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Revision 1.144 by root, Mon Apr 7 12:33:29 2008 UTC vs.
Revision 1.199 by root, Thu Oct 23 07:18:21 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 is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
226	}	250	}
227		251
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
252		276
253	=back	277	=back
254		278
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<ev_loop *>. The library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260		284
261	=over 4	285	=over 4
262		286
…		…
274	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
275	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
276		300
277	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
278	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
279	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
280	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
282	C<ev_default_init>.	306	C<ev_default_init>.
283		307
284	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
293	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
294	thing, believe me).	318	thing, believe me).
295		319
296	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
297		321
298	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
299	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
300	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
301	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
302	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
303	around bugs.	327	around bugs.
…		…
310		334
311	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
312	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
313	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
314	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
315	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
316	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
317		341
318	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
319	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
320	flag.	344	flag.
321		345
322	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
323	environment variable.	347	environment variable.
324		348
325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
326		350
327	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
329	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
330	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
331	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
332		356
333	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
334	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
335	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
336	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
337	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
338	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
339		367
340	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
341		369
342	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
343	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
344	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
345	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
346	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
347	performance tips.	375	performance tips.
348		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
349	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
350		381
351	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
352	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
353	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
354	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
355	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
356	cases and requiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
357	support for dup.	388	support for dup.
358		389
359	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
360	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
361	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
362	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
363	very well if you register events for both fds.	394	very well if you register events for both fds.
364		395
365	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
366	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
367	(or space) is available.	398	(or space) is available.
368		399
369	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
370	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
371	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
372		405
373	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
374	all kernel versions tested so far.	407	all kernel versions tested so far.
375		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
377		413
378	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
379	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
380	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
381	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
382	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
383	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
384	system like NetBSD.
385		420
386	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
387	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
388	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
389		424
390	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
391	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
392	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
393	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
394	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
395	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
396		431
397	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
398		433
399	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
400	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
401	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
402	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
404	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
405		444
406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
407		446
408	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
409	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
414		453
415	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
416	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
417		456
418	Please note that solaris event ports can deliver a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
419	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
420	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
421		460
422	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
423	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
425	might perform better.	464	might perform better.
426		465
427	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
428	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
429	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
430		473
431	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
432		475
433	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
434	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
436		479
437	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
438		481
439	=back	482	=back
440		483
441	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
442	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
443	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
444		487
445	The most typical usage is like this:	488	Example: This is the most typical usage.
446		489
447	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
449		492
450	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
451	environment settings to be taken into account:	494	environment settings to be taken into account:
452		495
453	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
454		497
455	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
456	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
457	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
458		502
459	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
460		504
461	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
462		506
463	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
464	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
…		…
469	libev with threads is indeed to create one loop per thread, and using the	513	libev with threads is indeed to create one loop per thread, and using the
470	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
471		515
472	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
473		517
474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
475	if (!epoller)	519	if (!epoller)
476	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
477		521
478	=item ev_default_destroy ()	522	=item ev_default_destroy ()
479		523
480	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
481	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
482	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
483	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
484	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
485	the easiest thing, you can just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
486	for example).	530	for example).
487		531
488	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
520		564
521	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
522		566
523	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
524	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
525	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
526		571
527	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
528		573
529	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
530		576
531	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
532		578
533	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
534	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
549	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
550	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
551	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
552	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
553		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
554	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
555		613
556	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
557	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
558	events.	616	events.
…		…
560	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
561	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
562		620
563	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
564	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
565	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
566	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
567	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
568		627
569	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
570	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
571	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
572		632
573	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
574	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
575	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
576	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
577	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
578	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
579	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
580		644
581	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
582		646
583	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
584	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
585	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
586	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
587	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
588	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
589	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
590	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
591	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
592	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
593	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
594	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
595	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
596	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
597	- Queue all outstanding timers.	662	- Queue all expired timers.
598	- Queue all outstanding periodics.	663	- Queue all expired periodics.
599	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
600	- Queue all check watchers.	665	- Queue all check watchers.
601	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
602	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
603	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
604	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
609	anymore.	674	anymore.
610		675
611	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
612	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
613	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
614	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
615		680
616	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
617		682
618	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
619	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
620	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
621	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
622		687
623	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
624		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
625	=item ev_ref (loop)	692	=item ev_ref (loop)
626		693
627	=item ev_unref (loop)	694	=item ev_unref (loop)
628		695
629	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
630	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
631	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
632	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
633	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
634	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
635	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
636	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
637	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
638	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
639	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
640	respectively).	710	respectively).
641		711
642	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
643	running when nothing else is active.	713	running when nothing else is active.
644		714
645	struct ev_signal exitsig;	715	ev_signal exitsig;
646	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
647	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
648	evf_unref (loop);	718	evf_unref (loop);
649		719
650	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
651		721
652	ev_ref (loop);	722	ev_ref (loop);
653	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
654		724
655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
656		726
657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
658		728
659	These advanced functions influence the time that libev will spend waiting	729	These advanced functions influence the time that libev will spend waiting
660	for events. Both are by default C<0>, meaning that libev will try to	730	for events. Both time intervals are by default C<0>, meaning that libev
661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
662		733
663	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
664	allows libev to delay invocation of I/O and timer/periodic callbacks to	735	allows libev to delay invocation of I/O and timer/periodic callbacks
665	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
666		738
667	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
668	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
669	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
670	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
671	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
672		744
673	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
674	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
676	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
677	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
678		750
679	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
680	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
681	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
682	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
683	any overhead in libev.	755	value will not introduce any overhead in libev.
684		756
685	Many (busy) programs can usually benefit by setting the io collect	757	Many (busy) programs can usually benefit by setting the I/O collect
686	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
687	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
688	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
689	as this approsaches the timing granularity of most systems.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
690		781
691	=back	782	=back
692		783
693		784
694	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
695		786
696	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
697	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
698	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
699		790
700	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
701	{	792	{
702	ev_io_stop (w);	793	ev_io_stop (w);
703	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
704	}	795	}
705		796
706	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
707	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
708	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
709	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
710	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
711	ev_loop (loop, 0);	802	ev_loop (loop, 0);
712		803
713	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
714	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
715	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
716		807
717	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
718	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
719	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
720	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
721	is readable and/or writable).	812	is readable and/or writable).
722		813
723	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
724	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
800		891
801	The given async watcher has been asynchronously notified (see C<ev_async>).	892	The given async watcher has been asynchronously notified (see C<ev_async>).
802		893
803	=item C<EV_ERROR>	894	=item C<EV_ERROR>
804		895
805	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
806	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
807	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
808	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
809	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
810		905
811	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
812	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
813	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
814	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
815	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
816		912
817	=back	913	=back
818		914
819	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
820		916
…		…
833	which rolls both calls into one.	929	which rolls both calls into one.
834		930
835	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
836	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
837		933
838	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
839	int revents)>.	935	int revents)>.
		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
840		942
841	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
842		944
843	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
844	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
…		…
847	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
848		950
849	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
850	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
851		953
		954	See C<ev_init>, above, for an example.
		955
852	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
853		957
854	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
855	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
856	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
857		965
858	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
859		967
860	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
861	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
862		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
863	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
864		977
865	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
866	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
867	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
868	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
869	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
870	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
871		986
872	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
873		988
874	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
875	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
923		1038
924	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
925		1040
926	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
927	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
928	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
929		1045
930	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
931		1047
932	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
933	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
934	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
935		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
936	=back	1055	=back
937		1056
938		1057
939	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
940		1059
941	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
942	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
943	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
944	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
945	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
946	data:	1065	data:
947		1066
948	struct my_io	1067	struct my_io
949	{	1068	{
950	struct ev_io io;	1069	ev_io io;
951	int otherfd;	1070	int otherfd;
952	void *somedata;	1071	void *somedata;
953	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
954	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
955		1078
956	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
957	can cast it back to your own type:	1080	can cast it back to your own type:
958		1081
959	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
960	{	1083	{
961	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
962	...	1085	...
963	}	1086	}
964		1087
965	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
966	instead have been omitted.	1089	instead have been omitted.
967		1090
968	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
969	watchers:	1092	embedded watchers:
970		1093
971	struct my_biggy	1094	struct my_biggy
972	{	1095	{
973	int some_data;	1096	int some_data;
974	ev_timer t1;	1097	ev_timer t1;
975	ev_timer t2;	1098	ev_timer t2;
976	}	1099	}
977		1100
978	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
979	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
980		1106
981	#include <stddef.h>	1107	#include <stddef.h>
982		1108
983	static void	1109	static void
984	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
985	{	1111	{
986	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
987	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
988	}	1114	}
989		1115
990	static void	1116	static void
991	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
992	{	1118	{
993	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
995	}	1121	}
996		1122
997		1123
998	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
999		1125
1000	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
1024	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
1025	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
1026	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
1027	required if you know what you are doing).	1153	required if you know what you are doing).
1028		1154
1029	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1030	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1031	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1032		1158
1033	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1034	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1035	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1036	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1037	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1038	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1039	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1040	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1041		1167
1042	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1043	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
1044	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1045	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1046	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1047		1177
1048	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1049		1179
1050	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1051	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1052	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1053	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1054	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1055	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1056	fact, a different file descriptor.	1186	fact, a different file descriptor.
1057		1187
…		…
1088	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1089	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1090		1220
1091	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1092		1222
1093	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1094	when reading from a pipe whose other end has been closed, your program	1224	when writing to a pipe whose other end has been closed, your program gets
1095	gets send a SIGPIPE, which, by default, aborts your program. For most	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1096	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1097	undesirable.
1098		1227
1099	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1101	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
1102		1231
…		…
1108	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1109		1238
1110	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1111		1240
1112	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1113	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1114	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1115		1244
1116	=item int fd [read-only]	1245	=item int fd [read-only]
1117		1246
1118	The file descriptor being watched.	1247	The file descriptor being watched.
1119		1248
…		…
1127		1256
1128	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1129	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1130	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1131		1260
1132	static void	1261	static void
1133	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1134	{	1263	{
1135	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1136	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1137	}	1266	}
1138		1267
1139	...	1268	...
1140	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1141	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1142	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1143	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1144	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1145		1274
1146		1275
1147	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
1148		1277
1149	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1150	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1151		1280
1152	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1153	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
1154	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1155	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1156	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems involve some kind of timeout, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	What follows are some ways to handle this problem, from obvious and
		1298	inefficient to smart and efficient.
		1299
		1300	In the following, a 60 second activity timeout is assumed - a timeout that
		1301	gets reset to 60 seconds each time there is activity (e.g. each time some
		1302	data or other life sign was received).
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1315	and start it again:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there is
		1322	some activity, libev will first have to remove the timer from its internal
		1323	data structure and then add it again. Libev tries to be fast, but it's
		1324	still not a constant-time operation.
		1325
		1326	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1327
		1328	This is the easiest way, and involves using C<ev_timer_again> instead of
		1329	C<ev_timer_start>.
		1330
		1331	To implement this, configure an C<ev_timer> with a C<repeat> value
		1332	of C<60> and then call C<ev_timer_again> at start and each time you
		1333	successfully read or write some data. If you go into an idle state where
		1334	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1335	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1336
		1337	That means you can ignore both the C<ev_timer_start> function and the
		1338	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1339	member and C<ev_timer_again>.
		1340
		1341	At start:
		1342
		1343	ev_timer_init (timer, callback);
		1344	timer->repeat = 60.;
		1345	ev_timer_again (loop, timer);
		1346
		1347	Each time there is some activity:
		1348
		1349	ev_timer_again (loop, timer);
		1350
		1351	It is even possible to change the time-out on the fly, regardless of
		1352	whether the watcher is active or not:
		1353
		1354	timer->repeat = 30.;
		1355	ev_timer_again (loop, timer);
		1356
		1357	This is slightly more efficient then stopping/starting the timer each time
		1358	you want to modify its timeout value, as libev does not have to completely
		1359	remove and re-insert the timer from/into its internal data structure.
		1360
		1361	It is, however, even simpler than the "obvious" way to do it.
		1362
		1363	=item 3. Let the timer time out, but then re-arm it as required.
		1364
		1365	This method is more tricky, but usually most efficient: Most timeouts are
		1366	relatively long compared to the intervals between other activity - in
		1367	our example, within 60 seconds, there are usually many I/O events with
		1368	associated activity resets.
		1369
		1370	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1371	but remember the time of last activity, and check for a real timeout only
		1372	within the callback:
		1373
		1374	ev_tstamp last_activity; // time of last activity
		1375
		1376	static void
		1377	callback (EV_P_ ev_timer *w, int revents)
		1378	{
		1379	ev_tstamp now = ev_now (EV_A);
		1380	ev_tstamp timeout = last_activity + 60.;
		1381
		1382	// if last_activity + 60. is older than now, we did time out
		1383	if (timeout < now)
		1384	{
		1385	// timeout occured, take action
		1386	}
		1387	else
		1388	{
		1389	// callback was invoked, but there was some activity, re-arm
		1390	// the watcher to fire in last_activity + 60, which is
		1391	// guaranteed to be in the future, so "again" is positive:
		1392	w->again = timeout - now;
		1393	ev_timer_again (EV_A_ w);
		1394	}
		1395	}
		1396
		1397	To summarise the callback: first calculate the real timeout (defined
		1398	as "60 seconds after the last activity"), then check if that time has
		1399	been reached, which means something I<did>, in fact, time out. Otherwise
		1400	the callback was invoked too early (C<timeout> is in the future), so
		1401	re-schedule the timer to fire at that future time, to see if maybe we have
		1402	a timeout then.
		1403
		1404	Note how C<ev_timer_again> is used, taking advantage of the
		1405	C<ev_timer_again> optimisation when the timer is already running.
		1406
		1407	This scheme causes more callback invocations (about one every 60 seconds
		1408	minus half the average time between activity), but virtually no calls to
		1409	libev to change the timeout.
		1410
		1411	To start the timer, simply initialise the watcher and set C<last_activity>
		1412	to the current time (meaning we just have some activity :), then call the
		1413	callback, which will "do the right thing" and start the timer:
		1414
		1415	ev_timer_init (timer, callback);
		1416	last_activity = ev_now (loop);
		1417	callback (loop, timer, EV_TIMEOUT);
		1418
		1419	And when there is some activity, simply store the current time in
		1420	C<last_activity>, no libev calls at all:
		1421
		1422	last_actiivty = ev_now (loop);
		1423
		1424	This technique is slightly more complex, but in most cases where the
		1425	time-out is unlikely to be triggered, much more efficient.
		1426
		1427	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1428	callback :) - just change the timeout and invoke the callback, which will
		1429	fix things for you.
		1430
		1431	=item 4. Whee, use a double-linked list for your timeouts.
		1432
		1433	If there is not one request, but many thousands, all employing some kind
		1434	of timeout with the same timeout value, then one can do even better:
		1435
		1436	When starting the timeout, calculate the timeout value and put the timeout
		1437	at the I<end> of the list.
		1438
		1439	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1440	the list is expected to fire (for example, using the technique #3).
		1441
		1442	When there is some activity, remove the timer from the list, recalculate
		1443	the timeout, append it to the end of the list again, and make sure to
		1444	update the C<ev_timer> if it was taken from the beginning of the list.
		1445
		1446	This way, one can manage an unlimited number of timeouts in O(1) time for
		1447	starting, stopping and updating the timers, at the expense of a major
		1448	complication, and having to use a constant timeout. The constant timeout
		1449	ensures that the list stays sorted.
		1450
		1451	=back
		1452
		1453	So what method is the best?
		1454
		1455	The method #2 is a simple no-brain-required solution that is adequate in
		1456	most situations. Method #3 requires a bit more thinking, but handles many
		1457	cases better, and isn't very complicated either. In most case, choosing
		1458	either one is fine.
		1459
		1460	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1461	rather complicated, but extremely efficient, something that really pays
		1462	off after the first or so million of active timers, i.e. it's usually
		1463	overkill :)
		1464
		1465	=head3 The special problem of time updates
		1466
		1467	Establishing the current time is a costly operation (it usually takes at
		1468	least two system calls): EV therefore updates its idea of the current
		1469	time only before and after C<ev_loop> collects new events, which causes a
		1470	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1471	lots of events in one iteration.
1157		1472
1158	The relative timeouts are calculated relative to the C<ev_now ()>	1473	The relative timeouts are calculated relative to the C<ev_now ()>
1159	time. This is usually the right thing as this timestamp refers to the time	1474	time. This is usually the right thing as this timestamp refers to the time
1160	of the event triggering whatever timeout you are modifying/starting. If	1475	of the event triggering whatever timeout you are modifying/starting. If
1161	you suspect event processing to be delayed and you I<need> to base the timeout	1476	you suspect event processing to be delayed and you I<need> to base the
1162	on the current time, use something like this to adjust for this:	1477	timeout on the current time, use something like this to adjust for this:
1163		1478
1164	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1479	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1165		1480
1166	The callback is guarenteed to be invoked only when its timeout has passed,	1481	If the event loop is suspended for a long time, you can also force an
1167	but if multiple timers become ready during the same loop iteration then	1482	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1168	order of execution is undefined.	1483	()>.
1169		1484
1170	=head3 Watcher-Specific Functions and Data Members	1485	=head3 Watcher-Specific Functions and Data Members
1171		1486
1172	=over 4	1487	=over 4
1173		1488
1174	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1489	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1175		1490
1176	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1491	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1177		1492
1178	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1493	Configure the timer to trigger after C<after> seconds. If C<repeat>
1179	C<0.>, then it will automatically be stopped. If it is positive, then the	1494	is C<0.>, then it will automatically be stopped once the timeout is
1180	timer will automatically be configured to trigger again C<repeat> seconds	1495	reached. If it is positive, then the timer will automatically be
1181	later, again, and again, until stopped manually.	1496	configured to trigger again C<repeat> seconds later, again, and again,
		1497	until stopped manually.
1182		1498
1183	The timer itself will do a best-effort at avoiding drift, that is, if you	1499	The timer itself will do a best-effort at avoiding drift, that is, if
1184	configure a timer to trigger every 10 seconds, then it will trigger at	1500	you configure a timer to trigger every 10 seconds, then it will normally
1185	exactly 10 second intervals. If, however, your program cannot keep up with	1501	trigger at exactly 10 second intervals. If, however, your program cannot
1186	the timer (because it takes longer than those 10 seconds to do stuff) the	1502	keep up with the timer (because it takes longer than those 10 seconds to
1187	timer will not fire more than once per event loop iteration.	1503	do stuff) the timer will not fire more than once per event loop iteration.
1188		1504
1189	=item ev_timer_again (loop, ev_timer *)	1505	=item ev_timer_again (loop, ev_timer *)
1190		1506
1191	This will act as if the timer timed out and restart it again if it is	1507	This will act as if the timer timed out and restart it again if it is
1192	repeating. The exact semantics are:	1508	repeating. The exact semantics are:
1193		1509
1194	If the timer is pending, its pending status is cleared.	1510	If the timer is pending, its pending status is cleared.
1195		1511
1196	If the timer is started but nonrepeating, stop it (as if it timed out).	1512	If the timer is started but non-repeating, stop it (as if it timed out).
1197		1513
1198	If the timer is repeating, either start it if necessary (with the	1514	If the timer is repeating, either start it if necessary (with the
1199	C<repeat> value), or reset the running timer to the C<repeat> value.	1515	C<repeat> value), or reset the running timer to the C<repeat> value.
1200		1516
1201	This sounds a bit complicated, but here is a useful and typical	1517	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1202	example: Imagine you have a tcp connection and you want a so-called idle	1518	usage example.
1203	timeout, that is, you want to be called when there have been, say, 60
1204	seconds of inactivity on the socket. The easiest way to do this is to
1205	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1206	C<ev_timer_again> each time you successfully read or write some data. If
1207	you go into an idle state where you do not expect data to travel on the
1208	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1209	automatically restart it if need be.
1210
1211	That means you can ignore the C<after> value and C<ev_timer_start>
1212	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1213
1214	ev_timer_init (timer, callback, 0., 5.);
1215	ev_timer_again (loop, timer);
1216	...
1217	timer->again = 17.;
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 10.;
1221	ev_timer_again (loop, timer);
1222
1223	This is more slightly efficient then stopping/starting the timer each time
1224	you want to modify its timeout value.
1225		1519
1226	=item ev_tstamp repeat [read-write]	1520	=item ev_tstamp repeat [read-write]
1227		1521
1228	The current C<repeat> value. Will be used each time the watcher times out	1522	The current C<repeat> value. Will be used each time the watcher times out
1229	or C<ev_timer_again> is called and determines the next timeout (if any),	1523	or C<ev_timer_again> is called, and determines the next timeout (if any),
1230	which is also when any modifications are taken into account.	1524	which is also when any modifications are taken into account.
1231		1525
1232	=back	1526	=back
1233		1527
1234	=head3 Examples	1528	=head3 Examples
1235		1529
1236	Example: Create a timer that fires after 60 seconds.	1530	Example: Create a timer that fires after 60 seconds.
1237		1531
1238	static void	1532	static void
1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1533	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	1534	{
1241	.. one minute over, w is actually stopped right here	1535	.. one minute over, w is actually stopped right here
1242	}	1536	}
1243		1537
1244	struct ev_timer mytimer;	1538	ev_timer mytimer;
1245	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1539	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1246	ev_timer_start (loop, &mytimer);	1540	ev_timer_start (loop, &mytimer);
1247		1541
1248	Example: Create a timeout timer that times out after 10 seconds of	1542	Example: Create a timeout timer that times out after 10 seconds of
1249	inactivity.	1543	inactivity.
1250		1544
1251	static void	1545	static void
1252	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1546	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1253	{	1547	{
1254	.. ten seconds without any activity	1548	.. ten seconds without any activity
1255	}	1549	}
1256		1550
1257	struct ev_timer mytimer;	1551	ev_timer mytimer;
1258	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1552	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1259	ev_timer_again (&mytimer); /* start timer */	1553	ev_timer_again (&mytimer); /* start timer */
1260	ev_loop (loop, 0);	1554	ev_loop (loop, 0);
1261		1555
1262	// and in some piece of code that gets executed on any "activity":	1556	// and in some piece of code that gets executed on any "activity":
1263	// reset the timeout to start ticking again at 10 seconds	1557	// reset the timeout to start ticking again at 10 seconds
1264	ev_timer_again (&mytimer);	1558	ev_timer_again (&mytimer);
1265		1559
1266		1560
1267	=head2 C<ev_periodic> - to cron or not to cron?	1561	=head2 C<ev_periodic> - to cron or not to cron?
1268		1562
1269	Periodic watchers are also timers of a kind, but they are very versatile	1563	Periodic watchers are also timers of a kind, but they are very versatile
1270	(and unfortunately a bit complex).	1564	(and unfortunately a bit complex).
1271		1565
1272	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1566	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1273	but on wallclock time (absolute time). You can tell a periodic watcher	1567	but on wall clock time (absolute time). You can tell a periodic watcher
1274	to trigger "at" some specific point in time. For example, if you tell a	1568	to trigger after some specific point in time. For example, if you tell a
1275	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1569	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1276	+ 10.>) and then reset your system clock to the last year, then it will	1570	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1571	clock to January of the previous year, then it will take more than year
1277	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1572	to trigger the event (unlike an C<ev_timer>, which would still trigger
1278	roughly 10 seconds later).	1573	roughly 10 seconds later as it uses a relative timeout).
1279		1574
1280	They can also be used to implement vastly more complex timers, such as	1575	C<ev_periodic>s can also be used to implement vastly more complex timers,
1281	triggering an event on each midnight, local time or other, complicated,	1576	such as triggering an event on each "midnight, local time", or other
1282	rules.	1577	complicated rules.
1283		1578
1284	As with timers, the callback is guarenteed to be invoked only when the	1579	As with timers, the callback is guaranteed to be invoked only when the
1285	time (C<at>) has been passed, but if multiple periodic timers become ready	1580	time (C<at>) has passed, but if multiple periodic timers become ready
1286	during the same loop iteration then order of execution is undefined.	1581	during the same loop iteration, then order of execution is undefined.
1287		1582
1288	=head3 Watcher-Specific Functions and Data Members	1583	=head3 Watcher-Specific Functions and Data Members
1289		1584
1290	=over 4	1585	=over 4
1291		1586
1292	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1587	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1293		1588
1294	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1589	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1295		1590
1296	Lots of arguments, lets sort it out... There are basically three modes of	1591	Lots of arguments, lets sort it out... There are basically three modes of
1297	operation, and we will explain them from simplest to complex:	1592	operation, and we will explain them from simplest to most complex:
1298		1593
1299	=over 4	1594	=over 4
1300		1595
1301	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1596	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1302		1597
1303	In this configuration the watcher triggers an event at the wallclock time	1598	In this configuration the watcher triggers an event after the wall clock
1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1599	time C<at> has passed. It will not repeat and will not adjust when a time
1305	that is, if it is to be run at January 1st 2011 then it will run when the	1600	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1306	system time reaches or surpasses this time.	1601	only run when the system clock reaches or surpasses this time.
1307		1602
1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1603	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1309		1604
1310	In this mode the watcher will always be scheduled to time out at the next	1605	In this mode the watcher will always be scheduled to time out at the next
1311	C<at + N * interval> time (for some integer N, which can also be negative)	1606	C<at + N * interval> time (for some integer N, which can also be negative)
1312	and then repeat, regardless of any time jumps.	1607	and then repeat, regardless of any time jumps.
1313		1608
1314	This can be used to create timers that do not drift with respect to system	1609	This can be used to create timers that do not drift with respect to the
1315	time:	1610	system clock, for example, here is a C<ev_periodic> that triggers each
		1611	hour, on the hour:
1316		1612
1317	ev_periodic_set (&periodic, 0., 3600., 0);	1613	ev_periodic_set (&periodic, 0., 3600., 0);
1318		1614
1319	This doesn't mean there will always be 3600 seconds in between triggers,	1615	This doesn't mean there will always be 3600 seconds in between triggers,
1320	but only that the the callback will be called when the system time shows a	1616	but only that the callback will be called when the system time shows a
1321	full hour (UTC), or more correctly, when the system time is evenly divisible	1617	full hour (UTC), or more correctly, when the system time is evenly divisible
1322	by 3600.	1618	by 3600.
1323		1619
1324	Another way to think about it (for the mathematically inclined) is that	1620	Another way to think about it (for the mathematically inclined) is that
1325	C<ev_periodic> will try to run the callback in this mode at the next possible	1621	C<ev_periodic> will try to run the callback in this mode at the next possible
1326	time where C<time = at (mod interval)>, regardless of any time jumps.	1622	time where C<time = at (mod interval)>, regardless of any time jumps.
1327		1623
1328	For numerical stability it is preferable that the C<at> value is near	1624	For numerical stability it is preferable that the C<at> value is near
1329	C<ev_now ()> (the current time), but there is no range requirement for	1625	C<ev_now ()> (the current time), but there is no range requirement for
1330	this value.	1626	this value, and in fact is often specified as zero.
		1627
		1628	Note also that there is an upper limit to how often a timer can fire (CPU
		1629	speed for example), so if C<interval> is very small then timing stability
		1630	will of course deteriorate. Libev itself tries to be exact to be about one
		1631	millisecond (if the OS supports it and the machine is fast enough).
1331		1632
1332	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1633	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1333		1634
1334	In this mode the values for C<interval> and C<at> are both being	1635	In this mode the values for C<interval> and C<at> are both being
1335	ignored. Instead, each time the periodic watcher gets scheduled, the	1636	ignored. Instead, each time the periodic watcher gets scheduled, the
1336	reschedule callback will be called with the watcher as first, and the	1637	reschedule callback will be called with the watcher as first, and the
1337	current time as second argument.	1638	current time as second argument.
1338		1639
1339	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1640	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1340	ever, or make any event loop modifications>. If you need to stop it,	1641	ever, or make ANY event loop modifications whatsoever>.
1341	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1342	starting an C<ev_prepare> watcher, which is legal).
1343		1642
		1643	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1644	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1645	only event loop modification you are allowed to do).
		1646
1344	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1647	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1345	ev_tstamp now)>, e.g.:	1648	*w, ev_tstamp now)>, e.g.:
1346		1649
		1650	static ev_tstamp
1347	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1651	my_rescheduler (ev_periodic *w, ev_tstamp now)
1348	{	1652	{
1349	return now + 60.;	1653	return now + 60.;
1350	}	1654	}
1351		1655
1352	It must return the next time to trigger, based on the passed time value	1656	It must return the next time to trigger, based on the passed time value
1353	(that is, the lowest time value larger than to the second argument). It	1657	(that is, the lowest time value larger than to the second argument). It
1354	will usually be called just before the callback will be triggered, but	1658	will usually be called just before the callback will be triggered, but
1355	might be called at other times, too.	1659	might be called at other times, too.
1356		1660
1357	NOTE: I<< This callback must always return a time that is later than the	1661	NOTE: I<< This callback must always return a time that is higher than or
1358	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1662	equal to the passed C<now> value >>.
1359		1663
1360	This can be used to create very complex timers, such as a timer that	1664	This can be used to create very complex timers, such as a timer that
1361	triggers on each midnight, local time. To do this, you would calculate the	1665	triggers on "next midnight, local time". To do this, you would calculate the
1362	next midnight after C<now> and return the timestamp value for this. How	1666	next midnight after C<now> and return the timestamp value for this. How
1363	you do this is, again, up to you (but it is not trivial, which is the main	1667	you do this is, again, up to you (but it is not trivial, which is the main
1364	reason I omitted it as an example).	1668	reason I omitted it as an example).
1365		1669
1366	=back	1670	=back
…		…
1370	Simply stops and restarts the periodic watcher again. This is only useful	1674	Simply stops and restarts the periodic watcher again. This is only useful
1371	when you changed some parameters or the reschedule callback would return	1675	when you changed some parameters or the reschedule callback would return
1372	a different time than the last time it was called (e.g. in a crond like	1676	a different time than the last time it was called (e.g. in a crond like
1373	program when the crontabs have changed).	1677	program when the crontabs have changed).
1374		1678
		1679	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1680
		1681	When active, returns the absolute time that the watcher is supposed to
		1682	trigger next.
		1683
1375	=item ev_tstamp offset [read-write]	1684	=item ev_tstamp offset [read-write]
1376		1685
1377	When repeating, this contains the offset value, otherwise this is the	1686	When repeating, this contains the offset value, otherwise this is the
1378	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1687	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1379		1688
…		…
1384		1693
1385	The current interval value. Can be modified any time, but changes only	1694	The current interval value. Can be modified any time, but changes only
1386	take effect when the periodic timer fires or C<ev_periodic_again> is being	1695	take effect when the periodic timer fires or C<ev_periodic_again> is being
1387	called.	1696	called.
1388		1697
1389	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1698	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1390		1699
1391	The current reschedule callback, or C<0>, if this functionality is	1700	The current reschedule callback, or C<0>, if this functionality is
1392	switched off. Can be changed any time, but changes only take effect when	1701	switched off. Can be changed any time, but changes only take effect when
1393	the periodic timer fires or C<ev_periodic_again> is being called.	1702	the periodic timer fires or C<ev_periodic_again> is being called.
1394		1703
1395	=item ev_tstamp at [read-only]
1396
1397	When active, contains the absolute time that the watcher is supposed to
1398	trigger next.
1399
1400	=back	1704	=back
1401		1705
1402	=head3 Examples	1706	=head3 Examples
1403		1707
1404	Example: Call a callback every hour, or, more precisely, whenever the	1708	Example: Call a callback every hour, or, more precisely, whenever the
1405	system clock is divisible by 3600. The callback invocation times have	1709	system time is divisible by 3600. The callback invocation times have
1406	potentially a lot of jittering, but good long-term stability.	1710	potentially a lot of jitter, but good long-term stability.
1407		1711
1408	static void	1712	static void
1409	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1713	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1410	{	1714	{
1411	... its now a full hour (UTC, or TAI or whatever your clock follows)	1715	... its now a full hour (UTC, or TAI or whatever your clock follows)
1412	}	1716	}
1413		1717
1414	struct ev_periodic hourly_tick;	1718	ev_periodic hourly_tick;
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1719	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1416	ev_periodic_start (loop, &hourly_tick);	1720	ev_periodic_start (loop, &hourly_tick);
1417		1721
1418	Example: The same as above, but use a reschedule callback to do it:	1722	Example: The same as above, but use a reschedule callback to do it:
1419		1723
1420	#include <math.h>	1724	#include <math.h>
1421		1725
1422	static ev_tstamp	1726	static ev_tstamp
1423	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1727	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1424	{	1728	{
1425	return fmod (now, 3600.) + 3600.;	1729	return now + (3600. - fmod (now, 3600.));
1426	}	1730	}
1427		1731
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1732	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1429		1733
1430	Example: Call a callback every hour, starting now:	1734	Example: Call a callback every hour, starting now:
1431		1735
1432	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1433	ev_periodic_init (&hourly_tick, clock_cb,	1737	ev_periodic_init (&hourly_tick, clock_cb,
1434	fmod (ev_now (loop), 3600.), 3600., 0);	1738	fmod (ev_now (loop), 3600.), 3600., 0);
1435	ev_periodic_start (loop, &hourly_tick);	1739	ev_periodic_start (loop, &hourly_tick);
1436		1740
1437		1741
1438	=head2 C<ev_signal> - signal me when a signal gets signalled!	1742	=head2 C<ev_signal> - signal me when a signal gets signalled!
1439		1743
1440	Signal watchers will trigger an event when the process receives a specific	1744	Signal watchers will trigger an event when the process receives a specific
1441	signal one or more times. Even though signals are very asynchronous, libev	1745	signal one or more times. Even though signals are very asynchronous, libev
1442	will try it's best to deliver signals synchronously, i.e. as part of the	1746	will try it's best to deliver signals synchronously, i.e. as part of the
1443	normal event processing, like any other event.	1747	normal event processing, like any other event.
1444		1748
		1749	If you want signals asynchronously, just use C<sigaction> as you would
		1750	do without libev and forget about sharing the signal. You can even use
		1751	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1752
1445	You can configure as many watchers as you like per signal. Only when the	1753	You can configure as many watchers as you like per signal. Only when the
1446	first watcher gets started will libev actually register a signal watcher	1754	first watcher gets started will libev actually register a signal handler
1447	with the kernel (thus it coexists with your own signal handlers as long	1755	with the kernel (thus it coexists with your own signal handlers as long as
1448	as you don't register any with libev). Similarly, when the last signal	1756	you don't register any with libev for the same signal). Similarly, when
1449	watcher for a signal is stopped libev will reset the signal handler to	1757	the last signal watcher for a signal is stopped, libev will reset the
1450	SIG_DFL (regardless of what it was set to before).	1758	signal handler to SIG_DFL (regardless of what it was set to before).
1451		1759
1452	If possible and supported, libev will install its handlers with	1760	If possible and supported, libev will install its handlers with
1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1761	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1454	interrupted. If you have a problem with syscalls getting interrupted by	1762	interrupted. If you have a problem with system calls getting interrupted by
1455	signals you can block all signals in an C<ev_check> watcher and unblock	1763	signals you can block all signals in an C<ev_check> watcher and unblock
1456	them in an C<ev_prepare> watcher.	1764	them in an C<ev_prepare> watcher.
1457		1765
1458	=head3 Watcher-Specific Functions and Data Members	1766	=head3 Watcher-Specific Functions and Data Members
1459		1767
…		…
1472		1780
1473	=back	1781	=back
1474		1782
1475	=head3 Examples	1783	=head3 Examples
1476		1784
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1785	Example: Try to exit cleanly on SIGINT.
1478		1786
1479	static void	1787	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1788	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1481	{	1789	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1790	ev_unloop (loop, EVUNLOOP_ALL);
1483	}	1791	}
1484		1792
1485	struct ev_signal signal_watcher;	1793	ev_signal signal_watcher;
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1794	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1487	ev_signal_start (loop, &sigint_cb);	1795	ev_signal_start (loop, &signal_watcher);
1488		1796
1489		1797
1490	=head2 C<ev_child> - watch out for process status changes	1798	=head2 C<ev_child> - watch out for process status changes
1491		1799
1492	Child watchers trigger when your process receives a SIGCHLD in response to	1800	Child watchers trigger when your process receives a SIGCHLD in response to
1493	some child status changes (most typically when a child of yours dies). It	1801	some child status changes (most typically when a child of yours dies or
1494	is permissible to install a child watcher I<after> the child has been	1802	exits). It is permissible to install a child watcher I<after> the child
1495	forked (which implies it might have already exited), as long as the event	1803	has been forked (which implies it might have already exited), as long
1496	loop isn't entered (or is continued from a watcher).	1804	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1805	forking and then immediately registering a watcher for the child is fine,
		1806	but forking and registering a watcher a few event loop iterations later is
		1807	not.
1497		1808
1498	Only the default event loop is capable of handling signals, and therefore	1809	Only the default event loop is capable of handling signals, and therefore
1499	you can only rgeister child watchers in the default event loop.	1810	you can only register child watchers in the default event loop.
1500		1811
1501	=head3 Process Interaction	1812	=head3 Process Interaction
1502		1813
1503	Libev grabs C<SIGCHLD> as soon as the default event loop is	1814	Libev grabs C<SIGCHLD> as soon as the default event loop is
1504	initialised. This is necessary to guarantee proper behaviour even if	1815	initialised. This is necessary to guarantee proper behaviour even if
1505	the first child watcher is started after the child exits. The occurance	1816	the first child watcher is started after the child exits. The occurrence
1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1817	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1507	synchronously as part of the event loop processing. Libev always reaps all	1818	synchronously as part of the event loop processing. Libev always reaps all
1508	children, even ones not watched.	1819	children, even ones not watched.
1509		1820
1510	=head3 Overriding the Built-In Processing	1821	=head3 Overriding the Built-In Processing
…		…
1514	handler, you can override it easily by installing your own handler for	1825	handler, you can override it easily by installing your own handler for
1515	C<SIGCHLD> after initialising the default loop, and making sure the	1826	C<SIGCHLD> after initialising the default loop, and making sure the
1516	default loop never gets destroyed. You are encouraged, however, to use an	1827	default loop never gets destroyed. You are encouraged, however, to use an
1517	event-based approach to child reaping and thus use libev's support for	1828	event-based approach to child reaping and thus use libev's support for
1518	that, so other libev users can use C<ev_child> watchers freely.	1829	that, so other libev users can use C<ev_child> watchers freely.
		1830
		1831	=head3 Stopping the Child Watcher
		1832
		1833	Currently, the child watcher never gets stopped, even when the
		1834	child terminates, so normally one needs to stop the watcher in the
		1835	callback. Future versions of libev might stop the watcher automatically
		1836	when a child exit is detected.
1519		1837
1520	=head3 Watcher-Specific Functions and Data Members	1838	=head3 Watcher-Specific Functions and Data Members
1521		1839
1522	=over 4	1840	=over 4
1523		1841
…		…
1552	=head3 Examples	1870	=head3 Examples
1553		1871
1554	Example: C<fork()> a new process and install a child handler to wait for	1872	Example: C<fork()> a new process and install a child handler to wait for
1555	its completion.	1873	its completion.
1556		1874
1557	ev_child cw;	1875	ev_child cw;
1558		1876
1559	static void	1877	static void
1560	child_cb (EV_P_ struct ev_child *w, int revents)	1878	child_cb (EV_P_ ev_child *w, int revents)
1561	{	1879	{
1562	ev_child_stop (EV_A_ w);	1880	ev_child_stop (EV_A_ w);
1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1881	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1564	}	1882	}
1565		1883
1566	pid_t pid = fork ();	1884	pid_t pid = fork ();
1567		1885
1568	if (pid < 0)	1886	if (pid < 0)
1569	// error	1887	// error
1570	else if (pid == 0)	1888	else if (pid == 0)
1571	{	1889	{
1572	// the forked child executes here	1890	// the forked child executes here
1573	exit (1);	1891	exit (1);
1574	}	1892	}
1575	else	1893	else
1576	{	1894	{
1577	ev_child_init (&cw, child_cb, pid, 0);	1895	ev_child_init (&cw, child_cb, pid, 0);
1578	ev_child_start (EV_DEFAULT_ &cw);	1896	ev_child_start (EV_DEFAULT_ &cw);
1579	}	1897	}
1580		1898
1581		1899
1582	=head2 C<ev_stat> - did the file attributes just change?	1900	=head2 C<ev_stat> - did the file attributes just change?
1583		1901
1584	This watches a filesystem path for attribute changes. That is, it calls	1902	This watches a file system path for attribute changes. That is, it calls
1585	C<stat> regularly (or when the OS says it changed) and sees if it changed	1903	C<stat> regularly (or when the OS says it changed) and sees if it changed
1586	compared to the last time, invoking the callback if it did.	1904	compared to the last time, invoking the callback if it did.
1587		1905
1588	The path does not need to exist: changing from "path exists" to "path does	1906	The path does not need to exist: changing from "path exists" to "path does
1589	not exist" is a status change like any other. The condition "path does	1907	not exist" is a status change like any other. The condition "path does
…		…
1592	the stat buffer having unspecified contents.	1910	the stat buffer having unspecified contents.
1593		1911
1594	The path I<should> be absolute and I<must not> end in a slash. If it is	1912	The path I<should> be absolute and I<must not> end in a slash. If it is
1595	relative and your working directory changes, the behaviour is undefined.	1913	relative and your working directory changes, the behaviour is undefined.
1596		1914
1597	Since there is no standard to do this, the portable implementation simply	1915	Since there is no standard kernel interface to do this, the portable
1598	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1916	implementation simply calls C<stat (2)> regularly on the path to see if
1599	can specify a recommended polling interval for this case. If you specify	1917	it changed somehow. You can specify a recommended polling interval for
1600	a polling interval of C<0> (highly recommended!) then a I<suitable,	1918	this case. If you specify a polling interval of C<0> (highly recommended!)
1601	unspecified default> value will be used (which you can expect to be around	1919	then a I<suitable, unspecified default> value will be used (which
1602	five seconds, although this might change dynamically). Libev will also	1920	you can expect to be around five seconds, although this might change
1603	impose a minimum interval which is currently around C<0.1>, but thats	1921	dynamically). Libev will also impose a minimum interval which is currently
1604	usually overkill.	1922	around C<0.1>, but thats usually overkill.
1605		1923
1606	This watcher type is not meant for massive numbers of stat watchers,	1924	This watcher type is not meant for massive numbers of stat watchers,
1607	as even with OS-supported change notifications, this can be	1925	as even with OS-supported change notifications, this can be
1608	resource-intensive.	1926	resource-intensive.
1609		1927
1610	At the time of this writing, only the Linux inotify interface is	1928	At the time of this writing, the only OS-specific interface implemented
1611	implemented (implementing kqueue support is left as an exercise for the	1929	is the Linux inotify interface (implementing kqueue support is left as
1612	reader). Inotify will be used to give hints only and should not change the	1930	an exercise for the reader. Note, however, that the author sees no way
1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1931	of implementing C<ev_stat> semantics with kqueue).
1614	to fall back to regular polling again even with inotify, but changes are
1615	usually detected immediately, and if the file exists there will be no
1616	polling.
1617		1932
1618	=head3 ABI Issues (Largefile Support)	1933	=head3 ABI Issues (Largefile Support)
1619		1934
1620	Libev by default (unless the user overrides this) uses the default	1935	Libev by default (unless the user overrides this) uses the default
1621	compilation environment, which means that on systems with optionally	1936	compilation environment, which means that on systems with large file
1622	disabled large file support, you get the 32 bit version of the stat	1937	support disabled by default, you get the 32 bit version of the stat
1623	structure. When using the library from programs that change the ABI to	1938	structure. When using the library from programs that change the ABI to
1624	use 64 bit file offsets the programs will fail. In that case you have to	1939	use 64 bit file offsets the programs will fail. In that case you have to
1625	compile libev with the same flags to get binary compatibility. This is	1940	compile libev with the same flags to get binary compatibility. This is
1626	obviously the case with any flags that change the ABI, but the problem is	1941	obviously the case with any flags that change the ABI, but the problem is
1627	most noticably with ev_stat and largefile support.	1942	most noticeably disabled with ev_stat and large file support.
1628		1943
1629	=head3 Inotify	1944	The solution for this is to lobby your distribution maker to make large
		1945	file interfaces available by default (as e.g. FreeBSD does) and not
		1946	optional. Libev cannot simply switch on large file support because it has
		1947	to exchange stat structures with application programs compiled using the
		1948	default compilation environment.
1630		1949
		1950	=head3 Inotify and Kqueue
		1951
1631	When C<inotify (7)> support has been compiled into libev (generally only	1952	When C<inotify (7)> support has been compiled into libev (generally
		1953	only available with Linux 2.6.25 or above due to bugs in earlier
1632	available on Linux) and present at runtime, it will be used to speed up	1954	implementations) and present at runtime, it will be used to speed up
1633	change detection where possible. The inotify descriptor will be created lazily	1955	change detection where possible. The inotify descriptor will be created
1634	when the first C<ev_stat> watcher is being started.	1956	lazily when the first C<ev_stat> watcher is being started.
1635		1957
1636	Inotify presense does not change the semantics of C<ev_stat> watchers	1958	Inotify presence does not change the semantics of C<ev_stat> watchers
1637	except that changes might be detected earlier, and in some cases, to avoid	1959	except that changes might be detected earlier, and in some cases, to avoid
1638	making regular C<stat> calls. Even in the presense of inotify support	1960	making regular C<stat> calls. Even in the presence of inotify support
1639	there are many cases where libev has to resort to regular C<stat> polling.	1961	there are many cases where libev has to resort to regular C<stat> polling,
		1962	but as long as the path exists, libev usually gets away without polling.
1640		1963
1641	(There is no support for kqueue, as apparently it cannot be used to	1964	There is no support for kqueue, as apparently it cannot be used to
1642	implement this functionality, due to the requirement of having a file	1965	implement this functionality, due to the requirement of having a file
1643	descriptor open on the object at all times).	1966	descriptor open on the object at all times, and detecting renames, unlinks
		1967	etc. is difficult.
1644		1968
1645	=head3 The special problem of stat time resolution	1969	=head3 The special problem of stat time resolution
1646		1970
1647	The C<stat ()> syscall only supports full-second resolution portably, and	1971	The C<stat ()> system call only supports full-second resolution portably, and
1648	even on systems where the resolution is higher, many filesystems still	1972	even on systems where the resolution is higher, most file systems still
1649	only support whole seconds.	1973	only support whole seconds.
1650		1974
1651	That means that, if the time is the only thing that changes, you might	1975	That means that, if the time is the only thing that changes, you can
1652	miss updates: on the first update, C<ev_stat> detects a change and calls	1976	easily miss updates: on the first update, C<ev_stat> detects a change and
1653	your callback, which does something. When there is another update within	1977	calls your callback, which does something. When there is another update
1654	the same second, C<ev_stat> will be unable to detect it.	1978	within the same second, C<ev_stat> will be unable to detect unless the
		1979	stat data does change in other ways (e.g. file size).
1655		1980
1656	The solution to this is to delay acting on a change for a second (or till	1981	The solution to this is to delay acting on a change for slightly more
1657	the next second boundary), using a roughly one-second delay C<ev_timer>	1982	than a second (or till slightly after the next full second boundary), using
1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1983	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1659	is added to work around small timing inconsistencies of some operating	1984	ev_timer_again (loop, w)>).
1660	systems.	1985
		1986	The C<.02> offset is added to work around small timing inconsistencies
		1987	of some operating systems (where the second counter of the current time
		1988	might be be delayed. One such system is the Linux kernel, where a call to
		1989	C<gettimeofday> might return a timestamp with a full second later than
		1990	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1991	update file times then there will be a small window where the kernel uses
		1992	the previous second to update file times but libev might already execute
		1993	the timer callback).
1661		1994
1662	=head3 Watcher-Specific Functions and Data Members	1995	=head3 Watcher-Specific Functions and Data Members
1663		1996
1664	=over 4	1997	=over 4
1665		1998
…		…
1671	C<path>. The C<interval> is a hint on how quickly a change is expected to	2004	C<path>. The C<interval> is a hint on how quickly a change is expected to
1672	be detected and should normally be specified as C<0> to let libev choose	2005	be detected and should normally be specified as C<0> to let libev choose
1673	a suitable value. The memory pointed to by C<path> must point to the same	2006	a suitable value. The memory pointed to by C<path> must point to the same
1674	path for as long as the watcher is active.	2007	path for as long as the watcher is active.
1675		2008
1676	The callback will be receive C<EV_STAT> when a change was detected,	2009	The callback will receive an C<EV_STAT> event when a change was detected,
1677	relative to the attributes at the time the watcher was started (or the	2010	relative to the attributes at the time the watcher was started (or the
1678	last change was detected).	2011	last change was detected).
1679		2012
1680	=item ev_stat_stat (loop, ev_stat *)	2013	=item ev_stat_stat (loop, ev_stat *)
1681		2014
1682	Updates the stat buffer immediately with new values. If you change the	2015	Updates the stat buffer immediately with new values. If you change the
1683	watched path in your callback, you could call this fucntion to avoid	2016	watched path in your callback, you could call this function to avoid
1684	detecting this change (while introducing a race condition). Can also be	2017	detecting this change (while introducing a race condition if you are not
1685	useful simply to find out the new values.	2018	the only one changing the path). Can also be useful simply to find out the
		2019	new values.
