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Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC vs.
Revision 1.298 by sf-exg, Sat Jul 31 23:00:11 2010 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity 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
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practise
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
176	as this indicates an incompatible change. Minor versions are usually	192	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	193	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	194	not a problem.
179		195
180	Example: Make sure we haven't accidentally been linked against the wrong	196	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	197	version (note, however, that this will not detect ABI mismatches :).
182		198
183	assert (("libev version mismatch",	199	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	200	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	201	&& ev_version_minor () >= EV_VERSION_MINOR));
186		202
187	=item unsigned int ev_supported_backends ()	203	=item unsigned int ev_supported_backends ()
188		204
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	205	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	206	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	208	a description of the set values.
193		209
194	Example: make sure we have the epoll method, because yeah this is cool and	210	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	211	a must have and can we have a torrent of it please!!!11
196		212
197	assert (("sorry, no epoll, no sex",	213	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	214	ev_supported_backends () & EVBACKEND_EPOLL));
199		215
200	=item unsigned int ev_recommended_backends ()	216	=item unsigned int ev_recommended_backends ()
201		217
202	Return the set of all backends compiled into this binary of libev and also	218	Return the set of all backends compiled into this binary of libev and also
203	recommended for this platform. This set is often smaller than the one	219	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	231	recommended ones.
216		232
217	See the description of C<ev_embed> watchers for more info.	233	See the description of C<ev_embed> watchers for more info.
218		234
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		236
221	Sets the allocation function to use (the prototype is similar - the	237	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	239	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	240	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	266	}
251		267
252	...	268	...
253	ev_set_allocator (persistent_realloc);	269	ev_set_allocator (persistent_realloc);
254		270
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		272
257	Set the callback function to call on a retryable system call error (such	273	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	274	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	275	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	276	callback is set, then libev will expect it to remedy the situation, no
…		…
276		292
277	=back	293	=back
278		294
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		296
281	An event loop is described by a C<struct ev_loop *>. The library knows two	297	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	298	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	299	I<function>).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created loops which do
		303	not.
284		304
285	=over 4	305	=over 4
286		306
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		308
…		…
294	If you don't know what event loop to use, use the one returned from this	314	If you don't know what event loop to use, use the one returned from this
295	function.	315	function.
296		316
297	Note that this function is I<not> thread-safe, so if you want to use it	317	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	318	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
300		320
301	The default loop is the only loop that can handle C<ev_signal> and	321	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	322	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	323	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
326	useful to try out specific backends to test their performance, or to work	346	useful to try out specific backends to test their performance, or to work
327	around bugs.	347	around bugs.
328		348
329	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
330		350
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	351	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	352	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		353
335	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	398	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	399	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	400	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	401	readiness notifications you get per iteration.
363		402
		403	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		404	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		405	C<exceptfds> set on that platform).
		406
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	407	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		408
366	And this is your standard poll(2) backend. It's more complicated	409	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	410	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	411	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	412	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	413	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	414	performance tips.
372		415
		416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		418
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
374		423
375	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	427	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	428
380	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
382		445
383	While stopping, setting and starting an I/O watcher in the same iteration	446	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	447	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	448	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
388		451	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		452
393	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	454	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	455	i.e. keep at least one watcher active per fd at all times. Stopping and
		456	starting a watcher (without re-setting it) also usually doesn't cause
		457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
396		464
397	While nominally embeddable in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	466	all kernel versions tested so far.
		467
		468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		469	C<EVBACKEND_POLL>.
399		470
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		472
402	Kqueue deserves special mention, as at the time of this writing, it	473	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	474	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	475	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	476	it's completely useless). Unlike epoll, however, whose brokenness
		477	is by design, these kqueue bugs can (and eventually will) be fixed
		478	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	481	system like NetBSD.
409		482
410	You still can embed kqueue into a normal poll or select backend and use it	483	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	484	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		486
414	It scales in the same way as the epoll backend, but the interface to the	487	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	488	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	489	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	491	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
420		494
421	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
422		496
423	While nominally embeddable in other event loops, this doesn't work	497	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	498	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	499	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	500	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
		503
		504	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		506	C<NOTE_EOF>.
429		507
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	508	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		509
432	This is not implemented yet (and might never be, unless you send me an	510	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	511	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	524	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	525	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	527	might perform better.
450		528
451	On the positive side, ignoring the spurious readiness notifications, this	529	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	530	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	531	in all tests and is fully embeddable, which is a rare feat among the
		532	OS-specific backends (I vastly prefer correctness over speed hacks).
		533
		534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		535	C<EVBACKEND_POLL>.
454		536
455	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
456		538
457	Try all backends (even potentially broken ones that wouldn't be tried	539	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		542
461	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
462		544
463	=back	545	=back
464		546
465	If one or more of these are or'ed into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
468		551
469	The most typical usage is like this:	552	Example: This is the most typical usage.
470		553
471	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		556
474	Restrict libev to the select and poll backends, and do not allow	557	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	558	environment settings to be taken into account:
476		559
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		561
479	Use whatever libev has to offer, but make sure that kqueue is used if	562	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	563	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	564	private event loop and only if you know the OS supports your types of
		565	fds):
482		566
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		568
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	569	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		570
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	571	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot	572	always distinct from the default loop.
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491		573
492	Note that this function I<is> thread-safe, and the recommended way to use	574	Note that this function I<is> thread-safe, and one common way to use
493	libev with threads is indeed to create one loop per thread, and using the	575	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	576	default loop in the "main" or "initial" thread.
495		577
496	Example: Try to create a event loop that uses epoll and nothing else.	578	Example: Try to create a event loop that uses epoll and nothing else.
497		579
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	581	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	582	fatal ("no epoll found here, maybe it hides under your chair");
501		583
502	=item ev_default_destroy ()	584	=item ev_default_destroy ()
503		585
504	Destroys the default loop again (frees all memory and kernel state	586	Destroys the default loop (frees all memory and kernel state etc.). None
505	etc.). None of the active event watchers will be stopped in the normal	587	of the active event watchers will be stopped in the normal sense, so
506	sense, so e.g. C<ev_is_active> might still return true. It is your	588	e.g. C<ev_is_active> might still return true. It is your responsibility to
507	responsibility to either stop all watchers cleanly yourself I<before>	589	either stop all watchers cleanly yourself I<before> calling this function,
508	calling this function, or cope with the fact afterwards (which is usually	590	or cope with the fact afterwards (which is usually the easiest thing, you
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	591	can just ignore the watchers and/or C<free ()> them for example).
510	for example).
511		592
512	Note that certain global state, such as signal state, will not be freed by	593	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	594	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	595	as signal and child watchers) would need to be stopped manually.
515		596
516	In general it is not advisable to call this function except in the	597	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	598	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	599	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	600	C<ev_loop_new> and C<ev_loop_destroy>.
520		601
521	=item ev_loop_destroy (loop)	602	=item ev_loop_destroy (loop)
522		603
523	Like C<ev_default_destroy>, but destroys an event loop created by an	604	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.	605	earlier call to C<ev_loop_new>.
…		…
530	name, you can call it anytime, but it makes most sense after forking, in	611	name, you can call it anytime, but it makes most sense after forking, in
531	the child process (or both child and parent, but that again makes little	612	the child process (or both child and parent, but that again makes little
532	sense). You I<must> call it in the child before using any of the libev	613	sense). You I<must> call it in the child before using any of the libev
533	functions, and it will only take effect at the next C<ev_loop> iteration.	614	functions, and it will only take effect at the next C<ev_loop> iteration.
534		615
		616	Again, you I<have> to call it on I<any> loop that you want to re-use after
		617	a fork, I<even if you do not plan to use the loop in the parent>. This is
		618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		619	during fork.
		620
535	On the other hand, you only need to call this function in the child	621	On the other hand, you only need to call this function in the child
536	process if and only if you want to use the event library in the child. If	622	process if and only if you want to use the event loop in the child. If you
537	you just fork+exec, you don't have to call it at all.	623	just fork+exec or create a new loop in the child, you don't have to call
		624	it at all.
538		625
539	The function itself is quite fast and it's usually not a problem to call	626	The function itself is quite fast and it's usually not a problem to call
540	it just in case after a fork. To make this easy, the function will fit in	627	it just in case after a fork. To make this easy, the function will fit in
541	quite nicely into a call to C<pthread_atfork>:	628	quite nicely into a call to C<pthread_atfork>:
542		629
…		…
544		631
545	=item ev_loop_fork (loop)	632	=item ev_loop_fork (loop)
546		633
547	Like C<ev_default_fork>, but acts on an event loop created by	634	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	636	after fork that you want to re-use in the child, and how you keep track of
		637	them is entirely your own problem.
550		638
551	=item int ev_is_default_loop (loop)	639	=item int ev_is_default_loop (loop)
552		640
553	Returns true when the given loop actually is the default loop, false otherwise.	641	Returns true when the given loop is, in fact, the default loop, and false
		642	otherwise.
554		643
555	=item unsigned int ev_loop_count (loop)	644	=item unsigned int ev_iteration (loop)
556		645
557	Returns the count of loop iterations for the loop, which is identical to	646	Returns the current iteration count for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	647	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	648	happily wraps around with enough iterations.
560		649
561	This value can sometimes be useful as a generation counter of sorts (it	650	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	651	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	652	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		653	prepare and check phases.
		654
		655	=item unsigned int ev_depth (loop)
		656
		657	Returns the number of times C<ev_loop> was entered minus the number of
		658	times C<ev_loop> was exited, in other words, the recursion depth.
		659
		660	Outside C<ev_loop>, this number is zero. In a callback, this number is
		661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		662	in which case it is higher.
		663
		664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		665	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		666	ungentleman behaviour unless it's really convenient.
564		667
565	=item unsigned int ev_backend (loop)	668	=item unsigned int ev_backend (loop)
566		669
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	671	use.
…		…
573	received events and started processing them. This timestamp does not	676	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	677	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	678	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	679	event occurring (or more correctly, libev finding out about it).
577		680
		681	=item ev_now_update (loop)
		682
		683	Establishes the current time by querying the kernel, updating the time
		684	returned by C<ev_now ()> in the progress. This is a costly operation and
		685	is usually done automatically within C<ev_loop ()>.
		686
		687	This function is rarely useful, but when some event callback runs for a
		688	very long time without entering the event loop, updating libev's idea of
		689	the current time is a good idea.
		690
		691	See also L<The special problem of time updates> in the C<ev_timer> section.
		692
		693	=item ev_suspend (loop)
		694
		695	=item ev_resume (loop)
		696
		697	These two functions suspend and resume a loop, for use when the loop is
		698	not used for a while and timeouts should not be processed.
		699
		700	A typical use case would be an interactive program such as a game: When
		701	the user presses C<^Z> to suspend the game and resumes it an hour later it
		702	would be best to handle timeouts as if no time had actually passed while
		703	the program was suspended. This can be achieved by calling C<ev_suspend>
		704	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		705	C<ev_resume> directly afterwards to resume timer processing.
		706
		707	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		709	will be rescheduled (that is, they will lose any events that would have
		710	occurred while suspended).
		711
		712	After calling C<ev_suspend> you B<must not> call I<any> function on the
		713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		714	without a previous call to C<ev_suspend>.
		715
		716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		717	event loop time (see C<ev_now_update>).
		718
578	=item ev_loop (loop, int flags)	719	=item ev_loop (loop, int flags)
579		720
580	Finally, this is it, the event handler. This function usually is called	721	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	722	after you have initialised all your watchers and you want to start
582	events.	723	handling events.
583		724
584	If the flags argument is specified as C<0>, it will not return until	725	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	726	either no event watchers are active anymore or C<ev_unloop> was called.
586		727
587	Please note that an explicit C<ev_unloop> is usually better than	728	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	729	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	730	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	731	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	732	of relying on its watchers stopping correctly, that is truly a thing of
		733	beauty.
592		734
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	736	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	737	process in case there are no events and will return after one iteration of
		738	the loop.
596		739
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	741	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	742	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	743	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	744	user-registered callback will be called), and will return after one
		745	iteration of the loop.
		746
		747	This is useful if you are waiting for some external event in conjunction
		748	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	750	usually a better approach for this kind of thing.
604		751
605	Here are the gory details of what C<ev_loop> does:	752	Here are the gory details of what C<ev_loop> does:
606		753
607	- Before the first iteration, call any pending watchers.	754	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	755	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	756	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	757	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	758	- If we have been forked, detach and recreate the kernel state
		759	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	760	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	761	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	762	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	763	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	764	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	765	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	766	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	767	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	769	- Queue all expired timers.
622	- Queue all outstanding periodics.	770	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	771	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	772	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	773	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	774	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	775	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	781	anymore.
634		782
635	... queue jobs here, make sure they register event watchers as long	783	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	784	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	785	ev_loop (my_loop, 0);
638	... jobs done. yeah!	786	... jobs done or somebody called unloop. yeah!
639		787
640	=item ev_unloop (loop, how)	788	=item ev_unloop (loop, how)
641		789
642	Can be used to make a call to C<ev_loop> return early (but only after it	790	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	791	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		794
647	This "unloop state" will be cleared when entering C<ev_loop> again.	795	This "unloop state" will be cleared when entering C<ev_loop> again.
648		796
		797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
		798
649	=item ev_ref (loop)	799	=item ev_ref (loop)
650		800
651	=item ev_unref (loop)	801	=item ev_unref (loop)
652		802
653	Ref/unref can be used to add or remove a reference count on the event	803	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	804	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	805	count is nonzero, C<ev_loop> will not return on its own.
656	a watcher you never unregister that should not keep C<ev_loop> from	806
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	807	This is useful when you have a watcher that you never intend to
		808	unregister, but that nevertheless should not keep C<ev_loop> from
		809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		810	before stopping it.
		811
658	example, libev itself uses this for its internal signal pipe: It is not	812	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	813	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	814	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	815	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	816	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	817	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	818	before, respectively. Note also that libev might stop watchers itself
		819	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		820	in the callback).
665		821
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	823	running when nothing else is active.
668		824
669	struct ev_signal exitsig;	825	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	826	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	827	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	828	evf_unref (loop);
673		829
674	Example: For some weird reason, unregister the above signal handler again.	830	Example: For some weird reason, unregister the above signal handler again.
675		831
676	ev_ref (loop);	832	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	833	ev_signal_stop (loop, &exitsig);
678		834
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	835	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		836
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	837	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		838
683	These advanced functions influence the time that libev will spend waiting	839	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	840	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	841	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		842	latency.
686		843
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	844	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	845	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	846	to increase efficiency of loop iterations (or to increase power-saving
		847	opportunities).
690		848
691	The background is that sometimes your program runs just fast enough to	849	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	850	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	851	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	852	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	853	overhead for the actual polling but can deliver many events at once.
696		854
697	By setting a higher I<io collect interval> you allow libev to spend more	855	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	856	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	858	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	859	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		860	sleep time ensures that libev will not poll for I/O events more often then
		861	once per this interval, on average.
702		862
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	863	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	864	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	865	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	866	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	867	value will not introduce any overhead in libev.
708		868
709	Many (busy) programs can usually benefit by setting the I/O collect	869	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	870	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	871	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	872	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	873	as this approaches the timing granularity of most systems. Note that if
		874	you do transactions with the outside world and you can't increase the
		875	parallelity, then this setting will limit your transaction rate (if you
		876	need to poll once per transaction and the I/O collect interval is 0.01,
		877	then you can't do more than 100 transactions per second).
		878
		879	Setting the I<timeout collect interval> can improve the opportunity for
		880	saving power, as the program will "bundle" timer callback invocations that
		881	are "near" in time together, by delaying some, thus reducing the number of
		882	times the process sleeps and wakes up again. Another useful technique to
		883	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		884	they fire on, say, one-second boundaries only.
		885
		886	Example: we only need 0.1s timeout granularity, and we wish not to poll
		887	more often than 100 times per second:
		888
		889	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		891
		892	=item ev_invoke_pending (loop)
		893
		894	This call will simply invoke all pending watchers while resetting their
		895	pending state. Normally, C<ev_loop> does this automatically when required,
		896	but when overriding the invoke callback this call comes handy.
		897
		898	=item int ev_pending_count (loop)
		899
		900	Returns the number of pending watchers - zero indicates that no watchers
		901	are pending.
		902
		903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		904
		905	This overrides the invoke pending functionality of the loop: Instead of
		906	invoking all pending watchers when there are any, C<ev_loop> will call
		907	this callback instead. This is useful, for example, when you want to
		908	invoke the actual watchers inside another context (another thread etc.).
		909
		910	If you want to reset the callback, use C<ev_invoke_pending> as new
		911	callback.
		912
		913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		914
		915	Sometimes you want to share the same loop between multiple threads. This
		916	can be done relatively simply by putting mutex_lock/unlock calls around
		917	each call to a libev function.
		918
		919	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		920	wait for it to return. One way around this is to wake up the loop via
		921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		922	and I<acquire> callbacks on the loop.
		923
		924	When set, then C<release> will be called just before the thread is
		925	suspended waiting for new events, and C<acquire> is called just
		926	afterwards.
		927
		928	Ideally, C<release> will just call your mutex_unlock function, and
		929	C<acquire> will just call the mutex_lock function again.
		930
		931	While event loop modifications are allowed between invocations of
		932	C<release> and C<acquire> (that's their only purpose after all), no
		933	modifications done will affect the event loop, i.e. adding watchers will
		934	have no effect on the set of file descriptors being watched, or the time
		935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		936	to take note of any changes you made.
		937
		938	In theory, threads executing C<ev_loop> will be async-cancel safe between
		939	invocations of C<release> and C<acquire>.
		940
		941	See also the locking example in the C<THREADS> section later in this
		942	document.
		943
		944	=item ev_set_userdata (loop, void *data)
		945
		946	=item ev_userdata (loop)
		947
		948	Set and retrieve a single C<void *> associated with a loop. When
		949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		950	C<0.>
		951
		952	These two functions can be used to associate arbitrary data with a loop,
		953	and are intended solely for the C<invoke_pending_cb>, C<release> and
		954	C<acquire> callbacks described above, but of course can be (ab-)used for
		955	any other purpose as well.
714		956
715	=item ev_loop_verify (loop)	957	=item ev_loop_verify (loop)
716		958
717	This function only does something when C<EV_VERIFY> support has been	959	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	960	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	961	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	962	is found to be inconsistent, it will print an error message to standard
		963	error and call C<abort ()>.
721		964
722	This can be used to catch bugs inside libev itself: under normal	965	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	966	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	967	data structures consistent.
725		968
726	=back	969	=back
727		970
728		971
729	=head1 ANATOMY OF A WATCHER	972	=head1 ANATOMY OF A WATCHER
730		973
		974	In the following description, uppercase C<TYPE> in names stands for the
		975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		976	watchers and C<ev_io_start> for I/O watchers.
		977
731	A watcher is a structure that you create and register to record your	978	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	979	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	980	become readable, you would create an C<ev_io> watcher for that:
734		981
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	983	{
737	ev_io_stop (w);	984	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	985	ev_unloop (loop, EVUNLOOP_ALL);
739	}	986	}
740		987
741	struct ev_loop *loop = ev_default_loop (0);	988	struct ev_loop *loop = ev_default_loop (0);
		989
742	struct ev_io stdin_watcher;	990	ev_io stdin_watcher;
		991
743	ev_init (&stdin_watcher, my_cb);	992	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	994	ev_io_start (loop, &stdin_watcher);
		995
746	ev_loop (loop, 0);	996	ev_loop (loop, 0);
747		997
748	As you can see, you are responsible for allocating the memory for your	998	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	999	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	1000	stack).
		1001
		1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		1004
752	Each watcher structure must be initialised by a call to C<ev_init	1005	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	1006	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	1007	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	1008	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	1009	is readable and/or writable).
757		1010
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1012	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1013	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1014	ev_TYPE_init (watcher *, callback, ...) >>.
762		1015
763	To make the watcher actually watch out for events, you have to start it	1016	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1017	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1018	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1019	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1020
768	As long as your watcher is active (has been started but not stopped) you	1021	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1022	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1023	reinitialise it or call its C<ev_TYPE_set> macro.
771		1024
772	Each and every callback receives the event loop pointer as first, the	1025	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1026	registered watcher structure as second, and a bitset of received events as
774	third argument.	1027	third argument.
775		1028
…		…
784	=item C<EV_WRITE>	1037	=item C<EV_WRITE>
785		1038
786	The file descriptor in the C<ev_io> watcher has become readable and/or	1039	The file descriptor in the C<ev_io> watcher has become readable and/or
787	writable.	1040	writable.
788		1041
789	=item C<EV_TIMEOUT>	1042	=item C<EV_TIMER>
790		1043
791	The C<ev_timer> watcher has timed out.	1044	The C<ev_timer> watcher has timed out.
792		1045
793	=item C<EV_PERIODIC>	1046	=item C<EV_PERIODIC>
794		1047
…		…
833		1086
834	=item C<EV_ASYNC>	1087	=item C<EV_ASYNC>
835		1088
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1089	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1090
		1091	=item C<EV_CUSTOM>
		1092
		1093	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1094	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1095
838	=item C<EV_ERROR>	1096	=item C<EV_ERROR>
839		1097
840	An unspecified error has occurred, the watcher has been stopped. This might	1098	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1099	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1100	ran out of memory, a file descriptor was found to be closed or any other
		1101	problem. Libev considers these application bugs.
		1102
843	problem. You best act on it by reporting the problem and somehow coping	1103	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1104	watcher being stopped. Note that well-written programs should not receive
		1105	an error ever, so when your watcher receives it, this usually indicates a
		1106	bug in your program.
845		1107
846	Libev will usually signal a few "dummy" events together with an error,	1108	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1109	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1110	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1111	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1112	programs, though, as the fd could already be closed and reused for another
		1113	thing, so beware.
851		1114
852	=back	1115	=back
853		1116
854	=head2 GENERIC WATCHER FUNCTIONS	1117	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1118
859	=over 4	1119	=over 4
860		1120
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1121	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1122
…		…
868	which rolls both calls into one.	1128	which rolls both calls into one.
869		1129
870	You can reinitialise a watcher at any time as long as it has been stopped	1130	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1131	(or never started) and there are no pending events outstanding.
872		1132
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1133	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1134	int revents)>.
875		1135
		1136	Example: Initialise an C<ev_io> watcher in two steps.
		1137
		1138	ev_io w;
		1139	ev_init (&w, my_cb);
		1140	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1141
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1142	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
877		1143
878	This macro initialises the type-specific parts of a watcher. You need to	1144	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1145	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	1146	call C<ev_TYPE_set> any number of times. You must not, however, call this
881	macro on a watcher that is active (it can be pending, however, which is a	1147	macro on a watcher that is active (it can be pending, however, which is a
882	difference to the C<ev_init> macro).	1148	difference to the C<ev_init> macro).
883		1149
884	Although some watcher types do not have type-specific arguments	1150	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1151	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1152
		1153	See C<ev_init>, above, for an example.
		1154
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1155	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1156
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1157	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1158	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1159	a watcher. The same limitations apply, of course.
892		1160
		1161	Example: Initialise and set an C<ev_io> watcher in one step.
		1162
		1163	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1164
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
894		1166
895	Starts (activates) the given watcher. Only active watchers will receive	1167	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1168	events. If the watcher is already active nothing will happen.
897		1169
		1170	Example: Start the C<ev_io> watcher that is being abused as example in this
		1171	whole section.
		1172
		1173	ev_io_start (EV_DEFAULT_UC, &w);
		1174
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1175	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
899		1176
900	Stops the given watcher again (if active) and clears the pending	1177	Stops the given watcher if active, and clears the pending status (whether
		1178	the watcher was active or not).
		1179
901	status. It is possible that stopped watchers are pending (for example,	1180	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1181	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1182	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1183	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1184	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1185
907	=item bool ev_is_active (ev_TYPE *watcher)	1186	=item bool ev_is_active (ev_TYPE *watcher)
908		1187
909	Returns a true value iff the watcher is active (i.e. it has been started	1188	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1189	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926	=item ev_cb_set (ev_TYPE *watcher, callback)	1205	=item ev_cb_set (ev_TYPE *watcher, callback)
927		1206
928	Change the callback. You can change the callback at virtually any time	1207	Change the callback. You can change the callback at virtually any time
929	(modulo threads).	1208	(modulo threads).
930		1209
931	=item ev_set_priority (ev_TYPE *watcher, priority)	1210	=item ev_set_priority (ev_TYPE *watcher, int priority)
932		1211
933	=item int ev_priority (ev_TYPE *watcher)	1212	=item int ev_priority (ev_TYPE *watcher)
934		1213
935	Set and query the priority of the watcher. The priority is a small	1214	Set and query the priority of the watcher. The priority is a small
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1215	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1216	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1217	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1218	from being executed (except for C<ev_idle> watchers).
940		1219
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1220	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1221	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1222
949	You I<must not> change the priority of a watcher as long as it is active or	1223	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1224	pending.
951		1225
		1226	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1227	fine, as long as you do not mind that the priority value you query might
		1228	or might not have been clamped to the valid range.
		1229
952	The default priority used by watchers when no priority has been set is	1230	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1231	always C<0>, which is supposed to not be too high and not be too low :).
954		1232
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1234	priorities.
957	or might not have been adjusted to be within valid range.
958		1235
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1237
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1239	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1240	can deal with that fact, as both are simply passed through to the
		1241	callback.
964		1242
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1243	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1244
967	If the watcher is pending, this function returns clears its pending status	1245	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1246	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1247	watcher isn't pending it does nothing and returns C<0>.
970		1248
		1249	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1250	callback to be invoked, which can be accomplished with this function.
		1251
		1252	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1253
		1254	Feeds the given event set into the event loop, as if the specified event
		1255	had happened for the specified watcher (which must be a pointer to an
		1256	initialised but not necessarily started event watcher). Obviously you must
		1257	not free the watcher as long as it has pending events.
		1258
		1259	Stopping the watcher, letting libev invoke it, or calling
		1260	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1261	not started in the first place.
		1262
		1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1264	functions that do not need a watcher.
		1265
971	=back	1266	=back
972		1267
973		1268
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1270
976	Each watcher has, by default, a member C<void *data> that you can change	1271	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1272	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1273	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1274	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1275	member, you can also "subclass" the watcher type and provide your own
981	data:	1276	data:
982		1277
983	struct my_io	1278	struct my_io
984	{	1279	{
985	struct ev_io io;	1280	ev_io io;
986	int otherfd;	1281	int otherfd;
987	void *somedata;	1282	void *somedata;
988	struct whatever *mostinteresting;	1283	struct whatever *mostinteresting;
989	}	1284	};
		1285
		1286	...
		1287	struct my_io w;
		1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1289
991	And since your callback will be called with a pointer to the watcher, you	1290	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1291	can cast it back to your own type:
993		1292
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1294	{
996	struct my_io *w = (struct my_io *)w_;	1295	struct my_io *w = (struct my_io *)w_;
997	...	1296	...
998	}	1297	}
999		1298
1000	More interesting and less C-conformant ways of casting your callback type	1299	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1300	instead have been omitted.
1002		1301
1003	Another common scenario is having some data structure with multiple	1302	Another common scenario is to use some data structure with multiple
1004	watchers:	1303	embedded watchers:
1005		1304
1006	struct my_biggy	1305	struct my_biggy
1007	{	1306	{
1008	int some_data;	1307	int some_data;
1009	ev_timer t1;	1308	ev_timer t1;
1010	ev_timer t2;	1309	ev_timer t2;
1011	}	1310	}
1012		1311
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1312	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1313	complicated: Either you store the address of your C<my_biggy> struct
		1314	in the C<data> member of the watcher (for woozies), or you need to use
		1315	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1316	programmers):
1015		1317
1016	#include <stddef.h>	1318	#include <stddef.h>
1017		1319
1018	static void	1320	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1321	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1322	{
1021	struct my_biggy big = (struct my_biggy *	1323	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1324	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1325	}
1024		1326
1025	static void	1327	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1328	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1329	{
1028	struct my_biggy big = (struct my_biggy *	1330	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1331	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1332	}
		1333
		1334	=head2 WATCHER PRIORITY MODELS
		1335
		1336	Many event loops support I<watcher priorities>, which are usually small
		1337	integers that influence the ordering of event callback invocation
		1338	between watchers in some way, all else being equal.
		1339
		1340	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1341	description for the more technical details such as the actual priority
		1342	range.
		1343
		1344	There are two common ways how these these priorities are being interpreted
		1345	by event loops:
		1346
		1347	In the more common lock-out model, higher priorities "lock out" invocation
		1348	of lower priority watchers, which means as long as higher priority
		1349	watchers receive events, lower priority watchers are not being invoked.
		1350
		1351	The less common only-for-ordering model uses priorities solely to order
		1352	callback invocation within a single event loop iteration: Higher priority
		1353	watchers are invoked before lower priority ones, but they all get invoked
		1354	before polling for new events.
		1355
		1356	Libev uses the second (only-for-ordering) model for all its watchers
		1357	except for idle watchers (which use the lock-out model).
		1358
		1359	The rationale behind this is that implementing the lock-out model for
		1360	watchers is not well supported by most kernel interfaces, and most event
		1361	libraries will just poll for the same events again and again as long as
		1362	their callbacks have not been executed, which is very inefficient in the
		1363	common case of one high-priority watcher locking out a mass of lower
		1364	priority ones.
		1365
		1366	Static (ordering) priorities are most useful when you have two or more
		1367	watchers handling the same resource: a typical usage example is having an
		1368	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1369	timeouts. Under load, data might be received while the program handles
		1370	other jobs, but since timers normally get invoked first, the timeout
		1371	handler will be executed before checking for data. In that case, giving
		1372	the timer a lower priority than the I/O watcher ensures that I/O will be
		1373	handled first even under adverse conditions (which is usually, but not
		1374	always, what you want).
		1375
		1376	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1377	will only be executed when no same or higher priority watchers have
		1378	received events, they can be used to implement the "lock-out" model when
		1379	required.
		1380
		1381	For example, to emulate how many other event libraries handle priorities,
		1382	you can associate an C<ev_idle> watcher to each such watcher, and in
		1383	the normal watcher callback, you just start the idle watcher. The real
		1384	processing is done in the idle watcher callback. This causes libev to
		1385	continuously poll and process kernel event data for the watcher, but when
		1386	the lock-out case is known to be rare (which in turn is rare :), this is
		1387	workable.
		1388
		1389	Usually, however, the lock-out model implemented that way will perform
		1390	miserably under the type of load it was designed to handle. In that case,
		1391	it might be preferable to stop the real watcher before starting the
		1392	idle watcher, so the kernel will not have to process the event in case
		1393	the actual processing will be delayed for considerable time.
		1394
		1395	Here is an example of an I/O watcher that should run at a strictly lower
		1396	priority than the default, and which should only process data when no
		1397	other events are pending:
		1398
		1399	ev_idle idle; // actual processing watcher
		1400	ev_io io; // actual event watcher
		1401
		1402	static void
		1403	io_cb (EV_P_ ev_io *w, int revents)
		1404	{
		1405	// stop the I/O watcher, we received the event, but
		1406	// are not yet ready to handle it.
		1407	ev_io_stop (EV_A_ w);
		1408
		1409	// start the idle watcher to handle the actual event.
		1410	// it will not be executed as long as other watchers
		1411	// with the default priority are receiving events.
		1412	ev_idle_start (EV_A_ &idle);
		1413	}
		1414
		1415	static void
		1416	idle_cb (EV_P_ ev_idle *w, int revents)
		1417	{
		1418	// actual processing
		1419	read (STDIN_FILENO, ...);
		1420
		1421	// have to start the I/O watcher again, as
		1422	// we have handled the event
		1423	ev_io_start (EV_P_ &io);
		1424	}
		1425
		1426	// initialisation
		1427	ev_idle_init (&idle, idle_cb);
		1428	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1429	ev_io_start (EV_DEFAULT_ &io);
		1430
		1431	In the "real" world, it might also be beneficial to start a timer, so that
		1432	low-priority connections can not be locked out forever under load. This
		1433	enables your program to keep a lower latency for important connections
		1434	during short periods of high load, while not completely locking out less
		1435	important ones.
1031		1436
1032		1437
1033	=head1 WATCHER TYPES	1438	=head1 WATCHER TYPES
1034		1439
1035	This section describes each watcher in detail, but will not repeat	1440	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1464	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1465	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1466	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1467	required if you know what you are doing).
1063		1468
1064	If you must do this, then force the use of a known-to-be-good backend	1469	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1470	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1472	descriptors for which non-blocking operation makes no sense (such as
		1473	files) - libev doesn't guarantee any specific behaviour in that case.
1067		1474
1068	Another thing you have to watch out for is that it is quite easy to	1475	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1476	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1478	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1479	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1480	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1483
1077	If you cannot run the fd in non-blocking mode (for example you should not	1484	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1485	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1486	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1487	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1488	does this on its own, so its quite safe to use). Some people additionally
		1489	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1490	indefinitely.
		1491
		1492	But really, best use non-blocking mode.
1082		1493
1083	=head3 The special problem of disappearing file descriptors	1494	=head3 The special problem of disappearing file descriptors
1084		1495
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1496	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1497	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1498	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1499	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1500	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1501	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1502	fact, a different file descriptor.
1092		1503
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1535	C<EVBACKEND_POLL>.
1125		1536
1126	=head3 The special problem of SIGPIPE	1537	=head3 The special problem of SIGPIPE
1127		1538
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1540	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1541	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1542	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1543
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1544	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1545	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1546	somewhere, as that would have given you a big clue).
1137		1547
		1548	=head3 The special problem of accept()ing when you can't
		1549
		1550	Many implementations of the POSIX C<accept> function (for example,
		1551	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1552	connection from the pending queue in all error cases.
		1553
		1554	For example, larger servers often run out of file descriptors (because
		1555	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1556	rejecting the connection, leading to libev signalling readiness on
		1557	the next iteration again (the connection still exists after all), and
		1558	typically causing the program to loop at 100% CPU usage.
		1559
		1560	Unfortunately, the set of errors that cause this issue differs between
		1561	operating systems, there is usually little the app can do to remedy the
		1562	situation, and no known thread-safe method of removing the connection to
		1563	cope with overload is known (to me).
		1564
		1565	One of the easiest ways to handle this situation is to just ignore it
		1566	- when the program encounters an overload, it will just loop until the
		1567	situation is over. While this is a form of busy waiting, no OS offers an
		1568	event-based way to handle this situation, so it's the best one can do.
		1569
		1570	A better way to handle the situation is to log any errors other than
		1571	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1572	messages, and continue as usual, which at least gives the user an idea of
		1573	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1574	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1575	usage.
		1576
		1577	If your program is single-threaded, then you could also keep a dummy file
		1578	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1579	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1580	close that fd, and create a new dummy fd. This will gracefully refuse
		1581	clients under typical overload conditions.
		1582
		1583	The last way to handle it is to simply log the error and C<exit>, as
		1584	is often done with C<malloc> failures, but this results in an easy
		1585	opportunity for a DoS attack.
1138		1586
1139	=head3 Watcher-Specific Functions	1587	=head3 Watcher-Specific Functions
1140		1588
1141	=over 4	1589	=over 4
1142		1590
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1591	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1592
1145	=item ev_io_set (ev_io *, int fd, int events)	1593	=item ev_io_set (ev_io *, int fd, int events)
1146		1594
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1595	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1596	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1597	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1598
1151	=item int fd [read-only]	1599	=item int fd [read-only]
1152		1600
1153	The file descriptor being watched.	1601	The file descriptor being watched.
1154		1602
…		…
1162		1610
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1611	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1612	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1613	attempt to read a whole line in the callback.
1166		1614
1167	static void	1615	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1616	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1617	{
1170	ev_io_stop (loop, w);	1618	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1619	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1620	}
1173		1621
1174	...	1622	...
1175	struct ev_loop *loop = ev_default_init (0);	1623	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1624	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1626	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1627	ev_loop (loop, 0);
1180		1628
1181		1629
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1630	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1631
1184	Timer watchers are simple relative timers that generate an event after a	1632	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1633	given time, and optionally repeating in regular intervals after that.
1186		1634
1187	The timers are based on real time, that is, if you register an event that	1635	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1636	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1637	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1639	monotonic clock option helps a lot here).
		1640
		1641	The callback is guaranteed to be invoked only I<after> its timeout has
		1642	passed (not I<at>, so on systems with very low-resolution clocks this
		1643	might introduce a small delay). If multiple timers become ready during the
		1644	same loop iteration then the ones with earlier time-out values are invoked
		1645	before ones of the same priority with later time-out values (but this is
		1646	no longer true when a callback calls C<ev_loop> recursively).
		1647
		1648	=head3 Be smart about timeouts
		1649
		1650	Many real-world problems involve some kind of timeout, usually for error
		1651	recovery. A typical example is an HTTP request - if the other side hangs,
		1652	you want to raise some error after a while.
		1653
		1654	What follows are some ways to handle this problem, from obvious and
		1655	inefficient to smart and efficient.
		1656
		1657	In the following, a 60 second activity timeout is assumed - a timeout that
		1658	gets reset to 60 seconds each time there is activity (e.g. each time some
		1659	data or other life sign was received).
		1660
		1661	=over 4
		1662
		1663	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1664
		1665	This is the most obvious, but not the most simple way: In the beginning,
		1666	start the watcher:
		1667
		1668	ev_timer_init (timer, callback, 60., 0.);
		1669	ev_timer_start (loop, timer);
		1670
		1671	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1672	and start it again:
		1673
		1674	ev_timer_stop (loop, timer);
		1675	ev_timer_set (timer, 60., 0.);
		1676	ev_timer_start (loop, timer);
		1677
		1678	This is relatively simple to implement, but means that each time there is
		1679	some activity, libev will first have to remove the timer from its internal
		1680	data structure and then add it again. Libev tries to be fast, but it's
		1681	still not a constant-time operation.
		1682
		1683	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1684
		1685	This is the easiest way, and involves using C<ev_timer_again> instead of
		1686	C<ev_timer_start>.
		1687
		1688	To implement this, configure an C<ev_timer> with a C<repeat> value
		1689	of C<60> and then call C<ev_timer_again> at start and each time you
		1690	successfully read or write some data. If you go into an idle state where
		1691	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1692	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1693
		1694	That means you can ignore both the C<ev_timer_start> function and the
		1695	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1696	member and C<ev_timer_again>.
		1697
		1698	At start:
		1699
		1700	ev_init (timer, callback);
		1701	timer->repeat = 60.;
		1702	ev_timer_again (loop, timer);
		1703
		1704	Each time there is some activity:
		1705
		1706	ev_timer_again (loop, timer);
		1707
		1708	It is even possible to change the time-out on the fly, regardless of
		1709	whether the watcher is active or not:
		1710
		1711	timer->repeat = 30.;
		1712	ev_timer_again (loop, timer);
		1713
		1714	This is slightly more efficient then stopping/starting the timer each time
		1715	you want to modify its timeout value, as libev does not have to completely
		1716	remove and re-insert the timer from/into its internal data structure.
		1717
		1718	It is, however, even simpler than the "obvious" way to do it.
		1719
		1720	=item 3. Let the timer time out, but then re-arm it as required.
		1721
		1722	This method is more tricky, but usually most efficient: Most timeouts are
		1723	relatively long compared to the intervals between other activity - in
		1724	our example, within 60 seconds, there are usually many I/O events with
		1725	associated activity resets.
		1726
		1727	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1728	but remember the time of last activity, and check for a real timeout only
		1729	within the callback:
		1730
		1731	ev_tstamp last_activity; // time of last activity
		1732
		1733	static void
		1734	callback (EV_P_ ev_timer *w, int revents)
		1735	{
		1736	ev_tstamp now = ev_now (EV_A);
		1737	ev_tstamp timeout = last_activity + 60.;
		1738
		1739	// if last_activity + 60. is older than now, we did time out
		1740	if (timeout < now)
		1741	{
		1742	// timeout occurred, take action
		1743	}
		1744	else
		1745	{
		1746	// callback was invoked, but there was some activity, re-arm
		1747	// the watcher to fire in last_activity + 60, which is
		1748	// guaranteed to be in the future, so "again" is positive:
		1749	w->repeat = timeout - now;
		1750	ev_timer_again (EV_A_ w);
		1751	}
		1752	}
		1753
		1754	To summarise the callback: first calculate the real timeout (defined
		1755	as "60 seconds after the last activity"), then check if that time has
		1756	been reached, which means something I<did>, in fact, time out. Otherwise
		1757	the callback was invoked too early (C<timeout> is in the future), so
		1758	re-schedule the timer to fire at that future time, to see if maybe we have
		1759	a timeout then.
		1760
		1761	Note how C<ev_timer_again> is used, taking advantage of the
		1762	C<ev_timer_again> optimisation when the timer is already running.
		1763
		1764	This scheme causes more callback invocations (about one every 60 seconds
		1765	minus half the average time between activity), but virtually no calls to
		1766	libev to change the timeout.
		1767
		1768	To start the timer, simply initialise the watcher and set C<last_activity>
		1769	to the current time (meaning we just have some activity :), then call the
		1770	callback, which will "do the right thing" and start the timer:
		1771
		1772	ev_init (timer, callback);
		1773	last_activity = ev_now (loop);
		1774	callback (loop, timer, EV_TIMER);
		1775
		1776	And when there is some activity, simply store the current time in
		1777	C<last_activity>, no libev calls at all:
		1778
		1779	last_activity = ev_now (loop);
		1780
		1781	This technique is slightly more complex, but in most cases where the
		1782	time-out is unlikely to be triggered, much more efficient.
		1783
		1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1785	callback :) - just change the timeout and invoke the callback, which will
		1786	fix things for you.
		1787
		1788	=item 4. Wee, just use a double-linked list for your timeouts.
		1789
		1790	If there is not one request, but many thousands (millions...), all
		1791	employing some kind of timeout with the same timeout value, then one can
		1792	do even better:
		1793
		1794	When starting the timeout, calculate the timeout value and put the timeout
		1795	at the I<end> of the list.
		1796
		1797	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1798	the list is expected to fire (for example, using the technique #3).
		1799
		1800	When there is some activity, remove the timer from the list, recalculate
		1801	the timeout, append it to the end of the list again, and make sure to
		1802	update the C<ev_timer> if it was taken from the beginning of the list.
		1803
		1804	This way, one can manage an unlimited number of timeouts in O(1) time for
		1805	starting, stopping and updating the timers, at the expense of a major
		1806	complication, and having to use a constant timeout. The constant timeout
		1807	ensures that the list stays sorted.
		1808
		1809	=back
		1810
		1811	So which method the best?
		1812
		1813	Method #2 is a simple no-brain-required solution that is adequate in most
		1814	situations. Method #3 requires a bit more thinking, but handles many cases
		1815	better, and isn't very complicated either. In most case, choosing either
		1816	one is fine, with #3 being better in typical situations.
		1817
		1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1819	rather complicated, but extremely efficient, something that really pays
		1820	off after the first million or so of active timers, i.e. it's usually
		1821	overkill :)
		1822
		1823	=head3 The special problem of time updates
		1824
		1825	Establishing the current time is a costly operation (it usually takes at
		1826	least two system calls): EV therefore updates its idea of the current
		1827	time only before and after C<ev_loop> collects new events, which causes a
		1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1829	lots of events in one iteration.
1192		1830
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1831	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1832	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1833	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1834	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1835	timeout on the current time, use something like this to adjust for this:
1198		1836
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1838
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1839	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1841	()>.
		1842
		1843	=head3 The special problems of suspended animation
		1844
		1845	When you leave the server world it is quite customary to hit machines that
		1846	can suspend/hibernate - what happens to the clocks during such a suspend?
		1847
		1848	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1849	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1850	to run until the system is suspended, but they will not advance while the
		1851	system is suspended. That means, on resume, it will be as if the program
		1852	was frozen for a few seconds, but the suspend time will not be counted
		1853	towards C<ev_timer> when a monotonic clock source is used. The real time
		1854	clock advanced as expected, but if it is used as sole clocksource, then a
		1855	long suspend would be detected as a time jump by libev, and timers would
		1856	be adjusted accordingly.
		1857
		1858	I would not be surprised to see different behaviour in different between
		1859	operating systems, OS versions or even different hardware.
		1860
		1861	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1862	time jump in the monotonic clocks and the realtime clock. If the program
		1863	is suspended for a very long time, and monotonic clock sources are in use,
		1864	then you can expect C<ev_timer>s to expire as the full suspension time
		1865	will be counted towards the timers. When no monotonic clock source is in
		1866	use, then libev will again assume a timejump and adjust accordingly.
		1867
		1868	It might be beneficial for this latter case to call C<ev_suspend>
		1869	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1870	deterministic behaviour in this case (you can do nothing against
		1871	C<SIGSTOP>).
1204		1872
1205	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1206		1874
1207	=over 4	1875	=over 4
1208		1876
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1900	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1901
1234	If the timer is repeating, either start it if necessary (with the	1902	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1903	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1904
1237	This sounds a bit complicated, but here is a useful and typical	1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1906	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		1907
1247	That means you can ignore the C<after> value and C<ev_timer_start>	1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		1909
1250	ev_timer_init (timer, callback, 0., 5.);	1910	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	1911	then this time is relative to the current event loop time, otherwise it's
1252	...	1912	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		1913
1259	This is more slightly efficient then stopping/starting the timer each time	1914	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	1915	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1916	will return C<4>. When the timer expires and is restarted, it will return
		1917	roughly C<7> (likely slightly less as callback invocation takes some time,
		1918	too), and so on.
1261		1919
1262	=item ev_tstamp repeat [read-write]	1920	=item ev_tstamp repeat [read-write]
1263		1921
1264	The current C<repeat> value. Will be used each time the watcher times out	1922	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1923	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1924	which is also when any modifications are taken into account.
1267		1925
1268	=back	1926	=back
1269		1927
1270	=head3 Examples	1928	=head3 Examples
1271		1929
1272	Example: Create a timer that fires after 60 seconds.	1930	Example: Create a timer that fires after 60 seconds.
1273		1931
1274	static void	1932	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1933	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1934	{
1277	.. one minute over, w is actually stopped right here	1935	.. one minute over, w is actually stopped right here
1278	}	1936	}
1279		1937
1280	struct ev_timer mytimer;	1938	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1939	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1940	ev_timer_start (loop, &mytimer);
1283		1941
1284	Example: Create a timeout timer that times out after 10 seconds of	1942	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1943	inactivity.
1286		1944
1287	static void	1945	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1946	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1947	{
1290	.. ten seconds without any activity	1948	.. ten seconds without any activity
1291	}	1949	}
1292		1950
1293	struct ev_timer mytimer;	1951	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1953	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1954	ev_loop (loop, 0);
1297		1955
1298	// and in some piece of code that gets executed on any "activity":	1956	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1957	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1958	ev_timer_again (&mytimer);
1301		1959
1302		1960
1303	=head2 C<ev_periodic> - to cron or not to cron?	1961	=head2 C<ev_periodic> - to cron or not to cron?
1304		1962
1305	Periodic watchers are also timers of a kind, but they are very versatile	1963	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1964	(and unfortunately a bit complex).
1307		1965
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1967	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1968	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1969	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1970	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1971	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1972
		1973	You can tell a periodic watcher to trigger after some specific point
		1974	in time: for example, if you tell a periodic watcher to trigger "in 10
		1975	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1976	not a delay) and then reset your system clock to January of the previous
		1977	year, then it will take a year or more to trigger the event (unlike an
		1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1979	it, as it uses a relative timeout).
		1980
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1981	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1982	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1984	those cannot react to time jumps.
1320		1985
1321	As with timers, the callback is guaranteed to be invoked only when the	1986	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1987	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1988	timers become ready during the same loop iteration then the ones with
		1989	earlier time-out values are invoked before ones with later time-out values
		1990	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1991
1325	=head3 Watcher-Specific Functions and Data Members	1992	=head3 Watcher-Specific Functions and Data Members
1326		1993
1327	=over 4	1994	=over 4
1328		1995
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1996	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1997
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1998	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1999
1333	Lots of arguments, lets sort it out... There are basically three modes of	2000	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	2001	operation, and we will explain them from simplest to most complex:
1335		2002
1336	=over 4	2003	=over 4
1337		2004
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2005	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		2006
1340	In this configuration the watcher triggers an event after the wall clock	2007	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	2008	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2009	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	2010	will be stopped and invoked when the system clock reaches or surpasses
		2011	this point in time.
1344		2012
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2013	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		2014
1347	In this mode the watcher will always be scheduled to time out at the next	2015	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	2016	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	2017	negative) and then repeat, regardless of any time jumps. The C<offset>
		2018	argument is merely an offset into the C<interval> periods.
1350		2019
1351	This can be used to create timers that do not drift with respect to system	2020	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	2021	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	2022	hour, on the hour (with respect to UTC):
1354		2023
1355	ev_periodic_set (&periodic, 0., 3600., 0);	2024	ev_periodic_set (&periodic, 0., 3600., 0);
1356		2025
1357	This doesn't mean there will always be 3600 seconds in between triggers,	2026	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	2027	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	2028	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	2029	by 3600.
1361		2030
1362	Another way to think about it (for the mathematically inclined) is that	2031	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	2032	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	2033	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		2034
1366	For numerical stability it is preferable that the C<at> value is near	2035	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	2036	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	2037	this value, and in fact is often specified as zero.
1369		2038
1370	Note also that there is an upper limit to how often a timer can fire (CPU	2039	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	2040	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	2041	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	2042	millisecond (if the OS supports it and the machine is fast enough).
1374		2043
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2044	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		2045
1377	In this mode the values for C<interval> and C<at> are both being	2046	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	2047	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	2048	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2049	current time as second argument.
1381		2050
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2051	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2052	or make ANY other event loop modifications whatsoever, unless explicitly
		2053	allowed by documentation here>.
1384		2054
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2055	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2056	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2057	only event loop modification you are allowed to do).
1388		2058
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2059	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2060	*w, ev_tstamp now)>, e.g.:
1391		2061
		2062	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2063	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2064	{
1394	return now + 60.;	2065	return now + 60.;
1395	}	2066	}
1396		2067
1397	It must return the next time to trigger, based on the passed time value	2068	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2088	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2089	program when the crontabs have changed).
1419		2090
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2091	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2092
1422	When active, returns the absolute time that the watcher is supposed to	2093	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2094	to trigger next. This is not the same as the C<offset> argument to
		2095	C<ev_periodic_set>, but indeed works even in interval and manual
		2096	rescheduling modes.
1424		2097
1425	=item ev_tstamp offset [read-write]	2098	=item ev_tstamp offset [read-write]
1426		2099
1427	When repeating, this contains the offset value, otherwise this is the	2100	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2101	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2102	although libev might modify this value for better numerical stability).
1429		2103
1430	Can be modified any time, but changes only take effect when the periodic	2104	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2105	timer fires or C<ev_periodic_again> is being called.
1432		2106
1433	=item ev_tstamp interval [read-write]	2107	=item ev_tstamp interval [read-write]
1434		2108
1435	The current interval value. Can be modified any time, but changes only	2109	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2110	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2111	called.
1438		2112
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2113	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2114
1441	The current reschedule callback, or C<0>, if this functionality is	2115	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2116	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2117	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2118
1445	=back	2119	=back
1446		2120
1447	=head3 Examples	2121	=head3 Examples
1448		2122
1449	Example: Call a callback every hour, or, more precisely, whenever the	2123	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2124	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2125	potentially a lot of jitter, but good long-term stability.
1452		2126
1453	static void	2127	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	2129	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2130	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2131	}
1458		2132
1459	struct ev_periodic hourly_tick;	2133	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2134	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2135	ev_periodic_start (loop, &hourly_tick);
1462		2136
1463	Example: The same as above, but use a reschedule callback to do it:	2137	Example: The same as above, but use a reschedule callback to do it:
1464		2138
1465	#include <math.h>	2139	#include <math.h>
1466		2140
1467	static ev_tstamp	2141	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2142	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2143	{
1470	return fmod (now, 3600.) + 3600.;	2144	return now + (3600. - fmod (now, 3600.));
1471	}	2145	}
1472		2146
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2147	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2148
1475	Example: Call a callback every hour, starting now:	2149	Example: Call a callback every hour, starting now:
1476		2150
1477	struct ev_periodic hourly_tick;	2151	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2152	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2153	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2154	ev_periodic_start (loop, &hourly_tick);
1481		2155
1482		2156
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	2157	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		2158
1485	Signal watchers will trigger an event when the process receives a specific	2159	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2160	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2161	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2162	normal event processing, like any other event.
1489		2163
		2164	If you want signals to be delivered truly asynchronously, just use
		2165	C<sigaction> as you would do without libev and forget about sharing
		2166	the signal. You can even use C<ev_async> from a signal handler to
		2167	synchronously wake up an event loop.
		2168
1490	You can configure as many watchers as you like per signal. Only when the	2169	You can configure as many watchers as you like for the same signal, but
		2170	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2171	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2172	C<SIGINT> in both the default loop and another loop at the same time. At
		2173	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2174
1491	first watcher gets started will libev actually register a signal watcher	2175	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2176	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2177	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2178
1497	If possible and supported, libev will install its handlers with	2179	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2181	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2182	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2183	and unblock them in an C<ev_prepare> watcher.
		2184
		2185	=head3 The special problem of inheritance over fork/execve/pthread_create
		2186
		2187	Both the signal mask (C<sigprocmask>) and the signal disposition
		2188	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2189	stopping it again), that is, libev might or might not block the signal,
		2190	and might or might not set or restore the installed signal handler.
		2191
		2192	While this does not matter for the signal disposition (libev never
		2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2194	C<execve>), this matters for the signal mask: many programs do not expect
		2195	certain signals to be blocked.
		2196
		2197	This means that before calling C<exec> (from the child) you should reset
		2198	the signal mask to whatever "default" you expect (all clear is a good
		2199	choice usually).
		2200
		2201	The simplest way to ensure that the signal mask is reset in the child is
		2202	to install a fork handler with C<pthread_atfork> that resets it. That will
		2203	catch fork calls done by libraries (such as the libc) as well.
		2204
		2205	In current versions of libev, the signal will not be blocked indefinitely
		2206	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2207	the window of opportunity for problems, it will not go away, as libev
		2208	I<has> to modify the signal mask, at least temporarily.
		2209
		2210	So I can't stress this enough: I<If you do not reset your signal mask when
		2211	you expect it to be empty, you have a race condition in your code>. This
		2212	is not a libev-specific thing, this is true for most event libraries.
1502		2213
1503	=head3 Watcher-Specific Functions and Data Members	2214	=head3 Watcher-Specific Functions and Data Members
1504		2215
1505	=over 4	2216	=over 4
1506		2217
…		…
1517		2228
1518	=back	2229	=back
1519		2230
1520	=head3 Examples	2231	=head3 Examples
1521		2232
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2233	Example: Try to exit cleanly on SIGINT.
1523		2234
1524	static void	2235	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2237	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2238	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	2239	}
1529		2240
1530	struct ev_signal signal_watcher;	2241	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2243	ev_signal_start (loop, &signal_watcher);
1533		2244
1534		2245
1535	=head2 C<ev_child> - watch out for process status changes	2246	=head2 C<ev_child> - watch out for process status changes
1536		2247
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2248	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2249	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2250	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2251	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2252	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2253	forking and then immediately registering a watcher for the child is fine,
		2254	but forking and registering a watcher a few event loop iterations later or
		2255	in the next callback invocation is not.
1542		2256
1543	Only the default event loop is capable of handling signals, and therefore	2257	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2258	you can only register child watchers in the default event loop.
1545		2259
		2260	Due to some design glitches inside libev, child watchers will always be
		2261	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2262	libev)
		2263
1546	=head3 Process Interaction	2264	=head3 Process Interaction
1547		2265
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2266	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2267	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2268	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2269	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2270	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2271	children, even ones not watched.
1554		2272
1555	=head3 Overriding the Built-In Processing	2273	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2277	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2278	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2279	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2280	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2281	that, so other libev users can use C<ev_child> watchers freely.
		2282
		2283	=head3 Stopping the Child Watcher
		2284
		2285	Currently, the child watcher never gets stopped, even when the
		2286	child terminates, so normally one needs to stop the watcher in the
		2287	callback. Future versions of libev might stop the watcher automatically
		2288	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2289	problem).
1564		2290
1565	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1566		2292
1567	=over 4	2293	=over 4
1568		2294
…		…
1597	=head3 Examples	2323	=head3 Examples
1598		2324
1599	Example: C<fork()> a new process and install a child handler to wait for	2325	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	2326	its completion.
1601		2327
1602	ev_child cw;	2328	ev_child cw;
1603		2329
1604	static void	2330	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2331	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2332	{
1607	ev_child_stop (EV_A_ w);	2333	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2334	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2335	}
1610		2336
1611	pid_t pid = fork ();	2337	pid_t pid = fork ();
1612		2338
1613	if (pid < 0)	2339	if (pid < 0)
1614	// error	2340	// error
1615	else if (pid == 0)	2341	else if (pid == 0)
1616	{	2342	{
1617	// the forked child executes here	2343	// the forked child executes here
1618	exit (1);	2344	exit (1);
1619	}	2345	}
1620	else	2346	else
1621	{	2347	{
1622	ev_child_init (&cw, child_cb, pid, 0);	2348	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	2349	ev_child_start (EV_DEFAULT_ &cw);
1624	}	2350	}
1625		2351
1626		2352
1627	=head2 C<ev_stat> - did the file attributes just change?	2353	=head2 C<ev_stat> - did the file attributes just change?
1628		2354
1629	This watches a file system path for attribute changes. That is, it calls	2355	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2356	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2357	and sees if it changed compared to the last time, invoking the callback if
		2358	it did.
1632		2359
1633	The path does not need to exist: changing from "path exists" to "path does	2360	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2361	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2362	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2363	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2364	least one) and all the other fields of the stat buffer having unspecified
		2365	contents.
1638		2366
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2367	The path I<must not> end in a slash or contain special components such as
		2368	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2369	your working directory changes, then the behaviour is undefined.
1641		2370
1642	Since there is no standard to do this, the portable implementation simply	2371	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2372	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2373	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2374	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2375	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2376	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2377	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2378	currently around C<0.1>, but that's usually overkill.
1650		2379
1651	This watcher type is not meant for massive numbers of stat watchers,	2380	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2381	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2382	resource-intensive.
1654		2383
1655	At the time of this writing, only the Linux inotify interface is	2384	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2385	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2386	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2387	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2388
1664	=head3 ABI Issues (Largefile Support)	2389	=head3 ABI Issues (Largefile Support)
1665		2390
1666	Libev by default (unless the user overrides this) uses the default	2391	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2392	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2393	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2394	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2395	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2396	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2397	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2398	most noticeably displayed with ev_stat and large file support.
1674		2399
1675	=head3 Inotify	2400	The solution for this is to lobby your distribution maker to make large
		2401	file interfaces available by default (as e.g. FreeBSD does) and not
		2402	optional. Libev cannot simply switch on large file support because it has
		2403	to exchange stat structures with application programs compiled using the
		2404	default compilation environment.
1676		2405
		2406	=head3 Inotify and Kqueue
		2407
1677	When C<inotify (7)> support has been compiled into libev (generally only	2408	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2409	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2410	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2411	watcher is being started.
1681		2412
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2413	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2414	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2415	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2416	there are many cases where libev has to resort to regular C<stat> polling,
		2417	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2418	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2419	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2420	xfs are fully working) libev usually gets away without polling.
1686		2421
1687	(There is no support for kqueue, as apparently it cannot be used to	2422	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2423	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2424	descriptor open on the object at all times, and detecting renames, unlinks
		2425	etc. is difficult.
		2426
		2427	=head3 C<stat ()> is a synchronous operation
		2428
		2429	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2430	the process. The exception are C<ev_stat> watchers - those call C<stat
		2431	()>, which is a synchronous operation.
		2432
		2433	For local paths, this usually doesn't matter: unless the system is very
		2434	busy or the intervals between stat's are large, a stat call will be fast,
		2435	as the path data is usually in memory already (except when starting the
		2436	watcher).
		2437
		2438	For networked file systems, calling C<stat ()> can block an indefinite
		2439	time due to network issues, and even under good conditions, a stat call
		2440	often takes multiple milliseconds.
		2441
		2442	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2443	paths, although this is fully supported by libev.
1690		2444
1691	=head3 The special problem of stat time resolution	2445	=head3 The special problem of stat time resolution
1692		2446
1693	The C<stat ()> system call only supports full-second resolution portably, and	2447	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2448	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2449	still only support whole seconds.
1696		2450
1697	That means that, if the time is the only thing that changes, you can	2451	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2452	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2453	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2454	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2455	stat data does change in other ways (e.g. file size).
1702		2456
1703	The solution to this is to delay acting on a change for slightly more	2457	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2458	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2459	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2460	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2480	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2481	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2482	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2483	path for as long as the watcher is active.
1730		2484
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2485	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2486	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2487	last change was detected).
1734		2488
1735	=item ev_stat_stat (loop, ev_stat *)	2489	=item ev_stat_stat (loop, ev_stat *)
1736		2490
1737	Updates the stat buffer immediately with new values. If you change the	2491	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2492	watched path in your callback, you could call this function to avoid
…		…
1767		2521
1768	=head3 Examples	2522	=head3 Examples
1769		2523
1770	Example: Watch C</etc/passwd> for attribute changes.	2524	Example: Watch C</etc/passwd> for attribute changes.
1771		2525
1772	static void	2526	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2527	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2528	{
1775	/* /etc/passwd changed in some way */	2529	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2530	if (w->attr.st_nlink)
1777	{	2531	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2532	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2533	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2534	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2535	}
1782	else	2536	else
1783	/* you shalt not abuse printf for puts */	2537	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2538	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2539	"if this is windows, they already arrived\n");
1786	}	2540	}
1787		2541
1788	...	2542	...
1789	ev_stat passwd;	2543	ev_stat passwd;
1790		2544
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2545	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2546	ev_stat_start (loop, &passwd);
1793		2547
1794	Example: Like above, but additionally use a one-second delay so we do not	2548	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2549	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2550	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2551	C<ev_timer> callback invocation).
1798		2552
1799	static ev_stat passwd;	2553	static ev_stat passwd;
1800	static ev_timer timer;	2554	static ev_timer timer;
1801		2555
1802	static void	2556	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2557	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2558	{
1805	ev_timer_stop (EV_A_ w);	2559	ev_timer_stop (EV_A_ w);
1806		2560
1807	/* now it's one second after the most recent passwd change */	2561	/* now it's one second after the most recent passwd change */
1808	}	2562	}
1809		2563
1810	static void	2564	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2565	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2566	{
1813	/* reset the one-second timer */	2567	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2568	ev_timer_again (EV_A_ &timer);
1815	}	2569	}
1816		2570
1817	...	2571	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2572	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2573	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2574	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2575
1822		2576
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2577	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2578
1825	Idle watchers trigger events when no other events of the same or higher	2579	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2580	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2581	as receiving "events").
1828		2582
1829	That is, as long as your process is busy handling sockets or timeouts	2583	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2584	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2585	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2586	are pending), the idle watchers are being called once per event loop
…		…
1843		2597
1844	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1845		2599
1846	=over 4	2600	=over 4
1847		2601
1848	=item ev_idle_init (ev_signal *, callback)	2602	=item ev_idle_init (ev_idle *, callback)
1849		2603
1850	Initialises and configures the idle watcher - it has no parameters of any	2604	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2605	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2606	believe me.
1853		2607
…		…
1856	=head3 Examples	2610	=head3 Examples
1857		2611
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2612	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2613	callback, free it. Also, use no error checking, as usual.
1860		2614
1861	static void	2615	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2617	{
1864	free (w);	2618	free (w);
1865	// now do something you wanted to do when the program has	2619	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2620	// no longer anything immediate to do.
1867	}	2621	}
1868		2622
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2624	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2625	ev_idle_start (loop, idle_watcher);
1872		2626
1873		2627
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2629
1876	Prepare and check watchers are usually (but not always) used in tandem:	2630	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2631	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2632	afterwards.
1879		2633
1880	You I<must not> call C<ev_loop> or similar functions that enter	2634	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2635	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2639	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2640	called in pairs bracketing the blocking call.
1887		2641
1888	Their main purpose is to integrate other event mechanisms into libev and	2642	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2643	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2644	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2645	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2646	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2647	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2648	watcher).
1895		2649
1896	This is done by examining in each prepare call which file descriptors need	2650	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2651	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2652	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2653	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2654	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2655	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2656	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2657	nevertheless, because you never know, you know?).
1904		2658
1905	As another example, the Perl Coro module uses these hooks to integrate	2659	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2660	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2661	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2662	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2665	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2666	low-priority coroutines to idle/background tasks).
1913		2667
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2669	priority, to ensure that they are being run before any other watchers
		2670	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2671
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2673	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2674	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2675	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2676	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2678	others).
1923		2679
1924	=head3 Watcher-Specific Functions and Data Members	2680	=head3 Watcher-Specific Functions and Data Members
1925		2681
1926	=over 4	2682	=over 4
1927		2683
…		…
1929		2685
1930	=item ev_check_init (ev_check *, callback)	2686	=item ev_check_init (ev_check *, callback)
1931		2687
1932	Initialises and configures the prepare or check watcher - they have no	2688	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2689	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2690	macros, but using them is utterly, utterly, utterly and completely
		2691	pointless.
1935		2692
1936	=back	2693	=back
1937		2694
1938	=head3 Examples	2695	=head3 Examples
1939		2696
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2705	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2706	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2707	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2708	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2709
1953	static ev_io iow [nfd];	2710	static ev_io iow [nfd];
1954	static ev_timer tw;	2711	static ev_timer tw;
1955		2712
1956	static void	2713	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2714	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2715	{
1959	}	2716	}
1960		2717
1961	// create io watchers for each fd and a timer before blocking	2718	// create io watchers for each fd and a timer before blocking
1962	static void	2719	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2720	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2721	{
1965	int timeout = 3600000;	2722	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2723	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2724	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2725	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2726
1970	/* the callback is illegal, but won't be called as we stop during check */	2727	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2728	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2729	ev_timer_start (loop, &tw);
1973		2730
1974	// create one ev_io per pollfd	2731	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2732	for (int i = 0; i < nfd; ++i)
1976	{	2733	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2734	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2735	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2736	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2737
1981	fds [i].revents = 0;	2738	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2739	ev_io_start (loop, iow + i);
1983	}	2740	}
1984	}	2741	}
1985		2742
1986	// stop all watchers after blocking	2743	// stop all watchers after blocking
1987	static void	2744	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2745	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2746	{
1990	ev_timer_stop (loop, &tw);	2747	ev_timer_stop (loop, &tw);
1991		2748
1992	for (int i = 0; i < nfd; ++i)	2749	for (int i = 0; i < nfd; ++i)
1993	{	2750	{
1994	// set the relevant poll flags	2751	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2752	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2753	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2754	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2755	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2756	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2757
2001	// now stop the watcher	2758	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2759	ev_io_stop (loop, iow + i);
2003	}	2760	}
2004		2761
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2762	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2763	}
2007		2764
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2765	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2766	in the prepare watcher and would dispose of the check watcher.
2010		2767
2011	Method 3: If the module to be embedded supports explicit event	2768	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2769	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2770	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2771
2015	static void	2772	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2773	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2774	{
2018	adns_state ads = (adns_state)w->data;	2775	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2776	update_now (EV_A);
2020		2777
2021	adns_processtimeouts (ads, &tv_now);	2778	adns_processtimeouts (ads, &tv_now);
2022	}	2779	}
2023		2780
2024	static void	2781	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2782	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2783	{
2027	adns_state ads = (adns_state)w->data;	2784	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2785	update_now (EV_A);
2029		2786
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2787	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2788	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2789	}
2033		2790
2034	// do not ever call adns_afterpoll	2791	// do not ever call adns_afterpoll
2035		2792
2036	Method 4: Do not use a prepare or check watcher because the module you	2793	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2794	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2795	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2796	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2797	this approach, effectively embedding EV as a client into the horrible
		2798	libglib event loop.
2041		2799
2042	static gint	2800	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2801	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2802	{
2045	int got_events = 0;	2803	int got_events = 0;
2046		2804
2047	for (n = 0; n < nfds; ++n)	2805	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2806	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2807
2050	if (timeout >= 0)	2808	if (timeout >= 0)
2051	// create/start timer	2809	// create/start timer
2052		2810
2053	// poll	2811	// poll
2054	ev_loop (EV_A_ 0);	2812	ev_loop (EV_A_ 0);
2055		2813
2056	// stop timer again	2814	// stop timer again
2057	if (timeout >= 0)	2815	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2816	ev_timer_stop (EV_A_ &to);
2059		2817
2060	// stop io watchers again - their callbacks should have set	2818	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2819	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2820	ev_io_stop (EV_A_ iow [n]);
2063		2821
2064	return got_events;	2822	return got_events;
2065	}	2823	}
2066		2824
2067		2825
2068	=head2 C<ev_embed> - when one backend isn't enough...	2826	=head2 C<ev_embed> - when one backend isn't enough...
2069		2827
2070	This is a rather advanced watcher type that lets you embed one event loop	2828	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2834	prioritise I/O.
2077		2835
2078	As an example for a bug workaround, the kqueue backend might only support	2836	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2837	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2838	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2839	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2840	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2841	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2842	C<kevent>, but at least you can use both mechanisms for what they are
		2843	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2844
2086	As for prioritising I/O: rarely you have the case where some fds have	2845	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2846	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2847	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2848	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2849	the rest in a second one, and embed the second one in the first.
2091		2850
2092	As long as the watcher is active, the callback will be invoked every time	2851	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2852	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2853	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2854	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2855	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2856	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2857
2100	As long as the watcher is started it will automatically handle events. The	2858	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2859	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2860
2105	Also, there have not currently been made special provisions for forking:	2861	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2862	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2863	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2864	C<ev_loop_fork> on the embedded loop.
2109		2865
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2866	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2867	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2868	portable one.
2113		2869
2114	So when you want to use this feature you will always have to be prepared	2870	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2871	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2872	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2873	create it, and if that fails, use the normal loop for everything.
		2874
		2875	=head3 C<ev_embed> and fork
		2876
		2877	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2878	automatically be applied to the embedded loop as well, so no special
		2879	fork handling is required in that case. When the watcher is not running,
		2880	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2881	as applicable.
2118		2882
2119	=head3 Watcher-Specific Functions and Data Members	2883	=head3 Watcher-Specific Functions and Data Members
2120		2884
2121	=over 4	2885	=over 4
2122		2886
…		…
2148	event loop. If that is not possible, use the default loop. The default	2912	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	2913	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2914	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2915	used).
2152		2916
2153	struct ev_loop *loop_hi = ev_default_init (0);	2917	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2918	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2919	ev_embed embed;
2156		2920
2157	// see if there is a chance of getting one that works	2921	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2922	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2925	: 0;
2162		2926
2163	// if we got one, then embed it, otherwise default to loop_hi	2927	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2928	if (loop_lo)
2165	{	2929	{
2166	ev_embed_init (&embed, 0, loop_lo);	2930	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2931	ev_embed_start (loop_hi, &embed);
2168	}	2932	}
2169	else	2933	else
2170	loop_lo = loop_hi;	2934	loop_lo = loop_hi;
2171		2935
2172	Example: Check if kqueue is available but not recommended and create	2936	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2937	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2938	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2940
2177	struct ev_loop *loop = ev_default_init (0);	2941	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2942	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2943	ev_embed embed;
2180		2944
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2947	{
2184	ev_embed_init (&embed, 0, loop_socket);	2948	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2949	ev_embed_start (loop, &embed);
2186	}	2950	}
2187		2951
2188	if (!loop_socket)	2952	if (!loop_socket)
2189	loop_socket = loop;	2953	loop_socket = loop;
2190		2954
2191	// now use loop_socket for all sockets, and loop for everything else	2955	// now use loop_socket for all sockets, and loop for everything else
2192		2956
2193		2957
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2959
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2960	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2963	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2964	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2966	handlers will be invoked, too, of course.
2203		2967
		2968	=head3 The special problem of life after fork - how is it possible?
		2969
		2970	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2971	up/change the process environment, followed by a call to C<exec()>. This
		2972	sequence should be handled by libev without any problems.
		2973
		2974	This changes when the application actually wants to do event handling
		2975	in the child, or both parent in child, in effect "continuing" after the
		2976	fork.
		2977
		2978	The default mode of operation (for libev, with application help to detect
		2979	forks) is to duplicate all the state in the child, as would be expected
		2980	when I<either> the parent I<or> the child process continues.
		2981
		2982	When both processes want to continue using libev, then this is usually the
		2983	wrong result. In that case, usually one process (typically the parent) is
		2984	supposed to continue with all watchers in place as before, while the other
		2985	process typically wants to start fresh, i.e. without any active watchers.
		2986
		2987	The cleanest and most efficient way to achieve that with libev is to
		2988	simply create a new event loop, which of course will be "empty", and
		2989	use that for new watchers. This has the advantage of not touching more
		2990	memory than necessary, and thus avoiding the copy-on-write, and the
		2991	disadvantage of having to use multiple event loops (which do not support
		2992	signal watchers).
		2993
		2994	When this is not possible, or you want to use the default loop for
		2995	other reasons, then in the process that wants to start "fresh", call
		2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2997	the default loop will "orphan" (not stop) all registered watchers, so you
		2998	have to be careful not to execute code that modifies those watchers. Note
		2999	also that in that case, you have to re-register any signal watchers.
		3000
2204	=head3 Watcher-Specific Functions and Data Members	3001	=head3 Watcher-Specific Functions and Data Members
2205		3002
2206	=over 4	3003	=over 4
2207		3004
2208	=item ev_fork_init (ev_signal *, callback)	3005	=item ev_fork_init (ev_signal *, callback)
…		…
2237	=head3 Queueing	3034	=head3 Queueing
2238		3035
2239	C<ev_async> does not support queueing of data in any way. The reason	3036	C<ev_async> does not support queueing of data in any way. The reason
2240	is that the author does not know of a simple (or any) algorithm for a	3037	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	3038	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	3039	need elaborate support such as pthreads or unportable memory access
		3040	semantics.
2243		3041
2244	That means that if you want to queue data, you have to provide your own	3042	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	3043	queue. But at least I can tell you how to implement locking around your
2246	queue:	3044	queue:
2247		3045
2248	=over 4	3046	=over 4
2249		3047
2250	=item queueing from a signal handler context	3048	=item queueing from a signal handler context
2251		3049
2252	To implement race-free queueing, you simply add to the queue in the signal	3050	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3051	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	3052	an example that does that for some fictitious SIGUSR1 handler:
2255		3053
2256	static ev_async mysig;	3054	static ev_async mysig;
2257		3055
2258	static void	3056	static void
2259	sigusr1_handler (void)	3057	sigusr1_handler (void)
…		…
2325	=over 4	3123	=over 4
2326		3124
2327	=item ev_async_init (ev_async *, callback)	3125	=item ev_async_init (ev_async *, callback)
2328		3126
2329	Initialises and configures the async watcher - it has no parameters of any	3127	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3128	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3129	trust me.
2332		3130
2333	=item ev_async_send (loop, ev_async *)	3131	=item ev_async_send (loop, ev_async *)
2334		3132
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3133	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3134	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3135	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3136	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3137	section below on what exactly this means).
2340		3138
		3139	Note that, as with other watchers in libev, multiple events might get
		3140	compressed into a single callback invocation (another way to look at this
		3141	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3142	reset when the event loop detects that).
		3143
2341	This call incurs the overhead of a system call only once per loop iteration,	3144	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3145	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3146	repeated calls to C<ev_async_send> for the same event loop.
2344		3147
2345	=item bool = ev_async_pending (ev_async *)	3148	=item bool = ev_async_pending (ev_async *)
2346		3149
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3150	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3151	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3154	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3155	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3156	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3157	quickly check whether invoking the loop might be a good idea.
2355		3158
2356	Not that this does I<not> check whether the watcher itself is pending, only	3159	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3160	only whether it has been requested to make this watcher pending: there
		3161	is a time window between the event loop checking and resetting the async
		3162	notification, and the callback being invoked.
2358		3163
2359	=back	3164	=back
2360		3165
2361		3166
2362	=head1 OTHER FUNCTIONS	3167	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3171	=over 4
2367		3172
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3173	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3174
2370	This function combines a simple timer and an I/O watcher, calls your	3175	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3176	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3177	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3178	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3179	more watchers yourself.
2375		3180
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3181	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3182	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3183	the given C<fd> and C<events> set will be created and started.
2379		3184
2380	If C<timeout> is less than 0, then no timeout watcher will be	3185	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3186	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3187	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3188
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3189	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2386	passed an C<revents> set like normal event callbacks (a combination of	3190	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3191	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2388	value passed to C<ev_once>:	3192	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3193	a timeout and an io event at the same time - you probably should give io
		3194	events precedence.
2389		3195
		3196	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3197
2390	static void stdin_ready (int revents, void *arg)	3198	static void stdin_ready (int revents, void *arg)
2391	{	3199	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	3200	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	3201	/* stdin might have data for us, joy! */;
		3202	else if (revents & EV_TIMER)
		3203	/* doh, nothing entered */;
2396	}	3204	}
2397		3205
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3206	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3207
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3208	=item ev_feed_fd_event (loop, int fd, int revents)
2407		3209
2408	Feed an event on the given fd, as if a file descriptor backend detected	3210	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3211	the given events it.
2410		3212
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3213	=item ev_feed_signal_event (loop, int signum)
2412		3214
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3215	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3216	loop!).
2415		3217
2416	=back	3218	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	3254	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	3255	the callback model to a model using method callbacks on objects.
2454		3256
2455	To use it,	3257	To use it,
2456		3258
2457	#include <ev++.h>	3259	#include <ev++.h>
2458		3260
2459	This automatically includes F<ev.h> and puts all of its definitions (many	3261	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	3262	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	3263	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3264	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2496		3298
2497	=over 4	3299	=over 4
2498		3300
2499	=item ev::TYPE::TYPE ()	3301	=item ev::TYPE::TYPE ()
2500		3302
2501	=item ev::TYPE::TYPE (struct ev_loop *)	3303	=item ev::TYPE::TYPE (loop)
2502		3304
2503	=item ev::TYPE::~TYPE	3305	=item ev::TYPE::~TYPE
2504		3306
2505	The constructor (optionally) takes an event loop to associate the watcher	3307	The constructor (optionally) takes an event loop to associate the watcher
2506	with. If it is omitted, it will use C<EV_DEFAULT>.	3308	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	3331	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	3332	thunking function, making it as fast as a direct C callback.
2531		3333
2532	Example: simple class declaration and watcher initialisation	3334	Example: simple class declaration and watcher initialisation
2533		3335
2534	struct myclass	3336	struct myclass
2535	{	3337	{
2536	void io_cb (ev::io &w, int revents) { }	3338	void io_cb (ev::io &w, int revents) { }
2537	}	3339	}
2538		3340
2539	myclass obj;	3341	myclass obj;
2540	ev::io iow;	3342	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3343	iow.set <myclass, &myclass::io_cb> (&obj);
		3344
		3345	=item w->set (object *)
		3346
		3347	This is a variation of a method callback - leaving out the method to call
		3348	will default the method to C<operator ()>, which makes it possible to use
		3349	functor objects without having to manually specify the C<operator ()> all
		3350	the time. Incidentally, you can then also leave out the template argument
		3351	list.
		3352
		3353	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3354	int revents)>.
		3355
		3356	See the method-C<set> above for more details.
		3357
		3358	Example: use a functor object as callback.
		3359
		3360	struct myfunctor
		3361	{
		3362	void operator() (ev::io &w, int revents)
		3363	{
		3364	...
		3365	}
		3366	}
		3367
		3368	myfunctor f;
		3369
		3370	ev::io w;
		3371	w.set (&f);
2542		3372
2543	=item w->set<function> (void *data = 0)	3373	=item w->set<function> (void *data = 0)
2544		3374
2545	Also sets a callback, but uses a static method or plain function as	3375	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3376	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		3378
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3379	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3380
2551	See the method-C<set> above for more details.	3381	See the method-C<set> above for more details.
2552		3382
2553	Example:	3383	Example: Use a plain function as callback.
2554		3384
2555	static void io_cb (ev::io &w, int revents) { }	3385	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3386	iow.set <io_cb> ();
2557		3387
2558	=item w->set (struct ev_loop *)	3388	=item w->set (loop)
2559		3389
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3390	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3391	do this when the watcher is inactive (and not pending either).
2562		3392
2563	=item w->set ([arguments])	3393	=item w->set ([arguments])
…		…
2594	=back	3424	=back
2595		3425
2596	Example: Define a class with an IO and idle watcher, start one of them in	3426	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3427	the constructor.
2598		3428
2599	class myclass	3429	class myclass
2600	{	3430	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3431	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3432	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3433
2604	myclass (int fd)	3434	myclass (int fd)
2605	{	3435	{
2606	io .set <myclass, &myclass::io_cb > (this);	3436	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3437	idle.set <myclass, &myclass::idle_cb> (this);
2608		3438
2609	io.start (fd, ev::READ);	3439	io.start (fd, ev::READ);
2610	}	3440	}
2611	};	3441	};
2612		3442
2613		3443
2614	=head1 OTHER LANGUAGE BINDINGS	3444	=head1 OTHER LANGUAGE BINDINGS
2615		3445
2616	Libev does not offer other language bindings itself, but bindings for a	3446	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	3453	=item Perl
2624		3454
2625	The EV module implements the full libev API and is actually used to test	3455	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3456	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3457	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3458	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3459	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3460	and C<EV::Glib>).
2630		3461
2631	It can be found and installed via CPAN, its homepage is found at	3462	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3463	L<http://software.schmorp.de/pkg/EV>.
		3464
		3465	=item Python
		3466
		3467	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3468	seems to be quite complete and well-documented.
2633		3469
2634	=item Ruby	3470	=item Ruby
2635		3471
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3472	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3473	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3474	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3475	L<http://rev.rubyforge.org/>.
2640		3476
		3477	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3478	makes rev work even on mingw.
		3479
		3480	=item Haskell
		3481
		3482	A haskell binding to libev is available at
		3483	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3484
2641	=item D	3485	=item D
2642		3486
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3487	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3488	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3489
		3490	=item Ocaml
		3491
		3492	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3493	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3494
		3495	=item Lua
		3496
		3497	Brian Maher has written a partial interface to libev for lua (at the
		3498	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3499	L<http://github.com/brimworks/lua-ev>.
2645		3500
2646	=back	3501	=back
2647		3502
2648		3503
2649	=head1 MACRO MAGIC	3504	=head1 MACRO MAGIC
…		…
2661		3516
2662	This provides the loop I<argument> for functions, if one is required ("ev	3517	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3518	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3519	C<EV_A_> is used when other arguments are following. Example:
2665		3520
2666	ev_unref (EV_A);	3521	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3522	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3523	ev_loop (EV_A_ 0);
2669		3524
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3525	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3526	which is often provided by the following macro.
2672		3527
2673	=item C<EV_P>, C<EV_P_>	3528	=item C<EV_P>, C<EV_P_>
2674		3529
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3530	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3531	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	3532	C<EV_P_> is used when other parameters are following. Example:
2678		3533
2679	// this is how ev_unref is being declared	3534	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3535	static void ev_unref (EV_P);
2681		3536
2682	// this is how you can declare your typical callback	3537	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3538	static void cb (EV_P_ ev_timer *w, int revents)
2684		3539
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3540	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3541	suitable for use with C<EV_A>.
2687		3542
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3543	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3559
2705	Example: Declare and initialise a check watcher, utilising the above	3560	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3561	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3562	or not.
2708		3563
2709	static void	3564	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3565	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3566	{
2712	ev_check_stop (EV_A_ w);	3567	ev_check_stop (EV_A_ w);
2713	}	3568	}
2714		3569
2715	ev_check check;	3570	ev_check check;
2716	ev_check_init (&check, check_cb);	3571	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3572	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3573	ev_loop (EV_DEFAULT_ 0);
2719		3574
2720	=head1 EMBEDDING	3575	=head1 EMBEDDING
2721		3576
2722	Libev can (and often is) directly embedded into host	3577	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3578	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3592	=head3 CORE EVENT LOOP
2738		3593
2739	To include only the libev core (all the C<ev_*> functions), with manual	3594	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3595	configuration (no autoconf):
2741		3596
2742	#define EV_STANDALONE 1	3597	#define EV_STANDALONE 1
2743	#include "ev.c"	3598	#include "ev.c"
2744		3599
2745	This will automatically include F<ev.h>, too, and should be done in a	3600	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	3601	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	3602	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	3603	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3604	where you can put other configuration options):
2750		3605
2751	#define EV_STANDALONE 1	3606	#define EV_STANDALONE 1
2752	#include "ev.h"	3607	#include "ev.h"
2753		3608
2754	Both header files and implementation files can be compiled with a C++	3609	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3610	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3611	as a bug).
2757		3612
2758	You need the following files in your source tree, or in a directory	3613	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3614	in your include path (e.g. in libev/ when using -Ilibev):
2760		3615
2761	ev.h	3616	ev.h
2762	ev.c	3617	ev.c
2763	ev_vars.h	3618	ev_vars.h
2764	ev_wrap.h	3619	ev_wrap.h
2765		3620
2766	ev_win32.c required on win32 platforms only	3621	ev_win32.c required on win32 platforms only
2767		3622
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3623	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	3624	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3625	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3626	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	3627	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3628
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3629	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3630	to compile this single file.
2776		3631
2777	=head3 LIBEVENT COMPATIBILITY API	3632	=head3 LIBEVENT COMPATIBILITY API
2778		3633
2779	To include the libevent compatibility API, also include:	3634	To include the libevent compatibility API, also include:
2780		3635
2781	#include "event.c"	3636	#include "event.c"
2782		3637
2783	in the file including F<ev.c>, and:	3638	in the file including F<ev.c>, and:
2784		3639
2785	#include "event.h"	3640	#include "event.h"
2786		3641
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3642	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3643
2789	You need the following additional files for this:	3644	You need the following additional files for this:
2790		3645
2791	event.h	3646	event.h
2792	event.c	3647	event.c
2793		3648
2794	=head3 AUTOCONF SUPPORT	3649	=head3 AUTOCONF SUPPORT
2795		3650
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3651	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	3652	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3653	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3654	include F<config.h> and configure itself accordingly.
2800		3655
2801	For this of course you need the m4 file:	3656	For this of course you need the m4 file:
2802		3657
2803	libev.m4	3658	libev.m4
2804		3659
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3660	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3661
2807	Libev can be configured via a variety of preprocessor symbols you have to	3662	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3663	define before including (or compiling) any of its files. The default in
2809	autoconf is noted for every option.	3664	the absence of autoconf is documented for every option.
		3665
		3666	Symbols marked with "(h)" do not change the ABI, and can have different
		3667	values when compiling libev vs. including F<ev.h>, so it is permissible
		3668	to redefine them before including F<ev.h> without breaking compatibility
		3669	to a compiled library. All other symbols change the ABI, which means all
		3670	users of libev and the libev code itself must be compiled with compatible
		3671	settings.
2810		3672
2811	=over 4	3673	=over 4
2812		3674
2813	=item EV_STANDALONE	3675	=item EV_STANDALONE (h)
2814		3676
2815	Must always be C<1> if you do not use autoconf configuration, which	3677	Must always be C<1> if you do not use autoconf configuration, which
2816	keeps libev from including F<config.h>, and it also defines dummy	3678	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3679	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3680	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3681	F<event.h> that are not directly supported by the libev core alone.
2820		3682
		3683	In standalone mode, libev will still try to automatically deduce the
		3684	configuration, but has to be more conservative.
		3685
2821	=item EV_USE_MONOTONIC	3686	=item EV_USE_MONOTONIC
2822		3687
2823	If defined to be C<1>, libev will try to detect the availability of the	3688	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3689	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3690	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3691	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3692	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3693	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3694	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3695
2831	=item EV_USE_REALTIME	3696	=item EV_USE_REALTIME
2832		3697
2833	If defined to be C<1>, libev will try to detect the availability of the	3698	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3699	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3700	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3701	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3702	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3703	correctness. See the note about libraries in the description of
		3704	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3705	C<EV_USE_CLOCK_SYSCALL>.
		3706
		3707	=item EV_USE_CLOCK_SYSCALL
		3708
		3709	If defined to be C<1>, libev will try to use a direct syscall instead
		3710	of calling the system-provided C<clock_gettime> function. This option
		3711	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3712	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3713	programs needlessly. Using a direct syscall is slightly slower (in
		3714	theory), because no optimised vdso implementation can be used, but avoids
		3715	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3716	higher, as it simplifies linking (no need for C<-lrt>).
2839		3717
2840	=item EV_USE_NANOSLEEP	3718	=item EV_USE_NANOSLEEP
2841		3719
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3720	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3721	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3737
2860	=item EV_SELECT_USE_FD_SET	3738	=item EV_SELECT_USE_FD_SET
2861		3739
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3740	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3741	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3742	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3743	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3744	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3745	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3746	configures the maximum size of the C<fd_set>.
2869		3747
2870	=item EV_SELECT_IS_WINSOCKET	3748	=item EV_SELECT_IS_WINSOCKET
2871		3749
2872	When defined to C<1>, the select backend will assume that	3750	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3751	select/socket/connect etc. don't understand file descriptors but
…		…
2875	be used is the winsock select). This means that it will call	3753	be used is the winsock select). This means that it will call
2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3754	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2877	it is assumed that all these functions actually work on fds, even	3755	it is assumed that all these functions actually work on fds, even
2878	on win32. Should not be defined on non-win32 platforms.	3756	on win32. Should not be defined on non-win32 platforms.
2879		3757
2880	=item EV_FD_TO_WIN32_HANDLE	3758	=item EV_FD_TO_WIN32_HANDLE(fd)
2881		3759
2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3760	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2883	file descriptors to socket handles. When not defining this symbol (the	3761	file descriptors to socket handles. When not defining this symbol (the
2884	default), then libev will call C<_get_osfhandle>, which is usually	3762	default), then libev will call C<_get_osfhandle>, which is usually
2885	correct. In some cases, programs use their own file descriptor management,	3763	correct. In some cases, programs use their own file descriptor management,
2886	in which case they can provide this function to map fds to socket handles.	3764	in which case they can provide this function to map fds to socket handles.
		3765
		3766	=item EV_WIN32_HANDLE_TO_FD(handle)
		3767
		3768	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3769	using the standard C<_open_osfhandle> function. For programs implementing
		3770	their own fd to handle mapping, overwriting this function makes it easier
		3771	to do so. This can be done by defining this macro to an appropriate value.
		3772
		3773	=item EV_WIN32_CLOSE_FD(fd)
		3774
		3775	If programs implement their own fd to handle mapping on win32, then this
		3776	macro can be used to override the C<close> function, useful to unregister
		3777	file descriptors again. Note that the replacement function has to close
		3778	the underlying OS handle.
2887		3779
2888	=item EV_USE_POLL	3780	=item EV_USE_POLL
2889		3781
2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3782	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2891	backend. Otherwise it will be enabled on non-win32 platforms. It	3783	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2938	as well as for signal and thread safety in C<ev_async> watchers.	3830	as well as for signal and thread safety in C<ev_async> watchers.
2939		3831
2940	In the absence of this define, libev will use C<sig_atomic_t volatile>	3832	In the absence of this define, libev will use C<sig_atomic_t volatile>
2941	(from F<signal.h>), which is usually good enough on most platforms.	3833	(from F<signal.h>), which is usually good enough on most platforms.
2942		3834
2943	=item EV_H	3835	=item EV_H (h)
2944		3836
2945	The name of the F<ev.h> header file used to include it. The default if	3837	The name of the F<ev.h> header file used to include it. The default if
2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3838	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2947	used to virtually rename the F<ev.h> header file in case of conflicts.	3839	used to virtually rename the F<ev.h> header file in case of conflicts.
2948		3840
2949	=item EV_CONFIG_H	3841	=item EV_CONFIG_H (h)
2950		3842
2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3843	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3844	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2953	C<EV_H>, above.	3845	C<EV_H>, above.
2954		3846
2955	=item EV_EVENT_H	3847	=item EV_EVENT_H (h)
2956		3848
2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3849	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2958	of how the F<event.h> header can be found, the default is C<"event.h">.	3850	of how the F<event.h> header can be found, the default is C<"event.h">.
2959		3851
2960	=item EV_PROTOTYPES	3852	=item EV_PROTOTYPES (h)
2961		3853
2962	If defined to be C<0>, then F<ev.h> will not define any function	3854	If defined to be C<0>, then F<ev.h> will not define any function
2963	prototypes, but still define all the structs and other symbols. This is	3855	prototypes, but still define all the structs and other symbols. This is
2964	occasionally useful if you want to provide your own wrapper functions	3856	occasionally useful if you want to provide your own wrapper functions
2965	around libev functions.	3857	around libev functions.
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3876	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3877	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3878	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3879	fine.
2988		3880
2989	If your embedding application does not need any priorities, defining these both to	3881	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3882	both to C<0> will save some memory and CPU.
2991		3883
2992	=item EV_PERIODIC_ENABLE	3884	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3885	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3886	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2993		3887
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3888	If undefined or defined to be C<1> (and the platform supports it), then
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3889	the respective watcher type is supported. If defined to be C<0>, then it
2996	code.	3890	is not. Disabling watcher types mainly saves codesize.
2997		3891
2998	=item EV_IDLE_ENABLE	3892	=item EV_FEATURES
2999
3000	If undefined or defined to be C<1>, then idle watchers are supported. If
3001	defined to be C<0>, then they are not. Disabling them saves a few kB of
3002	code.
3003
3004	=item EV_EMBED_ENABLE
3005
3006	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.
3008
3009	=item EV_STAT_ENABLE
3010
3011	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.
3013
3014	=item EV_FORK_ENABLE
3015
3016	If undefined or defined to be C<1>, then fork watchers are supported. If
3017	defined to be C<0>, then they are not.
3018
3019	=item EV_ASYNC_ENABLE
3020
3021	If undefined or defined to be C<1>, then async watchers are supported. If
3022	defined to be C<0>, then they are not.
3023
3024	=item EV_MINIMAL
3025		3893
3026	If you need to shave off some kilobytes of code at the expense of some	3894	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	3895	speed (but with the full API), you can define this symbol to request
3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3896	certain subsets of functionality. The default is to enable all features
3029	much smaller 2-heap for timer management over the default 4-heap.	3897	that can be enabled on the platform.
		3898
		3899	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3900	with some broad features you want) and then selectively re-enable
		3901	additional parts you want, for example if you want everything minimal,
		3902	but multiple event loop support, async and child watchers and the poll
		3903	backend, use this:
		3904
		3905	#define EV_FEATURES 0
		3906	#define EV_MULTIPLICITY 1
		3907	#define EV_USE_POLL 1
		3908	#define EV_CHILD_ENABLE 1
		3909	#define EV_ASYNC_ENABLE 1
		3910
		3911	The actual value is a bitset, it can be a combination of the following
		3912	values:
		3913
		3914	=over 4
		3915
		3916	=item C<1> - faster/larger code
		3917
		3918	Use larger code to speed up some operations.
		3919
		3920	Currently this is used to override some inlining decisions (enlarging the roughly
		3921	30% code size on amd64.
		3922
		3923	When optimising for size, use of compiler flags such as C<-Os> with
		3924	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3925	assertions.
		3926
		3927	=item C<2> - faster/larger data structures
		3928
		3929	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3930	hash table sizes and so on. This will usually further increase codesize
		3931	and can additionally have an effect on the size of data structures at
		3932	runtime.
		3933
		3934	=item C<4> - full API configuration
		3935
		3936	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3937	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3938
		3939	=item C<8> - full API
		3940
		3941	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3942	details on which parts of the API are still available without this
		3943	feature, and do not complain if this subset changes over time.
		3944
		3945	=item C<16> - enable all optional watcher types
		3946
		3947	Enables all optional watcher types. If you want to selectively enable
		3948	only some watcher types other than I/O and timers (e.g. prepare,
		3949	embed, async, child...) you can enable them manually by defining
		3950	C<EV_watchertype_ENABLE> to C<1> instead.
		3951
		3952	=item C<32> - enable all backends
		3953
		3954	This enables all backends - without this feature, you need to enable at
		3955	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3956
		3957	=item C<64> - enable OS-specific "helper" APIs
		3958
		3959	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3960	default.
		3961
		3962	=back
		3963
		3964	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3965	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3966	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3967	watchers, timers and monotonic clock support.
		3968
		3969	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3970	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3971	your program might be left out as well - a binary starting a timer and an
		3972	I/O watcher then might come out at only 5Kb.
		3973
		3974	=item EV_AVOID_STDIO
		3975
		3976	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3977	functions (printf, scanf, perror etc.). This will increase the codesize
		3978	somewhat, but if your program doesn't otherwise depend on stdio and your
		3979	libc allows it, this avoids linking in the stdio library which is quite
		3980	big.
		3981
		3982	Note that error messages might become less precise when this option is
		3983	enabled.
		3984
		3985	=item EV_NSIG
		3986
		3987	The highest supported signal number, +1 (or, the number of
		3988	signals): Normally, libev tries to deduce the maximum number of signals
		3989	automatically, but sometimes this fails, in which case it can be
		3990	specified. Also, using a lower number than detected (C<32> should be
		3991	good for about any system in existence) can save some memory, as libev
		3992	statically allocates some 12-24 bytes per signal number.
3030		3993
3031	=item EV_PID_HASHSIZE	3994	=item EV_PID_HASHSIZE
3032		3995
3033	C<ev_child> watchers use a small hash table to distribute workload by	3996	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3997	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3035	than enough. If you need to manage thousands of children you might want to	3998	usually more than enough. If you need to manage thousands of children you
3036	increase this value (I<must> be a power of two).	3999	might want to increase this value (I<must> be a power of two).
3037		4000
3038	=item EV_INOTIFY_HASHSIZE	4001	=item EV_INOTIFY_HASHSIZE
3039		4002
3040	C<ev_stat> watchers use a small hash table to distribute workload by	4003	C<ev_stat> watchers use a small hash table to distribute workload by
3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4004	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3042	usually more than enough. If you need to manage thousands of C<ev_stat>	4005	disabled), usually more than enough. If you need to manage thousands of
3043	watchers you might want to increase this value (I<must> be a power of	4006	C<ev_stat> watchers you might want to increase this value (I<must> be a
3044	two).	4007	power of two).
3045		4008
3046	=item EV_USE_4HEAP	4009	=item EV_USE_4HEAP
3047		4010
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4011	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4012	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	4013	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	4014	faster performance with many (thousands) of watchers.
3052		4015
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4016	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3054	(disabled).	4017	will be C<0>.
3055		4018
3056	=item EV_HEAP_CACHE_AT	4019	=item EV_HEAP_CACHE_AT
3057		4020
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4021	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	4022	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	4025	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	4026	noticeably with many (hundreds) of watchers.
3064		4027
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4028	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3066	(disabled).	4029	will be C<0>.
3067		4030
3068	=item EV_VERIFY	4031	=item EV_VERIFY
3069		4032
3070	Controls how much internal verification (see C<ev_loop_verify ()>) will	4033	Controls how much internal verification (see C<ev_loop_verify ()>) will
3071	be done: If set to C<0>, no internal verification code will be compiled	4034	be done: If set to C<0>, no internal verification code will be compiled
…		…
3073	called. If set to C<2>, then the internal verification code will be	4036	called. If set to C<2>, then the internal verification code will be
3074	called once per loop, which can slow down libev. If set to C<3>, then the	4037	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	4038	verification code will be called very frequently, which will slow down
3076	libev considerably.	4039	libev considerably.
3077		4040
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4041	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3079	C<0.>	4042	will be C<0>.
3080		4043
3081	=item EV_COMMON	4044	=item EV_COMMON
3082		4045
3083	By default, all watchers have a C<void *data> member. By redefining	4046	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	4047	this macro to a something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	4048	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	4049	though, and it must be identical each time.
3087		4050
3088	For example, the perl EV module uses something like this:	4051	For example, the perl EV module uses something like this:
3089		4052
3090	#define EV_COMMON \	4053	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	4054	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	4055	SV *cb_sv, *fh /* note no trailing ";" */
3093		4056
3094	=item EV_CB_DECLARE (type)	4057	=item EV_CB_DECLARE (type)
3095		4058
3096	=item EV_CB_INVOKE (watcher, revents)	4059	=item EV_CB_INVOKE (watcher, revents)
3097		4060
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	4065	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	4066	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4067	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	4068	method calls instead of plain function calls in C++.
3106		4069
		4070	=back
		4071
3107	=head2 EXPORTED API SYMBOLS	4072	=head2 EXPORTED API SYMBOLS
3108		4073
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	4074	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	4075	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	4076	all public symbols, one per line:
3112		4077
3113	Symbols.ev for libev proper	4078	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	4079	Symbols.event for the libevent emulation
3115		4080
3116	This can also be used to rename all public symbols to avoid clashes with	4081	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	4082	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	4083	itself, but sometimes it is inconvenient to avoid this).
3119		4084
…		…
3140	file.	4105	file.
3141		4106
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4107	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	4108	that everybody includes and which overrides some configure choices:
3144		4109
3145	#define EV_MINIMAL 1	4110	#define EV_FEATURES 8
3146	#define EV_USE_POLL 0	4111	#define EV_USE_SELECT 1
3147	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	4112	#define EV_PREPARE_ENABLE 1
		4113	#define EV_IDLE_ENABLE 1
3149	#define EV_STAT_ENABLE 0	4114	#define EV_SIGNAL_ENABLE 1
3150	#define EV_FORK_ENABLE 0	4115	#define EV_CHILD_ENABLE 1
		4116	#define EV_USE_STDEXCEPT 0
3151	#define EV_CONFIG_H <config.h>	4117	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0
3154		4118
3155	#include "ev++.h"	4119	#include "ev++.h"
3156		4120
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4121	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		4122
3159	#include "ev_cpp.h"	4123	#include "ev_cpp.h"
3160	#include "ev.c"	4124	#include "ev.c"
3161		4125
		4126	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		4127
3163	=head1 THREADS AND COROUTINES	4128	=head2 THREADS AND COROUTINES
3164		4129
3165	=head2 THREADS	4130	=head3 THREADS
3166		4131
3167	Libev itself is completely thread-safe, but it uses no locking. This	4132	All libev functions are reentrant and thread-safe unless explicitly
		4133	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	4134	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	4135	are no concurrent calls into any libev function with the same loop
3170	parameter.	4136	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4137	of course): libev guarantees that different event loops share no data
		4138	structures that need any locking.
3171		4139
3172	Or put differently: calls with different loop parameters can be done in	4140	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	4141	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	4142	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	4143	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	4144	a mutex per loop).
3177		4145
3178	If you want to know which design is best for your problem, then I cannot	4146	Specifically to support threads (and signal handlers), libev implements
		4147	so-called C<ev_async> watchers, which allow some limited form of
		4148	concurrency on the same event loop, namely waking it up "from the
		4149	outside".
		4150
		4151	If you want to know which design (one loop, locking, or multiple loops
		4152	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	4153	help you, but here is some generic advice:
3180		4154
3181	=over 4	4155	=over 4
3182		4156
3183	=item * most applications have a main thread: use the default libev loop	4157	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	4158	in that thread, or create a separate thread running only the default loop.
…		…
3196		4170
3197	Choosing a model is hard - look around, learn, know that usually you can do	4171	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	4172	better than you currently do :-)
3199		4173
3200	=item * often you need to talk to some other thread which blocks in the	4174	=item * often you need to talk to some other thread which blocks in the
		4175	event loop.
		4176
3201	event loop - C<ev_async> watchers can be used to wake them up from other	4177	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	4178	(or from signal contexts...).
		4179
		4180	An example use would be to communicate signals or other events that only
		4181	work in the default loop by registering the signal watcher with the
		4182	default loop and triggering an C<ev_async> watcher from the default loop
		4183	watcher callback into the event loop interested in the signal.
3203		4184
3204	=back	4185	=back
3205		4186
		4187	=head4 THREAD LOCKING EXAMPLE
		4188
		4189	Here is a fictitious example of how to run an event loop in a different
		4190	thread than where callbacks are being invoked and watchers are
		4191	created/added/removed.
		4192
		4193	For a real-world example, see the C<EV::Loop::Async> perl module,
		4194	which uses exactly this technique (which is suited for many high-level
		4195	languages).
		4196
		4197	The example uses a pthread mutex to protect the loop data, a condition
		4198	variable to wait for callback invocations, an async watcher to notify the
		4199	event loop thread and an unspecified mechanism to wake up the main thread.
		4200
		4201	First, you need to associate some data with the event loop:
		4202
		4203	typedef struct {
		4204	mutex_t lock; /* global loop lock */
		4205	ev_async async_w;
		4206	thread_t tid;
		4207	cond_t invoke_cv;
		4208	} userdata;
		4209
		4210	void prepare_loop (EV_P)
		4211	{
		4212	// for simplicity, we use a static userdata struct.
		4213	static userdata u;
		4214
		4215	ev_async_init (&u->async_w, async_cb);
		4216	ev_async_start (EV_A_ &u->async_w);
		4217
		4218	pthread_mutex_init (&u->lock, 0);
		4219	pthread_cond_init (&u->invoke_cv, 0);
		4220
		4221	// now associate this with the loop
		4222	ev_set_userdata (EV_A_ u);
		4223	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4224	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4225
		4226	// then create the thread running ev_loop
		4227	pthread_create (&u->tid, 0, l_run, EV_A);
		4228	}
		4229
		4230	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4231	solely to wake up the event loop so it takes notice of any new watchers
		4232	that might have been added:
		4233
		4234	static void
		4235	async_cb (EV_P_ ev_async *w, int revents)
		4236	{
		4237	// just used for the side effects
		4238	}
		4239
		4240	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4241	protecting the loop data, respectively.
		4242
		4243	static void
		4244	l_release (EV_P)
		4245	{
		4246	userdata *u = ev_userdata (EV_A);
		4247	pthread_mutex_unlock (&u->lock);
		4248	}
		4249
		4250	static void
		4251	l_acquire (EV_P)
		4252	{
		4253	userdata *u = ev_userdata (EV_A);
		4254	pthread_mutex_lock (&u->lock);
		4255	}
		4256
		4257	The event loop thread first acquires the mutex, and then jumps straight
		4258	into C<ev_loop>:
		4259
		4260	void *
		4261	l_run (void *thr_arg)
		4262	{
		4263	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4264
		4265	l_acquire (EV_A);
		4266	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4267	ev_loop (EV_A_ 0);
		4268	l_release (EV_A);
		4269
		4270	return 0;
		4271	}
		4272
		4273	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4274	signal the main thread via some unspecified mechanism (signals? pipe
		4275	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4276	have been called (in a while loop because a) spurious wakeups are possible
		4277	and b) skipping inter-thread-communication when there are no pending
		4278	watchers is very beneficial):
		4279
		4280	static void
		4281	l_invoke (EV_P)
		4282	{
		4283	userdata *u = ev_userdata (EV_A);
		4284
		4285	while (ev_pending_count (EV_A))
		4286	{
		4287	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4288	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4289	}
		4290	}
		4291
		4292	Now, whenever the main thread gets told to invoke pending watchers, it
		4293	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4294	thread to continue:
		4295
		4296	static void
		4297	real_invoke_pending (EV_P)
		4298	{
		4299	userdata *u = ev_userdata (EV_A);
		4300
		4301	pthread_mutex_lock (&u->lock);
		4302	ev_invoke_pending (EV_A);
		4303	pthread_cond_signal (&u->invoke_cv);
		4304	pthread_mutex_unlock (&u->lock);
		4305	}
		4306
		4307	Whenever you want to start/stop a watcher or do other modifications to an
		4308	event loop, you will now have to lock:
		4309
		4310	ev_timer timeout_watcher;
		4311	userdata *u = ev_userdata (EV_A);
		4312
		4313	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4314
		4315	pthread_mutex_lock (&u->lock);
		4316	ev_timer_start (EV_A_ &timeout_watcher);
		4317	ev_async_send (EV_A_ &u->async_w);
		4318	pthread_mutex_unlock (&u->lock);
		4319
		4320	Note that sending the C<ev_async> watcher is required because otherwise
		4321	an event loop currently blocking in the kernel will have no knowledge
		4322	about the newly added timer. By waking up the loop it will pick up any new
		4323	watchers in the next event loop iteration.
		4324
3206	=head2 COROUTINES	4325	=head3 COROUTINES
3207		4326
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	4327	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4328	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4329	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4330	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4331	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4332	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4333
3215	Care has been invested into making sure that libev does not keep local	4334	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4335	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	4336	they do not call any callbacks.
3218		4337
		4338	=head2 COMPILER WARNINGS
3219		4339
3220	=head1 COMPLEXITIES	4340	Depending on your compiler and compiler settings, you might get no or a
		4341	lot of warnings when compiling libev code. Some people are apparently
		4342	scared by this.
3221		4343
3222	In this section the complexities of (many of) the algorithms used inside	4344	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4345	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4346	warning options. "Warn-free" code therefore cannot be a goal except when
		4347	targeting a specific compiler and compiler-version.
3225		4348
3226	All of the following are about amortised time: If an array needs to be	4349	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4350	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4351	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4352
3232	=over 4	4353	And of course, some compiler warnings are just plain stupid, or simply
		4354	wrong (because they don't actually warn about the condition their message
		4355	seems to warn about). For example, certain older gcc versions had some
		4356	warnings that resulted an extreme number of false positives. These have
		4357	been fixed, but some people still insist on making code warn-free with
		4358	such buggy versions.
3233		4359
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4360	While libev is written to generate as few warnings as possible,
		4361	"warn-free" code is not a goal, and it is recommended not to build libev
		4362	with any compiler warnings enabled unless you are prepared to cope with
		4363	them (e.g. by ignoring them). Remember that warnings are just that:
		4364	warnings, not errors, or proof of bugs.
3235		4365
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4366
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4367	=head2 VALGRIND
3241		4368
3242	That means that changing a timer costs less than removing/adding them	4369	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4370	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4371
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4372	If you think you found a bug (memory leak, uninitialised data access etc.)
		4373	in libev, then check twice: If valgrind reports something like:
3246		4374
3247	These just add the watcher into an array or at the head of a list.	4375	==2274== definitely lost: 0 bytes in 0 blocks.
		4376	==2274== possibly lost: 0 bytes in 0 blocks.
		4377	==2274== still reachable: 256 bytes in 1 blocks.
3248		4378
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4379	Then there is no memory leak, just as memory accounted to global variables
		4380	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4381
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4382	Similarly, under some circumstances, valgrind might report kernel bugs
		4383	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4384	although an acceptable workaround has been found here), or it might be
		4385	confused.
3252		4386
3253	These watchers are stored in lists then need to be walked to find the	4387	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4388	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4389
3257	=item Finding the next timer in each loop iteration: O(1)	4390	If you are unsure about something, feel free to contact the mailing list
		4391	with the full valgrind report and an explanation on why you think this
		4392	is a bug in libev (best check the archives, too :). However, don't be
		4393	annoyed when you get a brisk "this is no bug" answer and take the chance
		4394	of learning how to interpret valgrind properly.
3258		4395
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4396	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4397	I suggest using suppression lists.
3261		4398
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4399
3264	A change means an I/O watcher gets started or stopped, which requires	4400	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		4401
3268	=item Activating one watcher (putting it into the pending state): O(1)	4402	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 Win32 platform limitations and workarounds
3291		4403
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4404	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4405	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4406	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4407	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3302	way (note also that glib is the slowest event library known to man).	4414	way (note also that glib is the slowest event library known to man).
3303		4415
3304	There is no supported compilation method available on windows except	4416	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4417	embedding it into other applications.
3306		4418
		4419	Sensible signal handling is officially unsupported by Microsoft - libev
		4420	tries its best, but under most conditions, signals will simply not work.
		4421
		4422	Not a libev limitation but worth mentioning: windows apparently doesn't
		4423	accept large writes: instead of resulting in a partial write, windows will
		4424	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4425	so make sure you only write small amounts into your sockets (less than a
		4426	megabyte seems safe, but this apparently depends on the amount of memory
		4427	available).
		4428
3307	Due to the many, low, and arbitrary limits on the win32 platform and	4429	Due to the many, low, and arbitrary limits on the win32 platform and
3308	the abysmal performance of winsockets, using a large number of sockets	4430	the abysmal performance of winsockets, using a large number of sockets
3309	is not recommended (and not reasonable). If your program needs to use	4431	is not recommended (and not reasonable). If your program needs to use
3310	more than a hundred or so sockets, then likely it needs to use a totally	4432	more than a hundred or so sockets, then likely it needs to use a totally
3311	different implementation for windows, as libev offers the POSIX readiness	4433	different implementation for windows, as libev offers the POSIX readiness
3312	notification model, which cannot be implemented efficiently on windows	4434	notification model, which cannot be implemented efficiently on windows
3313	(Microsoft monopoly games).	4435	(due to Microsoft monopoly games).
		4436
		4437	A typical way to use libev under windows is to embed it (see the embedding
		4438	section for details) and use the following F<evwrap.h> header file instead
		4439	of F<ev.h>:
		4440
		4441	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4442	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4443
		4444	#include "ev.h"
		4445
		4446	And compile the following F<evwrap.c> file into your project (make sure
		4447	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4448
		4449	#include "evwrap.h"
		4450	#include "ev.c"
3314		4451
3315	=over 4	4452	=over 4
3316		4453
3317	=item The winsocket select function	4454	=item The winsocket select function
3318		4455
3319	The winsocket C<select> function doesn't follow POSIX in that it	4456	The winsocket C<select> function doesn't follow POSIX in that it
3320	requires socket I<handles> and not socket I<file descriptors> (it is	4457	requires socket I<handles> and not socket I<file descriptors> (it is
3321	also extremely buggy). This makes select very inefficient, and also	4458	also extremely buggy). This makes select very inefficient, and also
3322	requires a mapping from file descriptors to socket handles. See the	4459	requires a mapping from file descriptors to socket handles (the Microsoft
		4460	C runtime provides the function C<_open_osfhandle> for this). See the
3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4461	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4462	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3325		4463
3326	The configuration for a "naked" win32 using the Microsoft runtime	4464	The configuration for a "naked" win32 using the Microsoft runtime
3327	libraries and raw winsocket select is:	4465	libraries and raw winsocket select is:
3328		4466
3329	#define EV_USE_SELECT 1	4467	#define EV_USE_SELECT 1
3330	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4468	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3331		4469
3332	Note that winsockets handling of fd sets is O(n), so you can easily get a	4470	Note that winsockets handling of fd sets is O(n), so you can easily get a
3333	complexity in the O(n²) range when using win32.	4471	complexity in the O(n²) range when using win32.
3334		4472
3335	=item Limited number of file descriptors	4473	=item Limited number of file descriptors
…		…
3338		4476
3339	Early versions of winsocket's select only supported waiting for a maximum	4477	Early versions of winsocket's select only supported waiting for a maximum
3340	of C<64> handles (probably owning to the fact that all windows kernels	4478	of C<64> handles (probably owning to the fact that all windows kernels
3341	can only wait for C<64> things at the same time internally; Microsoft	4479	can only wait for C<64> things at the same time internally; Microsoft
3342	recommends spawning a chain of threads and wait for 63 handles and the	4480	recommends spawning a chain of threads and wait for 63 handles and the
3343	previous thread in each. Great).	4481	previous thread in each. Sounds great!).
3344		4482
3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4483	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3346	to some high number (e.g. C<2048>) before compiling the winsocket select	4484	to some high number (e.g. C<2048>) before compiling the winsocket select
3347	call (which might be in libev or elsewhere, for example, perl does its own	4485	call (which might be in libev or elsewhere, for example, perl and many
3348	select emulation on windows).	4486	other interpreters do their own select emulation on windows).
3349		4487
3350	Another limit is the number of file descriptors in the Microsoft runtime	4488	Another limit is the number of file descriptors in the Microsoft runtime
3351	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4489	libraries, which by default is C<64> (there must be a hidden I<64>
3352	or something like this inside Microsoft). You can increase this by calling	4490	fetish or something like this inside Microsoft). You can increase this
3353	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4491	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3354	arbitrary limit), but is broken in many versions of the Microsoft runtime	4492	(another arbitrary limit), but is broken in many versions of the Microsoft
3355	libraries.
3356
3357	This might get you to about C<512> or C<2048> sockets (depending on	4493	runtime libraries. This might get you to about C<512> or C<2048> sockets
3358	windows version and/or the phase of the moon). To get more, you need to	4494	(depending on windows version and/or the phase of the moon). To get more,
3359	wrap all I/O functions and provide your own fd management, but the cost of	4495	you need to wrap all I/O functions and provide your own fd management, but
3360	calling select (O(n²)) will likely make this unworkable.	4496	the cost of calling select (O(n²)) will likely make this unworkable.
3361		4497
3362	=back	4498	=back
3363		4499
3364
3365	=head1 PORTABILITY REQUIREMENTS	4500	=head2 PORTABILITY REQUIREMENTS
3366		4501
3367	In addition to a working ISO-C implementation, libev relies on a few	4502	In addition to a working ISO-C implementation and of course the
3368	additional extensions:	4503	backend-specific APIs, libev relies on a few additional extensions:
3369		4504
3370	=over 4	4505	=over 4
3371		4506
		4507	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4508	calling conventions regardless of C<ev_watcher_type *>.
		4509
		4510	Libev assumes not only that all watcher pointers have the same internal
		4511	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4512	assumes that the same (machine) code can be used to call any watcher
		4513	callback: The watcher callbacks have different type signatures, but libev
		4514	calls them using an C<ev_watcher *> internally.
		4515
3372	=item C<sig_atomic_t volatile> must be thread-atomic as well	4516	=item C<sig_atomic_t volatile> must be thread-atomic as well
3373		4517
3374	The type C<sig_atomic_t volatile> (or whatever is defined as	4518	The type C<sig_atomic_t volatile> (or whatever is defined as
3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4519	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3376	threads. This is not part of the specification for C<sig_atomic_t>, but is	4520	threads. This is not part of the specification for C<sig_atomic_t>, but is
3377	believed to be sufficiently portable.	4521	believed to be sufficiently portable.
3378		4522
3379	=item C<sigprocmask> must work in a threaded environment	4523	=item C<sigprocmask> must work in a threaded environment
3380		4524
…		…
3389	except the initial one, and run the default loop in the initial thread as	4533	except the initial one, and run the default loop in the initial thread as
3390	well.	4534	well.
3391		4535
3392	=item C<long> must be large enough for common memory allocation sizes	4536	=item C<long> must be large enough for common memory allocation sizes
3393		4537
3394	To improve portability and simplify using libev, libev uses C<long>	4538	To improve portability and simplify its API, libev uses C<long> internally
3395	internally instead of C<size_t> when allocating its data structures. On	4539	instead of C<size_t> when allocating its data structures. On non-POSIX
3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4540	systems (Microsoft...) this might be unexpectedly low, but is still at
3397	is still at least 31 bits everywhere, which is enough for hundreds of	4541	least 31 bits everywhere, which is enough for hundreds of millions of
3398	millions of watchers.	4542	watchers.
3399		4543
3400	=item C<double> must hold a time value in seconds with enough accuracy	4544	=item C<double> must hold a time value in seconds with enough accuracy
3401		4545
3402	The type C<double> is used to represent timestamps. It is required to	4546	The type C<double> is used to represent timestamps. It is required to
3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4547	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3404	enough for at least into the year 4000. This requirement is fulfilled by	4548	enough for at least into the year 4000. This requirement is fulfilled by
3405	implementations implementing IEEE 754 (basically all existing ones).	4549	implementations implementing IEEE 754, which is basically all existing
		4550	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4551	2200.
3406		4552
3407	=back	4553	=back
3408		4554
3409	If you know of other additional requirements drop me a note.	4555	If you know of other additional requirements drop me a note.
3410		4556
3411		4557
3412	=head1 COMPILER WARNINGS	4558	=head1 ALGORITHMIC COMPLEXITIES
3413		4559
3414	Depending on your compiler and compiler settings, you might get no or a	4560	In this section the complexities of (many of) the algorithms used inside
3415	lot of warnings when compiling libev code. Some people are apparently	4561	libev will be documented. For complexity discussions about backends see
3416	scared by this.	4562	the documentation for C<ev_default_init>.
3417		4563
3418	However, these are unavoidable for many reasons. For one, each compiler	4564	All of the following are about amortised time: If an array needs to be
3419	has different warnings, and each user has different tastes regarding	4565	extended, libev needs to realloc and move the whole array, but this
3420	warning options. "Warn-free" code therefore cannot be a goal except when	4566	happens asymptotically rarer with higher number of elements, so O(1) might
3421	targeting a specific compiler and compiler-version.	4567	mean that libev does a lengthy realloc operation in rare cases, but on
		4568	average it is much faster and asymptotically approaches constant time.
3422		4569
3423	Another reason is that some compiler warnings require elaborate	4570	=over 4
3424	workarounds, or other changes to the code that make it less clear and less
3425	maintainable.
3426		4571
3427	And of course, some compiler warnings are just plain stupid, or simply	4572	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3428	wrong (because they don't actually warn about the condition their message
3429	seems to warn about).
3430		4573
3431	While libev is written to generate as few warnings as possible,	4574	This means that, when you have a watcher that triggers in one hour and
3432	"warn-free" code is not a goal, and it is recommended not to build libev	4575	there are 100 watchers that would trigger before that, then inserting will
3433	with any compiler warnings enabled unless you are prepared to cope with	4576	have to skip roughly seven (C<ld 100>) of these watchers.
3434	them (e.g. by ignoring them). Remember that warnings are just that:
3435	warnings, not errors, or proof of bugs.
3436		4577
		4578	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3437		4579
3438	=head1 VALGRIND	4580	That means that changing a timer costs less than removing/adding them,
		4581	as only the relative motion in the event queue has to be paid for.
3439		4582
3440	Valgrind has a special section here because it is a popular tool that is	4583	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3441	highly useful, but valgrind reports are very hard to interpret.
3442		4584
3443	If you think you found a bug (memory leak, uninitialised data access etc.)	4585	These just add the watcher into an array or at the head of a list.
3444	in libev, then check twice: If valgrind reports something like:
3445		4586
3446	==2274== definitely lost: 0 bytes in 0 blocks.	4587	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3447	==2274== possibly lost: 0 bytes in 0 blocks.
3448	==2274== still reachable: 256 bytes in 1 blocks.
3449		4588
3450	Then there is no memory leak. Similarly, under some circumstances,	4589	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3451	valgrind might report kernel bugs as if it were a bug in libev, or it
3452	might be confused (it is a very good tool, but only a tool).
3453		4590
3454	If you are unsure about something, feel free to contact the mailing list	4591	These watchers are stored in lists, so they need to be walked to find the
3455	with the full valgrind report and an explanation on why you think this is	4592	correct watcher to remove. The lists are usually short (you don't usually
3456	a bug in libev. However, don't be annoyed when you get a brisk "this is	4593	have many watchers waiting for the same fd or signal: one is typical, two
3457	no bug" answer and take the chance of learning how to interpret valgrind	4594	is rare).
3458	properly.
3459		4595
3460	If you need, for some reason, empty reports from valgrind for your project	4596	=item Finding the next timer in each loop iteration: O(1)
3461	I suggest using suppression lists.
3462		4597
		4598	By virtue of using a binary or 4-heap, the next timer is always found at a
		4599	fixed position in the storage array.
		4600
		4601	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4602
		4603	A change means an I/O watcher gets started or stopped, which requires
		4604	libev to recalculate its status (and possibly tell the kernel, depending
		4605	on backend and whether C<ev_io_set> was used).
		4606
		4607	=item Activating one watcher (putting it into the pending state): O(1)
		4608
		4609	=item Priority handling: O(number_of_priorities)
		4610
		4611	Priorities are implemented by allocating some space for each
		4612	priority. When doing priority-based operations, libev usually has to
		4613	linearly search all the priorities, but starting/stopping and activating
		4614	watchers becomes O(1) with respect to priority handling.
		4615
		4616	=item Sending an ev_async: O(1)
		4617
		4618	=item Processing ev_async_send: O(number_of_async_watchers)
		4619
		4620	=item Processing signals: O(max_signal_number)
		4621
		4622	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4623	calls in the current loop iteration. Checking for async and signal events
		4624	involves iterating over all running async watchers or all signal numbers.
		4625
		4626	=back
		4627
		4628
		4629	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4630
		4631	The major version 4 introduced some minor incompatible changes to the API.
		4632
		4633	At the moment, the C<ev.h> header file tries to implement superficial
		4634	compatibility, so most programs should still compile. Those might be
		4635	removed in later versions of libev, so better update early than late.
		4636
		4637	=over 4
		4638
		4639	=item C<ev_loop_count> renamed to C<ev_iteration>
		4640
		4641	=item C<ev_loop_depth> renamed to C<ev_depth>
		4642
		4643	=item C<ev_loop_verify> renamed to C<ev_verify>
		4644
		4645	Most functions working on C<struct ev_loop> objects don't have an
		4646	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4647	still called C<ev_loop_fork> because it would otherwise clash with the
		4648	C<ev_fork> typedef.
		4649
		4650	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4651
		4652	This is a simple rename - all other watcher types use their name
		4653	as revents flag, and now C<ev_timer> does, too.
		4654
		4655	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4656	and continue to be present for the foreseeable future, so this is mostly a
		4657	documentation change.
		4658
		4659	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4660
		4661	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4662	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4663	and work, but the library code will of course be larger.
		4664
		4665	=back
		4666
		4667
		4668	=head1 GLOSSARY
		4669
		4670	=over 4
		4671
		4672	=item active
		4673
		4674	A watcher is active as long as it has been started (has been attached to
		4675	an event loop) but not yet stopped (disassociated from the event loop).
		4676
		4677	=item application
		4678
		4679	In this document, an application is whatever is using libev.
		4680
		4681	=item callback
		4682
		4683	The address of a function that is called when some event has been
		4684	detected. Callbacks are being passed the event loop, the watcher that
		4685	received the event, and the actual event bitset.
		4686
		4687	=item callback invocation
		4688
		4689	The act of calling the callback associated with a watcher.
		4690
		4691	=item event
		4692
		4693	A change of state of some external event, such as data now being available
		4694	for reading on a file descriptor, time having passed or simply not having
		4695	any other events happening anymore.
		4696
		4697	In libev, events are represented as single bits (such as C<EV_READ> or
		4698	C<EV_TIMER>).
		4699
		4700	=item event library
		4701
		4702	A software package implementing an event model and loop.
		4703
		4704	=item event loop
		4705
		4706	An entity that handles and processes external events and converts them
		4707	into callback invocations.
		4708
		4709	=item event model
		4710
		4711	The model used to describe how an event loop handles and processes
		4712	watchers and events.
		4713
		4714	=item pending
		4715
		4716	A watcher is pending as soon as the corresponding event has been detected,
		4717	and stops being pending as soon as the watcher will be invoked or its
		4718	pending status is explicitly cleared by the application.
		4719
		4720	A watcher can be pending, but not active. Stopping a watcher also clears
		4721	its pending status.
		4722
		4723	=item real time
		4724
		4725	The physical time that is observed. It is apparently strictly monotonic :)
		4726
		4727	=item wall-clock time
		4728
		4729	The time and date as shown on clocks. Unlike real time, it can actually
		4730	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4731	clock.
		4732
		4733	=item watcher
		4734
		4735	A data structure that describes interest in certain events. Watchers need
		4736	to be started (attached to an event loop) before they can receive events.
		4737
		4738	=item watcher invocation
		4739
		4740	The act of calling the callback associated with a watcher.
		4741
		4742	=back
3463		4743
3464	=head1 AUTHOR	4744	=head1 AUTHOR
3465		4745
3466	Marc Lehmann <libev@schmorp.de>.	4746	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3467		4747

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