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Revision 1.150 by root, Tue May 6 23:34:16 2008 UTC vs.
Revision 1.253 by root, Tue Jul 14 18:33:48 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://cvs.schmorp.de/libev/ev.html>.	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_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		868
		869	This overrides the invoke pending functionality of the loop: Instead of
		870	invoking all pending watchers when there are any, C<ev_loop> will call
		871	this callback instead. This is useful, for example, when you want to
		872	invoke the actual watchers inside another context (another thread etc.).
		873
		874	If you want to reset the callback, use C<ev_invoke_pending> as new
		875	callback.
		876
		877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		878
		879	Sometimes you want to share the same loop between multiple threads. This
		880	can be done relatively simply by putting mutex_lock/unlock calls around
		881	each call to a libev function.
		882
		883	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		884	wait for it to return. One way around this is to wake up the loop via
		885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		886	and I<acquire> callbacks on the loop.
		887
		888	When set, then C<release> will be called just before the thread is
		889	suspended waiting for new events, and C<acquire> is called just
		890	afterwards.
		891
		892	Ideally, C<release> will just call your mutex_unlock function, and
		893	C<acquire> will just call the mutex_lock function again.
		894
		895	=item ev_set_userdata (loop, void *data)
		896
		897	=item ev_userdata (loop)
		898
		899	Set and retrieve a single C<void *> associated with a loop. When
		900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		901	C<0.>
		902
		903	These two functions can be used to associate arbitrary data with a loop,
		904	and are intended solely for the C<invoke_pending_cb>, C<release> and
		905	C<acquire> callbacks described above, but of course can be (ab-)used for
		906	any other purpose as well.
		907
		908	=item ev_loop_verify (loop)
		909
		910	This function only does something when C<EV_VERIFY> support has been
		911	compiled in, which is the default for non-minimal builds. It tries to go
		912	through all internal structures and checks them for validity. If anything
		913	is found to be inconsistent, it will print an error message to standard
		914	error and call C<abort ()>.
		915
		916	This can be used to catch bugs inside libev itself: under normal
		917	circumstances, this function will never abort as of course libev keeps its
		918	data structures consistent.
693		919
694	=back	920	=back
695		921
696		922
697	=head1 ANATOMY OF A WATCHER	923	=head1 ANATOMY OF A WATCHER
		924
		925	In the following description, uppercase C<TYPE> in names stands for the
		926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		927	watchers and C<ev_io_start> for I/O watchers.
698		928
699	A watcher is a structure that you create and register to record your	929	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	930	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:	931	become readable, you would create an C<ev_io> watcher for that:
702		932
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	934	{
705	ev_io_stop (w);	935	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	936	ev_unloop (loop, EVUNLOOP_ALL);
707	}	937	}
708		938
709	struct ev_loop *loop = ev_default_loop (0);	939	struct ev_loop *loop = ev_default_loop (0);
		940
710	struct ev_io stdin_watcher;	941	ev_io stdin_watcher;
		942
711	ev_init (&stdin_watcher, my_cb);	943	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	945	ev_io_start (loop, &stdin_watcher);
		946
714	ev_loop (loop, 0);	947	ev_loop (loop, 0);
715		948
716	As you can see, you are responsible for allocating the memory for your	949	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,	950	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	951	stack).
		952
		953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		955
720	Each watcher structure must be initialised by a call to C<ev_init	956	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	957	(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	958	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	959	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	960	is readable and/or writable).
725		961
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	962	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	963	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	964	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	965	ev_TYPE_init (watcher *, callback, ...) >>.
730		966
731	To make the watcher actually watch out for events, you have to start it	967	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	968	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	969	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	970	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		971
736	As long as your watcher is active (has been started but not stopped) you	972	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	973	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	974	reinitialise it or call its C<ev_TYPE_set> macro.
739		975
740	Each and every callback receives the event loop pointer as first, the	976	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	977	registered watcher structure as second, and a bitset of received events as
742	third argument.	978	third argument.
743		979
…		…
801		1037
802	=item C<EV_ASYNC>	1038	=item C<EV_ASYNC>
803		1039
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1040	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1041
		1042	=item C<EV_CUSTOM>
		1043
		1044	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1045	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1046
806	=item C<EV_ERROR>	1047	=item C<EV_ERROR>
807		1048
808	An unspecified error has occured, the watcher has been stopped. This might	1049	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1050	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	1051	ran out of memory, a file descriptor was found to be closed or any other
		1052	problem. Libev considers these application bugs.
		1053
811	problem. You best act on it by reporting the problem and somehow coping	1054	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1055	watcher being stopped. Note that well-written programs should not receive
		1056	an error ever, so when your watcher receives it, this usually indicates a
		1057	bug in your program.
813		1058
814	Libev will usually signal a few "dummy" events together with an error,	1059	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	1060	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	1061	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	1062	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1063	programs, though, as the fd could already be closed and reused for another
		1064	thing, so beware.
819		1065
820	=back	1066	=back
821		1067
822	=head2 GENERIC WATCHER FUNCTIONS	1068	=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		1069
827	=over 4	1070	=over 4
828		1071
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1072	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1073
…		…
836	which rolls both calls into one.	1079	which rolls both calls into one.
837		1080
838	You can reinitialise a watcher at any time as long as it has been stopped	1081	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.	1082	(or never started) and there are no pending events outstanding.
840		1083
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1084	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1085	int revents)>.
		1086
		1087	Example: Initialise an C<ev_io> watcher in two steps.
		1088
		1089	ev_io w;
		1090	ev_init (&w, my_cb);
		1091	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		1092
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		1094
846	This macro initialises the type-specific parts of a watcher. You need to	1095	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	1096	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	1099	difference to the C<ev_init> macro).
851		1100
852	Although some watcher types do not have type-specific arguments	1101	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.	1102	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1103
		1104	See C<ev_init>, above, for an example.
		1105
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1106	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1107
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1108	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	1109	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1110	a watcher. The same limitations apply, of course.
		1111
		1112	Example: Initialise and set an C<ev_io> watcher in one step.
		1113
		1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		1115
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		1117
863	Starts (activates) the given watcher. Only active watchers will receive	1118	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1119	events. If the watcher is already active nothing will happen.
865		1120
		1121	Example: Start the C<ev_io> watcher that is being abused as example in this
		1122	whole section.
		1123
		1124	ev_io_start (EV_DEFAULT_UC, &w);
		1125
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1127
868	Stops the given watcher again (if active) and clears the pending	1128	Stops the given watcher if active, and clears the pending status (whether
		1129	the watcher was active or not).
		1130
869	status. It is possible that stopped watchers are pending (for example,	1131	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1132	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	1133	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	1134	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.	1135	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1136
875	=item bool ev_is_active (ev_TYPE *watcher)	1137	=item bool ev_is_active (ev_TYPE *watcher)
876		1138
877	Returns a true value iff the watcher is active (i.e. it has been started	1139	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	1140	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>	1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1167	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1168	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1169	from being executed (except for C<ev_idle> watchers).
908		1170
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	1171	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.	1172	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1173
917	You I<must not> change the priority of a watcher as long as it is active or	1174	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1175	pending.
919		1176
		1177	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1178	fine, as long as you do not mind that the priority value you query might
		1179	or might not have been clamped to the valid range.
		1180
920	The default priority used by watchers when no priority has been set is	1181	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 :).	1182	always C<0>, which is supposed to not be too high and not be too low :).
922		1183
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1184	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	1185	priorities.
925	or might not have been adjusted to be within valid range.
926		1186
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1188
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1189	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	1190	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1191	can deal with that fact, as both are simply passed through to the
		1192	callback.
932		1193
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1194	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1195
935	If the watcher is pending, this function returns clears its pending status	1196	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	1197	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>.	1198	watcher isn't pending it does nothing and returns C<0>.
938		1199
		1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1201	callback to be invoked, which can be accomplished with this function.
		1202
939	=back	1203	=back
940		1204
941		1205
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1207
944	Each watcher has, by default, a member C<void *data> that you can change	1208	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	1209	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	1210	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	1211	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	1212	member, you can also "subclass" the watcher type and provide your own
949	data:	1213	data:
950		1214
951	struct my_io	1215	struct my_io
952	{	1216	{
953	struct ev_io io;	1217	ev_io io;
954	int otherfd;	1218	int otherfd;
955	void *somedata;	1219	void *somedata;
956	struct whatever *mostinteresting;	1220	struct whatever *mostinteresting;
957	}	1221	};
		1222
		1223	...
		1224	struct my_io w;
		1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1226
959	And since your callback will be called with a pointer to the watcher, you	1227	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1228	can cast it back to your own type:
961		1229
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1231	{
964	struct my_io *w = (struct my_io *)w_;	1232	struct my_io *w = (struct my_io *)w_;
965	...	1233	...
966	}	1234	}
967		1235
968	More interesting and less C-conformant ways of casting your callback type	1236	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1237	instead have been omitted.
970		1238
971	Another common scenario is having some data structure with multiple	1239	Another common scenario is to use some data structure with multiple
972	watchers:	1240	embedded watchers:
973		1241
974	struct my_biggy	1242	struct my_biggy
975	{	1243	{
976	int some_data;	1244	int some_data;
977	ev_timer t1;	1245	ev_timer t1;
978	ev_timer t2;	1246	ev_timer t2;
979	}	1247	}
980		1248
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1249	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1250	complicated: Either you store the address of your C<my_biggy> struct
		1251	in the C<data> member of the watcher (for woozies), or you need to use
		1252	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1253	programmers):
983		1254
984	#include <stddef.h>	1255	#include <stddef.h>
985		1256
986	static void	1257	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1258	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1259	{
989	struct my_biggy big = (struct my_biggy *	1260	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1261	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1262	}
992		1263
993	static void	1264	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1265	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1266	{
996	struct my_biggy big = (struct my_biggy *	1267	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1268	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1269	}
		1270
		1271	=head2 WATCHER PRIORITY MODELS
		1272
		1273	Many event loops support I<watcher priorities>, which are usually small
		1274	integers that influence the ordering of event callback invocation
		1275	between watchers in some way, all else being equal.
		1276
		1277	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1278	description for the more technical details such as the actual priority
		1279	range.
		1280
		1281	There are two common ways how these these priorities are being interpreted
		1282	by event loops:
		1283
		1284	In the more common lock-out model, higher priorities "lock out" invocation
		1285	of lower priority watchers, which means as long as higher priority
		1286	watchers receive events, lower priority watchers are not being invoked.
		1287
		1288	The less common only-for-ordering model uses priorities solely to order
		1289	callback invocation within a single event loop iteration: Higher priority
		1290	watchers are invoked before lower priority ones, but they all get invoked
		1291	before polling for new events.
		1292
		1293	Libev uses the second (only-for-ordering) model for all its watchers
		1294	except for idle watchers (which use the lock-out model).
		1295
		1296	The rationale behind this is that implementing the lock-out model for
		1297	watchers is not well supported by most kernel interfaces, and most event
		1298	libraries will just poll for the same events again and again as long as
		1299	their callbacks have not been executed, which is very inefficient in the
		1300	common case of one high-priority watcher locking out a mass of lower
		1301	priority ones.
		1302
		1303	Static (ordering) priorities are most useful when you have two or more
		1304	watchers handling the same resource: a typical usage example is having an
		1305	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1306	timeouts. Under load, data might be received while the program handles
		1307	other jobs, but since timers normally get invoked first, the timeout
		1308	handler will be executed before checking for data. In that case, giving
		1309	the timer a lower priority than the I/O watcher ensures that I/O will be
		1310	handled first even under adverse conditions (which is usually, but not
		1311	always, what you want).
		1312
		1313	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1314	will only be executed when no same or higher priority watchers have
		1315	received events, they can be used to implement the "lock-out" model when
		1316	required.
		1317
		1318	For example, to emulate how many other event libraries handle priorities,
		1319	you can associate an C<ev_idle> watcher to each such watcher, and in
		1320	the normal watcher callback, you just start the idle watcher. The real
		1321	processing is done in the idle watcher callback. This causes libev to
		1322	continously poll and process kernel event data for the watcher, but when
		1323	the lock-out case is known to be rare (which in turn is rare :), this is
		1324	workable.
		1325
		1326	Usually, however, the lock-out model implemented that way will perform
		1327	miserably under the type of load it was designed to handle. In that case,
		1328	it might be preferable to stop the real watcher before starting the
		1329	idle watcher, so the kernel will not have to process the event in case
		1330	the actual processing will be delayed for considerable time.
		1331
		1332	Here is an example of an I/O watcher that should run at a strictly lower
		1333	priority than the default, and which should only process data when no
		1334	other events are pending:
		1335
		1336	ev_idle idle; // actual processing watcher
		1337	ev_io io; // actual event watcher
		1338
		1339	static void
		1340	io_cb (EV_P_ ev_io *w, int revents)
		1341	{
		1342	// stop the I/O watcher, we received the event, but
		1343	// are not yet ready to handle it.
		1344	ev_io_stop (EV_A_ w);
		1345
		1346	// start the idle watcher to ahndle the actual event.
		1347	// it will not be executed as long as other watchers
		1348	// with the default priority are receiving events.
		1349	ev_idle_start (EV_A_ &idle);
		1350	}
		1351
		1352	static void
		1353	idle_cb (EV_P_ ev_idle *w, int revents)
		1354	{
		1355	// actual processing
		1356	read (STDIN_FILENO, ...);
		1357
		1358	// have to start the I/O watcher again, as
		1359	// we have handled the event
		1360	ev_io_start (EV_P_ &io);
		1361	}
		1362
		1363	// initialisation
		1364	ev_idle_init (&idle, idle_cb);
		1365	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1366	ev_io_start (EV_DEFAULT_ &io);
		1367
		1368	In the "real" world, it might also be beneficial to start a timer, so that
		1369	low-priority connections can not be locked out forever under load. This
		1370	enables your program to keep a lower latency for important connections
		1371	during short periods of high load, while not completely locking out less
		1372	important ones.
999		1373
1000		1374
1001	=head1 WATCHER TYPES	1375	=head1 WATCHER TYPES
1002		1376
1003	This section describes each watcher in detail, but will not repeat	1377	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	1401	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	1402	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	1403	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1404	required if you know what you are doing).
1031		1405
1032	If you must do this, then force the use of a known-to-be-good backend	1406	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	1407	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1409	descriptors for which non-blocking operation makes no sense (such as
		1410	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1411
1036	Another thing you have to watch out for is that it is quite easy to	1412	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	1413	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	1414	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	1415	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	1416	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	1417	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	1418	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.	1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1420
1045	If you cannot run the fd in non-blocking mode (for example you should not	1421	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	1422	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	1423	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	1424	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1425	does this on its own, so its quite safe to use). Some people additionally
		1426	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1427	indefinitely.
		1428
		1429	But really, best use non-blocking mode.
1050		1430
1051	=head3 The special problem of disappearing file descriptors	1431	=head3 The special problem of disappearing file descriptors
1052		1432
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1433	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,	1434	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	1435	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	1436	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	1437	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	1438	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1439	fact, a different file descriptor.
1060		1440
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1472	C<EVBACKEND_POLL>.
1093		1473
1094	=head3 The special problem of SIGPIPE	1474	=head3 The special problem of SIGPIPE
1095		1475
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1476	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	1477	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	1478	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1479	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1480
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1481	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	1482	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).	1483	somewhere, as that would have given you a big clue).
1105		1484
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1490	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1491
1113	=item ev_io_set (ev_io *, int fd, int events)	1492	=item ev_io_set (ev_io *, int fd, int events)
1114		1493
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1494	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	1495	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.	1496	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1497
1119	=item int fd [read-only]	1498	=item int fd [read-only]
1120		1499
1121	The file descriptor being watched.	1500	The file descriptor being watched.
1122		1501
…		…
1130		1509
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1510	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	1511	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1512	attempt to read a whole line in the callback.
1134		1513
1135	static void	1514	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1515	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1516	{
1138	ev_io_stop (loop, w);	1517	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1518	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1519	}
1141		1520
1142	...	1521	...
1143	struct ev_loop *loop = ev_default_init (0);	1522	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1523	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1525	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1526	ev_loop (loop, 0);
1148		1527
1149		1528
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1529	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1530
1152	Timer watchers are simple relative timers that generate an event after a	1531	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1532	given time, and optionally repeating in regular intervals after that.
1154		1533
1155	The timers are based on real time, that is, if you register an event that	1534	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	1535	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	1536	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1538	monotonic clock option helps a lot here).
		1539
		1540	The callback is guaranteed to be invoked only I<after> its timeout has
		1541	passed (not I<at>, so on systems with very low-resolution clocks this
		1542	might introduce a small delay). If multiple timers become ready during the
		1543	same loop iteration then the ones with earlier time-out values are invoked
		1544	before ones of the same priority with later time-out values (but this is
		1545	no longer true when a callback calls C<ev_loop> recursively).
		1546
		1547	=head3 Be smart about timeouts
		1548
		1549	Many real-world problems involve some kind of timeout, usually for error
		1550	recovery. A typical example is an HTTP request - if the other side hangs,
		1551	you want to raise some error after a while.
		1552
		1553	What follows are some ways to handle this problem, from obvious and
		1554	inefficient to smart and efficient.
		1555
		1556	In the following, a 60 second activity timeout is assumed - a timeout that
		1557	gets reset to 60 seconds each time there is activity (e.g. each time some
		1558	data or other life sign was received).
		1559
		1560	=over 4
		1561
		1562	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1563
		1564	This is the most obvious, but not the most simple way: In the beginning,
		1565	start the watcher:
		1566
		1567	ev_timer_init (timer, callback, 60., 0.);
		1568	ev_timer_start (loop, timer);
		1569
		1570	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1571	and start it again:
		1572
		1573	ev_timer_stop (loop, timer);
		1574	ev_timer_set (timer, 60., 0.);
		1575	ev_timer_start (loop, timer);
		1576
		1577	This is relatively simple to implement, but means that each time there is
		1578	some activity, libev will first have to remove the timer from its internal
		1579	data structure and then add it again. Libev tries to be fast, but it's
		1580	still not a constant-time operation.
		1581
		1582	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1583
		1584	This is the easiest way, and involves using C<ev_timer_again> instead of
		1585	C<ev_timer_start>.
		1586
		1587	To implement this, configure an C<ev_timer> with a C<repeat> value
		1588	of C<60> and then call C<ev_timer_again> at start and each time you
		1589	successfully read or write some data. If you go into an idle state where
		1590	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1591	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1592
		1593	That means you can ignore both the C<ev_timer_start> function and the
		1594	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1595	member and C<ev_timer_again>.
		1596
		1597	At start:
		1598
		1599	ev_init (timer, callback);
		1600	timer->repeat = 60.;
		1601	ev_timer_again (loop, timer);
		1602
		1603	Each time there is some activity:
		1604
		1605	ev_timer_again (loop, timer);
		1606
		1607	It is even possible to change the time-out on the fly, regardless of
		1608	whether the watcher is active or not:
		1609
		1610	timer->repeat = 30.;
		1611	ev_timer_again (loop, timer);
		1612
		1613	This is slightly more efficient then stopping/starting the timer each time
		1614	you want to modify its timeout value, as libev does not have to completely
		1615	remove and re-insert the timer from/into its internal data structure.
		1616
		1617	It is, however, even simpler than the "obvious" way to do it.
		1618
		1619	=item 3. Let the timer time out, but then re-arm it as required.
		1620
		1621	This method is more tricky, but usually most efficient: Most timeouts are
		1622	relatively long compared to the intervals between other activity - in
		1623	our example, within 60 seconds, there are usually many I/O events with
		1624	associated activity resets.
		1625
		1626	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1627	but remember the time of last activity, and check for a real timeout only
		1628	within the callback:
		1629
		1630	ev_tstamp last_activity; // time of last activity
		1631
		1632	static void
		1633	callback (EV_P_ ev_timer *w, int revents)
		1634	{
		1635	ev_tstamp now = ev_now (EV_A);
		1636	ev_tstamp timeout = last_activity + 60.;
		1637
		1638	// if last_activity + 60. is older than now, we did time out
		1639	if (timeout < now)
		1640	{
		1641	// timeout occured, take action
		1642	}
		1643	else
		1644	{
		1645	// callback was invoked, but there was some activity, re-arm
		1646	// the watcher to fire in last_activity + 60, which is
		1647	// guaranteed to be in the future, so "again" is positive:
		1648	w->repeat = timeout - now;
		1649	ev_timer_again (EV_A_ w);
		1650	}
		1651	}
		1652
		1653	To summarise the callback: first calculate the real timeout (defined
		1654	as "60 seconds after the last activity"), then check if that time has
		1655	been reached, which means something I<did>, in fact, time out. Otherwise
		1656	the callback was invoked too early (C<timeout> is in the future), so
		1657	re-schedule the timer to fire at that future time, to see if maybe we have
		1658	a timeout then.
		1659
		1660	Note how C<ev_timer_again> is used, taking advantage of the
		1661	C<ev_timer_again> optimisation when the timer is already running.
		1662
		1663	This scheme causes more callback invocations (about one every 60 seconds
		1664	minus half the average time between activity), but virtually no calls to
		1665	libev to change the timeout.
		1666
		1667	To start the timer, simply initialise the watcher and set C<last_activity>
		1668	to the current time (meaning we just have some activity :), then call the
		1669	callback, which will "do the right thing" and start the timer:
		1670
		1671	ev_init (timer, callback);
		1672	last_activity = ev_now (loop);
		1673	callback (loop, timer, EV_TIMEOUT);
		1674
		1675	And when there is some activity, simply store the current time in
		1676	C<last_activity>, no libev calls at all:
		1677
		1678	last_actiivty = ev_now (loop);
		1679
		1680	This technique is slightly more complex, but in most cases where the
		1681	time-out is unlikely to be triggered, much more efficient.
		1682
		1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1684	callback :) - just change the timeout and invoke the callback, which will
		1685	fix things for you.
		1686
		1687	=item 4. Wee, just use a double-linked list for your timeouts.
		1688
		1689	If there is not one request, but many thousands (millions...), all
		1690	employing some kind of timeout with the same timeout value, then one can
		1691	do even better:
		1692
		1693	When starting the timeout, calculate the timeout value and put the timeout
		1694	at the I<end> of the list.
		1695
		1696	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1697	the list is expected to fire (for example, using the technique #3).
		1698
		1699	When there is some activity, remove the timer from the list, recalculate
		1700	the timeout, append it to the end of the list again, and make sure to
		1701	update the C<ev_timer> if it was taken from the beginning of the list.
		1702
		1703	This way, one can manage an unlimited number of timeouts in O(1) time for
		1704	starting, stopping and updating the timers, at the expense of a major
		1705	complication, and having to use a constant timeout. The constant timeout
		1706	ensures that the list stays sorted.
		1707
		1708	=back
		1709
		1710	So which method the best?
		1711
		1712	Method #2 is a simple no-brain-required solution that is adequate in most
		1713	situations. Method #3 requires a bit more thinking, but handles many cases
		1714	better, and isn't very complicated either. In most case, choosing either
		1715	one is fine, with #3 being better in typical situations.
		1716
		1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1718	rather complicated, but extremely efficient, something that really pays
		1719	off after the first million or so of active timers, i.e. it's usually
		1720	overkill :)
		1721
		1722	=head3 The special problem of time updates
		1723
		1724	Establishing the current time is a costly operation (it usually takes at
		1725	least two system calls): EV therefore updates its idea of the current
		1726	time only before and after C<ev_loop> collects new events, which causes a
		1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1728	lots of events in one iteration.
1160		1729
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1730	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	1731	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	1732	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	1733	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:	1734	timeout on the current time, use something like this to adjust for this:
1166		1735
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1736	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1737
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1738	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	1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1740	()>.
1172		1741
1173	=head3 Watcher-Specific Functions and Data Members	1742	=head3 Watcher-Specific Functions and Data Members
1174		1743
1175	=over 4	1744	=over 4
1176		1745
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1746	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1747
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1748	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1749
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1750	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	1751	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	1752	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1753	configured to trigger again C<repeat> seconds later, again, and again,
		1754	until stopped manually.
1185		1755
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1756	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	1757	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	1758	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	1759	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.	1760	do stuff) the timer will not fire more than once per event loop iteration.
1191		1761
1192	=item ev_timer_again (loop, ev_timer *)	1762	=item ev_timer_again (loop, ev_timer *)
1193		1763
1194	This will act as if the timer timed out and restart it again if it is	1764	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1765	repeating. The exact semantics are:
1196		1766
1197	If the timer is pending, its pending status is cleared.	1767	If the timer is pending, its pending status is cleared.
1198		1768
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1769	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1770
1201	If the timer is repeating, either start it if necessary (with the	1771	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.	1772	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1773
1204	This sounds a bit complicated, but here is a useful and typical	1774	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	1775	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		1776
1229	=item ev_tstamp repeat [read-write]	1777	=item ev_tstamp repeat [read-write]
1230		1778
1231	The current C<repeat> value. Will be used each time the watcher times out	1779	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),	1780	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.	1781	which is also when any modifications are taken into account.
1234		1782
1235	=back	1783	=back
1236		1784
1237	=head3 Examples	1785	=head3 Examples
1238		1786
1239	Example: Create a timer that fires after 60 seconds.	1787	Example: Create a timer that fires after 60 seconds.
1240		1788
1241	static void	1789	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1790	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1791	{
1244	.. one minute over, w is actually stopped right here	1792	.. one minute over, w is actually stopped right here
1245	}	1793	}
1246		1794
1247	struct ev_timer mytimer;	1795	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1796	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1797	ev_timer_start (loop, &mytimer);
1250		1798
1251	Example: Create a timeout timer that times out after 10 seconds of	1799	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1800	inactivity.
1253		1801
1254	static void	1802	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1804	{
1257	.. ten seconds without any activity	1805	.. ten seconds without any activity
1258	}	1806	}
1259		1807
1260	struct ev_timer mytimer;	1808	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1810	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1811	ev_loop (loop, 0);
1264		1812
1265	// and in some piece of code that gets executed on any "activity":	1813	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1814	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1815	ev_timer_again (&mytimer);
1268		1816
1269		1817
1270	=head2 C<ev_periodic> - to cron or not to cron?	1818	=head2 C<ev_periodic> - to cron or not to cron?
1271		1819
1272	Periodic watchers are also timers of a kind, but they are very versatile	1820	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1821	(and unfortunately a bit complex).