1686		2020
1687	=item ev_statdata attr [read-only]	2021	=item ev_statdata attr [read-only]
1688		2022
1689	The most-recently detected attributes of the file. Although the type is of	2023	The most-recently detected attributes of the file. Although the type is
1690	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2024	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1691	suitable for your system. If the C<st_nlink> member is C<0>, then there	2025	suitable for your system, but you can only rely on the POSIX-standardised
		2026	members to be present. If the C<st_nlink> member is C<0>, then there was
1692	was some error while C<stat>ing the file.	2027	some error while C<stat>ing the file.
1693		2028
1694	=item ev_statdata prev [read-only]	2029	=item ev_statdata prev [read-only]
1695		2030
1696	The previous attributes of the file. The callback gets invoked whenever	2031	The previous attributes of the file. The callback gets invoked whenever
1697	C<prev> != C<attr>.	2032	C<prev> != C<attr>, or, more precisely, one or more of these members
		2033	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2034	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1698		2035
1699	=item ev_tstamp interval [read-only]	2036	=item ev_tstamp interval [read-only]
1700		2037
1701	The specified interval.	2038	The specified interval.
1702		2039
1703	=item const char *path [read-only]	2040	=item const char *path [read-only]
1704		2041
1705	The filesystem path that is being watched.	2042	The file system path that is being watched.
1706		2043
1707	=back	2044	=back
1708		2045
1709	=head3 Examples	2046	=head3 Examples
1710		2047
1711	Example: Watch C</etc/passwd> for attribute changes.	2048	Example: Watch C</etc/passwd> for attribute changes.
1712		2049
1713	static void	2050	static void
1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2051	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1715	{	2052	{
1716	/* /etc/passwd changed in some way */	2053	/* /etc/passwd changed in some way */
1717	if (w->attr.st_nlink)	2054	if (w->attr.st_nlink)
1718	{	2055	{
1719	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2056	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1720	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2057	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1721	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2058	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1722	}	2059	}
1723	else	2060	else
1724	/* you shalt not abuse printf for puts */	2061	/* you shalt not abuse printf for puts */
1725	puts ("wow, /etc/passwd is not there, expect problems. "	2062	puts ("wow, /etc/passwd is not there, expect problems. "
1726	"if this is windows, they already arrived\n");	2063	"if this is windows, they already arrived\n");
1727	}	2064	}
1728		2065
1729	...	2066	...
1730	ev_stat passwd;	2067	ev_stat passwd;
1731		2068
1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2069	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1733	ev_stat_start (loop, &passwd);	2070	ev_stat_start (loop, &passwd);
1734		2071
1735	Example: Like above, but additionally use a one-second delay so we do not	2072	Example: Like above, but additionally use a one-second delay so we do not
1736	miss updates (however, frequent updates will delay processing, too, so	2073	miss updates (however, frequent updates will delay processing, too, so
1737	one might do the work both on C<ev_stat> callback invocation I<and> on	2074	one might do the work both on C<ev_stat> callback invocation I<and> on
1738	C<ev_timer> callback invocation).	2075	C<ev_timer> callback invocation).
1739		2076
1740	static ev_stat passwd;	2077	static ev_stat passwd;
1741	static ev_timer timer;	2078	static ev_timer timer;
1742		2079
1743	static void	2080	static void
1744	timer_cb (EV_P_ ev_timer *w, int revents)	2081	timer_cb (EV_P_ ev_timer *w, int revents)
1745	{	2082	{
1746	ev_timer_stop (EV_A_ w);	2083	ev_timer_stop (EV_A_ w);
1747		2084
1748	/* now it's one second after the most recent passwd change */	2085	/* now it's one second after the most recent passwd change */
1749	}	2086	}
1750		2087
1751	static void	2088	static void
1752	stat_cb (EV_P_ ev_stat *w, int revents)	2089	stat_cb (EV_P_ ev_stat *w, int revents)
1753	{	2090	{
1754	/* reset the one-second timer */	2091	/* reset the one-second timer */
1755	ev_timer_again (EV_A_ &timer);	2092	ev_timer_again (EV_A_ &timer);
1756	}	2093	}
1757		2094
1758	...	2095	...
1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2096	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	2097	ev_stat_start (loop, &passwd);
1761	ev_timer_init (&timer, timer_cb, 0., 1.01);	2098	ev_timer_init (&timer, timer_cb, 0., 1.02);
1762		2099
1763		2100
1764	=head2 C<ev_idle> - when you've got nothing better to do...	2101	=head2 C<ev_idle> - when you've got nothing better to do...
1765		2102
1766	Idle watchers trigger events when no other events of the same or higher	2103	Idle watchers trigger events when no other events of the same or higher
1767	priority are pending (prepare, check and other idle watchers do not	2104	priority are pending (prepare, check and other idle watchers do not count
1768	count).	2105	as receiving "events").
1769		2106
1770	That is, as long as your process is busy handling sockets or timeouts	2107	That is, as long as your process is busy handling sockets or timeouts
1771	(or even signals, imagine) of the same or higher priority it will not be	2108	(or even signals, imagine) of the same or higher priority it will not be
1772	triggered. But when your process is idle (or only lower-priority watchers	2109	triggered. But when your process is idle (or only lower-priority watchers
1773	are pending), the idle watchers are being called once per event loop	2110	are pending), the idle watchers are being called once per event loop
…		…
1797	=head3 Examples	2134	=head3 Examples
1798		2135
1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2136	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1800	callback, free it. Also, use no error checking, as usual.	2137	callback, free it. Also, use no error checking, as usual.
1801		2138
1802	static void	2139	static void
1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2140	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1804	{	2141	{
1805	free (w);	2142	free (w);
1806	// now do something you wanted to do when the program has	2143	// now do something you wanted to do when the program has
1807	// no longer anything immediate to do.	2144	// no longer anything immediate to do.
1808	}	2145	}
1809		2146
1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2147	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1811	ev_idle_init (idle_watcher, idle_cb);	2148	ev_idle_init (idle_watcher, idle_cb);
1812	ev_idle_start (loop, idle_cb);	2149	ev_idle_start (loop, idle_cb);
1813		2150
1814		2151
1815	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2152	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1816		2153
1817	Prepare and check watchers are usually (but not always) used in tandem:	2154	Prepare and check watchers are usually (but not always) used in pairs:
1818	prepare watchers get invoked before the process blocks and check watchers	2155	prepare watchers get invoked before the process blocks and check watchers
1819	afterwards.	2156	afterwards.
1820		2157
1821	You I<must not> call C<ev_loop> or similar functions that enter	2158	You I<must not> call C<ev_loop> or similar functions that enter
1822	the current event loop from either C<ev_prepare> or C<ev_check>	2159	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1825	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2162	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1826	C<ev_check> so if you have one watcher of each kind they will always be	2163	C<ev_check> so if you have one watcher of each kind they will always be
1827	called in pairs bracketing the blocking call.	2164	called in pairs bracketing the blocking call.
1828		2165
1829	Their main purpose is to integrate other event mechanisms into libev and	2166	Their main purpose is to integrate other event mechanisms into libev and
1830	their use is somewhat advanced. This could be used, for example, to track	2167	their use is somewhat advanced. They could be used, for example, to track
1831	variable changes, implement your own watchers, integrate net-snmp or a	2168	variable changes, implement your own watchers, integrate net-snmp or a
1832	coroutine library and lots more. They are also occasionally useful if	2169	coroutine library and lots more. They are also occasionally useful if
1833	you cache some data and want to flush it before blocking (for example,	2170	you cache some data and want to flush it before blocking (for example,
1834	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2171	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1835	watcher).	2172	watcher).
1836		2173
1837	This is done by examining in each prepare call which file descriptors need	2174	This is done by examining in each prepare call which file descriptors
1838	to be watched by the other library, registering C<ev_io> watchers for	2175	need to be watched by the other library, registering C<ev_io> watchers
1839	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2176	for them and starting an C<ev_timer> watcher for any timeouts (many
1840	provide just this functionality). Then, in the check watcher you check for	2177	libraries provide exactly this functionality). Then, in the check watcher,
1841	any events that occured (by checking the pending status of all watchers	2178	you check for any events that occurred (by checking the pending status
1842	and stopping them) and call back into the library. The I/O and timer	2179	of all watchers and stopping them) and call back into the library. The
1843	callbacks will never actually be called (but must be valid nevertheless,	2180	I/O and timer callbacks will never actually be called (but must be valid
1844	because you never know, you know?).	2181	nevertheless, because you never know, you know?).
1845		2182
1846	As another example, the Perl Coro module uses these hooks to integrate	2183	As another example, the Perl Coro module uses these hooks to integrate
1847	coroutines into libev programs, by yielding to other active coroutines	2184	coroutines into libev programs, by yielding to other active coroutines
1848	during each prepare and only letting the process block if no coroutines	2185	during each prepare and only letting the process block if no coroutines
1849	are ready to run (it's actually more complicated: it only runs coroutines	2186	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1852	loop from blocking if lower-priority coroutines are active, thus mapping	2189	loop from blocking if lower-priority coroutines are active, thus mapping
1853	low-priority coroutines to idle/background tasks).	2190	low-priority coroutines to idle/background tasks).
1854		2191
1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2192	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1856	priority, to ensure that they are being run before any other watchers	2193	priority, to ensure that they are being run before any other watchers
		2194	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2195
1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2196	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1858	too) should not activate ("feed") events into libev. While libev fully	2197	activate ("feed") events into libev. While libev fully supports this, they
1859	supports this, they will be called before other C<ev_check> watchers	2198	might get executed before other C<ev_check> watchers did their job. As
1860	did their job. As C<ev_check> watchers are often used to embed other	2199	C<ev_check> watchers are often used to embed other (non-libev) event
1861	(non-libev) event loops those other event loops might be in an unusable	2200	loops those other event loops might be in an unusable state until their
1862	state until their C<ev_check> watcher ran (always remind yourself to	2201	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1863	coexist peacefully with others).	2202	others).
1864		2203
1865	=head3 Watcher-Specific Functions and Data Members	2204	=head3 Watcher-Specific Functions and Data Members
1866		2205
1867	=over 4	2206	=over 4
1868		2207
…		…
1870		2209
1871	=item ev_check_init (ev_check *, callback)	2210	=item ev_check_init (ev_check *, callback)
1872		2211
1873	Initialises and configures the prepare or check watcher - they have no	2212	Initialises and configures the prepare or check watcher - they have no
1874	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2213	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1875	macros, but using them is utterly, utterly and completely pointless.	2214	macros, but using them is utterly, utterly, utterly and completely
		2215	pointless.
1876		2216
1877	=back	2217	=back
1878		2218
1879	=head3 Examples	2219	=head3 Examples
1880		2220
1881	There are a number of principal ways to embed other event loops or modules	2221	There are a number of principal ways to embed other event loops or modules
1882	into libev. Here are some ideas on how to include libadns into libev	2222	into libev. Here are some ideas on how to include libadns into libev
1883	(there is a Perl module named C<EV::ADNS> that does this, which you could	2223	(there is a Perl module named C<EV::ADNS> that does this, which you could
1884	use for an actually working example. Another Perl module named C<EV::Glib>	2224	use as a working example. Another Perl module named C<EV::Glib> embeds a
1885	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2225	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1886	into the Glib event loop).	2226	Glib event loop).
1887		2227
1888	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2228	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1889	and in a check watcher, destroy them and call into libadns. What follows	2229	and in a check watcher, destroy them and call into libadns. What follows
1890	is pseudo-code only of course. This requires you to either use a low	2230	is pseudo-code only of course. This requires you to either use a low
1891	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2231	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1892	the callbacks for the IO/timeout watchers might not have been called yet.	2232	the callbacks for the IO/timeout watchers might not have been called yet.
1893		2233
1894	static ev_io iow [nfd];	2234	static ev_io iow [nfd];
1895	static ev_timer tw;	2235	static ev_timer tw;
1896		2236
1897	static void	2237	static void
1898	io_cb (ev_loop *loop, ev_io *w, int revents)	2238	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1899	{	2239	{
1900	}	2240	}
1901		2241
1902	// create io watchers for each fd and a timer before blocking	2242	// create io watchers for each fd and a timer before blocking
1903	static void	2243	static void
1904	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2244	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1905	{	2245	{
1906	int timeout = 3600000;	2246	int timeout = 3600000;
1907	struct pollfd fds [nfd];	2247	struct pollfd fds [nfd];
1908	// actual code will need to loop here and realloc etc.	2248	// actual code will need to loop here and realloc etc.
1909	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2249	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1910		2250
1911	/* the callback is illegal, but won't be called as we stop during check */	2251	/* the callback is illegal, but won't be called as we stop during check */
1912	ev_timer_init (&tw, 0, timeout * 1e-3);	2252	ev_timer_init (&tw, 0, timeout * 1e-3);
1913	ev_timer_start (loop, &tw);	2253	ev_timer_start (loop, &tw);
1914		2254
1915	// create one ev_io per pollfd	2255	// create one ev_io per pollfd
1916	for (int i = 0; i < nfd; ++i)	2256	for (int i = 0; i < nfd; ++i)
1917	{	2257	{
1918	ev_io_init (iow + i, io_cb, fds [i].fd,	2258	ev_io_init (iow + i, io_cb, fds [i].fd,
1919	((fds [i].events & POLLIN ? EV_READ : 0)	2259	((fds [i].events & POLLIN ? EV_READ : 0)
1920	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2260	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1921		2261
1922	fds [i].revents = 0;	2262	fds [i].revents = 0;
1923	ev_io_start (loop, iow + i);	2263	ev_io_start (loop, iow + i);
1924	}	2264	}
1925	}	2265	}
1926		2266
1927	// stop all watchers after blocking	2267	// stop all watchers after blocking
1928	static void	2268	static void
1929	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2269	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1930	{	2270	{
1931	ev_timer_stop (loop, &tw);	2271	ev_timer_stop (loop, &tw);
1932		2272
1933	for (int i = 0; i < nfd; ++i)	2273	for (int i = 0; i < nfd; ++i)
1934	{	2274	{
1935	// set the relevant poll flags	2275	// set the relevant poll flags
1936	// could also call adns_processreadable etc. here	2276	// could also call adns_processreadable etc. here
1937	struct pollfd *fd = fds + i;	2277	struct pollfd *fd = fds + i;
1938	int revents = ev_clear_pending (iow + i);	2278	int revents = ev_clear_pending (iow + i);
1939	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2279	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1940	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2280	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1941		2281
1942	// now stop the watcher	2282	// now stop the watcher
1943	ev_io_stop (loop, iow + i);	2283	ev_io_stop (loop, iow + i);
1944	}	2284	}
1945		2285
1946	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2286	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1947	}	2287	}
1948		2288
1949	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2289	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1950	in the prepare watcher and would dispose of the check watcher.	2290	in the prepare watcher and would dispose of the check watcher.
1951		2291
1952	Method 3: If the module to be embedded supports explicit event	2292	Method 3: If the module to be embedded supports explicit event
1953	notification (adns does), you can also make use of the actual watcher	2293	notification (libadns does), you can also make use of the actual watcher
1954	callbacks, and only destroy/create the watchers in the prepare watcher.	2294	callbacks, and only destroy/create the watchers in the prepare watcher.
1955		2295
1956	static void	2296	static void
1957	timer_cb (EV_P_ ev_timer *w, int revents)	2297	timer_cb (EV_P_ ev_timer *w, int revents)
1958	{	2298	{
1959	adns_state ads = (adns_state)w->data;	2299	adns_state ads = (adns_state)w->data;
1960	update_now (EV_A);	2300	update_now (EV_A);
1961		2301
1962	adns_processtimeouts (ads, &tv_now);	2302	adns_processtimeouts (ads, &tv_now);
1963	}	2303	}
1964		2304
1965	static void	2305	static void
1966	io_cb (EV_P_ ev_io *w, int revents)	2306	io_cb (EV_P_ ev_io *w, int revents)
1967	{	2307	{
1968	adns_state ads = (adns_state)w->data;	2308	adns_state ads = (adns_state)w->data;
1969	update_now (EV_A);	2309	update_now (EV_A);
1970		2310
1971	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2311	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1972	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2312	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1973	}	2313	}
1974		2314
1975	// do not ever call adns_afterpoll	2315	// do not ever call adns_afterpoll
1976		2316
1977	Method 4: Do not use a prepare or check watcher because the module you	2317	Method 4: Do not use a prepare or check watcher because the module you
1978	want to embed is too inflexible to support it. Instead, youc na override	2318	want to embed is not flexible enough to support it. Instead, you can
1979	their poll function. The drawback with this solution is that the main	2319	override their poll function. The drawback with this solution is that the
1980	loop is now no longer controllable by EV. The C<Glib::EV> module does	2320	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1981	this.	2321	this approach, effectively embedding EV as a client into the horrible
		2322	libglib event loop.
1982		2323
1983	static gint	2324	static gint
1984	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2325	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1985	{	2326	{
1986	int got_events = 0;	2327	int got_events = 0;
1987		2328
1988	for (n = 0; n < nfds; ++n)	2329	for (n = 0; n < nfds; ++n)
1989	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2330	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1990		2331
1991	if (timeout >= 0)	2332	if (timeout >= 0)
1992	// create/start timer	2333	// create/start timer
1993		2334
1994	// poll	2335	// poll
1995	ev_loop (EV_A_ 0);	2336	ev_loop (EV_A_ 0);
1996		2337
1997	// stop timer again	2338	// stop timer again
1998	if (timeout >= 0)	2339	if (timeout >= 0)
1999	ev_timer_stop (EV_A_ &to);	2340	ev_timer_stop (EV_A_ &to);
2000		2341
2001	// stop io watchers again - their callbacks should have set	2342	// stop io watchers again - their callbacks should have set
2002	for (n = 0; n < nfds; ++n)	2343	for (n = 0; n < nfds; ++n)
2003	ev_io_stop (EV_A_ iow [n]);	2344	ev_io_stop (EV_A_ iow [n]);
2004		2345
2005	return got_events;	2346	return got_events;
2006	}	2347	}
2007		2348
2008		2349
2009	=head2 C<ev_embed> - when one backend isn't enough...	2350	=head2 C<ev_embed> - when one backend isn't enough...
2010		2351
2011	This is a rather advanced watcher type that lets you embed one event loop	2352	This is a rather advanced watcher type that lets you embed one event loop
…		…
2017	prioritise I/O.	2358	prioritise I/O.
2018		2359
2019	As an example for a bug workaround, the kqueue backend might only support	2360	As an example for a bug workaround, the kqueue backend might only support
2020	sockets on some platform, so it is unusable as generic backend, but you	2361	sockets on some platform, so it is unusable as generic backend, but you
2021	still want to make use of it because you have many sockets and it scales	2362	still want to make use of it because you have many sockets and it scales
2022	so nicely. In this case, you would create a kqueue-based loop and embed it	2363	so nicely. In this case, you would create a kqueue-based loop and embed
2023	into your default loop (which might use e.g. poll). Overall operation will	2364	it into your default loop (which might use e.g. poll). Overall operation
2024	be a bit slower because first libev has to poll and then call kevent, but	2365	will be a bit slower because first libev has to call C<poll> and then
2025	at least you can use both at what they are best.	2366	C<kevent>, but at least you can use both mechanisms for what they are
		2367	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2026		2368
2027	As for prioritising I/O: rarely you have the case where some fds have	2369	As for prioritising I/O: under rare circumstances you have the case where
2028	to be watched and handled very quickly (with low latency), and even	2370	some fds have to be watched and handled very quickly (with low latency),
2029	priorities and idle watchers might have too much overhead. In this case	2371	and even priorities and idle watchers might have too much overhead. In
2030	you would put all the high priority stuff in one loop and all the rest in	2372	this case you would put all the high priority stuff in one loop and all
2031	a second one, and embed the second one in the first.	2373	the rest in a second one, and embed the second one in the first.
2032		2374
2033	As long as the watcher is active, the callback will be invoked every time	2375	As long as the watcher is active, the callback will be invoked every time
2034	there might be events pending in the embedded loop. The callback must then	2376	there might be events pending in the embedded loop. The callback must then
2035	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2377	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2036	their callbacks (you could also start an idle watcher to give the embedded	2378	their callbacks (you could also start an idle watcher to give the embedded
…		…
2044	interested in that.	2386	interested in that.
2045		2387
2046	Also, there have not currently been made special provisions for forking:	2388	Also, there have not currently been made special provisions for forking:
2047	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2389	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2048	but you will also have to stop and restart any C<ev_embed> watchers	2390	but you will also have to stop and restart any C<ev_embed> watchers
2049	yourself.	2391	yourself - but you can use a fork watcher to handle this automatically,
		2392	and future versions of libev might do just that.
2050		2393
2051	Unfortunately, not all backends are embeddable, only the ones returned by	2394	Unfortunately, not all backends are embeddable: only the ones returned by
2052	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2395	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2053	portable one.	2396	portable one.
2054		2397
2055	So when you want to use this feature you will always have to be prepared	2398	So when you want to use this feature you will always have to be prepared
2056	that you cannot get an embeddable loop. The recommended way to get around	2399	that you cannot get an embeddable loop. The recommended way to get around
2057	this is to have a separate variables for your embeddable loop, try to	2400	this is to have a separate variables for your embeddable loop, try to
2058	create it, and if that fails, use the normal loop for everything.	2401	create it, and if that fails, use the normal loop for everything.
2059		2402
		2403	=head3 C<ev_embed> and fork
		2404
		2405	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2406	automatically be applied to the embedded loop as well, so no special
		2407	fork handling is required in that case. When the watcher is not running,
		2408	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2409	as applicable.
		2410
2060	=head3 Watcher-Specific Functions and Data Members	2411	=head3 Watcher-Specific Functions and Data Members
2061		2412
2062	=over 4	2413	=over 4
2063		2414
2064	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2415	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2067		2418
2068	Configures the watcher to embed the given loop, which must be	2419	Configures the watcher to embed the given loop, which must be
2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2420	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2070	invoked automatically, otherwise it is the responsibility of the callback	2421	invoked automatically, otherwise it is the responsibility of the callback
2071	to invoke it (it will continue to be called until the sweep has been done,	2422	to invoke it (it will continue to be called until the sweep has been done,
2072	if you do not want thta, you need to temporarily stop the embed watcher).	2423	if you do not want that, you need to temporarily stop the embed watcher).
2073		2424
2074	=item ev_embed_sweep (loop, ev_embed *)	2425	=item ev_embed_sweep (loop, ev_embed *)
2075		2426
2076	Make a single, non-blocking sweep over the embedded loop. This works	2427	Make a single, non-blocking sweep over the embedded loop. This works
2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2428	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2078	apropriate way for embedded loops.	2429	appropriate way for embedded loops.
2079		2430
2080	=item struct ev_loop *other [read-only]	2431	=item struct ev_loop *other [read-only]
2081		2432
2082	The embedded event loop.	2433	The embedded event loop.
2083		2434
…		…
2085		2436
2086	=head3 Examples	2437	=head3 Examples
2087		2438
2088	Example: Try to get an embeddable event loop and embed it into the default	2439	Example: Try to get an embeddable event loop and embed it into the default
2089	event loop. If that is not possible, use the default loop. The default	2440	event loop. If that is not possible, use the default loop. The default
2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2441	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2442	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2092	used).	2443	used).
2093		2444
2094	struct ev_loop *loop_hi = ev_default_init (0);	2445	struct ev_loop *loop_hi = ev_default_init (0);
2095	struct ev_loop *loop_lo = 0;	2446	struct ev_loop *loop_lo = 0;
2096	struct ev_embed embed;	2447	ev_embed embed;
2097		2448
2098	// see if there is a chance of getting one that works	2449	// see if there is a chance of getting one that works
2099	// (remember that a flags value of 0 means autodetection)	2450	// (remember that a flags value of 0 means autodetection)
2100	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2451	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2101	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2452	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2102	: 0;	2453	: 0;
2103		2454
2104	// if we got one, then embed it, otherwise default to loop_hi	2455	// if we got one, then embed it, otherwise default to loop_hi
2105	if (loop_lo)	2456	if (loop_lo)
2106	{	2457	{
2107	ev_embed_init (&embed, 0, loop_lo);	2458	ev_embed_init (&embed, 0, loop_lo);
2108	ev_embed_start (loop_hi, &embed);	2459	ev_embed_start (loop_hi, &embed);
2109	}	2460	}
2110	else	2461	else
2111	loop_lo = loop_hi;	2462	loop_lo = loop_hi;
2112		2463
2113	Example: Check if kqueue is available but not recommended and create	2464	Example: Check if kqueue is available but not recommended and create
2114	a kqueue backend for use with sockets (which usually work with any	2465	a kqueue backend for use with sockets (which usually work with any
2115	kqueue implementation). Store the kqueue/socket-only event loop in	2466	kqueue implementation). Store the kqueue/socket-only event loop in
2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2467	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2117		2468
2118	struct ev_loop *loop = ev_default_init (0);	2469	struct ev_loop *loop = ev_default_init (0);
2119	struct ev_loop *loop_socket = 0;	2470	struct ev_loop *loop_socket = 0;
2120	struct ev_embed embed;	2471	ev_embed embed;
2121		2472
2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2473	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2474	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2124	{	2475	{
2125	ev_embed_init (&embed, 0, loop_socket);	2476	ev_embed_init (&embed, 0, loop_socket);
2126	ev_embed_start (loop, &embed);	2477	ev_embed_start (loop, &embed);
2127	}	2478	}
2128		2479
2129	if (!loop_socket)	2480	if (!loop_socket)
2130	loop_socket = loop;	2481	loop_socket = loop;
2131		2482
2132	// now use loop_socket for all sockets, and loop for everything else	2483	// now use loop_socket for all sockets, and loop for everything else
2133		2484
2134		2485
2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2486	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2136		2487
2137	Fork watchers are called when a C<fork ()> was detected (usually because	2488	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2181	is that the author does not know of a simple (or any) algorithm for a	2532	is that the author does not know of a simple (or any) algorithm for a
2182	multiple-writer-single-reader queue that works in all cases and doesn't	2533	multiple-writer-single-reader queue that works in all cases and doesn't
2183	need elaborate support such as pthreads.	2534	need elaborate support such as pthreads.
2184		2535
2185	That means that if you want to queue data, you have to provide your own	2536	That means that if you want to queue data, you have to provide your own
2186	queue. But at least I can tell you would implement locking around your	2537	queue. But at least I can tell you how to implement locking around your
2187	queue:	2538	queue:
2188		2539
2189	=over 4	2540	=over 4
2190		2541
2191	=item queueing from a signal handler context	2542	=item queueing from a signal handler context
2192		2543
2193	To implement race-free queueing, you simply add to the queue in the signal	2544	To implement race-free queueing, you simply add to the queue in the signal
2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2545	handler but you block the signal handler in the watcher callback. Here is
2195	some fictitiuous SIGUSR1 handler:	2546	an example that does that for some fictitious SIGUSR1 handler:
2196		2547
2197	static ev_async mysig;	2548	static ev_async mysig;
2198		2549
2199	static void	2550	static void
2200	sigusr1_handler (void)	2551	sigusr1_handler (void)
…		…
2267		2618
2268	=item ev_async_init (ev_async *, callback)	2619	=item ev_async_init (ev_async *, callback)
2269		2620
2270	Initialises and configures the async watcher - it has no parameters of any	2621	Initialises and configures the async watcher - it has no parameters of any
2271	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2622	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2272	believe me.	2623	trust me.
2273		2624
2274	=item ev_async_send (loop, ev_async *)	2625	=item ev_async_send (loop, ev_async *)
2275		2626
2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2627	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2628	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2278	C<ev_feed_event>, this call is safe to do in other threads, signal or	2629	C<ev_feed_event>, this call is safe to do from other threads, signal or
2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2630	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2280	section below on what exactly this means).	2631	section below on what exactly this means).
2281		2632
2282	This call incurs the overhead of a syscall only once per loop iteration,	2633	This call incurs the overhead of a system call only once per loop iteration,
2283	so while the overhead might be noticable, it doesn't apply to repeated	2634	so while the overhead might be noticeable, it doesn't apply to repeated
2284	calls to C<ev_async_send>.	2635	calls to C<ev_async_send>.
2285		2636
2286	=item bool = ev_async_pending (ev_async *)	2637	=item bool = ev_async_pending (ev_async *)
2287		2638
2288	Returns a non-zero value when C<ev_async_send> has been called on the	2639	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2290	event loop.	2641	event loop.
2291		2642
2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2643	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2293	the loop iterates next and checks for the watcher to have become active,	2644	the loop iterates next and checks for the watcher to have become active,
2294	it will reset the flag again. C<ev_async_pending> can be used to very	2645	it will reset the flag again. C<ev_async_pending> can be used to very
2295	quickly check wether invoking the loop might be a good idea.	2646	quickly check whether invoking the loop might be a good idea.
2296		2647
2297	Not that this does I<not> check wether the watcher itself is pending, only	2648	Not that this does I<not> check whether the watcher itself is pending, only
2298	wether it has been requested to make this watcher pending.	2649	whether it has been requested to make this watcher pending.
2299		2650
2300	=back	2651	=back
2301		2652
2302		2653
2303	=head1 OTHER FUNCTIONS	2654	=head1 OTHER FUNCTIONS
…		…
2307	=over 4	2658	=over 4
2308		2659
2309	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2660	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2310		2661
2311	This function combines a simple timer and an I/O watcher, calls your	2662	This function combines a simple timer and an I/O watcher, calls your
2312	callback on whichever event happens first and automatically stop both	2663	callback on whichever event happens first and automatically stops both
2313	watchers. This is useful if you want to wait for a single event on an fd	2664	watchers. This is useful if you want to wait for a single event on an fd
2314	or timeout without having to allocate/configure/start/stop/free one or	2665	or timeout without having to allocate/configure/start/stop/free one or
2315	more watchers yourself.	2666	more watchers yourself.
2316		2667
2317	If C<fd> is less than 0, then no I/O watcher will be started and events	2668	If C<fd> is less than 0, then no I/O watcher will be started and the
2318	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2669	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2319	C<events> set will be craeted and started.	2670	the given C<fd> and C<events> set will be created and started.
2320		2671
2321	If C<timeout> is less than 0, then no timeout watcher will be	2672	If C<timeout> is less than 0, then no timeout watcher will be
2322	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2673	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2323	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2674	repeat = 0) will be started. C<0> is a valid timeout.
2324	dubious value.
2325		2675
2326	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2676	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2327	passed an C<revents> set like normal event callbacks (a combination of	2677	passed an C<revents> set like normal event callbacks (a combination of
2328	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2678	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2329	value passed to C<ev_once>:	2679	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2680	a timeout and an io event at the same time - you probably should give io
		2681	events precedence.
2330		2682
		2683	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2684
2331	static void stdin_ready (int revents, void *arg)	2685	static void stdin_ready (int revents, void *arg)
2332	{	2686	{
2333	if (revents & EV_TIMEOUT)
2334	/* doh, nothing entered */;
2335	else if (revents & EV_READ)	2687	if (revents & EV_READ)
2336	/* stdin might have data for us, joy! */;	2688	/* stdin might have data for us, joy! */;
		2689	else if (revents & EV_TIMEOUT)
		2690	/* doh, nothing entered */;
2337	}	2691	}
2338		2692
2339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2693	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2340		2694
2341	=item ev_feed_event (ev_loop *, watcher *, int revents)	2695	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2342		2696
2343	Feeds the given event set into the event loop, as if the specified event	2697	Feeds the given event set into the event loop, as if the specified event
2344	had happened for the specified watcher (which must be a pointer to an	2698	had happened for the specified watcher (which must be a pointer to an
2345	initialised but not necessarily started event watcher).	2699	initialised but not necessarily started event watcher).
2346		2700
2347	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2701	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2348		2702
2349	Feed an event on the given fd, as if a file descriptor backend detected	2703	Feed an event on the given fd, as if a file descriptor backend detected
2350	the given events it.	2704	the given events it.
2351		2705
2352	=item ev_feed_signal_event (ev_loop *loop, int signum)	2706	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2353		2707
2354	Feed an event as if the given signal occured (C<loop> must be the default	2708	Feed an event as if the given signal occurred (C<loop> must be the default
2355	loop!).	2709	loop!).
2356		2710
2357	=back	2711	=back
2358		2712
2359		2713
…		…
2375		2729
2376	=item * Priorities are not currently supported. Initialising priorities	2730	=item * Priorities are not currently supported. Initialising priorities
2377	will fail and all watchers will have the same priority, even though there	2731	will fail and all watchers will have the same priority, even though there
2378	is an ev_pri field.	2732	is an ev_pri field.
2379		2733
		2734	=item * In libevent, the last base created gets the signals, in libev, the
		2735	first base created (== the default loop) gets the signals.
		2736
2380	=item * Other members are not supported.	2737	=item * Other members are not supported.
2381		2738
2382	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2739	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2383	to use the libev header file and library.	2740	to use the libev header file and library.
2384		2741
2385	=back	2742	=back
2386		2743
2387	=head1 C++ SUPPORT	2744	=head1 C++ SUPPORT
2388		2745
2389	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2746	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2390	you to use some convinience methods to start/stop watchers and also change	2747	you to use some convenience methods to start/stop watchers and also change
2391	the callback model to a model using method callbacks on objects.	2748	the callback model to a model using method callbacks on objects.
2392		2749
2393	To use it,	2750	To use it,
2394		2751
2395	#include <ev++.h>	2752	#include <ev++.h>
2396		2753
2397	This automatically includes F<ev.h> and puts all of its definitions (many	2754	This automatically includes F<ev.h> and puts all of its definitions (many
2398	of them macros) into the global namespace. All C++ specific things are	2755	of them macros) into the global namespace. All C++ specific things are
2399	put into the C<ev> namespace. It should support all the same embedding	2756	put into the C<ev> namespace. It should support all the same embedding
2400	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2757	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2467	your compiler is good :), then the method will be fully inlined into the	2824	your compiler is good :), then the method will be fully inlined into the
2468	thunking function, making it as fast as a direct C callback.	2825	thunking function, making it as fast as a direct C callback.
2469		2826
2470	Example: simple class declaration and watcher initialisation	2827	Example: simple class declaration and watcher initialisation
2471		2828
2472	struct myclass	2829	struct myclass
2473	{	2830	{
2474	void io_cb (ev::io &w, int revents) { }	2831	void io_cb (ev::io &w, int revents) { }
2475	}	2832	}
2476		2833
2477	myclass obj;	2834	myclass obj;
2478	ev::io iow;	2835	ev::io iow;
2479	iow.set <myclass, &myclass::io_cb> (&obj);	2836	iow.set <myclass, &myclass::io_cb> (&obj);
2480		2837
2481	=item w->set<function> (void *data = 0)	2838	=item w->set<function> (void *data = 0)
2482		2839
2483	Also sets a callback, but uses a static method or plain function as	2840	Also sets a callback, but uses a static method or plain function as
2484	callback. The optional C<data> argument will be stored in the watcher's	2841	callback. The optional C<data> argument will be stored in the watcher's
…		…
2486		2843
2487	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2844	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2488		2845
2489	See the method-C<set> above for more details.	2846	See the method-C<set> above for more details.
2490		2847
2491	Example:	2848	Example: Use a plain function as callback.
2492		2849
2493	static void io_cb (ev::io &w, int revents) { }	2850	static void io_cb (ev::io &w, int revents) { }
2494	iow.set <io_cb> ();	2851	iow.set <io_cb> ();
2495		2852
2496	=item w->set (struct ev_loop *)	2853	=item w->set (struct ev_loop *)
2497		2854
2498	Associates a different C<struct ev_loop> with this watcher. You can only	2855	Associates a different C<struct ev_loop> with this watcher. You can only
2499	do this when the watcher is inactive (and not pending either).	2856	do this when the watcher is inactive (and not pending either).
2500		2857
2501	=item w->set ([args])	2858	=item w->set ([arguments])
2502		2859
2503	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2860	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2504	called at least once. Unlike the C counterpart, an active watcher gets	2861	called at least once. Unlike the C counterpart, an active watcher gets
2505	automatically stopped and restarted when reconfiguring it with this	2862	automatically stopped and restarted when reconfiguring it with this
2506	method.	2863	method.
2507		2864
2508	=item w->start ()	2865	=item w->start ()
…		…
2532	=back	2889	=back
2533		2890
2534	Example: Define a class with an IO and idle watcher, start one of them in	2891	Example: Define a class with an IO and idle watcher, start one of them in
2535	the constructor.	2892	the constructor.
2536		2893
2537	class myclass	2894	class myclass
2538	{	2895	{
2539	ev::io io; void io_cb (ev::io &w, int revents);	2896	ev::io io ; void io_cb (ev::io &w, int revents);
2540	ev:idle idle void idle_cb (ev::idle &w, int revents);	2897	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2541		2898
2542	myclass (int fd)	2899	myclass (int fd)
2543	{	2900	{
2544	io .set <myclass, &myclass::io_cb > (this);	2901	io .set <myclass, &myclass::io_cb > (this);
2545	idle.set <myclass, &myclass::idle_cb> (this);	2902	idle.set <myclass, &myclass::idle_cb> (this);
2546		2903
2547	io.start (fd, ev::READ);	2904	io.start (fd, ev::READ);
2548	}	2905	}
2549	};	2906	};
2550		2907
2551		2908
2552	=head1 OTHER LANGUAGE BINDINGS	2909	=head1 OTHER LANGUAGE BINDINGS
2553		2910
2554	Libev does not offer other language bindings itself, but bindings for a	2911	Libev does not offer other language bindings itself, but bindings for a
2555	numbe rof languages exist in the form of third-party packages. If you know	2912	number of languages exist in the form of third-party packages. If you know
2556	any interesting language binding in addition to the ones listed here, drop	2913	any interesting language binding in addition to the ones listed here, drop
2557	me a note.	2914	me a note.
2558		2915
2559	=over 4	2916	=over 4
2560		2917
2561	=item Perl	2918	=item Perl
2562		2919
2563	The EV module implements the full libev API and is actually used to test	2920	The EV module implements the full libev API and is actually used to test
2564	libev. EV is developed together with libev. Apart from the EV core module,	2921	libev. EV is developed together with libev. Apart from the EV core module,
2565	there are additional modules that implement libev-compatible interfaces	2922	there are additional modules that implement libev-compatible interfaces
2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2923	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2924	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2925	and C<EV::Glib>).
2568		2926
2569	It can be found and installed via CPAN, its homepage is found at	2927	It can be found and installed via CPAN, its homepage is at
2570	L<http://software.schmorp.de/pkg/EV>.	2928	L<http://software.schmorp.de/pkg/EV>.
2571		2929
		2930	=item Python
		2931
		2932	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2933	seems to be quite complete and well-documented. Note, however, that the
		2934	patch they require for libev is outright dangerous as it breaks the ABI
		2935	for everybody else, and therefore, should never be applied in an installed
		2936	libev (if python requires an incompatible ABI then it needs to embed
		2937	libev).
		2938
2572	=item Ruby	2939	=item Ruby
2573		2940
2574	Tony Arcieri has written a ruby extension that offers access to a subset	2941	Tony Arcieri has written a ruby extension that offers access to a subset
2575	of the libev API and adds filehandle abstractions, asynchronous DNS and	2942	of the libev API and adds file handle abstractions, asynchronous DNS and
2576	more on top of it. It can be found via gem servers. Its homepage is at	2943	more on top of it. It can be found via gem servers. Its homepage is at
2577	L<http://rev.rubyforge.org/>.	2944	L<http://rev.rubyforge.org/>.
2578		2945
2579	=item D	2946	=item D
2580		2947
2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2948	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2949	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2583		2950
2584	=back	2951	=back
2585		2952
2586		2953
2587	=head1 MACRO MAGIC	2954	=head1 MACRO MAGIC
2588		2955
2589	Libev can be compiled with a variety of options, the most fundamantal	2956	Libev can be compiled with a variety of options, the most fundamental
2590	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2957	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2591	functions and callbacks have an initial C<struct ev_loop *> argument.	2958	functions and callbacks have an initial C<struct ev_loop *> argument.
2592		2959
2593	To make it easier to write programs that cope with either variant, the	2960	To make it easier to write programs that cope with either variant, the
2594	following macros are defined:	2961	following macros are defined:
…		…
2599		2966
2600	This provides the loop I<argument> for functions, if one is required ("ev	2967	This provides the loop I<argument> for functions, if one is required ("ev
2601	loop argument"). The C<EV_A> form is used when this is the sole argument,	2968	loop argument"). The C<EV_A> form is used when this is the sole argument,
2602	C<EV_A_> is used when other arguments are following. Example:	2969	C<EV_A_> is used when other arguments are following. Example:
2603		2970
2604	ev_unref (EV_A);	2971	ev_unref (EV_A);
2605	ev_timer_add (EV_A_ watcher);	2972	ev_timer_add (EV_A_ watcher);
2606	ev_loop (EV_A_ 0);	2973	ev_loop (EV_A_ 0);
2607		2974
2608	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2975	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2609	which is often provided by the following macro.	2976	which is often provided by the following macro.
2610		2977
2611	=item C<EV_P>, C<EV_P_>	2978	=item C<EV_P>, C<EV_P_>
2612		2979
2613	This provides the loop I<parameter> for functions, if one is required ("ev	2980	This provides the loop I<parameter> for functions, if one is required ("ev
2614	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2981	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2615	C<EV_P_> is used when other parameters are following. Example:	2982	C<EV_P_> is used when other parameters are following. Example:
2616		2983
2617	// this is how ev_unref is being declared	2984	// this is how ev_unref is being declared
2618	static void ev_unref (EV_P);	2985	static void ev_unref (EV_P);
2619		2986
2620	// this is how you can declare your typical callback	2987	// this is how you can declare your typical callback
2621	static void cb (EV_P_ ev_timer *w, int revents)	2988	static void cb (EV_P_ ev_timer *w, int revents)
2622		2989
2623	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2990	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2624	suitable for use with C<EV_A>.	2991	suitable for use with C<EV_A>.
2625		2992
2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2993	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2642		3009
2643	Example: Declare and initialise a check watcher, utilising the above	3010	Example: Declare and initialise a check watcher, utilising the above
2644	macros so it will work regardless of whether multiple loops are supported	3011	macros so it will work regardless of whether multiple loops are supported
2645	or not.	3012	or not.
2646		3013
2647	static void	3014	static void
2648	check_cb (EV_P_ ev_timer *w, int revents)	3015	check_cb (EV_P_ ev_timer *w, int revents)
2649	{	3016	{
2650	ev_check_stop (EV_A_ w);	3017	ev_check_stop (EV_A_ w);
2651	}	3018	}
2652		3019
2653	ev_check check;	3020	ev_check check;
2654	ev_check_init (&check, check_cb);	3021	ev_check_init (&check, check_cb);
2655	ev_check_start (EV_DEFAULT_ &check);	3022	ev_check_start (EV_DEFAULT_ &check);
2656	ev_loop (EV_DEFAULT_ 0);	3023	ev_loop (EV_DEFAULT_ 0);
2657		3024
2658	=head1 EMBEDDING	3025	=head1 EMBEDDING
2659		3026
2660	Libev can (and often is) directly embedded into host	3027	Libev can (and often is) directly embedded into host
2661	applications. Examples of applications that embed it include the Deliantra	3028	applications. Examples of applications that embed it include the Deliantra
…		…
2668	libev somewhere in your source tree).	3035	libev somewhere in your source tree).
2669		3036
2670	=head2 FILESETS	3037	=head2 FILESETS
2671		3038
2672	Depending on what features you need you need to include one or more sets of files	3039	Depending on what features you need you need to include one or more sets of files
2673	in your app.	3040	in your application.
2674		3041
2675	=head3 CORE EVENT LOOP	3042	=head3 CORE EVENT LOOP
2676		3043
2677	To include only the libev core (all the C<ev_*> functions), with manual	3044	To include only the libev core (all the C<ev_*> functions), with manual
2678	configuration (no autoconf):	3045	configuration (no autoconf):
2679		3046
2680	#define EV_STANDALONE 1	3047	#define EV_STANDALONE 1
2681	#include "ev.c"	3048	#include "ev.c"
2682		3049
2683	This will automatically include F<ev.h>, too, and should be done in a	3050	This will automatically include F<ev.h>, too, and should be done in a
2684	single C source file only to provide the function implementations. To use	3051	single C source file only to provide the function implementations. To use
2685	it, do the same for F<ev.h> in all files wishing to use this API (best	3052	it, do the same for F<ev.h> in all files wishing to use this API (best
2686	done by writing a wrapper around F<ev.h> that you can include instead and	3053	done by writing a wrapper around F<ev.h> that you can include instead and
2687	where you can put other configuration options):	3054	where you can put other configuration options):
2688		3055
2689	#define EV_STANDALONE 1	3056	#define EV_STANDALONE 1
2690	#include "ev.h"	3057	#include "ev.h"
2691		3058
2692	Both header files and implementation files can be compiled with a C++	3059	Both header files and implementation files can be compiled with a C++
2693	compiler (at least, thats a stated goal, and breakage will be treated	3060	compiler (at least, thats a stated goal, and breakage will be treated
2694	as a bug).	3061	as a bug).
2695		3062
2696	You need the following files in your source tree, or in a directory	3063	You need the following files in your source tree, or in a directory
2697	in your include path (e.g. in libev/ when using -Ilibev):	3064	in your include path (e.g. in libev/ when using -Ilibev):
2698		3065
2699	ev.h	3066	ev.h
2700	ev.c	3067	ev.c
2701	ev_vars.h	3068	ev_vars.h
2702	ev_wrap.h	3069	ev_wrap.h
2703		3070
2704	ev_win32.c required on win32 platforms only	3071	ev_win32.c required on win32 platforms only
2705		3072
2706	ev_select.c only when select backend is enabled (which is enabled by default)	3073	ev_select.c only when select backend is enabled (which is enabled by default)
2707	ev_poll.c only when poll backend is enabled (disabled by default)	3074	ev_poll.c only when poll backend is enabled (disabled by default)
2708	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3075	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2709	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3076	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2710	ev_port.c only when the solaris port backend is enabled (disabled by default)	3077	ev_port.c only when the solaris port backend is enabled (disabled by default)
2711		3078
2712	F<ev.c> includes the backend files directly when enabled, so you only need	3079	F<ev.c> includes the backend files directly when enabled, so you only need
2713	to compile this single file.	3080	to compile this single file.
2714		3081
2715	=head3 LIBEVENT COMPATIBILITY API	3082	=head3 LIBEVENT COMPATIBILITY API
2716		3083
2717	To include the libevent compatibility API, also include:	3084	To include the libevent compatibility API, also include:
2718		3085
2719	#include "event.c"	3086	#include "event.c"
2720		3087
2721	in the file including F<ev.c>, and:	3088	in the file including F<ev.c>, and:
2722		3089
2723	#include "event.h"	3090	#include "event.h"
2724		3091
2725	in the files that want to use the libevent API. This also includes F<ev.h>.	3092	in the files that want to use the libevent API. This also includes F<ev.h>.
2726		3093
2727	You need the following additional files for this:	3094	You need the following additional files for this:
2728		3095
2729	event.h	3096	event.h
2730	event.c	3097	event.c
2731		3098
2732	=head3 AUTOCONF SUPPORT	3099	=head3 AUTOCONF SUPPORT
2733		3100
2734	Instead of using C<EV_STANDALONE=1> and providing your config in	3101	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2735	whatever way you want, you can also C<m4_include([libev.m4])> in your	3102	whatever way you want, you can also C<m4_include([libev.m4])> in your
2736	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3103	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2737	include F<config.h> and configure itself accordingly.	3104	include F<config.h> and configure itself accordingly.
2738		3105
2739	For this of course you need the m4 file:	3106	For this of course you need the m4 file:
2740		3107
2741	libev.m4	3108	libev.m4
2742		3109
2743	=head2 PREPROCESSOR SYMBOLS/MACROS	3110	=head2 PREPROCESSOR SYMBOLS/MACROS
2744		3111
2745	Libev can be configured via a variety of preprocessor symbols you have to	3112	Libev can be configured via a variety of preprocessor symbols you have to
2746	define before including any of its files. The default in the absense of	3113	define before including any of its files. The default in the absence of
2747	autoconf is noted for every option.	3114	autoconf is documented for every option.
2748		3115
2749	=over 4	3116	=over 4
2750		3117
2751	=item EV_STANDALONE	3118	=item EV_STANDALONE
2752		3119
…		…
2757	F<event.h> that are not directly supported by the libev core alone.	3124	F<event.h> that are not directly supported by the libev core alone.
2758		3125
2759	=item EV_USE_MONOTONIC	3126	=item EV_USE_MONOTONIC
2760		3127
2761	If defined to be C<1>, libev will try to detect the availability of the	3128	If defined to be C<1>, libev will try to detect the availability of the
2762	monotonic clock option at both compiletime and runtime. Otherwise no use	3129	monotonic clock option at both compile time and runtime. Otherwise no use
2763	of the monotonic clock option will be attempted. If you enable this, you	3130	of the monotonic clock option will be attempted. If you enable this, you
2764	usually have to link against librt or something similar. Enabling it when	3131	usually have to link against librt or something similar. Enabling it when
2765	the functionality isn't available is safe, though, although you have	3132	the functionality isn't available is safe, though, although you have
2766	to make sure you link against any libraries where the C<clock_gettime>	3133	to make sure you link against any libraries where the C<clock_gettime>
2767	function is hiding in (often F<-lrt>).	3134	function is hiding in (often F<-lrt>).
2768		3135
2769	=item EV_USE_REALTIME	3136	=item EV_USE_REALTIME
2770		3137
2771	If defined to be C<1>, libev will try to detect the availability of the	3138	If defined to be C<1>, libev will try to detect the availability of the
2772	realtime clock option at compiletime (and assume its availability at	3139	real-time clock option at compile time (and assume its availability at
2773	runtime if successful). Otherwise no use of the realtime clock option will	3140	runtime if successful). Otherwise no use of the real-time clock option will
2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3141	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3142	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3143	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2777		3144
2778	=item EV_USE_NANOSLEEP	3145	=item EV_USE_NANOSLEEP
…		…
2789	2.7 or newer, otherwise disabled.	3156	2.7 or newer, otherwise disabled.
2790		3157
2791	=item EV_USE_SELECT	3158	=item EV_USE_SELECT
2792		3159
2793	If undefined or defined to be C<1>, libev will compile in support for the	3160	If undefined or defined to be C<1>, libev will compile in support for the
2794	C<select>(2) backend. No attempt at autodetection will be done: if no	3161	C<select>(2) backend. No attempt at auto-detection will be done: if no
2795	other method takes over, select will be it. Otherwise the select backend	3162	other method takes over, select will be it. Otherwise the select backend
2796	will not be compiled in.	3163	will not be compiled in.
2797		3164
2798	=item EV_SELECT_USE_FD_SET	3165	=item EV_SELECT_USE_FD_SET
2799		3166
2800	If defined to C<1>, then the select backend will use the system C<fd_set>	3167	If defined to C<1>, then the select backend will use the system C<fd_set>
2801	structure. This is useful if libev doesn't compile due to a missing	3168	structure. This is useful if libev doesn't compile due to a missing
2802	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3169	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2803	exotic systems. This usually limits the range of file descriptors to some	3170	exotic systems. This usually limits the range of file descriptors to some
2804	low limit such as 1024 or might have other limitations (winsocket only	3171	low limit such as 1024 or might have other limitations (winsocket only
2805	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3172	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2806	influence the size of the C<fd_set> used.	3173	influence the size of the C<fd_set> used.
2807		3174
…		…
2856	otherwise another method will be used as fallback. This is the preferred	3223	otherwise another method will be used as fallback. This is the preferred
2857	backend for Solaris 10 systems.	3224	backend for Solaris 10 systems.
2858		3225
2859	=item EV_USE_DEVPOLL	3226	=item EV_USE_DEVPOLL
2860		3227
2861	reserved for future expansion, works like the USE symbols above.	3228	Reserved for future expansion, works like the USE symbols above.
2862		3229
2863	=item EV_USE_INOTIFY	3230	=item EV_USE_INOTIFY
2864		3231
2865	If defined to be C<1>, libev will compile in support for the Linux inotify	3232	If defined to be C<1>, libev will compile in support for the Linux inotify
2866	interface to speed up C<ev_stat> watchers. Its actual availability will	3233	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2873	access is atomic with respect to other threads or signal contexts. No such	3240	access is atomic with respect to other threads or signal contexts. No such
2874	type is easily found in the C language, so you can provide your own type	3241	type is easily found in the C language, so you can provide your own type
2875	that you know is safe for your purposes. It is used both for signal handler "locking"	3242	that you know is safe for your purposes. It is used both for signal handler "locking"
2876	as well as for signal and thread safety in C<ev_async> watchers.	3243	as well as for signal and thread safety in C<ev_async> watchers.
2877		3244
2878	In the absense of this define, libev will use C<sig_atomic_t volatile>	3245	In the absence of this define, libev will use C<sig_atomic_t volatile>
2879	(from F<signal.h>), which is usually good enough on most platforms.	3246	(from F<signal.h>), which is usually good enough on most platforms.
2880		3247
2881	=item EV_H	3248	=item EV_H
2882		3249
2883	The name of the F<ev.h> header file used to include it. The default if	3250	The name of the F<ev.h> header file used to include it. The default if
…		…
2922	When doing priority-based operations, libev usually has to linearly search	3289	When doing priority-based operations, libev usually has to linearly search
2923	all the priorities, so having many of them (hundreds) uses a lot of space	3290	all the priorities, so having many of them (hundreds) uses a lot of space
2924	and time, so using the defaults of five priorities (-2 .. +2) is usually	3291	and time, so using the defaults of five priorities (-2 .. +2) is usually
2925	fine.	3292	fine.
2926		3293
2927	If your embedding app does not need any priorities, defining these both to	3294	If your embedding application does not need any priorities, defining these
2928	C<0> will save some memory and cpu.	3295	both to C<0> will save some memory and CPU.
2929		3296
2930	=item EV_PERIODIC_ENABLE	3297	=item EV_PERIODIC_ENABLE
2931		3298
2932	If undefined or defined to be C<1>, then periodic timers are supported. If	3299	If undefined or defined to be C<1>, then periodic timers are supported. If
2933	defined to be C<0>, then they are not. Disabling them saves a few kB of	3300	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2940	code.	3307	code.
2941		3308
2942	=item EV_EMBED_ENABLE	3309	=item EV_EMBED_ENABLE
2943		3310
2944	If undefined or defined to be C<1>, then embed watchers are supported. If	3311	If undefined or defined to be C<1>, then embed watchers are supported. If
2945	defined to be C<0>, then they are not.	3312	defined to be C<0>, then they are not. Embed watchers rely on most other
		3313	watcher types, which therefore must not be disabled.
2946		3314
2947	=item EV_STAT_ENABLE	3315	=item EV_STAT_ENABLE
2948		3316
2949	If undefined or defined to be C<1>, then stat watchers are supported. If	3317	If undefined or defined to be C<1>, then stat watchers are supported. If
2950	defined to be C<0>, then they are not.	3318	defined to be C<0>, then they are not.
…		…
2960	defined to be C<0>, then they are not.	3328	defined to be C<0>, then they are not.
2961		3329
2962	=item EV_MINIMAL	3330	=item EV_MINIMAL
2963		3331
2964	If you need to shave off some kilobytes of code at the expense of some	3332	If you need to shave off some kilobytes of code at the expense of some
2965	speed, define this symbol to C<1>. Currently only used for gcc to override	3333	speed, define this symbol to C<1>. Currently this is used to override some
2966	some inlining decisions, saves roughly 30% codesize of amd64.	3334	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3335	much smaller 2-heap for timer management over the default 4-heap.
2967		3336
2968	=item EV_PID_HASHSIZE	3337	=item EV_PID_HASHSIZE
2969		3338
2970	C<ev_child> watchers use a small hash table to distribute workload by	3339	C<ev_child> watchers use a small hash table to distribute workload by
2971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3340	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3347	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2979	usually more than enough. If you need to manage thousands of C<ev_stat>	3348	usually more than enough. If you need to manage thousands of C<ev_stat>
2980	watchers you might want to increase this value (I<must> be a power of	3349	watchers you might want to increase this value (I<must> be a power of
2981	two).	3350	two).
2982		3351
		3352	=item EV_USE_4HEAP
		3353
		3354	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3355	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3356	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3357	faster performance with many (thousands) of watchers.
		3358
		3359	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3360	(disabled).
		3361
		3362	=item EV_HEAP_CACHE_AT
		3363
		3364	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3365	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3366	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3367	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3368	but avoids random read accesses on heap changes. This improves performance
		3369	noticeably with many (hundreds) of watchers.
		3370
		3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3372	(disabled).
		3373
		3374	=item EV_VERIFY
		3375
		3376	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3377	be done: If set to C<0>, no internal verification code will be compiled
		3378	in. If set to C<1>, then verification code will be compiled in, but not
		3379	called. If set to C<2>, then the internal verification code will be
		3380	called once per loop, which can slow down libev. If set to C<3>, then the
		3381	verification code will be called very frequently, which will slow down
		3382	libev considerably.
		3383
		3384	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3385	C<0>.
		3386
2983	=item EV_COMMON	3387	=item EV_COMMON
2984		3388
2985	By default, all watchers have a C<void *data> member. By redefining	3389	By default, all watchers have a C<void *data> member. By redefining
2986	this macro to a something else you can include more and other types of	3390	this macro to a something else you can include more and other types of
2987	members. You have to define it each time you include one of the files,	3391	members. You have to define it each time you include one of the files,
2988	though, and it must be identical each time.	3392	though, and it must be identical each time.
2989		3393
2990	For example, the perl EV module uses something like this:	3394	For example, the perl EV module uses something like this:
2991		3395
2992	#define EV_COMMON \	3396	#define EV_COMMON \
2993	SV *self; /* contains this struct */ \	3397	SV *self; /* contains this struct */ \
2994	SV *cb_sv, *fh /* note no trailing ";" */	3398	SV *cb_sv, *fh /* note no trailing ";" */
2995		3399
2996	=item EV_CB_DECLARE (type)	3400	=item EV_CB_DECLARE (type)
2997		3401
2998	=item EV_CB_INVOKE (watcher, revents)	3402	=item EV_CB_INVOKE (watcher, revents)
2999		3403
…		…
3004	definition and a statement, respectively. See the F<ev.h> header file for	3408	definition and a statement, respectively. See the F<ev.h> header file for
3005	their default definitions. One possible use for overriding these is to	3409	their default definitions. One possible use for overriding these is to
3006	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3410	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3007	method calls instead of plain function calls in C++.	3411	method calls instead of plain function calls in C++.
3008		3412
		3413	=back
		3414
3009	=head2 EXPORTED API SYMBOLS	3415	=head2 EXPORTED API SYMBOLS
3010		3416
3011	If you need to re-export the API (e.g. via a dll) and you need a list of	3417	If you need to re-export the API (e.g. via a DLL) and you need a list of
3012	exported symbols, you can use the provided F<Symbol.*> files which list	3418	exported symbols, you can use the provided F<Symbol.*> files which list
3013	all public symbols, one per line:	3419	all public symbols, one per line:
3014		3420
3015	Symbols.ev for libev proper	3421	Symbols.ev for libev proper
3016	Symbols.event for the libevent emulation	3422	Symbols.event for the libevent emulation
3017		3423
3018	This can also be used to rename all public symbols to avoid clashes with	3424	This can also be used to rename all public symbols to avoid clashes with
3019	multiple versions of libev linked together (which is obviously bad in	3425	multiple versions of libev linked together (which is obviously bad in
3020	itself, but sometimes it is inconvinient to avoid this).	3426	itself, but sometimes it is inconvenient to avoid this).
3021		3427
3022	A sed command like this will create wrapper C<#define>'s that you need to	3428	A sed command like this will create wrapper C<#define>'s that you need to
3023	include before including F<ev.h>:	3429	include before including F<ev.h>:
3024		3430
3025	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3431	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3042	file.	3448	file.
3043		3449
3044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3450	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3045	that everybody includes and which overrides some configure choices:	3451	that everybody includes and which overrides some configure choices:
3046		3452
3047	#define EV_MINIMAL 1	3453	#define EV_MINIMAL 1
3048	#define EV_USE_POLL 0	3454	#define EV_USE_POLL 0
3049	#define EV_MULTIPLICITY 0	3455	#define EV_MULTIPLICITY 0
3050	#define EV_PERIODIC_ENABLE 0	3456	#define EV_PERIODIC_ENABLE 0
3051	#define EV_STAT_ENABLE 0	3457	#define EV_STAT_ENABLE 0
3052	#define EV_FORK_ENABLE 0	3458	#define EV_FORK_ENABLE 0
3053	#define EV_CONFIG_H <config.h>	3459	#define EV_CONFIG_H <config.h>
3054	#define EV_MINPRI 0	3460	#define EV_MINPRI 0
3055	#define EV_MAXPRI 0	3461	#define EV_MAXPRI 0
3056		3462
3057	#include "ev++.h"	3463	#include "ev++.h"
3058		3464
3059	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3465	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3060		3466
3061	#include "ev_cpp.h"	3467	#include "ev_cpp.h"
3062	#include "ev.c"	3468	#include "ev.c"
3063		3469
		3470	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3064		3471
3065	=head1 THREADS AND COROUTINES	3472	=head2 THREADS AND COROUTINES
3066		3473
3067	=head2 THREADS	3474	=head3 THREADS
3068		3475
3069	Libev itself is completely threadsafe, but it uses no locking. This	3476	All libev functions are reentrant and thread-safe unless explicitly
		3477	documented otherwise, but libev implements no locking itself. This means
3070	means that you can use as many loops as you want in parallel, as long as	3478	that you can use as many loops as you want in parallel, as long as there
3071	only one thread ever calls into one libev function with the same loop	3479	are no concurrent calls into any libev function with the same loop
3072	parameter.	3480	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3481	of course): libev guarantees that different event loops share no data
		3482	structures that need any locking.
3073		3483
3074	Or put differently: calls with different loop parameters can be done in	3484	Or to put it differently: calls with different loop parameters can be done
3075	parallel from multiple threads, calls with the same loop parameter must be	3485	concurrently from multiple threads, calls with the same loop parameter
3076	done serially (but can be done from different threads, as long as only one	3486	must be done serially (but can be done from different threads, as long as
3077	thread ever is inside a call at any point in time, e.g. by using a mutex	3487	only one thread ever is inside a call at any point in time, e.g. by using
3078	per loop).	3488	a mutex per loop).
3079		3489
3080	If you want to know which design is best for your problem, then I cannot	3490	Specifically to support threads (and signal handlers), libev implements
		3491	so-called C<ev_async> watchers, which allow some limited form of
		3492	concurrency on the same event loop, namely waking it up "from the
		3493	outside".
		3494
		3495	If you want to know which design (one loop, locking, or multiple loops
		3496	without or something else still) is best for your problem, then I cannot
3081	help you but by giving some generic advice:	3497	help you, but here is some generic advice:
3082		3498
3083	=over 4	3499	=over 4
3084		3500
3085	=item * most applications have a main thread: use the default libev loop	3501	=item * most applications have a main thread: use the default libev loop
3086	in that thread, or create a seperate thread running only the default loop.	3502	in that thread, or create a separate thread running only the default loop.
3087		3503
3088	This helps integrating other libraries or software modules that use libev	3504	This helps integrating other libraries or software modules that use libev
3089	themselves and don't care/know about threading.	3505	themselves and don't care/know about threading.
3090		3506
3091	=item * one loop per thread is usually a good model.	3507	=item * one loop per thread is usually a good model.
3092		3508
3093	Doing this is almost never wrong, sometimes a better-performance model	3509	Doing this is almost never wrong, sometimes a better-performance model
3094	exists, but it is always a good start.	3510	exists, but it is always a good start.
3095		3511
3096	=item * other models exist, such as the leader/follower pattern, where one	3512	=item * other models exist, such as the leader/follower pattern, where one
3097	loop is handed through multiple threads in a kind of round-robbin fashion.	3513	loop is handed through multiple threads in a kind of round-robin fashion.
3098		3514
3099	Chosing a model is hard - look around, learn, know that usually you cna do	3515	Choosing a model is hard - look around, learn, know that usually you can do
3100	better than you currently do :-)	3516	better than you currently do :-)
3101		3517
3102	=item * often you need to talk to some other thread which blocks in the	3518	=item * often you need to talk to some other thread which blocks in the
		3519	event loop.
		3520
3103	event loop - C<ev_async> watchers can be used to wake them up from other	3521	C<ev_async> watchers can be used to wake them up from other threads safely
3104	threads safely (or from signal contexts...).	3522	(or from signal contexts...).
		3523
		3524	An example use would be to communicate signals or other events that only
		3525	work in the default loop by registering the signal watcher with the
		3526	default loop and triggering an C<ev_async> watcher from the default loop
		3527	watcher callback into the event loop interested in the signal.
3105		3528
3106	=back	3529	=back
3107		3530
3108	=head2 COROUTINES	3531	=head3 COROUTINES
3109		3532
3110	Libev is much more accomodating to coroutines ("cooperative threads"):	3533	Libev is very accommodating to coroutines ("cooperative threads"):
3111	libev fully supports nesting calls to it's functions from different	3534	libev fully supports nesting calls to its functions from different
3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3535	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3113	different coroutines and switch freely between both coroutines running the	3536	different coroutines, and switch freely between both coroutines running the
3114	loop, as long as you don't confuse yourself). The only exception is that	3537	loop, as long as you don't confuse yourself). The only exception is that
3115	you must not do this from C<ev_periodic> reschedule callbacks.	3538	you must not do this from C<ev_periodic> reschedule callbacks.
3116		3539
3117	Care has been invested into making sure that libev does not keep local	3540	Care has been taken to ensure that libev does not keep local state inside
3118	state inside C<ev_loop>, and other calls do not usually allow coroutine	3541	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3119	switches.	3542	they do not clal any callbacks.
3120		3543
		3544	=head2 COMPILER WARNINGS
3121		3545
3122	=head1 COMPLEXITIES	3546	Depending on your compiler and compiler settings, you might get no or a
		3547	lot of warnings when compiling libev code. Some people are apparently
		3548	scared by this.
3123		3549
3124	In this section the complexities of (many of) the algorithms used inside	3550	However, these are unavoidable for many reasons. For one, each compiler
3125	libev will be explained. For complexity discussions about backends see the	3551	has different warnings, and each user has different tastes regarding
3126	documentation for C<ev_default_init>.	3552	warning options. "Warn-free" code therefore cannot be a goal except when
		3553	targeting a specific compiler and compiler-version.
3127		3554
3128	All of the following are about amortised time: If an array needs to be	3555	Another reason is that some compiler warnings require elaborate
3129	extended, libev needs to realloc and move the whole array, but this	3556	workarounds, or other changes to the code that make it less clear and less
3130	happens asymptotically never with higher number of elements, so O(1) might	3557	maintainable.
3131	mean it might do a lengthy realloc operation in rare cases, but on average
3132	it is much faster and asymptotically approaches constant time.
3133		3558
3134	=over 4	3559	And of course, some compiler warnings are just plain stupid, or simply
		3560	wrong (because they don't actually warn about the condition their message
		3561	seems to warn about). For example, certain older gcc versions had some
		3562	warnings that resulted an extreme number of false positives. These have
		3563	been fixed, but some people still insist on making code warn-free with
		3564	such buggy versions.
3135		3565
3136	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3566	While libev is written to generate as few warnings as possible,
		3567	"warn-free" code is not a goal, and it is recommended not to build libev
		3568	with any compiler warnings enabled unless you are prepared to cope with
		3569	them (e.g. by ignoring them). Remember that warnings are just that:
		3570	warnings, not errors, or proof of bugs.
3137		3571
3138	This means that, when you have a watcher that triggers in one hour and
3139	there are 100 watchers that would trigger before that then inserting will
3140	have to skip roughly seven (C<ld 100>) of these watchers.
3141		3572
3142	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3573	=head2 VALGRIND
3143		3574
3144	That means that changing a timer costs less than removing/adding them	3575	Valgrind has a special section here because it is a popular tool that is
3145	as only the relative motion in the event queue has to be paid for.	3576	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3146		3577
3147	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3578	If you think you found a bug (memory leak, uninitialised data access etc.)
		3579	in libev, then check twice: If valgrind reports something like:
3148		3580
3149	These just add the watcher into an array or at the head of a list.	3581	==2274== definitely lost: 0 bytes in 0 blocks.
		3582	==2274== possibly lost: 0 bytes in 0 blocks.
		3583	==2274== still reachable: 256 bytes in 1 blocks.
3150		3584
3151	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3585	Then there is no memory leak, just as memory accounted to global variables
		3586	is not a memleak - the memory is still being refernced, and didn't leak.
3152		3587
3153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3588	Similarly, under some circumstances, valgrind might report kernel bugs
		3589	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3590	although an acceptable workaround has been found here), or it might be
		3591	confused.
3154		3592
3155	These watchers are stored in lists then need to be walked to find the	3593	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3156	correct watcher to remove. The lists are usually short (you don't usually	3594	make it into some kind of religion.
3157	have many watchers waiting for the same fd or signal).
3158		3595
3159	=item Finding the next timer in each loop iteration: O(1)	3596	If you are unsure about something, feel free to contact the mailing list
		3597	with the full valgrind report and an explanation on why you think this
		3598	is a bug in libev (best check the archives, too :). However, don't be
		3599	annoyed when you get a brisk "this is no bug" answer and take the chance
		3600	of learning how to interpret valgrind properly.
3160		3601
3161	By virtue of using a binary heap, the next timer is always found at the	3602	If you need, for some reason, empty reports from valgrind for your project
3162	beginning of the storage array.	3603	I suggest using suppression lists.
3163		3604
3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3165		3605
3166	A change means an I/O watcher gets started or stopped, which requires	3606	=head1 PORTABILITY NOTES
3167	libev to recalculate its status (and possibly tell the kernel, depending
3168	on backend and wether C<ev_io_set> was used).
3169		3607
3170	=item Activating one watcher (putting it into the pending state): O(1)	3608	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3171
3172	=item Priority handling: O(number_of_priorities)
3173
3174	Priorities are implemented by allocating some space for each
3175	priority. When doing priority-based operations, libev usually has to
3176	linearly search all the priorities, but starting/stopping and activating
3177	watchers becomes O(1) w.r.t. priority handling.
3178
3179	=item Sending an ev_async: O(1)
3180
3181	=item Processing ev_async_send: O(number_of_async_watchers)
3182
3183	=item Processing signals: O(max_signal_number)
3184
3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3186	calls in the current loop iteration. Checking for async and signal events
3187	involves iterating over all running async watchers or all signal numbers.
3188
3189	=back
3190
3191
3192	=head1 Win32 platform limitations and workarounds
3193		3609
3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3195	requires, and its I/O model is fundamentally incompatible with the POSIX	3611	requires, and its I/O model is fundamentally incompatible with the POSIX
3196	model. Libev still offers limited functionality on this platform in	3612	model. Libev still offers limited functionality on this platform in
3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3198	descriptors. This only applies when using Win32 natively, not when using	3614	descriptors. This only applies when using Win32 natively, not when using
3199	e.g. cygwin.	3615	e.g. cygwin.
3200		3616
		3617	Lifting these limitations would basically require the full
		3618	re-implementation of the I/O system. If you are into these kinds of
		3619	things, then note that glib does exactly that for you in a very portable
		3620	way (note also that glib is the slowest event library known to man).
		3621
3201	There is no supported compilation method available on windows except	3622	There is no supported compilation method available on windows except
3202	embedding it into other applications.	3623	embedding it into other applications.
3203		3624
		3625	Not a libev limitation but worth mentioning: windows apparently doesn't
		3626	accept large writes: instead of resulting in a partial write, windows will
		3627	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3628	so make sure you only write small amounts into your sockets (less than a
		3629	megabyte seems safe, but this apparently depends on the amount of memory
		3630	available).
		3631
3204	Due to the many, low, and arbitrary limits on the win32 platform and the	3632	Due to the many, low, and arbitrary limits on the win32 platform and
3205	abysmal performance of winsockets, using a large number of sockets is not	3633	the abysmal performance of winsockets, using a large number of sockets
3206	recommended (and not reasonable). If your program needs to use more than	3634	is not recommended (and not reasonable). If your program needs to use
3207	a hundred or so sockets, then likely it needs to use a totally different	3635	more than a hundred or so sockets, then likely it needs to use a totally
3208	implementation for windows, as libev offers the POSIX model, which cannot	3636	different implementation for windows, as libev offers the POSIX readiness
3209	be implemented efficiently on windows (microsoft monopoly games).	3637	notification model, which cannot be implemented efficiently on windows
		3638	(Microsoft monopoly games).
		3639
		3640	A typical way to use libev under windows is to embed it (see the embedding
		3641	section for details) and use the following F<evwrap.h> header file instead
		3642	of F<ev.h>:
		3643
		3644	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3645	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3646
		3647	#include "ev.h"
		3648
		3649	And compile the following F<evwrap.c> file into your project (make sure
		3650	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3651
		3652	#include "evwrap.h"
		3653	#include "ev.c"
3210		3654
3211	=over 4	3655	=over 4
3212		3656
3213	=item The winsocket select function	3657	=item The winsocket select function
3214		3658
3215	The winsocket C<select> function doesn't follow POSIX in that it requires	3659	The winsocket C<select> function doesn't follow POSIX in that it
3216	socket I<handles> and not socket I<file descriptors>. This makes select	3660	requires socket I<handles> and not socket I<file descriptors> (it is
3217	very inefficient, and also requires a mapping from file descriptors	3661	also extremely buggy). This makes select very inefficient, and also
3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3662	requires a mapping from file descriptors to socket handles (the Microsoft
3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3663	C runtime provides the function C<_open_osfhandle> for this). See the
3220	symbols for more info.	3664	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3665	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3221		3666
3222	The configuration for a "naked" win32 using the microsoft runtime	3667	The configuration for a "naked" win32 using the Microsoft runtime
3223	libraries and raw winsocket select is:	3668	libraries and raw winsocket select is:
3224		3669
3225	#define EV_USE_SELECT 1	3670	#define EV_USE_SELECT 1
3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3671	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3227		3672
3228	Note that winsockets handling of fd sets is O(n), so you can easily get a	3673	Note that winsockets handling of fd sets is O(n), so you can easily get a
3229	complexity in the O(n²) range when using win32.	3674	complexity in the O(n²) range when using win32.
3230		3675
3231	=item Limited number of file descriptors	3676	=item Limited number of file descriptors
3232		3677
3233	Windows has numerous arbitrary (and low) limits on things. Early versions	3678	Windows has numerous arbitrary (and low) limits on things.
3234	of winsocket's select only supported waiting for a max. of C<64> handles	3679
		3680	Early versions of winsocket's select only supported waiting for a maximum
3235	(probably owning to the fact that all windows kernels can only wait for	3681	of C<64> handles (probably owning to the fact that all windows kernels
3236	C<64> things at the same time internally; microsoft recommends spawning a	3682	can only wait for C<64> things at the same time internally; Microsoft
3237	chain of threads and wait for 63 handles and the previous thread in each).	3683	recommends spawning a chain of threads and wait for 63 handles and the
		3684	previous thread in each. Great).
3238		3685
3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3686	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3240	to some high number (e.g. C<2048>) before compiling the winsocket select	3687	to some high number (e.g. C<2048>) before compiling the winsocket select
3241	call (which might be in libev or elsewhere, for example, perl does its own	3688	call (which might be in libev or elsewhere, for example, perl does its own
3242	select emulation on windows).	3689	select emulation on windows).
3243		3690
3244	Another limit is the number of file descriptors in the microsoft runtime	3691	Another limit is the number of file descriptors in the Microsoft runtime
3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3692	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3246	or something like this inside microsoft). You can increase this by calling	3693	or something like this inside Microsoft). You can increase this by calling
3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3694	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3248	arbitrary limit), but is broken in many versions of the microsoft runtime	3695	arbitrary limit), but is broken in many versions of the Microsoft runtime
3249	libraries.	3696	libraries.
3250		3697
3251	This might get you to about C<512> or C<2048> sockets (depending on	3698	This might get you to about C<512> or C<2048> sockets (depending on
3252	windows version and/or the phase of the moon). To get more, you need to	3699	windows version and/or the phase of the moon). To get more, you need to
3253	wrap all I/O functions and provide your own fd management, but the cost of	3700	wrap all I/O functions and provide your own fd management, but the cost of
3254	calling select (O(n²)) will likely make this unworkable.	3701	calling select (O(n²)) will likely make this unworkable.
3255		3702
3256	=back	3703	=back
3257		3704
		3705	=head2 PORTABILITY REQUIREMENTS
		3706
		3707	In addition to a working ISO-C implementation and of course the
		3708	backend-specific APIs, libev relies on a few additional extensions:
		3709
		3710	=over 4
		3711
		3712	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3713	calling conventions regardless of C<ev_watcher_type *>.
		3714
		3715	Libev assumes not only that all watcher pointers have the same internal
		3716	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3717	assumes that the same (machine) code can be used to call any watcher
		3718	callback: The watcher callbacks have different type signatures, but libev
		3719	calls them using an C<ev_watcher *> internally.
		3720
		3721	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3722
		3723	The type C<sig_atomic_t volatile> (or whatever is defined as
		3724	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3725	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3726	believed to be sufficiently portable.
		3727
		3728	=item C<sigprocmask> must work in a threaded environment
		3729
		3730	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3731	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3732	pthread implementations will either allow C<sigprocmask> in the "main
		3733	thread" or will block signals process-wide, both behaviours would
		3734	be compatible with libev. Interaction between C<sigprocmask> and
		3735	C<pthread_sigmask> could complicate things, however.
		3736
		3737	The most portable way to handle signals is to block signals in all threads
		3738	except the initial one, and run the default loop in the initial thread as
		3739	well.
		3740
		3741	=item C<long> must be large enough for common memory allocation sizes
		3742
		3743	To improve portability and simplify its API, libev uses C<long> internally
		3744	instead of C<size_t> when allocating its data structures. On non-POSIX
		3745	systems (Microsoft...) this might be unexpectedly low, but is still at
		3746	least 31 bits everywhere, which is enough for hundreds of millions of
		3747	watchers.
		3748
		3749	=item C<double> must hold a time value in seconds with enough accuracy
		3750
		3751	The type C<double> is used to represent timestamps. It is required to
		3752	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3753	enough for at least into the year 4000. This requirement is fulfilled by
		3754	implementations implementing IEEE 754 (basically all existing ones).
		3755
		3756	=back
		3757
		3758	If you know of other additional requirements drop me a note.
		3759
		3760
		3761	=head1 ALGORITHMIC COMPLEXITIES
		3762
		3763	In this section the complexities of (many of) the algorithms used inside
		3764	libev will be documented. For complexity discussions about backends see
		3765	the documentation for C<ev_default_init>.
		3766
		3767	All of the following are about amortised time: If an array needs to be
		3768	extended, libev needs to realloc and move the whole array, but this
		3769	happens asymptotically rarer with higher number of elements, so O(1) might
		3770	mean that libev does a lengthy realloc operation in rare cases, but on
		3771	average it is much faster and asymptotically approaches constant time.
		3772
		3773	=over 4
		3774
		3775	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3776
		3777	This means that, when you have a watcher that triggers in one hour and
		3778	there are 100 watchers that would trigger before that, then inserting will
		3779	have to skip roughly seven (C<ld 100>) of these watchers.
		3780
		3781	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3782
		3783	That means that changing a timer costs less than removing/adding them,
		3784	as only the relative motion in the event queue has to be paid for.
		3785
		3786	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3787
		3788	These just add the watcher into an array or at the head of a list.
		3789
		3790	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3791
		3792	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3793
		3794	These watchers are stored in lists, so they need to be walked to find the
		3795	correct watcher to remove. The lists are usually short (you don't usually
		3796	have many watchers waiting for the same fd or signal: one is typical, two
		3797	is rare).
		3798
		3799	=item Finding the next timer in each loop iteration: O(1)
		3800
		3801	By virtue of using a binary or 4-heap, the next timer is always found at a
		3802	fixed position in the storage array.
		3803
		3804	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3805
		3806	A change means an I/O watcher gets started or stopped, which requires
		3807	libev to recalculate its status (and possibly tell the kernel, depending
		3808	on backend and whether C<ev_io_set> was used).
		3809
		3810	=item Activating one watcher (putting it into the pending state): O(1)
		3811
		3812	=item Priority handling: O(number_of_priorities)
		3813
		3814	Priorities are implemented by allocating some space for each
		3815	priority. When doing priority-based operations, libev usually has to
		3816	linearly search all the priorities, but starting/stopping and activating
		3817	watchers becomes O(1) with respect to priority handling.
		3818
		3819	=item Sending an ev_async: O(1)
		3820
		3821	=item Processing ev_async_send: O(number_of_async_watchers)
		3822
		3823	=item Processing signals: O(max_signal_number)
		3824
		3825	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3826	calls in the current loop iteration. Checking for async and signal events
		3827	involves iterating over all running async watchers or all signal numbers.
		3828
		3829	=back
		3830
3258		3831
3259	=head1 AUTHOR	3832	=head1 AUTHOR
3260		3833
3261	Marc Lehmann <libev@schmorp.de>.	3834	Marc Lehmann <libev@schmorp.de>.
3262		3835

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