ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.163 by root, Sat May 31 23:19:23 2008 UTC vs.
Revision 1.232 by root, Thu Apr 16 06:17:26 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 DESCRIPTION
66		68
67	The newest version of this document is also available as an html-formatted	69	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	70	web page you might find easier to navigate when reading it for the first
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
178	not a problem.	180	not a problem.
179		181
180	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	183	version.
182		184
183	assert (("libev version mismatch",	185	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
186		188
187	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
188		190
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	194	a description of the set values.
193		195
194	Example: make sure we have the epoll method, because yeah this is cool and	196	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	197	a must have and can we have a torrent of it please!!!11
196		198
197	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
199		201
200	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
201		203
202	Return the set of all backends compiled into this binary of libev and also	204	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	205	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	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	224	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	225	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	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	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	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	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	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	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	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	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,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	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	308	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	309	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	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	365	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	366	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	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	368	readiness notifications you get per iteration.
363		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
		373
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		375
366	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	377	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	378	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,	379	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	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	381	performance tips.
372		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		387
375	For few fds, this backend is a bit little slower than poll and select,	388	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	389	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),	390	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	391	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	392
380	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
382		409
383	While stopping, setting and starting an I/O watcher in the same iteration	410	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	411	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	412	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	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
388		415	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		416
393	Best performance from this backend is achieved by not unregistering all	417	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.	418	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
396		428
397	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
399		434
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		436
402	Kqueue deserves special mention, as at the time of this writing, it	437	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	438	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	439	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"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	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	443	"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)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	445	system like NetBSD.
409		446
410	You still can embed kqueue into a normal poll or select backend and use it	447	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	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		450
414	It scales in the same way as the epoll backend, but the interface to the	451	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	452	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	453	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	454	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	455	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
420		458
421	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
422		460
423	While nominally embeddable in other event loops, this doesn't work	461	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	462	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	463	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	464	(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	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
429		471
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		473
432	This is not implemented yet (and might never be, unless you send me an	474	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	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	488	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	489	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	491	might perform better.
450		492
451	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
454		500
455	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
456		502
457	Try all backends (even potentially broken ones that wouldn't be tried	503	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	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		510
465	If one or more of these are or'ed into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		514
469	The most typical usage is like this:	515	Example: This is the most typical usage.
470		516
471	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		519
474	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	521	environment settings to be taken into account:
476		522
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		524
479	Use whatever libev has to offer, but make sure that kqueue is used if	525	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	526	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):	527	private event loop and only if you know the OS supports your types of
		528	fds):
482		529
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		531
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		533
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	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	535	always distinct from the default loop. Unlike the default loop, it cannot
…		…
493	libev with threads is indeed to create one loop per thread, and using the	540	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	541	default loop in the "main" or "initial" thread.
495		542
496	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
497		544
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	546	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
501		548
502	=item ev_default_destroy ()	549	=item ev_default_destroy ()
503		550
504	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	557	for example).
511		558
512	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
515		562
516	In general it is not advisable to call this function except in the	563	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	564	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	565	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		591
545	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
546		593
547	Like C<ev_default_fork>, but acts on an event loop created by	594	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	595	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.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
550		598
551	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
552		600
553	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
554		603
555	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
556		605
557	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	622	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	623	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	624	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).	625	event occurring (or more correctly, libev finding out about it).
577		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
578	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
579		666
580	Finally, this is it, the event handler. This function usually is called	667	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	668	after you initialised all your watchers and you want to start handling
582	events.	669	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	671	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.	672	either no event watchers are active anymore or C<ev_unloop> was called.
586		673
587	Please note that an explicit C<ev_unloop> is usually better than	674	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	675	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	677	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.	678	of relying on its watchers stopping correctly, that is truly a thing of
		679	beauty.
592		680
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	681	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	682	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.	683	process in case there are no events and will return after one iteration of
		684	the loop.
596		685
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	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	687	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	688	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	689	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	690	user-registered callback will be called), and will return after one
		691	iteration of the loop.
		692
		693	This is useful if you are waiting for some external event in conjunction
		694	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	695	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.	696	usually a better approach for this kind of thing.
604		697
605	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
606		699
607	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	701	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	702	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	703	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	704	- If we have been forked, detach and recreate the kernel state
		705	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	706	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	707	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	708	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	709	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	715	- Queue all expired timers.
622	- Queue all outstanding periodics.	716	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	718	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	719	- 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	720	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	721	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	727	anymore.
634		728
635	... queue jobs here, make sure they register event watchers as long	729	... 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..)	730	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	731	ev_loop (my_loop, 0);
638	... jobs done. yeah!	732	... jobs done or somebody called unloop. yeah!
639		733
640	=item ev_unloop (loop, how)	734	=item ev_unloop (loop, how)
641		735
642	Can be used to make a call to C<ev_loop> return early (but only after it	736	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	737	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	738	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.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		740
647	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
648		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
649	=item ev_ref (loop)	745	=item ev_ref (loop)
650		746
651	=item ev_unref (loop)	747	=item ev_unref (loop)
652		748
653	Ref/unref can be used to add or remove a reference count on the event	749	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	750	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	751	count is nonzero, C<ev_loop> will not return on its own.
		752
656	a watcher you never unregister that should not keep C<ev_loop> from	753	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	754	from returning, call ev_unref() after starting, and ev_ref() before
		755	stopping it.
		756
658	example, libev itself uses this for its internal signal pipe: It is not	757	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	758	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	759	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	760	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>	761	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,	762	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
665		766
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	768	running when nothing else is active.
668		769
669	struct ev_signal exitsig;	770	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	773	evf_unref (loop);
673		774
674	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
675		776
676	ev_ref (loop);	777	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	778	ev_signal_stop (loop, &exitsig);
678		779
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	780	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		781
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	782	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		783
683	These advanced functions influence the time that libev will spend waiting	784	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	785	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.	786	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		787	latency.
686		788
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	789	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	790	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	791	to increase efficiency of loop iterations (or to increase power-saving
		792	opportunities).
690		793
691	The background is that sometimes your program runs just fast enough to	794	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	795	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	796	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	797	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	798	overhead for the actual polling but can deliver many events at once.
696		799
697	By setting a higher I<io collect interval> you allow libev to spend more	800	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,	801	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	803	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.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		805
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	806	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	810	value will not introduce any overhead in libev.
708		811
709	Many (busy) programs can usually benefit by setting the I/O collect	812	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	813	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	814	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>,	815	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.	816	as this approaches the timing granularity of most systems.
714		817
		818	Setting the I<timeout collect interval> can improve the opportunity for
		819	saving power, as the program will "bundle" timer callback invocations that
		820	are "near" in time together, by delaying some, thus reducing the number of
		821	times the process sleeps and wakes up again. Another useful technique to
		822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		823	they fire on, say, one-second boundaries only.
		824
715	=item ev_loop_verify (loop)	825	=item ev_loop_verify (loop)
716		826
717	This function only does something when C<EV_VERIFY> support has been	827	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	828	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	829	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	830	is found to be inconsistent, it will print an error message to standard
		831	error and call C<abort ()>.
721		832
722	This can be used to catch bugs inside libev itself: under normal	833	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	834	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	835	data structures consistent.
725		836
726	=back	837	=back
727		838
728		839
729	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
730		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
		845
731	A watcher is a structure that you create and register to record your	846	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	847	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:	848	become readable, you would create an C<ev_io> watcher for that:
734		849
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	851	{
737	ev_io_stop (w);	852	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
739	}	854	}
740		855
741	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
742	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
743	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
746	ev_loop (loop, 0);	864	ev_loop (loop, 0);
747		865
748	As you can see, you are responsible for allocating the memory for your	866	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,	867	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		872
752	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	874	(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	875	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	876	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	877	is readable and/or writable).
757		878
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	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	880	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	881	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
762		883
763	To make the watcher actually watch out for events, you have to start it	884	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	885	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	886	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		888
768	As long as your watcher is active (has been started but not stopped) you	889	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	890	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
771		892
772	Each and every callback receives the event loop pointer as first, the	893	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	894	registered watcher structure as second, and a bitset of received events as
774	third argument.	895	third argument.
775		896
…		…
833		954
834	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
835		956
836	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
837		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
838	=item C<EV_ERROR>	964	=item C<EV_ERROR>
839		965
840	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	967	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	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
843	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
845		975
846	Libev will usually signal a few "dummy" events together with an error,	976	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	977	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	978	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	979	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
851		982
852	=back	983	=back
853		984
854	=head2 GENERIC WATCHER FUNCTIONS	985	=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		986
859	=over 4	987	=over 4
860		988
861	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
862		990
…		…
868	which rolls both calls into one.	996	which rolls both calls into one.
869		997
870	You can reinitialise a watcher at any time as long as it has been stopped	998	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.	999	(or never started) and there are no pending events outstanding.
872		1000
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1002	int revents)>.
		1003
		1004	Example: Initialise an C<ev_io> watcher in two steps.
		1005
		1006	ev_io w;
		1007	ev_init (&w, my_cb);
		1008	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1009
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1011
878	This macro initialises the type-specific parts of a watcher. You need to	1012	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	1013	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
883		1017
884	Although some watcher types do not have type-specific arguments	1018	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.	1019	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1020
		1021	See C<ev_init>, above, for an example.
		1022
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1024
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1025	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	1026	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1027	a watcher. The same limitations apply, of course.
892		1028
		1029	Example: Initialise and set an C<ev_io> watcher in one step.
		1030
		1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1032
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1034
895	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
897		1037
		1038	Example: Start the C<ev_io> watcher that is being abused as example in this
		1039	whole section.
