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Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.259 by root, Sun Jul 19 01:36:34 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
		135
		136	=head1 ERROR HANDLING
		137
		138	Libev knows three classes of errors: operating system errors, usage errors
		139	and internal errors (bugs).
		140
		141	When libev catches an operating system error it cannot handle (for example
		142	a system call indicating a condition libev cannot fix), it calls the callback
		143	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		144	abort. The default is to print a diagnostic message and to call C<abort
		145	()>.
		146
		147	When libev detects a usage error such as a negative timer interval, then
		148	it will print a diagnostic message and abort (via the C<assert> mechanism,
		149	so C<NDEBUG> will disable this checking): these are programming errors in
		150	the libev caller and need to be fixed there.
		151
		152	Libev also has a few internal error-checking C<assert>ions, and also has
		153	extensive consistency checking code. These do not trigger under normal
		154	circumstances, as they indicate either a bug in libev or worse.
		155
121		156
122	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
123		158
124	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
125	library in any way.	160	library in any way.
…		…
134		169
135	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
136		171
137	Sleep for the given interval: The current thread will be blocked until	172	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	173	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
140		175
141	=item int ev_version_major ()	176	=item int ev_version_major ()
142		177
143	=item int ev_version_minor ()	178	=item int ev_version_minor ()
144		179
…		…
157	not a problem.	192	not a problem.
158		193
159	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	195	version.
161		196
162	assert (("libev version mismatch",	197	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
165		200
166	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
167		202
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	206	a description of the set values.
172		207
173	Example: make sure we have the epoll method, because yeah this is cool and	208	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	209	a must have and can we have a torrent of it please!!!11
175		210
176	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
178		213
179	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
180		215
181	Return the set of all backends compiled into this binary of libev and also	216	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	217	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	218	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	219	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	220	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	221	libev will probe for if you specify no backends explicitly.
187		222
188	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
189		224
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	229	recommended ones.
195		230
196	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
197		232
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		234
200	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	264	}
230		265
231	...	266	...
232	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
233		268
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		270
236	Set the callback function to call on a retryable syscall error (such	271	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	274	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	275	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	276	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	277	(such as abort).
243		278
244	Example: This is basically the same thing that libev does internally, too.	279	Example: This is basically the same thing that libev does internally, too.
…		…
255		290
256	=back	291	=back
257		292
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		294
260	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
263		302
264	=over 4	303	=over 4
265		304
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		306
…		…
273	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
274	function.	313	function.
275		314
276	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
279		318
280	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	324	C<ev_default_init>.
286		325
287	The flags argument can be used to specify special behaviour or specific	326	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	335	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	336	thing, believe me).
298		337
299	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
300		339
301	If this flag bit is ored into the flag value (or the program runs setuid	340	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	341	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	343	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	344	useful to try out specific backends to test their performance, or to work
306	around bugs.	345	around bugs.
…		…
313		352
314	This works by calling C<getpid ()> on every iteration of the loop,	353	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	354	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	355	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
320		359
321	The big advantage of this flag is that you can forget about fork (and	360	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	361	forget about forgetting to tell libev about forking) when you use this
323	flag.	362	flag.
324		363
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	365	environment variable.
327		366
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		368
330	This is your standard select(2) backend. Not I<completely> standard, as	369	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	371	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	372	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	373	usually the fastest backend for a low number of (low-numbered :) fds.
335		374
336	To get good performance out of this backend you need a high amount of	375	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	376	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness 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 readiness 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 int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
693		925
694	=item ev_loop_verify (loop)	926	=item ev_loop_verify (loop)
695		927
696	This function only does something when C<EV_VERIFY> support has been	928	This function only does something when C<EV_VERIFY> support has been
697	compiled in. It tries to go through all internal structures and checks	929	compiled in, which is the default for non-minimal builds. It tries to go
698	them for validity. If anything is found to be inconsistent, it will print	930	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
700		933
701	This can be used to catch bugs inside libev itself: under normal	934	This can be used to catch bugs inside libev itself: under normal
702	circumstances, this function will never abort as of course libev keeps its	935	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	936	data structures consistent.
704		937
705	=back	938	=back
706		939
707		940
708	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
709		942
		943	In the following description, uppercase C<TYPE> in names stands for the
		944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		945	watchers and C<ev_io_start> for I/O watchers.
		946
710	A watcher is a structure that you create and register to record your	947	A watcher is a structure that you create and register to record your
711	interest in some event. For instance, if you want to wait for STDIN to	948	interest in some event. For instance, if you want to wait for STDIN to
712	become readable, you would create an C<ev_io> watcher for that:	949	become readable, you would create an C<ev_io> watcher for that:
713		950
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	952	{
716	ev_io_stop (w);	953	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
718	}	955	}
719		956
720	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
721	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
722	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
725	ev_loop (loop, 0);	965	ev_loop (loop, 0);
726		966
727	As you can see, you are responsible for allocating the memory for your	967	As you can see, you are responsible for allocating the memory for your
728	watcher structures (and it is usually a bad idea to do this on the stack,	968	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	969	stack).
		970
		971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
730		973
731	Each watcher structure must be initialised by a call to C<ev_init	974	Each watcher structure must be initialised by a call to C<ev_init
732	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
733	callback gets invoked each time the event occurs (or, in the case of io	976	callback gets invoked each time the event occurs (or, in the case of I/O
734	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
735	is readable and/or writable).	978	is readable and/or writable).
736		979
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
738	with arguments specific to this watcher type. There is also a macro	981	macro to configure it, with arguments specific to the watcher type. There
739	to combine initialisation and setting in one call: C<< ev_<type>_init	982	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
741		984
742	To make the watcher actually watch out for events, you have to start it	985	To make the watcher actually watch out for events, you have to start it
743	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	986	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
744	*) >>), and you can stop watching for events at any time by calling the	987	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		989
747	As long as your watcher is active (has been started but not stopped) you	990	As long as your watcher is active (has been started but not stopped) you
748	must not touch the values stored in it. Most specifically you must never	991	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
750		993
751	Each and every callback receives the event loop pointer as first, the	994	Each and every callback receives the event loop pointer as first, the
752	registered watcher structure as second, and a bitset of received events as	995	registered watcher structure as second, and a bitset of received events as
753	third argument.	996	third argument.
754		997
…		…
812		1055
813	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
814		1057
815	The given async watcher has been asynchronously notified (see C<ev_async>).	1058	The given async watcher has been asynchronously notified (see C<ev_async>).
816		1059
		1060	=item C<EV_CUSTOM>
		1061
		1062	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1063	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1064
817	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
818		1066
819	An unspecified error has occured, the watcher has been stopped. This might	1067	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
821	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
822	problem. You best act on it by reporting the problem and somehow coping	1072	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	1073	watcher being stopped. Note that well-written programs should not receive
		1074	an error ever, so when your watcher receives it, this usually indicates a
		1075	bug in your program.
824		1076
825	Libev will usually signal a few "dummy" events together with an error,	1077	Libev will usually signal a few "dummy" events together with an error, for
826	for example it might indicate that a fd is readable or writable, and if	1078	example it might indicate that a fd is readable or writable, and if your
827	your callbacks is well-written it can just attempt the operation and cope	1079	callbacks is well-written it can just attempt the operation and cope with
828	with the error from read() or write(). This will not work in multithreaded	1080	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
830		1083
831	=back	1084	=back
832		1085
833	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
834
835	In the following description, C<TYPE> stands for the watcher type,
836	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
837		1087
838	=over 4	1088	=over 4
839		1089
840	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
841		1091
…		…
847	which rolls both calls into one.	1097	which rolls both calls into one.
848		1098
849	You can reinitialise a watcher at any time as long as it has been stopped	1099	You can reinitialise a watcher at any time as long as it has been stopped
850	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
851		1101
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1102	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	1103	int revents)>.
		1104
		1105	Example: Initialise an C<ev_io> watcher in two steps.
		1106
		1107	ev_io w;
		1108	ev_init (&w, my_cb);
		1109	ev_io_set (&w, STDIN_FILENO, EV_READ);
854		1110
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
856		1112
857	This macro initialises the type-specific parts of a watcher. You need to	1113	This macro initialises the type-specific parts of a watcher. You need to
858	call C<ev_init> at least once before you call this macro, but you can	1114	call C<ev_init> at least once before you call this macro, but you can
…		…
861	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
862		1118
863	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
864	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		1121
		1122	See C<ev_init>, above, for an example.
		1123
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		1125
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1126	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
869	calls into a single call. This is the most convinient method to initialise	1127	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	1128	a watcher. The same limitations apply, of course.
		1129
		1130	Example: Initialise and set an C<ev_io> watcher in one step.
		1131
		1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
871		1133
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
873		1135
874	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
876		1138
		1139	Example: Start the C<ev_io> watcher that is being abused as example in this
		1140	whole section.
		1141
		1142	ev_io_start (EV_DEFAULT_UC, &w);
		1143
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
878		1145
879	Stops the given watcher again (if active) and clears the pending	1146	Stops the given watcher if active, and clears the pending status (whether
		1147	the watcher was active or not).
		1148
880	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
882	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
883	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
884	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1154
886	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
887		1156
888	Returns a true value iff the watcher is active (i.e. it has been started	1157	Returns a true value iff the watcher is active (i.e. it has been started
889	and not yet been stopped). As long as a watcher is active you must not modify	1158	and not yet been stopped). As long as a watcher is active you must not modify
…		…
915	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
916	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
917	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
918	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
919		1188
920	This means that priorities are I<only> used for ordering callback
921	invocation after new events have been received. This is useful, for
922	example, to reduce latency after idling, or more often, to bind two
923	watchers on the same event and make sure one is called first.
924
925	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
926	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
927		1191
928	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
929	pending.	1193	pending.
930		1194
		1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1196	fine, as long as you do not mind that the priority value you query might
		1197	or might not have been clamped to the valid range.
		1198
931	The default priority used by watchers when no priority has been set is	1199	The default priority used by watchers when no priority has been set is
932	always C<0>, which is supposed to not be too high and not be too low :).	1200	always C<0>, which is supposed to not be too high and not be too low :).
933		1201
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
935	fine, as long as you do not mind that the priority value you query might	1203	priorities.
936	or might not have been adjusted to be within valid range.
937		1204
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1206
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
941	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
943		1211
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1213
946	If the watcher is pending, this function returns clears its pending status	1214	If the watcher is pending, this function clears its pending status and
947	and returns its C<revents> bitset (as if its callback was invoked). If the	1215	returns its C<revents> bitset (as if its callback was invoked). If the
948	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
949		1217
		1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1219	callback to be invoked, which can be accomplished with this function.
		1220
950	=back	1221	=back
951		1222
952		1223
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
954		1225
955	Each watcher has, by default, a member C<void *data> that you can change	1226	Each watcher has, by default, a member C<void *data> that you can change
956	and read at any time, libev will completely ignore it. This can be used	1227	and read at any time: libev will completely ignore it. This can be used
957	to associate arbitrary data with your watcher. If you need more data and	1228	to associate arbitrary data with your watcher. If you need more data and
958	don't want to allocate memory and store a pointer to it in that data	1229	don't want to allocate memory and store a pointer to it in that data
959	member, you can also "subclass" the watcher type and provide your own	1230	member, you can also "subclass" the watcher type and provide your own
960	data:	1231	data:
961		1232
962	struct my_io	1233	struct my_io
963	{	1234	{
964	struct ev_io io;	1235	ev_io io;
965	int otherfd;	1236	int otherfd;
966	void *somedata;	1237	void *somedata;
967	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
968	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
969		1244
970	And since your callback will be called with a pointer to the watcher, you	1245	And since your callback will be called with a pointer to the watcher, you
971	can cast it back to your own type:	1246	can cast it back to your own type:
972		1247
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
974	{	1249	{
975	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
976	...	1251	...
977	}	1252	}
978		1253
979	More interesting and less C-conformant ways of casting your callback type	1254	More interesting and less C-conformant ways of casting your callback type
980	instead have been omitted.	1255	instead have been omitted.
981		1256
982	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
983	watchers:	1258	embedded watchers:
984		1259
985	struct my_biggy	1260	struct my_biggy
986	{	1261	{
987	int some_data;	1262	int some_data;
988	ev_timer t1;	1263	ev_timer t1;
989	ev_timer t2;	1264	ev_timer t2;
990	}	1265	}
991		1266
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1267	In this case getting the pointer to C<my_biggy> is a bit more
993	you need to use C<offsetof>:	1268	complicated: Either you store the address of your C<my_biggy> struct
		1269	in the C<data> member of the watcher (for woozies), or you need to use
		1270	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1271	programmers):
994		1272
995	#include <stddef.h>	1273	#include <stddef.h>
996		1274
997	static void	1275	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
999	{	1277	{
1000	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
1002	}	1280	}
1003		1281
1004	static void	1282	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
1006	{	1284	{
1007	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
1009	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
1010		1391
1011		1392
1012	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
1013		1394
1014	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1038	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1039	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1040	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1422	required if you know what you are doing).
1042		1423
1043	If you must do this, then force the use of a known-to-be-good backend	1424	If you cannot use non-blocking mode, then force the use of a
1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1425	known-to-be-good backend (at the time of this writing, this includes only
1045	C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1046		1429
1047	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1048	receive "spurious" readiness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1050	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1051	lot of those (for example solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1052	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1054	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1055		1438
1056	If you cannot run the fd in non-blocking mode (for example you should not	1439	If you cannot run the fd in non-blocking mode (for example you should
1057	play around with an Xlib connection), then you have to seperately re-test	1440	not play around with an Xlib connection), then you have to separately
1058	whether a file descriptor is really ready with a known-to-be good interface	1441	re-test whether a file descriptor is really ready with a known-to-be good
1059	such as poll (fortunately in our Xlib example, Xlib already does this on	1442	interface such as poll (fortunately in our Xlib example, Xlib already
1060	its own, so its quite safe to use).	1443	does this on its own, so its quite safe to use). Some people additionally
		1444	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1445	indefinitely.
		1446
		1447	But really, best use non-blocking mode.
1061		1448
1062	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1063		1450
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1451	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1065	descriptor (either by calling C<close> explicitly or by any other means,	1452	descriptor (either due to calling C<close> explicitly or any other means,
1066	such as C<dup>). The reason is that you register interest in some file	1453	such as C<dup2>). The reason is that you register interest in some file
1067	descriptor, but when it goes away, the operating system will silently drop	1454	descriptor, but when it goes away, the operating system will silently drop
1068	this interest. If another file descriptor with the same number then is	1455	this interest. If another file descriptor with the same number then is
1069	registered with libev, there is no efficient way to see that this is, in	1456	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1457	fact, a different file descriptor.
1071		1458
…		…
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1103	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1104		1491
1105	=head3 The special problem of SIGPIPE	1492	=head3 The special problem of SIGPIPE
1106		1493
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1108	when reading from a pipe whose other end has been closed, your program	1495	when writing to a pipe whose other end has been closed, your program gets
1109	gets send a SIGPIPE, which, by default, aborts your program. For most	1496	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1497	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1498
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1499	So when you encounter spurious, unexplained daemon exits, make sure you
1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1115	somewhere, as that would have given you a big clue).	1501	somewhere, as that would have given you a big clue).
1116		1502
…		…
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1509
1124	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1125		1511
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1512	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1127	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1513	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1128	C<EV_READ | EV_WRITE> to receive the given events.	1514	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1515
1130	=item int fd [read-only]	1516	=item int fd [read-only]
1131		1517
1132	The file descriptor being watched.	1518	The file descriptor being watched.
1133		1519
…		…
1141		1527
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1528	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1143	readable, but only once. Since it is likely line-buffered, you could	1529	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1145		1531
1146	static void	1532	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1533	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1534	{
1149	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1536	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1537	}
1152		1538
1153	...	1539	...
1154	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1159		1545
1160		1546
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1547	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1548
1163	Timer watchers are simple relative timers that generate an event after a	1549	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1165		1551
1166	The timers are based on real time, that is, if you register an event that	1552	The timers are based on real time, that is, if you register an event that
1167	times out after an hour and you reset your system clock to january last	1553	times out after an hour and you reset your system clock to January last
1168	year, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
		1557
		1558	The callback is guaranteed to be invoked only I<after> its timeout has
		1559	passed (not I<at>, so on systems with very low-resolution clocks this
		1560	might introduce a small delay). If multiple timers become ready during the
		1561	same loop iteration then the ones with earlier time-out values are invoked
		1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
		1564
		1565	=head3 Be smart about timeouts
		1566
		1567	Many real-world problems involve some kind of timeout, usually for error
		1568	recovery. A typical example is an HTTP request - if the other side hangs,
		1569	you want to raise some error after a while.
		1570
		1571	What follows are some ways to handle this problem, from obvious and
		1572	inefficient to smart and efficient.
		1573
		1574	In the following, a 60 second activity timeout is assumed - a timeout that
		1575	gets reset to 60 seconds each time there is activity (e.g. each time some
		1576	data or other life sign was received).
		1577
		1578	=over 4
		1579
		1580	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1581
		1582	This is the most obvious, but not the most simple way: In the beginning,
		1583	start the watcher:
		1584
		1585	ev_timer_init (timer, callback, 60., 0.);
		1586	ev_timer_start (loop, timer);
		1587
		1588	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1589	and start it again:
		1590
		1591	ev_timer_stop (loop, timer);
		1592	ev_timer_set (timer, 60., 0.);
		1593	ev_timer_start (loop, timer);
		1594
		1595	This is relatively simple to implement, but means that each time there is
		1596	some activity, libev will first have to remove the timer from its internal
		1597	data structure and then add it again. Libev tries to be fast, but it's
		1598	still not a constant-time operation.
		1599
		1600	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1601
		1602	This is the easiest way, and involves using C<ev_timer_again> instead of
		1603	C<ev_timer_start>.
		1604
		1605	To implement this, configure an C<ev_timer> with a C<repeat> value
		1606	of C<60> and then call C<ev_timer_again> at start and each time you
		1607	successfully read or write some data. If you go into an idle state where
		1608	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1609	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1610
		1611	That means you can ignore both the C<ev_timer_start> function and the
		1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1613	member and C<ev_timer_again>.
		1614
		1615	At start:
		1616
		1617	ev_init (timer, callback);
		1618	timer->repeat = 60.;
		1619	ev_timer_again (loop, timer);
		1620
		1621	Each time there is some activity:
		1622
		1623	ev_timer_again (loop, timer);
		1624
		1625	It is even possible to change the time-out on the fly, regardless of
		1626	whether the watcher is active or not:
		1627
		1628	timer->repeat = 30.;
		1629	ev_timer_again (loop, timer);
		1630
		1631	This is slightly more efficient then stopping/starting the timer each time
		1632	you want to modify its timeout value, as libev does not have to completely
		1633	remove and re-insert the timer from/into its internal data structure.
		1634
		1635	It is, however, even simpler than the "obvious" way to do it.
		1636
		1637	=item 3. Let the timer time out, but then re-arm it as required.
		1638
		1639	This method is more tricky, but usually most efficient: Most timeouts are
		1640	relatively long compared to the intervals between other activity - in
		1641	our example, within 60 seconds, there are usually many I/O events with
		1642	associated activity resets.
		1643
		1644	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1645	but remember the time of last activity, and check for a real timeout only
		1646	within the callback:
		1647
		1648	ev_tstamp last_activity; // time of last activity
		1649
		1650	static void
		1651	callback (EV_P_ ev_timer *w, int revents)
		1652	{
		1653	ev_tstamp now = ev_now (EV_A);
		1654	ev_tstamp timeout = last_activity + 60.;
		1655
		1656	// if last_activity + 60. is older than now, we did time out
		1657	if (timeout < now)
		1658	{
		1659	// timeout occured, take action
		1660	}
		1661	else
		1662	{
		1663	// callback was invoked, but there was some activity, re-arm
		1664	// the watcher to fire in last_activity + 60, which is
		1665	// guaranteed to be in the future, so "again" is positive:
		1666	w->repeat = timeout - now;
		1667	ev_timer_again (EV_A_ w);
		1668	}
		1669	}
		1670
		1671	To summarise the callback: first calculate the real timeout (defined
		1672	as "60 seconds after the last activity"), then check if that time has
		1673	been reached, which means something I<did>, in fact, time out. Otherwise
		1674	the callback was invoked too early (C<timeout> is in the future), so
		1675	re-schedule the timer to fire at that future time, to see if maybe we have
		1676	a timeout then.
		1677
		1678	Note how C<ev_timer_again> is used, taking advantage of the
		1679	C<ev_timer_again> optimisation when the timer is already running.
		1680
		1681	This scheme causes more callback invocations (about one every 60 seconds
		1682	minus half the average time between activity), but virtually no calls to
		1683	libev to change the timeout.
		1684
		1685	To start the timer, simply initialise the watcher and set C<last_activity>
		1686	to the current time (meaning we just have some activity :), then call the
		1687	callback, which will "do the right thing" and start the timer:
		1688
		1689	ev_init (timer, callback);
		1690	last_activity = ev_now (loop);
		1691	callback (loop, timer, EV_TIMEOUT);
		1692
		1693	And when there is some activity, simply store the current time in
		1694	C<last_activity>, no libev calls at all:
		1695
		1696	last_actiivty = ev_now (loop);
		1697
		1698	This technique is slightly more complex, but in most cases where the
		1699	time-out is unlikely to be triggered, much more efficient.
		1700
		1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1702	callback :) - just change the timeout and invoke the callback, which will
		1703	fix things for you.
		1704
		1705	=item 4. Wee, just use a double-linked list for your timeouts.
		1706
		1707	If there is not one request, but many thousands (millions...), all
		1708	employing some kind of timeout with the same timeout value, then one can
		1709	do even better:
		1710
		1711	When starting the timeout, calculate the timeout value and put the timeout
		1712	at the I<end> of the list.
		1713
		1714	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1715	the list is expected to fire (for example, using the technique #3).
		1716
		1717	When there is some activity, remove the timer from the list, recalculate
		1718	the timeout, append it to the end of the list again, and make sure to
		1719	update the C<ev_timer> if it was taken from the beginning of the list.
		1720
		1721	This way, one can manage an unlimited number of timeouts in O(1) time for
		1722	starting, stopping and updating the timers, at the expense of a major
		1723	complication, and having to use a constant timeout. The constant timeout
		1724	ensures that the list stays sorted.
		1725
		1726	=back
		1727
		1728	So which method the best?
		1729
		1730	Method #2 is a simple no-brain-required solution that is adequate in most
		1731	situations. Method #3 requires a bit more thinking, but handles many cases
		1732	better, and isn't very complicated either. In most case, choosing either
		1733	one is fine, with #3 being better in typical situations.
		1734
		1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1736	rather complicated, but extremely efficient, something that really pays
		1737	off after the first million or so of active timers, i.e. it's usually
		1738	overkill :)
		1739
		1740	=head3 The special problem of time updates
		1741
		1742	Establishing the current time is a costly operation (it usually takes at
		1743	least two system calls): EV therefore updates its idea of the current
		1744	time only before and after C<ev_loop> collects new events, which causes a
		1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1746	lots of events in one iteration.
1171		1747
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1173	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1174	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1175	you suspect event processing to be delayed and you I<need> to base the timeout	1751	you suspect event processing to be delayed and you I<need> to base the
1176	on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1177		1753
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1755
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1756	If the event loop is suspended for a long time, you can also force an
1181	but if multiple timers become ready during the same loop iteration then	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1758	()>.
		1759
		1760	=head3 The special problems of suspended animation
		1761
		1762	When you leave the server world it is quite customary to hit machines that
		1763	can suspend/hibernate - what happens to the clocks during such a suspend?
		1764
		1765	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1766	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1767	to run until the system is suspended, but they will not advance while the
		1768	system is suspended. That means, on resume, it will be as if the program
		1769	was frozen for a few seconds, but the suspend time will not be counted
		1770	towards C<ev_timer> when a monotonic clock source is used. The real time
		1771	clock advanced as expected, but if it is used as sole clocksource, then a
		1772	long suspend would be detected as a time jump by libev, and timers would
		1773	be adjusted accordingly.
		1774
		1775	I would not be surprised to see different behaviour in different between
		1776	operating systems, OS versions or even different hardware.
		1777
		1778	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1779	time jump in the monotonic clocks and the realtime clock. If the program
		1780	is suspended for a very long time, and monotonic clock sources are in use,
		1781	then you can expect C<ev_timer>s to expire as the full suspension time
		1782	will be counted towards the timers. When no monotonic clock source is in
		1783	use, then libev will again assume a timejump and adjust accordingly.
		1784
		1785	It might be beneficial for this latter case to call C<ev_suspend>
		1786	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1787	deterministic behaviour in this case (you can do nothing against
		1788	C<SIGSTOP>).
1183		1789
1184	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1185		1791
1186	=over 4	1792	=over 4
1187		1793
…		…
1206	This will act as if the timer timed out and restart it again if it is	1812	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	1813	repeating. The exact semantics are:
1208		1814
1209	If the timer is pending, its pending status is cleared.	1815	If the timer is pending, its pending status is cleared.
1210		1816
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	1817	If the timer is started but non-repeating, stop it (as if it timed out).
1212		1818
1213	If the timer is repeating, either start it if necessary (with the	1819	If the timer is repeating, either start it if necessary (with the
1214	C<repeat> value), or reset the running timer to the C<repeat> value.	1820	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		1821
1216	This sounds a bit complicated, but here is a useful and typical	1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1217	example: Imagine you have a tcp connection and you want a so-called idle	1823	usage example.
1218	timeout, that is, you want to be called when there have been, say, 60
1219	seconds of inactivity on the socket. The easiest way to do this is to
1220	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1221	C<ev_timer_again> each time you successfully read or write some data. If
1222	you go into an idle state where you do not expect data to travel on the
1223	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1224	automatically restart it if need be.
1225		1824
1226	That means you can ignore the C<after> value and C<ev_timer_start>	1825	=item ev_timer_remaining (loop, ev_timer *)
1227	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1228		1826
1229	ev_timer_init (timer, callback, 0., 5.);	1827	Returns the remaining time until a timer fires. If the timer is active,
1230	ev_timer_again (loop, timer);	1828	then this time is relative to the current event loop time, otherwise it's
1231	...	1829	the timeout value currently configured.
1232	timer->again = 17.;
1233	ev_timer_again (loop, timer);
1234	...
1235	timer->again = 10.;
1236	ev_timer_again (loop, timer);
1237		1830
1238	This is more slightly efficient then stopping/starting the timer each time	1831	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1239	you want to modify its timeout value.	1832	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1833	will return C<4>. When the timer expires and is restarted, it will return
		1834	roughly C<7> (likely slightly less as callback invocation takes some time,
		1835	too), and so on.
1240		1836
1241	=item ev_tstamp repeat [read-write]	1837	=item ev_tstamp repeat [read-write]
1242		1838
1243	The current C<repeat> value. Will be used each time the watcher times out	1839	The current C<repeat> value. Will be used each time the watcher times out
1244	or C<ev_timer_again> is called and determines the next timeout (if any),	1840	or C<ev_timer_again> is called, and determines the next timeout (if any),
1245	which is also when any modifications are taken into account.	1841	which is also when any modifications are taken into account.
1246		1842
1247	=back	1843	=back
1248		1844
1249	=head3 Examples	1845	=head3 Examples
1250		1846
1251	Example: Create a timer that fires after 60 seconds.	1847	Example: Create a timer that fires after 60 seconds.
1252		1848
1253	static void	1849	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1850	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	1851	{
1256	.. one minute over, w is actually stopped right here	1852	.. one minute over, w is actually stopped right here
1257	}	1853	}
1258		1854
1259	struct ev_timer mytimer;	1855	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1856	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	1857	ev_timer_start (loop, &mytimer);
1262		1858
1263	Example: Create a timeout timer that times out after 10 seconds of	1859	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	1860	inactivity.
1265		1861
1266	static void	1862	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1863	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	1864	{
1269	.. ten seconds without any activity	1865	.. ten seconds without any activity
1270	}	1866	}
1271		1867
1272	struct ev_timer mytimer;	1868	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1869	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	1870	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	1871	ev_loop (loop, 0);
1276		1872
1277	// and in some piece of code that gets executed on any "activity":	1873	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	1874	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	1875	ev_timer_again (&mytimer);
1280		1876
1281		1877
1282	=head2 C<ev_periodic> - to cron or not to cron?	1878	=head2 C<ev_periodic> - to cron or not to cron?
1283		1879
1284	Periodic watchers are also timers of a kind, but they are very versatile	1880	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	1881	(and unfortunately a bit complex).
1286		1882
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1883	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1288	but on wallclock time (absolute time). You can tell a periodic watcher	1884	relative time, the physical time that passes) but on wall clock time
1289	to trigger after some specific point in time. For example, if you tell a	1885	(absolute time, the thing you can read on your calender or clock). The
1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1886	difference is that wall clock time can run faster or slower than real
1291	+ 10.>, that is, an absolute time not a delay) and then reset your system	1887	time, and time jumps are not uncommon (e.g. when you adjust your
1292	clock to january of the previous year, then it will take more than year	1888	wrist-watch).
1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1294	roughly 10 seconds later as it uses a relative timeout).
1295		1889
		1890	You can tell a periodic watcher to trigger after some specific point
		1891	in time: for example, if you tell a periodic watcher to trigger "in 10
		1892	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1893	not a delay) and then reset your system clock to January of the previous
		1894	year, then it will take a year or more to trigger the event (unlike an
		1895	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1896	it, as it uses a relative timeout).
		1897
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	1898	C<ev_periodic> watchers can also be used to implement vastly more complex
1297	such as triggering an event on each "midnight, local time", or other	1899	timers, such as triggering an event on each "midnight, local time", or
1298	complicated, rules.	1900	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1901	those cannot react to time jumps.
1299		1902
1300	As with timers, the callback is guarenteed to be invoked only when the	1903	As with timers, the callback is guaranteed to be invoked only when the
1301	time (C<at>) has passed, but if multiple periodic timers become ready	1904	point in time where it is supposed to trigger has passed. If multiple
1302	during the same loop iteration then order of execution is undefined.	1905	timers become ready during the same loop iteration then the ones with
		1906	earlier time-out values are invoked before ones with later time-out values
		1907	(but this is no longer true when a callback calls C<ev_loop> recursively).
1303		1908
1304	=head3 Watcher-Specific Functions and Data Members	1909	=head3 Watcher-Specific Functions and Data Members
1305		1910
1306	=over 4	1911	=over 4
1307		1912
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1913	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1309		1914
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1915	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1311		1916
1312	Lots of arguments, lets sort it out... There are basically three modes of	1917	Lots of arguments, let's sort it out... There are basically three modes of
1313	operation, and we will explain them from simplest to complex:	1918	operation, and we will explain them from simplest to most complex:
1314		1919
1315	=over 4	1920	=over 4
1316		1921
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1922	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1318		1923
1319	In this configuration the watcher triggers an event after the wallclock	1924	In this configuration the watcher triggers an event after the wall clock
1320	time C<at> has passed and doesn't repeat. It will not adjust when a time	1925	time C<offset> has passed. It will not repeat and will not adjust when a
1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1926	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1322	run when the system time reaches or surpasses this time.	1927	will be stopped and invoked when the system clock reaches or surpasses
		1928	this point in time.
1323		1929
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1930	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1325		1931
1326	In this mode the watcher will always be scheduled to time out at the next	1932	In this mode the watcher will always be scheduled to time out at the next
1327	C<at + N * interval> time (for some integer N, which can also be negative)	1933	C<offset + N * interval> time (for some integer N, which can also be
1328	and then repeat, regardless of any time jumps.	1934	negative) and then repeat, regardless of any time jumps. The C<offset>
		1935	argument is merely an offset into the C<interval> periods.
1329		1936
1330	This can be used to create timers that do not drift with respect to system	1937	This can be used to create timers that do not drift with respect to the
1331	time, for example, here is a C<ev_periodic> that triggers each hour, on	1938	system clock, for example, here is an C<ev_periodic> that triggers each
1332	the hour:	1939	hour, on the hour (with respect to UTC):
1333		1940
1334	ev_periodic_set (&periodic, 0., 3600., 0);	1941	ev_periodic_set (&periodic, 0., 3600., 0);
1335		1942
1336	This doesn't mean there will always be 3600 seconds in between triggers,	1943	This doesn't mean there will always be 3600 seconds in between triggers,
1337	but only that the the callback will be called when the system time shows a	1944	but only that the callback will be called when the system time shows a
1338	full hour (UTC), or more correctly, when the system time is evenly divisible	1945	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	1946	by 3600.
1340		1947
1341	Another way to think about it (for the mathematically inclined) is that	1948	Another way to think about it (for the mathematically inclined) is that
1342	C<ev_periodic> will try to run the callback in this mode at the next possible	1949	C<ev_periodic> will try to run the callback in this mode at the next possible
1343	time where C<time = at (mod interval)>, regardless of any time jumps.	1950	time where C<time = offset (mod interval)>, regardless of any time jumps.
1344		1951
1345	For numerical stability it is preferable that the C<at> value is near	1952	For numerical stability it is preferable that the C<offset> value is near
1346	C<ev_now ()> (the current time), but there is no range requirement for	1953	C<ev_now ()> (the current time), but there is no range requirement for
1347	this value, and in fact is often specified as zero.	1954	this value, and in fact is often specified as zero.
1348		1955
1349	Note also that there is an upper limit to how often a timer can fire (cpu	1956	Note also that there is an upper limit to how often a timer can fire (CPU
1350	speed for example), so if C<interval> is very small then timing stability	1957	speed for example), so if C<interval> is very small then timing stability
1351	will of course detoriate. Libev itself tries to be exact to be about one	1958	will of course deteriorate. Libev itself tries to be exact to be about one
1352	millisecond (if the OS supports it and the machine is fast enough).	1959	millisecond (if the OS supports it and the machine is fast enough).
1353		1960
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1961	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1355		1962
1356	In this mode the values for C<interval> and C<at> are both being	1963	In this mode the values for C<interval> and C<offset> are both being
1357	ignored. Instead, each time the periodic watcher gets scheduled, the	1964	ignored. Instead, each time the periodic watcher gets scheduled, the
1358	reschedule callback will be called with the watcher as first, and the	1965	reschedule callback will be called with the watcher as first, and the
1359	current time as second argument.	1966	current time as second argument.
1360		1967
1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1968	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1362	ever, or make ANY event loop modifications whatsoever>.	1969	or make ANY other event loop modifications whatsoever, unless explicitly
		1970	allowed by documentation here>.
1363		1971
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1972	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1973	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	1974	only event loop modification you are allowed to do).
1367		1975
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1976	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	1977	*w, ev_tstamp now)>, e.g.:
1370		1978
		1979	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1980	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	1981	{
1373	return now + 60.;	1982	return now + 60.;
1374	}	1983	}
1375		1984
1376	It must return the next time to trigger, based on the passed time value	1985	It must return the next time to trigger, based on the passed time value
…		…
1396	a different time than the last time it was called (e.g. in a crond like	2005	a different time than the last time it was called (e.g. in a crond like
1397	program when the crontabs have changed).	2006	program when the crontabs have changed).
1398		2007
1399	=item ev_tstamp ev_periodic_at (ev_periodic *)	2008	=item ev_tstamp ev_periodic_at (ev_periodic *)
1400		2009
1401	When active, returns the absolute time that the watcher is supposed to	2010	When active, returns the absolute time that the watcher is supposed
1402	trigger next.	2011	to trigger next. This is not the same as the C<offset> argument to
		2012	C<ev_periodic_set>, but indeed works even in interval and manual
		2013	rescheduling modes.
1403		2014
1404	=item ev_tstamp offset [read-write]	2015	=item ev_tstamp offset [read-write]
1405		2016
1406	When repeating, this contains the offset value, otherwise this is the	2017	When repeating, this contains the offset value, otherwise this is the
1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2018	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2019	although libev might modify this value for better numerical stability).
1408		2020
1409	Can be modified any time, but changes only take effect when the periodic	2021	Can be modified any time, but changes only take effect when the periodic
1410	timer fires or C<ev_periodic_again> is being called.	2022	timer fires or C<ev_periodic_again> is being called.
1411		2023
1412	=item ev_tstamp interval [read-write]	2024	=item ev_tstamp interval [read-write]
1413		2025
1414	The current interval value. Can be modified any time, but changes only	2026	The current interval value. Can be modified any time, but changes only
1415	take effect when the periodic timer fires or C<ev_periodic_again> is being	2027	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	2028	called.
1417		2029
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2030	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		2031
1420	The current reschedule callback, or C<0>, if this functionality is	2032	The current reschedule callback, or C<0>, if this functionality is
1421	switched off. Can be changed any time, but changes only take effect when	2033	switched off. Can be changed any time, but changes only take effect when
1422	the periodic timer fires or C<ev_periodic_again> is being called.	2034	the periodic timer fires or C<ev_periodic_again> is being called.
1423		2035
1424	=back	2036	=back
1425		2037
1426	=head3 Examples	2038	=head3 Examples
1427		2039
1428	Example: Call a callback every hour, or, more precisely, whenever the	2040	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	2041	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	2042	potentially a lot of jitter, but good long-term stability.
1431		2043
1432	static void	2044	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2045	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1434	{	2046	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	2047	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	2048	}
1437		2049
1438	struct ev_periodic hourly_tick;	2050	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2051	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	2052	ev_periodic_start (loop, &hourly_tick);
1441		2053
1442	Example: The same as above, but use a reschedule callback to do it:	2054	Example: The same as above, but use a reschedule callback to do it:
1443		2055
1444	#include <math.h>	2056	#include <math.h>
1445		2057
1446	static ev_tstamp	2058	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2059	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	2060	{
1449	return fmod (now, 3600.) + 3600.;	2061	return now + (3600. - fmod (now, 3600.));
1450	}	2062	}
1451		2063
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2064	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		2065
1454	Example: Call a callback every hour, starting now:	2066	Example: Call a callback every hour, starting now:
1455		2067
1456	struct ev_periodic hourly_tick;	2068	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	2069	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	2070	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	2071	ev_periodic_start (loop, &hourly_tick);
1460		2072
1461		2073
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	2074	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		2075
1464	Signal watchers will trigger an event when the process receives a specific	2076	Signal watchers will trigger an event when the process receives a specific
1465	signal one or more times. Even though signals are very asynchronous, libev	2077	signal one or more times. Even though signals are very asynchronous, libev
1466	will try it's best to deliver signals synchronously, i.e. as part of the	2078	will try it's best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	2079	normal event processing, like any other event.
1468		2080
		2081	Note that only the default loop supports registering signal watchers
		2082	currently.
		2083
		2084	If you want signals asynchronously, just use C<sigaction> as you would
		2085	do without libev and forget about sharing the signal. You can even use
		2086	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2087
1469	You can configure as many watchers as you like per signal. Only when the	2088	You can configure as many watchers as you like per signal. Only when the
1470	first watcher gets started will libev actually register a signal watcher	2089	first watcher gets started will libev actually register something with
1471	with the kernel (thus it coexists with your own signal handlers as long	2090	the kernel (thus it coexists with your own signal handlers as long as you
1472	as you don't register any with libev). Similarly, when the last signal	2091	don't register any with libev for the same signal).
1473	watcher for a signal is stopped libev will reset the signal handler to	2092
1474	SIG_DFL (regardless of what it was set to before).	2093	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2094	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2095	sotpping it again), that is, libev might or might not block the signal,
		2096	and might or might not set or restore the installed signal handler.
1475		2097
1476	If possible and supported, libev will install its handlers with	2098	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2099	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1478	interrupted. If you have a problem with syscalls getting interrupted by	2100	not be unduly interrupted. If you have a problem with system calls getting
1479	signals you can block all signals in an C<ev_check> watcher and unblock	2101	interrupted by signals you can block all signals in an C<ev_check> watcher
1480	them in an C<ev_prepare> watcher.	2102	and unblock them in an C<ev_prepare> watcher.
1481		2103
1482	=head3 Watcher-Specific Functions and Data Members	2104	=head3 Watcher-Specific Functions and Data Members
1483		2105
1484	=over 4	2106	=over 4
1485		2107
…		…
1496		2118
1497	=back	2119	=back
1498		2120
1499	=head3 Examples	2121	=head3 Examples
1500		2122
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	2123	Example: Try to exit cleanly on SIGINT.
1502		2124
1503	static void	2125	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2126	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	2127	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	2128	ev_unloop (loop, EVUNLOOP_ALL);
1507	}	2129	}
1508		2130
1509	struct ev_signal signal_watcher;	2131	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2132	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	2133	ev_signal_start (loop, &signal_watcher);
1512		2134
1513		2135
1514	=head2 C<ev_child> - watch out for process status changes	2136	=head2 C<ev_child> - watch out for process status changes
1515		2137
1516	Child watchers trigger when your process receives a SIGCHLD in response to	2138	Child watchers trigger when your process receives a SIGCHLD in response to
1517	some child status changes (most typically when a child of yours dies). It	2139	some child status changes (most typically when a child of yours dies or
1518	is permissible to install a child watcher I<after> the child has been	2140	exits). It is permissible to install a child watcher I<after> the child
1519	forked (which implies it might have already exited), as long as the event	2141	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	2142	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2143	forking and then immediately registering a watcher for the child is fine,
		2144	but forking and registering a watcher a few event loop iterations later or
		2145	in the next callback invocation is not.
1521		2146
1522	Only the default event loop is capable of handling signals, and therefore	2147	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	2148	you can only register child watchers in the default event loop.
		2149
		2150	Due to some design glitches inside libev, child watchers will always be
		2151	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2152	libev)
1524		2153
1525	=head3 Process Interaction	2154	=head3 Process Interaction
1526		2155
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	2156	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	2157	initialised. This is necessary to guarantee proper behaviour even if the
1529	the first child watcher is started after the child exits. The occurance	2158	first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2159	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	2160	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	2161	children, even ones not watched.
1533		2162
1534	=head3 Overriding the Built-In Processing	2163	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	2167	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	2168	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	2169	default loop never gets destroyed. You are encouraged, however, to use an
1541	event-based approach to child reaping and thus use libev's support for	2170	event-based approach to child reaping and thus use libev's support for
1542	that, so other libev users can use C<ev_child> watchers freely.	2171	that, so other libev users can use C<ev_child> watchers freely.
		2172
		2173	=head3 Stopping the Child Watcher
		2174
		2175	Currently, the child watcher never gets stopped, even when the
		2176	child terminates, so normally one needs to stop the watcher in the
		2177	callback. Future versions of libev might stop the watcher automatically
		2178	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2179	problem).
1543		2180
1544	=head3 Watcher-Specific Functions and Data Members	2181	=head3 Watcher-Specific Functions and Data Members
1545		2182
1546	=over 4	2183	=over 4
1547		2184
…		…
1576	=head3 Examples	2213	=head3 Examples
1577		2214
1578	Example: C<fork()> a new process and install a child handler to wait for	2215	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	2216	its completion.
1580		2217
1581	ev_child cw;	2218	ev_child cw;
1582		2219
1583	static void	2220	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	2221	child_cb (EV_P_ ev_child *w, int revents)
1585	{	2222	{
1586	ev_child_stop (EV_A_ w);	2223	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2224	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	2225	}
1589		2226
1590	pid_t pid = fork ();	2227	pid_t pid = fork ();
1591		2228
1592	if (pid < 0)	2229	if (pid < 0)
1593	// error	2230	// error
1594	else if (pid == 0)	2231	else if (pid == 0)
1595	{	2232	{
1596	// the forked child executes here	2233	// the forked child executes here
1597	exit (1);	2234	exit (1);
1598	}	2235	}
1599	else	2236	else
1600	{	2237	{
1601	ev_child_init (&cw, child_cb, pid, 0);	2238	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	2239	ev_child_start (EV_DEFAULT_ &cw);
1603	}	2240	}
1604		2241
1605		2242
1606	=head2 C<ev_stat> - did the file attributes just change?	2243	=head2 C<ev_stat> - did the file attributes just change?
1607		2244
1608	This watches a filesystem path for attribute changes. That is, it calls	2245	This watches a file system path for attribute changes. That is, it calls
1609	C<stat> regularly (or when the OS says it changed) and sees if it changed	2246	C<stat> on that path in regular intervals (or when the OS says it changed)
1610	compared to the last time, invoking the callback if it did.	2247	and sees if it changed compared to the last time, invoking the callback if
		2248	it did.
1611		2249
1612	The path does not need to exist: changing from "path exists" to "path does	2250	The path does not need to exist: changing from "path exists" to "path does
1613	not exist" is a status change like any other. The condition "path does	2251	not exist" is a status change like any other. The condition "path does not
1614	not exist" is signified by the C<st_nlink> field being zero (which is	2252	exist" (or more correctly "path cannot be stat'ed") is signified by the
1615	otherwise always forced to be at least one) and all the other fields of	2253	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	2254	least one) and all the other fields of the stat buffer having unspecified
		2255	contents.
1617		2256
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	2257	The path I<must not> end in a slash or contain special components such as
		2258	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1619	relative and your working directory changes, the behaviour is undefined.	2259	your working directory changes, then the behaviour is undefined.
1620		2260
1621	Since there is no standard to do this, the portable implementation simply	2261	Since there is no portable change notification interface available, the
1622	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2262	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	2263	to see if it changed somehow. You can specify a recommended polling
1624	a polling interval of C<0> (highly recommended!) then a I<suitable,	2264	interval for this case. If you specify a polling interval of C<0> (highly
1625	unspecified default> value will be used (which you can expect to be around	2265	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	2266	(which you can expect to be around five seconds, although this might
1627	impose a minimum interval which is currently around C<0.1>, but thats	2267	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	2268	currently around C<0.1>, but that's usually overkill.
1629		2269
1630	This watcher type is not meant for massive numbers of stat watchers,	2270	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	2271	as even with OS-supported change notifications, this can be
1632	resource-intensive.	2272	resource-intensive.
1633		2273
1634	At the time of this writing, only the Linux inotify interface is	2274	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	2275	is the Linux inotify interface (implementing kqueue support is left as an
1636	reader, note, however, that the author sees no way of implementing ev_stat	2276	exercise for the reader. Note, however, that the author sees no way of
1637	semantics with kqueue). Inotify will be used to give hints only and should	2277	implementing C<ev_stat> semantics with kqueue, except as a hint).
1638	not change the semantics of C<ev_stat> watchers, which means that libev
1639	sometimes needs to fall back to regular polling again even with inotify,
1640	but changes are usually detected immediately, and if the file exists there
1641	will be no polling.
1642		2278
1643	=head3 ABI Issues (Largefile Support)	2279	=head3 ABI Issues (Largefile Support)
1644		2280
1645	Libev by default (unless the user overrides this) uses the default	2281	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	2282	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	2283	support disabled by default, you get the 32 bit version of the stat
1648	structure. When using the library from programs that change the ABI to	2284	structure. When using the library from programs that change the ABI to
1649	use 64 bit file offsets the programs will fail. In that case you have to	2285	use 64 bit file offsets the programs will fail. In that case you have to
1650	compile libev with the same flags to get binary compatibility. This is	2286	compile libev with the same flags to get binary compatibility. This is
1651	obviously the case with any flags that change the ABI, but the problem is	2287	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	2288	most noticeably displayed with ev_stat and large file support.
1653		2289
1654	=head3 Inotify	2290	The solution for this is to lobby your distribution maker to make large
		2291	file interfaces available by default (as e.g. FreeBSD does) and not
		2292	optional. Libev cannot simply switch on large file support because it has
		2293	to exchange stat structures with application programs compiled using the
		2294	default compilation environment.
1655		2295
		2296	=head3 Inotify and Kqueue
		2297
1656	When C<inotify (7)> support has been compiled into libev (generally only	2298	When C<inotify (7)> support has been compiled into libev and present at
1657	available on Linux) and present at runtime, it will be used to speed up	2299	runtime, it will be used to speed up change detection where possible. The
1658	change detection where possible. The inotify descriptor will be created lazily	2300	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	2301	watcher is being started.
1660		2302
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	2303	Inotify presence does not change the semantics of C<ev_stat> watchers
1662	except that changes might be detected earlier, and in some cases, to avoid	2304	except that changes might be detected earlier, and in some cases, to avoid
1663	making regular C<stat> calls. Even in the presence of inotify support	2305	making regular C<stat> calls. Even in the presence of inotify support
1664	there are many cases where libev has to resort to regular C<stat> polling.	2306	there are many cases where libev has to resort to regular C<stat> polling,
		2307	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2308	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2309	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2310	xfs are fully working) libev usually gets away without polling.
1665		2311
1666	(There is no support for kqueue, as apparently it cannot be used to	2312	There is no support for kqueue, as apparently it cannot be used to
1667	implement this functionality, due to the requirement of having a file	2313	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2314	descriptor open on the object at all times, and detecting renames, unlinks
		2315	etc. is difficult.
		2316
		2317	=head3 C<stat ()> is a synchronous operation
		2318
		2319	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2320	the process. The exception are C<ev_stat> watchers - those call C<stat
		2321	()>, which is a synchronous operation.
		2322
		2323	For local paths, this usually doesn't matter: unless the system is very
		2324	busy or the intervals between stat's are large, a stat call will be fast,
		2325	as the path data is usually in memory already (except when starting the
		2326	watcher).
		2327
		2328	For networked file systems, calling C<stat ()> can block an indefinite
		2329	time due to network issues, and even under good conditions, a stat call
		2330	often takes multiple milliseconds.
		2331
		2332	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2333	paths, although this is fully supported by libev.
1669		2334
1670	=head3 The special problem of stat time resolution	2335	=head3 The special problem of stat time resolution
1671		2336
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2337	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2338	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2339	still only support whole seconds.
1675		2340
1676	That means that, if the time is the only thing that changes, you can	2341	That means that, if the time is the only thing that changes, you can
1677	easily miss updates: on the first update, C<ev_stat> detects a change and	2342	easily miss updates: on the first update, C<ev_stat> detects a change and
1678	calls your callback, which does something. When there is another update	2343	calls your callback, which does something. When there is another update
1679	within the same second, C<ev_stat> will be unable to detect it as the stat	2344	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2345	stat data does change in other ways (e.g. file size).
1681		2346
1682	The solution to this is to delay acting on a change for slightly more	2347	The solution to this is to delay acting on a change for slightly more
1683	than a second (or till slightly after the next full second boundary), using	2348	than a second (or till slightly after the next full second boundary), using
1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2349	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2350	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2370	C<path>. The C<interval> is a hint on how quickly a change is expected to
1706	be detected and should normally be specified as C<0> to let libev choose	2371	be detected and should normally be specified as C<0> to let libev choose
1707	a suitable value. The memory pointed to by C<path> must point to the same	2372	a suitable value. The memory pointed to by C<path> must point to the same
1708	path for as long as the watcher is active.	2373	path for as long as the watcher is active.
1709		2374
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2375	The callback will receive an C<EV_STAT> event when a change was detected,
1711	to the attributes at the time the watcher was started (or the last change	2376	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2377	last change was detected).
1713		2378
1714	=item ev_stat_stat (loop, ev_stat *)	2379	=item ev_stat_stat (loop, ev_stat *)
1715		2380
1716	Updates the stat buffer immediately with new values. If you change the	2381	Updates the stat buffer immediately with new values. If you change the
1717	watched path in your callback, you could call this function to avoid	2382	watched path in your callback, you could call this function to avoid
…		…
1738		2403
1739	The specified interval.	2404	The specified interval.
1740		2405
1741	=item const char *path [read-only]	2406	=item const char *path [read-only]
1742		2407
1743	The filesystem path that is being watched.	2408	The file system path that is being watched.
1744		2409
1745	=back	2410	=back
1746		2411
1747	=head3 Examples	2412	=head3 Examples
1748		2413
1749	Example: Watch C</etc/passwd> for attribute changes.	2414	Example: Watch C</etc/passwd> for attribute changes.
1750		2415
1751	static void	2416	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2417	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2418	{
1754	/* /etc/passwd changed in some way */	2419	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2420	if (w->attr.st_nlink)
1756	{	2421	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2422	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2423	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2424	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2425	}
1761	else	2426	else
1762	/* you shalt not abuse printf for puts */	2427	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2428	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2429	"if this is windows, they already arrived\n");
1765	}	2430	}
1766		2431
1767	...	2432	...
1768	ev_stat passwd;	2433	ev_stat passwd;
1769		2434
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2435	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2436	ev_stat_start (loop, &passwd);
1772		2437
1773	Example: Like above, but additionally use a one-second delay so we do not	2438	Example: Like above, but additionally use a one-second delay so we do not
1774	miss updates (however, frequent updates will delay processing, too, so	2439	miss updates (however, frequent updates will delay processing, too, so
1775	one might do the work both on C<ev_stat> callback invocation I<and> on	2440	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2441	C<ev_timer> callback invocation).
1777		2442
1778	static ev_stat passwd;	2443	static ev_stat passwd;
1779	static ev_timer timer;	2444	static ev_timer timer;
1780		2445
1781	static void	2446	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2447	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2448	{
1784	ev_timer_stop (EV_A_ w);	2449	ev_timer_stop (EV_A_ w);
1785		2450
1786	/* now it's one second after the most recent passwd change */	2451	/* now it's one second after the most recent passwd change */
1787	}	2452	}
1788		2453
1789	static void	2454	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2455	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2456	{
1792	/* reset the one-second timer */	2457	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2458	ev_timer_again (EV_A_ &timer);
1794	}	2459	}
1795		2460
1796	...	2461	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2462	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2463	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2464	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2465
1801		2466
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2467	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2468
1804	Idle watchers trigger events when no other events of the same or higher	2469	Idle watchers trigger events when no other events of the same or higher
1805	priority are pending (prepare, check and other idle watchers do not	2470	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2471	as receiving "events").
1807		2472
1808	That is, as long as your process is busy handling sockets or timeouts	2473	That is, as long as your process is busy handling sockets or timeouts
1809	(or even signals, imagine) of the same or higher priority it will not be	2474	(or even signals, imagine) of the same or higher priority it will not be
1810	triggered. But when your process is idle (or only lower-priority watchers	2475	triggered. But when your process is idle (or only lower-priority watchers
1811	are pending), the idle watchers are being called once per event loop	2476	are pending), the idle watchers are being called once per event loop
…		…
1822		2487
1823	=head3 Watcher-Specific Functions and Data Members	2488	=head3 Watcher-Specific Functions and Data Members
1824		2489
1825	=over 4	2490	=over 4
1826		2491
1827	=item ev_idle_init (ev_signal *, callback)	2492	=item ev_idle_init (ev_idle *, callback)
1828		2493
1829	Initialises and configures the idle watcher - it has no parameters of any	2494	Initialises and configures the idle watcher - it has no parameters of any
1830	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2495	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1831	believe me.	2496	believe me.
1832		2497
…		…
1835	=head3 Examples	2500	=head3 Examples
1836		2501
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2502	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2503	callback, free it. Also, use no error checking, as usual.
1839		2504
1840	static void	2505	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2506	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2507	{
1843	free (w);	2508	free (w);
1844	// now do something you wanted to do when the program has	2509	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2510	// no longer anything immediate to do.
1846	}	2511	}
1847		2512
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2513	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2514	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2515	ev_idle_start (loop, idle_watcher);
1851		2516
1852		2517
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2518	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2519
1855	Prepare and check watchers are usually (but not always) used in tandem:	2520	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2521	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2522	afterwards.
1858		2523
1859	You I<must not> call C<ev_loop> or similar functions that enter	2524	You I<must not> call C<ev_loop> or similar functions that enter
1860	the current event loop from either C<ev_prepare> or C<ev_check>	2525	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1863	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2528	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1864	C<ev_check> so if you have one watcher of each kind they will always be	2529	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2530	called in pairs bracketing the blocking call.
1866		2531
1867	Their main purpose is to integrate other event mechanisms into libev and	2532	Their main purpose is to integrate other event mechanisms into libev and
1868	their use is somewhat advanced. This could be used, for example, to track	2533	their use is somewhat advanced. They could be used, for example, to track
1869	variable changes, implement your own watchers, integrate net-snmp or a	2534	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2535	coroutine library and lots more. They are also occasionally useful if
1871	you cache some data and want to flush it before blocking (for example,	2536	you cache some data and want to flush it before blocking (for example,
1872	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2537	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2538	watcher).
1874		2539
1875	This is done by examining in each prepare call which file descriptors need	2540	This is done by examining in each prepare call which file descriptors
1876	to be watched by the other library, registering C<ev_io> watchers for	2541	need to be watched by the other library, registering C<ev_io> watchers
1877	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2542	for them and starting an C<ev_timer> watcher for any timeouts (many
1878	provide just this functionality). Then, in the check watcher you check for	2543	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2544	you check for any events that occurred (by checking the pending status
1880	and stopping them) and call back into the library. The I/O and timer	2545	of all watchers and stopping them) and call back into the library. The
1881	callbacks will never actually be called (but must be valid nevertheless,	2546	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2547	nevertheless, because you never know, you know?).
1883		2548
1884	As another example, the Perl Coro module uses these hooks to integrate	2549	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2550	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2551	during each prepare and only letting the process block if no coroutines
1887	are ready to run (it's actually more complicated: it only runs coroutines	2552	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1890	loop from blocking if lower-priority coroutines are active, thus mapping	2555	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2556	low-priority coroutines to idle/background tasks).
1892		2557
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2558	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1894	priority, to ensure that they are being run before any other watchers	2559	priority, to ensure that they are being run before any other watchers
		2560	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2561
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2562	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1896	too) should not activate ("feed") events into libev. While libev fully	2563	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2564	might get executed before other C<ev_check> watchers did their job. As
1898	did their job. As C<ev_check> watchers are often used to embed other	2565	C<ev_check> watchers are often used to embed other (non-libev) event
1899	(non-libev) event loops those other event loops might be in an unusable	2566	loops those other event loops might be in an unusable state until their
1900	state until their C<ev_check> watcher ran (always remind yourself to	2567	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2568	others).
1902		2569
1903	=head3 Watcher-Specific Functions and Data Members	2570	=head3 Watcher-Specific Functions and Data Members
1904		2571
1905	=over 4	2572	=over 4
1906		2573
…		…
1908		2575
1909	=item ev_check_init (ev_check *, callback)	2576	=item ev_check_init (ev_check *, callback)
1910		2577
1911	Initialises and configures the prepare or check watcher - they have no	2578	Initialises and configures the prepare or check watcher - they have no
1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2579	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1913	macros, but using them is utterly, utterly and completely pointless.	2580	macros, but using them is utterly, utterly, utterly and completely
		2581	pointless.
1914		2582
1915	=back	2583	=back
1916		2584
1917	=head3 Examples	2585	=head3 Examples
1918		2586
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2595	and in a check watcher, destroy them and call into libadns. What follows
1928	is pseudo-code only of course. This requires you to either use a low	2596	is pseudo-code only of course. This requires you to either use a low
1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2597	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1930	the callbacks for the IO/timeout watchers might not have been called yet.	2598	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2599
1932	static ev_io iow [nfd];	2600	static ev_io iow [nfd];
1933	static ev_timer tw;	2601	static ev_timer tw;
1934		2602
1935	static void	2603	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2604	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2605	{
1938	}	2606	}
1939		2607
1940	// create io watchers for each fd and a timer before blocking	2608	// create io watchers for each fd and a timer before blocking
1941	static void	2609	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2610	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2611	{
1944	int timeout = 3600000;	2612	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2613	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2614	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2615	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2616
1949	/* the callback is illegal, but won't be called as we stop during check */	2617	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2618	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1951	ev_timer_start (loop, &tw);	2619	ev_timer_start (loop, &tw);
1952		2620
1953	// create one ev_io per pollfd	2621	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2622	for (int i = 0; i < nfd; ++i)
1955	{	2623	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2624	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2625	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2626	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2627
1960	fds [i].revents = 0;	2628	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2629	ev_io_start (loop, iow + i);
1962	}	2630	}
1963	}	2631	}
1964		2632
1965	// stop all watchers after blocking	2633	// stop all watchers after blocking
1966	static void	2634	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2635	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2636	{
1969	ev_timer_stop (loop, &tw);	2637	ev_timer_stop (loop, &tw);
1970		2638
1971	for (int i = 0; i < nfd; ++i)	2639	for (int i = 0; i < nfd; ++i)
1972	{	2640	{
1973	// set the relevant poll flags	2641	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2642	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2643	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2644	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2645	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2646	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2647
1980	// now stop the watcher	2648	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2649	ev_io_stop (loop, iow + i);
1982	}	2650	}
1983		2651
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2652	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2653	}
1986		2654
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2655	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1988	in the prepare watcher and would dispose of the check watcher.	2656	in the prepare watcher and would dispose of the check watcher.
1989		2657
1990	Method 3: If the module to be embedded supports explicit event	2658	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2659	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2660	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2661
1994	static void	2662	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2663	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2664	{
1997	adns_state ads = (adns_state)w->data;	2665	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2666	update_now (EV_A);
1999		2667
2000	adns_processtimeouts (ads, &tv_now);	2668	adns_processtimeouts (ads, &tv_now);
2001	}	2669	}
2002		2670
2003	static void	2671	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2672	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2673	{
2006	adns_state ads = (adns_state)w->data;	2674	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2675	update_now (EV_A);
2008		2676
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2677	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2678	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2679	}
2012		2680
2013	// do not ever call adns_afterpoll	2681	// do not ever call adns_afterpoll
2014		2682
2015	Method 4: Do not use a prepare or check watcher because the module you	2683	Method 4: Do not use a prepare or check watcher because the module you
2016	want to embed is too inflexible to support it. Instead, youc na override	2684	want to embed is not flexible enough to support it. Instead, you can
2017	their poll function. The drawback with this solution is that the main	2685	override their poll function. The drawback with this solution is that the
2018	loop is now no longer controllable by EV. The C<Glib::EV> module does	2686	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2687	this approach, effectively embedding EV as a client into the horrible
		2688	libglib event loop.
2020		2689
2021	static gint	2690	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2691	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2692	{
2024	int got_events = 0;	2693	int got_events = 0;
2025		2694
2026	for (n = 0; n < nfds; ++n)	2695	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2696	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2697
2029	if (timeout >= 0)	2698	if (timeout >= 0)
2030	// create/start timer	2699	// create/start timer
2031		2700
2032	// poll	2701	// poll
2033	ev_loop (EV_A_ 0);	2702	ev_loop (EV_A_ 0);
2034		2703
2035	// stop timer again	2704	// stop timer again
2036	if (timeout >= 0)	2705	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2706	ev_timer_stop (EV_A_ &to);
2038		2707
2039	// stop io watchers again - their callbacks should have set	2708	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2709	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2710	ev_io_stop (EV_A_ iow [n]);
2042		2711
2043	return got_events;	2712	return got_events;
2044	}	2713	}
2045		2714
2046		2715
2047	=head2 C<ev_embed> - when one backend isn't enough...	2716	=head2 C<ev_embed> - when one backend isn't enough...
2048		2717
2049	This is a rather advanced watcher type that lets you embed one event loop	2718	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2724	prioritise I/O.
2056		2725
2057	As an example for a bug workaround, the kqueue backend might only support	2726	As an example for a bug workaround, the kqueue backend might only support
2058	sockets on some platform, so it is unusable as generic backend, but you	2727	sockets on some platform, so it is unusable as generic backend, but you
2059	still want to make use of it because you have many sockets and it scales	2728	still want to make use of it because you have many sockets and it scales
2060	so nicely. In this case, you would create a kqueue-based loop and embed it	2729	so nicely. In this case, you would create a kqueue-based loop and embed
2061	into your default loop (which might use e.g. poll). Overall operation will	2730	it into your default loop (which might use e.g. poll). Overall operation
2062	be a bit slower because first libev has to poll and then call kevent, but	2731	will be a bit slower because first libev has to call C<poll> and then
2063	at least you can use both at what they are best.	2732	C<kevent>, but at least you can use both mechanisms for what they are
		2733	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2734
2065	As for prioritising I/O: rarely you have the case where some fds have	2735	As for prioritising I/O: under rare circumstances you have the case where
2066	to be watched and handled very quickly (with low latency), and even	2736	some fds have to be watched and handled very quickly (with low latency),
2067	priorities and idle watchers might have too much overhead. In this case	2737	and even priorities and idle watchers might have too much overhead. In
2068	you would put all the high priority stuff in one loop and all the rest in	2738	this case you would put all the high priority stuff in one loop and all
2069	a second one, and embed the second one in the first.	2739	the rest in a second one, and embed the second one in the first.
2070		2740
2071	As long as the watcher is active, the callback will be invoked every time	2741	As long as the watcher is active, the callback will be invoked every
2072	there might be events pending in the embedded loop. The callback must then	2742	time there might be events pending in the embedded loop. The callback
2073	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2743	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2074	their callbacks (you could also start an idle watcher to give the embedded	2744	sweep and invoke their callbacks (the callback doesn't need to invoke the
2075	loop strictly lower priority for example). You can also set the callback	2745	C<ev_embed_sweep> function directly, it could also start an idle watcher
2076	to C<0>, in which case the embed watcher will automatically execute the	2746	to give the embedded loop strictly lower priority for example).
2077	embedded loop sweep.
2078		2747
2079	As long as the watcher is started it will automatically handle events. The	2748	You can also set the callback to C<0>, in which case the embed watcher
2080	callback will be invoked whenever some events have been handled. You can	2749	will automatically execute the embedded loop sweep whenever necessary.
2081	set the callback to C<0> to avoid having to specify one if you are not
2082	interested in that.
2083		2750
2084	Also, there have not currently been made special provisions for forking:	2751	Fork detection will be handled transparently while the C<ev_embed> watcher
2085	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2752	is active, i.e., the embedded loop will automatically be forked when the
2086	but you will also have to stop and restart any C<ev_embed> watchers	2753	embedding loop forks. In other cases, the user is responsible for calling
2087	yourself.	2754	C<ev_loop_fork> on the embedded loop.
2088		2755
2089	Unfortunately, not all backends are embeddable, only the ones returned by	2756	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2757	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	2758	portable one.
2092		2759
2093	So when you want to use this feature you will always have to be prepared	2760	So when you want to use this feature you will always have to be prepared
2094	that you cannot get an embeddable loop. The recommended way to get around	2761	that you cannot get an embeddable loop. The recommended way to get around
2095	this is to have a separate variables for your embeddable loop, try to	2762	this is to have a separate variables for your embeddable loop, try to
2096	create it, and if that fails, use the normal loop for everything.	2763	create it, and if that fails, use the normal loop for everything.
2097		2764
		2765	=head3 C<ev_embed> and fork
		2766
		2767	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2768	automatically be applied to the embedded loop as well, so no special
		2769	fork handling is required in that case. When the watcher is not running,
		2770	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2771	as applicable.
		2772
2098	=head3 Watcher-Specific Functions and Data Members	2773	=head3 Watcher-Specific Functions and Data Members
2099		2774
2100	=over 4	2775	=over 4
2101		2776
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2777	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		2780
2106	Configures the watcher to embed the given loop, which must be	2781	Configures the watcher to embed the given loop, which must be
2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2782	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2108	invoked automatically, otherwise it is the responsibility of the callback	2783	invoked automatically, otherwise it is the responsibility of the callback
2109	to invoke it (it will continue to be called until the sweep has been done,	2784	to invoke it (it will continue to be called until the sweep has been done,
2110	if you do not want thta, you need to temporarily stop the embed watcher).	2785	if you do not want that, you need to temporarily stop the embed watcher).
2111		2786
2112	=item ev_embed_sweep (loop, ev_embed *)	2787	=item ev_embed_sweep (loop, ev_embed *)
2113		2788
2114	Make a single, non-blocking sweep over the embedded loop. This works	2789	Make a single, non-blocking sweep over the embedded loop. This works
2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2790	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2116	apropriate way for embedded loops.	2791	appropriate way for embedded loops.
2117		2792
2118	=item struct ev_loop *other [read-only]	2793	=item struct ev_loop *other [read-only]
2119		2794
2120	The embedded event loop.	2795	The embedded event loop.
2121		2796
…		…
2123		2798
2124	=head3 Examples	2799	=head3 Examples
2125		2800
2126	Example: Try to get an embeddable event loop and embed it into the default	2801	Example: Try to get an embeddable event loop and embed it into the default
2127	event loop. If that is not possible, use the default loop. The default	2802	event loop. If that is not possible, use the default loop. The default
2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2803	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2804	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	2805	used).
2131		2806
2132	struct ev_loop *loop_hi = ev_default_init (0);	2807	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	2808	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	2809	ev_embed embed;
2135		2810
2136	// see if there is a chance of getting one that works	2811	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	2812	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2813	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2814	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	2815	: 0;
2141		2816
2142	// if we got one, then embed it, otherwise default to loop_hi	2817	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	2818	if (loop_lo)
2144	{	2819	{
2145	ev_embed_init (&embed, 0, loop_lo);	2820	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	2821	ev_embed_start (loop_hi, &embed);
2147	}	2822	}
2148	else	2823	else
2149	loop_lo = loop_hi;	2824	loop_lo = loop_hi;
2150		2825
2151	Example: Check if kqueue is available but not recommended and create	2826	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	2827	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	2828	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2829	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		2830
2156	struct ev_loop *loop = ev_default_init (0);	2831	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	2832	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	2833	ev_embed embed;
2159		2834
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2835	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2836	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	2837	{
2163	ev_embed_init (&embed, 0, loop_socket);	2838	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	2839	ev_embed_start (loop, &embed);
2165	}	2840	}
2166		2841
2167	if (!loop_socket)	2842	if (!loop_socket)
2168	loop_socket = loop;	2843	loop_socket = loop;
2169		2844
2170	// now use loop_socket for all sockets, and loop for everything else	2845	// now use loop_socket for all sockets, and loop for everything else
2171		2846
2172		2847
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2848	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		2849
2175	Fork watchers are called when a C<fork ()> was detected (usually because	2850	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2178	event loop blocks next and before C<ev_check> watchers are being called,	2853	event loop blocks next and before C<ev_check> watchers are being called,
2179	and only in the child after the fork. If whoever good citizen calling	2854	and only in the child after the fork. If whoever good citizen calling
2180	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2855	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2181	handlers will be invoked, too, of course.	2856	handlers will be invoked, too, of course.
2182		2857
		2858	=head3 The special problem of life after fork - how is it possible?
		2859
		2860	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2861	up/change the process environment, followed by a call to C<exec()>. This
		2862	sequence should be handled by libev without any problems.
		2863
		2864	This changes when the application actually wants to do event handling
		2865	in the child, or both parent in child, in effect "continuing" after the
		2866	fork.
		2867
		2868	The default mode of operation (for libev, with application help to detect
		2869	forks) is to duplicate all the state in the child, as would be expected
		2870	when I<either> the parent I<or> the child process continues.
		2871
		2872	When both processes want to continue using libev, then this is usually the
		2873	wrong result. In that case, usually one process (typically the parent) is
		2874	supposed to continue with all watchers in place as before, while the other
		2875	process typically wants to start fresh, i.e. without any active watchers.
		2876
		2877	The cleanest and most efficient way to achieve that with libev is to
		2878	simply create a new event loop, which of course will be "empty", and
		2879	use that for new watchers. This has the advantage of not touching more
		2880	memory than necessary, and thus avoiding the copy-on-write, and the
		2881	disadvantage of having to use multiple event loops (which do not support
		2882	signal watchers).
		2883
		2884	When this is not possible, or you want to use the default loop for
		2885	other reasons, then in the process that wants to start "fresh", call
		2886	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2887	the default loop will "orphan" (not stop) all registered watchers, so you
		2888	have to be careful not to execute code that modifies those watchers. Note
		2889	also that in that case, you have to re-register any signal watchers.
		2890
2183	=head3 Watcher-Specific Functions and Data Members	2891	=head3 Watcher-Specific Functions and Data Members
2184		2892
2185	=over 4	2893	=over 4
2186		2894
2187	=item ev_fork_init (ev_signal *, callback)	2895	=item ev_fork_init (ev_signal *, callback)
…		…
2219	is that the author does not know of a simple (or any) algorithm for a	2927	is that the author does not know of a simple (or any) algorithm for a
2220	multiple-writer-single-reader queue that works in all cases and doesn't	2928	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	2929	need elaborate support such as pthreads.
2222		2930
2223	That means that if you want to queue data, you have to provide your own	2931	That means that if you want to queue data, you have to provide your own
2224	queue. But at least I can tell you would implement locking around your	2932	queue. But at least I can tell you how to implement locking around your
2225	queue:	2933	queue:
2226		2934
2227	=over 4	2935	=over 4
2228		2936
2229	=item queueing from a signal handler context	2937	=item queueing from a signal handler context
2230		2938
2231	To implement race-free queueing, you simply add to the queue in the signal	2939	To implement race-free queueing, you simply add to the queue in the signal
2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2940	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	2941	an example that does that for some fictitious SIGUSR1 handler:
2234		2942
2235	static ev_async mysig;	2943	static ev_async mysig;
2236		2944
2237	static void	2945	static void
2238	sigusr1_handler (void)	2946	sigusr1_handler (void)
…		…
2304	=over 4	3012	=over 4
2305		3013
2306	=item ev_async_init (ev_async *, callback)	3014	=item ev_async_init (ev_async *, callback)
2307		3015
2308	Initialises and configures the async watcher - it has no parameters of any	3016	Initialises and configures the async watcher - it has no parameters of any
2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3017	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	3018	trust me.
2311		3019
2312	=item ev_async_send (loop, ev_async *)	3020	=item ev_async_send (loop, ev_async *)
2313		3021
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3022	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3023	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2316	C<ev_feed_event>, this call is safe to do in other threads, signal or	3024	C<ev_feed_event>, this call is safe to do from other threads, signal or
2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3025	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2318	section below on what exactly this means).	3026	section below on what exactly this means).
2319		3027
		3028	Note that, as with other watchers in libev, multiple events might get
		3029	compressed into a single callback invocation (another way to look at this
		3030	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3031	reset when the event loop detects that).
		3032
2320	This call incurs the overhead of a syscall only once per loop iteration,	3033	This call incurs the overhead of a system call only once per event loop
2321	so while the overhead might be noticable, it doesn't apply to repeated	3034	iteration, so while the overhead might be noticeable, it doesn't apply to
2322	calls to C<ev_async_send>.	3035	repeated calls to C<ev_async_send> for the same event loop.
2323		3036
2324	=item bool = ev_async_pending (ev_async *)	3037	=item bool = ev_async_pending (ev_async *)
2325		3038
2326	Returns a non-zero value when C<ev_async_send> has been called on the	3039	Returns a non-zero value when C<ev_async_send> has been called on the
2327	watcher but the event has not yet been processed (or even noted) by the	3040	watcher but the event has not yet been processed (or even noted) by the
2328	event loop.	3041	event loop.
2329		3042
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3043	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2331	the loop iterates next and checks for the watcher to have become active,	3044	the loop iterates next and checks for the watcher to have become active,
2332	it will reset the flag again. C<ev_async_pending> can be used to very	3045	it will reset the flag again. C<ev_async_pending> can be used to very
2333	quickly check wether invoking the loop might be a good idea.	3046	quickly check whether invoking the loop might be a good idea.
2334		3047
2335	Not that this does I<not> check wether the watcher itself is pending, only	3048	Not that this does I<not> check whether the watcher itself is pending,
2336	wether it has been requested to make this watcher pending.	3049	only whether it has been requested to make this watcher pending: there
		3050	is a time window between the event loop checking and resetting the async
		3051	notification, and the callback being invoked.
2337		3052
2338	=back	3053	=back
2339		3054
2340		3055
2341	=head1 OTHER FUNCTIONS	3056	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	3060	=over 4
2346		3061
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3062	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		3063
2349	This function combines a simple timer and an I/O watcher, calls your	3064	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	3065	callback on whichever event happens first and automatically stops both
2351	watchers. This is useful if you want to wait for a single event on an fd	3066	watchers. This is useful if you want to wait for a single event on an fd
2352	or timeout without having to allocate/configure/start/stop/free one or	3067	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	3068	more watchers yourself.
2354		3069
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	3070	If C<fd> is less than 0, then no I/O watcher will be started and the
2356	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3071	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	3072	the given C<fd> and C<events> set will be created and started.
2358		3073
2359	If C<timeout> is less than 0, then no timeout watcher will be	3074	If C<timeout> is less than 0, then no timeout watcher will be
2360	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3075	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2361	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3076	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		3077
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3078	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2365	passed an C<revents> set like normal event callbacks (a combination of	3079	passed an C<revents> set like normal event callbacks (a combination of
2366	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3080	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2367	value passed to C<ev_once>:	3081	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3082	a timeout and an io event at the same time - you probably should give io
		3083	events precedence.
2368		3084
		3085	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3086
2369	static void stdin_ready (int revents, void *arg)	3087	static void stdin_ready (int revents, void *arg)
2370	{	3088	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	3089	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	3090	/* stdin might have data for us, joy! */;
		3091	else if (revents & EV_TIMEOUT)
		3092	/* doh, nothing entered */;
2375	}	3093	}
2376		3094
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3095	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		3096
2379	=item ev_feed_event (ev_loop *, watcher *, int revents)	3097	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2380		3098
2381	Feeds the given event set into the event loop, as if the specified event	3099	Feeds the given event set into the event loop, as if the specified event
2382	had happened for the specified watcher (which must be a pointer to an	3100	had happened for the specified watcher (which must be a pointer to an
2383	initialised but not necessarily started event watcher).	3101	initialised but not necessarily started event watcher).
2384		3102
2385	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3103	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2386		3104
2387	Feed an event on the given fd, as if a file descriptor backend detected	3105	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	3106	the given events it.
2389		3107
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	3108	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2391		3109
2392	Feed an event as if the given signal occured (C<loop> must be the default	3110	Feed an event as if the given signal occurred (C<loop> must be the default
2393	loop!).	3111	loop!).
2394		3112
2395	=back	3113	=back
2396		3114
2397		3115
…		…
2426	=back	3144	=back
2427		3145
2428	=head1 C++ SUPPORT	3146	=head1 C++ SUPPORT
2429		3147
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3148	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2431	you to use some convinience methods to start/stop watchers and also change	3149	you to use some convenience methods to start/stop watchers and also change
2432	the callback model to a model using method callbacks on objects.	3150	the callback model to a model using method callbacks on objects.
2433		3151
2434	To use it,	3152	To use it,
2435		3153
2436	#include <ev++.h>	3154	#include <ev++.h>
2437		3155
2438	This automatically includes F<ev.h> and puts all of its definitions (many	3156	This automatically includes F<ev.h> and puts all of its definitions (many
2439	of them macros) into the global namespace. All C++ specific things are	3157	of them macros) into the global namespace. All C++ specific things are
2440	put into the C<ev> namespace. It should support all the same embedding	3158	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3159	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2508	your compiler is good :), then the method will be fully inlined into the	3226	your compiler is good :), then the method will be fully inlined into the
2509	thunking function, making it as fast as a direct C callback.	3227	thunking function, making it as fast as a direct C callback.
2510		3228
2511	Example: simple class declaration and watcher initialisation	3229	Example: simple class declaration and watcher initialisation
2512		3230
2513	struct myclass	3231	struct myclass
2514	{	3232	{
2515	void io_cb (ev::io &w, int revents) { }	3233	void io_cb (ev::io &w, int revents) { }
2516	}	3234	}
2517		3235
2518	myclass obj;	3236	myclass obj;
2519	ev::io iow;	3237	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	3238	iow.set <myclass, &myclass::io_cb> (&obj);
		3239
		3240	=item w->set (object *)
		3241
		3242	This is an B<experimental> feature that might go away in a future version.
		3243
		3244	This is a variation of a method callback - leaving out the method to call
		3245	will default the method to C<operator ()>, which makes it possible to use
		3246	functor objects without having to manually specify the C<operator ()> all
		3247	the time. Incidentally, you can then also leave out the template argument
		3248	list.
		3249
		3250	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3251	int revents)>.
		3252
		3253	See the method-C<set> above for more details.
		3254
		3255	Example: use a functor object as callback.
		3256
		3257	struct myfunctor
		3258	{
		3259	void operator() (ev::io &w, int revents)
		3260	{
		3261	...
		3262	}
		3263	}
		3264
		3265	myfunctor f;
		3266
		3267	ev::io w;
		3268	w.set (&f);
2521		3269
2522	=item w->set<function> (void *data = 0)	3270	=item w->set<function> (void *data = 0)
2523		3271
2524	Also sets a callback, but uses a static method or plain function as	3272	Also sets a callback, but uses a static method or plain function as
2525	callback. The optional C<data> argument will be stored in the watcher's	3273	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		3275
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3276	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		3277
2530	See the method-C<set> above for more details.	3278	See the method-C<set> above for more details.
2531		3279
2532	Example:	3280	Example: Use a plain function as callback.
2533		3281
2534	static void io_cb (ev::io &w, int revents) { }	3282	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	3283	iow.set <io_cb> ();
2536		3284
2537	=item w->set (struct ev_loop *)	3285	=item w->set (struct ev_loop *)
2538		3286
2539	Associates a different C<struct ev_loop> with this watcher. You can only	3287	Associates a different C<struct ev_loop> with this watcher. You can only
2540	do this when the watcher is inactive (and not pending either).	3288	do this when the watcher is inactive (and not pending either).
2541		3289
2542	=item w->set ([args])	3290	=item w->set ([arguments])
2543		3291
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3292	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2545	called at least once. Unlike the C counterpart, an active watcher gets	3293	called at least once. Unlike the C counterpart, an active watcher gets
2546	automatically stopped and restarted when reconfiguring it with this	3294	automatically stopped and restarted when reconfiguring it with this
2547	method.	3295	method.
2548		3296
2549	=item w->start ()	3297	=item w->start ()
…		…
2573	=back	3321	=back
2574		3322
2575	Example: Define a class with an IO and idle watcher, start one of them in	3323	Example: Define a class with an IO and idle watcher, start one of them in
2576	the constructor.	3324	the constructor.
2577		3325
2578	class myclass	3326	class myclass
2579	{	3327	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	3328	ev::io io ; void io_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	3329	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		3330
2583	myclass (int fd)	3331	myclass (int fd)
2584	{	3332	{
2585	io .set <myclass, &myclass::io_cb > (this);	3333	io .set <myclass, &myclass::io_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	3334	idle.set <myclass, &myclass::idle_cb> (this);
2587		3335
2588	io.start (fd, ev::READ);	3336	io.start (fd, ev::READ);
2589	}	3337	}
2590	};	3338	};
2591		3339
2592		3340
2593	=head1 OTHER LANGUAGE BINDINGS	3341	=head1 OTHER LANGUAGE BINDINGS
2594		3342
2595	Libev does not offer other language bindings itself, but bindings for a	3343	Libev does not offer other language bindings itself, but bindings for a
2596	numbe rof languages exist in the form of third-party packages. If you know	3344	number of languages exist in the form of third-party packages. If you know
2597	any interesting language binding in addition to the ones listed here, drop	3345	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	3346	me a note.
2599		3347
2600	=over 4	3348	=over 4
2601		3349
2602	=item Perl	3350	=item Perl
2603		3351
2604	The EV module implements the full libev API and is actually used to test	3352	The EV module implements the full libev API and is actually used to test
2605	libev. EV is developed together with libev. Apart from the EV core module,	3353	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	3354	there are additional modules that implement libev-compatible interfaces
2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3355	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3356	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3357	and C<EV::Glib>).
2609		3358
2610	It can be found and installed via CPAN, its homepage is found at	3359	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	3360	L<http://software.schmorp.de/pkg/EV>.
2612		3361
		3362	=item Python
		3363
		3364	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3365	seems to be quite complete and well-documented.
		3366
2613	=item Ruby	3367	=item Ruby
2614		3368
2615	Tony Arcieri has written a ruby extension that offers access to a subset	3369	Tony Arcieri has written a ruby extension that offers access to a subset
2616	of the libev API and adds filehandle abstractions, asynchronous DNS and	3370	of the libev API and adds file handle abstractions, asynchronous DNS and
2617	more on top of it. It can be found via gem servers. Its homepage is at	3371	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	3372	L<http://rev.rubyforge.org/>.
2619		3373
		3374	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3375	makes rev work even on mingw.
		3376
		3377	=item Haskell
		3378
		3379	A haskell binding to libev is available at
		3380	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3381
2620	=item D	3382	=item D
2621		3383
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3384	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3385	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3386
		3387	=item Ocaml
		3388
		3389	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3390	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2624		3391
2625	=back	3392	=back
2626		3393
2627		3394
2628	=head1 MACRO MAGIC	3395	=head1 MACRO MAGIC
2629		3396
2630	Libev can be compiled with a variety of options, the most fundamantal	3397	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3398	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	3399	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		3400
2634	To make it easier to write programs that cope with either variant, the	3401	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	3402	following macros are defined:
…		…
2640		3407
2641	This provides the loop I<argument> for functions, if one is required ("ev	3408	This provides the loop I<argument> for functions, if one is required ("ev
2642	loop argument"). The C<EV_A> form is used when this is the sole argument,	3409	loop argument"). The C<EV_A> form is used when this is the sole argument,
2643	C<EV_A_> is used when other arguments are following. Example:	3410	C<EV_A_> is used when other arguments are following. Example:
2644		3411
2645	ev_unref (EV_A);	3412	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	3413	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	3414	ev_loop (EV_A_ 0);
2648		3415
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3416	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	3417	which is often provided by the following macro.
2651		3418
2652	=item C<EV_P>, C<EV_P_>	3419	=item C<EV_P>, C<EV_P_>
2653		3420
2654	This provides the loop I<parameter> for functions, if one is required ("ev	3421	This provides the loop I<parameter> for functions, if one is required ("ev
2655	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3422	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2656	C<EV_P_> is used when other parameters are following. Example:	3423	C<EV_P_> is used when other parameters are following. Example:
2657		3424
2658	// this is how ev_unref is being declared	3425	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	3426	static void ev_unref (EV_P);
2660		3427
2661	// this is how you can declare your typical callback	3428	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	3429	static void cb (EV_P_ ev_timer *w, int revents)
2663		3430
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3431	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	3432	suitable for use with C<EV_A>.
2666		3433
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3434	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		3450
2684	Example: Declare and initialise a check watcher, utilising the above	3451	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	3452	macros so it will work regardless of whether multiple loops are supported
2686	or not.	3453	or not.
2687		3454
2688	static void	3455	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	3456	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	3457	{
2691	ev_check_stop (EV_A_ w);	3458	ev_check_stop (EV_A_ w);
2692	}	3459	}
2693		3460
2694	ev_check check;	3461	ev_check check;
2695	ev_check_init (&check, check_cb);	3462	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	3463	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	3464	ev_loop (EV_DEFAULT_ 0);
2698		3465
2699	=head1 EMBEDDING	3466	=head1 EMBEDDING
2700		3467
2701	Libev can (and often is) directly embedded into host	3468	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	3469	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	3476	libev somewhere in your source tree).
2710		3477
2711	=head2 FILESETS	3478	=head2 FILESETS
2712		3479
2713	Depending on what features you need you need to include one or more sets of files	3480	Depending on what features you need you need to include one or more sets of files
2714	in your app.	3481	in your application.
2715		3482
2716	=head3 CORE EVENT LOOP	3483	=head3 CORE EVENT LOOP
2717		3484
2718	To include only the libev core (all the C<ev_*> functions), with manual	3485	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	3486	configuration (no autoconf):
2720		3487
2721	#define EV_STANDALONE 1	3488	#define EV_STANDALONE 1
2722	#include "ev.c"	3489	#include "ev.c"
2723		3490
2724	This will automatically include F<ev.h>, too, and should be done in a	3491	This will automatically include F<ev.h>, too, and should be done in a
2725	single C source file only to provide the function implementations. To use	3492	single C source file only to provide the function implementations. To use
2726	it, do the same for F<ev.h> in all files wishing to use this API (best	3493	it, do the same for F<ev.h> in all files wishing to use this API (best
2727	done by writing a wrapper around F<ev.h> that you can include instead and	3494	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	3495	where you can put other configuration options):
2729		3496
2730	#define EV_STANDALONE 1	3497	#define EV_STANDALONE 1
2731	#include "ev.h"	3498	#include "ev.h"
2732		3499
2733	Both header files and implementation files can be compiled with a C++	3500	Both header files and implementation files can be compiled with a C++
2734	compiler (at least, thats a stated goal, and breakage will be treated	3501	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	3502	as a bug).
2736		3503
2737	You need the following files in your source tree, or in a directory	3504	You need the following files in your source tree, or in a directory
2738	in your include path (e.g. in libev/ when using -Ilibev):	3505	in your include path (e.g. in libev/ when using -Ilibev):
2739		3506
2740	ev.h	3507	ev.h
2741	ev.c	3508	ev.c
2742	ev_vars.h	3509	ev_vars.h
2743	ev_wrap.h	3510	ev_wrap.h
2744		3511
2745	ev_win32.c required on win32 platforms only	3512	ev_win32.c required on win32 platforms only
2746		3513
2747	ev_select.c only when select backend is enabled (which is enabled by default)	3514	ev_select.c only when select backend is enabled (which is enabled by default)
2748	ev_poll.c only when poll backend is enabled (disabled by default)	3515	ev_poll.c only when poll backend is enabled (disabled by default)
2749	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3516	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2750	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3517	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2751	ev_port.c only when the solaris port backend is enabled (disabled by default)	3518	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		3519
2753	F<ev.c> includes the backend files directly when enabled, so you only need	3520	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	3521	to compile this single file.
2755		3522
2756	=head3 LIBEVENT COMPATIBILITY API	3523	=head3 LIBEVENT COMPATIBILITY API
2757		3524
2758	To include the libevent compatibility API, also include:	3525	To include the libevent compatibility API, also include:
2759		3526
2760	#include "event.c"	3527	#include "event.c"
2761		3528
2762	in the file including F<ev.c>, and:	3529	in the file including F<ev.c>, and:
2763		3530
2764	#include "event.h"	3531	#include "event.h"
2765		3532
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	3533	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		3534
2768	You need the following additional files for this:	3535	You need the following additional files for this:
2769		3536
2770	event.h	3537	event.h
2771	event.c	3538	event.c
2772		3539
2773	=head3 AUTOCONF SUPPORT	3540	=head3 AUTOCONF SUPPORT
2774		3541
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	3542	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2776	whatever way you want, you can also C<m4_include([libev.m4])> in your	3543	whatever way you want, you can also C<m4_include([libev.m4])> in your
2777	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3544	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	3545	include F<config.h> and configure itself accordingly.
2779		3546
2780	For this of course you need the m4 file:	3547	For this of course you need the m4 file:
2781		3548
2782	libev.m4	3549	libev.m4
2783		3550
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	3551	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		3552
2786	Libev can be configured via a variety of preprocessor symbols you have to	3553	Libev can be configured via a variety of preprocessor symbols you have to
2787	define before including any of its files. The default in the absense of	3554	define before including any of its files. The default in the absence of
2788	autoconf is noted for every option.	3555	autoconf is documented for every option.
2789		3556
2790	=over 4	3557	=over 4
2791		3558
2792	=item EV_STANDALONE	3559	=item EV_STANDALONE
2793		3560
…		…
2795	keeps libev from including F<config.h>, and it also defines dummy	3562	keeps libev from including F<config.h>, and it also defines dummy
2796	implementations for some libevent functions (such as logging, which is not	3563	implementations for some libevent functions (such as logging, which is not
2797	supported). It will also not define any of the structs usually found in	3564	supported). It will also not define any of the structs usually found in
2798	F<event.h> that are not directly supported by the libev core alone.	3565	F<event.h> that are not directly supported by the libev core alone.
2799		3566
		3567	In stanbdalone mode, libev will still try to automatically deduce the
		3568	configuration, but has to be more conservative.
		3569
2800	=item EV_USE_MONOTONIC	3570	=item EV_USE_MONOTONIC
2801		3571
2802	If defined to be C<1>, libev will try to detect the availability of the	3572	If defined to be C<1>, libev will try to detect the availability of the
2803	monotonic clock option at both compiletime and runtime. Otherwise no use	3573	monotonic clock option at both compile time and runtime. Otherwise no
2804	of the monotonic clock option will be attempted. If you enable this, you	3574	use of the monotonic clock option will be attempted. If you enable this,
2805	usually have to link against librt or something similar. Enabling it when	3575	you usually have to link against librt or something similar. Enabling it
2806	the functionality isn't available is safe, though, although you have	3576	when the functionality isn't available is safe, though, although you have
2807	to make sure you link against any libraries where the C<clock_gettime>	3577	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	3578	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2809		3579
2810	=item EV_USE_REALTIME	3580	=item EV_USE_REALTIME
2811		3581
2812	If defined to be C<1>, libev will try to detect the availability of the	3582	If defined to be C<1>, libev will try to detect the availability of the
2813	realtime clock option at compiletime (and assume its availability at	3583	real-time clock option at compile time (and assume its availability
2814	runtime if successful). Otherwise no use of the realtime clock option will	3584	at runtime if successful). Otherwise no use of the real-time clock
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3585	option will be attempted. This effectively replaces C<gettimeofday>
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3586	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3587	correctness. See the note about libraries in the description of
		3588	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3589	C<EV_USE_CLOCK_SYSCALL>.
		3590
		3591	=item EV_USE_CLOCK_SYSCALL
		3592
		3593	If defined to be C<1>, libev will try to use a direct syscall instead
		3594	of calling the system-provided C<clock_gettime> function. This option
		3595	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3596	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3597	programs needlessly. Using a direct syscall is slightly slower (in
		3598	theory), because no optimised vdso implementation can be used, but avoids
		3599	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3600	higher, as it simplifies linking (no need for C<-lrt>).
2818		3601
2819	=item EV_USE_NANOSLEEP	3602	=item EV_USE_NANOSLEEP
2820		3603
2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3604	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2822	and will use it for delays. Otherwise it will use C<select ()>.	3605	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2830	2.7 or newer, otherwise disabled.	3613	2.7 or newer, otherwise disabled.
2831		3614
2832	=item EV_USE_SELECT	3615	=item EV_USE_SELECT
2833		3616
2834	If undefined or defined to be C<1>, libev will compile in support for the	3617	If undefined or defined to be C<1>, libev will compile in support for the
2835	C<select>(2) backend. No attempt at autodetection will be done: if no	3618	C<select>(2) backend. No attempt at auto-detection will be done: if no
2836	other method takes over, select will be it. Otherwise the select backend	3619	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	3620	will not be compiled in.
2838		3621
2839	=item EV_SELECT_USE_FD_SET	3622	=item EV_SELECT_USE_FD_SET
2840		3623
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	3624	If defined to C<1>, then the select backend will use the system C<fd_set>
2842	structure. This is useful if libev doesn't compile due to a missing	3625	structure. This is useful if libev doesn't compile due to a missing
2843	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3626	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2844	exotic systems. This usually limits the range of file descriptors to some	3627	on exotic systems. This usually limits the range of file descriptors to
2845	low limit such as 1024 or might have other limitations (winsocket only	3628	some low limit such as 1024 or might have other limitations (winsocket
2846	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3629	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2847	influence the size of the C<fd_set> used.	3630	configures the maximum size of the C<fd_set>.
2848		3631
2849	=item EV_SELECT_IS_WINSOCKET	3632	=item EV_SELECT_IS_WINSOCKET
2850		3633
2851	When defined to C<1>, the select backend will assume that	3634	When defined to C<1>, the select backend will assume that
2852	select/socket/connect etc. don't understand file descriptors but	3635	select/socket/connect etc. don't understand file descriptors but
…		…
2897	otherwise another method will be used as fallback. This is the preferred	3680	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	3681	backend for Solaris 10 systems.
2899		3682
2900	=item EV_USE_DEVPOLL	3683	=item EV_USE_DEVPOLL
2901		3684
2902	reserved for future expansion, works like the USE symbols above.	3685	Reserved for future expansion, works like the USE symbols above.
2903		3686
2904	=item EV_USE_INOTIFY	3687	=item EV_USE_INOTIFY
2905		3688
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	3689	If defined to be C<1>, libev will compile in support for the Linux inotify
2907	interface to speed up C<ev_stat> watchers. Its actual availability will	3690	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2914	access is atomic with respect to other threads or signal contexts. No such	3697	access is atomic with respect to other threads or signal contexts. No such
2915	type is easily found in the C language, so you can provide your own type	3698	type is easily found in the C language, so you can provide your own type
2916	that you know is safe for your purposes. It is used both for signal handler "locking"	3699	that you know is safe for your purposes. It is used both for signal handler "locking"
2917	as well as for signal and thread safety in C<ev_async> watchers.	3700	as well as for signal and thread safety in C<ev_async> watchers.
2918		3701
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	3702	In the absence of this define, libev will use C<sig_atomic_t volatile>
2920	(from F<signal.h>), which is usually good enough on most platforms.	3703	(from F<signal.h>), which is usually good enough on most platforms.
2921		3704
2922	=item EV_H	3705	=item EV_H
2923		3706
2924	The name of the F<ev.h> header file used to include it. The default if	3707	The name of the F<ev.h> header file used to include it. The default if
…		…
2963	When doing priority-based operations, libev usually has to linearly search	3746	When doing priority-based operations, libev usually has to linearly search
2964	all the priorities, so having many of them (hundreds) uses a lot of space	3747	all the priorities, so having many of them (hundreds) uses a lot of space
2965	and time, so using the defaults of five priorities (-2 .. +2) is usually	3748	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	3749	fine.
2967		3750
2968	If your embedding app does not need any priorities, defining these both to	3751	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	3752	both to C<0> will save some memory and CPU.
2970		3753
2971	=item EV_PERIODIC_ENABLE	3754	=item EV_PERIODIC_ENABLE
2972		3755
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	3756	If undefined or defined to be C<1>, then periodic timers are supported. If
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	3757	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2981	code.	3764	code.
2982		3765
2983	=item EV_EMBED_ENABLE	3766	=item EV_EMBED_ENABLE
2984		3767
2985	If undefined or defined to be C<1>, then embed watchers are supported. If	3768	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.	3769	defined to be C<0>, then they are not. Embed watchers rely on most other
		3770	watcher types, which therefore must not be disabled.
2987		3771
2988	=item EV_STAT_ENABLE	3772	=item EV_STAT_ENABLE
2989		3773
2990	If undefined or defined to be C<1>, then stat watchers are supported. If	3774	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.	3775	defined to be C<0>, then they are not.
…		…
3001	defined to be C<0>, then they are not.	3785	defined to be C<0>, then they are not.
3002		3786
3003	=item EV_MINIMAL	3787	=item EV_MINIMAL
3004		3788
3005	If you need to shave off some kilobytes of code at the expense of some	3789	If you need to shave off some kilobytes of code at the expense of some
3006	speed, define this symbol to C<1>. Currently this is used to override some	3790	speed (but with the full API), define this symbol to C<1>. Currently this
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3791	is used to override some inlining decisions, saves roughly 30% code size
3008	much smaller 2-heap for timer management over the default 4-heap.	3792	on amd64. It also selects a much smaller 2-heap for timer management over
		3793	the default 4-heap.
		3794
		3795	You can save even more by disabling watcher types you do not need
		3796	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3797	(C<-DNDEBUG>) will usually reduce code size a lot.
		3798
		3799	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3800	provide a bare-bones event library. See C<ev.h> for details on what parts
		3801	of the API are still available, and do not complain if this subset changes
		3802	over time.
3009		3803
3010	=item EV_PID_HASHSIZE	3804	=item EV_PID_HASHSIZE
3011		3805
3012	C<ev_child> watchers use a small hash table to distribute workload by	3806	C<ev_child> watchers use a small hash table to distribute workload by
3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3807	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3023	two).	3817	two).
3024		3818
3025	=item EV_USE_4HEAP	3819	=item EV_USE_4HEAP
3026		3820
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3821	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3822	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3029	to C<1>. The 4-heap uses more complicated (longer) code but has	3823	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	3824	faster performance with many (thousands) of watchers.
3031		3825
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3826	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3033	(disabled).	3827	(disabled).
3034		3828
3035	=item EV_HEAP_CACHE_AT	3829	=item EV_HEAP_CACHE_AT
3036		3830
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3831	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3038	timer and periodics heap, libev can cache the timestamp (I<at>) within	3832	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3833	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3834	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3041	but avoids random read accesses on heap changes. This improves performance	3835	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	3836	noticeably with many (hundreds) of watchers.
3043		3837
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3838	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3045	(disabled).	3839	(disabled).
3046		3840
3047	=item EV_VERIFY	3841	=item EV_VERIFY
…		…
3053	called once per loop, which can slow down libev. If set to C<3>, then the	3847	called once per loop, which can slow down libev. If set to C<3>, then the
3054	verification code will be called very frequently, which will slow down	3848	verification code will be called very frequently, which will slow down
3055	libev considerably.	3849	libev considerably.
3056		3850
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3851	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3058	C<0.>	3852	C<0>.
3059		3853
3060	=item EV_COMMON	3854	=item EV_COMMON
3061		3855
3062	By default, all watchers have a C<void *data> member. By redefining	3856	By default, all watchers have a C<void *data> member. By redefining
3063	this macro to a something else you can include more and other types of	3857	this macro to a something else you can include more and other types of
3064	members. You have to define it each time you include one of the files,	3858	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	3859	though, and it must be identical each time.
3066		3860
3067	For example, the perl EV module uses something like this:	3861	For example, the perl EV module uses something like this:
3068		3862
3069	#define EV_COMMON \	3863	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	3864	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	3865	SV *cb_sv, *fh /* note no trailing ";" */
3072		3866
3073	=item EV_CB_DECLARE (type)	3867	=item EV_CB_DECLARE (type)
3074		3868
3075	=item EV_CB_INVOKE (watcher, revents)	3869	=item EV_CB_INVOKE (watcher, revents)
3076		3870
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	3875	definition and a statement, respectively. See the F<ev.h> header file for
3082	their default definitions. One possible use for overriding these is to	3876	their default definitions. One possible use for overriding these is to
3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3877	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3084	method calls instead of plain function calls in C++.	3878	method calls instead of plain function calls in C++.
3085		3879
		3880	=back
		3881
3086	=head2 EXPORTED API SYMBOLS	3882	=head2 EXPORTED API SYMBOLS
3087		3883
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	3884	If you need to re-export the API (e.g. via a DLL) and you need a list of
3089	exported symbols, you can use the provided F<Symbol.*> files which list	3885	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	3886	all public symbols, one per line:
3091		3887
3092	Symbols.ev for libev proper	3888	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	3889	Symbols.event for the libevent emulation
3094		3890
3095	This can also be used to rename all public symbols to avoid clashes with	3891	This can also be used to rename all public symbols to avoid clashes with
3096	multiple versions of libev linked together (which is obviously bad in	3892	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	3893	itself, but sometimes it is inconvenient to avoid this).
3098		3894
3099	A sed command like this will create wrapper C<#define>'s that you need to	3895	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	3896	include before including F<ev.h>:
3101		3897
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3898	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	3915	file.
3120		3916
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3917	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3122	that everybody includes and which overrides some configure choices:	3918	that everybody includes and which overrides some configure choices:
3123		3919
3124	#define EV_MINIMAL 1	3920	#define EV_MINIMAL 1
3125	#define EV_USE_POLL 0	3921	#define EV_USE_POLL 0
3126	#define EV_MULTIPLICITY 0	3922	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	3923	#define EV_PERIODIC_ENABLE 0
3128	#define EV_STAT_ENABLE 0	3924	#define EV_STAT_ENABLE 0
3129	#define EV_FORK_ENABLE 0	3925	#define EV_FORK_ENABLE 0
3130	#define EV_CONFIG_H <config.h>	3926	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0	3927	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0	3928	#define EV_MAXPRI 0
3133		3929
3134	#include "ev++.h"	3930	#include "ev++.h"
3135		3931
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3932	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		3933
3138	#include "ev_cpp.h"	3934	#include "ev_cpp.h"
3139	#include "ev.c"	3935	#include "ev.c"
3140		3936
		3937	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3141		3938
3142	=head1 THREADS AND COROUTINES	3939	=head2 THREADS AND COROUTINES
3143		3940
3144	=head2 THREADS	3941	=head3 THREADS
3145		3942
3146	Libev itself is completely threadsafe, but it uses no locking. This	3943	All libev functions are reentrant and thread-safe unless explicitly
		3944	documented otherwise, but libev implements no locking itself. This means
3147	means that you can use as many loops as you want in parallel, as long as	3945	that you can use as many loops as you want in parallel, as long as there
3148	only one thread ever calls into one libev function with the same loop	3946	are no concurrent calls into any libev function with the same loop
3149	parameter.	3947	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3948	of course): libev guarantees that different event loops share no data
		3949	structures that need any locking.
3150		3950
3151	Or put differently: calls with different loop parameters can be done in	3951	Or to put it differently: calls with different loop parameters can be done
3152	parallel from multiple threads, calls with the same loop parameter must be	3952	concurrently from multiple threads, calls with the same loop parameter
3153	done serially (but can be done from different threads, as long as only one	3953	must be done serially (but can be done from different threads, as long as
3154	thread ever is inside a call at any point in time, e.g. by using a mutex	3954	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	3955	a mutex per loop).
3156		3956
3157	If you want to know which design is best for your problem, then I cannot	3957	Specifically to support threads (and signal handlers), libev implements
		3958	so-called C<ev_async> watchers, which allow some limited form of
		3959	concurrency on the same event loop, namely waking it up "from the
		3960	outside".
		3961
		3962	If you want to know which design (one loop, locking, or multiple loops
		3963	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	3964	help you, but here is some generic advice:
3159		3965
3160	=over 4	3966	=over 4
3161		3967
3162	=item * most applications have a main thread: use the default libev loop	3968	=item * most applications have a main thread: use the default libev loop
3163	in that thread, or create a seperate thread running only the default loop.	3969	in that thread, or create a separate thread running only the default loop.
3164		3970
3165	This helps integrating other libraries or software modules that use libev	3971	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	3972	themselves and don't care/know about threading.
3167		3973
3168	=item * one loop per thread is usually a good model.	3974	=item * one loop per thread is usually a good model.
3169		3975
3170	Doing this is almost never wrong, sometimes a better-performance model	3976	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	3977	exists, but it is always a good start.
3172		3978
3173	=item * other models exist, such as the leader/follower pattern, where one	3979	=item * other models exist, such as the leader/follower pattern, where one
3174	loop is handed through multiple threads in a kind of round-robbin fashion.	3980	loop is handed through multiple threads in a kind of round-robin fashion.
3175		3981
3176	Chosing a model is hard - look around, learn, know that usually you cna do	3982	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	3983	better than you currently do :-)
3178		3984
3179	=item * often you need to talk to some other thread which blocks in the	3985	=item * often you need to talk to some other thread which blocks in the
		3986	event loop.
		3987
3180	event loop - C<ev_async> watchers can be used to wake them up from other	3988	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	3989	(or from signal contexts...).
		3990
		3991	An example use would be to communicate signals or other events that only
		3992	work in the default loop by registering the signal watcher with the
		3993	default loop and triggering an C<ev_async> watcher from the default loop
		3994	watcher callback into the event loop interested in the signal.
3182		3995
3183	=back	3996	=back
3184		3997
		3998	=head4 THREAD LOCKING EXAMPLE
		3999
		4000	Here is a fictitious example of how to run an event loop in a different
		4001	thread than where callbacks are being invoked and watchers are
		4002	created/added/removed.
		4003
		4004	For a real-world example, see the C<EV::Loop::Async> perl module,
		4005	which uses exactly this technique (which is suited for many high-level
		4006	languages).
		4007
		4008	The example uses a pthread mutex to protect the loop data, a condition
		4009	variable to wait for callback invocations, an async watcher to notify the
		4010	event loop thread and an unspecified mechanism to wake up the main thread.
		4011
		4012	First, you need to associate some data with the event loop:
		4013
		4014	typedef struct {
		4015	mutex_t lock; /* global loop lock */
		4016	ev_async async_w;
		4017	thread_t tid;
		4018	cond_t invoke_cv;
		4019	} userdata;
		4020
		4021	void prepare_loop (EV_P)
		4022	{
		4023	// for simplicity, we use a static userdata struct.
		4024	static userdata u;
		4025
		4026	ev_async_init (&u->async_w, async_cb);
		4027	ev_async_start (EV_A_ &u->async_w);
		4028
		4029	pthread_mutex_init (&u->lock, 0);
		4030	pthread_cond_init (&u->invoke_cv, 0);
		4031
		4032	// now associate this with the loop
		4033	ev_set_userdata (EV_A_ u);
		4034	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4035	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4036
		4037	// then create the thread running ev_loop
		4038	pthread_create (&u->tid, 0, l_run, EV_A);
		4039	}
		4040
		4041	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4042	solely to wake up the event loop so it takes notice of any new watchers
		4043	that might have been added:
		4044
		4045	static void
		4046	async_cb (EV_P_ ev_async *w, int revents)
		4047	{
		4048	// just used for the side effects
		4049	}
		4050
		4051	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4052	protecting the loop data, respectively.
		4053
		4054	static void
		4055	l_release (EV_P)
		4056	{
		4057	userdata *u = ev_userdata (EV_A);
		4058	pthread_mutex_unlock (&u->lock);
		4059	}
		4060
		4061	static void
		4062	l_acquire (EV_P)
		4063	{
		4064	userdata *u = ev_userdata (EV_A);
		4065	pthread_mutex_lock (&u->lock);
		4066	}
		4067
		4068	The event loop thread first acquires the mutex, and then jumps straight
		4069	into C<ev_loop>:
		4070
		4071	void *
		4072	l_run (void *thr_arg)
		4073	{
		4074	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4075
		4076	l_acquire (EV_A);
		4077	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4078	ev_loop (EV_A_ 0);
		4079	l_release (EV_A);
		4080
		4081	return 0;
		4082	}
		4083
		4084	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4085	signal the main thread via some unspecified mechanism (signals? pipe
		4086	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4087	have been called (in a while loop because a) spurious wakeups are possible
		4088	and b) skipping inter-thread-communication when there are no pending
		4089	watchers is very beneficial):
		4090
		4091	static void
		4092	l_invoke (EV_P)
		4093	{
		4094	userdata *u = ev_userdata (EV_A);
		4095
		4096	while (ev_pending_count (EV_A))
		4097	{
		4098	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4099	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4100	}
		4101	}
		4102
		4103	Now, whenever the main thread gets told to invoke pending watchers, it
		4104	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4105	thread to continue:
		4106
		4107	static void
		4108	real_invoke_pending (EV_P)
		4109	{
		4110	userdata *u = ev_userdata (EV_A);
		4111
		4112	pthread_mutex_lock (&u->lock);
		4113	ev_invoke_pending (EV_A);
		4114	pthread_cond_signal (&u->invoke_cv);
		4115	pthread_mutex_unlock (&u->lock);
		4116	}
		4117
		4118	Whenever you want to start/stop a watcher or do other modifications to an
		4119	event loop, you will now have to lock:
		4120
		4121	ev_timer timeout_watcher;
		4122	userdata *u = ev_userdata (EV_A);
		4123
		4124	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4125
		4126	pthread_mutex_lock (&u->lock);
		4127	ev_timer_start (EV_A_ &timeout_watcher);
		4128	ev_async_send (EV_A_ &u->async_w);
		4129	pthread_mutex_unlock (&u->lock);
		4130
		4131	Note that sending the C<ev_async> watcher is required because otherwise
		4132	an event loop currently blocking in the kernel will have no knowledge
		4133	about the newly added timer. By waking up the loop it will pick up any new
		4134	watchers in the next event loop iteration.
		4135
3185	=head2 COROUTINES	4136	=head3 COROUTINES
3186		4137
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	4138	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	4139	libev fully supports nesting calls to its functions from different
3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4140	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3190	different coroutines and switch freely between both coroutines running the	4141	different coroutines, and switch freely between both coroutines running
3191	loop, as long as you don't confuse yourself). The only exception is that	4142	the loop, as long as you don't confuse yourself). The only exception is
3192	you must not do this from C<ev_periodic> reschedule callbacks.	4143	that you must not do this from C<ev_periodic> reschedule callbacks.
3193		4144
3194	Care has been invested into making sure that libev does not keep local	4145	Care has been taken to ensure that libev does not keep local state inside
3195	state inside C<ev_loop>, and other calls do not usually allow coroutine	4146	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3196	switches.	4147	they do not call any callbacks.
3197		4148
		4149	=head2 COMPILER WARNINGS
3198		4150
3199	=head1 COMPLEXITIES	4151	Depending on your compiler and compiler settings, you might get no or a
		4152	lot of warnings when compiling libev code. Some people are apparently
		4153	scared by this.
3200		4154
3201	In this section the complexities of (many of) the algorithms used inside	4155	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	4156	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	4157	warning options. "Warn-free" code therefore cannot be a goal except when
		4158	targeting a specific compiler and compiler-version.
3204		4159
3205	All of the following are about amortised time: If an array needs to be	4160	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	4161	workarounds, or other changes to the code that make it less clear and less
3207	happens asymptotically never with higher number of elements, so O(1) might	4162	maintainable.
3208	mean it might do a lengthy realloc operation in rare cases, but on average
3209	it is much faster and asymptotically approaches constant time.
3210		4163
3211	=over 4	4164	And of course, some compiler warnings are just plain stupid, or simply
		4165	wrong (because they don't actually warn about the condition their message
		4166	seems to warn about). For example, certain older gcc versions had some
		4167	warnings that resulted an extreme number of false positives. These have
		4168	been fixed, but some people still insist on making code warn-free with
		4169	such buggy versions.
3212		4170
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4171	While libev is written to generate as few warnings as possible,
		4172	"warn-free" code is not a goal, and it is recommended not to build libev
		4173	with any compiler warnings enabled unless you are prepared to cope with
		4174	them (e.g. by ignoring them). Remember that warnings are just that:
		4175	warnings, not errors, or proof of bugs.
3214		4176
3215	This means that, when you have a watcher that triggers in one hour and
3216	there are 100 watchers that would trigger before that then inserting will
3217	have to skip roughly seven (C<ld 100>) of these watchers.
3218		4177
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4178	=head2 VALGRIND
3220		4179
3221	That means that changing a timer costs less than removing/adding them	4180	Valgrind has a special section here because it is a popular tool that is
3222	as only the relative motion in the event queue has to be paid for.	4181	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		4182
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4183	If you think you found a bug (memory leak, uninitialised data access etc.)
		4184	in libev, then check twice: If valgrind reports something like:
3225		4185
3226	These just add the watcher into an array or at the head of a list.	4186	==2274== definitely lost: 0 bytes in 0 blocks.
		4187	==2274== possibly lost: 0 bytes in 0 blocks.
		4188	==2274== still reachable: 256 bytes in 1 blocks.
3227		4189
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4190	Then there is no memory leak, just as memory accounted to global variables
		4191	is not a memleak - the memory is still being referenced, and didn't leak.
3229		4192
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4193	Similarly, under some circumstances, valgrind might report kernel bugs
		4194	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4195	although an acceptable workaround has been found here), or it might be
		4196	confused.
3231		4197
3232	These watchers are stored in lists then need to be walked to find the	4198	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3233	correct watcher to remove. The lists are usually short (you don't usually	4199	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		4200
3236	=item Finding the next timer in each loop iteration: O(1)	4201	If you are unsure about something, feel free to contact the mailing list
		4202	with the full valgrind report and an explanation on why you think this
		4203	is a bug in libev (best check the archives, too :). However, don't be
		4204	annoyed when you get a brisk "this is no bug" answer and take the chance
		4205	of learning how to interpret valgrind properly.
3237		4206
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	4207	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	4208	I suggest using suppression lists.
3240		4209
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		4210
3243	A change means an I/O watcher gets started or stopped, which requires	4211	=head1 PORTABILITY NOTES
3244	libev to recalculate its status (and possibly tell the kernel, depending
3245	on backend and wether C<ev_io_set> was used).
3246		4212
3247	=item Activating one watcher (putting it into the pending state): O(1)	4213	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3248
3249	=item Priority handling: O(number_of_priorities)
3250
3251	Priorities are implemented by allocating some space for each
3252	priority. When doing priority-based operations, libev usually has to
3253	linearly search all the priorities, but starting/stopping and activating
3254	watchers becomes O(1) w.r.t. priority handling.
3255
3256	=item Sending an ev_async: O(1)
3257
3258	=item Processing ev_async_send: O(number_of_async_watchers)
3259
3260	=item Processing signals: O(max_signal_number)
3261
3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3263	calls in the current loop iteration. Checking for async and signal events
3264	involves iterating over all running async watchers or all signal numbers.
3265
3266	=back
3267
3268
3269	=head1 Win32 platform limitations and workarounds
3270		4214
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4215	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3272	requires, and its I/O model is fundamentally incompatible with the POSIX	4216	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	4217	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4218	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3281	way (note also that glib is the slowest event library known to man).	4225	way (note also that glib is the slowest event library known to man).
3282		4226
3283	There is no supported compilation method available on windows except	4227	There is no supported compilation method available on windows except
3284	embedding it into other applications.	4228	embedding it into other applications.
3285		4229
		4230	Sensible signal handling is officially unsupported by Microsoft - libev
		4231	tries its best, but under most conditions, signals will simply not work.
		4232
		4233	Not a libev limitation but worth mentioning: windows apparently doesn't
		4234	accept large writes: instead of resulting in a partial write, windows will
		4235	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4236	so make sure you only write small amounts into your sockets (less than a
		4237	megabyte seems safe, but this apparently depends on the amount of memory
		4238	available).
		4239
3286	Due to the many, low, and arbitrary limits on the win32 platform and	4240	Due to the many, low, and arbitrary limits on the win32 platform and
3287	the abysmal performance of winsockets, using a large number of sockets	4241	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	4242	is not recommended (and not reasonable). If your program needs to use
3289	more than a hundred or so sockets, then likely it needs to use a totally	4243	more than a hundred or so sockets, then likely it needs to use a totally
3290	different implementation for windows, as libev offers the POSIX readiness	4244	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	4245	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	4246	(due to Microsoft monopoly games).
		4247
		4248	A typical way to use libev under windows is to embed it (see the embedding
		4249	section for details) and use the following F<evwrap.h> header file instead
		4250	of F<ev.h>:
		4251
		4252	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4253	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4254
		4255	#include "ev.h"
		4256
		4257	And compile the following F<evwrap.c> file into your project (make sure
		4258	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4259
		4260	#include "evwrap.h"
		4261	#include "ev.c"
3293		4262
3294	=over 4	4263	=over 4
3295		4264
3296	=item The winsocket select function	4265	=item The winsocket select function
3297		4266
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	4267	The winsocket C<select> function doesn't follow POSIX in that it
3299	socket I<handles> and not socket I<file descriptors>. This makes select	4268	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	4269	also extremely buggy). This makes select very inefficient, and also
3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4270	requires a mapping from file descriptors to socket handles (the Microsoft
3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4271	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	4272	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4273	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		4274
3305	The configuration for a "naked" win32 using the microsoft runtime	4275	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	4276	libraries and raw winsocket select is:
3307		4277
3308	#define EV_USE_SELECT 1	4278	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4279	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		4280
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	4281	Note that winsockets handling of fd sets is O(n), so you can easily get a
3312	complexity in the O(n²) range when using win32.	4282	complexity in the O(n²) range when using win32.
3313		4283
3314	=item Limited number of file descriptors	4284	=item Limited number of file descriptors
3315		4285
3316	Windows has numerous arbitrary (and low) limits on things.	4286	Windows has numerous arbitrary (and low) limits on things.
3317		4287
3318	Early versions of winsocket's select only supported waiting for a maximum	4288	Early versions of winsocket's select only supported waiting for a maximum
3319	of C<64> handles (probably owning to the fact that all windows kernels	4289	of C<64> handles (probably owning to the fact that all windows kernels
3320	can only wait for C<64> things at the same time internally; microsoft	4290	can only wait for C<64> things at the same time internally; Microsoft
3321	recommends spawning a chain of threads and wait for 63 handles and the	4291	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	4292	previous thread in each. Sounds great!).
3323		4293
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4294	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3325	to some high number (e.g. C<2048>) before compiling the winsocket select	4295	to some high number (e.g. C<2048>) before compiling the winsocket select
3326	call (which might be in libev or elsewhere, for example, perl does its own	4296	call (which might be in libev or elsewhere, for example, perl and many
3327	select emulation on windows).	4297	other interpreters do their own select emulation on windows).
3328		4298
3329	Another limit is the number of file descriptors in the microsoft runtime	4299	Another limit is the number of file descriptors in the Microsoft runtime
3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4300	libraries, which by default is C<64> (there must be a hidden I<64>
3331	or something like this inside microsoft). You can increase this by calling	4301	fetish or something like this inside Microsoft). You can increase this
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4302	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3333	arbitrary limit), but is broken in many versions of the microsoft runtime	4303	(another arbitrary limit), but is broken in many versions of the Microsoft
3334	libraries.
3335
3336	This might get you to about C<512> or C<2048> sockets (depending on	4304	runtime libraries. This might get you to about C<512> or C<2048> sockets
3337	windows version and/or the phase of the moon). To get more, you need to	4305	(depending on windows version and/or the phase of the moon). To get more,
3338	wrap all I/O functions and provide your own fd management, but the cost of	4306	you need to wrap all I/O functions and provide your own fd management, but
3339	calling select (O(n²)) will likely make this unworkable.	4307	the cost of calling select (O(n²)) will likely make this unworkable.
3340		4308
3341	=back	4309	=back
3342		4310
3343
3344	=head1 PORTABILITY REQUIREMENTS	4311	=head2 PORTABILITY REQUIREMENTS
3345		4312
3346	In addition to a working ISO-C implementation, libev relies on a few	4313	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	4314	backend-specific APIs, libev relies on a few additional extensions:
3348		4315
3349	=over 4	4316	=over 4
3350		4317
		4318	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4319	calling conventions regardless of C<ev_watcher_type *>.
		4320
		4321	Libev assumes not only that all watcher pointers have the same internal
		4322	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4323	assumes that the same (machine) code can be used to call any watcher
		4324	callback: The watcher callbacks have different type signatures, but libev
		4325	calls them using an C<ev_watcher *> internally.
		4326
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	4327	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		4328
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	4329	The type C<sig_atomic_t volatile> (or whatever is defined as
3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4330	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3355	threads. This is not part of the specification for C<sig_atomic_t>, but is	4331	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	4332	believed to be sufficiently portable.
3357		4333
3358	=item C<sigprocmask> must work in a threaded environment	4334	=item C<sigprocmask> must work in a threaded environment
3359		4335
…		…
3368	except the initial one, and run the default loop in the initial thread as	4344	except the initial one, and run the default loop in the initial thread as
3369	well.	4345	well.
3370		4346
3371	=item C<long> must be large enough for common memory allocation sizes	4347	=item C<long> must be large enough for common memory allocation sizes
3372		4348
3373	To improve portability and simplify using libev, libev uses C<long>	4349	To improve portability and simplify its API, libev uses C<long> internally
3374	internally instead of C<size_t> when allocating its data structures. On	4350	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4351	systems (Microsoft...) this might be unexpectedly low, but is still at
3376	is still at least 31 bits everywhere, which is enough for hundreds of	4352	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	4353	watchers.
3378		4354
3379	=item C<double> must hold a time value in seconds with enough accuracy	4355	=item C<double> must hold a time value in seconds with enough accuracy
3380		4356
3381	The type C<double> is used to represent timestamps. It is required to	4357	The type C<double> is used to represent timestamps. It is required to
3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3383	enough for at least into the year 4000. This requirement is fulfilled by	4359	enough for at least into the year 4000. This requirement is fulfilled by
3384	implementations implementing IEEE 754 (basically all existing ones).	4360	implementations implementing IEEE 754, which is basically all existing
		4361	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4362	2200.
3385		4363
3386	=back	4364	=back
3387		4365
3388	If you know of other additional requirements drop me a note.	4366	If you know of other additional requirements drop me a note.
3389		4367
3390		4368
3391	=head1 VALGRIND	4369	=head1 ALGORITHMIC COMPLEXITIES
3392		4370
3393	Valgrind has a special section here because it is a popular tool that is	4371	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	4372	libev will be documented. For complexity discussions about backends see
		4373	the documentation for C<ev_default_init>.
3395		4374
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	4375	All of the following are about amortised time: If an array needs to be
3397	in libev, then check twice: If valgrind reports something like:	4376	extended, libev needs to realloc and move the whole array, but this
		4377	happens asymptotically rarer with higher number of elements, so O(1) might
		4378	mean that libev does a lengthy realloc operation in rare cases, but on
		4379	average it is much faster and asymptotically approaches constant time.
3398		4380
3399	==2274== definitely lost: 0 bytes in 0 blocks.	4381	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		4382
3403	then there is no memory leak. Similarly, under some circumstances,	4383	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3404	valgrind might report kernel bugs as if it were a bug in libev, or it
3405	might be confused (it is a very good tool, but only a tool).
3406		4384
3407	If you are unsure about something, feel free to contact the mailing list	4385	This means that, when you have a watcher that triggers in one hour and
3408	with the full valgrind report and an explanation on why you think this is	4386	there are 100 watchers that would trigger before that, then inserting will
3409	a bug in libev. However, don't be annoyed when you get a brisk "this is	4387	have to skip roughly seven (C<ld 100>) of these watchers.
3410	no bug" answer and take the chance of learning how to interpret valgrind
3411	properly.
3412		4388
3413	If you need, for some reason, empty reports from valgrind for your project	4389	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.
3415		4390
		4391	That means that changing a timer costs less than removing/adding them,
		4392	as only the relative motion in the event queue has to be paid for.
		4393
		4394	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4395
		4396	These just add the watcher into an array or at the head of a list.
		4397
		4398	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4399
		4400	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4401
		4402	These watchers are stored in lists, so they need to be walked to find the
		4403	correct watcher to remove. The lists are usually short (you don't usually
		4404	have many watchers waiting for the same fd or signal: one is typical, two
		4405	is rare).
		4406
		4407	=item Finding the next timer in each loop iteration: O(1)
		4408
		4409	By virtue of using a binary or 4-heap, the next timer is always found at a
		4410	fixed position in the storage array.
		4411
		4412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4413
		4414	A change means an I/O watcher gets started or stopped, which requires
		4415	libev to recalculate its status (and possibly tell the kernel, depending
		4416	on backend and whether C<ev_io_set> was used).
		4417
		4418	=item Activating one watcher (putting it into the pending state): O(1)
		4419
		4420	=item Priority handling: O(number_of_priorities)
		4421
		4422	Priorities are implemented by allocating some space for each
		4423	priority. When doing priority-based operations, libev usually has to
		4424	linearly search all the priorities, but starting/stopping and activating
		4425	watchers becomes O(1) with respect to priority handling.
		4426
		4427	=item Sending an ev_async: O(1)
		4428
		4429	=item Processing ev_async_send: O(number_of_async_watchers)
		4430
		4431	=item Processing signals: O(max_signal_number)
		4432
		4433	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4434	calls in the current loop iteration. Checking for async and signal events
		4435	involves iterating over all running async watchers or all signal numbers.
		4436
		4437	=back
		4438
		4439
		4440	=head1 GLOSSARY
		4441
		4442	=over 4
		4443
		4444	=item active
		4445
		4446	A watcher is active as long as it has been started (has been attached to
		4447	an event loop) but not yet stopped (disassociated from the event loop).
		4448
		4449	=item application
		4450
		4451	In this document, an application is whatever is using libev.
		4452
		4453	=item callback
		4454
		4455	The address of a function that is called when some event has been
		4456	detected. Callbacks are being passed the event loop, the watcher that
		4457	received the event, and the actual event bitset.
		4458
		4459	=item callback invocation
		4460
		4461	The act of calling the callback associated with a watcher.
		4462
		4463	=item event
		4464
		4465	A change of state of some external event, such as data now being available
		4466	for reading on a file descriptor, time having passed or simply not having
		4467	any other events happening anymore.
		4468
		4469	In libev, events are represented as single bits (such as C<EV_READ> or
		4470	C<EV_TIMEOUT>).
		4471
		4472	=item event library
		4473
		4474	A software package implementing an event model and loop.
		4475
		4476	=item event loop
		4477
		4478	An entity that handles and processes external events and converts them
		4479	into callback invocations.
		4480
		4481	=item event model
		4482
		4483	The model used to describe how an event loop handles and processes
		4484	watchers and events.
		4485
		4486	=item pending
		4487
		4488	A watcher is pending as soon as the corresponding event has been detected,
		4489	and stops being pending as soon as the watcher will be invoked or its
		4490	pending status is explicitly cleared by the application.
		4491
		4492	A watcher can be pending, but not active. Stopping a watcher also clears
		4493	its pending status.
		4494
		4495	=item real time
		4496
		4497	The physical time that is observed. It is apparently strictly monotonic :)
		4498
		4499	=item wall-clock time
		4500
		4501	The time and date as shown on clocks. Unlike real time, it can actually
		4502	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4503	clock.
		4504
		4505	=item watcher
		4506
		4507	A data structure that describes interest in certain events. Watchers need
		4508	to be started (attached to an event loop) before they can receive events.
		4509
		4510	=item watcher invocation
		4511
		4512	The act of calling the callback associated with a watcher.
		4513
		4514	=back
3416		4515
3417	=head1 AUTHOR	4516	=head1 AUTHOR
3418		4517
3419	Marc Lehmann <libev@schmorp.de>.	4518	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3420		4519

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