1274		1822
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1823	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	1824	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	1825	(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 ()	1826	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	1827	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	1828	wrist-watch).
1281	roughly 10 seconds later).
1282		1829
1283	They can also be used to implement vastly more complex timers, such as	1830	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1831	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1832	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1833	not a delay) and then reset your system clock to January of the previous
		1834	year, then it will take a year or more to trigger the event (unlike an
		1835	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1836	it, as it uses a relative timeout).
1286		1837
		1838	C<ev_periodic> watchers can also be used to implement vastly more complex
		1839	timers, such as triggering an event on each "midnight, local time", or
		1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1841	those cannot react to time jumps.
		1842
1287	As with timers, the callback is guarenteed to be invoked only when the	1843	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	1844	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.	1845	timers become ready during the same loop iteration then the ones with
		1846	earlier time-out values are invoked before ones with later time-out values
		1847	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1848
1291	=head3 Watcher-Specific Functions and Data Members	1849	=head3 Watcher-Specific Functions and Data Members
1292		1850
1293	=over 4	1851	=over 4
1294		1852
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1853	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1854
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1855	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1856
1299	Lots of arguments, lets sort it out... There are basically three modes of	1857	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:	1858	operation, and we will explain them from simplest to most complex:
1301		1859
1302	=over 4	1860	=over 4
1303		1861
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1862	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1863
1306	In this configuration the watcher triggers an event at the wallclock time	1864	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,	1865	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	1866	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.	1867	will be stopped and invoked when the system clock reaches or surpasses
		1868	this point in time.
1310		1869
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1870	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1871
1313	In this mode the watcher will always be scheduled to time out at the next	1872	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)	1873	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1874	negative) and then repeat, regardless of any time jumps. The C<offset>
		1875	argument is merely an offset into the C<interval> periods.
1316		1876
1317	This can be used to create timers that do not drift with respect to system	1877	This can be used to create timers that do not drift with respect to the
1318	time:	1878	system clock, for example, here is an C<ev_periodic> that triggers each
		1879	hour, on the hour (with respect to UTC):
1319		1880
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1881	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1882
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1883	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	1884	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	1885	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1886	by 3600.
1326		1887
1327	Another way to think about it (for the mathematically inclined) is that	1888	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	1889	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.	1890	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1891
1331	For numerical stability it is preferable that the C<at> value is near	1892	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	1893	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1894	this value, and in fact is often specified as zero.
1334		1895
		1896	Note also that there is an upper limit to how often a timer can fire (CPU
		1897	speed for example), so if C<interval> is very small then timing stability
		1898	will of course deteriorate. Libev itself tries to be exact to be about one
		1899	millisecond (if the OS supports it and the machine is fast enough).
		1900
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1901	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1902
1337	In this mode the values for C<interval> and C<at> are both being	1903	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	1904	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1905	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1906	current time as second argument.
1341		1907
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1908	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,	1909	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	1910	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1911
		1912	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1913	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1914	only event loop modification you are allowed to do).
		1915
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1916	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1917	*w, ev_tstamp now)>, e.g.:
1349		1918
		1919	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1920	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1921	{
1352	return now + 60.;	1922	return now + 60.;
1353	}	1923	}
1354		1924
1355	It must return the next time to trigger, based on the passed time value	1925	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	1926	(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	1927	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1928	might be called at other times, too.
1359		1929
1360	NOTE: I<< This callback must always return a time that is later than the	1930	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.	1931	equal to the passed C<now> value >>.
1362		1932
1363	This can be used to create very complex timers, such as a timer that	1933	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	1934	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	1935	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	1936	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).	1937	reason I omitted it as an example).
1368		1938
1369	=back	1939	=back
…		…
1375	a different time than the last time it was called (e.g. in a crond like	1945	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1946	program when the crontabs have changed).
1377		1947
1378	=item ev_tstamp ev_periodic_at (ev_periodic *)	1948	=item ev_tstamp ev_periodic_at (ev_periodic *)
1379		1949
1380	When active, returns the absolute time that the watcher is supposed to	1950	When active, returns the absolute time that the watcher is supposed
1381	trigger next.	1951	to trigger next. This is not the same as the C<offset> argument to
		1952	C<ev_periodic_set>, but indeed works even in interval and manual
		1953	rescheduling modes.
1382		1954
1383	=item ev_tstamp offset [read-write]	1955	=item ev_tstamp offset [read-write]
1384		1956
1385	When repeating, this contains the offset value, otherwise this is the	1957	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>).	1958	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1959	although libev might modify this value for better numerical stability).
1387		1960
1388	Can be modified any time, but changes only take effect when the periodic	1961	Can be modified any time, but changes only take effect when the periodic
1389	timer fires or C<ev_periodic_again> is being called.	1962	timer fires or C<ev_periodic_again> is being called.
1390		1963
1391	=item ev_tstamp interval [read-write]	1964	=item ev_tstamp interval [read-write]
1392		1965
1393	The current interval value. Can be modified any time, but changes only	1966	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	1967	take effect when the periodic timer fires or C<ev_periodic_again> is being
1395	called.	1968	called.
1396		1969
1397	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1970	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1398		1971
1399	The current reschedule callback, or C<0>, if this functionality is	1972	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	1973	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.	1974	the periodic timer fires or C<ev_periodic_again> is being called.
1402		1975
1403	=back	1976	=back
1404		1977
1405	=head3 Examples	1978	=head3 Examples
1406		1979
1407	Example: Call a callback every hour, or, more precisely, whenever the	1980	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1981	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1982	potentially a lot of jitter, but good long-term stability.
1410		1983
1411	static void	1984	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	1986	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1987	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1988	}
1416		1989
1417	struct ev_periodic hourly_tick;	1990	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1991	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1992	ev_periodic_start (loop, &hourly_tick);
1420		1993
1421	Example: The same as above, but use a reschedule callback to do it:	1994	Example: The same as above, but use a reschedule callback to do it:
1422		1995
1423	#include <math.h>	1996	#include <math.h>
1424		1997
1425	static ev_tstamp	1998	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1999	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	2000	{
1428	return fmod (now, 3600.) + 3600.;	2001	return now + (3600. - fmod (now, 3600.));
1429	}	2002	}
1430		2003
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		2005
1433	Example: Call a callback every hour, starting now:	2006	Example: Call a callback every hour, starting now:
1434		2007
1435	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	2009	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	2010	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	2011	ev_periodic_start (loop, &hourly_tick);
1439		2012
1440		2013
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	2014	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		2015
1443	Signal watchers will trigger an event when the process receives a specific	2016	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	2017	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	2018	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	2019	normal event processing, like any other event.
1447		2020
		2021	If you want signals asynchronously, just use C<sigaction> as you would
		2022	do without libev and forget about sharing the signal. You can even use
		2023	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2024
1448	You can configure as many watchers as you like per signal. Only when the	2025	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	2026	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	2027	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	2028	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	2029	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	2030	signal handler to SIG_DFL (regardless of what it was set to before).
1454		2031
1455	If possible and supported, libev will install its handlers with	2032	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	2034	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	2035	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	2036	them in an C<ev_prepare> watcher.
1460		2037
1461	=head3 Watcher-Specific Functions and Data Members	2038	=head3 Watcher-Specific Functions and Data Members
1462		2039
…		…
1475		2052
1476	=back	2053	=back
1477		2054
1478	=head3 Examples	2055	=head3 Examples
1479		2056
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2057	Example: Try to exit cleanly on SIGINT.
1481		2058
1482	static void	2059	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2061	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2062	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	2063	}
1487		2064
1488	struct ev_signal signal_watcher;	2065	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2067	ev_signal_start (loop, &signal_watcher);
1491		2068
1492		2069
1493	=head2 C<ev_child> - watch out for process status changes	2070	=head2 C<ev_child> - watch out for process status changes
1494		2071
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2072	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	2073	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	2074	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	2075	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2076	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2077	forking and then immediately registering a watcher for the child is fine,
		2078	but forking and registering a watcher a few event loop iterations later or
		2079	in the next callback invocation is not.
1500		2080
1501	Only the default event loop is capable of handling signals, and therefore	2081	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2082	you can only register child watchers in the default event loop.
		2083
		2084	Due to some design glitches inside libev, child watchers will always be
		2085	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2086	libev)
1503		2087
1504	=head3 Process Interaction	2088	=head3 Process Interaction
1505		2089
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2090	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2091	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	2092	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2093	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2094	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2095	children, even ones not watched.
1512		2096
1513	=head3 Overriding the Built-In Processing	2097	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2101	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2102	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2103	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	2104	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.	2105	that, so other libev users can use C<ev_child> watchers freely.
		2106
		2107	=head3 Stopping the Child Watcher
		2108
		2109	Currently, the child watcher never gets stopped, even when the
		2110	child terminates, so normally one needs to stop the watcher in the
		2111	callback. Future versions of libev might stop the watcher automatically
		2112	when a child exit is detected.
1522		2113
1523	=head3 Watcher-Specific Functions and Data Members	2114	=head3 Watcher-Specific Functions and Data Members
1524		2115
1525	=over 4	2116	=over 4
1526		2117
…		…
1555	=head3 Examples	2146	=head3 Examples
1556		2147
1557	Example: C<fork()> a new process and install a child handler to wait for	2148	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2149	its completion.
1559		2150
1560	ev_child cw;	2151	ev_child cw;
1561		2152
1562	static void	2153	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2154	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2155	{
1565	ev_child_stop (EV_A_ w);	2156	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2157	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2158	}
1568		2159
1569	pid_t pid = fork ();	2160	pid_t pid = fork ();
1570		2161
1571	if (pid < 0)	2162	if (pid < 0)
1572	// error	2163	// error
1573	else if (pid == 0)	2164	else if (pid == 0)
1574	{	2165	{
1575	// the forked child executes here	2166	// the forked child executes here
1576	exit (1);	2167	exit (1);
1577	}	2168	}
1578	else	2169	else
1579	{	2170	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2171	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2172	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2173	}
1583		2174
1584		2175
1585	=head2 C<ev_stat> - did the file attributes just change?	2176	=head2 C<ev_stat> - did the file attributes just change?
1586		2177
1587	This watches a filesystem path for attribute changes. That is, it calls	2178	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	2179	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.	2180	and sees if it changed compared to the last time, invoking the callback if
		2181	it did.
1590		2182
1591	The path does not need to exist: changing from "path exists" to "path does	2183	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	2184	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	2185	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	2186	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2187	least one) and all the other fields of the stat buffer having unspecified
		2188	contents.
1596		2189
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2190	The path I<must not> end in a slash or contain special components such as
		2191	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.	2192	your working directory changes, then the behaviour is undefined.
1599		2193
1600	Since there is no standard to do this, the portable implementation simply	2194	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	2195	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2196	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,	2197	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	2198	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2199	(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	2200	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2201	currently around C<0.1>, but that's usually overkill.
1608		2202
1609	This watcher type is not meant for massive numbers of stat watchers,	2203	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2204	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2205	resource-intensive.
1612		2206
1613	At the time of this writing, only the Linux inotify interface is	2207	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2208	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	2209	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	2210	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		2211
1622	=head3 ABI Issues (Largefile Support)	2212	=head3 ABI Issues (Largefile Support)
1623		2213
1624	Libev by default (unless the user overrides this) uses the default	2214	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	2215	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	2216	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	2217	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	2218	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	2219	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	2220	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	2221	most noticeably displayed with ev_stat and large file support.
1632		2222
1633	=head3 Inotify	2223	The solution for this is to lobby your distribution maker to make large
		2224	file interfaces available by default (as e.g. FreeBSD does) and not
		2225	optional. Libev cannot simply switch on large file support because it has
		2226	to exchange stat structures with application programs compiled using the
		2227	default compilation environment.
1634		2228
		2229	=head3 Inotify and Kqueue
		2230
1635	When C<inotify (7)> support has been compiled into libev (generally only	2231	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	2232	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	2233	inotify descriptor will be created lazily when the first C<ev_stat>
1638	when the first C<ev_stat> watcher is being started.	2234	watcher is being started.
1639		2235
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	2236	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	2237	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	2238	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.	2239	there are many cases where libev has to resort to regular C<stat> polling,
		2240	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2241	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2242	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2243	xfs are fully working) libev usually gets away without polling.
1644		2244
1645	(There is no support for kqueue, as apparently it cannot be used to	2245	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	2246	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	2247	descriptor open on the object at all times, and detecting renames, unlinks
		2248	etc. is difficult.
		2249
		2250	=head3 C<stat ()> is a synchronous operation
		2251
		2252	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2253	the process. The exception are C<ev_stat> watchers - those call C<stat
		2254	()>, which is a synchronous operation.
		2255
		2256	For local paths, this usually doesn't matter: unless the system is very
		2257	busy or the intervals between stat's are large, a stat call will be fast,
		2258	as the path data is usually in memory already (except when starting the
		2259	watcher).
		2260
		2261	For networked file systems, calling C<stat ()> can block an indefinite
		2262	time due to network issues, and even under good conditions, a stat call
		2263	often takes multiple milliseconds.
		2264
		2265	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2266	paths, although this is fully supported by libev.
1648		2267
1649	=head3 The special problem of stat time resolution	2268	=head3 The special problem of stat time resolution
1650		2269
1651	The C<stat ()> syscall only supports full-second resolution portably, and	2270	The C<stat ()> system call only supports full-second resolution portably,
1652	even on systems where the resolution is higher, many filesystems still	2271	and even on systems where the resolution is higher, most file systems
1653	only support whole seconds.	2272	still only support whole seconds.
1654		2273
1655	That means that, if the time is the only thing that changes, you can	2274	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	2275	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	2276	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	2277	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	2278	stat data does change in other ways (e.g. file size).
1660		2279
1661	The solution to this is to delay acting on a change for slightly more	2280	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	2281	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);	2282	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	2283	ev_timer_again (loop, w)>).
1665		2284
1666	The C<.02> offset is added to work around small timing inconsistencies	2285	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	2286	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	2303	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	2304	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	2305	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.	2306	path for as long as the watcher is active.
1688		2307
1689	The callback will receive C<EV_STAT> when a change was detected, relative	2308	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	2309	relative to the attributes at the time the watcher was started (or the
1691	was detected).	2310	last change was detected).
1692		2311
1693	=item ev_stat_stat (loop, ev_stat *)	2312	=item ev_stat_stat (loop, ev_stat *)
1694		2313
1695	Updates the stat buffer immediately with new values. If you change the	2314	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	2315	watched path in your callback, you could call this function to avoid
…		…
1717		2336
1718	The specified interval.	2337	The specified interval.
1719		2338
1720	=item const char *path [read-only]	2339	=item const char *path [read-only]
1721		2340
1722	The filesystem path that is being watched.	2341	The file system path that is being watched.
1723		2342
1724	=back	2343	=back
1725		2344
1726	=head3 Examples	2345	=head3 Examples
1727		2346
1728	Example: Watch C</etc/passwd> for attribute changes.	2347	Example: Watch C</etc/passwd> for attribute changes.
1729		2348
1730	static void	2349	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2350	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	2351	{
1733	/* /etc/passwd changed in some way */	2352	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	2353	if (w->attr.st_nlink)
1735	{	2354	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2355	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2356	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2357	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	2358	}
1740	else	2359	else
1741	/* you shalt not abuse printf for puts */	2360	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	2361	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	2362	"if this is windows, they already arrived\n");
1744	}	2363	}
1745		2364
1746	...	2365	...
1747	ev_stat passwd;	2366	ev_stat passwd;
1748		2367
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2368	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	2369	ev_stat_start (loop, &passwd);
1751		2370
1752	Example: Like above, but additionally use a one-second delay so we do not	2371	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	2372	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	2373	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	2374	C<ev_timer> callback invocation).
1756		2375
1757	static ev_stat passwd;	2376	static ev_stat passwd;
1758	static ev_timer timer;	2377	static ev_timer timer;
1759		2378
1760	static void	2379	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	2380	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	2381	{
1763	ev_timer_stop (EV_A_ w);	2382	ev_timer_stop (EV_A_ w);
1764		2383
1765	/* now it's one second after the most recent passwd change */	2384	/* now it's one second after the most recent passwd change */
1766	}	2385	}
1767		2386
1768	static void	2387	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	2388	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	2389	{
1771	/* reset the one-second timer */	2390	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	2391	ev_timer_again (EV_A_ &timer);
1773	}	2392	}
1774		2393
1775	...	2394	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2395	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	2396	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	2397	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		2398
1780		2399
1781	=head2 C<ev_idle> - when you've got nothing better to do...	2400	=head2 C<ev_idle> - when you've got nothing better to do...
1782		2401
1783	Idle watchers trigger events when no other events of the same or higher	2402	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	2403	priority are pending (prepare, check and other idle watchers do not count
1785	count).	2404	as receiving "events").
1786		2405
1787	That is, as long as your process is busy handling sockets or timeouts	2406	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	2407	(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	2408	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	2409	are pending), the idle watchers are being called once per event loop
…		…
1801		2420
1802	=head3 Watcher-Specific Functions and Data Members	2421	=head3 Watcher-Specific Functions and Data Members
1803		2422
1804	=over 4	2423	=over 4
1805		2424
1806	=item ev_idle_init (ev_signal *, callback)	2425	=item ev_idle_init (ev_idle *, callback)
1807		2426
1808	Initialises and configures the idle watcher - it has no parameters of any	2427	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,	2428	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1810	believe me.	2429	believe me.
1811		2430
…		…
1814	=head3 Examples	2433	=head3 Examples
1815		2434
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2435	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	2436	callback, free it. Also, use no error checking, as usual.
1818		2437
1819	static void	2438	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1821	{	2440	{
1822	free (w);	2441	free (w);
1823	// now do something you wanted to do when the program has	2442	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	2443	// no longer anything immediate to do.
1825	}	2444	}
1826		2445
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2447	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2448	ev_idle_start (loop, idle_watcher);
1830		2449
1831		2450
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2452
1834	Prepare and check watchers are usually (but not always) used in tandem:	2453	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2454	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2455	afterwards.
1837		2456
1838	You I<must not> call C<ev_loop> or similar functions that enter	2457	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>	2458	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,	2461	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	2462	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2463	called in pairs bracketing the blocking call.
1845		2464
1846	Their main purpose is to integrate other event mechanisms into libev and	2465	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	2466	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	2467	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2468	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,	2469	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>	2470	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2471	watcher).
1853		2472
1854	This is done by examining in each prepare call which file descriptors need	2473	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	2474	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	2475	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	2476	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2477	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	2478	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,	2479	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2480	nevertheless, because you never know, you know?).
1862		2481
1863	As another example, the Perl Coro module uses these hooks to integrate	2482	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2483	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2484	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	2485	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	2488	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2489	low-priority coroutines to idle/background tasks).
1871		2490
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2491	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	2492	priority, to ensure that they are being run before any other watchers
		2493	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2494
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2495	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	2496	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2497	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	2498	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	2499	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	2500	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2501	others).
1881		2502
1882	=head3 Watcher-Specific Functions and Data Members	2503	=head3 Watcher-Specific Functions and Data Members
1883		2504
1884	=over 4	2505	=over 4
1885		2506
…		…
1887		2508
1888	=item ev_check_init (ev_check *, callback)	2509	=item ev_check_init (ev_check *, callback)
1889		2510
1890	Initialises and configures the prepare or check watcher - they have no	2511	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>	2512	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.	2513	macros, but using them is utterly, utterly, utterly and completely
		2514	pointless.
1893		2515
1894	=back	2516	=back
1895		2517
1896	=head3 Examples	2518	=head3 Examples
1897		2519
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2528	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	2529	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	2530	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.	2531	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2532
1911	static ev_io iow [nfd];	2533	static ev_io iow [nfd];
1912	static ev_timer tw;	2534	static ev_timer tw;
1913		2535
1914	static void	2536	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2537	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1916	{	2538	{
1917	}	2539	}
1918		2540
1919	// create io watchers for each fd and a timer before blocking	2541	// create io watchers for each fd and a timer before blocking
1920	static void	2542	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2543	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1922	{	2544	{
1923	int timeout = 3600000;	2545	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2546	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2547	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2548	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2549
1928	/* the callback is illegal, but won't be called as we stop during check */	2550	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2551	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1930	ev_timer_start (loop, &tw);	2552	ev_timer_start (loop, &tw);
1931		2553
1932	// create one ev_io per pollfd	2554	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2555	for (int i = 0; i < nfd; ++i)
1934	{	2556	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2557	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2558	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2559	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2560
1939	fds [i].revents = 0;	2561	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2562	ev_io_start (loop, iow + i);
1941	}	2563	}
1942	}	2564	}
1943		2565
1944	// stop all watchers after blocking	2566	// stop all watchers after blocking
1945	static void	2567	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2568	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1947	{	2569	{
1948	ev_timer_stop (loop, &tw);	2570	ev_timer_stop (loop, &tw);
1949		2571
1950	for (int i = 0; i < nfd; ++i)	2572	for (int i = 0; i < nfd; ++i)
1951	{	2573	{
1952	// set the relevant poll flags	2574	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2575	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2576	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2577	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2578	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2579	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2580
1959	// now stop the watcher	2581	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2582	ev_io_stop (loop, iow + i);
1961	}	2583	}
1962		2584
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2585	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2586	}
1965		2587
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2588	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.	2589	in the prepare watcher and would dispose of the check watcher.
1968		2590
1969	Method 3: If the module to be embedded supports explicit event	2591	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2592	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2593	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2594
1973	static void	2595	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2596	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2597	{
1976	adns_state ads = (adns_state)w->data;	2598	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2599	update_now (EV_A);
1978		2600
1979	adns_processtimeouts (ads, &tv_now);	2601	adns_processtimeouts (ads, &tv_now);
1980	}	2602	}
1981		2603
1982	static void	2604	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2605	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2606	{
1985	adns_state ads = (adns_state)w->data;	2607	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2608	update_now (EV_A);
1987		2609
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2610	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2611	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2612	}
1991		2613
1992	// do not ever call adns_afterpoll	2614	// do not ever call adns_afterpoll
1993		2615
1994	Method 4: Do not use a prepare or check watcher because the module you	2616	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	2617	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	2618	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	2619	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2620	this approach, effectively embedding EV as a client into the horrible
		2621	libglib event loop.
1999		2622
2000	static gint	2623	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2625	{
2003	int got_events = 0;	2626	int got_events = 0;
2004		2627
2005	for (n = 0; n < nfds; ++n)	2628	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2629	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2630
2008	if (timeout >= 0)	2631	if (timeout >= 0)
2009	// create/start timer	2632	// create/start timer
2010		2633
2011	// poll	2634	// poll
2012	ev_loop (EV_A_ 0);	2635	ev_loop (EV_A_ 0);
2013		2636
2014	// stop timer again	2637	// stop timer again
2015	if (timeout >= 0)	2638	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2639	ev_timer_stop (EV_A_ &to);
2017		2640
2018	// stop io watchers again - their callbacks should have set	2641	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2642	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2643	ev_io_stop (EV_A_ iow [n]);
2021		2644
2022	return got_events;	2645	return got_events;
2023	}	2646	}
2024		2647
2025		2648
2026	=head2 C<ev_embed> - when one backend isn't enough...	2649	=head2 C<ev_embed> - when one backend isn't enough...
2027		2650
2028	This is a rather advanced watcher type that lets you embed one event loop	2651	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2657	prioritise I/O.
2035		2658
2036	As an example for a bug workaround, the kqueue backend might only support	2659	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	2660	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	2661	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	2662	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	2663	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	2664	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.	2665	C<kevent>, but at least you can use both mechanisms for what they are
		2666	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2667
2044	As for prioritising I/O: rarely you have the case where some fds have	2668	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	2669	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	2670	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	2671	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.	2672	the rest in a second one, and embed the second one in the first.
2049		2673
2050	As long as the watcher is active, the callback will be invoked every time	2674	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	2675	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	2676	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	2677	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	2678	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	2679	to give the embedded loop strictly lower priority for example).
2056	embedded loop sweep.
2057		2680
2058	As long as the watcher is started it will automatically handle events. The	2681	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	2682	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		2683
2063	Also, there have not currently been made special provisions for forking:	2684	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,	2685	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	2686	embedding loop forks. In other cases, the user is responsible for calling
2066	yourself.	2687	C<ev_loop_fork> on the embedded loop.
2067		2688
2068	Unfortunately, not all backends are embeddable, only the ones returned by	2689	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2690	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	2691	portable one.
2071		2692
2072	So when you want to use this feature you will always have to be prepared	2693	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	2694	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	2695	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.	2696	create it, and if that fails, use the normal loop for everything.
2076		2697
		2698	=head3 C<ev_embed> and fork
		2699
		2700	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2701	automatically be applied to the embedded loop as well, so no special
		2702	fork handling is required in that case. When the watcher is not running,
		2703	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2704	as applicable.
		2705
2077	=head3 Watcher-Specific Functions and Data Members	2706	=head3 Watcher-Specific Functions and Data Members
2078		2707
2079	=over 4	2708	=over 4
2080		2709
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2710	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		2713
2085	Configures the watcher to embed the given loop, which must be	2714	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	2715	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	2716	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,	2717	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).	2718	if you do not want that, you need to temporarily stop the embed watcher).
2090		2719
2091	=item ev_embed_sweep (loop, ev_embed *)	2720	=item ev_embed_sweep (loop, ev_embed *)
2092		2721
2093	Make a single, non-blocking sweep over the embedded loop. This works	2722	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	2723	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095	apropriate way for embedded loops.	2724	appropriate way for embedded loops.
2096		2725
2097	=item struct ev_loop *other [read-only]	2726	=item struct ev_loop *other [read-only]
2098		2727
2099	The embedded event loop.	2728	The embedded event loop.
2100		2729
…		…
2102		2731
2103	=head3 Examples	2732	=head3 Examples
2104		2733
2105	Example: Try to get an embeddable event loop and embed it into the default	2734	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	2735	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	2736	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	2737	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	2738	used).
2110		2739
2111	struct ev_loop *loop_hi = ev_default_init (0);	2740	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	2741	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	2742	ev_embed embed;
2114		2743
2115	// see if there is a chance of getting one that works	2744	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	2745	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	2748	: 0;
2120		2749
2121	// if we got one, then embed it, otherwise default to loop_hi	2750	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	2751	if (loop_lo)
2123	{	2752	{
2124	ev_embed_init (&embed, 0, loop_lo);	2753	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	2754	ev_embed_start (loop_hi, &embed);
2126	}	2755	}
2127	else	2756	else
2128	loop_lo = loop_hi;	2757	loop_lo = loop_hi;
2129		2758
2130	Example: Check if kqueue is available but not recommended and create	2759	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	2760	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	2761	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		2763
2135	struct ev_loop *loop = ev_default_init (0);	2764	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	2765	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	2766	ev_embed embed;
2138		2767
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	2770	{
2142	ev_embed_init (&embed, 0, loop_socket);	2771	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	2772	ev_embed_start (loop, &embed);
2144	}	2773	}
2145		2774
2146	if (!loop_socket)	2775	if (!loop_socket)
2147	loop_socket = loop;	2776	loop_socket = loop;
2148		2777
2149	// now use loop_socket for all sockets, and loop for everything else	2778	// now use loop_socket for all sockets, and loop for everything else
2150		2779
2151		2780
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2781	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		2782
2154	Fork watchers are called when a C<fork ()> was detected (usually because	2783	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,	2786	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	2787	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	2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2160	handlers will be invoked, too, of course.	2789	handlers will be invoked, too, of course.
2161		2790
		2791	=head3 The special problem of life after fork - how is it possible?
		2792
		2793	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2794	up/change the process environment, followed by a call to C<exec()>. This
		2795	sequence should be handled by libev without any problems.
		2796
		2797	This changes when the application actually wants to do event handling
		2798	in the child, or both parent in child, in effect "continuing" after the
		2799	fork.
		2800
		2801	The default mode of operation (for libev, with application help to detect
		2802	forks) is to duplicate all the state in the child, as would be expected
		2803	when I<either> the parent I<or> the child process continues.
		2804
		2805	When both processes want to continue using libev, then this is usually the
		2806	wrong result. In that case, usually one process (typically the parent) is
		2807	supposed to continue with all watchers in place as before, while the other
		2808	process typically wants to start fresh, i.e. without any active watchers.
		2809
		2810	The cleanest and most efficient way to achieve that with libev is to
		2811	simply create a new event loop, which of course will be "empty", and
		2812	use that for new watchers. This has the advantage of not touching more
		2813	memory than necessary, and thus avoiding the copy-on-write, and the
		2814	disadvantage of having to use multiple event loops (which do not support
		2815	signal watchers).
		2816
		2817	When this is not possible, or you want to use the default loop for
		2818	other reasons, then in the process that wants to start "fresh", call
		2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2820	the default loop will "orphan" (not stop) all registered watchers, so you
		2821	have to be careful not to execute code that modifies those watchers. Note
		2822	also that in that case, you have to re-register any signal watchers.
		2823
2162	=head3 Watcher-Specific Functions and Data Members	2824	=head3 Watcher-Specific Functions and Data Members
2163		2825
2164	=over 4	2826	=over 4
2165		2827
2166	=item ev_fork_init (ev_signal *, callback)	2828	=item ev_fork_init (ev_signal *, callback)
…		…
2198	is that the author does not know of a simple (or any) algorithm for a	2860	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	2861	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	2862	need elaborate support such as pthreads.
2201		2863
2202	That means that if you want to queue data, you have to provide your own	2864	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	2865	queue. But at least I can tell you how to implement locking around your
2204	queue:	2866	queue:
2205		2867
2206	=over 4	2868	=over 4
2207		2869
2208	=item queueing from a signal handler context	2870	=item queueing from a signal handler context
2209		2871
2210	To implement race-free queueing, you simply add to the queue in the signal	2872	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	2873	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	2874	an example that does that for some fictitious SIGUSR1 handler:
2213		2875
2214	static ev_async mysig;	2876	static ev_async mysig;
2215		2877
2216	static void	2878	static void
2217	sigusr1_handler (void)	2879	sigusr1_handler (void)
…		…
2283	=over 4	2945	=over 4
2284		2946
2285	=item ev_async_init (ev_async *, callback)	2947	=item ev_async_init (ev_async *, callback)
2286		2948
2287	Initialises and configures the async watcher - it has no parameters of any	2949	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,	2950	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2289	believe me.	2951	trust me.
2290		2952
2291	=item ev_async_send (loop, ev_async *)	2953	=item ev_async_send (loop, ev_async *)
2292		2954
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2955	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	2956	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	2957	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	2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297	section below on what exactly this means).	2959	section below on what exactly this means).
2298		2960
		2961	Note that, as with other watchers in libev, multiple events might get
		2962	compressed into a single callback invocation (another way to look at this
		2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2964	reset when the event loop detects that).
		2965
2299	This call incurs the overhead of a syscall only once per loop iteration,	2966	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	2967	iteration, so while the overhead might be noticeable, it doesn't apply to
2301	calls to C<ev_async_send>.	2968	repeated calls to C<ev_async_send> for the same event loop.
2302		2969
2303	=item bool = ev_async_pending (ev_async *)	2970	=item bool = ev_async_pending (ev_async *)
2304		2971
2305	Returns a non-zero value when C<ev_async_send> has been called on the	2972	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	2973	watcher but the event has not yet been processed (or even noted) by the
2307	event loop.	2974	event loop.
2308		2975
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2976	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,	2977	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	2978	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.	2979	quickly check whether invoking the loop might be a good idea.
2313		2980
2314	Not that this does I<not> check wether the watcher itself is pending, only	2981	Not that this does I<not> check whether the watcher itself is pending,
2315	wether it has been requested to make this watcher pending.	2982	only whether it has been requested to make this watcher pending: there
		2983	is a time window between the event loop checking and resetting the async
		2984	notification, and the callback being invoked.
2316		2985
2317	=back	2986	=back
2318		2987
2319		2988
2320	=head1 OTHER FUNCTIONS	2989	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	2993	=over 4
2325		2994
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2995	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		2996
2328	This function combines a simple timer and an I/O watcher, calls your	2997	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	2998	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	2999	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	3000	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	3001	more watchers yourself.
2333		3002
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	3003	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	3004	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	3005	the given C<fd> and C<events> set will be created and started.
2337		3006
2338	If C<timeout> is less than 0, then no timeout watcher will be	3007	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	3008	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	3009	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		3010
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3011	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	3012	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>	3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346	value passed to C<ev_once>:	3014	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3015	a timeout and an io event at the same time - you probably should give io
		3016	events precedence.
2347		3017
		3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3019
2348	static void stdin_ready (int revents, void *arg)	3020	static void stdin_ready (int revents, void *arg)
2349	{	3021	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	3022	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	3023	/* stdin might have data for us, joy! */;
		3024	else if (revents & EV_TIMEOUT)
		3025	/* doh, nothing entered */;
2354	}	3026	}
2355		3027
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		3029
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)	3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2359		3031
2360	Feeds the given event set into the event loop, as if the specified event	3032	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	3033	had happened for the specified watcher (which must be a pointer to an
2362	initialised but not necessarily started event watcher).	3034	initialised but not necessarily started event watcher).
2363		3035
2364	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2365		3037
2366	Feed an event on the given fd, as if a file descriptor backend detected	3038	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	3039	the given events it.
2368		3040
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2370		3042
2371	Feed an event as if the given signal occured (C<loop> must be the default	3043	Feed an event as if the given signal occurred (C<loop> must be the default
2372	loop!).	3044	loop!).
2373		3045
2374	=back	3046	=back
2375		3047
2376		3048
…		…
2405	=back	3077	=back
2406		3078
2407	=head1 C++ SUPPORT	3079	=head1 C++ SUPPORT
2408		3080
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3081	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	3082	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.	3083	the callback model to a model using method callbacks on objects.
2412		3084
2413	To use it,	3085	To use it,
2414		3086
2415	#include <ev++.h>	3087	#include <ev++.h>
2416		3088
2417	This automatically includes F<ev.h> and puts all of its definitions (many	3089	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	3090	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	3091	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3092	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	3159	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.	3160	thunking function, making it as fast as a direct C callback.
2489		3161
2490	Example: simple class declaration and watcher initialisation	3162	Example: simple class declaration and watcher initialisation
2491		3163
2492	struct myclass	3164	struct myclass
2493	{	3165	{
2494	void io_cb (ev::io &w, int revents) { }	3166	void io_cb (ev::io &w, int revents) { }
2495	}	3167	}
2496		3168
2497	myclass obj;	3169	myclass obj;
2498	ev::io iow;	3170	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	3171	iow.set <myclass, &myclass::io_cb> (&obj);
		3172
		3173	=item w->set (object *)
		3174
		3175	This is an B<experimental> feature that might go away in a future version.
		3176
		3177	This is a variation of a method callback - leaving out the method to call
		3178	will default the method to C<operator ()>, which makes it possible to use
		3179	functor objects without having to manually specify the C<operator ()> all
		3180	the time. Incidentally, you can then also leave out the template argument
		3181	list.
		3182
		3183	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3184	int revents)>.
		3185
		3186	See the method-C<set> above for more details.
		3187
		3188	Example: use a functor object as callback.
		3189
		3190	struct myfunctor
		3191	{
		3192	void operator() (ev::io &w, int revents)
		3193	{
		3194	...
		3195	}
		3196	}
		3197
		3198	myfunctor f;
		3199
		3200	ev::io w;
		3201	w.set (&f);
2500		3202
2501	=item w->set<function> (void *data = 0)	3203	=item w->set<function> (void *data = 0)
2502		3204
2503	Also sets a callback, but uses a static method or plain function as	3205	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	3206	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		3208
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3209	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		3210
2509	See the method-C<set> above for more details.	3211	See the method-C<set> above for more details.
2510		3212
2511	Example:	3213	Example: Use a plain function as callback.
2512		3214
2513	static void io_cb (ev::io &w, int revents) { }	3215	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	3216	iow.set <io_cb> ();
2515		3217
2516	=item w->set (struct ev_loop *)	3218	=item w->set (struct ev_loop *)
2517		3219
2518	Associates a different C<struct ev_loop> with this watcher. You can only	3220	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).	3221	do this when the watcher is inactive (and not pending either).
2520		3222
2521	=item w->set ([args])	3223	=item w->set ([arguments])
2522		3224
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3225	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	3226	called at least once. Unlike the C counterpart, an active watcher gets
2525	automatically stopped and restarted when reconfiguring it with this	3227	automatically stopped and restarted when reconfiguring it with this
2526	method.	3228	method.
2527		3229
2528	=item w->start ()	3230	=item w->start ()
…		…
2552	=back	3254	=back
2553		3255
2554	Example: Define a class with an IO and idle watcher, start one of them in	3256	Example: Define a class with an IO and idle watcher, start one of them in
2555	the constructor.	3257	the constructor.
2556		3258
2557	class myclass	3259	class myclass
2558	{	3260	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	3261	ev::io io ; void io_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		3263
2562	myclass (int fd)	3264	myclass (int fd)
2563	{	3265	{
2564	io .set <myclass, &myclass::io_cb > (this);	3266	io .set <myclass, &myclass::io_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	3267	idle.set <myclass, &myclass::idle_cb> (this);
2566		3268
2567	io.start (fd, ev::READ);	3269	io.start (fd, ev::READ);
2568	}	3270	}
2569	};	3271	};
2570		3272
2571		3273
2572	=head1 OTHER LANGUAGE BINDINGS	3274	=head1 OTHER LANGUAGE BINDINGS
2573		3275
2574	Libev does not offer other language bindings itself, but bindings for a	3276	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	3277	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	3278	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	3279	me a note.
2578		3280
2579	=over 4	3281	=over 4
2580		3282
2581	=item Perl	3283	=item Perl
2582		3284
2583	The EV module implements the full libev API and is actually used to test	3285	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,	3286	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	3287	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	3288	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>).	3289	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3290	and C<EV::Glib>).
2588		3291
2589	It can be found and installed via CPAN, its homepage is found at	3292	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	3293	L<http://software.schmorp.de/pkg/EV>.
2591		3294
		3295	=item Python
		3296
		3297	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3298	seems to be quite complete and well-documented.
		3299
2592	=item Ruby	3300	=item Ruby
2593		3301
2594	Tony Arcieri has written a ruby extension that offers access to a subset	3302	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	3303	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	3304	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	3305	L<http://rev.rubyforge.org/>.
2598		3306
		3307	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3308	makes rev work even on mingw.
		3309
		3310	=item Haskell
		3311
		3312	A haskell binding to libev is available at
		3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3314
2599	=item D	3315	=item D
2600		3316
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3317	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>.	3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3319
		3320	=item Ocaml
		3321
		3322	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2603		3324
2604	=back	3325	=back
2605		3326
2606		3327
2607	=head1 MACRO MAGIC	3328	=head1 MACRO MAGIC
2608		3329
2609	Libev can be compiled with a variety of options, the most fundamantal	3330	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3331	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	3332	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		3333
2613	To make it easier to write programs that cope with either variant, the	3334	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	3335	following macros are defined:
…		…
2619		3340
2620	This provides the loop I<argument> for functions, if one is required ("ev	3341	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,	3342	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:	3343	C<EV_A_> is used when other arguments are following. Example:
2623		3344
2624	ev_unref (EV_A);	3345	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	3346	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	3347	ev_loop (EV_A_ 0);
2627		3348
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3349	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	3350	which is often provided by the following macro.
2630		3351
2631	=item C<EV_P>, C<EV_P_>	3352	=item C<EV_P>, C<EV_P_>
2632		3353
2633	This provides the loop I<parameter> for functions, if one is required ("ev	3354	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,	3355	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:	3356	C<EV_P_> is used when other parameters are following. Example:
2636		3357
2637	// this is how ev_unref is being declared	3358	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	3359	static void ev_unref (EV_P);
2639		3360
2640	// this is how you can declare your typical callback	3361	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	3362	static void cb (EV_P_ ev_timer *w, int revents)
2642		3363
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3364	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	3365	suitable for use with C<EV_A>.
2645		3366
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3367	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		3383
2663	Example: Declare and initialise a check watcher, utilising the above	3384	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	3385	macros so it will work regardless of whether multiple loops are supported
2665	or not.	3386	or not.
2666		3387
2667	static void	3388	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	3389	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	3390	{
2670	ev_check_stop (EV_A_ w);	3391	ev_check_stop (EV_A_ w);
2671	}	3392	}
2672		3393
2673	ev_check check;	3394	ev_check check;
2674	ev_check_init (&check, check_cb);	3395	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	3396	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	3397	ev_loop (EV_DEFAULT_ 0);
2677		3398
2678	=head1 EMBEDDING	3399	=head1 EMBEDDING
2679		3400
2680	Libev can (and often is) directly embedded into host	3401	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	3402	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	3409	libev somewhere in your source tree).
2689		3410
2690	=head2 FILESETS	3411	=head2 FILESETS
2691		3412
2692	Depending on what features you need you need to include one or more sets of files	3413	Depending on what features you need you need to include one or more sets of files
2693	in your app.	3414	in your application.
2694		3415
2695	=head3 CORE EVENT LOOP	3416	=head3 CORE EVENT LOOP
2696		3417
2697	To include only the libev core (all the C<ev_*> functions), with manual	3418	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	3419	configuration (no autoconf):
2699		3420
2700	#define EV_STANDALONE 1	3421	#define EV_STANDALONE 1
2701	#include "ev.c"	3422	#include "ev.c"
2702		3423
2703	This will automatically include F<ev.h>, too, and should be done in a	3424	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	3425	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	3426	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	3427	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	3428	where you can put other configuration options):
2708		3429
2709	#define EV_STANDALONE 1	3430	#define EV_STANDALONE 1
2710	#include "ev.h"	3431	#include "ev.h"
2711		3432
2712	Both header files and implementation files can be compiled with a C++	3433	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	3434	compiler (at least, that's a stated goal, and breakage will be treated
2714	as a bug).	3435	as a bug).
2715		3436
2716	You need the following files in your source tree, or in a directory	3437	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):	3438	in your include path (e.g. in libev/ when using -Ilibev):
2718		3439
2719	ev.h	3440	ev.h
2720	ev.c	3441	ev.c
2721	ev_vars.h	3442	ev_vars.h
2722	ev_wrap.h	3443	ev_wrap.h
2723		3444
2724	ev_win32.c required on win32 platforms only	3445	ev_win32.c required on win32 platforms only
2725		3446
2726	ev_select.c only when select backend is enabled (which is enabled by default)	3447	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)	3448	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)	3449	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)	3450	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)	3451	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		3452
2732	F<ev.c> includes the backend files directly when enabled, so you only need	3453	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	3454	to compile this single file.
2734		3455
2735	=head3 LIBEVENT COMPATIBILITY API	3456	=head3 LIBEVENT COMPATIBILITY API
2736		3457
2737	To include the libevent compatibility API, also include:	3458	To include the libevent compatibility API, also include:
2738		3459
2739	#include "event.c"	3460	#include "event.c"
2740		3461
2741	in the file including F<ev.c>, and:	3462	in the file including F<ev.c>, and:
2742		3463
2743	#include "event.h"	3464	#include "event.h"
2744		3465
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	3466	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		3467
2747	You need the following additional files for this:	3468	You need the following additional files for this:
2748		3469
2749	event.h	3470	event.h
2750	event.c	3471	event.c
2751		3472
2752	=head3 AUTOCONF SUPPORT	3473	=head3 AUTOCONF SUPPORT
2753		3474
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	3475	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	3476	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	3477	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	3478	include F<config.h> and configure itself accordingly.
2758		3479
2759	For this of course you need the m4 file:	3480	For this of course you need the m4 file:
2760		3481
2761	libev.m4	3482	libev.m4
2762		3483
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	3484	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		3485
2765	Libev can be configured via a variety of preprocessor symbols you have to	3486	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	3487	define before including any of its files. The default in the absence of
2767	autoconf is noted for every option.	3488	autoconf is documented for every option.
2768		3489
2769	=over 4	3490	=over 4
2770		3491
2771	=item EV_STANDALONE	3492	=item EV_STANDALONE
2772		3493
…		…
2774	keeps libev from including F<config.h>, and it also defines dummy	3495	keeps libev from including F<config.h>, and it also defines dummy
2775	implementations for some libevent functions (such as logging, which is not	3496	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	3497	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.	3498	F<event.h> that are not directly supported by the libev core alone.
2778		3499
		3500	In stanbdalone mode, libev will still try to automatically deduce the
		3501	configuration, but has to be more conservative.
		3502
2779	=item EV_USE_MONOTONIC	3503	=item EV_USE_MONOTONIC
2780		3504
2781	If defined to be C<1>, libev will try to detect the availability of the	3505	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	3506	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	3507	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	3508	you usually have to link against librt or something similar. Enabling it
2785	the functionality isn't available is safe, though, although you have	3509	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>	3510	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	3511	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2788		3512
2789	=item EV_USE_REALTIME	3513	=item EV_USE_REALTIME
2790		3514
2791	If defined to be C<1>, libev will try to detect the availability of the	3515	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	3516	real-time clock option at compile time (and assume its availability
2793	runtime if successful). Otherwise no use of the realtime clock option will	3517	at runtime if successful). Otherwise no use of the real-time clock
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3518	option will be attempted. This effectively replaces C<gettimeofday>
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3519	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3520	correctness. See the note about libraries in the description of
		3521	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3522	C<EV_USE_CLOCK_SYSCALL>.
		3523
		3524	=item EV_USE_CLOCK_SYSCALL
		3525
		3526	If defined to be C<1>, libev will try to use a direct syscall instead
		3527	of calling the system-provided C<clock_gettime> function. This option
		3528	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3529	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3530	programs needlessly. Using a direct syscall is slightly slower (in
		3531	theory), because no optimised vdso implementation can be used, but avoids
		3532	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3533	higher, as it simplifies linking (no need for C<-lrt>).
2797		3534
2798	=item EV_USE_NANOSLEEP	3535	=item EV_USE_NANOSLEEP
2799		3536
2800	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3537	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 ()>.	3538	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2809	2.7 or newer, otherwise disabled.	3546	2.7 or newer, otherwise disabled.
2810		3547
2811	=item EV_USE_SELECT	3548	=item EV_USE_SELECT
2812		3549
2813	If undefined or defined to be C<1>, libev will compile in support for the	3550	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	3551	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	3552	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	3553	will not be compiled in.
2817		3554
2818	=item EV_SELECT_USE_FD_SET	3555	=item EV_SELECT_USE_FD_SET
2819		3556
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	3557	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	3558	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	3559	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	3560	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	3561	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	3562	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2826	influence the size of the C<fd_set> used.	3563	configures the maximum size of the C<fd_set>.
2827		3564
2828	=item EV_SELECT_IS_WINSOCKET	3565	=item EV_SELECT_IS_WINSOCKET
2829		3566
2830	When defined to C<1>, the select backend will assume that	3567	When defined to C<1>, the select backend will assume that
2831	select/socket/connect etc. don't understand file descriptors but	3568	select/socket/connect etc. don't understand file descriptors but
…		…
2876	otherwise another method will be used as fallback. This is the preferred	3613	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	3614	backend for Solaris 10 systems.
2878		3615
2879	=item EV_USE_DEVPOLL	3616	=item EV_USE_DEVPOLL
2880		3617
2881	reserved for future expansion, works like the USE symbols above.	3618	Reserved for future expansion, works like the USE symbols above.
2882		3619
2883	=item EV_USE_INOTIFY	3620	=item EV_USE_INOTIFY
2884		3621
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	3622	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	3623	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	3630	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	3631	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"	3632	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.	3633	as well as for signal and thread safety in C<ev_async> watchers.
2897		3634
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	3635	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.	3636	(from F<signal.h>), which is usually good enough on most platforms.
2900		3637
2901	=item EV_H	3638	=item EV_H
2902		3639
2903	The name of the F<ev.h> header file used to include it. The default if	3640	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	3679	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	3680	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	3681	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	3682	fine.
2946		3683
2947	If your embedding app does not need any priorities, defining these both to	3684	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	3685	both to C<0> will save some memory and CPU.
2949		3686
2950	=item EV_PERIODIC_ENABLE	3687	=item EV_PERIODIC_ENABLE
2951		3688
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	3689	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	3690	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	code.	3697	code.
2961		3698
2962	=item EV_EMBED_ENABLE	3699	=item EV_EMBED_ENABLE
2963		3700
2964	If undefined or defined to be C<1>, then embed watchers are supported. If	3701	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.	3702	defined to be C<0>, then they are not. Embed watchers rely on most other
		3703	watcher types, which therefore must not be disabled.
2966		3704
2967	=item EV_STAT_ENABLE	3705	=item EV_STAT_ENABLE
2968		3706
2969	If undefined or defined to be C<1>, then stat watchers are supported. If	3707	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.	3708	defined to be C<0>, then they are not.
…		…
2980	defined to be C<0>, then they are not.	3718	defined to be C<0>, then they are not.
2981		3719
2982	=item EV_MINIMAL	3720	=item EV_MINIMAL
2983		3721
2984	If you need to shave off some kilobytes of code at the expense of some	3722	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently only used for gcc to override	3723	speed (but with the full API), define this symbol to C<1>. Currently this
2986	some inlining decisions, saves roughly 30% codesize of amd64.	3724	is used to override some inlining decisions, saves roughly 30% code size
		3725	on amd64. It also selects a much smaller 2-heap for timer management over
		3726	the default 4-heap.
		3727
		3728	You can save even more by disabling watcher types you do not need
		3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3730	(C<-DNDEBUG>) will usually reduce code size a lot.
		3731
		3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3733	provide a bare-bones event library. See C<ev.h> for details on what parts
		3734	of the API are still available, and do not complain if this subset changes
		3735	over time.
2987		3736
2988	=item EV_PID_HASHSIZE	3737	=item EV_PID_HASHSIZE
2989		3738
2990	C<ev_child> watchers use a small hash table to distribute workload by	3739	C<ev_child> watchers use a small hash table to distribute workload by
2991	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2998	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3747	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2999	usually more than enough. If you need to manage thousands of C<ev_stat>	3748	usually more than enough. If you need to manage thousands of C<ev_stat>
3000	watchers you might want to increase this value (I<must> be a power of	3749	watchers you might want to increase this value (I<must> be a power of
3001	two).	3750	two).
3002		3751
		3752	=item EV_USE_4HEAP
		3753
		3754	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3755	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3757	faster performance with many (thousands) of watchers.
		3758
		3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3760	(disabled).
		3761
		3762	=item EV_HEAP_CACHE_AT
		3763
		3764	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3765	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3766	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3767	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3768	but avoids random read accesses on heap changes. This improves performance
		3769	noticeably with many (hundreds) of watchers.
		3770
		3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3772	(disabled).
		3773
		3774	=item EV_VERIFY
		3775
		3776	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3777	be done: If set to C<0>, no internal verification code will be compiled
		3778	in. If set to C<1>, then verification code will be compiled in, but not
		3779	called. If set to C<2>, then the internal verification code will be
		3780	called once per loop, which can slow down libev. If set to C<3>, then the
		3781	verification code will be called very frequently, which will slow down
		3782	libev considerably.
		3783
		3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3785	C<0>.
		3786
3003	=item EV_COMMON	3787	=item EV_COMMON
3004		3788
3005	By default, all watchers have a C<void *data> member. By redefining	3789	By default, all watchers have a C<void *data> member. By redefining
3006	this macro to a something else you can include more and other types of	3790	this macro to a something else you can include more and other types of
3007	members. You have to define it each time you include one of the files,	3791	members. You have to define it each time you include one of the files,
3008	though, and it must be identical each time.	3792	though, and it must be identical each time.
3009		3793
3010	For example, the perl EV module uses something like this:	3794	For example, the perl EV module uses something like this:
3011		3795
3012	#define EV_COMMON \	3796	#define EV_COMMON \
3013	SV *self; /* contains this struct */ \	3797	SV *self; /* contains this struct */ \
3014	SV *cb_sv, *fh /* note no trailing ";" */	3798	SV *cb_sv, *fh /* note no trailing ";" */
3015		3799
3016	=item EV_CB_DECLARE (type)	3800	=item EV_CB_DECLARE (type)
3017		3801
3018	=item EV_CB_INVOKE (watcher, revents)	3802	=item EV_CB_INVOKE (watcher, revents)
3019		3803
…		…
3024	definition and a statement, respectively. See the F<ev.h> header file for	3808	definition and a statement, respectively. See the F<ev.h> header file for
3025	their default definitions. One possible use for overriding these is to	3809	their default definitions. One possible use for overriding these is to
3026	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3810	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3027	method calls instead of plain function calls in C++.	3811	method calls instead of plain function calls in C++.
3028		3812
		3813	=back
		3814
3029	=head2 EXPORTED API SYMBOLS	3815	=head2 EXPORTED API SYMBOLS
3030		3816
3031	If you need to re-export the API (e.g. via a dll) and you need a list of	3817	If you need to re-export the API (e.g. via a DLL) and you need a list of
3032	exported symbols, you can use the provided F<Symbol.*> files which list	3818	exported symbols, you can use the provided F<Symbol.*> files which list
3033	all public symbols, one per line:	3819	all public symbols, one per line:
3034		3820
3035	Symbols.ev for libev proper	3821	Symbols.ev for libev proper
3036	Symbols.event for the libevent emulation	3822	Symbols.event for the libevent emulation
3037		3823
3038	This can also be used to rename all public symbols to avoid clashes with	3824	This can also be used to rename all public symbols to avoid clashes with
3039	multiple versions of libev linked together (which is obviously bad in	3825	multiple versions of libev linked together (which is obviously bad in
3040	itself, but sometimes it is inconvinient to avoid this).	3826	itself, but sometimes it is inconvenient to avoid this).
3041		3827
3042	A sed command like this will create wrapper C<#define>'s that you need to	3828	A sed command like this will create wrapper C<#define>'s that you need to
3043	include before including F<ev.h>:	3829	include before including F<ev.h>:
3044		3830
3045	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3831	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3062	file.	3848	file.
3063		3849
3064	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3850	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3065	that everybody includes and which overrides some configure choices:	3851	that everybody includes and which overrides some configure choices:
3066		3852
3067	#define EV_MINIMAL 1	3853	#define EV_MINIMAL 1
3068	#define EV_USE_POLL 0	3854	#define EV_USE_POLL 0
3069	#define EV_MULTIPLICITY 0	3855	#define EV_MULTIPLICITY 0
3070	#define EV_PERIODIC_ENABLE 0	3856	#define EV_PERIODIC_ENABLE 0
3071	#define EV_STAT_ENABLE 0	3857	#define EV_STAT_ENABLE 0
3072	#define EV_FORK_ENABLE 0	3858	#define EV_FORK_ENABLE 0
3073	#define EV_CONFIG_H <config.h>	3859	#define EV_CONFIG_H <config.h>
3074	#define EV_MINPRI 0	3860	#define EV_MINPRI 0
3075	#define EV_MAXPRI 0	3861	#define EV_MAXPRI 0
3076		3862
3077	#include "ev++.h"	3863	#include "ev++.h"
3078		3864
3079	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3080		3866
3081	#include "ev_cpp.h"	3867	#include "ev_cpp.h"
3082	#include "ev.c"	3868	#include "ev.c"
3083		3869
		3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3084		3871
3085	=head1 THREADS AND COROUTINES	3872	=head2 THREADS AND COROUTINES
3086		3873
3087	=head2 THREADS	3874	=head3 THREADS
3088		3875
3089	Libev itself is completely threadsafe, but it uses no locking. This	3876	All libev functions are reentrant and thread-safe unless explicitly
		3877	documented otherwise, but libev implements no locking itself. This means
3090	means that you can use as many loops as you want in parallel, as long as	3878	that you can use as many loops as you want in parallel, as long as there
3091	only one thread ever calls into one libev function with the same loop	3879	are no concurrent calls into any libev function with the same loop
3092	parameter.	3880	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3881	of course): libev guarantees that different event loops share no data
		3882	structures that need any locking.
3093		3883
3094	Or put differently: calls with different loop parameters can be done in	3884	Or to put it differently: calls with different loop parameters can be done
3095	parallel from multiple threads, calls with the same loop parameter must be	3885	concurrently from multiple threads, calls with the same loop parameter
3096	done serially (but can be done from different threads, as long as only one	3886	must be done serially (but can be done from different threads, as long as
3097	thread ever is inside a call at any point in time, e.g. by using a mutex	3887	only one thread ever is inside a call at any point in time, e.g. by using
3098	per loop).	3888	a mutex per loop).
3099		3889
3100	If you want to know which design is best for your problem, then I cannot	3890	Specifically to support threads (and signal handlers), libev implements
		3891	so-called C<ev_async> watchers, which allow some limited form of
		3892	concurrency on the same event loop, namely waking it up "from the
		3893	outside".
		3894
		3895	If you want to know which design (one loop, locking, or multiple loops
		3896	without or something else still) is best for your problem, then I cannot
3101	help you but by giving some generic advice:	3897	help you, but here is some generic advice:
3102		3898
3103	=over 4	3899	=over 4
3104		3900
3105	=item * most applications have a main thread: use the default libev loop	3901	=item * most applications have a main thread: use the default libev loop
3106	in that thread, or create a seperate thread running only the default loop.	3902	in that thread, or create a separate thread running only the default loop.
3107		3903
3108	This helps integrating other libraries or software modules that use libev	3904	This helps integrating other libraries or software modules that use libev
3109	themselves and don't care/know about threading.	3905	themselves and don't care/know about threading.
3110		3906
3111	=item * one loop per thread is usually a good model.	3907	=item * one loop per thread is usually a good model.
3112		3908
3113	Doing this is almost never wrong, sometimes a better-performance model	3909	Doing this is almost never wrong, sometimes a better-performance model
3114	exists, but it is always a good start.	3910	exists, but it is always a good start.
3115		3911
3116	=item * other models exist, such as the leader/follower pattern, where one	3912	=item * other models exist, such as the leader/follower pattern, where one
3117	loop is handed through multiple threads in a kind of round-robbin fashion.	3913	loop is handed through multiple threads in a kind of round-robin fashion.
3118		3914
3119	Chosing a model is hard - look around, learn, know that usually you cna do	3915	Choosing a model is hard - look around, learn, know that usually you can do
3120	better than you currently do :-)	3916	better than you currently do :-)
3121		3917
3122	=item * often you need to talk to some other thread which blocks in the	3918	=item * often you need to talk to some other thread which blocks in the
		3919	event loop.
		3920
3123	event loop - C<ev_async> watchers can be used to wake them up from other	3921	C<ev_async> watchers can be used to wake them up from other threads safely
3124	threads safely (or from signal contexts...).	3922	(or from signal contexts...).
		3923
		3924	An example use would be to communicate signals or other events that only
		3925	work in the default loop by registering the signal watcher with the
		3926	default loop and triggering an C<ev_async> watcher from the default loop
		3927	watcher callback into the event loop interested in the signal.
3125		3928
3126	=back	3929	=back
3127		3930
		3931	=head4 THREAD LOCKING EXAMPLE
		3932
3128	=head2 COROUTINES	3933	=head3 COROUTINES
3129		3934
3130	Libev is much more accomodating to coroutines ("cooperative threads"):	3935	Libev is very accommodating to coroutines ("cooperative threads"):
3131	libev fully supports nesting calls to it's functions from different	3936	libev fully supports nesting calls to its functions from different
3132	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3133	different coroutines and switch freely between both coroutines running the	3938	different coroutines, and switch freely between both coroutines running the
3134	loop, as long as you don't confuse yourself). The only exception is that	3939	loop, as long as you don't confuse yourself). The only exception is that
3135	you must not do this from C<ev_periodic> reschedule callbacks.	3940	you must not do this from C<ev_periodic> reschedule callbacks.
3136		3941
3137	Care has been invested into making sure that libev does not keep local	3942	Care has been taken to ensure that libev does not keep local state inside
3138	state inside C<ev_loop>, and other calls do not usually allow coroutine	3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3139	switches.	3944	they do not call any callbacks.
3140		3945
		3946	=head2 COMPILER WARNINGS
3141		3947
3142	=head1 COMPLEXITIES	3948	Depending on your compiler and compiler settings, you might get no or a
		3949	lot of warnings when compiling libev code. Some people are apparently
		3950	scared by this.
3143		3951
3144	In this section the complexities of (many of) the algorithms used inside	3952	However, these are unavoidable for many reasons. For one, each compiler
3145	libev will be explained. For complexity discussions about backends see the	3953	has different warnings, and each user has different tastes regarding
3146	documentation for C<ev_default_init>.	3954	warning options. "Warn-free" code therefore cannot be a goal except when
		3955	targeting a specific compiler and compiler-version.
3147		3956
3148	All of the following are about amortised time: If an array needs to be	3957	Another reason is that some compiler warnings require elaborate
3149	extended, libev needs to realloc and move the whole array, but this	3958	workarounds, or other changes to the code that make it less clear and less
3150	happens asymptotically never with higher number of elements, so O(1) might	3959	maintainable.
3151	mean it might do a lengthy realloc operation in rare cases, but on average
3152	it is much faster and asymptotically approaches constant time.
3153		3960
3154	=over 4	3961	And of course, some compiler warnings are just plain stupid, or simply
		3962	wrong (because they don't actually warn about the condition their message
		3963	seems to warn about). For example, certain older gcc versions had some
		3964	warnings that resulted an extreme number of false positives. These have
		3965	been fixed, but some people still insist on making code warn-free with
		3966	such buggy versions.
3155		3967
3156	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3968	While libev is written to generate as few warnings as possible,
		3969	"warn-free" code is not a goal, and it is recommended not to build libev
		3970	with any compiler warnings enabled unless you are prepared to cope with
		3971	them (e.g. by ignoring them). Remember that warnings are just that:
		3972	warnings, not errors, or proof of bugs.
3157		3973
3158	This means that, when you have a watcher that triggers in one hour and
3159	there are 100 watchers that would trigger before that then inserting will
3160	have to skip roughly seven (C<ld 100>) of these watchers.
3161		3974
3162	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3975	=head2 VALGRIND
3163		3976
3164	That means that changing a timer costs less than removing/adding them	3977	Valgrind has a special section here because it is a popular tool that is
3165	as only the relative motion in the event queue has to be paid for.	3978	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3166		3979
3167	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3980	If you think you found a bug (memory leak, uninitialised data access etc.)
		3981	in libev, then check twice: If valgrind reports something like:
3168		3982
3169	These just add the watcher into an array or at the head of a list.	3983	==2274== definitely lost: 0 bytes in 0 blocks.
		3984	==2274== possibly lost: 0 bytes in 0 blocks.
		3985	==2274== still reachable: 256 bytes in 1 blocks.
3170		3986
3171	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3987	Then there is no memory leak, just as memory accounted to global variables
		3988	is not a memleak - the memory is still being referenced, and didn't leak.
3172		3989
3173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3990	Similarly, under some circumstances, valgrind might report kernel bugs
		3991	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3992	although an acceptable workaround has been found here), or it might be
		3993	confused.
3174		3994
3175	These watchers are stored in lists then need to be walked to find the	3995	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3176	correct watcher to remove. The lists are usually short (you don't usually	3996	make it into some kind of religion.
3177	have many watchers waiting for the same fd or signal).
3178		3997
3179	=item Finding the next timer in each loop iteration: O(1)	3998	If you are unsure about something, feel free to contact the mailing list
		3999	with the full valgrind report and an explanation on why you think this
		4000	is a bug in libev (best check the archives, too :). However, don't be
		4001	annoyed when you get a brisk "this is no bug" answer and take the chance
		4002	of learning how to interpret valgrind properly.
3180		4003
3181	By virtue of using a binary heap, the next timer is always found at the	4004	If you need, for some reason, empty reports from valgrind for your project
3182	beginning of the storage array.	4005	I suggest using suppression lists.
3183		4006
3184	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3185		4007
3186	A change means an I/O watcher gets started or stopped, which requires	4008	=head1 PORTABILITY NOTES
3187	libev to recalculate its status (and possibly tell the kernel, depending
3188	on backend and wether C<ev_io_set> was used).
3189		4009
3190	=item Activating one watcher (putting it into the pending state): O(1)	4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3191
3192	=item Priority handling: O(number_of_priorities)
3193
3194	Priorities are implemented by allocating some space for each
3195	priority. When doing priority-based operations, libev usually has to
3196	linearly search all the priorities, but starting/stopping and activating
3197	watchers becomes O(1) w.r.t. priority handling.
3198
3199	=item Sending an ev_async: O(1)
3200
3201	=item Processing ev_async_send: O(number_of_async_watchers)
3202
3203	=item Processing signals: O(max_signal_number)
3204
3205	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3206	calls in the current loop iteration. Checking for async and signal events
3207	involves iterating over all running async watchers or all signal numbers.
3208
3209	=back
3210
3211
3212	=head1 Win32 platform limitations and workarounds
3213		4011
3214	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3215	requires, and its I/O model is fundamentally incompatible with the POSIX	4013	requires, and its I/O model is fundamentally incompatible with the POSIX
3216	model. Libev still offers limited functionality on this platform in	4014	model. Libev still offers limited functionality on this platform in
3217	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3224	way (note also that glib is the slowest event library known to man).	4022	way (note also that glib is the slowest event library known to man).
3225		4023
3226	There is no supported compilation method available on windows except	4024	There is no supported compilation method available on windows except
3227	embedding it into other applications.	4025	embedding it into other applications.
3228		4026
		4027	Sensible signal handling is officially unsupported by Microsoft - libev
		4028	tries its best, but under most conditions, signals will simply not work.
		4029
		4030	Not a libev limitation but worth mentioning: windows apparently doesn't
		4031	accept large writes: instead of resulting in a partial write, windows will
		4032	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4033	so make sure you only write small amounts into your sockets (less than a
		4034	megabyte seems safe, but this apparently depends on the amount of memory
		4035	available).
		4036
3229	Due to the many, low, and arbitrary limits on the win32 platform and	4037	Due to the many, low, and arbitrary limits on the win32 platform and
3230	the abysmal performance of winsockets, using a large number of sockets	4038	the abysmal performance of winsockets, using a large number of sockets
3231	is not recommended (and not reasonable). If your program needs to use	4039	is not recommended (and not reasonable). If your program needs to use
3232	more than a hundred or so sockets, then likely it needs to use a totally	4040	more than a hundred or so sockets, then likely it needs to use a totally
3233	different implementation for windows, as libev offers the POSIX readyness	4041	different implementation for windows, as libev offers the POSIX readiness
3234	notification model, which cannot be implemented efficiently on windows	4042	notification model, which cannot be implemented efficiently on windows
3235	(microsoft monopoly games).	4043	(due to Microsoft monopoly games).
		4044
		4045	A typical way to use libev under windows is to embed it (see the embedding
		4046	section for details) and use the following F<evwrap.h> header file instead
		4047	of F<ev.h>:
		4048
		4049	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4050	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4051
		4052	#include "ev.h"
		4053
		4054	And compile the following F<evwrap.c> file into your project (make sure
		4055	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4056
		4057	#include "evwrap.h"
		4058	#include "ev.c"
3236		4059
3237	=over 4	4060	=over 4
3238		4061
3239	=item The winsocket select function	4062	=item The winsocket select function
3240		4063
3241	The winsocket C<select> function doesn't follow POSIX in that it requires	4064	The winsocket C<select> function doesn't follow POSIX in that it
3242	socket I<handles> and not socket I<file descriptors>. This makes select	4065	requires socket I<handles> and not socket I<file descriptors> (it is
3243	very inefficient, and also requires a mapping from file descriptors	4066	also extremely buggy). This makes select very inefficient, and also
3244	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4067	requires a mapping from file descriptors to socket handles (the Microsoft
3245	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4068	C runtime provides the function C<_open_osfhandle> for this). See the
3246	symbols for more info.	4069	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4070	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3247		4071
3248	The configuration for a "naked" win32 using the microsoft runtime	4072	The configuration for a "naked" win32 using the Microsoft runtime
3249	libraries and raw winsocket select is:	4073	libraries and raw winsocket select is:
3250		4074
3251	#define EV_USE_SELECT 1	4075	#define EV_USE_SELECT 1
3252	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4076	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3253		4077
3254	Note that winsockets handling of fd sets is O(n), so you can easily get a	4078	Note that winsockets handling of fd sets is O(n), so you can easily get a
3255	complexity in the O(n²) range when using win32.	4079	complexity in the O(n²) range when using win32.
3256		4080
3257	=item Limited number of file descriptors	4081	=item Limited number of file descriptors
3258		4082
3259	Windows has numerous arbitrary (and low) limits on things.	4083	Windows has numerous arbitrary (and low) limits on things.
3260		4084
3261	Early versions of winsocket's select only supported waiting for a maximum	4085	Early versions of winsocket's select only supported waiting for a maximum
3262	of C<64> handles (probably owning to the fact that all windows kernels	4086	of C<64> handles (probably owning to the fact that all windows kernels
3263	can only wait for C<64> things at the same time internally; microsoft	4087	can only wait for C<64> things at the same time internally; Microsoft
3264	recommends spawning a chain of threads and wait for 63 handles and the	4088	recommends spawning a chain of threads and wait for 63 handles and the
3265	previous thread in each. Great).	4089	previous thread in each. Sounds great!).
3266		4090
3267	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4091	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3268	to some high number (e.g. C<2048>) before compiling the winsocket select	4092	to some high number (e.g. C<2048>) before compiling the winsocket select
3269	call (which might be in libev or elsewhere, for example, perl does its own	4093	call (which might be in libev or elsewhere, for example, perl and many
3270	select emulation on windows).	4094	other interpreters do their own select emulation on windows).
3271		4095
3272	Another limit is the number of file descriptors in the microsoft runtime	4096	Another limit is the number of file descriptors in the Microsoft runtime
3273	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4097	libraries, which by default is C<64> (there must be a hidden I<64>
3274	or something like this inside microsoft). You can increase this by calling	4098	fetish or something like this inside Microsoft). You can increase this
3275	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4099	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3276	arbitrary limit), but is broken in many versions of the microsoft runtime	4100	(another arbitrary limit), but is broken in many versions of the Microsoft
3277	libraries.
3278
3279	This might get you to about C<512> or C<2048> sockets (depending on	4101	runtime libraries. This might get you to about C<512> or C<2048> sockets
3280	windows version and/or the phase of the moon). To get more, you need to	4102	(depending on windows version and/or the phase of the moon). To get more,
3281	wrap all I/O functions and provide your own fd management, but the cost of	4103	you need to wrap all I/O functions and provide your own fd management, but
3282	calling select (O(n²)) will likely make this unworkable.	4104	the cost of calling select (O(n²)) will likely make this unworkable.
3283		4105
3284	=back	4106	=back
3285		4107
3286
3287	=head1 PORTABILITY REQUIREMENTS	4108	=head2 PORTABILITY REQUIREMENTS
3288		4109
3289	In addition to a working ISO-C implementation, libev relies on a few	4110	In addition to a working ISO-C implementation and of course the
3290	additional extensions:	4111	backend-specific APIs, libev relies on a few additional extensions:
3291		4112
3292	=over 4	4113	=over 4
3293		4114
		4115	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4116	calling conventions regardless of C<ev_watcher_type *>.
		4117
		4118	Libev assumes not only that all watcher pointers have the same internal
		4119	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4120	assumes that the same (machine) code can be used to call any watcher
		4121	callback: The watcher callbacks have different type signatures, but libev
		4122	calls them using an C<ev_watcher *> internally.
		4123
3294	=item C<sig_atomic_t volatile> must be thread-atomic as well	4124	=item C<sig_atomic_t volatile> must be thread-atomic as well
3295		4125
3296	The type C<sig_atomic_t volatile> (or whatever is defined as	4126	The type C<sig_atomic_t volatile> (or whatever is defined as
3297	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3298	threads. This is not part of the specification for C<sig_atomic_t>, but is	4128	threads. This is not part of the specification for C<sig_atomic_t>, but is
3299	believed to be sufficiently portable.	4129	believed to be sufficiently portable.
3300		4130
3301	=item C<sigprocmask> must work in a threaded environment	4131	=item C<sigprocmask> must work in a threaded environment
3302		4132
…		…
3311	except the initial one, and run the default loop in the initial thread as	4141	except the initial one, and run the default loop in the initial thread as
3312	well.	4142	well.
3313		4143
3314	=item C<long> must be large enough for common memory allocation sizes	4144	=item C<long> must be large enough for common memory allocation sizes
3315		4145
3316	To improve portability and simplify using libev, libev uses C<long>	4146	To improve portability and simplify its API, libev uses C<long> internally
3317	internally instead of C<size_t> when allocating its data structures. On	4147	instead of C<size_t> when allocating its data structures. On non-POSIX
3318	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4148	systems (Microsoft...) this might be unexpectedly low, but is still at
3319	is still at least 31 bits everywhere, which is enough for hundreds of	4149	least 31 bits everywhere, which is enough for hundreds of millions of
3320	millions of watchers.	4150	watchers.
3321		4151
3322	=item C<double> must hold a time value in seconds with enough accuracy	4152	=item C<double> must hold a time value in seconds with enough accuracy
3323		4153
3324	The type C<double> is used to represent timestamps. It is required to have	4154	The type C<double> is used to represent timestamps. It is required to
3325	at least 51 bits of mantissa, which is good enough for at least into the	4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3326	year 4000. This requirement is fulfilled by implementations implementing	4156	enough for at least into the year 4000. This requirement is fulfilled by
3327	IEEE 754 (basically all existing ones).	4157	implementations implementing IEEE 754, which is basically all existing
		4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4159	2200.
3328		4160
3329	=back	4161	=back
3330		4162
3331	If you know of other additional requirements drop me a note.	4163	If you know of other additional requirements drop me a note.
3332		4164
3333		4165
		4166	=head1 ALGORITHMIC COMPLEXITIES
		4167
		4168	In this section the complexities of (many of) the algorithms used inside
		4169	libev will be documented. For complexity discussions about backends see
		4170	the documentation for C<ev_default_init>.
		4171
		4172	All of the following are about amortised time: If an array needs to be
		4173	extended, libev needs to realloc and move the whole array, but this
		4174	happens asymptotically rarer with higher number of elements, so O(1) might
		4175	mean that libev does a lengthy realloc operation in rare cases, but on
		4176	average it is much faster and asymptotically approaches constant time.
		4177
		4178	=over 4
		4179
		4180	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4181
		4182	This means that, when you have a watcher that triggers in one hour and
		4183	there are 100 watchers that would trigger before that, then inserting will
		4184	have to skip roughly seven (C<ld 100>) of these watchers.
		4185
		4186	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4187
		4188	That means that changing a timer costs less than removing/adding them,
		4189	as only the relative motion in the event queue has to be paid for.
		4190
		4191	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4192
		4193	These just add the watcher into an array or at the head of a list.
		4194
		4195	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4196
		4197	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4198
		4199	These watchers are stored in lists, so they need to be walked to find the
		4200	correct watcher to remove. The lists are usually short (you don't usually
		4201	have many watchers waiting for the same fd or signal: one is typical, two
		4202	is rare).
		4203
		4204	=item Finding the next timer in each loop iteration: O(1)
		4205
		4206	By virtue of using a binary or 4-heap, the next timer is always found at a
		4207	fixed position in the storage array.
		4208
		4209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4210
		4211	A change means an I/O watcher gets started or stopped, which requires
		4212	libev to recalculate its status (and possibly tell the kernel, depending
		4213	on backend and whether C<ev_io_set> was used).
		4214
		4215	=item Activating one watcher (putting it into the pending state): O(1)
		4216
		4217	=item Priority handling: O(number_of_priorities)
		4218
		4219	Priorities are implemented by allocating some space for each
		4220	priority. When doing priority-based operations, libev usually has to
		4221	linearly search all the priorities, but starting/stopping and activating
		4222	watchers becomes O(1) with respect to priority handling.
		4223
		4224	=item Sending an ev_async: O(1)
		4225
		4226	=item Processing ev_async_send: O(number_of_async_watchers)
		4227
		4228	=item Processing signals: O(max_signal_number)
		4229
		4230	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4231	calls in the current loop iteration. Checking for async and signal events
		4232	involves iterating over all running async watchers or all signal numbers.
		4233
		4234	=back
		4235
		4236
		4237	=head1 GLOSSARY
		4238
		4239	=over 4
		4240
		4241	=item active
		4242
		4243	A watcher is active as long as it has been started (has been attached to
		4244	an event loop) but not yet stopped (disassociated from the event loop).
		4245
		4246	=item application
		4247
		4248	In this document, an application is whatever is using libev.
		4249
		4250	=item callback
		4251
		4252	The address of a function that is called when some event has been
		4253	detected. Callbacks are being passed the event loop, the watcher that
		4254	received the event, and the actual event bitset.
		4255
		4256	=item callback invocation
		4257
		4258	The act of calling the callback associated with a watcher.
		4259
		4260	=item event
		4261
		4262	A change of state of some external event, such as data now being available
		4263	for reading on a file descriptor, time having passed or simply not having
		4264	any other events happening anymore.
		4265
		4266	In libev, events are represented as single bits (such as C<EV_READ> or
		4267	C<EV_TIMEOUT>).
		4268
		4269	=item event library
		4270
		4271	A software package implementing an event model and loop.
		4272
		4273	=item event loop
		4274
		4275	An entity that handles and processes external events and converts them
		4276	into callback invocations.
		4277
		4278	=item event model
		4279
		4280	The model used to describe how an event loop handles and processes
		4281	watchers and events.
		4282
		4283	=item pending
		4284
		4285	A watcher is pending as soon as the corresponding event has been detected,
		4286	and stops being pending as soon as the watcher will be invoked or its
		4287	pending status is explicitly cleared by the application.
		4288
		4289	A watcher can be pending, but not active. Stopping a watcher also clears
		4290	its pending status.
		4291
		4292	=item real time
		4293
		4294	The physical time that is observed. It is apparently strictly monotonic :)
		4295
		4296	=item wall-clock time
		4297
		4298	The time and date as shown on clocks. Unlike real time, it can actually
		4299	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4300	clock.
		4301
		4302	=item watcher
		4303
		4304	A data structure that describes interest in certain events. Watchers need
		4305	to be started (attached to an event loop) before they can receive events.
		4306
		4307	=item watcher invocation
		4308
		4309	The act of calling the callback associated with a watcher.
		4310
		4311	=back
		4312
3334	=head1 AUTHOR	4313	=head1 AUTHOR
3335		4314
3336	Marc Lehmann <libev@schmorp.de>.	4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3337		4316

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