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Revision 1.163 by root, Sat May 31 23:19:23 2008 UTC vs.
Revision 1.216 by root, Thu Nov 13 15:55:38 2008 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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	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	68	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)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
178	not a problem.	178	not a problem.
179		179
180	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	181	version.
182		182
183	assert (("libev version mismatch",	183	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
186		186
187	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
188		188
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	192	a description of the set values.
193		193
194	Example: make sure we have the epoll method, because yeah this is cool and	194	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	195	a must have and can we have a torrent of it please!!!11
196		196
197	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
199		199
200	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
201		201
202	Return the set of all backends compiled into this binary of libev and also	202	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	203	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	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	222	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	223	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	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	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	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	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	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	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,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	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	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
363		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
		371
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		373
366	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	379	performance tips.
372		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		385
375	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	390
380	cases and requiring a system call per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
382		407
383	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	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	410	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	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
388		413	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		414
393	Best performance from this backend is achieved by not unregistering all	415	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.	416	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
		422
		423	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		424	faster than epoll for maybe up to a hundred file descriptors, depending on
		425	the usage. So sad.
396		426
397	While nominally embeddable in other event loops, this feature is broken in	427	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	428	all kernel versions tested so far.
		429
		430	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		431	C<EVBACKEND_POLL>.
399		432
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	433	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		434
402	Kqueue deserves special mention, as at the time of this writing, it	435	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	436	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	437	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"	438	it's completely useless). Unlike epoll, however, whose brokenness
		439	is by design, these kqueue bugs can (and eventually will) be fixed
		440	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	441	"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)	442	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	443	system like NetBSD.
409		444
410	You still can embed kqueue into a normal poll or select backend and use it	445	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	446	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		448
414	It scales in the same way as the epoll backend, but the interface to the	449	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	450	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	451	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	452	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	453	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	454	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		455	cases
420		456
421	This backend usually performs well under most conditions.	457	This backend usually performs well under most conditions.
422		458
423	While nominally embeddable in other event loops, this doesn't work	459	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	460	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	461	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	462	(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	463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	464	using it only for sockets.
		465
		466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		468	C<NOTE_EOF>.
429		469
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	470	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		471
432	This is not implemented yet (and might never be, unless you send me an	472	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	473	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	486	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	487	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	488	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	489	might perform better.
450		490
451	On the positive side, ignoring the spurious readiness notifications, this	491	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	492	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	493	in all tests and is fully embeddable, which is a rare feat among the
		494	OS-specific backends (I vastly prefer correctness over speed hacks).
		495
		496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		497	C<EVBACKEND_POLL>.
454		498
455	=item C<EVBACKEND_ALL>	499	=item C<EVBACKEND_ALL>
456		500
457	Try all backends (even potentially broken ones that wouldn't be tried	501	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	502	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		508
465	If one or more of these are or'ed into the flags value, then only these	509	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	510	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.	511	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		512
469	The most typical usage is like this:	513	Example: This is the most typical usage.
470		514
471	if (!ev_default_loop (0))	515	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		517
474	Restrict libev to the select and poll backends, and do not allow	518	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	519	environment settings to be taken into account:
476		520
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		522
479	Use whatever libev has to offer, but make sure that kqueue is used if	523	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	524	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):	525	private event loop and only if you know the OS supports your types of
		526	fds):
482		527
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		529
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	530	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		531
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	532	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	533	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	538	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	539	default loop in the "main" or "initial" thread.
495		540
496	Example: Try to create a event loop that uses epoll and nothing else.	541	Example: Try to create a event loop that uses epoll and nothing else.
497		542
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	544	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	545	fatal ("no epoll found here, maybe it hides under your chair");
501		546
502	=item ev_default_destroy ()	547	=item ev_default_destroy ()
503		548
504	Destroys the default loop again (frees all memory and kernel state	549	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	550	etc.). None of the active event watchers will be stopped in the normal
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	552	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	553	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	554	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	555	for example).
511		556
512	Note that certain global state, such as signal state, will not be freed by	557	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	558	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	559	as signal and child watchers) would need to be stopped manually.
515		560
516	In general it is not advisable to call this function except in the	561	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	562	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	563	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	564	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		589
545	=item ev_loop_fork (loop)	590	=item ev_loop_fork (loop)
546		591
547	Like C<ev_default_fork>, but acts on an event loop created by	592	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	593	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.	594	after fork that you want to re-use in the child, and how you do this is
		595	entirely your own problem.
550		596
551	=item int ev_is_default_loop (loop)	597	=item int ev_is_default_loop (loop)
552		598
553	Returns true when the given loop actually is the default loop, false otherwise.	599	Returns true when the given loop is, in fact, the default loop, and false
		600	otherwise.
554		601
555	=item unsigned int ev_loop_count (loop)	602	=item unsigned int ev_loop_count (loop)
556		603
557	Returns the count of loop iterations for the loop, which is identical to	604	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	605	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	620	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	621	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	622	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).	623	event occurring (or more correctly, libev finding out about it).
577		624
		625	=item ev_now_update (loop)
		626
		627	Establishes the current time by querying the kernel, updating the time
		628	returned by C<ev_now ()> in the progress. This is a costly operation and
		629	is usually done automatically within C<ev_loop ()>.
		630
		631	This function is rarely useful, but when some event callback runs for a
		632	very long time without entering the event loop, updating libev's idea of
		633	the current time is a good idea.
		634
		635	See also "The special problem of time updates" in the C<ev_timer> section.
		636
578	=item ev_loop (loop, int flags)	637	=item ev_loop (loop, int flags)
579		638
580	Finally, this is it, the event handler. This function usually is called	639	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	640	after you initialised all your watchers and you want to start handling
582	events.	641	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	643	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.	644	either no event watchers are active anymore or C<ev_unloop> was called.
586		645
587	Please note that an explicit C<ev_unloop> is usually better than	646	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	647	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	648	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	649	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.	650	of relying on its watchers stopping correctly, that is truly a thing of
		651	beauty.
592		652
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	653	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	654	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.	655	process in case there are no events and will return after one iteration of
		656	the loop.
596		657
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	658	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	659	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	660	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	661	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	662	user-registered callback will be called), and will return after one
		663	iteration of the loop.
		664
		665	This is useful if you are waiting for some external event in conjunction
		666	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	667	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.	668	usually a better approach for this kind of thing.
604		669
605	Here are the gory details of what C<ev_loop> does:	670	Here are the gory details of what C<ev_loop> does:
606		671
607	- Before the first iteration, call any pending watchers.	672	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	673	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	674	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	675	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	676	- If we have been forked, detach and recreate the kernel state
		677	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	678	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	679	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	680	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	681	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	682	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	683	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	684	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	685	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	687	- Queue all expired timers.
622	- Queue all outstanding periodics.	688	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	689	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	690	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	691	- 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	692	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	693	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	699	anymore.
634		700
635	... queue jobs here, make sure they register event watchers as long	701	... 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..)	702	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	703	ev_loop (my_loop, 0);
638	... jobs done. yeah!	704	... jobs done or somebody called unloop. yeah!
639		705
640	=item ev_unloop (loop, how)	706	=item ev_unloop (loop, how)
641		707
642	Can be used to make a call to C<ev_loop> return early (but only after it	708	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	709	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	710	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.	711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		712
647	This "unloop state" will be cleared when entering C<ev_loop> again.	713	This "unloop state" will be cleared when entering C<ev_loop> again.
648		714
		715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		716
649	=item ev_ref (loop)	717	=item ev_ref (loop)
650		718
651	=item ev_unref (loop)	719	=item ev_unref (loop)
652		720
653	Ref/unref can be used to add or remove a reference count on the event	721	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	722	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	723	count is nonzero, C<ev_loop> will not return on its own.
		724
656	a watcher you never unregister that should not keep C<ev_loop> from	725	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	726	from returning, call ev_unref() after starting, and ev_ref() before
		727	stopping it.
		728
658	example, libev itself uses this for its internal signal pipe: It is not	729	As an example, libev itself uses this for its internal signal pipe: It is
659	visible to the libev user and should not keep C<ev_loop> from exiting if	730	not visible to the libev user and should not keep C<ev_loop> from exiting
660	no event watchers registered by it are active. It is also an excellent	731	if no event watchers registered by it are active. It is also an excellent
661	way to do this for generic recurring timers or from within third-party	732	way to do this for generic recurring timers or from within third-party
662	libraries. Just remember to I<unref after start> and I<ref before stop>	733	libraries. Just remember to I<unref after start> and I<ref before stop>
663	(but only if the watcher wasn't active before, or was active before,	734	(but only if the watcher wasn't active before, or was active before,
664	respectively).	735	respectively).
665		736
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	738	running when nothing else is active.
668		739
669	struct ev_signal exitsig;	740	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	741	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	742	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	743	evf_unref (loop);
673		744
674	Example: For some weird reason, unregister the above signal handler again.	745	Example: For some weird reason, unregister the above signal handler again.
675		746
676	ev_ref (loop);	747	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	748	ev_signal_stop (loop, &exitsig);
678		749
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	750	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		751
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		753
683	These advanced functions influence the time that libev will spend waiting	754	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	755	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.	756	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		757	latency.
686		758
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	759	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	760	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	761	to increase efficiency of loop iterations (or to increase power-saving
		762	opportunities).
690		763
691	The background is that sometimes your program runs just fast enough to	764	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	765	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	766	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	767	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	768	overhead for the actual polling but can deliver many events at once.
696		769
697	By setting a higher I<io collect interval> you allow libev to spend more	770	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,	771	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	773	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.	774	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		775
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	776	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	777	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	778	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	779	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	780	value will not introduce any overhead in libev.
708		781
709	Many (busy) programs can usually benefit by setting the I/O collect	782	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	783	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	784	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>,	785	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.	786	as this approaches the timing granularity of most systems.
714		787
		788	Setting the I<timeout collect interval> can improve the opportunity for
		789	saving power, as the program will "bundle" timer callback invocations that
		790	are "near" in time together, by delaying some, thus reducing the number of
		791	times the process sleeps and wakes up again. Another useful technique to
		792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		793	they fire on, say, one-second boundaries only.
		794
715	=item ev_loop_verify (loop)	795	=item ev_loop_verify (loop)
716		796
717	This function only does something when C<EV_VERIFY> support has been	797	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	798	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	799	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	800	is found to be inconsistent, it will print an error message to standard
		801	error and call C<abort ()>.
721		802
722	This can be used to catch bugs inside libev itself: under normal	803	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	804	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	805	data structures consistent.
725		806
726	=back	807	=back
727		808
728		809
729	=head1 ANATOMY OF A WATCHER	810	=head1 ANATOMY OF A WATCHER
730		811
		812	In the following description, uppercase C<TYPE> in names stands for the
		813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		814	watchers and C<ev_io_start> for I/O watchers.
		815
731	A watcher is a structure that you create and register to record your	816	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	817	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:	818	become readable, you would create an C<ev_io> watcher for that:
734		819
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	821	{
737	ev_io_stop (w);	822	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	823	ev_unloop (loop, EVUNLOOP_ALL);
739	}	824	}
740		825
741	struct ev_loop *loop = ev_default_loop (0);	826	struct ev_loop *loop = ev_default_loop (0);
		827
742	struct ev_io stdin_watcher;	828	ev_io stdin_watcher;
		829
743	ev_init (&stdin_watcher, my_cb);	830	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	832	ev_io_start (loop, &stdin_watcher);
		833
746	ev_loop (loop, 0);	834	ev_loop (loop, 0);
747		835
748	As you can see, you are responsible for allocating the memory for your	836	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,	837	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	838	stack).
		839
		840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		842
752	Each watcher structure must be initialised by a call to C<ev_init	843	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	844	(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	845	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	846	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	847	is readable and/or writable).
757		848
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	849	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	850	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	851	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	852	ev_TYPE_init (watcher *, callback, ...) >>.
762		853
763	To make the watcher actually watch out for events, you have to start it	854	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	855	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	856	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	857	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		858
768	As long as your watcher is active (has been started but not stopped) you	859	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	860	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	861	reinitialise it or call its C<ev_TYPE_set> macro.
771		862
772	Each and every callback receives the event loop pointer as first, the	863	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	864	registered watcher structure as second, and a bitset of received events as
774	third argument.	865	third argument.
775		866
…		…
838	=item C<EV_ERROR>	929	=item C<EV_ERROR>
839		930
840	An unspecified error has occurred, the watcher has been stopped. This might	931	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	932	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	933	ran out of memory, a file descriptor was found to be closed or any other
		934	problem. Libev considers these application bugs.
		935
843	problem. You best act on it by reporting the problem and somehow coping	936	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	937	watcher being stopped. Note that well-written programs should not receive
		938	an error ever, so when your watcher receives it, this usually indicates a
		939	bug in your program.
845		940
846	Libev will usually signal a few "dummy" events together with an error,	941	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	942	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	943	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	944	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	945	programs, though, as the fd could already be closed and reused for another
		946	thing, so beware.
851		947
852	=back	948	=back
853		949
854	=head2 GENERIC WATCHER FUNCTIONS	950	=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		951
859	=over 4	952	=over 4
860		953
861	=item C<ev_init> (ev_TYPE *watcher, callback)	954	=item C<ev_init> (ev_TYPE *watcher, callback)
862		955
…		…
868	which rolls both calls into one.	961	which rolls both calls into one.
869		962
870	You can reinitialise a watcher at any time as long as it has been stopped	963	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.	964	(or never started) and there are no pending events outstanding.
872		965
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	966	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	967	int revents)>.
		968
		969	Example: Initialise an C<ev_io> watcher in two steps.
		970
		971	ev_io w;
		972	ev_init (&w, my_cb);
		973	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		974
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	975	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		976
878	This macro initialises the type-specific parts of a watcher. You need to	977	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	978	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	981	difference to the C<ev_init> macro).
883		982
884	Although some watcher types do not have type-specific arguments	983	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.	984	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		985
		986	See C<ev_init>, above, for an example.
		987
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	988	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		989
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	990	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	991	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	992	a watcher. The same limitations apply, of course.
892		993
		994	Example: Initialise and set an C<ev_io> watcher in one step.
		995
		996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		997
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		999
895	Starts (activates) the given watcher. Only active watchers will receive	1000	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1001	events. If the watcher is already active nothing will happen.
897		1002
		1003	Example: Start the C<ev_io> watcher that is being abused as example in this
		1004	whole section.
		1005
		1006	ev_io_start (EV_DEFAULT_UC, &w);
		1007
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1009
900	Stops the given watcher again (if active) and clears the pending	1010	Stops the given watcher if active, and clears the pending status (whether
		1011	the watcher was active or not).
		1012
901	status. It is possible that stopped watchers are pending (for example,	1013	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1014	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	1015	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	1016	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.	1017	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1018
907	=item bool ev_is_active (ev_TYPE *watcher)	1019	=item bool ev_is_active (ev_TYPE *watcher)
908		1020
909	Returns a true value iff the watcher is active (i.e. it has been started	1021	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	1022	and not yet been stopped). As long as a watcher is active you must not modify
…		…
952	The default priority used by watchers when no priority has been set is	1064	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 :).	1065	always C<0>, which is supposed to not be too high and not be too low :).
954		1066
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1067	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	1068	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.	1069	or might not have been clamped to the valid range.
958		1070
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1072
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1073	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	1074	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1075	can deal with that fact, as both are simply passed through to the
		1076	callback.
964		1077
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1078	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1079
967	If the watcher is pending, this function returns clears its pending status	1080	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	1081	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>.	1082	watcher isn't pending it does nothing and returns C<0>.
970		1083
		1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1085	callback to be invoked, which can be accomplished with this function.
		1086
971	=back	1087	=back
972		1088
973		1089
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1091
976	Each watcher has, by default, a member C<void *data> that you can change	1092	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	1093	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	1094	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	1095	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	1096	member, you can also "subclass" the watcher type and provide your own
981	data:	1097	data:
982		1098
983	struct my_io	1099	struct my_io
984	{	1100	{
985	struct ev_io io;	1101	ev_io io;
986	int otherfd;	1102	int otherfd;
987	void *somedata;	1103	void *somedata;
988	struct whatever *mostinteresting;	1104	struct whatever *mostinteresting;
989	}	1105	};
		1106
		1107	...
		1108	struct my_io w;
		1109	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1110
991	And since your callback will be called with a pointer to the watcher, you	1111	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1112	can cast it back to your own type:
993		1113
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1114	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1115	{
996	struct my_io *w = (struct my_io *)w_;	1116	struct my_io *w = (struct my_io *)w_;
997	...	1117	...
998	}	1118	}
999		1119
1000	More interesting and less C-conformant ways of casting your callback type	1120	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1121	instead have been omitted.
1002		1122
1003	Another common scenario is having some data structure with multiple	1123	Another common scenario is to use some data structure with multiple
1004	watchers:	1124	embedded watchers:
1005		1125
1006	struct my_biggy	1126	struct my_biggy
1007	{	1127	{
1008	int some_data;	1128	int some_data;
1009	ev_timer t1;	1129	ev_timer t1;
1010	ev_timer t2;	1130	ev_timer t2;
1011	}	1131	}
1012		1132
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1133	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1134	complicated: Either you store the address of your C<my_biggy> struct
		1135	in the C<data> member of the watcher (for woozies), or you need to use
		1136	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1137	programmers):
1015		1138
1016	#include <stddef.h>	1139	#include <stddef.h>
1017		1140
1018	static void	1141	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1142	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1143	{
1021	struct my_biggy big = (struct my_biggy *	1144	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1145	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1146	}
1024		1147
1025	static void	1148	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1149	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1150	{
1028	struct my_biggy big = (struct my_biggy *	1151	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1152	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1153	}
1031		1154
1032		1155
1033	=head1 WATCHER TYPES	1156	=head1 WATCHER TYPES
1034		1157
1035	This section describes each watcher in detail, but will not repeat	1158	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	1182	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	1183	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	1184	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1185	required if you know what you are doing).
1063		1186
1064	If you must do this, then force the use of a known-to-be-good backend	1187	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	1188	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1190
1068	Another thing you have to watch out for is that it is quite easy to	1191	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	1192	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	1193	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	1194	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	1195	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	1196	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	1197	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.	1198	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1199
1077	If you cannot run the fd in non-blocking mode (for example you should not	1200	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	1201	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	1202	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	1203	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1204	does this on its own, so its quite safe to use). Some people additionally
		1205	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1206	indefinitely.
		1207
		1208	But really, best use non-blocking mode.
1082		1209
1083	=head3 The special problem of disappearing file descriptors	1210	=head3 The special problem of disappearing file descriptors
1084		1211
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1212	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,	1213	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	1214	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	1215	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	1216	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	1217	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1218	fact, a different file descriptor.
1092		1219
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1250	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1251	C<EVBACKEND_POLL>.
1125		1252
1126	=head3 The special problem of SIGPIPE	1253	=head3 The special problem of SIGPIPE
1127		1254
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1255	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	1256	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	1257	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1258	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1259
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1260	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	1261	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).	1262	somewhere, as that would have given you a big clue).
1137		1263
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1269	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1270
1145	=item ev_io_set (ev_io *, int fd, int events)	1271	=item ev_io_set (ev_io *, int fd, int events)
1146		1272
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1273	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	1274	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.	1275	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1276
1151	=item int fd [read-only]	1277	=item int fd [read-only]
1152		1278
1153	The file descriptor being watched.	1279	The file descriptor being watched.
1154		1280
…		…
1162		1288
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1289	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	1290	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1291	attempt to read a whole line in the callback.
1166		1292
1167	static void	1293	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1294	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1295	{
1170	ev_io_stop (loop, w);	1296	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1297	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1298	}
1173		1299
1174	...	1300	...
1175	struct ev_loop *loop = ev_default_init (0);	1301	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1302	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1304	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1180		1306
1181		1307
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1308	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1309
1184	Timer watchers are simple relative timers that generate an event after a	1310	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1311	given time, and optionally repeating in regular intervals after that.
1186		1312
1187	The timers are based on real time, that is, if you register an event that	1313	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	1314	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	1315	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1317	monotonic clock option helps a lot here).
		1318
		1319	The callback is guaranteed to be invoked only I<after> its timeout has
		1320	passed, but if multiple timers become ready during the same loop iteration
		1321	then order of execution is undefined.
		1322
		1323	=head3 Be smart about timeouts
		1324
		1325	Many real-world problems involve some kind of timeout, usually for error
		1326	recovery. A typical example is an HTTP request - if the other side hangs,
		1327	you want to raise some error after a while.
		1328
		1329	What follows are some ways to handle this problem, from obvious and
		1330	inefficient to smart and efficient.
		1331
		1332	In the following, a 60 second activity timeout is assumed - a timeout that
		1333	gets reset to 60 seconds each time there is activity (e.g. each time some
		1334	data or other life sign was received).
		1335
		1336	=over 4
		1337
		1338	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1339
		1340	This is the most obvious, but not the most simple way: In the beginning,
		1341	start the watcher:
		1342
		1343	ev_timer_init (timer, callback, 60., 0.);
		1344	ev_timer_start (loop, timer);
		1345
		1346	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1347	and start it again:
		1348
		1349	ev_timer_stop (loop, timer);
		1350	ev_timer_set (timer, 60., 0.);
		1351	ev_timer_start (loop, timer);
		1352
		1353	This is relatively simple to implement, but means that each time there is
		1354	some activity, libev will first have to remove the timer from its internal
		1355	data structure and then add it again. Libev tries to be fast, but it's
		1356	still not a constant-time operation.
		1357
		1358	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1359
		1360	This is the easiest way, and involves using C<ev_timer_again> instead of
		1361	C<ev_timer_start>.
		1362
		1363	To implement this, configure an C<ev_timer> with a C<repeat> value
		1364	of C<60> and then call C<ev_timer_again> at start and each time you
		1365	successfully read or write some data. If you go into an idle state where
		1366	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1367	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1368
		1369	That means you can ignore both the C<ev_timer_start> function and the
		1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1371	member and C<ev_timer_again>.
		1372
		1373	At start:
		1374
		1375	ev_timer_init (timer, callback);
		1376	timer->repeat = 60.;
		1377	ev_timer_again (loop, timer);
		1378
		1379	Each time there is some activity:
		1380
		1381	ev_timer_again (loop, timer);
		1382
		1383	It is even possible to change the time-out on the fly, regardless of
		1384	whether the watcher is active or not:
		1385
		1386	timer->repeat = 30.;
		1387	ev_timer_again (loop, timer);
		1388
		1389	This is slightly more efficient then stopping/starting the timer each time
		1390	you want to modify its timeout value, as libev does not have to completely
		1391	remove and re-insert the timer from/into its internal data structure.
		1392
		1393	It is, however, even simpler than the "obvious" way to do it.
		1394
		1395	=item 3. Let the timer time out, but then re-arm it as required.
		1396
		1397	This method is more tricky, but usually most efficient: Most timeouts are
		1398	relatively long compared to the intervals between other activity - in
		1399	our example, within 60 seconds, there are usually many I/O events with
		1400	associated activity resets.
		1401
		1402	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1403	but remember the time of last activity, and check for a real timeout only
		1404	within the callback:
		1405
		1406	ev_tstamp last_activity; // time of last activity
		1407
		1408	static void
		1409	callback (EV_P_ ev_timer *w, int revents)
		1410	{
		1411	ev_tstamp now = ev_now (EV_A);
		1412	ev_tstamp timeout = last_activity + 60.;
		1413
		1414	// if last_activity + 60. is older than now, we did time out
		1415	if (timeout < now)
		1416	{
		1417	// timeout occured, take action
		1418	}
		1419	else
		1420	{
		1421	// callback was invoked, but there was some activity, re-arm
		1422	// the watcher to fire in last_activity + 60, which is
		1423	// guaranteed to be in the future, so "again" is positive:
		1424	w->repeat = timeout - now;
		1425	ev_timer_again (EV_A_ w);
		1426	}
		1427	}
		1428
		1429	To summarise the callback: first calculate the real timeout (defined
		1430	as "60 seconds after the last activity"), then check if that time has
		1431	been reached, which means something I<did>, in fact, time out. Otherwise
		1432	the callback was invoked too early (C<timeout> is in the future), so
		1433	re-schedule the timer to fire at that future time, to see if maybe we have
		1434	a timeout then.
		1435
		1436	Note how C<ev_timer_again> is used, taking advantage of the
		1437	C<ev_timer_again> optimisation when the timer is already running.
		1438
		1439	This scheme causes more callback invocations (about one every 60 seconds
		1440	minus half the average time between activity), but virtually no calls to
		1441	libev to change the timeout.
		1442
		1443	To start the timer, simply initialise the watcher and set C<last_activity>
		1444	to the current time (meaning we just have some activity :), then call the
		1445	callback, which will "do the right thing" and start the timer:
		1446
		1447	ev_timer_init (timer, callback);
		1448	last_activity = ev_now (loop);
		1449	callback (loop, timer, EV_TIMEOUT);
		1450
		1451	And when there is some activity, simply store the current time in
		1452	C<last_activity>, no libev calls at all:
		1453
		1454	last_actiivty = ev_now (loop);
		1455
		1456	This technique is slightly more complex, but in most cases where the
		1457	time-out is unlikely to be triggered, much more efficient.
		1458
		1459	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1460	callback :) - just change the timeout and invoke the callback, which will
		1461	fix things for you.
		1462
		1463	=item 4. Wee, just use a double-linked list for your timeouts.
		1464
		1465	If there is not one request, but many thousands (millions...), all
		1466	employing some kind of timeout with the same timeout value, then one can
		1467	do even better:
		1468
		1469	When starting the timeout, calculate the timeout value and put the timeout
		1470	at the I<end> of the list.
		1471
		1472	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1473	the list is expected to fire (for example, using the technique #3).
		1474
		1475	When there is some activity, remove the timer from the list, recalculate
		1476	the timeout, append it to the end of the list again, and make sure to
		1477	update the C<ev_timer> if it was taken from the beginning of the list.
		1478
		1479	This way, one can manage an unlimited number of timeouts in O(1) time for
		1480	starting, stopping and updating the timers, at the expense of a major
		1481	complication, and having to use a constant timeout. The constant timeout
		1482	ensures that the list stays sorted.
		1483
		1484	=back
		1485
		1486	So which method the best?
		1487
		1488	Method #2 is a simple no-brain-required solution that is adequate in most
		1489	situations. Method #3 requires a bit more thinking, but handles many cases
		1490	better, and isn't very complicated either. In most case, choosing either
		1491	one is fine, with #3 being better in typical situations.
		1492
		1493	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1494	rather complicated, but extremely efficient, something that really pays
		1495	off after the first million or so of active timers, i.e. it's usually
		1496	overkill :)
		1497
		1498	=head3 The special problem of time updates
		1499
		1500	Establishing the current time is a costly operation (it usually takes at
		1501	least two system calls): EV therefore updates its idea of the current
		1502	time only before and after C<ev_loop> collects new events, which causes a
		1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1504	lots of events in one iteration.
1192		1505
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1506	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	1507	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	1508	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	1509	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:	1510	timeout on the current time, use something like this to adjust for this:
1198		1511
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1512	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1513
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1514	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	1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1516	()>.
1204		1517
1205	=head3 Watcher-Specific Functions and Data Members	1518	=head3 Watcher-Specific Functions and Data Members
1206		1519
1207	=over 4	1520	=over 4
1208		1521
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1545	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1546
1234	If the timer is repeating, either start it if necessary (with the	1547	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.	1548	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1549
1237	This sounds a bit complicated, but here is a useful and typical	1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1551	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		1552
1262	=item ev_tstamp repeat [read-write]	1553	=item ev_tstamp repeat [read-write]
1263		1554
1264	The current C<repeat> value. Will be used each time the watcher times out	1555	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),	1556	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.	1557	which is also when any modifications are taken into account.
1267		1558
1268	=back	1559	=back
1269		1560
1270	=head3 Examples	1561	=head3 Examples
1271		1562
1272	Example: Create a timer that fires after 60 seconds.	1563	Example: Create a timer that fires after 60 seconds.
1273		1564
1274	static void	1565	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1566	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1567	{
1277	.. one minute over, w is actually stopped right here	1568	.. one minute over, w is actually stopped right here
1278	}	1569	}
1279		1570
1280	struct ev_timer mytimer;	1571	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1572	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1573	ev_timer_start (loop, &mytimer);
1283		1574
1284	Example: Create a timeout timer that times out after 10 seconds of	1575	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1576	inactivity.
1286		1577
1287	static void	1578	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1579	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1580	{
1290	.. ten seconds without any activity	1581	.. ten seconds without any activity
1291	}	1582	}
1292		1583
1293	struct ev_timer mytimer;	1584	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1586	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1587	ev_loop (loop, 0);
1297		1588
1298	// and in some piece of code that gets executed on any "activity":	1589	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1590	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1591	ev_timer_again (&mytimer);
1301		1592
1302		1593
1303	=head2 C<ev_periodic> - to cron or not to cron?	1594	=head2 C<ev_periodic> - to cron or not to cron?
1304		1595
1305	Periodic watchers are also timers of a kind, but they are very versatile	1596	Periodic watchers are also timers of a kind, but they are very versatile
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1606	roughly 10 seconds later as it uses a relative timeout).
1316		1607
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1608	C<ev_periodic>s can also be used to implement vastly more complex timers,
1318	such as triggering an event on each "midnight, local time", or other	1609	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1610	complicated rules.
1320		1611
1321	As with timers, the callback is guaranteed to be invoked only when the	1612	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	1613	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1614	during the same loop iteration, then order of execution is undefined.
1324		1615
1325	=head3 Watcher-Specific Functions and Data Members	1616	=head3 Watcher-Specific Functions and Data Members
1326		1617
1327	=over 4	1618	=over 4
1328		1619
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1621
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1623
1333	Lots of arguments, lets sort it out... There are basically three modes of	1624	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1625	operation, and we will explain them from simplest to most complex:
1335		1626
1336	=over 4	1627	=over 4
1337		1628
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1630
1340	In this configuration the watcher triggers an event after the wall clock	1631	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	1632	time C<at> has passed. It will not repeat and will not adjust when a time
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1343	run when the system time reaches or surpasses this time.	1634	only run when the system clock reaches or surpasses this time.
1344		1635
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1637
1347	In this mode the watcher will always be scheduled to time out at the next	1638	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)	1639	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1640	and then repeat, regardless of any time jumps.
1350		1641
1351	This can be used to create timers that do not drift with respect to system	1642	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	1643	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1644	hour, on the hour:
1354		1645
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1646	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1647
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1648	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	1649	but only that the callback will be called when the system time shows a
…		…
1384		1675
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1676	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	1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1678	only event loop modification you are allowed to do).
1388		1679
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1680	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1681	*w, ev_tstamp now)>, e.g.:
1391		1682
		1683	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1684	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1685	{
1394	return now + 60.;	1686	return now + 60.;
1395	}	1687	}
1396		1688
1397	It must return the next time to trigger, based on the passed time value	1689	It must return the next time to trigger, based on the passed time value
…		…
1434		1726
1435	The current interval value. Can be modified any time, but changes only	1727	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	1728	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1729	called.
1438		1730
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1731	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1732
1441	The current reschedule callback, or C<0>, if this functionality is	1733	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	1734	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.	1735	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1736
1445	=back	1737	=back
1446		1738
1447	=head3 Examples	1739	=head3 Examples
1448		1740
1449	Example: Call a callback every hour, or, more precisely, whenever the	1741	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1742	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1743	potentially a lot of jitter, but good long-term stability.
1452		1744
1453	static void	1745	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1747	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1748	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1749	}
1458		1750
1459	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1752	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1753	ev_periodic_start (loop, &hourly_tick);
1462		1754
1463	Example: The same as above, but use a reschedule callback to do it:	1755	Example: The same as above, but use a reschedule callback to do it:
1464		1756
1465	#include <math.h>	1757	#include <math.h>
1466		1758
1467	static ev_tstamp	1759	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1760	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1761	{
1470	return fmod (now, 3600.) + 3600.;	1762	return now + (3600. - fmod (now, 3600.));
1471	}	1763	}
1472		1764
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1765	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1766
1475	Example: Call a callback every hour, starting now:	1767	Example: Call a callback every hour, starting now:
1476		1768
1477	struct ev_periodic hourly_tick;	1769	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1770	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1771	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1772	ev_periodic_start (loop, &hourly_tick);
1481		1773
1482		1774
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	1775	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		1776
1485	Signal watchers will trigger an event when the process receives a specific	1777	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	1778	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	1779	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1780	normal event processing, like any other event.
1489		1781
		1782	If you want signals asynchronously, just use C<sigaction> as you would
		1783	do without libev and forget about sharing the signal. You can even use
		1784	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1785
1490	You can configure as many watchers as you like per signal. Only when the	1786	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	1787	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	1788	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	1789	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	1790	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1791	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1792
1497	If possible and supported, libev will install its handlers with	1793	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1794	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	1795	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	1796	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1813
1518	=back	1814	=back
1519		1815
1520	=head3 Examples	1816	=head3 Examples
1521		1817
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1818	Example: Try to exit cleanly on SIGINT.
1523		1819
1524	static void	1820	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1822	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1823	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1824	}
1529		1825
1530	struct ev_signal signal_watcher;	1826	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1828	ev_signal_start (loop, &signal_watcher);
1533		1829
1534		1830
1535	=head2 C<ev_child> - watch out for process status changes	1831	=head2 C<ev_child> - watch out for process status changes
1536		1832
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1833	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	1834	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	1835	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	1836	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1837	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1838	forking and then immediately registering a watcher for the child is fine,
		1839	but forking and registering a watcher a few event loop iterations later is
		1840	not.
1542		1841
1543	Only the default event loop is capable of handling signals, and therefore	1842	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1843	you can only register child watchers in the default event loop.
1545		1844
1546	=head3 Process Interaction	1845	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1858	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1859	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1860	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	1861	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.	1862	that, so other libev users can use C<ev_child> watchers freely.
		1863
		1864	=head3 Stopping the Child Watcher
		1865
		1866	Currently, the child watcher never gets stopped, even when the
		1867	child terminates, so normally one needs to stop the watcher in the
		1868	callback. Future versions of libev might stop the watcher automatically
		1869	when a child exit is detected.
1564		1870
1565	=head3 Watcher-Specific Functions and Data Members	1871	=head3 Watcher-Specific Functions and Data Members
1566		1872
1567	=over 4	1873	=over 4
1568		1874
…		…
1597	=head3 Examples	1903	=head3 Examples
1598		1904
1599	Example: C<fork()> a new process and install a child handler to wait for	1905	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	1906	its completion.
1601		1907
1602	ev_child cw;	1908	ev_child cw;
1603		1909
1604	static void	1910	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1911	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1912	{
1607	ev_child_stop (EV_A_ w);	1913	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1914	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1915	}
1610		1916
1611	pid_t pid = fork ();	1917	pid_t pid = fork ();
1612		1918
1613	if (pid < 0)	1919	if (pid < 0)
1614	// error	1920	// error
1615	else if (pid == 0)	1921	else if (pid == 0)
1616	{	1922	{
1617	// the forked child executes here	1923	// the forked child executes here
1618	exit (1);	1924	exit (1);
1619	}	1925	}
1620	else	1926	else
1621	{	1927	{
1622	ev_child_init (&cw, child_cb, pid, 0);	1928	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	1929	ev_child_start (EV_DEFAULT_ &cw);
1624	}	1930	}
1625		1931
1626		1932
1627	=head2 C<ev_stat> - did the file attributes just change?	1933	=head2 C<ev_stat> - did the file attributes just change?
1628		1934
1629	This watches a file system path for attribute changes. That is, it calls	1935	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	1936	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.	1937	and sees if it changed compared to the last time, invoking the callback if
		1938	it did.
1632		1939
1633	The path does not need to exist: changing from "path exists" to "path does	1940	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	1941	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	1942	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	1943	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	1944	least one) and all the other fields of the stat buffer having unspecified
		1945	contents.
1638		1946
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1947	The path I<must not> end in a slash or contain special components such as
		1948	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.	1949	your working directory changes, then the behaviour is undefined.
1641		1950
1642	Since there is no standard to do this, the portable implementation simply	1951	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	1952	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	1953	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,	1954	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	1955	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	1956	(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	1957	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	1958	currently around C<0.1>, but that's usually overkill.
1650		1959
1651	This watcher type is not meant for massive numbers of stat watchers,	1960	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1961	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1962	resource-intensive.
1654		1963
1655	At the time of this writing, only the Linux inotify interface is	1964	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1965	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	1966	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	1967	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		1968
1664	=head3 ABI Issues (Largefile Support)	1969	=head3 ABI Issues (Largefile Support)
1665		1970
1666	Libev by default (unless the user overrides this) uses the default	1971	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1972	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1973	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	1974	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	1975	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	1976	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	1977	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1978	most noticeably displayed with ev_stat and large file support.
1674		1979
1675	=head3 Inotify	1980	The solution for this is to lobby your distribution maker to make large
		1981	file interfaces available by default (as e.g. FreeBSD does) and not
		1982	optional. Libev cannot simply switch on large file support because it has
		1983	to exchange stat structures with application programs compiled using the
		1984	default compilation environment.
1676		1985
		1986	=head3 Inotify and Kqueue
		1987
1677	When C<inotify (7)> support has been compiled into libev (generally only	1988	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	1989	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	1990	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	1991	watcher is being started.
1681		1992
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1993	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	1994	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	1995	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.	1996	there are many cases where libev has to resort to regular C<stat> polling,
		1997	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1998	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1999	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2000	xfs are fully working) libev usually gets away without polling.
1686		2001
1687	(There is no support for kqueue, as apparently it cannot be used to	2002	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	2003	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2004	descriptor open on the object at all times, and detecting renames, unlinks
		2005	etc. is difficult.
		2006
		2007	=head3 C<stat ()> is a synchronous operation
		2008
		2009	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2010	the process. The exception are C<ev_stat> watchers - those call C<stat
		2011	()>, which is a synchronous operation.
		2012
		2013	For local paths, this usually doesn't matter: unless the system is very
		2014	busy or the intervals between stat's are large, a stat call will be fast,
		2015	as the path data is suually in memory already (except when starting the
		2016	watcher).
		2017
		2018	For networked file systems, calling C<stat ()> can block an indefinite
		2019	time due to network issues, and even under good conditions, a stat call
		2020	often takes multiple milliseconds.
		2021
		2022	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2023	paths, although this is fully supported by libev.
1690		2024
1691	=head3 The special problem of stat time resolution	2025	=head3 The special problem of stat time resolution
1692		2026
1693	The C<stat ()> system call only supports full-second resolution portably, and	2027	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2028	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2029	still only support whole seconds.
1696		2030
1697	That means that, if the time is the only thing that changes, you can	2031	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	2032	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	2033	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	2034	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2035	stat data does change in other ways (e.g. file size).
1702		2036
1703	The solution to this is to delay acting on a change for slightly more	2037	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	2038	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);	2039	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2040	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2060	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	2061	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	2062	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.	2063	path for as long as the watcher is active.
1730		2064
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2065	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	2066	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2067	last change was detected).
1734		2068
1735	=item ev_stat_stat (loop, ev_stat *)	2069	=item ev_stat_stat (loop, ev_stat *)
1736		2070
1737	Updates the stat buffer immediately with new values. If you change the	2071	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	2072	watched path in your callback, you could call this function to avoid
…		…
1767		2101
1768	=head3 Examples	2102	=head3 Examples
1769		2103
1770	Example: Watch C</etc/passwd> for attribute changes.	2104	Example: Watch C</etc/passwd> for attribute changes.
1771		2105
1772	static void	2106	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2107	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2108	{
1775	/* /etc/passwd changed in some way */	2109	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2110	if (w->attr.st_nlink)
1777	{	2111	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2112	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2113	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2114	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2115	}
1782	else	2116	else
1783	/* you shalt not abuse printf for puts */	2117	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2118	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2119	"if this is windows, they already arrived\n");
1786	}	2120	}
1787		2121
1788	...	2122	...
1789	ev_stat passwd;	2123	ev_stat passwd;
1790		2124
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2125	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2126	ev_stat_start (loop, &passwd);
1793		2127
1794	Example: Like above, but additionally use a one-second delay so we do not	2128	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	2129	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	2130	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2131	C<ev_timer> callback invocation).
1798		2132
1799	static ev_stat passwd;	2133	static ev_stat passwd;
1800	static ev_timer timer;	2134	static ev_timer timer;
1801		2135
1802	static void	2136	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2137	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2138	{
1805	ev_timer_stop (EV_A_ w);	2139	ev_timer_stop (EV_A_ w);
1806		2140
1807	/* now it's one second after the most recent passwd change */	2141	/* now it's one second after the most recent passwd change */
1808	}	2142	}
1809		2143
1810	static void	2144	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2145	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2146	{
1813	/* reset the one-second timer */	2147	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2148	ev_timer_again (EV_A_ &timer);
1815	}	2149	}
1816		2150
1817	...	2151	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2152	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2153	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2154	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2155
1822		2156
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2157	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2158
1825	Idle watchers trigger events when no other events of the same or higher	2159	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	2160	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2161	as receiving "events").
1828		2162
1829	That is, as long as your process is busy handling sockets or timeouts	2163	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	2164	(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	2165	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	2166	are pending), the idle watchers are being called once per event loop
…		…
1856	=head3 Examples	2190	=head3 Examples
1857		2191
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2192	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2193	callback, free it. Also, use no error checking, as usual.
1860		2194
1861	static void	2195	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2196	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2197	{
1864	free (w);	2198	free (w);
1865	// now do something you wanted to do when the program has	2199	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2200	// no longer anything immediate to do.
1867	}	2201	}
1868		2202
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2204	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2205	ev_idle_start (loop, idle_cb);
1872		2206
1873		2207
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2209
1876	Prepare and check watchers are usually (but not always) used in tandem:	2210	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2211	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2212	afterwards.
1879		2213
1880	You I<must not> call C<ev_loop> or similar functions that enter	2214	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>	2215	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,	2218	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	2219	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2220	called in pairs bracketing the blocking call.
1887		2221
1888	Their main purpose is to integrate other event mechanisms into libev and	2222	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	2223	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	2224	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2225	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,	2226	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>	2227	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2228	watcher).
1895		2229
1896	This is done by examining in each prepare call which file descriptors need	2230	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	2231	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	2232	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	2233	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2234	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	2235	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,	2236	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2237	nevertheless, because you never know, you know?).
1904		2238
1905	As another example, the Perl Coro module uses these hooks to integrate	2239	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2240	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2241	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	2242	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	2245	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2246	low-priority coroutines to idle/background tasks).
1913		2247
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2248	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	2249	priority, to ensure that they are being run before any other watchers
		2250	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2251
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2252	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	2253	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2254	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	2255	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	2256	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	2257	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2258	others).
1923		2259
1924	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
1925		2261
1926	=over 4	2262	=over 4
1927		2263
…		…
1929		2265
1930	=item ev_check_init (ev_check *, callback)	2266	=item ev_check_init (ev_check *, callback)
1931		2267
1932	Initialises and configures the prepare or check watcher - they have no	2268	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>	2269	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.	2270	macros, but using them is utterly, utterly, utterly and completely
		2271	pointless.
1935		2272
1936	=back	2273	=back
1937		2274
1938	=head3 Examples	2275	=head3 Examples
1939		2276
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2285	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	2286	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	2287	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.	2288	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2289
1953	static ev_io iow [nfd];	2290	static ev_io iow [nfd];
1954	static ev_timer tw;	2291	static ev_timer tw;
1955		2292
1956	static void	2293	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2294	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2295	{
1959	}	2296	}
1960		2297
1961	// create io watchers for each fd and a timer before blocking	2298	// create io watchers for each fd and a timer before blocking
1962	static void	2299	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2300	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2301	{
1965	int timeout = 3600000;	2302	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2303	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2304	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2306
1970	/* the callback is illegal, but won't be called as we stop during check */	2307	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2308	ev_timer_init (&tw, 0, timeout * 1e-3);
1972	ev_timer_start (loop, &tw);	2309	ev_timer_start (loop, &tw);
1973		2310
1974	// create one ev_io per pollfd	2311	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2312	for (int i = 0; i < nfd; ++i)
1976	{	2313	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2314	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2315	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2316	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2317
1981	fds [i].revents = 0;	2318	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2319	ev_io_start (loop, iow + i);
1983	}	2320	}
1984	}	2321	}
1985		2322
1986	// stop all watchers after blocking	2323	// stop all watchers after blocking
1987	static void	2324	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2325	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2326	{
1990	ev_timer_stop (loop, &tw);	2327	ev_timer_stop (loop, &tw);
1991		2328
1992	for (int i = 0; i < nfd; ++i)	2329	for (int i = 0; i < nfd; ++i)
1993	{	2330	{
1994	// set the relevant poll flags	2331	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2332	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2333	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2334	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2335	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2336	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2337
2001	// now stop the watcher	2338	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2339	ev_io_stop (loop, iow + i);
2003	}	2340	}
2004		2341
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2342	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2343	}
2007		2344
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2345	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.	2346	in the prepare watcher and would dispose of the check watcher.
2010		2347
2011	Method 3: If the module to be embedded supports explicit event	2348	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2349	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2350	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2351
2015	static void	2352	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2353	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2354	{
2018	adns_state ads = (adns_state)w->data;	2355	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2356	update_now (EV_A);
2020		2357
2021	adns_processtimeouts (ads, &tv_now);	2358	adns_processtimeouts (ads, &tv_now);
2022	}	2359	}
2023		2360
2024	static void	2361	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2362	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2363	{
2027	adns_state ads = (adns_state)w->data;	2364	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2365	update_now (EV_A);
2029		2366
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2367	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2368	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2369	}
2033		2370
2034	// do not ever call adns_afterpoll	2371	// do not ever call adns_afterpoll
2035		2372
2036	Method 4: Do not use a prepare or check watcher because the module you	2373	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	2374	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	2375	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	2376	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2377	this approach, effectively embedding EV as a client into the horrible
		2378	libglib event loop.
2041		2379
2042	static gint	2380	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2381	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2382	{
2045	int got_events = 0;	2383	int got_events = 0;
2046		2384
2047	for (n = 0; n < nfds; ++n)	2385	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2386	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2387
2050	if (timeout >= 0)	2388	if (timeout >= 0)
2051	// create/start timer	2389	// create/start timer
2052		2390
2053	// poll	2391	// poll
2054	ev_loop (EV_A_ 0);	2392	ev_loop (EV_A_ 0);
2055		2393
2056	// stop timer again	2394	// stop timer again
2057	if (timeout >= 0)	2395	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2396	ev_timer_stop (EV_A_ &to);
2059		2397
2060	// stop io watchers again - their callbacks should have set	2398	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2399	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2400	ev_io_stop (EV_A_ iow [n]);
2063		2401
2064	return got_events;	2402	return got_events;
2065	}	2403	}
2066		2404
2067		2405
2068	=head2 C<ev_embed> - when one backend isn't enough...	2406	=head2 C<ev_embed> - when one backend isn't enough...
2069		2407
2070	This is a rather advanced watcher type that lets you embed one event loop	2408	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2414	prioritise I/O.
2077		2415
2078	As an example for a bug workaround, the kqueue backend might only support	2416	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	2417	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	2418	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	2419	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	2420	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	2421	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.	2422	C<kevent>, but at least you can use both mechanisms for what they are
		2423	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2424
2086	As for prioritising I/O: rarely you have the case where some fds have	2425	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	2426	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	2427	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	2428	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.	2429	the rest in a second one, and embed the second one in the first.
2091		2430
2092	As long as the watcher is active, the callback will be invoked every time	2431	As long as the watcher is active, the callback will be invoked every time
2093	there might be events pending in the embedded loop. The callback must then	2432	there might be events pending in the embedded loop. The callback must then
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2095	their callbacks (you could also start an idle watcher to give the embedded	2434	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2442	interested in that.
2104		2443
2105	Also, there have not currently been made special provisions for forking:	2444	Also, there have not currently been made special provisions for forking:
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2107	but you will also have to stop and restart any C<ev_embed> watchers	2446	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2447	yourself - but you can use a fork watcher to handle this automatically,
		2448	and future versions of libev might do just that.
2109		2449
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2450	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2452	portable one.
2113		2453
2114	So when you want to use this feature you will always have to be prepared	2454	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	2455	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	2456	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.	2457	create it, and if that fails, use the normal loop for everything.
		2458
		2459	=head3 C<ev_embed> and fork
		2460
		2461	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2462	automatically be applied to the embedded loop as well, so no special
		2463	fork handling is required in that case. When the watcher is not running,
		2464	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2465	as applicable.
2118		2466
2119	=head3 Watcher-Specific Functions and Data Members	2467	=head3 Watcher-Specific Functions and Data Members
2120		2468
2121	=over 4	2469	=over 4
2122		2470
…		…
2148	event loop. If that is not possible, use the default loop. The default	2496	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	2497	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	2498	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2499	used).
2152		2500
2153	struct ev_loop *loop_hi = ev_default_init (0);	2501	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2502	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2503	ev_embed embed;
2156		2504
2157	// see if there is a chance of getting one that works	2505	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2506	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2507	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2508	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2509	: 0;
2162		2510
2163	// if we got one, then embed it, otherwise default to loop_hi	2511	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2512	if (loop_lo)
2165	{	2513	{
2166	ev_embed_init (&embed, 0, loop_lo);	2514	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2515	ev_embed_start (loop_hi, &embed);
2168	}	2516	}
2169	else	2517	else
2170	loop_lo = loop_hi;	2518	loop_lo = loop_hi;
2171		2519
2172	Example: Check if kqueue is available but not recommended and create	2520	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2521	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2522	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2523	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2524
2177	struct ev_loop *loop = ev_default_init (0);	2525	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2526	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2527	ev_embed embed;
2180		2528
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2529	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2530	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2531	{
2184	ev_embed_init (&embed, 0, loop_socket);	2532	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2533	ev_embed_start (loop, &embed);
2186	}	2534	}
2187		2535
2188	if (!loop_socket)	2536	if (!loop_socket)
2189	loop_socket = loop;	2537	loop_socket = loop;
2190		2538
2191	// now use loop_socket for all sockets, and loop for everything else	2539	// now use loop_socket for all sockets, and loop for everything else
2192		2540
2193		2541
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2542	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2543
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2544	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	2588	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	2589	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2590	need elaborate support such as pthreads.
2243		2591
2244	That means that if you want to queue data, you have to provide your own	2592	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	2593	queue. But at least I can tell you how to implement locking around your
2246	queue:	2594	queue:
2247		2595
2248	=over 4	2596	=over 4
2249		2597
2250	=item queueing from a signal handler context	2598	=item queueing from a signal handler context
2251		2599
2252	To implement race-free queueing, you simply add to the queue in the signal	2600	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	2601	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2602	an example that does that for some fictitious SIGUSR1 handler:
2255		2603
2256	static ev_async mysig;	2604	static ev_async mysig;
2257		2605
2258	static void	2606	static void
2259	sigusr1_handler (void)	2607	sigusr1_handler (void)
…		…
2325	=over 4	2673	=over 4
2326		2674
2327	=item ev_async_init (ev_async *, callback)	2675	=item ev_async_init (ev_async *, callback)
2328		2676
2329	Initialises and configures the async watcher - it has no parameters of any	2677	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,	2678	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2679	trust me.
2332		2680
2333	=item ev_async_send (loop, ev_async *)	2681	=item ev_async_send (loop, ev_async *)
2334		2682
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2683	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	2684	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	2685	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	2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2687	section below on what exactly this means).
2340		2688
2341	This call incurs the overhead of a system call only once per loop iteration,	2689	This call incurs the overhead of a system call only once per loop iteration,
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2690	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2714	=over 4
2367		2715
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2716	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2717
2370	This function combines a simple timer and an I/O watcher, calls your	2718	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2719	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	2720	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	2721	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2722	more watchers yourself.
2375		2723
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2724	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	2725	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2726	the given C<fd> and C<events> set will be created and started.
2379		2727
2380	If C<timeout> is less than 0, then no timeout watcher will be	2728	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	2729	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	2730	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2731
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2732	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	2733	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>	2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2735	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2736	a timeout and an io event at the same time - you probably should give io
		2737	events precedence.
2389		2738
		2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2740
2390	static void stdin_ready (int revents, void *arg)	2741	static void stdin_ready (int revents, void *arg)
2391	{	2742	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	2743	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	2744	/* stdin might have data for us, joy! */;
		2745	else if (revents & EV_TIMEOUT)
		2746	/* doh, nothing entered */;
2396	}	2747	}
2397		2748
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2750
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2752
2402	Feeds the given event set into the event loop, as if the specified event	2753	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	2754	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2755	initialised but not necessarily started event watcher).
2405		2756
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2758
2408	Feed an event on the given fd, as if a file descriptor backend detected	2759	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2760	the given events it.
2410		2761
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2763
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2764	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2765	loop!).
2415		2766
2416	=back	2767	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	2803	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.	2804	the callback model to a model using method callbacks on objects.
2454		2805
2455	To use it,	2806	To use it,
2456		2807
2457	#include <ev++.h>	2808	#include <ev++.h>
2458		2809
2459	This automatically includes F<ev.h> and puts all of its definitions (many	2810	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	2811	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	2812	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2813	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	2880	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.	2881	thunking function, making it as fast as a direct C callback.
2531		2882
2532	Example: simple class declaration and watcher initialisation	2883	Example: simple class declaration and watcher initialisation
2533		2884
2534	struct myclass	2885	struct myclass
2535	{	2886	{
2536	void io_cb (ev::io &w, int revents) { }	2887	void io_cb (ev::io &w, int revents) { }
2537	}	2888	}
2538		2889
2539	myclass obj;	2890	myclass obj;
2540	ev::io iow;	2891	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	2892	iow.set <myclass, &myclass::io_cb> (&obj);
2542		2893
2543	=item w->set<function> (void *data = 0)	2894	=item w->set<function> (void *data = 0)
2544		2895
2545	Also sets a callback, but uses a static method or plain function as	2896	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	2897	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		2899
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2900	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2901
2551	See the method-C<set> above for more details.	2902	See the method-C<set> above for more details.
2552		2903
2553	Example:	2904	Example: Use a plain function as callback.
2554		2905
2555	static void io_cb (ev::io &w, int revents) { }	2906	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2907	iow.set <io_cb> ();
2557		2908
2558	=item w->set (struct ev_loop *)	2909	=item w->set (struct ev_loop *)
2559		2910
2560	Associates a different C<struct ev_loop> with this watcher. You can only	2911	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).	2912	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	2945	=back
2595		2946
2596	Example: Define a class with an IO and idle watcher, start one of them in	2947	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2948	the constructor.
2598		2949
2599	class myclass	2950	class myclass
2600	{	2951	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2952	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2954
2604	myclass (int fd)	2955	myclass (int fd)
2605	{	2956	{
2606	io .set <myclass, &myclass::io_cb > (this);	2957	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2958	idle.set <myclass, &myclass::idle_cb> (this);
2608		2959
2609	io.start (fd, ev::READ);	2960	io.start (fd, ev::READ);
2610	}	2961	}
2611	};	2962	};
2612		2963
2613		2964
2614	=head1 OTHER LANGUAGE BINDINGS	2965	=head1 OTHER LANGUAGE BINDINGS
2615		2966
2616	Libev does not offer other language bindings itself, but bindings for a	2967	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	2974	=item Perl
2624		2975
2625	The EV module implements the full libev API and is actually used to test	2976	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,	2977	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2978	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	2979	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>).	2980	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2981	and C<EV::Glib>).
2630		2982
2631	It can be found and installed via CPAN, its homepage is found at	2983	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2984	L<http://software.schmorp.de/pkg/EV>.
		2985
		2986	=item Python
		2987
		2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2989	seems to be quite complete and well-documented. Note, however, that the
		2990	patch they require for libev is outright dangerous as it breaks the ABI
		2991	for everybody else, and therefore, should never be applied in an installed
		2992	libev (if python requires an incompatible ABI then it needs to embed
		2993	libev).
2633		2994
2634	=item Ruby	2995	=item Ruby
2635		2996
2636	Tony Arcieri has written a ruby extension that offers access to a subset	2997	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	2998	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
2639	L<http://rev.rubyforge.org/>.	3000	L<http://rev.rubyforge.org/>.
2640		3001
2641	=item D	3002	=item D
2642		3003
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3004	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>.	3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3006
		3007	=item Ocaml
		3008
		3009	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		3011
2646	=back	3012	=back
2647		3013
2648		3014
2649	=head1 MACRO MAGIC	3015	=head1 MACRO MAGIC
…		…
2661		3027
2662	This provides the loop I<argument> for functions, if one is required ("ev	3028	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,	3029	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:	3030	C<EV_A_> is used when other arguments are following. Example:
2665		3031
2666	ev_unref (EV_A);	3032	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3033	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3034	ev_loop (EV_A_ 0);
2669		3035
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3037	which is often provided by the following macro.
2672		3038
2673	=item C<EV_P>, C<EV_P_>	3039	=item C<EV_P>, C<EV_P_>
2674		3040
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3041	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,	3042	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:	3043	C<EV_P_> is used when other parameters are following. Example:
2678		3044
2679	// this is how ev_unref is being declared	3045	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3046	static void ev_unref (EV_P);
2681		3047
2682	// this is how you can declare your typical callback	3048	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3049	static void cb (EV_P_ ev_timer *w, int revents)
2684		3050
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3051	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3052	suitable for use with C<EV_A>.
2687		3053
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3054	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3070
2705	Example: Declare and initialise a check watcher, utilising the above	3071	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3072	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3073	or not.
2708		3074
2709	static void	3075	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3076	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3077	{
2712	ev_check_stop (EV_A_ w);	3078	ev_check_stop (EV_A_ w);
2713	}	3079	}
2714		3080
2715	ev_check check;	3081	ev_check check;
2716	ev_check_init (&check, check_cb);	3082	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3083	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3084	ev_loop (EV_DEFAULT_ 0);
2719		3085
2720	=head1 EMBEDDING	3086	=head1 EMBEDDING
2721		3087
2722	Libev can (and often is) directly embedded into host	3088	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3089	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3103	=head3 CORE EVENT LOOP
2738		3104
2739	To include only the libev core (all the C<ev_*> functions), with manual	3105	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3106	configuration (no autoconf):
2741		3107
2742	#define EV_STANDALONE 1	3108	#define EV_STANDALONE 1
2743	#include "ev.c"	3109	#include "ev.c"
2744		3110
2745	This will automatically include F<ev.h>, too, and should be done in a	3111	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	3112	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	3113	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	3114	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3115	where you can put other configuration options):
2750		3116
2751	#define EV_STANDALONE 1	3117	#define EV_STANDALONE 1
2752	#include "ev.h"	3118	#include "ev.h"
2753		3119
2754	Both header files and implementation files can be compiled with a C++	3120	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	3121	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3122	as a bug).
2757		3123
2758	You need the following files in your source tree, or in a directory	3124	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):	3125	in your include path (e.g. in libev/ when using -Ilibev):
2760		3126
2761	ev.h	3127	ev.h
2762	ev.c	3128	ev.c
2763	ev_vars.h	3129	ev_vars.h
2764	ev_wrap.h	3130	ev_wrap.h
2765		3131
2766	ev_win32.c required on win32 platforms only	3132	ev_win32.c required on win32 platforms only
2767		3133
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3134	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)	3135	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)	3136	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)	3137	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)	3138	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3139
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3140	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3141	to compile this single file.
2776		3142
2777	=head3 LIBEVENT COMPATIBILITY API	3143	=head3 LIBEVENT COMPATIBILITY API
2778		3144
2779	To include the libevent compatibility API, also include:	3145	To include the libevent compatibility API, also include:
2780		3146
2781	#include "event.c"	3147	#include "event.c"
2782		3148
2783	in the file including F<ev.c>, and:	3149	in the file including F<ev.c>, and:
2784		3150
2785	#include "event.h"	3151	#include "event.h"
2786		3152
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3153	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3154
2789	You need the following additional files for this:	3155	You need the following additional files for this:
2790		3156
2791	event.h	3157	event.h
2792	event.c	3158	event.c
2793		3159
2794	=head3 AUTOCONF SUPPORT	3160	=head3 AUTOCONF SUPPORT
2795		3161
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3162	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	3163	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	3164	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3165	include F<config.h> and configure itself accordingly.
2800		3166
2801	For this of course you need the m4 file:	3167	For this of course you need the m4 file:
2802		3168
2803	libev.m4	3169	libev.m4
2804		3170
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3171	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3172
2807	Libev can be configured via a variety of preprocessor symbols you have to	3173	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	3174	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3175	autoconf is documented for every option.
2810		3176
2811	=over 4	3177	=over 4
2812		3178
2813	=item EV_STANDALONE	3179	=item EV_STANDALONE
2814		3180
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3350	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	3351	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	3352	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3353	fine.
2988		3354
2989	If your embedding application does not need any priorities, defining these both to	3355	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3356	both to C<0> will save some memory and CPU.
2991		3357
2992	=item EV_PERIODIC_ENABLE	3358	=item EV_PERIODIC_ENABLE
2993		3359
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3360	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	3361	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3368	code.
3003		3369
3004	=item EV_EMBED_ENABLE	3370	=item EV_EMBED_ENABLE
3005		3371
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3373	defined to be C<0>, then they are not. Embed watchers rely on most other
		3374	watcher types, which therefore must not be disabled.
3008		3375
3009	=item EV_STAT_ENABLE	3376	=item EV_STAT_ENABLE
3010		3377
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3379	defined to be C<0>, then they are not.
…		…
3044	two).	3411	two).
3045		3412
3046	=item EV_USE_4HEAP	3413	=item EV_USE_4HEAP
3047		3414
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3415	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	3416	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	3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3418	faster performance with many (thousands) of watchers.
3052		3419
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3421	(disabled).
3055		3422
3056	=item EV_HEAP_CACHE_AT	3423	=item EV_HEAP_CACHE_AT
3057		3424
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3425	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	3426	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>),	3427	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,	3428	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	3429	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3430	noticeably with many (hundreds) of watchers.
3064		3431
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3433	(disabled).
3067		3434
3068	=item EV_VERIFY	3435	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3441	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	3442	verification code will be called very frequently, which will slow down
3076	libev considerably.	3443	libev considerably.
3077		3444
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3446	C<0>.
3080		3447
3081	=item EV_COMMON	3448	=item EV_COMMON
3082		3449
3083	By default, all watchers have a C<void *data> member. By redefining	3450	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	3451	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,	3452	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3453	though, and it must be identical each time.
3087		3454
3088	For example, the perl EV module uses something like this:	3455	For example, the perl EV module uses something like this:
3089		3456
3090	#define EV_COMMON \	3457	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3458	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3459	SV *cb_sv, *fh /* note no trailing ";" */
3093		3460
3094	=item EV_CB_DECLARE (type)	3461	=item EV_CB_DECLARE (type)
3095		3462
3096	=item EV_CB_INVOKE (watcher, revents)	3463	=item EV_CB_INVOKE (watcher, revents)
3097		3464
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3469	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	3470	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	3471	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++.	3472	method calls instead of plain function calls in C++.
3106		3473
		3474	=back
		3475
3107	=head2 EXPORTED API SYMBOLS	3476	=head2 EXPORTED API SYMBOLS
3108		3477
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3478	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	3479	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3480	all public symbols, one per line:
3112		3481
3113	Symbols.ev for libev proper	3482	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3483	Symbols.event for the libevent emulation
3115		3484
3116	This can also be used to rename all public symbols to avoid clashes with	3485	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	3486	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3487	itself, but sometimes it is inconvenient to avoid this).
3119		3488
…		…
3140	file.	3509	file.
3141		3510
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3511	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:	3512	that everybody includes and which overrides some configure choices:
3144		3513
3145	#define EV_MINIMAL 1	3514	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3515	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3516	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3517	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3518	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3519	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3520	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3521	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3522	#define EV_MAXPRI 0
3154		3523
3155	#include "ev++.h"	3524	#include "ev++.h"
3156		3525
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3527
3159	#include "ev_cpp.h"	3528	#include "ev_cpp.h"
3160	#include "ev.c"	3529	#include "ev.c"
3161		3530
		3531	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3532
3163	=head1 THREADS AND COROUTINES	3533	=head2 THREADS AND COROUTINES
3164		3534
3165	=head2 THREADS	3535	=head3 THREADS
3166		3536
3167	Libev itself is completely thread-safe, but it uses no locking. This	3537	All libev functions are reentrant and thread-safe unless explicitly
		3538	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	3539	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	3540	are no concurrent calls into any libev function with the same loop
3170	parameter.	3541	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3542	of course): libev guarantees that different event loops share no data
		3543	structures that need any locking.
3171		3544
3172	Or put differently: calls with different loop parameters can be done in	3545	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	3546	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	3547	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	3548	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3549	a mutex per loop).
3177		3550
3178	If you want to know which design is best for your problem, then I cannot	3551	Specifically to support threads (and signal handlers), libev implements
		3552	so-called C<ev_async> watchers, which allow some limited form of
		3553	concurrency on the same event loop, namely waking it up "from the
		3554	outside".
		3555
		3556	If you want to know which design (one loop, locking, or multiple loops
		3557	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3558	help you, but here is some generic advice:
3180		3559
3181	=over 4	3560	=over 4
3182		3561
3183	=item * most applications have a main thread: use the default libev loop	3562	=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.	3563	in that thread, or create a separate thread running only the default loop.
…		…
3196		3575
3197	Choosing a model is hard - look around, learn, know that usually you can do	3576	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3577	better than you currently do :-)
3199		3578
3200	=item * often you need to talk to some other thread which blocks in the	3579	=item * often you need to talk to some other thread which blocks in the
		3580	event loop.
		3581
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3582	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3583	(or from signal contexts...).
		3584
		3585	An example use would be to communicate signals or other events that only
		3586	work in the default loop by registering the signal watcher with the
		3587	default loop and triggering an C<ev_async> watcher from the default loop
		3588	watcher callback into the event loop interested in the signal.
3203		3589
3204	=back	3590	=back
3205		3591
3206	=head2 COROUTINES	3592	=head3 COROUTINES
3207		3593
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3594	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3595	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	3596	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	3597	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	3598	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.	3599	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3600
3215	Care has been invested into making sure that libev does not keep local	3601	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	3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3603	they do not call any callbacks.
3218		3604
		3605	=head2 COMPILER WARNINGS
3219		3606
3220	=head1 COMPLEXITIES	3607	Depending on your compiler and compiler settings, you might get no or a
		3608	lot of warnings when compiling libev code. Some people are apparently
		3609	scared by this.
3221		3610
3222	In this section the complexities of (many of) the algorithms used inside	3611	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3612	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3613	warning options. "Warn-free" code therefore cannot be a goal except when
		3614	targeting a specific compiler and compiler-version.
3225		3615
3226	All of the following are about amortised time: If an array needs to be	3616	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3617	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	3618	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		3619
3232	=over 4	3620	And of course, some compiler warnings are just plain stupid, or simply
		3621	wrong (because they don't actually warn about the condition their message
		3622	seems to warn about). For example, certain older gcc versions had some
		3623	warnings that resulted an extreme number of false positives. These have
		3624	been fixed, but some people still insist on making code warn-free with
		3625	such buggy versions.
3233		3626
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
3235		3632
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		3633
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3634	=head2 VALGRIND
3241		3635
3242	That means that changing a timer costs less than removing/adding them	3636	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.	3637	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3638
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
3246		3641
3247	These just add the watcher into an array or at the head of a list.	3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
3248		3645
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3646	Then there is no memory leak, just as memory accounted to global variables
		3647	is not a memleak - the memory is still being referenced, and didn't leak.
3250		3648
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3649	Similarly, under some circumstances, valgrind might report kernel bugs
		3650	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3651	although an acceptable workaround has been found here), or it might be
		3652	confused.
3252		3653
3253	These watchers are stored in lists then need to be walked to find the	3654	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	3655	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3656
3257	=item Finding the next timer in each loop iteration: O(1)	3657	If you are unsure about something, feel free to contact the mailing list
		3658	with the full valgrind report and an explanation on why you think this
		3659	is a bug in libev (best check the archives, too :). However, don't be
		3660	annoyed when you get a brisk "this is no bug" answer and take the chance
		3661	of learning how to interpret valgrind properly.
3258		3662
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3663	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3664	I suggest using suppression lists.
3261		3665
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3666
3264	A change means an I/O watcher gets started or stopped, which requires	3667	=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		3668
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	3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3291		3670
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3671	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	3672	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3673	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3306		3685
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3686	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3687	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,	3688	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	3689	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	3690	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3691	available).
3313		3692
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3693	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	3694	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3695	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	3696	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	3697	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3698	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3699	(Microsoft monopoly games).
3321		3700
		3701	A typical way to use libev under windows is to embed it (see the embedding
		3702	section for details) and use the following F<evwrap.h> header file instead
		3703	of F<ev.h>:
		3704
		3705	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3706	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3707
		3708	#include "ev.h"
		3709
		3710	And compile the following F<evwrap.c> file into your project (make sure
		3711	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3712
		3713	#include "evwrap.h"
		3714	#include "ev.c"
		3715
3322	=over 4	3716	=over 4
3323		3717
3324	=item The winsocket select function	3718	=item The winsocket select function
3325		3719
3326	The winsocket C<select> function doesn't follow POSIX in that it	3720	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	3721	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3722	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3723	requires a mapping from file descriptors to socket handles (the Microsoft
		3724	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	3725	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.	3726	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3727
3333	The configuration for a "naked" win32 using the Microsoft runtime	3728	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3729	libraries and raw winsocket select is:
3335		3730
3336	#define EV_USE_SELECT 1	3731	#define EV_USE_SELECT 1
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		3733
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	3734	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.	3735	complexity in the O(n²) range when using win32.
3341		3736
3342	=item Limited number of file descriptors	3737	=item Limited number of file descriptors
…		…
3366	wrap all I/O functions and provide your own fd management, but the cost of	3761	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.	3762	calling select (O(n²)) will likely make this unworkable.
3368		3763
3369	=back	3764	=back
3370		3765
3371
3372	=head1 PORTABILITY REQUIREMENTS	3766	=head2 PORTABILITY REQUIREMENTS
3373		3767
3374	In addition to a working ISO-C implementation, libev relies on a few	3768	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	3769	backend-specific APIs, libev relies on a few additional extensions:
3376		3770
3377	=over 4	3771	=over 4
3378		3772
		3773	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3774	calling conventions regardless of C<ev_watcher_type *>.
		3775
		3776	Libev assumes not only that all watcher pointers have the same internal
		3777	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3778	assumes that the same (machine) code can be used to call any watcher
		3779	callback: The watcher callbacks have different type signatures, but libev
		3780	calls them using an C<ev_watcher *> internally.
		3781
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	3782	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		3783
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	3784	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	3785	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	3786	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	3787	believed to be sufficiently portable.
3385		3788
3386	=item C<sigprocmask> must work in a threaded environment	3789	=item C<sigprocmask> must work in a threaded environment
3387		3790
…		…
3396	except the initial one, and run the default loop in the initial thread as	3799	except the initial one, and run the default loop in the initial thread as
3397	well.	3800	well.
3398		3801
3399	=item C<long> must be large enough for common memory allocation sizes	3802	=item C<long> must be large enough for common memory allocation sizes
3400		3803
3401	To improve portability and simplify using libev, libev uses C<long>	3804	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	3805	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3806	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	3807	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	3808	watchers.
3406		3809
3407	=item C<double> must hold a time value in seconds with enough accuracy	3810	=item C<double> must hold a time value in seconds with enough accuracy
3408		3811
3409	The type C<double> is used to represent timestamps. It is required to	3812	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	3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3414	=back	3817	=back
3415		3818
3416	If you know of other additional requirements drop me a note.	3819	If you know of other additional requirements drop me a note.
3417		3820
3418		3821
3419	=head1 COMPILER WARNINGS	3822	=head1 ALGORITHMIC COMPLEXITIES
3420		3823
3421	Depending on your compiler and compiler settings, you might get no or a	3824	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	3825	libev will be documented. For complexity discussions about backends see
3423	scared by this.	3826	the documentation for C<ev_default_init>.
3424		3827
3425	However, these are unavoidable for many reasons. For one, each compiler	3828	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	3829	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	3830	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	3831	mean that libev does a lengthy realloc operation in rare cases, but on
		3832	average it is much faster and asymptotically approaches constant time.
3429		3833
3430	Another reason is that some compiler warnings require elaborate	3834	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		3835
3434	And of course, some compiler warnings are just plain stupid, or simply	3836	=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		3837
3438	While libev is written to generate as few warnings as possible,	3838	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	3839	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	3840	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		3841
		3842	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		3843
3445	=head1 VALGRIND	3844	That means that changing a timer costs less than removing/adding them,
		3845	as only the relative motion in the event queue has to be paid for.
3446		3846
3447	Valgrind has a special section here because it is a popular tool that is	3847	=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		3848
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	3849	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		3850
3453	==2274== definitely lost: 0 bytes in 0 blocks.	3851	=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		3852
3457	Then there is no memory leak. Similarly, under some circumstances,	3853	=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		3854
3461	If you are unsure about something, feel free to contact the mailing list	3855	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	3856	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	3857	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	3858	is rare).
3465	properly.
3466		3859
3467	If you need, for some reason, empty reports from valgrind for your project	3860	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.	3861
		3862	By virtue of using a binary or 4-heap, the next timer is always found at a
		3863	fixed position in the storage array.
		3864
		3865	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3866
		3867	A change means an I/O watcher gets started or stopped, which requires
		3868	libev to recalculate its status (and possibly tell the kernel, depending
		3869	on backend and whether C<ev_io_set> was used).
		3870
		3871	=item Activating one watcher (putting it into the pending state): O(1)
		3872
		3873	=item Priority handling: O(number_of_priorities)
		3874
		3875	Priorities are implemented by allocating some space for each
		3876	priority. When doing priority-based operations, libev usually has to
		3877	linearly search all the priorities, but starting/stopping and activating
		3878	watchers becomes O(1) with respect to priority handling.
		3879
		3880	=item Sending an ev_async: O(1)
		3881
		3882	=item Processing ev_async_send: O(number_of_async_watchers)
		3883
		3884	=item Processing signals: O(max_signal_number)
		3885
		3886	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3887	calls in the current loop iteration. Checking for async and signal events
		3888	involves iterating over all running async watchers or all signal numbers.
		3889
		3890	=back
3469		3891
3470		3892
3471	=head1 AUTHOR	3893	=head1 AUTHOR
3472		3894
3473	Marc Lehmann <libev@schmorp.de>.	3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3474		3896

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