ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC vs.
Revision 1.206 by root, Tue Oct 28 12:31:38 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_ 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_ 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	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
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
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.
…		…
255		276
256	=back	277	=back
257		278
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		280
260	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
263		288
264	=over 4	289	=over 4
265		290
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		292
…		…
277	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	303	as loops cannot bes hared easily between threads anyway).
279		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	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	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	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	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	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	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	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	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	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	340	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	341	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	342	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	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	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	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	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	357	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	358	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.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	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	362	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	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	390
359	cases and requiring a syscall per fd change, no fork support and bad	391	The epoll syscalls are the most misdesigned of the more advanced event
360	support for dup.	392	mechanisms: problems include silently dropping fds, requiring a system
		393	call per change per fd (and unnecessary guessing of parameters), problems
		394	with dup and so on. The biggest issue is fork races, however - if a
		395	program forks then I<both> parent and child process have to recreate the
		396	epoll set, which can take considerable time (one syscall per fd) and is of
		397	course hard to detect.
		398
		399	Epoll is also notoriously buggy - embedding epoll fds should work, but
		400	of course doesn't, and epoll just loves to report events for totally
		401	I<different> file descriptors (even already closed ones, so one cannot
		402	even remove them from the set) than registered in the set (especially
		403	on SMP systems). Libev tries to counter these spurious notifications by
		404	employing an additional generation counter and comparing that against the
		405	events to filter out spurious ones.
361		406
362	While stopping, setting and starting an I/O watcher in the same iteration	407	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	408	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	409	(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	410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	411	very well if you register events for both fds.
367		412
368	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
370	(or space) is available.
371
372	Best performance from this backend is achieved by not unregistering all	413	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.	414	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	415	i.e. keep at least one watcher active per fd at all times. Stopping and
		416	starting a watcher (without re-setting it) also usually doesn't cause
		417	extra overhead. A fork can both result in spurious notifications as well
		418	as in libev having to destroy and recreate the epoll object, which can
		419	take considerable time and thus should be avoided.
375		420
376	While nominally embeddeble in other event loops, this feature is broken in	421	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	422	all kernel versions tested so far.
378		423
		424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		425	C<EVBACKEND_POLL>.
		426
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		428
381	Kqueue deserves special mention, as at the time of this writing, it	429	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	430	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	431	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"	432	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	433	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)	434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		435
389	You still can embed kqueue into a normal poll or select backend and use it	436	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	437	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.	438	the target platform). See C<ev_embed> watchers for more info.
392		439
393	It scales in the same way as the epoll backend, but the interface to the	440	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	441	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	442	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	443	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	444	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		446	cases
399		447
400	This backend usually performs well under most conditions.	448	This backend usually performs well under most conditions.
401		449
402	While nominally embeddable in other event loops, this doesn't work	450	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	451	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	452	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	453	(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	454	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	455	using it only for sockets.
		456
		457	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		458	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		459	C<NOTE_EOF>.
408		460
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	461	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		462
411	This is not implemented yet (and might never be, unless you send me an	463	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	464	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	468	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		469
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	470	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)).	471	it's really slow, but it still scales very well (O(active_fds)).
420		472
421	Please note that solaris event ports can deliver a lot of spurious	473	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	474	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	475	blocking when no data (or space) is available.
424		476
425	While this backend scales well, it requires one system call per active	477	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	478	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	480	might perform better.
429		481
430	On the positive side, ignoring the spurious readyness notifications, this	482	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	483	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	484	in all tests and is fully embeddable, which is a rare feat among the
		485	OS-specific backends (I vastly prefer correctness over speed hacks).
		486
		487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		488	C<EVBACKEND_POLL>.
433		489
434	=item C<EVBACKEND_ALL>	490	=item C<EVBACKEND_ALL>
435		491
436	Try all backends (even potentially broken ones that wouldn't be tried	492	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	493	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		495
440	It is definitely not recommended to use this flag.	496	It is definitely not recommended to use this flag.
441		497
442	=back	498	=back
443		499
444	If one or more of these are ored into the flags value, then only these	500	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	501	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.	502	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		503
448	The most typical usage is like this:	504	Example: This is the most typical usage.
449		505
450	if (!ev_default_loop (0))	506	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		508
453	Restrict libev to the select and poll backends, and do not allow	509	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	510	environment settings to be taken into account:
455		511
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		513
458	Use whatever libev has to offer, but make sure that kqueue is used if	514	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	515	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):	516	private event loop and only if you know the OS supports your types of
		517	fds):
461		518
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		520
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	521	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		522
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	523	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	524	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	529	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	530	default loop in the "main" or "initial" thread.
474		531
475	Example: Try to create a event loop that uses epoll and nothing else.	532	Example: Try to create a event loop that uses epoll and nothing else.
476		533
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	534	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	535	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	536	fatal ("no epoll found here, maybe it hides under your chair");
480		537
481	=item ev_default_destroy ()	538	=item ev_default_destroy ()
482		539
483	Destroys the default loop again (frees all memory and kernel state	540	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	541	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	542	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>	543	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	544	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	545	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	546	for example).
490		547
491	Note that certain global state, such as signal state, will not be freed by	548	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	549	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	550	as signal and child watchers) would need to be stopped manually.
494		551
495	In general it is not advisable to call this function except in the	552	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	553	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	554	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	555	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		580
524	=item ev_loop_fork (loop)	581	=item ev_loop_fork (loop)
525		582
526	Like C<ev_default_fork>, but acts on an event loop created by	583	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	584	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.	585	after fork that you want to re-use in the child, and how you do this is
		586	entirely your own problem.
529		587
530	=item int ev_is_default_loop (loop)	588	=item int ev_is_default_loop (loop)
531		589
532	Returns true when the given loop actually is the default loop, false otherwise.	590	Returns true when the given loop is, in fact, the default loop, and false
		591	otherwise.
533		592
534	=item unsigned int ev_loop_count (loop)	593	=item unsigned int ev_loop_count (loop)
535		594
536	Returns the count of loop iterations for the loop, which is identical to	595	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	596	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	611	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	612	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	613	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).	614	event occurring (or more correctly, libev finding out about it).
556		615
		616	=item ev_now_update (loop)
		617
		618	Establishes the current time by querying the kernel, updating the time
		619	returned by C<ev_now ()> in the progress. This is a costly operation and
		620	is usually done automatically within C<ev_loop ()>.
		621
		622	This function is rarely useful, but when some event callback runs for a
		623	very long time without entering the event loop, updating libev's idea of
		624	the current time is a good idea.
		625
		626	See also "The special problem of time updates" in the C<ev_timer> section.
		627
557	=item ev_loop (loop, int flags)	628	=item ev_loop (loop, int flags)
558		629
559	Finally, this is it, the event handler. This function usually is called	630	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	631	after you initialised all your watchers and you want to start handling
561	events.	632	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	634	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.	635	either no event watchers are active anymore or C<ev_unloop> was called.
565		636
566	Please note that an explicit C<ev_unloop> is usually better than	637	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	638	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	639	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	640	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.	641	of relying on its watchers stopping correctly, that is truly a thing of
		642	beauty.
571		643
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	644	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	645	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.	646	process in case there are no events and will return after one iteration of
		647	the loop.
575		648
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	649	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	650	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	651	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	652	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	653	user-registered callback will be called), and will return after one
		654	iteration of the loop.
		655
		656	This is useful if you are waiting for some external event in conjunction
		657	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	658	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.	659	usually a better approach for this kind of thing.
583		660
584	Here are the gory details of what C<ev_loop> does:	661	Here are the gory details of what C<ev_loop> does:
585		662
586	- Before the first iteration, call any pending watchers.	663	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	664	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	665	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	666	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	667	- If we have been forked, detach and recreate the kernel state
		668	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	669	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	670	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	671	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	672	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	673	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	674	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	675	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	676	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	678	- Queue all expired timers.
601	- Queue all outstanding periodics.	679	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	680	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	681	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	682	- 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	683	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	684	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	685	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	690	anymore.
613		691
614	... queue jobs here, make sure they register event watchers as long	692	... 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..)	693	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	694	ev_loop (my_loop, 0);
617	... jobs done. yeah!	695	... jobs done or somebody called unloop. yeah!
618		696
619	=item ev_unloop (loop, how)	697	=item ev_unloop (loop, how)
620		698
621	Can be used to make a call to C<ev_loop> return early (but only after it	699	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	700	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	701	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.	702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		703
626	This "unloop state" will be cleared when entering C<ev_loop> again.	704	This "unloop state" will be cleared when entering C<ev_loop> again.
627		705
		706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		707
628	=item ev_ref (loop)	708	=item ev_ref (loop)
629		709
630	=item ev_unref (loop)	710	=item ev_unref (loop)
631		711
632	Ref/unref can be used to add or remove a reference count on the event	712	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	713	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	714	count is nonzero, C<ev_loop> will not return on its own.
		715
635	a watcher you never unregister that should not keep C<ev_loop> from	716	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	717	from returning, call ev_unref() after starting, and ev_ref() before
		718	stopping it.
		719
637	example, libev itself uses this for its internal signal pipe: It is not	720	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	721	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	722	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	723	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>	724	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,	725	(but only if the watcher wasn't active before, or was active before,
643	respectively).	726	respectively).
644		727
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	729	running when nothing else is active.
647		730
648	struct ev_signal exitsig;	731	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	732	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	733	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	734	evf_unref (loop);
652		735
653	Example: For some weird reason, unregister the above signal handler again.	736	Example: For some weird reason, unregister the above signal handler again.
654		737
655	ev_ref (loop);	738	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	739	ev_signal_stop (loop, &exitsig);
657		740
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	741	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		742
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	743	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		744
662	These advanced functions influence the time that libev will spend waiting	745	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	746	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.	747	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		748	latency.
665		749
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	750	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	751	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	752	to increase efficiency of loop iterations (or to increase power-saving
		753	opportunities).
669		754
670	The background is that sometimes your program runs just fast enough to	755	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	756	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	757	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	758	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	759	overhead for the actual polling but can deliver many events at once.
675		760
676	By setting a higher I<io collect interval> you allow libev to spend more	761	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,	762	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	764	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.	765	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		766
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	767	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	768	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	769	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	770	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	771	value will not introduce any overhead in libev.
687		772
688	Many (busy) programs can usually benefit by setting the io collect	773	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	774	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	775	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>,	776	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.	777	as this approaches the timing granularity of most systems.
		778
		779	Setting the I<timeout collect interval> can improve the opportunity for
		780	saving power, as the program will "bundle" timer callback invocations that
		781	are "near" in time together, by delaying some, thus reducing the number of
		782	times the process sleeps and wakes up again. Another useful technique to
		783	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		784	they fire on, say, one-second boundaries only.
		785
		786	=item ev_loop_verify (loop)
		787
		788	This function only does something when C<EV_VERIFY> support has been
		789	compiled in, which is the default for non-minimal builds. It tries to go
		790	through all internal structures and checks them for validity. If anything
		791	is found to be inconsistent, it will print an error message to standard
		792	error and call C<abort ()>.
		793
		794	This can be used to catch bugs inside libev itself: under normal
		795	circumstances, this function will never abort as of course libev keeps its
		796	data structures consistent.
693		797
694	=back	798	=back
695		799
696		800
697	=head1 ANATOMY OF A WATCHER	801	=head1 ANATOMY OF A WATCHER
		802
		803	In the following description, uppercase C<TYPE> in names stands for the
		804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		805	watchers and C<ev_io_start> for I/O watchers.
698		806
699	A watcher is a structure that you create and register to record your	807	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	808	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:	809	become readable, you would create an C<ev_io> watcher for that:
702		810
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	812	{
705	ev_io_stop (w);	813	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	814	ev_unloop (loop, EVUNLOOP_ALL);
707	}	815	}
708		816
709	struct ev_loop *loop = ev_default_loop (0);	817	struct ev_loop *loop = ev_default_loop (0);
		818
710	struct ev_io stdin_watcher;	819	ev_io stdin_watcher;
		820
711	ev_init (&stdin_watcher, my_cb);	821	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	823	ev_io_start (loop, &stdin_watcher);
		824
714	ev_loop (loop, 0);	825	ev_loop (loop, 0);
715		826
716	As you can see, you are responsible for allocating the memory for your	827	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,	828	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	829	stack).
		830
		831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		833
720	Each watcher structure must be initialised by a call to C<ev_init	834	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	835	(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	836	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	837	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	838	is readable and/or writable).
725		839
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	841	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	842	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	843	ev_TYPE_init (watcher *, callback, ...) >>.
730		844
731	To make the watcher actually watch out for events, you have to start it	845	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	846	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	847	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		849
736	As long as your watcher is active (has been started but not stopped) you	850	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	851	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	852	reinitialise it or call its C<ev_TYPE_set> macro.
739		853
740	Each and every callback receives the event loop pointer as first, the	854	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	855	registered watcher structure as second, and a bitset of received events as
742	third argument.	856	third argument.
743		857
…		…
803		917
804	The given async watcher has been asynchronously notified (see C<ev_async>).	918	The given async watcher has been asynchronously notified (see C<ev_async>).
805		919
806	=item C<EV_ERROR>	920	=item C<EV_ERROR>
807		921
808	An unspecified error has occured, the watcher has been stopped. This might	922	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	923	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	924	ran out of memory, a file descriptor was found to be closed or any other
		925	problem. Libev considers these application bugs.
		926
811	problem. You best act on it by reporting the problem and somehow coping	927	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	928	watcher being stopped. Note that well-written programs should not receive
		929	an error ever, so when your watcher receives it, this usually indicates a
		930	bug in your program.
813		931
814	Libev will usually signal a few "dummy" events together with an error,	932	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	933	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	934	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	935	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	936	programs, though, as the fd could already be closed and reused for another
		937	thing, so beware.
819		938
820	=back	939	=back
821		940
822	=head2 GENERIC WATCHER FUNCTIONS	941	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		942
827	=over 4	943	=over 4
828		944
829	=item C<ev_init> (ev_TYPE *watcher, callback)	945	=item C<ev_init> (ev_TYPE *watcher, callback)
830		946
…		…
836	which rolls both calls into one.	952	which rolls both calls into one.
837		953
838	You can reinitialise a watcher at any time as long as it has been stopped	954	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	955	(or never started) and there are no pending events outstanding.
840		956
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	957	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	958	int revents)>.
		959
		960	Example: Initialise an C<ev_io> watcher in two steps.
		961
		962	ev_io w;
		963	ev_init (&w, my_cb);
		964	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		965
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	966	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		967
846	This macro initialises the type-specific parts of a watcher. You need to	968	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	969	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	972	difference to the C<ev_init> macro).
851		973
852	Although some watcher types do not have type-specific arguments	974	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.	975	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		976
		977	See C<ev_init>, above, for an example.
		978
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	979	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		980
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	981	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	982	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	983	a watcher. The same limitations apply, of course.
		984
		985	Example: Initialise and set an C<ev_io> watcher in one step.
		986
		987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		988
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		990
863	Starts (activates) the given watcher. Only active watchers will receive	991	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	992	events. If the watcher is already active nothing will happen.
865		993
		994	Example: Start the C<ev_io> watcher that is being abused as example in this
		995	whole section.
		996
		997	ev_io_start (EV_DEFAULT_UC, &w);
		998
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1000
868	Stops the given watcher again (if active) and clears the pending	1001	Stops the given watcher if active, and clears the pending status (whether
		1002	the watcher was active or not).
		1003
869	status. It is possible that stopped watchers are pending (for example,	1004	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1005	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	1006	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	1007	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.	1008	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1009
875	=item bool ev_is_active (ev_TYPE *watcher)	1010	=item bool ev_is_active (ev_TYPE *watcher)
876		1011
877	Returns a true value iff the watcher is active (i.e. it has been started	1012	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	1013	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1055	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1056	always C<0>, which is supposed to not be too high and not be too low :).
922		1057
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1059	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1060	or might not have been clamped to the valid range.
926		1061
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1063
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1064	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	1065	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1066	can deal with that fact, as both are simply passed through to the
		1067	callback.
932		1068
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1069	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1070
935	If the watcher is pending, this function returns clears its pending status	1071	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	1072	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>.	1073	watcher isn't pending it does nothing and returns C<0>.
938		1074
		1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1076	callback to be invoked, which can be accomplished with this function.
		1077
939	=back	1078	=back
940		1079
941		1080
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1082
944	Each watcher has, by default, a member C<void *data> that you can change	1083	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	1084	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	1085	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	1086	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	1087	member, you can also "subclass" the watcher type and provide your own
949	data:	1088	data:
950		1089
951	struct my_io	1090	struct my_io
952	{	1091	{
953	struct ev_io io;	1092	ev_io io;
954	int otherfd;	1093	int otherfd;
955	void *somedata;	1094	void *somedata;
956	struct whatever *mostinteresting;	1095	struct whatever *mostinteresting;
957	}	1096	};
		1097
		1098	...
		1099	struct my_io w;
		1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1101
959	And since your callback will be called with a pointer to the watcher, you	1102	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1103	can cast it back to your own type:
961		1104
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1105	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1106	{
964	struct my_io *w = (struct my_io *)w_;	1107	struct my_io *w = (struct my_io *)w_;
965	...	1108	...
966	}	1109	}
967		1110
968	More interesting and less C-conformant ways of casting your callback type	1111	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1112	instead have been omitted.
970		1113
971	Another common scenario is having some data structure with multiple	1114	Another common scenario is to use some data structure with multiple
972	watchers:	1115	embedded watchers:
973		1116
974	struct my_biggy	1117	struct my_biggy
975	{	1118	{
976	int some_data;	1119	int some_data;
977	ev_timer t1;	1120	ev_timer t1;
978	ev_timer t2;	1121	ev_timer t2;
979	}	1122	}
980		1123
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1124	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1125	complicated: Either you store the address of your C<my_biggy> struct
		1126	in the C<data> member of the watcher (for woozies), or you need to use
		1127	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1128	programmers):
983		1129
984	#include <stddef.h>	1130	#include <stddef.h>
985		1131
986	static void	1132	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1133	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1134	{
989	struct my_biggy big = (struct my_biggy *	1135	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1136	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1137	}
992		1138
993	static void	1139	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1140	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1141	{
996	struct my_biggy big = (struct my_biggy *	1142	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1143	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1144	}
999		1145
1000		1146
1001	=head1 WATCHER TYPES	1147	=head1 WATCHER TYPES
1002		1148
1003	This section describes each watcher in detail, but will not repeat	1149	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	1173	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	1174	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	1175	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1176	required if you know what you are doing).
1031		1177
1032	If you must do this, then force the use of a known-to-be-good backend	1178	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	1179	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1181
1036	Another thing you have to watch out for is that it is quite easy to	1182	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	1183	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	1184	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	1185	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	1186	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	1187	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	1188	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.	1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1190
1045	If you cannot run the fd in non-blocking mode (for example you should not	1191	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	1192	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	1193	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	1194	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1195	does this on its own, so its quite safe to use). Some people additionally
		1196	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1197	indefinitely.
		1198
		1199	But really, best use non-blocking mode.
1050		1200
1051	=head3 The special problem of disappearing file descriptors	1201	=head3 The special problem of disappearing file descriptors
1052		1202
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1203	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,	1204	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	1205	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	1206	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	1207	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	1208	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1209	fact, a different file descriptor.
1060		1210
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1242	C<EVBACKEND_POLL>.
1093		1243
1094	=head3 The special problem of SIGPIPE	1244	=head3 The special problem of SIGPIPE
1095		1245
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1246	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	1247	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	1248	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1249	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1250
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1251	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	1252	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).	1253	somewhere, as that would have given you a big clue).
1105		1254
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1260	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1261
1113	=item ev_io_set (ev_io *, int fd, int events)	1262	=item ev_io_set (ev_io *, int fd, int events)
1114		1263
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1264	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	1265	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.	1266	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1267
1119	=item int fd [read-only]	1268	=item int fd [read-only]
1120		1269
1121	The file descriptor being watched.	1270	The file descriptor being watched.
1122		1271
…		…
1130		1279
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1280	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	1281	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1282	attempt to read a whole line in the callback.
1134		1283
1135	static void	1284	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1285	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1286	{
1138	ev_io_stop (loop, w);	1287	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1288	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1289	}
1141		1290
1142	...	1291	...
1143	struct ev_loop *loop = ev_default_init (0);	1292	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1293	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1295	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1148		1297
1149		1298
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1299	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1300
1152	Timer watchers are simple relative timers that generate an event after a	1301	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1302	given time, and optionally repeating in regular intervals after that.
1154		1303
1155	The timers are based on real time, that is, if you register an event that	1304	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	1305	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	1306	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1308	monotonic clock option helps a lot here).
		1309
		1310	The callback is guaranteed to be invoked only I<after> its timeout has
		1311	passed, but if multiple timers become ready during the same loop iteration
		1312	then order of execution is undefined.
		1313
		1314	=head3 Be smart about timeouts
		1315
		1316	Many real-world problems involve some kind of timeout, usually for error
		1317	recovery. A typical example is an HTTP request - if the other side hangs,
		1318	you want to raise some error after a while.
		1319
		1320	What follows are some ways to handle this problem, from obvious and
		1321	inefficient to smart and efficient.
		1322
		1323	In the following, a 60 second activity timeout is assumed - a timeout that
		1324	gets reset to 60 seconds each time there is activity (e.g. each time some
		1325	data or other life sign was received).
		1326
		1327	=over 4
		1328
		1329	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1330
		1331	This is the most obvious, but not the most simple way: In the beginning,
		1332	start the watcher:
		1333
		1334	ev_timer_init (timer, callback, 60., 0.);
		1335	ev_timer_start (loop, timer);
		1336
		1337	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1338	and start it again:
		1339
		1340	ev_timer_stop (loop, timer);
		1341	ev_timer_set (timer, 60., 0.);
		1342	ev_timer_start (loop, timer);
		1343
		1344	This is relatively simple to implement, but means that each time there is
		1345	some activity, libev will first have to remove the timer from its internal
		1346	data structure and then add it again. Libev tries to be fast, but it's
		1347	still not a constant-time operation.
		1348
		1349	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1350
		1351	This is the easiest way, and involves using C<ev_timer_again> instead of
		1352	C<ev_timer_start>.
		1353
		1354	To implement this, configure an C<ev_timer> with a C<repeat> value
		1355	of C<60> and then call C<ev_timer_again> at start and each time you
		1356	successfully read or write some data. If you go into an idle state where
		1357	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1358	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1359
		1360	That means you can ignore both the C<ev_timer_start> function and the
		1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1362	member and C<ev_timer_again>.
		1363
		1364	At start:
		1365
		1366	ev_timer_init (timer, callback);
		1367	timer->repeat = 60.;
		1368	ev_timer_again (loop, timer);
		1369
		1370	Each time there is some activity:
		1371
		1372	ev_timer_again (loop, timer);
		1373
		1374	It is even possible to change the time-out on the fly, regardless of
		1375	whether the watcher is active or not:
		1376
		1377	timer->repeat = 30.;
		1378	ev_timer_again (loop, timer);
		1379
		1380	This is slightly more efficient then stopping/starting the timer each time
		1381	you want to modify its timeout value, as libev does not have to completely
		1382	remove and re-insert the timer from/into its internal data structure.
		1383
		1384	It is, however, even simpler than the "obvious" way to do it.
		1385
		1386	=item 3. Let the timer time out, but then re-arm it as required.
		1387
		1388	This method is more tricky, but usually most efficient: Most timeouts are
		1389	relatively long compared to the intervals between other activity - in
		1390	our example, within 60 seconds, there are usually many I/O events with
		1391	associated activity resets.
		1392
		1393	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1394	but remember the time of last activity, and check for a real timeout only
		1395	within the callback:
		1396
		1397	ev_tstamp last_activity; // time of last activity
		1398
		1399	static void
		1400	callback (EV_P_ ev_timer *w, int revents)
		1401	{
		1402	ev_tstamp now = ev_now (EV_A);
		1403	ev_tstamp timeout = last_activity + 60.;
		1404
		1405	// if last_activity + 60. is older than now, we did time out
		1406	if (timeout < now)
		1407	{
		1408	// timeout occured, take action
		1409	}
		1410	else
		1411	{
		1412	// callback was invoked, but there was some activity, re-arm
		1413	// the watcher to fire in last_activity + 60, which is
		1414	// guaranteed to be in the future, so "again" is positive:
		1415	w->again = timeout - now;
		1416	ev_timer_again (EV_A_ w);
		1417	}
		1418	}
		1419
		1420	To summarise the callback: first calculate the real timeout (defined
		1421	as "60 seconds after the last activity"), then check if that time has
		1422	been reached, which means something I<did>, in fact, time out. Otherwise
		1423	the callback was invoked too early (C<timeout> is in the future), so
		1424	re-schedule the timer to fire at that future time, to see if maybe we have
		1425	a timeout then.
		1426
		1427	Note how C<ev_timer_again> is used, taking advantage of the
		1428	C<ev_timer_again> optimisation when the timer is already running.
		1429
		1430	This scheme causes more callback invocations (about one every 60 seconds
		1431	minus half the average time between activity), but virtually no calls to
		1432	libev to change the timeout.
		1433
		1434	To start the timer, simply initialise the watcher and set C<last_activity>
		1435	to the current time (meaning we just have some activity :), then call the
		1436	callback, which will "do the right thing" and start the timer:
		1437
		1438	ev_timer_init (timer, callback);
		1439	last_activity = ev_now (loop);
		1440	callback (loop, timer, EV_TIMEOUT);
		1441
		1442	And when there is some activity, simply store the current time in
		1443	C<last_activity>, no libev calls at all:
		1444
		1445	last_actiivty = ev_now (loop);
		1446
		1447	This technique is slightly more complex, but in most cases where the
		1448	time-out is unlikely to be triggered, much more efficient.
		1449
		1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1451	callback :) - just change the timeout and invoke the callback, which will
		1452	fix things for you.
		1453
		1454	=item 4. Wee, just use a double-linked list for your timeouts.
		1455
		1456	If there is not one request, but many thousands (millions...), all
		1457	employing some kind of timeout with the same timeout value, then one can
		1458	do even better:
		1459
		1460	When starting the timeout, calculate the timeout value and put the timeout
		1461	at the I<end> of the list.
		1462
		1463	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1464	the list is expected to fire (for example, using the technique #3).
		1465
		1466	When there is some activity, remove the timer from the list, recalculate
		1467	the timeout, append it to the end of the list again, and make sure to
		1468	update the C<ev_timer> if it was taken from the beginning of the list.
		1469
		1470	This way, one can manage an unlimited number of timeouts in O(1) time for
		1471	starting, stopping and updating the timers, at the expense of a major
		1472	complication, and having to use a constant timeout. The constant timeout
		1473	ensures that the list stays sorted.
		1474
		1475	=back
		1476
		1477	So which method the best?
		1478
		1479	Method #2 is a simple no-brain-required solution that is adequate in most
		1480	situations. Method #3 requires a bit more thinking, but handles many cases
		1481	better, and isn't very complicated either. In most case, choosing either
		1482	one is fine, with #3 being better in typical situations.
		1483
		1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1485	rather complicated, but extremely efficient, something that really pays
		1486	off after the first million or so of active timers, i.e. it's usually
		1487	overkill :)
		1488
		1489	=head3 The special problem of time updates
		1490
		1491	Establishing the current time is a costly operation (it usually takes at
		1492	least two system calls): EV therefore updates its idea of the current
		1493	time only before and after C<ev_loop> collects new events, which causes a
		1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1495	lots of events in one iteration.
1160		1496
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1497	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	1498	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	1499	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	1500	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:	1501	timeout on the current time, use something like this to adjust for this:
1166		1502
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1503	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1504
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1505	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	1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1507	()>.
1172		1508
1173	=head3 Watcher-Specific Functions and Data Members	1509	=head3 Watcher-Specific Functions and Data Members
1174		1510
1175	=over 4	1511	=over 4
1176		1512
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1513	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1514
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1515	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1516
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1517	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	1518	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	1519	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1520	configured to trigger again C<repeat> seconds later, again, and again,
		1521	until stopped manually.
1185		1522
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1523	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	1524	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	1525	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	1526	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.	1527	do stuff) the timer will not fire more than once per event loop iteration.
1191		1528
1192	=item ev_timer_again (loop, ev_timer *)	1529	=item ev_timer_again (loop, ev_timer *)
1193		1530
1194	This will act as if the timer timed out and restart it again if it is	1531	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1532	repeating. The exact semantics are:
1196		1533
1197	If the timer is pending, its pending status is cleared.	1534	If the timer is pending, its pending status is cleared.
1198		1535
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1536	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1537
1201	If the timer is repeating, either start it if necessary (with the	1538	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.	1539	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1540
1204	This sounds a bit complicated, but here is a useful and typical	1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1542	usage example.
1206	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
1208	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
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213
1214	That means you can ignore the C<after> value and C<ev_timer_start>
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216
1217	ev_timer_init (timer, callback, 0., 5.);
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225
1226	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.
1228		1543
1229	=item ev_tstamp repeat [read-write]	1544	=item ev_tstamp repeat [read-write]
1230		1545
1231	The current C<repeat> value. Will be used each time the watcher times out	1546	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),	1547	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.	1548	which is also when any modifications are taken into account.
1234		1549
1235	=back	1550	=back
1236		1551
1237	=head3 Examples	1552	=head3 Examples
1238		1553
1239	Example: Create a timer that fires after 60 seconds.	1554	Example: Create a timer that fires after 60 seconds.
1240		1555
1241	static void	1556	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1557	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1558	{
1244	.. one minute over, w is actually stopped right here	1559	.. one minute over, w is actually stopped right here
1245	}	1560	}
1246		1561
1247	struct ev_timer mytimer;	1562	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1563	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1564	ev_timer_start (loop, &mytimer);
1250		1565
1251	Example: Create a timeout timer that times out after 10 seconds of	1566	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1567	inactivity.
1253		1568
1254	static void	1569	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1570	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1571	{
1257	.. ten seconds without any activity	1572	.. ten seconds without any activity
1258	}	1573	}
1259		1574
1260	struct ev_timer mytimer;	1575	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1577	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1264		1579
1265	// and in some piece of code that gets executed on any "activity":	1580	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1581	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1582	ev_timer_again (&mytimer);
1268		1583
1269		1584
1270	=head2 C<ev_periodic> - to cron or not to cron?	1585	=head2 C<ev_periodic> - to cron or not to cron?
1271		1586
1272	Periodic watchers are also timers of a kind, but they are very versatile	1587	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1588	(and unfortunately a bit complex).
1274		1589
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1590	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	1591	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	1592	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 ()	1593	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	1594	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1595	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	1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1597	roughly 10 seconds later as it uses a relative timeout).
1282		1598
1283	They can also be used to implement vastly more complex timers, such as	1599	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,	1600	such as triggering an event on each "midnight, local time", or other
1285	rules.	1601	complicated rules.
1286		1602
1287	As with timers, the callback is guarenteed to be invoked only when the	1603	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	1604	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1605	during the same loop iteration, then order of execution is undefined.
1290		1606
1291	=head3 Watcher-Specific Functions and Data Members	1607	=head3 Watcher-Specific Functions and Data Members
1292		1608
1293	=over 4	1609	=over 4
1294		1610
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1296		1612
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1298		1614
1299	Lots of arguments, lets sort it out... There are basically three modes of	1615	Lots of arguments, lets sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1616	operation, and we will explain them from simplest to most complex:
1301		1617
1302	=over 4	1618	=over 4
1303		1619
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1621
1306	In this configuration the watcher triggers an event at the wallclock time	1622	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,	1623	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	1624	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.	1625	only run when the system clock reaches or surpasses this time.
1310		1626
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1628
1313	In this mode the watcher will always be scheduled to time out at the next	1629	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)	1630	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1631	and then repeat, regardless of any time jumps.
1316		1632
1317	This can be used to create timers that do not drift with respect to system	1633	This can be used to create timers that do not drift with respect to the
1318	time:	1634	system clock, for example, here is a C<ev_periodic> that triggers each
		1635	hour, on the hour:
1319		1636
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1637	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1638
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1639	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	1640	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	1641	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1642	by 3600.
1326		1643
1327	Another way to think about it (for the mathematically inclined) is that	1644	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	1645	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.	1646	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1647
1331	For numerical stability it is preferable that the C<at> value is near	1648	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	1649	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1650	this value, and in fact is often specified as zero.
		1651
		1652	Note also that there is an upper limit to how often a timer can fire (CPU
		1653	speed for example), so if C<interval> is very small then timing stability
		1654	will of course deteriorate. Libev itself tries to be exact to be about one
		1655	millisecond (if the OS supports it and the machine is fast enough).
1334		1656
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1657	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1658
1337	In this mode the values for C<interval> and C<at> are both being	1659	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	1660	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1661	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1662	current time as second argument.
1341		1663
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1664	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,	1665	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		1666
		1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1669	only event loop modification you are allowed to do).
		1670
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1671	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1672	*w, ev_tstamp now)>, e.g.:
1349		1673
		1674	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1675	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1676	{
1352	return now + 60.;	1677	return now + 60.;
1353	}	1678	}
1354		1679
1355	It must return the next time to trigger, based on the passed time value	1680	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	1681	(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	1682	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1683	might be called at other times, too.
1359		1684
1360	NOTE: I<< This callback must always return a time that is later than the	1685	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.	1686	equal to the passed C<now> value >>.
1362		1687
1363	This can be used to create very complex timers, such as a timer that	1688	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	1689	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	1690	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	1691	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).	1692	reason I omitted it as an example).
1368		1693
1369	=back	1694	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	1698	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	1699	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	1700	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1701	program when the crontabs have changed).
1377		1702
		1703	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1704
		1705	When active, returns the absolute time that the watcher is supposed to
		1706	trigger next.
		1707
1378	=item ev_tstamp offset [read-write]	1708	=item ev_tstamp offset [read-write]
1379		1709
1380	When repeating, this contains the offset value, otherwise this is the	1710	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>).	1711	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1382		1712
…		…
1387		1717
1388	The current interval value. Can be modified any time, but changes only	1718	The current interval value. Can be modified any time, but changes only
1389	take effect when the periodic timer fires or C<ev_periodic_again> is being	1719	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	1720	called.
1391		1721
1392	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1722	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1393		1723
1394	The current reschedule callback, or C<0>, if this functionality is	1724	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	1725	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.	1726	the periodic timer fires or C<ev_periodic_again> is being called.
1397		1727
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	1728	=back
1404		1729
1405	=head3 Examples	1730	=head3 Examples
1406		1731
1407	Example: Call a callback every hour, or, more precisely, whenever the	1732	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1733	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1734	potentially a lot of jitter, but good long-term stability.
1410		1735
1411	static void	1736	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	1738	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1739	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1740	}
1416		1741
1417	struct ev_periodic hourly_tick;	1742	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1743	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1744	ev_periodic_start (loop, &hourly_tick);
1420		1745
1421	Example: The same as above, but use a reschedule callback to do it:	1746	Example: The same as above, but use a reschedule callback to do it:
1422		1747
1423	#include <math.h>	1748	#include <math.h>
1424		1749
1425	static ev_tstamp	1750	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1751	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1752	{
1428	return fmod (now, 3600.) + 3600.;	1753	return now + (3600. - fmod (now, 3600.));
1429	}	1754	}
1430		1755
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1756	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1757
1433	Example: Call a callback every hour, starting now:	1758	Example: Call a callback every hour, starting now:
1434		1759
1435	struct ev_periodic hourly_tick;	1760	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1761	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1762	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1763	ev_periodic_start (loop, &hourly_tick);
1439		1764
1440		1765
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1766	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1767
1443	Signal watchers will trigger an event when the process receives a specific	1768	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	1769	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	1770	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1771	normal event processing, like any other event.
1447		1772
		1773	If you want signals asynchronously, just use C<sigaction> as you would
		1774	do without libev and forget about sharing the signal. You can even use
		1775	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1776
1448	You can configure as many watchers as you like per signal. Only when the	1777	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	1778	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	1779	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	1780	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	1781	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1782	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1783
1455	If possible and supported, libev will install its handlers with	1784	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1786	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	1787	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1788	them in an C<ev_prepare> watcher.
1460		1789
1461	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1462		1791
…		…
1475		1804
1476	=back	1805	=back
1477		1806
1478	=head3 Examples	1807	=head3 Examples
1479		1808
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1809	Example: Try to exit cleanly on SIGINT.
1481		1810
1482	static void	1811	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	1813	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1814	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1815	}
1487		1816
1488	struct ev_signal signal_watcher;	1817	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1819	ev_signal_start (loop, &signal_watcher);
1491		1820
1492		1821
1493	=head2 C<ev_child> - watch out for process status changes	1822	=head2 C<ev_child> - watch out for process status changes
1494		1823
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1824	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	1825	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	1826	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	1827	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	1828	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1829	forking and then immediately registering a watcher for the child is fine,
		1830	but forking and registering a watcher a few event loop iterations later is
		1831	not.
1500		1832
1501	Only the default event loop is capable of handling signals, and therefore	1833	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	1834	you can only register child watchers in the default event loop.
1503		1835
1504	=head3 Process Interaction	1836	=head3 Process Interaction
1505		1837
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	1838	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	1839	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	1840	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1841	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	1842	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	1843	children, even ones not watched.
1512		1844
1513	=head3 Overriding the Built-In Processing	1845	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	1849	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	1850	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	1851	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	1852	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.	1853	that, so other libev users can use C<ev_child> watchers freely.
		1854
		1855	=head3 Stopping the Child Watcher
		1856
		1857	Currently, the child watcher never gets stopped, even when the
		1858	child terminates, so normally one needs to stop the watcher in the
		1859	callback. Future versions of libev might stop the watcher automatically
		1860	when a child exit is detected.
1522		1861
1523	=head3 Watcher-Specific Functions and Data Members	1862	=head3 Watcher-Specific Functions and Data Members
1524		1863
1525	=over 4	1864	=over 4
1526		1865
…		…
1555	=head3 Examples	1894	=head3 Examples
1556		1895
1557	Example: C<fork()> a new process and install a child handler to wait for	1896	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	1897	its completion.
1559		1898
1560	ev_child cw;	1899	ev_child cw;
1561		1900
1562	static void	1901	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	1902	child_cb (EV_P_ ev_child *w, int revents)
1564	{	1903	{
1565	ev_child_stop (EV_A_ w);	1904	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1905	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	1906	}
1568		1907
1569	pid_t pid = fork ();	1908	pid_t pid = fork ();
1570		1909
1571	if (pid < 0)	1910	if (pid < 0)
1572	// error	1911	// error
1573	else if (pid == 0)	1912	else if (pid == 0)
1574	{	1913	{
1575	// the forked child executes here	1914	// the forked child executes here
1576	exit (1);	1915	exit (1);
1577	}	1916	}
1578	else	1917	else
1579	{	1918	{
1580	ev_child_init (&cw, child_cb, pid, 0);	1919	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	1920	ev_child_start (EV_DEFAULT_ &cw);
1582	}	1921	}
1583		1922
1584		1923
1585	=head2 C<ev_stat> - did the file attributes just change?	1924	=head2 C<ev_stat> - did the file attributes just change?
1586		1925
1587	This watches a filesystem path for attribute changes. That is, it calls	1926	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	1927	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.	1928	compared to the last time, invoking the callback if it did.
1590		1929
1591	The path does not need to exist: changing from "path exists" to "path does	1930	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	1931	not exist" is a status change like any other. The condition "path does
…		…
1595	the stat buffer having unspecified contents.	1934	the stat buffer having unspecified contents.
1596		1935
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	1936	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.	1937	relative and your working directory changes, the behaviour is undefined.
1599		1938
1600	Since there is no standard to do this, the portable implementation simply	1939	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	1940	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	1941	it changed somehow. You can specify a recommended polling interval for
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	1942	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	1943	then a I<suitable, unspecified default> value will be used (which
1605	five seconds, although this might change dynamically). Libev will also	1944	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	1945	dynamically). Libev will also impose a minimum interval which is currently
1607	usually overkill.	1946	around C<0.1>, but thats usually overkill.
1608		1947
1609	This watcher type is not meant for massive numbers of stat watchers,	1948	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	1949	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1950	resource-intensive.
1612		1951
1613	At the time of this writing, only the Linux inotify interface is	1952	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	1953	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	1954	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	1955	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		1956
1621	=head3 ABI Issues (Largefile Support)	1957	=head3 ABI Issues (Largefile Support)
1622		1958
1623	Libev by default (unless the user overrides this) uses the default	1959	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	1960	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	1961	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	1962	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	1963	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	1964	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	1965	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	1966	most noticeably disabled with ev_stat and large file support.
1631		1967
1632	=head3 Inotify	1968	The solution for this is to lobby your distribution maker to make large
		1969	file interfaces available by default (as e.g. FreeBSD does) and not
		1970	optional. Libev cannot simply switch on large file support because it has
		1971	to exchange stat structures with application programs compiled using the
		1972	default compilation environment.
1633		1973
		1974	=head3 Inotify and Kqueue
		1975
1634	When C<inotify (7)> support has been compiled into libev (generally only	1976	When C<inotify (7)> support has been compiled into libev (generally
		1977	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	1978	implementations) and present at runtime, it will be used to speed up
1636	change detection where possible. The inotify descriptor will be created lazily	1979	change detection where possible. The inotify descriptor will be created
1637	when the first C<ev_stat> watcher is being started.	1980	lazily when the first C<ev_stat> watcher is being started.
1638		1981
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	1982	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	1983	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	1984	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.	1985	there are many cases where libev has to resort to regular C<stat> polling,
		1986	but as long as the path exists, libev usually gets away without polling.
1643		1987
1644	(There is no support for kqueue, as apparently it cannot be used to	1988	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	1989	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	1990	descriptor open on the object at all times, and detecting renames, unlinks
		1991	etc. is difficult.
1647		1992
1648	=head3 The special problem of stat time resolution	1993	=head3 The special problem of stat time resolution
1649		1994
1650	The C<stat ()> syscall only supports full-second resolution portably, and	1995	The C<stat ()> system call only supports full-second resolution portably, and
1651	even on systems where the resolution is higher, many filesystems still	1996	even on systems where the resolution is higher, most file systems still
1652	only support whole seconds.	1997	only support whole seconds.
1653		1998
1654	That means that, if the time is the only thing that changes, you might	1999	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	2000	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	2001	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2002	within the same second, C<ev_stat> will be unable to detect unless the
		2003	stat data does change in other ways (e.g. file size).
1658		2004
1659	The solution to this is to delay acting on a change for a second (or till	2005	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>	2006	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>	2007	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	2008	ev_timer_again (loop, w)>).
1663	systems.	2009
		2010	The C<.02> offset is added to work around small timing inconsistencies
		2011	of some operating systems (where the second counter of the current time
		2012	might be be delayed. One such system is the Linux kernel, where a call to
		2013	C<gettimeofday> might return a timestamp with a full second later than
		2014	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2015	update file times then there will be a small window where the kernel uses
		2016	the previous second to update file times but libev might already execute
		2017	the timer callback).
1664		2018
1665	=head3 Watcher-Specific Functions and Data Members	2019	=head3 Watcher-Specific Functions and Data Members
1666		2020
1667	=over 4	2021	=over 4
1668		2022
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2028	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	2029	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	2030	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.	2031	path for as long as the watcher is active.
1678		2032
1679	The callback will be receive C<EV_STAT> when a change was detected,	2033	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	2034	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2035	last change was detected).
1682		2036
1683	=item ev_stat_stat (loop, ev_stat *)	2037	=item ev_stat_stat (loop, ev_stat *)
1684		2038
1685	Updates the stat buffer immediately with new values. If you change the	2039	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	2040	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2041	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2042	the only one changing the path). Can also be useful simply to find out the
		2043	new values.
1689		2044
1690	=item ev_statdata attr [read-only]	2045	=item ev_statdata attr [read-only]
1691		2046
1692	The most-recently detected attributes of the file. Although the type is of	2047	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	2048	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	2049	suitable for your system, but you can only rely on the POSIX-standardised
		2050	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.	2051	some error while C<stat>ing the file.
1696		2052
1697	=item ev_statdata prev [read-only]	2053	=item ev_statdata prev [read-only]
1698		2054
1699	The previous attributes of the file. The callback gets invoked whenever	2055	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2056	C<prev> != C<attr>, or, more precisely, one or more of these members
		2057	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2058	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2059
1702	=item ev_tstamp interval [read-only]	2060	=item ev_tstamp interval [read-only]
1703		2061
1704	The specified interval.	2062	The specified interval.
1705		2063
1706	=item const char *path [read-only]	2064	=item const char *path [read-only]
1707		2065
1708	The filesystem path that is being watched.	2066	The file system path that is being watched.
1709		2067
1710	=back	2068	=back
1711		2069
1712	=head3 Examples	2070	=head3 Examples
1713		2071
1714	Example: Watch C</etc/passwd> for attribute changes.	2072	Example: Watch C</etc/passwd> for attribute changes.
1715		2073
1716	static void	2074	static void
1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2075	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1718	{	2076	{
1719	/* /etc/passwd changed in some way */	2077	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2078	if (w->attr.st_nlink)
1721	{	2079	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2080	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2081	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2082	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2083	}
1726	else	2084	else
1727	/* you shalt not abuse printf for puts */	2085	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2086	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2087	"if this is windows, they already arrived\n");
1730	}	2088	}
1731		2089
1732	...	2090	...
1733	ev_stat passwd;	2091	ev_stat passwd;
1734		2092
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2093	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2094	ev_stat_start (loop, &passwd);
1737		2095
1738	Example: Like above, but additionally use a one-second delay so we do not	2096	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	2097	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	2098	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2099	C<ev_timer> callback invocation).
1742		2100
1743	static ev_stat passwd;	2101	static ev_stat passwd;
1744	static ev_timer timer;	2102	static ev_timer timer;
1745		2103
1746	static void	2104	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2105	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2106	{
1749	ev_timer_stop (EV_A_ w);	2107	ev_timer_stop (EV_A_ w);
1750		2108
1751	/* now it's one second after the most recent passwd change */	2109	/* now it's one second after the most recent passwd change */
1752	}	2110	}
1753		2111
1754	static void	2112	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2113	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2114	{
1757	/* reset the one-second timer */	2115	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2116	ev_timer_again (EV_A_ &timer);
1759	}	2117	}
1760		2118
1761	...	2119	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2120	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2121	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2122	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2123
1766		2124
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2125	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2126
1769	Idle watchers trigger events when no other events of the same or higher	2127	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	2128	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2129	as receiving "events").
1772		2130
1773	That is, as long as your process is busy handling sockets or timeouts	2131	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	2132	(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	2133	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	2134	are pending), the idle watchers are being called once per event loop
…		…
1800	=head3 Examples	2158	=head3 Examples
1801		2159
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2160	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2161	callback, free it. Also, use no error checking, as usual.
1804		2162
1805	static void	2163	static void
1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2164	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1807	{	2165	{
1808	free (w);	2166	free (w);
1809	// now do something you wanted to do when the program has	2167	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2168	// no longer anything immediate to do.
1811	}	2169	}
1812		2170
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2171	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2172	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2173	ev_idle_start (loop, idle_cb);
1816		2174
1817		2175
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2176	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2177
1820	Prepare and check watchers are usually (but not always) used in tandem:	2178	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2179	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2180	afterwards.
1823		2181
1824	You I<must not> call C<ev_loop> or similar functions that enter	2182	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>	2183	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,	2186	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	2187	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2188	called in pairs bracketing the blocking call.
1831		2189
1832	Their main purpose is to integrate other event mechanisms into libev and	2190	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	2191	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	2192	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2193	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,	2194	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>	2195	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2196	watcher).
1839		2197
1840	This is done by examining in each prepare call which file descriptors need	2198	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	2199	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	2200	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	2201	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2202	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	2203	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,	2204	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2205	nevertheless, because you never know, you know?).
1848		2206
1849	As another example, the Perl Coro module uses these hooks to integrate	2207	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2208	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2209	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	2210	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	2213	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2214	low-priority coroutines to idle/background tasks).
1857		2215
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2216	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	2217	priority, to ensure that they are being run before any other watchers
		2218	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2219
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2220	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	2221	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2222	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	2223	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	2224	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	2225	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2226	others).
1867		2227
1868	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1869		2229
1870	=over 4	2230	=over 4
1871		2231
…		…
1873		2233
1874	=item ev_check_init (ev_check *, callback)	2234	=item ev_check_init (ev_check *, callback)
1875		2235
1876	Initialises and configures the prepare or check watcher - they have no	2236	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>	2237	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.	2238	macros, but using them is utterly, utterly, utterly and completely
		2239	pointless.
1879		2240
1880	=back	2241	=back
1881		2242
1882	=head3 Examples	2243	=head3 Examples
1883		2244
1884	There are a number of principal ways to embed other event loops or modules	2245	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	2246	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	2247	(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>	2248	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	2249	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2250	Glib event loop).
1890		2251
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2252	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	2253	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	2254	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	2255	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.	2256	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2257
1897	static ev_io iow [nfd];	2258	static ev_io iow [nfd];
1898	static ev_timer tw;	2259	static ev_timer tw;
1899		2260
1900	static void	2261	static void
1901	io_cb (ev_loop *loop, ev_io *w, int revents)	2262	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1902	{	2263	{
1903	}	2264	}
1904		2265
1905	// create io watchers for each fd and a timer before blocking	2266	// create io watchers for each fd and a timer before blocking
1906	static void	2267	static void
1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2268	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1908	{	2269	{
1909	int timeout = 3600000;	2270	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2271	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2272	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2273	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2274
1914	/* the callback is illegal, but won't be called as we stop during check */	2275	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2276	ev_timer_init (&tw, 0, timeout * 1e-3);
1916	ev_timer_start (loop, &tw);	2277	ev_timer_start (loop, &tw);
1917		2278
1918	// create one ev_io per pollfd	2279	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2280	for (int i = 0; i < nfd; ++i)
1920	{	2281	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2282	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2283	((fds [i].events & POLLIN ? EV_READ : 0)
1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2284	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2285
1925	fds [i].revents = 0;	2286	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2287	ev_io_start (loop, iow + i);
1927	}	2288	}
1928	}	2289	}
1929		2290
1930	// stop all watchers after blocking	2291	// stop all watchers after blocking
1931	static void	2292	static void
1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2293	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1933	{	2294	{
1934	ev_timer_stop (loop, &tw);	2295	ev_timer_stop (loop, &tw);
1935		2296
1936	for (int i = 0; i < nfd; ++i)	2297	for (int i = 0; i < nfd; ++i)
1937	{	2298	{
1938	// set the relevant poll flags	2299	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2300	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2301	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2302	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2303	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2304	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1944		2305
1945	// now stop the watcher	2306	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2307	ev_io_stop (loop, iow + i);
1947	}	2308	}
1948		2309
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2310	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2311	}
1951		2312
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2313	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.	2314	in the prepare watcher and would dispose of the check watcher.
1954		2315
1955	Method 3: If the module to be embedded supports explicit event	2316	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2317	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2318	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2319
1959	static void	2320	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2321	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2322	{
1962	adns_state ads = (adns_state)w->data;	2323	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2324	update_now (EV_A);
1964		2325
1965	adns_processtimeouts (ads, &tv_now);	2326	adns_processtimeouts (ads, &tv_now);
1966	}	2327	}
1967		2328
1968	static void	2329	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2330	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2331	{
1971	adns_state ads = (adns_state)w->data;	2332	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2333	update_now (EV_A);
1973		2334
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2335	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2336	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2337	}
1977		2338
1978	// do not ever call adns_afterpoll	2339	// do not ever call adns_afterpoll
1979		2340
1980	Method 4: Do not use a prepare or check watcher because the module you	2341	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	2342	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	2343	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	2344	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2345	this approach, effectively embedding EV as a client into the horrible
		2346	libglib event loop.
1985		2347
1986	static gint	2348	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2349	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2350	{
1989	int got_events = 0;	2351	int got_events = 0;
1990		2352
1991	for (n = 0; n < nfds; ++n)	2353	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2354	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2355
1994	if (timeout >= 0)	2356	if (timeout >= 0)
1995	// create/start timer	2357	// create/start timer
1996		2358
1997	// poll	2359	// poll
1998	ev_loop (EV_A_ 0);	2360	ev_loop (EV_A_ 0);
1999		2361
2000	// stop timer again	2362	// stop timer again
2001	if (timeout >= 0)	2363	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2364	ev_timer_stop (EV_A_ &to);
2003		2365
2004	// stop io watchers again - their callbacks should have set	2366	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2367	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2368	ev_io_stop (EV_A_ iow [n]);
2007		2369
2008	return got_events;	2370	return got_events;
2009	}	2371	}
2010		2372
2011		2373
2012	=head2 C<ev_embed> - when one backend isn't enough...	2374	=head2 C<ev_embed> - when one backend isn't enough...
2013		2375
2014	This is a rather advanced watcher type that lets you embed one event loop	2376	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2382	prioritise I/O.
2021		2383
2022	As an example for a bug workaround, the kqueue backend might only support	2384	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	2385	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	2386	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	2387	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	2388	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	2389	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.	2390	C<kevent>, but at least you can use both mechanisms for what they are
		2391	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2392
2030	As for prioritising I/O: rarely you have the case where some fds have	2393	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	2394	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	2395	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	2396	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.	2397	the rest in a second one, and embed the second one in the first.
2035		2398
2036	As long as the watcher is active, the callback will be invoked every time	2399	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	2400	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	2401	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	2402	their callbacks (you could also start an idle watcher to give the embedded
…		…
2047	interested in that.	2410	interested in that.
2048		2411
2049	Also, there have not currently been made special provisions for forking:	2412	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,	2413	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	2414	but you will also have to stop and restart any C<ev_embed> watchers
2052	yourself.	2415	yourself - but you can use a fork watcher to handle this automatically,
		2416	and future versions of libev might do just that.
2053		2417
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2418	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2419	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2420	portable one.
2057		2421
2058	So when you want to use this feature you will always have to be prepared	2422	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	2423	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	2424	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.	2425	create it, and if that fails, use the normal loop for everything.
2062		2426
		2427	=head3 C<ev_embed> and fork
		2428
		2429	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2430	automatically be applied to the embedded loop as well, so no special
		2431	fork handling is required in that case. When the watcher is not running,
		2432	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2433	as applicable.
		2434
2063	=head3 Watcher-Specific Functions and Data Members	2435	=head3 Watcher-Specific Functions and Data Members
2064		2436
2065	=over 4	2437	=over 4
2066		2438
2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2439	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2070		2442
2071	Configures the watcher to embed the given loop, which must be	2443	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	2444	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	2445	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,	2446	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).	2447	if you do not want that, you need to temporarily stop the embed watcher).
2076		2448
2077	=item ev_embed_sweep (loop, ev_embed *)	2449	=item ev_embed_sweep (loop, ev_embed *)
2078		2450
2079	Make a single, non-blocking sweep over the embedded loop. This works	2451	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	2452	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2453	appropriate way for embedded loops.
2082		2454
2083	=item struct ev_loop *other [read-only]	2455	=item struct ev_loop *other [read-only]
2084		2456
2085	The embedded event loop.	2457	The embedded event loop.
2086		2458
…		…
2088		2460
2089	=head3 Examples	2461	=head3 Examples
2090		2462
2091	Example: Try to get an embeddable event loop and embed it into the default	2463	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	2464	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	2465	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	2466	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2467	used).
2096		2468
2097	struct ev_loop *loop_hi = ev_default_init (0);	2469	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2470	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2471	ev_embed embed;
2100		2472
2101	// see if there is a chance of getting one that works	2473	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2474	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2475	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2476	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2477	: 0;
2106		2478
2107	// if we got one, then embed it, otherwise default to loop_hi	2479	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2480	if (loop_lo)
2109	{	2481	{
2110	ev_embed_init (&embed, 0, loop_lo);	2482	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2483	ev_embed_start (loop_hi, &embed);
2112	}	2484	}
2113	else	2485	else
2114	loop_lo = loop_hi;	2486	loop_lo = loop_hi;
2115		2487
2116	Example: Check if kqueue is available but not recommended and create	2488	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2489	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2490	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2491	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2492
2121	struct ev_loop *loop = ev_default_init (0);	2493	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2494	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2495	ev_embed embed;
2124		2496
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2497	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2498	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2499	{
2128	ev_embed_init (&embed, 0, loop_socket);	2500	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2501	ev_embed_start (loop, &embed);
2130	}	2502	}
2131		2503
2132	if (!loop_socket)	2504	if (!loop_socket)
2133	loop_socket = loop;	2505	loop_socket = loop;
2134		2506
2135	// now use loop_socket for all sockets, and loop for everything else	2507	// now use loop_socket for all sockets, and loop for everything else
2136		2508
2137		2509
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2510	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2511
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2512	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	2556	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	2557	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2558	need elaborate support such as pthreads.
2187		2559
2188	That means that if you want to queue data, you have to provide your own	2560	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	2561	queue. But at least I can tell you how to implement locking around your
2190	queue:	2562	queue:
2191		2563
2192	=over 4	2564	=over 4
2193		2565
2194	=item queueing from a signal handler context	2566	=item queueing from a signal handler context
2195		2567
2196	To implement race-free queueing, you simply add to the queue in the signal	2568	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	2569	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2570	an example that does that for some fictitious SIGUSR1 handler:
2199		2571
2200	static ev_async mysig;	2572	static ev_async mysig;
2201		2573
2202	static void	2574	static void
2203	sigusr1_handler (void)	2575	sigusr1_handler (void)
…		…
2270		2642
2271	=item ev_async_init (ev_async *, callback)	2643	=item ev_async_init (ev_async *, callback)
2272		2644
2273	Initialises and configures the async watcher - it has no parameters of any	2645	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,	2646	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2275	believe me.	2647	trust me.
2276		2648
2277	=item ev_async_send (loop, ev_async *)	2649	=item ev_async_send (loop, ev_async *)
2278		2650
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2651	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	2652	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	2653	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	2654	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	2655	section below on what exactly this means).
2284		2656
2285	This call incurs the overhead of a syscall only once per loop iteration,	2657	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	2658	so while the overhead might be noticeable, it doesn't apply to repeated
2287	calls to C<ev_async_send>.	2659	calls to C<ev_async_send>.
2288		2660
2289	=item bool = ev_async_pending (ev_async *)	2661	=item bool = ev_async_pending (ev_async *)
2290		2662
2291	Returns a non-zero value when C<ev_async_send> has been called on the	2663	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2293	event loop.	2665	event loop.
2294		2666
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2667	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,	2668	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	2669	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.	2670	quickly check whether invoking the loop might be a good idea.
2299		2671
2300	Not that this does I<not> check wether the watcher itself is pending, only	2672	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.	2673	whether it has been requested to make this watcher pending.
2302		2674
2303	=back	2675	=back
2304		2676
2305		2677
2306	=head1 OTHER FUNCTIONS	2678	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	2682	=over 4
2311		2683
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2684	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		2685
2314	This function combines a simple timer and an I/O watcher, calls your	2686	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	2687	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	2688	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	2689	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	2690	more watchers yourself.
2319		2691
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	2692	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	2693	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	2694	the given C<fd> and C<events> set will be created and started.
2323		2695
2324	If C<timeout> is less than 0, then no timeout watcher will be	2696	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	2697	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	2698	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		2699
2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2700	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	2701	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>	2702	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	2703	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2704	a timeout and an io event at the same time - you probably should give io
		2705	events precedence.
2333		2706
		2707	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2708
2334	static void stdin_ready (int revents, void *arg)	2709	static void stdin_ready (int revents, void *arg)
2335	{	2710	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	2711	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	2712	/* stdin might have data for us, joy! */;
		2713	else if (revents & EV_TIMEOUT)
		2714	/* doh, nothing entered */;
2340	}	2715	}
2341		2716
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2717	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		2718
2344	=item ev_feed_event (ev_loop *, watcher *, int revents)	2719	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2345		2720
2346	Feeds the given event set into the event loop, as if the specified event	2721	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	2722	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).	2723	initialised but not necessarily started event watcher).
2349		2724
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2725	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2351		2726
2352	Feed an event on the given fd, as if a file descriptor backend detected	2727	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	2728	the given events it.
2354		2729
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	2730	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2356		2731
2357	Feed an event as if the given signal occured (C<loop> must be the default	2732	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	2733	loop!).
2359		2734
2360	=back	2735	=back
2361		2736
2362		2737
…		…
2391	=back	2766	=back
2392		2767
2393	=head1 C++ SUPPORT	2768	=head1 C++ SUPPORT
2394		2769
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2770	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	2771	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.	2772	the callback model to a model using method callbacks on objects.
2398		2773
2399	To use it,	2774	To use it,
2400		2775
2401	#include <ev++.h>	2776	#include <ev++.h>
2402		2777
2403	This automatically includes F<ev.h> and puts all of its definitions (many	2778	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	2779	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	2780	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2781	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	2848	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.	2849	thunking function, making it as fast as a direct C callback.
2475		2850
2476	Example: simple class declaration and watcher initialisation	2851	Example: simple class declaration and watcher initialisation
2477		2852
2478	struct myclass	2853	struct myclass
2479	{	2854	{
2480	void io_cb (ev::io &w, int revents) { }	2855	void io_cb (ev::io &w, int revents) { }
2481	}	2856	}
2482		2857
2483	myclass obj;	2858	myclass obj;
2484	ev::io iow;	2859	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	2860	iow.set <myclass, &myclass::io_cb> (&obj);
2486		2861
2487	=item w->set<function> (void *data = 0)	2862	=item w->set<function> (void *data = 0)
2488		2863
2489	Also sets a callback, but uses a static method or plain function as	2864	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	2865	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		2867
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2868	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		2869
2495	See the method-C<set> above for more details.	2870	See the method-C<set> above for more details.
2496		2871
2497	Example:	2872	Example: Use a plain function as callback.
2498		2873
2499	static void io_cb (ev::io &w, int revents) { }	2874	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	2875	iow.set <io_cb> ();
2501		2876
2502	=item w->set (struct ev_loop *)	2877	=item w->set (struct ev_loop *)
2503		2878
2504	Associates a different C<struct ev_loop> with this watcher. You can only	2879	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).	2880	do this when the watcher is inactive (and not pending either).
2506		2881
2507	=item w->set ([args])	2882	=item w->set ([arguments])
2508		2883
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2884	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	2885	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	2886	automatically stopped and restarted when reconfiguring it with this
2512	method.	2887	method.
2513		2888
2514	=item w->start ()	2889	=item w->start ()
…		…
2538	=back	2913	=back
2539		2914
2540	Example: Define a class with an IO and idle watcher, start one of them in	2915	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	2916	the constructor.
2542		2917
2543	class myclass	2918	class myclass
2544	{	2919	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	2920	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	2921	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		2922
2548	myclass (int fd)	2923	myclass (int fd)
2549	{	2924	{
2550	io .set <myclass, &myclass::io_cb > (this);	2925	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	2926	idle.set <myclass, &myclass::idle_cb> (this);
2552		2927
2553	io.start (fd, ev::READ);	2928	io.start (fd, ev::READ);
2554	}	2929	}
2555	};	2930	};
2556		2931
2557		2932
2558	=head1 OTHER LANGUAGE BINDINGS	2933	=head1 OTHER LANGUAGE BINDINGS
2559		2934
2560	Libev does not offer other language bindings itself, but bindings for a	2935	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	2936	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	2937	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	2938	me a note.
2564		2939
2565	=over 4	2940	=over 4
2566		2941
2567	=item Perl	2942	=item Perl
2568		2943
2569	The EV module implements the full libev API and is actually used to test	2944	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,	2945	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	2946	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	2947	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>).	2948	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2949	and C<EV::Glib>).
2574		2950
2575	It can be found and installed via CPAN, its homepage is found at	2951	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	2952	L<http://software.schmorp.de/pkg/EV>.
2577		2953
		2954	=item Python
		2955
		2956	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2957	seems to be quite complete and well-documented. Note, however, that the
		2958	patch they require for libev is outright dangerous as it breaks the ABI
		2959	for everybody else, and therefore, should never be applied in an installed
		2960	libev (if python requires an incompatible ABI then it needs to embed
		2961	libev).
		2962
2578	=item Ruby	2963	=item Ruby
2579		2964
2580	Tony Arcieri has written a ruby extension that offers access to a subset	2965	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	2966	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	2967	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	2968	L<http://rev.rubyforge.org/>.
2584		2969
2585	=item D	2970	=item D
2586		2971
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2972	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>.	2973	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2974
		2975	=item Ocaml
		2976
		2977	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2978	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2589		2979
2590	=back	2980	=back
2591		2981
2592		2982
2593	=head1 MACRO MAGIC	2983	=head1 MACRO MAGIC
2594		2984
2595	Libev can be compiled with a variety of options, the most fundamantal	2985	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2986	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	2987	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		2988
2599	To make it easier to write programs that cope with either variant, the	2989	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	2990	following macros are defined:
…		…
2605		2995
2606	This provides the loop I<argument> for functions, if one is required ("ev	2996	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,	2997	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:	2998	C<EV_A_> is used when other arguments are following. Example:
2609		2999
2610	ev_unref (EV_A);	3000	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3001	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3002	ev_loop (EV_A_ 0);
2613		3003
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3004	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3005	which is often provided by the following macro.
2616		3006
2617	=item C<EV_P>, C<EV_P_>	3007	=item C<EV_P>, C<EV_P_>
2618		3008
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3009	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,	3010	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:	3011	C<EV_P_> is used when other parameters are following. Example:
2622		3012
2623	// this is how ev_unref is being declared	3013	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3014	static void ev_unref (EV_P);
2625		3015
2626	// this is how you can declare your typical callback	3016	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3017	static void cb (EV_P_ ev_timer *w, int revents)
2628		3018
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3019	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3020	suitable for use with C<EV_A>.
2631		3021
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3022	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3038
2649	Example: Declare and initialise a check watcher, utilising the above	3039	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3040	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3041	or not.
2652		3042
2653	static void	3043	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3044	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	3045	{
2656	ev_check_stop (EV_A_ w);	3046	ev_check_stop (EV_A_ w);
2657	}	3047	}
2658		3048
2659	ev_check check;	3049	ev_check check;
2660	ev_check_init (&check, check_cb);	3050	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	3051	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	3052	ev_loop (EV_DEFAULT_ 0);
2663		3053
2664	=head1 EMBEDDING	3054	=head1 EMBEDDING
2665		3055
2666	Libev can (and often is) directly embedded into host	3056	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	3057	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	3064	libev somewhere in your source tree).
2675		3065
2676	=head2 FILESETS	3066	=head2 FILESETS
2677		3067
2678	Depending on what features you need you need to include one or more sets of files	3068	Depending on what features you need you need to include one or more sets of files
2679	in your app.	3069	in your application.
2680		3070
2681	=head3 CORE EVENT LOOP	3071	=head3 CORE EVENT LOOP
2682		3072
2683	To include only the libev core (all the C<ev_*> functions), with manual	3073	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	3074	configuration (no autoconf):
2685		3075
2686	#define EV_STANDALONE 1	3076	#define EV_STANDALONE 1
2687	#include "ev.c"	3077	#include "ev.c"
2688		3078
2689	This will automatically include F<ev.h>, too, and should be done in a	3079	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	3080	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	3081	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	3082	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	3083	where you can put other configuration options):
2694		3084
2695	#define EV_STANDALONE 1	3085	#define EV_STANDALONE 1
2696	#include "ev.h"	3086	#include "ev.h"
2697		3087
2698	Both header files and implementation files can be compiled with a C++	3088	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	3089	compiler (at least, thats a stated goal, and breakage will be treated
2700	as a bug).	3090	as a bug).
2701		3091
2702	You need the following files in your source tree, or in a directory	3092	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):	3093	in your include path (e.g. in libev/ when using -Ilibev):
2704		3094
2705	ev.h	3095	ev.h
2706	ev.c	3096	ev.c
2707	ev_vars.h	3097	ev_vars.h
2708	ev_wrap.h	3098	ev_wrap.h
2709		3099
2710	ev_win32.c required on win32 platforms only	3100	ev_win32.c required on win32 platforms only
2711		3101
2712	ev_select.c only when select backend is enabled (which is enabled by default)	3102	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)	3103	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)	3104	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)	3105	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)	3106	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		3107
2718	F<ev.c> includes the backend files directly when enabled, so you only need	3108	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	3109	to compile this single file.
2720		3110
2721	=head3 LIBEVENT COMPATIBILITY API	3111	=head3 LIBEVENT COMPATIBILITY API
2722		3112
2723	To include the libevent compatibility API, also include:	3113	To include the libevent compatibility API, also include:
2724		3114
2725	#include "event.c"	3115	#include "event.c"
2726		3116
2727	in the file including F<ev.c>, and:	3117	in the file including F<ev.c>, and:
2728		3118
2729	#include "event.h"	3119	#include "event.h"
2730		3120
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	3121	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		3122
2733	You need the following additional files for this:	3123	You need the following additional files for this:
2734		3124
2735	event.h	3125	event.h
2736	event.c	3126	event.c
2737		3127
2738	=head3 AUTOCONF SUPPORT	3128	=head3 AUTOCONF SUPPORT
2739		3129
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	3130	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	3131	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	3132	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	3133	include F<config.h> and configure itself accordingly.
2744		3134
2745	For this of course you need the m4 file:	3135	For this of course you need the m4 file:
2746		3136
2747	libev.m4	3137	libev.m4
2748		3138
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	3139	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		3140
2751	Libev can be configured via a variety of preprocessor symbols you have to	3141	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	3142	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	3143	autoconf is documented for every option.
2754		3144
2755	=over 4	3145	=over 4
2756		3146
2757	=item EV_STANDALONE	3147	=item EV_STANDALONE
2758		3148
…		…
2763	F<event.h> that are not directly supported by the libev core alone.	3153	F<event.h> that are not directly supported by the libev core alone.
2764		3154
2765	=item EV_USE_MONOTONIC	3155	=item EV_USE_MONOTONIC
2766		3156
2767	If defined to be C<1>, libev will try to detect the availability of the	3157	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	3158	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	3159	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	3160	usually have to link against librt or something similar. Enabling it when
2771	the functionality isn't available is safe, though, although you have	3161	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>	3162	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	3163	function is hiding in (often F<-lrt>).
2774		3164
2775	=item EV_USE_REALTIME	3165	=item EV_USE_REALTIME
2776		3166
2777	If defined to be C<1>, libev will try to detect the availability of the	3167	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	3168	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	3169	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	3170	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3171	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3172	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2783		3173
2784	=item EV_USE_NANOSLEEP	3174	=item EV_USE_NANOSLEEP
…		…
2795	2.7 or newer, otherwise disabled.	3185	2.7 or newer, otherwise disabled.
2796		3186
2797	=item EV_USE_SELECT	3187	=item EV_USE_SELECT
2798		3188
2799	If undefined or defined to be C<1>, libev will compile in support for the	3189	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	3190	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	3191	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3192	will not be compiled in.
2803		3193
2804	=item EV_SELECT_USE_FD_SET	3194	=item EV_SELECT_USE_FD_SET
2805		3195
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3196	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	3197	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	3198	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	3199	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	3200	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	3201	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2812	influence the size of the C<fd_set> used.	3202	influence the size of the C<fd_set> used.
2813		3203
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3252	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3253	backend for Solaris 10 systems.
2864		3254
2865	=item EV_USE_DEVPOLL	3255	=item EV_USE_DEVPOLL
2866		3256
2867	reserved for future expansion, works like the USE symbols above.	3257	Reserved for future expansion, works like the USE symbols above.
2868		3258
2869	=item EV_USE_INOTIFY	3259	=item EV_USE_INOTIFY
2870		3260
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3261	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	3262	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	3269	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	3270	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"	3271	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.	3272	as well as for signal and thread safety in C<ev_async> watchers.
2883		3273
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3274	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.	3275	(from F<signal.h>), which is usually good enough on most platforms.
2886		3276
2887	=item EV_H	3277	=item EV_H
2888		3278
2889	The name of the F<ev.h> header file used to include it. The default if	3279	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	3318	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	3319	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	3320	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3321	fine.
2932		3322
2933	If your embedding app does not need any priorities, defining these both to	3323	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3324	both to C<0> will save some memory and CPU.
2935		3325
2936	=item EV_PERIODIC_ENABLE	3326	=item EV_PERIODIC_ENABLE
2937		3327
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3328	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	3329	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3336	code.
2947		3337
2948	=item EV_EMBED_ENABLE	3338	=item EV_EMBED_ENABLE
2949		3339
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3340	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not. Embed watchers rely on most other
		3342	watcher types, which therefore must not be disabled.
2952		3343
2953	=item EV_STAT_ENABLE	3344	=item EV_STAT_ENABLE
2954		3345
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3346	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3347	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3357	defined to be C<0>, then they are not.
2967		3358
2968	=item EV_MINIMAL	3359	=item EV_MINIMAL
2969		3360
2970	If you need to shave off some kilobytes of code at the expense of some	3361	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	3362	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3363	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3364	much smaller 2-heap for timer management over the default 4-heap.
2973		3365
2974	=item EV_PID_HASHSIZE	3366	=item EV_PID_HASHSIZE
2975		3367
2976	C<ev_child> watchers use a small hash table to distribute workload by	3368	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	3369	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>),	3376	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>	3377	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	3378	watchers you might want to increase this value (I<must> be a power of
2987	two).	3379	two).
2988		3380
		3381	=item EV_USE_4HEAP
		3382
		3383	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3384	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3385	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3386	faster performance with many (thousands) of watchers.
		3387
		3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3389	(disabled).
		3390
		3391	=item EV_HEAP_CACHE_AT
		3392
		3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3394	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3395	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3396	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3397	but avoids random read accesses on heap changes. This improves performance
		3398	noticeably with many (hundreds) of watchers.
		3399
		3400	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3401	(disabled).
		3402
		3403	=item EV_VERIFY
		3404
		3405	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3406	be done: If set to C<0>, no internal verification code will be compiled
		3407	in. If set to C<1>, then verification code will be compiled in, but not
		3408	called. If set to C<2>, then the internal verification code will be
		3409	called once per loop, which can slow down libev. If set to C<3>, then the
		3410	verification code will be called very frequently, which will slow down
		3411	libev considerably.
		3412
		3413	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3414	C<0>.
		3415
2989	=item EV_COMMON	3416	=item EV_COMMON
2990		3417
2991	By default, all watchers have a C<void *data> member. By redefining	3418	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	3419	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,	3420	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3421	though, and it must be identical each time.
2995		3422
2996	For example, the perl EV module uses something like this:	3423	For example, the perl EV module uses something like this:
2997		3424
2998	#define EV_COMMON \	3425	#define EV_COMMON \
2999	SV *self; /* contains this struct */ \	3426	SV *self; /* contains this struct */ \
3000	SV *cb_sv, *fh /* note no trailing ";" */	3427	SV *cb_sv, *fh /* note no trailing ";" */
3001		3428
3002	=item EV_CB_DECLARE (type)	3429	=item EV_CB_DECLARE (type)
3003		3430
3004	=item EV_CB_INVOKE (watcher, revents)	3431	=item EV_CB_INVOKE (watcher, revents)
3005		3432
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3437	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	3438	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	3439	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++.	3440	method calls instead of plain function calls in C++.
3014		3441
		3442	=back
		3443
3015	=head2 EXPORTED API SYMBOLS	3444	=head2 EXPORTED API SYMBOLS
3016		3445
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3446	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	3447	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3448	all public symbols, one per line:
3020		3449
3021	Symbols.ev for libev proper	3450	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3451	Symbols.event for the libevent emulation
3023		3452
3024	This can also be used to rename all public symbols to avoid clashes with	3453	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	3454	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3455	itself, but sometimes it is inconvenient to avoid this).
3027		3456
3028	A sed command like this will create wrapper C<#define>'s that you need to	3457	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3458	include before including F<ev.h>:
3030		3459
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3460	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3477	file.
3049		3478
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3479	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:	3480	that everybody includes and which overrides some configure choices:
3052		3481
3053	#define EV_MINIMAL 1	3482	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3483	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3484	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3485	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3486	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3487	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3488	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3489	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3490	#define EV_MAXPRI 0
3062		3491
3063	#include "ev++.h"	3492	#include "ev++.h"
3064		3493
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3494	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3495
3067	#include "ev_cpp.h"	3496	#include "ev_cpp.h"
3068	#include "ev.c"	3497	#include "ev.c"
3069		3498
		3499	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3500
3071	=head1 THREADS AND COROUTINES	3501	=head2 THREADS AND COROUTINES
3072		3502
3073	=head2 THREADS	3503	=head3 THREADS
3074		3504
3075	Libev itself is completely threadsafe, but it uses no locking. This	3505	All libev functions are reentrant and thread-safe unless explicitly
		3506	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	3507	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	3508	are no concurrent calls into any libev function with the same loop
3078	parameter.	3509	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3510	of course): libev guarantees that different event loops share no data
		3511	structures that need any locking.
3079		3512
3080	Or put differently: calls with different loop parameters can be done in	3513	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	3514	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	3515	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	3516	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3517	a mutex per loop).
3085		3518
3086	If you want to know which design is best for your problem, then I cannot	3519	Specifically to support threads (and signal handlers), libev implements
		3520	so-called C<ev_async> watchers, which allow some limited form of
		3521	concurrency on the same event loop, namely waking it up "from the
		3522	outside".
		3523
		3524	If you want to know which design (one loop, locking, or multiple loops
		3525	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3526	help you, but here is some generic advice:
3088		3527
3089	=over 4	3528	=over 4
3090		3529
3091	=item * most applications have a main thread: use the default libev loop	3530	=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.	3531	in that thread, or create a separate thread running only the default loop.
3093		3532
3094	This helps integrating other libraries or software modules that use libev	3533	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	3534	themselves and don't care/know about threading.
3096		3535
3097	=item * one loop per thread is usually a good model.	3536	=item * one loop per thread is usually a good model.
3098		3537
3099	Doing this is almost never wrong, sometimes a better-performance model	3538	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	3539	exists, but it is always a good start.
3101		3540
3102	=item * other models exist, such as the leader/follower pattern, where one	3541	=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.	3542	loop is handed through multiple threads in a kind of round-robin fashion.
3104		3543
3105	Chosing a model is hard - look around, learn, know that usually you cna do	3544	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	3545	better than you currently do :-)
3107		3546
3108	=item * often you need to talk to some other thread which blocks in the	3547	=item * often you need to talk to some other thread which blocks in the
		3548	event loop.
		3549
3109	event loop - C<ev_async> watchers can be used to wake them up from other	3550	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	3551	(or from signal contexts...).
		3552
		3553	An example use would be to communicate signals or other events that only
		3554	work in the default loop by registering the signal watcher with the
		3555	default loop and triggering an C<ev_async> watcher from the default loop
		3556	watcher callback into the event loop interested in the signal.
3111		3557
3112	=back	3558	=back
3113		3559
3114	=head2 COROUTINES	3560	=head3 COROUTINES
3115		3561
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	3562	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	3563	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	3564	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	3565	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	3566	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.	3567	you must not do this from C<ev_periodic> reschedule callbacks.
3122		3568
3123	Care has been invested into making sure that libev does not keep local	3569	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	3570	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	3571	they do not clal any callbacks.
3126		3572
		3573	=head2 COMPILER WARNINGS
3127		3574
3128	=head1 COMPLEXITIES	3575	Depending on your compiler and compiler settings, you might get no or a
		3576	lot of warnings when compiling libev code. Some people are apparently
		3577	scared by this.
3129		3578
3130	In this section the complexities of (many of) the algorithms used inside	3579	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	3580	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	3581	warning options. "Warn-free" code therefore cannot be a goal except when
		3582	targeting a specific compiler and compiler-version.
3133		3583
3134	All of the following are about amortised time: If an array needs to be	3584	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	3585	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	3586	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		3587
3140	=over 4	3588	And of course, some compiler warnings are just plain stupid, or simply
		3589	wrong (because they don't actually warn about the condition their message
		3590	seems to warn about). For example, certain older gcc versions had some
		3591	warnings that resulted an extreme number of false positives. These have
		3592	been fixed, but some people still insist on making code warn-free with
		3593	such buggy versions.
3141		3594
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3595	While libev is written to generate as few warnings as possible,
		3596	"warn-free" code is not a goal, and it is recommended not to build libev
		3597	with any compiler warnings enabled unless you are prepared to cope with
		3598	them (e.g. by ignoring them). Remember that warnings are just that:
		3599	warnings, not errors, or proof of bugs.
3143		3600
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		3601
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3602	=head2 VALGRIND
3149		3603
3150	That means that changing a timer costs less than removing/adding them	3604	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.	3605	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		3606
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3607	If you think you found a bug (memory leak, uninitialised data access etc.)
		3608	in libev, then check twice: If valgrind reports something like:
3154		3609
3155	These just add the watcher into an array or at the head of a list.	3610	==2274== definitely lost: 0 bytes in 0 blocks.
		3611	==2274== possibly lost: 0 bytes in 0 blocks.
		3612	==2274== still reachable: 256 bytes in 1 blocks.
3156		3613
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3614	Then there is no memory leak, just as memory accounted to global variables
		3615	is not a memleak - the memory is still being refernced, and didn't leak.
3158		3616
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3617	Similarly, under some circumstances, valgrind might report kernel bugs
		3618	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3619	although an acceptable workaround has been found here), or it might be
		3620	confused.
3160		3621
3161	These watchers are stored in lists then need to be walked to find the	3622	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	3623	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		3624
3165	=item Finding the next timer in each loop iteration: O(1)	3625	If you are unsure about something, feel free to contact the mailing list
		3626	with the full valgrind report and an explanation on why you think this
		3627	is a bug in libev (best check the archives, too :). However, don't be
		3628	annoyed when you get a brisk "this is no bug" answer and take the chance
		3629	of learning how to interpret valgrind properly.
3166		3630
3167	By virtue of using a binary heap, the next timer is always found at the	3631	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	3632	I suggest using suppression lists.
3169		3633
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3634
3172	A change means an I/O watcher gets started or stopped, which requires	3635	=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		3636
3176	=item Activating one watcher (putting it into the pending state): O(1)	3637	=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		3638
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3639	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	3640	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	3641	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3642	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3643	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3644	e.g. cygwin.
3206		3645
		3646	Lifting these limitations would basically require the full
		3647	re-implementation of the I/O system. If you are into these kinds of
		3648	things, then note that glib does exactly that for you in a very portable
		3649	way (note also that glib is the slowest event library known to man).
		3650
3207	There is no supported compilation method available on windows except	3651	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3652	embedding it into other applications.
3209		3653
		3654	Not a libev limitation but worth mentioning: windows apparently doesn't
		3655	accept large writes: instead of resulting in a partial write, windows will
		3656	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3657	so make sure you only write small amounts into your sockets (less than a
		3658	megabyte seems safe, but this apparently depends on the amount of memory
		3659	available).
		3660
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3661	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	3662	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3663	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	3664	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	3665	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3666	notification model, which cannot be implemented efficiently on windows
		3667	(Microsoft monopoly games).
		3668
		3669	A typical way to use libev under windows is to embed it (see the embedding
		3670	section for details) and use the following F<evwrap.h> header file instead
		3671	of F<ev.h>:
		3672
		3673	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3674	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3675
		3676	#include "ev.h"
		3677
		3678	And compile the following F<evwrap.c> file into your project (make sure
		3679	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3680
		3681	#include "evwrap.h"
		3682	#include "ev.c"
3216		3683
3217	=over 4	3684	=over 4
3218		3685
3219	=item The winsocket select function	3686	=item The winsocket select function
3220		3687
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3688	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	3689	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3690	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>,	3691	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	3692	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	3693	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3694	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3695
3228	The configuration for a "naked" win32 using the microsoft runtime	3696	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	3697	libraries and raw winsocket select is:
3230		3698
3231	#define EV_USE_SELECT 1	3699	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3700	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		3701
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3702	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.	3703	complexity in the O(n²) range when using win32.
3236		3704
3237	=item Limited number of file descriptors	3705	=item Limited number of file descriptors
3238		3706
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3707	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3708
		3709	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	3710	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	3711	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).	3712	recommends spawning a chain of threads and wait for 63 handles and the
		3713	previous thread in each. Great).
3244		3714
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3715	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	3716	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	3717	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3718	select emulation on windows).
3249		3719
3250	Another limit is the number of file descriptors in the microsoft runtime	3720	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	3721	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	3722	or something like this inside Microsoft). You can increase this by calling
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3723	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	3724	arbitrary limit), but is broken in many versions of the Microsoft runtime
3255	libraries.	3725	libraries.
3256		3726
3257	This might get you to about C<512> or C<2048> sockets (depending on	3727	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	3728	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	3729	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.	3730	calling select (O(n²)) will likely make this unworkable.
3261		3731
3262	=back	3732	=back
3263		3733
3264
3265	=head1 PORTABILITY REQUIREMENTS	3734	=head2 PORTABILITY REQUIREMENTS
3266		3735
3267	In addition to a working ISO-C implementation, libev relies on a few	3736	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	3737	backend-specific APIs, libev relies on a few additional extensions:
3269		3738
3270	=over 4	3739	=over 4
3271		3740
		3741	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3742	calling conventions regardless of C<ev_watcher_type *>.
		3743
		3744	Libev assumes not only that all watcher pointers have the same internal
		3745	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3746	assumes that the same (machine) code can be used to call any watcher
		3747	callback: The watcher callbacks have different type signatures, but libev
		3748	calls them using an C<ev_watcher *> internally.
		3749
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	3750	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		3751
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	3752	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	3753	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	3754	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	3755	believed to be sufficiently portable.
3278		3756
3279	=item C<sigprocmask> must work in a threaded environment	3757	=item C<sigprocmask> must work in a threaded environment
3280		3758
…		…
3287		3765
3288	The most portable way to handle signals is to block signals in all threads	3766	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	3767	except the initial one, and run the default loop in the initial thread as
3290	well.	3768	well.
3291		3769
		3770	=item C<long> must be large enough for common memory allocation sizes
		3771
		3772	To improve portability and simplify its API, libev uses C<long> internally
		3773	instead of C<size_t> when allocating its data structures. On non-POSIX
		3774	systems (Microsoft...) this might be unexpectedly low, but is still at
		3775	least 31 bits everywhere, which is enough for hundreds of millions of
		3776	watchers.
		3777
		3778	=item C<double> must hold a time value in seconds with enough accuracy
		3779
		3780	The type C<double> is used to represent timestamps. It is required to
		3781	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3782	enough for at least into the year 4000. This requirement is fulfilled by
		3783	implementations implementing IEEE 754 (basically all existing ones).
		3784
3292	=back	3785	=back
3293		3786
3294	If you know of other additional requirements drop me a note.	3787	If you know of other additional requirements drop me a note.
3295		3788
3296		3789
		3790	=head1 ALGORITHMIC COMPLEXITIES
		3791
		3792	In this section the complexities of (many of) the algorithms used inside
		3793	libev will be documented. For complexity discussions about backends see
		3794	the documentation for C<ev_default_init>.
		3795
		3796	All of the following are about amortised time: If an array needs to be
		3797	extended, libev needs to realloc and move the whole array, but this
		3798	happens asymptotically rarer with higher number of elements, so O(1) might
		3799	mean that libev does a lengthy realloc operation in rare cases, but on
		3800	average it is much faster and asymptotically approaches constant time.
		3801
		3802	=over 4
		3803
		3804	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3805
		3806	This means that, when you have a watcher that triggers in one hour and
		3807	there are 100 watchers that would trigger before that, then inserting will
		3808	have to skip roughly seven (C<ld 100>) of these watchers.
		3809
		3810	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3811
		3812	That means that changing a timer costs less than removing/adding them,
		3813	as only the relative motion in the event queue has to be paid for.
		3814
		3815	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3816
		3817	These just add the watcher into an array or at the head of a list.
		3818
		3819	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3820
		3821	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3822
		3823	These watchers are stored in lists, so they need to be walked to find the
		3824	correct watcher to remove. The lists are usually short (you don't usually
		3825	have many watchers waiting for the same fd or signal: one is typical, two
		3826	is rare).
		3827
		3828	=item Finding the next timer in each loop iteration: O(1)
		3829
		3830	By virtue of using a binary or 4-heap, the next timer is always found at a
		3831	fixed position in the storage array.
		3832
		3833	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3834
		3835	A change means an I/O watcher gets started or stopped, which requires
		3836	libev to recalculate its status (and possibly tell the kernel, depending
		3837	on backend and whether C<ev_io_set> was used).
		3838
		3839	=item Activating one watcher (putting it into the pending state): O(1)
		3840
		3841	=item Priority handling: O(number_of_priorities)
		3842
		3843	Priorities are implemented by allocating some space for each
		3844	priority. When doing priority-based operations, libev usually has to
		3845	linearly search all the priorities, but starting/stopping and activating
		3846	watchers becomes O(1) with respect to priority handling.
		3847
		3848	=item Sending an ev_async: O(1)
		3849
		3850	=item Processing ev_async_send: O(number_of_async_watchers)
		3851
		3852	=item Processing signals: O(max_signal_number)
		3853
		3854	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3855	calls in the current loop iteration. Checking for async and signal events
		3856	involves iterating over all running async watchers or all signal numbers.
		3857
		3858	=back
		3859
		3860
3297	=head1 AUTHOR	3861	=head1 AUTHOR
3298		3862
3299	Marc Lehmann <libev@schmorp.de>.	3863	Marc Lehmann <libev@schmorp.de>.
3300		3864

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines