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Revision 1.247 by root, Wed Jul 8 02:46:05 2009 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	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	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	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	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	121	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	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	132	on 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	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
		135
		136	=head1 ERROR HANDLING
		137
		138	Libev knows three classes of errors: operating system errors, usage errors
		139	and internal errors (bugs).
		140
		141	When libev catches an operating system error it cannot handle (for example
		142	a system call indicating a condition libev cannot fix), it calls the callback
		143	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		144	abort. The default is to print a diagnostic message and to call C<abort
		145	()>.
		146
		147	When libev detects a usage error such as a negative timer interval, then
		148	it will print a diagnostic message and abort (via the C<assert> mechanism,
		149	so C<NDEBUG> will disable this checking): these are programming errors in
		150	the libev caller and need to be fixed there.
		151
		152	Libev also has a few internal error-checking C<assert>ions, and also has
		153	extensive consistency checking code. These do not trigger under normal
		154	circumstances, as they indicate either a bug in libev or worse.
		155
121		156
122	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
123		158
124	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
125	library in any way.	160	library in any way.
…		…
134		169
135	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
136		171
137	Sleep for the given interval: The current thread will be blocked until	172	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	173	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
140		175
141	=item int ev_version_major ()	176	=item int ev_version_major ()
142		177
143	=item int ev_version_minor ()	178	=item int ev_version_minor ()
144		179
…		…
157	not a problem.	192	not a problem.
158		193
159	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	195	version.
161		196
162	assert (("libev version mismatch",	197	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
165		200
166	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
167		202
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	206	a description of the set values.
172		207
173	Example: make sure we have the epoll method, because yeah this is cool and	208	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	209	a must have and can we have a torrent of it please!!!11
175		210
176	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
178		213
179	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
180		215
181	Return the set of all backends compiled into this binary of libev and also	216	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	217	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	218	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	219	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	220	(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.	221	libev will probe for if you specify no backends explicitly.
187		222
188	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
189		224
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	229	recommended ones.
195		230
196	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
197		232
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		234
200	Sets the allocation function to use (the prototype is similar - the	235	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	236	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	237	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	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	264	}
230		265
231	...	266	...
232	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
233		268
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		270
236	Set the callback function to call on a retryable syscall error (such	271	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	272	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	273	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	274	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	275	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	276	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	277	(such as abort).
243		278
244	Example: This is basically the same thing that libev does internally, too.	279	Example: This is basically the same thing that libev does internally, too.
…		…
255		290
256	=back	291	=back
257		292
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		294
260	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
263		302
264	=over 4	303	=over 4
265		304
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		306
…		…
273	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
274	function.	313	function.
275		314
276	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
279		318
280	The default loop is the only loop that can handle C<ev_signal> and	319	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	320	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	321	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	322	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	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	324	C<ev_default_init>.
286		325
287	The flags argument can be used to specify special behaviour or specific	326	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	335	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	336	thing, believe me).
298		337
299	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
300		339
301	If this flag bit is ored into the flag value (or the program runs setuid	340	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	341	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	343	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	344	useful to try out specific backends to test their performance, or to work
306	around bugs.	345	around bugs.
…		…
313		352
314	This works by calling C<getpid ()> on every iteration of the loop,	353	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	354	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	355	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	356	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	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
320		359
321	The big advantage of this flag is that you can forget about fork (and	360	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	361	forget about forgetting to tell libev about forking) when you use this
323	flag.	362	flag.
324		363
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	365	environment variable.
327		366
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		368
330	This is your standard select(2) backend. Not I<completely> standard, as	369	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	371	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	372	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.	373	usually the fastest backend for a low number of (low-numbered :) fds.
335		374
336	To get good performance out of this backend you need a high amount of	375	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	376	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	377	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	378	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	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	380	readiness notifications you get per iteration.
		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
342		385
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		387
345	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	389	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	390	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,	391	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	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	393	performance tips.
351		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		399
354	For few fds, this backend is a bit little slower than poll and select,	400	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	401	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),	402	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	403	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	404
359	cases and requiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
361		421
362	While stopping, setting and starting an I/O watcher in the same iteration	422	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	423	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
367		427	file descriptors.
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		428
372	Best performance from this backend is achieved by not unregistering all	429	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.	430	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
375		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
		440
376	While nominally embeddeble in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
378		446
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		448
381	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	457	system like NetBSD.
388		458
389	You still can embed kqueue into a normal poll or select backend and use it	459	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	460	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.	461	the target platform). See C<ev_embed> watchers for more info.
392		462
393	It scales in the same way as the epoll backend, but the interface to the	463	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	464	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	465	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	466	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	467	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
399		470
400	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
401		472
402	While nominally embeddable in other event loops, this doesn't work	473	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	474	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	475	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	476	(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	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
408		483
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		485
411	This is not implemented yet (and might never be, unless you send me an	486	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	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		492
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	493	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)).	494	it's really slow, but it still scales very well (O(active_fds)).
420		495
421	Please note that solaris event ports can deliver a lot of spurious	496	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	497	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
424		499
425	While this backend scales well, it requires one system call per active	500	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	501	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	503	might perform better.
429		504
430	On the positive side, ignoring the spurious readyness notifications, this	505	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
433		512
434	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
435		514
436	Try all backends (even potentially broken ones that wouldn't be tried	515	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	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		518
440	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
441		520
442	=back	521	=back
443		522
444	If one or more of these are ored into the flags value, then only these	523	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	524	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.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		526
448	The most typical usage is like this:	527	Example: This is the most typical usage.
449		528
450	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		531
453	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	533	environment settings to be taken into account:
455		534
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		536
458	Use whatever libev has to offer, but make sure that kqueue is used if	537	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	538	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):	539	private event loop and only if you know the OS supports your types of
		540	fds):
461		541
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		543
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		545
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	546	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	547	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	552	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	553	default loop in the "main" or "initial" thread.
474		554
475	Example: Try to create a event loop that uses epoll and nothing else.	555	Example: Try to create a event loop that uses epoll and nothing else.
476		556
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	558	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
480		560
481	=item ev_default_destroy ()	561	=item ev_default_destroy ()
482		562
483	Destroys the default loop again (frees all memory and kernel state	563	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	564	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	565	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>	566	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	567	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	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	569	for example).
490		570
491	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
494		574
495	In general it is not advisable to call this function except in the	575	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	576	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	577	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		603
524	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
525		605
526	Like C<ev_default_fork>, but acts on an event loop created by	606	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	607	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.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
529		610
530	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
531		612
532	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
533		615
534	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
535		617
536	Returns the count of loop iterations for the loop, which is identical to	618	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	619	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
539		621
540	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
543		637
544	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
545		639
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	641	use.
…		…
552	received events and started processing them. This timestamp does not	646	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	647	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	648	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).	649	event occurring (or more correctly, libev finding out about it).
556		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
557	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
558		690
559	Finally, this is it, the event handler. This function usually is called	691	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	692	after you initialised all your watchers and you want to start handling
561	events.	693	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	695	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.	696	either no event watchers are active anymore or C<ev_unloop> was called.
565		697
566	Please note that an explicit C<ev_unloop> is usually better than	698	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	699	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	701	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.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
571		704
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	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	706	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.	707	process in case there are no events and will return after one iteration of
		708	the loop.
575		709
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	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	711	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	712	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	713	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	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	719	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.	720	usually a better approach for this kind of thing.
583		721
584	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
585		723
586	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	726	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	728	- If we have been forked, detach and recreate the kernel state
		729	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	739	- Queue all expired timers.
601	- Queue all outstanding periodics.	740	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	742	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- 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	744	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	751	anymore.
613		752
614	... queue jobs here, make sure they register event watchers as long	753	... 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..)	754	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
617	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
618		757
619	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
620		759
621	Can be used to make a call to C<ev_loop> return early (but only after it	760	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	761	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	762	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.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		764
626	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
627		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
628	=item ev_ref (loop)	769	=item ev_ref (loop)
629		770
630	=item ev_unref (loop)	771	=item ev_unref (loop)
631		772
632	Ref/unref can be used to add or remove a reference count on the event	773	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	774	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	775	count is nonzero, C<ev_loop> will not return on its own.
		776
635	a watcher you never unregister that should not keep C<ev_loop> from	777	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	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
637	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
638	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
639	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
640	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
641	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
642	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
644		790
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	792	running when nothing else is active.
647		793
648	struct ev_signal exitsig;	794	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	797	evf_unref (loop);
652		798
653	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
654		800
655	ev_ref (loop);	801	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
657		803
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		805
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		807
662	These advanced functions influence the time that libev will spend waiting	808	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	809	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.	810	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		811	latency.
665		812
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	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	814	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
669		817
670	The background is that sometimes your program runs just fast enough to	818	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	819	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	820	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	821	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
675		823
676	By setting a higher I<io collect interval> you allow libev to spend more	824	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,	825	time collecting I/O events, so you can handle more events per iteration,
678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	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.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
681		831
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	836	value will not introduce any overhead in libev.
687		837
688	Many (busy) programs can usually benefit by setting the io collect	838	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	839	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	840	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>,	841	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.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
		847
		848	Setting the I<timeout collect interval> can improve the opportunity for
		849	saving power, as the program will "bundle" timer callback invocations that
		850	are "near" in time together, by delaying some, thus reducing the number of
		851	times the process sleeps and wakes up again. Another useful technique to
		852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		853	they fire on, say, one-second boundaries only.
		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_loop_verify (loop)
		862
		863	This function only does something when C<EV_VERIFY> support has been
		864	compiled in, which is the default for non-minimal builds. It tries to go
		865	through all internal structures and checks them for validity. If anything
		866	is found to be inconsistent, it will print an error message to standard
		867	error and call C<abort ()>.
		868
		869	This can be used to catch bugs inside libev itself: under normal
		870	circumstances, this function will never abort as of course libev keeps its
		871	data structures consistent.
693		872
694	=back	873	=back
695		874
696		875
697	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
698		881
699	A watcher is a structure that you create and register to record your	882	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	883	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:	884	become readable, you would create an C<ev_io> watcher for that:
702		885
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	887	{
705	ev_io_stop (w);	888	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
707	}	890	}
708		891
709	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
710	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
711	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
714	ev_loop (loop, 0);	900	ev_loop (loop, 0);
715		901
716	As you can see, you are responsible for allocating the memory for your	902	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,	903	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		908
720	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	910	(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	911	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	912	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	913	is readable and/or writable).
725		914
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	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	916	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	917	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
730		919
731	To make the watcher actually watch out for events, you have to start it	920	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	921	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	922	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		924
736	As long as your watcher is active (has been started but not stopped) you	925	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	926	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
739		928
740	Each and every callback receives the event loop pointer as first, the	929	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	930	registered watcher structure as second, and a bitset of received events as
742	third argument.	931	third argument.
743		932
…		…
801		990
802	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
803		992
804	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
805		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
806	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
807		1001
808	An unspecified error has occured, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1003	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	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
811	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
813		1011
814	Libev will usually signal a few "dummy" events together with an error,	1012	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	1013	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	1014	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	1015	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
819		1018
820	=back	1019	=back
821		1020
822	=head2 GENERIC WATCHER FUNCTIONS	1021	=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		1022
827	=over 4	1023	=over 4
828		1024
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1026
…		…
836	which rolls both calls into one.	1032	which rolls both calls into one.
837		1033
838	You can reinitialise a watcher at any time as long as it has been stopped	1034	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.	1035	(or never started) and there are no pending events outstanding.
840		1036
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1038	int revents)>.
		1039
		1040	Example: Initialise an C<ev_io> watcher in two steps.
		1041
		1042	ev_io w;
		1043	ev_init (&w, my_cb);
		1044	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		1045
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		1047
846	This macro initialises the type-specific parts of a watcher. You need to	1048	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	1049	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
851		1053
852	Although some watcher types do not have type-specific arguments	1054	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.	1055	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1056
		1057	See C<ev_init>, above, for an example.
		1058
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1060
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1061	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	1062	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1063	a watcher. The same limitations apply, of course.
		1064
		1065	Example: Initialise and set an C<ev_io> watcher in one step.
		1066
		1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		1068
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		1070
863	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
865		1073
		1074	Example: Start the C<ev_io> watcher that is being abused as example in this
		1075	whole section.
		1076
		1077	ev_io_start (EV_DEFAULT_UC, &w);
		1078
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1080
868	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
869	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1085	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	1086	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	1087	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.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1089
875	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
876		1091
877	Returns a true value iff the watcher is active (i.e. it has been started	1092	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	1093	and not yet been stopped). As long as a watcher is active you must not modify
…		…
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
908		1123
909	This means that priorities are I<only> used for ordering callback
910	invocation after new events have been received. This is useful, for
911	example, to reduce latency after idling, or more often, to bind two
912	watchers on the same event and make sure one is called first.
913
914	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
915	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1126
917	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1128	pending.
919		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
920	The default priority used by watchers when no priority has been set is	1134	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 :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
922		1136
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
924	fine, as long as you do not mind that the priority value you query might	1138	priorities.
925	or might not have been adjusted to be within valid range.
926		1139
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1141
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	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	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
932		1146
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1148
935	If the watcher is pending, this function returns clears its pending status	1149	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	1150	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>.	1151	watcher isn't pending it does nothing and returns C<0>.
938		1152
		1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1154	callback to be invoked, which can be accomplished with this function.
		1155
939	=back	1156	=back
940		1157
941		1158
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1160
944	Each watcher has, by default, a member C<void *data> that you can change	1161	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	1162	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	1163	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	1164	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	1165	member, you can also "subclass" the watcher type and provide your own
949	data:	1166	data:
950		1167
951	struct my_io	1168	struct my_io
952	{	1169	{
953	struct ev_io io;	1170	ev_io io;
954	int otherfd;	1171	int otherfd;
955	void *somedata;	1172	void *somedata;
956	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
957	}	1174	};
		1175
		1176	...
		1177	struct my_io w;
		1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1179
959	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1181	can cast it back to your own type:
961		1182
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1184	{
964	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
965	...	1186	...
966	}	1187	}
967		1188
968	More interesting and less C-conformant ways of casting your callback type	1189	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1190	instead have been omitted.
970		1191
971	Another common scenario is having some data structure with multiple	1192	Another common scenario is to use some data structure with multiple
972	watchers:	1193	embedded watchers:
973		1194
974	struct my_biggy	1195	struct my_biggy
975	{	1196	{
976	int some_data;	1197	int some_data;
977	ev_timer t1;	1198	ev_timer t1;
978	ev_timer t2;	1199	ev_timer t2;
979	}	1200	}
980		1201
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1202	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1203	complicated: Either you store the address of your C<my_biggy> struct
		1204	in the C<data> member of the watcher (for woozies), or you need to use
		1205	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1206	programmers):
983		1207
984	#include <stddef.h>	1208	#include <stddef.h>
985		1209
986	static void	1210	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1212	{
989	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1215	}
992		1216
993	static void	1217	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1219	{
996	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
999		1326
1000		1327
1001	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1002		1329
1003	This section describes each watcher in detail, but will not repeat	1330	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	1354	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	1355	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	1356	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1357	required if you know what you are doing).
1031		1358
1032	If you must do this, then force the use of a known-to-be-good backend	1359	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	1360	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1364
1036	Another thing you have to watch out for is that it is quite easy to	1365	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1366	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	1367	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	1368	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	1369	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	1370	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	1371	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.	1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1373
1045	If you cannot run the fd in non-blocking mode (for example you should not	1374	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	1375	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	1376	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	1377	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1378	does this on its own, so its quite safe to use). Some people additionally
		1379	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1380	indefinitely.
		1381
		1382	But really, best use non-blocking mode.
1050		1383
1051	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1052		1385
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1386	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,	1387	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	1388	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	1389	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	1390	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	1391	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1392	fact, a different file descriptor.
1060		1393
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1093		1426
1094	=head3 The special problem of SIGPIPE	1427	=head3 The special problem of SIGPIPE
1095		1428
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1429	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	1430	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	1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1432	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1433
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1434	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	1435	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).	1436	somewhere, as that would have given you a big clue).
1105		1437
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1444
1113	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1114		1446
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1447	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	1448	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.	1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1450
1119	=item int fd [read-only]	1451	=item int fd [read-only]
1120		1452
1121	The file descriptor being watched.	1453	The file descriptor being watched.
1122		1454
…		…
1130		1462
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	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	1464	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1134		1466
1135	static void	1467	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1469	{
1138	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1472	}
1141		1473
1142	...	1474	...
1143	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1148		1480
1149		1481
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1482	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1483
1152	Timer watchers are simple relative timers that generate an event after a	1484	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1154		1486
1155	The timers are based on real time, that is, if you register an event that	1487	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1488	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
		1492
		1493	The callback is guaranteed to be invoked only I<after> its timeout has
		1494	passed (not I<at>, so on systems with very low-resolution clocks this
		1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones with later time-out values (but this is no longer true when a
		1498	callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
		1674
		1675	=head3 The special problem of time updates
		1676
		1677	Establishing the current time is a costly operation (it usually takes at
		1678	least two system calls): EV therefore updates its idea of the current
		1679	time only before and after C<ev_loop> collects new events, which causes a
		1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1681	lots of events in one iteration.
1160		1682
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1683	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	1684	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	1685	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	1686	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:	1687	timeout on the current time, use something like this to adjust for this:
1166		1688
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1690
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1691	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	1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1693	()>.
1172		1694
1173	=head3 Watcher-Specific Functions and Data Members	1695	=head3 Watcher-Specific Functions and Data Members
1174		1696
1175	=over 4	1697	=over 4
1176		1698
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1700
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1701	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1702
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1703	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1704	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1705	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1706	configured to trigger again C<repeat> seconds later, again, and again,
		1707	until stopped manually.
1185		1708
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1709	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1710	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1711	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1712	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1713	do stuff) the timer will not fire more than once per event loop iteration.
1191		1714
1192	=item ev_timer_again (loop, ev_timer *)	1715	=item ev_timer_again (loop, ev_timer *)
1193		1716
1194	This will act as if the timer timed out and restart it again if it is	1717	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1718	repeating. The exact semantics are:
1196		1719
1197	If the timer is pending, its pending status is cleared.	1720	If the timer is pending, its pending status is cleared.
1198		1721
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1723
1201	If the timer is repeating, either start it if necessary (with the	1724	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1726
1204	This sounds a bit complicated, but here is a useful and typical	1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1728	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213
1214	That means you can ignore the C<after> value and C<ev_timer_start>
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216
1217	ev_timer_init (timer, callback, 0., 5.);
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225
1226	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.
1228		1729
1229	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1230		1731
1231	The current C<repeat> value. Will be used each time the watcher times out	1732	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1733	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1734	which is also when any modifications are taken into account.
1234		1735
1235	=back	1736	=back
1236		1737
1237	=head3 Examples	1738	=head3 Examples
1238		1739
1239	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1240		1741
1241	static void	1742	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1744	{
1244	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1245	}	1746	}
1246		1747
1247	struct ev_timer mytimer;	1748	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1250		1751
1251	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1753	inactivity.
1253		1754
1254	static void	1755	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1757	{
1257	.. ten seconds without any activity	1758	.. ten seconds without any activity
1258	}	1759	}
1259		1760
1260	struct ev_timer mytimer;	1761	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1264		1765
1265	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1767	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1768	ev_timer_again (&mytimer);
1268		1769
1269		1770
1270	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1271		1772
1272	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1274		1775
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1777	relative time, the physical time that passes) but on wall clock time
1277	to trigger "at" some specific point in time. For example, if you tell a	1778	(absolute time, the thing you can read on your calender or clock). The
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1779	difference is that wall clock time can run faster or slower than real
1279	+ 10.>) and then reset your system clock to the last year, then it will	1780	time, and time jumps are not uncommon (e.g. when you adjust your
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1781	wrist-watch).
1281	roughly 10 seconds later).
1282		1782
1283	They can also be used to implement vastly more complex timers, such as	1783	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1784	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
1286		1790
		1791	C<ev_periodic> watchers can also be used to implement vastly more complex
		1792	timers, such as triggering an event on each "midnight, local time", or
		1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
		1795
1287	As with timers, the callback is guarenteed to be invoked only when the	1796	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1797	point in time where it is supposed to trigger has passed. If multiple
1289	during the same loop iteration then order of execution is undefined.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1801
1291	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1292		1803
1293	=over 4	1804	=over 4
1294		1805
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1807
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1809
1299	Lots of arguments, lets sort it out... There are basically three modes of	1810	Lots of arguments, let's sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1811	operation, and we will explain them from simplest to most complex:
1301		1812
1302	=over 4	1813	=over 4
1303		1814
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1816
1306	In this configuration the watcher triggers an event at the wallclock time	1817	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1818	time C<offset> has passed. It will not repeat and will not adjust when a
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1819	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1309	system time reaches or surpasses this time.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1310		1822
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1824
1313	In this mode the watcher will always be scheduled to time out at the next	1825	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1826	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1316		1829
1317	This can be used to create timers that do not drift with respect to system	1830	This can be used to create timers that do not drift with respect to the
1318	time:	1831	system clock, for example, here is an C<ev_periodic> that triggers each
		1832	hour, on the hour (with respect to UTC):
1319		1833
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1835
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1836	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1837	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1839	by 3600.
1326		1840
1327	Another way to think about it (for the mathematically inclined) is that	1841	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1842	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1844
1331	For numerical stability it is preferable that the C<at> value is near	1845	For numerical stability it is preferable that the C<offset> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1846	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1847	this value, and in fact is often specified as zero.
1334		1848
		1849	Note also that there is an upper limit to how often a timer can fire (CPU
		1850	speed for example), so if C<interval> is very small then timing stability
		1851	will of course deteriorate. Libev itself tries to be exact to be about one
		1852	millisecond (if the OS supports it and the machine is fast enough).
		1853
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1855
1337	In this mode the values for C<interval> and C<at> are both being	1856	In this mode the values for C<interval> and C<offset> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1859	current time as second argument.
1341		1860
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1343	ever, or make any event loop modifications>. If you need to stop it,	1862	or make ANY other event loop modifications whatsoever, unless explicitly
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1863	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1864
		1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1867	only event loop modification you are allowed to do).
		1868
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1349		1871
		1872	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1874	{
1352	return now + 60.;	1875	return now + 60.;
1353	}	1876	}
1354		1877
1355	It must return the next time to trigger, based on the passed time value	1878	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1879	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1880	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1881	might be called at other times, too.
1359		1882
1360	NOTE: I<< This callback must always return a time that is later than the	1883	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1884	equal to the passed C<now> value >>.
1362		1885
1363	This can be used to create very complex timers, such as a timer that	1886	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1887	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1888	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1889	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1890	reason I omitted it as an example).
1368		1891
1369	=back	1892	=back
…		…
1375	a different time than the last time it was called (e.g. in a crond like	1898	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1899	program when the crontabs have changed).
1377		1900
1378	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1379		1902
1380	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1381	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1382		1907
1383	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1384		1909
1385	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1386	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1387		1913
1388	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1389	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1390		1916
1391	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1392		1918
1393	The current interval value. Can be modified any time, but changes only	1919	The current interval value. Can be modified any time, but changes only
1394	take effect when the periodic timer fires or C<ev_periodic_again> is being	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1395	called.	1921	called.
1396		1922
1397	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1398		1924
1399	The current reschedule callback, or C<0>, if this functionality is	1925	The current reschedule callback, or C<0>, if this functionality is
1400	switched off. Can be changed any time, but changes only take effect when	1926	switched off. Can be changed any time, but changes only take effect when
1401	the periodic timer fires or C<ev_periodic_again> is being called.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1402		1928
1403	=back	1929	=back
1404		1930
1405	=head3 Examples	1931	=head3 Examples
1406		1932
1407	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1410		1936
1411	static void	1937	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	1939	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1941	}
1416		1942
1417	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1420		1946
1421	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1422		1948
1423	#include <math.h>	1949	#include <math.h>
1424		1950
1425	static ev_tstamp	1951	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1953	{
1428	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1429	}	1955	}
1430		1956
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1958
1433	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1434		1960
1435	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1439		1965
1440		1966
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1967	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1968
1443	Signal watchers will trigger an event when the process receives a specific	1969	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1970	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1971	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1972	normal event processing, like any other event.
1447		1973
		1974	If you want signals asynchronously, just use C<sigaction> as you would
		1975	do without libev and forget about sharing the signal. You can even use
		1976	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1977
1448	You can configure as many watchers as you like per signal. Only when the	1978	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1979	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1980	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1981	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1982	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1984
1455	If possible and supported, libev will install its handlers with	1985	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1987	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1988	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1989	them in an C<ev_prepare> watcher.
1460		1990
1461	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1462		1992
…		…
1475		2005
1476	=back	2006	=back
1477		2007
1478	=head3 Examples	2008	=head3 Examples
1479		2009
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1481		2011
1482	static void	2012	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2014	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	2016	}
1487		2017
1488	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1491		2021
1492		2022
1493	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1494		2024
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2025	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	2026	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	2027	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	2028	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2030	forking and then immediately registering a watcher for the child is fine,
		2031	but forking and registering a watcher a few event loop iterations later or
		2032	in the next callback invocation is not.
1500		2033
1501	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
1503		2036
1504	=head3 Process Interaction	2037	=head3 Process Interaction
1505		2038
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2039	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2040	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	2041	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2042	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2043	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2044	children, even ones not watched.
1512		2045
1513	=head3 Overriding the Built-In Processing	2046	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2050	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2051	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2052	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	2053	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	2054	that, so other libev users can use C<ev_child> watchers freely.
		2055
		2056	=head3 Stopping the Child Watcher
		2057
		2058	Currently, the child watcher never gets stopped, even when the
		2059	child terminates, so normally one needs to stop the watcher in the
		2060	callback. Future versions of libev might stop the watcher automatically
		2061	when a child exit is detected.
1522		2062
1523	=head3 Watcher-Specific Functions and Data Members	2063	=head3 Watcher-Specific Functions and Data Members
1524		2064
1525	=over 4	2065	=over 4
1526		2066
…		…
1555	=head3 Examples	2095	=head3 Examples
1556		2096
1557	Example: C<fork()> a new process and install a child handler to wait for	2097	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2098	its completion.
1559		2099
1560	ev_child cw;	2100	ev_child cw;
1561		2101
1562	static void	2102	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2103	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2104	{
1565	ev_child_stop (EV_A_ w);	2105	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2106	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2107	}
1568		2108
1569	pid_t pid = fork ();	2109	pid_t pid = fork ();
1570		2110
1571	if (pid < 0)	2111	if (pid < 0)
1572	// error	2112	// error
1573	else if (pid == 0)	2113	else if (pid == 0)
1574	{	2114	{
1575	// the forked child executes here	2115	// the forked child executes here
1576	exit (1);	2116	exit (1);
1577	}	2117	}
1578	else	2118	else
1579	{	2119	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2120	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2121	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2122	}
1583		2123
1584		2124
1585	=head2 C<ev_stat> - did the file attributes just change?	2125	=head2 C<ev_stat> - did the file attributes just change?
1586		2126
1587	This watches a filesystem path for attribute changes. That is, it calls	2127	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	2128	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	2129	and sees if it changed compared to the last time, invoking the callback if
		2130	it did.
1590		2131
1591	The path does not need to exist: changing from "path exists" to "path does	2132	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	2133	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	2134	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	2135	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2136	least one) and all the other fields of the stat buffer having unspecified
		2137	contents.
1596		2138
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2139	The path I<must not> end in a slash or contain special components such as
		2140	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	2141	your working directory changes, then the behaviour is undefined.
1599		2142
1600	Since there is no standard to do this, the portable implementation simply	2143	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2144	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2145	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	2146	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	2147	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2148	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	2149	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2150	currently around C<0.1>, but that's usually overkill.
1608		2151
1609	This watcher type is not meant for massive numbers of stat watchers,	2152	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2153	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2154	resource-intensive.
1612		2155
1613	At the time of this writing, only the Linux inotify interface is	2156	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2157	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader, note, however, that the author sees no way of implementing ev_stat	2158	exercise for the reader. Note, however, that the author sees no way of
1616	semantics with kqueue). Inotify will be used to give hints only and should	2159	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	not change the semantics of C<ev_stat> watchers, which means that libev
1618	sometimes needs to fall back to regular polling again even with inotify,
1619	but changes are usually detected immediately, and if the file exists there
1620	will be no polling.
1621		2160
1622	=head3 ABI Issues (Largefile Support)	2161	=head3 ABI Issues (Largefile Support)
1623		2162
1624	Libev by default (unless the user overrides this) uses the default	2163	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	2164	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	2165	support disabled by default, you get the 32 bit version of the stat
1627	structure. When using the library from programs that change the ABI to	2166	structure. When using the library from programs that change the ABI to
1628	use 64 bit file offsets the programs will fail. In that case you have to	2167	use 64 bit file offsets the programs will fail. In that case you have to
1629	compile libev with the same flags to get binary compatibility. This is	2168	compile libev with the same flags to get binary compatibility. This is
1630	obviously the case with any flags that change the ABI, but the problem is	2169	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	2170	most noticeably displayed with ev_stat and large file support.
1632		2171
1633	=head3 Inotify	2172	The solution for this is to lobby your distribution maker to make large
		2173	file interfaces available by default (as e.g. FreeBSD does) and not
		2174	optional. Libev cannot simply switch on large file support because it has
		2175	to exchange stat structures with application programs compiled using the
		2176	default compilation environment.
1634		2177
		2178	=head3 Inotify and Kqueue
		2179
1635	When C<inotify (7)> support has been compiled into libev (generally only	2180	When C<inotify (7)> support has been compiled into libev and present at
1636	available on Linux) and present at runtime, it will be used to speed up	2181	runtime, it will be used to speed up change detection where possible. The
1637	change detection where possible. The inotify descriptor will be created lazily	2182	inotify descriptor will be created lazily when the first C<ev_stat>
1638	when the first C<ev_stat> watcher is being started.	2183	watcher is being started.
1639		2184
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	2185	Inotify presence does not change the semantics of C<ev_stat> watchers
1641	except that changes might be detected earlier, and in some cases, to avoid	2186	except that changes might be detected earlier, and in some cases, to avoid
1642	making regular C<stat> calls. Even in the presence of inotify support	2187	making regular C<stat> calls. Even in the presence of inotify support
1643	there are many cases where libev has to resort to regular C<stat> polling.	2188	there are many cases where libev has to resort to regular C<stat> polling,
		2189	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2190	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2191	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2192	xfs are fully working) libev usually gets away without polling.
1644		2193
1645	(There is no support for kqueue, as apparently it cannot be used to	2194	There is no support for kqueue, as apparently it cannot be used to
1646	implement this functionality, due to the requirement of having a file	2195	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	2196	descriptor open on the object at all times, and detecting renames, unlinks
		2197	etc. is difficult.
		2198
		2199	=head3 C<stat ()> is a synchronous operation
		2200
		2201	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2202	the process. The exception are C<ev_stat> watchers - those call C<stat
		2203	()>, which is a synchronous operation.
		2204
		2205	For local paths, this usually doesn't matter: unless the system is very
		2206	busy or the intervals between stat's are large, a stat call will be fast,
		2207	as the path data is usually in memory already (except when starting the
		2208	watcher).
		2209
		2210	For networked file systems, calling C<stat ()> can block an indefinite
		2211	time due to network issues, and even under good conditions, a stat call
		2212	often takes multiple milliseconds.
		2213
		2214	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2215	paths, although this is fully supported by libev.
1648		2216
1649	=head3 The special problem of stat time resolution	2217	=head3 The special problem of stat time resolution
1650		2218
1651	The C<stat ()> syscall only supports full-second resolution portably, and	2219	The C<stat ()> system call only supports full-second resolution portably,
1652	even on systems where the resolution is higher, many filesystems still	2220	and even on systems where the resolution is higher, most file systems
1653	only support whole seconds.	2221	still only support whole seconds.
1654		2222
1655	That means that, if the time is the only thing that changes, you can	2223	That means that, if the time is the only thing that changes, you can
1656	easily miss updates: on the first update, C<ev_stat> detects a change and	2224	easily miss updates: on the first update, C<ev_stat> detects a change and
1657	calls your callback, which does something. When there is another update	2225	calls your callback, which does something. When there is another update
1658	within the same second, C<ev_stat> will be unable to detect it as the stat	2226	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	2227	stat data does change in other ways (e.g. file size).
1660		2228
1661	The solution to this is to delay acting on a change for slightly more	2229	The solution to this is to delay acting on a change for slightly more
1662	than second (or till slightly after the next full second boundary), using	2230	than a second (or till slightly after the next full second boundary), using
1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2231	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	2232	ev_timer_again (loop, w)>).
1665		2233
1666	The C<.02> offset is added to work around small timing inconsistencies	2234	The C<.02> offset is added to work around small timing inconsistencies
1667	of some operating systems (where the second counter of the current time	2235	of some operating systems (where the second counter of the current time
…		…
1684	C<path>. The C<interval> is a hint on how quickly a change is expected to	2252	C<path>. The C<interval> is a hint on how quickly a change is expected to
1685	be detected and should normally be specified as C<0> to let libev choose	2253	be detected and should normally be specified as C<0> to let libev choose
1686	a suitable value. The memory pointed to by C<path> must point to the same	2254	a suitable value. The memory pointed to by C<path> must point to the same
1687	path for as long as the watcher is active.	2255	path for as long as the watcher is active.
1688		2256
1689	The callback will receive C<EV_STAT> when a change was detected, relative	2257	The callback will receive an C<EV_STAT> event when a change was detected,
1690	to the attributes at the time the watcher was started (or the last change	2258	relative to the attributes at the time the watcher was started (or the
1691	was detected).	2259	last change was detected).
1692		2260
1693	=item ev_stat_stat (loop, ev_stat *)	2261	=item ev_stat_stat (loop, ev_stat *)
1694		2262
1695	Updates the stat buffer immediately with new values. If you change the	2263	Updates the stat buffer immediately with new values. If you change the
1696	watched path in your callback, you could call this function to avoid	2264	watched path in your callback, you could call this function to avoid
…		…
1717		2285
1718	The specified interval.	2286	The specified interval.
1719		2287
1720	=item const char *path [read-only]	2288	=item const char *path [read-only]
1721		2289
1722	The filesystem path that is being watched.	2290	The file system path that is being watched.
1723		2291
1724	=back	2292	=back
1725		2293
1726	=head3 Examples	2294	=head3 Examples
1727		2295
1728	Example: Watch C</etc/passwd> for attribute changes.	2296	Example: Watch C</etc/passwd> for attribute changes.
1729		2297
1730	static void	2298	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2299	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	2300	{
1733	/* /etc/passwd changed in some way */	2301	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	2302	if (w->attr.st_nlink)
1735	{	2303	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2304	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2305	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2306	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	2307	}
1740	else	2308	else
1741	/* you shalt not abuse printf for puts */	2309	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	2310	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	2311	"if this is windows, they already arrived\n");
1744	}	2312	}
1745		2313
1746	...	2314	...
1747	ev_stat passwd;	2315	ev_stat passwd;
1748		2316
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2317	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	2318	ev_stat_start (loop, &passwd);
1751		2319
1752	Example: Like above, but additionally use a one-second delay so we do not	2320	Example: Like above, but additionally use a one-second delay so we do not
1753	miss updates (however, frequent updates will delay processing, too, so	2321	miss updates (however, frequent updates will delay processing, too, so
1754	one might do the work both on C<ev_stat> callback invocation I<and> on	2322	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	2323	C<ev_timer> callback invocation).
1756		2324
1757	static ev_stat passwd;	2325	static ev_stat passwd;
1758	static ev_timer timer;	2326	static ev_timer timer;
1759		2327
1760	static void	2328	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	2329	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	2330	{
1763	ev_timer_stop (EV_A_ w);	2331	ev_timer_stop (EV_A_ w);
1764		2332
1765	/* now it's one second after the most recent passwd change */	2333	/* now it's one second after the most recent passwd change */
1766	}	2334	}
1767		2335
1768	static void	2336	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	2337	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	2338	{
1771	/* reset the one-second timer */	2339	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	2340	ev_timer_again (EV_A_ &timer);
1773	}	2341	}
1774		2342
1775	...	2343	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2344	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	2345	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	2346	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		2347
1780		2348
1781	=head2 C<ev_idle> - when you've got nothing better to do...	2349	=head2 C<ev_idle> - when you've got nothing better to do...
1782		2350
1783	Idle watchers trigger events when no other events of the same or higher	2351	Idle watchers trigger events when no other events of the same or higher
1784	priority are pending (prepare, check and other idle watchers do not	2352	priority are pending (prepare, check and other idle watchers do not count
1785	count).	2353	as receiving "events").
1786		2354
1787	That is, as long as your process is busy handling sockets or timeouts	2355	That is, as long as your process is busy handling sockets or timeouts
1788	(or even signals, imagine) of the same or higher priority it will not be	2356	(or even signals, imagine) of the same or higher priority it will not be
1789	triggered. But when your process is idle (or only lower-priority watchers	2357	triggered. But when your process is idle (or only lower-priority watchers
1790	are pending), the idle watchers are being called once per event loop	2358	are pending), the idle watchers are being called once per event loop
…		…
1801		2369
1802	=head3 Watcher-Specific Functions and Data Members	2370	=head3 Watcher-Specific Functions and Data Members
1803		2371
1804	=over 4	2372	=over 4
1805		2373
1806	=item ev_idle_init (ev_signal *, callback)	2374	=item ev_idle_init (ev_idle *, callback)
1807		2375
1808	Initialises and configures the idle watcher - it has no parameters of any	2376	Initialises and configures the idle watcher - it has no parameters of any
1809	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2377	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1810	believe me.	2378	believe me.
1811		2379
…		…
1814	=head3 Examples	2382	=head3 Examples
1815		2383
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2384	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	2385	callback, free it. Also, use no error checking, as usual.
1818		2386
1819	static void	2387	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2388	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1821	{	2389	{
1822	free (w);	2390	free (w);
1823	// now do something you wanted to do when the program has	2391	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	2392	// no longer anything immediate to do.
1825	}	2393	}
1826		2394
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2395	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2396	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2397	ev_idle_start (loop, idle_watcher);
1830		2398
1831		2399
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2400	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2401
1834	Prepare and check watchers are usually (but not always) used in tandem:	2402	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2403	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2404	afterwards.
1837		2405
1838	You I<must not> call C<ev_loop> or similar functions that enter	2406	You I<must not> call C<ev_loop> or similar functions that enter
1839	the current event loop from either C<ev_prepare> or C<ev_check>	2407	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1842	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2410	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1843	C<ev_check> so if you have one watcher of each kind they will always be	2411	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2412	called in pairs bracketing the blocking call.
1845		2413
1846	Their main purpose is to integrate other event mechanisms into libev and	2414	Their main purpose is to integrate other event mechanisms into libev and
1847	their use is somewhat advanced. This could be used, for example, to track	2415	their use is somewhat advanced. They could be used, for example, to track
1848	variable changes, implement your own watchers, integrate net-snmp or a	2416	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2417	coroutine library and lots more. They are also occasionally useful if
1850	you cache some data and want to flush it before blocking (for example,	2418	you cache some data and want to flush it before blocking (for example,
1851	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2419	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2420	watcher).
1853		2421
1854	This is done by examining in each prepare call which file descriptors need	2422	This is done by examining in each prepare call which file descriptors
1855	to be watched by the other library, registering C<ev_io> watchers for	2423	need to be watched by the other library, registering C<ev_io> watchers
1856	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2424	for them and starting an C<ev_timer> watcher for any timeouts (many
1857	provide just this functionality). Then, in the check watcher you check for	2425	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2426	you check for any events that occurred (by checking the pending status
1859	and stopping them) and call back into the library. The I/O and timer	2427	of all watchers and stopping them) and call back into the library. The
1860	callbacks will never actually be called (but must be valid nevertheless,	2428	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2429	nevertheless, because you never know, you know?).
1862		2430
1863	As another example, the Perl Coro module uses these hooks to integrate	2431	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2432	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2433	during each prepare and only letting the process block if no coroutines
1866	are ready to run (it's actually more complicated: it only runs coroutines	2434	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1869	loop from blocking if lower-priority coroutines are active, thus mapping	2437	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2438	low-priority coroutines to idle/background tasks).
1871		2439
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2440	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1873	priority, to ensure that they are being run before any other watchers	2441	priority, to ensure that they are being run before any other watchers
		2442	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2443
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2444	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1875	too) should not activate ("feed") events into libev. While libev fully	2445	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2446	might get executed before other C<ev_check> watchers did their job. As
1877	did their job. As C<ev_check> watchers are often used to embed other	2447	C<ev_check> watchers are often used to embed other (non-libev) event
1878	(non-libev) event loops those other event loops might be in an unusable	2448	loops those other event loops might be in an unusable state until their
1879	state until their C<ev_check> watcher ran (always remind yourself to	2449	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2450	others).
1881		2451
1882	=head3 Watcher-Specific Functions and Data Members	2452	=head3 Watcher-Specific Functions and Data Members
1883		2453
1884	=over 4	2454	=over 4
1885		2455
…		…
1887		2457
1888	=item ev_check_init (ev_check *, callback)	2458	=item ev_check_init (ev_check *, callback)
1889		2459
1890	Initialises and configures the prepare or check watcher - they have no	2460	Initialises and configures the prepare or check watcher - they have no
1891	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2461	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1892	macros, but using them is utterly, utterly and completely pointless.	2462	macros, but using them is utterly, utterly, utterly and completely
		2463	pointless.
1893		2464
1894	=back	2465	=back
1895		2466
1896	=head3 Examples	2467	=head3 Examples
1897		2468
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2477	and in a check watcher, destroy them and call into libadns. What follows
1907	is pseudo-code only of course. This requires you to either use a low	2478	is pseudo-code only of course. This requires you to either use a low
1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2479	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909	the callbacks for the IO/timeout watchers might not have been called yet.	2480	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2481
1911	static ev_io iow [nfd];	2482	static ev_io iow [nfd];
1912	static ev_timer tw;	2483	static ev_timer tw;
1913		2484
1914	static void	2485	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2486	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1916	{	2487	{
1917	}	2488	}
1918		2489
1919	// create io watchers for each fd and a timer before blocking	2490	// create io watchers for each fd and a timer before blocking
1920	static void	2491	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2492	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1922	{	2493	{
1923	int timeout = 3600000;	2494	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2495	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2496	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2497	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2498
1928	/* the callback is illegal, but won't be called as we stop during check */	2499	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2500	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1930	ev_timer_start (loop, &tw);	2501	ev_timer_start (loop, &tw);
1931		2502
1932	// create one ev_io per pollfd	2503	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2504	for (int i = 0; i < nfd; ++i)
1934	{	2505	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2506	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2507	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2508	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2509
1939	fds [i].revents = 0;	2510	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2511	ev_io_start (loop, iow + i);
1941	}	2512	}
1942	}	2513	}
1943		2514
1944	// stop all watchers after blocking	2515	// stop all watchers after blocking
1945	static void	2516	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2517	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1947	{	2518	{
1948	ev_timer_stop (loop, &tw);	2519	ev_timer_stop (loop, &tw);
1949		2520
1950	for (int i = 0; i < nfd; ++i)	2521	for (int i = 0; i < nfd; ++i)
1951	{	2522	{
1952	// set the relevant poll flags	2523	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2524	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2525	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2526	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2527	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2528	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2529
1959	// now stop the watcher	2530	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2531	ev_io_stop (loop, iow + i);
1961	}	2532	}
1962		2533
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2534	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2535	}
1965		2536
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2537	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967	in the prepare watcher and would dispose of the check watcher.	2538	in the prepare watcher and would dispose of the check watcher.
1968		2539
1969	Method 3: If the module to be embedded supports explicit event	2540	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2541	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2542	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2543
1973	static void	2544	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2545	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2546	{
1976	adns_state ads = (adns_state)w->data;	2547	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2548	update_now (EV_A);
1978		2549
1979	adns_processtimeouts (ads, &tv_now);	2550	adns_processtimeouts (ads, &tv_now);
1980	}	2551	}
1981		2552
1982	static void	2553	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2554	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2555	{
1985	adns_state ads = (adns_state)w->data;	2556	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2557	update_now (EV_A);
1987		2558
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2559	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2560	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2561	}
1991		2562
1992	// do not ever call adns_afterpoll	2563	// do not ever call adns_afterpoll
1993		2564
1994	Method 4: Do not use a prepare or check watcher because the module you	2565	Method 4: Do not use a prepare or check watcher because the module you
1995	want to embed is too inflexible to support it. Instead, youc na override	2566	want to embed is not flexible enough to support it. Instead, you can
1996	their poll function. The drawback with this solution is that the main	2567	override their poll function. The drawback with this solution is that the
1997	loop is now no longer controllable by EV. The C<Glib::EV> module does	2568	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2569	this approach, effectively embedding EV as a client into the horrible
		2570	libglib event loop.
1999		2571
2000	static gint	2572	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2573	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2574	{
2003	int got_events = 0;	2575	int got_events = 0;
2004		2576
2005	for (n = 0; n < nfds; ++n)	2577	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2578	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2579
2008	if (timeout >= 0)	2580	if (timeout >= 0)
2009	// create/start timer	2581	// create/start timer
2010		2582
2011	// poll	2583	// poll
2012	ev_loop (EV_A_ 0);	2584	ev_loop (EV_A_ 0);
2013		2585
2014	// stop timer again	2586	// stop timer again
2015	if (timeout >= 0)	2587	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2588	ev_timer_stop (EV_A_ &to);
2017		2589
2018	// stop io watchers again - their callbacks should have set	2590	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2591	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2592	ev_io_stop (EV_A_ iow [n]);
2021		2593
2022	return got_events;	2594	return got_events;
2023	}	2595	}
2024		2596
2025		2597
2026	=head2 C<ev_embed> - when one backend isn't enough...	2598	=head2 C<ev_embed> - when one backend isn't enough...
2027		2599
2028	This is a rather advanced watcher type that lets you embed one event loop	2600	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2606	prioritise I/O.
2035		2607
2036	As an example for a bug workaround, the kqueue backend might only support	2608	As an example for a bug workaround, the kqueue backend might only support
2037	sockets on some platform, so it is unusable as generic backend, but you	2609	sockets on some platform, so it is unusable as generic backend, but you
2038	still want to make use of it because you have many sockets and it scales	2610	still want to make use of it because you have many sockets and it scales
2039	so nicely. In this case, you would create a kqueue-based loop and embed it	2611	so nicely. In this case, you would create a kqueue-based loop and embed
2040	into your default loop (which might use e.g. poll). Overall operation will	2612	it into your default loop (which might use e.g. poll). Overall operation
2041	be a bit slower because first libev has to poll and then call kevent, but	2613	will be a bit slower because first libev has to call C<poll> and then
2042	at least you can use both at what they are best.	2614	C<kevent>, but at least you can use both mechanisms for what they are
		2615	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2616
2044	As for prioritising I/O: rarely you have the case where some fds have	2617	As for prioritising I/O: under rare circumstances you have the case where
2045	to be watched and handled very quickly (with low latency), and even	2618	some fds have to be watched and handled very quickly (with low latency),
2046	priorities and idle watchers might have too much overhead. In this case	2619	and even priorities and idle watchers might have too much overhead. In
2047	you would put all the high priority stuff in one loop and all the rest in	2620	this case you would put all the high priority stuff in one loop and all
2048	a second one, and embed the second one in the first.	2621	the rest in a second one, and embed the second one in the first.
2049		2622
2050	As long as the watcher is active, the callback will be invoked every time	2623	As long as the watcher is active, the callback will be invoked every
2051	there might be events pending in the embedded loop. The callback must then	2624	time there might be events pending in the embedded loop. The callback
2052	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2625	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2053	their callbacks (you could also start an idle watcher to give the embedded	2626	sweep and invoke their callbacks (the callback doesn't need to invoke the
2054	loop strictly lower priority for example). You can also set the callback	2627	C<ev_embed_sweep> function directly, it could also start an idle watcher
2055	to C<0>, in which case the embed watcher will automatically execute the	2628	to give the embedded loop strictly lower priority for example).
2056	embedded loop sweep.
2057		2629
2058	As long as the watcher is started it will automatically handle events. The	2630	You can also set the callback to C<0>, in which case the embed watcher
2059	callback will be invoked whenever some events have been handled. You can	2631	will automatically execute the embedded loop sweep whenever necessary.
2060	set the callback to C<0> to avoid having to specify one if you are not
2061	interested in that.
2062		2632
2063	Also, there have not currently been made special provisions for forking:	2633	Fork detection will be handled transparently while the C<ev_embed> watcher
2064	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2634	is active, i.e., the embedded loop will automatically be forked when the
2065	but you will also have to stop and restart any C<ev_embed> watchers	2635	embedding loop forks. In other cases, the user is responsible for calling
2066	yourself.	2636	C<ev_loop_fork> on the embedded loop.
2067		2637
2068	Unfortunately, not all backends are embeddable, only the ones returned by	2638	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2639	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	2640	portable one.
2071		2641
2072	So when you want to use this feature you will always have to be prepared	2642	So when you want to use this feature you will always have to be prepared
2073	that you cannot get an embeddable loop. The recommended way to get around	2643	that you cannot get an embeddable loop. The recommended way to get around
2074	this is to have a separate variables for your embeddable loop, try to	2644	this is to have a separate variables for your embeddable loop, try to
2075	create it, and if that fails, use the normal loop for everything.	2645	create it, and if that fails, use the normal loop for everything.
2076		2646
		2647	=head3 C<ev_embed> and fork
		2648
		2649	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2650	automatically be applied to the embedded loop as well, so no special
		2651	fork handling is required in that case. When the watcher is not running,
		2652	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2653	as applicable.
		2654
2077	=head3 Watcher-Specific Functions and Data Members	2655	=head3 Watcher-Specific Functions and Data Members
2078		2656
2079	=over 4	2657	=over 4
2080		2658
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2659	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		2662
2085	Configures the watcher to embed the given loop, which must be	2663	Configures the watcher to embed the given loop, which must be
2086	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2664	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087	invoked automatically, otherwise it is the responsibility of the callback	2665	invoked automatically, otherwise it is the responsibility of the callback
2088	to invoke it (it will continue to be called until the sweep has been done,	2666	to invoke it (it will continue to be called until the sweep has been done,
2089	if you do not want thta, you need to temporarily stop the embed watcher).	2667	if you do not want that, you need to temporarily stop the embed watcher).
2090		2668
2091	=item ev_embed_sweep (loop, ev_embed *)	2669	=item ev_embed_sweep (loop, ev_embed *)
2092		2670
2093	Make a single, non-blocking sweep over the embedded loop. This works	2671	Make a single, non-blocking sweep over the embedded loop. This works
2094	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2672	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095	apropriate way for embedded loops.	2673	appropriate way for embedded loops.
2096		2674
2097	=item struct ev_loop *other [read-only]	2675	=item struct ev_loop *other [read-only]
2098		2676
2099	The embedded event loop.	2677	The embedded event loop.
2100		2678
…		…
2102		2680
2103	=head3 Examples	2681	=head3 Examples
2104		2682
2105	Example: Try to get an embeddable event loop and embed it into the default	2683	Example: Try to get an embeddable event loop and embed it into the default
2106	event loop. If that is not possible, use the default loop. The default	2684	event loop. If that is not possible, use the default loop. The default
2107	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2685	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2686	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	2687	used).
2110		2688
2111	struct ev_loop *loop_hi = ev_default_init (0);	2689	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	2690	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	2691	ev_embed embed;
2114		2692
2115	// see if there is a chance of getting one that works	2693	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	2694	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2695	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2696	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	2697	: 0;
2120		2698
2121	// if we got one, then embed it, otherwise default to loop_hi	2699	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	2700	if (loop_lo)
2123	{	2701	{
2124	ev_embed_init (&embed, 0, loop_lo);	2702	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	2703	ev_embed_start (loop_hi, &embed);
2126	}	2704	}
2127	else	2705	else
2128	loop_lo = loop_hi;	2706	loop_lo = loop_hi;
2129		2707
2130	Example: Check if kqueue is available but not recommended and create	2708	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	2709	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	2710	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2711	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		2712
2135	struct ev_loop *loop = ev_default_init (0);	2713	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	2714	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	2715	ev_embed embed;
2138		2716
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2717	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2718	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	2719	{
2142	ev_embed_init (&embed, 0, loop_socket);	2720	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	2721	ev_embed_start (loop, &embed);
2144	}	2722	}
2145		2723
2146	if (!loop_socket)	2724	if (!loop_socket)
2147	loop_socket = loop;	2725	loop_socket = loop;
2148		2726
2149	// now use loop_socket for all sockets, and loop for everything else	2727	// now use loop_socket for all sockets, and loop for everything else
2150		2728
2151		2729
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2730	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		2731
2154	Fork watchers are called when a C<fork ()> was detected (usually because	2732	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2157	event loop blocks next and before C<ev_check> watchers are being called,	2735	event loop blocks next and before C<ev_check> watchers are being called,
2158	and only in the child after the fork. If whoever good citizen calling	2736	and only in the child after the fork. If whoever good citizen calling
2159	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2737	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2160	handlers will be invoked, too, of course.	2738	handlers will be invoked, too, of course.
2161		2739
		2740	=head3 The special problem of life after fork - how is it possible?
		2741
		2742	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2743	up/change the process environment, followed by a call to C<exec()>. This
		2744	sequence should be handled by libev without any problems.
		2745
		2746	This changes when the application actually wants to do event handling
		2747	in the child, or both parent in child, in effect "continuing" after the
		2748	fork.
		2749
		2750	The default mode of operation (for libev, with application help to detect
		2751	forks) is to duplicate all the state in the child, as would be expected
		2752	when I<either> the parent I<or> the child process continues.
		2753
		2754	When both processes want to continue using libev, then this is usually the
		2755	wrong result. In that case, usually one process (typically the parent) is
		2756	supposed to continue with all watchers in place as before, while the other
		2757	process typically wants to start fresh, i.e. without any active watchers.
		2758
		2759	The cleanest and most efficient way to achieve that with libev is to
		2760	simply create a new event loop, which of course will be "empty", and
		2761	use that for new watchers. This has the advantage of not touching more
		2762	memory than necessary, and thus avoiding the copy-on-write, and the
		2763	disadvantage of having to use multiple event loops (which do not support
		2764	signal watchers).
		2765
		2766	When this is not possible, or you want to use the default loop for
		2767	other reasons, then in the process that wants to start "fresh", call
		2768	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2769	the default loop will "orphan" (not stop) all registered watchers, so you
		2770	have to be careful not to execute code that modifies those watchers. Note
		2771	also that in that case, you have to re-register any signal watchers.
		2772
2162	=head3 Watcher-Specific Functions and Data Members	2773	=head3 Watcher-Specific Functions and Data Members
2163		2774
2164	=over 4	2775	=over 4
2165		2776
2166	=item ev_fork_init (ev_signal *, callback)	2777	=item ev_fork_init (ev_signal *, callback)
…		…
2198	is that the author does not know of a simple (or any) algorithm for a	2809	is that the author does not know of a simple (or any) algorithm for a
2199	multiple-writer-single-reader queue that works in all cases and doesn't	2810	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	2811	need elaborate support such as pthreads.
2201		2812
2202	That means that if you want to queue data, you have to provide your own	2813	That means that if you want to queue data, you have to provide your own
2203	queue. But at least I can tell you would implement locking around your	2814	queue. But at least I can tell you how to implement locking around your
2204	queue:	2815	queue:
2205		2816
2206	=over 4	2817	=over 4
2207		2818
2208	=item queueing from a signal handler context	2819	=item queueing from a signal handler context
2209		2820
2210	To implement race-free queueing, you simply add to the queue in the signal	2821	To implement race-free queueing, you simply add to the queue in the signal
2211	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2822	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	2823	an example that does that for some fictitious SIGUSR1 handler:
2213		2824
2214	static ev_async mysig;	2825	static ev_async mysig;
2215		2826
2216	static void	2827	static void
2217	sigusr1_handler (void)	2828	sigusr1_handler (void)
…		…
2283	=over 4	2894	=over 4
2284		2895
2285	=item ev_async_init (ev_async *, callback)	2896	=item ev_async_init (ev_async *, callback)
2286		2897
2287	Initialises and configures the async watcher - it has no parameters of any	2898	Initialises and configures the async watcher - it has no parameters of any
2288	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2899	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2289	believe me.	2900	trust me.
2290		2901
2291	=item ev_async_send (loop, ev_async *)	2902	=item ev_async_send (loop, ev_async *)
2292		2903
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2904	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2905	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2295	C<ev_feed_event>, this call is safe to do in other threads, signal or	2906	C<ev_feed_event>, this call is safe to do from other threads, signal or
2296	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2907	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297	section below on what exactly this means).	2908	section below on what exactly this means).
2298		2909
		2910	Note that, as with other watchers in libev, multiple events might get
		2911	compressed into a single callback invocation (another way to look at this
		2912	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2913	reset when the event loop detects that).
		2914
2299	This call incurs the overhead of a syscall only once per loop iteration,	2915	This call incurs the overhead of a system call only once per event loop
2300	so while the overhead might be noticable, it doesn't apply to repeated	2916	iteration, so while the overhead might be noticeable, it doesn't apply to
2301	calls to C<ev_async_send>.	2917	repeated calls to C<ev_async_send> for the same event loop.
2302		2918
2303	=item bool = ev_async_pending (ev_async *)	2919	=item bool = ev_async_pending (ev_async *)
2304		2920
2305	Returns a non-zero value when C<ev_async_send> has been called on the	2921	Returns a non-zero value when C<ev_async_send> has been called on the
2306	watcher but the event has not yet been processed (or even noted) by the	2922	watcher but the event has not yet been processed (or even noted) by the
2307	event loop.	2923	event loop.
2308		2924
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2925	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310	the loop iterates next and checks for the watcher to have become active,	2926	the loop iterates next and checks for the watcher to have become active,
2311	it will reset the flag again. C<ev_async_pending> can be used to very	2927	it will reset the flag again. C<ev_async_pending> can be used to very
2312	quickly check wether invoking the loop might be a good idea.	2928	quickly check whether invoking the loop might be a good idea.
2313		2929
2314	Not that this does I<not> check wether the watcher itself is pending, only	2930	Not that this does I<not> check whether the watcher itself is pending,
2315	wether it has been requested to make this watcher pending.	2931	only whether it has been requested to make this watcher pending: there
		2932	is a time window between the event loop checking and resetting the async
		2933	notification, and the callback being invoked.
2316		2934
2317	=back	2935	=back
2318		2936
2319		2937
2320	=head1 OTHER FUNCTIONS	2938	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	2942	=over 4
2325		2943
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2944	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		2945
2328	This function combines a simple timer and an I/O watcher, calls your	2946	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	2947	callback on whichever event happens first and automatically stops both
2330	watchers. This is useful if you want to wait for a single event on an fd	2948	watchers. This is useful if you want to wait for a single event on an fd
2331	or timeout without having to allocate/configure/start/stop/free one or	2949	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	2950	more watchers yourself.
2333		2951
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	2952	If C<fd> is less than 0, then no I/O watcher will be started and the
2335	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2953	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	2954	the given C<fd> and C<events> set will be created and started.
2337		2955
2338	If C<timeout> is less than 0, then no timeout watcher will be	2956	If C<timeout> is less than 0, then no timeout watcher will be
2339	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2957	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2958	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		2959
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2960	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2344	passed an C<revents> set like normal event callbacks (a combination of	2961	passed an C<revents> set like normal event callbacks (a combination of
2345	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2962	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346	value passed to C<ev_once>:	2963	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2964	a timeout and an io event at the same time - you probably should give io
		2965	events precedence.
2347		2966
		2967	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2968
2348	static void stdin_ready (int revents, void *arg)	2969	static void stdin_ready (int revents, void *arg)
2349	{	2970	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	2971	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	2972	/* stdin might have data for us, joy! */;
		2973	else if (revents & EV_TIMEOUT)
		2974	/* doh, nothing entered */;
2354	}	2975	}
2355		2976
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2977	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		2978
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)	2979	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2359		2980
2360	Feeds the given event set into the event loop, as if the specified event	2981	Feeds the given event set into the event loop, as if the specified event
2361	had happened for the specified watcher (which must be a pointer to an	2982	had happened for the specified watcher (which must be a pointer to an
2362	initialised but not necessarily started event watcher).	2983	initialised but not necessarily started event watcher).
2363		2984
2364	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2985	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2365		2986
2366	Feed an event on the given fd, as if a file descriptor backend detected	2987	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	2988	the given events it.
2368		2989
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	2990	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2370		2991
2371	Feed an event as if the given signal occured (C<loop> must be the default	2992	Feed an event as if the given signal occurred (C<loop> must be the default
2372	loop!).	2993	loop!).
2373		2994
2374	=back	2995	=back
2375		2996
2376		2997
…		…
2405	=back	3026	=back
2406		3027
2407	=head1 C++ SUPPORT	3028	=head1 C++ SUPPORT
2408		3029
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3030	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410	you to use some convinience methods to start/stop watchers and also change	3031	you to use some convenience methods to start/stop watchers and also change
2411	the callback model to a model using method callbacks on objects.	3032	the callback model to a model using method callbacks on objects.
2412		3033
2413	To use it,	3034	To use it,
2414		3035
2415	#include <ev++.h>	3036	#include <ev++.h>
2416		3037
2417	This automatically includes F<ev.h> and puts all of its definitions (many	3038	This automatically includes F<ev.h> and puts all of its definitions (many
2418	of them macros) into the global namespace. All C++ specific things are	3039	of them macros) into the global namespace. All C++ specific things are
2419	put into the C<ev> namespace. It should support all the same embedding	3040	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3041	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	3108	your compiler is good :), then the method will be fully inlined into the
2488	thunking function, making it as fast as a direct C callback.	3109	thunking function, making it as fast as a direct C callback.
2489		3110
2490	Example: simple class declaration and watcher initialisation	3111	Example: simple class declaration and watcher initialisation
2491		3112
2492	struct myclass	3113	struct myclass
2493	{	3114	{
2494	void io_cb (ev::io &w, int revents) { }	3115	void io_cb (ev::io &w, int revents) { }
2495	}	3116	}
2496		3117
2497	myclass obj;	3118	myclass obj;
2498	ev::io iow;	3119	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	3120	iow.set <myclass, &myclass::io_cb> (&obj);
		3121
		3122	=item w->set (object *)
		3123
		3124	This is an B<experimental> feature that might go away in a future version.
		3125
		3126	This is a variation of a method callback - leaving out the method to call
		3127	will default the method to C<operator ()>, which makes it possible to use
		3128	functor objects without having to manually specify the C<operator ()> all
		3129	the time. Incidentally, you can then also leave out the template argument
		3130	list.
		3131
		3132	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3133	int revents)>.
		3134
		3135	See the method-C<set> above for more details.
		3136
		3137	Example: use a functor object as callback.
		3138
		3139	struct myfunctor
		3140	{
		3141	void operator() (ev::io &w, int revents)
		3142	{
		3143	...
		3144	}
		3145	}
		3146
		3147	myfunctor f;
		3148
		3149	ev::io w;
		3150	w.set (&f);
2500		3151
2501	=item w->set<function> (void *data = 0)	3152	=item w->set<function> (void *data = 0)
2502		3153
2503	Also sets a callback, but uses a static method or plain function as	3154	Also sets a callback, but uses a static method or plain function as
2504	callback. The optional C<data> argument will be stored in the watcher's	3155	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		3157
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3158	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		3159
2509	See the method-C<set> above for more details.	3160	See the method-C<set> above for more details.
2510		3161
2511	Example:	3162	Example: Use a plain function as callback.
2512		3163
2513	static void io_cb (ev::io &w, int revents) { }	3164	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	3165	iow.set <io_cb> ();
2515		3166
2516	=item w->set (struct ev_loop *)	3167	=item w->set (struct ev_loop *)
2517		3168
2518	Associates a different C<struct ev_loop> with this watcher. You can only	3169	Associates a different C<struct ev_loop> with this watcher. You can only
2519	do this when the watcher is inactive (and not pending either).	3170	do this when the watcher is inactive (and not pending either).
2520		3171
2521	=item w->set ([args])	3172	=item w->set ([arguments])
2522		3173
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3174	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2524	called at least once. Unlike the C counterpart, an active watcher gets	3175	called at least once. Unlike the C counterpart, an active watcher gets
2525	automatically stopped and restarted when reconfiguring it with this	3176	automatically stopped and restarted when reconfiguring it with this
2526	method.	3177	method.
2527		3178
2528	=item w->start ()	3179	=item w->start ()
…		…
2552	=back	3203	=back
2553		3204
2554	Example: Define a class with an IO and idle watcher, start one of them in	3205	Example: Define a class with an IO and idle watcher, start one of them in
2555	the constructor.	3206	the constructor.
2556		3207
2557	class myclass	3208	class myclass
2558	{	3209	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	3210	ev::io io ; void io_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	3211	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		3212
2562	myclass (int fd)	3213	myclass (int fd)
2563	{	3214	{
2564	io .set <myclass, &myclass::io_cb > (this);	3215	io .set <myclass, &myclass::io_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	3216	idle.set <myclass, &myclass::idle_cb> (this);
2566		3217
2567	io.start (fd, ev::READ);	3218	io.start (fd, ev::READ);
2568	}	3219	}
2569	};	3220	};
2570		3221
2571		3222
2572	=head1 OTHER LANGUAGE BINDINGS	3223	=head1 OTHER LANGUAGE BINDINGS
2573		3224
2574	Libev does not offer other language bindings itself, but bindings for a	3225	Libev does not offer other language bindings itself, but bindings for a
2575	numbe rof languages exist in the form of third-party packages. If you know	3226	number of languages exist in the form of third-party packages. If you know
2576	any interesting language binding in addition to the ones listed here, drop	3227	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	3228	me a note.
2578		3229
2579	=over 4	3230	=over 4
2580		3231
2581	=item Perl	3232	=item Perl
2582		3233
2583	The EV module implements the full libev API and is actually used to test	3234	The EV module implements the full libev API and is actually used to test
2584	libev. EV is developed together with libev. Apart from the EV core module,	3235	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	3236	there are additional modules that implement libev-compatible interfaces
2586	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3237	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2587	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3238	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3239	and C<EV::Glib>).
2588		3240
2589	It can be found and installed via CPAN, its homepage is found at	3241	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	3242	L<http://software.schmorp.de/pkg/EV>.
2591		3243
		3244	=item Python
		3245
		3246	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3247	seems to be quite complete and well-documented.
		3248
2592	=item Ruby	3249	=item Ruby
2593		3250
2594	Tony Arcieri has written a ruby extension that offers access to a subset	3251	Tony Arcieri has written a ruby extension that offers access to a subset
2595	of the libev API and adds filehandle abstractions, asynchronous DNS and	3252	of the libev API and adds file handle abstractions, asynchronous DNS and
2596	more on top of it. It can be found via gem servers. Its homepage is at	3253	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	3254	L<http://rev.rubyforge.org/>.
2598		3255
		3256	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3257	makes rev work even on mingw.
		3258
		3259	=item Haskell
		3260
		3261	A haskell binding to libev is available at
		3262	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3263
2599	=item D	3264	=item D
2600		3265
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3266	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3267	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3268
		3269	=item Ocaml
		3270
		3271	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3272	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2603		3273
2604	=back	3274	=back
2605		3275
2606		3276
2607	=head1 MACRO MAGIC	3277	=head1 MACRO MAGIC
2608		3278
2609	Libev can be compiled with a variety of options, the most fundamantal	3279	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3280	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	3281	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		3282
2613	To make it easier to write programs that cope with either variant, the	3283	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	3284	following macros are defined:
…		…
2619		3289
2620	This provides the loop I<argument> for functions, if one is required ("ev	3290	This provides the loop I<argument> for functions, if one is required ("ev
2621	loop argument"). The C<EV_A> form is used when this is the sole argument,	3291	loop argument"). The C<EV_A> form is used when this is the sole argument,
2622	C<EV_A_> is used when other arguments are following. Example:	3292	C<EV_A_> is used when other arguments are following. Example:
2623		3293
2624	ev_unref (EV_A);	3294	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	3295	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	3296	ev_loop (EV_A_ 0);
2627		3297
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3298	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	3299	which is often provided by the following macro.
2630		3300
2631	=item C<EV_P>, C<EV_P_>	3301	=item C<EV_P>, C<EV_P_>
2632		3302
2633	This provides the loop I<parameter> for functions, if one is required ("ev	3303	This provides the loop I<parameter> for functions, if one is required ("ev
2634	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3304	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635	C<EV_P_> is used when other parameters are following. Example:	3305	C<EV_P_> is used when other parameters are following. Example:
2636		3306
2637	// this is how ev_unref is being declared	3307	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	3308	static void ev_unref (EV_P);
2639		3309
2640	// this is how you can declare your typical callback	3310	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	3311	static void cb (EV_P_ ev_timer *w, int revents)
2642		3312
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3313	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	3314	suitable for use with C<EV_A>.
2645		3315
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3316	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		3332
2663	Example: Declare and initialise a check watcher, utilising the above	3333	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	3334	macros so it will work regardless of whether multiple loops are supported
2665	or not.	3335	or not.
2666		3336
2667	static void	3337	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	3338	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	3339	{
2670	ev_check_stop (EV_A_ w);	3340	ev_check_stop (EV_A_ w);
2671	}	3341	}
2672		3342
2673	ev_check check;	3343	ev_check check;
2674	ev_check_init (&check, check_cb);	3344	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	3345	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	3346	ev_loop (EV_DEFAULT_ 0);
2677		3347
2678	=head1 EMBEDDING	3348	=head1 EMBEDDING
2679		3349
2680	Libev can (and often is) directly embedded into host	3350	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	3351	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	3358	libev somewhere in your source tree).
2689		3359
2690	=head2 FILESETS	3360	=head2 FILESETS
2691		3361
2692	Depending on what features you need you need to include one or more sets of files	3362	Depending on what features you need you need to include one or more sets of files
2693	in your app.	3363	in your application.
2694		3364
2695	=head3 CORE EVENT LOOP	3365	=head3 CORE EVENT LOOP
2696		3366
2697	To include only the libev core (all the C<ev_*> functions), with manual	3367	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	3368	configuration (no autoconf):
2699		3369
2700	#define EV_STANDALONE 1	3370	#define EV_STANDALONE 1
2701	#include "ev.c"	3371	#include "ev.c"
2702		3372
2703	This will automatically include F<ev.h>, too, and should be done in a	3373	This will automatically include F<ev.h>, too, and should be done in a
2704	single C source file only to provide the function implementations. To use	3374	single C source file only to provide the function implementations. To use
2705	it, do the same for F<ev.h> in all files wishing to use this API (best	3375	it, do the same for F<ev.h> in all files wishing to use this API (best
2706	done by writing a wrapper around F<ev.h> that you can include instead and	3376	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	3377	where you can put other configuration options):
2708		3378
2709	#define EV_STANDALONE 1	3379	#define EV_STANDALONE 1
2710	#include "ev.h"	3380	#include "ev.h"
2711		3381
2712	Both header files and implementation files can be compiled with a C++	3382	Both header files and implementation files can be compiled with a C++
2713	compiler (at least, thats a stated goal, and breakage will be treated	3383	compiler (at least, that's a stated goal, and breakage will be treated
2714	as a bug).	3384	as a bug).
2715		3385
2716	You need the following files in your source tree, or in a directory	3386	You need the following files in your source tree, or in a directory
2717	in your include path (e.g. in libev/ when using -Ilibev):	3387	in your include path (e.g. in libev/ when using -Ilibev):
2718		3388
2719	ev.h	3389	ev.h
2720	ev.c	3390	ev.c
2721	ev_vars.h	3391	ev_vars.h
2722	ev_wrap.h	3392	ev_wrap.h
2723		3393
2724	ev_win32.c required on win32 platforms only	3394	ev_win32.c required on win32 platforms only
2725		3395
2726	ev_select.c only when select backend is enabled (which is enabled by default)	3396	ev_select.c only when select backend is enabled (which is enabled by default)
2727	ev_poll.c only when poll backend is enabled (disabled by default)	3397	ev_poll.c only when poll backend is enabled (disabled by default)
2728	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3398	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3399	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730	ev_port.c only when the solaris port backend is enabled (disabled by default)	3400	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		3401
2732	F<ev.c> includes the backend files directly when enabled, so you only need	3402	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	3403	to compile this single file.
2734		3404
2735	=head3 LIBEVENT COMPATIBILITY API	3405	=head3 LIBEVENT COMPATIBILITY API
2736		3406
2737	To include the libevent compatibility API, also include:	3407	To include the libevent compatibility API, also include:
2738		3408
2739	#include "event.c"	3409	#include "event.c"
2740		3410
2741	in the file including F<ev.c>, and:	3411	in the file including F<ev.c>, and:
2742		3412
2743	#include "event.h"	3413	#include "event.h"
2744		3414
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	3415	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		3416
2747	You need the following additional files for this:	3417	You need the following additional files for this:
2748		3418
2749	event.h	3419	event.h
2750	event.c	3420	event.c
2751		3421
2752	=head3 AUTOCONF SUPPORT	3422	=head3 AUTOCONF SUPPORT
2753		3423
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	3424	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755	whatever way you want, you can also C<m4_include([libev.m4])> in your	3425	whatever way you want, you can also C<m4_include([libev.m4])> in your
2756	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3426	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	3427	include F<config.h> and configure itself accordingly.
2758		3428
2759	For this of course you need the m4 file:	3429	For this of course you need the m4 file:
2760		3430
2761	libev.m4	3431	libev.m4
2762		3432
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	3433	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		3434
2765	Libev can be configured via a variety of preprocessor symbols you have to	3435	Libev can be configured via a variety of preprocessor symbols you have to
2766	define before including any of its files. The default in the absense of	3436	define before including any of its files. The default in the absence of
2767	autoconf is noted for every option.	3437	autoconf is documented for every option.
2768		3438
2769	=over 4	3439	=over 4
2770		3440
2771	=item EV_STANDALONE	3441	=item EV_STANDALONE
2772		3442
…		…
2774	keeps libev from including F<config.h>, and it also defines dummy	3444	keeps libev from including F<config.h>, and it also defines dummy
2775	implementations for some libevent functions (such as logging, which is not	3445	implementations for some libevent functions (such as logging, which is not
2776	supported). It will also not define any of the structs usually found in	3446	supported). It will also not define any of the structs usually found in
2777	F<event.h> that are not directly supported by the libev core alone.	3447	F<event.h> that are not directly supported by the libev core alone.
2778		3448
		3449	In stanbdalone mode, libev will still try to automatically deduce the
		3450	configuration, but has to be more conservative.
		3451
2779	=item EV_USE_MONOTONIC	3452	=item EV_USE_MONOTONIC
2780		3453
2781	If defined to be C<1>, libev will try to detect the availability of the	3454	If defined to be C<1>, libev will try to detect the availability of the
2782	monotonic clock option at both compiletime and runtime. Otherwise no use	3455	monotonic clock option at both compile time and runtime. Otherwise no
2783	of the monotonic clock option will be attempted. If you enable this, you	3456	use of the monotonic clock option will be attempted. If you enable this,
2784	usually have to link against librt or something similar. Enabling it when	3457	you usually have to link against librt or something similar. Enabling it
2785	the functionality isn't available is safe, though, although you have	3458	when the functionality isn't available is safe, though, although you have
2786	to make sure you link against any libraries where the C<clock_gettime>	3459	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	3460	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2788		3461
2789	=item EV_USE_REALTIME	3462	=item EV_USE_REALTIME
2790		3463
2791	If defined to be C<1>, libev will try to detect the availability of the	3464	If defined to be C<1>, libev will try to detect the availability of the
2792	realtime clock option at compiletime (and assume its availability at	3465	real-time clock option at compile time (and assume its availability
2793	runtime if successful). Otherwise no use of the realtime clock option will	3466	at runtime if successful). Otherwise no use of the real-time clock
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3467	option will be attempted. This effectively replaces C<gettimeofday>
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3468	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3469	correctness. See the note about libraries in the description of
		3470	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3471	C<EV_USE_CLOCK_SYSCALL>.
		3472
		3473	=item EV_USE_CLOCK_SYSCALL
		3474
		3475	If defined to be C<1>, libev will try to use a direct syscall instead
		3476	of calling the system-provided C<clock_gettime> function. This option
		3477	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3478	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3479	programs needlessly. Using a direct syscall is slightly slower (in
		3480	theory), because no optimised vdso implementation can be used, but avoids
		3481	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3482	higher, as it simplifies linking (no need for C<-lrt>).
2797		3483
2798	=item EV_USE_NANOSLEEP	3484	=item EV_USE_NANOSLEEP
2799		3485
2800	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3486	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2801	and will use it for delays. Otherwise it will use C<select ()>.	3487	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2809	2.7 or newer, otherwise disabled.	3495	2.7 or newer, otherwise disabled.
2810		3496
2811	=item EV_USE_SELECT	3497	=item EV_USE_SELECT
2812		3498
2813	If undefined or defined to be C<1>, libev will compile in support for the	3499	If undefined or defined to be C<1>, libev will compile in support for the
2814	C<select>(2) backend. No attempt at autodetection will be done: if no	3500	C<select>(2) backend. No attempt at auto-detection will be done: if no
2815	other method takes over, select will be it. Otherwise the select backend	3501	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	3502	will not be compiled in.
2817		3503
2818	=item EV_SELECT_USE_FD_SET	3504	=item EV_SELECT_USE_FD_SET
2819		3505
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	3506	If defined to C<1>, then the select backend will use the system C<fd_set>
2821	structure. This is useful if libev doesn't compile due to a missing	3507	structure. This is useful if libev doesn't compile due to a missing
2822	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3508	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2823	exotic systems. This usually limits the range of file descriptors to some	3509	on exotic systems. This usually limits the range of file descriptors to
2824	low limit such as 1024 or might have other limitations (winsocket only	3510	some low limit such as 1024 or might have other limitations (winsocket
2825	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3511	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2826	influence the size of the C<fd_set> used.	3512	configures the maximum size of the C<fd_set>.
2827		3513
2828	=item EV_SELECT_IS_WINSOCKET	3514	=item EV_SELECT_IS_WINSOCKET
2829		3515
2830	When defined to C<1>, the select backend will assume that	3516	When defined to C<1>, the select backend will assume that
2831	select/socket/connect etc. don't understand file descriptors but	3517	select/socket/connect etc. don't understand file descriptors but
…		…
2876	otherwise another method will be used as fallback. This is the preferred	3562	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	3563	backend for Solaris 10 systems.
2878		3564
2879	=item EV_USE_DEVPOLL	3565	=item EV_USE_DEVPOLL
2880		3566
2881	reserved for future expansion, works like the USE symbols above.	3567	Reserved for future expansion, works like the USE symbols above.
2882		3568
2883	=item EV_USE_INOTIFY	3569	=item EV_USE_INOTIFY
2884		3570
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	3571	If defined to be C<1>, libev will compile in support for the Linux inotify
2886	interface to speed up C<ev_stat> watchers. Its actual availability will	3572	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2893	access is atomic with respect to other threads or signal contexts. No such	3579	access is atomic with respect to other threads or signal contexts. No such
2894	type is easily found in the C language, so you can provide your own type	3580	type is easily found in the C language, so you can provide your own type
2895	that you know is safe for your purposes. It is used both for signal handler "locking"	3581	that you know is safe for your purposes. It is used both for signal handler "locking"
2896	as well as for signal and thread safety in C<ev_async> watchers.	3582	as well as for signal and thread safety in C<ev_async> watchers.
2897		3583
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	3584	In the absence of this define, libev will use C<sig_atomic_t volatile>
2899	(from F<signal.h>), which is usually good enough on most platforms.	3585	(from F<signal.h>), which is usually good enough on most platforms.
2900		3586
2901	=item EV_H	3587	=item EV_H
2902		3588
2903	The name of the F<ev.h> header file used to include it. The default if	3589	The name of the F<ev.h> header file used to include it. The default if
…		…
2942	When doing priority-based operations, libev usually has to linearly search	3628	When doing priority-based operations, libev usually has to linearly search
2943	all the priorities, so having many of them (hundreds) uses a lot of space	3629	all the priorities, so having many of them (hundreds) uses a lot of space
2944	and time, so using the defaults of five priorities (-2 .. +2) is usually	3630	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	3631	fine.
2946		3632
2947	If your embedding app does not need any priorities, defining these both to	3633	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	3634	both to C<0> will save some memory and CPU.
2949		3635
2950	=item EV_PERIODIC_ENABLE	3636	=item EV_PERIODIC_ENABLE
2951		3637
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	3638	If undefined or defined to be C<1>, then periodic timers are supported. If
2953	defined to be C<0>, then they are not. Disabling them saves a few kB of	3639	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	code.	3646	code.
2961		3647
2962	=item EV_EMBED_ENABLE	3648	=item EV_EMBED_ENABLE
2963		3649
2964	If undefined or defined to be C<1>, then embed watchers are supported. If	3650	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.	3651	defined to be C<0>, then they are not. Embed watchers rely on most other
		3652	watcher types, which therefore must not be disabled.
2966		3653
2967	=item EV_STAT_ENABLE	3654	=item EV_STAT_ENABLE
2968		3655
2969	If undefined or defined to be C<1>, then stat watchers are supported. If	3656	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.	3657	defined to be C<0>, then they are not.
…		…
2981		3668
2982	=item EV_MINIMAL	3669	=item EV_MINIMAL
2983		3670
2984	If you need to shave off some kilobytes of code at the expense of some	3671	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently this is used to override some	3672	speed, define this symbol to C<1>. Currently this is used to override some
2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3673	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2987	much smaller 2-heap for timer management over the default 4-heap.	3674	much smaller 2-heap for timer management over the default 4-heap.
2988		3675
2989	=item EV_PID_HASHSIZE	3676	=item EV_PID_HASHSIZE
2990		3677
2991	C<ev_child> watchers use a small hash table to distribute workload by	3678	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3002	two).	3689	two).
3003		3690
3004	=item EV_USE_4HEAP	3691	=item EV_USE_4HEAP
3005		3692
3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3693	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3694	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3008	to C<1>. The 4-heap uses more complicated (longer) code but has a	3695	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3009	noticable after performance with many (thousands) of watchers.	3696	faster performance with many (thousands) of watchers.
3010		3697
3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3012	(disabled).	3699	(disabled).
3013		3700
3014	=item EV_HEAP_CACHE_AT	3701	=item EV_HEAP_CACHE_AT
3015		3702
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3703	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev can cache the timestamp (I<at>) within	3704	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3705	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3706	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020	but avoids random read accesses on heap changes. This noticably improves	3707	but avoids random read accesses on heap changes. This improves performance
3021	performance noticably with with many (hundreds) of watchers.	3708	noticeably with many (hundreds) of watchers.
3022		3709
3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3710	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3024	(disabled).	3711	(disabled).
		3712
		3713	=item EV_VERIFY
		3714
		3715	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3716	be done: If set to C<0>, no internal verification code will be compiled
		3717	in. If set to C<1>, then verification code will be compiled in, but not
		3718	called. If set to C<2>, then the internal verification code will be
		3719	called once per loop, which can slow down libev. If set to C<3>, then the
		3720	verification code will be called very frequently, which will slow down
		3721	libev considerably.
		3722
		3723	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3724	C<0>.
3025		3725
3026	=item EV_COMMON	3726	=item EV_COMMON
3027		3727
3028	By default, all watchers have a C<void *data> member. By redefining	3728	By default, all watchers have a C<void *data> member. By redefining
3029	this macro to a something else you can include more and other types of	3729	this macro to a something else you can include more and other types of
3030	members. You have to define it each time you include one of the files,	3730	members. You have to define it each time you include one of the files,
3031	though, and it must be identical each time.	3731	though, and it must be identical each time.
3032		3732
3033	For example, the perl EV module uses something like this:	3733	For example, the perl EV module uses something like this:
3034		3734
3035	#define EV_COMMON \	3735	#define EV_COMMON \
3036	SV *self; /* contains this struct */ \	3736	SV *self; /* contains this struct */ \
3037	SV *cb_sv, *fh /* note no trailing ";" */	3737	SV *cb_sv, *fh /* note no trailing ";" */
3038		3738
3039	=item EV_CB_DECLARE (type)	3739	=item EV_CB_DECLARE (type)
3040		3740
3041	=item EV_CB_INVOKE (watcher, revents)	3741	=item EV_CB_INVOKE (watcher, revents)
3042		3742
…		…
3047	definition and a statement, respectively. See the F<ev.h> header file for	3747	definition and a statement, respectively. See the F<ev.h> header file for
3048	their default definitions. One possible use for overriding these is to	3748	their default definitions. One possible use for overriding these is to
3049	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3749	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050	method calls instead of plain function calls in C++.	3750	method calls instead of plain function calls in C++.
3051		3751
		3752	=back
		3753
3052	=head2 EXPORTED API SYMBOLS	3754	=head2 EXPORTED API SYMBOLS
3053		3755
3054	If you need to re-export the API (e.g. via a dll) and you need a list of	3756	If you need to re-export the API (e.g. via a DLL) and you need a list of
3055	exported symbols, you can use the provided F<Symbol.*> files which list	3757	exported symbols, you can use the provided F<Symbol.*> files which list
3056	all public symbols, one per line:	3758	all public symbols, one per line:
3057		3759
3058	Symbols.ev for libev proper	3760	Symbols.ev for libev proper
3059	Symbols.event for the libevent emulation	3761	Symbols.event for the libevent emulation
3060		3762
3061	This can also be used to rename all public symbols to avoid clashes with	3763	This can also be used to rename all public symbols to avoid clashes with
3062	multiple versions of libev linked together (which is obviously bad in	3764	multiple versions of libev linked together (which is obviously bad in
3063	itself, but sometimes it is inconvinient to avoid this).	3765	itself, but sometimes it is inconvenient to avoid this).
3064		3766
3065	A sed command like this will create wrapper C<#define>'s that you need to	3767	A sed command like this will create wrapper C<#define>'s that you need to
3066	include before including F<ev.h>:	3768	include before including F<ev.h>:
3067		3769
3068	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3770	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3085	file.	3787	file.
3086		3788
3087	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3789	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088	that everybody includes and which overrides some configure choices:	3790	that everybody includes and which overrides some configure choices:
3089		3791
3090	#define EV_MINIMAL 1	3792	#define EV_MINIMAL 1
3091	#define EV_USE_POLL 0	3793	#define EV_USE_POLL 0
3092	#define EV_MULTIPLICITY 0	3794	#define EV_MULTIPLICITY 0
3093	#define EV_PERIODIC_ENABLE 0	3795	#define EV_PERIODIC_ENABLE 0
3094	#define EV_STAT_ENABLE 0	3796	#define EV_STAT_ENABLE 0
3095	#define EV_FORK_ENABLE 0	3797	#define EV_FORK_ENABLE 0
3096	#define EV_CONFIG_H <config.h>	3798	#define EV_CONFIG_H <config.h>
3097	#define EV_MINPRI 0	3799	#define EV_MINPRI 0
3098	#define EV_MAXPRI 0	3800	#define EV_MAXPRI 0
3099		3801
3100	#include "ev++.h"	3802	#include "ev++.h"
3101		3803
3102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3804	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103		3805
3104	#include "ev_cpp.h"	3806	#include "ev_cpp.h"
3105	#include "ev.c"	3807	#include "ev.c"
3106		3808
		3809	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3107		3810
3108	=head1 THREADS AND COROUTINES	3811	=head2 THREADS AND COROUTINES
3109		3812
3110	=head2 THREADS	3813	=head3 THREADS
3111		3814
3112	Libev itself is completely threadsafe, but it uses no locking. This	3815	All libev functions are reentrant and thread-safe unless explicitly
		3816	documented otherwise, but libev implements no locking itself. This means
3113	means that you can use as many loops as you want in parallel, as long as	3817	that you can use as many loops as you want in parallel, as long as there
3114	only one thread ever calls into one libev function with the same loop	3818	are no concurrent calls into any libev function with the same loop
3115	parameter.	3819	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3820	of course): libev guarantees that different event loops share no data
		3821	structures that need any locking.
3116		3822
3117	Or put differently: calls with different loop parameters can be done in	3823	Or to put it differently: calls with different loop parameters can be done
3118	parallel from multiple threads, calls with the same loop parameter must be	3824	concurrently from multiple threads, calls with the same loop parameter
3119	done serially (but can be done from different threads, as long as only one	3825	must be done serially (but can be done from different threads, as long as
3120	thread ever is inside a call at any point in time, e.g. by using a mutex	3826	only one thread ever is inside a call at any point in time, e.g. by using
3121	per loop).	3827	a mutex per loop).
3122		3828
3123	If you want to know which design is best for your problem, then I cannot	3829	Specifically to support threads (and signal handlers), libev implements
		3830	so-called C<ev_async> watchers, which allow some limited form of
		3831	concurrency on the same event loop, namely waking it up "from the
		3832	outside".
		3833
		3834	If you want to know which design (one loop, locking, or multiple loops
		3835	without or something else still) is best for your problem, then I cannot
3124	help you but by giving some generic advice:	3836	help you, but here is some generic advice:
3125		3837
3126	=over 4	3838	=over 4
3127		3839
3128	=item * most applications have a main thread: use the default libev loop	3840	=item * most applications have a main thread: use the default libev loop
3129	in that thread, or create a seperate thread running only the default loop.	3841	in that thread, or create a separate thread running only the default loop.
3130		3842
3131	This helps integrating other libraries or software modules that use libev	3843	This helps integrating other libraries or software modules that use libev
3132	themselves and don't care/know about threading.	3844	themselves and don't care/know about threading.
3133		3845
3134	=item * one loop per thread is usually a good model.	3846	=item * one loop per thread is usually a good model.
3135		3847
3136	Doing this is almost never wrong, sometimes a better-performance model	3848	Doing this is almost never wrong, sometimes a better-performance model
3137	exists, but it is always a good start.	3849	exists, but it is always a good start.
3138		3850
3139	=item * other models exist, such as the leader/follower pattern, where one	3851	=item * other models exist, such as the leader/follower pattern, where one
3140	loop is handed through multiple threads in a kind of round-robbin fashion.	3852	loop is handed through multiple threads in a kind of round-robin fashion.
3141		3853
3142	Chosing a model is hard - look around, learn, know that usually you cna do	3854	Choosing a model is hard - look around, learn, know that usually you can do
3143	better than you currently do :-)	3855	better than you currently do :-)
3144		3856
3145	=item * often you need to talk to some other thread which blocks in the	3857	=item * often you need to talk to some other thread which blocks in the
		3858	event loop.
		3859
3146	event loop - C<ev_async> watchers can be used to wake them up from other	3860	C<ev_async> watchers can be used to wake them up from other threads safely
3147	threads safely (or from signal contexts...).	3861	(or from signal contexts...).
		3862
		3863	An example use would be to communicate signals or other events that only
		3864	work in the default loop by registering the signal watcher with the
		3865	default loop and triggering an C<ev_async> watcher from the default loop
		3866	watcher callback into the event loop interested in the signal.
3148		3867
3149	=back	3868	=back
3150		3869
3151	=head2 COROUTINES	3870	=head3 COROUTINES
3152		3871
3153	Libev is much more accomodating to coroutines ("cooperative threads"):	3872	Libev is very accommodating to coroutines ("cooperative threads"):
3154	libev fully supports nesting calls to it's functions from different	3873	libev fully supports nesting calls to its functions from different
3155	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3874	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3156	different coroutines and switch freely between both coroutines running the	3875	different coroutines, and switch freely between both coroutines running the
3157	loop, as long as you don't confuse yourself). The only exception is that	3876	loop, as long as you don't confuse yourself). The only exception is that
3158	you must not do this from C<ev_periodic> reschedule callbacks.	3877	you must not do this from C<ev_periodic> reschedule callbacks.
3159		3878
3160	Care has been invested into making sure that libev does not keep local	3879	Care has been taken to ensure that libev does not keep local state inside
3161	state inside C<ev_loop>, and other calls do not usually allow coroutine	3880	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3162	switches.	3881	they do not call any callbacks.
3163		3882
		3883	=head2 COMPILER WARNINGS
3164		3884
3165	=head1 COMPLEXITIES	3885	Depending on your compiler and compiler settings, you might get no or a
		3886	lot of warnings when compiling libev code. Some people are apparently
		3887	scared by this.
3166		3888
3167	In this section the complexities of (many of) the algorithms used inside	3889	However, these are unavoidable for many reasons. For one, each compiler
3168	libev will be explained. For complexity discussions about backends see the	3890	has different warnings, and each user has different tastes regarding
3169	documentation for C<ev_default_init>.	3891	warning options. "Warn-free" code therefore cannot be a goal except when
		3892	targeting a specific compiler and compiler-version.
3170		3893
3171	All of the following are about amortised time: If an array needs to be	3894	Another reason is that some compiler warnings require elaborate
3172	extended, libev needs to realloc and move the whole array, but this	3895	workarounds, or other changes to the code that make it less clear and less
3173	happens asymptotically never with higher number of elements, so O(1) might	3896	maintainable.
3174	mean it might do a lengthy realloc operation in rare cases, but on average
3175	it is much faster and asymptotically approaches constant time.
3176		3897
3177	=over 4	3898	And of course, some compiler warnings are just plain stupid, or simply
		3899	wrong (because they don't actually warn about the condition their message
		3900	seems to warn about). For example, certain older gcc versions had some
		3901	warnings that resulted an extreme number of false positives. These have
		3902	been fixed, but some people still insist on making code warn-free with
		3903	such buggy versions.
3178		3904
3179	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3905	While libev is written to generate as few warnings as possible,
		3906	"warn-free" code is not a goal, and it is recommended not to build libev
		3907	with any compiler warnings enabled unless you are prepared to cope with
		3908	them (e.g. by ignoring them). Remember that warnings are just that:
		3909	warnings, not errors, or proof of bugs.
3180		3910
3181	This means that, when you have a watcher that triggers in one hour and
3182	there are 100 watchers that would trigger before that then inserting will
3183	have to skip roughly seven (C<ld 100>) of these watchers.
3184		3911
3185	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3912	=head2 VALGRIND
3186		3913
3187	That means that changing a timer costs less than removing/adding them	3914	Valgrind has a special section here because it is a popular tool that is
3188	as only the relative motion in the event queue has to be paid for.	3915	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3189		3916
3190	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3917	If you think you found a bug (memory leak, uninitialised data access etc.)
		3918	in libev, then check twice: If valgrind reports something like:
3191		3919
3192	These just add the watcher into an array or at the head of a list.	3920	==2274== definitely lost: 0 bytes in 0 blocks.
		3921	==2274== possibly lost: 0 bytes in 0 blocks.
		3922	==2274== still reachable: 256 bytes in 1 blocks.
3193		3923
3194	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3924	Then there is no memory leak, just as memory accounted to global variables
		3925	is not a memleak - the memory is still being referenced, and didn't leak.
3195		3926
3196	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3927	Similarly, under some circumstances, valgrind might report kernel bugs
		3928	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3929	although an acceptable workaround has been found here), or it might be
		3930	confused.
3197		3931
3198	These watchers are stored in lists then need to be walked to find the	3932	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3199	correct watcher to remove. The lists are usually short (you don't usually	3933	make it into some kind of religion.
3200	have many watchers waiting for the same fd or signal).
3201		3934
3202	=item Finding the next timer in each loop iteration: O(1)	3935	If you are unsure about something, feel free to contact the mailing list
		3936	with the full valgrind report and an explanation on why you think this
		3937	is a bug in libev (best check the archives, too :). However, don't be
		3938	annoyed when you get a brisk "this is no bug" answer and take the chance
		3939	of learning how to interpret valgrind properly.
3203		3940
3204	By virtue of using a binary or 4-heap, the next timer is always found at a	3941	If you need, for some reason, empty reports from valgrind for your project
3205	fixed position in the storage array.	3942	I suggest using suppression lists.
3206		3943
3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208		3944
3209	A change means an I/O watcher gets started or stopped, which requires	3945	=head1 PORTABILITY NOTES
3210	libev to recalculate its status (and possibly tell the kernel, depending
3211	on backend and wether C<ev_io_set> was used).
3212		3946
3213	=item Activating one watcher (putting it into the pending state): O(1)	3947	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3214
3215	=item Priority handling: O(number_of_priorities)
3216
3217	Priorities are implemented by allocating some space for each
3218	priority. When doing priority-based operations, libev usually has to
3219	linearly search all the priorities, but starting/stopping and activating
3220	watchers becomes O(1) w.r.t. priority handling.
3221
3222	=item Sending an ev_async: O(1)
3223
3224	=item Processing ev_async_send: O(number_of_async_watchers)
3225
3226	=item Processing signals: O(max_signal_number)
3227
3228	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3229	calls in the current loop iteration. Checking for async and signal events
3230	involves iterating over all running async watchers or all signal numbers.
3231
3232	=back
3233
3234
3235	=head1 Win32 platform limitations and workarounds
3236		3948
3237	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3949	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238	requires, and its I/O model is fundamentally incompatible with the POSIX	3950	requires, and its I/O model is fundamentally incompatible with the POSIX
3239	model. Libev still offers limited functionality on this platform in	3951	model. Libev still offers limited functionality on this platform in
3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3952	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3247	way (note also that glib is the slowest event library known to man).	3959	way (note also that glib is the slowest event library known to man).
3248		3960
3249	There is no supported compilation method available on windows except	3961	There is no supported compilation method available on windows except
3250	embedding it into other applications.	3962	embedding it into other applications.
3251		3963
		3964	Sensible signal handling is officially unsupported by Microsoft - libev
		3965	tries its best, but under most conditions, signals will simply not work.
		3966
		3967	Not a libev limitation but worth mentioning: windows apparently doesn't
		3968	accept large writes: instead of resulting in a partial write, windows will
		3969	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3970	so make sure you only write small amounts into your sockets (less than a
		3971	megabyte seems safe, but this apparently depends on the amount of memory
		3972	available).
		3973
3252	Due to the many, low, and arbitrary limits on the win32 platform and	3974	Due to the many, low, and arbitrary limits on the win32 platform and
3253	the abysmal performance of winsockets, using a large number of sockets	3975	the abysmal performance of winsockets, using a large number of sockets
3254	is not recommended (and not reasonable). If your program needs to use	3976	is not recommended (and not reasonable). If your program needs to use
3255	more than a hundred or so sockets, then likely it needs to use a totally	3977	more than a hundred or so sockets, then likely it needs to use a totally
3256	different implementation for windows, as libev offers the POSIX readyness	3978	different implementation for windows, as libev offers the POSIX readiness
3257	notification model, which cannot be implemented efficiently on windows	3979	notification model, which cannot be implemented efficiently on windows
3258	(microsoft monopoly games).	3980	(due to Microsoft monopoly games).
		3981
		3982	A typical way to use libev under windows is to embed it (see the embedding
		3983	section for details) and use the following F<evwrap.h> header file instead
		3984	of F<ev.h>:
		3985
		3986	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3987	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3988
		3989	#include "ev.h"
		3990
		3991	And compile the following F<evwrap.c> file into your project (make sure
		3992	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3993
		3994	#include "evwrap.h"
		3995	#include "ev.c"
3259		3996
3260	=over 4	3997	=over 4
3261		3998
3262	=item The winsocket select function	3999	=item The winsocket select function
3263		4000
3264	The winsocket C<select> function doesn't follow POSIX in that it requires	4001	The winsocket C<select> function doesn't follow POSIX in that it
3265	socket I<handles> and not socket I<file descriptors>. This makes select	4002	requires socket I<handles> and not socket I<file descriptors> (it is
3266	very inefficient, and also requires a mapping from file descriptors	4003	also extremely buggy). This makes select very inefficient, and also
3267	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4004	requires a mapping from file descriptors to socket handles (the Microsoft
3268	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4005	C runtime provides the function C<_open_osfhandle> for this). See the
3269	symbols for more info.	4006	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4007	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270		4008
3271	The configuration for a "naked" win32 using the microsoft runtime	4009	The configuration for a "naked" win32 using the Microsoft runtime
3272	libraries and raw winsocket select is:	4010	libraries and raw winsocket select is:
3273		4011
3274	#define EV_USE_SELECT 1	4012	#define EV_USE_SELECT 1
3275	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4013	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276		4014
3277	Note that winsockets handling of fd sets is O(n), so you can easily get a	4015	Note that winsockets handling of fd sets is O(n), so you can easily get a
3278	complexity in the O(n²) range when using win32.	4016	complexity in the O(n²) range when using win32.
3279		4017
3280	=item Limited number of file descriptors	4018	=item Limited number of file descriptors
3281		4019
3282	Windows has numerous arbitrary (and low) limits on things.	4020	Windows has numerous arbitrary (and low) limits on things.
3283		4021
3284	Early versions of winsocket's select only supported waiting for a maximum	4022	Early versions of winsocket's select only supported waiting for a maximum
3285	of C<64> handles (probably owning to the fact that all windows kernels	4023	of C<64> handles (probably owning to the fact that all windows kernels
3286	can only wait for C<64> things at the same time internally; microsoft	4024	can only wait for C<64> things at the same time internally; Microsoft
3287	recommends spawning a chain of threads and wait for 63 handles and the	4025	recommends spawning a chain of threads and wait for 63 handles and the
3288	previous thread in each. Great).	4026	previous thread in each. Sounds great!).
3289		4027
3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4028	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291	to some high number (e.g. C<2048>) before compiling the winsocket select	4029	to some high number (e.g. C<2048>) before compiling the winsocket select
3292	call (which might be in libev or elsewhere, for example, perl does its own	4030	call (which might be in libev or elsewhere, for example, perl and many
3293	select emulation on windows).	4031	other interpreters do their own select emulation on windows).
3294		4032
3295	Another limit is the number of file descriptors in the microsoft runtime	4033	Another limit is the number of file descriptors in the Microsoft runtime
3296	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4034	libraries, which by default is C<64> (there must be a hidden I<64>
3297	or something like this inside microsoft). You can increase this by calling	4035	fetish or something like this inside Microsoft). You can increase this
3298	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4036	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3299	arbitrary limit), but is broken in many versions of the microsoft runtime	4037	(another arbitrary limit), but is broken in many versions of the Microsoft
3300	libraries.
3301
3302	This might get you to about C<512> or C<2048> sockets (depending on	4038	runtime libraries. This might get you to about C<512> or C<2048> sockets
3303	windows version and/or the phase of the moon). To get more, you need to	4039	(depending on windows version and/or the phase of the moon). To get more,
3304	wrap all I/O functions and provide your own fd management, but the cost of	4040	you need to wrap all I/O functions and provide your own fd management, but
3305	calling select (O(n²)) will likely make this unworkable.	4041	the cost of calling select (O(n²)) will likely make this unworkable.
3306		4042
3307	=back	4043	=back
3308		4044
3309
3310	=head1 PORTABILITY REQUIREMENTS	4045	=head2 PORTABILITY REQUIREMENTS
3311		4046
3312	In addition to a working ISO-C implementation, libev relies on a few	4047	In addition to a working ISO-C implementation and of course the
3313	additional extensions:	4048	backend-specific APIs, libev relies on a few additional extensions:
3314		4049
3315	=over 4	4050	=over 4
3316		4051
		4052	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4053	calling conventions regardless of C<ev_watcher_type *>.
		4054
		4055	Libev assumes not only that all watcher pointers have the same internal
		4056	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4057	assumes that the same (machine) code can be used to call any watcher
		4058	callback: The watcher callbacks have different type signatures, but libev
		4059	calls them using an C<ev_watcher *> internally.
		4060
3317	=item C<sig_atomic_t volatile> must be thread-atomic as well	4061	=item C<sig_atomic_t volatile> must be thread-atomic as well
3318		4062
3319	The type C<sig_atomic_t volatile> (or whatever is defined as	4063	The type C<sig_atomic_t volatile> (or whatever is defined as
3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4064	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3321	threads. This is not part of the specification for C<sig_atomic_t>, but is	4065	threads. This is not part of the specification for C<sig_atomic_t>, but is
3322	believed to be sufficiently portable.	4066	believed to be sufficiently portable.
3323		4067
3324	=item C<sigprocmask> must work in a threaded environment	4068	=item C<sigprocmask> must work in a threaded environment
3325		4069
…		…
3334	except the initial one, and run the default loop in the initial thread as	4078	except the initial one, and run the default loop in the initial thread as
3335	well.	4079	well.
3336		4080
3337	=item C<long> must be large enough for common memory allocation sizes	4081	=item C<long> must be large enough for common memory allocation sizes
3338		4082
3339	To improve portability and simplify using libev, libev uses C<long>	4083	To improve portability and simplify its API, libev uses C<long> internally
3340	internally instead of C<size_t> when allocating its data structures. On	4084	instead of C<size_t> when allocating its data structures. On non-POSIX
3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4085	systems (Microsoft...) this might be unexpectedly low, but is still at
3342	is still at least 31 bits everywhere, which is enough for hundreds of	4086	least 31 bits everywhere, which is enough for hundreds of millions of
3343	millions of watchers.	4087	watchers.
3344		4088
3345	=item C<double> must hold a time value in seconds with enough accuracy	4089	=item C<double> must hold a time value in seconds with enough accuracy
3346		4090
3347	The type C<double> is used to represent timestamps. It is required to	4091	The type C<double> is used to represent timestamps. It is required to
3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4092	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3349	enough for at least into the year 4000. This requirement is fulfilled by	4093	enough for at least into the year 4000. This requirement is fulfilled by
3350	implementations implementing IEEE 754 (basically all existing ones).	4094	implementations implementing IEEE 754, which is basically all existing
		4095	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4096	2200.
3351		4097
3352	=back	4098	=back
3353		4099
3354	If you know of other additional requirements drop me a note.	4100	If you know of other additional requirements drop me a note.
3355		4101
3356		4102
		4103	=head1 ALGORITHMIC COMPLEXITIES
		4104
		4105	In this section the complexities of (many of) the algorithms used inside
		4106	libev will be documented. For complexity discussions about backends see
		4107	the documentation for C<ev_default_init>.
		4108
		4109	All of the following are about amortised time: If an array needs to be
		4110	extended, libev needs to realloc and move the whole array, but this
		4111	happens asymptotically rarer with higher number of elements, so O(1) might
		4112	mean that libev does a lengthy realloc operation in rare cases, but on
		4113	average it is much faster and asymptotically approaches constant time.
		4114
		4115	=over 4
		4116
		4117	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4118
		4119	This means that, when you have a watcher that triggers in one hour and
		4120	there are 100 watchers that would trigger before that, then inserting will
		4121	have to skip roughly seven (C<ld 100>) of these watchers.
		4122
		4123	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4124
		4125	That means that changing a timer costs less than removing/adding them,
		4126	as only the relative motion in the event queue has to be paid for.
		4127
		4128	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4129
		4130	These just add the watcher into an array or at the head of a list.
		4131
		4132	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4133
		4134	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4135
		4136	These watchers are stored in lists, so they need to be walked to find the
		4137	correct watcher to remove. The lists are usually short (you don't usually
		4138	have many watchers waiting for the same fd or signal: one is typical, two
		4139	is rare).
		4140
		4141	=item Finding the next timer in each loop iteration: O(1)
		4142
		4143	By virtue of using a binary or 4-heap, the next timer is always found at a
		4144	fixed position in the storage array.
		4145
		4146	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4147
		4148	A change means an I/O watcher gets started or stopped, which requires
		4149	libev to recalculate its status (and possibly tell the kernel, depending
		4150	on backend and whether C<ev_io_set> was used).
		4151
		4152	=item Activating one watcher (putting it into the pending state): O(1)
		4153
		4154	=item Priority handling: O(number_of_priorities)
		4155
		4156	Priorities are implemented by allocating some space for each
		4157	priority. When doing priority-based operations, libev usually has to
		4158	linearly search all the priorities, but starting/stopping and activating
		4159	watchers becomes O(1) with respect to priority handling.
		4160
		4161	=item Sending an ev_async: O(1)
		4162
		4163	=item Processing ev_async_send: O(number_of_async_watchers)
		4164
		4165	=item Processing signals: O(max_signal_number)
		4166
		4167	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4168	calls in the current loop iteration. Checking for async and signal events
		4169	involves iterating over all running async watchers or all signal numbers.
		4170
		4171	=back
		4172
		4173
		4174	=head1 GLOSSARY
		4175
		4176	=over 4
		4177
		4178	=item active
		4179
		4180	A watcher is active as long as it has been started (has been attached to
		4181	an event loop) but not yet stopped (disassociated from the event loop).
		4182
		4183	=item application
		4184
		4185	In this document, an application is whatever is using libev.
		4186
		4187	=item callback
		4188
		4189	The address of a function that is called when some event has been
		4190	detected. Callbacks are being passed the event loop, the watcher that
		4191	received the event, and the actual event bitset.
		4192
		4193	=item callback invocation
		4194
		4195	The act of calling the callback associated with a watcher.
		4196
		4197	=item event
		4198
		4199	A change of state of some external event, such as data now being available
		4200	for reading on a file descriptor, time having passed or simply not having
		4201	any other events happening anymore.
		4202
		4203	In libev, events are represented as single bits (such as C<EV_READ> or
		4204	C<EV_TIMEOUT>).
		4205
		4206	=item event library
		4207
		4208	A software package implementing an event model and loop.
		4209
		4210	=item event loop
		4211
		4212	An entity that handles and processes external events and converts them
		4213	into callback invocations.
		4214
		4215	=item event model
		4216
		4217	The model used to describe how an event loop handles and processes
		4218	watchers and events.
		4219
		4220	=item pending
		4221
		4222	A watcher is pending as soon as the corresponding event has been detected,
		4223	and stops being pending as soon as the watcher will be invoked or its
		4224	pending status is explicitly cleared by the application.
		4225
		4226	A watcher can be pending, but not active. Stopping a watcher also clears
		4227	its pending status.
		4228
		4229	=item real time
		4230
		4231	The physical time that is observed. It is apparently strictly monotonic :)
		4232
		4233	=item wall-clock time
		4234
		4235	The time and date as shown on clocks. Unlike real time, it can actually
		4236	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4237	clock.
		4238
		4239	=item watcher
		4240
		4241	A data structure that describes interest in certain events. Watchers need
		4242	to be started (attached to an event loop) before they can receive events.
		4243
		4244	=item watcher invocation
		4245
		4246	The act of calling the callback associated with a watcher.
		4247
		4248	=back
		4249
3357	=head1 AUTHOR	4250	=head1 AUTHOR
3358		4251
3359	Marc Lehmann <libev@schmorp.de>.	4252	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3360		4253

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