence the time that libev will spend waiting	729	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	730	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
665		733
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	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	735	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
669		738
670	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	741	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	742	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
675		744
676	By setting a higher I<io collect interval> you allow libev to spend more	745	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,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	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.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		750
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	755	value will not introduce any overhead in libev.
687		756
688	Many (busy) programs can usually benefit by setting the io collect	757	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	758	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	759	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>,	760	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.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
693		781
694	=back	782	=back
695		783
696		784
697	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
698		786
699	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
702		790
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
704	{	792	{
705	ev_io_stop (w);	793	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
707	}	795	}
708		796
709	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
710	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
711	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
714	ev_loop (loop, 0);	802	ev_loop (loop, 0);
715		803
716	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
718	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
719		807
720	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	812	is readable and/or writable).
725		813
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
727	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
803		891
804	The given async watcher has been asynchronously notified (see C<ev_async>).	892	The given async watcher has been asynchronously notified (see C<ev_async>).
805		893
806	=item C<EV_ERROR>	894	=item C<EV_ERROR>
807		895
808	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
811	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
812	with the watcher being stopped.	900	with the watcher being stopped.
813		901
814	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
819		908
820	=back	909	=back
821		910
822	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
823		912
…		…
839	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
840		929
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	931	int revents)>.
843		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		940
846	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
850	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
851		946
852	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		949
		950	See C<ev_init>, above, for an example.
		951
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		953
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	955	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		961
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		963
863	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
865		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
		971
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		973
868	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher if active, and clears the pending status (whether
		975	the watcher was active or not).
		976
869	status. It is possible that stopped watchers are pending (for example,	977	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	978	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	979	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	980	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	981	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		982
875	=item bool ev_is_active (ev_TYPE *watcher)	983	=item bool ev_is_active (ev_TYPE *watcher)
876		984
877	Returns a true value iff the watcher is active (i.e. it has been started	985	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	986	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926		1034
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1036
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1038	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1039	can deal with that fact, as both are simply passed through to the
		1040	callback.
932		1041
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1042	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1043
935	If the watcher is pending, this function returns clears its pending status	1044	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1045	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1046	watcher isn't pending it does nothing and returns C<0>.
938		1047
		1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1049	callback to be invoked, which can be accomplished with this function.
		1050
939	=back	1051	=back
940		1052
941		1053
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1055
944	Each watcher has, by default, a member C<void *data> that you can change	1056	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1057	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1058	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1059	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1060	member, you can also "subclass" the watcher type and provide your own
949	data:	1061	data:
950		1062
951	struct my_io	1063	struct my_io
952	{	1064	{
953	struct ev_io io;	1065	struct ev_io io;
954	int otherfd;	1066	int otherfd;
955	void *somedata;	1067	void *somedata;
956	struct whatever *mostinteresting;	1068	struct whatever *mostinteresting;
957	}	1069	};
		1070
		1071	...
		1072	struct my_io w;
		1073	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1074
959	And since your callback will be called with a pointer to the watcher, you	1075	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1076	can cast it back to your own type:
961		1077
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
963	{	1079	{
964	struct my_io *w = (struct my_io *)w_;	1080	struct my_io *w = (struct my_io *)w_;
965	...	1081	...
966	}	1082	}
967		1083
968	More interesting and less C-conformant ways of casting your callback type	1084	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1085	instead have been omitted.
970		1086
971	Another common scenario is having some data structure with multiple	1087	Another common scenario is to use some data structure with multiple
972	watchers:	1088	embedded watchers:
973		1089
974	struct my_biggy	1090	struct my_biggy
975	{	1091	{
976	int some_data;	1092	int some_data;
977	ev_timer t1;	1093	ev_timer t1;
978	ev_timer t2;	1094	ev_timer t2;
979	}	1095	}
980		1096
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1097	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1098	complicated: Either you store the address of your C<my_biggy> struct
		1099	in the C<data> member of the watcher (for woozies), or you need to use
		1100	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1101	programmers):
983		1102
984	#include <stddef.h>	1103	#include <stddef.h>
985		1104
986	static void	1105	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1106	t1_cb (EV_P_ struct ev_timer *w, int revents)
988	{	1107	{
989	struct my_biggy big = (struct my_biggy *	1108	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1109	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1110	}
992		1111
993	static void	1112	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1113	t2_cb (EV_P_ struct ev_timer *w, int revents)
995	{	1114	{
996	struct my_biggy big = (struct my_biggy *	1115	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1116	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1117	}
999		1118
1000		1119
1001	=head1 WATCHER TYPES	1120	=head1 WATCHER TYPES
1002		1121
1003	This section describes each watcher in detail, but will not repeat	1122	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1146	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1147	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1148	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1149	required if you know what you are doing).
1031		1150
1032	If you must do this, then force the use of a known-to-be-good backend	1151	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1152	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1154
1036	Another thing you have to watch out for is that it is quite easy to	1155	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1156	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1158	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1159	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1160	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1161	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1162	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1163
1045	If you cannot run the fd in non-blocking mode (for example you should not	1164	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1165	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1166	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1167	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1168	does this on its own, so its quite safe to use). Some people additionally
		1169	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1170	indefinitely.
		1171
		1172	But really, best use non-blocking mode.
1050		1173
1051	=head3 The special problem of disappearing file descriptors	1174	=head3 The special problem of disappearing file descriptors
1052		1175
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1176	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1177	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1178	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1179	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1180	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1181	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1182	fact, a different file descriptor.
1060		1183
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1214	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1215	C<EVBACKEND_POLL>.
1093		1216
1094	=head3 The special problem of SIGPIPE	1217	=head3 The special problem of SIGPIPE
1095		1218
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1219	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1220	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1221	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1222	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1223
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1224	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	1225	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).	1226	somewhere, as that would have given you a big clue).
1105		1227
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1233	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1234
1113	=item ev_io_set (ev_io *, int fd, int events)	1235	=item ev_io_set (ev_io *, int fd, int events)
1114		1236
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1237	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1238	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1239	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1240
1119	=item int fd [read-only]	1241	=item int fd [read-only]
1120		1242
1121	The file descriptor being watched.	1243	The file descriptor being watched.
1122		1244
…		…
1130		1252
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1254	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1255	attempt to read a whole line in the callback.
1134		1256
1135	static void	1257	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137	{	1259	{
1138	ev_io_stop (loop, w);	1260	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1261	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1262	}
1141		1263
1142	...	1264	...
1143	struct ev_loop *loop = ev_default_init (0);	1265	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1266	struct ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1268	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1269	ev_loop (loop, 0);
1148		1270
1149		1271
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1272	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1273
1152	Timer watchers are simple relative timers that generate an event after a	1274	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1275	given time, and optionally repeating in regular intervals after that.
1154		1276
1155	The timers are based on real time, that is, if you register an event that	1277	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1278	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1279	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1281	monotonic clock option helps a lot here).
		1282
		1283	The callback is guaranteed to be invoked only I<after> its timeout has
		1284	passed, but if multiple timers become ready during the same loop iteration
		1285	then order of execution is undefined.
		1286
		1287	=head3 The special problem of time updates
		1288
		1289	Establishing the current time is a costly operation (it usually takes at
		1290	least two system calls): EV therefore updates its idea of the current
		1291	time only before and after C<ev_loop> collects new events, which causes a
		1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1293	lots of events in one iteration.
1160		1294
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1295	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1296	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1297	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1298	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1299	timeout on the current time, use something like this to adjust for this:
1166		1300
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1301	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1302
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1303	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1305	()>.
1172		1306
1173	=head3 Watcher-Specific Functions and Data Members	1307	=head3 Watcher-Specific Functions and Data Members
1174		1308
1175	=over 4	1309	=over 4
1176		1310
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1312
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1313	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1314
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1315	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1316	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1317	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1318	configured to trigger again C<repeat> seconds later, again, and again,
		1319	until stopped manually.
1185		1320
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1321	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1322	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1323	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1324	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1325	do stuff) the timer will not fire more than once per event loop iteration.
1191		1326
1192	=item ev_timer_again (loop, ev_timer *)	1327	=item ev_timer_again (loop, ev_timer *)
1193		1328
1194	This will act as if the timer timed out and restart it again if it is	1329	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1330	repeating. The exact semantics are:
1196		1331
1197	If the timer is pending, its pending status is cleared.	1332	If the timer is pending, its pending status is cleared.
1198		1333
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1334	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1335
1201	If the timer is repeating, either start it if necessary (with the	1336	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1337	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1338
1204	This sounds a bit complicated, but here is a useful and typical	1339	This sounds a bit complicated, but here is a useful and typical
1205	example: Imagine you have a tcp connection and you want a so-called idle	1340	example: Imagine you have a TCP connection and you want a so-called idle
1206	timeout, that is, you want to be called when there have been, say, 60	1341	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to	1342	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If	1344	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the	1345	you go into an idle state where you do not expect data to travel on the
…		…
1224	ev_timer_again (loop, timer);	1359	ev_timer_again (loop, timer);
1225		1360
1226	This is more slightly efficient then stopping/starting the timer each time	1361	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.	1362	you want to modify its timeout value.
1228		1363
		1364	Note, however, that it is often even more efficient to remember the
		1365	time of the last activity and let the timer time-out naturally. In the
		1366	callback, you then check whether the time-out is real, or, if there was
		1367	some activity, you reschedule the watcher to time-out in "last_activity +
		1368	timeout - ev_now ()" seconds.
		1369
1229	=item ev_tstamp repeat [read-write]	1370	=item ev_tstamp repeat [read-write]
1230		1371
1231	The current C<repeat> value. Will be used each time the watcher times out	1372	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1373	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1374	which is also when any modifications are taken into account.
1234		1375
1235	=back	1376	=back
1236		1377
1237	=head3 Examples	1378	=head3 Examples
1238		1379
1239	Example: Create a timer that fires after 60 seconds.	1380	Example: Create a timer that fires after 60 seconds.
1240		1381
1241	static void	1382	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1243	{	1384	{
1244	.. one minute over, w is actually stopped right here	1385	.. one minute over, w is actually stopped right here
1245	}	1386	}
1246		1387
1247	struct ev_timer mytimer;	1388	struct ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1390	ev_timer_start (loop, &mytimer);
1250		1391
1251	Example: Create a timeout timer that times out after 10 seconds of	1392	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1393	inactivity.
1253		1394
1254	static void	1395	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1256	{	1397	{
1257	.. ten seconds without any activity	1398	.. ten seconds without any activity
1258	}	1399	}
1259		1400
1260	struct ev_timer mytimer;	1401	struct ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1403	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1404	ev_loop (loop, 0);
1264		1405
1265	// and in some piece of code that gets executed on any "activity":	1406	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1407	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1408	ev_timer_again (&mytimer);
1268		1409
1269		1410
1270	=head2 C<ev_periodic> - to cron or not to cron?	1411	=head2 C<ev_periodic> - to cron or not to cron?
1271		1412
1272	Periodic watchers are also timers of a kind, but they are very versatile	1413	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1414	(and unfortunately a bit complex).
1274		1415
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1417	but on wall clock time (absolute time). You can tell a periodic watcher
1277	to trigger "at" some specific point in time. For example, if you tell a	1418	to trigger after some specific point in time. For example, if you tell a
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1279	+ 10.>) and then reset your system clock to the last year, then it will	1420	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1421	clock to January of the previous year, then it will take more than year
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1423	roughly 10 seconds later as it uses a relative timeout).
1282		1424
1283	They can also be used to implement vastly more complex timers, such as	1425	C<ev_periodic>s can also be used to implement vastly more complex timers,
1284	triggering an event on each midnight, local time or other, complicated,	1426	such as triggering an event on each "midnight, local time", or other
1285	rules.	1427	complicated rules.
1286		1428
1287	As with timers, the callback is guarenteed to be invoked only when the	1429	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1430	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1431	during the same loop iteration, then order of execution is undefined.
1290		1432
1291	=head3 Watcher-Specific Functions and Data Members	1433	=head3 Watcher-Specific Functions and Data Members
1292		1434
1293	=over 4	1435	=over 4
1294		1436
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1296		1438
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1298		1440
1299	Lots of arguments, lets sort it out... There are basically three modes of	1441	Lots of arguments, lets sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1442	operation, and we will explain them from simplest to most complex:
1301		1443
1302	=over 4	1444	=over 4
1303		1445
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1447
1306	In this configuration the watcher triggers an event at the wallclock time	1448	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1449	time C<at> has passed. It will not repeat and will not adjust when a time
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309	system time reaches or surpasses this time.	1451	only run when the system clock reaches or surpasses this time.
1310		1452
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1454
1313	In this mode the watcher will always be scheduled to time out at the next	1455	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1456	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1457	and then repeat, regardless of any time jumps.
1316		1458
1317	This can be used to create timers that do not drift with respect to system	1459	This can be used to create timers that do not drift with respect to the
1318	time:	1460	system clock, for example, here is a C<ev_periodic> that triggers each
		1461	hour, on the hour:
1319		1462
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1463	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1464
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1465	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1466	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1467	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1468	by 3600.
1326		1469
1327	Another way to think about it (for the mathematically inclined) is that	1470	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1471	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1472	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1473
1331	For numerical stability it is preferable that the C<at> value is near	1474	For numerical stability it is preferable that the C<at> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1475	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1476	this value, and in fact is often specified as zero.
		1477
		1478	Note also that there is an upper limit to how often a timer can fire (CPU
		1479	speed for example), so if C<interval> is very small then timing stability
		1480	will of course deteriorate. Libev itself tries to be exact to be about one
		1481	millisecond (if the OS supports it and the machine is fast enough).
1334		1482
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1484
1337	In this mode the values for C<interval> and C<at> are both being	1485	In this mode the values for C<interval> and C<at> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1486	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1487	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1488	current time as second argument.
1341		1489
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343	ever, or make any event loop modifications>. If you need to stop it,	1491	ever, or make ANY event loop modifications whatsoever>.
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1492
		1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1495	only event loop modification you are allowed to do).
		1496
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1348	ev_tstamp now)>, e.g.:	1498	*w, ev_tstamp now)>, e.g.:
1349		1499
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1351	{	1501	{
1352	return now + 60.;	1502	return now + 60.;
1353	}	1503	}
…		…
1355	It must return the next time to trigger, based on the passed time value	1505	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1506	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1507	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1508	might be called at other times, too.
1359		1509
1360	NOTE: I<< This callback must always return a time that is later than the	1510	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1511	equal to the passed C<now> value >>.
1362		1512
1363	This can be used to create very complex timers, such as a timer that	1513	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1514	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1515	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1516	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1517	reason I omitted it as an example).
1368		1518
1369	=back	1519	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	1523	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	1524	when you changed some parameters or the reschedule callback would return
1375	a different time than the last time it was called (e.g. in a crond like	1525	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1526	program when the crontabs have changed).
1377		1527
		1528	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1529
		1530	When active, returns the absolute time that the watcher is supposed to
		1531	trigger next.
		1532
1378	=item ev_tstamp offset [read-write]	1533	=item ev_tstamp offset [read-write]
1379		1534
1380	When repeating, this contains the offset value, otherwise this is the	1535	When repeating, this contains the offset value, otherwise this is the
1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1382		1537
…		…
1393		1548
1394	The current reschedule callback, or C<0>, if this functionality is	1549	The current reschedule callback, or C<0>, if this functionality is
1395	switched off. Can be changed any time, but changes only take effect when	1550	switched off. Can be changed any time, but changes only take effect when
1396	the periodic timer fires or C<ev_periodic_again> is being called.	1551	the periodic timer fires or C<ev_periodic_again> is being called.
1397		1552
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402
1403	=back	1553	=back
1404		1554
1405	=head3 Examples	1555	=head3 Examples
1406		1556
1407	Example: Call a callback every hour, or, more precisely, whenever the	1557	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1558	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1559	potentially a lot of jitter, but good long-term stability.
1410		1560
1411	static void	1561	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1413	{	1563	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1564	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1565	}
1416		1566
1417	struct ev_periodic hourly_tick;	1567	struct ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1569	ev_periodic_start (loop, &hourly_tick);
1420		1570
1421	Example: The same as above, but use a reschedule callback to do it:	1571	Example: The same as above, but use a reschedule callback to do it:
1422		1572
1423	#include <math.h>	1573	#include <math.h>
1424		1574
1425	static ev_tstamp	1575	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1427	{	1577	{
1428	return fmod (now, 3600.) + 3600.;	1578	return now + (3600. - fmod (now, 3600.));
1429	}	1579	}
1430		1580
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1582
1433	Example: Call a callback every hour, starting now:	1583	Example: Call a callback every hour, starting now:
1434		1584
1435	struct ev_periodic hourly_tick;	1585	struct ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1586	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1587	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1588	ev_periodic_start (loop, &hourly_tick);
1439		1589
1440		1590
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1591	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1592
1443	Signal watchers will trigger an event when the process receives a specific	1593	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1594	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1595	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1596	normal event processing, like any other event.
1447		1597
		1598	If you want signals asynchronously, just use C<sigaction> as you would
		1599	do without libev and forget about sharing the signal. You can even use
		1600	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1601
1448	You can configure as many watchers as you like per signal. Only when the	1602	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1603	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1604	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1605	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1606	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1607	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1608
1455	If possible and supported, libev will install its handlers with	1609	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1611	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1612	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1613	them in an C<ev_prepare> watcher.
1460		1614
1461	=head3 Watcher-Specific Functions and Data Members	1615	=head3 Watcher-Specific Functions and Data Members
1462		1616
…		…
1475		1629
1476	=back	1630	=back
1477		1631
1478	=head3 Examples	1632	=head3 Examples
1479		1633
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1634	Example: Try to exit cleanly on SIGINT.
1481		1635
1482	static void	1636	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1484	{	1638	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1639	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1640	}
1487		1641
1488	struct ev_signal signal_watcher;	1642	struct ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1644	ev_signal_start (loop, &signal_watcher);
1491		1645
1492		1646
1493	=head2 C<ev_child> - watch out for process status changes	1647	=head2 C<ev_child> - watch out for process status changes
1494		1648
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1649	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	1650	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	1651	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	1652	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	1653	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1654	forking and then immediately registering a watcher for the child is fine,
		1655	but forking and registering a watcher a few event loop iterations later is
		1656	not.
1500		1657
1501	Only the default event loop is capable of handling signals, and therefore	1658	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	1659	you can only register child watchers in the default event loop.
1503		1660
1504	=head3 Process Interaction	1661	=head3 Process Interaction
1505		1662
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	1663	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	1664	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	1665	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	1667	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	1668	children, even ones not watched.
1512		1669
1513	=head3 Overriding the Built-In Processing	1670	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	1674	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	1675	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	1676	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	1677	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.	1678	that, so other libev users can use C<ev_child> watchers freely.
		1679
		1680	=head3 Stopping the Child Watcher
		1681
		1682	Currently, the child watcher never gets stopped, even when the
		1683	child terminates, so normally one needs to stop the watcher in the
		1684	callback. Future versions of libev might stop the watcher automatically
		1685	when a child exit is detected.
1522		1686
1523	=head3 Watcher-Specific Functions and Data Members	1687	=head3 Watcher-Specific Functions and Data Members
1524		1688
1525	=over 4	1689	=over 4
1526		1690
…		…
1555	=head3 Examples	1719	=head3 Examples
1556		1720
1557	Example: C<fork()> a new process and install a child handler to wait for	1721	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	1722	its completion.
1559		1723
1560	ev_child cw;	1724	ev_child cw;
1561		1725
1562	static void	1726	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	1727	child_cb (EV_P_ struct ev_child *w, int revents)
1564	{	1728	{
1565	ev_child_stop (EV_A_ w);	1729	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	1731	}
1568		1732
1569	pid_t pid = fork ();	1733	pid_t pid = fork ();
1570		1734
1571	if (pid < 0)	1735	if (pid < 0)
1572	// error	1736	// error
1573	else if (pid == 0)	1737	else if (pid == 0)
1574	{	1738	{
1575	// the forked child executes here	1739	// the forked child executes here
1576	exit (1);	1740	exit (1);
1577	}	1741	}
1578	else	1742	else
1579	{	1743	{
1580	ev_child_init (&cw, child_cb, pid, 0);	1744	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	1745	ev_child_start (EV_DEFAULT_ &cw);
1582	}	1746	}
1583		1747
1584		1748
1585	=head2 C<ev_stat> - did the file attributes just change?	1749	=head2 C<ev_stat> - did the file attributes just change?
1586		1750
1587	This watches a filesystem path for attribute changes. That is, it calls	1751	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	1752	C<stat> regularly (or when the OS says it changed) and sees if it changed
1589	compared to the last time, invoking the callback if it did.	1753	compared to the last time, invoking the callback if it did.
1590		1754
1591	The path does not need to exist: changing from "path exists" to "path does	1755	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	1756	not exist" is a status change like any other. The condition "path does
…		…
1595	the stat buffer having unspecified contents.	1759	the stat buffer having unspecified contents.
1596		1760
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	1761	The path I<should> be absolute and I<must not> end in a slash. If it is
1598	relative and your working directory changes, the behaviour is undefined.	1762	relative and your working directory changes, the behaviour is undefined.
1599		1763
1600	Since there is no standard to do this, the portable implementation simply	1764	Since there is no standard kernel interface to do this, the portable
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1765	implementation simply calls C<stat (2)> regularly on the path to see if
1602	can specify a recommended polling interval for this case. If you specify	1766	it changed somehow. You can specify a recommended polling interval for
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	1767	this case. If you specify a polling interval of C<0> (highly recommended!)
1604	unspecified default> value will be used (which you can expect to be around	1768	then a I<suitable, unspecified default> value will be used (which
1605	five seconds, although this might change dynamically). Libev will also	1769	you can expect to be around five seconds, although this might change
1606	impose a minimum interval which is currently around C<0.1>, but thats	1770	dynamically). Libev will also impose a minimum interval which is currently
1607	usually overkill.	1771	around C<0.1>, but thats usually overkill.
1608		1772
1609	This watcher type is not meant for massive numbers of stat watchers,	1773	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	1774	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1775	resource-intensive.
1612		1776
1613	At the time of this writing, only the Linux inotify interface is	1777	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	1778	is the Linux inotify interface (implementing kqueue support is left as
1615	reader). Inotify will be used to give hints only and should not change the	1779	an exercise for the reader. Note, however, that the author sees no way
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1780	of implementing C<ev_stat> semantics with kqueue).
1617	to fall back to regular polling again even with inotify, but changes are
1618	usually detected immediately, and if the file exists there will be no
1619	polling.
1620		1781
1621	=head3 ABI Issues (Largefile Support)	1782	=head3 ABI Issues (Largefile Support)
1622		1783
1623	Libev by default (unless the user overrides this) uses the default	1784	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	1785	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	1786	support disabled by default, you get the 32 bit version of the stat
1626	structure. When using the library from programs that change the ABI to	1787	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	1788	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	1789	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	1790	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	1791	most noticeably disabled with ev_stat and large file support.
1631		1792
1632	=head3 Inotify	1793	The solution for this is to lobby your distribution maker to make large
		1794	file interfaces available by default (as e.g. FreeBSD does) and not
		1795	optional. Libev cannot simply switch on large file support because it has
		1796	to exchange stat structures with application programs compiled using the
		1797	default compilation environment.
1633		1798
		1799	=head3 Inotify and Kqueue
		1800
1634	When C<inotify (7)> support has been compiled into libev (generally only	1801	When C<inotify (7)> support has been compiled into libev (generally
		1802	only available with Linux 2.6.25 or above due to bugs in earlier
1635	available on Linux) and present at runtime, it will be used to speed up	1803	implementations) and present at runtime, it will be used to speed up
1636	change detection where possible. The inotify descriptor will be created lazily	1804	change detection where possible. The inotify descriptor will be created
1637	when the first C<ev_stat> watcher is being started.	1805	lazily when the first C<ev_stat> watcher is being started.
1638		1806
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	1807	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	1808	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	1809	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.	1810	there are many cases where libev has to resort to regular C<stat> polling,
		1811	but as long as the path exists, libev usually gets away without polling.
1643		1812
1644	(There is no support for kqueue, as apparently it cannot be used to	1813	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	1814	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	1815	descriptor open on the object at all times, and detecting renames, unlinks
		1816	etc. is difficult.
1647		1817
1648	=head3 The special problem of stat time resolution	1818	=head3 The special problem of stat time resolution
1649		1819
1650	The C<stat ()> syscall only supports full-second resolution portably, and	1820	The C<stat ()> system call only supports full-second resolution portably, and
1651	even on systems where the resolution is higher, many filesystems still	1821	even on systems where the resolution is higher, most file systems still
1652	only support whole seconds.	1822	only support whole seconds.
1653		1823
1654	That means that, if the time is the only thing that changes, you might	1824	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	1825	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	1826	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	1827	within the same second, C<ev_stat> will be unable to detect unless the
		1828	stat data does change in other ways (e.g. file size).
1658		1829
1659	The solution to this is to delay acting on a change for a second (or till	1830	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	1831	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1832	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	1833	ev_timer_again (loop, w)>).
1663	systems.	1834
		1835	The C<.02> offset is added to work around small timing inconsistencies
		1836	of some operating systems (where the second counter of the current time
		1837	might be be delayed. One such system is the Linux kernel, where a call to
		1838	C<gettimeofday> might return a timestamp with a full second later than
		1839	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1840	update file times then there will be a small window where the kernel uses
		1841	the previous second to update file times but libev might already execute
		1842	the timer callback).
1664		1843
1665	=head3 Watcher-Specific Functions and Data Members	1844	=head3 Watcher-Specific Functions and Data Members
1666		1845
1667	=over 4	1846	=over 4
1668		1847
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	1853	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	1854	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	1855	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	1856	path for as long as the watcher is active.
1678		1857
1679	The callback will be receive C<EV_STAT> when a change was detected,	1858	The callback will receive an C<EV_STAT> event when a change was detected,
1680	relative to the attributes at the time the watcher was started (or the	1859	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	1860	last change was detected).
1682		1861
1683	=item ev_stat_stat (loop, ev_stat *)	1862	=item ev_stat_stat (loop, ev_stat *)
1684		1863
1685	Updates the stat buffer immediately with new values. If you change the	1864	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	1865	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	1866	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	1867	the only one changing the path). Can also be useful simply to find out the
		1868	new values.
1689		1869
1690	=item ev_statdata attr [read-only]	1870	=item ev_statdata attr [read-only]
1691		1871
1692	The most-recently detected attributes of the file. Although the type is of	1872	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1873	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	1874	suitable for your system, but you can only rely on the POSIX-standardised
		1875	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	1876	some error while C<stat>ing the file.
1696		1877
1697	=item ev_statdata prev [read-only]	1878	=item ev_statdata prev [read-only]
1698		1879
1699	The previous attributes of the file. The callback gets invoked whenever	1880	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	1881	C<prev> != C<attr>, or, more precisely, one or more of these members
		1882	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1883	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		1884
1702	=item ev_tstamp interval [read-only]	1885	=item ev_tstamp interval [read-only]
1703		1886
1704	The specified interval.	1887	The specified interval.
1705		1888
1706	=item const char *path [read-only]	1889	=item const char *path [read-only]
1707		1890
1708	The filesystem path that is being watched.	1891	The file system path that is being watched.
1709		1892
1710	=back	1893	=back
1711		1894
1712	=head3 Examples	1895	=head3 Examples
1713		1896
1714	Example: Watch C</etc/passwd> for attribute changes.	1897	Example: Watch C</etc/passwd> for attribute changes.
1715		1898
1716	static void	1899	static void
1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1900	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1718	{	1901	{
1719	/* /etc/passwd changed in some way */	1902	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	1903	if (w->attr.st_nlink)
1721	{	1904	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1905	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1906	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1907	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	1908	}
1726	else	1909	else
1727	/* you shalt not abuse printf for puts */	1910	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	1911	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	1912	"if this is windows, they already arrived\n");
1730	}	1913	}
1731		1914
1732	...	1915	...
1733	ev_stat passwd;	1916	ev_stat passwd;
1734		1917
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1918	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	1919	ev_stat_start (loop, &passwd);
1737		1920
1738	Example: Like above, but additionally use a one-second delay so we do not	1921	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	1922	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	1923	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	1924	C<ev_timer> callback invocation).
1742		1925
1743	static ev_stat passwd;	1926	static ev_stat passwd;
1744	static ev_timer timer;	1927	static ev_timer timer;
1745		1928
1746	static void	1929	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	1930	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	1931	{
1749	ev_timer_stop (EV_A_ w);	1932	ev_timer_stop (EV_A_ w);
1750		1933
1751	/* now it's one second after the most recent passwd change */	1934	/* now it's one second after the most recent passwd change */
1752	}	1935	}
1753		1936
1754	static void	1937	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	1938	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	1939	{
1757	/* reset the one-second timer */	1940	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	1941	ev_timer_again (EV_A_ &timer);
1759	}	1942	}
1760		1943
1761	...	1944	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1945	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	1946	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	1947	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		1948
1766		1949
1767	=head2 C<ev_idle> - when you've got nothing better to do...	1950	=head2 C<ev_idle> - when you've got nothing better to do...
1768		1951
1769	Idle watchers trigger events when no other events of the same or higher	1952	Idle watchers trigger events when no other events of the same or higher
1770	priority are pending (prepare, check and other idle watchers do not	1953	priority are pending (prepare, check and other idle watchers do not count
1771	count).	1954	as receiving "events").
1772		1955
1773	That is, as long as your process is busy handling sockets or timeouts	1956	That is, as long as your process is busy handling sockets or timeouts
1774	(or even signals, imagine) of the same or higher priority it will not be	1957	(or even signals, imagine) of the same or higher priority it will not be
1775	triggered. But when your process is idle (or only lower-priority watchers	1958	triggered. But when your process is idle (or only lower-priority watchers
1776	are pending), the idle watchers are being called once per event loop	1959	are pending), the idle watchers are being called once per event loop
…		…
1800	=head3 Examples	1983	=head3 Examples
1801		1984
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1985	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	1986	callback, free it. Also, use no error checking, as usual.
1804		1987
1805	static void	1988	static void
1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1989	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1807	{	1990	{
1808	free (w);	1991	free (w);
1809	// now do something you wanted to do when the program has	1992	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	1993	// no longer anything immediate to do.
1811	}	1994	}
1812		1995
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1996	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	1997	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	1998	ev_idle_start (loop, idle_cb);
1816		1999
1817		2000
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2002
1820	Prepare and check watchers are usually (but not always) used in tandem:	2003	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2004	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2005	afterwards.
1823		2006
1824	You I<must not> call C<ev_loop> or similar functions that enter	2007	You I<must not> call C<ev_loop> or similar functions that enter
1825	the current event loop from either C<ev_prepare> or C<ev_check>	2008	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2011	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1829	C<ev_check> so if you have one watcher of each kind they will always be	2012	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2013	called in pairs bracketing the blocking call.
1831		2014
1832	Their main purpose is to integrate other event mechanisms into libev and	2015	Their main purpose is to integrate other event mechanisms into libev and
1833	their use is somewhat advanced. This could be used, for example, to track	2016	their use is somewhat advanced. They could be used, for example, to track
1834	variable changes, implement your own watchers, integrate net-snmp or a	2017	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2018	coroutine library and lots more. They are also occasionally useful if
1836	you cache some data and want to flush it before blocking (for example,	2019	you cache some data and want to flush it before blocking (for example,
1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2020	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2021	watcher).
1839		2022
1840	This is done by examining in each prepare call which file descriptors need	2023	This is done by examining in each prepare call which file descriptors
1841	to be watched by the other library, registering C<ev_io> watchers for	2024	need to be watched by the other library, registering C<ev_io> watchers
1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2025	for them and starting an C<ev_timer> watcher for any timeouts (many
1843	provide just this functionality). Then, in the check watcher you check for	2026	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2027	you check for any events that occurred (by checking the pending status
1845	and stopping them) and call back into the library. The I/O and timer	2028	of all watchers and stopping them) and call back into the library. The
1846	callbacks will never actually be called (but must be valid nevertheless,	2029	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2030	nevertheless, because you never know, you know?).
1848		2031
1849	As another example, the Perl Coro module uses these hooks to integrate	2032	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2033	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2034	during each prepare and only letting the process block if no coroutines
1852	are ready to run (it's actually more complicated: it only runs coroutines	2035	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1855	loop from blocking if lower-priority coroutines are active, thus mapping	2038	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2039	low-priority coroutines to idle/background tasks).
1857		2040
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2041	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	2042	priority, to ensure that they are being run before any other watchers
		2043	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2044
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2045	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1861	too) should not activate ("feed") events into libev. While libev fully	2046	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2047	might get executed before other C<ev_check> watchers did their job. As
1863	did their job. As C<ev_check> watchers are often used to embed other	2048	C<ev_check> watchers are often used to embed other (non-libev) event
1864	(non-libev) event loops those other event loops might be in an unusable	2049	loops those other event loops might be in an unusable state until their
1865	state until their C<ev_check> watcher ran (always remind yourself to	2050	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2051	others).
1867		2052
1868	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1869		2054
1870	=over 4	2055	=over 4
1871		2056
…		…
1873		2058
1874	=item ev_check_init (ev_check *, callback)	2059	=item ev_check_init (ev_check *, callback)
1875		2060
1876	Initialises and configures the prepare or check watcher - they have no	2061	Initialises and configures the prepare or check watcher - they have no
1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2062	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1878	macros, but using them is utterly, utterly and completely pointless.	2063	macros, but using them is utterly, utterly, utterly and completely
		2064	pointless.
1879		2065
1880	=back	2066	=back
1881		2067
1882	=head3 Examples	2068	=head3 Examples
1883		2069
1884	There are a number of principal ways to embed other event loops or modules	2070	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	2071	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	2072	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	2073	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2074	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2075	Glib event loop).
1890		2076
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2077	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	2078	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	2079	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2080	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1895	the callbacks for the IO/timeout watchers might not have been called yet.	2081	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2082
1897	static ev_io iow [nfd];	2083	static ev_io iow [nfd];
1898	static ev_timer tw;	2084	static ev_timer tw;
1899		2085
1900	static void	2086	static void
1901	io_cb (ev_loop *loop, ev_io *w, int revents)	2087	io_cb (ev_loop *loop, ev_io *w, int revents)
1902	{	2088	{
1903	}	2089	}
1904		2090
1905	// create io watchers for each fd and a timer before blocking	2091	// create io watchers for each fd and a timer before blocking
1906	static void	2092	static void
1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2093	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1908	{	2094	{
1909	int timeout = 3600000;	2095	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2096	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2097	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2098	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2099
1914	/* the callback is illegal, but won't be called as we stop during check */	2100	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2101	ev_timer_init (&tw, 0, timeout * 1e-3);
1916	ev_timer_start (loop, &tw);	2102	ev_timer_start (loop, &tw);
1917		2103
1918	// create one ev_io per pollfd	2104	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2105	for (int i = 0; i < nfd; ++i)
1920	{	2106	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2107	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2108	((fds [i].events & POLLIN ? EV_READ : 0)
1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2109	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2110
1925	fds [i].revents = 0;	2111	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2112	ev_io_start (loop, iow + i);
1927	}	2113	}
1928	}	2114	}
1929		2115
1930	// stop all watchers after blocking	2116	// stop all watchers after blocking
1931	static void	2117	static void
1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2118	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1933	{	2119	{
1934	ev_timer_stop (loop, &tw);	2120	ev_timer_stop (loop, &tw);
1935		2121
1936	for (int i = 0; i < nfd; ++i)	2122	for (int i = 0; i < nfd; ++i)
1937	{	2123	{
1938	// set the relevant poll flags	2124	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2125	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2126	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2127	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2128	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2129	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1944		2130
1945	// now stop the watcher	2131	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2132	ev_io_stop (loop, iow + i);
1947	}	2133	}
1948		2134
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2135	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2136	}
1951		2137
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2138	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1953	in the prepare watcher and would dispose of the check watcher.	2139	in the prepare watcher and would dispose of the check watcher.
1954		2140
1955	Method 3: If the module to be embedded supports explicit event	2141	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2142	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2143	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2144
1959	static void	2145	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2146	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2147	{
1962	adns_state ads = (adns_state)w->data;	2148	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2149	update_now (EV_A);
1964		2150
1965	adns_processtimeouts (ads, &tv_now);	2151	adns_processtimeouts (ads, &tv_now);
1966	}	2152	}
1967		2153
1968	static void	2154	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2155	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2156	{
1971	adns_state ads = (adns_state)w->data;	2157	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2158	update_now (EV_A);
1973		2159
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2160	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2161	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2162	}
1977		2163
1978	// do not ever call adns_afterpoll	2164	// do not ever call adns_afterpoll
1979		2165
1980	Method 4: Do not use a prepare or check watcher because the module you	2166	Method 4: Do not use a prepare or check watcher because the module you
1981	want to embed is too inflexible to support it. Instead, youc na override	2167	want to embed is not flexible enough to support it. Instead, you can
1982	their poll function. The drawback with this solution is that the main	2168	override their poll function. The drawback with this solution is that the
1983	loop is now no longer controllable by EV. The C<Glib::EV> module does	2169	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2170	this approach, effectively embedding EV as a client into the horrible
		2171	libglib event loop.
1985		2172
1986	static gint	2173	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2174	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2175	{
1989	int got_events = 0;	2176	int got_events = 0;
1990		2177
1991	for (n = 0; n < nfds; ++n)	2178	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2179	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2180
1994	if (timeout >= 0)	2181	if (timeout >= 0)
1995	// create/start timer	2182	// create/start timer
1996		2183
1997	// poll	2184	// poll
1998	ev_loop (EV_A_ 0);	2185	ev_loop (EV_A_ 0);
1999		2186
2000	// stop timer again	2187	// stop timer again
2001	if (timeout >= 0)	2188	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2189	ev_timer_stop (EV_A_ &to);
2003		2190
2004	// stop io watchers again - their callbacks should have set	2191	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2192	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2193	ev_io_stop (EV_A_ iow [n]);
2007		2194
2008	return got_events;	2195	return got_events;
2009	}	2196	}
2010		2197
2011		2198
2012	=head2 C<ev_embed> - when one backend isn't enough...	2199	=head2 C<ev_embed> - when one backend isn't enough...
2013		2200
2014	This is a rather advanced watcher type that lets you embed one event loop	2201	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2207	prioritise I/O.
2021		2208
2022	As an example for a bug workaround, the kqueue backend might only support	2209	As an example for a bug workaround, the kqueue backend might only support
2023	sockets on some platform, so it is unusable as generic backend, but you	2210	sockets on some platform, so it is unusable as generic backend, but you
2024	still want to make use of it because you have many sockets and it scales	2211	still want to make use of it because you have many sockets and it scales
2025	so nicely. In this case, you would create a kqueue-based loop and embed it	2212	so nicely. In this case, you would create a kqueue-based loop and embed
2026	into your default loop (which might use e.g. poll). Overall operation will	2213	it into your default loop (which might use e.g. poll). Overall operation
2027	be a bit slower because first libev has to poll and then call kevent, but	2214	will be a bit slower because first libev has to call C<poll> and then
2028	at least you can use both at what they are best.	2215	C<kevent>, but at least you can use both mechanisms for what they are
		2216	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2217
2030	As for prioritising I/O: rarely you have the case where some fds have	2218	As for prioritising I/O: under rare circumstances you have the case where
2031	to be watched and handled very quickly (with low latency), and even	2219	some fds have to be watched and handled very quickly (with low latency),
2032	priorities and idle watchers might have too much overhead. In this case	2220	and even priorities and idle watchers might have too much overhead. In
2033	you would put all the high priority stuff in one loop and all the rest in	2221	this case you would put all the high priority stuff in one loop and all
2034	a second one, and embed the second one in the first.	2222	the rest in a second one, and embed the second one in the first.
2035		2223
2036	As long as the watcher is active, the callback will be invoked every time	2224	As long as the watcher is active, the callback will be invoked every time
2037	there might be events pending in the embedded loop. The callback must then	2225	there might be events pending in the embedded loop. The callback must then
2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2039	their callbacks (you could also start an idle watcher to give the embedded	2227	their callbacks (you could also start an idle watcher to give the embedded
…		…
2047	interested in that.	2235	interested in that.
2048		2236
2049	Also, there have not currently been made special provisions for forking:	2237	Also, there have not currently been made special provisions for forking:
2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2051	but you will also have to stop and restart any C<ev_embed> watchers	2239	but you will also have to stop and restart any C<ev_embed> watchers
2052	yourself.	2240	yourself - but you can use a fork watcher to handle this automatically,
		2241	and future versions of libev might do just that.
2053		2242
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2243	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2245	portable one.
2057		2246
2058	So when you want to use this feature you will always have to be prepared	2247	So when you want to use this feature you will always have to be prepared
2059	that you cannot get an embeddable loop. The recommended way to get around	2248	that you cannot get an embeddable loop. The recommended way to get around
2060	this is to have a separate variables for your embeddable loop, try to	2249	this is to have a separate variables for your embeddable loop, try to
2061	create it, and if that fails, use the normal loop for everything.	2250	create it, and if that fails, use the normal loop for everything.
2062		2251
		2252	=head3 C<ev_embed> and fork
		2253
		2254	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2255	automatically be applied to the embedded loop as well, so no special
		2256	fork handling is required in that case. When the watcher is not running,
		2257	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2258	as applicable.
		2259
2063	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
2064		2261
2065	=over 4	2262	=over 4
2066		2263
2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2264	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2070		2267
2071	Configures the watcher to embed the given loop, which must be	2268	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	2269	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	2270	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,	2271	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).	2272	if you do not want that, you need to temporarily stop the embed watcher).
2076		2273
2077	=item ev_embed_sweep (loop, ev_embed *)	2274	=item ev_embed_sweep (loop, ev_embed *)
2078		2275
2079	Make a single, non-blocking sweep over the embedded loop. This works	2276	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	2277	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2278	appropriate way for embedded loops.
2082		2279
2083	=item struct ev_loop *other [read-only]	2280	=item struct ev_loop *other [read-only]
2084		2281
2085	The embedded event loop.	2282	The embedded event loop.
2086		2283
…		…
2088		2285
2089	=head3 Examples	2286	=head3 Examples
2090		2287
2091	Example: Try to get an embeddable event loop and embed it into the default	2288	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	2289	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	2290	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2291	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2292	used).
2096		2293
2097	struct ev_loop *loop_hi = ev_default_init (0);	2294	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2295	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2296	struct ev_embed embed;
2100		2297
2101	// see if there is a chance of getting one that works	2298	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2299	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2300	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2301	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2302	: 0;
2106		2303
2107	// if we got one, then embed it, otherwise default to loop_hi	2304	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2305	if (loop_lo)
2109	{	2306	{
2110	ev_embed_init (&embed, 0, loop_lo);	2307	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2308	ev_embed_start (loop_hi, &embed);
2112	}	2309	}
2113	else	2310	else
2114	loop_lo = loop_hi;	2311	loop_lo = loop_hi;
2115		2312
2116	Example: Check if kqueue is available but not recommended and create	2313	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2314	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2315	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2316	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2317
2121	struct ev_loop *loop = ev_default_init (0);	2318	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2319	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2320	struct ev_embed embed;
2124		2321
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2322	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2323	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2324	{
2128	ev_embed_init (&embed, 0, loop_socket);	2325	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2326	ev_embed_start (loop, &embed);
2130	}	2327	}
2131		2328
2132	if (!loop_socket)	2329	if (!loop_socket)
2133	loop_socket = loop;	2330	loop_socket = loop;
2134		2331
2135	// now use loop_socket for all sockets, and loop for everything else	2332	// now use loop_socket for all sockets, and loop for everything else
2136		2333
2137		2334
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2335	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2336
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2337	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2184	is that the author does not know of a simple (or any) algorithm for a	2381	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	2382	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2383	need elaborate support such as pthreads.
2187		2384
2188	That means that if you want to queue data, you have to provide your own	2385	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	2386	queue. But at least I can tell you how to implement locking around your
2190	queue:	2387	queue:
2191		2388
2192	=over 4	2389	=over 4
2193		2390
2194	=item queueing from a signal handler context	2391	=item queueing from a signal handler context
2195		2392
2196	To implement race-free queueing, you simply add to the queue in the signal	2393	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	2394	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2395	an example that does that for some fictitious SIGUSR1 handler:
2199		2396
2200	static ev_async mysig;	2397	static ev_async mysig;
2201		2398
2202	static void	2399	static void
2203	sigusr1_handler (void)	2400	sigusr1_handler (void)
…		…
2270		2467
2271	=item ev_async_init (ev_async *, callback)	2468	=item ev_async_init (ev_async *, callback)
2272		2469
2273	Initialises and configures the async watcher - it has no parameters of any	2470	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,	2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2275	believe me.	2472	trust me.
2276		2473
2277	=item ev_async_send (loop, ev_async *)	2474	=item ev_async_send (loop, ev_async *)
2278		2475
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2476	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	2477	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	2478	C<ev_feed_event>, this call is safe to do from other threads, signal or
2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	2480	section below on what exactly this means).
2284		2481
2285	This call incurs the overhead of a syscall only once per loop iteration,	2482	This call incurs the overhead of a system call only once per loop iteration,
2286	so while the overhead might be noticable, it doesn't apply to repeated	2483	so while the overhead might be noticeable, it doesn't apply to repeated
2287	calls to C<ev_async_send>.	2484	calls to C<ev_async_send>.
2288		2485
2289	=item bool = ev_async_pending (ev_async *)	2486	=item bool = ev_async_pending (ev_async *)
2290		2487
2291	Returns a non-zero value when C<ev_async_send> has been called on the	2488	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2293	event loop.	2490	event loop.
2294		2491
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2492	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,	2493	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	2494	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.	2495	quickly check whether invoking the loop might be a good idea.
2299		2496
2300	Not that this does I<not> check wether the watcher itself is pending, only	2497	Not that this does I<not> check whether the watcher itself is pending, only
2301	wether it has been requested to make this watcher pending.	2498	whether it has been requested to make this watcher pending.
2302		2499
2303	=back	2500	=back
2304		2501
2305		2502
2306	=head1 OTHER FUNCTIONS	2503	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	2507	=over 4
2311		2508
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2509	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		2510
2314	This function combines a simple timer and an I/O watcher, calls your	2511	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	2512	callback on whichever event happens first and automatically stops both
2316	watchers. This is useful if you want to wait for a single event on an fd	2513	watchers. This is useful if you want to wait for a single event on an fd
2317	or timeout without having to allocate/configure/start/stop/free one or	2514	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	2515	more watchers yourself.
2319		2516
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	2517	If C<fd> is less than 0, then no I/O watcher will be started and the
2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2518	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	2519	the given C<fd> and C<events> set will be created and started.
2323		2520
2324	If C<timeout> is less than 0, then no timeout watcher will be	2521	If C<timeout> is less than 0, then no timeout watcher will be
2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2522	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2523	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		2524
2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2525	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2330	passed an C<revents> set like normal event callbacks (a combination of	2526	passed an C<revents> set like normal event callbacks (a combination of
2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2527	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	2528	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2529	a timeout and an io event at the same time - you probably should give io
		2530	events precedence.
2333		2531
		2532	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2533
2334	static void stdin_ready (int revents, void *arg)	2534	static void stdin_ready (int revents, void *arg)
2335	{	2535	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	2536	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	2537	/* stdin might have data for us, joy! */;
		2538	else if (revents & EV_TIMEOUT)
		2539	/* doh, nothing entered */;
2340	}	2540	}
2341		2541
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		2543
2344	=item ev_feed_event (ev_loop *, watcher *, int revents)	2544	=item ev_feed_event (ev_loop *, watcher *, int revents)
2345		2545
2346	Feeds the given event set into the event loop, as if the specified event	2546	Feeds the given event set into the event loop, as if the specified event
2347	had happened for the specified watcher (which must be a pointer to an	2547	had happened for the specified watcher (which must be a pointer to an
…		…
2352	Feed an event on the given fd, as if a file descriptor backend detected	2552	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	2553	the given events it.
2354		2554
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	2555	=item ev_feed_signal_event (ev_loop *loop, int signum)
2356		2556
2357	Feed an event as if the given signal occured (C<loop> must be the default	2557	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	2558	loop!).
2359		2559
2360	=back	2560	=back
2361		2561
2362		2562
…		…
2391	=back	2591	=back
2392		2592
2393	=head1 C++ SUPPORT	2593	=head1 C++ SUPPORT
2394		2594
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2595	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2396	you to use some convinience methods to start/stop watchers and also change	2596	you to use some convenience methods to start/stop watchers and also change
2397	the callback model to a model using method callbacks on objects.	2597	the callback model to a model using method callbacks on objects.
2398		2598
2399	To use it,	2599	To use it,
2400		2600
2401	#include <ev++.h>	2601	#include <ev++.h>
2402		2602
2403	This automatically includes F<ev.h> and puts all of its definitions (many	2603	This automatically includes F<ev.h> and puts all of its definitions (many
2404	of them macros) into the global namespace. All C++ specific things are	2604	of them macros) into the global namespace. All C++ specific things are
2405	put into the C<ev> namespace. It should support all the same embedding	2605	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2606	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	2673	your compiler is good :), then the method will be fully inlined into the
2474	thunking function, making it as fast as a direct C callback.	2674	thunking function, making it as fast as a direct C callback.
2475		2675
2476	Example: simple class declaration and watcher initialisation	2676	Example: simple class declaration and watcher initialisation
2477		2677
2478	struct myclass	2678	struct myclass
2479	{	2679	{
2480	void io_cb (ev::io &w, int revents) { }	2680	void io_cb (ev::io &w, int revents) { }
2481	}	2681	}
2482		2682
2483	myclass obj;	2683	myclass obj;
2484	ev::io iow;	2684	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	2685	iow.set <myclass, &myclass::io_cb> (&obj);
2486		2686
2487	=item w->set<function> (void *data = 0)	2687	=item w->set<function> (void *data = 0)
2488		2688
2489	Also sets a callback, but uses a static method or plain function as	2689	Also sets a callback, but uses a static method or plain function as
2490	callback. The optional C<data> argument will be stored in the watcher's	2690	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		2692
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2693	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		2694
2495	See the method-C<set> above for more details.	2695	See the method-C<set> above for more details.
2496		2696
2497	Example:	2697	Example: Use a plain function as callback.
2498		2698
2499	static void io_cb (ev::io &w, int revents) { }	2699	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	2700	iow.set <io_cb> ();
2501		2701
2502	=item w->set (struct ev_loop *)	2702	=item w->set (struct ev_loop *)
2503		2703
2504	Associates a different C<struct ev_loop> with this watcher. You can only	2704	Associates a different C<struct ev_loop> with this watcher. You can only
2505	do this when the watcher is inactive (and not pending either).	2705	do this when the watcher is inactive (and not pending either).
2506		2706
2507	=item w->set ([args])	2707	=item w->set ([arguments])
2508		2708
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2709	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2510	called at least once. Unlike the C counterpart, an active watcher gets	2710	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	2711	automatically stopped and restarted when reconfiguring it with this
2512	method.	2712	method.
2513		2713
2514	=item w->start ()	2714	=item w->start ()
…		…
2538	=back	2738	=back
2539		2739
2540	Example: Define a class with an IO and idle watcher, start one of them in	2740	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	2741	the constructor.
2542		2742
2543	class myclass	2743	class myclass
2544	{	2744	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	2745	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	2746	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		2747
2548	myclass (int fd)	2748	myclass (int fd)
2549	{	2749	{
2550	io .set <myclass, &myclass::io_cb > (this);	2750	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	2751	idle.set <myclass, &myclass::idle_cb> (this);
2552		2752
2553	io.start (fd, ev::READ);	2753	io.start (fd, ev::READ);
2554	}	2754	}
2555	};	2755	};
2556		2756
2557		2757
2558	=head1 OTHER LANGUAGE BINDINGS	2758	=head1 OTHER LANGUAGE BINDINGS
2559		2759
2560	Libev does not offer other language bindings itself, but bindings for a	2760	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	2761	number of 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	2762	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	2763	me a note.
2564		2764
2565	=over 4	2765	=over 4
2566		2766
2567	=item Perl	2767	=item Perl
2568		2768
2569	The EV module implements the full libev API and is actually used to test	2769	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,	2770	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	2771	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	2772	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2773	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2774	and C<EV::Glib>).
2574		2775
2575	It can be found and installed via CPAN, its homepage is found at	2776	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	2777	L<http://software.schmorp.de/pkg/EV>.
2577		2778
		2779	=item Python
		2780
		2781	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2782	seems to be quite complete and well-documented. Note, however, that the
		2783	patch they require for libev is outright dangerous as it breaks the ABI
		2784	for everybody else, and therefore, should never be applied in an installed
		2785	libev (if python requires an incompatible ABI then it needs to embed
		2786	libev).
		2787
2578	=item Ruby	2788	=item Ruby
2579		2789
2580	Tony Arcieri has written a ruby extension that offers access to a subset	2790	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	2791	of the libev API and adds file handle abstractions, asynchronous DNS and
2582	more on top of it. It can be found via gem servers. Its homepage is at	2792	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	2793	L<http://rev.rubyforge.org/>.
2584		2794
2585	=item D	2795	=item D
2586		2796
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2797	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>.	2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2589		2799
2590	=back	2800	=back
2591		2801
2592		2802
2593	=head1 MACRO MAGIC	2803	=head1 MACRO MAGIC
2594		2804
2595	Libev can be compiled with a variety of options, the most fundamantal	2805	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2806	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	2807	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		2808
2599	To make it easier to write programs that cope with either variant, the	2809	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	2810	following macros are defined:
…		…
2605		2815
2606	This provides the loop I<argument> for functions, if one is required ("ev	2816	This provides the loop I<argument> for functions, if one is required ("ev
2607	loop argument"). The C<EV_A> form is used when this is the sole argument,	2817	loop argument"). The C<EV_A> form is used when this is the sole argument,
2608	C<EV_A_> is used when other arguments are following. Example:	2818	C<EV_A_> is used when other arguments are following. Example:
2609		2819
2610	ev_unref (EV_A);	2820	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	2821	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	2822	ev_loop (EV_A_ 0);
2613		2823
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2824	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	2825	which is often provided by the following macro.
2616		2826
2617	=item C<EV_P>, C<EV_P_>	2827	=item C<EV_P>, C<EV_P_>
2618		2828
2619	This provides the loop I<parameter> for functions, if one is required ("ev	2829	This provides the loop I<parameter> for functions, if one is required ("ev
2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2830	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2621	C<EV_P_> is used when other parameters are following. Example:	2831	C<EV_P_> is used when other parameters are following. Example:
2622		2832
2623	// this is how ev_unref is being declared	2833	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	2834	static void ev_unref (EV_P);
2625		2835
2626	// this is how you can declare your typical callback	2836	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	2837	static void cb (EV_P_ ev_timer *w, int revents)
2628		2838
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2839	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	2840	suitable for use with C<EV_A>.
2631		2841
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2842	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		2858
2649	Example: Declare and initialise a check watcher, utilising the above	2859	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	2860	macros so it will work regardless of whether multiple loops are supported
2651	or not.	2861	or not.
2652		2862
2653	static void	2863	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	2864	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	2865	{
2656	ev_check_stop (EV_A_ w);	2866	ev_check_stop (EV_A_ w);
2657	}	2867	}
2658		2868
2659	ev_check check;	2869	ev_check check;
2660	ev_check_init (&check, check_cb);	2870	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	2871	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	2872	ev_loop (EV_DEFAULT_ 0);
2663		2873
2664	=head1 EMBEDDING	2874	=head1 EMBEDDING
2665		2875
2666	Libev can (and often is) directly embedded into host	2876	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	2877	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	2884	libev somewhere in your source tree).
2675		2885
2676	=head2 FILESETS	2886	=head2 FILESETS
2677		2887
2678	Depending on what features you need you need to include one or more sets of files	2888	Depending on what features you need you need to include one or more sets of files
2679	in your app.	2889	in your application.
2680		2890
2681	=head3 CORE EVENT LOOP	2891	=head3 CORE EVENT LOOP
2682		2892
2683	To include only the libev core (all the C<ev_*> functions), with manual	2893	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	2894	configuration (no autoconf):
2685		2895
2686	#define EV_STANDALONE 1	2896	#define EV_STANDALONE 1
2687	#include "ev.c"	2897	#include "ev.c"
2688		2898
2689	This will automatically include F<ev.h>, too, and should be done in a	2899	This will automatically include F<ev.h>, too, and should be done in a
2690	single C source file only to provide the function implementations. To use	2900	single C source file only to provide the function implementations. To use
2691	it, do the same for F<ev.h> in all files wishing to use this API (best	2901	it, do the same for F<ev.h> in all files wishing to use this API (best
2692	done by writing a wrapper around F<ev.h> that you can include instead and	2902	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	2903	where you can put other configuration options):
2694		2904
2695	#define EV_STANDALONE 1	2905	#define EV_STANDALONE 1
2696	#include "ev.h"	2906	#include "ev.h"
2697		2907
2698	Both header files and implementation files can be compiled with a C++	2908	Both header files and implementation files can be compiled with a C++
2699	compiler (at least, thats a stated goal, and breakage will be treated	2909	compiler (at least, thats a stated goal, and breakage will be treated
2700	as a bug).	2910	as a bug).
2701		2911
2702	You need the following files in your source tree, or in a directory	2912	You need the following files in your source tree, or in a directory
2703	in your include path (e.g. in libev/ when using -Ilibev):	2913	in your include path (e.g. in libev/ when using -Ilibev):
2704		2914
2705	ev.h	2915	ev.h
2706	ev.c	2916	ev.c
2707	ev_vars.h	2917	ev_vars.h
2708	ev_wrap.h	2918	ev_wrap.h
2709		2919
2710	ev_win32.c required on win32 platforms only	2920	ev_win32.c required on win32 platforms only
2711		2921
2712	ev_select.c only when select backend is enabled (which is enabled by default)	2922	ev_select.c only when select backend is enabled (which is enabled by default)
2713	ev_poll.c only when poll backend is enabled (disabled by default)	2923	ev_poll.c only when poll backend is enabled (disabled by default)
2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2924	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2925	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2716	ev_port.c only when the solaris port backend is enabled (disabled by default)	2926	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		2927
2718	F<ev.c> includes the backend files directly when enabled, so you only need	2928	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	2929	to compile this single file.
2720		2930
2721	=head3 LIBEVENT COMPATIBILITY API	2931	=head3 LIBEVENT COMPATIBILITY API
2722		2932
2723	To include the libevent compatibility API, also include:	2933	To include the libevent compatibility API, also include:
2724		2934
2725	#include "event.c"	2935	#include "event.c"
2726		2936
2727	in the file including F<ev.c>, and:	2937	in the file including F<ev.c>, and:
2728		2938
2729	#include "event.h"	2939	#include "event.h"
2730		2940
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	2941	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		2942
2733	You need the following additional files for this:	2943	You need the following additional files for this:
2734		2944
2735	event.h	2945	event.h
2736	event.c	2946	event.c
2737		2947
2738	=head3 AUTOCONF SUPPORT	2948	=head3 AUTOCONF SUPPORT
2739		2949
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	2950	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2741	whatever way you want, you can also C<m4_include([libev.m4])> in your	2951	whatever way you want, you can also C<m4_include([libev.m4])> in your
2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2952	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	2953	include F<config.h> and configure itself accordingly.
2744		2954
2745	For this of course you need the m4 file:	2955	For this of course you need the m4 file:
2746		2956
2747	libev.m4	2957	libev.m4
2748		2958
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	2959	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		2960
2751	Libev can be configured via a variety of preprocessor symbols you have to	2961	Libev can be configured via a variety of preprocessor symbols you have to
2752	define before including any of its files. The default in the absense of	2962	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	2963	autoconf is documented for every option.
2754		2964
2755	=over 4	2965	=over 4
2756		2966
2757	=item EV_STANDALONE	2967	=item EV_STANDALONE
2758		2968
…		…
2763	F<event.h> that are not directly supported by the libev core alone.	2973	F<event.h> that are not directly supported by the libev core alone.
2764		2974
2765	=item EV_USE_MONOTONIC	2975	=item EV_USE_MONOTONIC
2766		2976
2767	If defined to be C<1>, libev will try to detect the availability of the	2977	If defined to be C<1>, libev will try to detect the availability of the
2768	monotonic clock option at both compiletime and runtime. Otherwise no use	2978	monotonic clock option at both compile time and runtime. Otherwise no use
2769	of the monotonic clock option will be attempted. If you enable this, you	2979	of the monotonic clock option will be attempted. If you enable this, you
2770	usually have to link against librt or something similar. Enabling it when	2980	usually have to link against librt or something similar. Enabling it when
2771	the functionality isn't available is safe, though, although you have	2981	the functionality isn't available is safe, though, although you have
2772	to make sure you link against any libraries where the C<clock_gettime>	2982	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	2983	function is hiding in (often F<-lrt>).
2774		2984
2775	=item EV_USE_REALTIME	2985	=item EV_USE_REALTIME
2776		2986
2777	If defined to be C<1>, libev will try to detect the availability of the	2987	If defined to be C<1>, libev will try to detect the availability of the
2778	realtime clock option at compiletime (and assume its availability at	2988	real-time clock option at compile time (and assume its availability at
2779	runtime if successful). Otherwise no use of the realtime clock option will	2989	runtime if successful). Otherwise no use of the real-time clock option will
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2990	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2991	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2992	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2783		2993
2784	=item EV_USE_NANOSLEEP	2994	=item EV_USE_NANOSLEEP
…		…
2795	2.7 or newer, otherwise disabled.	3005	2.7 or newer, otherwise disabled.
2796		3006
2797	=item EV_USE_SELECT	3007	=item EV_USE_SELECT
2798		3008
2799	If undefined or defined to be C<1>, libev will compile in support for the	3009	If undefined or defined to be C<1>, libev will compile in support for the
2800	C<select>(2) backend. No attempt at autodetection will be done: if no	3010	C<select>(2) backend. No attempt at auto-detection will be done: if no
2801	other method takes over, select will be it. Otherwise the select backend	3011	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3012	will not be compiled in.
2803		3013
2804	=item EV_SELECT_USE_FD_SET	3014	=item EV_SELECT_USE_FD_SET
2805		3015
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3016	If defined to C<1>, then the select backend will use the system C<fd_set>
2807	structure. This is useful if libev doesn't compile due to a missing	3017	structure. This is useful if libev doesn't compile due to a missing
2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3018	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2809	exotic systems. This usually limits the range of file descriptors to some	3019	exotic systems. This usually limits the range of file descriptors to some
2810	low limit such as 1024 or might have other limitations (winsocket only	3020	low limit such as 1024 or might have other limitations (winsocket only
2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3021	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2812	influence the size of the C<fd_set> used.	3022	influence the size of the C<fd_set> used.
2813		3023
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3072	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3073	backend for Solaris 10 systems.
2864		3074
2865	=item EV_USE_DEVPOLL	3075	=item EV_USE_DEVPOLL
2866		3076
2867	reserved for future expansion, works like the USE symbols above.	3077	Reserved for future expansion, works like the USE symbols above.
2868		3078
2869	=item EV_USE_INOTIFY	3079	=item EV_USE_INOTIFY
2870		3080
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3081	If defined to be C<1>, libev will compile in support for the Linux inotify
2872	interface to speed up C<ev_stat> watchers. Its actual availability will	3082	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2879	access is atomic with respect to other threads or signal contexts. No such	3089	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	3090	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"	3091	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.	3092	as well as for signal and thread safety in C<ev_async> watchers.
2883		3093
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3094	In the absence of this define, libev will use C<sig_atomic_t volatile>
2885	(from F<signal.h>), which is usually good enough on most platforms.	3095	(from F<signal.h>), which is usually good enough on most platforms.
2886		3096
2887	=item EV_H	3097	=item EV_H
2888		3098
2889	The name of the F<ev.h> header file used to include it. The default if	3099	The name of the F<ev.h> header file used to include it. The default if
…		…
2928	When doing priority-based operations, libev usually has to linearly search	3138	When doing priority-based operations, libev usually has to linearly search
2929	all the priorities, so having many of them (hundreds) uses a lot of space	3139	all the priorities, so having many of them (hundreds) uses a lot of space
2930	and time, so using the defaults of five priorities (-2 .. +2) is usually	3140	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3141	fine.
2932		3142
2933	If your embedding app does not need any priorities, defining these both to	3143	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3144	both to C<0> will save some memory and CPU.
2935		3145
2936	=item EV_PERIODIC_ENABLE	3146	=item EV_PERIODIC_ENABLE
2937		3147
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3148	If undefined or defined to be C<1>, then periodic timers are supported. If
2939	defined to be C<0>, then they are not. Disabling them saves a few kB of	3149	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3156	code.
2947		3157
2948	=item EV_EMBED_ENABLE	3158	=item EV_EMBED_ENABLE
2949		3159
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3160	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3161	defined to be C<0>, then they are not. Embed watchers rely on most other
		3162	watcher types, which therefore must not be disabled.
2952		3163
2953	=item EV_STAT_ENABLE	3164	=item EV_STAT_ENABLE
2954		3165
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3166	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3167	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3177	defined to be C<0>, then they are not.
2967		3178
2968	=item EV_MINIMAL	3179	=item EV_MINIMAL
2969		3180
2970	If you need to shave off some kilobytes of code at the expense of some	3181	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	3182	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3183	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3184	much smaller 2-heap for timer management over the default 4-heap.
2973		3185
2974	=item EV_PID_HASHSIZE	3186	=item EV_PID_HASHSIZE
2975		3187
2976	C<ev_child> watchers use a small hash table to distribute workload by	3188	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3189	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3196	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3197	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3198	watchers you might want to increase this value (I<must> be a power of
2987	two).	3199	two).
2988		3200
		3201	=item EV_USE_4HEAP
		3202
		3203	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3204	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3205	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3206	faster performance with many (thousands) of watchers.
		3207
		3208	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3209	(disabled).
		3210
		3211	=item EV_HEAP_CACHE_AT
		3212
		3213	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3214	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3215	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3216	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3217	but avoids random read accesses on heap changes. This improves performance
		3218	noticeably with many (hundreds) of watchers.
		3219
		3220	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3221	(disabled).
		3222
		3223	=item EV_VERIFY
		3224
		3225	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3226	be done: If set to C<0>, no internal verification code will be compiled
		3227	in. If set to C<1>, then verification code will be compiled in, but not
		3228	called. If set to C<2>, then the internal verification code will be
		3229	called once per loop, which can slow down libev. If set to C<3>, then the
		3230	verification code will be called very frequently, which will slow down
		3231	libev considerably.
		3232
		3233	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3234	C<0>.
		3235
2989	=item EV_COMMON	3236	=item EV_COMMON
2990		3237
2991	By default, all watchers have a C<void *data> member. By redefining	3238	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3239	this macro to a something else you can include more and other types of
2993	members. You have to define it each time you include one of the files,	3240	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3241	though, and it must be identical each time.
2995		3242
2996	For example, the perl EV module uses something like this:	3243	For example, the perl EV module uses something like this:
2997		3244
2998	#define EV_COMMON \	3245	#define EV_COMMON \
2999	SV *self; /* contains this struct */ \	3246	SV *self; /* contains this struct */ \
3000	SV *cb_sv, *fh /* note no trailing ";" */	3247	SV *cb_sv, *fh /* note no trailing ";" */
3001		3248
3002	=item EV_CB_DECLARE (type)	3249	=item EV_CB_DECLARE (type)
3003		3250
3004	=item EV_CB_INVOKE (watcher, revents)	3251	=item EV_CB_INVOKE (watcher, revents)
3005		3252
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3257	definition and a statement, respectively. See the F<ev.h> header file for
3011	their default definitions. One possible use for overriding these is to	3258	their default definitions. One possible use for overriding these is to
3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3259	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3013	method calls instead of plain function calls in C++.	3260	method calls instead of plain function calls in C++.
3014		3261
		3262	=back
		3263
3015	=head2 EXPORTED API SYMBOLS	3264	=head2 EXPORTED API SYMBOLS
3016		3265
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3266	If you need to re-export the API (e.g. via a DLL) and you need a list of
3018	exported symbols, you can use the provided F<Symbol.*> files which list	3267	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3268	all public symbols, one per line:
3020		3269
3021	Symbols.ev for libev proper	3270	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3271	Symbols.event for the libevent emulation
3023		3272
3024	This can also be used to rename all public symbols to avoid clashes with	3273	This can also be used to rename all public symbols to avoid clashes with
3025	multiple versions of libev linked together (which is obviously bad in	3274	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3275	itself, but sometimes it is inconvenient to avoid this).
3027		3276
3028	A sed command like this will create wrapper C<#define>'s that you need to	3277	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3278	include before including F<ev.h>:
3030		3279
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3280	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3297	file.
3049		3298
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3299	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3051	that everybody includes and which overrides some configure choices:	3300	that everybody includes and which overrides some configure choices:
3052		3301
3053	#define EV_MINIMAL 1	3302	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3303	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3304	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3305	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3306	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3307	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3308	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3309	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3310	#define EV_MAXPRI 0
3062		3311
3063	#include "ev++.h"	3312	#include "ev++.h"
3064		3313
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3314	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3315
3067	#include "ev_cpp.h"	3316	#include "ev_cpp.h"
3068	#include "ev.c"	3317	#include "ev.c"
3069		3318
		3319	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3320
3071	=head1 THREADS AND COROUTINES	3321	=head2 THREADS AND COROUTINES
3072		3322
3073	=head2 THREADS	3323	=head3 THREADS
3074		3324
3075	Libev itself is completely threadsafe, but it uses no locking. This	3325	All libev functions are reentrant and thread-safe unless explicitly
		3326	documented otherwise, but libev implements no locking itself. This means
3076	means that you can use as many loops as you want in parallel, as long as	3327	that you can use as many loops as you want in parallel, as long as there
3077	only one thread ever calls into one libev function with the same loop	3328	are no concurrent calls into any libev function with the same loop
3078	parameter.	3329	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3330	of course): libev guarantees that different event loops share no data
		3331	structures that need any locking.
3079		3332
3080	Or put differently: calls with different loop parameters can be done in	3333	Or to put it differently: calls with different loop parameters can be done
3081	parallel from multiple threads, calls with the same loop parameter must be	3334	concurrently from multiple threads, calls with the same loop parameter
3082	done serially (but can be done from different threads, as long as only one	3335	must be done serially (but can be done from different threads, as long as
3083	thread ever is inside a call at any point in time, e.g. by using a mutex	3336	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3337	a mutex per loop).
3085		3338
3086	If you want to know which design is best for your problem, then I cannot	3339	Specifically to support threads (and signal handlers), libev implements
		3340	so-called C<ev_async> watchers, which allow some limited form of
		3341	concurrency on the same event loop, namely waking it up "from the
		3342	outside".
		3343
		3344	If you want to know which design (one loop, locking, or multiple loops
		3345	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3346	help you, but here is some generic advice:
3088		3347
3089	=over 4	3348	=over 4
3090		3349
3091	=item * most applications have a main thread: use the default libev loop	3350	=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.	3351	in that thread, or create a separate thread running only the default loop.
3093		3352
3094	This helps integrating other libraries or software modules that use libev	3353	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	3354	themselves and don't care/know about threading.
3096		3355
3097	=item * one loop per thread is usually a good model.	3356	=item * one loop per thread is usually a good model.
3098		3357
3099	Doing this is almost never wrong, sometimes a better-performance model	3358	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	3359	exists, but it is always a good start.
3101		3360
3102	=item * other models exist, such as the leader/follower pattern, where one	3361	=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.	3362	loop is handed through multiple threads in a kind of round-robin fashion.
3104		3363
3105	Chosing a model is hard - look around, learn, know that usually you cna do	3364	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	3365	better than you currently do :-)
3107		3366
3108	=item * often you need to talk to some other thread which blocks in the	3367	=item * often you need to talk to some other thread which blocks in the
		3368	event loop.
		3369
3109	event loop - C<ev_async> watchers can be used to wake them up from other	3370	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	3371	(or from signal contexts...).
		3372
		3373	An example use would be to communicate signals or other events that only
		3374	work in the default loop by registering the signal watcher with the
		3375	default loop and triggering an C<ev_async> watcher from the default loop
		3376	watcher callback into the event loop interested in the signal.
3111		3377
3112	=back	3378	=back
3113		3379
3114	=head2 COROUTINES	3380	=head3 COROUTINES
3115		3381
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	3382	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	3383	libev fully supports nesting calls to its functions from different
3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3384	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	3385	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	3386	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.	3387	you must not do this from C<ev_periodic> reschedule callbacks.
3122		3388
3123	Care has been invested into making sure that libev does not keep local	3389	Care has been taken to ensure that libev does not keep local state inside
3124	state inside C<ev_loop>, and other calls do not usually allow coroutine	3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	3391	they do not clal any callbacks.
3126		3392
		3393	=head2 COMPILER WARNINGS
3127		3394
3128	=head1 COMPLEXITIES	3395	Depending on your compiler and compiler settings, you might get no or a
		3396	lot of warnings when compiling libev code. Some people are apparently
		3397	scared by this.
3129		3398
3130	In this section the complexities of (many of) the algorithms used inside	3399	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	3400	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	3401	warning options. "Warn-free" code therefore cannot be a goal except when
		3402	targeting a specific compiler and compiler-version.
3133		3403
3134	All of the following are about amortised time: If an array needs to be	3404	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	3405	workarounds, or other changes to the code that make it less clear and less
3136	happens asymptotically never with higher number of elements, so O(1) might	3406	maintainable.
3137	mean it might do a lengthy realloc operation in rare cases, but on average
3138	it is much faster and asymptotically approaches constant time.
3139		3407
3140	=over 4	3408	And of course, some compiler warnings are just plain stupid, or simply
		3409	wrong (because they don't actually warn about the condition their message
		3410	seems to warn about). For example, certain older gcc versions had some
		3411	warnings that resulted an extreme number of false positives. These have
		3412	been fixed, but some people still insist on making code warn-free with
		3413	such buggy versions.
3141		3414
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3415	While libev is written to generate as few warnings as possible,
		3416	"warn-free" code is not a goal, and it is recommended not to build libev
		3417	with any compiler warnings enabled unless you are prepared to cope with
		3418	them (e.g. by ignoring them). Remember that warnings are just that:
		3419	warnings, not errors, or proof of bugs.
3143		3420
3144	This means that, when you have a watcher that triggers in one hour and
3145	there are 100 watchers that would trigger before that then inserting will
3146	have to skip roughly seven (C<ld 100>) of these watchers.
3147		3421
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3422	=head2 VALGRIND
3149		3423
3150	That means that changing a timer costs less than removing/adding them	3424	Valgrind has a special section here because it is a popular tool that is
3151	as only the relative motion in the event queue has to be paid for.	3425	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		3426
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3427	If you think you found a bug (memory leak, uninitialised data access etc.)
		3428	in libev, then check twice: If valgrind reports something like:
3154		3429
3155	These just add the watcher into an array or at the head of a list.	3430	==2274== definitely lost: 0 bytes in 0 blocks.
		3431	==2274== possibly lost: 0 bytes in 0 blocks.
		3432	==2274== still reachable: 256 bytes in 1 blocks.
3156		3433
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3434	Then there is no memory leak, just as memory accounted to global variables
		3435	is not a memleak - the memory is still being refernced, and didn't leak.
3158		3436
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3437	Similarly, under some circumstances, valgrind might report kernel bugs
		3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3439	although an acceptable workaround has been found here), or it might be
		3440	confused.
3160		3441
3161	These watchers are stored in lists then need to be walked to find the	3442	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3162	correct watcher to remove. The lists are usually short (you don't usually	3443	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		3444
3165	=item Finding the next timer in each loop iteration: O(1)	3445	If you are unsure about something, feel free to contact the mailing list
		3446	with the full valgrind report and an explanation on why you think this
		3447	is a bug in libev (best check the archives, too :). However, don't be
		3448	annoyed when you get a brisk "this is no bug" answer and take the chance
		3449	of learning how to interpret valgrind properly.
3166		3450
3167	By virtue of using a binary heap, the next timer is always found at the	3451	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	3452	I suggest using suppression lists.
3169		3453
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3454
3172	A change means an I/O watcher gets started or stopped, which requires	3455	=head1 PORTABILITY NOTES
3173	libev to recalculate its status (and possibly tell the kernel, depending
3174	on backend and wether C<ev_io_set> was used).
3175		3456
3176	=item Activating one watcher (putting it into the pending state): O(1)	3457	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3177
3178	=item Priority handling: O(number_of_priorities)
3179
3180	Priorities are implemented by allocating some space for each
3181	priority. When doing priority-based operations, libev usually has to
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.
3194
3195	=back
3196
3197
3198	=head1 Win32 platform limitations and workarounds
3199		3458
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3459	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	3460	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	3461	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3462	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3463	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3464	e.g. cygwin.
3206		3465
		3466	Lifting these limitations would basically require the full
		3467	re-implementation of the I/O system. If you are into these kinds of
		3468	things, then note that glib does exactly that for you in a very portable
		3469	way (note also that glib is the slowest event library known to man).
		3470
3207	There is no supported compilation method available on windows except	3471	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3472	embedding it into other applications.
3209		3473
		3474	Not a libev limitation but worth mentioning: windows apparently doesn't
		3475	accept large writes: instead of resulting in a partial write, windows will
		3476	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3477	so make sure you only write small amounts into your sockets (less than a
		3478	megabyte seems safe, but this apparently depends on the amount of memory
		3479	available).
		3480
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3481	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	3482	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3483	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	3484	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	3485	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3486	notification model, which cannot be implemented efficiently on windows
		3487	(Microsoft monopoly games).
		3488
		3489	A typical way to use libev under windows is to embed it (see the embedding
		3490	section for details) and use the following F<evwrap.h> header file instead
		3491	of F<ev.h>:
		3492
		3493	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3494	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3495
		3496	#include "ev.h"
		3497
		3498	And compile the following F<evwrap.c> file into your project (make sure
		3499	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3500
		3501	#include "evwrap.h"
		3502	#include "ev.c"
3216		3503
3217	=over 4	3504	=over 4
3218		3505
3219	=item The winsocket select function	3506	=item The winsocket select function
3220		3507
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3508	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	3509	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3510	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3511	requires a mapping from file descriptors to socket handles (the Microsoft
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3512	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	3513	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3514	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3515
3228	The configuration for a "naked" win32 using the microsoft runtime	3516	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	3517	libraries and raw winsocket select is:
3230		3518
3231	#define EV_USE_SELECT 1	3519	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3520	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		3521
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3522	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.	3523	complexity in the O(n²) range when using win32.
3236		3524
3237	=item Limited number of file descriptors	3525	=item Limited number of file descriptors
3238		3526
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3527	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3528
		3529	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	3530	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	3531	can only wait for C<64> things at the same time internally; Microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	3532	recommends spawning a chain of threads and wait for 63 handles and the
		3533	previous thread in each. Great).
3244		3534
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3535	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	3536	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	3537	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3538	select emulation on windows).
3249		3539
3250	Another limit is the number of file descriptors in the microsoft runtime	3540	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	3541	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	3542	or something like this inside Microsoft). You can increase this by calling
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3543	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	3544	arbitrary limit), but is broken in many versions of the Microsoft runtime
3255	libraries.	3545	libraries.
3256		3546
3257	This might get you to about C<512> or C<2048> sockets (depending on	3547	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	3548	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	3549	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.	3550	calling select (O(n²)) will likely make this unworkable.
3261		3551
3262	=back	3552	=back
3263		3553
3264
3265	=head1 PORTABILITY REQUIREMENTS	3554	=head2 PORTABILITY REQUIREMENTS
3266		3555
3267	In addition to a working ISO-C implementation, libev relies on a few	3556	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	3557	backend-specific APIs, libev relies on a few additional extensions:
3269		3558
3270	=over 4	3559	=over 4
3271		3560
		3561	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3562	calling conventions regardless of C<ev_watcher_type *>.
		3563
		3564	Libev assumes not only that all watcher pointers have the same internal
		3565	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3566	assumes that the same (machine) code can be used to call any watcher
		3567	callback: The watcher callbacks have different type signatures, but libev
		3568	calls them using an C<ev_watcher *> internally.
		3569
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	3570	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		3571
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	3572	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	3573	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3276	threads. This is not part of the specification for C<sig_atomic_t>, but is	3574	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	3575	believed to be sufficiently portable.
3278		3576
3279	=item C<sigprocmask> must work in a threaded environment	3577	=item C<sigprocmask> must work in a threaded environment
3280		3578
…		…
3287		3585
3288	The most portable way to handle signals is to block signals in all threads	3586	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	3587	except the initial one, and run the default loop in the initial thread as
3290	well.	3588	well.
3291		3589
		3590	=item C<long> must be large enough for common memory allocation sizes
		3591
		3592	To improve portability and simplify its API, libev uses C<long> internally
		3593	instead of C<size_t> when allocating its data structures. On non-POSIX
		3594	systems (Microsoft...) this might be unexpectedly low, but is still at
		3595	least 31 bits everywhere, which is enough for hundreds of millions of
		3596	watchers.
		3597
		3598	=item C<double> must hold a time value in seconds with enough accuracy
		3599
		3600	The type C<double> is used to represent timestamps. It is required to
		3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3602	enough for at least into the year 4000. This requirement is fulfilled by
		3603	implementations implementing IEEE 754 (basically all existing ones).
		3604
3292	=back	3605	=back
3293		3606
3294	If you know of other additional requirements drop me a note.	3607	If you know of other additional requirements drop me a note.
3295		3608
3296		3609
		3610	=head1 ALGORITHMIC COMPLEXITIES
		3611
		3612	In this section the complexities of (many of) the algorithms used inside
		3613	libev will be documented. For complexity discussions about backends see
		3614	the documentation for C<ev_default_init>.
		3615
		3616	All of the following are about amortised time: If an array needs to be
		3617	extended, libev needs to realloc and move the whole array, but this
		3618	happens asymptotically rarer with higher number of elements, so O(1) might
		3619	mean that libev does a lengthy realloc operation in rare cases, but on
		3620	average it is much faster and asymptotically approaches constant time.
		3621
		3622	=over 4
		3623
		3624	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3625
		3626	This means that, when you have a watcher that triggers in one hour and
		3627	there are 100 watchers that would trigger before that, then inserting will
		3628	have to skip roughly seven (C<ld 100>) of these watchers.
		3629
		3630	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3631
		3632	That means that changing a timer costs less than removing/adding them,
		3633	as only the relative motion in the event queue has to be paid for.
		3634
		3635	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3636
		3637	These just add the watcher into an array or at the head of a list.
		3638
		3639	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3640
		3641	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3642
		3643	These watchers are stored in lists, so they need to be walked to find the
		3644	correct watcher to remove. The lists are usually short (you don't usually
		3645	have many watchers waiting for the same fd or signal: one is typical, two
		3646	is rare).
		3647
		3648	=item Finding the next timer in each loop iteration: O(1)
		3649
		3650	By virtue of using a binary or 4-heap, the next timer is always found at a
		3651	fixed position in the storage array.
		3652
		3653	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3654
		3655	A change means an I/O watcher gets started or stopped, which requires
		3656	libev to recalculate its status (and possibly tell the kernel, depending
		3657	on backend and whether C<ev_io_set> was used).
		3658
		3659	=item Activating one watcher (putting it into the pending state): O(1)
		3660
		3661	=item Priority handling: O(number_of_priorities)
		3662
		3663	Priorities are implemented by allocating some space for each
		3664	priority. When doing priority-based operations, libev usually has to
		3665	linearly search all the priorities, but starting/stopping and activating
		3666	watchers becomes O(1) with respect to priority handling.
		3667
		3668	=item Sending an ev_async: O(1)
		3669
		3670	=item Processing ev_async_send: O(number_of_async_watchers)
		3671
		3672	=item Processing signals: O(max_signal_number)
		3673
		3674	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3675	calls in the current loop iteration. Checking for async and signal events
		3676	involves iterating over all running async watchers or all signal numbers.
		3677
		3678	=back
		3679
		3680
3297	=head1 AUTHOR	3681	=head1 AUTHOR
3298		3682
3299	Marc Lehmann <libev@schmorp.de>.	3683	Marc Lehmann <libev@schmorp.de>.
3300		3684

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