		1040
		1041	ev_io_start (EV_DEFAULT_UC, &w);
		1042
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1044
900	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
901	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1049	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	1050	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	1051	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.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1053
907	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
908		1055
909	Returns a true value iff the watcher is active (i.e. it has been started	1056	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	1057	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
940		1087
		1088	See L<
		1089
941	This means that priorities are I<only> used for ordering callback	1090	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for	1091	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two	1092	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.	1093	watchers on the same event and make sure one is called first.
945		1094
…		…
952	The default priority used by watchers when no priority has been set is	1101	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 :).	1102	always C<0>, which is supposed to not be too high and not be too low :).
954		1103
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1104	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
956	fine, as long as you do not mind that the priority value you query might	1105	fine, as long as you do not mind that the priority value you query might
957	or might not have been adjusted to be within valid range.	1106	or might not have been clamped to the valid range.
958		1107
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1108	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1109
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1110	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	1111	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1112	can deal with that fact, as both are simply passed through to the
		1113	callback.
964		1114
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1115	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1116
967	If the watcher is pending, this function returns clears its pending status	1117	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	1118	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>.	1119	watcher isn't pending it does nothing and returns C<0>.
970		1120
		1121	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1122	callback to be invoked, which can be accomplished with this function.
		1123
971	=back	1124	=back
972		1125
973		1126
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1127	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1128
976	Each watcher has, by default, a member C<void *data> that you can change	1129	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	1130	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	1131	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	1132	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	1133	member, you can also "subclass" the watcher type and provide your own
981	data:	1134	data:
982		1135
983	struct my_io	1136	struct my_io
984	{	1137	{
985	struct ev_io io;	1138	ev_io io;
986	int otherfd;	1139	int otherfd;
987	void *somedata;	1140	void *somedata;
988	struct whatever *mostinteresting;	1141	struct whatever *mostinteresting;
989	}	1142	};
		1143
		1144	...
		1145	struct my_io w;
		1146	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1147
991	And since your callback will be called with a pointer to the watcher, you	1148	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1149	can cast it back to your own type:
993		1150
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1151	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1152	{
996	struct my_io *w = (struct my_io *)w_;	1153	struct my_io *w = (struct my_io *)w_;
997	...	1154	...
998	}	1155	}
999		1156
1000	More interesting and less C-conformant ways of casting your callback type	1157	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1158	instead have been omitted.
1002		1159
1003	Another common scenario is having some data structure with multiple	1160	Another common scenario is to use some data structure with multiple
1004	watchers:	1161	embedded watchers:
1005		1162
1006	struct my_biggy	1163	struct my_biggy
1007	{	1164	{
1008	int some_data;	1165	int some_data;
1009	ev_timer t1;	1166	ev_timer t1;
1010	ev_timer t2;	1167	ev_timer t2;
1011	}	1168	}
1012		1169
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1170	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1171	complicated: Either you store the address of your C<my_biggy> struct
		1172	in the C<data> member of the watcher (for woozies), or you need to use
		1173	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1174	programmers):
1015		1175
1016	#include <stddef.h>	1176	#include <stddef.h>
1017		1177
1018	static void	1178	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1179	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1180	{
1021	struct my_biggy big = (struct my_biggy *	1181	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1182	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1183	}
1024		1184
1025	static void	1185	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1186	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1187	{
1028	struct my_biggy big = (struct my_biggy *	1188	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1189	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1190	}
1031		1191
1032		1192
1033	=head1 WATCHER TYPES	1193	=head1 WATCHER TYPES
1034		1194
1035	This section describes each watcher in detail, but will not repeat	1195	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	1219	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	1220	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	1221	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1222	required if you know what you are doing).
1063		1223
1064	If you must do this, then force the use of a known-to-be-good backend	1224	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	1225	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1226	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1227
1068	Another thing you have to watch out for is that it is quite easy to	1228	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	1229	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	1230	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	1231	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	1232	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	1233	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	1234	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.	1235	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1236
1077	If you cannot run the fd in non-blocking mode (for example you should not	1237	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	1238	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	1239	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	1240	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1241	does this on its own, so its quite safe to use). Some people additionally
		1242	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1243	indefinitely.
		1244
		1245	But really, best use non-blocking mode.
1082		1246
1083	=head3 The special problem of disappearing file descriptors	1247	=head3 The special problem of disappearing file descriptors
1084		1248
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1249	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,	1250	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	1251	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	1252	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	1253	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	1254	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1255	fact, a different file descriptor.
1092		1256
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1287	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1288	C<EVBACKEND_POLL>.
1125		1289
1126	=head3 The special problem of SIGPIPE	1290	=head3 The special problem of SIGPIPE
1127		1291
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1292	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	1293	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	1294	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1295	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1296
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1297	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	1298	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).	1299	somewhere, as that would have given you a big clue).
1137		1300
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1306	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1307
1145	=item ev_io_set (ev_io *, int fd, int events)	1308	=item ev_io_set (ev_io *, int fd, int events)
1146		1309
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1310	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	1311	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.	1312	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1313
1151	=item int fd [read-only]	1314	=item int fd [read-only]
1152		1315
1153	The file descriptor being watched.	1316	The file descriptor being watched.
1154		1317
…		…
1162		1325
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1326	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	1327	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1328	attempt to read a whole line in the callback.
1166		1329
1167	static void	1330	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1331	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1332	{
1170	ev_io_stop (loop, w);	1333	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1334	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1335	}
1173		1336
1174	...	1337	...
1175	struct ev_loop *loop = ev_default_init (0);	1338	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1339	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1340	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1341	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1342	ev_loop (loop, 0);
1180		1343
1181		1344
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1345	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1346
1184	Timer watchers are simple relative timers that generate an event after a	1347	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1348	given time, and optionally repeating in regular intervals after that.
1186		1349
1187	The timers are based on real time, that is, if you register an event that	1350	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	1351	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	1352	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1353	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1354	monotonic clock option helps a lot here).
		1355
		1356	The callback is guaranteed to be invoked only I<after> its timeout has
		1357	passed. If multiple timers become ready during the same loop iteration
		1358	then the ones with earlier time-out values are invoked before ones with
		1359	later time-out values (but this is no longer true when a callback calls
		1360	C<ev_loop> recursively).
		1361
		1362	=head3 Be smart about timeouts
		1363
		1364	Many real-world problems involve some kind of timeout, usually for error
		1365	recovery. A typical example is an HTTP request - if the other side hangs,
		1366	you want to raise some error after a while.
		1367
		1368	What follows are some ways to handle this problem, from obvious and
		1369	inefficient to smart and efficient.
		1370
		1371	In the following, a 60 second activity timeout is assumed - a timeout that
		1372	gets reset to 60 seconds each time there is activity (e.g. each time some
		1373	data or other life sign was received).
		1374
		1375	=over 4
		1376
		1377	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1378
		1379	This is the most obvious, but not the most simple way: In the beginning,
		1380	start the watcher:
		1381
		1382	ev_timer_init (timer, callback, 60., 0.);
		1383	ev_timer_start (loop, timer);
		1384
		1385	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1386	and start it again:
		1387
		1388	ev_timer_stop (loop, timer);
		1389	ev_timer_set (timer, 60., 0.);
		1390	ev_timer_start (loop, timer);
		1391
		1392	This is relatively simple to implement, but means that each time there is
		1393	some activity, libev will first have to remove the timer from its internal
		1394	data structure and then add it again. Libev tries to be fast, but it's
		1395	still not a constant-time operation.
		1396
		1397	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1398
		1399	This is the easiest way, and involves using C<ev_timer_again> instead of
		1400	C<ev_timer_start>.
		1401
		1402	To implement this, configure an C<ev_timer> with a C<repeat> value
		1403	of C<60> and then call C<ev_timer_again> at start and each time you
		1404	successfully read or write some data. If you go into an idle state where
		1405	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1406	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1407
		1408	That means you can ignore both the C<ev_timer_start> function and the
		1409	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1410	member and C<ev_timer_again>.
		1411
		1412	At start:
		1413
		1414	ev_timer_init (timer, callback);
		1415	timer->repeat = 60.;
		1416	ev_timer_again (loop, timer);
		1417
		1418	Each time there is some activity:
		1419
		1420	ev_timer_again (loop, timer);
		1421
		1422	It is even possible to change the time-out on the fly, regardless of
		1423	whether the watcher is active or not:
		1424
		1425	timer->repeat = 30.;
		1426	ev_timer_again (loop, timer);
		1427
		1428	This is slightly more efficient then stopping/starting the timer each time
		1429	you want to modify its timeout value, as libev does not have to completely
		1430	remove and re-insert the timer from/into its internal data structure.
		1431
		1432	It is, however, even simpler than the "obvious" way to do it.
		1433
		1434	=item 3. Let the timer time out, but then re-arm it as required.
		1435
		1436	This method is more tricky, but usually most efficient: Most timeouts are
		1437	relatively long compared to the intervals between other activity - in
		1438	our example, within 60 seconds, there are usually many I/O events with
		1439	associated activity resets.
		1440
		1441	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1442	but remember the time of last activity, and check for a real timeout only
		1443	within the callback:
		1444
		1445	ev_tstamp last_activity; // time of last activity
		1446
		1447	static void
		1448	callback (EV_P_ ev_timer *w, int revents)
		1449	{
		1450	ev_tstamp now = ev_now (EV_A);
		1451	ev_tstamp timeout = last_activity + 60.;
		1452
		1453	// if last_activity + 60. is older than now, we did time out
		1454	if (timeout < now)
		1455	{
		1456	// timeout occured, take action
		1457	}
		1458	else
		1459	{
		1460	// callback was invoked, but there was some activity, re-arm
		1461	// the watcher to fire in last_activity + 60, which is
		1462	// guaranteed to be in the future, so "again" is positive:
		1463	w->repeat = timeout - now;
		1464	ev_timer_again (EV_A_ w);
		1465	}
		1466	}
		1467
		1468	To summarise the callback: first calculate the real timeout (defined
		1469	as "60 seconds after the last activity"), then check if that time has
		1470	been reached, which means something I<did>, in fact, time out. Otherwise
		1471	the callback was invoked too early (C<timeout> is in the future), so
		1472	re-schedule the timer to fire at that future time, to see if maybe we have
		1473	a timeout then.
		1474
		1475	Note how C<ev_timer_again> is used, taking advantage of the
		1476	C<ev_timer_again> optimisation when the timer is already running.
		1477
		1478	This scheme causes more callback invocations (about one every 60 seconds
		1479	minus half the average time between activity), but virtually no calls to
		1480	libev to change the timeout.
		1481
		1482	To start the timer, simply initialise the watcher and set C<last_activity>
		1483	to the current time (meaning we just have some activity :), then call the
		1484	callback, which will "do the right thing" and start the timer:
		1485
		1486	ev_timer_init (timer, callback);
		1487	last_activity = ev_now (loop);
		1488	callback (loop, timer, EV_TIMEOUT);
		1489
		1490	And when there is some activity, simply store the current time in
		1491	C<last_activity>, no libev calls at all:
		1492
		1493	last_actiivty = ev_now (loop);
		1494
		1495	This technique is slightly more complex, but in most cases where the
		1496	time-out is unlikely to be triggered, much more efficient.
		1497
		1498	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1499	callback :) - just change the timeout and invoke the callback, which will
		1500	fix things for you.
		1501
		1502	=item 4. Wee, just use a double-linked list for your timeouts.
		1503
		1504	If there is not one request, but many thousands (millions...), all
		1505	employing some kind of timeout with the same timeout value, then one can
		1506	do even better:
		1507
		1508	When starting the timeout, calculate the timeout value and put the timeout
		1509	at the I<end> of the list.
		1510
		1511	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1512	the list is expected to fire (for example, using the technique #3).
		1513
		1514	When there is some activity, remove the timer from the list, recalculate
		1515	the timeout, append it to the end of the list again, and make sure to
		1516	update the C<ev_timer> if it was taken from the beginning of the list.
		1517
		1518	This way, one can manage an unlimited number of timeouts in O(1) time for
		1519	starting, stopping and updating the timers, at the expense of a major
		1520	complication, and having to use a constant timeout. The constant timeout
		1521	ensures that the list stays sorted.
		1522
		1523	=back
		1524
		1525	So which method the best?
		1526
		1527	Method #2 is a simple no-brain-required solution that is adequate in most
		1528	situations. Method #3 requires a bit more thinking, but handles many cases
		1529	better, and isn't very complicated either. In most case, choosing either
		1530	one is fine, with #3 being better in typical situations.
		1531
		1532	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1533	rather complicated, but extremely efficient, something that really pays
		1534	off after the first million or so of active timers, i.e. it's usually
		1535	overkill :)
		1536
		1537	=head3 The special problem of time updates
		1538
		1539	Establishing the current time is a costly operation (it usually takes at
		1540	least two system calls): EV therefore updates its idea of the current
		1541	time only before and after C<ev_loop> collects new events, which causes a
		1542	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1543	lots of events in one iteration.
1192		1544
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1545	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	1546	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	1547	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	1548	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:	1549	timeout on the current time, use something like this to adjust for this:
1198		1550
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1551	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1552
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1553	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	1554	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1555	()>.
1204		1556
1205	=head3 Watcher-Specific Functions and Data Members	1557	=head3 Watcher-Specific Functions and Data Members
1206		1558
1207	=over 4	1559	=over 4
1208		1560
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1584	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1585
1234	If the timer is repeating, either start it if necessary (with the	1586	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.	1587	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1588
1237	This sounds a bit complicated, but here is a useful and typical	1589	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	1590	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
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1591
1262	=item ev_tstamp repeat [read-write]	1592	=item ev_tstamp repeat [read-write]
1263		1593
1264	The current C<repeat> value. Will be used each time the watcher times out	1594	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),	1595	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.	1596	which is also when any modifications are taken into account.
1267		1597
1268	=back	1598	=back
1269		1599
1270	=head3 Examples	1600	=head3 Examples
1271		1601
1272	Example: Create a timer that fires after 60 seconds.	1602	Example: Create a timer that fires after 60 seconds.
1273		1603
1274	static void	1604	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1605	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1606	{
1277	.. one minute over, w is actually stopped right here	1607	.. one minute over, w is actually stopped right here
1278	}	1608	}
1279		1609
1280	struct ev_timer mytimer;	1610	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1611	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1612	ev_timer_start (loop, &mytimer);
1283		1613
1284	Example: Create a timeout timer that times out after 10 seconds of	1614	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1615	inactivity.
1286		1616
1287	static void	1617	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1618	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1619	{
1290	.. ten seconds without any activity	1620	.. ten seconds without any activity
1291	}	1621	}
1292		1622
1293	struct ev_timer mytimer;	1623	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1624	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1625	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1626	ev_loop (loop, 0);
1297		1627
1298	// and in some piece of code that gets executed on any "activity":	1628	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1629	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1630	ev_timer_again (&mytimer);
1301		1631
1302		1632
1303	=head2 C<ev_periodic> - to cron or not to cron?	1633	=head2 C<ev_periodic> - to cron or not to cron?
1304		1634
1305	Periodic watchers are also timers of a kind, but they are very versatile	1635	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1636	(and unfortunately a bit complex).
1307		1637
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1638	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	1639	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	1640	(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 ()	1641	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	1642	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	1643	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		1644
		1645	You can tell a periodic watcher to trigger after some specific point
		1646	in time: for example, if you tell a periodic watcher to trigger "in 10
		1647	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1648	not a delay) and then reset your system clock to January of the previous
		1649	year, then it will take a year or more to trigger the event (unlike an
		1650	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1651	it, as it uses a relative timeout).
		1652
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1653	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	1654	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1655	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1656	those cannot react to time jumps.
1320		1657
1321	As with timers, the callback is guaranteed to be invoked only when the	1658	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	1659	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.	1660	timers become ready during the same loop iteration then the ones with
		1661	earlier time-out values are invoked before ones with later time-out values
		1662	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1663
1325	=head3 Watcher-Specific Functions and Data Members	1664	=head3 Watcher-Specific Functions and Data Members
1326		1665
1327	=over 4	1666	=over 4
1328		1667
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1668	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1669
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1670	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1671
1333	Lots of arguments, lets sort it out... There are basically three modes of	1672	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:	1673	operation, and we will explain them from simplest to most complex:
1335		1674
1336	=over 4	1675	=over 4
1337		1676
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1677	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1678
1340	In this configuration the watcher triggers an event after the wall clock	1679	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	1680	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	1681	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.	1682	will be stopped and invoked when the system clock reaches or surpasses
		1683	this point in time.
1344		1684
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1685	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1686
1347	In this mode the watcher will always be scheduled to time out at the next	1687	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)	1688	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1689	negative) and then repeat, regardless of any time jumps. The C<offset>
		1690	argument is merely an offset into the C<interval> periods.
1350		1691
1351	This can be used to create timers that do not drift with respect to system	1692	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	1693	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1694	hour, on the hour (with respect to UTC):
1354		1695
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1696	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1697
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1698	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	1699	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	1700	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1701	by 3600.
1361		1702
1362	Another way to think about it (for the mathematically inclined) is that	1703	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	1704	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.	1705	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1706
1366	For numerical stability it is preferable that the C<at> value is near	1707	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	1708	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1709	this value, and in fact is often specified as zero.
1369		1710
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1711	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	1712	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	1713	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).	1714	millisecond (if the OS supports it and the machine is fast enough).
1374		1715
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1716	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1717
1377	In this mode the values for C<interval> and C<at> are both being	1718	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	1719	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1720	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1721	current time as second argument.
1381		1722
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1723	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1724	or make ANY other event loop modifications whatsoever, unless explicitly
		1725	allowed by documentation here>.
1384		1726
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1727	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	1728	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1729	only event loop modification you are allowed to do).
1388		1730
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1731	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1732	*w, ev_tstamp now)>, e.g.:
1391		1733
		1734	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1735	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1736	{
1394	return now + 60.;	1737	return now + 60.;
1395	}	1738	}
1396		1739
1397	It must return the next time to trigger, based on the passed time value	1740	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	1760	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	1761	program when the crontabs have changed).
1419		1762
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	1763	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		1764
1422	When active, returns the absolute time that the watcher is supposed to	1765	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	1766	to trigger next. This is not the same as the C<offset> argument to
		1767	C<ev_periodic_set>, but indeed works even in interval and manual
		1768	rescheduling modes.
1424		1769
1425	=item ev_tstamp offset [read-write]	1770	=item ev_tstamp offset [read-write]
1426		1771
1427	When repeating, this contains the offset value, otherwise this is the	1772	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>).	1773	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1774	although libev might modify this value for better numerical stability).
1429		1775
1430	Can be modified any time, but changes only take effect when the periodic	1776	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	1777	timer fires or C<ev_periodic_again> is being called.
1432		1778
1433	=item ev_tstamp interval [read-write]	1779	=item ev_tstamp interval [read-write]
1434		1780
1435	The current interval value. Can be modified any time, but changes only	1781	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	1782	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1783	called.
1438		1784
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1785	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1786
1441	The current reschedule callback, or C<0>, if this functionality is	1787	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	1788	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.	1789	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1790
1445	=back	1791	=back
1446		1792
1447	=head3 Examples	1793	=head3 Examples
1448		1794
1449	Example: Call a callback every hour, or, more precisely, whenever the	1795	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1796	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1797	potentially a lot of jitter, but good long-term stability.
1452		1798
1453	static void	1799	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1800	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1801	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1802	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1803	}
1458		1804
1459	struct ev_periodic hourly_tick;	1805	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1806	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1807	ev_periodic_start (loop, &hourly_tick);
1462		1808
1463	Example: The same as above, but use a reschedule callback to do it:	1809	Example: The same as above, but use a reschedule callback to do it:
1464		1810
1465	#include <math.h>	1811	#include <math.h>
1466		1812
1467	static ev_tstamp	1813	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1814	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1815	{
1470	return fmod (now, 3600.) + 3600.;	1816	return now + (3600. - fmod (now, 3600.));
1471	}	1817	}
1472		1818
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1819	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1820
1475	Example: Call a callback every hour, starting now:	1821	Example: Call a callback every hour, starting now:
1476		1822
1477	struct ev_periodic hourly_tick;	1823	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1824	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1825	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1826	ev_periodic_start (loop, &hourly_tick);
1481		1827
1482		1828
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	1829	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		1830
1485	Signal watchers will trigger an event when the process receives a specific	1831	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	1832	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	1833	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1834	normal event processing, like any other event.
1489		1835
		1836	If you want signals asynchronously, just use C<sigaction> as you would
		1837	do without libev and forget about sharing the signal. You can even use
		1838	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1839
1490	You can configure as many watchers as you like per signal. Only when the	1840	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1841	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1842	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	1843	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1844	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1845	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1846
1497	If possible and supported, libev will install its handlers with	1847	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1848	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1849	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1850	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1867
1518	=back	1868	=back
1519		1869
1520	=head3 Examples	1870	=head3 Examples
1521		1871
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1872	Example: Try to exit cleanly on SIGINT.
1523		1873
1524	static void	1874	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1875	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1876	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1877	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1878	}
1529		1879
1530	struct ev_signal signal_watcher;	1880	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1881	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1882	ev_signal_start (loop, &signal_watcher);
1533		1883
1534		1884
1535	=head2 C<ev_child> - watch out for process status changes	1885	=head2 C<ev_child> - watch out for process status changes
1536		1886
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1887	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	1888	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	1889	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	1890	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1891	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1892	forking and then immediately registering a watcher for the child is fine,
		1893	but forking and registering a watcher a few event loop iterations later is
		1894	not.
1542		1895
1543	Only the default event loop is capable of handling signals, and therefore	1896	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1897	you can only register child watchers in the default event loop.
1545		1898
1546	=head3 Process Interaction	1899	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1912	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1913	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1914	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	1915	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.	1916	that, so other libev users can use C<ev_child> watchers freely.
		1917
		1918	=head3 Stopping the Child Watcher
		1919
		1920	Currently, the child watcher never gets stopped, even when the
		1921	child terminates, so normally one needs to stop the watcher in the
		1922	callback. Future versions of libev might stop the watcher automatically
		1923	when a child exit is detected.
1564		1924
1565	=head3 Watcher-Specific Functions and Data Members	1925	=head3 Watcher-Specific Functions and Data Members
1566		1926
1567	=over 4	1927	=over 4
1568		1928
…		…
1597	=head3 Examples	1957	=head3 Examples
1598		1958
1599	Example: C<fork()> a new process and install a child handler to wait for	1959	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	1960	its completion.
1601		1961
1602	ev_child cw;	1962	ev_child cw;
1603		1963
1604	static void	1964	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1965	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1966	{
1607	ev_child_stop (EV_A_ w);	1967	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1968	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1969	}
1610		1970
1611	pid_t pid = fork ();	1971	pid_t pid = fork ();
1612		1972
1613	if (pid < 0)	1973	if (pid < 0)
1614	// error	1974	// error
1615	else if (pid == 0)	1975	else if (pid == 0)
1616	{	1976	{
1617	// the forked child executes here	1977	// the forked child executes here
1618	exit (1);	1978	exit (1);
1619	}	1979	}
1620	else	1980	else
1621	{	1981	{
1622	ev_child_init (&cw, child_cb, pid, 0);	1982	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	1983	ev_child_start (EV_DEFAULT_ &cw);
1624	}	1984	}
1625		1985
1626		1986
1627	=head2 C<ev_stat> - did the file attributes just change?	1987	=head2 C<ev_stat> - did the file attributes just change?
1628		1988
1629	This watches a file system path for attribute changes. That is, it calls	1989	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	1990	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.	1991	and sees if it changed compared to the last time, invoking the callback if
		1992	it did.
1632		1993
1633	The path does not need to exist: changing from "path exists" to "path does	1994	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	1995	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	1996	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	1997	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	1998	least one) and all the other fields of the stat buffer having unspecified
		1999	contents.
1638		2000
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2001	The path I<must not> end in a slash or contain special components such as
		2002	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.	2003	your working directory changes, then the behaviour is undefined.
1641		2004
1642	Since there is no standard to do this, the portable implementation simply	2005	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	2006	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2007	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,	2008	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	2009	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2010	(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	2011	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2012	currently around C<0.1>, but that's usually overkill.
1650		2013
1651	This watcher type is not meant for massive numbers of stat watchers,	2014	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2015	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2016	resource-intensive.
1654		2017
1655	At the time of this writing, only the Linux inotify interface is	2018	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2019	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	2020	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	2021	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		2022
1664	=head3 ABI Issues (Largefile Support)	2023	=head3 ABI Issues (Largefile Support)
1665		2024
1666	Libev by default (unless the user overrides this) uses the default	2025	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2026	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2027	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	2028	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	2029	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	2030	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	2031	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2032	most noticeably displayed with ev_stat and large file support.
1674		2033
1675	=head3 Inotify	2034	The solution for this is to lobby your distribution maker to make large
		2035	file interfaces available by default (as e.g. FreeBSD does) and not
		2036	optional. Libev cannot simply switch on large file support because it has
		2037	to exchange stat structures with application programs compiled using the
		2038	default compilation environment.
1676		2039
		2040	=head3 Inotify and Kqueue
		2041
1677	When C<inotify (7)> support has been compiled into libev (generally only	2042	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	2043	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	2044	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2045	watcher is being started.
1681		2046
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2047	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	2048	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	2049	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.	2050	there are many cases where libev has to resort to regular C<stat> polling,
		2051	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2052	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2053	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2054	xfs are fully working) libev usually gets away without polling.
1686		2055
1687	(There is no support for kqueue, as apparently it cannot be used to	2056	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	2057	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2058	descriptor open on the object at all times, and detecting renames, unlinks
		2059	etc. is difficult.
		2060
		2061	=head3 C<stat ()> is a synchronous operation
		2062
		2063	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2064	the process. The exception are C<ev_stat> watchers - those call C<stat
		2065	()>, which is a synchronous operation.
		2066
		2067	For local paths, this usually doesn't matter: unless the system is very
		2068	busy or the intervals between stat's are large, a stat call will be fast,
		2069	as the path data is usually in memory already (except when starting the
		2070	watcher).
		2071
		2072	For networked file systems, calling C<stat ()> can block an indefinite
		2073	time due to network issues, and even under good conditions, a stat call
		2074	often takes multiple milliseconds.
		2075
		2076	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2077	paths, although this is fully supported by libev.
1690		2078
1691	=head3 The special problem of stat time resolution	2079	=head3 The special problem of stat time resolution
1692		2080
1693	The C<stat ()> system call only supports full-second resolution portably, and	2081	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2082	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2083	still only support whole seconds.
1696		2084
1697	That means that, if the time is the only thing that changes, you can	2085	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	2086	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	2087	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	2088	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2089	stat data does change in other ways (e.g. file size).
1702		2090
1703	The solution to this is to delay acting on a change for slightly more	2091	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	2092	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);	2093	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2094	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2114	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	2115	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	2116	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.	2117	path for as long as the watcher is active.
1730		2118
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2119	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	2120	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2121	last change was detected).
1734		2122
1735	=item ev_stat_stat (loop, ev_stat *)	2123	=item ev_stat_stat (loop, ev_stat *)
1736		2124
1737	Updates the stat buffer immediately with new values. If you change the	2125	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	2126	watched path in your callback, you could call this function to avoid
…		…
1767		2155
1768	=head3 Examples	2156	=head3 Examples
1769		2157
1770	Example: Watch C</etc/passwd> for attribute changes.	2158	Example: Watch C</etc/passwd> for attribute changes.
1771		2159
1772	static void	2160	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2161	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2162	{
1775	/* /etc/passwd changed in some way */	2163	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2164	if (w->attr.st_nlink)
1777	{	2165	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2166	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2167	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2168	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2169	}
1782	else	2170	else
1783	/* you shalt not abuse printf for puts */	2171	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2172	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2173	"if this is windows, they already arrived\n");
1786	}	2174	}
1787		2175
1788	...	2176	...
1789	ev_stat passwd;	2177	ev_stat passwd;
1790		2178
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2179	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2180	ev_stat_start (loop, &passwd);
1793		2181
1794	Example: Like above, but additionally use a one-second delay so we do not	2182	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	2183	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	2184	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2185	C<ev_timer> callback invocation).
1798		2186
1799	static ev_stat passwd;	2187	static ev_stat passwd;
1800	static ev_timer timer;	2188	static ev_timer timer;
1801		2189
1802	static void	2190	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2191	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2192	{
1805	ev_timer_stop (EV_A_ w);	2193	ev_timer_stop (EV_A_ w);
1806		2194
1807	/* now it's one second after the most recent passwd change */	2195	/* now it's one second after the most recent passwd change */
1808	}	2196	}
1809		2197
1810	static void	2198	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2199	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2200	{
1813	/* reset the one-second timer */	2201	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2202	ev_timer_again (EV_A_ &timer);
1815	}	2203	}
1816		2204
1817	...	2205	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2206	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2207	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2208	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2209
1822		2210
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2211	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2212
1825	Idle watchers trigger events when no other events of the same or higher	2213	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	2214	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2215	as receiving "events").
1828		2216
1829	That is, as long as your process is busy handling sockets or timeouts	2217	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	2218	(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	2219	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	2220	are pending), the idle watchers are being called once per event loop
…		…
1843		2231
1844	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1845		2233
1846	=over 4	2234	=over 4
1847		2235
1848	=item ev_idle_init (ev_signal *, callback)	2236	=item ev_idle_init (ev_idle *, callback)
1849		2237
1850	Initialises and configures the idle watcher - it has no parameters of any	2238	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,	2239	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2240	believe me.
1853		2241
…		…
1856	=head3 Examples	2244	=head3 Examples
1857		2245
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2246	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2247	callback, free it. Also, use no error checking, as usual.
1860		2248
1861	static void	2249	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2250	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2251	{
1864	free (w);	2252	free (w);
1865	// now do something you wanted to do when the program has	2253	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2254	// no longer anything immediate to do.
1867	}	2255	}
1868		2256
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2257	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2258	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2259	ev_idle_start (loop, idle_cb);
1872		2260
1873		2261
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2262	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2263
1876	Prepare and check watchers are usually (but not always) used in tandem:	2264	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2265	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2266	afterwards.
1879		2267
1880	You I<must not> call C<ev_loop> or similar functions that enter	2268	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>	2269	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,	2272	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	2273	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2274	called in pairs bracketing the blocking call.
1887		2275
1888	Their main purpose is to integrate other event mechanisms into libev and	2276	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	2277	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	2278	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2279	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,	2280	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>	2281	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2282	watcher).
1895		2283
1896	This is done by examining in each prepare call which file descriptors need	2284	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	2285	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	2286	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	2287	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2288	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	2289	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,	2290	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2291	nevertheless, because you never know, you know?).
1904		2292
1905	As another example, the Perl Coro module uses these hooks to integrate	2293	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2294	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2295	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	2296	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	2299	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2300	low-priority coroutines to idle/background tasks).
1913		2301
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2302	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	2303	priority, to ensure that they are being run before any other watchers
		2304	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2305
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2306	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	2307	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2308	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	2309	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	2310	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	2311	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2312	others).
1923		2313
1924	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1925		2315
1926	=over 4	2316	=over 4
1927		2317
…		…
1929		2319
1930	=item ev_check_init (ev_check *, callback)	2320	=item ev_check_init (ev_check *, callback)
1931		2321
1932	Initialises and configures the prepare or check watcher - they have no	2322	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>	2323	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.	2324	macros, but using them is utterly, utterly, utterly and completely
		2325	pointless.
1935		2326
1936	=back	2327	=back
1937		2328
1938	=head3 Examples	2329	=head3 Examples
1939		2330
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2339	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	2340	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	2341	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.	2342	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2343
1953	static ev_io iow [nfd];	2344	static ev_io iow [nfd];
1954	static ev_timer tw;	2345	static ev_timer tw;
1955		2346
1956	static void	2347	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2348	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2349	{
1959	}	2350	}
1960		2351
1961	// create io watchers for each fd and a timer before blocking	2352	// create io watchers for each fd and a timer before blocking
1962	static void	2353	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2354	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2355	{
1965	int timeout = 3600000;	2356	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2357	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2358	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2360
1970	/* the callback is illegal, but won't be called as we stop during check */	2361	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2362	ev_timer_init (&tw, 0, timeout * 1e-3);
1972	ev_timer_start (loop, &tw);	2363	ev_timer_start (loop, &tw);
1973		2364
1974	// create one ev_io per pollfd	2365	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2366	for (int i = 0; i < nfd; ++i)
1976	{	2367	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2368	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2369	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2370	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2371
1981	fds [i].revents = 0;	2372	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2373	ev_io_start (loop, iow + i);
1983	}	2374	}
1984	}	2375	}
1985		2376
1986	// stop all watchers after blocking	2377	// stop all watchers after blocking
1987	static void	2378	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2379	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2380	{
1990	ev_timer_stop (loop, &tw);	2381	ev_timer_stop (loop, &tw);
1991		2382
1992	for (int i = 0; i < nfd; ++i)	2383	for (int i = 0; i < nfd; ++i)
1993	{	2384	{
1994	// set the relevant poll flags	2385	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2386	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2387	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2388	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2389	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2390	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2391
2001	// now stop the watcher	2392	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2393	ev_io_stop (loop, iow + i);
2003	}	2394	}
2004		2395
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2396	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2397	}
2007		2398
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2399	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.	2400	in the prepare watcher and would dispose of the check watcher.
2010		2401
2011	Method 3: If the module to be embedded supports explicit event	2402	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2403	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2404	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2405
2015	static void	2406	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2407	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2408	{
2018	adns_state ads = (adns_state)w->data;	2409	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2410	update_now (EV_A);
2020		2411
2021	adns_processtimeouts (ads, &tv_now);	2412	adns_processtimeouts (ads, &tv_now);
2022	}	2413	}
2023		2414
2024	static void	2415	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2416	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2417	{
2027	adns_state ads = (adns_state)w->data;	2418	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2419	update_now (EV_A);
2029		2420
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2421	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2422	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2423	}
2033		2424
2034	// do not ever call adns_afterpoll	2425	// do not ever call adns_afterpoll
2035		2426
2036	Method 4: Do not use a prepare or check watcher because the module you	2427	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	2428	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	2429	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	2430	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2431	this approach, effectively embedding EV as a client into the horrible
		2432	libglib event loop.
2041		2433
2042	static gint	2434	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2435	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2436	{
2045	int got_events = 0;	2437	int got_events = 0;
2046		2438
2047	for (n = 0; n < nfds; ++n)	2439	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2440	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2441
2050	if (timeout >= 0)	2442	if (timeout >= 0)
2051	// create/start timer	2443	// create/start timer
2052		2444
2053	// poll	2445	// poll
2054	ev_loop (EV_A_ 0);	2446	ev_loop (EV_A_ 0);
2055		2447
2056	// stop timer again	2448	// stop timer again
2057	if (timeout >= 0)	2449	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2450	ev_timer_stop (EV_A_ &to);
2059		2451
2060	// stop io watchers again - their callbacks should have set	2452	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2453	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2454	ev_io_stop (EV_A_ iow [n]);
2063		2455
2064	return got_events;	2456	return got_events;
2065	}	2457	}
2066		2458
2067		2459
2068	=head2 C<ev_embed> - when one backend isn't enough...	2460	=head2 C<ev_embed> - when one backend isn't enough...
2069		2461
2070	This is a rather advanced watcher type that lets you embed one event loop	2462	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2468	prioritise I/O.
2077		2469
2078	As an example for a bug workaround, the kqueue backend might only support	2470	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	2471	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	2472	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	2473	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	2474	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	2475	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.	2476	C<kevent>, but at least you can use both mechanisms for what they are
		2477	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2478
2086	As for prioritising I/O: rarely you have the case where some fds have	2479	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	2480	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	2481	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	2482	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.	2483	the rest in a second one, and embed the second one in the first.
2091		2484
2092	As long as the watcher is active, the callback will be invoked every time	2485	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	2486	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	2487	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	2488	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	2489	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	2490	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2491
2100	As long as the watcher is started it will automatically handle events. The	2492	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	2493	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		2494
2105	Also, there have not currently been made special provisions for forking:	2495	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,	2496	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	2497	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2498	C<ev_loop_fork> on the embedded loop.
2109		2499
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2500	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2501	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2502	portable one.
2113		2503
2114	So when you want to use this feature you will always have to be prepared	2504	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	2505	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	2506	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.	2507	create it, and if that fails, use the normal loop for everything.
		2508
		2509	=head3 C<ev_embed> and fork
		2510
		2511	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2512	automatically be applied to the embedded loop as well, so no special
		2513	fork handling is required in that case. When the watcher is not running,
		2514	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2515	as applicable.
2118		2516
2119	=head3 Watcher-Specific Functions and Data Members	2517	=head3 Watcher-Specific Functions and Data Members
2120		2518
2121	=over 4	2519	=over 4
2122		2520
…		…
2148	event loop. If that is not possible, use the default loop. The default	2546	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	2547	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	2548	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2549	used).
2152		2550
2153	struct ev_loop *loop_hi = ev_default_init (0);	2551	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2552	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2553	ev_embed embed;
2156		2554
2157	// see if there is a chance of getting one that works	2555	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2556	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2557	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2558	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2559	: 0;
2162		2560
2163	// if we got one, then embed it, otherwise default to loop_hi	2561	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2562	if (loop_lo)
2165	{	2563	{
2166	ev_embed_init (&embed, 0, loop_lo);	2564	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2565	ev_embed_start (loop_hi, &embed);
2168	}	2566	}
2169	else	2567	else
2170	loop_lo = loop_hi;	2568	loop_lo = loop_hi;
2171		2569
2172	Example: Check if kqueue is available but not recommended and create	2570	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2571	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2572	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2573	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2574
2177	struct ev_loop *loop = ev_default_init (0);	2575	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2576	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2577	ev_embed embed;
2180		2578
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2579	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2580	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2581	{
2184	ev_embed_init (&embed, 0, loop_socket);	2582	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2583	ev_embed_start (loop, &embed);
2186	}	2584	}
2187		2585
2188	if (!loop_socket)	2586	if (!loop_socket)
2189	loop_socket = loop;	2587	loop_socket = loop;
2190		2588
2191	// now use loop_socket for all sockets, and loop for everything else	2589	// now use loop_socket for all sockets, and loop for everything else
2192		2590
2193		2591
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2592	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2593
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2594	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2638	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	2639	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2640	need elaborate support such as pthreads.
2243		2641
2244	That means that if you want to queue data, you have to provide your own	2642	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	2643	queue. But at least I can tell you how to implement locking around your
2246	queue:	2644	queue:
2247		2645
2248	=over 4	2646	=over 4
2249		2647
2250	=item queueing from a signal handler context	2648	=item queueing from a signal handler context
2251		2649
2252	To implement race-free queueing, you simply add to the queue in the signal	2650	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	2651	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2652	an example that does that for some fictitious SIGUSR1 handler:
2255		2653
2256	static ev_async mysig;	2654	static ev_async mysig;
2257		2655
2258	static void	2656	static void
2259	sigusr1_handler (void)	2657	sigusr1_handler (void)
…		…
2325	=over 4	2723	=over 4
2326		2724
2327	=item ev_async_init (ev_async *, callback)	2725	=item ev_async_init (ev_async *, callback)
2328		2726
2329	Initialises and configures the async watcher - it has no parameters of any	2727	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,	2728	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2729	trust me.
2332		2730
2333	=item ev_async_send (loop, ev_async *)	2731	=item ev_async_send (loop, ev_async *)
2334		2732
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2733	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	2734	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	2735	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	2736	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2737	section below on what exactly this means).
2340		2738
		2739	Note that, as with other watchers in libev, multiple events might get
		2740	compressed into a single callback invocation (another way to look at this
		2741	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2742	reset when the event loop detects that).
		2743
2341	This call incurs the overhead of a system call only once per loop iteration,	2744	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	2745	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	2746	repeated calls to C<ev_async_send> for the same event loop.
2344		2747
2345	=item bool = ev_async_pending (ev_async *)	2748	=item bool = ev_async_pending (ev_async *)
2346		2749
2347	Returns a non-zero value when C<ev_async_send> has been called on the	2750	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	2751	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	2754	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,	2755	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	2756	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.	2757	quickly check whether invoking the loop might be a good idea.
2355		2758
2356	Not that this does I<not> check whether the watcher itself is pending, only	2759	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	2760	only whether it has been requested to make this watcher pending: there
		2761	is a time window between the event loop checking and resetting the async
		2762	notification, and the callback being invoked.
2358		2763
2359	=back	2764	=back
2360		2765
2361		2766
2362	=head1 OTHER FUNCTIONS	2767	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	2771	=over 4
2367		2772
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2773	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2774
2370	This function combines a simple timer and an I/O watcher, calls your	2775	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2776	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	2777	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	2778	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2779	more watchers yourself.
2375		2780
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2781	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	2782	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2783	the given C<fd> and C<events> set will be created and started.
2379		2784
2380	If C<timeout> is less than 0, then no timeout watcher will be	2785	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	2786	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	2787	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2788
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2789	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2790	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>	2791	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2792	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2793	a timeout and an io event at the same time - you probably should give io
		2794	events precedence.
2389		2795
		2796	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2797
2390	static void stdin_ready (int revents, void *arg)	2798	static void stdin_ready (int revents, void *arg)
2391	{	2799	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	2800	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	2801	/* stdin might have data for us, joy! */;
		2802	else if (revents & EV_TIMEOUT)
		2803	/* doh, nothing entered */;
2396	}	2804	}
2397		2805
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2806	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2807
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2808	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2809
2402	Feeds the given event set into the event loop, as if the specified event	2810	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	2811	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2812	initialised but not necessarily started event watcher).
2405		2813
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2814	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2815
2408	Feed an event on the given fd, as if a file descriptor backend detected	2816	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2817	the given events it.
2410		2818
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2819	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2820
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2821	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2822	loop!).
2415		2823
2416	=back	2824	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	2860	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.	2861	the callback model to a model using method callbacks on objects.
2454		2862
2455	To use it,	2863	To use it,
2456		2864
2457	#include <ev++.h>	2865	#include <ev++.h>
2458		2866
2459	This automatically includes F<ev.h> and puts all of its definitions (many	2867	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	2868	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	2869	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2870	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	2937	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.	2938	thunking function, making it as fast as a direct C callback.
2531		2939
2532	Example: simple class declaration and watcher initialisation	2940	Example: simple class declaration and watcher initialisation
2533		2941
2534	struct myclass	2942	struct myclass
2535	{	2943	{
2536	void io_cb (ev::io &w, int revents) { }	2944	void io_cb (ev::io &w, int revents) { }
2537	}	2945	}
2538		2946
2539	myclass obj;	2947	myclass obj;
2540	ev::io iow;	2948	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	2949	iow.set <myclass, &myclass::io_cb> (&obj);
		2950
		2951	=item w->set (object *)
		2952
		2953	This is an B<experimental> feature that might go away in a future version.
		2954
		2955	This is a variation of a method callback - leaving out the method to call
		2956	will default the method to C<operator ()>, which makes it possible to use
		2957	functor objects without having to manually specify the C<operator ()> all
		2958	the time. Incidentally, you can then also leave out the template argument
		2959	list.
		2960
		2961	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2962	int revents)>.
		2963
		2964	See the method-C<set> above for more details.
		2965
		2966	Example: use a functor object as callback.
		2967
		2968	struct myfunctor
		2969	{
		2970	void operator() (ev::io &w, int revents)
		2971	{
		2972	...
		2973	}
		2974	}
		2975
		2976	myfunctor f;
		2977
		2978	ev::io w;
		2979	w.set (&f);
2542		2980
2543	=item w->set<function> (void *data = 0)	2981	=item w->set<function> (void *data = 0)
2544		2982
2545	Also sets a callback, but uses a static method or plain function as	2983	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	2984	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		2986
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2987	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2988
2551	See the method-C<set> above for more details.	2989	See the method-C<set> above for more details.
2552		2990
2553	Example:	2991	Example: Use a plain function as callback.
2554		2992
2555	static void io_cb (ev::io &w, int revents) { }	2993	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2994	iow.set <io_cb> ();
2557		2995
2558	=item w->set (struct ev_loop *)	2996	=item w->set (struct ev_loop *)
2559		2997
2560	Associates a different C<struct ev_loop> with this watcher. You can only	2998	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).	2999	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	3032	=back
2595		3033
2596	Example: Define a class with an IO and idle watcher, start one of them in	3034	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3035	the constructor.
2598		3036
2599	class myclass	3037	class myclass
2600	{	3038	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3039	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3040	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3041
2604	myclass (int fd)	3042	myclass (int fd)
2605	{	3043	{
2606	io .set <myclass, &myclass::io_cb > (this);	3044	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3045	idle.set <myclass, &myclass::idle_cb> (this);
2608		3046
2609	io.start (fd, ev::READ);	3047	io.start (fd, ev::READ);
2610	}	3048	}
2611	};	3049	};
2612		3050
2613		3051
2614	=head1 OTHER LANGUAGE BINDINGS	3052	=head1 OTHER LANGUAGE BINDINGS
2615		3053
2616	Libev does not offer other language bindings itself, but bindings for a	3054	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	3061	=item Perl
2624		3062
2625	The EV module implements the full libev API and is actually used to test	3063	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,	3064	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3065	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	3066	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>).	3067	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3068	and C<EV::Glib>).
2630		3069
2631	It can be found and installed via CPAN, its homepage is found at	3070	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3071	L<http://software.schmorp.de/pkg/EV>.
		3072
		3073	=item Python
		3074
		3075	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3076	seems to be quite complete and well-documented.
2633		3077
2634	=item Ruby	3078	=item Ruby
2635		3079
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3080	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	3081	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	3082	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3083	L<http://rev.rubyforge.org/>.
2640		3084
		3085	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3086	makes rev work even on mingw.
		3087
		3088	=item Haskell
		3089
		3090	A haskell binding to libev is available at
		3091	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3092
2641	=item D	3093	=item D
2642		3094
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3095	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>.	3096	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3097
		3098	=item Ocaml
		3099
		3100	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3101	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		3102
2646	=back	3103	=back
2647		3104
2648		3105
2649	=head1 MACRO MAGIC	3106	=head1 MACRO MAGIC
…		…
2661		3118
2662	This provides the loop I<argument> for functions, if one is required ("ev	3119	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,	3120	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:	3121	C<EV_A_> is used when other arguments are following. Example:
2665		3122
2666	ev_unref (EV_A);	3123	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3124	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3125	ev_loop (EV_A_ 0);
2669		3126
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3127	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3128	which is often provided by the following macro.
2672		3129
2673	=item C<EV_P>, C<EV_P_>	3130	=item C<EV_P>, C<EV_P_>
2674		3131
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3132	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,	3133	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:	3134	C<EV_P_> is used when other parameters are following. Example:
2678		3135
2679	// this is how ev_unref is being declared	3136	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3137	static void ev_unref (EV_P);
2681		3138
2682	// this is how you can declare your typical callback	3139	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3140	static void cb (EV_P_ ev_timer *w, int revents)
2684		3141
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3142	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3143	suitable for use with C<EV_A>.
2687		3144
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3145	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3161
2705	Example: Declare and initialise a check watcher, utilising the above	3162	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3163	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3164	or not.
2708		3165
2709	static void	3166	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3167	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3168	{
2712	ev_check_stop (EV_A_ w);	3169	ev_check_stop (EV_A_ w);
2713	}	3170	}
2714		3171
2715	ev_check check;	3172	ev_check check;
2716	ev_check_init (&check, check_cb);	3173	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3174	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3175	ev_loop (EV_DEFAULT_ 0);
2719		3176
2720	=head1 EMBEDDING	3177	=head1 EMBEDDING
2721		3178
2722	Libev can (and often is) directly embedded into host	3179	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3180	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3194	=head3 CORE EVENT LOOP
2738		3195
2739	To include only the libev core (all the C<ev_*> functions), with manual	3196	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3197	configuration (no autoconf):
2741		3198
2742	#define EV_STANDALONE 1	3199	#define EV_STANDALONE 1
2743	#include "ev.c"	3200	#include "ev.c"
2744		3201
2745	This will automatically include F<ev.h>, too, and should be done in a	3202	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	3203	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	3204	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	3205	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3206	where you can put other configuration options):
2750		3207
2751	#define EV_STANDALONE 1	3208	#define EV_STANDALONE 1
2752	#include "ev.h"	3209	#include "ev.h"
2753		3210
2754	Both header files and implementation files can be compiled with a C++	3211	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	3212	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3213	as a bug).
2757		3214
2758	You need the following files in your source tree, or in a directory	3215	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):	3216	in your include path (e.g. in libev/ when using -Ilibev):
2760		3217
2761	ev.h	3218	ev.h
2762	ev.c	3219	ev.c
2763	ev_vars.h	3220	ev_vars.h
2764	ev_wrap.h	3221	ev_wrap.h
2765		3222
2766	ev_win32.c required on win32 platforms only	3223	ev_win32.c required on win32 platforms only
2767		3224
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3225	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)	3226	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)	3227	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)	3228	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)	3229	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3230
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3231	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3232	to compile this single file.
2776		3233
2777	=head3 LIBEVENT COMPATIBILITY API	3234	=head3 LIBEVENT COMPATIBILITY API
2778		3235
2779	To include the libevent compatibility API, also include:	3236	To include the libevent compatibility API, also include:
2780		3237
2781	#include "event.c"	3238	#include "event.c"
2782		3239
2783	in the file including F<ev.c>, and:	3240	in the file including F<ev.c>, and:
2784		3241
2785	#include "event.h"	3242	#include "event.h"
2786		3243
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3244	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3245
2789	You need the following additional files for this:	3246	You need the following additional files for this:
2790		3247
2791	event.h	3248	event.h
2792	event.c	3249	event.c
2793		3250
2794	=head3 AUTOCONF SUPPORT	3251	=head3 AUTOCONF SUPPORT
2795		3252
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3253	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	3254	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	3255	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3256	include F<config.h> and configure itself accordingly.
2800		3257
2801	For this of course you need the m4 file:	3258	For this of course you need the m4 file:
2802		3259
2803	libev.m4	3260	libev.m4
2804		3261
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3262	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3263
2807	Libev can be configured via a variety of preprocessor symbols you have to	3264	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	3265	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3266	autoconf is documented for every option.
2810		3267
2811	=over 4	3268	=over 4
2812		3269
2813	=item EV_STANDALONE	3270	=item EV_STANDALONE
2814		3271
…		…
2816	keeps libev from including F<config.h>, and it also defines dummy	3273	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3274	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	3275	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.	3276	F<event.h> that are not directly supported by the libev core alone.
2820		3277
		3278	In stanbdalone mode, libev will still try to automatically deduce the
		3279	configuration, but has to be more conservative.
		3280
2821	=item EV_USE_MONOTONIC	3281	=item EV_USE_MONOTONIC
2822		3282
2823	If defined to be C<1>, libev will try to detect the availability of the	3283	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	3284	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	3285	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	3286	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3287	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>	3288	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3289	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3290
2831	=item EV_USE_REALTIME	3291	=item EV_USE_REALTIME
2832		3292
2833	If defined to be C<1>, libev will try to detect the availability of the	3293	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	3294	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	3295	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3296	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3297	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3298	correctness. See the note about libraries in the description of
		3299	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3300	C<EV_USE_CLOCK_SYSCALL>.
		3301
		3302	=item EV_USE_CLOCK_SYSCALL
		3303
		3304	If defined to be C<1>, libev will try to use a direct syscall instead
		3305	of calling the system-provided C<clock_gettime> function. This option
		3306	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3307	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3308	programs needlessly. Using a direct syscall is slightly slower (in
		3309	theory), because no optimised vdso implementation can be used, but avoids
		3310	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3311	higher, as it simplifies linking (no need for C<-lrt>).
2839		3312
2840	=item EV_USE_NANOSLEEP	3313	=item EV_USE_NANOSLEEP
2841		3314
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3315	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 ()>.	3316	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3332
2860	=item EV_SELECT_USE_FD_SET	3333	=item EV_SELECT_USE_FD_SET
2861		3334
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3335	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	3336	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	3337	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	3338	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	3339	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	3340	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3341	configures the maximum size of the C<fd_set>.
2869		3342
2870	=item EV_SELECT_IS_WINSOCKET	3343	=item EV_SELECT_IS_WINSOCKET
2871		3344
2872	When defined to C<1>, the select backend will assume that	3345	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3346	select/socket/connect etc. don't understand file descriptors but
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3457	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	3458	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	3459	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3460	fine.
2988		3461
2989	If your embedding application does not need any priorities, defining these both to	3462	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3463	both to C<0> will save some memory and CPU.
2991		3464
2992	=item EV_PERIODIC_ENABLE	3465	=item EV_PERIODIC_ENABLE
2993		3466
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3467	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3468	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3475	code.
3003		3476
3004	=item EV_EMBED_ENABLE	3477	=item EV_EMBED_ENABLE
3005		3478
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3479	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3480	defined to be C<0>, then they are not. Embed watchers rely on most other
		3481	watcher types, which therefore must not be disabled.
3008		3482
3009	=item EV_STAT_ENABLE	3483	=item EV_STAT_ENABLE
3010		3484
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3485	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3486	defined to be C<0>, then they are not.
…		…
3044	two).	3518	two).
3045		3519
3046	=item EV_USE_4HEAP	3520	=item EV_USE_4HEAP
3047		3521
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3522	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	3523	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	3524	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3525	faster performance with many (thousands) of watchers.
3052		3526
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3527	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3528	(disabled).
3055		3529
3056	=item EV_HEAP_CACHE_AT	3530	=item EV_HEAP_CACHE_AT
3057		3531
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3532	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	3533	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>),	3534	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,	3535	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	3536	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3537	noticeably with many (hundreds) of watchers.
3064		3538
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3539	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3540	(disabled).
3067		3541
3068	=item EV_VERIFY	3542	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3548	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	3549	verification code will be called very frequently, which will slow down
3076	libev considerably.	3550	libev considerably.
3077		3551
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3552	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3553	C<0>.
3080		3554
3081	=item EV_COMMON	3555	=item EV_COMMON
3082		3556
3083	By default, all watchers have a C<void *data> member. By redefining	3557	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	3558	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,	3559	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3560	though, and it must be identical each time.
3087		3561
3088	For example, the perl EV module uses something like this:	3562	For example, the perl EV module uses something like this:
3089		3563
3090	#define EV_COMMON \	3564	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3565	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3566	SV *cb_sv, *fh /* note no trailing ";" */
3093		3567
3094	=item EV_CB_DECLARE (type)	3568	=item EV_CB_DECLARE (type)
3095		3569
3096	=item EV_CB_INVOKE (watcher, revents)	3570	=item EV_CB_INVOKE (watcher, revents)
3097		3571
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3576	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	3577	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	3578	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++.	3579	method calls instead of plain function calls in C++.
3106		3580
		3581	=back
		3582
3107	=head2 EXPORTED API SYMBOLS	3583	=head2 EXPORTED API SYMBOLS
3108		3584
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3585	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	3586	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3587	all public symbols, one per line:
3112		3588
3113	Symbols.ev for libev proper	3589	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3590	Symbols.event for the libevent emulation
3115		3591
3116	This can also be used to rename all public symbols to avoid clashes with	3592	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	3593	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3594	itself, but sometimes it is inconvenient to avoid this).
3119		3595
…		…
3140	file.	3616	file.
3141		3617
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3618	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:	3619	that everybody includes and which overrides some configure choices:
3144		3620
3145	#define EV_MINIMAL 1	3621	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3622	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3623	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3624	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3625	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3626	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3627	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3628	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3629	#define EV_MAXPRI 0
3154		3630
3155	#include "ev++.h"	3631	#include "ev++.h"
3156		3632
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3633	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3634
3159	#include "ev_cpp.h"	3635	#include "ev_cpp.h"
3160	#include "ev.c"	3636	#include "ev.c"
3161		3637
		3638	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3639
3163	=head1 THREADS AND COROUTINES	3640	=head2 THREADS AND COROUTINES
3164		3641
3165	=head2 THREADS	3642	=head3 THREADS
3166		3643
3167	Libev itself is completely thread-safe, but it uses no locking. This	3644	All libev functions are reentrant and thread-safe unless explicitly
		3645	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	3646	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	3647	are no concurrent calls into any libev function with the same loop
3170	parameter.	3648	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3649	of course): libev guarantees that different event loops share no data
		3650	structures that need any locking.
3171		3651
3172	Or put differently: calls with different loop parameters can be done in	3652	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	3653	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	3654	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	3655	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3656	a mutex per loop).
3177		3657
3178	If you want to know which design is best for your problem, then I cannot	3658	Specifically to support threads (and signal handlers), libev implements
		3659	so-called C<ev_async> watchers, which allow some limited form of
		3660	concurrency on the same event loop, namely waking it up "from the
		3661	outside".
		3662
		3663	If you want to know which design (one loop, locking, or multiple loops
		3664	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3665	help you, but here is some generic advice:
3180		3666
3181	=over 4	3667	=over 4
3182		3668
3183	=item * most applications have a main thread: use the default libev loop	3669	=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.	3670	in that thread, or create a separate thread running only the default loop.
…		…
3196		3682
3197	Choosing a model is hard - look around, learn, know that usually you can do	3683	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3684	better than you currently do :-)
3199		3685
3200	=item * often you need to talk to some other thread which blocks in the	3686	=item * often you need to talk to some other thread which blocks in the
		3687	event loop.
		3688
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3689	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3690	(or from signal contexts...).
		3691
		3692	An example use would be to communicate signals or other events that only
		3693	work in the default loop by registering the signal watcher with the
		3694	default loop and triggering an C<ev_async> watcher from the default loop
		3695	watcher callback into the event loop interested in the signal.
3203		3696
3204	=back	3697	=back
3205		3698
3206	=head2 COROUTINES	3699	=head3 COROUTINES
3207		3700
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3701	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3702	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	3703	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	3704	different coroutines, and switch freely between both coroutines running the
3212	loop, as long as you don't confuse yourself). The only exception is that	3705	loop, as long as you don't confuse yourself). The only exception is that
3213	you must not do this from C<ev_periodic> reschedule callbacks.	3706	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3707
3215	Care has been invested into making sure that libev does not keep local	3708	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	3709	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3710	they do not call any callbacks.
3218		3711
		3712	=head2 COMPILER WARNINGS
3219		3713
3220	=head1 COMPLEXITIES	3714	Depending on your compiler and compiler settings, you might get no or a
		3715	lot of warnings when compiling libev code. Some people are apparently
		3716	scared by this.
3221		3717
3222	In this section the complexities of (many of) the algorithms used inside	3718	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3719	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3720	warning options. "Warn-free" code therefore cannot be a goal except when
		3721	targeting a specific compiler and compiler-version.
3225		3722
3226	All of the following are about amortised time: If an array needs to be	3723	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3724	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	3725	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		3726
3232	=over 4	3727	And of course, some compiler warnings are just plain stupid, or simply
		3728	wrong (because they don't actually warn about the condition their message
		3729	seems to warn about). For example, certain older gcc versions had some
		3730	warnings that resulted an extreme number of false positives. These have
		3731	been fixed, but some people still insist on making code warn-free with
		3732	such buggy versions.
3233		3733
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3734	While libev is written to generate as few warnings as possible,
		3735	"warn-free" code is not a goal, and it is recommended not to build libev
		3736	with any compiler warnings enabled unless you are prepared to cope with
		3737	them (e.g. by ignoring them). Remember that warnings are just that:
		3738	warnings, not errors, or proof of bugs.
3235		3739
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		3740
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3741	=head2 VALGRIND
3241		3742
3242	That means that changing a timer costs less than removing/adding them	3743	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.	3744	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3745
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3746	If you think you found a bug (memory leak, uninitialised data access etc.)
		3747	in libev, then check twice: If valgrind reports something like:
3246		3748
3247	These just add the watcher into an array or at the head of a list.	3749	==2274== definitely lost: 0 bytes in 0 blocks.
		3750	==2274== possibly lost: 0 bytes in 0 blocks.
		3751	==2274== still reachable: 256 bytes in 1 blocks.
3248		3752
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3753	Then there is no memory leak, just as memory accounted to global variables
		3754	is not a memleak - the memory is still being referenced, and didn't leak.
3250		3755
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3756	Similarly, under some circumstances, valgrind might report kernel bugs
		3757	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3758	although an acceptable workaround has been found here), or it might be
		3759	confused.
3252		3760
3253	These watchers are stored in lists then need to be walked to find the	3761	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	3762	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3763
3257	=item Finding the next timer in each loop iteration: O(1)	3764	If you are unsure about something, feel free to contact the mailing list
		3765	with the full valgrind report and an explanation on why you think this
		3766	is a bug in libev (best check the archives, too :). However, don't be
		3767	annoyed when you get a brisk "this is no bug" answer and take the chance
		3768	of learning how to interpret valgrind properly.
3258		3769
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3770	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3771	I suggest using suppression lists.
3261		3772
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3773
3264	A change means an I/O watcher gets started or stopped, which requires	3774	=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		3775
3268	=item Activating one watcher (putting it into the pending state): O(1)
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	3776	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3291		3777
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3778	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	3779	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3780	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3781	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3306		3792
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3793	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3794	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	3795	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	3796	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	3797	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3798	available).
3313		3799
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3800	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	3801	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3802	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	3803	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	3804	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3805	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3806	(Microsoft monopoly games).
3321		3807
		3808	A typical way to use libev under windows is to embed it (see the embedding
		3809	section for details) and use the following F<evwrap.h> header file instead
		3810	of F<ev.h>:
		3811
		3812	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3813	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3814
		3815	#include "ev.h"
		3816
		3817	And compile the following F<evwrap.c> file into your project (make sure
		3818	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3819
		3820	#include "evwrap.h"
		3821	#include "ev.c"
		3822
3322	=over 4	3823	=over 4
3323		3824
3324	=item The winsocket select function	3825	=item The winsocket select function
3325		3826
3326	The winsocket C<select> function doesn't follow POSIX in that it	3827	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	3828	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3829	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3830	requires a mapping from file descriptors to socket handles (the Microsoft
		3831	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3832	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3833	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3834
3333	The configuration for a "naked" win32 using the Microsoft runtime	3835	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3836	libraries and raw winsocket select is:
3335		3837
3336	#define EV_USE_SELECT 1	3838	#define EV_USE_SELECT 1
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3839	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		3840
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	3841	Note that winsockets handling of fd sets is O(n), so you can easily get a
3340	complexity in the O(n²) range when using win32.	3842	complexity in the O(n²) range when using win32.
3341		3843
3342	=item Limited number of file descriptors	3844	=item Limited number of file descriptors
…		…
3366	wrap all I/O functions and provide your own fd management, but the cost of	3868	wrap all I/O functions and provide your own fd management, but the cost of
3367	calling select (O(n²)) will likely make this unworkable.	3869	calling select (O(n²)) will likely make this unworkable.
3368		3870
3369	=back	3871	=back
3370		3872
3371
3372	=head1 PORTABILITY REQUIREMENTS	3873	=head2 PORTABILITY REQUIREMENTS
3373		3874
3374	In addition to a working ISO-C implementation, libev relies on a few	3875	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	3876	backend-specific APIs, libev relies on a few additional extensions:
3376		3877
3377	=over 4	3878	=over 4
3378		3879
		3880	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3881	calling conventions regardless of C<ev_watcher_type *>.
		3882
		3883	Libev assumes not only that all watcher pointers have the same internal
		3884	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3885	assumes that the same (machine) code can be used to call any watcher
		3886	callback: The watcher callbacks have different type signatures, but libev
		3887	calls them using an C<ev_watcher *> internally.
		3888
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	3889	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		3890
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	3891	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3892	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	3893	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	3894	believed to be sufficiently portable.
3385		3895
3386	=item C<sigprocmask> must work in a threaded environment	3896	=item C<sigprocmask> must work in a threaded environment
3387		3897
…		…
3396	except the initial one, and run the default loop in the initial thread as	3906	except the initial one, and run the default loop in the initial thread as
3397	well.	3907	well.
3398		3908
3399	=item C<long> must be large enough for common memory allocation sizes	3909	=item C<long> must be large enough for common memory allocation sizes
3400		3910
3401	To improve portability and simplify using libev, libev uses C<long>	3911	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	3912	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3913	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	3914	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	3915	watchers.
3406		3916
3407	=item C<double> must hold a time value in seconds with enough accuracy	3917	=item C<double> must hold a time value in seconds with enough accuracy
3408		3918
3409	The type C<double> is used to represent timestamps. It is required to	3919	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3920	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3414	=back	3924	=back
3415		3925
3416	If you know of other additional requirements drop me a note.	3926	If you know of other additional requirements drop me a note.
3417		3927
3418		3928
3419	=head1 COMPILER WARNINGS	3929	=head1 ALGORITHMIC COMPLEXITIES
3420		3930
3421	Depending on your compiler and compiler settings, you might get no or a	3931	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	3932	libev will be documented. For complexity discussions about backends see
3423	scared by this.	3933	the documentation for C<ev_default_init>.
3424		3934
3425	However, these are unavoidable for many reasons. For one, each compiler	3935	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	3936	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	3937	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	3938	mean that libev does a lengthy realloc operation in rare cases, but on
		3939	average it is much faster and asymptotically approaches constant time.
3429		3940
3430	Another reason is that some compiler warnings require elaborate	3941	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		3942
3434	And of course, some compiler warnings are just plain stupid, or simply	3943	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		3944
3438	While libev is written to generate as few warnings as possible,	3945	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	3946	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	3947	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		3948
		3949	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		3950
3445	=head1 VALGRIND	3951	That means that changing a timer costs less than removing/adding them,
		3952	as only the relative motion in the event queue has to be paid for.
3446		3953
3447	Valgrind has a special section here because it is a popular tool that is	3954	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		3955
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	3956	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		3957
3453	==2274== definitely lost: 0 bytes in 0 blocks.	3958	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		3959
3457	Then there is no memory leak. Similarly, under some circumstances,	3960	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		3961
3461	If you are unsure about something, feel free to contact the mailing list	3962	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	3963	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	3964	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	3965	is rare).
3465	properly.
3466		3966
3467	If you need, for some reason, empty reports from valgrind for your project	3967	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.	3968
		3969	By virtue of using a binary or 4-heap, the next timer is always found at a
		3970	fixed position in the storage array.
		3971
		3972	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3973
		3974	A change means an I/O watcher gets started or stopped, which requires
		3975	libev to recalculate its status (and possibly tell the kernel, depending
		3976	on backend and whether C<ev_io_set> was used).
		3977
		3978	=item Activating one watcher (putting it into the pending state): O(1)
		3979
		3980	=item Priority handling: O(number_of_priorities)
		3981
		3982	Priorities are implemented by allocating some space for each
		3983	priority. When doing priority-based operations, libev usually has to
		3984	linearly search all the priorities, but starting/stopping and activating
		3985	watchers becomes O(1) with respect to priority handling.
		3986
		3987	=item Sending an ev_async: O(1)
		3988
		3989	=item Processing ev_async_send: O(number_of_async_watchers)
		3990
		3991	=item Processing signals: O(max_signal_number)
		3992
		3993	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3994	calls in the current loop iteration. Checking for async and signal events
		3995	involves iterating over all running async watchers or all signal numbers.
		3996
		3997	=back
3469		3998
3470		3999
3471	=head1 AUTHOR	4000	=head1 AUTHOR
3472		4001
3473	Marc Lehmann <libev@schmorp.de>.	4002	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3474		4003

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines