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Revision 1.144 by root, Mon Apr 7 12:33:29 2008 UTC vs.
Revision 1.257 by root, Wed Jul 15 16:08:24 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
		135
		136	=head1 ERROR HANDLING
		137
		138	Libev knows three classes of errors: operating system errors, usage errors
		139	and internal errors (bugs).
		140
		141	When libev catches an operating system error it cannot handle (for example
		142	a system call indicating a condition libev cannot fix), it calls the callback
		143	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		144	abort. The default is to print a diagnostic message and to call C<abort
		145	()>.
		146
		147	When libev detects a usage error such as a negative timer interval, then
		148	it will print a diagnostic message and abort (via the C<assert> mechanism,
		149	so C<NDEBUG> will disable this checking): these are programming errors in
		150	the libev caller and need to be fixed there.
		151
		152	Libev also has a few internal error-checking C<assert>ions, and also has
		153	extensive consistency checking code. These do not trigger under normal
		154	circumstances, as they indicate either a bug in libev or worse.
		155
121		156
122	=head1 GLOBAL FUNCTIONS	157	=head1 GLOBAL FUNCTIONS
123		158
124	These functions can be called anytime, even before initialising the	159	These functions can be called anytime, even before initialising the
125	library in any way.	160	library in any way.
…		…
134		169
135	=item ev_sleep (ev_tstamp interval)	170	=item ev_sleep (ev_tstamp interval)
136		171
137	Sleep for the given interval: The current thread will be blocked until	172	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	173	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	174	this is a sub-second-resolution C<sleep ()>.
140		175
141	=item int ev_version_major ()	176	=item int ev_version_major ()
142		177
143	=item int ev_version_minor ()	178	=item int ev_version_minor ()
144		179
…		…
157	not a problem.	192	not a problem.
158		193
159	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	195	version.
161		196
162	assert (("libev version mismatch",	197	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
165		200
166	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
167		202
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	206	a description of the set values.
172		207
173	Example: make sure we have the epoll method, because yeah this is cool and	208	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	209	a must have and can we have a torrent of it please!!!11
175		210
176	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
178		213
179	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
180		215
181	Return the set of all backends compiled into this binary of libev and also	216	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	217	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	218	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	219	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	220	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	221	libev will probe for if you specify no backends explicitly.
187		222
188	=item unsigned int ev_embeddable_backends ()	223	=item unsigned int ev_embeddable_backends ()
189		224
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	229	recommended ones.
195		230
196	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
197		232
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		234
200	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	237	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	238	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	239	or take some potentially destructive action.
205	function.	240
		241	Since some systems (at least OpenBSD and Darwin) fail to implement
		242	correct C<realloc> semantics, libev will use a wrapper around the system
		243	C<realloc> and C<free> functions by default.
206		244
207	You could override this function in high-availability programs to, say,	245	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	246	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	247	or even to sleep a while and retry until some memory is available.
210		248
211	Example: Replace the libev allocator with one that waits a bit and then	249	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	250	retries (example requires a standards-compliant C<realloc>).
213		251
214	static void *	252	static void *
215	persistent_realloc (void *ptr, size_t size)	253	persistent_realloc (void *ptr, size_t size)
216	{	254	{
217	for (;;)	255	for (;;)
…		…
226	}	264	}
227		265
228	...	266	...
229	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
230		268
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		270
233	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
234	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
235	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	274	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	275	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	276	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	277	(such as abort).
240		278
241	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.
…		…
252		290
253	=back	291	=back
254		292
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		294
257	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>
258	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>
259	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.
260		302
261	=over 4	303	=over 4
262		304
263	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
264		306
…		…
270	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
271	function.	313	function.
272		314
273	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
274	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,
275	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
276		318
277	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
278	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
279	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
280	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
281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
282	C<ev_default_init>.	324	C<ev_default_init>.
283		325
284	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
…		…
293	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
294	thing, believe me).	336	thing, believe me).
295		337
296	=item C<EVFLAG_NOENV>	338	=item C<EVFLAG_NOENV>
297		339
298	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
299	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
300	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
301	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
302	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
303	around bugs.	345	around bugs.
…		…
310		352
311	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,
312	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
313	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
314	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
315	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
316	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
317		359
318	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
319	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
320	flag.	362	flag.
321		363
322	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>
323	environment variable.	365	environment variable.
324		366
325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
326		368
327	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
…		…
329	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
330	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
331	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.
332		374
333	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
334	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
335	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
336	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
337	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
338	readyness notifications you get per iteration.	380	readiness notifications you get per iteration.
		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
339		385
340	=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)
341		387
342	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
343	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
344	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
345	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
346	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
347	performance tips.	393	performance tips.
348		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
349	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
350		399
351	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,
352	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
353	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
354	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
355	of shortcomings, such as silently dropping events in some hard-to-detect	404
356	cases and requiring a syscall per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
357	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.
358		421
359	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
360	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
361	(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
362	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
363	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
364		427	file descriptors.
365	Please note that epoll sometimes generates spurious notifications, so you
366	need to use non-blocking I/O or other means to avoid blocking when no data
367	(or space) is available.
368		428
369	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
370	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
371	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.
372		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
373	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
374	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>.
375		446
376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
377		448
378	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
379	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
380	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
381	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
382	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
383	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)
384	system like NetBSD.	457	system like NetBSD.
385		458
386	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
387	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
388	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
389		462
390	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
391	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
392	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
393	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
394	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
395	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
396		470
397	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
398		472
399	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
400	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
401	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
402	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
404	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>.
405		483
406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
407		485
408	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
409	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
414		492
415	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,
416	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)).
417		495
418	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
419	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
420	blocking when no data (or space) is available.	498	blocking when no data (or space) is available.
421		499
422	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
423	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
424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
425	might perform better.	503	might perform better.
426		504
427	On the positive side, ignoring the spurious readyness notifications, this	505	On the positive side, with the exception of the spurious readiness
428	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
429	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>.
430		512
431	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
432		514
433	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
434	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
…		…
436		518
437	It is definitely not recommended to use this flag.	519	It is definitely not recommended to use this flag.
438		520
439	=back	521	=back
440		522
441	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
442	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
443	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
444		526
445	The most typical usage is like this:	527	Example: This is the most typical usage.
446		528
447	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
449		531
450	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
451	environment settings to be taken into account:	533	environment settings to be taken into account:
452		534
453	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
454		536
455	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
456	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
457	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
458		541
459	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
460		543
461	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
462		545
463	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
464	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
…		…
469	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
470	default loop in the "main" or "initial" thread.	553	default loop in the "main" or "initial" thread.
471		554
472	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.
473		556
474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
475	if (!epoller)	558	if (!epoller)
476	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
477		560
478	=item ev_default_destroy ()	561	=item ev_default_destroy ()
479		562
480	Destroys the default loop again (frees all memory and kernel state	563	Destroys the default loop again (frees all memory and kernel state
481	etc.). None of the active event watchers will be stopped in the normal	564	etc.). None of the active event watchers will be stopped in the normal
482	sense, so e.g. C<ev_is_active> might still return true. It is your	565	sense, so e.g. C<ev_is_active> might still return true. It is your
483	responsibility to either stop all watchers cleanly yoursef I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
484	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
485	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
486	for example).	569	for example).
487		570
488	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
489	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
490	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
491		574
492	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
493	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
494	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
495	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
520		603
521	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
522		605
523	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
524	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
525	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.
526		610
527	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
528		612
529	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.
530		615
531	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
532		617
533	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
534	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
535	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
536		621
537	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
538	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
539	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.
540		637
541	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
542		639
543	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
544	use.	641	use.
…		…
549	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
550	change as long as callbacks are being processed, and this is also the base	647	change as long as callbacks are being processed, and this is also the base
551	time used for relative timers. You can treat it as the timestamp of the	648	time used for relative timers. You can treat it as the timestamp of the
552	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
553		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
554	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
555		690
556	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
557	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
558	events.	693	events.
…		…
560	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
561	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.
562		697
563	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
564	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
565	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
566	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
567	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.
568		704
569	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
570	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
571	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.
572		709
573	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
574	neccessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
575	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
576	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
577	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
578	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
579	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
580		721
581	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
582		723
583	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
584	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
585	- 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.
586	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
587	- 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.
588	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
589	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
590	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
591	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
592	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
593	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
594	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
595	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
596	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
597	- Queue all outstanding timers.	739	- Queue all expired timers.
598	- Queue all outstanding periodics.	740	- Queue all expired periodics.
599	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
600	- Queue all check watchers.	742	- Queue all check watchers.
601	- 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).
602	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
603	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
604	- 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
…		…
609	anymore.	751	anymore.
610		752
611	... queue jobs here, make sure they register event watchers as long	753	... queue jobs here, make sure they register event watchers as long
612	... as they still have work to do (even an idle watcher will do..)	754	... as they still have work to do (even an idle watcher will do..)
613	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
614	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
615		757
616	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
617		759
618	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
619	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
620	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
621	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.
622		764
623	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.
624		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
625	=item ev_ref (loop)	769	=item ev_ref (loop)
626		770
627	=item ev_unref (loop)	771	=item ev_unref (loop)
628		772
629	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
630	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
631	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
632	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>
633	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
634	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
635	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
636	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
637	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
638	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
639	(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
640	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).
641		790
642	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>
643	running when nothing else is active.	792	running when nothing else is active.
644		793
645	struct ev_signal exitsig;	794	ev_signal exitsig;
646	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
647	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
648	evf_unref (loop);	797	evf_unref (loop);
649		798
650	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
651		800
652	ev_ref (loop);	801	ev_ref (loop);
653	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
654		803
655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
656		805
657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
658		807
659	These advanced functions influence the time that libev will spend waiting	808	These advanced functions influence the time that libev will spend waiting
660	for events. Both are by default C<0>, meaning that libev will try to	809	for events. Both time intervals are by default C<0>, meaning that libev
661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	810	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		811	latency.
662		812
663	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>)
664	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
665	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
666		817
667	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
668	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
669	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
670	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
671	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.
672		823
673	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
674	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,
675	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
676	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
677	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.
678		831
679	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
680	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
681	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
682	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
683	any overhead in libev.	836	value will not introduce any overhead in libev.
684		837
685	Many (busy) programs can usually benefit by setting the io collect	838	Many (busy) programs can usually benefit by setting the I/O collect
686	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
687	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
688	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
689	as this approsaches the timing granularity of most systems.	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.
		925
		926	=item ev_loop_verify (loop)
		927
		928	This function only does something when C<EV_VERIFY> support has been
		929	compiled in, which is the default for non-minimal builds. It tries to go
		930	through all internal structures and checks them for validity. If anything
		931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
		933
		934	This can be used to catch bugs inside libev itself: under normal
		935	circumstances, this function will never abort as of course libev keeps its
		936	data structures consistent.
690		937
691	=back	938	=back
692		939
693		940
694	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
		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.
695		946
696	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
697	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
698	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:
699		950
700	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)
701	{	952	{
702	ev_io_stop (w);	953	ev_io_stop (w);
703	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
704	}	955	}
705		956
706	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
707	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
708	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
709	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
710	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
711	ev_loop (loop, 0);	965	ev_loop (loop, 0);
712		966
713	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
714	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
715	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).
716		973
717	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
718	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
719	callback gets invoked each time the event occurs (or, in the case of io	976	callback gets invoked each time the event occurs (or, in the case of I/O
720	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
721	is readable and/or writable).	978	is readable and/or writable).
722		979
723	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 *, ...) >>
724	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
725	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<<
726	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
727		984
728	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
729	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
730	*) >>), 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
731	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
732		989
733	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
734	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
735	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
736		993
737	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
738	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
739	third argument.	996	third argument.
740		997
…		…
798		1055
799	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
800		1057
801	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>).
802		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
803	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
804		1066
805	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
806	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
807	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
808	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
809	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.
810		1076
811	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
812	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
813	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
814	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
815	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
816		1083
817	=back	1084	=back
818		1085
819	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
820
821	In the following description, C<TYPE> stands for the watcher type,
822	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
823		1087
824	=over 4	1088	=over 4
825		1089
826	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
827		1091
…		…
833	which rolls both calls into one.	1097	which rolls both calls into one.
834		1098
835	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
836	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
837		1101
838	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,
839	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);
840		1110
841	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
842		1112
843	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
844	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
…		…
847	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
848		1118
849	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
850	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
851		1121
		1122	See C<ev_init>, above, for an example.
		1123
852	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
853		1125
854	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
855	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
856	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);
857		1133
858	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
859		1135
860	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
861	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
862		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
863	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
864		1145
865	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
866	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
867	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
868	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
869	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
870	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
871		1154
872	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
873		1156
874	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
875	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
…		…
901	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>
902	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
903	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
904	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
905		1188
906	This means that priorities are I<only> used for ordering callback
907	invocation after new events have been received. This is useful, for
908	example, to reduce latency after idling, or more often, to bind two
909	watchers on the same event and make sure one is called first.
910
911	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
912	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.
913		1191
914	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
915	pending.	1193	pending.
916		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
917	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
918	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 :).
919		1201
920	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
921	fine, as long as you do not mind that the priority value you query might	1203	priorities.
922	or might not have been adjusted to be within valid range.
923		1204
924	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
925		1206
926	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
927	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
928	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
929		1211
930	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
931		1213
932	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
933	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
934	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
935		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
936	=back	1221	=back
937		1222
938		1223
939	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
940		1225
941	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
942	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
943	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
944	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
945	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
946	data:	1231	data:
947		1232
948	struct my_io	1233	struct my_io
949	{	1234	{
950	struct ev_io io;	1235	ev_io io;
951	int otherfd;	1236	int otherfd;
952	void *somedata;	1237	void *somedata;
953	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
954	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
955		1244
956	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
957	can cast it back to your own type:	1246	can cast it back to your own type:
958		1247
959	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)
960	{	1249	{
961	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
962	...	1251	...
963	}	1252	}
964		1253
965	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
966	instead have been omitted.	1255	instead have been omitted.
967		1256
968	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
969	watchers:	1258	embedded watchers:
970		1259
971	struct my_biggy	1260	struct my_biggy
972	{	1261	{
973	int some_data;	1262	int some_data;
974	ev_timer t1;	1263	ev_timer t1;
975	ev_timer t2;	1264	ev_timer t2;
976	}	1265	}
977		1266
978	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
979	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):
980		1272
981	#include <stddef.h>	1273	#include <stddef.h>
982		1274
983	static void	1275	static void
984	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
985	{	1277	{
986	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
987	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
988	}	1280	}
989		1281
990	static void	1282	static void
991	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
992	{	1284	{
993	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
994	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
995	}	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.
996		1391
997		1392
998	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
999		1394
1000	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1024	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1025	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1026	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1027	required if you know what you are doing).	1422	required if you know what you are doing).
1028		1423
1029	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
1030	(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
1031	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.
1032		1429
1033	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
1034	receive "spurious" readyness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1035	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1036	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1037	lot of those (for example solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1038	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1039	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1040	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1041		1438
1042	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
1043	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
1044	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
1045	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
1046	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.
1047		1448
1048	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1049		1450
1050	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
1051	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,
1052	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
1053	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
1054	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
1055	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
1056	fact, a different file descriptor.	1457	fact, a different file descriptor.
1057		1458
…		…
1088	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1089	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1090		1491
1091	=head3 The special problem of SIGPIPE	1492	=head3 The special problem of SIGPIPE
1092		1493
1093	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>:
1094	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
1095	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
1096	programs this is sensible behaviour, for daemons, this is usually	1497	this is sensible behaviour, for daemons, this is usually undesirable.
1097	undesirable.
1098		1498
1099	So when you encounter spurious, unexplained daemon exits, make sure you	1499	So when you encounter spurious, unexplained daemon exits, make sure you
1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1101	somewhere, as that would have given you a big clue).	1501	somewhere, as that would have given you a big clue).
1102		1502
…		…
1108	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1109		1509
1110	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1111		1511
1112	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
1113	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
1114	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.
1115		1515
1116	=item int fd [read-only]	1516	=item int fd [read-only]
1117		1517
1118	The file descriptor being watched.	1518	The file descriptor being watched.
1119		1519
…		…
1127		1527
1128	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
1129	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
1130	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1131		1531
1132	static void	1532	static void
1133	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)
1134	{	1534	{
1135	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1136	.. 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
1137	}	1537	}
1138		1538
1139	...	1539	...
1140	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1141	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1142	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);
1143	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1144	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1145		1545
1146		1546
1147	=head2 C<ev_timer> - relative and optionally repeating timeouts	1547	=head2 C<ev_timer> - relative and optionally repeating timeouts
1148		1548
1149	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
1150	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1151		1551
1152	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
1153	times out after an hour and you reset your system clock to last years	1553	times out after an hour and you reset your system clock to January last
1154	time, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1155	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1156	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.
1157		1747
1158	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1159	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1160	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1161	you suspect event processing to be delayed and you I<need> to base the timeout	1751	you suspect event processing to be delayed and you I<need> to base the
1162	on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1163		1753
1164	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1165		1755
1166	The callback is guarenteed to be invoked only when its timeout has passed,	1756	If the event loop is suspended for a long time, you can also force an
1167	but if multiple timers become ready during the same loop iteration then	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1168	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>).
1169		1789
1170	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1171		1791
1172	=over 4	1792	=over 4
1173		1793
1174	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1794	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1175		1795
1176	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1796	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1177		1797
1178	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1798	Configure the timer to trigger after C<after> seconds. If C<repeat>
1179	C<0.>, then it will automatically be stopped. If it is positive, then the	1799	is C<0.>, then it will automatically be stopped once the timeout is
1180	timer will automatically be configured to trigger again C<repeat> seconds	1800	reached. If it is positive, then the timer will automatically be
1181	later, again, and again, until stopped manually.	1801	configured to trigger again C<repeat> seconds later, again, and again,
		1802	until stopped manually.
1182		1803
1183	The timer itself will do a best-effort at avoiding drift, that is, if you	1804	The timer itself will do a best-effort at avoiding drift, that is, if
1184	configure a timer to trigger every 10 seconds, then it will trigger at	1805	you configure a timer to trigger every 10 seconds, then it will normally
1185	exactly 10 second intervals. If, however, your program cannot keep up with	1806	trigger at exactly 10 second intervals. If, however, your program cannot
1186	the timer (because it takes longer than those 10 seconds to do stuff) the	1807	keep up with the timer (because it takes longer than those 10 seconds to
1187	timer will not fire more than once per event loop iteration.	1808	do stuff) the timer will not fire more than once per event loop iteration.
1188		1809
1189	=item ev_timer_again (loop, ev_timer *)	1810	=item ev_timer_again (loop, ev_timer *)
1190		1811
1191	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
1192	repeating. The exact semantics are:	1813	repeating. The exact semantics are:
1193		1814
1194	If the timer is pending, its pending status is cleared.	1815	If the timer is pending, its pending status is cleared.
1195		1816
1196	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).
1197		1818
1198	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
1199	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.
1200		1821
1201	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
1202	example: Imagine you have a tcp connection and you want a so-called idle	1823	usage example.
1203	timeout, that is, you want to be called when there have been, say, 60
1204	seconds of inactivity on the socket. The easiest way to do this is to
1205	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1206	C<ev_timer_again> each time you successfully read or write some data. If
1207	you go into an idle state where you do not expect data to travel on the
1208	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1209	automatically restart it if need be.
1210
1211	That means you can ignore the C<after> value and C<ev_timer_start>
1212	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1213
1214	ev_timer_init (timer, callback, 0., 5.);
1215	ev_timer_again (loop, timer);
1216	...
1217	timer->again = 17.;
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 10.;
1221	ev_timer_again (loop, timer);
1222
1223	This is more slightly efficient then stopping/starting the timer each time
1224	you want to modify its timeout value.
1225		1824
1226	=item ev_tstamp repeat [read-write]	1825	=item ev_tstamp repeat [read-write]
1227		1826
1228	The current C<repeat> value. Will be used each time the watcher times out	1827	The current C<repeat> value. Will be used each time the watcher times out
1229	or C<ev_timer_again> is called and determines the next timeout (if any),	1828	or C<ev_timer_again> is called, and determines the next timeout (if any),
1230	which is also when any modifications are taken into account.	1829	which is also when any modifications are taken into account.
1231		1830
1232	=back	1831	=back
1233		1832
1234	=head3 Examples	1833	=head3 Examples
1235		1834
1236	Example: Create a timer that fires after 60 seconds.	1835	Example: Create a timer that fires after 60 seconds.
1237		1836
1238	static void	1837	static void
1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1838	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	1839	{
1241	.. one minute over, w is actually stopped right here	1840	.. one minute over, w is actually stopped right here
1242	}	1841	}
1243		1842
1244	struct ev_timer mytimer;	1843	ev_timer mytimer;
1245	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1844	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1246	ev_timer_start (loop, &mytimer);	1845	ev_timer_start (loop, &mytimer);
1247		1846
1248	Example: Create a timeout timer that times out after 10 seconds of	1847	Example: Create a timeout timer that times out after 10 seconds of
1249	inactivity.	1848	inactivity.
1250		1849
1251	static void	1850	static void
1252	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1851	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1253	{	1852	{
1254	.. ten seconds without any activity	1853	.. ten seconds without any activity
1255	}	1854	}
1256		1855
1257	struct ev_timer mytimer;	1856	ev_timer mytimer;
1258	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1259	ev_timer_again (&mytimer); /* start timer */	1858	ev_timer_again (&mytimer); /* start timer */
1260	ev_loop (loop, 0);	1859	ev_loop (loop, 0);
1261		1860
1262	// and in some piece of code that gets executed on any "activity":	1861	// and in some piece of code that gets executed on any "activity":
1263	// reset the timeout to start ticking again at 10 seconds	1862	// reset the timeout to start ticking again at 10 seconds
1264	ev_timer_again (&mytimer);	1863	ev_timer_again (&mytimer);
1265		1864
1266		1865
1267	=head2 C<ev_periodic> - to cron or not to cron?	1866	=head2 C<ev_periodic> - to cron or not to cron?
1268		1867
1269	Periodic watchers are also timers of a kind, but they are very versatile	1868	Periodic watchers are also timers of a kind, but they are very versatile
1270	(and unfortunately a bit complex).	1869	(and unfortunately a bit complex).
1271		1870
1272	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1871	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1273	but on wallclock time (absolute time). You can tell a periodic watcher	1872	relative time, the physical time that passes) but on wall clock time
1274	to trigger "at" some specific point in time. For example, if you tell a	1873	(absolute time, the thing you can read on your calender or clock). The
1275	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1874	difference is that wall clock time can run faster or slower than real
1276	+ 10.>) and then reset your system clock to the last year, then it will	1875	time, and time jumps are not uncommon (e.g. when you adjust your
1277	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1876	wrist-watch).
1278	roughly 10 seconds later).
1279		1877
1280	They can also be used to implement vastly more complex timers, such as	1878	You can tell a periodic watcher to trigger after some specific point
1281	triggering an event on each midnight, local time or other, complicated,	1879	in time: for example, if you tell a periodic watcher to trigger "in 10
1282	rules.	1880	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1881	not a delay) and then reset your system clock to January of the previous
		1882	year, then it will take a year or more to trigger the event (unlike an
		1883	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1884	it, as it uses a relative timeout).
1283		1885
		1886	C<ev_periodic> watchers can also be used to implement vastly more complex
		1887	timers, such as triggering an event on each "midnight, local time", or
		1888	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1889	those cannot react to time jumps.
		1890
1284	As with timers, the callback is guarenteed to be invoked only when the	1891	As with timers, the callback is guaranteed to be invoked only when the
1285	time (C<at>) has been passed, but if multiple periodic timers become ready	1892	point in time where it is supposed to trigger has passed. If multiple
1286	during the same loop iteration then order of execution is undefined.	1893	timers become ready during the same loop iteration then the ones with
		1894	earlier time-out values are invoked before ones with later time-out values
		1895	(but this is no longer true when a callback calls C<ev_loop> recursively).
1287		1896
1288	=head3 Watcher-Specific Functions and Data Members	1897	=head3 Watcher-Specific Functions and Data Members
1289		1898
1290	=over 4	1899	=over 4
1291		1900
1292	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1901	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1293		1902
1294	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1903	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1295		1904
1296	Lots of arguments, lets sort it out... There are basically three modes of	1905	Lots of arguments, let's sort it out... There are basically three modes of
1297	operation, and we will explain them from simplest to complex:	1906	operation, and we will explain them from simplest to most complex:
1298		1907
1299	=over 4	1908	=over 4
1300		1909
1301	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1910	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1302		1911
1303	In this configuration the watcher triggers an event at the wallclock time	1912	In this configuration the watcher triggers an event after the wall clock
1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1913	time C<offset> has passed. It will not repeat and will not adjust when a
1305	that is, if it is to be run at January 1st 2011 then it will run when the	1914	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1306	system time reaches or surpasses this time.	1915	will be stopped and invoked when the system clock reaches or surpasses
		1916	this point in time.
1307		1917
1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1918	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1309		1919
1310	In this mode the watcher will always be scheduled to time out at the next	1920	In this mode the watcher will always be scheduled to time out at the next
1311	C<at + N * interval> time (for some integer N, which can also be negative)	1921	C<offset + N * interval> time (for some integer N, which can also be
1312	and then repeat, regardless of any time jumps.	1922	negative) and then repeat, regardless of any time jumps. The C<offset>
		1923	argument is merely an offset into the C<interval> periods.
1313		1924
1314	This can be used to create timers that do not drift with respect to system	1925	This can be used to create timers that do not drift with respect to the
1315	time:	1926	system clock, for example, here is an C<ev_periodic> that triggers each
		1927	hour, on the hour (with respect to UTC):
1316		1928
1317	ev_periodic_set (&periodic, 0., 3600., 0);	1929	ev_periodic_set (&periodic, 0., 3600., 0);
1318		1930
1319	This doesn't mean there will always be 3600 seconds in between triggers,	1931	This doesn't mean there will always be 3600 seconds in between triggers,
1320	but only that the the callback will be called when the system time shows a	1932	but only that the callback will be called when the system time shows a
1321	full hour (UTC), or more correctly, when the system time is evenly divisible	1933	full hour (UTC), or more correctly, when the system time is evenly divisible
1322	by 3600.	1934	by 3600.
1323		1935
1324	Another way to think about it (for the mathematically inclined) is that	1936	Another way to think about it (for the mathematically inclined) is that
1325	C<ev_periodic> will try to run the callback in this mode at the next possible	1937	C<ev_periodic> will try to run the callback in this mode at the next possible
1326	time where C<time = at (mod interval)>, regardless of any time jumps.	1938	time where C<time = offset (mod interval)>, regardless of any time jumps.
1327		1939
1328	For numerical stability it is preferable that the C<at> value is near	1940	For numerical stability it is preferable that the C<offset> value is near
1329	C<ev_now ()> (the current time), but there is no range requirement for	1941	C<ev_now ()> (the current time), but there is no range requirement for
1330	this value.	1942	this value, and in fact is often specified as zero.
1331		1943
		1944	Note also that there is an upper limit to how often a timer can fire (CPU
		1945	speed for example), so if C<interval> is very small then timing stability
		1946	will of course deteriorate. Libev itself tries to be exact to be about one
		1947	millisecond (if the OS supports it and the machine is fast enough).
		1948
1332	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1949	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1333		1950
1334	In this mode the values for C<interval> and C<at> are both being	1951	In this mode the values for C<interval> and C<offset> are both being
1335	ignored. Instead, each time the periodic watcher gets scheduled, the	1952	ignored. Instead, each time the periodic watcher gets scheduled, the
1336	reschedule callback will be called with the watcher as first, and the	1953	reschedule callback will be called with the watcher as first, and the
1337	current time as second argument.	1954	current time as second argument.
1338		1955
1339	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1956	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1340	ever, or make any event loop modifications>. If you need to stop it,	1957	or make ANY other event loop modifications whatsoever, unless explicitly
1341	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1958	allowed by documentation here>.
1342	starting an C<ev_prepare> watcher, which is legal).
1343		1959
		1960	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1961	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1962	only event loop modification you are allowed to do).
		1963
1344	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1964	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1345	ev_tstamp now)>, e.g.:	1965	*w, ev_tstamp now)>, e.g.:
1346		1966
		1967	static ev_tstamp
1347	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1968	my_rescheduler (ev_periodic *w, ev_tstamp now)
1348	{	1969	{
1349	return now + 60.;	1970	return now + 60.;
1350	}	1971	}
1351		1972
1352	It must return the next time to trigger, based on the passed time value	1973	It must return the next time to trigger, based on the passed time value
1353	(that is, the lowest time value larger than to the second argument). It	1974	(that is, the lowest time value larger than to the second argument). It
1354	will usually be called just before the callback will be triggered, but	1975	will usually be called just before the callback will be triggered, but
1355	might be called at other times, too.	1976	might be called at other times, too.
1356		1977
1357	NOTE: I<< This callback must always return a time that is later than the	1978	NOTE: I<< This callback must always return a time that is higher than or
1358	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1979	equal to the passed C<now> value >>.
1359		1980
1360	This can be used to create very complex timers, such as a timer that	1981	This can be used to create very complex timers, such as a timer that
1361	triggers on each midnight, local time. To do this, you would calculate the	1982	triggers on "next midnight, local time". To do this, you would calculate the
1362	next midnight after C<now> and return the timestamp value for this. How	1983	next midnight after C<now> and return the timestamp value for this. How
1363	you do this is, again, up to you (but it is not trivial, which is the main	1984	you do this is, again, up to you (but it is not trivial, which is the main
1364	reason I omitted it as an example).	1985	reason I omitted it as an example).
1365		1986
1366	=back	1987	=back
…		…
1370	Simply stops and restarts the periodic watcher again. This is only useful	1991	Simply stops and restarts the periodic watcher again. This is only useful
1371	when you changed some parameters or the reschedule callback would return	1992	when you changed some parameters or the reschedule callback would return
1372	a different time than the last time it was called (e.g. in a crond like	1993	a different time than the last time it was called (e.g. in a crond like
1373	program when the crontabs have changed).	1994	program when the crontabs have changed).
1374		1995
		1996	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1997
		1998	When active, returns the absolute time that the watcher is supposed
		1999	to trigger next. This is not the same as the C<offset> argument to
		2000	C<ev_periodic_set>, but indeed works even in interval and manual
		2001	rescheduling modes.
		2002
1375	=item ev_tstamp offset [read-write]	2003	=item ev_tstamp offset [read-write]
1376		2004
1377	When repeating, this contains the offset value, otherwise this is the	2005	When repeating, this contains the offset value, otherwise this is the
1378	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2006	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2007	although libev might modify this value for better numerical stability).
1379		2008
1380	Can be modified any time, but changes only take effect when the periodic	2009	Can be modified any time, but changes only take effect when the periodic
1381	timer fires or C<ev_periodic_again> is being called.	2010	timer fires or C<ev_periodic_again> is being called.
1382		2011
1383	=item ev_tstamp interval [read-write]	2012	=item ev_tstamp interval [read-write]
1384		2013
1385	The current interval value. Can be modified any time, but changes only	2014	The current interval value. Can be modified any time, but changes only
1386	take effect when the periodic timer fires or C<ev_periodic_again> is being	2015	take effect when the periodic timer fires or C<ev_periodic_again> is being
1387	called.	2016	called.
1388		2017
1389	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2018	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1390		2019
1391	The current reschedule callback, or C<0>, if this functionality is	2020	The current reschedule callback, or C<0>, if this functionality is
1392	switched off. Can be changed any time, but changes only take effect when	2021	switched off. Can be changed any time, but changes only take effect when
1393	the periodic timer fires or C<ev_periodic_again> is being called.	2022	the periodic timer fires or C<ev_periodic_again> is being called.
1394		2023
1395	=item ev_tstamp at [read-only]
1396
1397	When active, contains the absolute time that the watcher is supposed to
1398	trigger next.
1399
1400	=back	2024	=back
1401		2025
1402	=head3 Examples	2026	=head3 Examples
1403		2027
1404	Example: Call a callback every hour, or, more precisely, whenever the	2028	Example: Call a callback every hour, or, more precisely, whenever the
1405	system clock is divisible by 3600. The callback invocation times have	2029	system time is divisible by 3600. The callback invocation times have
1406	potentially a lot of jittering, but good long-term stability.	2030	potentially a lot of jitter, but good long-term stability.
1407		2031
1408	static void	2032	static void
1409	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2033	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1410	{	2034	{
1411	... its now a full hour (UTC, or TAI or whatever your clock follows)	2035	... its now a full hour (UTC, or TAI or whatever your clock follows)
1412	}	2036	}
1413		2037
1414	struct ev_periodic hourly_tick;	2038	ev_periodic hourly_tick;
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1416	ev_periodic_start (loop, &hourly_tick);	2040	ev_periodic_start (loop, &hourly_tick);
1417		2041
1418	Example: The same as above, but use a reschedule callback to do it:	2042	Example: The same as above, but use a reschedule callback to do it:
1419		2043
1420	#include <math.h>	2044	#include <math.h>
1421		2045
1422	static ev_tstamp	2046	static ev_tstamp
1423	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2047	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1424	{	2048	{
1425	return fmod (now, 3600.) + 3600.;	2049	return now + (3600. - fmod (now, 3600.));
1426	}	2050	}
1427		2051
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1429		2053
1430	Example: Call a callback every hour, starting now:	2054	Example: Call a callback every hour, starting now:
1431		2055
1432	struct ev_periodic hourly_tick;	2056	ev_periodic hourly_tick;
1433	ev_periodic_init (&hourly_tick, clock_cb,	2057	ev_periodic_init (&hourly_tick, clock_cb,
1434	fmod (ev_now (loop), 3600.), 3600., 0);	2058	fmod (ev_now (loop), 3600.), 3600., 0);
1435	ev_periodic_start (loop, &hourly_tick);	2059	ev_periodic_start (loop, &hourly_tick);
1436		2060
1437		2061
1438	=head2 C<ev_signal> - signal me when a signal gets signalled!	2062	=head2 C<ev_signal> - signal me when a signal gets signalled!
1439		2063
1440	Signal watchers will trigger an event when the process receives a specific	2064	Signal watchers will trigger an event when the process receives a specific
1441	signal one or more times. Even though signals are very asynchronous, libev	2065	signal one or more times. Even though signals are very asynchronous, libev
1442	will try it's best to deliver signals synchronously, i.e. as part of the	2066	will try it's best to deliver signals synchronously, i.e. as part of the
1443	normal event processing, like any other event.	2067	normal event processing, like any other event.
1444		2068
		2069	If you want signals asynchronously, just use C<sigaction> as you would
		2070	do without libev and forget about sharing the signal. You can even use
		2071	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2072
1445	You can configure as many watchers as you like per signal. Only when the	2073	You can configure as many watchers as you like per signal. Only when the
1446	first watcher gets started will libev actually register a signal watcher	2074	first watcher gets started will libev actually register a signal handler
1447	with the kernel (thus it coexists with your own signal handlers as long	2075	with the kernel (thus it coexists with your own signal handlers as long as
1448	as you don't register any with libev). Similarly, when the last signal	2076	you don't register any with libev for the same signal). Similarly, when
1449	watcher for a signal is stopped libev will reset the signal handler to	2077	the last signal watcher for a signal is stopped, libev will reset the
1450	SIG_DFL (regardless of what it was set to before).	2078	signal handler to SIG_DFL (regardless of what it was set to before).
1451		2079
1452	If possible and supported, libev will install its handlers with	2080	If possible and supported, libev will install its handlers with
1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2081	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1454	interrupted. If you have a problem with syscalls getting interrupted by	2082	interrupted. If you have a problem with system calls getting interrupted by
1455	signals you can block all signals in an C<ev_check> watcher and unblock	2083	signals you can block all signals in an C<ev_check> watcher and unblock
1456	them in an C<ev_prepare> watcher.	2084	them in an C<ev_prepare> watcher.
1457		2085
1458	=head3 Watcher-Specific Functions and Data Members	2086	=head3 Watcher-Specific Functions and Data Members
1459		2087
…		…
1472		2100
1473	=back	2101	=back
1474		2102
1475	=head3 Examples	2103	=head3 Examples
1476		2104
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	2105	Example: Try to exit cleanly on SIGINT.
1478		2106
1479	static void	2107	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2108	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1481	{	2109	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	2110	ev_unloop (loop, EVUNLOOP_ALL);
1483	}	2111	}
1484		2112
1485	struct ev_signal signal_watcher;	2113	ev_signal signal_watcher;
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2114	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1487	ev_signal_start (loop, &sigint_cb);	2115	ev_signal_start (loop, &signal_watcher);
1488		2116
1489		2117
1490	=head2 C<ev_child> - watch out for process status changes	2118	=head2 C<ev_child> - watch out for process status changes
1491		2119
1492	Child watchers trigger when your process receives a SIGCHLD in response to	2120	Child watchers trigger when your process receives a SIGCHLD in response to
1493	some child status changes (most typically when a child of yours dies). It	2121	some child status changes (most typically when a child of yours dies or
1494	is permissible to install a child watcher I<after> the child has been	2122	exits). It is permissible to install a child watcher I<after> the child
1495	forked (which implies it might have already exited), as long as the event	2123	has been forked (which implies it might have already exited), as long
1496	loop isn't entered (or is continued from a watcher).	2124	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2125	forking and then immediately registering a watcher for the child is fine,
		2126	but forking and registering a watcher a few event loop iterations later or
		2127	in the next callback invocation is not.
1497		2128
1498	Only the default event loop is capable of handling signals, and therefore	2129	Only the default event loop is capable of handling signals, and therefore
1499	you can only rgeister child watchers in the default event loop.	2130	you can only register child watchers in the default event loop.
		2131
		2132	Due to some design glitches inside libev, child watchers will always be
		2133	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2134	libev)
1500		2135
1501	=head3 Process Interaction	2136	=head3 Process Interaction
1502		2137
1503	Libev grabs C<SIGCHLD> as soon as the default event loop is	2138	Libev grabs C<SIGCHLD> as soon as the default event loop is
1504	initialised. This is necessary to guarantee proper behaviour even if	2139	initialised. This is necessary to guarantee proper behaviour even if
1505	the first child watcher is started after the child exits. The occurance	2140	the first child watcher is started after the child exits. The occurrence
1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2141	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1507	synchronously as part of the event loop processing. Libev always reaps all	2142	synchronously as part of the event loop processing. Libev always reaps all
1508	children, even ones not watched.	2143	children, even ones not watched.
1509		2144
1510	=head3 Overriding the Built-In Processing	2145	=head3 Overriding the Built-In Processing
…		…
1514	handler, you can override it easily by installing your own handler for	2149	handler, you can override it easily by installing your own handler for
1515	C<SIGCHLD> after initialising the default loop, and making sure the	2150	C<SIGCHLD> after initialising the default loop, and making sure the
1516	default loop never gets destroyed. You are encouraged, however, to use an	2151	default loop never gets destroyed. You are encouraged, however, to use an
1517	event-based approach to child reaping and thus use libev's support for	2152	event-based approach to child reaping and thus use libev's support for
1518	that, so other libev users can use C<ev_child> watchers freely.	2153	that, so other libev users can use C<ev_child> watchers freely.
		2154
		2155	=head3 Stopping the Child Watcher
		2156
		2157	Currently, the child watcher never gets stopped, even when the
		2158	child terminates, so normally one needs to stop the watcher in the
		2159	callback. Future versions of libev might stop the watcher automatically
		2160	when a child exit is detected.
1519		2161
1520	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1521		2163
1522	=over 4	2164	=over 4
1523		2165
…		…
1552	=head3 Examples	2194	=head3 Examples
1553		2195
1554	Example: C<fork()> a new process and install a child handler to wait for	2196	Example: C<fork()> a new process and install a child handler to wait for
1555	its completion.	2197	its completion.
1556		2198
1557	ev_child cw;	2199	ev_child cw;
1558		2200
1559	static void	2201	static void
1560	child_cb (EV_P_ struct ev_child *w, int revents)	2202	child_cb (EV_P_ ev_child *w, int revents)
1561	{	2203	{
1562	ev_child_stop (EV_A_ w);	2204	ev_child_stop (EV_A_ w);
1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2205	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1564	}	2206	}
1565		2207
1566	pid_t pid = fork ();	2208	pid_t pid = fork ();
1567		2209
1568	if (pid < 0)	2210	if (pid < 0)
1569	// error	2211	// error
1570	else if (pid == 0)	2212	else if (pid == 0)
1571	{	2213	{
1572	// the forked child executes here	2214	// the forked child executes here
1573	exit (1);	2215	exit (1);
1574	}	2216	}
1575	else	2217	else
1576	{	2218	{
1577	ev_child_init (&cw, child_cb, pid, 0);	2219	ev_child_init (&cw, child_cb, pid, 0);
1578	ev_child_start (EV_DEFAULT_ &cw);	2220	ev_child_start (EV_DEFAULT_ &cw);
1579	}	2221	}
1580		2222
1581		2223
1582	=head2 C<ev_stat> - did the file attributes just change?	2224	=head2 C<ev_stat> - did the file attributes just change?
1583		2225
1584	This watches a filesystem path for attribute changes. That is, it calls	2226	This watches a file system path for attribute changes. That is, it calls
1585	C<stat> regularly (or when the OS says it changed) and sees if it changed	2227	C<stat> on that path in regular intervals (or when the OS says it changed)
1586	compared to the last time, invoking the callback if it did.	2228	and sees if it changed compared to the last time, invoking the callback if
		2229	it did.
1587		2230
1588	The path does not need to exist: changing from "path exists" to "path does	2231	The path does not need to exist: changing from "path exists" to "path does
1589	not exist" is a status change like any other. The condition "path does	2232	not exist" is a status change like any other. The condition "path does not
1590	not exist" is signified by the C<st_nlink> field being zero (which is	2233	exist" (or more correctly "path cannot be stat'ed") is signified by the
1591	otherwise always forced to be at least one) and all the other fields of	2234	C<st_nlink> field being zero (which is otherwise always forced to be at
1592	the stat buffer having unspecified contents.	2235	least one) and all the other fields of the stat buffer having unspecified
		2236	contents.
1593		2237
1594	The path I<should> be absolute and I<must not> end in a slash. If it is	2238	The path I<must not> end in a slash or contain special components such as
		2239	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1595	relative and your working directory changes, the behaviour is undefined.	2240	your working directory changes, then the behaviour is undefined.
1596		2241
1597	Since there is no standard to do this, the portable implementation simply	2242	Since there is no portable change notification interface available, the
1598	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2243	portable implementation simply calls C<stat(2)> regularly on the path
1599	can specify a recommended polling interval for this case. If you specify	2244	to see if it changed somehow. You can specify a recommended polling
1600	a polling interval of C<0> (highly recommended!) then a I<suitable,	2245	interval for this case. If you specify a polling interval of C<0> (highly
1601	unspecified default> value will be used (which you can expect to be around	2246	recommended!) then a I<suitable, unspecified default> value will be used
1602	five seconds, although this might change dynamically). Libev will also	2247	(which you can expect to be around five seconds, although this might
1603	impose a minimum interval which is currently around C<0.1>, but thats	2248	change dynamically). Libev will also impose a minimum interval which is
1604	usually overkill.	2249	currently around C<0.1>, but that's usually overkill.
1605		2250
1606	This watcher type is not meant for massive numbers of stat watchers,	2251	This watcher type is not meant for massive numbers of stat watchers,
1607	as even with OS-supported change notifications, this can be	2252	as even with OS-supported change notifications, this can be
1608	resource-intensive.	2253	resource-intensive.
1609		2254
1610	At the time of this writing, only the Linux inotify interface is	2255	At the time of this writing, the only OS-specific interface implemented
1611	implemented (implementing kqueue support is left as an exercise for the	2256	is the Linux inotify interface (implementing kqueue support is left as an
1612	reader). Inotify will be used to give hints only and should not change the	2257	exercise for the reader. Note, however, that the author sees no way of
1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2258	implementing C<ev_stat> semantics with kqueue, except as a hint).
1614	to fall back to regular polling again even with inotify, but changes are
1615	usually detected immediately, and if the file exists there will be no
1616	polling.
1617		2259
1618	=head3 ABI Issues (Largefile Support)	2260	=head3 ABI Issues (Largefile Support)
1619		2261
1620	Libev by default (unless the user overrides this) uses the default	2262	Libev by default (unless the user overrides this) uses the default
1621	compilation environment, which means that on systems with optionally	2263	compilation environment, which means that on systems with large file
1622	disabled large file support, you get the 32 bit version of the stat	2264	support disabled by default, you get the 32 bit version of the stat
1623	structure. When using the library from programs that change the ABI to	2265	structure. When using the library from programs that change the ABI to
1624	use 64 bit file offsets the programs will fail. In that case you have to	2266	use 64 bit file offsets the programs will fail. In that case you have to
1625	compile libev with the same flags to get binary compatibility. This is	2267	compile libev with the same flags to get binary compatibility. This is
1626	obviously the case with any flags that change the ABI, but the problem is	2268	obviously the case with any flags that change the ABI, but the problem is
1627	most noticably with ev_stat and largefile support.	2269	most noticeably displayed with ev_stat and large file support.
1628		2270
1629	=head3 Inotify	2271	The solution for this is to lobby your distribution maker to make large
		2272	file interfaces available by default (as e.g. FreeBSD does) and not
		2273	optional. Libev cannot simply switch on large file support because it has
		2274	to exchange stat structures with application programs compiled using the
		2275	default compilation environment.
1630		2276
		2277	=head3 Inotify and Kqueue
		2278
1631	When C<inotify (7)> support has been compiled into libev (generally only	2279	When C<inotify (7)> support has been compiled into libev and present at
1632	available on Linux) and present at runtime, it will be used to speed up	2280	runtime, it will be used to speed up change detection where possible. The
1633	change detection where possible. The inotify descriptor will be created lazily	2281	inotify descriptor will be created lazily when the first C<ev_stat>
1634	when the first C<ev_stat> watcher is being started.	2282	watcher is being started.
1635		2283
1636	Inotify presense does not change the semantics of C<ev_stat> watchers	2284	Inotify presence does not change the semantics of C<ev_stat> watchers
1637	except that changes might be detected earlier, and in some cases, to avoid	2285	except that changes might be detected earlier, and in some cases, to avoid
1638	making regular C<stat> calls. Even in the presense of inotify support	2286	making regular C<stat> calls. Even in the presence of inotify support
1639	there are many cases where libev has to resort to regular C<stat> polling.	2287	there are many cases where libev has to resort to regular C<stat> polling,
		2288	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2289	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2290	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2291	xfs are fully working) libev usually gets away without polling.
1640		2292
1641	(There is no support for kqueue, as apparently it cannot be used to	2293	There is no support for kqueue, as apparently it cannot be used to
1642	implement this functionality, due to the requirement of having a file	2294	implement this functionality, due to the requirement of having a file
1643	descriptor open on the object at all times).	2295	descriptor open on the object at all times, and detecting renames, unlinks
		2296	etc. is difficult.
		2297
		2298	=head3 C<stat ()> is a synchronous operation
		2299
		2300	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2301	the process. The exception are C<ev_stat> watchers - those call C<stat
		2302	()>, which is a synchronous operation.
		2303
		2304	For local paths, this usually doesn't matter: unless the system is very
		2305	busy or the intervals between stat's are large, a stat call will be fast,
		2306	as the path data is usually in memory already (except when starting the
		2307	watcher).
		2308
		2309	For networked file systems, calling C<stat ()> can block an indefinite
		2310	time due to network issues, and even under good conditions, a stat call
		2311	often takes multiple milliseconds.
		2312
		2313	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2314	paths, although this is fully supported by libev.
1644		2315
1645	=head3 The special problem of stat time resolution	2316	=head3 The special problem of stat time resolution
1646		2317
1647	The C<stat ()> syscall only supports full-second resolution portably, and	2318	The C<stat ()> system call only supports full-second resolution portably,
1648	even on systems where the resolution is higher, many filesystems still	2319	and even on systems where the resolution is higher, most file systems
1649	only support whole seconds.	2320	still only support whole seconds.
1650		2321
1651	That means that, if the time is the only thing that changes, you might	2322	That means that, if the time is the only thing that changes, you can
1652	miss updates: on the first update, C<ev_stat> detects a change and calls	2323	easily miss updates: on the first update, C<ev_stat> detects a change and
1653	your callback, which does something. When there is another update within	2324	calls your callback, which does something. When there is another update
1654	the same second, C<ev_stat> will be unable to detect it.	2325	within the same second, C<ev_stat> will be unable to detect unless the
		2326	stat data does change in other ways (e.g. file size).
1655		2327
1656	The solution to this is to delay acting on a change for a second (or till	2328	The solution to this is to delay acting on a change for slightly more
1657	the next second boundary), using a roughly one-second delay C<ev_timer>	2329	than a second (or till slightly after the next full second boundary), using
1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2330	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1659	is added to work around small timing inconsistencies of some operating	2331	ev_timer_again (loop, w)>).
1660	systems.	2332
		2333	The C<.02> offset is added to work around small timing inconsistencies
		2334	of some operating systems (where the second counter of the current time
		2335	might be be delayed. One such system is the Linux kernel, where a call to
		2336	C<gettimeofday> might return a timestamp with a full second later than
		2337	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2338	update file times then there will be a small window where the kernel uses
		2339	the previous second to update file times but libev might already execute
		2340	the timer callback).
1661		2341
1662	=head3 Watcher-Specific Functions and Data Members	2342	=head3 Watcher-Specific Functions and Data Members
1663		2343
1664	=over 4	2344	=over 4
1665		2345
…		…
1671	C<path>. The C<interval> is a hint on how quickly a change is expected to	2351	C<path>. The C<interval> is a hint on how quickly a change is expected to
1672	be detected and should normally be specified as C<0> to let libev choose	2352	be detected and should normally be specified as C<0> to let libev choose
1673	a suitable value. The memory pointed to by C<path> must point to the same	2353	a suitable value. The memory pointed to by C<path> must point to the same
1674	path for as long as the watcher is active.	2354	path for as long as the watcher is active.
1675		2355
1676	The callback will be receive C<EV_STAT> when a change was detected,	2356	The callback will receive an C<EV_STAT> event when a change was detected,
1677	relative to the attributes at the time the watcher was started (or the	2357	relative to the attributes at the time the watcher was started (or the
1678	last change was detected).	2358	last change was detected).
1679		2359
1680	=item ev_stat_stat (loop, ev_stat *)	2360	=item ev_stat_stat (loop, ev_stat *)
1681		2361
1682	Updates the stat buffer immediately with new values. If you change the	2362	Updates the stat buffer immediately with new values. If you change the
1683	watched path in your callback, you could call this fucntion to avoid	2363	watched path in your callback, you could call this function to avoid
1684	detecting this change (while introducing a race condition). Can also be	2364	detecting this change (while introducing a race condition if you are not
1685	useful simply to find out the new values.	2365	the only one changing the path). Can also be useful simply to find out the
		2366	new values.
1686		2367
1687	=item ev_statdata attr [read-only]	2368	=item ev_statdata attr [read-only]
1688		2369
1689	The most-recently detected attributes of the file. Although the type is of	2370	The most-recently detected attributes of the file. Although the type is
1690	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2371	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1691	suitable for your system. If the C<st_nlink> member is C<0>, then there	2372	suitable for your system, but you can only rely on the POSIX-standardised
		2373	members to be present. If the C<st_nlink> member is C<0>, then there was
1692	was some error while C<stat>ing the file.	2374	some error while C<stat>ing the file.
1693		2375
1694	=item ev_statdata prev [read-only]	2376	=item ev_statdata prev [read-only]
1695		2377
1696	The previous attributes of the file. The callback gets invoked whenever	2378	The previous attributes of the file. The callback gets invoked whenever
1697	C<prev> != C<attr>.	2379	C<prev> != C<attr>, or, more precisely, one or more of these members
		2380	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2381	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1698		2382
1699	=item ev_tstamp interval [read-only]	2383	=item ev_tstamp interval [read-only]
1700		2384
1701	The specified interval.	2385	The specified interval.
1702		2386
1703	=item const char *path [read-only]	2387	=item const char *path [read-only]
1704		2388
1705	The filesystem path that is being watched.	2389	The file system path that is being watched.
1706		2390
1707	=back	2391	=back
1708		2392
1709	=head3 Examples	2393	=head3 Examples
1710		2394
1711	Example: Watch C</etc/passwd> for attribute changes.	2395	Example: Watch C</etc/passwd> for attribute changes.
1712		2396
1713	static void	2397	static void
1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2398	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1715	{	2399	{
1716	/* /etc/passwd changed in some way */	2400	/* /etc/passwd changed in some way */
1717	if (w->attr.st_nlink)	2401	if (w->attr.st_nlink)
1718	{	2402	{
1719	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2403	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1720	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2404	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1721	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2405	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1722	}	2406	}
1723	else	2407	else
1724	/* you shalt not abuse printf for puts */	2408	/* you shalt not abuse printf for puts */
1725	puts ("wow, /etc/passwd is not there, expect problems. "	2409	puts ("wow, /etc/passwd is not there, expect problems. "
1726	"if this is windows, they already arrived\n");	2410	"if this is windows, they already arrived\n");
1727	}	2411	}
1728		2412
1729	...	2413	...
1730	ev_stat passwd;	2414	ev_stat passwd;
1731		2415
1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2416	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1733	ev_stat_start (loop, &passwd);	2417	ev_stat_start (loop, &passwd);
1734		2418
1735	Example: Like above, but additionally use a one-second delay so we do not	2419	Example: Like above, but additionally use a one-second delay so we do not
1736	miss updates (however, frequent updates will delay processing, too, so	2420	miss updates (however, frequent updates will delay processing, too, so
1737	one might do the work both on C<ev_stat> callback invocation I<and> on	2421	one might do the work both on C<ev_stat> callback invocation I<and> on
1738	C<ev_timer> callback invocation).	2422	C<ev_timer> callback invocation).
1739		2423
1740	static ev_stat passwd;	2424	static ev_stat passwd;
1741	static ev_timer timer;	2425	static ev_timer timer;
1742		2426
1743	static void	2427	static void
1744	timer_cb (EV_P_ ev_timer *w, int revents)	2428	timer_cb (EV_P_ ev_timer *w, int revents)
1745	{	2429	{
1746	ev_timer_stop (EV_A_ w);	2430	ev_timer_stop (EV_A_ w);
1747		2431
1748	/* now it's one second after the most recent passwd change */	2432	/* now it's one second after the most recent passwd change */
1749	}	2433	}
1750		2434
1751	static void	2435	static void
1752	stat_cb (EV_P_ ev_stat *w, int revents)	2436	stat_cb (EV_P_ ev_stat *w, int revents)
1753	{	2437	{
1754	/* reset the one-second timer */	2438	/* reset the one-second timer */
1755	ev_timer_again (EV_A_ &timer);	2439	ev_timer_again (EV_A_ &timer);
1756	}	2440	}
1757		2441
1758	...	2442	...
1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2443	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	2444	ev_stat_start (loop, &passwd);
1761	ev_timer_init (&timer, timer_cb, 0., 1.01);	2445	ev_timer_init (&timer, timer_cb, 0., 1.02);
1762		2446
1763		2447
1764	=head2 C<ev_idle> - when you've got nothing better to do...	2448	=head2 C<ev_idle> - when you've got nothing better to do...
1765		2449
1766	Idle watchers trigger events when no other events of the same or higher	2450	Idle watchers trigger events when no other events of the same or higher
1767	priority are pending (prepare, check and other idle watchers do not	2451	priority are pending (prepare, check and other idle watchers do not count
1768	count).	2452	as receiving "events").
1769		2453
1770	That is, as long as your process is busy handling sockets or timeouts	2454	That is, as long as your process is busy handling sockets or timeouts
1771	(or even signals, imagine) of the same or higher priority it will not be	2455	(or even signals, imagine) of the same or higher priority it will not be
1772	triggered. But when your process is idle (or only lower-priority watchers	2456	triggered. But when your process is idle (or only lower-priority watchers
1773	are pending), the idle watchers are being called once per event loop	2457	are pending), the idle watchers are being called once per event loop
…		…
1784		2468
1785	=head3 Watcher-Specific Functions and Data Members	2469	=head3 Watcher-Specific Functions and Data Members
1786		2470
1787	=over 4	2471	=over 4
1788		2472
1789	=item ev_idle_init (ev_signal *, callback)	2473	=item ev_idle_init (ev_idle *, callback)
1790		2474
1791	Initialises and configures the idle watcher - it has no parameters of any	2475	Initialises and configures the idle watcher - it has no parameters of any
1792	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2476	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1793	believe me.	2477	believe me.
1794		2478
…		…
1797	=head3 Examples	2481	=head3 Examples
1798		2482
1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2483	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1800	callback, free it. Also, use no error checking, as usual.	2484	callback, free it. Also, use no error checking, as usual.
1801		2485
1802	static void	2486	static void
1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2487	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1804	{	2488	{
1805	free (w);	2489	free (w);
1806	// now do something you wanted to do when the program has	2490	// now do something you wanted to do when the program has
1807	// no longer anything immediate to do.	2491	// no longer anything immediate to do.
1808	}	2492	}
1809		2493
1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2494	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1811	ev_idle_init (idle_watcher, idle_cb);	2495	ev_idle_init (idle_watcher, idle_cb);
1812	ev_idle_start (loop, idle_cb);	2496	ev_idle_start (loop, idle_watcher);
1813		2497
1814		2498
1815	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2499	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1816		2500
1817	Prepare and check watchers are usually (but not always) used in tandem:	2501	Prepare and check watchers are usually (but not always) used in pairs:
1818	prepare watchers get invoked before the process blocks and check watchers	2502	prepare watchers get invoked before the process blocks and check watchers
1819	afterwards.	2503	afterwards.
1820		2504
1821	You I<must not> call C<ev_loop> or similar functions that enter	2505	You I<must not> call C<ev_loop> or similar functions that enter
1822	the current event loop from either C<ev_prepare> or C<ev_check>	2506	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1825	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2509	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1826	C<ev_check> so if you have one watcher of each kind they will always be	2510	C<ev_check> so if you have one watcher of each kind they will always be
1827	called in pairs bracketing the blocking call.	2511	called in pairs bracketing the blocking call.
1828		2512
1829	Their main purpose is to integrate other event mechanisms into libev and	2513	Their main purpose is to integrate other event mechanisms into libev and
1830	their use is somewhat advanced. This could be used, for example, to track	2514	their use is somewhat advanced. They could be used, for example, to track
1831	variable changes, implement your own watchers, integrate net-snmp or a	2515	variable changes, implement your own watchers, integrate net-snmp or a
1832	coroutine library and lots more. They are also occasionally useful if	2516	coroutine library and lots more. They are also occasionally useful if
1833	you cache some data and want to flush it before blocking (for example,	2517	you cache some data and want to flush it before blocking (for example,
1834	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2518	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1835	watcher).	2519	watcher).
1836		2520
1837	This is done by examining in each prepare call which file descriptors need	2521	This is done by examining in each prepare call which file descriptors
1838	to be watched by the other library, registering C<ev_io> watchers for	2522	need to be watched by the other library, registering C<ev_io> watchers
1839	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2523	for them and starting an C<ev_timer> watcher for any timeouts (many
1840	provide just this functionality). Then, in the check watcher you check for	2524	libraries provide exactly this functionality). Then, in the check watcher,
1841	any events that occured (by checking the pending status of all watchers	2525	you check for any events that occurred (by checking the pending status
1842	and stopping them) and call back into the library. The I/O and timer	2526	of all watchers and stopping them) and call back into the library. The
1843	callbacks will never actually be called (but must be valid nevertheless,	2527	I/O and timer callbacks will never actually be called (but must be valid
1844	because you never know, you know?).	2528	nevertheless, because you never know, you know?).
1845		2529
1846	As another example, the Perl Coro module uses these hooks to integrate	2530	As another example, the Perl Coro module uses these hooks to integrate
1847	coroutines into libev programs, by yielding to other active coroutines	2531	coroutines into libev programs, by yielding to other active coroutines
1848	during each prepare and only letting the process block if no coroutines	2532	during each prepare and only letting the process block if no coroutines
1849	are ready to run (it's actually more complicated: it only runs coroutines	2533	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1852	loop from blocking if lower-priority coroutines are active, thus mapping	2536	loop from blocking if lower-priority coroutines are active, thus mapping
1853	low-priority coroutines to idle/background tasks).	2537	low-priority coroutines to idle/background tasks).
1854		2538
1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2539	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1856	priority, to ensure that they are being run before any other watchers	2540	priority, to ensure that they are being run before any other watchers
		2541	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2542
1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2543	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1858	too) should not activate ("feed") events into libev. While libev fully	2544	activate ("feed") events into libev. While libev fully supports this, they
1859	supports this, they will be called before other C<ev_check> watchers	2545	might get executed before other C<ev_check> watchers did their job. As
1860	did their job. As C<ev_check> watchers are often used to embed other	2546	C<ev_check> watchers are often used to embed other (non-libev) event
1861	(non-libev) event loops those other event loops might be in an unusable	2547	loops those other event loops might be in an unusable state until their
1862	state until their C<ev_check> watcher ran (always remind yourself to	2548	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1863	coexist peacefully with others).	2549	others).
1864		2550
1865	=head3 Watcher-Specific Functions and Data Members	2551	=head3 Watcher-Specific Functions and Data Members
1866		2552
1867	=over 4	2553	=over 4
1868		2554
…		…
1870		2556
1871	=item ev_check_init (ev_check *, callback)	2557	=item ev_check_init (ev_check *, callback)
1872		2558
1873	Initialises and configures the prepare or check watcher - they have no	2559	Initialises and configures the prepare or check watcher - they have no
1874	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2560	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1875	macros, but using them is utterly, utterly and completely pointless.	2561	macros, but using them is utterly, utterly, utterly and completely
		2562	pointless.
1876		2563
1877	=back	2564	=back
1878		2565
1879	=head3 Examples	2566	=head3 Examples
1880		2567
1881	There are a number of principal ways to embed other event loops or modules	2568	There are a number of principal ways to embed other event loops or modules
1882	into libev. Here are some ideas on how to include libadns into libev	2569	into libev. Here are some ideas on how to include libadns into libev
1883	(there is a Perl module named C<EV::ADNS> that does this, which you could	2570	(there is a Perl module named C<EV::ADNS> that does this, which you could
1884	use for an actually working example. Another Perl module named C<EV::Glib>	2571	use as a working example. Another Perl module named C<EV::Glib> embeds a
1885	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2572	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1886	into the Glib event loop).	2573	Glib event loop).
1887		2574
1888	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2575	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1889	and in a check watcher, destroy them and call into libadns. What follows	2576	and in a check watcher, destroy them and call into libadns. What follows
1890	is pseudo-code only of course. This requires you to either use a low	2577	is pseudo-code only of course. This requires you to either use a low
1891	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2578	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1892	the callbacks for the IO/timeout watchers might not have been called yet.	2579	the callbacks for the IO/timeout watchers might not have been called yet.
1893		2580
1894	static ev_io iow [nfd];	2581	static ev_io iow [nfd];
1895	static ev_timer tw;	2582	static ev_timer tw;
1896		2583
1897	static void	2584	static void
1898	io_cb (ev_loop *loop, ev_io *w, int revents)	2585	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1899	{	2586	{
1900	}	2587	}
1901		2588
1902	// create io watchers for each fd and a timer before blocking	2589	// create io watchers for each fd and a timer before blocking
1903	static void	2590	static void
1904	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2591	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1905	{	2592	{
1906	int timeout = 3600000;	2593	int timeout = 3600000;
1907	struct pollfd fds [nfd];	2594	struct pollfd fds [nfd];
1908	// actual code will need to loop here and realloc etc.	2595	// actual code will need to loop here and realloc etc.
1909	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2596	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1910		2597
1911	/* the callback is illegal, but won't be called as we stop during check */	2598	/* the callback is illegal, but won't be called as we stop during check */
1912	ev_timer_init (&tw, 0, timeout * 1e-3);	2599	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1913	ev_timer_start (loop, &tw);	2600	ev_timer_start (loop, &tw);
1914		2601
1915	// create one ev_io per pollfd	2602	// create one ev_io per pollfd
1916	for (int i = 0; i < nfd; ++i)	2603	for (int i = 0; i < nfd; ++i)
1917	{	2604	{
1918	ev_io_init (iow + i, io_cb, fds [i].fd,	2605	ev_io_init (iow + i, io_cb, fds [i].fd,
1919	((fds [i].events & POLLIN ? EV_READ : 0)	2606	((fds [i].events & POLLIN ? EV_READ : 0)
1920	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2607	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1921		2608
1922	fds [i].revents = 0;	2609	fds [i].revents = 0;
1923	ev_io_start (loop, iow + i);	2610	ev_io_start (loop, iow + i);
1924	}	2611	}
1925	}	2612	}
1926		2613
1927	// stop all watchers after blocking	2614	// stop all watchers after blocking
1928	static void	2615	static void
1929	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2616	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1930	{	2617	{
1931	ev_timer_stop (loop, &tw);	2618	ev_timer_stop (loop, &tw);
1932		2619
1933	for (int i = 0; i < nfd; ++i)	2620	for (int i = 0; i < nfd; ++i)
1934	{	2621	{
1935	// set the relevant poll flags	2622	// set the relevant poll flags
1936	// could also call adns_processreadable etc. here	2623	// could also call adns_processreadable etc. here
1937	struct pollfd *fd = fds + i;	2624	struct pollfd *fd = fds + i;
1938	int revents = ev_clear_pending (iow + i);	2625	int revents = ev_clear_pending (iow + i);
1939	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2626	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1940	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2627	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1941		2628
1942	// now stop the watcher	2629	// now stop the watcher
1943	ev_io_stop (loop, iow + i);	2630	ev_io_stop (loop, iow + i);
1944	}	2631	}
1945		2632
1946	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2633	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1947	}	2634	}
1948		2635
1949	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2636	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1950	in the prepare watcher and would dispose of the check watcher.	2637	in the prepare watcher and would dispose of the check watcher.
1951		2638
1952	Method 3: If the module to be embedded supports explicit event	2639	Method 3: If the module to be embedded supports explicit event
1953	notification (adns does), you can also make use of the actual watcher	2640	notification (libadns does), you can also make use of the actual watcher
1954	callbacks, and only destroy/create the watchers in the prepare watcher.	2641	callbacks, and only destroy/create the watchers in the prepare watcher.
1955		2642
1956	static void	2643	static void
1957	timer_cb (EV_P_ ev_timer *w, int revents)	2644	timer_cb (EV_P_ ev_timer *w, int revents)
1958	{	2645	{
1959	adns_state ads = (adns_state)w->data;	2646	adns_state ads = (adns_state)w->data;
1960	update_now (EV_A);	2647	update_now (EV_A);
1961		2648
1962	adns_processtimeouts (ads, &tv_now);	2649	adns_processtimeouts (ads, &tv_now);
1963	}	2650	}
1964		2651
1965	static void	2652	static void
1966	io_cb (EV_P_ ev_io *w, int revents)	2653	io_cb (EV_P_ ev_io *w, int revents)
1967	{	2654	{
1968	adns_state ads = (adns_state)w->data;	2655	adns_state ads = (adns_state)w->data;
1969	update_now (EV_A);	2656	update_now (EV_A);
1970		2657
1971	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2658	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1972	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2659	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1973	}	2660	}
1974		2661
1975	// do not ever call adns_afterpoll	2662	// do not ever call adns_afterpoll
1976		2663
1977	Method 4: Do not use a prepare or check watcher because the module you	2664	Method 4: Do not use a prepare or check watcher because the module you
1978	want to embed is too inflexible to support it. Instead, youc na override	2665	want to embed is not flexible enough to support it. Instead, you can
1979	their poll function. The drawback with this solution is that the main	2666	override their poll function. The drawback with this solution is that the
1980	loop is now no longer controllable by EV. The C<Glib::EV> module does	2667	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1981	this.	2668	this approach, effectively embedding EV as a client into the horrible
		2669	libglib event loop.
1982		2670
1983	static gint	2671	static gint
1984	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1985	{	2673	{
1986	int got_events = 0;	2674	int got_events = 0;
1987		2675
1988	for (n = 0; n < nfds; ++n)	2676	for (n = 0; n < nfds; ++n)
1989	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1990		2678
1991	if (timeout >= 0)	2679	if (timeout >= 0)
1992	// create/start timer	2680	// create/start timer
1993		2681
1994	// poll	2682	// poll
1995	ev_loop (EV_A_ 0);	2683	ev_loop (EV_A_ 0);
1996		2684
1997	// stop timer again	2685	// stop timer again
1998	if (timeout >= 0)	2686	if (timeout >= 0)
1999	ev_timer_stop (EV_A_ &to);	2687	ev_timer_stop (EV_A_ &to);
2000		2688
2001	// stop io watchers again - their callbacks should have set	2689	// stop io watchers again - their callbacks should have set
2002	for (n = 0; n < nfds; ++n)	2690	for (n = 0; n < nfds; ++n)
2003	ev_io_stop (EV_A_ iow [n]);	2691	ev_io_stop (EV_A_ iow [n]);
2004		2692
2005	return got_events;	2693	return got_events;
2006	}	2694	}
2007		2695
2008		2696
2009	=head2 C<ev_embed> - when one backend isn't enough...	2697	=head2 C<ev_embed> - when one backend isn't enough...
2010		2698
2011	This is a rather advanced watcher type that lets you embed one event loop	2699	This is a rather advanced watcher type that lets you embed one event loop
…		…
2017	prioritise I/O.	2705	prioritise I/O.
2018		2706
2019	As an example for a bug workaround, the kqueue backend might only support	2707	As an example for a bug workaround, the kqueue backend might only support
2020	sockets on some platform, so it is unusable as generic backend, but you	2708	sockets on some platform, so it is unusable as generic backend, but you
2021	still want to make use of it because you have many sockets and it scales	2709	still want to make use of it because you have many sockets and it scales
2022	so nicely. In this case, you would create a kqueue-based loop and embed it	2710	so nicely. In this case, you would create a kqueue-based loop and embed
2023	into your default loop (which might use e.g. poll). Overall operation will	2711	it into your default loop (which might use e.g. poll). Overall operation
2024	be a bit slower because first libev has to poll and then call kevent, but	2712	will be a bit slower because first libev has to call C<poll> and then
2025	at least you can use both at what they are best.	2713	C<kevent>, but at least you can use both mechanisms for what they are
		2714	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2026		2715
2027	As for prioritising I/O: rarely you have the case where some fds have	2716	As for prioritising I/O: under rare circumstances you have the case where
2028	to be watched and handled very quickly (with low latency), and even	2717	some fds have to be watched and handled very quickly (with low latency),
2029	priorities and idle watchers might have too much overhead. In this case	2718	and even priorities and idle watchers might have too much overhead. In
2030	you would put all the high priority stuff in one loop and all the rest in	2719	this case you would put all the high priority stuff in one loop and all
2031	a second one, and embed the second one in the first.	2720	the rest in a second one, and embed the second one in the first.
2032		2721
2033	As long as the watcher is active, the callback will be invoked every time	2722	As long as the watcher is active, the callback will be invoked every
2034	there might be events pending in the embedded loop. The callback must then	2723	time there might be events pending in the embedded loop. The callback
2035	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2724	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2036	their callbacks (you could also start an idle watcher to give the embedded	2725	sweep and invoke their callbacks (the callback doesn't need to invoke the
2037	loop strictly lower priority for example). You can also set the callback	2726	C<ev_embed_sweep> function directly, it could also start an idle watcher
2038	to C<0>, in which case the embed watcher will automatically execute the	2727	to give the embedded loop strictly lower priority for example).
2039	embedded loop sweep.
2040		2728
2041	As long as the watcher is started it will automatically handle events. The	2729	You can also set the callback to C<0>, in which case the embed watcher
2042	callback will be invoked whenever some events have been handled. You can	2730	will automatically execute the embedded loop sweep whenever necessary.
2043	set the callback to C<0> to avoid having to specify one if you are not
2044	interested in that.
2045		2731
2046	Also, there have not currently been made special provisions for forking:	2732	Fork detection will be handled transparently while the C<ev_embed> watcher
2047	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2733	is active, i.e., the embedded loop will automatically be forked when the
2048	but you will also have to stop and restart any C<ev_embed> watchers	2734	embedding loop forks. In other cases, the user is responsible for calling
2049	yourself.	2735	C<ev_loop_fork> on the embedded loop.
2050		2736
2051	Unfortunately, not all backends are embeddable, only the ones returned by	2737	Unfortunately, not all backends are embeddable: only the ones returned by
2052	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2738	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2053	portable one.	2739	portable one.
2054		2740
2055	So when you want to use this feature you will always have to be prepared	2741	So when you want to use this feature you will always have to be prepared
2056	that you cannot get an embeddable loop. The recommended way to get around	2742	that you cannot get an embeddable loop. The recommended way to get around
2057	this is to have a separate variables for your embeddable loop, try to	2743	this is to have a separate variables for your embeddable loop, try to
2058	create it, and if that fails, use the normal loop for everything.	2744	create it, and if that fails, use the normal loop for everything.
2059		2745
		2746	=head3 C<ev_embed> and fork
		2747
		2748	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2749	automatically be applied to the embedded loop as well, so no special
		2750	fork handling is required in that case. When the watcher is not running,
		2751	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2752	as applicable.
		2753
2060	=head3 Watcher-Specific Functions and Data Members	2754	=head3 Watcher-Specific Functions and Data Members
2061		2755
2062	=over 4	2756	=over 4
2063		2757
2064	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2758	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2067		2761
2068	Configures the watcher to embed the given loop, which must be	2762	Configures the watcher to embed the given loop, which must be
2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2763	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2070	invoked automatically, otherwise it is the responsibility of the callback	2764	invoked automatically, otherwise it is the responsibility of the callback
2071	to invoke it (it will continue to be called until the sweep has been done,	2765	to invoke it (it will continue to be called until the sweep has been done,
2072	if you do not want thta, you need to temporarily stop the embed watcher).	2766	if you do not want that, you need to temporarily stop the embed watcher).
2073		2767
2074	=item ev_embed_sweep (loop, ev_embed *)	2768	=item ev_embed_sweep (loop, ev_embed *)
2075		2769
2076	Make a single, non-blocking sweep over the embedded loop. This works	2770	Make a single, non-blocking sweep over the embedded loop. This works
2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2771	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2078	apropriate way for embedded loops.	2772	appropriate way for embedded loops.
2079		2773
2080	=item struct ev_loop *other [read-only]	2774	=item struct ev_loop *other [read-only]
2081		2775
2082	The embedded event loop.	2776	The embedded event loop.
2083		2777
…		…
2085		2779
2086	=head3 Examples	2780	=head3 Examples
2087		2781
2088	Example: Try to get an embeddable event loop and embed it into the default	2782	Example: Try to get an embeddable event loop and embed it into the default
2089	event loop. If that is not possible, use the default loop. The default	2783	event loop. If that is not possible, use the default loop. The default
2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2784	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2785	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2092	used).	2786	used).
2093		2787
2094	struct ev_loop *loop_hi = ev_default_init (0);	2788	struct ev_loop *loop_hi = ev_default_init (0);
2095	struct ev_loop *loop_lo = 0;	2789	struct ev_loop *loop_lo = 0;
2096	struct ev_embed embed;	2790	ev_embed embed;
2097		2791
2098	// see if there is a chance of getting one that works	2792	// see if there is a chance of getting one that works
2099	// (remember that a flags value of 0 means autodetection)	2793	// (remember that a flags value of 0 means autodetection)
2100	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2794	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2101	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2795	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2102	: 0;	2796	: 0;
2103		2797
2104	// if we got one, then embed it, otherwise default to loop_hi	2798	// if we got one, then embed it, otherwise default to loop_hi
2105	if (loop_lo)	2799	if (loop_lo)
2106	{	2800	{
2107	ev_embed_init (&embed, 0, loop_lo);	2801	ev_embed_init (&embed, 0, loop_lo);
2108	ev_embed_start (loop_hi, &embed);	2802	ev_embed_start (loop_hi, &embed);
2109	}	2803	}
2110	else	2804	else
2111	loop_lo = loop_hi;	2805	loop_lo = loop_hi;
2112		2806
2113	Example: Check if kqueue is available but not recommended and create	2807	Example: Check if kqueue is available but not recommended and create
2114	a kqueue backend for use with sockets (which usually work with any	2808	a kqueue backend for use with sockets (which usually work with any
2115	kqueue implementation). Store the kqueue/socket-only event loop in	2809	kqueue implementation). Store the kqueue/socket-only event loop in
2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2810	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2117		2811
2118	struct ev_loop *loop = ev_default_init (0);	2812	struct ev_loop *loop = ev_default_init (0);
2119	struct ev_loop *loop_socket = 0;	2813	struct ev_loop *loop_socket = 0;
2120	struct ev_embed embed;	2814	ev_embed embed;
2121		2815
2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2816	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2817	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2124	{	2818	{
2125	ev_embed_init (&embed, 0, loop_socket);	2819	ev_embed_init (&embed, 0, loop_socket);
2126	ev_embed_start (loop, &embed);	2820	ev_embed_start (loop, &embed);
2127	}	2821	}
2128		2822
2129	if (!loop_socket)	2823	if (!loop_socket)
2130	loop_socket = loop;	2824	loop_socket = loop;
2131		2825
2132	// now use loop_socket for all sockets, and loop for everything else	2826	// now use loop_socket for all sockets, and loop for everything else
2133		2827
2134		2828
2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2829	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2136		2830
2137	Fork watchers are called when a C<fork ()> was detected (usually because	2831	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2140	event loop blocks next and before C<ev_check> watchers are being called,	2834	event loop blocks next and before C<ev_check> watchers are being called,
2141	and only in the child after the fork. If whoever good citizen calling	2835	and only in the child after the fork. If whoever good citizen calling
2142	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2836	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2143	handlers will be invoked, too, of course.	2837	handlers will be invoked, too, of course.
2144		2838
		2839	=head3 The special problem of life after fork - how is it possible?
		2840
		2841	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2842	up/change the process environment, followed by a call to C<exec()>. This
		2843	sequence should be handled by libev without any problems.
		2844
		2845	This changes when the application actually wants to do event handling
		2846	in the child, or both parent in child, in effect "continuing" after the
		2847	fork.
		2848
		2849	The default mode of operation (for libev, with application help to detect
		2850	forks) is to duplicate all the state in the child, as would be expected
		2851	when I<either> the parent I<or> the child process continues.
		2852
		2853	When both processes want to continue using libev, then this is usually the
		2854	wrong result. In that case, usually one process (typically the parent) is
		2855	supposed to continue with all watchers in place as before, while the other
		2856	process typically wants to start fresh, i.e. without any active watchers.
		2857
		2858	The cleanest and most efficient way to achieve that with libev is to
		2859	simply create a new event loop, which of course will be "empty", and
		2860	use that for new watchers. This has the advantage of not touching more
		2861	memory than necessary, and thus avoiding the copy-on-write, and the
		2862	disadvantage of having to use multiple event loops (which do not support
		2863	signal watchers).
		2864
		2865	When this is not possible, or you want to use the default loop for
		2866	other reasons, then in the process that wants to start "fresh", call
		2867	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2868	the default loop will "orphan" (not stop) all registered watchers, so you
		2869	have to be careful not to execute code that modifies those watchers. Note
		2870	also that in that case, you have to re-register any signal watchers.
		2871
2145	=head3 Watcher-Specific Functions and Data Members	2872	=head3 Watcher-Specific Functions and Data Members
2146		2873
2147	=over 4	2874	=over 4
2148		2875
2149	=item ev_fork_init (ev_signal *, callback)	2876	=item ev_fork_init (ev_signal *, callback)
…		…
2181	is that the author does not know of a simple (or any) algorithm for a	2908	is that the author does not know of a simple (or any) algorithm for a
2182	multiple-writer-single-reader queue that works in all cases and doesn't	2909	multiple-writer-single-reader queue that works in all cases and doesn't
2183	need elaborate support such as pthreads.	2910	need elaborate support such as pthreads.
2184		2911
2185	That means that if you want to queue data, you have to provide your own	2912	That means that if you want to queue data, you have to provide your own
2186	queue. But at least I can tell you would implement locking around your	2913	queue. But at least I can tell you how to implement locking around your
2187	queue:	2914	queue:
2188		2915
2189	=over 4	2916	=over 4
2190		2917
2191	=item queueing from a signal handler context	2918	=item queueing from a signal handler context
2192		2919
2193	To implement race-free queueing, you simply add to the queue in the signal	2920	To implement race-free queueing, you simply add to the queue in the signal
2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2921	handler but you block the signal handler in the watcher callback. Here is
2195	some fictitiuous SIGUSR1 handler:	2922	an example that does that for some fictitious SIGUSR1 handler:
2196		2923
2197	static ev_async mysig;	2924	static ev_async mysig;
2198		2925
2199	static void	2926	static void
2200	sigusr1_handler (void)	2927	sigusr1_handler (void)
…		…
2266	=over 4	2993	=over 4
2267		2994
2268	=item ev_async_init (ev_async *, callback)	2995	=item ev_async_init (ev_async *, callback)
2269		2996
2270	Initialises and configures the async watcher - it has no parameters of any	2997	Initialises and configures the async watcher - it has no parameters of any
2271	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2998	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2272	believe me.	2999	trust me.
2273		3000
2274	=item ev_async_send (loop, ev_async *)	3001	=item ev_async_send (loop, ev_async *)
2275		3002
2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3003	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3004	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2278	C<ev_feed_event>, this call is safe to do in other threads, signal or	3005	C<ev_feed_event>, this call is safe to do from other threads, signal or
2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3006	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2280	section below on what exactly this means).	3007	section below on what exactly this means).
2281		3008
		3009	Note that, as with other watchers in libev, multiple events might get
		3010	compressed into a single callback invocation (another way to look at this
		3011	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3012	reset when the event loop detects that).
		3013
2282	This call incurs the overhead of a syscall only once per loop iteration,	3014	This call incurs the overhead of a system call only once per event loop
2283	so while the overhead might be noticable, it doesn't apply to repeated	3015	iteration, so while the overhead might be noticeable, it doesn't apply to
2284	calls to C<ev_async_send>.	3016	repeated calls to C<ev_async_send> for the same event loop.
2285		3017
2286	=item bool = ev_async_pending (ev_async *)	3018	=item bool = ev_async_pending (ev_async *)
2287		3019
2288	Returns a non-zero value when C<ev_async_send> has been called on the	3020	Returns a non-zero value when C<ev_async_send> has been called on the
2289	watcher but the event has not yet been processed (or even noted) by the	3021	watcher but the event has not yet been processed (or even noted) by the
2290	event loop.	3022	event loop.
2291		3023
2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3024	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2293	the loop iterates next and checks for the watcher to have become active,	3025	the loop iterates next and checks for the watcher to have become active,
2294	it will reset the flag again. C<ev_async_pending> can be used to very	3026	it will reset the flag again. C<ev_async_pending> can be used to very
2295	quickly check wether invoking the loop might be a good idea.	3027	quickly check whether invoking the loop might be a good idea.
2296		3028
2297	Not that this does I<not> check wether the watcher itself is pending, only	3029	Not that this does I<not> check whether the watcher itself is pending,
2298	wether it has been requested to make this watcher pending.	3030	only whether it has been requested to make this watcher pending: there
		3031	is a time window between the event loop checking and resetting the async
		3032	notification, and the callback being invoked.
2299		3033
2300	=back	3034	=back
2301		3035
2302		3036
2303	=head1 OTHER FUNCTIONS	3037	=head1 OTHER FUNCTIONS
…		…
2307	=over 4	3041	=over 4
2308		3042
2309	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3043	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2310		3044
2311	This function combines a simple timer and an I/O watcher, calls your	3045	This function combines a simple timer and an I/O watcher, calls your
2312	callback on whichever event happens first and automatically stop both	3046	callback on whichever event happens first and automatically stops both
2313	watchers. This is useful if you want to wait for a single event on an fd	3047	watchers. This is useful if you want to wait for a single event on an fd
2314	or timeout without having to allocate/configure/start/stop/free one or	3048	or timeout without having to allocate/configure/start/stop/free one or
2315	more watchers yourself.	3049	more watchers yourself.
2316		3050
2317	If C<fd> is less than 0, then no I/O watcher will be started and events	3051	If C<fd> is less than 0, then no I/O watcher will be started and the
2318	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3052	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2319	C<events> set will be craeted and started.	3053	the given C<fd> and C<events> set will be created and started.
2320		3054
2321	If C<timeout> is less than 0, then no timeout watcher will be	3055	If C<timeout> is less than 0, then no timeout watcher will be
2322	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3056	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2323	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3057	repeat = 0) will be started. C<0> is a valid timeout.
2324	dubious value.
2325		3058
2326	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3059	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2327	passed an C<revents> set like normal event callbacks (a combination of	3060	passed an C<revents> set like normal event callbacks (a combination of
2328	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3061	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2329	value passed to C<ev_once>:	3062	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3063	a timeout and an io event at the same time - you probably should give io
		3064	events precedence.
2330		3065
		3066	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3067
2331	static void stdin_ready (int revents, void *arg)	3068	static void stdin_ready (int revents, void *arg)
2332	{	3069	{
2333	if (revents & EV_TIMEOUT)
2334	/* doh, nothing entered */;
2335	else if (revents & EV_READ)	3070	if (revents & EV_READ)
2336	/* stdin might have data for us, joy! */;	3071	/* stdin might have data for us, joy! */;
		3072	else if (revents & EV_TIMEOUT)
		3073	/* doh, nothing entered */;
2337	}	3074	}
2338		3075
2339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3076	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2340		3077
2341	=item ev_feed_event (ev_loop *, watcher *, int revents)	3078	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2342		3079
2343	Feeds the given event set into the event loop, as if the specified event	3080	Feeds the given event set into the event loop, as if the specified event
2344	had happened for the specified watcher (which must be a pointer to an	3081	had happened for the specified watcher (which must be a pointer to an
2345	initialised but not necessarily started event watcher).	3082	initialised but not necessarily started event watcher).
2346		3083
2347	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3084	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2348		3085
2349	Feed an event on the given fd, as if a file descriptor backend detected	3086	Feed an event on the given fd, as if a file descriptor backend detected
2350	the given events it.	3087	the given events it.
2351		3088
2352	=item ev_feed_signal_event (ev_loop *loop, int signum)	3089	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2353		3090
2354	Feed an event as if the given signal occured (C<loop> must be the default	3091	Feed an event as if the given signal occurred (C<loop> must be the default
2355	loop!).	3092	loop!).
2356		3093
2357	=back	3094	=back
2358		3095
2359		3096
…		…
2375		3112
2376	=item * Priorities are not currently supported. Initialising priorities	3113	=item * Priorities are not currently supported. Initialising priorities
2377	will fail and all watchers will have the same priority, even though there	3114	will fail and all watchers will have the same priority, even though there
2378	is an ev_pri field.	3115	is an ev_pri field.
2379		3116
		3117	=item * In libevent, the last base created gets the signals, in libev, the
		3118	first base created (== the default loop) gets the signals.
		3119
2380	=item * Other members are not supported.	3120	=item * Other members are not supported.
2381		3121
2382	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3122	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2383	to use the libev header file and library.	3123	to use the libev header file and library.
2384		3124
2385	=back	3125	=back
2386		3126
2387	=head1 C++ SUPPORT	3127	=head1 C++ SUPPORT
2388		3128
2389	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3129	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2390	you to use some convinience methods to start/stop watchers and also change	3130	you to use some convenience methods to start/stop watchers and also change
2391	the callback model to a model using method callbacks on objects.	3131	the callback model to a model using method callbacks on objects.
2392		3132
2393	To use it,	3133	To use it,
2394		3134
2395	#include <ev++.h>	3135	#include <ev++.h>
2396		3136
2397	This automatically includes F<ev.h> and puts all of its definitions (many	3137	This automatically includes F<ev.h> and puts all of its definitions (many
2398	of them macros) into the global namespace. All C++ specific things are	3138	of them macros) into the global namespace. All C++ specific things are
2399	put into the C<ev> namespace. It should support all the same embedding	3139	put into the C<ev> namespace. It should support all the same embedding
2400	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3140	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2467	your compiler is good :), then the method will be fully inlined into the	3207	your compiler is good :), then the method will be fully inlined into the
2468	thunking function, making it as fast as a direct C callback.	3208	thunking function, making it as fast as a direct C callback.
2469		3209
2470	Example: simple class declaration and watcher initialisation	3210	Example: simple class declaration and watcher initialisation
2471		3211
2472	struct myclass	3212	struct myclass
2473	{	3213	{
2474	void io_cb (ev::io &w, int revents) { }	3214	void io_cb (ev::io &w, int revents) { }
2475	}	3215	}
2476		3216
2477	myclass obj;	3217	myclass obj;
2478	ev::io iow;	3218	ev::io iow;
2479	iow.set <myclass, &myclass::io_cb> (&obj);	3219	iow.set <myclass, &myclass::io_cb> (&obj);
		3220
		3221	=item w->set (object *)
		3222
		3223	This is an B<experimental> feature that might go away in a future version.
		3224
		3225	This is a variation of a method callback - leaving out the method to call
		3226	will default the method to C<operator ()>, which makes it possible to use
		3227	functor objects without having to manually specify the C<operator ()> all
		3228	the time. Incidentally, you can then also leave out the template argument
		3229	list.
		3230
		3231	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3232	int revents)>.
		3233
		3234	See the method-C<set> above for more details.
		3235
		3236	Example: use a functor object as callback.
		3237
		3238	struct myfunctor
		3239	{
		3240	void operator() (ev::io &w, int revents)
		3241	{
		3242	...
		3243	}
		3244	}
		3245
		3246	myfunctor f;
		3247
		3248	ev::io w;
		3249	w.set (&f);
2480		3250
2481	=item w->set<function> (void *data = 0)	3251	=item w->set<function> (void *data = 0)
2482		3252
2483	Also sets a callback, but uses a static method or plain function as	3253	Also sets a callback, but uses a static method or plain function as
2484	callback. The optional C<data> argument will be stored in the watcher's	3254	callback. The optional C<data> argument will be stored in the watcher's
…		…
2486		3256
2487	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3257	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2488		3258
2489	See the method-C<set> above for more details.	3259	See the method-C<set> above for more details.
2490		3260
2491	Example:	3261	Example: Use a plain function as callback.
2492		3262
2493	static void io_cb (ev::io &w, int revents) { }	3263	static void io_cb (ev::io &w, int revents) { }
2494	iow.set <io_cb> ();	3264	iow.set <io_cb> ();
2495		3265
2496	=item w->set (struct ev_loop *)	3266	=item w->set (struct ev_loop *)
2497		3267
2498	Associates a different C<struct ev_loop> with this watcher. You can only	3268	Associates a different C<struct ev_loop> with this watcher. You can only
2499	do this when the watcher is inactive (and not pending either).	3269	do this when the watcher is inactive (and not pending either).
2500		3270
2501	=item w->set ([args])	3271	=item w->set ([arguments])
2502		3272
2503	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3273	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2504	called at least once. Unlike the C counterpart, an active watcher gets	3274	called at least once. Unlike the C counterpart, an active watcher gets
2505	automatically stopped and restarted when reconfiguring it with this	3275	automatically stopped and restarted when reconfiguring it with this
2506	method.	3276	method.
2507		3277
2508	=item w->start ()	3278	=item w->start ()
…		…
2532	=back	3302	=back
2533		3303
2534	Example: Define a class with an IO and idle watcher, start one of them in	3304	Example: Define a class with an IO and idle watcher, start one of them in
2535	the constructor.	3305	the constructor.
2536		3306
2537	class myclass	3307	class myclass
2538	{	3308	{
2539	ev::io io; void io_cb (ev::io &w, int revents);	3309	ev::io io ; void io_cb (ev::io &w, int revents);
2540	ev:idle idle void idle_cb (ev::idle &w, int revents);	3310	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2541		3311
2542	myclass (int fd)	3312	myclass (int fd)
2543	{	3313	{
2544	io .set <myclass, &myclass::io_cb > (this);	3314	io .set <myclass, &myclass::io_cb > (this);
2545	idle.set <myclass, &myclass::idle_cb> (this);	3315	idle.set <myclass, &myclass::idle_cb> (this);
2546		3316
2547	io.start (fd, ev::READ);	3317	io.start (fd, ev::READ);
2548	}	3318	}
2549	};	3319	};
2550		3320
2551		3321
2552	=head1 OTHER LANGUAGE BINDINGS	3322	=head1 OTHER LANGUAGE BINDINGS
2553		3323
2554	Libev does not offer other language bindings itself, but bindings for a	3324	Libev does not offer other language bindings itself, but bindings for a
2555	numbe rof languages exist in the form of third-party packages. If you know	3325	number of languages exist in the form of third-party packages. If you know
2556	any interesting language binding in addition to the ones listed here, drop	3326	any interesting language binding in addition to the ones listed here, drop
2557	me a note.	3327	me a note.
2558		3328
2559	=over 4	3329	=over 4
2560		3330
2561	=item Perl	3331	=item Perl
2562		3332
2563	The EV module implements the full libev API and is actually used to test	3333	The EV module implements the full libev API and is actually used to test
2564	libev. EV is developed together with libev. Apart from the EV core module,	3334	libev. EV is developed together with libev. Apart from the EV core module,
2565	there are additional modules that implement libev-compatible interfaces	3335	there are additional modules that implement libev-compatible interfaces
2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3336	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3337	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3338	and C<EV::Glib>).
2568		3339
2569	It can be found and installed via CPAN, its homepage is found at	3340	It can be found and installed via CPAN, its homepage is at
2570	L<http://software.schmorp.de/pkg/EV>.	3341	L<http://software.schmorp.de/pkg/EV>.
2571		3342
		3343	=item Python
		3344
		3345	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3346	seems to be quite complete and well-documented.
		3347
2572	=item Ruby	3348	=item Ruby
2573		3349
2574	Tony Arcieri has written a ruby extension that offers access to a subset	3350	Tony Arcieri has written a ruby extension that offers access to a subset
2575	of the libev API and adds filehandle abstractions, asynchronous DNS and	3351	of the libev API and adds file handle abstractions, asynchronous DNS and
2576	more on top of it. It can be found via gem servers. Its homepage is at	3352	more on top of it. It can be found via gem servers. Its homepage is at
2577	L<http://rev.rubyforge.org/>.	3353	L<http://rev.rubyforge.org/>.
2578		3354
		3355	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3356	makes rev work even on mingw.
		3357
		3358	=item Haskell
		3359
		3360	A haskell binding to libev is available at
		3361	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3362
2579	=item D	3363	=item D
2580		3364
2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3365	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3366	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3367
		3368	=item Ocaml
		3369
		3370	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3371	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2583		3372
2584	=back	3373	=back
2585		3374
2586		3375
2587	=head1 MACRO MAGIC	3376	=head1 MACRO MAGIC
2588		3377
2589	Libev can be compiled with a variety of options, the most fundamantal	3378	Libev can be compiled with a variety of options, the most fundamental
2590	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3379	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2591	functions and callbacks have an initial C<struct ev_loop *> argument.	3380	functions and callbacks have an initial C<struct ev_loop *> argument.
2592		3381
2593	To make it easier to write programs that cope with either variant, the	3382	To make it easier to write programs that cope with either variant, the
2594	following macros are defined:	3383	following macros are defined:
…		…
2599		3388
2600	This provides the loop I<argument> for functions, if one is required ("ev	3389	This provides the loop I<argument> for functions, if one is required ("ev
2601	loop argument"). The C<EV_A> form is used when this is the sole argument,	3390	loop argument"). The C<EV_A> form is used when this is the sole argument,
2602	C<EV_A_> is used when other arguments are following. Example:	3391	C<EV_A_> is used when other arguments are following. Example:
2603		3392
2604	ev_unref (EV_A);	3393	ev_unref (EV_A);
2605	ev_timer_add (EV_A_ watcher);	3394	ev_timer_add (EV_A_ watcher);
2606	ev_loop (EV_A_ 0);	3395	ev_loop (EV_A_ 0);
2607		3396
2608	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3397	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2609	which is often provided by the following macro.	3398	which is often provided by the following macro.
2610		3399
2611	=item C<EV_P>, C<EV_P_>	3400	=item C<EV_P>, C<EV_P_>
2612		3401
2613	This provides the loop I<parameter> for functions, if one is required ("ev	3402	This provides the loop I<parameter> for functions, if one is required ("ev
2614	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3403	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2615	C<EV_P_> is used when other parameters are following. Example:	3404	C<EV_P_> is used when other parameters are following. Example:
2616		3405
2617	// this is how ev_unref is being declared	3406	// this is how ev_unref is being declared
2618	static void ev_unref (EV_P);	3407	static void ev_unref (EV_P);
2619		3408
2620	// this is how you can declare your typical callback	3409	// this is how you can declare your typical callback
2621	static void cb (EV_P_ ev_timer *w, int revents)	3410	static void cb (EV_P_ ev_timer *w, int revents)
2622		3411
2623	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3412	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2624	suitable for use with C<EV_A>.	3413	suitable for use with C<EV_A>.
2625		3414
2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3415	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2642		3431
2643	Example: Declare and initialise a check watcher, utilising the above	3432	Example: Declare and initialise a check watcher, utilising the above
2644	macros so it will work regardless of whether multiple loops are supported	3433	macros so it will work regardless of whether multiple loops are supported
2645	or not.	3434	or not.
2646		3435
2647	static void	3436	static void
2648	check_cb (EV_P_ ev_timer *w, int revents)	3437	check_cb (EV_P_ ev_timer *w, int revents)
2649	{	3438	{
2650	ev_check_stop (EV_A_ w);	3439	ev_check_stop (EV_A_ w);
2651	}	3440	}
2652		3441
2653	ev_check check;	3442	ev_check check;
2654	ev_check_init (&check, check_cb);	3443	ev_check_init (&check, check_cb);
2655	ev_check_start (EV_DEFAULT_ &check);	3444	ev_check_start (EV_DEFAULT_ &check);
2656	ev_loop (EV_DEFAULT_ 0);	3445	ev_loop (EV_DEFAULT_ 0);
2657		3446
2658	=head1 EMBEDDING	3447	=head1 EMBEDDING
2659		3448
2660	Libev can (and often is) directly embedded into host	3449	Libev can (and often is) directly embedded into host
2661	applications. Examples of applications that embed it include the Deliantra	3450	applications. Examples of applications that embed it include the Deliantra
…		…
2668	libev somewhere in your source tree).	3457	libev somewhere in your source tree).
2669		3458
2670	=head2 FILESETS	3459	=head2 FILESETS
2671		3460
2672	Depending on what features you need you need to include one or more sets of files	3461	Depending on what features you need you need to include one or more sets of files
2673	in your app.	3462	in your application.
2674		3463
2675	=head3 CORE EVENT LOOP	3464	=head3 CORE EVENT LOOP
2676		3465
2677	To include only the libev core (all the C<ev_*> functions), with manual	3466	To include only the libev core (all the C<ev_*> functions), with manual
2678	configuration (no autoconf):	3467	configuration (no autoconf):
2679		3468
2680	#define EV_STANDALONE 1	3469	#define EV_STANDALONE 1
2681	#include "ev.c"	3470	#include "ev.c"
2682		3471
2683	This will automatically include F<ev.h>, too, and should be done in a	3472	This will automatically include F<ev.h>, too, and should be done in a
2684	single C source file only to provide the function implementations. To use	3473	single C source file only to provide the function implementations. To use
2685	it, do the same for F<ev.h> in all files wishing to use this API (best	3474	it, do the same for F<ev.h> in all files wishing to use this API (best
2686	done by writing a wrapper around F<ev.h> that you can include instead and	3475	done by writing a wrapper around F<ev.h> that you can include instead and
2687	where you can put other configuration options):	3476	where you can put other configuration options):
2688		3477
2689	#define EV_STANDALONE 1	3478	#define EV_STANDALONE 1
2690	#include "ev.h"	3479	#include "ev.h"
2691		3480
2692	Both header files and implementation files can be compiled with a C++	3481	Both header files and implementation files can be compiled with a C++
2693	compiler (at least, thats a stated goal, and breakage will be treated	3482	compiler (at least, that's a stated goal, and breakage will be treated
2694	as a bug).	3483	as a bug).
2695		3484
2696	You need the following files in your source tree, or in a directory	3485	You need the following files in your source tree, or in a directory
2697	in your include path (e.g. in libev/ when using -Ilibev):	3486	in your include path (e.g. in libev/ when using -Ilibev):
2698		3487
2699	ev.h	3488	ev.h
2700	ev.c	3489	ev.c
2701	ev_vars.h	3490	ev_vars.h
2702	ev_wrap.h	3491	ev_wrap.h
2703		3492
2704	ev_win32.c required on win32 platforms only	3493	ev_win32.c required on win32 platforms only
2705		3494
2706	ev_select.c only when select backend is enabled (which is enabled by default)	3495	ev_select.c only when select backend is enabled (which is enabled by default)
2707	ev_poll.c only when poll backend is enabled (disabled by default)	3496	ev_poll.c only when poll backend is enabled (disabled by default)
2708	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3497	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2709	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3498	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2710	ev_port.c only when the solaris port backend is enabled (disabled by default)	3499	ev_port.c only when the solaris port backend is enabled (disabled by default)
2711		3500
2712	F<ev.c> includes the backend files directly when enabled, so you only need	3501	F<ev.c> includes the backend files directly when enabled, so you only need
2713	to compile this single file.	3502	to compile this single file.
2714		3503
2715	=head3 LIBEVENT COMPATIBILITY API	3504	=head3 LIBEVENT COMPATIBILITY API
2716		3505
2717	To include the libevent compatibility API, also include:	3506	To include the libevent compatibility API, also include:
2718		3507
2719	#include "event.c"	3508	#include "event.c"
2720		3509
2721	in the file including F<ev.c>, and:	3510	in the file including F<ev.c>, and:
2722		3511
2723	#include "event.h"	3512	#include "event.h"
2724		3513
2725	in the files that want to use the libevent API. This also includes F<ev.h>.	3514	in the files that want to use the libevent API. This also includes F<ev.h>.
2726		3515
2727	You need the following additional files for this:	3516	You need the following additional files for this:
2728		3517
2729	event.h	3518	event.h
2730	event.c	3519	event.c
2731		3520
2732	=head3 AUTOCONF SUPPORT	3521	=head3 AUTOCONF SUPPORT
2733		3522
2734	Instead of using C<EV_STANDALONE=1> and providing your config in	3523	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2735	whatever way you want, you can also C<m4_include([libev.m4])> in your	3524	whatever way you want, you can also C<m4_include([libev.m4])> in your
2736	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3525	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2737	include F<config.h> and configure itself accordingly.	3526	include F<config.h> and configure itself accordingly.
2738		3527
2739	For this of course you need the m4 file:	3528	For this of course you need the m4 file:
2740		3529
2741	libev.m4	3530	libev.m4
2742		3531
2743	=head2 PREPROCESSOR SYMBOLS/MACROS	3532	=head2 PREPROCESSOR SYMBOLS/MACROS
2744		3533
2745	Libev can be configured via a variety of preprocessor symbols you have to	3534	Libev can be configured via a variety of preprocessor symbols you have to
2746	define before including any of its files. The default in the absense of	3535	define before including any of its files. The default in the absence of
2747	autoconf is noted for every option.	3536	autoconf is documented for every option.
2748		3537
2749	=over 4	3538	=over 4
2750		3539
2751	=item EV_STANDALONE	3540	=item EV_STANDALONE
2752		3541
…		…
2754	keeps libev from including F<config.h>, and it also defines dummy	3543	keeps libev from including F<config.h>, and it also defines dummy
2755	implementations for some libevent functions (such as logging, which is not	3544	implementations for some libevent functions (such as logging, which is not
2756	supported). It will also not define any of the structs usually found in	3545	supported). It will also not define any of the structs usually found in
2757	F<event.h> that are not directly supported by the libev core alone.	3546	F<event.h> that are not directly supported by the libev core alone.
2758		3547
		3548	In stanbdalone mode, libev will still try to automatically deduce the
		3549	configuration, but has to be more conservative.
		3550
2759	=item EV_USE_MONOTONIC	3551	=item EV_USE_MONOTONIC
2760		3552
2761	If defined to be C<1>, libev will try to detect the availability of the	3553	If defined to be C<1>, libev will try to detect the availability of the
2762	monotonic clock option at both compiletime and runtime. Otherwise no use	3554	monotonic clock option at both compile time and runtime. Otherwise no
2763	of the monotonic clock option will be attempted. If you enable this, you	3555	use of the monotonic clock option will be attempted. If you enable this,
2764	usually have to link against librt or something similar. Enabling it when	3556	you usually have to link against librt or something similar. Enabling it
2765	the functionality isn't available is safe, though, although you have	3557	when the functionality isn't available is safe, though, although you have
2766	to make sure you link against any libraries where the C<clock_gettime>	3558	to make sure you link against any libraries where the C<clock_gettime>
2767	function is hiding in (often F<-lrt>).	3559	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2768		3560
2769	=item EV_USE_REALTIME	3561	=item EV_USE_REALTIME
2770		3562
2771	If defined to be C<1>, libev will try to detect the availability of the	3563	If defined to be C<1>, libev will try to detect the availability of the
2772	realtime clock option at compiletime (and assume its availability at	3564	real-time clock option at compile time (and assume its availability
2773	runtime if successful). Otherwise no use of the realtime clock option will	3565	at runtime if successful). Otherwise no use of the real-time clock
2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3566	option will be attempted. This effectively replaces C<gettimeofday>
2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3567	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3568	correctness. See the note about libraries in the description of
		3569	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3570	C<EV_USE_CLOCK_SYSCALL>.
		3571
		3572	=item EV_USE_CLOCK_SYSCALL
		3573
		3574	If defined to be C<1>, libev will try to use a direct syscall instead
		3575	of calling the system-provided C<clock_gettime> function. This option
		3576	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3577	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3578	programs needlessly. Using a direct syscall is slightly slower (in
		3579	theory), because no optimised vdso implementation can be used, but avoids
		3580	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3581	higher, as it simplifies linking (no need for C<-lrt>).
2777		3582
2778	=item EV_USE_NANOSLEEP	3583	=item EV_USE_NANOSLEEP
2779		3584
2780	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3585	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2781	and will use it for delays. Otherwise it will use C<select ()>.	3586	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2789	2.7 or newer, otherwise disabled.	3594	2.7 or newer, otherwise disabled.
2790		3595
2791	=item EV_USE_SELECT	3596	=item EV_USE_SELECT
2792		3597
2793	If undefined or defined to be C<1>, libev will compile in support for the	3598	If undefined or defined to be C<1>, libev will compile in support for the
2794	C<select>(2) backend. No attempt at autodetection will be done: if no	3599	C<select>(2) backend. No attempt at auto-detection will be done: if no
2795	other method takes over, select will be it. Otherwise the select backend	3600	other method takes over, select will be it. Otherwise the select backend
2796	will not be compiled in.	3601	will not be compiled in.
2797		3602
2798	=item EV_SELECT_USE_FD_SET	3603	=item EV_SELECT_USE_FD_SET
2799		3604
2800	If defined to C<1>, then the select backend will use the system C<fd_set>	3605	If defined to C<1>, then the select backend will use the system C<fd_set>
2801	structure. This is useful if libev doesn't compile due to a missing	3606	structure. This is useful if libev doesn't compile due to a missing
2802	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3607	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2803	exotic systems. This usually limits the range of file descriptors to some	3608	on exotic systems. This usually limits the range of file descriptors to
2804	low limit such as 1024 or might have other limitations (winsocket only	3609	some low limit such as 1024 or might have other limitations (winsocket
2805	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3610	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2806	influence the size of the C<fd_set> used.	3611	configures the maximum size of the C<fd_set>.
2807		3612
2808	=item EV_SELECT_IS_WINSOCKET	3613	=item EV_SELECT_IS_WINSOCKET
2809		3614
2810	When defined to C<1>, the select backend will assume that	3615	When defined to C<1>, the select backend will assume that
2811	select/socket/connect etc. don't understand file descriptors but	3616	select/socket/connect etc. don't understand file descriptors but
…		…
2856	otherwise another method will be used as fallback. This is the preferred	3661	otherwise another method will be used as fallback. This is the preferred
2857	backend for Solaris 10 systems.	3662	backend for Solaris 10 systems.
2858		3663
2859	=item EV_USE_DEVPOLL	3664	=item EV_USE_DEVPOLL
2860		3665
2861	reserved for future expansion, works like the USE symbols above.	3666	Reserved for future expansion, works like the USE symbols above.
2862		3667
2863	=item EV_USE_INOTIFY	3668	=item EV_USE_INOTIFY
2864		3669
2865	If defined to be C<1>, libev will compile in support for the Linux inotify	3670	If defined to be C<1>, libev will compile in support for the Linux inotify
2866	interface to speed up C<ev_stat> watchers. Its actual availability will	3671	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2873	access is atomic with respect to other threads or signal contexts. No such	3678	access is atomic with respect to other threads or signal contexts. No such
2874	type is easily found in the C language, so you can provide your own type	3679	type is easily found in the C language, so you can provide your own type
2875	that you know is safe for your purposes. It is used both for signal handler "locking"	3680	that you know is safe for your purposes. It is used both for signal handler "locking"
2876	as well as for signal and thread safety in C<ev_async> watchers.	3681	as well as for signal and thread safety in C<ev_async> watchers.
2877		3682
2878	In the absense of this define, libev will use C<sig_atomic_t volatile>	3683	In the absence of this define, libev will use C<sig_atomic_t volatile>
2879	(from F<signal.h>), which is usually good enough on most platforms.	3684	(from F<signal.h>), which is usually good enough on most platforms.
2880		3685
2881	=item EV_H	3686	=item EV_H
2882		3687
2883	The name of the F<ev.h> header file used to include it. The default if	3688	The name of the F<ev.h> header file used to include it. The default if
…		…
2922	When doing priority-based operations, libev usually has to linearly search	3727	When doing priority-based operations, libev usually has to linearly search
2923	all the priorities, so having many of them (hundreds) uses a lot of space	3728	all the priorities, so having many of them (hundreds) uses a lot of space
2924	and time, so using the defaults of five priorities (-2 .. +2) is usually	3729	and time, so using the defaults of five priorities (-2 .. +2) is usually
2925	fine.	3730	fine.
2926		3731
2927	If your embedding app does not need any priorities, defining these both to	3732	If your embedding application does not need any priorities, defining these
2928	C<0> will save some memory and cpu.	3733	both to C<0> will save some memory and CPU.
2929		3734
2930	=item EV_PERIODIC_ENABLE	3735	=item EV_PERIODIC_ENABLE
2931		3736
2932	If undefined or defined to be C<1>, then periodic timers are supported. If	3737	If undefined or defined to be C<1>, then periodic timers are supported. If
2933	defined to be C<0>, then they are not. Disabling them saves a few kB of	3738	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2940	code.	3745	code.
2941		3746
2942	=item EV_EMBED_ENABLE	3747	=item EV_EMBED_ENABLE
2943		3748
2944	If undefined or defined to be C<1>, then embed watchers are supported. If	3749	If undefined or defined to be C<1>, then embed watchers are supported. If
2945	defined to be C<0>, then they are not.	3750	defined to be C<0>, then they are not. Embed watchers rely on most other
		3751	watcher types, which therefore must not be disabled.
2946		3752
2947	=item EV_STAT_ENABLE	3753	=item EV_STAT_ENABLE
2948		3754
2949	If undefined or defined to be C<1>, then stat watchers are supported. If	3755	If undefined or defined to be C<1>, then stat watchers are supported. If
2950	defined to be C<0>, then they are not.	3756	defined to be C<0>, then they are not.
…		…
2960	defined to be C<0>, then they are not.	3766	defined to be C<0>, then they are not.
2961		3767
2962	=item EV_MINIMAL	3768	=item EV_MINIMAL
2963		3769
2964	If you need to shave off some kilobytes of code at the expense of some	3770	If you need to shave off some kilobytes of code at the expense of some
2965	speed, define this symbol to C<1>. Currently only used for gcc to override	3771	speed (but with the full API), define this symbol to C<1>. Currently this
2966	some inlining decisions, saves roughly 30% codesize of amd64.	3772	is used to override some inlining decisions, saves roughly 30% code size
		3773	on amd64. It also selects a much smaller 2-heap for timer management over
		3774	the default 4-heap.
		3775
		3776	You can save even more by disabling watcher types you do not need
		3777	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3778	(C<-DNDEBUG>) will usually reduce code size a lot.
		3779
		3780	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3781	provide a bare-bones event library. See C<ev.h> for details on what parts
		3782	of the API are still available, and do not complain if this subset changes
		3783	over time.
2967		3784
2968	=item EV_PID_HASHSIZE	3785	=item EV_PID_HASHSIZE
2969		3786
2970	C<ev_child> watchers use a small hash table to distribute workload by	3787	C<ev_child> watchers use a small hash table to distribute workload by
2971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3788	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3795	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2979	usually more than enough. If you need to manage thousands of C<ev_stat>	3796	usually more than enough. If you need to manage thousands of C<ev_stat>
2980	watchers you might want to increase this value (I<must> be a power of	3797	watchers you might want to increase this value (I<must> be a power of
2981	two).	3798	two).
2982		3799
		3800	=item EV_USE_4HEAP
		3801
		3802	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3803	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3804	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3805	faster performance with many (thousands) of watchers.
		3806
		3807	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3808	(disabled).
		3809
		3810	=item EV_HEAP_CACHE_AT
		3811
		3812	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3813	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3814	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3815	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3816	but avoids random read accesses on heap changes. This improves performance
		3817	noticeably with many (hundreds) of watchers.
		3818
		3819	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3820	(disabled).
		3821
		3822	=item EV_VERIFY
		3823
		3824	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3825	be done: If set to C<0>, no internal verification code will be compiled
		3826	in. If set to C<1>, then verification code will be compiled in, but not
		3827	called. If set to C<2>, then the internal verification code will be
		3828	called once per loop, which can slow down libev. If set to C<3>, then the
		3829	verification code will be called very frequently, which will slow down
		3830	libev considerably.
		3831
		3832	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3833	C<0>.
		3834
2983	=item EV_COMMON	3835	=item EV_COMMON
2984		3836
2985	By default, all watchers have a C<void *data> member. By redefining	3837	By default, all watchers have a C<void *data> member. By redefining
2986	this macro to a something else you can include more and other types of	3838	this macro to a something else you can include more and other types of
2987	members. You have to define it each time you include one of the files,	3839	members. You have to define it each time you include one of the files,
2988	though, and it must be identical each time.	3840	though, and it must be identical each time.
2989		3841
2990	For example, the perl EV module uses something like this:	3842	For example, the perl EV module uses something like this:
2991		3843
2992	#define EV_COMMON \	3844	#define EV_COMMON \
2993	SV *self; /* contains this struct */ \	3845	SV *self; /* contains this struct */ \
2994	SV *cb_sv, *fh /* note no trailing ";" */	3846	SV *cb_sv, *fh /* note no trailing ";" */
2995		3847
2996	=item EV_CB_DECLARE (type)	3848	=item EV_CB_DECLARE (type)
2997		3849
2998	=item EV_CB_INVOKE (watcher, revents)	3850	=item EV_CB_INVOKE (watcher, revents)
2999		3851
…		…
3004	definition and a statement, respectively. See the F<ev.h> header file for	3856	definition and a statement, respectively. See the F<ev.h> header file for
3005	their default definitions. One possible use for overriding these is to	3857	their default definitions. One possible use for overriding these is to
3006	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3858	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3007	method calls instead of plain function calls in C++.	3859	method calls instead of plain function calls in C++.
3008		3860
		3861	=back
		3862
3009	=head2 EXPORTED API SYMBOLS	3863	=head2 EXPORTED API SYMBOLS
3010		3864
3011	If you need to re-export the API (e.g. via a dll) and you need a list of	3865	If you need to re-export the API (e.g. via a DLL) and you need a list of
3012	exported symbols, you can use the provided F<Symbol.*> files which list	3866	exported symbols, you can use the provided F<Symbol.*> files which list
3013	all public symbols, one per line:	3867	all public symbols, one per line:
3014		3868
3015	Symbols.ev for libev proper	3869	Symbols.ev for libev proper
3016	Symbols.event for the libevent emulation	3870	Symbols.event for the libevent emulation
3017		3871
3018	This can also be used to rename all public symbols to avoid clashes with	3872	This can also be used to rename all public symbols to avoid clashes with
3019	multiple versions of libev linked together (which is obviously bad in	3873	multiple versions of libev linked together (which is obviously bad in
3020	itself, but sometimes it is inconvinient to avoid this).	3874	itself, but sometimes it is inconvenient to avoid this).
3021		3875
3022	A sed command like this will create wrapper C<#define>'s that you need to	3876	A sed command like this will create wrapper C<#define>'s that you need to
3023	include before including F<ev.h>:	3877	include before including F<ev.h>:
3024		3878
3025	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3879	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3042	file.	3896	file.
3043		3897
3044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3898	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3045	that everybody includes and which overrides some configure choices:	3899	that everybody includes and which overrides some configure choices:
3046		3900
3047	#define EV_MINIMAL 1	3901	#define EV_MINIMAL 1
3048	#define EV_USE_POLL 0	3902	#define EV_USE_POLL 0
3049	#define EV_MULTIPLICITY 0	3903	#define EV_MULTIPLICITY 0
3050	#define EV_PERIODIC_ENABLE 0	3904	#define EV_PERIODIC_ENABLE 0
3051	#define EV_STAT_ENABLE 0	3905	#define EV_STAT_ENABLE 0
3052	#define EV_FORK_ENABLE 0	3906	#define EV_FORK_ENABLE 0
3053	#define EV_CONFIG_H <config.h>	3907	#define EV_CONFIG_H <config.h>
3054	#define EV_MINPRI 0	3908	#define EV_MINPRI 0
3055	#define EV_MAXPRI 0	3909	#define EV_MAXPRI 0
3056		3910
3057	#include "ev++.h"	3911	#include "ev++.h"
3058		3912
3059	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3913	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3060		3914
3061	#include "ev_cpp.h"	3915	#include "ev_cpp.h"
3062	#include "ev.c"	3916	#include "ev.c"
3063		3917
		3918	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3064		3919
3065	=head1 THREADS AND COROUTINES	3920	=head2 THREADS AND COROUTINES
3066		3921
3067	=head2 THREADS	3922	=head3 THREADS
3068		3923
3069	Libev itself is completely threadsafe, but it uses no locking. This	3924	All libev functions are reentrant and thread-safe unless explicitly
		3925	documented otherwise, but libev implements no locking itself. This means
3070	means that you can use as many loops as you want in parallel, as long as	3926	that you can use as many loops as you want in parallel, as long as there
3071	only one thread ever calls into one libev function with the same loop	3927	are no concurrent calls into any libev function with the same loop
3072	parameter.	3928	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3929	of course): libev guarantees that different event loops share no data
		3930	structures that need any locking.
3073		3931
3074	Or put differently: calls with different loop parameters can be done in	3932	Or to put it differently: calls with different loop parameters can be done
3075	parallel from multiple threads, calls with the same loop parameter must be	3933	concurrently from multiple threads, calls with the same loop parameter
3076	done serially (but can be done from different threads, as long as only one	3934	must be done serially (but can be done from different threads, as long as
3077	thread ever is inside a call at any point in time, e.g. by using a mutex	3935	only one thread ever is inside a call at any point in time, e.g. by using
3078	per loop).	3936	a mutex per loop).
3079		3937
3080	If you want to know which design is best for your problem, then I cannot	3938	Specifically to support threads (and signal handlers), libev implements
		3939	so-called C<ev_async> watchers, which allow some limited form of
		3940	concurrency on the same event loop, namely waking it up "from the
		3941	outside".
		3942
		3943	If you want to know which design (one loop, locking, or multiple loops
		3944	without or something else still) is best for your problem, then I cannot
3081	help you but by giving some generic advice:	3945	help you, but here is some generic advice:
3082		3946
3083	=over 4	3947	=over 4
3084		3948
3085	=item * most applications have a main thread: use the default libev loop	3949	=item * most applications have a main thread: use the default libev loop
3086	in that thread, or create a seperate thread running only the default loop.	3950	in that thread, or create a separate thread running only the default loop.
3087		3951
3088	This helps integrating other libraries or software modules that use libev	3952	This helps integrating other libraries or software modules that use libev
3089	themselves and don't care/know about threading.	3953	themselves and don't care/know about threading.
3090		3954
3091	=item * one loop per thread is usually a good model.	3955	=item * one loop per thread is usually a good model.
3092		3956
3093	Doing this is almost never wrong, sometimes a better-performance model	3957	Doing this is almost never wrong, sometimes a better-performance model
3094	exists, but it is always a good start.	3958	exists, but it is always a good start.
3095		3959
3096	=item * other models exist, such as the leader/follower pattern, where one	3960	=item * other models exist, such as the leader/follower pattern, where one
3097	loop is handed through multiple threads in a kind of round-robbin fashion.	3961	loop is handed through multiple threads in a kind of round-robin fashion.
3098		3962
3099	Chosing a model is hard - look around, learn, know that usually you cna do	3963	Choosing a model is hard - look around, learn, know that usually you can do
3100	better than you currently do :-)	3964	better than you currently do :-)
3101		3965
3102	=item * often you need to talk to some other thread which blocks in the	3966	=item * often you need to talk to some other thread which blocks in the
		3967	event loop.
		3968
3103	event loop - C<ev_async> watchers can be used to wake them up from other	3969	C<ev_async> watchers can be used to wake them up from other threads safely
3104	threads safely (or from signal contexts...).	3970	(or from signal contexts...).
		3971
		3972	An example use would be to communicate signals or other events that only
		3973	work in the default loop by registering the signal watcher with the
		3974	default loop and triggering an C<ev_async> watcher from the default loop
		3975	watcher callback into the event loop interested in the signal.
3105		3976
3106	=back	3977	=back
3107		3978
		3979	=head4 THREAD LOCKING EXAMPLE
		3980
		3981	Here is a fictitious example of how to run an event loop in a different
		3982	thread than where callbacks are being invoked and watchers are
		3983	created/added/removed.
		3984
		3985	For a real-world example, see the C<EV::Loop::Async> perl module,
		3986	which uses exactly this technique (which is suited for many high-level
		3987	languages).
		3988
		3989	The example uses a pthread mutex to protect the loop data, a condition
		3990	variable to wait for callback invocations, an async watcher to notify the
		3991	event loop thread and an unspecified mechanism to wake up the main thread.
		3992
		3993	First, you need to associate some data with the event loop:
		3994
		3995	typedef struct {
		3996	mutex_t lock; /* global loop lock */
		3997	ev_async async_w;
		3998	thread_t tid;
		3999	cond_t invoke_cv;
		4000	} userdata;
		4001
		4002	void prepare_loop (EV_P)
		4003	{
		4004	// for simplicity, we use a static userdata struct.
		4005	static userdata u;
		4006
		4007	ev_async_init (&u->async_w, async_cb);
		4008	ev_async_start (EV_A_ &u->async_w);
		4009
		4010	pthread_mutex_init (&u->lock, 0);
		4011	pthread_cond_init (&u->invoke_cv, 0);
		4012
		4013	// now associate this with the loop
		4014	ev_set_userdata (EV_A_ u);
		4015	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4016	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4017
		4018	// then create the thread running ev_loop
		4019	pthread_create (&u->tid, 0, l_run, EV_A);
		4020	}
		4021
		4022	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4023	solely to wake up the event loop so it takes notice of any new watchers
		4024	that might have been added:
		4025
		4026	static void
		4027	async_cb (EV_P_ ev_async *w, int revents)
		4028	{
		4029	// just used for the side effects
		4030	}
		4031
		4032	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4033	protecting the loop data, respectively.
		4034
		4035	static void
		4036	l_release (EV_P)
		4037	{
		4038	userdata *u = ev_userdata (EV_A);
		4039	pthread_mutex_unlock (&u->lock);
		4040	}
		4041
		4042	static void
		4043	l_acquire (EV_P)
		4044	{
		4045	userdata *u = ev_userdata (EV_A);
		4046	pthread_mutex_lock (&u->lock);
		4047	}
		4048
		4049	The event loop thread first acquires the mutex, and then jumps straight
		4050	into C<ev_loop>:
		4051
		4052	void *
		4053	l_run (void *thr_arg)
		4054	{
		4055	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4056
		4057	l_acquire (EV_A);
		4058	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4059	ev_loop (EV_A_ 0);
		4060	l_release (EV_A);
		4061
		4062	return 0;
		4063	}
		4064
		4065	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4066	signal the main thread via some unspecified mechanism (signals? pipe
		4067	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4068	have been called (in a while loop because a) spurious wakeups are possible
		4069	and b) skipping inter-thread-communication when there are no pending
		4070	watchers is very beneficial):
		4071
		4072	static void
		4073	l_invoke (EV_P)
		4074	{
		4075	userdata *u = ev_userdata (EV_A);
		4076
		4077	while (ev_pending_count (EV_A))
		4078	{
		4079	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4080	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4081	}
		4082	}
		4083
		4084	Now, whenever the main thread gets told to invoke pending watchers, it
		4085	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4086	thread to continue:
		4087
		4088	static void
		4089	real_invoke_pending (EV_P)
		4090	{
		4091	userdata *u = ev_userdata (EV_A);
		4092
		4093	pthread_mutex_lock (&u->lock);
		4094	ev_invoke_pending (EV_A);
		4095	pthread_cond_signal (&u->invoke_cv);
		4096	pthread_mutex_unlock (&u->lock);
		4097	}
		4098
		4099	Whenever you want to start/stop a watcher or do other modifications to an
		4100	event loop, you will now have to lock:
		4101
		4102	ev_timer timeout_watcher;
		4103	userdata *u = ev_userdata (EV_A);
		4104
		4105	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4106
		4107	pthread_mutex_lock (&u->lock);
		4108	ev_timer_start (EV_A_ &timeout_watcher);
		4109	ev_async_send (EV_A_ &u->async_w);
		4110	pthread_mutex_unlock (&u->lock);
		4111
		4112	Note that sending the C<ev_async> watcher is required because otherwise
		4113	an event loop currently blocking in the kernel will have no knowledge
		4114	about the newly added timer. By waking up the loop it will pick up any new
		4115	watchers in the next event loop iteration.
		4116
3108	=head2 COROUTINES	4117	=head3 COROUTINES
3109		4118
3110	Libev is much more accomodating to coroutines ("cooperative threads"):	4119	Libev is very accommodating to coroutines ("cooperative threads"):
3111	libev fully supports nesting calls to it's functions from different	4120	libev fully supports nesting calls to its functions from different
3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4121	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3113	different coroutines and switch freely between both coroutines running the	4122	different coroutines, and switch freely between both coroutines running
3114	loop, as long as you don't confuse yourself). The only exception is that	4123	the loop, as long as you don't confuse yourself). The only exception is
3115	you must not do this from C<ev_periodic> reschedule callbacks.	4124	that you must not do this from C<ev_periodic> reschedule callbacks.
3116		4125
3117	Care has been invested into making sure that libev does not keep local	4126	Care has been taken to ensure that libev does not keep local state inside
3118	state inside C<ev_loop>, and other calls do not usually allow coroutine	4127	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3119	switches.	4128	they do not call any callbacks.
3120		4129
		4130	=head2 COMPILER WARNINGS
3121		4131
3122	=head1 COMPLEXITIES	4132	Depending on your compiler and compiler settings, you might get no or a
		4133	lot of warnings when compiling libev code. Some people are apparently
		4134	scared by this.
3123		4135
3124	In this section the complexities of (many of) the algorithms used inside	4136	However, these are unavoidable for many reasons. For one, each compiler
3125	libev will be explained. For complexity discussions about backends see the	4137	has different warnings, and each user has different tastes regarding
3126	documentation for C<ev_default_init>.	4138	warning options. "Warn-free" code therefore cannot be a goal except when
		4139	targeting a specific compiler and compiler-version.
3127		4140
3128	All of the following are about amortised time: If an array needs to be	4141	Another reason is that some compiler warnings require elaborate
3129	extended, libev needs to realloc and move the whole array, but this	4142	workarounds, or other changes to the code that make it less clear and less
3130	happens asymptotically never with higher number of elements, so O(1) might	4143	maintainable.
3131	mean it might do a lengthy realloc operation in rare cases, but on average
3132	it is much faster and asymptotically approaches constant time.
3133		4144
3134	=over 4	4145	And of course, some compiler warnings are just plain stupid, or simply
		4146	wrong (because they don't actually warn about the condition their message
		4147	seems to warn about). For example, certain older gcc versions had some
		4148	warnings that resulted an extreme number of false positives. These have
		4149	been fixed, but some people still insist on making code warn-free with
		4150	such buggy versions.
3135		4151
3136	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4152	While libev is written to generate as few warnings as possible,
		4153	"warn-free" code is not a goal, and it is recommended not to build libev
		4154	with any compiler warnings enabled unless you are prepared to cope with
		4155	them (e.g. by ignoring them). Remember that warnings are just that:
		4156	warnings, not errors, or proof of bugs.
3137		4157
3138	This means that, when you have a watcher that triggers in one hour and
3139	there are 100 watchers that would trigger before that then inserting will
3140	have to skip roughly seven (C<ld 100>) of these watchers.
3141		4158
3142	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4159	=head2 VALGRIND
3143		4160
3144	That means that changing a timer costs less than removing/adding them	4161	Valgrind has a special section here because it is a popular tool that is
3145	as only the relative motion in the event queue has to be paid for.	4162	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3146		4163
3147	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4164	If you think you found a bug (memory leak, uninitialised data access etc.)
		4165	in libev, then check twice: If valgrind reports something like:
3148		4166
3149	These just add the watcher into an array or at the head of a list.	4167	==2274== definitely lost: 0 bytes in 0 blocks.
		4168	==2274== possibly lost: 0 bytes in 0 blocks.
		4169	==2274== still reachable: 256 bytes in 1 blocks.
3150		4170
3151	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4171	Then there is no memory leak, just as memory accounted to global variables
		4172	is not a memleak - the memory is still being referenced, and didn't leak.
3152		4173
3153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4174	Similarly, under some circumstances, valgrind might report kernel bugs
		4175	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4176	although an acceptable workaround has been found here), or it might be
		4177	confused.
3154		4178
3155	These watchers are stored in lists then need to be walked to find the	4179	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3156	correct watcher to remove. The lists are usually short (you don't usually	4180	make it into some kind of religion.
3157	have many watchers waiting for the same fd or signal).
3158		4181
3159	=item Finding the next timer in each loop iteration: O(1)	4182	If you are unsure about something, feel free to contact the mailing list
		4183	with the full valgrind report and an explanation on why you think this
		4184	is a bug in libev (best check the archives, too :). However, don't be
		4185	annoyed when you get a brisk "this is no bug" answer and take the chance
		4186	of learning how to interpret valgrind properly.
3160		4187
3161	By virtue of using a binary heap, the next timer is always found at the	4188	If you need, for some reason, empty reports from valgrind for your project
3162	beginning of the storage array.	4189	I suggest using suppression lists.
3163		4190
3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3165		4191
3166	A change means an I/O watcher gets started or stopped, which requires	4192	=head1 PORTABILITY NOTES
3167	libev to recalculate its status (and possibly tell the kernel, depending
3168	on backend and wether C<ev_io_set> was used).
3169		4193
3170	=item Activating one watcher (putting it into the pending state): O(1)	4194	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3171
3172	=item Priority handling: O(number_of_priorities)
3173
3174	Priorities are implemented by allocating some space for each
3175	priority. When doing priority-based operations, libev usually has to
3176	linearly search all the priorities, but starting/stopping and activating
3177	watchers becomes O(1) w.r.t. priority handling.
3178
3179	=item Sending an ev_async: O(1)
3180
3181	=item Processing ev_async_send: O(number_of_async_watchers)
3182
3183	=item Processing signals: O(max_signal_number)
3184
3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3186	calls in the current loop iteration. Checking for async and signal events
3187	involves iterating over all running async watchers or all signal numbers.
3188
3189	=back
3190
3191
3192	=head1 Win32 platform limitations and workarounds
3193		4195
3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4196	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3195	requires, and its I/O model is fundamentally incompatible with the POSIX	4197	requires, and its I/O model is fundamentally incompatible with the POSIX
3196	model. Libev still offers limited functionality on this platform in	4198	model. Libev still offers limited functionality on this platform in
3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3198	descriptors. This only applies when using Win32 natively, not when using	4200	descriptors. This only applies when using Win32 natively, not when using
3199	e.g. cygwin.	4201	e.g. cygwin.
3200		4202
		4203	Lifting these limitations would basically require the full
		4204	re-implementation of the I/O system. If you are into these kinds of
		4205	things, then note that glib does exactly that for you in a very portable
		4206	way (note also that glib is the slowest event library known to man).
		4207
3201	There is no supported compilation method available on windows except	4208	There is no supported compilation method available on windows except
3202	embedding it into other applications.	4209	embedding it into other applications.
3203		4210
		4211	Sensible signal handling is officially unsupported by Microsoft - libev
		4212	tries its best, but under most conditions, signals will simply not work.
		4213
		4214	Not a libev limitation but worth mentioning: windows apparently doesn't
		4215	accept large writes: instead of resulting in a partial write, windows will
		4216	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4217	so make sure you only write small amounts into your sockets (less than a
		4218	megabyte seems safe, but this apparently depends on the amount of memory
		4219	available).
		4220
3204	Due to the many, low, and arbitrary limits on the win32 platform and the	4221	Due to the many, low, and arbitrary limits on the win32 platform and
3205	abysmal performance of winsockets, using a large number of sockets is not	4222	the abysmal performance of winsockets, using a large number of sockets
3206	recommended (and not reasonable). If your program needs to use more than	4223	is not recommended (and not reasonable). If your program needs to use
3207	a hundred or so sockets, then likely it needs to use a totally different	4224	more than a hundred or so sockets, then likely it needs to use a totally
3208	implementation for windows, as libev offers the POSIX model, which cannot	4225	different implementation for windows, as libev offers the POSIX readiness
3209	be implemented efficiently on windows (microsoft monopoly games).	4226	notification model, which cannot be implemented efficiently on windows
		4227	(due to Microsoft monopoly games).
		4228
		4229	A typical way to use libev under windows is to embed it (see the embedding
		4230	section for details) and use the following F<evwrap.h> header file instead
		4231	of F<ev.h>:
		4232
		4233	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4234	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4235
		4236	#include "ev.h"
		4237
		4238	And compile the following F<evwrap.c> file into your project (make sure
		4239	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4240
		4241	#include "evwrap.h"
		4242	#include "ev.c"
3210		4243
3211	=over 4	4244	=over 4
3212		4245
3213	=item The winsocket select function	4246	=item The winsocket select function
3214		4247
3215	The winsocket C<select> function doesn't follow POSIX in that it requires	4248	The winsocket C<select> function doesn't follow POSIX in that it
3216	socket I<handles> and not socket I<file descriptors>. This makes select	4249	requires socket I<handles> and not socket I<file descriptors> (it is
3217	very inefficient, and also requires a mapping from file descriptors	4250	also extremely buggy). This makes select very inefficient, and also
3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4251	requires a mapping from file descriptors to socket handles (the Microsoft
3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4252	C runtime provides the function C<_open_osfhandle> for this). See the
3220	symbols for more info.	4253	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4254	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3221		4255
3222	The configuration for a "naked" win32 using the microsoft runtime	4256	The configuration for a "naked" win32 using the Microsoft runtime
3223	libraries and raw winsocket select is:	4257	libraries and raw winsocket select is:
3224		4258
3225	#define EV_USE_SELECT 1	4259	#define EV_USE_SELECT 1
3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4260	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3227		4261
3228	Note that winsockets handling of fd sets is O(n), so you can easily get a	4262	Note that winsockets handling of fd sets is O(n), so you can easily get a
3229	complexity in the O(n²) range when using win32.	4263	complexity in the O(n²) range when using win32.
3230		4264
3231	=item Limited number of file descriptors	4265	=item Limited number of file descriptors
3232		4266
3233	Windows has numerous arbitrary (and low) limits on things. Early versions	4267	Windows has numerous arbitrary (and low) limits on things.
3234	of winsocket's select only supported waiting for a max. of C<64> handles	4268
		4269	Early versions of winsocket's select only supported waiting for a maximum
3235	(probably owning to the fact that all windows kernels can only wait for	4270	of C<64> handles (probably owning to the fact that all windows kernels
3236	C<64> things at the same time internally; microsoft recommends spawning a	4271	can only wait for C<64> things at the same time internally; Microsoft
3237	chain of threads and wait for 63 handles and the previous thread in each).	4272	recommends spawning a chain of threads and wait for 63 handles and the
		4273	previous thread in each. Sounds great!).
3238		4274
3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4275	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3240	to some high number (e.g. C<2048>) before compiling the winsocket select	4276	to some high number (e.g. C<2048>) before compiling the winsocket select
3241	call (which might be in libev or elsewhere, for example, perl does its own	4277	call (which might be in libev or elsewhere, for example, perl and many
3242	select emulation on windows).	4278	other interpreters do their own select emulation on windows).
3243		4279
3244	Another limit is the number of file descriptors in the microsoft runtime	4280	Another limit is the number of file descriptors in the Microsoft runtime
3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4281	libraries, which by default is C<64> (there must be a hidden I<64>
3246	or something like this inside microsoft). You can increase this by calling	4282	fetish or something like this inside Microsoft). You can increase this
3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4283	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3248	arbitrary limit), but is broken in many versions of the microsoft runtime	4284	(another arbitrary limit), but is broken in many versions of the Microsoft
3249	libraries.
3250
3251	This might get you to about C<512> or C<2048> sockets (depending on	4285	runtime libraries. This might get you to about C<512> or C<2048> sockets
3252	windows version and/or the phase of the moon). To get more, you need to	4286	(depending on windows version and/or the phase of the moon). To get more,
3253	wrap all I/O functions and provide your own fd management, but the cost of	4287	you need to wrap all I/O functions and provide your own fd management, but
3254	calling select (O(n²)) will likely make this unworkable.	4288	the cost of calling select (O(n²)) will likely make this unworkable.
3255		4289
3256	=back	4290	=back
3257		4291
		4292	=head2 PORTABILITY REQUIREMENTS
		4293
		4294	In addition to a working ISO-C implementation and of course the
		4295	backend-specific APIs, libev relies on a few additional extensions:
		4296
		4297	=over 4
		4298
		4299	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4300	calling conventions regardless of C<ev_watcher_type *>.
		4301
		4302	Libev assumes not only that all watcher pointers have the same internal
		4303	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4304	assumes that the same (machine) code can be used to call any watcher
		4305	callback: The watcher callbacks have different type signatures, but libev
		4306	calls them using an C<ev_watcher *> internally.
		4307
		4308	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4309
		4310	The type C<sig_atomic_t volatile> (or whatever is defined as
		4311	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4312	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4313	believed to be sufficiently portable.
		4314
		4315	=item C<sigprocmask> must work in a threaded environment
		4316
		4317	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4318	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4319	pthread implementations will either allow C<sigprocmask> in the "main
		4320	thread" or will block signals process-wide, both behaviours would
		4321	be compatible with libev. Interaction between C<sigprocmask> and
		4322	C<pthread_sigmask> could complicate things, however.
		4323
		4324	The most portable way to handle signals is to block signals in all threads
		4325	except the initial one, and run the default loop in the initial thread as
		4326	well.
		4327
		4328	=item C<long> must be large enough for common memory allocation sizes
		4329
		4330	To improve portability and simplify its API, libev uses C<long> internally
		4331	instead of C<size_t> when allocating its data structures. On non-POSIX
		4332	systems (Microsoft...) this might be unexpectedly low, but is still at
		4333	least 31 bits everywhere, which is enough for hundreds of millions of
		4334	watchers.
		4335
		4336	=item C<double> must hold a time value in seconds with enough accuracy
		4337
		4338	The type C<double> is used to represent timestamps. It is required to
		4339	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4340	enough for at least into the year 4000. This requirement is fulfilled by
		4341	implementations implementing IEEE 754, which is basically all existing
		4342	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4343	2200.
		4344
		4345	=back
		4346
		4347	If you know of other additional requirements drop me a note.
		4348
		4349
		4350	=head1 ALGORITHMIC COMPLEXITIES
		4351
		4352	In this section the complexities of (many of) the algorithms used inside
		4353	libev will be documented. For complexity discussions about backends see
		4354	the documentation for C<ev_default_init>.
		4355
		4356	All of the following are about amortised time: If an array needs to be
		4357	extended, libev needs to realloc and move the whole array, but this
		4358	happens asymptotically rarer with higher number of elements, so O(1) might
		4359	mean that libev does a lengthy realloc operation in rare cases, but on
		4360	average it is much faster and asymptotically approaches constant time.
		4361
		4362	=over 4
		4363
		4364	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4365
		4366	This means that, when you have a watcher that triggers in one hour and
		4367	there are 100 watchers that would trigger before that, then inserting will
		4368	have to skip roughly seven (C<ld 100>) of these watchers.
		4369
		4370	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4371
		4372	That means that changing a timer costs less than removing/adding them,
		4373	as only the relative motion in the event queue has to be paid for.
		4374
		4375	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4376
		4377	These just add the watcher into an array or at the head of a list.
		4378
		4379	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4380
		4381	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4382
		4383	These watchers are stored in lists, so they need to be walked to find the
		4384	correct watcher to remove. The lists are usually short (you don't usually
		4385	have many watchers waiting for the same fd or signal: one is typical, two
		4386	is rare).
		4387
		4388	=item Finding the next timer in each loop iteration: O(1)
		4389
		4390	By virtue of using a binary or 4-heap, the next timer is always found at a
		4391	fixed position in the storage array.
		4392
		4393	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4394
		4395	A change means an I/O watcher gets started or stopped, which requires
		4396	libev to recalculate its status (and possibly tell the kernel, depending
		4397	on backend and whether C<ev_io_set> was used).
		4398
		4399	=item Activating one watcher (putting it into the pending state): O(1)
		4400
		4401	=item Priority handling: O(number_of_priorities)
		4402
		4403	Priorities are implemented by allocating some space for each
		4404	priority. When doing priority-based operations, libev usually has to
		4405	linearly search all the priorities, but starting/stopping and activating
		4406	watchers becomes O(1) with respect to priority handling.
		4407
		4408	=item Sending an ev_async: O(1)
		4409
		4410	=item Processing ev_async_send: O(number_of_async_watchers)
		4411
		4412	=item Processing signals: O(max_signal_number)
		4413
		4414	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4415	calls in the current loop iteration. Checking for async and signal events
		4416	involves iterating over all running async watchers or all signal numbers.
		4417
		4418	=back
		4419
		4420
		4421	=head1 GLOSSARY
		4422
		4423	=over 4
		4424
		4425	=item active
		4426
		4427	A watcher is active as long as it has been started (has been attached to
		4428	an event loop) but not yet stopped (disassociated from the event loop).
		4429
		4430	=item application
		4431
		4432	In this document, an application is whatever is using libev.
		4433
		4434	=item callback
		4435
		4436	The address of a function that is called when some event has been
		4437	detected. Callbacks are being passed the event loop, the watcher that
		4438	received the event, and the actual event bitset.
		4439
		4440	=item callback invocation
		4441
		4442	The act of calling the callback associated with a watcher.
		4443
		4444	=item event
		4445
		4446	A change of state of some external event, such as data now being available
		4447	for reading on a file descriptor, time having passed or simply not having
		4448	any other events happening anymore.
		4449
		4450	In libev, events are represented as single bits (such as C<EV_READ> or
		4451	C<EV_TIMEOUT>).
		4452
		4453	=item event library
		4454
		4455	A software package implementing an event model and loop.
		4456
		4457	=item event loop
		4458
		4459	An entity that handles and processes external events and converts them
		4460	into callback invocations.
		4461
		4462	=item event model
		4463
		4464	The model used to describe how an event loop handles and processes
		4465	watchers and events.
		4466
		4467	=item pending
		4468
		4469	A watcher is pending as soon as the corresponding event has been detected,
		4470	and stops being pending as soon as the watcher will be invoked or its
		4471	pending status is explicitly cleared by the application.
		4472
		4473	A watcher can be pending, but not active. Stopping a watcher also clears
		4474	its pending status.
		4475
		4476	=item real time
		4477
		4478	The physical time that is observed. It is apparently strictly monotonic :)
		4479
		4480	=item wall-clock time
		4481
		4482	The time and date as shown on clocks. Unlike real time, it can actually
		4483	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4484	clock.
		4485
		4486	=item watcher
		4487
		4488	A data structure that describes interest in certain events. Watchers need
		4489	to be started (attached to an event loop) before they can receive events.
		4490
		4491	=item watcher invocation
		4492
		4493	The act of calling the callback associated with a watcher.
		4494
		4495	=back
3258		4496
3259	=head1 AUTHOR	4497	=head1 AUTHOR
3260		4498
3261	Marc Lehmann <libev@schmorp.de>.	4499	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3262		4500

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