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Revision 1.158 by root, Wed May 21 12:51:38 2008 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 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
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	250	}
230		251
231	...	252	...
232	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
233		254
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		256
236	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	263	(such as abort).
243		264
244	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
255		276
256	=back	277	=back
257		278
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		280
260	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
263		288
264	=over 4	289	=over 4
265		290
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		292
…		…
277	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	303	as loops cannot bes hared easily between threads anyway).
279		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	362	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	390	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and requiring a syscall per fd change, no fork support and bad	391	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	392	support for dup.
361		393
		394	Epoll is also notoriously buggy - embedding epoll fds should work, but
		395	of course doesn't, and epoll just loves to report events for totally
		396	I<different> file descriptors (even already closed ones) than registered
		397	in the set (especially on SMP systems). Libev tries to counter these
		398	spurious notifications by employing an additional generation counter and
		399	comparing that against the events to filter out spurious ones.
		400
362	While stopping, setting and starting an I/O watcher in the same iteration	401	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	402	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	403	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	405	very well if you register events for both fds.
367		406
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371
372	Best performance from this backend is achieved by not unregistering all	407	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	408	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	409	i.e. keep at least one watcher active per fd at all times. Stopping and
		410	starting a watcher (without re-setting it) also usually doesn't cause
		411	extra overhead.
375		412
376	While nominally embeddeble in other event loops, this feature is broken in	413	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	414	all kernel versions tested so far.
378		415
		416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		417	C<EVBACKEND_POLL>.
		418
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		420
381	Kqueue deserves special mention, as at the time of this writing, it	421	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	422	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	423	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	424	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	425	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		427
389	You still can embed kqueue into a normal poll or select backend and use it	428	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	429	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	430	the target platform). See C<ev_embed> watchers for more info.
392		431
393	It scales in the same way as the epoll backend, but the interface to the	432	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	433	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	434	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	435	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	436	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	437	drops fds silently in similarly hard-to-detect cases.
399		438
400	This backend usually performs well under most conditions.	439	This backend usually performs well under most conditions.
401		440
402	While nominally embeddable in other event loops, this doesn't work	441	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	442	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	443	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	444	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	446	using it only for sockets.
		447
		448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		450	C<NOTE_EOF>.
408		451
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	452	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		453
411	This is not implemented yet (and might never be, unless you send me an	454	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	455	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	459	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		460
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	461	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	462	it's really slow, but it still scales very well (O(active_fds)).
420		463
421	Please note that solaris event ports can deliver a lot of spurious	464	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	465	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	466	blocking when no data (or space) is available.
424		467
425	While this backend scales well, it requires one system call per active	468	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	469	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	470	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	471	might perform better.
429		472
430	On the positive side, ignoring the spurious readiness notifications, this	473	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	474	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	475	in all tests and is fully embeddable, which is a rare feat among the
		476	OS-specific backends.
		477
		478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		479	C<EVBACKEND_POLL>.
433		480
434	=item C<EVBACKEND_ALL>	481	=item C<EVBACKEND_ALL>
435		482
436	Try all backends (even potentially broken ones that wouldn't be tried	483	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		486
440	It is definitely not recommended to use this flag.	487	It is definitely not recommended to use this flag.
441		488
442	=back	489	=back
443		490
444	If one or more of these are ored into the flags value, then only these	491	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	492	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	493	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		494
448	The most typical usage is like this:	495	Example: This is the most typical usage.
449		496
450	if (!ev_default_loop (0))	497	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		499
453	Restrict libev to the select and poll backends, and do not allow	500	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	501	environment settings to be taken into account:
455		502
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		504
458	Use whatever libev has to offer, but make sure that kqueue is used if	505	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	506	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	507	private event loop and only if you know the OS supports your types of
		508	fds):
461		509
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		511
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	512	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		513
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	514	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	515	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	520	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	521	default loop in the "main" or "initial" thread.
474		522
475	Example: Try to create a event loop that uses epoll and nothing else.	523	Example: Try to create a event loop that uses epoll and nothing else.
476		524
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	525	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	526	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	527	fatal ("no epoll found here, maybe it hides under your chair");
480		528
481	=item ev_default_destroy ()	529	=item ev_default_destroy ()
482		530
483	Destroys the default loop again (frees all memory and kernel state	531	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	532	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	533	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	534	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	535	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	536	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	537	for example).
490		538
491	Note that certain global state, such as signal state, will not be freed by	539	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	540	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	541	as signal and child watchers) would need to be stopped manually.
494		542
495	In general it is not advisable to call this function except in the	543	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	544	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	545	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	546	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		571
524	=item ev_loop_fork (loop)	572	=item ev_loop_fork (loop)
525		573
526	Like C<ev_default_fork>, but acts on an event loop created by	574	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	575	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	576	after fork that you want to re-use in the child, and how you do this is
		577	entirely your own problem.
529		578
530	=item int ev_is_default_loop (loop)	579	=item int ev_is_default_loop (loop)
531		580
532	Returns true when the given loop actually is the default loop, false otherwise.	581	Returns true when the given loop is, in fact, the default loop, and false
		582	otherwise.
533		583
534	=item unsigned int ev_loop_count (loop)	584	=item unsigned int ev_loop_count (loop)
535		585
536	Returns the count of loop iterations for the loop, which is identical to	586	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	587	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	602	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	603	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	604	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	605	event occurring (or more correctly, libev finding out about it).
556		606
		607	=item ev_now_update (loop)
		608
		609	Establishes the current time by querying the kernel, updating the time
		610	returned by C<ev_now ()> in the progress. This is a costly operation and
		611	is usually done automatically within C<ev_loop ()>.
		612
		613	This function is rarely useful, but when some event callback runs for a
		614	very long time without entering the event loop, updating libev's idea of
		615	the current time is a good idea.
		616
		617	See also "The special problem of time updates" in the C<ev_timer> section.
		618
557	=item ev_loop (loop, int flags)	619	=item ev_loop (loop, int flags)
558		620
559	Finally, this is it, the event handler. This function usually is called	621	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	622	after you initialised all your watchers and you want to start handling
561	events.	623	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	625	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	626	either no event watchers are active anymore or C<ev_unloop> was called.
565		627
566	Please note that an explicit C<ev_unloop> is usually better than	628	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	629	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	630	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	631	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	632	of relying on its watchers stopping correctly, that is truly a thing of
		633	beauty.
571		634
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	635	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	636	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	637	process in case there are no events and will return after one iteration of
		638	the loop.
575		639
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	640	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	641	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	642	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	643	be an event internal to libev itself, so there is no guarentee that a
580	external event in conjunction with something not expressible using other	644	user-registered callback will be called), and will return after one
		645	iteration of the loop.
		646
		647	This is useful if you are waiting for some external event in conjunction
		648	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	649	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	650	usually a better approach for this kind of thing.
583		651
584	Here are the gory details of what C<ev_loop> does:	652	Here are the gory details of what C<ev_loop> does:
585		653
586	- Before the first iteration, call any pending watchers.	654	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	655	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	656	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	657	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	658	- If we have been forked, detach and recreate the kernel state
		659	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	660	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	661	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	662	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	663	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	664	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	665	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	666	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	667	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	669	- Queue all expired timers.
601	- Queue all outstanding periodics.	670	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	671	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	672	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	673	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	674	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	675	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	681	anymore.
613		682
614	... queue jobs here, make sure they register event watchers as long	683	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	684	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	685	ev_loop (my_loop, 0);
617	... jobs done. yeah!	686	... jobs done or somebody called unloop. yeah!
618		687
619	=item ev_unloop (loop, how)	688	=item ev_unloop (loop, how)
620		689
621	Can be used to make a call to C<ev_loop> return early (but only after it	690	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	691	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	692	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		694
626	This "unloop state" will be cleared when entering C<ev_loop> again.	695	This "unloop state" will be cleared when entering C<ev_loop> again.
627		696
		697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		698
628	=item ev_ref (loop)	699	=item ev_ref (loop)
629		700
630	=item ev_unref (loop)	701	=item ev_unref (loop)
631		702
632	Ref/unref can be used to add or remove a reference count on the event	703	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	704	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	705	count is nonzero, C<ev_loop> will not return on its own.
		706
635	a watcher you never unregister that should not keep C<ev_loop> from	707	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	708	from returning, call ev_unref() after starting, and ev_ref() before
		709	stopping it.
		710
637	example, libev itself uses this for its internal signal pipe: It is not	711	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	712	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	713	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	714	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	715	libraries. Just remember to I<unref after start> and I<ref before stop>
642	(but only if the watcher wasn't active before, or was active before,	716	(but only if the watcher wasn't active before, or was active before,
643	respectively).	717	respectively).
644		718
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	720	running when nothing else is active.
647		721
648	struct ev_signal exitsig;	722	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	723	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	724	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	725	evf_unref (loop);
652		726
653	Example: For some weird reason, unregister the above signal handler again.	727	Example: For some weird reason, unregister the above signal handler again.
654		728
655	ev_ref (loop);	729	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	730	ev_signal_stop (loop, &exitsig);
657		731
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	732	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		733
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	734	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		735
662	These advanced functions influence the time that libev will spend waiting	736	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	737	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	738	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		739	latency.
665		740
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	741	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	742	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	743	to increase efficiency of loop iterations (or to increase power-saving
		744	opportunities).
669		745
670	The background is that sometimes your program runs just fast enough to	746	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	747	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	748	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	749	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	750	overhead for the actual polling but can deliver many events at once.
675		751
676	By setting a higher I<io collect interval> you allow libev to spend more	752	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	753	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	755	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	756	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		757
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	758	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	759	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	760	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	761	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	762	value will not introduce any overhead in libev.
687		763
688	Many (busy) programs can usually benefit by setting the io collect	764	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	765	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	766	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	767	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	768	as this approaches the timing granularity of most systems.
		769
		770	Setting the I<timeout collect interval> can improve the opportunity for
		771	saving power, as the program will "bundle" timer callback invocations that
		772	are "near" in time together, by delaying some, thus reducing the number of
		773	times the process sleeps and wakes up again. Another useful technique to
		774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		775	they fire on, say, one-second boundaries only.
		776
		777	=item ev_loop_verify (loop)
		778
		779	This function only does something when C<EV_VERIFY> support has been
		780	compiled in, which is the default for non-minimal builds. It tries to go
		781	through all internal structures and checks them for validity. If anything
		782	is found to be inconsistent, it will print an error message to standard
		783	error and call C<abort ()>.
		784
		785	This can be used to catch bugs inside libev itself: under normal
		786	circumstances, this function will never abort as of course libev keeps its
		787	data structures consistent.
693		788
694	=back	789	=back
695		790
696		791
697	=head1 ANATOMY OF A WATCHER	792	=head1 ANATOMY OF A WATCHER
		793
		794	In the following description, uppercase C<TYPE> in names stands for the
		795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		796	watchers and C<ev_io_start> for I/O watchers.
698		797
699	A watcher is a structure that you create and register to record your	798	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	799	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	800	become readable, you would create an C<ev_io> watcher for that:
702		801
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	803	{
705	ev_io_stop (w);	804	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	805	ev_unloop (loop, EVUNLOOP_ALL);
707	}	806	}
708		807
709	struct ev_loop *loop = ev_default_loop (0);	808	struct ev_loop *loop = ev_default_loop (0);
		809
710	struct ev_io stdin_watcher;	810	ev_io stdin_watcher;
		811
711	ev_init (&stdin_watcher, my_cb);	812	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	814	ev_io_start (loop, &stdin_watcher);
		815
714	ev_loop (loop, 0);	816	ev_loop (loop, 0);
715		817
716	As you can see, you are responsible for allocating the memory for your	818	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	819	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	820	stack).
		821
		822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		824
720	Each watcher structure must be initialised by a call to C<ev_init	825	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	826	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	827	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	828	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	829	is readable and/or writable).
725		830
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	832	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	833	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	834	ev_TYPE_init (watcher *, callback, ...) >>.
730		835
731	To make the watcher actually watch out for events, you have to start it	836	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	837	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	838	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	839	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		840
736	As long as your watcher is active (has been started but not stopped) you	841	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	842	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	843	reinitialise it or call its C<ev_TYPE_set> macro.
739		844
740	Each and every callback receives the event loop pointer as first, the	845	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	846	registered watcher structure as second, and a bitset of received events as
742	third argument.	847	third argument.
743		848
…		…
803		908
804	The given async watcher has been asynchronously notified (see C<ev_async>).	909	The given async watcher has been asynchronously notified (see C<ev_async>).
805		910
806	=item C<EV_ERROR>	911	=item C<EV_ERROR>
807		912
808	An unspecified error has occured, the watcher has been stopped. This might	913	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	914	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	915	ran out of memory, a file descriptor was found to be closed or any other
		916	problem. Libev considers these application bugs.
		917
811	problem. You best act on it by reporting the problem and somehow coping	918	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	919	watcher being stopped. Note that well-written programs should not receive
		920	an error ever, so when your watcher receives it, this usually indicates a
		921	bug in your program.
813		922
814	Libev will usually signal a few "dummy" events together with an error,	923	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	924	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	925	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	926	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	927	programs, though, as the fd could already be closed and reused for another
		928	thing, so beware.
819		929
820	=back	930	=back
821		931
822	=head2 GENERIC WATCHER FUNCTIONS	932	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		933
827	=over 4	934	=over 4
828		935
829	=item C<ev_init> (ev_TYPE *watcher, callback)	936	=item C<ev_init> (ev_TYPE *watcher, callback)
830		937
…		…
836	which rolls both calls into one.	943	which rolls both calls into one.
837		944
838	You can reinitialise a watcher at any time as long as it has been stopped	945	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	946	(or never started) and there are no pending events outstanding.
840		947
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	948	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	949	int revents)>.
		950
		951	Example: Initialise an C<ev_io> watcher in two steps.
		952
		953	ev_io w;
		954	ev_init (&w, my_cb);
		955	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		956
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	957	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		958
846	This macro initialises the type-specific parts of a watcher. You need to	959	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	960	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	963	difference to the C<ev_init> macro).
851		964
852	Although some watcher types do not have type-specific arguments	965	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	966	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		967
		968	See C<ev_init>, above, for an example.
		969
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	970	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		971
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	972	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	973	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	974	a watcher. The same limitations apply, of course.
		975
		976	Example: Initialise and set an C<ev_io> watcher in one step.
		977
		978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		979
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		981
863	Starts (activates) the given watcher. Only active watchers will receive	982	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	983	events. If the watcher is already active nothing will happen.
865		984
		985	Example: Start the C<ev_io> watcher that is being abused as example in this
		986	whole section.
		987
		988	ev_io_start (EV_DEFAULT_UC, &w);
		989
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		991
868	Stops the given watcher again (if active) and clears the pending	992	Stops the given watcher if active, and clears the pending status (whether
		993	the watcher was active or not).
		994
869	status. It is possible that stopped watchers are pending (for example,	995	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	996	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	997	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	998	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	999	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1000
875	=item bool ev_is_active (ev_TYPE *watcher)	1001	=item bool ev_is_active (ev_TYPE *watcher)
876		1002
877	Returns a true value iff the watcher is active (i.e. it has been started	1003	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1004	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1046	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1047	always C<0>, which is supposed to not be too high and not be too low :).
922		1048
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1050	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1051	or might not have been clamped to the valid range.
926		1052
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1054
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1055	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1056	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1057	can deal with that fact, as both are simply passed through to the
		1058	callback.
932		1059
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1060	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1061
935	If the watcher is pending, this function returns clears its pending status	1062	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1063	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1064	watcher isn't pending it does nothing and returns C<0>.
938		1065
		1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1067	callback to be invoked, which can be accomplished with this function.
		1068
939	=back	1069	=back
940		1070
941		1071
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1073
944	Each watcher has, by default, a member C<void *data> that you can change	1074	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1075	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1076	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1077	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1078	member, you can also "subclass" the watcher type and provide your own
949	data:	1079	data:
950		1080
951	struct my_io	1081	struct my_io
952	{	1082	{
953	struct ev_io io;	1083	ev_io io;
954	int otherfd;	1084	int otherfd;
955	void *somedata;	1085	void *somedata;
956	struct whatever *mostinteresting;	1086	struct whatever *mostinteresting;
957	}	1087	};
		1088
		1089	...
		1090	struct my_io w;
		1091	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1092
959	And since your callback will be called with a pointer to the watcher, you	1093	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1094	can cast it back to your own type:
961		1095
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1096	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1097	{
964	struct my_io *w = (struct my_io *)w_;	1098	struct my_io *w = (struct my_io *)w_;
965	...	1099	...
966	}	1100	}
967		1101
968	More interesting and less C-conformant ways of casting your callback type	1102	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1103	instead have been omitted.
970		1104
971	Another common scenario is having some data structure with multiple	1105	Another common scenario is to use some data structure with multiple
972	watchers:	1106	embedded watchers:
973		1107
974	struct my_biggy	1108	struct my_biggy
975	{	1109	{
976	int some_data;	1110	int some_data;
977	ev_timer t1;	1111	ev_timer t1;
978	ev_timer t2;	1112	ev_timer t2;
979	}	1113	}
980		1114
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1115	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1116	complicated: Either you store the address of your C<my_biggy> struct
		1117	in the C<data> member of the watcher (for woozies), or you need to use
		1118	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1119	programmers):
983		1120
984	#include <stddef.h>	1121	#include <stddef.h>
985		1122
986	static void	1123	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1124	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1125	{
989	struct my_biggy big = (struct my_biggy *	1126	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1127	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1128	}
992		1129
993	static void	1130	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1131	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1132	{
996	struct my_biggy big = (struct my_biggy *	1133	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1134	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1135	}
999		1136
1000		1137
1001	=head1 WATCHER TYPES	1138	=head1 WATCHER TYPES
1002		1139
1003	This section describes each watcher in detail, but will not repeat	1140	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1164	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1165	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1166	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1167	required if you know what you are doing).
1031		1168
1032	If you must do this, then force the use of a known-to-be-good backend	1169	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1170	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1172
1036	Another thing you have to watch out for is that it is quite easy to	1173	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1174	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1175	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1176	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1177	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1178	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1179	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1180	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1181
1045	If you cannot run the fd in non-blocking mode (for example you should not	1182	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1183	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1184	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1185	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1186	does this on its own, so its quite safe to use). Some people additionally
		1187	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1188	indefinitely.
		1189
		1190	But really, best use non-blocking mode.
1050		1191
1051	=head3 The special problem of disappearing file descriptors	1192	=head3 The special problem of disappearing file descriptors
1052		1193
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1194	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1195	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1196	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1197	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1198	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1199	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1200	fact, a different file descriptor.
1060		1201
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1232	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1233	C<EVBACKEND_POLL>.
1093		1234
1094	=head3 The special problem of SIGPIPE	1235	=head3 The special problem of SIGPIPE
1095		1236
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1237	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1238	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1239	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1240	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1241
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1242	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1243	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1244	somewhere, as that would have given you a big clue).
1105		1245
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1251	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1252
1113	=item ev_io_set (ev_io *, int fd, int events)	1253	=item ev_io_set (ev_io *, int fd, int events)
1114		1254
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1255	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1256	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1257	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1258
1119	=item int fd [read-only]	1259	=item int fd [read-only]
1120		1260
1121	The file descriptor being watched.	1261	The file descriptor being watched.
1122		1262
…		…
1130		1270
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1271	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1272	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1273	attempt to read a whole line in the callback.
1134		1274
1135	static void	1275	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1276	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1277	{
1138	ev_io_stop (loop, w);	1278	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1279	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1280	}
1141		1281
1142	...	1282	...
1143	struct ev_loop *loop = ev_default_init (0);	1283	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1284	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1286	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1287	ev_loop (loop, 0);
1148		1288
1149		1289
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1290	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1291
1152	Timer watchers are simple relative timers that generate an event after a	1292	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1293	given time, and optionally repeating in regular intervals after that.
1154		1294
1155	The timers are based on real time, that is, if you register an event that	1295	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1296	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1297	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1299	monotonic clock option helps a lot here).
		1300
		1301	The callback is guaranteed to be invoked only I<after> its timeout has
		1302	passed, but if multiple timers become ready during the same loop iteration
		1303	then order of execution is undefined.
		1304
		1305	=head3 Be smart about timeouts
		1306
		1307	Many real-world problems involve some kind of timeout, usually for error
		1308	recovery. A typical example is an HTTP request - if the other side hangs,
		1309	you want to raise some error after a while.
		1310
		1311	What follows are some ways to handle this problem, from obvious and
		1312	inefficient to smart and efficient.
		1313
		1314	In the following, a 60 second activity timeout is assumed - a timeout that
		1315	gets reset to 60 seconds each time there is activity (e.g. each time some
		1316	data or other life sign was received).
		1317
		1318	=over 4
		1319
		1320	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1321
		1322	This is the most obvious, but not the most simple way: In the beginning,
		1323	start the watcher:
		1324
		1325	ev_timer_init (timer, callback, 60., 0.);
		1326	ev_timer_start (loop, timer);
		1327
		1328	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1329	and start it again:
		1330
		1331	ev_timer_stop (loop, timer);
		1332	ev_timer_set (timer, 60., 0.);
		1333	ev_timer_start (loop, timer);
		1334
		1335	This is relatively simple to implement, but means that each time there is
		1336	some activity, libev will first have to remove the timer from its internal
		1337	data structure and then add it again. Libev tries to be fast, but it's
		1338	still not a constant-time operation.
		1339
		1340	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1341
		1342	This is the easiest way, and involves using C<ev_timer_again> instead of
		1343	C<ev_timer_start>.
		1344
		1345	To implement this, configure an C<ev_timer> with a C<repeat> value
		1346	of C<60> and then call C<ev_timer_again> at start and each time you
		1347	successfully read or write some data. If you go into an idle state where
		1348	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1349	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1350
		1351	That means you can ignore both the C<ev_timer_start> function and the
		1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1353	member and C<ev_timer_again>.
		1354
		1355	At start:
		1356
		1357	ev_timer_init (timer, callback);
		1358	timer->repeat = 60.;
		1359	ev_timer_again (loop, timer);
		1360
		1361	Each time there is some activity:
		1362
		1363	ev_timer_again (loop, timer);
		1364
		1365	It is even possible to change the time-out on the fly, regardless of
		1366	whether the watcher is active or not:
		1367
		1368	timer->repeat = 30.;
		1369	ev_timer_again (loop, timer);
		1370
		1371	This is slightly more efficient then stopping/starting the timer each time
		1372	you want to modify its timeout value, as libev does not have to completely
		1373	remove and re-insert the timer from/into its internal data structure.
		1374
		1375	It is, however, even simpler than the "obvious" way to do it.
		1376
		1377	=item 3. Let the timer time out, but then re-arm it as required.
		1378
		1379	This method is more tricky, but usually most efficient: Most timeouts are
		1380	relatively long compared to the intervals between other activity - in
		1381	our example, within 60 seconds, there are usually many I/O events with
		1382	associated activity resets.
		1383
		1384	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1385	but remember the time of last activity, and check for a real timeout only
		1386	within the callback:
		1387
		1388	ev_tstamp last_activity; // time of last activity
		1389
		1390	static void
		1391	callback (EV_P_ ev_timer *w, int revents)
		1392	{
		1393	ev_tstamp now = ev_now (EV_A);
		1394	ev_tstamp timeout = last_activity + 60.;
		1395
		1396	// if last_activity + 60. is older than now, we did time out
		1397	if (timeout < now)
		1398	{
		1399	// timeout occured, take action
		1400	}
		1401	else
		1402	{
		1403	// callback was invoked, but there was some activity, re-arm
		1404	// the watcher to fire in last_activity + 60, which is
		1405	// guaranteed to be in the future, so "again" is positive:
		1406	w->again = timeout - now;
		1407	ev_timer_again (EV_A_ w);
		1408	}
		1409	}
		1410
		1411	To summarise the callback: first calculate the real timeout (defined
		1412	as "60 seconds after the last activity"), then check if that time has
		1413	been reached, which means something I<did>, in fact, time out. Otherwise
		1414	the callback was invoked too early (C<timeout> is in the future), so
		1415	re-schedule the timer to fire at that future time, to see if maybe we have
		1416	a timeout then.
		1417
		1418	Note how C<ev_timer_again> is used, taking advantage of the
		1419	C<ev_timer_again> optimisation when the timer is already running.
		1420
		1421	This scheme causes more callback invocations (about one every 60 seconds
		1422	minus half the average time between activity), but virtually no calls to
		1423	libev to change the timeout.
		1424
		1425	To start the timer, simply initialise the watcher and set C<last_activity>
		1426	to the current time (meaning we just have some activity :), then call the
		1427	callback, which will "do the right thing" and start the timer:
		1428
		1429	ev_timer_init (timer, callback);
		1430	last_activity = ev_now (loop);
		1431	callback (loop, timer, EV_TIMEOUT);
		1432
		1433	And when there is some activity, simply store the current time in
		1434	C<last_activity>, no libev calls at all:
		1435
		1436	last_actiivty = ev_now (loop);
		1437
		1438	This technique is slightly more complex, but in most cases where the
		1439	time-out is unlikely to be triggered, much more efficient.
		1440
		1441	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1442	callback :) - just change the timeout and invoke the callback, which will
		1443	fix things for you.
		1444
		1445	=item 4. Wee, just use a double-linked list for your timeouts.
		1446
		1447	If there is not one request, but many thousands (millions...), all
		1448	employing some kind of timeout with the same timeout value, then one can
		1449	do even better:
		1450
		1451	When starting the timeout, calculate the timeout value and put the timeout
		1452	at the I<end> of the list.
		1453
		1454	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1455	the list is expected to fire (for example, using the technique #3).
		1456
		1457	When there is some activity, remove the timer from the list, recalculate
		1458	the timeout, append it to the end of the list again, and make sure to
		1459	update the C<ev_timer> if it was taken from the beginning of the list.
		1460
		1461	This way, one can manage an unlimited number of timeouts in O(1) time for
		1462	starting, stopping and updating the timers, at the expense of a major
		1463	complication, and having to use a constant timeout. The constant timeout
		1464	ensures that the list stays sorted.
		1465
		1466	=back
		1467
		1468	So which method the best?
		1469
		1470	Method #2 is a simple no-brain-required solution that is adequate in most
		1471	situations. Method #3 requires a bit more thinking, but handles many cases
		1472	better, and isn't very complicated either. In most case, choosing either
		1473	one is fine, with #3 being better in typical situations.
		1474
		1475	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1476	rather complicated, but extremely efficient, something that really pays
		1477	off after the first million or so of active timers, i.e. it's usually
		1478	overkill :)
		1479
		1480	=head3 The special problem of time updates
		1481
		1482	Establishing the current time is a costly operation (it usually takes at
		1483	least two system calls): EV therefore updates its idea of the current
		1484	time only before and after C<ev_loop> collects new events, which causes a
		1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1486	lots of events in one iteration.
1160		1487
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1488	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1489	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1490	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1491	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1492	timeout on the current time, use something like this to adjust for this:
1166		1493
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1494	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1495
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1496	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1498	()>.
1172		1499
1173	=head3 Watcher-Specific Functions and Data Members	1500	=head3 Watcher-Specific Functions and Data Members
1174		1501
1175	=over 4	1502	=over 4
1176		1503
…		…
1195	This will act as if the timer timed out and restart it again if it is	1522	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1523	repeating. The exact semantics are:
1197		1524
1198	If the timer is pending, its pending status is cleared.	1525	If the timer is pending, its pending status is cleared.
1199		1526
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1527	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1528
1202	If the timer is repeating, either start it if necessary (with the	1529	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1530	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1531
1205	This sounds a bit complicated, but here is a useful and typical	1532	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1206	example: Imagine you have a tcp connection and you want a so-called idle	1533	usage example.
1207	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the
1212	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1213	automatically restart it if need be.
1214
1215	That means you can ignore the C<after> value and C<ev_timer_start>
1216	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1217
1218	ev_timer_init (timer, callback, 0., 5.);
1219	ev_timer_again (loop, timer);
1220	...
1221	timer->again = 17.;
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 10.;
1225	ev_timer_again (loop, timer);
1226
1227	This is more slightly efficient then stopping/starting the timer each time
1228	you want to modify its timeout value.
1229		1534
1230	=item ev_tstamp repeat [read-write]	1535	=item ev_tstamp repeat [read-write]
1231		1536
1232	The current C<repeat> value. Will be used each time the watcher times out	1537	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1538	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1539	which is also when any modifications are taken into account.
1235		1540
1236	=back	1541	=back
1237		1542
1238	=head3 Examples	1543	=head3 Examples
1239		1544
1240	Example: Create a timer that fires after 60 seconds.	1545	Example: Create a timer that fires after 60 seconds.
1241		1546
1242	static void	1547	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1548	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1244	{	1549	{
1245	.. one minute over, w is actually stopped right here	1550	.. one minute over, w is actually stopped right here
1246	}	1551	}
1247		1552
1248	struct ev_timer mytimer;	1553	ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1554	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1555	ev_timer_start (loop, &mytimer);
1251		1556
1252	Example: Create a timeout timer that times out after 10 seconds of	1557	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1558	inactivity.
1254		1559
1255	static void	1560	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1561	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1257	{	1562	{
1258	.. ten seconds without any activity	1563	.. ten seconds without any activity
1259	}	1564	}
1260		1565
1261	struct ev_timer mytimer;	1566	ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1568	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1569	ev_loop (loop, 0);
1265		1570
1266	// and in some piece of code that gets executed on any "activity":	1571	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1572	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1573	ev_timer_again (&mytimer);
1269		1574
1270		1575
1271	=head2 C<ev_periodic> - to cron or not to cron?	1576	=head2 C<ev_periodic> - to cron or not to cron?
1272		1577
1273	Periodic watchers are also timers of a kind, but they are very versatile	1578	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1579	(and unfortunately a bit complex).
1275		1580
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1582	but on wall clock time (absolute time). You can tell a periodic watcher
1278	to trigger after some specific point in time. For example, if you tell a	1583	to trigger after some specific point in time. For example, if you tell a
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1584	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1585	+ 10.>, that is, an absolute time not a delay) and then reset your system
1281	clock to january of the previous year, then it will take more than year	1586	clock to January of the previous year, then it will take more than year
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger	1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).	1588	roughly 10 seconds later as it uses a relative timeout).
1284		1589
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1590	C<ev_periodic>s can also be used to implement vastly more complex timers,
1286	such as triggering an event on each "midnight, local time", or other	1591	such as triggering an event on each "midnight, local time", or other
1287	complicated, rules.	1592	complicated rules.
1288		1593
1289	As with timers, the callback is guarenteed to be invoked only when the	1594	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1595	time (C<at>) has passed, but if multiple periodic timers become ready
1291	during the same loop iteration then order of execution is undefined.	1596	during the same loop iteration, then order of execution is undefined.
1292		1597
1293	=head3 Watcher-Specific Functions and Data Members	1598	=head3 Watcher-Specific Functions and Data Members
1294		1599
1295	=over 4	1600	=over 4
1296		1601
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1298		1603
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1300		1605
1301	Lots of arguments, lets sort it out... There are basically three modes of	1606	Lots of arguments, lets sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1607	operation, and we will explain them from simplest to most complex:
1303		1608
1304	=over 4	1609	=over 4
1305		1610
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1307		1612
1308	In this configuration the watcher triggers an event after the wallclock	1613	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	1614	time C<at> has passed. It will not repeat and will not adjust when a time
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1615	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1311	run when the system time reaches or surpasses this time.	1616	only run when the system clock reaches or surpasses this time.
1312		1617
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1314		1619
1315	In this mode the watcher will always be scheduled to time out at the next	1620	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	1621	C<at + N * interval> time (for some integer N, which can also be negative)
1317	and then repeat, regardless of any time jumps.	1622	and then repeat, regardless of any time jumps.
1318		1623
1319	This can be used to create timers that do not drift with respect to system	1624	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	1625	system clock, for example, here is a C<ev_periodic> that triggers each
1321	the hour:	1626	hour, on the hour:
1322		1627
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1628	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1629
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1630	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	1631	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	1632	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1633	by 3600.
1329		1634
1330	Another way to think about it (for the mathematically inclined) is that	1635	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	1636	C<ev_periodic> will try to run the callback in this mode at the next possible
…		…
1333		1638
1334	For numerical stability it is preferable that the C<at> value is near	1639	For numerical stability it is preferable that the C<at> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	1640	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1641	this value, and in fact is often specified as zero.
1337		1642
1338	Note also that there is an upper limit to how often a timer can fire (cpu	1643	Note also that there is an upper limit to how often a timer can fire (CPU
1339	speed for example), so if C<interval> is very small then timing stability	1644	speed for example), so if C<interval> is very small then timing stability
1340	will of course detoriate. Libev itself tries to be exact to be about one	1645	will of course deteriorate. Libev itself tries to be exact to be about one
1341	millisecond (if the OS supports it and the machine is fast enough).	1646	millisecond (if the OS supports it and the machine is fast enough).
1342		1647
1343	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1648	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1344		1649
1345	In this mode the values for C<interval> and C<at> are both being	1650	In this mode the values for C<interval> and C<at> are both being
…		…
1352		1657
1353	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1354	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1355	only event loop modification you are allowed to do).	1660	only event loop modification you are allowed to do).
1356		1661
1357	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1662	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1358	*w, ev_tstamp now)>, e.g.:	1663	*w, ev_tstamp now)>, e.g.:
1359		1664
		1665	static ev_tstamp
1360	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1666	my_rescheduler (ev_periodic *w, ev_tstamp now)
1361	{	1667	{
1362	return now + 60.;	1668	return now + 60.;
1363	}	1669	}
1364		1670
1365	It must return the next time to trigger, based on the passed time value	1671	It must return the next time to trigger, based on the passed time value
…		…
1402		1708
1403	The current interval value. Can be modified any time, but changes only	1709	The current interval value. Can be modified any time, but changes only
1404	take effect when the periodic timer fires or C<ev_periodic_again> is being	1710	take effect when the periodic timer fires or C<ev_periodic_again> is being
1405	called.	1711	called.
1406		1712
1407	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1713	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1408		1714
1409	The current reschedule callback, or C<0>, if this functionality is	1715	The current reschedule callback, or C<0>, if this functionality is
1410	switched off. Can be changed any time, but changes only take effect when	1716	switched off. Can be changed any time, but changes only take effect when
1411	the periodic timer fires or C<ev_periodic_again> is being called.	1717	the periodic timer fires or C<ev_periodic_again> is being called.
1412		1718
1413	=back	1719	=back
1414		1720
1415	=head3 Examples	1721	=head3 Examples
1416		1722
1417	Example: Call a callback every hour, or, more precisely, whenever the	1723	Example: Call a callback every hour, or, more precisely, whenever the
1418	system clock is divisible by 3600. The callback invocation times have	1724	system time is divisible by 3600. The callback invocation times have
1419	potentially a lot of jittering, but good long-term stability.	1725	potentially a lot of jitter, but good long-term stability.
1420		1726
1421	static void	1727	static void
1422	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1423	{	1729	{
1424	... its now a full hour (UTC, or TAI or whatever your clock follows)	1730	... its now a full hour (UTC, or TAI or whatever your clock follows)
1425	}	1731	}
1426		1732
1427	struct ev_periodic hourly_tick;	1733	ev_periodic hourly_tick;
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1734	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1429	ev_periodic_start (loop, &hourly_tick);	1735	ev_periodic_start (loop, &hourly_tick);
1430		1736
1431	Example: The same as above, but use a reschedule callback to do it:	1737	Example: The same as above, but use a reschedule callback to do it:
1432		1738
1433	#include <math.h>	1739	#include <math.h>
1434		1740
1435	static ev_tstamp	1741	static ev_tstamp
1436	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1742	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1437	{	1743	{
1438	return fmod (now, 3600.) + 3600.;	1744	return now + (3600. - fmod (now, 3600.));
1439	}	1745	}
1440		1746
1441	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1747	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1442		1748
1443	Example: Call a callback every hour, starting now:	1749	Example: Call a callback every hour, starting now:
1444		1750
1445	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1446	ev_periodic_init (&hourly_tick, clock_cb,	1752	ev_periodic_init (&hourly_tick, clock_cb,
1447	fmod (ev_now (loop), 3600.), 3600., 0);	1753	fmod (ev_now (loop), 3600.), 3600., 0);
1448	ev_periodic_start (loop, &hourly_tick);	1754	ev_periodic_start (loop, &hourly_tick);
1449		1755
1450		1756
1451	=head2 C<ev_signal> - signal me when a signal gets signalled!	1757	=head2 C<ev_signal> - signal me when a signal gets signalled!
1452		1758
1453	Signal watchers will trigger an event when the process receives a specific	1759	Signal watchers will trigger an event when the process receives a specific
1454	signal one or more times. Even though signals are very asynchronous, libev	1760	signal one or more times. Even though signals are very asynchronous, libev
1455	will try it's best to deliver signals synchronously, i.e. as part of the	1761	will try it's best to deliver signals synchronously, i.e. as part of the
1456	normal event processing, like any other event.	1762	normal event processing, like any other event.
1457		1763
		1764	If you want signals asynchronously, just use C<sigaction> as you would
		1765	do without libev and forget about sharing the signal. You can even use
		1766	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1767
1458	You can configure as many watchers as you like per signal. Only when the	1768	You can configure as many watchers as you like per signal. Only when the
1459	first watcher gets started will libev actually register a signal watcher	1769	first watcher gets started will libev actually register a signal handler
1460	with the kernel (thus it coexists with your own signal handlers as long	1770	with the kernel (thus it coexists with your own signal handlers as long as
1461	as you don't register any with libev). Similarly, when the last signal	1771	you don't register any with libev for the same signal). Similarly, when
1462	watcher for a signal is stopped libev will reset the signal handler to	1772	the last signal watcher for a signal is stopped, libev will reset the
1463	SIG_DFL (regardless of what it was set to before).	1773	signal handler to SIG_DFL (regardless of what it was set to before).
1464		1774
1465	If possible and supported, libev will install its handlers with	1775	If possible and supported, libev will install its handlers with
1466	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1776	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1467	interrupted. If you have a problem with syscalls getting interrupted by	1777	interrupted. If you have a problem with system calls getting interrupted by
1468	signals you can block all signals in an C<ev_check> watcher and unblock	1778	signals you can block all signals in an C<ev_check> watcher and unblock
1469	them in an C<ev_prepare> watcher.	1779	them in an C<ev_prepare> watcher.
1470		1780
1471	=head3 Watcher-Specific Functions and Data Members	1781	=head3 Watcher-Specific Functions and Data Members
1472		1782
…		…
1485		1795
1486	=back	1796	=back
1487		1797
1488	=head3 Examples	1798	=head3 Examples
1489		1799
1490	Example: Try to exit cleanly on SIGINT and SIGTERM.	1800	Example: Try to exit cleanly on SIGINT.
1491		1801
1492	static void	1802	static void
1493	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1494	{	1804	{
1495	ev_unloop (loop, EVUNLOOP_ALL);	1805	ev_unloop (loop, EVUNLOOP_ALL);
1496	}	1806	}
1497		1807
1498	struct ev_signal signal_watcher;	1808	ev_signal signal_watcher;
1499	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1500	ev_signal_start (loop, &sigint_cb);	1810	ev_signal_start (loop, &signal_watcher);
1501		1811
1502		1812
1503	=head2 C<ev_child> - watch out for process status changes	1813	=head2 C<ev_child> - watch out for process status changes
1504		1814
1505	Child watchers trigger when your process receives a SIGCHLD in response to	1815	Child watchers trigger when your process receives a SIGCHLD in response to
1506	some child status changes (most typically when a child of yours dies). It	1816	some child status changes (most typically when a child of yours dies or
1507	is permissible to install a child watcher I<after> the child has been	1817	exits). It is permissible to install a child watcher I<after> the child
1508	forked (which implies it might have already exited), as long as the event	1818	has been forked (which implies it might have already exited), as long
1509	loop isn't entered (or is continued from a watcher).	1819	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1820	forking and then immediately registering a watcher for the child is fine,
		1821	but forking and registering a watcher a few event loop iterations later is
		1822	not.
1510		1823
1511	Only the default event loop is capable of handling signals, and therefore	1824	Only the default event loop is capable of handling signals, and therefore
1512	you can only rgeister child watchers in the default event loop.	1825	you can only register child watchers in the default event loop.
1513		1826
1514	=head3 Process Interaction	1827	=head3 Process Interaction
1515		1828
1516	Libev grabs C<SIGCHLD> as soon as the default event loop is	1829	Libev grabs C<SIGCHLD> as soon as the default event loop is
1517	initialised. This is necessary to guarantee proper behaviour even if	1830	initialised. This is necessary to guarantee proper behaviour even if
1518	the first child watcher is started after the child exits. The occurance	1831	the first child watcher is started after the child exits. The occurrence
1519	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1832	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1520	synchronously as part of the event loop processing. Libev always reaps all	1833	synchronously as part of the event loop processing. Libev always reaps all
1521	children, even ones not watched.	1834	children, even ones not watched.
1522		1835
1523	=head3 Overriding the Built-In Processing	1836	=head3 Overriding the Built-In Processing
…		…
1527	handler, you can override it easily by installing your own handler for	1840	handler, you can override it easily by installing your own handler for
1528	C<SIGCHLD> after initialising the default loop, and making sure the	1841	C<SIGCHLD> after initialising the default loop, and making sure the
1529	default loop never gets destroyed. You are encouraged, however, to use an	1842	default loop never gets destroyed. You are encouraged, however, to use an
1530	event-based approach to child reaping and thus use libev's support for	1843	event-based approach to child reaping and thus use libev's support for
1531	that, so other libev users can use C<ev_child> watchers freely.	1844	that, so other libev users can use C<ev_child> watchers freely.
		1845
		1846	=head3 Stopping the Child Watcher
		1847
		1848	Currently, the child watcher never gets stopped, even when the
		1849	child terminates, so normally one needs to stop the watcher in the
		1850	callback. Future versions of libev might stop the watcher automatically
		1851	when a child exit is detected.
1532		1852
1533	=head3 Watcher-Specific Functions and Data Members	1853	=head3 Watcher-Specific Functions and Data Members
1534		1854
1535	=over 4	1855	=over 4
1536		1856
…		…
1565	=head3 Examples	1885	=head3 Examples
1566		1886
1567	Example: C<fork()> a new process and install a child handler to wait for	1887	Example: C<fork()> a new process and install a child handler to wait for
1568	its completion.	1888	its completion.
1569		1889
1570	ev_child cw;	1890	ev_child cw;
1571		1891
1572	static void	1892	static void
1573	child_cb (EV_P_ struct ev_child *w, int revents)	1893	child_cb (EV_P_ ev_child *w, int revents)
1574	{	1894	{
1575	ev_child_stop (EV_A_ w);	1895	ev_child_stop (EV_A_ w);
1576	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1896	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1577	}	1897	}
1578		1898
1579	pid_t pid = fork ();	1899	pid_t pid = fork ();
1580		1900
1581	if (pid < 0)	1901	if (pid < 0)
1582	// error	1902	// error
1583	else if (pid == 0)	1903	else if (pid == 0)
1584	{	1904	{
1585	// the forked child executes here	1905	// the forked child executes here
1586	exit (1);	1906	exit (1);
1587	}	1907	}
1588	else	1908	else
1589	{	1909	{
1590	ev_child_init (&cw, child_cb, pid, 0);	1910	ev_child_init (&cw, child_cb, pid, 0);
1591	ev_child_start (EV_DEFAULT_ &cw);	1911	ev_child_start (EV_DEFAULT_ &cw);
1592	}	1912	}
1593		1913
1594		1914
1595	=head2 C<ev_stat> - did the file attributes just change?	1915	=head2 C<ev_stat> - did the file attributes just change?
1596		1916
1597	This watches a filesystem path for attribute changes. That is, it calls	1917	This watches a file system path for attribute changes. That is, it calls
1598	C<stat> regularly (or when the OS says it changed) and sees if it changed	1918	C<stat> regularly (or when the OS says it changed) and sees if it changed
1599	compared to the last time, invoking the callback if it did.	1919	compared to the last time, invoking the callback if it did.
1600		1920
1601	The path does not need to exist: changing from "path exists" to "path does	1921	The path does not need to exist: changing from "path exists" to "path does
1602	not exist" is a status change like any other. The condition "path does	1922	not exist" is a status change like any other. The condition "path does
…		…
1605	the stat buffer having unspecified contents.	1925	the stat buffer having unspecified contents.
1606		1926
1607	The path I<should> be absolute and I<must not> end in a slash. If it is	1927	The path I<should> be absolute and I<must not> end in a slash. If it is
1608	relative and your working directory changes, the behaviour is undefined.	1928	relative and your working directory changes, the behaviour is undefined.
1609		1929
1610	Since there is no standard to do this, the portable implementation simply	1930	Since there is no standard kernel interface to do this, the portable
1611	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1931	implementation simply calls C<stat (2)> regularly on the path to see if
1612	can specify a recommended polling interval for this case. If you specify	1932	it changed somehow. You can specify a recommended polling interval for
1613	a polling interval of C<0> (highly recommended!) then a I<suitable,	1933	this case. If you specify a polling interval of C<0> (highly recommended!)
1614	unspecified default> value will be used (which you can expect to be around	1934	then a I<suitable, unspecified default> value will be used (which
1615	five seconds, although this might change dynamically). Libev will also	1935	you can expect to be around five seconds, although this might change
1616	impose a minimum interval which is currently around C<0.1>, but thats	1936	dynamically). Libev will also impose a minimum interval which is currently
1617	usually overkill.	1937	around C<0.1>, but thats usually overkill.
1618		1938
1619	This watcher type is not meant for massive numbers of stat watchers,	1939	This watcher type is not meant for massive numbers of stat watchers,
1620	as even with OS-supported change notifications, this can be	1940	as even with OS-supported change notifications, this can be
1621	resource-intensive.	1941	resource-intensive.
1622		1942
1623	At the time of this writing, only the Linux inotify interface is	1943	At the time of this writing, the only OS-specific interface implemented
1624	implemented (implementing kqueue support is left as an exercise for the	1944	is the Linux inotify interface (implementing kqueue support is left as
1625	reader, note, however, that the author sees no way of implementing ev_stat	1945	an exercise for the reader. Note, however, that the author sees no way
1626	semantics with kqueue). Inotify will be used to give hints only and should	1946	of implementing C<ev_stat> semantics with kqueue).
1627	not change the semantics of C<ev_stat> watchers, which means that libev
1628	sometimes needs to fall back to regular polling again even with inotify,
1629	but changes are usually detected immediately, and if the file exists there
1630	will be no polling.
1631		1947
1632	=head3 ABI Issues (Largefile Support)	1948	=head3 ABI Issues (Largefile Support)
1633		1949
1634	Libev by default (unless the user overrides this) uses the default	1950	Libev by default (unless the user overrides this) uses the default
1635	compilation environment, which means that on systems with optionally	1951	compilation environment, which means that on systems with large file
1636	disabled large file support, you get the 32 bit version of the stat	1952	support disabled by default, you get the 32 bit version of the stat
1637	structure. When using the library from programs that change the ABI to	1953	structure. When using the library from programs that change the ABI to
1638	use 64 bit file offsets the programs will fail. In that case you have to	1954	use 64 bit file offsets the programs will fail. In that case you have to
1639	compile libev with the same flags to get binary compatibility. This is	1955	compile libev with the same flags to get binary compatibility. This is
1640	obviously the case with any flags that change the ABI, but the problem is	1956	obviously the case with any flags that change the ABI, but the problem is
1641	most noticably with ev_stat and largefile support.	1957	most noticeably disabled with ev_stat and large file support.
1642		1958
1643	=head3 Inotify	1959	The solution for this is to lobby your distribution maker to make large
		1960	file interfaces available by default (as e.g. FreeBSD does) and not
		1961	optional. Libev cannot simply switch on large file support because it has
		1962	to exchange stat structures with application programs compiled using the
		1963	default compilation environment.
1644		1964
		1965	=head3 Inotify and Kqueue
		1966
1645	When C<inotify (7)> support has been compiled into libev (generally only	1967	When C<inotify (7)> support has been compiled into libev (generally
		1968	only available with Linux 2.6.25 or above due to bugs in earlier
1646	available on Linux) and present at runtime, it will be used to speed up	1969	implementations) and present at runtime, it will be used to speed up
1647	change detection where possible. The inotify descriptor will be created lazily	1970	change detection where possible. The inotify descriptor will be created
1648	when the first C<ev_stat> watcher is being started.	1971	lazily when the first C<ev_stat> watcher is being started.
1649		1972
1650	Inotify presence does not change the semantics of C<ev_stat> watchers	1973	Inotify presence does not change the semantics of C<ev_stat> watchers
1651	except that changes might be detected earlier, and in some cases, to avoid	1974	except that changes might be detected earlier, and in some cases, to avoid
1652	making regular C<stat> calls. Even in the presence of inotify support	1975	making regular C<stat> calls. Even in the presence of inotify support
1653	there are many cases where libev has to resort to regular C<stat> polling.	1976	there are many cases where libev has to resort to regular C<stat> polling,
		1977	but as long as the path exists, libev usually gets away without polling.
1654		1978
1655	(There is no support for kqueue, as apparently it cannot be used to	1979	There is no support for kqueue, as apparently it cannot be used to
1656	implement this functionality, due to the requirement of having a file	1980	implement this functionality, due to the requirement of having a file
1657	descriptor open on the object at all times).	1981	descriptor open on the object at all times, and detecting renames, unlinks
		1982	etc. is difficult.
1658		1983
1659	=head3 The special problem of stat time resolution	1984	=head3 The special problem of stat time resolution
1660		1985
1661	The C<stat ()> syscall only supports full-second resolution portably, and	1986	The C<stat ()> system call only supports full-second resolution portably, and
1662	even on systems where the resolution is higher, many filesystems still	1987	even on systems where the resolution is higher, most file systems still
1663	only support whole seconds.	1988	only support whole seconds.
1664		1989
1665	That means that, if the time is the only thing that changes, you can	1990	That means that, if the time is the only thing that changes, you can
1666	easily miss updates: on the first update, C<ev_stat> detects a change and	1991	easily miss updates: on the first update, C<ev_stat> detects a change and
1667	calls your callback, which does something. When there is another update	1992	calls your callback, which does something. When there is another update
1668	within the same second, C<ev_stat> will be unable to detect it as the stat	1993	within the same second, C<ev_stat> will be unable to detect unless the
1669	data does not change.	1994	stat data does change in other ways (e.g. file size).
1670		1995
1671	The solution to this is to delay acting on a change for slightly more	1996	The solution to this is to delay acting on a change for slightly more
1672	than a second (or till slightly after the next full second boundary), using	1997	than a second (or till slightly after the next full second boundary), using
1673	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1998	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1674	ev_timer_again (loop, w)>).	1999	ev_timer_again (loop, w)>).
…		…
1694	C<path>. The C<interval> is a hint on how quickly a change is expected to	2019	C<path>. The C<interval> is a hint on how quickly a change is expected to
1695	be detected and should normally be specified as C<0> to let libev choose	2020	be detected and should normally be specified as C<0> to let libev choose
1696	a suitable value. The memory pointed to by C<path> must point to the same	2021	a suitable value. The memory pointed to by C<path> must point to the same
1697	path for as long as the watcher is active.	2022	path for as long as the watcher is active.
1698		2023
1699	The callback will receive C<EV_STAT> when a change was detected, relative	2024	The callback will receive an C<EV_STAT> event when a change was detected,
1700	to the attributes at the time the watcher was started (or the last change	2025	relative to the attributes at the time the watcher was started (or the
1701	was detected).	2026	last change was detected).
1702		2027
1703	=item ev_stat_stat (loop, ev_stat *)	2028	=item ev_stat_stat (loop, ev_stat *)
1704		2029
1705	Updates the stat buffer immediately with new values. If you change the	2030	Updates the stat buffer immediately with new values. If you change the
1706	watched path in your callback, you could call this function to avoid	2031	watched path in your callback, you could call this function to avoid
…		…
1727		2052
1728	The specified interval.	2053	The specified interval.
1729		2054
1730	=item const char *path [read-only]	2055	=item const char *path [read-only]
1731		2056
1732	The filesystem path that is being watched.	2057	The file system path that is being watched.
1733		2058
1734	=back	2059	=back
1735		2060
1736	=head3 Examples	2061	=head3 Examples
1737		2062
1738	Example: Watch C</etc/passwd> for attribute changes.	2063	Example: Watch C</etc/passwd> for attribute changes.
1739		2064
1740	static void	2065	static void
1741	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2066	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1742	{	2067	{
1743	/* /etc/passwd changed in some way */	2068	/* /etc/passwd changed in some way */
1744	if (w->attr.st_nlink)	2069	if (w->attr.st_nlink)
1745	{	2070	{
1746	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2071	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1747	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2072	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1748	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2073	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1749	}	2074	}
1750	else	2075	else
1751	/* you shalt not abuse printf for puts */	2076	/* you shalt not abuse printf for puts */
1752	puts ("wow, /etc/passwd is not there, expect problems. "	2077	puts ("wow, /etc/passwd is not there, expect problems. "
1753	"if this is windows, they already arrived\n");	2078	"if this is windows, they already arrived\n");
1754	}	2079	}
1755		2080
1756	...	2081	...
1757	ev_stat passwd;	2082	ev_stat passwd;
1758		2083
1759	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2084	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	2085	ev_stat_start (loop, &passwd);
1761		2086
1762	Example: Like above, but additionally use a one-second delay so we do not	2087	Example: Like above, but additionally use a one-second delay so we do not
1763	miss updates (however, frequent updates will delay processing, too, so	2088	miss updates (however, frequent updates will delay processing, too, so
1764	one might do the work both on C<ev_stat> callback invocation I<and> on	2089	one might do the work both on C<ev_stat> callback invocation I<and> on
1765	C<ev_timer> callback invocation).	2090	C<ev_timer> callback invocation).
1766		2091
1767	static ev_stat passwd;	2092	static ev_stat passwd;
1768	static ev_timer timer;	2093	static ev_timer timer;
1769		2094
1770	static void	2095	static void
1771	timer_cb (EV_P_ ev_timer *w, int revents)	2096	timer_cb (EV_P_ ev_timer *w, int revents)
1772	{	2097	{
1773	ev_timer_stop (EV_A_ w);	2098	ev_timer_stop (EV_A_ w);
1774		2099
1775	/* now it's one second after the most recent passwd change */	2100	/* now it's one second after the most recent passwd change */
1776	}	2101	}
1777		2102
1778	static void	2103	static void
1779	stat_cb (EV_P_ ev_stat *w, int revents)	2104	stat_cb (EV_P_ ev_stat *w, int revents)
1780	{	2105	{
1781	/* reset the one-second timer */	2106	/* reset the one-second timer */
1782	ev_timer_again (EV_A_ &timer);	2107	ev_timer_again (EV_A_ &timer);
1783	}	2108	}
1784		2109
1785	...	2110	...
1786	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2111	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1787	ev_stat_start (loop, &passwd);	2112	ev_stat_start (loop, &passwd);
1788	ev_timer_init (&timer, timer_cb, 0., 1.02);	2113	ev_timer_init (&timer, timer_cb, 0., 1.02);
1789		2114
1790		2115
1791	=head2 C<ev_idle> - when you've got nothing better to do...	2116	=head2 C<ev_idle> - when you've got nothing better to do...
1792		2117
1793	Idle watchers trigger events when no other events of the same or higher	2118	Idle watchers trigger events when no other events of the same or higher
1794	priority are pending (prepare, check and other idle watchers do not	2119	priority are pending (prepare, check and other idle watchers do not count
1795	count).	2120	as receiving "events").
1796		2121
1797	That is, as long as your process is busy handling sockets or timeouts	2122	That is, as long as your process is busy handling sockets or timeouts
1798	(or even signals, imagine) of the same or higher priority it will not be	2123	(or even signals, imagine) of the same or higher priority it will not be
1799	triggered. But when your process is idle (or only lower-priority watchers	2124	triggered. But when your process is idle (or only lower-priority watchers
1800	are pending), the idle watchers are being called once per event loop	2125	are pending), the idle watchers are being called once per event loop
…		…
1824	=head3 Examples	2149	=head3 Examples
1825		2150
1826	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2151	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1827	callback, free it. Also, use no error checking, as usual.	2152	callback, free it. Also, use no error checking, as usual.
1828		2153
1829	static void	2154	static void
1830	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2155	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1831	{	2156	{
1832	free (w);	2157	free (w);
1833	// now do something you wanted to do when the program has	2158	// now do something you wanted to do when the program has
1834	// no longer anything immediate to do.	2159	// no longer anything immediate to do.
1835	}	2160	}
1836		2161
1837	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1838	ev_idle_init (idle_watcher, idle_cb);	2163	ev_idle_init (idle_watcher, idle_cb);
1839	ev_idle_start (loop, idle_cb);	2164	ev_idle_start (loop, idle_cb);
1840		2165
1841		2166
1842	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1843		2168
1844	Prepare and check watchers are usually (but not always) used in tandem:	2169	Prepare and check watchers are usually (but not always) used in pairs:
1845	prepare watchers get invoked before the process blocks and check watchers	2170	prepare watchers get invoked before the process blocks and check watchers
1846	afterwards.	2171	afterwards.
1847		2172
1848	You I<must not> call C<ev_loop> or similar functions that enter	2173	You I<must not> call C<ev_loop> or similar functions that enter
1849	the current event loop from either C<ev_prepare> or C<ev_check>	2174	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1852	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2177	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1853	C<ev_check> so if you have one watcher of each kind they will always be	2178	C<ev_check> so if you have one watcher of each kind they will always be
1854	called in pairs bracketing the blocking call.	2179	called in pairs bracketing the blocking call.
1855		2180
1856	Their main purpose is to integrate other event mechanisms into libev and	2181	Their main purpose is to integrate other event mechanisms into libev and
1857	their use is somewhat advanced. This could be used, for example, to track	2182	their use is somewhat advanced. They could be used, for example, to track
1858	variable changes, implement your own watchers, integrate net-snmp or a	2183	variable changes, implement your own watchers, integrate net-snmp or a
1859	coroutine library and lots more. They are also occasionally useful if	2184	coroutine library and lots more. They are also occasionally useful if
1860	you cache some data and want to flush it before blocking (for example,	2185	you cache some data and want to flush it before blocking (for example,
1861	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2186	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1862	watcher).	2187	watcher).
1863		2188
1864	This is done by examining in each prepare call which file descriptors need	2189	This is done by examining in each prepare call which file descriptors
1865	to be watched by the other library, registering C<ev_io> watchers for	2190	need to be watched by the other library, registering C<ev_io> watchers
1866	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2191	for them and starting an C<ev_timer> watcher for any timeouts (many
1867	provide just this functionality). Then, in the check watcher you check for	2192	libraries provide exactly this functionality). Then, in the check watcher,
1868	any events that occured (by checking the pending status of all watchers	2193	you check for any events that occurred (by checking the pending status
1869	and stopping them) and call back into the library. The I/O and timer	2194	of all watchers and stopping them) and call back into the library. The
1870	callbacks will never actually be called (but must be valid nevertheless,	2195	I/O and timer callbacks will never actually be called (but must be valid
1871	because you never know, you know?).	2196	nevertheless, because you never know, you know?).
1872		2197
1873	As another example, the Perl Coro module uses these hooks to integrate	2198	As another example, the Perl Coro module uses these hooks to integrate
1874	coroutines into libev programs, by yielding to other active coroutines	2199	coroutines into libev programs, by yielding to other active coroutines
1875	during each prepare and only letting the process block if no coroutines	2200	during each prepare and only letting the process block if no coroutines
1876	are ready to run (it's actually more complicated: it only runs coroutines	2201	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1879	loop from blocking if lower-priority coroutines are active, thus mapping	2204	loop from blocking if lower-priority coroutines are active, thus mapping
1880	low-priority coroutines to idle/background tasks).	2205	low-priority coroutines to idle/background tasks).
1881		2206
1882	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2207	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1883	priority, to ensure that they are being run before any other watchers	2208	priority, to ensure that they are being run before any other watchers
		2209	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2210
1884	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2211	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1885	too) should not activate ("feed") events into libev. While libev fully	2212	activate ("feed") events into libev. While libev fully supports this, they
1886	supports this, they might get executed before other C<ev_check> watchers	2213	might get executed before other C<ev_check> watchers did their job. As
1887	did their job. As C<ev_check> watchers are often used to embed other	2214	C<ev_check> watchers are often used to embed other (non-libev) event
1888	(non-libev) event loops those other event loops might be in an unusable	2215	loops those other event loops might be in an unusable state until their
1889	state until their C<ev_check> watcher ran (always remind yourself to	2216	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1890	coexist peacefully with others).	2217	others).
1891		2218
1892	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1893		2220
1894	=over 4	2221	=over 4
1895		2222
…		…
1897		2224
1898	=item ev_check_init (ev_check *, callback)	2225	=item ev_check_init (ev_check *, callback)
1899		2226
1900	Initialises and configures the prepare or check watcher - they have no	2227	Initialises and configures the prepare or check watcher - they have no
1901	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2228	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1902	macros, but using them is utterly, utterly and completely pointless.	2229	macros, but using them is utterly, utterly, utterly and completely
		2230	pointless.
1903		2231
1904	=back	2232	=back
1905		2233
1906	=head3 Examples	2234	=head3 Examples
1907		2235
…		…
1916	and in a check watcher, destroy them and call into libadns. What follows	2244	and in a check watcher, destroy them and call into libadns. What follows
1917	is pseudo-code only of course. This requires you to either use a low	2245	is pseudo-code only of course. This requires you to either use a low
1918	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2246	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1919	the callbacks for the IO/timeout watchers might not have been called yet.	2247	the callbacks for the IO/timeout watchers might not have been called yet.
1920		2248
1921	static ev_io iow [nfd];	2249	static ev_io iow [nfd];
1922	static ev_timer tw;	2250	static ev_timer tw;
1923		2251
1924	static void	2252	static void
1925	io_cb (ev_loop *loop, ev_io *w, int revents)	2253	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1926	{	2254	{
1927	}	2255	}
1928		2256
1929	// create io watchers for each fd and a timer before blocking	2257	// create io watchers for each fd and a timer before blocking
1930	static void	2258	static void
1931	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2259	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1932	{	2260	{
1933	int timeout = 3600000;	2261	int timeout = 3600000;
1934	struct pollfd fds [nfd];	2262	struct pollfd fds [nfd];
1935	// actual code will need to loop here and realloc etc.	2263	// actual code will need to loop here and realloc etc.
1936	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1937		2265
1938	/* the callback is illegal, but won't be called as we stop during check */	2266	/* the callback is illegal, but won't be called as we stop during check */
1939	ev_timer_init (&tw, 0, timeout * 1e-3);	2267	ev_timer_init (&tw, 0, timeout * 1e-3);
1940	ev_timer_start (loop, &tw);	2268	ev_timer_start (loop, &tw);
1941		2269
1942	// create one ev_io per pollfd	2270	// create one ev_io per pollfd
1943	for (int i = 0; i < nfd; ++i)	2271	for (int i = 0; i < nfd; ++i)
1944	{	2272	{
1945	ev_io_init (iow + i, io_cb, fds [i].fd,	2273	ev_io_init (iow + i, io_cb, fds [i].fd,
1946	((fds [i].events & POLLIN ? EV_READ : 0)	2274	((fds [i].events & POLLIN ? EV_READ : 0)
1947	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2275	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1948		2276
1949	fds [i].revents = 0;	2277	fds [i].revents = 0;
1950	ev_io_start (loop, iow + i);	2278	ev_io_start (loop, iow + i);
1951	}	2279	}
1952	}	2280	}
1953		2281
1954	// stop all watchers after blocking	2282	// stop all watchers after blocking
1955	static void	2283	static void
1956	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2284	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1957	{	2285	{
1958	ev_timer_stop (loop, &tw);	2286	ev_timer_stop (loop, &tw);
1959		2287
1960	for (int i = 0; i < nfd; ++i)	2288	for (int i = 0; i < nfd; ++i)
1961	{	2289	{
1962	// set the relevant poll flags	2290	// set the relevant poll flags
1963	// could also call adns_processreadable etc. here	2291	// could also call adns_processreadable etc. here
1964	struct pollfd *fd = fds + i;	2292	struct pollfd *fd = fds + i;
1965	int revents = ev_clear_pending (iow + i);	2293	int revents = ev_clear_pending (iow + i);
1966	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2294	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1967	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2295	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1968		2296
1969	// now stop the watcher	2297	// now stop the watcher
1970	ev_io_stop (loop, iow + i);	2298	ev_io_stop (loop, iow + i);
1971	}	2299	}
1972		2300
1973	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2301	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1974	}	2302	}
1975		2303
1976	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2304	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1977	in the prepare watcher and would dispose of the check watcher.	2305	in the prepare watcher and would dispose of the check watcher.
1978		2306
1979	Method 3: If the module to be embedded supports explicit event	2307	Method 3: If the module to be embedded supports explicit event
1980	notification (adns does), you can also make use of the actual watcher	2308	notification (libadns does), you can also make use of the actual watcher
1981	callbacks, and only destroy/create the watchers in the prepare watcher.	2309	callbacks, and only destroy/create the watchers in the prepare watcher.
1982		2310
1983	static void	2311	static void
1984	timer_cb (EV_P_ ev_timer *w, int revents)	2312	timer_cb (EV_P_ ev_timer *w, int revents)
1985	{	2313	{
1986	adns_state ads = (adns_state)w->data;	2314	adns_state ads = (adns_state)w->data;
1987	update_now (EV_A);	2315	update_now (EV_A);
1988		2316
1989	adns_processtimeouts (ads, &tv_now);	2317	adns_processtimeouts (ads, &tv_now);
1990	}	2318	}
1991		2319
1992	static void	2320	static void
1993	io_cb (EV_P_ ev_io *w, int revents)	2321	io_cb (EV_P_ ev_io *w, int revents)
1994	{	2322	{
1995	adns_state ads = (adns_state)w->data;	2323	adns_state ads = (adns_state)w->data;
1996	update_now (EV_A);	2324	update_now (EV_A);
1997		2325
1998	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2326	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1999	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2327	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2000	}	2328	}
2001		2329
2002	// do not ever call adns_afterpoll	2330	// do not ever call adns_afterpoll
2003		2331
2004	Method 4: Do not use a prepare or check watcher because the module you	2332	Method 4: Do not use a prepare or check watcher because the module you
2005	want to embed is too inflexible to support it. Instead, youc na override	2333	want to embed is not flexible enough to support it. Instead, you can
2006	their poll function. The drawback with this solution is that the main	2334	override their poll function. The drawback with this solution is that the
2007	loop is now no longer controllable by EV. The C<Glib::EV> module does	2335	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2008	this.	2336	this approach, effectively embedding EV as a client into the horrible
		2337	libglib event loop.
2009		2338
2010	static gint	2339	static gint
2011	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2340	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2012	{	2341	{
2013	int got_events = 0;	2342	int got_events = 0;
2014		2343
2015	for (n = 0; n < nfds; ++n)	2344	for (n = 0; n < nfds; ++n)
2016	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2345	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2017		2346
2018	if (timeout >= 0)	2347	if (timeout >= 0)
2019	// create/start timer	2348	// create/start timer
2020		2349
2021	// poll	2350	// poll
2022	ev_loop (EV_A_ 0);	2351	ev_loop (EV_A_ 0);
2023		2352
2024	// stop timer again	2353	// stop timer again
2025	if (timeout >= 0)	2354	if (timeout >= 0)
2026	ev_timer_stop (EV_A_ &to);	2355	ev_timer_stop (EV_A_ &to);
2027		2356
2028	// stop io watchers again - their callbacks should have set	2357	// stop io watchers again - their callbacks should have set
2029	for (n = 0; n < nfds; ++n)	2358	for (n = 0; n < nfds; ++n)
2030	ev_io_stop (EV_A_ iow [n]);	2359	ev_io_stop (EV_A_ iow [n]);
2031		2360
2032	return got_events;	2361	return got_events;
2033	}	2362	}
2034		2363
2035		2364
2036	=head2 C<ev_embed> - when one backend isn't enough...	2365	=head2 C<ev_embed> - when one backend isn't enough...
2037		2366
2038	This is a rather advanced watcher type that lets you embed one event loop	2367	This is a rather advanced watcher type that lets you embed one event loop
…		…
2044	prioritise I/O.	2373	prioritise I/O.
2045		2374
2046	As an example for a bug workaround, the kqueue backend might only support	2375	As an example for a bug workaround, the kqueue backend might only support
2047	sockets on some platform, so it is unusable as generic backend, but you	2376	sockets on some platform, so it is unusable as generic backend, but you
2048	still want to make use of it because you have many sockets and it scales	2377	still want to make use of it because you have many sockets and it scales
2049	so nicely. In this case, you would create a kqueue-based loop and embed it	2378	so nicely. In this case, you would create a kqueue-based loop and embed
2050	into your default loop (which might use e.g. poll). Overall operation will	2379	it into your default loop (which might use e.g. poll). Overall operation
2051	be a bit slower because first libev has to poll and then call kevent, but	2380	will be a bit slower because first libev has to call C<poll> and then
2052	at least you can use both at what they are best.	2381	C<kevent>, but at least you can use both mechanisms for what they are
		2382	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2053		2383
2054	As for prioritising I/O: rarely you have the case where some fds have	2384	As for prioritising I/O: under rare circumstances you have the case where
2055	to be watched and handled very quickly (with low latency), and even	2385	some fds have to be watched and handled very quickly (with low latency),
2056	priorities and idle watchers might have too much overhead. In this case	2386	and even priorities and idle watchers might have too much overhead. In
2057	you would put all the high priority stuff in one loop and all the rest in	2387	this case you would put all the high priority stuff in one loop and all
2058	a second one, and embed the second one in the first.	2388	the rest in a second one, and embed the second one in the first.
2059		2389
2060	As long as the watcher is active, the callback will be invoked every time	2390	As long as the watcher is active, the callback will be invoked every time
2061	there might be events pending in the embedded loop. The callback must then	2391	there might be events pending in the embedded loop. The callback must then
2062	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2392	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2063	their callbacks (you could also start an idle watcher to give the embedded	2393	their callbacks (you could also start an idle watcher to give the embedded
…		…
2071	interested in that.	2401	interested in that.
2072		2402
2073	Also, there have not currently been made special provisions for forking:	2403	Also, there have not currently been made special provisions for forking:
2074	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2404	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2075	but you will also have to stop and restart any C<ev_embed> watchers	2405	but you will also have to stop and restart any C<ev_embed> watchers
2076	yourself.	2406	yourself - but you can use a fork watcher to handle this automatically,
		2407	and future versions of libev might do just that.
2077		2408
2078	Unfortunately, not all backends are embeddable, only the ones returned by	2409	Unfortunately, not all backends are embeddable: only the ones returned by
2079	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2080	portable one.	2411	portable one.
2081		2412
2082	So when you want to use this feature you will always have to be prepared	2413	So when you want to use this feature you will always have to be prepared
2083	that you cannot get an embeddable loop. The recommended way to get around	2414	that you cannot get an embeddable loop. The recommended way to get around
2084	this is to have a separate variables for your embeddable loop, try to	2415	this is to have a separate variables for your embeddable loop, try to
2085	create it, and if that fails, use the normal loop for everything.	2416	create it, and if that fails, use the normal loop for everything.
2086		2417
		2418	=head3 C<ev_embed> and fork
		2419
		2420	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2421	automatically be applied to the embedded loop as well, so no special
		2422	fork handling is required in that case. When the watcher is not running,
		2423	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2424	as applicable.
		2425
2087	=head3 Watcher-Specific Functions and Data Members	2426	=head3 Watcher-Specific Functions and Data Members
2088		2427
2089	=over 4	2428	=over 4
2090		2429
2091	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2430	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2094		2433
2095	Configures the watcher to embed the given loop, which must be	2434	Configures the watcher to embed the given loop, which must be
2096	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2435	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2097	invoked automatically, otherwise it is the responsibility of the callback	2436	invoked automatically, otherwise it is the responsibility of the callback
2098	to invoke it (it will continue to be called until the sweep has been done,	2437	to invoke it (it will continue to be called until the sweep has been done,
2099	if you do not want thta, you need to temporarily stop the embed watcher).	2438	if you do not want that, you need to temporarily stop the embed watcher).
2100		2439
2101	=item ev_embed_sweep (loop, ev_embed *)	2440	=item ev_embed_sweep (loop, ev_embed *)
2102		2441
2103	Make a single, non-blocking sweep over the embedded loop. This works	2442	Make a single, non-blocking sweep over the embedded loop. This works
2104	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2443	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2105	apropriate way for embedded loops.	2444	appropriate way for embedded loops.
2106		2445
2107	=item struct ev_loop *other [read-only]	2446	=item struct ev_loop *other [read-only]
2108		2447
2109	The embedded event loop.	2448	The embedded event loop.
2110		2449
…		…
2112		2451
2113	=head3 Examples	2452	=head3 Examples
2114		2453
2115	Example: Try to get an embeddable event loop and embed it into the default	2454	Example: Try to get an embeddable event loop and embed it into the default
2116	event loop. If that is not possible, use the default loop. The default	2455	event loop. If that is not possible, use the default loop. The default
2117	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2456	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2118	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2457	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2119	used).	2458	used).
2120		2459
2121	struct ev_loop *loop_hi = ev_default_init (0);	2460	struct ev_loop *loop_hi = ev_default_init (0);
2122	struct ev_loop *loop_lo = 0;	2461	struct ev_loop *loop_lo = 0;
2123	struct ev_embed embed;	2462	ev_embed embed;
2124		2463
2125	// see if there is a chance of getting one that works	2464	// see if there is a chance of getting one that works
2126	// (remember that a flags value of 0 means autodetection)	2465	// (remember that a flags value of 0 means autodetection)
2127	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2466	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2128	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2467	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2129	: 0;	2468	: 0;
2130		2469
2131	// if we got one, then embed it, otherwise default to loop_hi	2470	// if we got one, then embed it, otherwise default to loop_hi
2132	if (loop_lo)	2471	if (loop_lo)
2133	{	2472	{
2134	ev_embed_init (&embed, 0, loop_lo);	2473	ev_embed_init (&embed, 0, loop_lo);
2135	ev_embed_start (loop_hi, &embed);	2474	ev_embed_start (loop_hi, &embed);
2136	}	2475	}
2137	else	2476	else
2138	loop_lo = loop_hi;	2477	loop_lo = loop_hi;
2139		2478
2140	Example: Check if kqueue is available but not recommended and create	2479	Example: Check if kqueue is available but not recommended and create
2141	a kqueue backend for use with sockets (which usually work with any	2480	a kqueue backend for use with sockets (which usually work with any
2142	kqueue implementation). Store the kqueue/socket-only event loop in	2481	kqueue implementation). Store the kqueue/socket-only event loop in
2143	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2482	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2144		2483
2145	struct ev_loop *loop = ev_default_init (0);	2484	struct ev_loop *loop = ev_default_init (0);
2146	struct ev_loop *loop_socket = 0;	2485	struct ev_loop *loop_socket = 0;
2147	struct ev_embed embed;	2486	ev_embed embed;
2148		2487
2149	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2488	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2150	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2489	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2151	{	2490	{
2152	ev_embed_init (&embed, 0, loop_socket);	2491	ev_embed_init (&embed, 0, loop_socket);
2153	ev_embed_start (loop, &embed);	2492	ev_embed_start (loop, &embed);
2154	}	2493	}
2155		2494
2156	if (!loop_socket)	2495	if (!loop_socket)
2157	loop_socket = loop;	2496	loop_socket = loop;
2158		2497
2159	// now use loop_socket for all sockets, and loop for everything else	2498	// now use loop_socket for all sockets, and loop for everything else
2160		2499
2161		2500
2162	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2501	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2163		2502
2164	Fork watchers are called when a C<fork ()> was detected (usually because	2503	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2208	is that the author does not know of a simple (or any) algorithm for a	2547	is that the author does not know of a simple (or any) algorithm for a
2209	multiple-writer-single-reader queue that works in all cases and doesn't	2548	multiple-writer-single-reader queue that works in all cases and doesn't
2210	need elaborate support such as pthreads.	2549	need elaborate support such as pthreads.
2211		2550
2212	That means that if you want to queue data, you have to provide your own	2551	That means that if you want to queue data, you have to provide your own
2213	queue. But at least I can tell you would implement locking around your	2552	queue. But at least I can tell you how to implement locking around your
2214	queue:	2553	queue:
2215		2554
2216	=over 4	2555	=over 4
2217		2556
2218	=item queueing from a signal handler context	2557	=item queueing from a signal handler context
2219		2558
2220	To implement race-free queueing, you simply add to the queue in the signal	2559	To implement race-free queueing, you simply add to the queue in the signal
2221	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2560	handler but you block the signal handler in the watcher callback. Here is
2222	some fictitiuous SIGUSR1 handler:	2561	an example that does that for some fictitious SIGUSR1 handler:
2223		2562
2224	static ev_async mysig;	2563	static ev_async mysig;
2225		2564
2226	static void	2565	static void
2227	sigusr1_handler (void)	2566	sigusr1_handler (void)
…		…
2294		2633
2295	=item ev_async_init (ev_async *, callback)	2634	=item ev_async_init (ev_async *, callback)
2296		2635
2297	Initialises and configures the async watcher - it has no parameters of any	2636	Initialises and configures the async watcher - it has no parameters of any
2298	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2299	believe me.	2638	trust me.
2300		2639
2301	=item ev_async_send (loop, ev_async *)	2640	=item ev_async_send (loop, ev_async *)
2302		2641
2303	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2642	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2304	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2643	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2305	C<ev_feed_event>, this call is safe to do in other threads, signal or	2644	C<ev_feed_event>, this call is safe to do from other threads, signal or
2306	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2307	section below on what exactly this means).	2646	section below on what exactly this means).
2308		2647
2309	This call incurs the overhead of a syscall only once per loop iteration,	2648	This call incurs the overhead of a system call only once per loop iteration,
2310	so while the overhead might be noticable, it doesn't apply to repeated	2649	so while the overhead might be noticeable, it doesn't apply to repeated
2311	calls to C<ev_async_send>.	2650	calls to C<ev_async_send>.
2312		2651
2313	=item bool = ev_async_pending (ev_async *)	2652	=item bool = ev_async_pending (ev_async *)
2314		2653
2315	Returns a non-zero value when C<ev_async_send> has been called on the	2654	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2317	event loop.	2656	event loop.
2318		2657
2319	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2658	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2320	the loop iterates next and checks for the watcher to have become active,	2659	the loop iterates next and checks for the watcher to have become active,
2321	it will reset the flag again. C<ev_async_pending> can be used to very	2660	it will reset the flag again. C<ev_async_pending> can be used to very
2322	quickly check wether invoking the loop might be a good idea.	2661	quickly check whether invoking the loop might be a good idea.
2323		2662
2324	Not that this does I<not> check wether the watcher itself is pending, only	2663	Not that this does I<not> check whether the watcher itself is pending, only
2325	wether it has been requested to make this watcher pending.	2664	whether it has been requested to make this watcher pending.
2326		2665
2327	=back	2666	=back
2328		2667
2329		2668
2330	=head1 OTHER FUNCTIONS	2669	=head1 OTHER FUNCTIONS
…		…
2334	=over 4	2673	=over 4
2335		2674
2336	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2675	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2337		2676
2338	This function combines a simple timer and an I/O watcher, calls your	2677	This function combines a simple timer and an I/O watcher, calls your
2339	callback on whichever event happens first and automatically stop both	2678	callback on whichever event happens first and automatically stops both
2340	watchers. This is useful if you want to wait for a single event on an fd	2679	watchers. This is useful if you want to wait for a single event on an fd
2341	or timeout without having to allocate/configure/start/stop/free one or	2680	or timeout without having to allocate/configure/start/stop/free one or
2342	more watchers yourself.	2681	more watchers yourself.
2343		2682
2344	If C<fd> is less than 0, then no I/O watcher will be started and events	2683	If C<fd> is less than 0, then no I/O watcher will be started and the
2345	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2684	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2346	C<events> set will be craeted and started.	2685	the given C<fd> and C<events> set will be created and started.
2347		2686
2348	If C<timeout> is less than 0, then no timeout watcher will be	2687	If C<timeout> is less than 0, then no timeout watcher will be
2349	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2350	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2689	repeat = 0) will be started. C<0> is a valid timeout.
2351	dubious value.
2352		2690
2353	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2691	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2354	passed an C<revents> set like normal event callbacks (a combination of	2692	passed an C<revents> set like normal event callbacks (a combination of
2355	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2356	value passed to C<ev_once>:	2694	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2695	a timeout and an io event at the same time - you probably should give io
		2696	events precedence.
2357		2697
		2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2699
2358	static void stdin_ready (int revents, void *arg)	2700	static void stdin_ready (int revents, void *arg)
2359	{	2701	{
2360	if (revents & EV_TIMEOUT)
2361	/* doh, nothing entered */;
2362	else if (revents & EV_READ)	2702	if (revents & EV_READ)
2363	/* stdin might have data for us, joy! */;	2703	/* stdin might have data for us, joy! */;
		2704	else if (revents & EV_TIMEOUT)
		2705	/* doh, nothing entered */;
2364	}	2706	}
2365		2707
2366	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2367		2709
2368	=item ev_feed_event (ev_loop *, watcher *, int revents)	2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2369		2711
2370	Feeds the given event set into the event loop, as if the specified event	2712	Feeds the given event set into the event loop, as if the specified event
2371	had happened for the specified watcher (which must be a pointer to an	2713	had happened for the specified watcher (which must be a pointer to an
2372	initialised but not necessarily started event watcher).	2714	initialised but not necessarily started event watcher).
2373		2715
2374	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2375		2717
2376	Feed an event on the given fd, as if a file descriptor backend detected	2718	Feed an event on the given fd, as if a file descriptor backend detected
2377	the given events it.	2719	the given events it.
2378		2720
2379	=item ev_feed_signal_event (ev_loop *loop, int signum)	2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2380		2722
2381	Feed an event as if the given signal occured (C<loop> must be the default	2723	Feed an event as if the given signal occurred (C<loop> must be the default
2382	loop!).	2724	loop!).
2383		2725
2384	=back	2726	=back
2385		2727
2386		2728
…		…
2415	=back	2757	=back
2416		2758
2417	=head1 C++ SUPPORT	2759	=head1 C++ SUPPORT
2418		2760
2419	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2761	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2420	you to use some convinience methods to start/stop watchers and also change	2762	you to use some convenience methods to start/stop watchers and also change
2421	the callback model to a model using method callbacks on objects.	2763	the callback model to a model using method callbacks on objects.
2422		2764
2423	To use it,	2765	To use it,
2424		2766
2425	#include <ev++.h>	2767	#include <ev++.h>
2426		2768
2427	This automatically includes F<ev.h> and puts all of its definitions (many	2769	This automatically includes F<ev.h> and puts all of its definitions (many
2428	of them macros) into the global namespace. All C++ specific things are	2770	of them macros) into the global namespace. All C++ specific things are
2429	put into the C<ev> namespace. It should support all the same embedding	2771	put into the C<ev> namespace. It should support all the same embedding
2430	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2772	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2497	your compiler is good :), then the method will be fully inlined into the	2839	your compiler is good :), then the method will be fully inlined into the
2498	thunking function, making it as fast as a direct C callback.	2840	thunking function, making it as fast as a direct C callback.
2499		2841
2500	Example: simple class declaration and watcher initialisation	2842	Example: simple class declaration and watcher initialisation
2501		2843
2502	struct myclass	2844	struct myclass
2503	{	2845	{
2504	void io_cb (ev::io &w, int revents) { }	2846	void io_cb (ev::io &w, int revents) { }
2505	}	2847	}
2506		2848
2507	myclass obj;	2849	myclass obj;
2508	ev::io iow;	2850	ev::io iow;
2509	iow.set <myclass, &myclass::io_cb> (&obj);	2851	iow.set <myclass, &myclass::io_cb> (&obj);
2510		2852
2511	=item w->set<function> (void *data = 0)	2853	=item w->set<function> (void *data = 0)
2512		2854
2513	Also sets a callback, but uses a static method or plain function as	2855	Also sets a callback, but uses a static method or plain function as
2514	callback. The optional C<data> argument will be stored in the watcher's	2856	callback. The optional C<data> argument will be stored in the watcher's
…		…
2516		2858
2517	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2859	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2518		2860
2519	See the method-C<set> above for more details.	2861	See the method-C<set> above for more details.
2520		2862
2521	Example:	2863	Example: Use a plain function as callback.
2522		2864
2523	static void io_cb (ev::io &w, int revents) { }	2865	static void io_cb (ev::io &w, int revents) { }
2524	iow.set <io_cb> ();	2866	iow.set <io_cb> ();
2525		2867
2526	=item w->set (struct ev_loop *)	2868	=item w->set (struct ev_loop *)
2527		2869
2528	Associates a different C<struct ev_loop> with this watcher. You can only	2870	Associates a different C<struct ev_loop> with this watcher. You can only
2529	do this when the watcher is inactive (and not pending either).	2871	do this when the watcher is inactive (and not pending either).
2530		2872
2531	=item w->set ([args])	2873	=item w->set ([arguments])
2532		2874
2533	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2875	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2534	called at least once. Unlike the C counterpart, an active watcher gets	2876	called at least once. Unlike the C counterpart, an active watcher gets
2535	automatically stopped and restarted when reconfiguring it with this	2877	automatically stopped and restarted when reconfiguring it with this
2536	method.	2878	method.
2537		2879
2538	=item w->start ()	2880	=item w->start ()
…		…
2562	=back	2904	=back
2563		2905
2564	Example: Define a class with an IO and idle watcher, start one of them in	2906	Example: Define a class with an IO and idle watcher, start one of them in
2565	the constructor.	2907	the constructor.
2566		2908
2567	class myclass	2909	class myclass
2568	{	2910	{
2569	ev::io io; void io_cb (ev::io &w, int revents);	2911	ev::io io ; void io_cb (ev::io &w, int revents);
2570	ev:idle idle void idle_cb (ev::idle &w, int revents);	2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2571		2913
2572	myclass (int fd)	2914	myclass (int fd)
2573	{	2915	{
2574	io .set <myclass, &myclass::io_cb > (this);	2916	io .set <myclass, &myclass::io_cb > (this);
2575	idle.set <myclass, &myclass::idle_cb> (this);	2917	idle.set <myclass, &myclass::idle_cb> (this);
2576		2918
2577	io.start (fd, ev::READ);	2919	io.start (fd, ev::READ);
2578	}	2920	}
2579	};	2921	};
2580		2922
2581		2923
2582	=head1 OTHER LANGUAGE BINDINGS	2924	=head1 OTHER LANGUAGE BINDINGS
2583		2925
2584	Libev does not offer other language bindings itself, but bindings for a	2926	Libev does not offer other language bindings itself, but bindings for a
2585	numbe rof languages exist in the form of third-party packages. If you know	2927	number of languages exist in the form of third-party packages. If you know
2586	any interesting language binding in addition to the ones listed here, drop	2928	any interesting language binding in addition to the ones listed here, drop
2587	me a note.	2929	me a note.
2588		2930
2589	=over 4	2931	=over 4
2590		2932
2591	=item Perl	2933	=item Perl
2592		2934
2593	The EV module implements the full libev API and is actually used to test	2935	The EV module implements the full libev API and is actually used to test
2594	libev. EV is developed together with libev. Apart from the EV core module,	2936	libev. EV is developed together with libev. Apart from the EV core module,
2595	there are additional modules that implement libev-compatible interfaces	2937	there are additional modules that implement libev-compatible interfaces
2596	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2938	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2597	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2939	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2940	and C<EV::Glib>).
2598		2941
2599	It can be found and installed via CPAN, its homepage is found at	2942	It can be found and installed via CPAN, its homepage is at
2600	L<http://software.schmorp.de/pkg/EV>.	2943	L<http://software.schmorp.de/pkg/EV>.
2601		2944
		2945	=item Python
		2946
		2947	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2948	seems to be quite complete and well-documented. Note, however, that the
		2949	patch they require for libev is outright dangerous as it breaks the ABI
		2950	for everybody else, and therefore, should never be applied in an installed
		2951	libev (if python requires an incompatible ABI then it needs to embed
		2952	libev).
		2953
2602	=item Ruby	2954	=item Ruby
2603		2955
2604	Tony Arcieri has written a ruby extension that offers access to a subset	2956	Tony Arcieri has written a ruby extension that offers access to a subset
2605	of the libev API and adds filehandle abstractions, asynchronous DNS and	2957	of the libev API and adds file handle abstractions, asynchronous DNS and
2606	more on top of it. It can be found via gem servers. Its homepage is at	2958	more on top of it. It can be found via gem servers. Its homepage is at
2607	L<http://rev.rubyforge.org/>.	2959	L<http://rev.rubyforge.org/>.
2608		2960
2609	=item D	2961	=item D
2610		2962
2611	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2612	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2965
		2966	=item Ocaml
		2967
		2968	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2613		2970
2614	=back	2971	=back
2615		2972
2616		2973
2617	=head1 MACRO MAGIC	2974	=head1 MACRO MAGIC
2618		2975
2619	Libev can be compiled with a variety of options, the most fundamantal	2976	Libev can be compiled with a variety of options, the most fundamental
2620	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2977	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2621	functions and callbacks have an initial C<struct ev_loop *> argument.	2978	functions and callbacks have an initial C<struct ev_loop *> argument.
2622		2979
2623	To make it easier to write programs that cope with either variant, the	2980	To make it easier to write programs that cope with either variant, the
2624	following macros are defined:	2981	following macros are defined:
…		…
2629		2986
2630	This provides the loop I<argument> for functions, if one is required ("ev	2987	This provides the loop I<argument> for functions, if one is required ("ev
2631	loop argument"). The C<EV_A> form is used when this is the sole argument,	2988	loop argument"). The C<EV_A> form is used when this is the sole argument,
2632	C<EV_A_> is used when other arguments are following. Example:	2989	C<EV_A_> is used when other arguments are following. Example:
2633		2990
2634	ev_unref (EV_A);	2991	ev_unref (EV_A);
2635	ev_timer_add (EV_A_ watcher);	2992	ev_timer_add (EV_A_ watcher);
2636	ev_loop (EV_A_ 0);	2993	ev_loop (EV_A_ 0);
2637		2994
2638	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2995	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2639	which is often provided by the following macro.	2996	which is often provided by the following macro.
2640		2997
2641	=item C<EV_P>, C<EV_P_>	2998	=item C<EV_P>, C<EV_P_>
2642		2999
2643	This provides the loop I<parameter> for functions, if one is required ("ev	3000	This provides the loop I<parameter> for functions, if one is required ("ev
2644	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3001	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2645	C<EV_P_> is used when other parameters are following. Example:	3002	C<EV_P_> is used when other parameters are following. Example:
2646		3003
2647	// this is how ev_unref is being declared	3004	// this is how ev_unref is being declared
2648	static void ev_unref (EV_P);	3005	static void ev_unref (EV_P);
2649		3006
2650	// this is how you can declare your typical callback	3007	// this is how you can declare your typical callback
2651	static void cb (EV_P_ ev_timer *w, int revents)	3008	static void cb (EV_P_ ev_timer *w, int revents)
2652		3009
2653	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3010	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2654	suitable for use with C<EV_A>.	3011	suitable for use with C<EV_A>.
2655		3012
2656	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3013	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2672		3029
2673	Example: Declare and initialise a check watcher, utilising the above	3030	Example: Declare and initialise a check watcher, utilising the above
2674	macros so it will work regardless of whether multiple loops are supported	3031	macros so it will work regardless of whether multiple loops are supported
2675	or not.	3032	or not.
2676		3033
2677	static void	3034	static void
2678	check_cb (EV_P_ ev_timer *w, int revents)	3035	check_cb (EV_P_ ev_timer *w, int revents)
2679	{	3036	{
2680	ev_check_stop (EV_A_ w);	3037	ev_check_stop (EV_A_ w);
2681	}	3038	}
2682		3039
2683	ev_check check;	3040	ev_check check;
2684	ev_check_init (&check, check_cb);	3041	ev_check_init (&check, check_cb);
2685	ev_check_start (EV_DEFAULT_ &check);	3042	ev_check_start (EV_DEFAULT_ &check);
2686	ev_loop (EV_DEFAULT_ 0);	3043	ev_loop (EV_DEFAULT_ 0);
2687		3044
2688	=head1 EMBEDDING	3045	=head1 EMBEDDING
2689		3046
2690	Libev can (and often is) directly embedded into host	3047	Libev can (and often is) directly embedded into host
2691	applications. Examples of applications that embed it include the Deliantra	3048	applications. Examples of applications that embed it include the Deliantra
…		…
2698	libev somewhere in your source tree).	3055	libev somewhere in your source tree).
2699		3056
2700	=head2 FILESETS	3057	=head2 FILESETS
2701		3058
2702	Depending on what features you need you need to include one or more sets of files	3059	Depending on what features you need you need to include one or more sets of files
2703	in your app.	3060	in your application.
2704		3061
2705	=head3 CORE EVENT LOOP	3062	=head3 CORE EVENT LOOP
2706		3063
2707	To include only the libev core (all the C<ev_*> functions), with manual	3064	To include only the libev core (all the C<ev_*> functions), with manual
2708	configuration (no autoconf):	3065	configuration (no autoconf):
2709		3066
2710	#define EV_STANDALONE 1	3067	#define EV_STANDALONE 1
2711	#include "ev.c"	3068	#include "ev.c"
2712		3069
2713	This will automatically include F<ev.h>, too, and should be done in a	3070	This will automatically include F<ev.h>, too, and should be done in a
2714	single C source file only to provide the function implementations. To use	3071	single C source file only to provide the function implementations. To use
2715	it, do the same for F<ev.h> in all files wishing to use this API (best	3072	it, do the same for F<ev.h> in all files wishing to use this API (best
2716	done by writing a wrapper around F<ev.h> that you can include instead and	3073	done by writing a wrapper around F<ev.h> that you can include instead and
2717	where you can put other configuration options):	3074	where you can put other configuration options):
2718		3075
2719	#define EV_STANDALONE 1	3076	#define EV_STANDALONE 1
2720	#include "ev.h"	3077	#include "ev.h"
2721		3078
2722	Both header files and implementation files can be compiled with a C++	3079	Both header files and implementation files can be compiled with a C++
2723	compiler (at least, thats a stated goal, and breakage will be treated	3080	compiler (at least, thats a stated goal, and breakage will be treated
2724	as a bug).	3081	as a bug).
2725		3082
2726	You need the following files in your source tree, or in a directory	3083	You need the following files in your source tree, or in a directory
2727	in your include path (e.g. in libev/ when using -Ilibev):	3084	in your include path (e.g. in libev/ when using -Ilibev):
2728		3085
2729	ev.h	3086	ev.h
2730	ev.c	3087	ev.c
2731	ev_vars.h	3088	ev_vars.h
2732	ev_wrap.h	3089	ev_wrap.h
2733		3090
2734	ev_win32.c required on win32 platforms only	3091	ev_win32.c required on win32 platforms only
2735		3092
2736	ev_select.c only when select backend is enabled (which is enabled by default)	3093	ev_select.c only when select backend is enabled (which is enabled by default)
2737	ev_poll.c only when poll backend is enabled (disabled by default)	3094	ev_poll.c only when poll backend is enabled (disabled by default)
2738	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3095	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2739	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3096	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2740	ev_port.c only when the solaris port backend is enabled (disabled by default)	3097	ev_port.c only when the solaris port backend is enabled (disabled by default)
2741		3098
2742	F<ev.c> includes the backend files directly when enabled, so you only need	3099	F<ev.c> includes the backend files directly when enabled, so you only need
2743	to compile this single file.	3100	to compile this single file.
2744		3101
2745	=head3 LIBEVENT COMPATIBILITY API	3102	=head3 LIBEVENT COMPATIBILITY API
2746		3103
2747	To include the libevent compatibility API, also include:	3104	To include the libevent compatibility API, also include:
2748		3105
2749	#include "event.c"	3106	#include "event.c"
2750		3107
2751	in the file including F<ev.c>, and:	3108	in the file including F<ev.c>, and:
2752		3109
2753	#include "event.h"	3110	#include "event.h"
2754		3111
2755	in the files that want to use the libevent API. This also includes F<ev.h>.	3112	in the files that want to use the libevent API. This also includes F<ev.h>.
2756		3113
2757	You need the following additional files for this:	3114	You need the following additional files for this:
2758		3115
2759	event.h	3116	event.h
2760	event.c	3117	event.c
2761		3118
2762	=head3 AUTOCONF SUPPORT	3119	=head3 AUTOCONF SUPPORT
2763		3120
2764	Instead of using C<EV_STANDALONE=1> and providing your config in	3121	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2765	whatever way you want, you can also C<m4_include([libev.m4])> in your	3122	whatever way you want, you can also C<m4_include([libev.m4])> in your
2766	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3123	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2767	include F<config.h> and configure itself accordingly.	3124	include F<config.h> and configure itself accordingly.
2768		3125
2769	For this of course you need the m4 file:	3126	For this of course you need the m4 file:
2770		3127
2771	libev.m4	3128	libev.m4
2772		3129
2773	=head2 PREPROCESSOR SYMBOLS/MACROS	3130	=head2 PREPROCESSOR SYMBOLS/MACROS
2774		3131
2775	Libev can be configured via a variety of preprocessor symbols you have to	3132	Libev can be configured via a variety of preprocessor symbols you have to
2776	define before including any of its files. The default in the absense of	3133	define before including any of its files. The default in the absence of
2777	autoconf is noted for every option.	3134	autoconf is documented for every option.
2778		3135
2779	=over 4	3136	=over 4
2780		3137
2781	=item EV_STANDALONE	3138	=item EV_STANDALONE
2782		3139
…		…
2787	F<event.h> that are not directly supported by the libev core alone.	3144	F<event.h> that are not directly supported by the libev core alone.
2788		3145
2789	=item EV_USE_MONOTONIC	3146	=item EV_USE_MONOTONIC
2790		3147
2791	If defined to be C<1>, libev will try to detect the availability of the	3148	If defined to be C<1>, libev will try to detect the availability of the
2792	monotonic clock option at both compiletime and runtime. Otherwise no use	3149	monotonic clock option at both compile time and runtime. Otherwise no use
2793	of the monotonic clock option will be attempted. If you enable this, you	3150	of the monotonic clock option will be attempted. If you enable this, you
2794	usually have to link against librt or something similar. Enabling it when	3151	usually have to link against librt or something similar. Enabling it when
2795	the functionality isn't available is safe, though, although you have	3152	the functionality isn't available is safe, though, although you have
2796	to make sure you link against any libraries where the C<clock_gettime>	3153	to make sure you link against any libraries where the C<clock_gettime>
2797	function is hiding in (often F<-lrt>).	3154	function is hiding in (often F<-lrt>).
2798		3155
2799	=item EV_USE_REALTIME	3156	=item EV_USE_REALTIME
2800		3157
2801	If defined to be C<1>, libev will try to detect the availability of the	3158	If defined to be C<1>, libev will try to detect the availability of the
2802	realtime clock option at compiletime (and assume its availability at	3159	real-time clock option at compile time (and assume its availability at
2803	runtime if successful). Otherwise no use of the realtime clock option will	3160	runtime if successful). Otherwise no use of the real-time clock option will
2804	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3161	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2805	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3162	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2806	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3163	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2807		3164
2808	=item EV_USE_NANOSLEEP	3165	=item EV_USE_NANOSLEEP
…		…
2819	2.7 or newer, otherwise disabled.	3176	2.7 or newer, otherwise disabled.
2820		3177
2821	=item EV_USE_SELECT	3178	=item EV_USE_SELECT
2822		3179
2823	If undefined or defined to be C<1>, libev will compile in support for the	3180	If undefined or defined to be C<1>, libev will compile in support for the
2824	C<select>(2) backend. No attempt at autodetection will be done: if no	3181	C<select>(2) backend. No attempt at auto-detection will be done: if no
2825	other method takes over, select will be it. Otherwise the select backend	3182	other method takes over, select will be it. Otherwise the select backend
2826	will not be compiled in.	3183	will not be compiled in.
2827		3184
2828	=item EV_SELECT_USE_FD_SET	3185	=item EV_SELECT_USE_FD_SET
2829		3186
2830	If defined to C<1>, then the select backend will use the system C<fd_set>	3187	If defined to C<1>, then the select backend will use the system C<fd_set>
2831	structure. This is useful if libev doesn't compile due to a missing	3188	structure. This is useful if libev doesn't compile due to a missing
2832	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3189	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2833	exotic systems. This usually limits the range of file descriptors to some	3190	exotic systems. This usually limits the range of file descriptors to some
2834	low limit such as 1024 or might have other limitations (winsocket only	3191	low limit such as 1024 or might have other limitations (winsocket only
2835	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3192	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2836	influence the size of the C<fd_set> used.	3193	influence the size of the C<fd_set> used.
2837		3194
…		…
2886	otherwise another method will be used as fallback. This is the preferred	3243	otherwise another method will be used as fallback. This is the preferred
2887	backend for Solaris 10 systems.	3244	backend for Solaris 10 systems.
2888		3245
2889	=item EV_USE_DEVPOLL	3246	=item EV_USE_DEVPOLL
2890		3247
2891	reserved for future expansion, works like the USE symbols above.	3248	Reserved for future expansion, works like the USE symbols above.
2892		3249
2893	=item EV_USE_INOTIFY	3250	=item EV_USE_INOTIFY
2894		3251
2895	If defined to be C<1>, libev will compile in support for the Linux inotify	3252	If defined to be C<1>, libev will compile in support for the Linux inotify
2896	interface to speed up C<ev_stat> watchers. Its actual availability will	3253	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2903	access is atomic with respect to other threads or signal contexts. No such	3260	access is atomic with respect to other threads or signal contexts. No such
2904	type is easily found in the C language, so you can provide your own type	3261	type is easily found in the C language, so you can provide your own type
2905	that you know is safe for your purposes. It is used both for signal handler "locking"	3262	that you know is safe for your purposes. It is used both for signal handler "locking"
2906	as well as for signal and thread safety in C<ev_async> watchers.	3263	as well as for signal and thread safety in C<ev_async> watchers.
2907		3264
2908	In the absense of this define, libev will use C<sig_atomic_t volatile>	3265	In the absence of this define, libev will use C<sig_atomic_t volatile>
2909	(from F<signal.h>), which is usually good enough on most platforms.	3266	(from F<signal.h>), which is usually good enough on most platforms.
2910		3267
2911	=item EV_H	3268	=item EV_H
2912		3269
2913	The name of the F<ev.h> header file used to include it. The default if	3270	The name of the F<ev.h> header file used to include it. The default if
…		…
2952	When doing priority-based operations, libev usually has to linearly search	3309	When doing priority-based operations, libev usually has to linearly search
2953	all the priorities, so having many of them (hundreds) uses a lot of space	3310	all the priorities, so having many of them (hundreds) uses a lot of space
2954	and time, so using the defaults of five priorities (-2 .. +2) is usually	3311	and time, so using the defaults of five priorities (-2 .. +2) is usually
2955	fine.	3312	fine.
2956		3313
2957	If your embedding app does not need any priorities, defining these both to	3314	If your embedding application does not need any priorities, defining these
2958	C<0> will save some memory and cpu.	3315	both to C<0> will save some memory and CPU.
2959		3316
2960	=item EV_PERIODIC_ENABLE	3317	=item EV_PERIODIC_ENABLE
2961		3318
2962	If undefined or defined to be C<1>, then periodic timers are supported. If	3319	If undefined or defined to be C<1>, then periodic timers are supported. If
2963	defined to be C<0>, then they are not. Disabling them saves a few kB of	3320	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2970	code.	3327	code.
2971		3328
2972	=item EV_EMBED_ENABLE	3329	=item EV_EMBED_ENABLE
2973		3330
2974	If undefined or defined to be C<1>, then embed watchers are supported. If	3331	If undefined or defined to be C<1>, then embed watchers are supported. If
2975	defined to be C<0>, then they are not.	3332	defined to be C<0>, then they are not. Embed watchers rely on most other
		3333	watcher types, which therefore must not be disabled.
2976		3334
2977	=item EV_STAT_ENABLE	3335	=item EV_STAT_ENABLE
2978		3336
2979	If undefined or defined to be C<1>, then stat watchers are supported. If	3337	If undefined or defined to be C<1>, then stat watchers are supported. If
2980	defined to be C<0>, then they are not.	3338	defined to be C<0>, then they are not.
…		…
2991		3349
2992	=item EV_MINIMAL	3350	=item EV_MINIMAL
2993		3351
2994	If you need to shave off some kilobytes of code at the expense of some	3352	If you need to shave off some kilobytes of code at the expense of some
2995	speed, define this symbol to C<1>. Currently this is used to override some	3353	speed, define this symbol to C<1>. Currently this is used to override some
2996	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3354	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2997	much smaller 2-heap for timer management over the default 4-heap.	3355	much smaller 2-heap for timer management over the default 4-heap.
2998		3356
2999	=item EV_PID_HASHSIZE	3357	=item EV_PID_HASHSIZE
3000		3358
3001	C<ev_child> watchers use a small hash table to distribute workload by	3359	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3012	two).	3370	two).
3013		3371
3014	=item EV_USE_4HEAP	3372	=item EV_USE_4HEAP
3015		3373
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3018	to C<1>. The 4-heap uses more complicated (longer) code but has	3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3019	noticably faster performance with many (thousands) of watchers.	3377	faster performance with many (thousands) of watchers.
3020		3378
3021	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3022	(disabled).	3380	(disabled).
3023		3381
3024	=item EV_HEAP_CACHE_AT	3382	=item EV_HEAP_CACHE_AT
3025		3383
3026	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3027	timer and periodics heap, libev can cache the timestamp (I<at>) within	3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3028	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3029	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3030	but avoids random read accesses on heap changes. This improves performance	3388	but avoids random read accesses on heap changes. This improves performance
3031	noticably with with many (hundreds) of watchers.	3389	noticeably with many (hundreds) of watchers.
3032		3390
3033	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3034	(disabled).	3392	(disabled).
		3393
		3394	=item EV_VERIFY
		3395
		3396	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3397	be done: If set to C<0>, no internal verification code will be compiled
		3398	in. If set to C<1>, then verification code will be compiled in, but not
		3399	called. If set to C<2>, then the internal verification code will be
		3400	called once per loop, which can slow down libev. If set to C<3>, then the
		3401	verification code will be called very frequently, which will slow down
		3402	libev considerably.
		3403
		3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3405	C<0>.
3035		3406
3036	=item EV_COMMON	3407	=item EV_COMMON
3037		3408
3038	By default, all watchers have a C<void *data> member. By redefining	3409	By default, all watchers have a C<void *data> member. By redefining
3039	this macro to a something else you can include more and other types of	3410	this macro to a something else you can include more and other types of
3040	members. You have to define it each time you include one of the files,	3411	members. You have to define it each time you include one of the files,
3041	though, and it must be identical each time.	3412	though, and it must be identical each time.
3042		3413
3043	For example, the perl EV module uses something like this:	3414	For example, the perl EV module uses something like this:
3044		3415
3045	#define EV_COMMON \	3416	#define EV_COMMON \
3046	SV *self; /* contains this struct */ \	3417	SV *self; /* contains this struct */ \
3047	SV *cb_sv, *fh /* note no trailing ";" */	3418	SV *cb_sv, *fh /* note no trailing ";" */
3048		3419
3049	=item EV_CB_DECLARE (type)	3420	=item EV_CB_DECLARE (type)
3050		3421
3051	=item EV_CB_INVOKE (watcher, revents)	3422	=item EV_CB_INVOKE (watcher, revents)
3052		3423
…		…
3057	definition and a statement, respectively. See the F<ev.h> header file for	3428	definition and a statement, respectively. See the F<ev.h> header file for
3058	their default definitions. One possible use for overriding these is to	3429	their default definitions. One possible use for overriding these is to
3059	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3430	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3060	method calls instead of plain function calls in C++.	3431	method calls instead of plain function calls in C++.
3061		3432
		3433	=back
		3434
3062	=head2 EXPORTED API SYMBOLS	3435	=head2 EXPORTED API SYMBOLS
3063		3436
3064	If you need to re-export the API (e.g. via a dll) and you need a list of	3437	If you need to re-export the API (e.g. via a DLL) and you need a list of
3065	exported symbols, you can use the provided F<Symbol.*> files which list	3438	exported symbols, you can use the provided F<Symbol.*> files which list
3066	all public symbols, one per line:	3439	all public symbols, one per line:
3067		3440
3068	Symbols.ev for libev proper	3441	Symbols.ev for libev proper
3069	Symbols.event for the libevent emulation	3442	Symbols.event for the libevent emulation
3070		3443
3071	This can also be used to rename all public symbols to avoid clashes with	3444	This can also be used to rename all public symbols to avoid clashes with
3072	multiple versions of libev linked together (which is obviously bad in	3445	multiple versions of libev linked together (which is obviously bad in
3073	itself, but sometimes it is inconvinient to avoid this).	3446	itself, but sometimes it is inconvenient to avoid this).
3074		3447
3075	A sed command like this will create wrapper C<#define>'s that you need to	3448	A sed command like this will create wrapper C<#define>'s that you need to
3076	include before including F<ev.h>:	3449	include before including F<ev.h>:
3077		3450
3078	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3451	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3095	file.	3468	file.
3096		3469
3097	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3470	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3098	that everybody includes and which overrides some configure choices:	3471	that everybody includes and which overrides some configure choices:
3099		3472
3100	#define EV_MINIMAL 1	3473	#define EV_MINIMAL 1
3101	#define EV_USE_POLL 0	3474	#define EV_USE_POLL 0
3102	#define EV_MULTIPLICITY 0	3475	#define EV_MULTIPLICITY 0
3103	#define EV_PERIODIC_ENABLE 0	3476	#define EV_PERIODIC_ENABLE 0
3104	#define EV_STAT_ENABLE 0	3477	#define EV_STAT_ENABLE 0
3105	#define EV_FORK_ENABLE 0	3478	#define EV_FORK_ENABLE 0
3106	#define EV_CONFIG_H <config.h>	3479	#define EV_CONFIG_H <config.h>
3107	#define EV_MINPRI 0	3480	#define EV_MINPRI 0
3108	#define EV_MAXPRI 0	3481	#define EV_MAXPRI 0
3109		3482
3110	#include "ev++.h"	3483	#include "ev++.h"
3111		3484
3112	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3113		3486
3114	#include "ev_cpp.h"	3487	#include "ev_cpp.h"
3115	#include "ev.c"	3488	#include "ev.c"
3116		3489
		3490	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3117		3491
3118	=head1 THREADS AND COROUTINES	3492	=head2 THREADS AND COROUTINES
3119		3493
3120	=head2 THREADS	3494	=head3 THREADS
3121		3495
3122	Libev itself is completely threadsafe, but it uses no locking. This	3496	All libev functions are reentrant and thread-safe unless explicitly
		3497	documented otherwise, but libev implements no locking itself. This means
3123	means that you can use as many loops as you want in parallel, as long as	3498	that you can use as many loops as you want in parallel, as long as there
3124	only one thread ever calls into one libev function with the same loop	3499	are no concurrent calls into any libev function with the same loop
3125	parameter.	3500	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3501	of course): libev guarantees that different event loops share no data
		3502	structures that need any locking.
3126		3503
3127	Or put differently: calls with different loop parameters can be done in	3504	Or to put it differently: calls with different loop parameters can be done
3128	parallel from multiple threads, calls with the same loop parameter must be	3505	concurrently from multiple threads, calls with the same loop parameter
3129	done serially (but can be done from different threads, as long as only one	3506	must be done serially (but can be done from different threads, as long as
3130	thread ever is inside a call at any point in time, e.g. by using a mutex	3507	only one thread ever is inside a call at any point in time, e.g. by using
3131	per loop).	3508	a mutex per loop).
3132		3509
3133	If you want to know which design is best for your problem, then I cannot	3510	Specifically to support threads (and signal handlers), libev implements
		3511	so-called C<ev_async> watchers, which allow some limited form of
		3512	concurrency on the same event loop, namely waking it up "from the
		3513	outside".
		3514
		3515	If you want to know which design (one loop, locking, or multiple loops
		3516	without or something else still) is best for your problem, then I cannot
3134	help you but by giving some generic advice:	3517	help you, but here is some generic advice:
3135		3518
3136	=over 4	3519	=over 4
3137		3520
3138	=item * most applications have a main thread: use the default libev loop	3521	=item * most applications have a main thread: use the default libev loop
3139	in that thread, or create a seperate thread running only the default loop.	3522	in that thread, or create a separate thread running only the default loop.
3140		3523
3141	This helps integrating other libraries or software modules that use libev	3524	This helps integrating other libraries or software modules that use libev
3142	themselves and don't care/know about threading.	3525	themselves and don't care/know about threading.
3143		3526
3144	=item * one loop per thread is usually a good model.	3527	=item * one loop per thread is usually a good model.
3145		3528
3146	Doing this is almost never wrong, sometimes a better-performance model	3529	Doing this is almost never wrong, sometimes a better-performance model
3147	exists, but it is always a good start.	3530	exists, but it is always a good start.
3148		3531
3149	=item * other models exist, such as the leader/follower pattern, where one	3532	=item * other models exist, such as the leader/follower pattern, where one
3150	loop is handed through multiple threads in a kind of round-robbin fashion.	3533	loop is handed through multiple threads in a kind of round-robin fashion.
3151		3534
3152	Chosing a model is hard - look around, learn, know that usually you cna do	3535	Choosing a model is hard - look around, learn, know that usually you can do
3153	better than you currently do :-)	3536	better than you currently do :-)
3154		3537
3155	=item * often you need to talk to some other thread which blocks in the	3538	=item * often you need to talk to some other thread which blocks in the
		3539	event loop.
		3540
3156	event loop - C<ev_async> watchers can be used to wake them up from other	3541	C<ev_async> watchers can be used to wake them up from other threads safely
3157	threads safely (or from signal contexts...).	3542	(or from signal contexts...).
		3543
		3544	An example use would be to communicate signals or other events that only
		3545	work in the default loop by registering the signal watcher with the
		3546	default loop and triggering an C<ev_async> watcher from the default loop
		3547	watcher callback into the event loop interested in the signal.
3158		3548
3159	=back	3549	=back
3160		3550
3161	=head2 COROUTINES	3551	=head3 COROUTINES
3162		3552
3163	Libev is much more accomodating to coroutines ("cooperative threads"):	3553	Libev is very accommodating to coroutines ("cooperative threads"):
3164	libev fully supports nesting calls to it's functions from different	3554	libev fully supports nesting calls to its functions from different
3165	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3166	different coroutines and switch freely between both coroutines running the	3556	different coroutines, and switch freely between both coroutines running the
3167	loop, as long as you don't confuse yourself). The only exception is that	3557	loop, as long as you don't confuse yourself). The only exception is that
3168	you must not do this from C<ev_periodic> reschedule callbacks.	3558	you must not do this from C<ev_periodic> reschedule callbacks.
3169		3559
3170	Care has been invested into making sure that libev does not keep local	3560	Care has been taken to ensure that libev does not keep local state inside
3171	state inside C<ev_loop>, and other calls do not usually allow coroutine	3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3172	switches.	3562	they do not clal any callbacks.
3173		3563
		3564	=head2 COMPILER WARNINGS
3174		3565
3175	=head1 COMPLEXITIES	3566	Depending on your compiler and compiler settings, you might get no or a
		3567	lot of warnings when compiling libev code. Some people are apparently
		3568	scared by this.
3176		3569
3177	In this section the complexities of (many of) the algorithms used inside	3570	However, these are unavoidable for many reasons. For one, each compiler
3178	libev will be explained. For complexity discussions about backends see the	3571	has different warnings, and each user has different tastes regarding
3179	documentation for C<ev_default_init>.	3572	warning options. "Warn-free" code therefore cannot be a goal except when
		3573	targeting a specific compiler and compiler-version.
3180		3574
3181	All of the following are about amortised time: If an array needs to be	3575	Another reason is that some compiler warnings require elaborate
3182	extended, libev needs to realloc and move the whole array, but this	3576	workarounds, or other changes to the code that make it less clear and less
3183	happens asymptotically never with higher number of elements, so O(1) might	3577	maintainable.
3184	mean it might do a lengthy realloc operation in rare cases, but on average
3185	it is much faster and asymptotically approaches constant time.
3186		3578
3187	=over 4	3579	And of course, some compiler warnings are just plain stupid, or simply
		3580	wrong (because they don't actually warn about the condition their message
		3581	seems to warn about). For example, certain older gcc versions had some
		3582	warnings that resulted an extreme number of false positives. These have
		3583	been fixed, but some people still insist on making code warn-free with
		3584	such buggy versions.
3188		3585
3189	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3586	While libev is written to generate as few warnings as possible,
		3587	"warn-free" code is not a goal, and it is recommended not to build libev
		3588	with any compiler warnings enabled unless you are prepared to cope with
		3589	them (e.g. by ignoring them). Remember that warnings are just that:
		3590	warnings, not errors, or proof of bugs.
3190		3591
3191	This means that, when you have a watcher that triggers in one hour and
3192	there are 100 watchers that would trigger before that then inserting will
3193	have to skip roughly seven (C<ld 100>) of these watchers.
3194		3592
3195	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3593	=head2 VALGRIND
3196		3594
3197	That means that changing a timer costs less than removing/adding them	3595	Valgrind has a special section here because it is a popular tool that is
3198	as only the relative motion in the event queue has to be paid for.	3596	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3199		3597
3200	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3598	If you think you found a bug (memory leak, uninitialised data access etc.)
		3599	in libev, then check twice: If valgrind reports something like:
3201		3600
3202	These just add the watcher into an array or at the head of a list.	3601	==2274== definitely lost: 0 bytes in 0 blocks.
		3602	==2274== possibly lost: 0 bytes in 0 blocks.
		3603	==2274== still reachable: 256 bytes in 1 blocks.
3203		3604
3204	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3605	Then there is no memory leak, just as memory accounted to global variables
		3606	is not a memleak - the memory is still being refernced, and didn't leak.
3205		3607
3206	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3608	Similarly, under some circumstances, valgrind might report kernel bugs
		3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3610	although an acceptable workaround has been found here), or it might be
		3611	confused.
3207		3612
3208	These watchers are stored in lists then need to be walked to find the	3613	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3209	correct watcher to remove. The lists are usually short (you don't usually	3614	make it into some kind of religion.
3210	have many watchers waiting for the same fd or signal).
3211		3615
3212	=item Finding the next timer in each loop iteration: O(1)	3616	If you are unsure about something, feel free to contact the mailing list
		3617	with the full valgrind report and an explanation on why you think this
		3618	is a bug in libev (best check the archives, too :). However, don't be
		3619	annoyed when you get a brisk "this is no bug" answer and take the chance
		3620	of learning how to interpret valgrind properly.
3213		3621
3214	By virtue of using a binary or 4-heap, the next timer is always found at a	3622	If you need, for some reason, empty reports from valgrind for your project
3215	fixed position in the storage array.	3623	I suggest using suppression lists.
3216		3624
3217	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3218		3625
3219	A change means an I/O watcher gets started or stopped, which requires	3626	=head1 PORTABILITY NOTES
3220	libev to recalculate its status (and possibly tell the kernel, depending
3221	on backend and wether C<ev_io_set> was used).
3222		3627
3223	=item Activating one watcher (putting it into the pending state): O(1)	3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3224
3225	=item Priority handling: O(number_of_priorities)
3226
3227	Priorities are implemented by allocating some space for each
3228	priority. When doing priority-based operations, libev usually has to
3229	linearly search all the priorities, but starting/stopping and activating
3230	watchers becomes O(1) w.r.t. priority handling.
3231
3232	=item Sending an ev_async: O(1)
3233
3234	=item Processing ev_async_send: O(number_of_async_watchers)
3235
3236	=item Processing signals: O(max_signal_number)
3237
3238	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3239	calls in the current loop iteration. Checking for async and signal events
3240	involves iterating over all running async watchers or all signal numbers.
3241
3242	=back
3243
3244
3245	=head1 Win32 platform limitations and workarounds
3246		3629
3247	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3248	requires, and its I/O model is fundamentally incompatible with the POSIX	3631	requires, and its I/O model is fundamentally incompatible with the POSIX
3249	model. Libev still offers limited functionality on this platform in	3632	model. Libev still offers limited functionality on this platform in
3250	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3257	way (note also that glib is the slowest event library known to man).	3640	way (note also that glib is the slowest event library known to man).
3258		3641
3259	There is no supported compilation method available on windows except	3642	There is no supported compilation method available on windows except
3260	embedding it into other applications.	3643	embedding it into other applications.
3261		3644
		3645	Not a libev limitation but worth mentioning: windows apparently doesn't
		3646	accept large writes: instead of resulting in a partial write, windows will
		3647	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3648	so make sure you only write small amounts into your sockets (less than a
		3649	megabyte seems safe, but this apparently depends on the amount of memory
		3650	available).
		3651
3262	Due to the many, low, and arbitrary limits on the win32 platform and	3652	Due to the many, low, and arbitrary limits on the win32 platform and
3263	the abysmal performance of winsockets, using a large number of sockets	3653	the abysmal performance of winsockets, using a large number of sockets
3264	is not recommended (and not reasonable). If your program needs to use	3654	is not recommended (and not reasonable). If your program needs to use
3265	more than a hundred or so sockets, then likely it needs to use a totally	3655	more than a hundred or so sockets, then likely it needs to use a totally
3266	different implementation for windows, as libev offers the POSIX readiness	3656	different implementation for windows, as libev offers the POSIX readiness
3267	notification model, which cannot be implemented efficiently on windows	3657	notification model, which cannot be implemented efficiently on windows
3268	(microsoft monopoly games).	3658	(Microsoft monopoly games).
		3659
		3660	A typical way to use libev under windows is to embed it (see the embedding
		3661	section for details) and use the following F<evwrap.h> header file instead
		3662	of F<ev.h>:
		3663
		3664	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3665	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3666
		3667	#include "ev.h"
		3668
		3669	And compile the following F<evwrap.c> file into your project (make sure
		3670	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3671
		3672	#include "evwrap.h"
		3673	#include "ev.c"
3269		3674
3270	=over 4	3675	=over 4
3271		3676
3272	=item The winsocket select function	3677	=item The winsocket select function
3273		3678
3274	The winsocket C<select> function doesn't follow POSIX in that it requires	3679	The winsocket C<select> function doesn't follow POSIX in that it
3275	socket I<handles> and not socket I<file descriptors>. This makes select	3680	requires socket I<handles> and not socket I<file descriptors> (it is
3276	very inefficient, and also requires a mapping from file descriptors	3681	also extremely buggy). This makes select very inefficient, and also
3277	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3682	requires a mapping from file descriptors to socket handles (the Microsoft
3278	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3683	C runtime provides the function C<_open_osfhandle> for this). See the
3279	symbols for more info.	3684	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3685	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3280		3686
3281	The configuration for a "naked" win32 using the microsoft runtime	3687	The configuration for a "naked" win32 using the Microsoft runtime
3282	libraries and raw winsocket select is:	3688	libraries and raw winsocket select is:
3283		3689
3284	#define EV_USE_SELECT 1	3690	#define EV_USE_SELECT 1
3285	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3691	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3286		3692
3287	Note that winsockets handling of fd sets is O(n), so you can easily get a	3693	Note that winsockets handling of fd sets is O(n), so you can easily get a
3288	complexity in the O(n²) range when using win32.	3694	complexity in the O(n²) range when using win32.
3289		3695
3290	=item Limited number of file descriptors	3696	=item Limited number of file descriptors
3291		3697
3292	Windows has numerous arbitrary (and low) limits on things.	3698	Windows has numerous arbitrary (and low) limits on things.
3293		3699
3294	Early versions of winsocket's select only supported waiting for a maximum	3700	Early versions of winsocket's select only supported waiting for a maximum
3295	of C<64> handles (probably owning to the fact that all windows kernels	3701	of C<64> handles (probably owning to the fact that all windows kernels
3296	can only wait for C<64> things at the same time internally; microsoft	3702	can only wait for C<64> things at the same time internally; Microsoft
3297	recommends spawning a chain of threads and wait for 63 handles and the	3703	recommends spawning a chain of threads and wait for 63 handles and the
3298	previous thread in each. Great).	3704	previous thread in each. Great).
3299		3705
3300	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3706	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3301	to some high number (e.g. C<2048>) before compiling the winsocket select	3707	to some high number (e.g. C<2048>) before compiling the winsocket select
3302	call (which might be in libev or elsewhere, for example, perl does its own	3708	call (which might be in libev or elsewhere, for example, perl does its own
3303	select emulation on windows).	3709	select emulation on windows).
3304		3710
3305	Another limit is the number of file descriptors in the microsoft runtime	3711	Another limit is the number of file descriptors in the Microsoft runtime
3306	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3712	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3307	or something like this inside microsoft). You can increase this by calling	3713	or something like this inside Microsoft). You can increase this by calling
3308	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3714	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3309	arbitrary limit), but is broken in many versions of the microsoft runtime	3715	arbitrary limit), but is broken in many versions of the Microsoft runtime
3310	libraries.	3716	libraries.
3311		3717
3312	This might get you to about C<512> or C<2048> sockets (depending on	3718	This might get you to about C<512> or C<2048> sockets (depending on
3313	windows version and/or the phase of the moon). To get more, you need to	3719	windows version and/or the phase of the moon). To get more, you need to
3314	wrap all I/O functions and provide your own fd management, but the cost of	3720	wrap all I/O functions and provide your own fd management, but the cost of
3315	calling select (O(n²)) will likely make this unworkable.	3721	calling select (O(n²)) will likely make this unworkable.
3316		3722
3317	=back	3723	=back
3318		3724
3319
3320	=head1 PORTABILITY REQUIREMENTS	3725	=head2 PORTABILITY REQUIREMENTS
3321		3726
3322	In addition to a working ISO-C implementation, libev relies on a few	3727	In addition to a working ISO-C implementation and of course the
3323	additional extensions:	3728	backend-specific APIs, libev relies on a few additional extensions:
3324		3729
3325	=over 4	3730	=over 4
3326		3731
		3732	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3733	calling conventions regardless of C<ev_watcher_type *>.
		3734
		3735	Libev assumes not only that all watcher pointers have the same internal
		3736	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3737	assumes that the same (machine) code can be used to call any watcher
		3738	callback: The watcher callbacks have different type signatures, but libev
		3739	calls them using an C<ev_watcher *> internally.
		3740
3327	=item C<sig_atomic_t volatile> must be thread-atomic as well	3741	=item C<sig_atomic_t volatile> must be thread-atomic as well
3328		3742
3329	The type C<sig_atomic_t volatile> (or whatever is defined as	3743	The type C<sig_atomic_t volatile> (or whatever is defined as
3330	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3331	threads. This is not part of the specification for C<sig_atomic_t>, but is	3745	threads. This is not part of the specification for C<sig_atomic_t>, but is
3332	believed to be sufficiently portable.	3746	believed to be sufficiently portable.
3333		3747
3334	=item C<sigprocmask> must work in a threaded environment	3748	=item C<sigprocmask> must work in a threaded environment
3335		3749
…		…
3344	except the initial one, and run the default loop in the initial thread as	3758	except the initial one, and run the default loop in the initial thread as
3345	well.	3759	well.
3346		3760
3347	=item C<long> must be large enough for common memory allocation sizes	3761	=item C<long> must be large enough for common memory allocation sizes
3348		3762
3349	To improve portability and simplify using libev, libev uses C<long>	3763	To improve portability and simplify its API, libev uses C<long> internally
3350	internally instead of C<size_t> when allocating its data structures. On	3764	instead of C<size_t> when allocating its data structures. On non-POSIX
3351	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3765	systems (Microsoft...) this might be unexpectedly low, but is still at
3352	is still at least 31 bits everywhere, which is enough for hundreds of	3766	least 31 bits everywhere, which is enough for hundreds of millions of
3353	millions of watchers.	3767	watchers.
3354		3768
3355	=item C<double> must hold a time value in seconds with enough accuracy	3769	=item C<double> must hold a time value in seconds with enough accuracy
3356		3770
3357	The type C<double> is used to represent timestamps. It is required to	3771	The type C<double> is used to represent timestamps. It is required to
3358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3362	=back	3776	=back
3363		3777
3364	If you know of other additional requirements drop me a note.	3778	If you know of other additional requirements drop me a note.
3365		3779
3366		3780
3367	=head1 VALGRIND	3781	=head1 ALGORITHMIC COMPLEXITIES
3368		3782
3369	Valgrind has a special section here because it is a popular tool that is	3783	In this section the complexities of (many of) the algorithms used inside
3370	highly useful, but valgrind reports are very hard to interpret.	3784	libev will be documented. For complexity discussions about backends see
		3785	the documentation for C<ev_default_init>.
3371		3786
3372	If you think you found a bug (memory leak, uninitialised data access etc.)	3787	All of the following are about amortised time: If an array needs to be
3373	in libev, then check twice: If valgrind reports something like:	3788	extended, libev needs to realloc and move the whole array, but this
		3789	happens asymptotically rarer with higher number of elements, so O(1) might
		3790	mean that libev does a lengthy realloc operation in rare cases, but on
		3791	average it is much faster and asymptotically approaches constant time.
3374		3792
3375	==2274== definitely lost: 0 bytes in 0 blocks.	3793	=over 4
3376	==2274== possibly lost: 0 bytes in 0 blocks.
3377	==2274== still reachable: 256 bytes in 1 blocks.
3378		3794
3379	then there is no memory leak. Similarly, under some circumstances,	3795	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3380	valgrind might report kernel bugs as if it were a bug in libev, or it
3381	might be confused (it is a very good tool, but only a tool).
3382		3796
3383	If you are unsure about something, feel free to contact the mailing list	3797	This means that, when you have a watcher that triggers in one hour and
3384	with the full valgrind report and an explanation on why you think this is	3798	there are 100 watchers that would trigger before that, then inserting will
3385	a bug in libev. However, don't be annoyed when you get a brisk "this is	3799	have to skip roughly seven (C<ld 100>) of these watchers.
3386	no bug" answer and take the chance of learning how to interpret valgrind
3387	properly.
3388		3800
3389	If you need, for some reason, empty reports from valgrind for your project	3801	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3390	I suggest using suppression lists.	3802
		3803	That means that changing a timer costs less than removing/adding them,
		3804	as only the relative motion in the event queue has to be paid for.
		3805
		3806	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3807
		3808	These just add the watcher into an array or at the head of a list.
		3809
		3810	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3811
		3812	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3813
		3814	These watchers are stored in lists, so they need to be walked to find the
		3815	correct watcher to remove. The lists are usually short (you don't usually
		3816	have many watchers waiting for the same fd or signal: one is typical, two
		3817	is rare).
		3818
		3819	=item Finding the next timer in each loop iteration: O(1)
		3820
		3821	By virtue of using a binary or 4-heap, the next timer is always found at a
		3822	fixed position in the storage array.
		3823
		3824	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3825
		3826	A change means an I/O watcher gets started or stopped, which requires
		3827	libev to recalculate its status (and possibly tell the kernel, depending
		3828	on backend and whether C<ev_io_set> was used).
		3829
		3830	=item Activating one watcher (putting it into the pending state): O(1)
		3831
		3832	=item Priority handling: O(number_of_priorities)
		3833
		3834	Priorities are implemented by allocating some space for each
		3835	priority. When doing priority-based operations, libev usually has to
		3836	linearly search all the priorities, but starting/stopping and activating
		3837	watchers becomes O(1) with respect to priority handling.
		3838
		3839	=item Sending an ev_async: O(1)
		3840
		3841	=item Processing ev_async_send: O(number_of_async_watchers)
		3842
		3843	=item Processing signals: O(max_signal_number)
		3844
		3845	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3846	calls in the current loop iteration. Checking for async and signal events
		3847	involves iterating over all running async watchers or all signal numbers.
		3848
		3849	=back
3391		3850
3392		3851
3393	=head1 AUTHOR	3852	=head1 AUTHOR
3394		3853
3395	Marc Lehmann <libev@schmorp.de>.	3854	Marc Lehmann <libev@schmorp.de>.

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